JP5672076B2 - Power amplifier, power amplifier control method, and power amplifier control program - Google Patents

Description

  The present invention relates to a power amplifier, a power amplifier control method, and a power amplifier control program suitable for use in a high output power amplifier used in a television transmitter for digital broadcasting.

  A high output power amplifier used in a television transmitter for digital broadcasting must satisfy a desired characteristic at a specified output in all UHF (Ultra High Frequency) frequency bands. In particular, it is difficult to make the gain, efficiency, and back-off of the final stage amplifier, which greatly affects the characteristics of the entire power amplifier, constant in the entire UHF frequency band, resulting in frequency characteristics.

  FIG. 11 is a block diagram showing a configuration of a high-output power amplifier 50 used in a related digital broadcast television transmitter. As shown in FIG. 11, the power amplifier 50 used in the digital broadcast television transmitter is configured by connecting a drive stage amplifier 62 and a final stage amplifier 63 in cascade.

  In FIG. 11, the input terminal 60 is connected to the input terminal of the drive stage amplifier 62 via the variable attenuator 61. The drive stage amplifier 62 is composed of an FET (Field Effect Transistor). The output terminal of the drive stage amplifier 62 is connected to the input terminal of the final stage amplifier 63. The output terminal of the final stage amplifier 63 is connected to the output terminal 64.

  The variable attenuator 61 controls the gain of the signal from the input terminal 60 based on the control signal from the variable attenuator control circuit 83. The drive stage amplifier 62 amplifies the transmission signal so that the final stage amplifier 63 can be sufficiently excited. The final stage amplifier 63 power-amplifies the transmission signal and outputs it from the output terminal 64.

  A directional coupler 74 is provided between the final stage amplifier 63 and the output terminal 64, and a part of the output signal of the final stage amplifier 63 is acquired by the directional coupler 74. Part of the output signal acquired by the directional coupler 74 is supplied to the level detector 75, and the output level of the final stage amplifier 63 is detected by the level detector 75.

  A directional coupler 77 is provided between the variable attenuator 61 and the drive stage amplifier 62, and a part of the input signal of the drive stage amplifier 62 is acquired by the directional coupler 77. A part of the output signal acquired by the directional coupler 77 is supplied to the level detector 78, and the input level of the drive stage amplifier 62 is detected by the level detector 78.

  The gain detector 79 is a gain between the drive stage amplifier 62 and the final stage amplifier 63 based on the output level of the final stage amplifier 63 from the level detector 75 and the input level of the drive stage amplifier 62 from the level detector 78. Is calculated. The detection output of the gain detector 79 is sent to the variable attenuator control circuit 83.

  The variable attenuator control circuit 83 controls the variable attenuator 61 according to the gain between the drive stage amplifier 62 and the final stage amplifier 63 detected by the gain detector 79. The drain voltage control circuit 70 is a power supply circuit including a circuit that can vary the drain voltage applied to the drive stage amplifier 62 and the final stage amplifier 63.

  FIG. 12 is a graph showing the characteristics of the drive stage amplifier 62 constituting the related power amplifier 50 shown in FIG. In FIG. 12, a characteristic 901 indicates an input / output characteristic of the drive stage amplifier 62 at the frequency F1, and a characteristic 902 is an input / output characteristic of the drive stage amplifier 62 at the frequency F2. B901 represents the back-off of the drive stage amplifier 62 at the frequency F1, and B902 represents the back-off of the drive stage amplifier 62 at the frequency F2. The backoff can be expressed by a decibel difference between the maximum output amplitude level and the output saturation power level.

  As shown in FIG. 12, the drive stage amplifier 62 that constitutes the power amplifier 50 as shown in FIG. 11 has a drive amount that is not optimized. Therefore, the backoff B901 of the drive stage amplifier 62 at the frequency F1 The amount of back-off differs from the back-off B902 of the drive stage amplifier 62 at the frequency F2.

