JP2002335108A - Method of designing impedance transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wide-band impedance transformer. SOLUTION: An impedance transformer is provided with a plurality of transmission lines having about 1/4 wavelength, an impedance step between the transmission times, and another impedance step between the transmission lines and input and output lines; and in a method of designing the transformer, the initial design of the lengths and characteristic impedance of the 1/4-wavelength lines as design parameters is conducted, in accordance with the conventional design procedure, in which the frequency characteristic of a susceptance due to discontinuity between the 1/4-wavelength lines is not taken into account in a step 1. Then frequencies of a number larger than the number of the design parameters are selected, and the insertion losses or reflection losses at the frequencies are specified in a step 2. Finally, the lengths are widths of the lines are optimized, by using the specified insertion losses or reflection losses as restraining conditions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention mainly relates to a VHF band,
The present invention relates to broadening the impedance transformer used in the UHF band, the microwave band, and the millimeter wave band.

[0002]

2. Description of the Related Art FIGS. 34 to 35 show S. Herbert, "Microstr.
ip Interdigital Filter Design, ”Microwave Journal
, pp. 187-188, Nov. 1990, or JAGMalherbe,
“Microwave Transmission Line Filters”, ARTECH H
OUSE, INC, pp.111-130, 1979. is a diagram showing the design procedure of a conventional high-frequency filter. FIG. 34 is a design flow, FIG. 35 is a circuit of a low-pass filter, and FIG. It is an equivalent circuit of a bandpass filter.
In FIG. 35, Ci '(i = 1,3) and Li' (i = 2,4) are the elements of the original low-pass filter, G0 'is the power supply impedance, G5' is the load impedance, and gi (i = 0,3). 1,…,
5) is a coefficient determined by the transfer function of the filter.
In FIG. 36, Li (i = 1,..., 4) is a parallel inductance, Ji, i + 1 (i, = 1,2,3) is a J inverter, and δ0
And δ5 are the impedance transformation ratios. Li and J
i and i + 1 are near the frequency where θ = π / 2 and are represented by equivalent circuits of the distributed constant lines shown in FIGS. 36 (b) and (c).

Next, the design procedure will be described. First, the element value of the original low-pass filter is determined from the desired pass band width, the ripple in the pass band, the number of resonator stages, and the coefficient of the Chebyshev series used as the transfer function.
Next, frequency conversion is performed on the original low-pass filter, and a J-inverter is introduced to convert it into an equivalent circuit of the band-pass filter shown in FIG. At this time J
The inverter and the parallel inductance are shown in FIG.
As shown in (c), the filter is replaced with a distributed constant type equivalent circuit using a tip short-circuit stub having an electrical length θ approximately near the center frequency of the filter. A conventional interdigital band-pass filter is designed using this distributed constant type equivalent circuit.

A high-frequency filter is generally constituted by a resonator having a distributed constant line, and the frequency characteristics can be calculated relatively accurately by an equivalent circuit shown in FIG. The reflection characteristic of the conventional high-frequency filter shown in FIG. 36 has a large error due to the approximation of FIGS. 36 (b) and (c) at frequencies away from the center frequency. As shown, the reflection loss increases at the pass band edge.

FIGS. 38 to 40 show RECollin, “F
oundations for Microwave Engineering ”, McGraw-Hi
ll, Inc., pp. 639-642, 1979. or another conventional high-frequency filter design procedure disclosed in Japanese Patent Application Laid-Open No. 6-216608. FIG. 38 is a design flow, and FIG. FIGS. 40 and 41 are equivalent circuits of a waveguide band-pass filter. In FIG. 39, Ci '(i = 1,3, ..., 11) and Li', (i = 2,4, ..., 10)
Is the element of the original low-pass filter, G0 'is the source impedance, G5' is the load impedance, gi, (i = 0,1,
.., 12) are coefficients determined by the transfer function of the filter. In FIG. 40A, Li (i = 1, 2,..., 1
1) is a series inductance, Ci (i = 1,2, ..., 11) is a series capacitance, and Ki, i + 1 (i, = 1,2,3) is a K inverter. In the vicinity of the frequency where θ = π, Ki, j
Is represented by a parallel susceptance Bi, j shown in FIG. Bi, j is realized, for example, by an inductive iris. A series resonance circuit composed of Li and Ci is represented by a waveguide circuit having an electrical length θi.

Next, the design procedure will be described. First, the element value of the original low-pass filter is determined from a desired pass bandwidth, ripple in the pass band, the number of resonator stages, and a coefficient obtained by series expansion of a Chebyshev function used as a transfer function. Next, frequency conversion is performed on the original low-pass filter, and further, a K inverter is introduced to convert to an equivalent circuit of the band-pass filter shown in FIG. At this time, near the center frequency of the filter,
As shown in FIGS. 40 (a) and (b), Ki, j is derived by approximating the parallel susceptance Bi, j, and approximating the series resonant circuit composed of Li and Ci by the waveguide circuit having the electrical length θi. The waveguide type bandpass filter is represented by a distributed constant type equivalent circuit shown in FIG. A conventional waveguide bandpass filter is designed using this distributed constant type equivalent circuit.

The reflection characteristic of the conventional waveguide band-pass filter shown in FIG. 41 shows that the error due to the approximation shown in FIGS. In particular, when the pass band is wide, the reflection loss increases at the end of the pass band as shown by the solid line in FIG. In particular, in a waveguide band-pass filter, the dispersion of the wavelength in the waveguide with respect to the frequency change is large, and the ratio of the electrical length change to the frequency change is large. Deterioration of characteristics becomes remarkable.

FIGS. 43 and 44 show RECollin,
“Foundations for Microwave Engineering”, McGra
FIG. 43 is a diagram showing a design procedure of a conventional impedance transformer shown in w-Hill, Inc., pp. 343-360, 1979.
Is a design flow, and FIG. 44 is an equivalent circuit. In FIG. 44, Zi (i = 1, 2,..., 4) is the characteristic impedance of the distributed constant line, Z0 is the characteristic impedance of the input line, ZL 'is the characteristic impedance of the output line, and θ is the electrical length of the distributed constant line. is there.

Next, the design procedure will be described. First, the number of stages of the impedance transformer is defined, and the expression of the reflection coefficient of the impedance transformer is obtained using the equivalent circuit of FIG. Assuming that the electric length of each distributed constant line is set equal and that the reflection at the connection surface between adjacent distributed constant lines is sufficiently small, the reflection coefficient is expanded into a polynomial using a trigonometric function. At this time, the reflection coefficient in the pass band is accurately expressed using the Chebyshev function if the pass band width and the number and magnitude of the ripples in the pass band are defined. The Chebyshev function can be expanded by a trigonometric function, and the characteristic impedance of each distributed constant line of the impedance transformer can be obtained by comparing the Chebyshev function with a polynomial of the reflection coefficient obtained from the equivalent circuit of FIG. At this time, the line length of the distributed constant line is set so that the electrical length θ is π / 2 at the center frequency.

In an actual impedance transformer,
Since physical steps such as conductor width occur at the connection between adjacent distributed constant lines with different characteristic impedances,
This discontinuity causes a susceptance. This susceptance has the function of equivalently changing the electric length of the distributed constant line. In a normal design, the distributed constant line is so controlled that the total electric length including this electric length change becomes π / 2 at the design center frequency. Determine the physical length of However, since the electrical length due to this susceptance differs in frequency from the electrical length of the distributed constant line, the reflection coefficient of the impedance transformer based on the equivalent circuit including the discontinuous susceptance component is based on the Chebyshev function at frequencies away from the center frequency. Shift. Accordingly, the reflection characteristic of the conventional impedance transformer shown in FIG. 44 shows that the reflection loss is large at the pass band edge as shown by the solid line in FIG. 45 at a frequency away from the center frequency as in the case of the filters of FIGS. Become.

[0011]

Since the conventional impedance transformer designing method is as described above, at a frequency distant from the center frequency of the design, the reflection characteristic by the equivalent circuit corresponding to the physical shape is changed by the transfer function. However, there has been a problem that the characteristic of reflection is deteriorated from the ideal reflection characteristic obtained from the above, and therefore, a characteristic of low reflection over a wide band cannot be obtained.

The present invention has been made to solve the above problems, and has as its object to provide a method of designing an impedance transformer capable of reducing reflection over a wide band.

[0013]

According to a first aspect of the present invention, there is provided a method for designing an impedance transformer, comprising: a plurality of transmission lines of approximately 1/4 wavelength; an impedance step between the transmission lines; In the impedance transformer between the line and the impedance step, the line length of the transmission line, and the number of the number of parameters or more to determine the characteristic impedance is selected, the frequency at the selected frequency The transmission line length and the characteristic impedance of the transmission line are determined so that the transmission characteristic or the reflection characteristic of the impedance transformer approaches a desired value.

