JP4813995B2 - Power amplifier and wireless communication device - Google Patents

Description

  The present invention relates to a power amplifier, and more particularly, to a power amplifier with improved linearity and a wireless communication apparatus using such a power amplifier.

  In recent years, the demand for wireless communication devices typified by mobile phones has been increasing. In such a wireless communication apparatus, the operation and quality of the power amplifier are important.

  Wireless communication devices used as mobile phones and wireless network devices that are generally used require power amplifiers with higher wireless transmission performance and higher linearity. High linearity means that the gain variation and phase variation depending on the input signal level are small. Further, there is a demand for a power amplifier with high output and high linearity.

  As a technique for improving the linearity of the power amplifier, there is a method in which the input signal and the output signal of the power amplifier are compared and the distortion is compensated by the attenuator and the phase shifter, as in the technique disclosed in Patent Document 1. According to this technique, it is necessary to always detect the input and output gains and phases. Then, feedback is performed using an attenuator and a phase shifter so that the gain and phase are constant.

  FIG. 1 is a circuit diagram showing a configuration of a conventional power amplifier 30. Referring to FIG. 1, the power amplifier 30 has an input terminal 40 and an output terminal 60, has an input connected to the input terminal 40, and first and second outputs. A first directional coupler 42 that outputs a part of the input signal from the first output as the input comparison signal 44 to the first output and the second to the second output, and a second output of the directional coupler 42 An input terminal connected to the control signal terminal, and an output terminal. The voltage of the phase control signal 50 applied to the control signal terminal is compared with a predetermined reference value, and the phase of the input signal is determined according to the comparison result. A variable phase shifter 46 for delaying or advancing and outputting, an input terminal connected to the output of the variable phase shifter 46, a control signal terminal, and an output terminal, and an amplitude given to the control signal terminal Based on the comparison result between the voltage of the control signal 52 and the reference value, the input signal is Without Attenuation, or attenuated in a ratio which depends on the voltage difference between the voltage and the reference value of the control signal and a variable attenuator 48 to output.

  The power amplifier 30 is further connected to an amplifier 54 having an input connected to the output terminal of the variable attenuator 48, an input connected to the output terminal of the amplifier 54, a first output terminal, and an output terminal 60. A second output terminal, which extracts a part of the output signal from the amplifying unit 54 as an output comparison signal 58 and outputs it from the first output, and outputs the rest to the output terminal 60. And a directional coupler 56.

  The power amplifier 30 further includes a first input connected to the first output of the second directional coupler 56 and a second input connected to the first output of the first directional coupler 42. The output comparison signal 58 from the first input and the input comparison signal 44 from the second input are compared in phase and amplitude, and the output comparison signal 58 is compared with the input comparison signal 44. A comparison circuit 62 that outputs a phase difference detection signal 64 that is a voltage signal proportional to the phase difference and an amplitude comparison signal 66 that is a voltage signal proportional to the amplitude ratio of the output comparison signal 58 to the input comparison signal 44, and a comparison circuit 62 Are connected to the first and second inputs connected to receive the phase difference detection signal 64 and the amplitude comparison signal 66, respectively, and the control signal terminal of the variable phase shifter 46 and the control signal terminal of the variable attenuator 48, respectively. First and second outputs And the voltages of the phase control signal 50 and the amplitude control signal 52 are changed so that the phase difference and the amplitude ratio represented by the phase difference detection signal 64 and the amplitude comparison signal 66 are kept constant, respectively. A variable phase shifter 46 and an adjustment circuit 68 for supplying control signal terminals to the variable attenuator 48.

  The power amplifier 30 operates as follows. The first directional coupler 42 extracts a part of the input signal input from the input terminal 40 as an input comparison signal 44 at a constant ratio, and provides it to the second input of the comparison circuit 62. The remainder of the input signal is fed to the variable phase shifter 46. The input signal is given a phase delay and attenuation corresponding to the voltages of the phase control signal 50 and the amplitude control signal 52 by the variable phase shifter 46 and the variable attenuator 48, respectively, and is given to the variable attenuator 48. The amplifier 54 amplifies this signal and outputs it. The second directional coupler 56 takes out a part of the signal amplified by the amplifying unit 54 as an output comparison signal 58 at a constant ratio, and gives it to the first input of the comparison circuit 62. The rest is output from the output terminal 60 as an output signal.

  The comparison circuit 62 detects the phase difference and amplitude ratio between the input comparison signal 44 and the output comparison signal 58 and outputs a phase difference detection signal 64 and an amplitude comparison signal 66. The adjustment circuit 68 uses the phase difference detection signal 64 and the amplitude comparison signal 66 to change the voltages of the phase control signal 50 and the amplitude control signal 52 so that the phase difference and the amplitude ratio are kept constant.

  With this configuration, it is possible to give a shift that cancels the amplification distortion of the amplification unit 54 to the signal entering the amplification unit 54. That is, a circuit including the first directional coupler 42, the variable phase shifter 46, the variable attenuator 48, the second directional coupler 56, the comparison circuit 62, and the adjustment circuit 68 functions as a distortion compensation circuit.

The detection of the amplification gain, which is the power ratio between the input comparison signal 44 and the output comparison signal 58, performed in the comparison circuit 62 can be performed relatively easily by detecting each signal and comparing the detected voltage. On the other hand, in Patent Document 1, the phase difference between the input comparison signal 44 and the output comparison signal 58 is obtained as a difference between voltage signals after shaping both signals by a limiter amplifier.
JP 2003-198273 A

  However, according to the method disclosed in Patent Document 1, the signal frequency increases, and it is difficult to maintain the shaping accuracy in the limiter amplifier and the subsequent mixing accuracy at necessary values, and the linear characteristics deteriorate. Alternatively, there is a problem that a circuit for maintaining accuracy becomes complicated.

  On the other hand, as another method for detecting the phase difference between the input comparison signal 44 and the output comparison signal 58, there is a method of demodulating both signals and comparing the phases in the baseband. However, this method has a problem that an extra demodulation circuit is required.

  Therefore, an object of the present invention is to provide a power amplifier having a simple circuit and good linear characteristics.

  Another object of the present invention is to provide a communication apparatus having a good linear characteristic using the power amplifier as described above.

  A power amplifier according to a first aspect of the present invention is a power amplifier having a signal input terminal and a signal output terminal, an amplifier circuit provided in a signal path between the signal input terminal and the signal output terminal, A first detection circuit connected between the input terminal and the input of the amplifier circuit for detecting the power of the input signal to the amplifier circuit and outputting an input detection signal; an output of the amplifier circuit and a signal output terminal; And a second detection circuit for detecting the power of the output signal of the amplifier circuit and outputting an output detection signal. The amplifier circuit has a grounded emitter bipolar transistor as an amplifier element. The power amplifier is further connected to receive the input detection signal and the output detection signal, and based on a comparison between the input detection signal and the output detection signal, the base bias current of the transistor is controlled to increase the amplification gain of the power amplifier. Control means for controlling to be constant and a predetermined electrical quantity of the input signal inserted at a predetermined position in the path of the input signal between the signal input terminal and the signal output terminal and having a predetermined relationship with the base bias current And a deviation giving means for giving a deviation.

  The first detection circuit detects the power of the input signal to the amplifier circuit and outputs an input detection signal. The second detection circuit detects the power of the output signal from the amplifier circuit and outputs an output detection signal. The control circuit controls the base bias current of the grounded-emitter bipolar transistor so that the amplification gain of the power amplifier is controlled to be constant based on the comparison between the input detection signal and the output detection signal. The inventor has found that the change in the base bias current of the transistor has a large correlation with the change in the phase deviation between the input and output signals of the amplifier circuit including the transistor. Therefore, for example, if a phase deviation corresponding to the magnitude of the base bias current is given to the input signal, this phase deviation cancels with the phase deviation due to the base bias current deviation of the amplifier circuit, and the phase deviation of the amplified signal of the power amplifier The change in decreases. When a gain deviation is given to the input signal, the base bias current changes in order to keep the gain of the power amplifier constant. If the gain deviation is matched with the gain deviation caused by the change in the base bias current, the change in phase deviation between the input and output of the power amplifier can be reduced. Therefore, with the above-described configuration, the input of the power amplifier caused by the amplifier circuit is caused by giving a deviation with respect to a predetermined electric quantity such as a phase deviation or a gain deviation to the input signal with a predetermined relationship with the base bias current. Changes in phase deviation between output signals can be reduced. As a result, the linear characteristic of the power amplifier is improved. In order to perform such control, it is not necessary to detect a phase difference between input and output signals, and it is only necessary to detect a base bias current that is controlled so as to keep the gain of the power amplifier constant. Compared with the prior art, this power amplifier does not need to detect the phase of the output signal for correcting the phase of the output signal, and does not require a complicated circuit. As a result, a power amplifier having a simple circuit and good linear characteristics can be provided.

