JP2002344255A - High-frequency power amplifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high-frequency power amplifier that can improve efficiency over a wide-range output power by giving a plurality of appropriate matching conditions. SOLUTION: This high-frequency power amplifier has a high-frequency matching circuit 18 using an active element 20 comprising a diode switch and the like, thus arbitrarily imparting the resonance frequency of the high-frequency matching circuit 18, according to the state transition of the active element 20, and hence providing the plurality of satisfactory matching conditions for improving efficiency over a wide-range output level.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency power amplifier provided with a field-effect transistor, a bipolar transistor, and the like, and more particularly to a high-efficiency amplifier used for mobile communication, microwave band communication equipment, and the like.

[0002]

2. Description of the Related Art FIG.
FIG. 1 is a schematic block diagram showing an example of a conventional high-frequency power amplifier described in Japanese Unexamined Patent Application Publication No. H11-157,004. A high-frequency power amplifier 1 for amplifying a high-frequency signal shown in FIG. 12 includes an amplifying element 2 for amplifying a high-frequency signal composed of an active element such as a field-effect transistor or a bipolar transistor, and a high-frequency signal input to a signal input terminal 3. An input matching circuit 4 performs impedance matching on the input signal, and an output matching circuit 5 performs impedance matching on a high-frequency signal output from the output terminal of the amplifier 2.

FIG. 13 is a circuit diagram showing a specific example of the high-frequency power amplifier shown in FIG. 13, the same reference numerals as those in FIG. 12 indicate that they are the same as or correspond to those shown in FIG.

As shown in FIG. 1, a field-effect transistor (hereinafter referred to as "FET") 2 having a source grounded is supplied with a drain bias voltage from a drain bias line 8, and a gate receives a high-frequency signal for amplification. Is done.
A bypass capacitor 7 is added in parallel to the drain bias line 8. The third harmonic matching circuit 6 adjusts the line length of the drain bias line 8 so as to perform impedance matching of the third harmonic, and to sufficiently increase the impedance of the third harmonic at the output terminal of the FET 2. With a short-circuit load. Further, the second harmonic matching circuit 9 includes the FET 2
By operating the impedance of the second harmonic at the output end of the open circuit with a sufficiently large open load, it operates as an inverse class F power amplifier. The signal amplified by the FET 2 and subjected to the harmonic processing by the third harmonic matching circuit 6 and the second harmonic matching circuit 9 is output from the signal output terminal 11 via the fundamental wave matching circuit 10.

[0005]

As described above, in the conventional high-frequency power amplifier, a fundamental wave matching circuit and a harmonic matching circuit are formed using passive elements such as resistors and capacitors and microstrip lines. . In other words, FET
When only a single matching condition is given to 2 and a plurality of conditions are desired to be given, it is necessary to give an optimum trade-off point between the characteristics to be traded off. Therefore, in such a case, there is a problem that the required performance as a high-frequency power amplifier is not always provided.

FIG. 14 is a diagram showing input / output characteristics of a conventional high-frequency power amplifier. The relationship 12 of the output power to the input power and the relationship 13 of the power conversion efficiency are shown. Conventionally, applications such as mobile communication devices require higher efficiency at the maximum output.As can be seen from the figure, in a power amplifier using an output matching circuit composed of passive elements, Conversion efficiency was also reduced.

FIG. 15 is a block diagram showing a front end portion of the mobile communication device. Now, with the adoption of a plurality of communication systems and an increase in frequency bands used for transmission and reception in the mobile communication device, the number of paths 15a, 15b, and 15c from the power amplifier 1 to the antenna 14 increases.
A loss difference occurs between 5a, 15b, and 15c, and the loss increases due to the influence of the filters 16a, 16b, and 16c. The switching of the paths 15a, 15b, 15c is performed by the switch 17. Also,
The control of the switch 17 is performed by the control unit 41 of the mobile communication device.
Done by

In order to compensate for such a loss difference between the paths 15a, 15b and 15c, switching of output power from the power amplifier 1 is currently required. Then, it is required as a precondition that the maximum output power be increased while maintaining the current electrical characteristics such as distortion characteristics. However, as shown in FIG. 14, increasing the maximum output power has a problem that the efficiency at the current output power is reduced under the conventional single matching condition.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and a high frequency power amplifier capable of improving the efficiency in a wide range of output power by providing a plurality of good matching conditions. The purpose is to get.

