JP2001127650A - Communication apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communication apparatus that is hardly affected by an unnecessary electromagnetic onto a balance/unbalance converter. SOLUTION: The communication apparatus has a push-pull circuit 16, balance/unbalance converters 13a, 13b connected to its input and output, and the balance/unbalance converters 13a, 13b are formed to be L-shape. Since the size of the balance/unbalance converters 13a, 13b in its length direction with respect to the sensitivity direction of an unnecessary electromagnetic wave can be decreased, the resonance frequency of the balance/unbalance converters 13a, 13b is shifted toward high frequencies. Thus, the frequency of a interference wave is shifted toward higher frequencies than a substantial objective signal frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication device,
In particular, the present invention relates to a communication device including a push-pull amplifier circuit and a balun converter.

[0002]

2. Description of the Related Art FIG. 8 shows a mobile communication (for example, PHS).
1 shows an electric circuit configuration of a transmission device employed in a base station of FIG. The transmitting device shown in FIG. 1 includes an amplifier circuit 1, bandpass filters 2a and 2b, balun converters 3a and 3b,
Matching circuits 4a-4d, DC cut capacitors 5a-5
c, a push-bull amplifier circuit 6 and an antenna 7.

In this device, a band-pass filter 2
a and 2b constitute an unbalanced circuit with respect to the ground, and the push-bull amplifier 6 includes matching circuits 4a to 4c and DC
Together with the cutting capacitors 5a to 5c, a balanced circuit is formed.

Here, as the baluns 3a and 3b, coaxial cables having a shaft core and an outer conductor and constituting a distributed constant circuit are employed, and the coaxial cables are formed linearly. The balance-unbalance converter 3a includes a matching circuit 4
a, 4b and the band pass filter 2a,
The balun converter 3b is connected between the matching circuits 4c and 4d and the bandpass filter 2b.

[0005]

By the way, as the above-mentioned balanced-unbalanced converters 3a and 3b, linear coaxial cables are adopted, and unnecessary electromagnetic waves (unwanted radiation) are used.
When it receives the signal, it operates as a receiving antenna corresponding to the longitudinal dimension of the coaxial cable.

Therefore, the balanced-unbalanced converters 3a and 3b are affected by interference waves caused by unnecessary electromagnetic waves. Specifically, in the balanced-unbalanced converters 3a and 3b, there is a problem that an interference wave due to an unnecessary electromagnetic wave is superimposed on a signal originally intended to cause an increase in spurious.

[0007] In view of the above, it is an object of the present invention to provide a communication device that is less likely to be affected by unnecessary electromagnetic waves on a balun.

[0008]

In order to achieve the above object, the present invention provides a push-pull amplifier (16) and an input side and an output side of the push-pull amplifier. Balanced-unbalanced converter (13)
a, 13b), wherein the balun converter connected to at least one of the input side and the output side of the push-pull amplifier circuit has an L-shape. I do.

As a result, as a balanced-unbalanced converter,
Since the size in the longitudinal direction with respect to the sensitivity direction of unnecessary electromagnetic waves can be shortened, the resonance frequency can be shifted to a higher frequency side. Therefore, the frequency of the interference wave to the balun converter can be shifted to a higher frequency side than the frequency of the originally intended signal. Therefore, the balanced-to-unbalanced converter can be substantially less affected by unnecessary electromagnetic waves.
Also, there is an advantage that the total length of the circuit when the circuit is mounted can be reduced.

According to the second aspect of the present invention, the push-pull amplifier circuit (16) and the balun converter (13) connected to the input and output sides of the push-pull amplifier circuit.
c, 13d), wherein the balun converter connected to at least one of the input side and the output side of the push-pull amplifier circuit is shaped like a step. . Thereby, the same operation and effect as those described in the first aspect can be obtained.

According to the third aspect of the present invention, the balun converter connected to at least one of the input side and the output side of the push-pull amplifier has a linear portion, and the length of the linear portion is The directional dimension is half the longitudinal dimension of the balun connected to at least one of the input side and the output side of the push-pull amplifier circuit.