  13 and 14 are graphs showing the characteristics of the final stage amplifier 63 constituting the related power amplifier 50 shown in FIG. 11. FIG. 13 shows the input / output characteristics of the final stage amplifier 63, and FIG. The frequency characteristic of the final stage amplifier 63 is shown. In FIG. 13, a characteristic 1001 indicates an input / output characteristic of the final stage amplifier 63 at the frequency F1, and a characteristic 1002 is an input / output characteristic of the final stage amplifier 63 at the frequency F2. B1001 is the back-off amount of the final amplifier 63 at the frequency F1, and B1002 is the back-off amount of the final amplifier 63 at the frequency F2.

  In FIG. 14, a characteristic 1101 indicates a gain characteristic of the final stage amplifier 63 at each frequency, a characteristic 1102 indicates a back-off characteristic of the final stage amplifier 63 at each frequency, and a characteristic 113 indicates an efficiency characteristic of the final stage amplifier 63 at each frequency. Indicates. Thus, in the final stage amplifier 63 used in the wideband power amplifier that covers the entire UHF frequency band, a large gain deviation of about several dB occurs depending on the frequency.

  15 and 16 are graphs showing the overall characteristics of the related power amplifier 50 shown in FIG. 11, FIG. 15 shows the overall input / output characteristics, and FIG. 16 shows the overall frequency characteristics. In FIG. 15, a characteristic 1201 indicates a total input / output characteristic at the frequency F1, and a characteristic 1202 is a total input / output characteristic at the frequency F2. B1201 is the backoff amount at the frequency F1, and B1202 is the backoff amount at the frequency F2.

  In FIG. 16, a characteristic 1301 indicates a gain characteristic at each frequency, a characteristic 1302 indicates a back-off characteristic at each frequency, and a characteristic 1303 indicates an efficiency characteristic at each frequency. In the power amplifier 50 shown in FIG. 11, the gain is made constant over the entire frequency band by controlling the attenuation amount of the variable attenuator 61 in accordance with the detection output of the gain detector 79.

  Further, making the transmission output power level constant is described in, for example, Patent Document 1 and Patent Document 2. Further, Patent Document 3 describes that an excessive input signal is detected and the operation voltage of the power amplifier is increased when there is an excessive input signal.

JP-A-6-338731 JP 2007-221308 A Special Table 2003-526980

  In the power amplifier 50 shown in FIG. 11, the final stage amplifier 63 has frequency characteristics. Therefore, the drive stage amplifier 62 is configured to amplify the input signal with a margin so that the final stage amplifier 63 can be sufficiently driven at any frequency. However, the gain deviation of the FET of the final stage amplifier 63 used in the wideband power amplifier that covers the entire UHF frequency band is as large as several dB, as shown in FIGS. For this reason, when the drive stage amplifier 62 is set so that the input signal can be amplified with a margin over the entire frequency band, the drive stage amplifier 62 has an excessive drive capability (= saturation) at a frequency where the gain of the final stage amplifier 63 is high. There is a risk that the final stage amplifier 63 may be damaged due to overdrive.

  That is, as indicated by the characteristic 1002 in FIG. 13, the gain of the final amplifier 63 in the power amplifier 50 shown in FIG. 11 is small at the frequency F2. For this reason, the drive amount of the drive stage amplifier 62 is set by data acquired in advance so that the final stage amplifier 63 can be sufficiently driven even at the frequency F2. However, with such a drive amount, the input power becomes excessive at the frequency F1 at which the gain of the final stage amplifier 63 becomes high, which may cause the FET of the final stage amplifier 63 to be damaged.

  Accordingly, it is conceivable to optimize the drive amount of the drive stage amplifier 62 so that the optimum drive capability can be maintained over the entire frequency band. Further, it is considered that the efficiency of the entire power amplifier can be improved by optimizing the drive amount so that the optimum drive capability can be maintained over the entire frequency band.

  Patent Documents 1 and 2 do not describe optimizing the drive amount of the drive stage amplifier 62. In Patent Document 3, a detection circuit that continuously samples an input signal to detect an excess input and a control circuit for a voltage of an amplifier corresponding to the excess input when an excess input is detected are required. , Processing becomes complicated.

  In view of the above problems, the present invention can optimize the drive amount of the drive stage amplifier over the entire frequency band to prevent overdrive of the final stage amplifier and improve the efficiency of the entire power amplifier. An object of the present invention is to provide a power amplifier, a power amplifier control method, and a power amplifier control program.