Further, a method of designing an impedance transformer according to a second aspect of the present invention is a method of designing an impedance transformer, comprising: a plurality of transmission lines of approximately 1/4 wavelength; an impedance step between the transmission lines; And a method for designing an impedance transformer having an impedance step of
A plurality of slope zeros of the Chebyshev function as a function of the frequency of the radio wave in the transmission line are set in the pass band of the impedance transformer, and a frequency corresponding to the plurality of slope zeros is defined as a reflection zero frequency or a reflection maximum frequency. The line length and the characteristic impedance of the transmission line are determined so that the reflection has a minimum value or a predetermined maximum value at the reflection zero frequency or the reflection maximum frequency.

In a third aspect of the present invention, there is provided a method for designing an impedance transformer, comprising: a plurality of substantially quarter-wave transmission lines; an impedance step between the transmission lines; And a method for designing an impedance transformer having an impedance step of
A plurality of zeros of the Chebyshev function as a function of the frequency of the radio wave in the transmission line are set in the pass band of the impedance transformer, and the frequencies corresponding to the plurality of zeros are defined as a reflection zero frequency, and the reflection zero frequency is defined. The line length and the characteristic impedance of the transmission line are determined so that the reflection is minimized.

In a fourth aspect of the present invention, there is provided a method for designing an impedance transformer, comprising the steps of: transmitting a plurality of substantially quarter-wave transmission lines; And a method for designing an impedance transformer having an impedance step of
A plurality of zeros of the Chebyshev function as a function of the frequency of the radio wave in the transmission line are set in the pass band of the impedance transformer, and the frequencies corresponding to the plurality of zeros are defined as a reflection zero frequency, and the reflection zero frequency is defined. The line length of the transmission line and the characteristic impedance are determined so that the reflection is minimized, and the reflection characteristics of the impedance transformer obtained using the above dimensions are determined from the characteristics of the ideal Chebyshev type transformer. Is selected, and the line length and the characteristic impedance of the transmission line are determined so that the reflection is equal to or less than a predetermined value at the large reflection frequency and the zero reflection frequency.

In a fifth aspect of the present invention, there is provided a method for designing an impedance transformer, comprising the steps of: transmitting a plurality of substantially quarter-wavelength transmission lines, an impedance step between the transmission lines, and a step between the transmission line and the input / output line; And a method for designing an impedance transformer having an impedance step of
A plurality of maximum points of the Chebyshev function as a function of the frequency of the radio wave in the transmission line are set in a pass band of the impedance transformer, and a frequency corresponding to the plurality of maximum points is defined as a reflection maximum frequency. The transmission line length and the characteristic impedance are determined so that the reflection has a predetermined maximum value at the maximum frequency.

In a sixth aspect of the present invention, there is provided a method for designing an impedance transformer, comprising the steps of: transmitting a plurality of substantially quarter-wavelength transmission lines; impedance steps between the transmission lines; And a method for designing an impedance transformer having an impedance step of
A plurality of maximum points of the Chebyshev function as a function of the frequency of the radio wave in the transmission line are set in a pass band of the impedance transformer, and a frequency corresponding to the plurality of maximum points is defined as a reflection maximum frequency. The line length of the transmission line and the characteristic impedance are determined so that the reflection has a predetermined maximum value at the maximum frequency, and among the reflection characteristics of the impedance transformer obtained using the above dimensions, the ideal Chebyshev type transformation is performed. The line length and the characteristic impedance of the transmission line are determined so that the reflection at a large frequency is selected from the characteristics of the device and the reflection is not more than a predetermined value at the large reflection frequency and the maximum reflection frequency.

The method of designing an impedance transformer according to a seventh aspect of the present invention is a method of designing an impedance transformer, comprising: a step of making a plurality of substantially quarter-wavelength waveguides between the waveguides in a height direction or a width direction; A method for designing a waveguide-type impedance transformer having a step in a height direction or a width direction between a tube and an input / output waveguide, the method comprising the steps of: A plurality of zeros of the Chebyshev function as a function of the guide wavelength are set, and a frequency corresponding to the guide wavelength of the plurality of zeros is defined as a reflection zero frequency, and the waveguide is set so that the reflection is minimized at the reflection zero frequency. It determines the axial length and height or width of the tube.

The method of designing an impedance transformer according to an eighth aspect of the present invention is a method of designing an impedance transformer, comprising: a plurality of substantially quarter-wavelength waveguides; A method for designing a waveguide-type impedance transformer having a step in a height direction or a width direction between a tube and an input / output waveguide, the method comprising the steps of: A plurality of zeros of the Chebyshev function as a function of the guide wavelength are set, and a frequency corresponding to the guide wavelength of the plurality of zeros is defined as a reflection zero frequency, and the waveguide is set so that the reflection is minimized at the reflection zero frequency. Determine the axial length of the tube and its height or width,
Of the reflection characteristics of the waveguide type impedance transformer obtained using the above dimensions, a frequency having a large reflection is selected from the characteristics of an ideal Chebyshev type transformer, and at the large reflection frequency and the zero reflection frequency. The axial length and the height or width of the waveguide are determined so that the reflection is equal to or less than a predetermined value.

A method of designing an impedance transformer according to a ninth aspect of the present invention is a method of designing an impedance transformer, comprising: a plurality of substantially quarter-wavelength waveguides; A method for designing a waveguide-type impedance transformer having a step in a height direction or a width direction between a tube and an input / output waveguide, the method comprising the steps of: A plurality of maximum points of the Chebyshev function as a function of the guide wavelength are set, a frequency corresponding to the guide wavelength of the plurality of local points is defined as a reflection maximum frequency, and the reflection at the reflection maximum frequency has a predetermined maximum value. Thus, the axial length and the height or width of the waveguide are determined.

A method for designing an impedance transformer according to a tenth aspect of the present invention is a method of designing an impedance transformer, comprising: a plurality of substantially quarter-wavelength waveguides;
In a method for designing a waveguide-type impedance transformer having a step in a height direction or a width direction between the waveguide and the input / output waveguide, the method includes designing the waveguide into a passband of the impedance transformer. A plurality of maximum points of the Chebyshev function as a function of the guide wavelength of the waveguide are set, and the frequency corresponding to the guide wavelength of the plurality of local points is defined as a reflection maximum frequency, and the reflection at the reflection maximum frequency has a predetermined maximum. The axial length of the waveguide, and the height or width are determined so as to be a value, and among the reflection characteristics of the waveguide type impedance transformer obtained using the above dimensions, the ideal Chebyshev type A frequency having a large reflection is selected from the characteristics of the transformer, and the axial length of the waveguide is set so that the reflection is equal to or less than a predetermined magnitude at the large reflection frequency and the maximum reflection frequency. It is obtained by determining the height or width.

[0023]

According to the first aspect of the present invention, the line length of the transmission line as a design parameter and frequencies equal to or greater than the number of parameters for determining the characteristic impedance are selected, and the pass characteristic or impedance characteristic of the impedance transformer is selected at the selected frequency. Since the line length of the transmission line and the characteristic impedance are determined so that the reflection characteristic approaches a desired value, not only the center frequency but also a plurality of frequencies within the range of the selected frequency and the number of the parameters or more are used. A conditional expression is set, and the value of the above-mentioned design parameter that can obtain a desired reflection characteristic can be determined by an optimization method or the like even when the pass band is wide.

In the second invention, a plurality of slope zeros of the Chebyshev function as a function of the frequency of the radio wave in the transmission line are set in the pass band of the impedance transformer, and the frequencies corresponding to the plurality of slope zeros are reflected. Since the line length of the transmission line as a design parameter and the characteristic impedance were determined so that the reflection would be a minimum value or a predetermined maximum value at the reflection zero frequency or the reflection maximum frequency as defined as the zero frequency or the reflection maximum frequency. The value of the design parameter that can obtain the desired reflection characteristic close to the ideal characteristic by the Chebyshev function at all frequencies in the passband can be determined by an optimization method or the like.

In the third invention, a plurality of zeros of the Chebyshev function as a function of the frequency of the radio wave in the transmission line are set in a pass band of the impedance transformer, and a frequency corresponding to the plurality of zeros is set to a reflection zero frequency. Stipulated as
Since the line length of the transmission line and the characteristic impedance as design parameters were determined so that the reflection was minimized at the zero reflection frequency, all frequencies in the passband were determined by an optimization method using the minimum frequency. The value of the above-mentioned design parameter can be determined to obtain a desired reflection characteristic close to the ideal characteristic by the Chebyshev function.