As a result, as a balanced-unbalanced converter,
The longitudinal dimension of the portion other than the straight portion is less than half the total length of the balun. Therefore, the balanced / unbalanced converter has a resonance frequency twice or more as compared with the case where a linearly formed balanced / unbalanced converter is employed. Becomes twice or more. Therefore, the balanced-unbalanced converter can be further less affected by unnecessary electromagnetic waves.

Incidentally, the reference numerals in parentheses of the above means are examples showing the correspondence with specific means described in the embodiments described later.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First Embodiment) FIG. 1 shows a first embodiment of a transmitting apparatus of a mobile communication base station to which a balun converter according to the present invention is applied. FIG. 1 shows an electric circuit configuration of the transmission device. The transmitting device includes an amplifier circuit 11, band pass filters 12a and 12b, coaxial balun converters 13a and
3b, matching circuits 14a to 14d, DC cut capacitors 15a to 15c, a push bull amplifier circuit 16, and an antenna 17.

The amplifier circuit 11 amplifies the input high-frequency signal and outputs an amplified signal.
a receives the amplified signal and outputs a filter signal. Here, the bandpass filter 12a forms an unbalanced circuit (unbalanced system) with respect to the ground. In the present embodiment, the input high frequency f is 1.
9 GHz is adopted.

Coaxial balun converter (coaxial balun) 13
a is a coaxial cable (Z _{0 =} 50Ω) having a shaft core (electric conductor) 130a and an outer conductor (electric conductor) 131a, and the total length of the coaxial cable is one of a filter signal (high-frequency signal). It is set to correspond to に wavelength.

Here, the core wire 130a at one end 132 of the coaxial balun converter 13a is an input terminal for inputting a filter signal output from the band-pass filter 12a. Outer conductor 13
1a is grounded.

As a result, the coaxial balun converter 13a
Has a core wire 130a and an outer conductor 131a to form a distributed constant circuit. The core wire 130a of the other end 133 of the coaxial balun converter 13a is connected to the matching circuit 1
The outer conductor 131a of the other end 133 is connected to one terminal of the matching circuit 14b.

The matching circuits 14a and 14b are impedance conversion circuits.
A p-channel field-effect transistor (hereinafter referred to as F
ET) 16a. Matching circuit 14b
The other terminal is connected to the FET 16b of the pushable amplifier circuit 16 via the DC cut capacitor 15b.

The push-bull amplifier circuit 16 includes FETs 16a and 16b connected in series (connected in series) and junction capacitors 16c and 16d. The push bull amplification circuit 16 includes the matching circuits 14a, 1
The push-bull amplification operation is performed according to the filter signal (high-frequency signal) output from 4b.

Here, the push bull amplification circuit 16 includes:
Although not shown in this drawing, FETs 16a, 16b
The power supply for driving is connected. The junction capacitor 16c is connected between the gates of both the FET 16a and the FET 16b.
It is connected between the drains of both the FETs 16a and 16b, and the sources of both the FETs 16a and 16b are grounded.

The matching circuits 14c and 14d
Similar to a and 14b, it is an impedance conversion circuit.
One terminal of the matching circuit 14c is connected to the FET of the pushable amplifier 16 via the DC cut capacitor 15c.
One terminal of the matching circuit 14d is connected to the drain of the FET 16b of the pushable amplifier 16 via the DC cut capacitor 15d.

Here, as shown in FIG. 1, the push-bull amplifier 16 constitutes a balanced circuit (balanced system) together with the matching circuits 14a to 14d and the DC cut capacitors 15a to 15c.

The coaxial balun converter 13b is a coaxial cable having a shaft core 130b and an outer conductor 131b, substantially in the same manner as the coaxial balun converter 13a. 1/4 of filter signal
Set to wavelength.

Here, the core wire 130b at one end 134 of the coaxial balun converter 13b is an input terminal for inputting a signal output from the matching circuit 14c, and the outer conductor 131b at one end 134 is , Input terminals for inputting the signal output from the matching circuit 14d.

The outer conductor 131b at the other end 135 of the coaxial balun 13b is grounded, and the core 130b at the other end 135 is connected to one terminal of the bandpass filter 12b. As a result, the coaxial balun converter 13b has a core 130b and the outer conductor 131b to form a distributed constant circuit.

