JP2011035706A - Reverse-phase distribution circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reverse-phase distribution circuit keeping distribution phase difference at about 180° and reducing distribution amplification difference for over a wide frequency band. <P>SOLUTION: The reverse-phase distribution circuit includes: a first transmission line 4 connected between an input terminal 1 and a first output terminal 2 and having 1/4 wavelength of electric length in the center frequency of a predetermined frequency band; a second transmission line 5 connected between the input terminal 1 and a second output terminal 3 and having 3/4 wavelength of electric length in the center frequency; and a third transmission line 6 connected between the first output terminal 2 and the second output terminal 3 and having 1/2 wavelength of electric length in the center frequency. The reverse-phase distribution circuit equalizes the value of characteristic impedance of the first transmission line 4 with that of the second transmission line 5, and makes the value of characteristic impedance of the third transmission line 6 smaller than the values of the characteristic impedance of the first transmission line 4 and the second transmission line 5. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a reverse phase distribution circuit used in a microwave band and a millimeter wave band.

  The conventional reverse phase distribution circuit includes a first transmission line connected between the input terminal and the first output terminal, a second transmission line connected between the input terminal and the second output terminal, A third transmission line connected between the output terminal and the second output terminal, distributing a high-frequency signal input to the input terminal, and outputting the opposite phases from the first output terminal and the second output terminal; is doing.

Here, the first transmission line, the second transmission line, and the third transmission line have electrical lengths of approximately 1/4 wavelength, 3/4 wavelength, and 1/2 wavelength, respectively, at the center frequency of a predetermined frequency band. ing. The characteristic impedances of the first transmission line, the second transmission line, and the third transmission line are set to be equal to each other.
In such a reverse phase distribution circuit, the phase difference between distributed high frequency signals, that is, the distribution phase difference can be maintained at approximately 180 ° over a wide frequency band including the center frequency (see, for example, Patent Document 1). .

JP 2004-32046 A

However, the prior art has the following problems.
In the conventional anti-phase distribution circuit, as described above, the distribution phase difference can be maintained at approximately 180 ° over a wide frequency band. However, the amplitude difference between the distributed high-frequency signals, that is, the distributed amplitude difference increases as the frequency of the high-frequency signal goes away from the center frequency even in the frequency band where the distributed phase difference is maintained at approximately 180 °. There was a problem that the transmission quality of the system deteriorated.

  The present invention has been made to solve the above-described problems, and maintains a distribution phase difference at approximately 180 ° over a wide frequency band and can reduce a distribution amplitude difference. The purpose is to obtain.

  A negative-phase distribution circuit according to the present invention is a negative-phase distribution circuit that distributes a high-frequency signal input to an input terminal and outputs the high-frequency signal from the first output terminal and the second output terminal in opposite phases to each other. A first transmission line connected between the first output terminal and having an electrical length of ¼ wavelength at a center frequency in a predetermined frequency band; and connected between the input terminal and the second output terminal; A second transmission line having an electrical length of 3/4 wavelength and a third transmission line connected between the first output terminal and the second output terminal and having an electrical length of ½ wavelength at the center frequency. Provided, the characteristic impedance of the first transmission line and the second transmission line are set to be equal to each other, and the characteristic impedance of the third transmission line is set to a value smaller than the characteristic impedance of the first transmission line and the second transmission line. .

  According to the reverse phase distribution circuit of the present invention, the first transmission line having an electrical length of ¼ wavelength at the center frequency of the predetermined frequency band and the second transmission having an electrical length of ¾ wavelength at the center frequency. The characteristic impedance with the line is made equal to each other, and the characteristic impedance of the third transmission line having an electrical length of ½ wavelength at the center frequency is made smaller than the characteristic impedance of the first transmission line and the second transmission line. Thus, it is possible to obtain an antiphase distribution circuit capable of maintaining the distribution phase difference at approximately 180 ° and reducing the distribution amplitude difference over a wide frequency band.

It is a circuit diagram which shows the negative phase distribution circuit which concerns on Embodiment 1 of this invention. It is explanatory drawing which illustrates the transmission characteristic of the negative phase distribution circuit which concerns on Embodiment 1 of this invention. It is explanatory drawing which illustrates the transmission characteristic of the conventional reverse phase distribution circuit.

  Hereinafter, preferred embodiments of the reverse phase distribution circuit of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts will be described with the same reference numerals.

Embodiment 1 FIG.
1 is a circuit diagram showing a negative phase distribution circuit according to Embodiment 1 of the present invention.
In FIG. 1, this anti-phase distribution circuit distributes the high-frequency signal input to the input terminal 1 and outputs the high-frequency signal from the first output terminal 2 and the second output terminal 3 in opposite phases.