Preferably, the control means is connected to receive the input detection signal and the output detection signal, and in response to the input detection signal and the output detection signal, the bipolar transistor so that the amplification gain by the power amplifier is constant. including means for supplying a base bias current to the base electrodes of the polarization difference providing means is connected so as receive a base bias current produced by the means for supplying, in accordance with a predetermined functional relationship and base bias current A means for outputting a control signal of varying magnitude and an input signal path between the signal input terminal and the signal output terminal are inserted so as to receive the control signal and are proportional to the control signal. Phase deviation providing means for providing a phase deviation to the input signal in magnitude.

  The means for supplying supplies a base bias current to the base electrode of the grounded-emitter bipolar transistor so that the amplification gain by the power amplifier becomes constant in response to the input detection signal and the output detection signal. The control signal output means outputs a control signal whose magnitude changes according to a predetermined functional relationship with the base bias current. The means for giving the phase deviation has a magnitude proportional to the control signal and gives the phase deviation to the input signal. In the amplification by the common-emitter bipolar transistor, the output signal undergoes a phase deviation that changes in the same manner as the magnitude of the base bias current. The phase change at the input / output of the power amplifier can be reduced. Therefore, it is not necessary to detect the phase difference between the input and output of the power amplifier, and a complicated circuit is not required for phase correction. As a result, a power amplifier having a simple circuit and good linear characteristics can be provided.

  Preferably, the control signal changes with a positive correlation with the base bias current, and the phase deviation adding means receives the control signal at any position in the path of the input signal between the signal input terminal and the signal output terminal. And means for responding to the control signal and providing a phase delay to the input signal having a magnitude proportional to the magnitude of the control signal.

  The means for providing a phase lag provides a phase lag proportional to the magnitude of the control signal in response to the control signal. In general, when the output power of the amplifier circuit increases, the phase deviation of the transistor output increases. By the way, the inventor paid attention to the fact that this phase deviation draws an increasing curve very similar to the base bias current of the grounded-emitter bipolar transistor in the amplifier circuit. Therefore, a phase delay is given to the signal amplified by the amplifier circuit by the control signal that changes with a positive correlation with the base bias current. As a result, this phase delay and the change in phase deviation caused by the transistor cancel each other. Therefore, the change of the phase deviation of the output signal can be reduced as the whole power amplifier. It is not necessary to detect the phase difference between the input and output signals of the power amplifier in order to reduce the change in the phase deviation of the output signal. That is, a complicated circuit is not required for phase correction. As a result, a power amplifier having a simple circuit and good linear characteristics can be provided.

  Preferably, the means for outputting the control signal generates the control signal in a region where the base bias current is large so that the amount of increase in the amount is smaller than in a region where the base bias current is small.

  According to the simulation, an increase in phase deviation can be suppressed in a region where the base bias current is large. In the power amplifier configured as described above, the amount of increase in the size of the control signal is smaller in the region where the base bias current is large than in the small region. That is, an appropriate amount of phase deviation can be given to the amplified signal in accordance with how the phase deviation occurs due to the magnitude of the base bias current. Therefore, as a whole power amplifier, linear characteristics can be improved even in a region where the base bias current is large.

  Preferably, the deviation giving means is inserted between the signal input terminal and the input of the power amplifier.

  The deviation may be given anywhere between the signal input terminal and the signal output terminal, but if the input power to the deviation giving means itself is large, the signal may be distorted by the deviation giving means itself. . Therefore, it is preferable that the input power to the deviation applying means is small, and it can be avoided that the power efficiency of the entire circuit is reduced by being inserted between the signal input terminal and the input of the power amplifier.

Preferably, the deviation applying unit includes a gain deviation applying unit which is inserted between the first detection circuit and the input of the amplifier circuit and gives a gain deviation to the input signal with a predetermined relationship with the base bias current.

According to this power amplifier, the gain deviation is given to the input signal with a predetermined relationship with the base bias current by the gain deviation giving means inserted between the first detection circuit and the input of the amplifier circuit. Since the gain of the entire power amplifier tends to change due to this gain deviation, it is necessary to change the gain of the amplifier circuit in order to keep the gain constant. That is, it is necessary to change the base bias current of the common emitter bipolar transistor. For example, when a negative gain deviation is given as the gain deviation, the base bias current increases. As a result, a gain deviation is caused by the amplifier circuit. This gain deviation and the gain deviation given by the gain deviation giving means cancel each other, and the change in phase deviation due to the entire power amplifier can be reduced. Therefore, the linear characteristic of the entire power amplifier circuit can be improved. In this case as well, it is not necessary to detect the phase deviation between the input and output signals, and therefore a complicated circuit is not required for phase correction. As a result, a power amplifier having a simple circuit and good linear characteristics can be provided.

Preferably, the control means is connected so as to receive the input detection signal and the output detection signal, and in response to the input detection signal and the output detection signal, the gain of the bipolar transistor is made constant so that the amplification gain by the power amplifier becomes constant. including means for supplying a base bias current to the base electrode, the gain deviation imparting means is connected so as receive a base Subaiasu current generated by the means for feeding, the size according to a predetermined functional relationship to the base bias current The control signal is inserted into the path of the input signal between the means for outputting the control signal whose level changes and the input of the first detection circuit and the amplifier circuit so as to receive the control signal. And a means for providing a gain deviation having a predetermined relationship.

  When the gain deviation is given to the input signal by the means for giving the gain deviation, the base bias current supplied to the common-emitter bipolar transistor changes so that the gain of the entire power amplifier becomes constant. Then, a phase deviation occurs in the amplifier circuit. In order to cancel this phase deviation, a control signal is output according to a predetermined functional relationship with respect to the magnitude of the base bias current, and a gain deviation is given to the input signal with a predetermined relationship with this control signal. This gain deviation and the phase deviation generated in the amplifier circuit cancel each other, and the change in phase deviation can be reduced. Therefore, the linear characteristic of the entire power amplifier circuit is improved. Therefore, it is not necessary to detect a phase shift between the input and output of the power amplifier, and a complicated circuit is not required for phase correction. As a result, a power amplifier having a simple circuit and good linear characteristics can be provided.

  Preferably, the means for providing the gain deviation includes means for providing the input signal with a negative gain deviation whose magnitude is proportional to the magnitude of the control signal.

  If a negative gain deviation with a magnitude proportional to the magnitude of the control signal is given to the input signal, this gain deviation and the gain deviation caused by the change in the base bias current are determined by appropriately determining the proportionality constant. It can be canceled, and the linear characteristic of the power amplifier as a whole is improved. Therefore, it is not necessary to detect a phase difference between input and output signals, and a complicated circuit is not required for phase correction. As a result, a power amplifier having a simple circuit and good linear characteristics can be provided.

  Preferably, the control means is connected so as to receive the input detection signal and the output detection signal, and in response to the input detection signal and the output detection signal, the gain of the bipolar transistor is made constant so that the amplification gain by the power amplifier becomes constant. Means for supplying a base bias current to the base electrode, the deviation giving means being connected to receive the base bias current generated by the means for supplying and sized according to a predetermined functional relationship with the base bias current; Is inserted between the signal input terminal and the input of the amplifier circuit, and for giving a phase deviation and a gain deviation to the input signal with a predetermined relationship with the magnitude of the control signal. Means.

  The deviation giving means gives a phase deviation and a gain deviation to the input signal with a predetermined relationship with the base bias current. By giving a phase deviation to the input signal, the phase deviation of the amplified signal can be changed. Also, the phase deviation of the amplified signal can be changed by giving a gain deviation to the input signal. Therefore, by giving both of these to the input signal, the phase deviation of the amplified signal can be changed, and the change in the phase deviation as a whole can be reduced. Therefore, it is not necessary to detect the phase difference between the input and output of the amplifier circuit, and a complicated circuit is not required for phase correction. As a result, a power amplifier having a simple circuit and good linear characteristics can be provided.

  Preferably, the sign and the magnitude of the gain deviation and the phase deviation given to the input signal by the means for giving the phase deviation and the gain deviation are selected so as to cause a phase delay as a result of the amplifier circuit.

  As a sign and a magnitude of the gain deviation and the phase deviation given to the input signal, a value is selected such that a phase delay occurs in the input signal as a result of an increase in the magnitude of the control signal. The control signal changes in correlation with the base bias current. As the base bias current increases, the phase deviation generated in the grounded emitter bipolar transistor increases. By canceling this phase deviation somewhat by the phase delay caused in the input signal due to the gain deviation and the phase deviation, the change of the phase deviation in the entire power amplifier is reduced, and the linear characteristic is improved. Therefore, it is not necessary to detect the phase difference between the input and output amounts, and a complicated circuit is not required for phase correction. As a result, a power amplifier having a simple circuit and good linear characteristics can be provided.

  Preferably, the means for providing the phase deviation and the gain deviation includes means for providing the input signal with a gain deviation and a phase deviation, both of which have a negative correlation with the magnitude of the control signal.

  According to this power amplifier, a gain deviation and a phase deviation that change with a negative correlation with the magnitude of the control signal are given to the input signal. As a result, when the base bias current is increased, both the phase lag caused by the gain deviation and the phase lag caused by the phase deviation cancel each other with the phase deviation caused by the power amplifier, and the change of the phase deviation in the entire power amplifier can be reduced. The linear characteristic of the power amplifier can be improved. Therefore, it is not necessary to detect a phase difference between input and output, and a complicated circuit is not required for phase correction. As a result, a power amplifier having a simple circuit and good linear characteristics can be provided.

