JPH0613806A - Power amplifier - Google Patents

Abstract

PURPOSE:To reduce the interference caused by the adverse influence to the performance of a power amplifier by connecting the reactance elements between each line having a certain length and a ground point respectively. CONSTITUTION:A microstrip connection line 5 has length L and is connected to an output matching circuit 3. One of both ends of the line 5 is grounded with the other end also grounded via a connection line 6 of length L1 and a capacitor C11. Meanwhile one of both ends of a microstrip connection line 7 is grounded with the other end also grounded via a connection line 8 of length L2 and a capacitor C12 respectively. The reactance elements are connected between both lines 6 and 8 and the ground point respectively. Then the lengths of both lines 6 and 8 are set at L1 and L2 so that a desired changing range of impedance is attained by a secondary higher harmonic matching circuit 20. Thus both capacitors C11 and C12 are varied and the highly efficient points are obtained. Then the adverse influence can be reduced to the performance of a power amplifier.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave semiconductor power amplifier used for satellite communication, terrestrial microwave communication and the like, which is highly efficient, that is, a power amplifier which reduces power consumption.

[0002]

2. Description of the Related Art A method of utilizing harmonics of a signal wave for the purpose of improving the efficiency of a power amplifier is known. That is,
At the output end of the amplification element, the output voltage waveform is shaped by adding a harmonic matching impedance that is short-circuited for even-order harmonics and open for odd-order harmonics. The power consumption is reduced by avoiding overlapping with. That is, in order to realize class F operation, current flows when the output voltage of the semiconductor amplification element such as FET is 0, while current flows when the output voltage of the semiconductor amplification element such as FET is generated. By reducing the power consumption to 0, the power consumption is reduced.

By the way, with respect to the harmonics generated at the output end of the amplification element, only the impedance for the harmonics of each order is affected, and the impedances of other frequencies including the fundamental wave are not affected at all. If a matching circuit dedicated to each harmonic can be configured, an output matching circuit that achieves the above object can be configured by combining a plurality of matching circuits for each harmonic.
However, in general, when the impedance for a certain frequency is changed in the matching circuit, the impedance for other frequencies also changes, so in practice it is difficult to realize the above matching impedance for all harmonics. is there.

Therefore, only the second harmonic having a large influence on power consumption is targeted and its output impedance is optimized to expect a sufficient reduction effect of power consumption.

[0005]

From this point of view,
The applicant of the present application, in Japanese Patent Application No. 3-295,133,
We have proposed a power amplifier that adds a matching impedance targeting only the second harmonic. The power amplifier proposed here is shown in FIG.

In FIG. 7, an amplifying element 1, an input matching circuit 2, an output matching circuit 3, and a second harmonic matching circuit 20.
a, a coupling capacitor C3, a DC cutting coupling capacitor C5, and a bias capacitor C
4, C6 and harmonic choke coils RFC1, RFC2
And are provided. In addition, the second harmonic matching circuit 20
The reference character a has a length of about ⅛ of the fundamental wave, the central portion thereof is grounded, and is coupled to the output matching circuit 3 by the coupled line 5a.
, Connection lines 6a and 8a, and capacitors C11 and C12
It consists of and.

FIG. 8 is a Smith chart for explaining the function of the second-order harmonic matching circuit 20a in the power amplifier shown in FIG. 7, in which the signal wave and the second-order harmonic wave can be matched independently of each other. It shows the situation. Signal frequency is 2.5
GHz, the second harmonic matching circuit 20a is coupled to an appropriate line, the length L0 of the coupling line 5a is set to 45 degrees in terms of the electrical length of the signal wave, and the length L of each of the connection lines 6a and 8a is L.
The Smith chart shown in FIG. 8 can be obtained by setting both 1 and L2 to 70 degrees in electrical length of the signal wave, setting the value of the capacitor C12 to about 5 pF and changing the value of the capacitor C11 from 1 pF to 21 pF.

As described above, when the values of the capacitors C11 and C12 are changed when the lengths of the connection lines 6a and 8a are appropriate, the amplified signal frequency is maintained while the output impedance with respect to the amplified signal frequency is kept constant. It is possible to independently change the output impedance with respect to the second harmonic of. Therefore, the two capacitors C11,
If the value of C12 is set appropriately, optimization of the output impedance for the second harmonic, that is, reduction of power consumption is achieved.