In order to solve the above-described problem, a power amplifier according to the present invention is a power amplifier in which a drive stage amplifier and a final stage amplifier are connected in cascade, and a transmission signal is amplified and output . Power supply control means for detecting a backoff and controlling the power supply of the drive stage amplifier so that the backoff of the drive stage amplifier has a predetermined value over the entire frequency band ; Gain control means for controlling so that the total gain consisting of becomes a desired gain.

The method of the power amplifier according to the present invention is to cascade a drive-stage amplifier and the final stage amplifier, a control method of a power amplifier that outputs a transmission signal to power amplification, the back-off of the drive stage amplifier The power supply of the drive stage amplifier is controlled so that the back-off of the drive stage amplifier becomes a predetermined value over the entire frequency band, and a total gain composed of the drive stage amplifier and the final stage amplifier is desired. Control is performed so as to obtain a gain.

A control program for a power amplifier according to the present invention is a control program for a power amplifier in which a drive stage amplifier and a final stage amplifier are connected in cascade, and a transmission signal is amplified and output , and the back-off of the drive stage amplifier is performed. A step of controlling the power supply of the drive stage amplifier so that the backoff of the drive stage amplifier becomes a predetermined value over the entire frequency band, and a total gain comprising the drive stage amplifier and the final stage amplifier is And controlling to obtain a desired gain.

  According to the present invention, it is possible to avoid damage to the final stage amplifier due to overdrive over the entire frequency band, and to improve the efficiency of the entire power amplifier.

It is a block diagram which shows the structure of the power amplifier in the 1st Embodiment of this invention. It is a flowchart which shows operation | movement of the power amplifier which concerns on the 1st Embodiment of this invention. It is a graph used for operation | movement description of the power amplifier which concerns on the 1st Embodiment of this invention. It is a graph used for operation | movement description of the power amplifier which concerns on the 1st Embodiment of this invention. It is the graph which showed the input-output characteristic of the drive stage amplifier which comprises the power amplifier which concerns on the 1st Embodiment of this invention. It is the graph which showed the frequency characteristic of the drive stage amplifier which comprises the power amplifier which concerns on the 1st Embodiment of this invention. It is the graph which showed the input-output characteristic of the last stage amplifier which comprises the power amplifier which concerns on the 1st Embodiment of this invention. It is the graph which showed the frequency characteristic of the last stage amplifier which comprises the power amplifier which concerns on the 1st Embodiment of this invention. 3 is a graph showing the overall input / output characteristics of the power amplifier according to the first embodiment of the present invention. It is the graph which showed the total frequency characteristic of the power amplifier which concerns on the 1st Embodiment of this invention. It is a block diagram which shows the structure of the related high output power amplifier used with the television transmitter for digital broadcasting. It is the graph which showed the input-output characteristic of the drive stage amplifier which comprises a related power amplifier. It is the graph which showed the input-output characteristic of the last stage amplifier which comprises a related power amplifier. It is the graph which showed the frequency characteristic of the last stage amplifier which comprises the related power amplifier. It is the graph which showed the total input / output characteristic of the related power amplifier. It is the graph which showed the total frequency characteristic of the related power amplifier.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a power amplifier 1 according to the first embodiment of the present invention. The first embodiment of the present invention is used as, for example, a high output power amplifier used in a digital broadcast television transmitter.

  In FIG. 1, an input terminal 10 is connected to an input terminal of a drive stage amplifier 12 via a variable attenuator 11. The drive stage amplifier 12 is composed of an FET. The output terminal of the drive stage amplifier 12 is connected to the input terminal of the final stage amplifier 13. The final stage amplifier 13 is configured by connecting a plurality of power amplification FETs in parallel. The output terminal of the final stage amplifier 13 is connected to the output terminal 14.

  The variable attenuator 11 controls the gain of the signal from the input terminal 10 based on the control signal from the variable attenuator control circuit 33. The drive stage amplifier 12 amplifies the transmission signal so that the final stage amplifier 13 can be sufficiently excited. The final stage amplifier 13 amplifies the power of the transmission signal and outputs it from the output terminal 14.