In the fourth invention, a plurality of zeros of the Chebyshev function as a function of the frequency of the radio wave in the transmission line are set in a pass band of the impedance transformer, and a frequency corresponding to the plurality of zeros is set to a reflection zero frequency. Stipulated as
The line length of the transmission line and the characteristic impedance as design parameters are determined so that the reflection is minimized at the reflection zero frequency, and among the reflection characteristics of the impedance transformer obtained using the above dimensions, the ideal Chebyshev Select a frequency with a large reflection from the characteristics of the shape transformer,
Since the axial length and height of the transmission line are determined so that the reflection is equal to or less than a predetermined value at the large reflection frequency and the zero reflection frequency, optimization is performed a plurality of times, and the minimum frequency is used. By using an optimized optimization method or the like, it is possible to determine the values of the design parameters that can obtain desired reflection characteristics very close to the ideal characteristics based on the Chebyshev function at all frequencies in the passband.

In the fifth invention, a plurality of maximum points of the Chebyshev function as a function of the frequency of the radio wave in the transmission line are set in the pass band of the impedance transformer, and the frequencies corresponding to the plurality of maximum points are reflected. Since the line length of the transmission line and the characteristic impedance as design parameters are determined so that the reflection has a predetermined maximum value at the above-mentioned reflection maximum frequency, an optimization method using the minimum frequency is specified. Thus, the values of the design parameters that can obtain the desired reflection characteristics close to the ideal characteristics based on the Chebyshev function at all frequencies within the passband can be determined.

In the sixth invention, a plurality of maximum points of the Chebyshev function as a function of the frequency of the radio wave in the transmission line are set in the pass band of the impedance transformer, and the frequencies corresponding to the plurality of maximum points are reflected. Defined as the maximum frequency, determine the line length of the transmission line as a design parameter and the characteristic impedance so that the reflection at the reflection maximum frequency has a predetermined maximum value, and determine the characteristic impedance of the impedance transformer obtained using the dimensions. Among the reflection characteristics, a frequency with a large reflection is selected from the characteristics of an ideal Chebyshev type transformer, and the line length of the transmission line is set so that the reflection is equal to or less than a predetermined value at the large reflection frequency and the maximum reflection frequency. , And the characteristic impedance has been determined, so optimization is performed multiple times, and optimization using the minimum frequency You can determine the value of the design parameters obtained of the desired reflection characteristics very close to the ideal characteristics of Chebyshev function at all frequencies within the passband by such law.

In the seventh invention, a plurality of zeros of the Chebyshev function as a function of the guide wavelength of the waveguide are set in the pass band of the impedance transformer, and a frequency corresponding to the guide wavelength of the plurality of zeros is set. Since the axial length of the waveguide as a design parameter and the height or width are determined so that the reflection is minimized at the zero reflection frequency, the frequency change of the susceptance due to the step is particularly large. For the waveguide-type impedance transformer, the above-mentioned design parameters that can obtain a desired reflection characteristic close to the ideal characteristic by the Chebyshev function at all frequencies in the passband by an optimization method using the minimum frequency and the like. Can be determined.

In the eighth invention, a plurality of zeros of the Chebyshev function as a function of the guide wavelength of the waveguide are set in a pass band of the impedance transformer, and a frequency corresponding to the guide wavelength of the plurality of zeros is set. Is defined as the zero reflection frequency, the axial length of the waveguide as a design parameter so that the reflection is minimal at the zero reflection frequency, and
The height or width is determined, and among the reflection characteristics of the waveguide type impedance transformer obtained by using the above dimensions, a frequency having a large reflection is selected from the characteristics of an ideal Chebyshev type transformer, and a large reflection is selected. Since the axial length and the height or width of the waveguide are determined so that the reflection is equal to or less than a predetermined value at the frequency and the reflection zero frequency, optimization is performed a plurality of times, and the frequency of the susceptance by the step is determined. Even for a waveguide-type impedance transformer with a particularly large change, the desired reflection characteristic very close to the ideal characteristic by the Chebyshev function at all the frequencies in the above passband by the optimization method using the minimum frequency, etc. Can be determined.

In the ninth invention, a plurality of maximum points of the Chebyshev function as a function of the guide wavelength of the waveguide are set in the pass band of the impedance transformer, and correspond to the guide wavelengths of the plurality of maximum points. The frequency is defined as the reflection maximum frequency, and the axial length of the waveguide as a design parameter and the height or width are determined so that the reflection has a predetermined maximum value at the reflection maximum frequency. Even for a waveguide-type impedance transformer having a particularly large frequency change, the desired reflection characteristic close to the ideal characteristic by the Chebyshev function is obtained at all the frequencies in the passband by an optimization method using the minimum frequency and the like. The value of the obtained design parameter can be determined.

In the tenth aspect, a plurality of maximum points of the Chebyshev function as a function of the guide wavelength of the waveguide are set in the pass band of the impedance transformer, and correspond to the guide wavelengths of the plurality of maximum points. The frequency is defined as the reflection maximum frequency, the axial length of the waveguide as a design parameter, and the height or width are determined so that the reflection at the reflection maximum frequency has a predetermined maximum value, and the above dimensions are used. Among the reflection characteristics of the obtained waveguide impedance transformer, a frequency having a large reflection is selected from the characteristics of an ideal Chebyshev type transformer, and the reflection has a predetermined magnitude at the large reflection frequency and the maximum reflection frequency. Since the axial length and the height or width of the waveguide were determined as follows, the frequency change of the susceptance due to the step was particularly large. Even for a waveguide-type impedance transformer, a desired reflection characteristic very close to the ideal characteristic by the Chebyshev function can be obtained at all the frequencies in the passband by an optimization method using the minimum frequency or the like. The value of the design parameter can be determined.

[0033]

[Embodiment 1] FIG. 1 is a schematic diagram showing an embodiment of the present invention, and FIG. 2 is a diagram showing the shape of an inner conductor pattern. In the drawings, reference numerals 1a and 1b denote dielectric substrates, and 2a denotes one surface of a dielectric substrate 1a. Outer conductors 3, 6 and 7 formed by closely attaching a conductive film to the entire surface are inner conductors formed by closely attaching a conductive film to the other surface of the dielectric substrate 1a, and 9 denotes a dielectric substrate 1a. 1b, outer conductors 2a, 2b, and inner conductor 3
A through-hole formed by closely adhering a conductor film continuous with the outer conductors 2a and 2b and the inner conductor 3 on the inner peripheral surface of the through-hole penetrating through the through holes 30 is a dielectric substrate 1a, 1b and the outer conductor 2
a, a strip line resonator comprising an inner conductor 3; 60, an input line of a strip line comprising dielectric substrates 1a, 1b, outer conductors 2a, 2b and an inner conductor 6;
Reference numeral 0 denotes an output line of a strip line composed of the dielectric substrates 1a and 1b, the outer conductors 2a and 2b, and the inner conductor 7, P1 denotes an input terminal, and P2 denotes an output terminal. The dielectric substrates 1a and 1b are
The inner conductors 3, 6, and 7 are overlapped so as to sandwich them. Each of the plurality of inner conductors 3 has a length set to approximately １ ／ wavelength, and one end is connected to the outer conductors 2 a and 2 b by a through hole 9 and short-circuited. For this reason, the resonator 30 is a quarter-wavelength resonator in which one end is short-circuited and the other end is open. All of the plurality of resonators 30 are arranged in parallel, and adjacent ones are alternately short-circuited at opposite ends by the through holes 9.

Next, the operation will be described. Since the adjacent resonators 30 are arranged so that the short-circuit end and the open end face each other, they are mutually coupled by an electric field. The amount of coupling is adjusted by the distance between the inner conductors 3 or the width of the inner conductors 3.

Now, assuming that the length of each of the inner conductors 3 is set to a predetermined length in the vicinity of 1/4 wavelength, and that all the resonators 30 resonate at the same frequency, for example, f0, At f0, the resonators 30 in the resonance state are strongly coupled to each other, are guided to the resonator 30 at the first stage of the incident wave to the input line 60, and are repeatedly coupled to the adjacent resonator by the electric field, thereby repeating the output line. 70. However, at frequencies other than f0, the coupling between the resonators 30 is very weak, and most of the power of the incident wave on the input line 60 is reflected. Thus, the stripline filters shown in FIGS. 1 and 2 have a function as a bandpass filter.

Next, the flow of the design procedure will be described with reference to FIG. First, in step 1, the equivalent of a band-pass filter having ideal Chebyshev characteristics, which is formed from a lumped-constant element and is deformed from the original low-pass filter, and a distributed constant type determined according to the physical shape of the filter of FIG. Compare the circuit at the center frequency of the passband of the filter,
An initial design of the resonator interval, resonator width, and resonator length as design parameters is performed. Step 1 is shown in FIG.
This is the same as the conventional design procedure shown in FIG. At this time,
A pair resonator obtained by taking out only two adjacent resonators in the filter of FIG. 1 is represented by an equivalent circuit including distributed constant lines as shown in FIG. In FIG. 4, reference numeral 10 denotes an equivalent circuit of a short-circuit stub having an electrical length θ, and reference numeral 11 denotes an equivalent circuit of a line having an electrical length θ. By using the equivalent circuit of FIG. 4 in combination, the filter of FIG. 1 is represented by a distributed constant line equivalent circuit similar to that shown in FIG.

