JP2012095196A - Power amplifier and transmitter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power amplifier and a transmitter having a smaller footprint than that of conventional one and capable of minimizing output signal losses.SOLUTION: The power amplifier 16 comprises a balance amplifier 21 having an amplifier circuit 24 provided between a hybrid power splitter 22 and a hybrid power combiner 23. A detector circuit 27 is connected to an isolation port 23d in the hybrid power combiner 23.

Description

  The present invention relates to a power amplifier and a transmitter having a balance amplifier.

  For example, a transmitter such as a block up converter (BUC) for satellite communication is widely known. Some block up converters adjust the output level of the output signal. An automatic gain control (AGC) amplifier and a variable attenuator are used for adjusting the output level. A part of the output signal is detected and used for controlling the AGC amplifier and the variable attenuator.

JP 2009-260472 A

  When connecting the detection circuit, for example, as disclosed in Patent Document 1, a directional coupler formed on a printed circuit board is widely used. Although the directional coupler can extract both signals in the forward and reverse directions of the line, the transmitter only needs to detect the signal in the direction toward the antenna, and the unnecessary terminal is the characteristic impedance of the line. It is terminated with a high-frequency resistor equivalent to. Thus, since the directional coupler extracts a part of the output signal, the output signal is exposed to a decrease in the output level. Moreover, the directional coupler occupies a relatively large area on the printed circuit board.

  The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a power amplifier and a transmitter that are arranged with a smaller occupied area than before and that can reduce loss of an output signal as much as possible. And

  In order to achieve the above object, there is provided a power amplifier including a detection circuit connected to an isolation port of a balance amplifier.

  In such a power amplifier, since detection is performed based on the output of the isolation port, a decrease in output level can be avoided at the output of the balance amplifier. In addition, since a so-called directional coupler is omitted, the space occupied by the power amplifier can be reduced. In addition, the termination resistor of the characteristic impedance used for the directional coupler can be omitted. Since such a terminating resistor uses a high-frequency resistor that is more expensive than a general resistor, the cost of power amplifier components can be significantly reduced in accordance with the omission of the directional coupler.

  The balance amplifier includes a front-stage hybrid power distributor, an amplifier circuit connected to each of two ports that output signals distributed by the hybrid power distributor, and a rear-stage hybrid power combiner connected to the amplifier circuit, Should be provided. According to such a balanced amplifier, the distributed signals are individually amplified and the outputs are combined to obtain output power. Therefore, the saturation of the individual amplifier circuits is avoided and the capacity of the individual amplifier circuits is exceeded. Output power (for example, when the output power of each amplifier circuit is 2 W, the power output as a balance amplifier is 4 W) is obtained. The detection circuit is connected to the isolation port of the hybrid power combiner.

  The power amplifier may further include a high-frequency termination resistor connected to the isolation port. In such a power amplifier, since the voltage across the high-frequency termination resistor is detected, a broadband detection circuit can be realized. In addition, the high-frequency termination resistor can be used as a DC component path of the detection circuit. The reflection characteristics are improved.

  The power amplifier may further include a matching circuit and a small signal amplifier inserted between the isolation port and the detection circuit. Since the small signal amplifier amplifies the output of the isolation port, the amplified output is input to the detection circuit. The detection accuracy of the detection circuit is improved compared to the output of a minute signal. Furthermore, the high-frequency termination resistor can be omitted for detection. Since an amplifying element that is less expensive than a high-frequency resistor can be used, the component cost of the power amplifier can be further reduced.

  The power amplifier may further include a matching circuit and a small signal amplifier connected to the isolation port of the hybrid power distributor. The high-frequency termination resistor to be connected to the isolation port can be omitted. Since the small signal amplifier can use an amplifying element that is less expensive than the high-frequency resistor, the component cost of the power amplifier can be further reduced.

  The aforementioned power amplifier can be incorporated into the transmitter. Such a transmitter has, for example, an output level adjustment circuit (AGC amplifier and / or variable attenuator) having variable characteristics, and an amplifier circuit provided between the hybrid power distributor and the hybrid power combiner. A balance amplifier that amplifies the power of the signal supplied from the output level adjustment circuit, a detection circuit connected to the isolation port of the hybrid power combiner, and the output level adjustment circuit is adjusted based on the output of the detection circuit And a control circuit.

  As described above, according to the disclosed power amplifier and transmitter, the occupied area can be reduced as compared with the conventional case, and the loss of the output signal can be reduced.