[0010]

A high-frequency power amplifier according to the present invention is connected to a first active element for amplifying a high-frequency signal and an output terminal of the first active element. A high-frequency power amplifier having an output matching circuit that performs impedance matching with respect to a high-frequency signal, the output matching circuit can perform impedance matching with respect to a fundamental wave that performs impedance matching with respect to a fundamental wave and impedance matching with respect to harmonics other than the fundamental wave. And a harmonic matching circuit having a second active element and capable of switching the resonance frequency.

In the harmonic matching circuit, the resonance frequency is switched by controlling the second active element by an external control signal.

Further, the second active element is a diode.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a circuit diagram showing a high-frequency power amplifier 100 according to an embodiment of the present invention. In FIG. 1, the same reference numerals as those in FIG. 13 indicate that they are the same as or correspond to those shown in FIG.

In the figure, 18 is a harmonic matching circuit using a diode switch, 20 is a PIN diode, 24, 25
Is a capacitor, 26 is a bias circuit, 27 is a bias power supply terminal, 28 is an inductor, and 29 is a resistor. The inductor 28 and the resistor 29 are connected in series to the bias circuit 26 so that the impedance after the terminal 27 is difficult to see.
Is added.

FIG. 2 is a block diagram showing a front end portion of a mobile communication terminal provided with the high-frequency power amplifier 100 according to the present embodiment. In FIG. 2, FIG.
The same reference numerals indicate that they are the same as or correspond to those shown in FIG. A in the figure is a control signal provided to the high-frequency power amplifier 100 from the control unit 41 of the mobile communication device.

Returning to FIG. 1, the state of the diode 20 is changed by the power supplied from the bias circuit 26 to the diode 20 based on the control signal A supplied from the control unit 41 to the bias power supply terminal 27, and the diode 20 is turned on.
In the state, for example, it works as a resistance component 22 of about 0.5Ω, and in the OFF state, it works as a capacitance component of about 0.6 pF, for example.

FIG. 3 shows the harmonic matching circuit 18 shown in FIG.
FIG. As shown in FIG. 3, the harmonic matching circuit 18 has a parallel variable capacitance circuit 39 added to a signal line 37. The variable capacitance circuit 39 includes two capacitors 24 (capacity value α) and 25 (capacity value α). Value β), PIN diode 20 and bias circuit 2 for diode 20
6.

In such a parallel variable capacitance circuit 39, when the diode 20 is in the ON state, the diode 20 functions as the resistance component 22 as in the equivalent circuit shown in FIG. Equation (1) below is obtained. C1 = α + β (1)

On the other hand, when the diode 20 is in the OFF state, the diode 20 functions as a capacitance component 23 (capacity value γ) as shown in an equivalent circuit shown in FIG. become that way. C2 = {α × (β + γ) + β × γ} / (β + γ) (2)

FIG. 4 is a diagram showing an equivalent circuit when the diode 20 is in the ON state in the parallel variable capacitance circuit 39 shown in FIG. 3, and FIG. 5 is a diagram showing the case where the diode 20 is in the OFF state. FIG. 3 is a diagram showing an equivalent circuit in FIG.

FIG. 6 shows a modification 19 of the harmonic matching circuit according to the present invention using a plurality of PIN diodes.
6, the same reference numerals as those in FIG. 1 indicate that they are the same as or correspond to those shown in FIG. As shown, any number of diodes 20a, 20b,.
Capacitors 21a, 21b... And bias circuit 26
a, 26b... By utilizing this, an arbitrary capacitance value can be selected by a combination of the ON / OFF state transition and the capacitor 21.