However, in the power amplifier shown in FIG. 7, since the central portion of the coupled line 5a is grounded, lines on both sides of the ground point having a common ground point interfere with each other, which adversely affects the performance. There's a problem. Further, since the matching circuit of the power amplifier used in the microwave band is generally composed of a distributed constant circuit, its shape has a great influence on the performance, and in the power amplifier shown in FIG. Coupled line 5 over about 1/8 of the length
Since it is combined with a, there is a problem that its arrangement and shape are limited.

An object of the present invention is to provide a harmonic control type power amplifier capable of reducing interference that adversely affects the performance, and to increase the degree of freedom in the arrangement and shape of the output matching circuit. It is an object of the present invention to provide a harmonic control type power amplifier that can be performed.

[0011]

The present invention relates to a power amplifier having a semiconductor amplifier element, an input / output matching circuit, and a second harmonic matching circuit, which is coupled to the output matching circuit and has one end grounded and a signal wave. A first coupled line coupled to the harmonics of
A first connection line having a finite line length connected to the other end of the first coupling line; a first reactance element connected between the first connection line and a ground point; The second line, which is provided at a finite distance from the coupling line, is coupled to the output matching circuit, is grounded at one end, and is coupled to the harmonics of the signal wave.
Coupling line, a second connection line having a finite line length connected to the other end of the second coupling line, and a second reactance connected between the second connection line and the ground point. The element forms the second harmonic matching circuit.

[0012]

According to the present invention, since the first coupling line and the second coupling line have independent grounding points, and the grounding points are provided at a distance, the performance is adversely affected. The interference can be reduced, and the output matching circuit can be divided into two parts, that is, the first coupling line and the second coupling line, so that the output matching circuit can be freely arranged and shaped. Increase.

[0013]

FIG. 1 is a diagram showing an embodiment of the present invention.

In this embodiment, the input matching circuit 2 and
The output matching circuit 3, the amplifying element 1 connected between the input matching circuit 2 and the output matching circuit 3, the second harmonic matching circuit 20, the coupling capacitor C3, and the DC-cut coupling capacitor C5. And the bias capacitor C
4, C6 and harmonic choke coils RFC1, RFC2
And are provided.

The second harmonic matching circuit 20 includes a microstrip coupling line 5, a connecting line 6, and a capacitor C1.
1, a microstrip coupling line 7, and a connecting line 8
And a capacitor C12.

The microstrip coupling line 5 has a length L.
And is coupled to the output matching circuit 3. Further, one end of the microstrip coupled line 5 is grounded, and the other end is grounded via the connection line 6 having a length L1 and the capacitor C11. The microstrip coupling line 7 has a length L, is coupled to the output matching circuit 3, and is connected to the output matching circuit 3 from the end of the microstrip coupling line 5.
Are provided at a distance of a length L3 in the extending direction. Further, one end of the microstrip coupled line 7 is grounded, and the other end is grounded via a connection line 8 having a length L2 and a capacitor C12.

The microstrip coupled line 5 is
The microstrip coupling line 7 is an example of a first coupling line that is coupled to an output matching circuit, has one end grounded, and couples to a harmonic of a signal wave. The microstrip coupling line 7 is located at a finite distance from the first coupling line. Is an example of a second coupling line that is provided as a connection to the output matching circuit, has one end grounded, and couples to a harmonic of a signal wave, and the connection line 6 is connected to the other end of the first coupling line. The connection line 8 is an example of a first connection line having a finite length, and the connection line 8 is connected to the other end of the second coupling line and has a finite length. The capacitor C11 is an example of a connection line, the capacitor C11 is an example of a first reactance element connected between the first connection line and the ground point, and the capacitor C12 is between the second connection line and the ground point. It is an example of the second reactance element connected to.

Next, the operation of the above embodiment will be described.

The signal wave input from the input terminal Ti is converted into an appropriate impedance by the input matching circuit 2 and input to the amplification element 1. The signal wave output from the amplification element 1 is converted into an appropriate impedance again by the output matching circuit 3 and output from the output terminal To of the power amplifier. The output of the amplifying element 1 contains the second harmonic generated by the non-linear characteristic of the amplifying element 1,
This second harmonic is matched by the second harmonic matching circuit 20 independently of the signal wave.