It is a block diagram which shows the structure of a transmitter roughly. 1 is a block diagram schematically showing a configuration of a power amplifier, that is, a power amplifier according to a first embodiment. It is a block diagram which shows roughly the structure of the balance amplifier which concerns on one specific example. It is a block diagram which shows roughly the structure of the balance amplifier which concerns on another specific example. It is a block diagram which shows roughly the structure of the power amplifier which concerns on 2nd Embodiment, ie, a power amplifier. It is a block diagram which shows roughly the structure of the power amplifier which concerns on 3rd Embodiment, ie, a power amplifier.

  Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 schematically shows the configuration of a transmitter. The transmitter 11 includes a variable attenuator 12 and an IF (intermediate frequency) amplifier 13. The intermediate frequency signal is attenuated by the variable attenuator 12 and amplified by the IF amplifier 13. The IF amplifier 13 can be shared with an automatic gain control (AGC) amplifier, for example. This type of transmitter 11 can be compared to a satellite communication transmitter such as a block up converter (BUC) or other wireless transmitter.

  A mixer 14 is connected to the IF amplifier 13. The mixer 14 mixes the local oscillation signal (LO) of the local oscillator with the intermediate frequency signal (IF). As a result, the signal frequency is the sum of the intermediate frequency signal (IF) and the local oscillation signal (LO), and an output frequency signal (RF) is generated. The frequency of the local oscillation signal (LO) is appropriately set, for example, in the microwave frequency band. Here, for example, it may be set in the range of 3 GHz to 30 GHz. An RF amplifier 15 is connected to the subsequent stage of the mixer 14. The RF amplifier 15 amplifies the output of the mixer 14.

  A power amplifier 16 is connected to the subsequent stage of the RF amplifier 15. The power amplifier 16 amplifies the output signal of the RF amplifier 15 to a specified output level. The output of the power amplifier 16, that is, the output frequency signal (RF) propagates from the antenna 17 to the space as a radio signal. In this way, a radio signal is transmitted from the transmitter 11. At the same time, the power amplifier 16 detects the output frequency signal (RF) and outputs it as a detection output. The detection output reflects the output level of the output frequency signal (RF) output from the power amplifier 16.

  A control circuit 18 is connected to the power amplifier 16. The detection output of the power amplifier 16 is input to the control circuit 18. The control circuit 18 controls the variable attenuator 12 and the AGC amplifier based on the detection output. The control circuit 18 controls at least one of the variable attenuator 12 and the AGC amplifier.

  FIG. 2 shows a power amplifier, that is, a power amplifier 16 according to the first embodiment of the present invention. The power amplifier 16 includes a balance amplifier 21. The balance amplifier 21 includes a front-stage hybrid power distributor 22 and a rear-stage hybrid power combiner 23. The output signal of the RF amplifier 15 is input to the input port 22 a of the hybrid power distributor 22. Amplifier circuits 24 and 24 are individually connected to the pair of output ports 22b and 22c of the hybrid power distributor 22, respectively. The amplifier circuit 24 is formed of an FET (field effect transistor) or an MMIC (monolithic microwave integrated circuit). The two amplifier circuits 24, 24 have the same characteristics. A pair of input ports 23 a and 23 b of the hybrid power combiner 23 are connected to the output of the amplifier circuit 24. An output frequency signal (RF) amplified to a specified output level is output from the output port 23 c of the hybrid power combiner 23. High-frequency termination resistors 25 and 26 are connected to the isolation port 22d of the hybrid power distributor 22 and the isolation port 23d of the hybrid power coupler 23, respectively. Since the transmission line has a characteristic impedance of 50Ω in this embodiment, 50Ω resistive elements are used for the high-frequency termination resistors 25 and 26.

  A detection circuit 27 is connected to the isolation port 23 d of the hybrid power coupler 23. The detection circuit 27 includes a diode 28 connected to the isolation port 23d. The diode 28 performs half-wave rectification on the high-frequency signal output from the isolation port 23d. A capacitor 29 and a resistor 31 are connected in parallel to the output of the diode 28. Signals are smoothed by the action of the capacitor 29 and the resistor 31. Thus, the output of the diode 28 becomes a detection signal. A detection output proportional to the intensity of the output frequency signal (RF) is input to the control circuit 18. The control circuit 18 controls the variable attenuator 12 and / or the AGC amplifier based on the detection output so that the output frequency signal (RF) is output at a constant output level.