FIG. 7 shows another modification 30 of the harmonic matching circuit according to the present invention. 7, the same reference numerals as those in FIG. 3 indicate that they are the same as or correspond to those shown in FIG. As shown in the figure, in the harmonic matching circuit 30, a series capacitance variable circuit 40 is added to the signal line 37, and as shown in FIG. Is the capacitance value of the following equation (3). C3 = (α × β) / (α + β) (3) On the other hand, as shown in FIG. 9, the capacitance value C4 in the OFF state
Is as shown in the following equation (4). C4 = α × (β + γ) / (α + β + γ) (4)

FIG. 8 is a diagram showing an equivalent circuit when the diode 20 is in the ON state in the parallel variable capacitance circuit 40 shown in FIG. 7, and FIG. 9 is a diagram showing the case where the diode 20 is in the OFF state. FIG. 3 is a diagram showing an equivalent circuit in FIG.

As described above, according to the present invention, since the harmonic matching circuit using the active element such as the diode switch is provided, the resonance frequency of the harmonic matching circuit can be arbitrarily adjusted by the state transition of the active element. Can be.

In the conventional high-frequency power amplifier shown in FIG.
The impedance of the second harmonic at the two output terminals is in an open load having a sufficiently large impedance. At this time, the capacitance value of the capacitor 38 connected to the second harmonic matching circuit 9 is determined based on the length of the signal line 37 and the frequency of the second harmonic.
In the vicinity of MHz, a capacitor of about 3 pF is added. At this time, the impedance of the fundamental wave obtained by optimizing the efficiency, the gain, the distortion, and the like is 33 shown in FIG.

On the other hand, by using the harmonic matching circuit 18 in the present embodiment, the capacitance of the parallel-type variable capacitance circuit 39 is reduced to about 3 pF when the diode 20 is in the OFF state and to 7 pF in the ON state.
The capacitances of the capacitors 24 and 25 are determined so as to be about pF. As a result, when the diode 20 is changed from the OFF state to the ON state, reference numerals 33 to 3 in FIG.
As shown by the movement to 4, the impedance of the fundamental wave at the FET end can be moved to the lower impedance.

As the matching condition of the fundamental wave moves to the lower impedance, a gain match is achieved, and the maximum output power can be increased while maintaining the distortion. However,
The harmonic matching circuit 18 functions as a stub of the second harmonic when the diode 20 is in the OFF state, but the resonance frequency deviates from the band of the second harmonic when the diode 20 is in the ON state. It loses its role as a wave matching circuit. That is, in the ON state, the maximum output power can be increased, but the spurious level of the second harmonic increases.

FIG. 11 shows the input / output characteristics of the high-frequency power amplifier shown in FIG. As shown in this figure, the range of high efficiency is widened.

According to the present invention, a power amplifier capable of switching the maximum output power is realized by using a harmonic matching circuit having an active element instead of a second harmonic matching circuit including a conventional passive element. Yes, so the range of high efficiency is widened. In other words, by having a plurality of good matching conditions, it is possible to increase the efficiency over a wide range of output levels.

The spurious level of the second harmonic is
When the power is switched (when the diode 20 is in the ON state), the power is deteriorated. However, in general, since a filter is inserted in the signal path of the mobile communication device, it is expected that the allowable amount of the spurious level will increase, and the degradation of the spurious level does not actually pose a problem.

[0031]

The high-frequency power amplifier according to the present invention has a first active element for amplifying a high-frequency signal and a high-frequency power amplifier connected to an output terminal of the first active element for receiving a high-frequency signal output from the output terminal. In a high-frequency power amplifier including an output matching circuit that performs impedance matching, the output matching circuit can perform impedance matching with respect to a harmonic other than the fundamental wave, and a fundamental wave matching circuit that performs impedance matching with respect to the fundamental wave. Since there is provided a harmonic matching circuit having a second active element and capable of switching the resonance frequency, it is possible to provide a plurality of favorable matching conditions, thereby improving the efficiency in a wide range of output power. Becomes possible.

In addition, since the harmonic matching circuit switches the resonance frequency by controlling the second active element by an external control signal, the matching condition can be easily switched.

Also, since the second active element is a diode, it is possible to manufacture a harmonic matching circuit at low cost.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram showing a high-frequency power amplifier according to an embodiment of the present invention.

FIG. 2 is a block diagram of a front end unit of a mobile communication terminal including a high-frequency power amplifier according to an embodiment of the present invention.