FIG. 2 is a diagram showing how the signal wave and the second harmonic can be matched independently of each other in the above embodiment. FIG. 3 is an explanatory diagram of the second harmonic matching circuit 20 in the above embodiment.

In FIG. 3, the signal frequency is 2.5 GHz.
Then, the second harmonic matching circuit 20 is coupled to an appropriate line, the lengths L of the coupling lines 5 and 7 are both set to 22.5 degrees in terms of the electrical length of the signal wave, and the respective lengths of the connection lines 6 and 8 are set. L
Both 1 and L2 have an electric length of the signal wave of 70 degrees, and the distance L3 between the end of the microstrip coupling line 5 and the end of the microstrip coupling line 7 has an electric length of the signal wave of 90 degrees. The value is about 5 pF, and the value of the capacitor C11 is changed from 1 pF to 21 pF. FIG. 2 shows, on the Smith chart, the input impedance Z1 of the line with respect to the signal wave and the input impedance Z2 of the same line with respect to the second harmonic when the above is performed.

As shown in FIG. 2, as the value of the capacitor C11 changes, the input impedance Z2 (the input impedance of the line with respect to the second-order harmonic) becomes almost one turn along the outer circumference of the Smith chart. While doing
The input impedance Z1 of the line with respect to the signal wave hardly moves. Therefore, if the output matching circuit 3 has a length necessary for coupling with the second harmonic matching coupling lines 5 and 7 at the second harmonic, the output matching circuit 3 outputs a signal. It may be designed only for wave matching. In addition, since the second harmonic matching circuit 20 does not affect the signal wave at all, the second harmonic matching circuit 20 can be freely adjusted.

As described above, when the impedances of the capacitors C11 and C12 provided at one ends of the connection lines 6 and 8 are changed, the impedance of the output matching circuit 3 with respect to the amplified signal frequency is kept constant and the signal frequency is kept constant. The impedance of the output matching circuit 3 with respect to the second harmonic can be changed independently, and if the impedance of the output matching circuit 3 with respect to the second harmonic is appropriate, the power consumption can be reduced. Therefore, high efficiency can be achieved by appropriately selecting the impedances of the capacitors C11 and C12. However, due to the influence of parasitic capacitance and inductance due to the package of the amplifying element 1, the bonding wire, etc., and the variation in the manufacturing of the amplifying element 1, etc.
Since the impedance to be realized by the second harmonic matching circuit 20 at the output connection point is not necessarily a short circuit, it is necessary to experimentally determine the impedance by combining them.

In the above embodiment, it is necessary to predetermine the required impedance change range and the lengths of the connection lines 6 and 8 at the design stage so that the second harmonic matching circuit 20 can be realized. There is. At the time of actual adjustment, the power amplifier is operated under the same conditions as when the power amplifier is used, and the efficiency is measured while changing each value of the capacitors C11 and C12. The value of C12 may actually be used.

As is clear from comparing FIGS. 2 and 8,
Also in the above-described embodiment (FIG. 2), the performance equivalent to the analysis of the proposed power amplifier (FIG. 8) can be obtained. Further, in the above-mentioned embodiment, since the influence of interference etc. can be reduced,
There is an advantage that a result closer to the analysis result can be obtained at the time of manufacturing, and the performance deterioration that occurs in the example shown in FIG. 7 can be prevented.

In the above embodiment, the microstrip coupling lines 5 and 7, the connecting lines 6 and 8 and the capacitor C1.
Second harmonic matching circuit 2 composed of 1 and C12
0 is coupled only to the output matching circuit 3, but this second
The second harmonic matching circuit 20 may be coupled to the output matching circuit 3 and the input matching circuit 2.

FIG. 4 is an explanatory diagram of another embodiment of the present invention.

The second harmonic matching circuit 21 shown in FIG.
Basically, it is the same as the second harmonic matching circuit 20, but the positions of the coupling line, the connecting line, and the capacitor are different from those of the second harmonic matching circuit 20. That is, the group including the coupled line 71 (similar to the coupled line 7), the connection line 81 (similar to the connection line 8), and the capacitor C12 is the coupled line 5, the connection line 6, and the capacitor C.
11 and the output matching circuit 3 are on the opposite side.

