KR20020019616A - Impedance matching circuit and antenna device - Google Patents

Abstract

First matching circuit 8-1 for matching impedance at frequency f2, transmission line 6b having a predetermined electric field, and open stub 14 and short stub 15 connected to transmission line 6b. And a second matching circuit 8-2 for matching impedance at the frequency f1, and providing the discontinuous portion 17 of the impedance so that the characteristic impedance is different in the open stub 14, The sum of the susceptance values of the open stub 14 and the short stub 15 is zero at frequency f2, and the sum of the susceptance values of the stub of the open stub 14 and short stub 15 at frequency f1. The impedance matching circuit which set the electric field of the open stub 14 and the short stub 15 so that it may become this predetermined value.

Description

Impedance matching circuit and antenna device

1 is a perspective view showing an antenna device including a conventional impedance matching circuit disclosed in, for example, Japanese Patent Application Laid-Open No. Hei 9-307331, and FIG. 2 is a circuit diagram of the antenna device shown in FIG. Is an enlarged view of the antenna 1 used in this antenna device. In Figs. 1 to 3, 1 is an antenna by a chip antenna or the like as shown in Fig. 3, 2 is an input terminal of the antenna 1, 1-2 is a radiating conductor of the antenna 1, 12-. 2 is a ceramic block covering the outside of the radiating conductor 1-2.

3a is a capacitance variable capacitance element, 3b is a capacitance fixed capacitance element, 4a is an inductance element, and 7 is an impedance matching circuit formed by them. As the capacitance-variable capacitance element 3a, an active element such as a varactor diode is used.

9 denotes an input terminal of the antenna device, and 10 denotes an external circuit by a power supply circuit or an RF circuit connected to the input terminal 9. 12 is a dielectric substrate on which the antenna 1 and the impedance matching circuit 7 are mounted, and 13a, 13b, and 13c are conductors formed on the front and rear surfaces of the dielectric substrate 12.

4 is an equivalent circuit of the antenna 1 shown in FIG. In Fig. 4, 2 shows an input terminal of the antenna 1, 3c shows a capacitance element, 4-2 shows a resistance element, and 4b shows an inductance element. That is, the antenna 1 is a single resonance antenna having a series resonance circuit operation by the capacitance element 3c, the resistance element 4-2, and the inductance element 4b connected in series.

Next, the operation will be described.

For example, it is assumed that at the frequency f1, the antenna 1 has a value of R1 + jX1 (both R1 and X1 are both) as the input impedance of the input terminal 2. At this time, in the impedance matching circuit 7 shown in FIG. 2, first, the capacitance value of the capacitance element 3a is adjusted by changing the bias voltage applied to the varactor diode constituting the capacitance element 3a. Thus, the reactance component (X1) is set to zero.

Then, the resistance portion R1 of the input impedance is converted into an external circuit using an impedance modification function obtained by an appropriate combination of the values of the inductance elements 4a arranged in series and the values of the capacitance elements 3b arranged in parallel. Match the characteristic impedance of 10). This makes it possible to reduce the generation of the reflected wave at the frequency f1 and to operate the antenna 1 efficiently from the external circuit 10.

Also, at a frequency f2 different from the frequency f1, the antenna 1 has a value of R2 + jX2 (both R2 and X2) as the input impedance of the input terminal 2, and the resistance thereof. When the value of the component R2 is not largely different from the value of R1, the bias voltage applied to the capacitance element 3a is changed and the capacitance value is changed to an appropriate value, so that the input thereof is similar to that of the frequency f1. The impedance can almost match the characteristic impedance of the external circuit 10. In this way, the antenna device shown in FIG. 1 can operate the antenna 1 efficiently at a plurality of frequencies.

Since the conventional antenna device is configured as described above, in order to perform impedance matching at a plurality of frequencies, the capacitance of the capacitance element 3a is made variable and the capacitance is adjusted to an appropriate value. This capacitance value is adjusted by providing a bias circuit and adjusting a bias voltage applied to the varactor diode or the like in the case of using an active element such as a varactor diode.

For this reason, it is necessary to provide a control circuit other than a bias circuit, and a circuit structure becomes complicated. The complexity of this circuit configuration and the increase in the number of parts contribute to the increase in manufacturing cost and the problem of increasing the power consumption. This problem is particularly important for portable wireless terminals such as mobile phones.

In addition, in the conventional impedance matching circuit 7, since the impedance matching is possible only for the antenna 1 having a specific input impedance characteristic, there is a problem that the application range is narrow.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and various types of single resonance antennas are operated efficiently in a wide range of frequency bands including two frequency bands or a band between these two frequency bands. It is an object of the present invention to provide an impedance matching circuit and an antenna device for low cost with a simple circuit configuration.

In addition, the "single resonance antenna" referred to in this specification is used as a generic term for a wide range of antennas, and is not limited to a specific antenna.

The present invention mainly relates to an impedance matching circuit applied to an antenna device for the VHF band, the UHF band, the microwave band, and the millimeter wave band, and an antenna device to which the impedance matching circuit is applied.

1 is a perspective view showing an antenna device including a conventional impedance matching circuit.

FIG. 2 is a circuit diagram of the antenna device shown in FIG. 1. FIG.

3 is an enlarged view of an antenna used in the antenna device shown in FIG. 1;

4 is an equivalent circuit of the antenna shown in FIG.

Fig. 5 is a perspective view showing an antenna device according to Embodiment 1 of the present invention.

FIG. 6 is a top view of the antenna device shown in FIG. 5. FIG.

FIG. 7 is a circuit diagram of the antenna device shown in FIG. 5. FIG.

FIG. 8 is a Smith diagram showing input impedance characteristics of the antenna when the antenna side is seen from the node A shown in the circuit diagram of FIG.

FIG. 9 is a Smith diagram showing characteristics when the antenna side is seen from the node B shown in the circuit diagram of FIG.

FIG. 10 is a Smith diagram showing characteristics when the antenna side is seen from the node C shown in the circuit diagram of FIG.

FIG. 11 is a Smith diagram showing characteristics when the antenna side is seen from the node D shown in the circuit diagram of FIG.

12 shows the frequency characteristic of the sum of the susceptance values of two stubs.

FIG. 13 is a Smith diagram showing the characteristic when the antenna side is seen from the node E shown in the circuit diagram of FIG.