  A wireless communication apparatus according to a second aspect of the present invention includes any one of the power amplifiers described above. Therefore, the linear characteristic is good as in the power amplifier described above.

  According to the power amplifier of the present invention, a phase deviation or a gain deviation or both are given to the input signal so as to correlate with the base bias current of the common emitter bipolar transistor. This causes a phase deviation in the output of the amplifier circuit. If the magnitude of the given phase deviation or gain deviation is correlated with the base bias current so as to cancel the phase deviation occurring in the output of the amplifier circuit, the phase deviation occurring in the output signal of the entire power amplifier can be reduced. it can. Therefore, in order to reduce the phase deviation, it is not necessary to detect the phase of the output signal, and a circuit for that purpose is not required. That is, a complicated circuit is not required for phase detection. As a result, a power amplifier having a simple circuit and good linear characteristics can be provided.

[First Embodiment]
<Configuration>
FIG. 2 is a circuit diagram showing the configuration of the power amplifier 80 according to the present embodiment. Referring to FIG. 2, the power amplifier 80 has an input terminal 98 and an output terminal 108, has an input connected to the input terminal 98, and first and second outputs, to the input terminal 98. A first detection circuit that outputs an input detection voltage signal 110, which is an input detection signal indicating the power of the input signal, from a first output and outputs the remaining input signal to a second output from a part of the input signal 100, an input connected to the second output of the first detection circuit 100, a control signal terminal to which the control signal 104 is applied, and an output terminal, and an input output from the first detection circuit 100 The signal has a predistortion circuit 102 that outputs a phase deviation according to the control signal 104, and an input connected to the output of the predistortion circuit 102, and amplifies and outputs the output signal of the predistortion circuit 102. A pre-stage amplifier 90, an input connected to the output of the pre-stage amplifier 90, a post-stage amplifier 92 for further amplifying and outputting the output of the pre-stage amplifier 90, and an input connected to the output of the post-stage amplifier 92 An output detection signal which is an output detection signal having a first output terminal and a second output terminal connected to the output terminal 108 and indicating a power of the output signal from a part of the output signal from the post-stage amplifier 92. A second detection circuit that outputs the voltage signal 112 from the first output and outputs the remainder of the output signal to the output terminal.

  The power amplifier 80 further includes an output detection signal terminal 172 and an input detection signal terminal 170 connected to the first output of the first detection circuit 100 and the first output of the second detection circuit 106, respectively, and a predistortion circuit. The control signal supply terminal 182 and the base bias current terminal 180 are connected to the control signal terminal 102 and the control terminal of the post-stage amplifier 92, respectively, and the input detection voltage signal 110 and the output detection voltage signal 112 are compared, and the input power The base bias current 96 and the control signal 104 having a voltage proportional to the base bias current 96 are supplied to the post-stage amplifier 92 and the predistortion circuit 102, respectively. A bias controller 94 is included.

  The first detection circuit 100 has an input connected to the input terminal 98, and first and second outputs, and a part of the input signal from the input terminal 98 is input to the input comparison signal 122. , A directional coupler 120 that outputs the rest to the predistortion circuit 102 via the second output, an input connected to the first output of the directional coupler 120, and an output of the bias controller 94 And a power detector 124 having an output connected to the detection signal terminal 172 and detecting the power of the input comparison signal 122 supplied from the directional coupler 120.

  The second detection circuit 106 has an input connected to receive the output of the post-stage amplifier 92, and first and second outputs, and a part of the input signal from the post-stage amplifier 92 is output to the first output. A directional coupler 140 that outputs the output comparison signal 142 to the output terminal 108 via the second output, an input connected to the first output of the directional coupler 140, and bias control. And a power detector 144 that detects the power of the output comparison signal 142 provided from the directional coupler 140.

  The post-stage amplifier 92 has a base bias terminal 138 connected to the collector bias terminal 136 and the base bias current terminal 180 of the bias controller 94. The post-stage amplifier 92 has an input connected to the output of the pre-stage amplifier 90 and an output connected to the base bias terminal 138, and matches the input impedance of the input signal. A bipolar transistor 130 having a base terminal connected to the output and base bias terminal 138, a collector terminal connected to the collector bias terminal 136, and a grounded emitter terminal; an input connected to the collector bias terminal 136; An output matching circuit 134 having an output connected to the input of the directional coupler 140 and matching the output impedance of the output signal.

  It is important to use an amplifier having good linearity up to the input signal power at which the rear-stage amplifier 92 reaches saturation as the front-stage amplifier 90. This is because the distortion of the preamplifier 90 does not fall within the correction target based on the principle of the present embodiment in which the phase deviation of the bipolar transistor 130 included in the post amplifier 92 is corrected based on its base bias. Since the pre-stage amplifier 90 has a low input signal power, an amplifier having a good linearity can be used relatively easily.

  FIG. 3 is a circuit diagram showing the configuration of the power detector 124. The configuration of the power detector 144 is the same. With reference to FIG. 3, the power detector 124 has an input terminal 150, a bias terminal 154, and an output terminal 158. The power detector 124 has an input connected to the input terminal 150 and an output. The attenuator 152 attenuates and outputs an input signal applied to the input, and one end connected to the output of the attenuator 152. And a resistor 160 having the other end connected to the bias terminal 154.

  The power detector 124 further has an input connected to the output of the attenuator 152 and a grounded output, and a detection diode 156 for detecting a predetermined frequency of the input signal, and an output of the attenuator 152. And a low pass filter 162 having an output connected to the output terminal 158.

  FIG. 4 is a circuit diagram showing the configuration of the bias controller 94. Referring to FIG. 4, the bias controller 94 includes an input detection signal terminal 170 that receives the input detection voltage signal 110 shown in FIG. 2, an output detection signal terminal 172 that receives the output detection voltage signal 112 shown in FIG. 2 has a base bias current terminal 180 that outputs a base bias current 96, a control current supply terminal 182 that outputs a control signal 104 shown in FIG. 2, a constant current source 184, and power supply terminals 186 and 188. The bias controller 94 has a first input connected to the input detection signal terminal 170, a second input connected to the output detection signal terminal 172, and an output for outputting a differential current 176, and a power supply terminal A differential amplifier 174 that receives the supply voltage from 186 and amplifies the differential voltage between the input detection voltage signal from the first input and the output detection voltage signal from the second input is included.

  The bias controller 94 is further connected to receive a first output connected to the base bias current terminal 180, a first input connected to the control current supply terminal 182, and the output of the differential amplifier 174. A current mirror circuit 178 that receives a power supply voltage from the power supply terminal 188 and converts the differential current 176 input from the differential amplifier 174 into a current of a predetermined ratio, a current mirror circuit 178, and a ground potential And a constant current source 184 that keeps the current flowing in the current mirror circuit 178 constant.

  The differential amplifier 174 used in this embodiment includes four MOS transistors 200, 202, 204, and 206 and a constant current source 208 connected to each other as shown in FIG. Operates in response to supply. An input detection signal terminal 170 is connected to the gate terminal of the MOS transistor 204, and an output detection signal terminal 172 is connected to the gate terminal of the MOS transistor 206. A differential current 176 is output to the current mirror circuit 178 from the connection point between the MOS transistor 202 and the MOS transistor 206.

  The current mirror circuit 178 used in this embodiment includes three MOS transistors 210, 212, and 214 connected as shown in FIG. 4, and operates by being supplied with a power supply voltage from a power supply terminal 188. The source terminals of the MOS transistors 210, 212, and 214 are connected to the power supply terminal 188, the drain terminal of the MOS transistor 210 is connected to the constant current source 184, and the drain terminals of the MOS transistors 212 and 214 are the base bias current terminal 180 and the control, respectively. The current supply terminal 182 is connected.

<Operation>
The operation of the power amplifier 80 according to the present embodiment will be described with reference to FIGS. First, the power amplifier 80 according to the present embodiment is operated by applying a predetermined bias voltage to the collector bias terminal 136. A base bias current 96 is supplied from the base bias current terminal 180 of the bias controller 94 to the base bias terminal 138.

  A part of the input signal inputted from the input terminal 98 (see FIG. 2) is taken out by the directional coupler 120 as the input comparison signal 122 at a constant signal distribution ratio, and then the control signal is outputted by the predistortion circuit 102. A phase deviation is given according to 104. The input signal to which the phase deviation is given is amplified by the pre-stage amplifier 90 and the post-stage amplifier 92 and output. A part of the amplified signal is extracted by the directional coupler 140 as an output comparison signal 142 at a constant signal distribution ratio. The rest of the signal is output from the output terminal 108 as an output signal.

  The power detector 124 detects the input comparison signal 122 and outputs the input detection voltage signal 110. The power detector 144 detects the output comparison signal 142 and outputs the output detection voltage signal 112.

  The bias controller 94 compares the input detection voltage signal 110 and the output detection voltage signal 112, and changes the base bias current 96 so that the power ratio between the input power and the output power is kept constant. The bias controller 94 creates a control signal 104 proportional to the base bias current 96 and outputs it from the control current supply terminal 182.