Next, in step 2, frequencies equal to or more than the number of design parameters are selected, and insertion loss or reflection loss at these frequencies is defined as shown in FIG.
FIG. 5 is a diagram showing desired pass and reflection characteristics of the filter of FIG. 1, wherein f1 to f13 are selected frequencies. In order to make the specified levels of the pass loss and the reflection loss the same, the reflection loss is specified at frequencies f2 to f10 in the pass band, and the pass loss is specified at frequencies f1 and f11 to f13 outside the pass band.

Finally, in Step 3, the filter characteristics are calculated using the above-mentioned distributed constant line type equivalent circuit, and the values of the reflection loss at the frequencies f2 to f10 and the insertion loss at the frequencies f1 and f11 to f13 are set to desired values. Optimize the parameters of the equivalent circuit. The resonator interval, resonator width, and resonator length are obtained from the parameters obtained by the optimization.

As described above, in the embodiment according to the design procedure of FIG. 3, since the reflection loss is set to a desired value at a plurality of frequencies in the pass band, even when the pass band is wide, the reflection loss at the end of the pass band is not affected. The increase in reflection is small, and good characteristics are obtained over the entire pass band.

Further, since the frequency is selected more than the number of parameters, the relational expression can be obtained more than the number of parameters, and there is a high possibility that the characteristic calculation result by the equivalent circuit approaches the desired characteristic at the time of optimization.

Embodiment 2 FIG. FIG. 6 is a flowchart showing the design procedure of another embodiment of the present invention.
In this case, the reflection zero and the maximum frequency of the Chebyshev characteristic are selected in the pass band, and the reflection loss at these frequencies is defined as shown in FIG. FIG. 7 is a diagram showing desired reflection characteristics of the filter of FIG.
1, f3, f5, and f7 are reflection zero frequencies, and are given by the following second equations.

[0042]

(Equation 1)

Also, f2, f4 and f6 are reflection maximum frequencies, and are given by the following third equation.

[0044]

(Equation 2)

As described above, in the embodiment according to the design procedure of FIG. 6, since all the reflection zero frequencies in the pass band are defined, even if the pass band is wide, the reflection increase at the end of the pass band or the reflection zero is not caused. The frequency shift is small, and an ideal reflection characteristic by the Chebyshev function can be obtained over the entire pass band.

Since the number of the reflection zero and the maximum frequency is smaller than the total number of parameters, not all parameters can be designated as variables for optimization. For example, only the resonator interval is designated as a variable and other parameters are designated. As for, good reflection characteristics can be realized by correcting the resonator length and the resonator width so that the resonance frequency and the characteristic impedance of each resonator do not change due to the change in the resonator spacing.

Therefore, the embodiment according to the design procedure of FIG.
As in the case of FIG. 3, in addition to being able to obtain a broadband stripline filter, there is an advantage that a filter having good reflection characteristics can be obtained only by defining the reflection loss for a small number of frequencies.

Embodiment 3 FIG. FIG. 8 is a flow chart showing a design procedure according to another embodiment of the present invention.
In this case, a reflection zero frequency having Chebyshev characteristics is selected in the pass band, and reflection losses at these frequencies are defined as shown in FIG. FIG. 9 shows the desired reflection characteristics of the filter of FIG. 1, where f1, f3, f5 and f7 are the zero reflection frequencies and are given by the second equation as in the case of FIG.

As described above, in the embodiment according to the design procedure of FIG. 8, since all the reflection zero frequencies within the pass band are defined, even if the pass band is wide, the reflection increase at the end of the pass band or the reflection zero is not required. The frequency shift is small, and an ideal reflection characteristic by the Chebyshev function can be obtained over the entire pass band.

Since the number of reflected zero frequencies is the same as the number of resonators, not all parameters can be specified as variables for optimization, but only the resonator spacing is specified as a variable.
As for other parameters, good reflection characteristics can be realized by correcting the resonator length and the resonator width so that the resonance frequency and the characteristic impedance of each resonator do not change due to the change in the resonator interval.

Therefore, the embodiment according to the design procedure of FIG.
As in the case of FIG. 3, in addition to being able to obtain a broadband stripline filter, there is an advantage that a filter having good reflection characteristics can be obtained only by defining the reflection loss for a smaller number of frequencies.

Embodiment 4 FIG. FIG. 10 is a flowchart showing a design procedure of another embodiment of the present invention. In step 2, reflection maximum frequencies having Chebyshev characteristics are selected in a pass band, and reflection frequencies at these frequencies are selected as shown in FIG. This is the case where the loss is specified. FIG. 11 shows desired reflection characteristics of the filter of FIG. 1. In FIG. 11, f2, f4, and f6 are reflection maximum frequencies, and are given by Expression (2) as in the case of FIG.

As described above, in the embodiment according to the design procedure of FIG. 10, since all the reflection maximum frequencies in the pass band are defined, even if the pass band is wide, the increase of the reflection at the end of the pass band and the reflection maximum. The frequency shift is small, and characteristics close to ideal reflection characteristics by the Chebyshev function can be obtained over the entire pass band. However, in this case, the reflection characteristics using the equivalent circuit parameters obtained by the optimization are as shown in FIG.
Note that the maximum value may be larger than the specified maximum value as shown in FIG.

Since the number of reflection maximum frequencies is one less than the number of resonators, all parameters cannot be specified as variables for optimization. However, only the resonator spacing is specified as a variable, and other parameters are specified. By correcting the resonator length and the resonator width so that the resonance frequency and the characteristic impedance of each resonator do not change due to the change in the resonator spacing, good reflection characteristics can be realized.

Therefore, in the embodiment according to the design procedure of FIG. 10, as in the case of FIG. 3, a broadband stripline filter can be obtained, and the return loss is defined for a minimum number of frequencies. Alone has the advantage that good reflection characteristics can be obtained.

Embodiment 5 FIG. FIG. 12 is a flow chart showing the design procedure of another embodiment of the present invention. In the embodiment of FIG. 10, in step 4, the reflection characteristics obtained up to step 3 are replaced with ideal Chebyshev characteristics. In this case, a frequency having a higher reflection than the ideal characteristic is selected as compared with the reflection characteristic, and the reflection loss at this frequency is set as a new constraint condition. The new frequency is given, for example, as f8 and f9 in FIG.

In step 5, f2, f4, f6, f
Using the reflection loss of 8 and f9 as a constraint condition, optimization is performed again, and the resonator spacing, resonator width, and resonator length are obtained from the obtained parameters.

As described above, in the embodiment based on the design procedure of FIG. 12, since all the reflection maximum frequencies within the pass band are defined, even if the pass band is wide, the reflection at the end of the pass band is increased or the reflection maximum is increased. Since the frequency shift is small and the optimization is performed a plurality of times, an ideal reflection characteristic by the Chebyshev function can be obtained over the entire pass band.

Since the number of reflection maximum frequencies is one less than the number of resonators, all parameters cannot be specified as variables at the time of optimization. However, only the resonator interval is specified as a variable, and other parameters are specified. By correcting the resonator length and the resonator width so that the resonance frequency and the characteristic impedance of each resonator do not change due to the change in the resonator spacing, good reflection characteristics can be realized.

Therefore, in the embodiment according to the design procedure of FIG. 12, as in the case of FIG. 3, a broadband stripline filter can be obtained, and only a reflection loss is specified for a small number of frequencies. Has an advantage that a material having good reflection characteristics can be obtained.

In the description of the above embodiment, the case where the reflection maximum frequency of the Chebyshev characteristic is selected in the pass band in step 2 has been described. In step 2, the reflection zero frequency of the Chebyshev characteristic is selected in the pass band. Even if is selected, an ideal reflection characteristic by the Chebyshev function can be similarly obtained over the entire pass band.

Embodiment 6 FIG. FIG. 14 is a schematic structural view showing another embodiment of the present invention, in which 12 is a rectangular waveguide, 13 is an inductive iris, and 14 is a cavity resonator having both ends partitioned by an inductive iris 13. , P1 are input terminals,
P2 is an output terminal. The cavity resonator 14 is a half-wavelength resonator with both ends substantially short-circuited.

Next, the operation will be described. Adjacent cavity resonators 14 are mutually coupled via the inductive iris 13, and the amount of coupling is adjusted by the size of the inductive iris 13.

Now, the length of each of the cavity resonators 14 is 1 /
A predetermined length is set near two wavelengths, and all cavity resonators 1 are set.
Assuming that the resonators 4 resonate at the same frequency, for example, f0, the cavity resonators 14 in resonance at the frequency f0 are strongly coupled to each other, and the incident wave to the input terminal P1 is in the first stage. Of the output terminal P2.
Output. However, at frequencies other than f0, the coupling between the cavity resonators 14 is very weak, and the input end P
The incident wave to 1 reflects most of its power. Thus, the waveguide filter shown in FIG. 14 has a function as a band-pass filter.