The band-pass filter 12b forms an unbalanced circuit with respect to the ground, and has matching circuits 14c, 1b.
It receives the signal from 4d and outputs the signal to antenna 17.

Next, the operation of the transmitting apparatus according to the present embodiment will be described with reference to FIG.

First, the amplifier circuit 11 linearly amplifies a high-frequency signal and outputs an amplified signal.
2a receives the amplified signal and converts the filtered signal into the axis 130a of the coaxial balun converter 13a, the matching circuit 14a and the D
The signal is output to the push-bull amplifier circuit 16 through the C-cut capacitor 15a.

Here, the FE of the push-bull amplifier 16
T16a is driven by the negative amplitude portion of the filter signal. Therefore, the FET 16a allows a current to flow from the antenna 17 to the ground through the bandpass filter 12b, the axis 130b of the coaxial balun converter 13b, the matching circuit 14c, and the DC cut capacitor 15c.

In the outer conductor 131a of the coaxial balun converter 13a, a signal having a polarity opposite to that of the filter signal (hereinafter referred to as a reverse polarity signal) is generated based on the electromagnetic induction effect of the filter signal.

Then, the FE of the push bull amplification circuit 16
T16b is driven by the negative amplitude portion of the reverse polarity signal. Thereby, the FET 16b is connected to the outer conductor 130b of the coaxial balun converter 13b, the matching circuit 14d and the D
A current flows to the ground through the C-cut capacitor 15d.

However, since the filter signal and the opposite polarity signal have opposite polarities, the FET 16a is driven alternately with the FET 16b.

Thus, a current having a polarity opposite to that of the current (hereinafter, referred to as “coaxial balun converter 13 b”) is applied to the shaft core 130 b of the coaxial balun converter 13 b by the electromagnetic induction effect of the current flowing through the outer conductor 130 b of the coaxial balun converter 13 b. Reverse current) flows.

Therefore, a current due to the driving of the FET 16a flows through the axis 130b of the coaxial balun converter 13b, and the above-mentioned reverse polarity current flows. That is, the shaft core 130b of the coaxial balance-unbalance converter 13b combines the current driven by the FET 16a with the reverse polarity current and outputs the combined signal as an amplified signal of the filter signal.

Therefore, the amplified signal of the filter signal is output from the axis 130b of the coaxial balun converter 13b to the antenna 17 through the band pass filter 12b.

Hereinafter, an example in which electromagnetic waves in the same frequency band as the filter signal are radiated from the outside (from other sources) in the transmitting apparatus of the present embodiment will be described with reference to FIGS.

First, the coaxial balun converter 3 shown in FIG.
An example in which a coaxial cable formed in a straight line is adopted as a will be described. Here, the entire length of the coaxial cable as the coaxial balun converter 3a is set to １ ／ wavelength.

For this reason, when an electromagnetic wave in the same frequency band as the filter signal is radiated from the outside, the coaxial balun converter 3a operates as a receiving antenna over the entire length of the coaxial balun converter 3a. Figure 2 shows this situation.
Shown in Reference numeral 21 in FIG. 2 indicates a radiation source of another peripheral circuit, 22
Is a model of a line of another circuit as an antenna.

Therefore, the electromagnetic wave radiated from the antenna 22 is received by the coaxial balun 3a.
Therefore, if there is a signal source that resonates with the coaxial balun converter 3a in another peripheral circuit, the coaxial balun converter 3a becomes a receiving antenna and receives a signal from the peripheral circuit as an interference wave. become.

In particular, if there is a ground pattern or a metal case on the printed circuit board around the coaxial balun converter 3a, the coaxial balun converter 3a will
It operates as a quarter-wavelength monopole antenna and easily picks up signals in the frequency band operated as the coaxial balun converter 3a.

As a result, an electromagnetic wave from another peripheral circuit is superimposed on the coaxial balun converter 3a as an interference wave, which causes an increase in spurious, an increase in adjacent channel leakage power, generation of noise or push. Oscillation occurs in the pull circuit 6 (see FIG. 8).