  The high-frequency signal (input comparison signal 122 or output comparison signal 142) input from the input terminal 150 (see FIG. 3) is attenuated by the attenuator 152. The attenuated high frequency signal is converted into a detection voltage by the detection diode 156 to which a predetermined bias voltage is applied from the bias terminal 154, and is output from the output terminal 158. Here, when the signal power from the input terminal 150 increases, a signal is output such that the detection voltage output from the output terminal 158 decreases.

  The resistor 160 is inserted to prevent a high-frequency signal input from the input terminal 150 from flowing out to the bias terminal 154. Similarly, the low pass filter 162 inserted between the detection diode 156 and the output terminal 158 prevents the high frequency signal from flowing out to the output terminal 158.

  The input detection voltage signal 110 (see FIG. 2) is input from the input detection signal terminal 170 (see FIG. 4), and the output detection voltage signal 112 (see FIG. 2) is input from the output detection signal terminal 172 (see FIG. 4). The The differential voltage between the input detection voltage signal 110 and the output detection voltage signal 112 is amplified by the differential amplifier 174, and a differential current 176 is output. The differential current 176 is converted into a current having a predetermined ratio by the current mirror circuit 178. A predetermined ratio of current is output from the base bias current supply terminal 180. This output current is a base bias current 96 (see FIG. 2).

  A current separately generated by the current mirror circuit 178 is output from the control current supply terminal 182. This output current is a control signal 104 (see FIG. 2).

  The control signal 104 proportional to the base bias current 96 (see FIG. 2) is output from the control current supply terminal 182 of the bias controller 94 by the method as described above.

<Comparison of simulation results>
In the following, the simulation results when the power amplifier 80 according to the present embodiment is operated are compared. Before comparing the simulation results, the operating conditions of the power amplifier 80 will be described.

  First, operation conditions and simulation results when the function of the predistortion circuit 102 (see FIG. 2) is ignored will be described below. In the power amplifier 80 according to the present embodiment, a coupler having the same signal distribution ratio is used for the directional couplers 120 and 140.

  The attenuation rate of the attenuator 152 (see FIG. 3) of the power detector 144 was set to be larger than a predetermined amount (X (dB)). The total gain of the predistortion circuit 102, the pre-stage amplifier 90, and the post-stage amplifier 92, which are circuits between the directional couplers 120 and 140, is Y (dB).

  When Y (dB) has the same value as X (dB), the signal reaching the detection diode 156 (see FIG. 3) has the same value at the power detectors 124 and 144, and the input detection voltage signal 110 and the output detection voltage that are output. The signal 112 has the same value. Therefore, the same voltage is supplied to the input detection signal terminal 170 and the output detection signal terminal 172 of the differential amplifier 174 of FIG. 4, and the differential current 176 is not output.

  On the other hand, when gain Y (dB) becomes smaller than attenuation factor X (dB), the detected voltage signal at power detector 144 becomes larger than the detected voltage signal at power detector 124. Then, the differential amplifier 174 (see FIG. 4) allows the differential current 176 to flow to the differential amplifier side (in a direction opposite to the direction indicated by the arrow in FIG. 4). The total current of the differential current 176 and the constant current source 184 is inverted by the current mirror circuit 178 and output from the base bias current terminal 180. As a result, the base bias current 96 increases.

  An amplifier circuit using a bipolar transistor with a common emitter has the effect that the gain increases as the base bias current increases, and the gain decreases as the base bias current decreases. As a result, when the gain Y (dB) which is the gain of the amplifier is increased, the base bias current is decreased (in the direction of decreasing the gain), and when the gain is decreased, the base bias current is increased (in the direction of increasing the gain). The circuit is controlled so that feedback is applied.

  If the loop gain of the feedback loop is sufficiently large, the gain Y (dB) which is the gain of the entire amplifier is kept constant. Specifically, if the sensitivity of the power detectors 124 and 144, the amplification factor of the differential amplifier 174, and the mirror ratio of the current mirror circuit 178 are sufficiently large, the gain Y (dB) that is the gain of the entire amplifier is It is to work to be kept constant.

  However, in the configuration as described above, the gain cannot be detected when there is no input signal from the input terminal 98. Even when the input signal is very small, the loop gain is insufficient and feedback does not work. A problem arises in a transient state where the input signal gradually increases from a very small input signal, the loop gain of the feedback loop becomes sufficiently large, and the gain of the entire circuit is kept constant by feedback. This is a problem that a transition period from a small signal gain, which is an amplification gain when the input signal is very small, to a gain kept constant by feedback occurs, and the linearity of the amplifier deteriorates during that period.

  The power amplifier 80 according to the present embodiment is configured such that the small signal gain and the gain kept constant by feedback coincide with each other in order to avoid the transition period in which the linearity deteriorates. Specifically, the two coincide with each other by adjusting the attenuation factor X (dB).

  Thereafter, unless otherwise specified, in the simulation calculation, the adjusted attenuation rate X (dB) matches the small signal gain with the gain kept constant by feedback.

  FIG. 5 is a graph showing a simulation result of gain controlled to be constant by feedback. The simulation result in FIG. 5 shows the calculation result when the predistortion circuit 102 (see FIG. 2) is stopped. In this simulation calculation, device parameters of a bipolar transistor on a GaAs substrate were used as an amplifier circuit, and characteristics of a diode and a field effect transistor on a Si substrate were used as a bias circuit, and the operating frequency was 5 GHz. The gain of the entire amplifier circuit is about 18 dB. Thereafter, the simulation calculation is performed under this condition.

  In FIG. 5, the horizontal axis represents output power (dBm), the left vertical axis represents gain change, and the right vertical axis represents phase change. A change in gain and a change in phase are represented by a gain deviation (unit: dB) and a phase deviation (unit: degree) as a change amount from a value at the time of a small signal.

  An example of the use of the power amplifier 80 according to the present embodiment is a wireless LAN (Local Area Network). In the OFDM (orthogonal frequency division multiplexing) modulation scheme (56QAMQPSK) of this wireless LAN standard, generally, the modulation accuracy (EVM: Error) which shows substantially the same linearity degradation at a ratio of 5 ° phase deviation to 1 dB gain deviation. Degradation of Vector Magnitude) often occurs. Therefore, the vertical axis direction is expressed as 1 dB = 5 ° so that the phase deviation 220 and the gain deviation 222 can be easily compared directly on the graph.

  Note that | gain deviation | <0.5 dB and | phase deviation | <2.5 ° are approximate guidelines that can be used as a linear amplifier in the wireless LAN.

  As described above, in this simulation calculation, since the gain is controlled to be constant, the gain deviation is very small. On the other hand, since the phase deviation is not controlled, the deviation becomes very large from around the output of 10 dBm.

  In the power amplifier 30 (see FIG. 1) according to the prior art, the phase deviation is detected and corrected by the variable phase shifter 46 in order to prevent a large deterioration in linearity due to the phase deviation. However, the inventor has noticed that the change in phase deviation is very similar to the change in base bias current.

  FIG. 6 is a graph showing the relationship between the phase deviation and the base bias current change. The base bias current change is shown as a base current deviation (unit: A) from an idle current (base current at no signal).

  Referring to FIG. 6, base current deviation 230 and phase deviation 232 show similar increasing curves. In particular, both start increasing from approximately the same output signal power (around 10 dBm) and follow a similar increasing curve until reaching an output value of about 25 dBm.

  Accordingly, the present inventor has come up with the idea that by adjusting the phase according to the base current deviation, the phase can be appropriately corrected without detecting the phase deviation as in the prior art. This is a method of controlling the phase using the same control current as the base current using a variable phase shifter as the predistortion circuit 102 which has been described with the operation stopped so far. If the coefficient of phase change of the control current versus the variable phase shifter is set appropriately, the above phase deviation should be able to be corrected.

  FIG. 7 is a graph showing the result of simulating the relationship between the gain deviation 240 and the phase deviation 242. This graph shows the gain deviation 240 and the phase deviation 242 as a result of simulation calculation of the predistortion circuit 102 as an ideal phase shifter that generates a phase change of −5 ° per 1 mA increase of the base bias current.

  Referring to FIG. 7, it can be seen that the significant phase deviation from the vicinity of the output of 10 dBm seen in FIG. 5 is suppressed, and the linearity of the amplifier circuit is improved. For a configuration that controls the phase shifter using the base current deviation, a feedback configuration in which the gain deviation is zero is extremely important.

  FIG. 8 is a graph showing the result of simulating the relationship between the gain deviation 250 and the phase deviation 252 under different conditions. In this graph, as an example in which the gain deviation cannot be kept constant, a simulation calculation result corresponding to the state of FIG. 5 (predistortion circuit 102) when the small signal gain and the gain kept constant by feedback are intentionally different by 1 dB. Simulation results of stopping the work of Referring to FIG. 8, a region 254 where the gain deviation 250 shifts occurs from output power −10 dBm to 10 dBm.