  A first transmission line 4 having an electrical length of ¼ wavelength (λ / 4) is connected between the input terminal 1 and the first output terminal 2 at the center frequency of a predetermined frequency band. A second transmission line 5 having an electrical length of 3/4 wavelength (3λ / 4) is connected between the input terminal 1 and the second output terminal 3 at the center frequency of a predetermined frequency band. A third transmission line 6 having an electrical length of ½ wavelength (λ / 2) is connected between the first output terminal 2 and the second output terminal 3 at the center frequency of a predetermined frequency band. ing.

  An input transmission line 7 is connected between a connection point P1 between the first transmission line 4 and the second transmission line 5 and the input terminal 1. A first output transmission line 8 is connected between a connection point P <b> 2 between the first transmission line 4 and the third transmission line 6 and the first output terminal 2. A second output transmission line 9 is connected between the connection point P 3 between the second transmission line 5 and the third transmission line 6 and the second output terminal 3. The first output transmission line 8 and the second output transmission line 9 are set to have the same electrical length.

  Here, the characteristic impedance of the first transmission line 4 is Zc1, the characteristic impedance of the second transmission line 5 is Zc2, the characteristic impedance of the third transmission line 6 is Zc3, the input transmission line 7, the first output transmission line 8, and the The characteristic impedance of the two-output transmission line 9 is Zc. Also, R is a load resistance connected to each of the input terminal 1, the first output terminal 2, and the second output terminal 3.

  Here, the characteristic impedance Zc of the input transmission line 7, the first output transmission line 8 and the second output transmission line 9 is connected to the input terminal 1, the first output terminal 2 and the second output terminal 3, respectively. The load resistance R is set to an equal value. That is, the input terminal 1, the first output terminal 2, and the second output terminal 3 are terminated by a load having the characteristic impedance Zc.

  The characteristic impedance Zc1 of the first transmission line 4 and the characteristic impedance Zc2 of the second transmission line 5 are set to be equal to each other (a value obtained by multiplying the load resistance R by the square root of 2 (√2)). The characteristic impedance Zc3 of the third transmission line 6 is set to a value smaller than the characteristic impedances Zc1 and Zc2 of the first transmission line 4 and the second transmission line 5.

Next, the operation of the negative phase distribution circuit having the above configuration will be described.
The high frequency signal input to the input terminal 1 is transmitted through the input transmission line 7 and divided into two at the connection point P1. The two distributed high frequency signals are transmitted to the connection points P2 and P3, respectively. Here, the high-frequency signal transmitted through the first transmission line 4 and reaching the connection point P2, and the high-frequency signal transmitted through the second transmission line 5 and the third transmission line 6 and reaching the connection point P2 are the center frequency. Therefore, the signal is transmitted through the first output transmission line 8 and output from the first output terminal 2.

  Further, the high frequency signal transmitted through the first transmission line 4 and the third transmission line 6 to reach the connection point P3 and the high frequency signal transmitted through the second transmission line 5 to the connection point P3 are at the center frequency. Since it is in phase, it is transmitted through the second output transmission line 9 and output from the second output terminal 3. At this time, the amplitudes of the high-frequency signals output from the first output terminal 2 and the second output terminal 3 are equal to each other.

  Further, the high frequency signals output from the first output terminal 2 and the second output terminal 3 respectively have a length from the connection point P1 to the connection point P2 and a length from the connection point P1 to the connection point P3 at the center frequency. It has a difference of λ / 2, that is, a phase difference of 180 °. That is, since the high-frequency signals output from the first output terminal 2 and the second output terminal 3 have the same amplitude and opposite phase, this circuit operates as an anti-phase distribution circuit.

Next, transmission characteristics of the anti-phase distribution circuit having the above configuration will be described.
In the first embodiment, the center frequency is 2 GHz, the load resistance R connected to each of the input terminal 1, the first output terminal 2 and the second output terminal 3 is 50Ω, and the characteristic impedance Zc3 of the third transmission line 6 is The characteristic impedances Zc1 and Zc2 of the first transmission line 4 and the second transmission line 5 are half the values. Therefore, the characteristic impedance Zc of the input transmission line 7, the first output transmission line 8 and the second output transmission line 9 is 50Ω, and the characteristic impedances Zc1 and Zc2 of the first transmission line 4 and the second transmission line 5 are 70.71Ω (= Zc × √2), the characteristic impedance Zc3 of the third transmission line 6 is 35.36Ω.