  As shown in FIG. 3, 3 dB 90 ° hybrid couplers (hereinafter referred to as “branch line couplers”) 33 and 34 may be used for the hybrid power divider 22 and the hybrid power combiner 23. In each branch line coupler 33, 34, a line having a characteristic impedance Z0 (= 50Ω) and a line length λ / 4 is formed as a branch between the first port 33a, 34a and the fourth port 33d, 34d. Similarly, a line having a characteristic impedance Z0 (= 50Ω) and a line length λ / 4 is formed as a branch between the second ports 33b and 34b and the third ports 33c and 34c. On the other hand, there is a characteristic impedance Z0 / √2 (= 35) between the first ports 33a, 34a and the second ports 33b, 34b and between the fourth ports 33d, 34d and the third ports 33c, 34c. .35Ω) and a line having a line length λ / 4 is formed as a branch. In the branch line coupler 33 at the previous stage, for example, when a 0 [dBm] signal is input from the first port 33a, the input signal is equally distributed and the second port 33b and the third port 33c receive a signal of -3 [dBm]. The signal is output with a phase difference of 90 °, and a signal of about −30 [dBm] appears from the fourth port 33d, that is, the isolation port 22d. Amplifier circuits 24 and 24 are connected to the second port 33b and the third port 33c of the branch line coupler 33 at the preceding stage. The outputs of the amplifier circuits 24, 24 are connected to the first port 34a and the fourth port 34d of the subsequent branch line coupler 34, respectively. If the amplification degree of each of the amplifier circuits 24 and 24 is 25 [dB], the output of each amplifier circuit 24 is synthesized in phase from the third port 34c of the branch line coupler 34 in the subsequent stage, and an output frequency signal of 25 [dBm] ( RF) is output. A signal of about −5 [dBm] appears at the second port 34b, that is, the isolation port 23d. The output of the second port 34b is used as a detection output.

  According to the power amplifier 16 as described above, the voltage at both ends of the high-frequency termination resistor 26 is detected, so that a broadband detection circuit 27 can be realized. In addition, the high-frequency termination resistor 26 can be used as a path for a DC component output from the detection circuit 27. Reflection can be reliably avoided. Since a signal is not extracted for detection from the output frequency signal (RF) output to the third port 34c at the time of detection, a decrease in the output level of the output frequency signal (RF) can be avoided. In addition, since a so-called directional coupler is not required, the area occupied by the power amplifier 16 on the printed circuit board can be reduced. Moreover, a 50Ω termination resistor used for the directional coupler is not necessary. Since such a terminating resistor is a high-frequency resistor that is more expensive and larger than a general resistor, the cost of components of the power amplifier 16 can be significantly reduced according to the omission of the directional coupler.

  In the power amplifier 16, 1.5λ 3 dB rat race hybrid (hereinafter referred to as “rat race hybrid”) 35 and 36 may be used instead of the branch line couplers 33 and 34. As shown in FIG. 4, in each of the rat race hybrids 35 and 36, the characteristic impedance √2Z0 (= 70.71Ω) and the line length of 3 / 2λ are set to four characteristic impedances Z0 (= 50Ω) line is connected. In the preceding race race hybrid 35, when a signal of 0 [dBm] is input from the first port 35a, the input signal is equally distributed and a signal of −3 [dBm] is 180 ° from the second port 35b and the third port. And a signal of about −30 [dBm] appears at the fourth port 35d. Amplifier circuits 24, 24 are connected to the second port 35b and the third port 35c of the rat race hybrid 35 at the preceding stage. The outputs of the amplifier circuits 24, 24 are connected to the third port 36c and the second port 36b of the subsequent rat race hybrid 36, respectively. When the amplification degree of each power amplifier is 25 [dB], each amplifier circuit 24 is synthesized in the same phase from the first port 36a of the rat race hybrid 36 in the subsequent stage, and an output frequency signal (RF) of 25 [dBm] is output. The A detection output of about −5 [dBm] is output from the fourth port 36d, that is, the isolation port 23d. Thus, the rat race hybrids 35 and 36 can form the balance amplifier 21 in the same manner as the branch line couplers 33 and 34.