Next, the flow of the design procedure will be described with reference to FIG. First, in step 1, the equivalent of a band-pass filter having ideal Chebyshev characteristics, which is formed from a lumped-constant element and is deformed from the original low-pass filter, and a distributed constant form determined according to the physical shape of the filter in FIG. The circuit is compared at the center frequency of the pass band of the filter, and the initial design of the resonator length as a design parameter and the susceptance value of the inductive iris is performed. Step 1 is the same as the conventional design procedure shown in FIGS. At this time, the equivalent circuit of the inductive iris 13 in the filter of FIG. 14 is represented by the parallel susceptance Ba as shown in FIG. Here, the parallel susceptance Ba is a function of the spacing d of the inductive iris and the wavelength in the waveguide. The equivalent circuit of the inductive post is as shown in FIG. 17 and can be used in place of the inductive iris. Using the relationship of FIG. 16, the filter of FIG. 14 is represented by a distributed constant type equivalent circuit of FIG.

Next, in step 2, as shown in FIG. 18, zero points of the Chebyshev function as a function of the wavelength in the waveguide are set in the pass band, and the frequencies of the plurality of zeros corresponding to the wavelength in the waveguide are set. Defined as the reflected zero frequency,
The reflection loss at these frequencies is defined. The characteristic shown by the solid line in FIG. 18 is a desired reflection characteristic of the filter of FIG. In the figure, f1 to f11 are zero reflection frequencies, and the corresponding wavelength λgp in the waveguide is given by the following fourth equation.

[0067]

(Equation 3)

Here, ω _p ′ / ω ₁ ′ is the reflection zero frequency of the original low-pass filter, λg0 is the guide wavelength at the center frequency, and λg1 and λg2 are the guide wavelengths at the lower and upper limits of the pass band, respectively.

Finally, in step 3, the characteristics of the filter are calculated using the distributed constant line type equivalent circuit, and the parameters of the equivalent circuit are optimized so that the value of the reflection loss at the frequencies f1 to f11 becomes a desired value. I do. From the parameters obtained by the optimization, the cavity length and the size of the inductive iris are determined. At this time, the susceptance value Bi of the i-th inductive iris obtained by the optimization is such that the susceptance value in the initial design is B0i and the number of resonator stages is N.
Then, it is obtained within the range of the following first equation.

1 <Bi / B0i <1.2 (1 ≦ i ≦ 0.2N, N ≦
i ≦ N + 1) 0.8 <Bi / B0i <1 (0.2N <i ≦ 0.4N,
0.8N ≦ i <N) 0.9 <Bi / B0i ≦ 1 (0.4N <i <0.8N)

As described above, in the embodiment based on the design procedure of FIG. 15, since all the reflection zero frequencies within the pass band are defined, even when the pass band is wide, the reflection increase at the end of the pass band or the reflection zero is not required. The frequency shift is small, and an ideal reflection characteristic by the Chebyshev function can be obtained over the entire pass band.

Since the number of reflected zero frequencies is the same as the number of resonators, not all parameters can be specified as variables for optimization. For example, only the susceptance value of the inductive iris 13 is specified as a variable. As for other parameters, good reflection characteristics can be realized by correcting the resonator length so that the resonance frequency of each resonator does not change due to a change in the susceptance value of the inductive iris 13.

Therefore, in the embodiment according to the design procedure of FIG. 15, a wide band waveguide filter can be obtained, and a filter having good reflection characteristics can be obtained only by defining the reflection loss for a small number of frequencies. Has the advantage of being

Further, the sixth embodiment can be applied to the fifth embodiment to perform the optimization again. The Chebyshev function can be performed at all the frequencies in the pass band by an optimization method using the minimum frequency. , The value of the above-mentioned design parameter can be determined so as to obtain a desired reflection characteristic very close to the ideal characteristic.

Embodiment 7 FIG. FIG. 19 is a flowchart showing the design procedure of another embodiment of the present invention. In step 2, the maximum reflection frequency is selected from the characteristics of the initial design in the pass band, and as shown in FIG. This is a case where the reflection loss in the above is defined. In FIG.
f1 to f6 are selected reflection maximum frequencies, and the solid line is f
It is a reflection characteristic after optimization by defining the reflection loss in 1 to f6. The reflection characteristics are greatly improved as compared with the characteristics of the wavy line obtained from the initial design.

As described above, in the embodiment according to the design procedure of FIG. 19, the reflection maximum value is defined at a plurality of frequencies in the pass band. Therefore, even when the pass band is wide, the reflection at the end of the pass band does not increase. A desired reflection loss can be obtained over the entire pass band. However, in this case, the reflection characteristic using the equivalent circuit parameter obtained by the optimization sometimes has a maximum value larger than the specified maximum value. In this case, the optimization similar to that shown in the fifth embodiment is performed. Need to do.

Since the number of reflection maximum frequencies is at most one less than the number of resonators, not all parameters can be designated as variables for optimization. For example, only the susceptance value of the inductive iris 13 is used as a variable. By specifying the other parameters and correcting the resonator length so that the resonance frequency of each resonator does not change due to a change in the susceptance value of the inductive iris 13, good reflection characteristics can be realized.

Therefore, in the embodiment according to the design procedure of FIG. 19, as in the case of FIG. 15, a broadband waveguide filter can be obtained, and in addition to the reflection loss for a minimum number of frequencies. There is an advantage that good reflection characteristics can be obtained only by specifying.

Embodiment 8 FIG. FIG. 21 is a schematic diagram showing another embodiment of the present invention. In the drawing, reference numeral 1 denotes a dielectric substrate, and 2 denotes an outer conductor formed by closely attaching a conductive film to one entire surface of the dielectric substrate 1. , 15 are strip conductors formed by closely attaching a conductive film to the other surface of the dielectric substrate 1, 16 is a microstrip line composed of the dielectric substrate 1, the outer conductor 2 and the inner conductor 15, and 17 is a microstrip line. A quarter wavelength line which constitutes a part of the line 16, P1 is an input end,
P2 is an output terminal. Here, four 1/4 wavelength lines 1
7, the line width is set wider as the line is closer to the output terminal P2 side.

Next, the operation will be described. Since the line width of the quarter wavelength line 17 is set wider as it is closer to the output end P2 side, there is a discontinuity in the line width on the connection surface between adjacent lines. In this discontinuity, reflection occurs according to the magnitude of the discontinuity.

Now, assuming that the line lengths of all quarter-wavelength lines 17 are set to be 1/4 wavelength at a predetermined frequency f0, the radio wave of frequency f0 incident from the input terminal P1 first Partly reflected at the discontinuity of. The radio wave passing through the first discontinuity passes through the second quarter wavelength line 17 and is partially reflected again at the second discontinuity. However, 1
Since the line length of the 波長 wavelength line 17 is set to １ ／ wavelength at f 0, the reflected wave reflected at the second discontinuity returns to the first discontinuity and then returns to the first discontinuity at the first discontinuity. Phase is 180 degrees, that is, 1
/ 2 wavelengths. Therefore, these two reflected waves cancel each other out, and if the relative magnitude of the discontinuity is adjusted, it is possible to prevent the reflected wave from returning to the input terminal P1 at all. For the third and subsequent discontinuities, mutual reflection can be canceled by the same principle. Therefore, the incidence from the input terminal P1 having a narrow line width and high impedance is hardly reflected when the frequency is f0. , From the output terminal P2 having a wide line width and a low impedance. Thus, FIG.
1 has a function as an impedance transformer.

Next, the flow of the design procedure will be described with reference to FIG. First, in step 1, according to a conventional design procedure that does not consider the frequency characteristics of susceptance due to discontinuity between quarter-wavelength lines, 1
Initially design the line length and characteristic impedance of the 波長 wavelength line. Step 1 is the same as the conventional design procedure shown in FIGS. At this time, in the impedance transformer shown in FIG.
The discontinuity between them is represented by a parallel susceptance as shown in FIG. In FIG. 23, B12 is a parallel susceptance due to discontinuity, and Z1 and Z2 are characteristic impedances of the quarter wavelength lines 17 at both ends. By using the equivalent circuit of FIG. 23 in combination, the filter of FIG. 21 is represented by the same equivalent circuit as that shown in FIG.

Next, in step 2, frequencies equal to or more than the number of design parameters are selected, and insertion loss or reflection loss at these frequencies is defined as shown in FIG.
FIG. 24 is a diagram showing desired transmission and reflection characteristics of the impedance transformer shown in FIG. 21, where f1 to f1 are shown.
3 is the selected frequency. Here, a reflection loss having a larger frequency characteristic than the insertion loss is defined.