FIG. 14 is a diagram showing frequency characteristics of the amount of reflection attenuation when the antenna side is seen from the node E shown in the circuit diagram of FIG.

FIG. 15 is a diagram showing a comparison of frequency characteristics of sum of susceptance values of two stubs when the open stub is not in the case where there are discontinuities. FIG.

Fig. 16 is a diagram showing a comparison of frequency characteristics of the amount of reflection attenuation of the antenna device at the input terminal when the open stub does not have a discontinuity.

FIG. 17 is a diagram showing the frequency characteristics of the amount of reflection attenuation when the antenna side is seen from the node E shown in the circuit diagram of FIG.

Fig. 18 is a perspective view showing an antenna device according to a second embodiment of the present invention.

19 is a top view of the antenna device shown in FIG. 18.

20 is a circuit diagram of the antenna device shown in FIG. 18. FIG.

Fig. 21 is a perspective view showing an antenna device according to Embodiment 3 of the present invention.

Fig. 22 is a top view of the antenna device shown in Fig. 21.

FIG. 23 is a circuit diagram of the antenna device shown in FIG. 21. FIG.

FIG. 24 is a Smith diagram showing input impedance characteristics of the antenna when the antenna side is seen from the node A shown in the circuit diagram of FIG. 23; FIG.

FIG. 25 is a Smith diagram showing input impedance characteristics of the antenna when the antenna side is seen from the node C shown in the circuit diagram of FIG. 23; FIG.

Fig. 26 is a perspective view showing an antenna device according to a fourth embodiment of the present invention.

FIG. 27 is an exploded view showing an outer surface of a cylindrical dielectric of the antenna device shown in FIG. 26; FIG.

FIG. 28 is an exploded view showing an inner side surface of a cylindrical dielectric of the antenna device shown in FIG. 26; FIG.

29 is an enlarged view of a slip conductor pattern of an impedance matching circuit portion of the antenna device shown in FIG. 27;

30 is a circuit diagram of the antenna device shown in FIG. 26;

Fig. 31 is a perspective view showing an antenna device according to Embodiment 4 of the present invention.

32 is an exploded view showing an outer surface of a cylindrical dielectric of the antenna device shown in FIG. 31;

33 is an exploded view showing an inner side surface of a cylindrical dielectric of the antenna device shown in FIG. 31;

34 is an enlarged view of a slip conductor pattern of an impedance matching circuit portion of the antenna device shown in FIG. 32;

35 is a circuit diagram of the antenna device shown in FIG. 31;

Disclosure of the Invention

The impedance matching circuit according to the present invention uses the input impedance of an antenna and the characteristic impedance of an external circuit for receiving a signal between the antennas at a frequency f1 and at a frequency band higher than the frequency f2. In the matching, a transmission line having a predetermined electric field and a transmission line having a predetermined electric field formed by a first matching circuit for matching impedance at the frequency f2 and a feeding line to the antenna are connected to the transmission line. And a second matching circuit composed of first and second stubs formed by the microstrip line, etc., for matching impedance at the frequency f1, and having a characteristic impedance in the first or second stub. The discontinuity of the impedance so as to be different and at the same time the susceptance of the first and second stubs at the frequency f2 The electric fields of the first and second stubs are set such that the sum of the susceptance values is 0 and the sum of the susceptance values of the first and second stubs is a predetermined value at the frequency f1.

This allows impedance matching to be performed in two different frequency bands, and can flexibly correspond to the frequency characteristics of the input impedance of the antenna to be impedance matched, and in one of the bands near the two frequencies. The return loss characteristic becomes narrowband or the loss in the impedance matching circuit does not increase, and there is an effect that a good return loss characteristic can be obtained in either band.

The impedance matching circuit according to the present invention is composed of a first matching circuit formed of a microstrip line or the like and having an transmission line having a predetermined electric field and an interdigital capacitor that provides capacitance in series with the transmission line.

As a result, since the chip element that requires mounting work is not used, fabrication is easy and fabrication can be performed at low cost, and capacitance element of arbitrary capacitance can be easily and precisely manufactured, and the characteristics are excellent. There is an effect that it is easy to obtain a good impedance matching circuit.

The impedance matching circuit according to the present invention comprises the first matching circuit as a quarter wavelength impedance transformer at the frequency f2.

This makes the circuit configuration simpler and has the effect of being able to be manufactured at low cost.

The impedance matching circuit according to the present invention includes a second matching circuit as a first stub with an open stub having an impedance discontinuity portion and an open stub with one end open, and a second stub with a short stub connected to one end of the lead. It is made up.

As a result, since no chip element requiring mounting work is used, fabrication can be facilitated, and an impedance matching circuit can be produced at low cost.

The impedance matching circuit according to the present invention is composed of a first stub by an open stub with an open end at one end and a discontinuity of impedance, and a second stub by an open stub with one open at the end.

As a result, since no chip element or a short stub that requires mounting work is used, it is easy to manufacture, and there is an effect that an impedance matching circuit can be manufactured at low cost.

The impedance matching circuit according to the present invention is formed in plural on the hollow cylindrical dielectric, and the frequency (f1) and the frequency (f1) of each input impedance of the plurality of antennas and the characteristic impedance of the external circuit which receives a signal between the plurality of antennas. In matching at a frequency band higher than f), a first matching circuit for matching impedance at the frequency f2 and a microstrip line serving as a feed line to the plurality of antennas are provided. And a second matching circuit formed by a transmission line having an electric field of? And the microstrip line, the first and second stubs connected to the transmission line, and matching impedance at the frequency f1; Providing discontinuities of impedance so that characteristic impedances are different in the first or second stub, and The sum of the susceptance values of the first and second stubs at frequency f2 is 0, and the sum of the susceptance values of the first and second stubs at frequency f1 is a predetermined value; The electric fields of the first and second stubs are set.

This allows impedance matching to be performed in two different frequency bands, and can flexibly correspond to the frequency characteristics of the input impedance of the antenna to be impedance matched, and in one of the bands near the two frequencies. The reflection attenuation amount characteristic does not become narrow band, or the loss in an impedance matching circuit does not increase, and there exists an effect that a favorable reflection attenuation characteristic can be obtained in either band.