  FIG. 9 is a graph showing the simulation results of the base current deviation 260 and the phase deviation 262 under the same conditions as the simulation calculation of FIG. Referring to FIG. 9, phase deviation 262 once becomes negative, and becomes positive again from the vicinity of 20 dBm output. On the other hand, the base current deviation 260 is always positive. Therefore, the relationship between the base current deviation 260 and the phase deviation 262 cannot be expressed by a simple relationship. As a result, the phase cannot be corrected using the relationship between the two. However, when attention is paid only to the signal intensity region 256 (see FIG. 8) in which the gain deviation 250 is controlled to be constant, the effect of the present invention appears remarkably.

  FIG. 10 is a graph showing simulation results of the gain deviation 270 and the phase deviation 272 under the same conditions as the simulation calculations of FIG. 8 and FIG. This graph shows a gain deviation 270 and a phase deviation 272 as a result of simulation calculation of the predistortion circuit 102 as an ideal phase shifter that generates a phase change of −5 ° per 1 mA increase of the base bias current.

  Referring to FIG. 10, when the output power is limited to around 10 dBm to 26 dBm, the phase deviation becomes constant and the linearity is improved. That is, in this embodiment, there is no effect unless there is a constant gain condition by feedback for controlling the base current. However, for example, even if the constant gain condition is not satisfied in a partial range of the output power, the effect of the other range in which the gain is constant is not hindered. As a result, the effect of the present invention is produced in a part of the range where the gain is constant.

  The reason why the base current deviation, which is a change in the base bias current, and the phase deviation behave in a similar manner under the above-described constant gain condition, is not exactly clarified. However, the outline will be described below.

  First, as the signal strength of the input signal increases, the base bias current must be increased in order to keep the gain of the common emitter bipolar transistor amplifier constant.

  In order to increase the base bias current, it is necessary to increase the bipolar base bias voltage.

  The phase of the amplified signal varies as the parameter of the amplifying element changes with the intensity of the amplified signal. Among them, the base emitter capacitance, the base collector capacitance, and the delay time of the collector current change depending on the base-emitter voltage and the collector current, which are the main causes of the phase shift.

  The base bias current and the base bias voltage are expressed by an exponential relational expression when DC measurement is performed. However, the base bias current and the base bias voltage that change with the input signal under feedback have a relationship that can be approximated as described below. In addition, in the relationship between the base current and the collector current, a proportional relationship related by the current amplification factor β is substantially established even under feedback, as in normal DC measurement.

  FIG. 11 is a graph showing the relationship between the base bias current, the base bias voltage, and the collector current. Here, the collector current deviation 280 and the base voltage deviation 282 are graphed with respect to the base current deviation, with the base bias current, the base bias voltage, and the collector current being changed from the values at the time of no signal, respectively.

  Base emitter capacitance, base collector capacitance, base-emitter voltage and collector current dependency of collector current delay time are first order approximations to base current, base voltage, and collector current before the amplified output reaches saturation. It shows a moderate dependency that can be made. As a result, it is possible to estimate and correct the phase deviation by the primary approximation using the base bias current.

  The above description is made only for the DC component during operation in the base voltage deviation, the collector current deviation, the base current deviation, and the like. However, strictly speaking, the base voltage deviation, the collector current deviation, the base current deviation, and the like are not only such changes in the DC component, but also the instantaneous voltage of the high frequency signal (the 5 GHz signal of the operating frequency in this embodiment). It is also influenced by the value and current value. As a result, since more complicated factors are combined and the phase is shifted, the phase deviation cannot be completely clarified. However, in reality, as described above, the phase deviation can be estimated very effectively by the direct current component of the base bias current. Then, the phase can be corrected using the estimation result.

  Note that the direct current component and the direct current voltage component in the above description are the current and voltage (WLAN (Wireless Local Area Network) signal) of each instantaneous moment that changes according to the modulation signal in the actual modulation wave. Current and voltage changing at a frequency of about 20 MHz or less. However, since the frequency is very low compared with the high frequency signal (5 GHz), the DC component is described here for the sake of simplicity.

  Further, as described in the present embodiment, it is not necessary to employ only a configuration for controlling the phase according to the base current deviation which is a predetermined electrical quantity. Similarly, the phase may be adjusted according to a base voltage deviation and a collector current deviation which are predetermined electrical quantities and are substantially proportional to the base current deviation. However, when the collector current deviation is detected and used as a control signal, the amplified high-frequency signal is superimposed, so that it is necessary to separate the high-frequency signal. Further, since the collector current detection circuit tends to cause a reduction in the efficiency of the entire amplifier, it is preferable to detect the base current and the base voltage.

  When detecting the base voltage, the voltage at the base terminal of the transistor itself is required, and the input matching of the amplifying element is affected. On the other hand, the base current can be detected by inserting a circuit for removing a high-frequency signal that is an amplified signal, such as a low-pass filter, between the detector and the base terminal. Further, as in the present embodiment, the base bias current and the control current can be made proportional to each other by a current mirror. Therefore, it is more preferable to detect the base current than to detect the base voltage.

  However, in the vicinity of the saturation output, the base voltage often exhibits a behavior closer to the phase deviation than the base current. Therefore, it may be preferable to detect the base voltage and control the phase based on the detected base voltage.

  FIG. 12 is a graph showing simulation results of the phase deviation 290 and the base voltage deviation 292 under the same conditions as the simulation calculation of FIG. In FIG. 6, while the base current deviation 230 continues to increase near the saturated output, the phase deviation 232 decreases and the correlation between the two is poor. On the other hand, in FIG. 12, since the base voltage deviation 292 decreases with the phase deviation 290 near the saturation output 294, the correlation between the two is good. Therefore, controlling the phase using the base voltage deviation 292 can suppress the phase deviation 290 more appropriately in the vicinity of the saturated output 294.

  Further, when the predistortion circuit 102 (see FIG. 2) is an ideal phase shifter as shown in the present embodiment, or is a phase shifter that is relatively close to ideal and has a gain with respect to phase adjustment. If the change is small enough, the gain is not affected. Therefore, the predistortion circuit 102 may be arranged at any position in the signal path from the input terminal 98 to the output terminal 108.

  For example, the predistortion circuit 102 is connected between the pre-stage amplifier 90 and the post-stage amplifier 92, between the post-stage amplifier 92 and the output terminal 108, between the input terminal 98 and the directional coupler 120, or with the directional coupler 140. It may be arranged between the output terminal 108. However, in practice, the predistortion circuit 102 causes a certain loss of power. Therefore, in order to reduce deterioration in power efficiency of the entire circuit, it is more preferable that the predistortion circuit 102 is disposed on the input terminal 98 side from the amplifying element.

  Further, the predistortion circuit 102 has a certain power durability characteristic, and when the input power is large, the predistortion circuit 102 itself may be distorted. Therefore, also from this point, it is preferable that the predistortion circuit 102 is disposed closer to the input terminal than the amplifying element, and the input power to the predistortion circuit 102 is reduced.

  In this embodiment, a current proportional to the base current supplied from the current mirror circuit 178 (see FIG. 4) is used as the control current. However, since it is the essence of the invention to use the timing at which the base current starts to increase and its increase curve, the control current may be converted into a voltage by a resistor and used.

  According to the power amplifier 80 according to the present embodiment, the phase is corrected by adjusting the base current using the predistortion circuit 102 as a phase shifter. Similarly, the phase bias can be estimated and corrected by adjusting the base bias current. Further, the phase can be corrected by adjusting the base voltage deviation. Therefore, a complicated circuit is not required for phase correction. As a result, a power amplifier having a simple circuit and good linear characteristics can be provided.

[Second Embodiment]
<Configuration>
The power amplifier according to the present embodiment has the same circuit configuration as that of the power amplifier 80 according to the first embodiment. Therefore, detailed description of the circuit configuration will not be repeated here.

  The predistortion circuit 102 is an ideal phase shifter having a phase change of −5 ° per 1 mA increase of the base bias current, similarly to the power amplifier 80 according to the first embodiment. However, in the present embodiment, the control current is not simply a current proportional to the base current.

  FIG. 13 is a graph 300 showing the relationship between the control current and the base current deviation of the power amplifier according to this embodiment. Referring to FIG. 13, the control current is assumed to be a current related to the base current deviation by a certain function. In the region where the current value is large, the increase in the control current is slightly suppressed, and an upper limit is set for the control current. This can be easily realized by processing the base bias current digitally or analogly to create a control current.

<Operation>
The operation of the power amplifier according to the present embodiment is the same as that of the power amplifier 80 according to the first embodiment. Therefore, detailed description of the operation will not be repeated here.

<Comparison of simulation results>
FIG. 14 shows the relationship between the phase deviation 310 and the gain deviation 312 of the amplifier when the control current of the power amplifier according to this embodiment is used. In the power amplifier 80 according to the first embodiment, in the region where the base current deviation and the phase deviation do not coincide with each other in the vicinity of the saturation output in FIG. 5 showing the relationship between the phase deviation 220 and the gain deviation 222 (range of 26 dBm or more). In FIG. 7, the phase deviation starts to increase. However, referring to FIG. 14, it is possible to read the effect that the phase deviation is suppressed in the same region.

  According to the power amplifier according to the present embodiment, it is possible to suppress the phase deviation even in a region where the base current deviation and the phase deviation do not match (range of output 26 dBm or more).