FIG. 3 is a diagram illustrating an example of a harmonic matching circuit according to the embodiment of the present invention.

FIG. 4 shows a configuration of the parallel variable capacitance circuit 39 shown in FIG.
FIG. 4 is a diagram illustrating an equivalent circuit when a diode is in an ON state.

FIG. 5 shows a configuration of the parallel variable capacitance circuit 39 shown in FIG.
FIG. 3 is a diagram illustrating an equivalent circuit when a diode is in an OFF state.

FIG. 6 is a diagram showing a modification of the harmonic matching circuit according to the embodiment of the present invention.

FIG. 7 is a diagram illustrating an example of a harmonic matching circuit according to an embodiment of the present invention.

8 is a circuit diagram of the series variable capacitance circuit 40 shown in FIG.
FIG. 4 is a diagram illustrating an equivalent circuit when a diode is in an ON state.

FIG. 9 shows a configuration of the series-type variable capacitance circuit 40 of FIG.
FIG. 4 is a diagram illustrating an equivalent circuit when a diode is in an ON state.

10 is a diagram showing a transition of the impedance of the fundamental wave when the maximum output power is switched using the high-frequency power amplifier shown in FIG. 1;

11 is a diagram illustrating input / output characteristics of the high-frequency power amplifier capable of switching maximum power illustrated in FIG. 1;

FIG. 12 is a schematic block diagram showing an example of a conventional high-frequency power amplifier.

13 is a diagram showing a specific example of a circuit of the high-frequency power amplifier shown in FIG.

FIG. 14 is a diagram showing input / output characteristics of the high-frequency power amplifier shown in FIG.

FIG. 15 is a block diagram of a front end unit of the mobile communication terminal.

[Description of Signs] 1 High-frequency power amplifier, 2 Amplifying element (first active element), 3 Signal input terminal, 4 Input matching circuit, 5
Output matching circuit, 6 Third harmonic matching circuit, 7, 7
a, 7b capacitor, 8 drain bias line,
9 second harmonic matching circuit, 10 fundamental matching circuit,
REFERENCE SIGNS LIST 11 signal output terminal, 12 relation of output power line to input power, 13 relation of power added efficiency to input power, 14 antenna, 15 a, 15 b, 15 c path, 16 a, 16 b, 16 c filter, 17 signal line switch, 18, 19 , 30 harmonic matching circuit, 20, 20a, 20b PIN diode (second
, 23, 24, 25, 38 Capacitor, 22, 29, 29a, 29b Resistor, 26
Bias circuit, 27, 27a, 27b bias power supply terminal, 28, 28a, 28b inductor, 31 connection terminal, 33 impedance of fundamental wave at normal output, 3
4 Impedance of fundamental wave at high output, 35 drain bias power supply terminal, 36, 37 signal line, 39
Parallel capacity variable circuit, 40 Series capacity variable circuit, 4
1 control part, 100 high frequency power amplifier.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Akira Ota 2-3-2 Marunouchi, Chiyoda-ku, Tokyo F-term (reference) 5J067 AA01 AA04 AA41 CA36 CA75 FA20 HA02 HA09 HA19 HA25 HA29 HA33 HA38 KA00 KA12 KA29 KA41 KA68 KS11 LS01 SA13 TA01 TA02 TA05 5J092 AA01 AA04 AA41 CA36 CA75 FA20 HA02 HA09 HA19 HA25 HA29 HA33 HA38 KA00 KA12 KA29 KA41 KA68 SA13 TA01 TA02 TA05

Claims (3)

[Claims] 1. A first active element for amplifying a high-frequency signal, and an output matching circuit connected to an output terminal of the first active element and performing impedance matching on a high-frequency signal output from the output terminal. The output matching circuit includes a fundamental matching circuit that performs impedance matching with respect to a fundamental wave, an impedance matching with respect to harmonics other than the fundamental wave, and a second active element. A high frequency power amplifier comprising: a harmonic matching circuit capable of switching frequencies. 2. The high-frequency power amplifier according to claim 1, wherein the harmonic matching circuit switches the resonance frequency by controlling the second active element by an external control signal. 3. The high-frequency power amplifier according to claim 1, wherein the second active element is a diode.