The impedance matching circuit according to the present invention is composed of a first matching circuit formed by a microstrip line and having a transmission line having a predetermined electric field and an interdigital capacitor which gives capacitance in series with the transmission line.

As a result, since no chip element that requires mounting work is used, fabrication can be facilitated and fabrication can be made at low cost, and capacitance element of arbitrary capacitance can be easily and precisely manufactured, and characteristics can be produced. There is an effect of easily obtaining a good impedance matching circuit.

The impedance matching circuit according to the present invention includes a second matching circuit as a first stub with an open stub having an impedance discontinuity portion and an open stub with one end open, and a second stub with a short stub connected to one end of the lead. It is made up.

As a result, since no chip element requiring mounting work is used, fabrication can be facilitated, and an impedance matching circuit can be produced at low cost.

The impedance matching circuit according to the present invention is composed of a first stub by an open stub with an open end at one end and a discontinuity of impedance, and a second stub by an open stub with an open end.

As a result, since no chip element or a short stub that requires mounting work is used, it is easy to manufacture, and there is an effect that an impedance matching circuit can be manufactured at low cost.

An antenna device according to the present invention is formed on a plurality of antennas and a hollow cylindrical dielectric formed on a hollow cylindrical dielectric, and connected to each of the antennas, and externally receiving a signal between the input impedance of each antenna and the respective antennas. A plurality of impedance matching circuits for matching the characteristic impedance of the circuit at a frequency f1 and a frequency band of a frequency f2 higher than the frequency f1 and the hollow cylindrical dielectric, and connected to the respective impedance matching circuits. And a plurality of distribution circuits for giving a predetermined phase difference to a signal from the external circuit, wherein each impedance matching circuit feeds power to the first matching circuit and the respective antennas for matching impedance at the frequency f2. Transmission with a predetermined electric field formed by the microstrip line, which becomes the line And a second matching circuit formed by the furnace and the microstrip line, the first and second stubs connected to the transmission line, and having a matching of impedance at the frequency f1, wherein the first or second stub is provided. The discontinuity part of the impedance is provided in the second stub so that the characteristic impedance is different, and the sum of the susceptance values of the first and second stubs at the frequency f2 is 0, and the first and second at the frequency f1. The electric fields of the first and second stubs are set such that the sum of the susceptance values of the second stubs is a predetermined value. .

This allows impedance matching to be performed in two different frequency bands, and can flexibly correspond to the frequency characteristics of the input impedance of the antenna to be impedance matched, and in one of the bands near the two frequencies. The reflection attenuation amount characteristic does not become narrow band, or the loss in an impedance matching circuit does not increase, and there exists an effect that a favorable reflection attenuation characteristic can be obtained in either band.

The antenna device according to the present invention is composed of a first matching circuit formed of a microstrip line, a transmission line having a predetermined electric field, and an interdigital capacitor that provides capacitance in series with the transmission line.

As a result, since no chip element that requires mounting work is used, fabrication can be facilitated and fabrication can be made at low cost, and capacitance element of arbitrary capacitance can be easily and precisely manufactured, and characteristics can be produced. There is an effect that it is easy to obtain a good antenna device.

The antenna device according to the present invention comprises a second matching circuit including a first stub with an open stub having an impedance discontinuity portion and an open stub with one end open, and a second stub with a short stub connected with one end to a conductor. will be.

This makes it easy to manufacture since there is no use of a chip element requiring mounting work, and there is an effect that an antenna device can be manufactured at low cost.

The antenna device according to the present invention comprises a first stub with an open stub and an impedance discontinuity with an open stub with one end of the second matching circuit, and a second stub with an open stub with one end open.

As a result, since no chip element or a short stub that requires mounting work is used, fabrication can be made easier, and an antenna device can be manufactured at low cost.

Best Mode for Carrying Out the Invention

EMBODIMENT OF THE INVENTION Hereinafter, the best form for implementing this invention in order to make this invention clear in detail is demonstrated with reference to attached drawing.

Example 1.

FIG. 5 is a perspective view showing the antenna device according to the first embodiment of the present invention, FIG. 6 is a top view of the antenna device shown in FIG. 5, and FIG. 7 is a circuit diagram of the antenna device shown in FIG. 5. This antenna device combines a small helical antenna used in a small wireless terminal such as a cellular phone and an impedance matching circuit formed of a microstrip line to operate in two frequency bands.

5 to 7, 1 denotes an antenna by a small helical antenna, 2 denotes an input terminal of the antenna 1, 12 denotes a dielectric substrate on which the antenna 1 and an impedance matching circuit 7 to be described later are mounted. A conductor formed on the back surface of the dielectric substrate 12, 18 is a strip conductor which, together with the dielectric substrate 12 and the conductor 13, forms a microstrip line which becomes a feed line of the antenna 1, 10 is an antenna ( An external circuit by a power supply circuit or an RF circuit that receives signals between 1) and 9 is an input terminal of the antenna device to which the external circuit 10 is connected.

6a is a transmission line formed by a microstrip line and has an electric field θa at a frequency f2, and 6b is a transmission line formed by a microstrip line and a electric field θb at a frequency f1. And 22 is an interdigital capacitor inserted between these transmission lines 6a and 6b to give capacitance in series.

14 is an open stub formed by a microstrip track. In the open stuff 14, the characteristic impedance of the line forming the stub is not constant in the stub, and has one discontinuous position 17 of the characteristic impedance, and a high impedance line is used near the open end. On the transmission line 6b side, a low impedance line is used. The electric field of the high impedance line is θ o1, and the electric field of the low impedance line is θ o2.

15 is a short stub formed by a microstrip line and has an electric field θ s, and 16 is a through hole provided at the tip of the short stub 15. The open stub 14 and the short stub 15 are connected to the same location of the strip conductor 18. As shown in FIG.

Here, the sum of the electric fields θo1 and θo2 and θs is set to be slightly larger than π / 2 or π / 2, and the sum of the susceptance values of the two stubs is set to zero at the frequency f2. That is, in the frequency band near the frequency f2, it operates as the 1/4 wavelength resonant circuit 5-2 shown in FIG.

The distribution of the electric fields θo1, θo2, θs is determined such that the sum of the susceptances of the open stub 14 and the short stub 15 shows a predetermined susceptance value at the frequency f1. . In addition, a required value is also selected for the electric field θb of the transmission line 6b.