Finally, in step 3, the filter characteristics are calculated using the equivalent circuit, and the frequencies f1 to f13 are calculated.
The electrical length and characteristic impedance of the 波長 wavelength line, which are the parameters of the equivalent circuit, are optimized so that the value of the reflection loss at becomes the desired value. From the parameters obtained by the optimization, the line length and line width of the 波長 wavelength line are obtained.

As described above, in the embodiment of FIG. 21 according to the design procedure of FIG. 22, the reflection loss is set to a desired value at a plurality of frequencies within the pass band. The increase in reflection at the edges is small, and good characteristics are obtained over the entire pass band.

Further, since the frequency is selected more than the number of parameters, the relational expression is obtained more than the number of parameters. At the time of optimization, there is a high possibility that the characteristic calculation result by the equivalent circuit approaches the desired characteristic.

Embodiment 9 FIG. FIG. 25 is a flow chart showing a design procedure of another embodiment of the present invention. In step 2, reflection zero and maximum frequency of Chebyshev characteristic are selected in a pass band, and these frequencies are selected as shown in FIG. This is a case where the reflection loss in the above is defined. FIG. 26 shows FIG.
FIG. 3 is a diagram showing desired reflection characteristics of the impedance transformer of FIG. 1 and prescribed frequencies and reflection losses. In the figure, f
1, f3, f5, and f7 are reflection zero frequencies, f2, f4,
And f6 is the maximum reflection frequency, which can be obtained in the same manner as in the conventional case.

As described above, in the embodiment according to the design procedure of FIG. 25, all the reflection zeros and the maximum frequencies in the pass band are defined. Therefore, even if the pass band is wide, the reflection at the end of the pass band does not increase. At least, an ideal reflection characteristic by the Chebyshev function can be obtained over the entire pass band.

Since the number of reflected zeros and the maximum frequency is smaller than the total number of parameters, not all parameters can be designated as variables for optimization. For example, only the characteristic impedance of the 波長 wavelength line 17 is used as a variable. Specify,
In response to the change in the characteristic impedance, the discontinuity, that is, the phase difference between the parallel susceptances does not change.
By correcting the electrical length of the four-wavelength line 17 subordinately, good reflection characteristics can be realized.

Therefore, in the embodiment according to the design procedure of FIG. 25, similarly to the case of FIG. 22, a wideband stripline type impedance transformer can be obtained, and the return loss is defined for a small number of frequencies. Alone has the advantage that good reflection characteristics can be obtained.

Embodiment 10 FIG. FIG. 27 is a flowchart showing a design procedure of another embodiment of the present invention. In step 2, reflection zero frequencies having Chebyshev characteristics are selected in a pass band, and reflections at these frequencies are selected as shown in FIG. This is the case where the loss is specified. FIG. 28 is a diagram showing desired reflection characteristics of the impedance transformer of FIG. 21 and prescribed frequencies and reflection losses. In the figure, f1, f3, f
5, and f7 are zero reflection frequencies, which can be obtained in the same manner as in the conventional case.

As described above, in the embodiment according to the design procedure of FIG. 27, since all the reflection zero frequencies within the pass band are defined, even if the pass band is wide, the increase in the reflection at the end of the pass band or the reflection zero is not required. The frequency shift is small, and an ideal reflection characteristic by the Chebyshev function can be obtained over the entire pass band.

Since the number of reflected zero frequencies is the same as the number of quarter-wave lines, not all parameters can be designated as variables for optimization. Only the variable is designated as a variable, and the electrical length of the 1/4 wavelength line 17 is subordinately corrected so that the discontinuity, that is, the phase difference between the parallel susceptances does not change in response to the change in the characteristic impedance. Reflection characteristics can be realized.

Therefore, in the embodiment according to the design procedure of FIG. 27, as in the case of FIG. 25, a wideband stripline type impedance transformer can be obtained, and the reflection loss is defined for a smaller number of frequencies. There is an advantage that a reflection characteristic can be obtained simply by performing the above operation.

Embodiment 11 FIG. FIG. 29 is a flowchart showing a design procedure of another embodiment of the present invention. In step 2, reflection maximum frequencies having Chebyshev characteristics are selected in a pass band, and reflection frequencies at these frequencies are selected as shown in FIG. This is the case where the loss is specified. FIG. 29 is a diagram showing desired reflection characteristics of the impedance transformer of FIG. 21 and prescribed frequencies and reflection losses. In the figure, f2, f4, and f6 are the zero reflection frequencies, which are obtained in the same manner as in the conventional case.

As described above, in the embodiment based on the design procedure of FIG. 29, all the reflection maximum frequencies in the pass band are defined, so that even if the pass band is wide, the reflection at the end of the pass band increases and the reflection maximum becomes large. The frequency shift is small, and characteristics close to ideal reflection characteristics by the Chebyshev function can be obtained over the entire pass band. However, in this case, the reflection characteristics using the equivalent circuit parameters obtained by the optimization are as shown in FIG.
Note that the maximum value may be larger than the specified maximum value as shown in FIG.

Since the number of reflected maximum frequencies is one less than the number of quarter-wave lines, not all parameters can be specified as variables for optimization. Is designated as a variable, and the electrical length of the ４ wavelength line 17 is subordinately corrected so that the discontinuity, that is, the phase difference between the parallel susceptances does not change in response to the change in the characteristic impedance. Reflection characteristics can be realized.

Therefore, in the embodiment according to the design procedure of FIG. 29, as in the case of FIG. 25, a broadband stripline impedance transformer can be obtained, and the return loss for a minimum number of frequencies can be obtained. Satisfactorily has the advantage that a reflection characteristic is good.

Embodiment 12 FIG. FIG. 31 is a flow chart showing the design procedure of another embodiment of the present invention. In the embodiment of FIG. 29, further, in step 4, the reflection characteristics obtained up to step 3 are converted to ideal Chebyshev characteristics. In this case, a frequency having higher reflection than the ideal characteristic is selected as compared with the reflection characteristic, and the reflection loss at this frequency is set as a new constraint condition. The new frequency is given, for example, as f8 and f9 in FIG.

In step 5, f2, f4, f6, f
With the reflection loss of 8 and f9 as a constraint, optimization is performed again, and the line length and line width of the 1/4 wavelength line are obtained from the obtained parameters.

As described above, in the embodiment according to the design procedure of FIG. 31, all the reflection maximum frequencies in the pass band are defined, so that even if the pass band is wide, the reflection at the end of the pass band increases or the reflection maximum is increased. Since the frequency shift is small and the optimization is performed a plurality of times, an ideal reflection characteristic by the Chebyshev function can be obtained over the entire pass band.

Since the number of reflected maximum frequencies is one less than the number of quarter-wave lines, not all parameters can be specified as variables for optimization. Is designated as a variable, and the electrical length of the ４ wavelength line 17 is subordinately corrected so that the discontinuity, that is, the phase difference between the parallel susceptances does not change in response to the change in the characteristic impedance. Reflection characteristics can be realized.

Therefore, in the embodiment according to the design procedure of FIG. 31, as in the case of FIG. 25, it is possible to obtain a wideband stripline type impedance transformer and also to define the reflection loss for a small number of frequencies. There is an advantage that a reflection characteristic can be obtained simply by performing the above operation.

Embodiment 13 FIG. FIG. 33 is a schematic diagram of another embodiment of the present invention, showing an impedance transformer using a rectangular waveguide. In the figure, 18 is a rectangular waveguide, 19 is a 1/4 wavelength waveguide, P1 is an input terminal, and P2 is an output terminal. Four quarter-wavelength waveguides 19 have output ends P
The closer to the two sides, the higher the height is set.

Next, the operation will be described. The waveguide height of the 1/4 wavelength waveguide 19 is set higher as it is closer to the output end P2 side, so that there is a discontinuity in the waveguide height at the connection surface between adjacent waveguides. . In this discontinuity, reflection occurs according to the magnitude of the discontinuity.

Now, assuming that the lengths of all the quarter-wavelength waveguides 19 are set to be 1/4 of the guide wavelength at a predetermined frequency f0, the frequency incident from the input terminal P1 is The radio wave of f0 is partially reflected at the first discontinuity. The radio wave passing through the first discontinuity passes through the second quarter wavelength waveguide 19 and is partially reflected again at the second discontinuity. However, since the line length of the 1/4 wavelength waveguide 19 is set to 1/4 wavelength at f0, the reflected wave reflected at the second discontinuity returns to 1 when returning to the first discontinuity.
The phase is 1 compared to the first discontinuous reflected wave
It is delayed by 80 degrees, that is, 波長 wavelength. Therefore, these two
The two reflected waves cancel each other out, and if the relative magnitude of the discontinuity is adjusted, the reflected waves can never return to the input terminal P1. For the third and subsequent discontinuities, mutual reflection can be canceled by the same principle. Therefore, the incidence from the input terminal P1 having a low waveguide height and low impedance is almost impossible when the frequency is f0. The light is not reflected and is taken out from the output end P2 where the waveguide height is high and the impedance is high. Thus, the waveguide circuit shown in FIG. 33 has a function as an impedance transformer.