[Third Embodiment]
<Configuration>
The power amplifier according to the present embodiment has a circuit configuration similar to that of power amplifier 80 according to the first embodiment. Therefore, detailed description of the circuit will not be repeated here. However, in the power amplifier according to the present embodiment, an attenuator is used as the predistortion circuit 102 instead of a phase shifter.

  When the predistortion circuit 102 is disposed between the input terminal 98 (see FIG. 2) and the directional coupler 120 or between the directional coupler 140 and the output terminal 108, the amount of attenuation by the predistortion circuit 102 is reduced. Is not detected. Therefore, the control circuit does not correct the gain to be constant. As a result, there is no change in the base bias current and the phase change is not corrected. Therefore, in the configuration of this embodiment using an attenuator as the predistortion circuit 102, the predistortion circuit 102 is disposed between the directional coupler 120 and the directional coupler 140, unlike the case of using a phase shifter. Things are necessary.

<Operation>
The operation of the power amplifier according to the present embodiment is almost the same as that of the power amplifier 80 according to the first embodiment. The only difference is that, in this embodiment, an attenuator is used instead of a phase shifter in the predistortion circuit 102, and a gain deviation is given by the predistortion circuit 102 in accordance with the control signal 104. Therefore, detailed description of the operation will not be repeated here.

<Comparison of simulation results>
FIG. 15 is a graph showing the result of simulating the relationship between the phase deviation 320 and the gain deviation 322. Here, the phase deviation 320 and the gain deviation 322 are shown as a result of simulation calculations using the predistortion circuit 102 as an ideal attenuator that produces an attenuation ratio of −0.55 dB per 1 mA increase in control current. Referring to FIG. 15, it can be seen that the significant phase deviation from the vicinity of the input 10 dBm seen in FIG. 6 is suppressed, and the linearity of the amplifier circuit is improved.

  As described in the first embodiment, the amplifier circuit controlled to have a constant gain generates the phase deviation 220 as shown in FIG. 5, and the phase needs to be corrected. However, when a signal is attenuated by using a variable attenuator as the predistortion circuit 102 (see FIG. 2), the base bias current 96 increases so that the gain of the entire circuit does not fluctuate due to feedback.

  In an amplifier circuit using a bipolar transistor with a common emitter, the phase of the amplified signal is delayed due to an increase in base bias current. In the configuration of the power amplifier according to the present embodiment, the phase is adjusted using this action.

  FIG. 16 is a graph showing the result of simulating the relationship between the gain deviation 330 and the phase deviation 332. Here, the relationship between the gain deviation 330 and the phase deviation 332 when simulation calculation is performed by controlling the base bias current of the post-stage amplifier 92 (see FIG. 2) to 2 to 5 mA forcibly at 5 dBm input. Indicates.

  Referring to FIG. 16, in order to keep the overall gain deviation constant, the base bias current increases so as to increase the gain deviation 330 of bipolar transistor 130 (see FIG. 2). This increase in the base bias current changes the phase deviation 332 to minus. As a result, the phase can be adjusted.

  Here, as in the first embodiment, the base voltage deviation and the collector current deviation can be used as the control signal in addition to the base current deviation.

  Further, similarly to the first embodiment, a signal that is calculated and processed based on the base current deviation, the base voltage deviation, and the collector current deviation can be used as the control signal.

  Furthermore, in this embodiment, an attenuator is used as the predistortion circuit 102. However, the present invention is not limited to an attenuator, and any device that can adjust a gain deviation appropriately can be used. Therefore, a variable gain amplifier in which the predistortion circuit 102 itself has a gain may be used.

  In the power amplifier according to the present embodiment, the base bias current increases so as to increase the gain of the bipolar transistor 130 in order to keep the overall gain deviation constant. This increase in base bias current changes the phase deviation to negative. As a result, a power amplifier capable of adjusting the phase can be provided.

[Fourth Embodiment]
<Configuration>
The power amplifier according to the present embodiment has substantially the same circuit configuration as the power amplifier according to the first embodiment. However, unlike the first embodiment, the predistortion circuit 102 (see FIG. 2) is characterized by using a phase shifter / attenuator that generates both a phase deviation and a gain deviation for the control signal. To do. Therefore, only the detailed configuration of the predistortion circuit will be described, and description of other parts will not be repeated.

  FIG. 17 is a circuit diagram showing a variable predistortion circuit 398 used in the power amplifier according to the present embodiment, the phase of which is delayed with the attenuation by the control voltage. Referring to FIG. 17, variable predistortion circuit 398 has an input terminal 340, a control terminal 344, and an output terminal 342. The variable predistortion circuit 398 has an input connected to the input terminal 340 and an output, a matching circuit 346 for matching the input impedance of the input signal, an input connected to the output of the matching circuit 346, and an output 4 stages of basic circuits 348A, 348B, 348C and 348D connected in series with each other, an input connected to the output of the basic circuit 348D, and an output connected to the output terminal 342, and an output And a matching circuit 350 for matching the output impedance of the signal.

  The four-stage basic circuits 348A, 348B, 348C, and 348D all have the same configuration. For example, the basic circuit 348A is connected to the output of the circuit 346, the capacitor 390A having one terminal connected to the output of the matching circuit 346, the resistor 396A connected between the other end of the capacitor 390A and the control terminal 344. A field effect transistor 394A having a source terminal and a gate terminal connected to a connection point of the capacitor 390A and the resistor 396A, and a capacitor 392A having one terminal connected to the connection point of the capacitor 390A and the resistor 396A.

  The basic circuits 348B, 348C, and 348D have the same configuration as the basic circuit 348A. These components include the same reference numbers (numerals) as the elements of the basic circuit 348A and elements “B” instead of “A” at the end of the elements corresponding to the elements of the basic circuit 348A. , “C” and “D” will be described, and the details of the connection relationship will not be repeated here.

  Note that the terminal of the capacitor 392A that is not connected to the capacitor 390A is connected to one terminal of the capacitor 390B of the adjacent basic circuit 348B, and the terminal of the capacitor 392B that is not connected to the capacitor 390B is the adjacent terminal. Connected to one terminal of the capacitor 390C of the basic circuit 348C, and so on. The source and drain of adjacent ones of the field effect transistors 394A, 394B, 394C and 394D of the basic circuits 348A, 348B, 348C and 348D are connected to each other.

  The matching circuit 346 is connected to the capacitor 380 having one terminal connected to the input terminal 340 and the other terminal grounded, one terminal connected to the input terminal 340, the capacitor 390A and the field effect transistor 394A. And an inductance 382 having the other terminal.

  Matching circuit 350 has an inductance 369 having one terminal connected to capacitor 392D, the other terminal connected to output terminal 342, one terminal connected to output terminal 342, and the other terminal grounded. And a capacitor 371.

  Since the power amplifier according to the present embodiment is designed for 5 GHz operation, the capacitance is 4 pF, the resistance is 5 KΩ, the field effect transistor (n-channel) gate length is 5 μm, and the gate width is 100 μm.

  In order to improve power durability, the basic circuits 348A to 348D are multistaged (four stages). Further, the inductances 382 and 369 are 1.8 mm for the mounting wire, and the capacitors 371 and 380 are 1 pF. By adding the matching circuits 346 and 350, the basic circuits 348A to 348D can be operated with low impedance. As a result, power durability is improved.

  The variable predistortion circuit 398 has a gain deviation. Thus, as in the case of the ideal attenuator shown in the third embodiment, the place where the variable predistortion circuit 398 is disposed is limited between the directional coupler 120 and the directional coupler 140.

<Operation>
The power amplifier according to the present embodiment operates substantially the same as the power amplifier 80 according to the first embodiment. The difference is that a phase shifter / attenuator that generates a phase deviation and a gain deviation with respect to the control signal is used as the variable predistortion circuit 398. Therefore, only the operation relating to variable predistortion circuit 398 will be described below, and description of the operation of other components will not be repeated.

  A part of the input signal input from the input terminal 98 (see FIG. 2) is extracted by the directional coupler 120 as the input comparison signal 122 at a constant signal distribution ratio. The extracted input comparison signal 122 is given a phase deviation and a gain deviation according to the control signal 104 by the variable predistortion circuit 398.

<Comparison of simulation results>
FIG. 18 is a graph showing the result of simulating the relationship between the gain deviation 400 and the phase deviation 402. Referring to FIG. 18, the signal transmission characteristic between input terminal 340 and output terminal 342 shows gain deviation 400 and phase deviation 402 with respect to the control voltage applied to control terminal 344 (see FIG. 17). It was.

  According to this result, the gain deviation 400 becomes negative with respect to the control voltage from about 0.5V to 2.5V. That is, it can be seen that there is a phase delay in which the attenuation rate increases and the phase deviation becomes negative.

  A circuit having linearity of about ± 0.2 dB and ± 1 ° is formed up to about 10 dBm by such a configuration that improves the power durability.