In Fig. 7, 8-1 is composed of a capacitance element 3 corresponding to the transmission line 6a and the interdigital capacitor 22, and the impedance matching of the antenna 1 at the frequency f2 is adjusted. A second matching circuit, which is composed of a transmission line 6b, an open stub 14, and a short stub 15, is a second matching circuit that performs impedance matching of the antenna 1 at a frequency f1. Circuit. 7 is an impedance matching circuit comprised of the 1st matching circuit 8-1 and the 2nd matching circuit 8-2, and performing impedance matching in two frequency bands.

7, the nodes A, B, C, D, and E of the circuit are shown for explanation of the operation described later.

Next, the operation will be described.

Here, the impedance matching circuit 7 of this antenna device is described as being designed to perform impedance matching at two frequencies f1 and f2 shown in FIG. In addition, the relationship between the frequencies f1 and f2 is f1 <f2, and for simplicity, the matching impedance, that is, the characteristic impedance on the external circuit 10 side, is the characteristic impedance Zo of the transmission lines 6a and 6b. It is the same as).

The impedance trajectory A shown in FIG. 8 shows the trajectory when the antenna 1 side is seen from the node A shown in the circuit diagram of FIG. 7. The transmission line 6a connected to the node A has an electric field θa which rotates the trajectory clockwise until the resistance of the impedance at the frequency f2 at the node B matches the characteristic impedance Zo. Has Therefore, the locus when the antenna B side is seen from the node B becomes the impedance locus B shown in FIG.

Next, at the node B, like the capacitance element 3, at the frequency f2, the reactance of the impedance at the frequency f2 in Fig. 9 is equal in magnitude and opposite in sign, i.e., negative reactance. The capacitive value giving is connected. As a result, the trajectory when the antenna 1 side is seen from the node C becomes the impedance trajectory C shown in FIG. 10. Here, the impedance at the frequency f2 corresponds to the characteristic impedance Zo, and the impedance matching is made. In this manner, the impedance matching at the frequency f2 is performed by the first matching circuit 8-1 shown in FIG.

Next, in the second matching circuit 8-2 connected to the node C, the transmission line 6b further rotates the impedance trajectory C shown in FIG. 10 clockwise. Here, the electric field θb at the frequency f1 of the transmission line 6b is selected so that the conductance at the frequency f1 is equal to 1 / Zo and the susceptance is a positive value. As a result, the trajectory of the node D viewed from the node D becomes the impedance trajectory D shown in FIG. At this time, the susceptance value at the frequency f1 is a standardized value, jb '. J is an imaginary unit.

12 is a diagram showing the frequency characteristics of the sum of the susceptance values of two stubs. Since the quarter-wave resonant circuit 5-2 is a parallel resonant circuit, as shown in Fig. 12, the sum of the susceptance values of the two stubs becomes zero at the frequency f2, and is higher than the frequency f2. At low frequencies, they show negative susceptance values. Therefore, since f1 < f2, a negative susceptibility value is given at f1. Here, the ratio of the lengths of the stub lengths θs, θo1, θo2 is selected so that the value f becomes -jb 'at the frequency f1.

As a result, the trajectory of the contact point E viewed from the antenna 1 side becomes the impedance trajectory E shown in FIG. 13, and impedance matching at the frequency f1 is performed. At this time, at the frequency f2, the quarter-wave resonant circuit 5-2 is in a resonant state, and therefore is in an open state, and the matched state of the impedance by the first matching circuit 8-1 is an open stub ( 14) Even if the short stub 15 is connected, it is maintained. In this manner, the impedance matching at the frequency f1 is performed by the second matching circuit 8-2 shown in FIG.

As a result, the frequency characteristic of the reflection attenuation amount of the antenna device in the input terminal 9 of FIG. 7 becomes a characteristic having a valley at the frequencies f1 and f2 as shown in FIG.

In addition, the electric field θo1, θo2, θs of the open stub 14, the short stub 15, and the electric field θb of the transmission line 6b are derived from equations (1) and (2) below. Obtained from the equation At the frequency f2,

(Susceptance of open stub 14) + (susceptance of short stub 15) = 0 (1)

At the frequency f1,

Zo ¹ (Y1 + jZo ¹ tanθb) / (Zo- ¹ + jY1tanθb) + (susceptance of open stub 14) + (susceptance of short stub 15) = Zo ¹ (2)

Here, Y1 in Equation (2) is an admittance in frequency f1 when the antenna C side is seen from the node C in FIG. 7, that is, the frequency f1 in FIG. 10. Admittance at). In addition, since Equation (2) is a complex number equation, the equation is divided into two equations, a real part and an imaginary part, and the simultaneous equation becomes three equations. Although there are four unknowns on one side, for example, by applying conditions such as θo1 = θo2, the electric fields θo1, θo2, θs of the open stub 14, the short stub 15, and the transmission line 6b The electric field θb can be obtained.

In this embodiment, a part of the open stub 14 is configured so that the characteristic impedance is different, and there is one discontinuous portion 17 of the impedance in the open stub 14. In the above method, if the size of the open stub 14 in which the discontinuity 17 is present is determined, the total length of the open stub 14 is different when the discontinuity 17 is absent, and the open stub ( The frequency characteristic of the susceptance value of 14) is also different. However, the susceptance values at the frequencies f1 and f2 are the same.

FIG. 15 is a diagram showing a comparison of frequency characteristics of susceptance values of the quarter-wave resonant circuit 5-2 when the open stub 14 does not have the discontinuity 17. Thus, by providing the discontinuous portion 17 in the open stub 14, it is possible to change the frequency characteristic of the susceptance value of the resonant circuit at the frequencies f1 and f2 to be impedance matched.

Therefore, the frequency characteristic of the amount of reflection attenuation obtained at the input terminal 9 also changes depending on the presence or absence of the discontinuous portion 17 of the open stub 14. FIG. 16 is a diagram showing a comparison of frequency characteristics of the amount of reflection attenuation of the antenna device in the input terminal 9 when the open stub 14 does not have a discontinuous portion 17. As shown in FIG. 16, by providing the discontinuous portion 17 in the open stub 14, the width of the band where the amount of reflection attenuation is good narrows slightly in the band near the frequency f2, but on the other hand, the frequency f1 In the band in the vicinity of the band), a band having a good reflection attenuation amount becomes wider.