  FIG. 5 shows a power amplifier, that is, a power amplifier 16a according to the second embodiment of the present invention. The power amplifier 16 a may be incorporated in the transmitter 11 instead of the power amplifier 16. In the figure, components equivalent to those of the power amplifier 16 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In this power amplifier 16 a, a small signal amplifier 37 is inserted between the isolation port 23 d of the hybrid power coupler 23 and the detection circuit 27. For the small signal amplifier 37, for example, a high frequency amplifying element such as HEMT (high electron mobility transistor) may be used. A matching circuit 38 is connected between the isolation port 23 d and the small signal amplifier 37, that is, at the input of the small signal amplifier 37. At the same time, a matching circuit 39 is connected between the small signal amplifier 37 and the detection circuit 27, that is, at the output of the small signal amplifier 37. The matching circuits 38 and 39 may be formed based on a wiring pattern such as a microstrip line such as a transmission line and a stub. The reflected waves to the isolation port 23d are suppressed by the functions of the matching circuits 38 and 39 and the small signal amplifier 37 designed to match the impedance to the output frequency signal (RF). A wide band is realized at the output. As a result, the characteristics of the balance amplifier 21 are improved. In addition, since the small signal amplifier 37 amplifies the output of the isolation port 23 d, the amplified signal output is input to the detection circuit 27. The detection accuracy of the detection circuit 27 is improved compared to the output of a minute signal. Further, the high-frequency termination resistor 26 is not required for detection, and an inexpensive amplifying element can be used as compared with the high-frequency resistor, so that the component cost of the power amplifier 16a can be further reduced.

  FIG. 6 shows a power amplifier, that is, a power amplifier 16b according to a third embodiment of the present invention. The power amplifier 16b may be incorporated in the transmitter 11 instead of the power amplifier 16. In the figure, components equivalent to those of the power amplifier 16 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In this power amplifier 16b, a small signal amplifier 41 is connected to the isolation port 22d of the preceding hybrid power distributor 22 in place of the high-frequency termination resistor 25. For the small signal amplifier 41, for example, an amplifying element such as HEMT (High Electron Mobility Transistor) may be used. A matching circuit 42 is connected between the isolation port 22d and the small signal amplifier 41, that is, at the input of the small signal amplifier 41. At the same time, a matching circuit 43 is connected to the output of the small signal amplifier 41. The matching circuits 42 and 43 may be formed based on a wiring pattern such as a microstrip line such as a transmission line and a stub. The reflected waves with respect to the isolation port 22d are suppressed by the functions of the matching circuits 42 and 43 and the small signal amplifier 41. A wide band is realized at the output. As a result, the characteristics of the balance amplifier 21 are improved. In addition, the high-frequency termination resistor 25 is not required, and an amplifying element that is less expensive than the high-frequency resistor can be used. Therefore, the component cost of the power amplifier 16b can be further reduced.

  Reference Signs List 11 transmitter, 12 variable attenuator, 13 intermediate frequency amplifier including automatic gain control (AGC) amplifier, 16 power amplifier as power amplifier, 16a power amplifier as power amplifier, 16b power amplifier as power amplifier, 18 control circuit, 21 Balance Amplifier, 22 Hybrid Power Divider, 22d Hybrid Power Divider Isolation Port, 23 Hybrid Power Coupler, 23d Hybrid Power Coupler Isolation Port, 24 Amplifier Circuit, 26 High Frequency Termination Resistor, 27 Detector Circuit, 33 3 dB 90 ° hybrid coupler as hybrid power divider, 34 3 dB 90 ° hybrid coupler as hybrid power combiner, 35 1.5λ type 3 dB rat race as hybrid power divider Hybrid, 36 1.5 [lambda] type 3dB rat race hybrid as hybrid power combiner, 37 small signal amplifier, 38 a matching circuit, 39 a matching circuit, 41 a small signal amplifier, 42 a matching circuit, 43 a matching circuit.

Claims (5)

  A power amplifier comprising: a balance amplifier having an amplifier circuit provided between a hybrid power distributor and a hybrid power combiner; and a detection circuit connected to an isolation port of the hybrid power combiner.   2. The power amplifier according to claim 1, wherein the hybrid power divider and the hybrid power combiner are configured by a branch line coupler or a rat race hybrid.   3. The power amplifier according to claim 1, further comprising a matching circuit and a small signal amplifier inserted between the isolation port and the detection circuit.   The power amplifier according to any one of claims 1 to 3, further comprising a matching circuit and a small signal amplifier in an isolation port of the hybrid power distributor. A variable attenuator and / or an automatic gain control amplifier;
A local signal oscillator and a mixer;
A balance amplifier that has an amplifier circuit provided between the hybrid power distributor and the hybrid power combiner, and amplifies the power of the signal supplied from the variable attenuator and / or the automatic gain control amplifier;
A detection circuit connected to an isolation port of the hybrid power combiner;
And a control circuit for adjusting the variable attenuator or the automatic gain control amplifier based on the output of the detection circuit.

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