  FIG. 19 is a graph showing the result of simulating the relationship between the gain deviation 410 and the phase deviation 412. This was obtained by performing simulation calculation of the amplifier circuit shown in FIG. 2 using the circuit of FIG. 17 as the predistortion circuit 102. The control current is generated at a ratio of 1: 1 to the base bias current by the current mirror circuit 178, is converted into a control voltage with a resistance of 200Ω, and is supplied to the control terminal 344 in FIG. Referring to FIG. 19, it can be seen that the significant deviation of the phase from around the output of 10 dBm seen in FIG. 5 is suppressed and the linearity of the amplifier circuit is improved.

  Unlike the cases of FIGS. 8 and 9, in this embodiment, the variable predistortion circuit 398 is not an ideal circuit. Therefore, the non-linearity between the phase deviation versus control current and the gain deviation versus control current has an effect, and the phase deviation is somewhat wavy. However, even if there is such a phase deviation, it can be used as a power amplifier.

  The circuit used as the variable predistortion circuit 398 may have a phase that slightly advances with attenuation, in addition to the phase delay with attenuation.

  Further, even if the attenuation and phase are opposite to the target adjustment direction with respect to the change in the control current, the change amount of one is main and the change amount of the other is small, which is canceled by the relationship of FIG. As a result, it is only necessary to leave a change in the phase deviation. Therefore, a circuit in which the phase change is main and the attenuation ratio slightly decreases with the phase delay (the gain deviation becomes +) may be used. However, when such a circuit is used, the phase shift action and the damping action cancel each other, so that the sensitivity of the phase deviation to the control current becomes dull. Therefore, it is most preferable that the phase is delayed with attenuation.

  In addition to the base current deviation, a base voltage deviation and a collector current deviation may be used as the control signal, as in the first embodiment.

  Further, as in the first embodiment, the control signal may be a signal that is calculated and processed based on the base current deviation, the base voltage deviation, and the collector current deviation.

  An ideal phase shifter and an ideal attenuator have a problem that the circuit size is large and it is practically difficult to apply to a small device such as a wireless terminal. However, in the configuration of the power amplifier according to the present embodiment, the circuit is configured by a predistortion circuit in which both the phase and the gain are changed. Therefore, the circuit can be reduced in size.

[Fifth Embodiment]
<Configuration>
FIG. 20 is a block diagram showing the configuration of radio communication apparatus 460 using power amplifier 80 according to the first embodiment. In addition, the same number is attached | subjected about the same component as 1st Embodiment.

  Referring to FIG. 20, radio communication apparatus 460 includes modulation section 420 that outputs an input signal as an OFDM modulated wave, amplification circuit 442 that amplifies and outputs the input signal modulated by modulation section 420, and amplification circuit 442. Transmission filter 426 that passes only the electric signal having a predetermined frequency among the electric signals amplified by, an antenna 430 for outputting the electric signal that has passed through transmission filter 426, and connection between transmission filter 426 and antenna 430 And a switch 428 for switching (opening and closing).

  The wireless communication device 460 further includes a reception filter 434 for passing only a predetermined frequency of electrical signals received from the antenna 430, and a switch 432 for switching the connection between the reception filter 434 and the antenna 430. The low noise amplifier 436 that amplifies the electrical signal that has passed through the reception filter 434, the demodulator 438 that demodulates the electrical signal amplified by the low noise amplifier 436, and the output of the transmission filter 426 and the input of the reception filter 434 And a switch 440 for opening and closing the connection.

  The wireless communication device 460 is further connected to receive the demodulation error signal 456 from the demodulator 438, and controls the operations of the modulator 420, the switches 428, 432, and 440, the demodulator 438, and the amplifier circuit 442, respectively. A control block 448 is included that controls at 464, 462, and 452.

  The amplifier circuit 442 detects the electric power of the electric signal using a part of the electric signal modulated by the modulation unit 420, outputs the input detection voltage signal 110, and supplies the remaining electric signal to the predistortion circuit 102. A detector 422, a predistortion circuit 102 that gives a phase deviation to the modulated electric signal, a preamplifier 90 that amplifies the electric signal given the phase deviation by the predistortion circuit 102, and the electric amplified by the preamplifier 90 A post-stage amplifier 92 that further amplifies the signal, and a part of the electric signal amplified by the post-stage amplifier 92 is used to detect the power of the output electric signal and output the output detection voltage signal 112, and the remaining output electric signal And a power detector 424 applied to the transmission filter 426 in the subsequent stage.

  The amplifier circuit 442 further compares the input detection voltage signal 110 given from the power detector 422 with the output detection voltage signal 112 given from the power detector 424, and the subsequent stage so that the gain of the amplifier circuit 442 becomes constant. The bias controller 94 that changes the base bias current 96 of the bipolar transistor in the amplifier 92 and the control signal 104 supplied from the bias controller 94 change the amplification factor according to the amplification control signal 446 supplied from the control block 448. And a variable current amplifier 444 that amplifies the signal and supplies it to the predistortion circuit 102.

  Here, the variable current amplifier circuit 444 is a deviation ratio control unit that adjusts the deviation ratio of the phase deviation or the gain deviation with respect to the control current of the predistortion circuit 102.

  FIG. 21 is a flowchart showing a method for controlling wireless communication apparatus 460. Referring to FIG. 21, when communication is started, in step 470, control block 448 performs a process of connecting switch 440 and disconnecting switch 428 and switch 432.

  In step 472, the control block 448 performs processing for causing the modulation unit 420 to transmit a reference signal and causing the demodulation unit 438 to start demodulation. In addition, the control block 448 performs a process of controlling the demodulation unit 438 to calculate the error frequency at the time of demodulation and to transmit the demodulation error signal 456 as needed. Further, the control block 448 performs control so as to change the current amplification factor of the variable current amplifier 444 while receiving the demodulation error signal 456 so as to obtain the current amplification factor with the lowest error frequency.

  In step 474, the control block 448 performs processing for setting the variable current amplifier 444 with the current amplification factor obtained in step 472 that minimizes the error frequency. Further, the control block 448 also performs processing of causing the modulation unit 420 to stop transmission of the reference signal, causing the demodulation unit 438 to stop demodulation, and stopping transmission of the demodulation error signal 456.

  In step 476, the control block 448 performs processing for disconnecting the switch 440.

  In step 478, the control block 448 performs the necessary transmission / reception processing while switching the switch 428 and the switch 432 in accordance with the transmission / reception.

  In step 480, processing for determining whether or not the communication is completed is performed. If communication is completed, the process is terminated. If communication is not completed, the process returns to step 470 and the subsequent processing is repeated.

  As the reference signal in step 472, a dummy signal of a modulated wave that can be demodulated by the demodulator 438 is used. The intensity of the reference signal is assumed to have a high correlation between the base bias current of the post-stage amplifier 92 and the phase deviation. This is within the signal intensity range up to 25 dBm of output power in FIG. In order to increase the detection sensitivity, it is preferable to set the signal intensity as high as possible.

<Operation>
Hereinafter, an operation of radio communication apparatus 460 according to the present embodiment will be described. Referring to FIG. 20, first, an OFDM modulated wave is output from modulation section 420 based on control signal 450 given from control block 448. The power detector 422 detects the power by using a part of the OFDM modulated wave, and outputs a detected voltage signal. The input detection voltage signal 110 is supplied to the bias controller 94. The remaining OFDM modulation wave is given to the predistortion circuit, and the phase deviation is given by the predistortion circuit 102. Note that the predistortion circuit 102 is controlled by a control signal 104 that is amplified by a variable current amplifier circuit 444 based on an amplification factor that changes in accordance with an amplification control signal 446 provided from the control block 448. The control signal 104 is proportional to the base bias current 96.

  The electric signal composed of the OFDM modulated wave to which the phase deviation is given is amplified by the pre-stage amplifier 90 and the post-stage amplifier 92. The operation of the post-stage amplifier 92 is controlled by a base bias current 96 that is changed based on a comparison between the input detection voltage signal 110 and the output detection voltage signal 112 in the bias controller 94. By this control, the gain of the amplifier circuit 442 becomes constant.

  The power detector 424 detects the power by using a part of the amplified electric signal, and supplies the output detection voltage signal 112 to the bias controller 94. The remaining electrical signals are supplied to the transmission filter 426, and only those having a predetermined frequency pass through the transmission filter 426. The signal that has passed through the transmission filter 426 is transmitted from the antenna 430 through the switch 428.

  The electrical signal received by the antenna 430 is given to the reception filter 434 through the switch 432. Of the applied electrical signals, only those having a predetermined frequency pass through the reception filter 434. The electric signal having a predetermined frequency that has passed through the reception filter 434 is amplified by the low noise amplifier 436. The amplified electrical signal is demodulated by the demodulator 438 based on the control signal 454 from the control block 448. A demodulation error signal 456 is input to the control block 448 from the demodulator 438.

  Based on the control signal 452 from the control block 448, the transmission signal is input from the transmission filter 426 to the reception circuit side by switching the switch 440.

  As described above, wireless communication apparatus 460 according to the present embodiment can detect a state with the highest linearity and perform wireless communication in that state. In the prior art, since it is not known at which input power the phase and gain distortion starts to occur and how they change, a method has been used in which both are always detected and corrected. However, in the present embodiment, since the phase is adjusted by the change in the base current, it is not necessary to detect the phase. As a result, it is possible to provide a communication device with good linearity characteristics by using a power amplifier with a simple circuit and good linear characteristics.

