JP2565084B2 - Signal transmission circuit - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal transmission circuit in microwave and millimeter wave frequency bands, and more particularly to a distributor and a multiplexer having frequency selectivity.

[0002]

2. Description of the Related Art A conventional band divider for frequency selection is
As shown in FIG. 8, a circulator (CIR) 13, a low pass filter (LPF) 14, a band pass filter (BP)
F) 15 and a terminator (LOAD) 10. In the signal output from the amplifier (AMP) 12, the signal in the in-band frequency range of the band pass filter 15 is output to the output terminal 16, and the signal in the range above the cut-off frequency of the low pass filter 14 is the terminal 17 of the circulator 13. , Is absorbed by the terminator 10, and is not reflected by the amplifier 12.

A signal having a harmonic frequency equal to or higher than the second harmonic is reflected by the low pass filter 14, rotated by the circulator 13, and absorbed by the terminator 10 via the terminal 17 of the circulator 13.

[0004]

In the conventional band divider, the circulator 13 covers the entire frequency range.
It needed to operate in a very wide band. It is difficult to manufacture such a wide band circulator, and it is difficult to sufficiently exhibit the distribution performance.

Further, the conventional band divider has a complicated circuit configuration, and the circulator used requires a very wide frequency band, so that the pass loss is small at the in-band frequency f ₀ ,
It was difficult to obtain sufficient distribution performance with large loss in the harmonic frequency band. Since a signal in the harmonic frequency band equal to or higher than the second harmonic passes through the band pass filter 15, it is necessary to put the low pass filter 14 in the signal path.
There was a problem that the circuit was complicated and the passage loss was large.

The present invention solves the above problems and provides a signal transmission circuit having a simple circuit configuration, a small pass loss at an in-band frequency and a large loss at a harmonic frequency band, and sufficient distribution performance. Is.

The harmonic frequency is represented by n × f ₀ , and n is an integer of 2 or more, but the power of the harmonic frequency component output from an amplifier or the like (hereinafter referred to as harmonic power) increases as n increases. It is generally said that the case of n = 2 should be considered because it decreases. Therefore, the main purpose is to reduce the harmonic power of the second harmonic.

[0008]

According to the present invention, in a signal transmission circuit having a two-line coupling line formed of a main line and a sub line provided in a case, the main line is provided. A first dielectric and a second dielectric are respectively inserted between the case and the case, and between the sub line and the case, and either the first dielectric or the second dielectric is inserted. By changing the relative permittivity of one of the relative permittivities and the relative permittivity of the capacitance between the main line and the sub line, the even-mode radio wave propagation constant in the coupled line is changed to the coupled line. A signal transmission circuit characterized in that it is an even multiple of the odd-mode radio wave propagation constant in (1) is obtained.

Further, according to the present invention, in a signal transmission circuit having a two-line coupling line formed by a main line and a sub line provided in a case, the main line and the sub line By inserting a dielectric into the coupling portion with and changing the relative permittivity of the dielectric, the even mode radio wave propagation constant in the coupling line is set to be an even fraction of the odd mode radio wave propagation constant in the coupling line. A signal transmission circuit characterized by the above is obtained.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a signal transmission circuit (hereinafter referred to as magic H) according to the present invention will be described with reference to FIGS. As shown in FIG. 1A, the magic H has a case 4
Two dielectrics 3 extending in a predetermined direction at equal intervals are arranged therein, and the two dielectrics 3 are configured to include a main line 1 and a sub-line 2, respectively. A cross-sectional view of FIG. 1A is shown in FIG. 2 (a) and 2 (b) are shown in FIG.
It is an equivalent circuit of the magic H shown in (a). The main line 1 and the sub line 2 are coupled, and conventionally, measures have been taken so that the even mode propagation constant γ _e and the odd mode propagation constant γ _{0 in} that case are equal. That is, because it was not possible to analyze the characteristics when the difference between the propagation constants γ _e and γ ₀ was large, it was thought that increasing the difference would lead to performance deterioration.

