KR20070017435A - Power amplifier - Google Patents

Abstract

The present invention can control the output power in a continuous power range in the case of a constant amplitude signal, and provides a power amplifier capable of amplifying less distortion and high efficiency in the case of a non-uniform amplitude signal. It is also an object of the present invention to provide a high-efficiency power amplifier that can produce an output signal of a constant amplitude with less distortion and higher efficiency in the output band. A power amplifier for receiving an input signal 10 and outputting an amplified signal in response to the input signal as an output signal 11 is disclosed. The amplifier includes N power amplification units 12 (N is an integer of 2 or more) connected in parallel to output an amplified signal in response to the input signal 10; An output synthesizing unit (14) for synthesizing the respective signals from the N power amplifying units (12) and outputting them as output signals (11) of the power amplifier; And an amplitude control unit 15 for selecting a power amplification unit to be operated from among the N power amplification units 12 based on the amplitude of the input signal 10. The amplitude control unit 15 also has N parallel amplitude adjusters for adjusting the amplitude of the input signal of the power amplifier, and N such that the amplitude of the output signal is a substantially continuous function of the amplitude of the input signal. And a controller for selecting and operating a power amplifying unit to be operated from the two power amplifying units, and controlling the amplitude adjuster. And a local oscillator for outputting a signal having a constant amplitude, receiving a modulated signal as the input signal, outputting a signal amplified by the modulated signal as an output signal, and N power amplifying units are provided from the local oscillator. And an N saturation amplification unit connected in parallel to amplify the output signal, wherein the amplitude control unit is configured as an amplitude control unit that controls each of the saturation amplification units on and off in accordance with the amplitude of the modulated signal.

Power amplifier, saturation amplification unit, amplitude control unit, output synthesis circuit

Description

Power amplifier {POWER AMPLIFIER}

1 is a block diagram of a linear power amplifier of a conventional example;

2 is a graph showing input / output power characteristics of a class F amplifier circuit;

3 is a block diagram of a power amplifier according to a basic embodiment of the present invention;

4 is a block diagram of a power amplifier according to Embodiment 1 of the present invention;

5 is a block diagram of a power amplifier according to Embodiment 2 of the present invention;

6 is a block diagram of a power amplifier according to Embodiment 3 of the present invention;

7 is a block diagram of a power amplifier according to a seventh embodiment of the present invention;

8 is a graph showing input and output power characteristics of the power amplifier according to the first embodiment of the present invention;

9 is a graph showing input / output power characteristics of the power amplifier according to the second embodiment of the present invention;

10 is a graph showing input and output power characteristics of the equivalent linear amplifier according to the second embodiment of the present invention;

11 is a view for explaining a method for compensating for nonlinearity of a power amplifying unit by an amplitude adjuster of Embodiment 3 of the present invention;

12 is a block diagram of a high efficiency transmission signal generator according to Embodiment 8 of the present invention;

13 is a block diagram of a high efficiency transmission signal generator according to Embodiment 9 of the present invention;

14 is a block diagram of a high efficiency transmission signal generator according to Embodiment 10 of the present invention;

15 is a block diagram of a high efficiency transmission signal generator according to Embodiment 11 of the present invention;

16 is a block diagram of a high efficiency transmission signal generator according to Embodiment 12 of the present invention;

17 is a block diagram of a high efficiency transmission signal generator according to Embodiment 13 of the present invention;

18 is a block diagram of an output synthesis circuit according to an embodiment of the present invention;

19 is a block diagram of a variable output matching circuit according to an embodiment of the present invention;

20 is a block diagram of an on / off configuration example of a saturation output unit according to an embodiment of the present invention; and

21 is a graph illustrating a modulated signal and a transmission output signal according to an embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

1: power amplifier

10: input signal

11: output signal

12: power amplification unit

15: amplitude control unit

The present invention relates generally to power amplifiers. More specifically, it relates to a power amplifier capable of controlling output power in a continuous power range, in particular a power amplifier that amplifies a modulated signal with high efficiency.

Conventionally, the technique which comprises a power amplifier using several power amplifier units in parallel in order to perform high efficiency amplification is known (nonpatent literature 1).

1 shows a conventional example of the basic configuration of a power amplifier. This conventional power amplifier is composed of a plurality of Class F amplifier circuits. Each Class F amplifier circuit includes a field effect transistor (hereinafter referred to as a FET), a λ / 4 transmission line connected to the drain of the FET, a capacitor C, a tuning circuit, a load, and a voltage V _dd . An RF choke coil (hereinafter referred to as RFC) for connecting a DC power supply to the FET and a driver for supplying a signal input level required for the FET. By connecting the λ / 4 transmission lines of the respective Class F amplifier circuits on the output side, the transmission output signals are combined with output signals from the plurality of Class F amplifier circuits.