In this way, by providing the discontinuous portions 17 of the characteristic impedance by varying the characteristic impedance in a part of the open stub 14, the frequency characteristic of the amount of reflection attenuation at the two frequency bands near the frequencies f1 and f2 can be adjusted. have. According to the frequency characteristic of the input impedance of the antenna 1 which should be matched with impedance, as shown in FIG. 16, when the discontinuous part 17 is not provided in the open stub 14, in the vicinity of the frequency f2, Although the band is relatively wide, it becomes an unbalanced reflection attenuation characteristic of extremely narrow band in the vicinity of the frequency f1. However, by providing the discontinuous portion 17 in the open stub 14, such a problem can be avoided, and the frequency f1 It becomes possible to obtain the reflection attenuation characteristic in which the bandwidths of both the vicinity and the f2 vicinity are substantially the same.

That is, by providing the discontinuous portion 17 in the open stub 14, it is possible to prevent narrowing in one frequency band and obtain better reflection attenuation characteristics. In addition, since the loss in the matching circuit increases in the narrow band, the discontinuity 17 is provided in the open stub 14 to reduce the loss in the matching circuit in the narrow band. Also leads.

Here, the frequency characteristic of the reflection attenuation amount depends on whether the frequency characteristic of the input impedance of the antenna 1 is steep or moderate, and the magnitude of the ratio of the characteristic impedance of the external circuit 10 to the resistance of the input impedance of the antenna 1. Change.

For example, when the frequency characteristic of the input impedance of the antenna 1 is steep and the resistance of the input impedance of the antenna 1 is small with respect to the characteristic impedance of the external circuit 10, as shown in FIG. 14, f1, Each frequency band of f2 is narrowed, and the level of reflection attenuation in the frequency band between the frequency bands of f1 and f2 is increased.

On the other hand, when the frequency characteristic of the input impedance of the antenna 1 is slow and the resistance of the input impedance of the antenna 1 is close to the characteristic impedance of the external circuit 10, as shown in FIG. 17, the angles of f1 and f2 are shown. The frequency band becomes wider, the level of the reflection attenuation in the frequency band between the frequency bands f1 and f2 becomes smaller, and the impedance matching can be efficiently achieved in a wide frequency band including the frequency band between the frequency bands f1 and f2. Can be.

The ratio of the position where the characteristic impedance is discontinuous, the number of discontinuities, and the characteristic impedance of the line constituting the discontinuity may be selected in consideration of the frequency characteristic of the input impedance of the antenna 1 to which impedance matching is to be made. In short, it goes without saying that the method of partial change in the characteristic impedance of the open stub 14 may not necessarily be the same as this antenna device.

In the first embodiment, the transmission lines 6a and 6b, the open stub 14, and the short stub 15 are formed as microstrip lines, but instead of the microstrip lines, strip lines, coay lines, and copper surfaces are used. It may be formed by a coplanar track or the like.

As described above, according to the impedance matching circuit of the first embodiment, it is possible to perform impedance matching in two different frequency bands or in a wide frequency band including the frequency bands of two frequency band sentences, and at the same time, the impedance matching must be performed. It is possible to flexibly correspond to the frequency characteristic of the input impedance of the antenna 1, and the reflection attenuation characteristic becomes narrow in one of the bands near the two frequencies, or the loss in the impedance matching circuit does not increase. It is possible to obtain an effect of obtaining a good return loss characteristic in the band of the band.

In addition, according to the first embodiment, although the transmission line 6a and the interdigital capacitor 22 are used as the first matching circuit 8-1, the circuit configuration of the first matching circuit 8-1 is changed. As a result, an effect that can flexibly cope with impedance matching of many kinds of antennas can be obtained. For example, when an inductance element is used instead of the interdigital capacitor 22, the input impedance can also correspond to an antenna having high impedance.

In addition, according to the first embodiment, in addition to configuring the resonant circuit by using the open stub 14 and the short stub 15, since the interdigital capacitor 22 is used, the chip element requiring mounting work is required. Since it can be produced simply by forming a strip conductor pattern on the dielectric substrate 12, it becomes easy to manufacture and the effect which can manufacture an impedance matching circuit at low cost is acquired.

In addition, according to the first embodiment, by using the interdigital capacitor 22, it is possible to easily and accurately manufacture capacitance elements of arbitrary capacitance, and to compare them when using chip elements or the like. Thus, the effect of easily obtaining an impedance matching circuit with good characteristics can be obtained.

Example 2.

18 is a perspective view showing an antenna device according to a second embodiment of the present invention, FIG. 19 is a top view of the antenna device shown in FIG. 18, and FIG. 20 is a circuit diagram of the antenna device shown in FIG.

18 to 20, 14a is formed by the microstrip line, the first open stub having the electric field θo, and 14b is the second open stub formed by the microstrip line. The second open stub 14b is formed by using a line having a different characteristic impedance in a part of the stub. As a result, there are two discontinuous portions 17a and 17b of the characteristic impedance in the stub. The electric fields are θ so1, θso2 and θso3 on the open end side. These two open stubs 14a and 14b are connected to the same location of the strip conductor 18. As shown in FIG.

8-2 is a 2nd matching circuit comprised from the transmission line 6b and the open stubs 14a and 14b and which performs impedance matching of the antenna 1 at the frequency f1. Other than that is the same as that shown in FIG. 7 in FIG.

Here, the sum of the electric fields of the two open stubs 14a and 14b becomes a value slightly larger than π or π at the frequency f2, and at the frequency f2, the sum of the susceptance values of the two stubs is It becomes 0, resonates as the 1/2 wavelength resonant circuit 5-3, and at the frequency f1, the distribution of the lengths is determined so that the sum of the susceptance values of the two stubs shows a predetermined susceptance value. have. In addition, a required value is also selected for the electric field θb of the transmission line 6b.

Next, the operation will be described.

In Fig. 20, the resonant circuit in the impedance matching circuit 7 is a quarter-wave resonant circuit formed by the combination of the open stub 14 and the short stub 15 in the first embodiment. In this case, the half-wave resonant circuit is formed by a combination of two open stubs 14a and 14b.