  The embodiment disclosed herein is merely an example, and the present invention is not limited to the above-described embodiment. The scope of the present invention is indicated by each of the claims after taking into account the description of the detailed description of the invention, and all modifications within the meaning and scope equivalent to the wording described therein are intended. Including.

It is a circuit diagram which shows the structure of the power amplifier 30 of a prior art. 1 is a circuit diagram showing a configuration of a power amplifier 80 according to a first embodiment. FIG. 3 is a circuit diagram showing a configuration of power detectors 124 and 144. FIG. 7 is a circuit diagram showing a configuration of a bias controller 94. FIG. It is a graph which shows the simulation result by which the gain was controlled uniformly by feedback. It is a graph which shows the relationship between a phase deviation and a base bias current change. It is a graph which shows the result of having simulated the relation between gain deviation 240 and phase deviation 242. FIG. It is a graph which shows the result of having simulated the relationship between the gain deviation 250 and the phase deviation 252 by changing conditions. It is a graph which shows the simulation result of the base current deviation 260 and the phase deviation 262 on the same conditions as the simulation calculation of FIG. 10 is a graph showing simulation results of gain deviation 270 and phase deviation 272 under the same conditions as in the simulation calculations of FIGS. 8 and 9. It is a graph which shows the relationship between a base bias current, a base bias voltage, and a collector current. It is a graph which shows the simulation result of the base voltage deviation 292 and the phase deviation 290 on the same conditions as the simulation calculation of FIG. It is the graph 300 which shows the relationship between the control current and base current deviation of the power amplifier which concerns on 2nd Embodiment. It is a graph which shows the relationship of the phase deviation 310 and the gain deviation 312 of an amplifier at the time of using the control current of the power amplification apparatus which concerns on 2nd Embodiment. It is a graph which shows the result of having simulated the relation between phase deviation 320 and gain deviation 322. FIG. It is a graph which shows the result of having simulated the relation between gain deviation 330 and phase deviation 332. It is a circuit diagram which shows the variable predistortion circuit 398 used for the power amplifier which concerns on 4th Embodiment, and a phase is delayed with attenuation | damping by a control voltage. It is a graph which shows the result of having simulated the relation between gain deviation 400 and phase deviation 402. FIG. It is a graph which shows the result of having simulated the relation between gain deviation 410 and phase deviation 412. FIG. It is a block diagram which shows the structure of the radio | wireless communication apparatus 460 using the power amplifier 80 which concerns on 1st Embodiment. 5 is a flowchart showing a method for controlling wireless communication apparatus 460.

Explanation of symbols

80 power amplifier, 90 preamplifier, 92 postamplifier, 94 bias controller, 100 first detection circuit, 102 predistortion circuit, 104 control signal, 106 second detection circuit, 108 output terminal, 110 input detection voltage signal, 112 output detection voltage signal, 120 and 140 directional coupler, 122 input comparison signal, 124 and 144 power detector, 130 bipolar transistor, 132 input matching circuit, 134 output matching circuit, 136 collector bias terminal, 138 base bias terminal, 142 Output comparison signal

Claims (9)

A power amplifier having a signal input terminal and a signal output terminal,
An amplifier circuit provided in a signal path between the signal input terminal and the signal output terminal;
A first detection circuit connected between the signal input terminal and the input of the amplifier circuit for detecting the power of the input signal to the amplifier circuit and outputting an input detection signal;
A second detection circuit connected between the output of the amplifier circuit and the signal output terminal for detecting the power of the output signal of the amplifier circuit and outputting an output detection signal;
The amplifier circuit has a grounded emitter bipolar transistor as an amplifier element,
The power amplifier further includes
An amplification gain of the power amplifier is connected to receive the input detection signal and the output detection signal, and controls a base bias current of the transistor based on a comparison between the input detection signal and the output detection signal. A control means for controlling
Inserted at a predetermined position in the path of the input signal between the signal input terminal and the signal output terminal, and gives a deviation to a predetermined electrical quantity of the input signal with a predetermined relationship with the base bias current. Deviation providing means for
The control means is connected to receive the input detection signal and the output detection signal, and in response to the input detection signal and the output detection signal, the amplification gain by the power amplifier becomes constant, Means for supplying a base bias current to a base electrode of the bipolar transistor;
The deviation giving means is
Means for outputting a control signal connected to receive the base bias current generated by the means for supplying and having a magnitude varying according to a predetermined functional relationship with the base bias current;
The input signal is inserted at any position in the path of the input signal between the signal input terminal and the signal output terminal so as to receive the control signal, and is proportional to the control signal and has a phase deviation in the input signal. And a phase deviation applying means for providing a power amplifier. The control signal changes with a positive correlation with the base bias current,
The phase deviation giving means is inserted to receive the control signal at an arbitrary position in the path of the input signal between the signal input terminal and the signal output terminal, and responds to the control signal, The power amplifier of claim 1 including means for providing a signal with a phase lag that is proportional to the magnitude of the control signal. The means for outputting the control signal generates the control signal in a region where the base bias current is large so that an increase amount of the base bias current is smaller than that in a region where the base bias current is small. Item 3. The power amplifier according to Item 2. The power amplifier according to any one of claims 1 to 3, wherein the deviation applying unit is inserted between the signal input terminal and an input of the power amplifier. A power amplifier having a signal input terminal and a signal output terminal,
An amplifier circuit provided in a signal path between the signal input terminal and the signal output terminal;
A first detection circuit connected between the signal input terminal and the input of the amplifier circuit for detecting the power of the input signal to the amplifier circuit and outputting an input detection signal;
A second detection circuit connected between the output of the amplifier circuit and the signal output terminal for detecting the power of the output signal of the amplifier circuit and outputting an output detection signal;
The amplifier circuit has a grounded emitter bipolar transistor as an amplifier element,
The power amplifier further includes
An amplification gain of the power amplifier is connected to receive the input detection signal and the output detection signal, and controls a base bias current of the transistor based on a comparison between the input detection signal and the output detection signal. A control means for controlling
Inserted at a predetermined position in the path of the input signal between the signal input terminal and the signal output terminal, and gives a deviation to a predetermined electrical quantity of the input signal with a predetermined relationship with the base bias current. Deviation providing means for
The deviation applying means is inserted between the first detection circuit and the input of the amplifier circuit, and has a predetermined relationship with the base bias current, and gain deviation applying means for giving a gain deviation to the input signal. seen including,
The control means is connected to receive the input detection signal and the output detection signal, and in response to the input detection signal and the output detection signal, the amplification gain by the power amplifier becomes constant, Means for supplying a base bias current to a base electrode of the bipolar transistor;
The gain deviation giving means is
Means for outputting a control signal connected to receive the base bias current generated by the means for supplying and varying in magnitude according to a predetermined functional relationship to the base bias current;
The input signal is inserted into a path of the input signal between the first detection circuit and the input of the amplifier circuit so as to receive the control signal, and the input signal has a magnitude proportional to the control signal. Means for providing a negative gain deviation of the power amplifier. A power amplifier having a signal input terminal and a signal output terminal,
An amplifier circuit provided in a signal path between the signal input terminal and the signal output terminal;
A first detection circuit connected between the signal input terminal and the input of the amplifier circuit for detecting the power of the input signal to the amplifier circuit and outputting an input detection signal;
A second detection circuit connected between the output of the amplifier circuit and the signal output terminal for detecting the power of the output signal of the amplifier circuit and outputting an output detection signal;
The amplifier circuit has a grounded emitter bipolar transistor as an amplifier element,
The power amplifier further includes
An amplification gain of the power amplifier is connected to receive the input detection signal and the output detection signal, and controls a base bias current of the transistor based on a comparison between the input detection signal and the output detection signal. A control means for controlling
Inserted at a predetermined position in the path of the input signal between the signal input terminal and the signal output terminal, and gives a deviation to a predetermined electrical quantity of the input signal with a predetermined relationship with the base bias current. Deviation providing means for
The control means is connected to receive the input detection signal and the output detection signal, and in response to the input detection signal and the output detection signal, the amplification gain by the power amplifier becomes constant, Means for supplying a base bias current to a base electrode of the bipolar transistor;
The deviation giving means is
Means for outputting a control signal connected to receive the base bias current generated by the means for supplying and having a magnitude varying according to a predetermined functional relationship with the base bias current;
A power amplifier, which is inserted between the signal input terminal and the input of the amplifier circuit and includes means for giving a phase deviation and a gain deviation to the input signal with a predetermined relationship with the magnitude of the control signal. The sign and magnitude of the gain deviation and the phase deviation given to the input signal by the means for giving the phase deviation and the gain deviation are selected so as to cause a phase delay by the amplifier circuit as a result. The power amplifier according to claim 6 . Means for providing the phase deviation and the gain deviation comprises means for providing a gain deviation and phase deviation changing with the size and any negative correlation of said control signal to said input signal, according to claim 7 Power amplifier. To any one of claims 1 to 8 comprising a power amplifier according wireless communication device.

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