In general, since the guide wavelength of a waveguide has a dispersive property with respect to frequency, the electrical length of the waveguide is proportional to the reciprocal of the guide wavelength, but not proportional to the frequency. Also in the impedance transformer of FIG. 33, it is necessary to consider the Chebyshev function used as the ideal reflection characteristic as a function of the guide wavelength.

By using the guide wavelength of the Chebyshev function with a zero gradient instead of the frequency with the zero gradient of the Chebyshev function in the eighth to twelfth embodiments according to FIG.
Is applicable to the same design procedure as that shown in Embodiments 8 to 12, and can realize a wide band.

Although the high-frequency filters shown in the first to seventh embodiments have the case where the number of resonators is four or eleven, the number of resonators is one to three, five to ten, or twelve or more. The same advantages and effects as those of the embodiment can be obtained.

Although the impedance transformer shown in each of the eighth to thirteenth embodiments has a case where the number of quarter-wavelength lines or waveguides is four, even if the number is one to three or five or more, Often, the same advantages and effects as those of the embodiment can be obtained.

Further, in the above embodiment, the case where the Chebyshev function is used as the transfer function has been described. However, a function such as a Bessel function or an elliptic function which can set a plurality of zeros, local maxima, and local minima in the passband is used. For example, it goes without saying that the design procedure used for the high-frequency filter or the impedance transformer of the present invention can be similarly applied.

[0112]

As described above, according to the first aspect of the present invention, not only the center frequency but also a plurality of frequencies within the range of the selected frequency are used to set conditional expressions equal to or more than the number of design parameters, and Even if the pass band is wide, it is possible to determine the value of the above-mentioned design parameter that can obtain a desired reflection characteristic, and it is possible to obtain an impedance transformer with small reflection over a wide band.

According to the second aspect of the present invention, it is possible to determine the value of the design parameter for obtaining the desired reflection characteristic close to the ideal characteristic by the Chebyshev function at all the frequencies in the passband by the optimization method or the like, Thus, there is an effect that an impedance transformer having small reflection can be obtained.

According to the third aspect of the present invention, a design parameter for obtaining a desired reflection characteristic close to the ideal characteristic by the Chebyshev function at all frequencies in the passband by an optimization method using the minimum frequency or the like. Is determined, and there is an effect that an impedance transformer having small reflection over a wide band can be obtained.

According to the fourth aspect of the present invention, optimization is performed a plurality of times by an optimization method using the minimum frequency and the like, and the ideal characteristic by the Chebyshev function at all frequencies within the pass band is very low. It is possible to determine the value of a design parameter that provides a near desired reflection characteristic, and there is an effect that an impedance transformer with small reflection can be obtained over a wide band.

According to the fifth aspect of the present invention, a design parameter for obtaining a desired reflection characteristic close to the ideal characteristic by the Chebyshev function at all frequencies in the pass band by an optimization method using the minimum frequency or the like. Is determined, and there is an effect that an impedance transformer having small reflection over a wide band can be obtained.

Further, according to the invention of claim 6, optimization is performed a plurality of times by an optimization method using the minimum frequency and the like, and the ideal characteristic by the Chebyshev function at all frequencies within the pass band is very low. It is possible to determine the value of a design parameter that provides a near desired reflection characteristic, and there is an effect that an impedance transformer with small reflection can be obtained over a wide band.

According to the seventh aspect of the present invention, even in a waveguide type impedance transformer in which the frequency of the susceptance changes greatly due to the step, the frequency within the pass band can be improved by the optimization method using the minimum frequency. Can be determined at all the frequencies of the design parameters that provide the desired reflection characteristics close to the ideal characteristics based on the Chebyshev function, and there is an effect that an impedance transformer with small reflection over a wide band can be obtained.

According to the eighth aspect of the present invention, even for a waveguide-type impedance transformer in which the frequency of the susceptance changes greatly due to the steps, the optimization method using the minimum frequency can be performed a plurality of times. It is possible to determine the values of the design parameters that are optimized and obtain the desired reflection characteristics very close to the ideal characteristics based on the Chebyshev function at all the frequencies in the passband, and to obtain an impedance transformer with small reflection over a wide band. Has the effect.

According to the ninth aspect of the present invention, even in the case of a waveguide type impedance transformer in which the frequency of the susceptance changes greatly due to the step, the passband can be reduced by the optimization method using the minimum frequency. Can be determined at all the frequencies of the design parameters that provide the desired reflection characteristics close to the ideal characteristics based on the Chebyshev function, and there is an effect that an impedance transformer with small reflection over a wide band can be obtained.

According to the tenth aspect of the present invention, even for a waveguide-type impedance transformer in which the frequency of the susceptance changes greatly due to the step, a plurality of times can be performed by the optimization method using the minimum frequency. It is possible to determine the values of the above design parameters that are optimized and obtain desired reflection characteristics very close to the ideal characteristics by the Chebyshev function at all frequencies in the pass band. There is an effect that can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a high-frequency filter according to Embodiment 1 of the present invention.

FIG. 2 is a diagram showing an inner conductor pattern of the high-frequency filter according to Embodiment 1 of the present invention.

FIG. 3 is a diagram showing a design procedure of a high-frequency filter according to Embodiment 1 of the present invention.

FIG. 4 is a diagram showing an equivalent circuit of a resonator of the high-frequency filter according to Embodiment 1 of the present invention.

FIG. 5 is a diagram illustrating characteristics of the high-frequency filter according to the first embodiment of the present invention.

FIG. 6 is a diagram showing a design procedure of a high-frequency filter according to Embodiment 2 of the present invention.

FIG. 7 is a diagram showing characteristics of a high-frequency filter according to Embodiment 2 of the present invention.

FIG. 8 is a diagram showing a design procedure of a high-frequency filter according to Embodiment 3 of the present invention.

FIG. 9 is a diagram illustrating characteristics of a high-frequency filter according to Embodiment 3 of the present invention.

FIG. 10 is a diagram showing a design procedure of a high-frequency filter according to Embodiment 4 of the present invention.

FIG. 11 is a diagram showing characteristics of a high-frequency filter according to Embodiment 4 of the present invention.

FIG. 12 is a diagram showing a design procedure of a high frequency filter according to Embodiment 5 of the present invention.

FIG. 13 is a diagram showing characteristics of a high frequency filter according to Embodiment 5 of the present invention.

FIG. 14 is a configuration diagram of a high-frequency filter according to Embodiment 6 of the present invention.

FIG. 15 is a diagram showing a design procedure of a high-frequency filter according to Embodiment 6 of the present invention.

FIG. 16 is a diagram illustrating a susceptance element of a high-frequency filter according to Embodiment 6 of the present invention.

FIG. 17 is a diagram illustrating a susceptance element of a high-frequency filter according to Embodiment 6 of the present invention.

FIG. 18 is a diagram showing reflection characteristics of a high frequency filter according to Embodiment 6 of the present invention.

FIG. 19 is a diagram showing a design procedure of a high-frequency filter according to Embodiment 7 of the present invention.

FIG. 20 shows characteristics of the high-frequency filter according to Embodiment 7 of the present invention.

FIG. 21 is a diagram showing a schematic configuration of an impedance transformer according to Embodiment 8 of the present invention.

FIG. 22 is a diagram showing a design procedure of the impedance transformer according to the eighth embodiment of the present invention.

FIG. 23 is a diagram showing discontinuity of an impedance transformer according to Embodiment 8 of the present invention.

FIG. 24 is a diagram showing characteristics of the impedance transformer according to the eighth embodiment of the present invention.

FIG. 25 is a diagram showing a design procedure of the impedance transformer according to the ninth embodiment of the present invention.

FIG. 26 is a diagram showing characteristics of the impedance transformer according to the ninth embodiment of the present invention.

FIG. 27 is a diagram showing a design procedure of the impedance transformer according to the tenth embodiment of the present invention.

FIG. 28 is a diagram showing characteristics of the impedance transformer according to the tenth embodiment of the present invention.

FIG. 29 is a diagram showing a design procedure of the impedance transformer according to the eleventh embodiment of the present invention.

FIG. 30 is a diagram showing characteristics of the impedance transformer according to Embodiment 11 of the present invention.

FIG. 31 is a diagram showing a design procedure of the impedance transformer according to the twelfth embodiment of the present invention.

FIG. 32 is a diagram showing characteristics of the impedance transformer according to the twelfth embodiment of the present invention.

FIG. 33 is a perspective view showing a configuration of an impedance transformer according to Embodiment 13 of the present invention.

FIG. 34 is a diagram showing a design procedure of a conventional high-frequency filter.

FIG. 35 is a circuit diagram of an original low-pass filter for describing a design procedure of a conventional high-frequency filter.

FIG. 36 is a diagram showing an equivalent circuit of a conventional high-frequency filter.