  A directional coupler 20 is provided in the path between the drive stage amplifier 12 and the final stage amplifier 13. A part of the output signal of the drive stage amplifier 12 is acquired by the directional coupler 20. The output signal of the directional coupler 20 is supplied to a level detector 21 and a backoff detector 22.

  The level detector 21 detects the output signal level of the drive stage amplifier 12. The output signal level of the drive stage amplifier 12 detected by the level detector 21 is supplied to the gain detector 23. The back-off detector 22 detects the back-off amount of the drive stage amplifier 12. The back-off amount of the drive stage amplifier 12 detected by the back-off detector 22 is supplied to the control circuit 35.

  The gain detector 23 calculates the gain of the final stage amplifier 13 based on the output signal level of the drive stage amplifier 12 from the level detector 21 and the output signal level of the final stage amplifier 13 from the level detector 25. The gain of the final stage amplifier 13 calculated by the gain detector 23 is supplied to the control circuit 35.

  A directional coupler 24 is provided in the path between the final stage amplifier 13 and the output terminal 14. The directional coupler 24 acquires a part of the output signal of the final stage amplifier 13. The output signal of the directional coupler 24 is supplied to a level detector 25 and a backoff detector 26.

  The level detector 25 detects the output signal level of the final stage amplifier 13. The output signal level of the final stage amplifier 13 detected by the level detector 25 is supplied to the gain detector 23 and also to the gain detector 29. The back-off detector 26 detects the back-off amount of the final stage amplifier 13. The back-off amount of the final amplifier 13 detected by the back-off detector 22 is supplied to the control circuit 35.

  A directional coupler 27 is provided between the variable attenuator 11 and the drive stage amplifier 12. The directional coupler 27 acquires a part of the input signal of the drive stage amplifier 12. The output signal of the directional coupler 27 is supplied to the level detector 28.

  The level detector 28 detects the input signal level of the drive stage amplifier 12. The input signal level of the drive stage amplifier 12 detected by the level detector 28 is supplied to the gain detector 29.

  Based on the output signal level of the final stage amplifier 13 from the level detector 25 and the input signal level of the drive stage amplifier 12 from the level detector 28, the gain detector 29 is connected to the final stage amplifier 13 from the drive stage amplifier 12. The gain between is calculated. The gain between the drive stage amplifier 12 and the final stage amplifier 13 calculated by the gain detector 23 is supplied to the control circuit 35 and also to the variable attenuator control circuit 33.

  The variable attenuator control circuit 33 is connected to the variable attenuator 11 and adjusts the gain of the power amplifier.

  The drain voltage control circuit 30 is a power supply circuit that can vary the drain voltage of the drive stage amplifier 12. The drain voltage control circuit 31 is a power supply circuit that can vary the drain voltage of the final stage amplifier 13.

  In the power amplifier 1 according to the first embodiment of the present invention, a transmission signal is supplied to the input terminal 10, and this transmission signal is supplied to the subordinate connection of the variable attenuator 11, the drive stage amplifier 12 and the final stage amplifier 13. The transmission signal is power amplified by the final stage amplifier 13, and this power amplified transmission signal is output from the output terminal 14.

  Further, in the power amplifier 1 according to the first embodiment of the present invention, the back-off amount of the drive stage amplifier 12 is detected from the detection output of the back-off detector 22, and the back-off amount becomes a predetermined value. The drain voltage of the drive stage amplifier 12 is set by the drain voltage control circuit 30. The variable attenuator 11 compensates for the variable gain of the drive stage amplifier 12 due to the drain voltage control of the drive stage amplifier 12. As a result, it is possible to secure the necessary minimum amount of back-off over the entire frequency band, and the gain and efficiency have almost no frequency characteristics. As a result, the drive capability of the drive stage amplifier 12 is optimized in any frequency band, and damage to the final stage amplifier 13 due to overdrive can be avoided.

  FIG. 2 is a flowchart showing the operation of the power amplifier 1 according to the first embodiment of the present invention.