Since the two open stubs 14a and 14b are connected in parallel to the transmission line 6b at the same location, the half-wave resonant circuit 5-3 can also be regarded as a kind of parallel resonant circuit. Therefore, the principle of operation is almost the same as in the first embodiment, and if the impedance trajectory of the antenna 1 can be given as shown in Fig. 8, at the nodes B to E, the impedance when the antenna 1 side is viewed 9 to 13 are similar to the trajectories shown in FIG. 13.

The electric fields of the two open stubs 14a and 14b and the electric fields of the transmission line 6b can be obtained from the following equations (3) and (4).

At the frequency f2,

(Susceptance of open stub 14a) + (susceptance of open stub 14b) = 0 (3)

At the frequency f1,

Zo ¹ (Y1 + jZo ¹ tanθb) / (Zo- ¹ + jY1tanθb) + (susceptance of open stub 14a) + (susceptance of open stub 14b) = Zo ¹ (4)

Here, Y1 in (4) is an admittance in frequency f1 when the antenna 1 side is seen from the node C of FIG. That is, Y1 corresponds to the admittance at f1 in FIG. Since equation (4) is a complex equation, the equation is divided into two equations, a real part and an imaginary part, and the above simultaneous equations become three equations. So, for example, when θso3 is an integer and conditions such as θso1 = θso2 are applied, the solution can be obtained with three unknowns.

In the second embodiment, the first open stub 14a and the second open stub 14b are formed by a microstrip line. Alternatively, the first open stub 14a and the second open stub 14b may be formed by a strip line, a coaxial line, a coplanar line, or the like instead of the microstrip line. .

As described above, according to the second embodiment, the same effects as those of the antenna device of the first embodiment can be obtained. In addition, according to the second embodiment, since the stub only uses the open stub and does not use the short stub, the passage hole is unnecessary, the production is easy, and the effect of manufacturing at low cost can be obtained.

Example 3.

21 is a perspective view showing an antenna device according to a third embodiment of the present invention, FIG. 22 is a top view of the antenna device shown in FIG. 21, and FIG. 23 is a circuit diagram of the antenna device shown in FIG. 21. This antenna device combines a circular microstrip antenna and an impedance matching circuit formed by a microstrip line to operate in two frequency bands.

21 to 23, 1 is an antenna by a circular microstrip antenna, 24 is a quarter-wave impedance transformer at frequency f2, and 8-1 is a quarter-wave impedance transformer 24. It is a 1st matching circuit, and the impedance matching of the antenna 1 is performed at the frequency f2. Other than that is the same as that shown in FIG. 20 in FIG. 18 of Example 2. FIG.

Next, the operation will be described.

FIG. 24 is a Smith diagram showing the input impedance characteristics of the antenna 1 by the circular microstrip antenna, and corresponds to the characteristics when the antenna 1 side is seen from the node A of FIG. In general, in such a circular microstrip antenna, when the microstrip line is connected and fed to the end of the microstrip antenna as shown, the characteristics of high impedance as shown in FIG. 24 are shown.

Here, it is assumed that the reactance is 0 at the frequency f2. When the impedance transformer 24 is connected for impedance matching at the frequency f2, the characteristics are the same as those in FIG. 25, and the frequency f2 in FIG. ), The resistance of the input impedance is converted into characteristic impedance Zo (standardized impedance or characteristic impedance of the external circuit 10). The operation shown in FIG. 25 is the same as that of the second embodiment for the operation of impedance matching also at the frequency f1 while maintaining the impedance matching state at the frequency f2.

As described above, according to the third embodiment, the same characteristics as those of the antenna device of the second embodiment can be obtained, and the same effects can be obtained. In addition, in the third embodiment, since the impedance transformer 24 is used for the first matching circuit 8-1 in consideration of the characteristics of the microstrip antenna, the circuit configuration becomes simpler and can be manufactured at low cost. The effect can be obtained.

Example 4.

Fig. 26 is a perspective view showing an antenna device according to a fourth embodiment of the present invention. This antenna device is used in a small wireless terminal such as a cellular phone, and is connected to a four-wire winding (N-line winding) helical antenna composed of four (N) helical elements and each of the four helical elements, Four (N) impedance matching circuits that perform impedance matching in the frequency band and four distribution circuits connected to the four impedance matching circuits and distributing or synthesizing microwaves while giving a predetermined phase difference thereto (N distribution circuits). ) Is formed on a hollow cylindrical dielectric. In other words, the antenna device is a hollow cylindrical dielectric, in which the antenna and the power feeding circuit are integrally formed.

The impedance matching circuit and the four-distribution circuit are each composed of a strip conductor formed on the outer side of the hollow cylindrical dielectric and a microstrip line made of a conductor formed on the inner side.

FIG. 27 is a developed view of a cylindrical outer surface of the antenna device shown in FIG. 26, and FIG. 28 is a developed view of a cylindrical inner surface of the antenna device shown in FIG. 26. As shown in Fig. 28, the conductor formed on the inner surface of the hollow cylindrical dielectric corresponds to the region where the strip conductors of the microstrip lines constituting the impedance matching circuit and the four-distribution circuit exist, and the lower side of the inner cylinder surface. It is formed in the part. FIG. 29 is an enlarged view of the strip conductor pattern of the impedance matching circuit portion, and FIG. 30 is a circuit diagram of the antenna device shown in FIGS. 26 to 29.

26 to 30, 21 is a hollow cylindrical dielectric, 1 is an antenna composed of four helical elements formed by forming a conductor pattern on the outer surface of the hollow cylindrical dielectric 21, and 2 is four inputs of the antenna 1. The terminal, 13 is a conductor formed on the inner side of the hollow cylindrical dielectric 21, 18 is a strip conductor constituting the microstrip line together with the hollow cylindrical dielectric 21 and the conductor 13.

6a is a transmission line formed by a microstrip line and has an electric field θa at a frequency f2, and 22 is an interdigital capacitor connected in series to the transmission line 6a, and this interdigital capacitor 22 Are shown as capacitors 3 connected in series in the circuit diagram of FIG. 6b is formed by a microstrip line, a transmission line having an electric field θb at a frequency f1, 14 is an open stub having an electric field θo formed by a microstrip line, and 15 is formed by a microstrip line. It is a short stub having an electric field θ s. 16 is provided in the front-end | tip of the short stub 15, and is a through hole which connects the strip conductor 18 and the conductor 13. FIG.