Here, the ratio of the even-mode propagation constant γ _e and the odd-mode propagation constant γ ₀ is set as K, and the ratio K is changed to perform the characteristic analysis of the magic H. When K = 1, the propagation constants of the even mode and the odd mode are equal, and the characteristics are shown in FIG. In FIG. 4, TR is a ratio P ₀ / P ₁₀ between the power P _{0 at} the terminal 5 and the output power P ₁₀ at the terminal 6 in FIG. 2, and is a passage attenuation amount. CP is a coupling attenuation amount, and is a ratio P ₀ / P ₁₀ of the input power P ₀ of the terminal 5 and the output power P ₂₁ of the terminal 7. IS is an isolation attenuation amount, and is a ratio P ₀ / P ₂₀ between the input power P ₀ of the terminal 5 and the output power P ₂₀ of the terminal 8. RL is the return loss, which is the ratio P ₀ / P _r between the input power P ₀ at the terminal 5 and the power P _r reflected at the terminal 5. When the output powers P ₁₀ , P ₂₁ , P _{20 of} each terminal and the reflected power P _r are added, they become equal to the input power P _0, and P ₀ = P ₁₀ + P ₂₁
It is represented by + P ₂₀ + P _r . From this state, K is changed to the larger one. As a result, the isolation characteristics and return loss characteristics deteriorated as expected. γ _e = K
When xγ ₀ was set and K was gradually increased from 1, the peak of the coupling characteristic decreased at 180 °, and the isolation characteristic tended to deteriorate in the high frequency region. FIG. 5 shows a characteristic analysis diagram when the value of K is further increased and K = 2.
Shown in As can be seen from FIG. 5, the isolation IS
Deteriorates at high frequencies, and θ
= 360 °, all input signals are output.

Next, a calculation method for analyzing the characteristic of the magic H according to the present invention and the characteristic will be described.

2 (a) and 2 (b) are equivalent circuits of the magic H shown in FIG. 1 (a). Here, the voltage and current at the main line input terminal 5 are V _1L and I, respectively.
And _1L, and the voltage, current and _{V 10, I 10,} respectively, in the main line output terminal 6, the voltage at the sub-line input terminal 7, and each _{V 2L, I 2L} current, in the sub-line output terminal 8 (isolated terminal) voltage, when V _20, I ₂₀ current, respectively, relation of voltage and current represented by the following equation (1).

[0014]

[Equation 1]

When input power is input to the input terminal 5, the output power output to the terminal 6 is P ₁₀ and the input power input to the terminal 5 is P _0. At this time, the passing attenuation amount TR at the terminal 6 is
It is represented by the P ₀ / P ₁₀ ratio between P ₀ and P ₁₀ . The output power output to the terminal 7 is P _21, and at this time, the coupling attenuation amount CP at the terminal 7 is the ratio P ₀ / P _{2 1 of} P ₀ and P _21.
It is represented by. The output power P ₂₀ output to the terminal 8 is set, and the isolation attenuation amount IS at the terminal 7 at this time is
It is represented by the ratio P ₀ / P ₂₀ of P ₀ and P ₂₀ . The power reflected at the terminal 5 is P _r, and the return loss RL at the terminal 5 at this time is represented by the ratio P ₀ / P _r of P ₀ and P _r . FIG. 4 shows the transmission characteristics to each terminal when the propagation constants of the even mode and the odd mode are equal, that is, when K = 1. In the calculation example in this case, when the coupling degree is 3 dB and the power source impedance is Z _i ,
The even mode impedance Z _e and the odd mode impedance Z ₀ are set to Z ₀ × Z _e 1.1Z _i ² .

The value of K set as γ _e = K × γ ₀ is 2
Then, the transmission characteristic to each terminal is as shown in FIG. Incidentally, FIG.
In the case of, the calculation example is a case where the coupling degree is set to 10 dB, and the coupling degree can be changed by two line coupling coefficients. The value of K at this time is ε1 which is the relative permittivity that constitutes the line capacitances of the main line 1 and the sub line 2, respectively.
1, ε _22, and the relative permittivity that constitutes the coupling capacitance between the lines is ε ₁₂ , it is represented by the ratio of ε ₁₁ or ε ₂₂ and ε ₁₂ , as shown in the following Expression 2.

[0017]

[Equation 2] It will be briefly described that the equation 2 holds from the coupling capacitance C ₁₂ between the lines and the line capacitances C ₁₁ and C ₂₂ . Since the capacitance is proportional to the relative permittivity of the constituent dielectric, the line capacitance and line inductance are used to calculate the even-mode odd-mode propagation constant ratio K. As shown on page 346 of the document "Transmission circuit" (author Risaburo Sato: Corona Publishing Co.), the phase constant of balanced transmission corresponding to the odd mode is expressed by the following mathematical expression 3.

(Equation 3) L _b is the balanced transmission inductance, ω is the angular frequency,
L ₁₁ , L ₂₂ , and L ₁₂ are corresponding line inductances. The phase constant β _b is expressed by Equation 4 below. still,
μ is the magnetic permeability.