  FIG. 2 shows the calculated values of the transmission characteristics (frequency characteristics of the S parameter) of the anti-phase distribution circuit given the conditions as described above. For comparison, FIG. 3 shows calculated values of the transmission characteristics (frequency characteristics of S parameters) of the above-described antiphase distribution circuit of Patent Document 1. In the antiphase distribution circuit of Patent Document 1, the characteristic impedance of the third transmission line is set to a value (70.71Ω) equal to the characteristic impedance of the first transmission line and the second transmission line. The same conditions as those of the antiphase distribution circuit of the form 1 are given.

2A to 2C, the horizontal axis indicates the frequency. The vertical axis in FIG. 2A represents the ratio of the amplitude of the high-frequency signal output from the first output terminal 2 and the second output terminal 3 to the amplitude of the high-frequency signal input to the input terminal 1, that is, the distribution amplitude | S. ₂₁ | and | S ₃₁ | The vertical axis in FIG. 2B indicates the phase difference between the high-frequency signals output from the first output terminal 2 and the second output terminal 3, that is, the distribution phase difference ∠ (S ₃₁ / S ₂₁ ). The vertical axis of FIG. 2C indicates the ratio of the amplitude of the high-frequency signal reflected at the input terminal 1 to the amplitude of the high-frequency signal input to the input terminal 1, that is, the input reflection amplitude | S ₁₁ |. . 3A to 3C, the horizontal axis and the vertical axis indicate the same as those in FIGS. 2A to 2C.

2A to 2C, for example, in the frequency band with a specific bandwidth of 10%, that is, in the frequency range of 1.9 to 2.1 GHz, the distribution amplitude | S ₂₁ | and the distribution amplitude | S ₃₁ | It can be seen that the difference is within 0.05 dB, the distribution phase difference ∠ (S ₃₁ / S ₂₁ ) is within −180 ° to ± 0.06 °, and the input reflection amplitude | S ₁₁ | is −40.7 dB or less. Further, in the frequency band with a specific bandwidth of 20%, that is, in the frequency range of 1.8 to 2.2 GHz, the difference between the distribution amplitude | S ₂₁ | and the distribution amplitude | S ₃₁ | is within 0.21 dB, and the distribution phase difference ∠ It can be seen that (S ₃₁ / S ₂₁ ) is within −0.52 ° from −180 °, and the input reflection amplitude | S ₁₁ | is −28.7 dB or less.

3A to 3C, for example, in the frequency band having a specific bandwidth of 10%, the difference between the distribution amplitude | S ₂₁ | and the distribution amplitude | S ₃₁ | is within 0.11 dB, and the distribution phase difference ∠ ( S ₃₁ / S ₂₁ ) is within −0.08 ° from −180 °, and the input reflection amplitude | S ₁₁ | is −31.0 dB or less. Further, in the frequency band with a specific bandwidth of 20%, the difference between the distribution amplitude | S ₂₁ | and the distribution amplitude | S ₃₁ | is within 0.46 dB, and the distribution phase difference ∠ (S ₃₁ / S ₂₁ ) is from −180 °. It can be seen that the input reflection amplitude | S ₁₁ | is −24.8 dB or less within ± 0.68 °.

  Here, when FIGS. 2A to 2C are compared with FIGS. 3A to 3C, the antiphase distribution circuit according to the first embodiment is disclosed in the patent document in the frequency band having a specific bandwidth of 10%. It can be seen that the distribution amplitude difference is improved by 0.06 dB and the input reflection amplitude is improved by 9.7 dB, compared with the 1 antiphase distribution circuit. Further, in the anti-phase distribution circuit of the first embodiment, the distribution amplitude difference is 0.25 dB and the input reflection amplitude is 3.9 dB, respectively, in the frequency band with a relative bandwidth of 20%, compared to the anti-phase distribution circuit of Patent Document 1. It can be seen that it is improved. In addition, it can be seen that, in the anti-phase distribution circuit of the first embodiment, the distribution phase difference is also improved although it is slight.

  That is, in the antiphase distribution circuit of the first embodiment, the distribution amplitude difference characteristic and the input reflection amplitude characteristic are improved while maintaining a good distribution phase difference characteristic in a wide frequency band such as a specific bandwidth of 10% or 20%. It is illustrated.