  In FIG. 2, the control circuit 35 controls the drain voltage control circuits 30 and 31, and sets the drain voltage Vdd_drive of the drive stage amplifier 12 based on the previously acquired characteristic data of the drive stage amplifier 12 and the final stage amplifier 13. The drain voltage Vdd_final of the final stage amplifier 13 is set to an appropriate value, and a signal is input to the input terminal 10 (step S101).

  Next, the control circuit 35 detects the back-off amount of the final stage amplifier 13 from the detection output of the back-off detector 26 (step S102), and the back-off amount of the final stage amplifier 13 exceeds the necessary minimum back-off amount. It is confirmed whether it is (step S103).

  For example, assume that the drain voltage Vdd_final of the final stage amplifier 13 is set to (Vdd_final = V11) in step S101. It is assumed that the input / output characteristic of the final stage amplifier 13 at this time changes as indicated by the characteristic 101 in FIG. In this case, in step S103, the control circuit 35 detects the back-off amount B11 at this time, and confirms whether or not the back-off amount B11 is equal to or greater than the minimum necessary back-off amount BR1. Here, the necessary minimum back-off amount is the minimum back-off amount that can satisfy the expected dynamic range.

  In FIG. 2, if the back-off amount of the final stage amplifier 13 is greater than or equal to the necessary minimum back-off amount in Step S103 (Yes in Step S103), then the control circuit 35 determines from the detection output of the gain detector 23. Then, the gain of the final stage amplifier 13 is calculated (step S104). If the back-off amount of the final stage amplifier 13 is not equal to or greater than the necessary minimum back-off amount (No in step S103), the set value is reviewed (step S109).

  Next, the control circuit 35 detects the back-off amount of the drive stage amplifier 12 from the detection output of the back-off detector 22 (step S105). Then, the control circuit 35 determines whether or not the back-off amount of the drive stage amplifier 12 is a predetermined back-off amount (step S106). Here, the predetermined back-off amount is a minimum necessary back-off amount of the drive stage amplifier 12.

  For example, assume that the drain voltage Vdd_drive of the drive stage amplifier 12 is set to (Vdd_drive = V21) in step S101. It is assumed that the input / output characteristics of the drive stage FET at this time change as indicated by the characteristics 201 in FIG. In this case, in step S105, the control circuit 35 detects the back-off amount B21 at this time, and determines whether the back-off amount B21 is the minimum required back-off amount BR2.

  In FIG. 2, if the back-off amount of the drive stage amplifier 12 is not the minimum required back-off amount in step S106 (No in step S106), the control circuit 35 changes the drain voltage of the drive stage amplifier 12. (Step S107), the process returns to Step S102.

  By repeating the processing from step S102 to step S107, the backoff amount of the drive stage amplifier 12 is converged so as to be the minimum necessary backoff amount, and the drive amount of the drive stage amplifier 12 is optimized.

  That is, in FIG. 4, when the drain voltage Vdd_drive is set to (Vdd_drive = V21), the input / output characteristics of the drive stage FET 12 change as shown by the characteristic 201 in FIG. , And increases by a predetermined back-off amount BR2. In this case, in step S106, the control circuit 35 determines that the back-off amount of the drive stage amplifier 12 is not the predetermined back-off amount, and changes the drain voltage of the drive stage amplifier 12. Here, it is assumed that when the drain voltage Vdd_drive is changed to (Vdd_drive = V22), the input / output characteristics of the drive stage FET 12 are as shown by the characteristics 202 in FIG. The backoff amount B22 at this time is almost equal to the predetermined backoff amount BR2. Therefore, when the drain voltage Vdd_drive is changed to (Vdd_drive = V22), the control circuit 35 determines in step S106 that the back-off amount of the drive stage amplifier 12 is a predetermined back-off amount. In this way, by changing the drain voltage Vdd_drive of the drive stage amplifier 12, the backoff amount of the drive stage amplifier 12 can be set to the predetermined backoff amount BR2.

  In FIG. 2, when it is determined in step S106 that the back-off amount of the drive stage amplifier 12 becomes a predetermined back-off amount, the control circuit 35 determines from the detection output of the gain detector 29 to the final stage amplifier from the drive stage amplifier 12. A gain of up to 13 is detected. The gain between the drive stage amplifier 12 and the final stage amplifier 13 at this time is the gain of the final stage amplifier 13 shown in FIG. 3 (= P12−P11) and the gain of the drive stage amplifier 12 shown in FIG. The gain (P22-P11) is obtained by adding P22-P21). Here, the gain is calculated in decibel notation.