[Equation 4] In the case of balanced transmission, if the main line and the sub line are tightly coupled, ε _b = ε ₁₂ can be set. Also in the case of unbalanced transmission corresponding to the even mode, as shown on page 347 of the above-mentioned document, the phase constant β _u is expressed by the following Expression 5.

(Equation 5) If the unbalanced transmission equivalent relative permittivity is β _u , it can be expressed as in the following Expression 6.

(Equation 6) In the case of unbalanced transmission, since the main line 1 and the sub line 2 have the same potential, it is understood that the following formula 7 is obtained.

(Equation 7) If we process ε ₁₁ = ε ₂₂ , we get the following equation 8.

(Equation 8) When the ratio K of the propagation constants of the odd mode and the even mode is calculated, the following equation 9 is obtained.

[Equation 9] The propagation constant γ has a relationship of γ = α + jβ, and the transmission loss α
Since is assumed to be 0, the ratio of propagation constants is expressed as the ratio of phase constants. As shown above, it can be seen that the propagation constant ratio K is expressed as an approximate value by the square root of the relative permittivity ratio between lines.

That is, as can be seen from the above equation 2, K = 2
In this case, it is understood that the dielectric constant ratio of ε ₁₁ and ε ₁₂ should be approximately 4. Also, it is understood that when K = 1/2, the permittivity ratio of ε ₁₁ and ε ₁₂ should be set to approximately 1/4. Note that at this time by changing the values of both epsilon ₁₁ and epsilon _12, may be set the value of the to be determined K, changing the value of either epsilon ₁₁ and epsilon _12, is determined The value of power K may be set. Also, the number 2
In is similar be replaced by epsilon ₁₁ to epsilon _22, epsilon ₁₁ by changing the value of epsilon ₂₂ instead of, or by setting the value of the to be determined K.

Assuming that f ₀ is the case of (1 / j) γ _e L = 360 °, the passing attenuation amount TR at the terminal 6 becomes large and almost no output is made at the terminal 6, as shown in FIG. Without it, the isolation attenuation amount IS at the terminal 7 becomes 0, so that it is understood that all the power input to the input terminal 5 is output to the output terminal 8. The frequency of 2 × f ₀ , which is the harmonic frequency, has a characteristic of (1 / j) γ _e L = 720 °, and as shown in FIG. 5, the isolation attenuation amount IS at the terminal 8 becomes large, and conversely, at the terminal 6 Since the passing attenuation amount TR becomes 0, it can be seen that the input power of the terminal 5 is all output to the terminal 6 at the harmonic frequency of 2 × f ₀ . In the frequency band of 2 × f ₀ or more, the output is output to the terminal 8 at a frequency that is an odd multiple of f ₀ , and is output to the terminal 6 at a frequency that is an even multiple.

FIG. 3 shows a block diagram in which the magic H according to the present invention is connected to the output part of the amplifier (AMP) 12.
The input terminal 5 of the magic H is connected to the output section of the amplifier (AMP) 12. A terminator 10 and a terminator 11 are connected to the terminals 6 and 7, respectively. With the above configuration, the circulator and the low-pass filter are not used as compared with the conventional case, so that the configuration is simple.
Further, as described above, the signal of the frequency component of 2 × f ₀ is not output from the terminal 8 but is output from the terminal 6 because the isolation attenuation amount IS at the terminal 8 is large.
That is, since only the fundamental wave and the signal of the frequency component of the odd multiple of f ₀ are output from the terminal 8, the signal of the double wave frequency component is separated from the signal of the fundamental wave and the frequency component of the odd multiple of f _0. , Can be removed. In addition, the magic H of the present invention
Has shown that γ _e = Kγ _0, and the frequency of the second harmonic wave is separated when K = 2. However, even when K is an even multiple, similar performance can be obtained from the repetitiveness of the electric wave.

Another embodiment of the magic H according to the present invention will be described with reference to FIGS. 6 and 7. 6 is a view showing the internal structure of the magic H, and FIG. 7 is a sectional view taken along the line AA ′ of FIG. A dielectric 3 is inserted and fixed in the coupling portion between the main line 1 (not visible in FIG. 6) and the sub line 2 where the odd mode is the main component. Inter-line coupling capacitance C ₁₂ (Fig. 2
(B)), the relative permittivity ε ₁₂ of the dielectric 3 is changed so that the value of K is divided into even numbers such as 1/2 and ¼, and the propagation constant γ _{0 of the} odd mode is even. Mode propagation constant γ
_Be larger than _e . For example, it was found that when γ _e = Kγ ₀ and K = 1/2, the second harmonic frequency component of the fundamental wave is separated. The value of K is 1 / N (N
Is an even number of 2 or more, the second harmonic frequency component of the fundamental wave is separated in the same manner as above.