  The distribution amplitude difference can be reduced as the characteristic impedance Zc3 of the third transmission line 6 is set to a value smaller than the characteristic impedances Zc1 and Zc2 of the first transmission line 4 and the second transmission line 5. However, if the characteristic impedance Zc3 of the third transmission line 6 is made smaller than a certain value, the input reflection amplitude is deteriorated. When the characteristic impedance Zc3 of the third transmission line 6 is approximately half the characteristic impedances Zc1 and Zc2 of the first transmission line 4 and the second transmission line 5, both the distribution amplitude difference and the input reflection amplitude are the most. Good characteristics can be obtained.

  As described above, according to the first embodiment, the first transmission line having an electrical length of ¼ wavelength at the center frequency of the predetermined frequency band, and the second having the electrical length of ¾ wavelength at the center frequency. The characteristic impedance of the transmission line is made equal to each other, and the characteristic impedance of the third transmission line having an electrical length of ½ wavelength at the center frequency is made smaller than the characteristic impedance of the first transmission line and the second transmission line. By doing so, it is possible to obtain an anti-phase distribution circuit capable of maintaining the distribution phase difference at approximately 180 ° and reducing the distribution amplitude difference over a wide frequency band.

  In the first embodiment, such a reverse phase distribution circuit includes, for example, a microstrip line including a strip conductor formed on the surface of the dielectric substrate and a ground conductor formed on the back surface of the dielectric substrate. Can be configured. In this case, the first transmission line 4, the second transmission line 5, the third transmission line 6, the input transmission line 7, the first output transmission line 8, and the second output transmission line 9 are configured by microstrip lines. As shown in FIG. 1, each transmission line is connected at connection points P1 to P3. Furthermore, the input terminal 1, the first output terminal 2, and the second output terminal 3 are respectively connected to the input transmission line 7, the first output transmission line 8, and the second output transmission line 9 that extend toward the end of the dielectric substrate. By connecting, a reverse phase distribution circuit is configured.

  In addition to this, the reverse phase distribution circuit includes, for example, a strip line (triplate line) formed of a strip conductor formed inside the dielectric substrate and a ground conductor formed on the front and back surfaces of the dielectric substrate. Can be used. In this case, the first transmission line 4, the second transmission line 5, the third transmission line 6, the input transmission line 7, the first output transmission line 8, and the second output transmission line 9 are configured by strip lines. As shown in FIG. 2, the respective transmission lines are connected at connection points P1 to P3. Furthermore, the input terminal 1, the first output terminal 2, and the second output terminal 3 are respectively connected to the input transmission line 7, the first output transmission line 8, and the second output transmission line 9 that extend toward the end of the dielectric substrate. By connecting, a reverse phase distribution circuit is configured.

  DESCRIPTION OF SYMBOLS 1 Input terminal, 2 1st output terminal, 3 2nd output terminal, 4 1st transmission line, 5 2nd transmission line, 6 3rd transmission line, Zc1, Zc2, Zc3 Characteristic impedance.

Claims (4)

A negative phase distribution circuit that distributes a high-frequency signal input to an input terminal and outputs the high-frequency signal from the first output terminal and the second output terminal in opposite phases;
A first transmission line connected between the input terminal and the first output terminal and having an electrical length of ¼ wavelength at a center frequency of a predetermined frequency band;
A second transmission line connected between the input terminal and the second output terminal and having an electrical length of 3/4 wavelength at the center frequency;
A third transmission line connected between the first output terminal and the second output terminal and having an electrical length of ½ wavelength at the center frequency;
The characteristic impedances of the first transmission line and the second transmission line are made equal to each other, and the characteristic impedance of the third transmission line is made smaller than the characteristic impedances of the first transmission line and the second transmission line. A reverse phase distribution circuit characterized by that. 2. The antiphase distribution circuit according to claim 1, wherein the characteristic impedance of the third transmission line is set to a value approximately half of the characteristic impedance of the first transmission line and the second transmission line. A dielectric substrate;
A strip conductor formed on the surface of the dielectric substrate;
A ground conductor formed on the back surface of the dielectric substrate,
The first transmission line, the second transmission line, and the third transmission line are each constituted by a microstrip line composed of the strip conductor and the ground conductor,
The reverse phase distribution circuit according to claim 1, wherein the input terminal, the first output terminal, and the second output terminal are disposed at an end portion of the dielectric substrate. A dielectric substrate;
A strip conductor formed inside the dielectric substrate;
A grounding conductor formed on the front and back surfaces of the dielectric substrate,
The first transmission line, the second transmission line, and the third transmission line are each constituted by a strip line composed of the strip conductor and the ground conductor,
The reverse phase distribution circuit according to claim 1, wherein the input terminal, the first output terminal, and the second output terminal are disposed at an end portion of the dielectric substrate.

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