  Then, the control circuit 35 controls the attenuation amount of the variable attenuator 11 by the variable attenuator control circuit 33 so that the total gain of the power amplifier 1 becomes a desired gain (step S108), and the processing is completed. In step S108, by changing the attenuation amount of the variable attenuator 11, the change in the gain of the drive stage amplifier 12 due to the control of the drain voltage of the drive stage amplifier 12 is corrected.

  Thus, in the first embodiment of the present invention, the drain voltage of the drive stage amplifier 12 is controlled so that the backoff of the drive stage amplifier 12 becomes a predetermined backoff amount. The back-off amount is required to be at least an amount that can satisfy the expected dynamic range, but no more back-off amount is required, and the efficiency decreases as the back-off amount increases. Further, if the back-off amount of the drive stage amplifier 12 is large, the drive capability becomes excessive with respect to the final stage amplifier 13, and there is a risk of damaging the final stage amplifier 13. In the first embodiment of the present invention, the drive amount of the drive stage amplifier 12 is optimized by controlling the drain voltage of the drive stage amplifier so that the backoff of the drive stage amplifier 12 becomes a predetermined backoff amount. Further, the final stage amplifier 13 can be prevented from being damaged, and the efficiency can be improved.

  5 and 6 are graphs showing the characteristics of the drive stage amplifier 12 constituting the power amplifier 1 according to the first embodiment of the present invention. FIG. 5 shows the input / output characteristics of the drive stage amplifier 12. FIG. 6 shows the frequency characteristics of the drive stage amplifier 12. In FIG. 5, a characteristic 301 indicates an input / output characteristic at the frequency F1, and a characteristic 302 is an input / output characteristic at the frequency F2. In the first embodiment of the present invention, the drain voltage of the drive stage amplifier 12 is controlled so that the back-off of the drive stage amplifier 12 becomes a predetermined amount. Accordingly, the backoff amount 301 at the frequency F1 and the backoff amount B302 at the frequency F2 are equal to each other with the minimum necessary backoff amount. As shown in FIG. 5, substantially the same input / output characteristics of the drive stage amplifier 12 are obtained for both the frequency F1 and the frequency F2.

In FIG. 6, a characteristic 401 indicates a gain characteristic at each frequency of the drive stage amplifier 12, a characteristic 402 indicates a back-off characteristic at each frequency of the drive stage amplifier 12, and a characteristic 403 indicates an efficiency characteristic at each frequency of the drive stage amplifier 12. Indicates. In the first embodiment of the present invention, the drive amount is optimized by controlling the drain voltage of the drive stage amplifier 12 so that the backoff amount of the drive stage amplifier 12 becomes the minimum necessary backoff amount. For this reason, the back-off characteristic 402 is substantially constant at any frequency. Also, the gain characteristic 401 and the efficiency characteristic 403 can be made substantially constant at any frequency. Characteristics 404, 405, and 406 indicate gain characteristics, back-off characteristics, and efficiency characteristics when the drain voltage of the drive stage amplifier 12 is controlled and the drive amount is not optimized.

  7 and 8 are graphs showing the characteristics of the final amplifier 13 constituting the power amplifier 1 according to the first embodiment of the present invention. FIG. 7 shows the input / output characteristics of the final amplifier 13, FIG. 8 shows the frequency characteristics of the final stage amplifier 13. In FIG. 7, a characteristic 501 indicates input / output characteristics of the final stage amplifier 13 at the frequency F1, and a characteristic 502 indicates input / output characteristics of the final stage amplifier 13 at the frequency F2. B51 is the backoff amount of the final stage amplifier 13 at the frequency F1, and B52 is the backoff amount B52 of the final stage amplifier 13 at the frequency F2.

  In FIG. 8, a characteristic 601 indicates a gain characteristic at each frequency, a characteristic 602 indicates a back-off characteristic of the final amplifier 13 at each frequency, and a characteristic 603 indicates an efficiency characteristic of the final amplifier 13 at each frequency. In this way, the final amplifier 13 has a gain deviation depending on the frequency.