In the open stub 14, the characteristic impedance of the line forming the stub is not constant in the stub, and a low impedance line is used in the middle portion of the stub, and two discrete positions 17a and 17b of the characteristic impedance are used. There is). The electric fields of the respective portions of the open stub 14 are θo1, θo2, and θo3 from the open end side. The open stub 14 and the short stub 15 are connected so as to oppose at the same location of the strip conductor 18.

Here, the sum of the electric fields θo1 and θo2 and θo3 and θs is set to be slightly larger than π / 2 or π / 2, and the sum of the susceptance values of the two stubs is set to zero at the frequency f2. That is, it operates as the quarter-wave resonant circuit 5-2 in the frequency band near the frequency f2. The distribution of the electric fields θo1, θo2, θo3, and θs is determined such that the sum of the susceptances of the open stub 14 and the short stub 15 shows a predetermined susceptance value at the frequency f1. In addition, a predetermined value is also selected for the electric field θb of the transmission line 6b.

8-1 is a first matching circuit composed of the transmission line 6a and the capacitor element 3 and performing impedance matching of the antenna 1 at the frequency f2. 8-2 is composed of a quarter-wave resonant circuit 5-2 by the transmission line 6b, the open stub 14 and the short stub 15, and the impedance of the antenna 1 at the frequency f1. It is a 2nd matching circuit which matches. 7 is an impedance matching circuit composed of the first matching circuit 8-1 and the second matching circuit 8-2 and performing impedance matching at two frequencies f1 and f2. The impedance matching circuit 7 4 (N pieces) are prepared corresponding to each helical element of the antenna 1. 9 is an input terminal of the impedance matching circuit 7.

23 is a four-distribution circuit (N distribution circuit), and is composed of a microstrip line consisting of a hollow cylindrical dielectric 21, a conductor 13, and a strip conductor 18, and each of the required distribution amplitude characteristics and distribution phase characteristics. There are four (N) distribution terminals, each of which is connected to each of the input terminals 9 of the four impedance matching circuits 7. The four-distribution circuit 23 is configured to generate a phase difference of about 90 degrees between the four input terminals 9.

25 is an input terminal of the four-distribution circuit 23, and is an input terminal of this antenna device. 10 is connected to the input terminal 25 as an external circuit by a power supply circuit or an RF circuit. In addition, in FIG. 29, nodes A, B, C, D, E, and F of the circuits are shown for the purpose of the operation described later.

Next, the operation will be described.

The four-wire wound helical antenna used in this antenna device radiates radio waves of circular polarization by feeding the quadrature circuit 23 with a phase difference of 90 degrees between four helical elements. Since the radiation directivity is wide and the range of the radiation is wide around the axial direction of the hollow cylindrical dielectric 21, the four-wire wound helical antenna is used in satellite portable terminals and the like. The antenna device according to the fourth embodiment makes it possible to use such a four-wire wound helical antenna in two frequency bands.

Since the four helical elements operate in combination with each other, the active impedance when the antenna 1 side is seen from the four input terminals 2 can be regarded as a load impedance to be matched with impedance. Therefore, the impedance matching circuit 7 is designed based on the active impedance of the antenna 1 side seen from each input terminal 2 (node A). Here, since the active impedance when the antenna 1 side is seen from the input terminal 2 is similar to the locus shown in the Smith diagram of FIG. 8, the operation of the four impedance matching circuits 7 is similar to that of the first embodiment. Is almost the same as the impedance matching circuit of the antenna device.

Therefore, the impedance trajectory when the antenna 1 side is seen from the nodes B to E becomes a trajectory similar to the trajectory shown in the Smith diagrams of Figs. Here, since the impedance matching has already been made in the two frequency bands at the node E, the impedance matching at the two frequencies f1 and f2 also in the characteristic when the antenna F side is seen at the node F. Is maintained. As a result, the reflection characteristic in the node F is as shown in FIG.

As described above, according to the fourth embodiment, the same characteristics as those of the antenna device of the first embodiment can be obtained, and the same effects can be obtained.

Further, according to the second embodiment, the parallel resonant circuit 5-2 of the second matching circuit 8-2 is constructed using a stub instead of a chip element, and an interdigital capacitor is used as the series capacitor. As a result, there is no chip, the production is easy, and the effect of manufacturing at low cost can be obtained. This point is very important from the standpoint of realization because the antenna device is formed using the hollow cylindrical dielectric 21.

In addition, according to the fourth embodiment, four helical elements for radiating radio waves, four impedance matching circuits 7 and four distribution circuits 23 operable at two frequencies f1 and f2 are provided. 21, which is formed integrally with each other, it is possible to obtain an effect that the wireless terminal device including the antenna device can be compactly constructed.

According to the fourth embodiment, the antenna 1 has four helical elements, and although there are four input terminals 2 of the antenna 1, since the four-distribution circuit is integrally formed, the external circuit Only one input terminal 25 for connecting with (10) is used, and the structure of the interface between the antenna device and the external circuit 10 is simplified, resulting in easy assembly, low cost, and a significant improvement in reliability. Can achieve the effect.

Example 5.

Fig. 31 is a perspective view showing an antenna device according to a fifth embodiment of the present invention. FIG. 32 is a developed view of a cylindrical outer surface of the antenna device shown in FIG. 31, and FIG. 33 is a developed view of a cylindrical inner surface of the antenna device shown in FIG. 31. 34 is an enlarged view of the strip conductor pattern of the impedance matching circuit portion, and FIG. 35 is a circuit diagram of the antenna device shown in FIGS. 31 to 34.

31 to 35, 14a is a first open stub formed by a microstrip line and has an electric field θo, and 14b is a second open stub formed by a microstrip line.

The second open stub 14b is formed using a line having a different characteristic impedance in a part of the stub. As a result, there are two discontinuous portions 17a and 17b of the characteristic impedance in the stub. Θso1, θso2, and θso3 from the open end side. Two open stubs 14a and 14b are connected so as to oppose each other at the same position of the strip conductor 18.