FIG. 7 shows an example of the result of calculation of the transmission characteristic when K = 1/2. As shown in FIG.
When (1 / j) γ _e L = 180 °, all the electric power input to the input terminal 5 is output to the terminal 8 and (1 / j) γ _e L =
When it is 360 °, it is output to the terminal 6. As in the case of K = 2, if the fundamental frequency f ₀ is adjusted to the position of 180 ° and the length L is adjusted, the frequency component of the second harmonic wave is separated and output to a terminal different from the fundamental wave. Is shown. Also in this case, if K is set to an even-numbered division of 2 or more, the angle is shifted by an even-numbered division, so that the separation characteristic for the second harmonic wave continues.

As described above, when the ratio K of the propagation constants of the even mode and the odd mode is set to be an even multiple or an even fraction, the output of the magic H is the fundamental frequency and the harmonic frequency of the odd multiple and even. It can be separated to double the harmonic frequency and output to another terminal.

As described above, K = 2 and 1/2 were performed, but similar characteristics can be obtained even if K is near the value because the basic characteristic is a wide band.

Although the separation performance has been described in this embodiment, the present invention also has a synthesis performance because the input and output are reversible. That is, when the fundamental frequency is input to the terminal 8 and the second harmonic frequency is input to the terminal 6 in FIG. 2A, both waves are combined and output to the terminal 5.

[0026]

According to the present invention, the odd-mode and even-frequency components are separated by setting the even-mode propagation constant and the odd-mode propagation constant to be even multiples or even fractions.
It is possible to take out to separate terminals, and it is possible to obtain sufficient distribution performance in which the passage loss is small at the in-band frequency f ₀ and the loss is large in the harmonic frequency band.

Further, since it is possible to separate the signals in the harmonic frequency band of the second harmonic or higher without inserting the band-even filter, the low-pass filter, and the circulator in the signal path, the circuit configuration is simplified. Therefore, the pass loss in the band pass filter and the low pass filter can be eliminated.

[Brief description of drawings]

1 (a) is a diagram showing an internal structure of a signal transmission circuit of the present invention, and FIG. 1 (b) is an A- line in FIG. 1 (a).
It is an A'line sectional view.

2 (a) is a diagram showing an equivalent circuit of the signal transmission circuit of the present invention, and FIG. 2 (b) is a main line, a sub-line, and a main line in the signal transmission circuit of FIG. 2 (a). It is the figure which showed the equivalent circuit which considered the capacitance between and and a line.

FIG. 3 is a block diagram showing a signal transmission circuit of the present invention.

FIG. 4 is a diagram showing characteristics of a conventional signal transmission circuit.

FIG. 5 is a diagram showing characteristics of the signal transmission circuit of the present invention.

6 (a) is a diagram showing the internal structure of another embodiment of the signal transmission circuit of the present invention, and FIG. 6 (b).
FIG. 7 is a sectional view taken along the line AA ′ of FIG.

FIG. 7 is a diagram showing characteristics of another embodiment of the signal transmission circuit of the present invention.

FIG. 8 is a block diagram showing another embodiment of a conventional signal transmission circuit.

[Explanation of symbols]

 1 Main Line 2 Sub Line 3 Dielectric 4 Case 5 Main Line Input Terminal 6 Main Line Output Terminal 7 Sub Line Input Terminal 8 Sub Line Output Terminal 9 Cover 10, 11 Terminator 12 Amplifier 13 Circulator 14 Low Pass Filter 15 Band Pass Filter 16 Band pass filter output terminal 17 Circulator terminal

Claims (2)

(57) [Claims] 1. A signal transmission circuit having a two-wire coupling line formed of a main line and a sub line provided in a case, wherein the main line and the case and the sub line are connected to each other. A first dielectric and a second dielectric are inserted between the line and the case, respectively, and the relative dielectric constant of either the first dielectric or the second dielectric and the main dielectric By changing the relative permittivity ratio between the relative permittivity and the relative permittivity that constitutes the capacitance between the line and the sub line, the even mode radio wave propagation constant in the coupling line is an even multiple of the odd mode radio wave propagation constant in the coupling line. A signal transmission circuit characterized in that. 2. A signal transmission circuit having a two-line coupling line formed of a main line and a sub line provided in a case, wherein a dielectric is provided at a coupling portion between the main line and the sub line. A body is inserted, and the relative permittivity of the dielectric is changed so that the even-mode radio wave propagation constant in the coupling line is set to an even fraction of the odd-mode radio wave propagation constant in the coupling line. Signal transmission circuit.