On the other hand, in the present embodiment, an L-shaped (orthogonal) bent coaxial cable is employed as the coaxial balun converter 13a. By doing so, the apparent total length of the coaxial balun converter 13a in the sensitivity direction of the electromagnetic wave can be shortened.

In the present embodiment, however, the length of the coaxial balun converter 13a is reduced to 1/4 of the total length of 1/4 wavelength.
It is bent so as to be orthogonal at a length of eight wavelengths. Thus, the resonance frequency can be shifted to a double high frequency range.

Therefore, the frequency of the interference wave due to the unnecessary electromagnetic wave can be shifted (shifted) to a high frequency region which is twice as high as that when the coaxial balun 3a formed linearly is employed. In the frequency band operated as the coaxial balun converter 13a, the influence of interference waves as electromagnetic waves from other peripheral circuits can be substantially reduced.

However, the frequency of the interference wave can be shifted to twice as high as that of the case where the coaxial balun 3a formed linearly is adopted. Easier to do.

Here, since the function of the coaxial balun converter 13a itself is determined by the size in the longitudinal direction and the characteristic impedance, there is no problem even if it is bent orthogonally as described above.

Therefore, the coaxial balun converter 13a functions as the coaxial balun converter 13a itself while suppressing spurious, reducing the increase in adjacent channel leakage power, suppressing noise, and Oscillation of the push-pull circuit 16 can be prevented.

The coaxial balun converter 13b has a total length of 1/4 as in the case of the coaxial balun converter 13a.
Since it is bent so as to be orthogonal to the length of 波長 wavelength so as to be half of the wavelength, the same effect as the coaxial balun converter 3a can be obtained.

Further, in the first embodiment, both the coaxial baluns 13a and 13b are bent so as to be orthogonal to each other at a length of 1/8 wavelength so as to be half of the total length of 1/4 wavelength. Although the example has been described, the present invention is not limited to this, and at least one of the coaxial balun converters 13a and 13b has a total length of 1
It may be bent so as to be orthogonal to the length of 波長 wavelength so as to be half of ／ wavelength.

(Second Embodiment) In the first embodiment,
Both of the coaxial balun converters 13a and 13b have a total length of 1 /
The example in which the optical fiber is bent so as to be orthogonal to the length of １ ／ wavelength so as to be half of the four wavelengths has been described.
A coaxial cable formed in a step shape (key shape) may be employed. FIG. 3 shows the configuration in this case.

In this embodiment, the coaxial balun converter 1
3c is employed instead of the coaxial balun converter 13a, and the coaxial balun converter 13d is employed instead of the coaxial balun converter 13b. The coaxial balun converters 13c and 13d employ coaxial cables formed in a step shape. Coaxial balun converter 13c, 1
The dimension (m in FIG. 3) of the straight portion 3d is half of the total length. The coaxial balun converters 13c, 13d
Are the shaft cores 130c and 130d and the outer conductors 131c and 1c.
31d.

FIG. 3 (a) shows the degree of mutual coupling when two coaxial baluns are arranged in parallel as a worst case in which a plurality of coaxial baluns are arranged.
This will be described with reference to FIG.

First, a linear coaxial cable, an L-shaped coaxial cable, and a stepped coaxial cable are adopted as the coaxial balun converters, and the degree of mutual coupling between the respective coaxial balun converters. Was measured, the following results were obtained.

That is, as shown in FIG. 3 (a), if the mutual coupling when linear coaxial cables are arranged in parallel is set to 0 dB as shown in FIG. 4, L shown in FIG. 3 (b) is obtained.
As shown in FIG. 4, the degree of mutual coupling when the U-shaped coaxial cables were arranged in parallel was -8 dB. FIG.
The degree of mutual coupling when the key-shaped coaxial cables shown in (b) were arranged in parallel was -9 dB as shown in FIG.

As described above, when the L-shaped coaxial cables are arranged in parallel, the degree of mutual coupling is smaller than when the linear coaxial cables are arranged in parallel, and the key-shaped coaxial cables are arranged in parallel. In this case, the degree of mutual coupling is smaller than when the L-shaped coaxial cables are arranged in parallel.