FIG. 5 is an explanatory view of still another embodiment of the present invention.

The second harmonic matching circuit 22 is an example in which the bent portion of the output matching circuit 3 is coupled to the coupling line, and the coupling line 72 (similar to the coupling line 7).
This is an example of a case in which the coupling line 5 and the coupling line 5 do not exist on a straight line. In this case, the connection line 82 connected to the coupling line 72
The (line similar to the connection line 8) exists on the same line as the coupling line 72, but the connection line 82 is rotated 90 degrees counterclockwise around the connection point between the coupling line 72 and the connection line 82. You may provide in a position. The portion indicated by the length L is the coupling line 72, and the portion indicated by the length L2 is the connection line 82.

FIG. 6 is an explanatory diagram of another embodiment of the present invention.

The second harmonic matching circuit 23 is an example in which two bent portions of the output matching circuit 3 are coupled to the coupling line, and a coupling line 73 (a line similar to the coupling line 7) is used. This is an example in which the coupling line 51 (a line similar to the coupling line 5) does not exist on the same straight line but exists in the same direction. In this case, the connection line 83 (a line similar to the connection line 8) connected to the connection line 73 exists on the same line as the connection line 73, but the connection line centered on the connection point between the connection line 73 and the connection line 83. The 83 may be provided at a position rotated 90 degrees clockwise. Further, a connection line 61 (a line similar to the connection line 6) connected to the coupling line 51 exists on the same line as the coupling line 51, but the connection line 61 is centered on the connection point between the coupling line 51 and the connection line 61. 9 clockwise
You may provide in the position rotated by 0 degree. The portions indicated by the length L are the coupled lines 51, 73, and the length L1,
The portions indicated by L2 are connection lines 61 and 83.

The capacitor C in each of the above embodiments
Although 11 and C12 are lumped constant capacitors, other reactance elements such as variable capacitors, inductors, and distributed constant elements may be used instead. That is, the connection lines 6, 61, 8, 81, 82, 83
Need only be grounded via a reactance element.

In each of the above embodiments, the coupled line 5,
The lengths of 51, 7, 71, 72, 73 are both L, but these coupled lines 5, 51, 7, 71, 72, 73 are
May have different lengths.

[0035]

According to the present invention, in a power amplifier having a semiconductor amplification element, an input matching circuit, an output matching circuit, and a second harmonic matching circuit, it is possible to reduce interference that adversely affects the performance. Moreover, it is possible to increase the degree of freedom in arrangement and shape of the output matching circuit.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration example of a power amplifier showing an embodiment of the present invention.

FIG. 2 is a second harmonic matching circuit 20 in the above embodiment.
3 is a Smith chart explaining the function of.

FIG. 3 is an explanatory diagram of the above embodiment.

FIG. 4 is an explanatory diagram of another embodiment of the present invention.

FIG. 5 is an explanatory diagram of still another embodiment of the present invention.

FIG. 6 is an explanatory diagram of another embodiment of the present invention.

FIG. 7 shows an example of a proposed power amplifier.

8 is a Smith chart explaining the function of the second-order harmonic matching circuit in the power amplifier shown in FIG. 7. FIG.

[Explanation of symbols]

1 ... Amplifier element, 2 ... Input matching circuit, 3 ... Output matching circuit, 5, 51, 7, 71, 72, 73 ... Microstrip coupling line, 6, 61, 8, 81, 82, 83 ... Connection line, C11 , C12 ... Capacitor, 20, 21, 22, 23 ... Second harmonic matching circuit.

Claims (1)

[Claims] 1. A power amplifier having a semiconductor amplifying element, an input matching circuit, an output matching circuit, and a second harmonic matching circuit, wherein the second harmonic matching circuit is coupled to the output matching circuit, A first coupling line having one end grounded and coupled to a harmonic of a signal wave; provided at a finite distance from the first coupling line, coupled to the output matching circuit, and having one end grounded A second coupling line coupled to a harmonic of a signal wave; a first coupling line connected to the other end of the first coupling line and having a line length of finite length; the second coupling A second connection line connected to the other end of the line and having a finite line length; a first reactance element connected between the first connection line and a ground point; the second Second reactance element connected between the connection line and the ground point When; power, characterized in that one having an amplifier.