Here, the sum of the electric fields of the two open stubs 14a and 14b is a value slightly larger than [pi] or [pi] at the frequency f2, and at the frequency f2 of the two open stubs 14a and 14b. The sum of the susceptance values becomes zero, resonates as the 1/2 wavelength resonant circuit 5-3, and at the frequency f1, the sum of the susceptance values of the two open stubs 14a and 14b is predetermined. The distribution of the lengths is determined to show the susceptance value of. At the same time, a predetermined value is also selected for the electric field θb of the transmission line 6b.

8-1 is a first matching circuit composed of the transmission line 6a and the capacitor element 3 and performing impedance matching of the antenna 1 at the frequency f2. 8-2 is composed of a half-wave resonant circuit 5-3 by the transmission line 6b and the open stubs 14a and 14b, and performs impedance matching of the antenna 1 at the frequency f1. 2 matching circuit. 7 is an impedance matching circuit composed of the first matching circuit 8-1 and the second matching circuit 8-2 and performing impedance matching at two frequencies f1 and f2. Others are the same as the same reference numerals shown in FIG. 30 in FIG. 26 of the fourth embodiment.

The four-wire wound helical antenna used in this antenna device operates in the same manner as the antenna device shown in the fourth embodiment.

As described above, according to the fifth embodiment, the same characteristics as those of the antenna device of the fourth embodiment can be obtained, and the same effects can be obtained.

In addition, according to the fifth embodiment, since the resonant circuit in the second matching circuit is composed of two open stubs 14a and 14b, a through hole is not required, making the antenna relatively easy and manufacturing at low cost. The effect of making the device can be obtained.

As described above, the impedance matching circuit and the antenna device according to the present invention efficiently operate various types of single resonance antennas in two frequency bands or in a wide frequency band including the frequency bands between the two frequency bands. It is suitable for operation.

Claims (13)

An impedance matching circuit for matching an input impedance of an antenna and a characteristic impedance of an external circuit that receives a signal between the antennas at a frequency f1 and a frequency band of a frequency f2 higher than the frequency f1. In A first matching circuit for matching impedance at the frequency f2, A transmission line formed by a microstrip line or the like that becomes a feed line to the antenna and having a predetermined electric field, and connected to the transmission line and formed of first and second stubs formed by the microstrip line or the like, A second matching circuit for matching impedance at the frequency f1, While providing discontinuities of impedance so that characteristic impedance is different in the first or second stub, The sum of the susceptance values of the first and second stubs at the frequency f2 is 0, and the sum of the susceptance values of the first and second stubs at the frequency f1 is a predetermined value. Impedance matching circuit, characterized in that the electric field of the first and second stub is set. The method of claim 1, An impedance matching circuit comprising a first matching circuit comprising a transmission line formed by a microstrip line or the like and having an electric field, and an interdigital capacitor that provides capacitance in series with the transmission line. The method of claim 1, An impedance matching circuit comprising the first matching circuit as a quarter wavelength impedance transformer at a frequency f2. The method of claim 1, Second matching circuit, An impedance matching circuit comprising a first stub with an open stub having an impedance discontinuity portion formed therein, and a second stub with a short stub connected at one end to a conductor. The method of claim 1, Second matching circuit, An impedance matching circuit comprising a first stub by an open stub with one end open and a second stub by an open stub with one end open. A plurality of hollow cylindrical dielectrics are formed, and the input impedances of the plurality of antennas and the characteristic impedances of the external circuits that receive signals between the plurality of antennas have a frequency f1 and a frequency f2 higher than the frequency f1. In the impedance matching circuit to match in the frequency band, A first matching circuit for matching impedance at the frequency f2, A transmission line formed by a microstrip line serving as a feed line to the plurality of antennas and having a predetermined electric field, and formed by the microstrip line, the first and second stubs connected to the transmission line, A second matching circuit for matching impedance at the frequency f1, While providing discontinuities of impedance so that characteristic impedance is different in the first or second stub, The sum of the susceptance values of the first and second stubs at the frequency f2 is 0, and the sum of the susceptance values of the first and second stubs at the frequency f1 is a predetermined value, An impedance matching circuit comprising setting electric fields of the first and second stubs. The method of claim 6, The impedance matching circuit as claimed in claim 1, wherein the first matching circuit is composed of a transmission line formed by a microstrip line and having a predetermined electric field, and an interdigital capacitor which provides capacitance in series with the transmission line. The method of claim 6, Second matching circuit, An impedance matching circuit comprising a first stub with an open stub having an impedance discontinuity portion formed therein, and a second stub with a short stub connected at one end to a conductor. The method of claim 6, Second matching circuit, An impedance matching circuit comprising a first stub by an open stub with one end open and a second stub by an open stub with one end open. A plurality of antennas formed in the hollow cylindrical dielectric, The characteristic impedance of the external circuit formed on the hollow cylindrical dielectric and connected to each of the antennas and receiving a signal between the antenna and the input impedance of each antenna is greater than the frequency f1 and the frequency f1. A plurality of impedance matching circuits that match in the frequency band of the high frequency f2, A plurality of distribution circuits formed on the hollow cylindrical dielectric and connected to the respective impedance matching circuits to give a predetermined phase difference to a signal from the external circuit, Each impedance matching circuit A first matching circuit for matching impedance at the frequency f2, A transmission line formed by a microstrip line serving as a feed line to each antenna and having a predetermined electric field, and formed by the microstrip line and first and second stubs connected to the transmission line, And a second matching circuit for matching impedance at frequency f1, While providing discontinuities of impedance so that characteristic impedance is different in the first or second stub, The sum of the susceptance values of the first and second stubs at the frequency f2 is 0, and the sum of the susceptance values of the first and second stubs at the frequency f1 is a predetermined value, An antenna device, wherein the electric fields of the first and second stubs are set. The method of claim 10, An antenna device comprising: a first matching circuit formed of a microstrip line, a transmission line having a predetermined electric field, and an interdigital capacitor that provides capacitance in series with the transmission line. The method of claim 10, Second matching circuit An antenna device comprising an impedance discontinuity portion and a first stub with an open stub with one end open, and a second stub with a short stub connected with one end to the conductor. The method of claim 10, Second matching circuit An antenna device comprising: a first stub with an open stub open at one end and a discontinuous portion of impedance; and a second stub with an open stub open at one end.