Therefore, when the key-shaped coaxial cables are arranged in parallel, the influence of electromagnetic waves as interference waves from other peripheral circuits is substantially reduced as compared with the case where the L-shaped coaxial cables are arranged in parallel. Can be reduced.

(Third Embodiment) In the second embodiment,
Although the example in which the coaxial cable is used as the balanced-unbalanced converter has been described, the present invention is not limited to this, and an example in which a microstrip line is used on a printed circuit board will be described. The configuration in this case will be described with reference to FIG.

In this embodiment, the coaxial balun converter 1 shown in FIG. 3 is used as the balun converter 30 shown in FIG.
3a (balanced / unbalanced converters 13b, 13c, 13d). As the balanced-unbalanced converter 30,
It comprises a printed circuit board 31 and L-shaped microstrip lines 32 and 33.

Here, the micro strip line 32
Are mounted on the printed circuit board 31, and the microstrip lines 33 are arranged so as to face the microstrip lines 32 with the printed circuit board 31 interposed therebetween. The microstrip lines 32 and 33 are set so that the total length is ４ wavelength, and are bent so as to be orthogonal to the length of １ ／ wavelength so as to be half of the total length. Embodiment) In the third embodiment, the example in which the microstrip lines 32 and 33 are formed in an L-shape has been described. However, the present invention is not limited to this, and the microstrip lines 32 and 33 may be formed in a key shape as shown in FIG. It may be.

The microstrip lines 32, 3
3, the total length is set to be 1/4 wavelength,
The dimension (m in FIG. 3) of the linear portion of the microstrip lines 32 and 33 is half of the entire length.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram showing a transmission device according to a first embodiment of the present invention.

FIG. 2 is a diagram for explaining an effect of the balun converter shown in FIG. 1;

FIG. 3 is an electric circuit diagram showing a transmission device according to a second embodiment of the present invention.

4 (a) to 4 (c) are perspective views showing the shape of a balanced-unbalanced converter.

FIG. 5 is a table showing measurement results of mutual coupling degrees when baluns are arranged in parallel.

FIG. 6A is a perspective view showing a balanced-unbalanced converter according to a third embodiment of the present invention, and FIG. 6B is a sectional view taken along line AA in FIG.

FIG. 7A is a perspective view showing a balanced-unbalanced converter according to a fourth embodiment of the present invention, and FIG. 7B is a sectional view taken along line BB in FIG.

FIG. 8 is an electric circuit diagram showing a transmission device of a conventional base station.

[Explanation of symbols]

16 ... push-pull circuit, 13a-13d, 30 ... balanced-unbalanced converter.

 ──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Tatsuo Kono 1-1-1, Showa-cho, Kariya-shi, Aichi Pref. F term (reference) 5J091 AA01 AA17 CA27 CA51 FA16 HA09 HA29 HA32 KA00 KA29 KA44 KA68 SA14 TA01 UW08 5K046 AA09 BA00 BB05 CC04 EE22 EE23 5K052 AA02 AA11 BB07 DD04 EE01 FF06 GG11 GG06 H05 GG11 GG06 LL15

Claims (3)

[Claims] 1. A communication device comprising a push-pull amplifier circuit (16) and balun converters (13a, 13b, 30) connected to an input side and an output side of the push-pull amplifier circuit, The balun converter connected to at least one of an input side and an output side of the push-pull amplifier circuit,
A communication device having an L-shape. 2. A communication device comprising a push-pull amplifier circuit (16) and balun converters (13c, 13d, 30) connected to an input side and an output side of the push-pull amplifier circuit, The balun converter connected to at least one of an input side and an output side of the push-pull amplifier circuit,
A balanced-unbalanced converter characterized by being formed in a step shape. 3. The balanced-unbalanced converter connected to at least one of an input side and an output side of the push-pull amplifier circuit has a linear portion, and the linear portion has a longitudinal dimension of: 3. The communication device according to claim 1, wherein a length of the balun converter connected to at least one of an input side and an output side of the push-pull amplifier circuit is half a longitudinal dimension. 4.