FIG. 37 is a diagram illustrating characteristics of a conventional high-frequency filter.

FIG. 38 is a diagram showing a procedure for designing a conventional high-frequency filter.

FIG. 39 is a circuit diagram of an original low-pass filter for describing a design procedure of a conventional high-frequency filter.

FIG. 40 is a diagram showing an equivalent circuit of a conventional high-frequency filter.

FIG. 41 is a diagram showing an equivalent circuit of a conventional high-frequency filter.

FIG. 42 is a diagram illustrating characteristics of a conventional high-frequency filter.

FIG. 43 is a diagram showing a design procedure of a conventional impedance transformer.

FIG. 44 is a diagram showing an equivalent circuit of a conventional impedance transformer.

FIG. 45 is a diagram showing characteristics of a conventional impedance transformer.

[Explanation of symbols]

1 dielectric substrate, 2 outer conductor, 3, 6, 7 inner conductor, 9
Through hole, 12 rectangular waveguide, 13 inductive iris, 14 cavity, 15 strip conductor, 16
Microstrip line, 17 1/4 wavelength line, 1
8 rectangular waveguide, 19 1/4 wavelength waveguide, 30 stripline resonator, 60 input lines, 70 output lines.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yu Nishino 5-1-1 Ofuna, Kamakura City Mitsubishi Electric Corporation Inside Electronic Systems Research Laboratories (72) Inventor Hidenori Yukawa 5-1-1 Ofuna, Kamakura City Mitsubishi Electric Corporation (72) Inventor Hideki Asao 5-1-1, Ofuna, Kamakura-shi Mitsubishi Electric Corporation Mitsubishi Electric Corporation (72) Inventor Shuji Urasaki 5-1-1, Ofuna, Kamakura-shi Mitsubishi Electric Corporation Inside the system laboratory

Claims (10)

[Claims] 1. A method for designing an impedance transformer comprising a plurality of substantially quarter-wave transmission lines, an impedance step between the transmission lines, and an impedance step between the transmission lines and an input / output line. The line length of the transmission line, and a number of frequencies equal to or greater than the number of parameters that determine the characteristic impedance are selected, and the above-described frequency is set so that the pass characteristic or the reflection characteristic of the impedance transformer approaches a desired value at the selected frequency. A method for designing an impedance transformer, comprising determining a line length and a characteristic impedance of a transmission line. 2. A method for designing an impedance transformer comprising a plurality of substantially quarter-wave transmission lines, an impedance step between the transmission lines, and an impedance step between the transmission lines and the input / output lines. A plurality of slope zeros of the Chebyshev function as a function of the frequency of the radio wave in the transmission line are set in the pass band of the impedance transformer, and a frequency corresponding to the plurality of slope zeros is defined as a reflection zero frequency or a reflection maximum frequency. A method of designing an impedance transformer, wherein the line length of the transmission line and the characteristic impedance are determined so that the reflection becomes a minimum value or a predetermined maximum value at the reflection zero frequency or the reflection maximum frequency. . 3. A method for designing an impedance transformer comprising a plurality of substantially quarter-wave transmission lines, an impedance step between the transmission lines, and an impedance step between the transmission lines and the input / output lines. A plurality of zeros of the Chebyshev function as a function of the frequency of the radio wave in the transmission line are set in the pass band of the impedance transformer, and the frequencies corresponding to the plurality of zeros are defined as a reflection zero frequency; A method for designing an impedance transformer, characterized in that a line length and a characteristic impedance of the transmission line are determined so that reflection is minimized at a frequency. 4. A method for designing an impedance transformer comprising a plurality of substantially quarter-wave transmission lines, an impedance step between the transmission lines, and an impedance step between the transmission lines and the input / output lines. A plurality of zeros of the Chebyshev function as a function of the frequency of the radio wave in the transmission line are set in a pass band of the impedance transformer, and a frequency corresponding to the plurality of zeros is defined as a reflection zero frequency; The line length of the transmission line and the characteristic impedance are determined so that the reflection is minimized at the frequency, and among the reflection characteristics of the impedance transformer obtained by using the above dimensions, the characteristics of the ideal Chebyshev type transformer are determined. Select a frequency with a large reflection and set the reflection to a predetermined magnitude at the large reflection frequency and the zero reflection frequency. A method for designing an impedance transformer, wherein a line length and a characteristic impedance of the transmission line are determined as follows. 5. A method for designing an impedance transformer comprising a plurality of substantially quarter-wave transmission lines, an impedance step between the transmission lines, and an impedance step between the transmission lines and the input / output lines. Setting a plurality of maximum points of the Chebyshev function as a function of the frequency of the radio wave in the transmission line in the pass band of the impedance transformer, defining a frequency corresponding to the plurality of maximum points as a reflection maximum frequency, The line length of the transmission line so that the reflection has a predetermined maximum value at the reflection maximum frequency,
And a characteristic impedance is determined. 6. A method for designing an impedance transformer comprising a plurality of substantially quarter-wave transmission lines, an impedance step between the transmission lines, and an impedance step between the transmission lines and the input / output lines. Setting a plurality of maximum points of the Chebyshev function as a function of the frequency of the radio wave in the transmission line in the pass band of the impedance transformer, defining a frequency corresponding to the plurality of maximum points as a reflection maximum frequency, The line length of the transmission line so that the reflection has a predetermined maximum value at the reflection maximum frequency,
And determine the characteristic impedance, of the reflection characteristics of the impedance transformer obtained using the dimensions,
A frequency having a large reflection is selected from the characteristics of the ideal Chebyshev type transformer, and the line length of the transmission line and the characteristic impedance are set so that the reflection is equal to or less than a predetermined magnitude at the large reflection frequency and the maximum reflection frequency. A method for designing an impedance transformer, characterized in that it is determined. 7. A step in a height direction or a width direction between a plurality of substantially quarter-wavelength waveguides and the waveguide, and a height direction between the waveguide and the input / output waveguide. Alternatively, in the method of designing a waveguide type impedance transformer having steps in the width direction, a plurality of zeros of a Chebyshev function as a function of the guide wavelength of the waveguide are set in a pass band of the impedance transformer. The frequency corresponding to the guide wavelength of the plurality of zeros is defined as the reflection zero frequency, and the axial length of the waveguide, and the height or width are determined so that the reflection is minimized at the reflection zero frequency. A method for designing an impedance transformer, comprising: 8. A step in a height direction or a width direction between a plurality of substantially quarter-wavelength waveguides and the waveguide, and a height direction between the waveguide and the input / output waveguide. Alternatively, in the method of designing a waveguide type impedance transformer having steps in the width direction, a plurality of zeros of a Chebyshev function as a function of the guide wavelength of the waveguide are set in a pass band of the impedance transformer. A frequency corresponding to the guide wavelength of the plurality of zeros is defined as a reflection zero frequency, and the axial length of the waveguide and the height or width are determined so that the reflection is minimized at the reflection zero frequency. Of the reflection characteristics of the waveguide type impedance transformer obtained using the above dimensions, a frequency having a large reflection is selected from the characteristics of an ideal Chebyshev type transformer, and a large frequency of the reflection and the reflection are selected. A method for designing an impedance transformer, characterized in that the axial length and the height or width of the waveguide are determined so that the reflection is equal to or smaller than a predetermined value at zero frequency. 9. A step in a height direction or a width direction between a plurality of substantially quarter-wavelength waveguides and the waveguide, and a height direction between the waveguide and the input / output waveguide. Alternatively, in the method for designing a waveguide-type impedance transformer having a step in the width direction, a plurality of local maximum points of the Chebyshev function as a function of the guide wavelength of the waveguide are set in a pass band of the impedance transformer. A frequency corresponding to the guide wavelength of the plurality of local maximum points is defined as a reflection maximum frequency, and the axial length of the waveguide so that the reflection at the reflection maximum frequency has a predetermined maximum value, and a height. Alternatively, a method for designing an impedance transformer, wherein the width is determined. 10. A step in a height direction or a width direction between a plurality of substantially quarter-wavelength waveguides and the waveguide, and a height direction between the waveguide and the input / output waveguide. Alternatively, in the method for designing a waveguide-type impedance transformer having a step in the width direction, a plurality of local maximum points of the Chebyshev function as a function of the guide wavelength of the waveguide are set in a pass band of the impedance transformer. Then, the frequency corresponding to the guide wavelength of the plurality of local maximum points is defined as the reflection maximum frequency, the axial length of the waveguide so that the reflection at the reflection maximum frequency has a predetermined maximum value, and height Or determine the width, of the reflection characteristics of the waveguide type impedance transformer obtained using the above dimensions, select a frequency of reflection greater than the ideal Chebyshev type transformer characteristics,
A method for designing an impedance transformer, wherein the axial length and the height or the width of the waveguide are determined so that the reflection is equal to or less than a predetermined magnitude at the large reflection frequency and the maximum reflection frequency. .