  9 and 10 are graphs showing the overall characteristics of the power amplifier 1 according to the first embodiment of the present invention. FIG. 9 shows the overall input / output characteristics, and FIG. 10 shows the overall frequency characteristics. . In FIG. 9, a characteristic 701 indicates an input / output characteristic at the frequency F1, and a characteristic 702 is an input / output characteristic at the frequency F2. In the first embodiment of the present invention, since the drain voltage of the drive stage amplifier 12 is controlled, the difference between the backoff amount B61 at the frequency F1 and the backoff amount B62 at the frequency F2 is reduced.

  In FIG. 10, a characteristic 801 indicates a total gain characteristic at each frequency, a characteristic 802 indicates a total back-off characteristic at each frequency, and a characteristic 803 indicates a total efficiency characteristic at each frequency. In the first embodiment of the present invention, the variable attenuator 11 is controlled so that the total gain is constant, whereby the gain characteristic 801 is constant at any frequency. In the first embodiment of the present invention, since the drive amount is optimized by controlling the drain voltage of the drive stage amplifier 12, the back-off characteristic 802 has a minimum required back-off amount at any frequency. It is almost constant. Further, since the back-off amount is set to be substantially constant at the minimum necessary, the efficiency of the efficiency characteristic 803 can be improved, and the efficiency is substantially constant at any frequency. Characteristics 805, 806, and 807 indicate gain characteristics, back-off characteristics, and efficiency characteristics when the drain voltage of the drive stage amplifier 12 is not optimized.

  As described above, in the first embodiment of the present invention, the back-off amount of the drive stage amplifier 12 is detected from the detection output of the back-off detector 22, and the back-off amount becomes a predetermined value. The drain voltage of the drive stage amplifier 12 is controlled. If the back-off amount of the drive stage amplifier 12 is the minimum and constant, the drive stage amplifier 12 is optimized with the optimum drive capability, and damage to the final stage amplifier 13 due to overdrive can be avoided. , Can also improve efficiency.

  The present invention is not limited to the above-described embodiments, and various modifications and applications can be made without departing from the gist of the present invention.

1: Power amplifier 10: Input terminal 11: Variable attenuator 12: Drive stage amplifier 13: Final stage amplifier 14: Output terminal 20: Directional coupler 21: Level detector 22: Back-off detector 23: Gain detector 24: Directional coupler 25: Level detector 26: Back-off detector 27: Directional coupler 28: Level detector 29: Gain detector 30, 31: Drain voltage control circuit 33: Variable attenuator control circuit 35: Control circuit

Claims (4)

A power amplifier that subordinately connects a drive stage amplifier and a final stage amplifier, amplifies a transmission signal, and outputs the amplified signal.
Power supply control means for detecting the backoff of the drive stage amplifier and controlling the power supply of the drive stage amplifier so that the backoff of the drive stage amplifier has a predetermined value over the entire frequency band;
A power amplifier comprising: gain control means for controlling the total gain of the drive stage amplifier and the final stage amplifier to be a desired gain.   The power amplifier according to claim 1, wherein the predetermined value of the back-off is a back-off amount that is a minimum necessary for securing a dynamic range. A control method for a power amplifier, in which a drive stage amplifier and a final stage amplifier are connected in cascade, and a transmission signal is amplified and output.
Detecting the back-off of the drive stage amplifier, and controlling the power source of the drive stage amplifier so that the back-off of the drive stage amplifier becomes a predetermined value over the entire frequency band,
A control method for a power amplifier, characterized in that control is performed so that a total gain of the drive stage amplifier and the final stage amplifier becomes a desired gain. A control program for a power amplifier, in which a drive stage amplifier and a final stage amplifier are connected in cascade, and a transmission signal is amplified and output.
Detecting a back-off of the drive stage amplifier, and controlling a power source of the drive stage amplifier so that the back-off of the drive stage amplifier becomes a predetermined value over the entire frequency band ;
A computer-executable control program for a power amplifier, comprising: controlling a total gain of the drive stage amplifier and the final stage amplifier to be a desired gain.

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