In addition, by turning off the output of the driver, the operation of the corresponding Class-F amplifier circuit can be stopped.

Each F class amplifying circuit generally has an input / output power characteristic (hereinafter referred to as an input / output characteristic) as shown in FIG. 2, and a power supply efficiency (that is, a ratio of the power of the output signal and the DC power supplied by the power, hereinafter). Simply referred to as efficiency) versus input power characteristics. When the output power is near the saturated output power Ps (or the input power is near the saturated input power), high efficiency can be obtained, but the input / output characteristic becomes strong nonlinearity. In addition, in the region where the input / output power is small, the input / output characteristic shows good linearity, but the efficiency is significantly reduced.

The conventional configuration shown in Fig. 1 is mainly used for amplifying a transmission input signal having a constant amplitude (amplitude constant), so that even if there is nonlinearity in input / output characteristics, it is not a problem. Therefore, high efficiency can be obtained by operating each class F amplifier circuit in the state of saturated output. In the conventional configuration of Fig. 1, the power levels of a plurality of transmission output signals can be obtained by controlling the number of Class F amplifier circuits that operate. That is, transmission power control can be performed. It is also highly efficient at different transmit power levels.

In addition, in order to prevent the deterioration of the intermodulation distortion of the composite output signal due to the change in the transmission frequency of the radio transmitter, the attenuation amount of the variable attenuator at the front end of the juxtaposition transistor power amplifier is controlled so that the operation state of the two transistor power amplifier circuits is large. The prior art in which a difference does not arise is also known (patent document 1).

[Non-Patent Document 1]

Alireza Shirvani, David K. Su, and Bruce A. Wooley, "A CMOS RF Power Amplifier With Parallel Amplification for Efficient Power Control," IEEE JOURNAL OF SOLID-STATE CIRCUITS. VOL.37, NO.6, JUNE 2002

[Patent Document 1]

Japanese Patent Laid-Open No. 2001-237651

The conventional configuration shown in Fig. 1 is suitable for high efficiency amplification and transmission power control of a constant amplitude signal. However, the transmission power control in the case of a signal whose amplitude is not constant has a problem that power levels are discrete, and continuous power levels cannot be obtained.

In addition, when power amplification of a non-uniform amplitude signal (signal having a constant amplitude) using this conventional configuration, a large distortion occurs in the transmission output signal due to the strong nonlinearity of each Class F amplifier circuit. There was a problem.

Moreover, even when power control (i.e., control of the average power) of the transmission output signal of the signal whose amplitude is not constant, there exists a problem that the average power level obtained is discrete, and continuous average power level cannot be obtained. .

Therefore, the present invention has been made in view of the above description, and in the case of a constant amplitude signal, the output power can be controlled in a continuous power range, while in the case of a non-uniform amplitude signal, high efficiency amplification can be performed. It is an object to provide a power amplifier, and also to provide a power amplifier capable of controlling the average power in a continuous power range.

It is also an object of the present invention to provide a high-efficiency power amplifier that can produce an output signal of a constant amplitude in the output band, which can further reduce distortion and with high efficiency.

A power amplifier according to a feature of the present invention for achieving the above object,

In the power amplifier 1 which inputs the input signal 10 and outputs the amplified signal in response to the input signal as the output signal 11 (Fig. 3),

In response to the input signal 10, N (N is an integer of 2 or more) power amplification units 12 connected in parallel to output an amplified signal,

An output synthesizing unit 14 for synthesizing the signals from the N power amplifying units 12 and outputting them as the output signals 11 of the power amplifiers;

Based on the amplitude of the input signal 10, it is composed of an amplitude control unit 15 for selecting a power amplification unit to operate from the N power amplification units 12.

In the power amplifier, the amplitude control unit 15 includes N parallel amplitude adjusters for adjusting the amplitude of the input signal of the power amplifier, and the amplitude of the output signal is substantially continuous relative to the amplitude of the input signal. It may be characterized by comprising a controller which selects and operates a power amplifying unit to be operated from the N power amplifying units so as to be a function, and controls the amplitude adjuster.

In the power amplifier, the controller may select the power amplification unit in accordance with the amplitude of the input signal and further control the amplitude adjuster.

The present invention is particularly applicable to power amplifiers in wireless communication transmitters, but is not limited thereto, and may be applied to power amplifiers for other purposes.

(Basic Example)

3 shows a power amplifier 1 according to a basic embodiment of the invention. The power amplifier 1 is composed of N (N is an integer of 2 or more) power amplification units 12, an output synthesis unit 14, and an amplitude control unit 15. In this embodiment, the power of the transmission input signal 10 is adjusted by the amplitude control unit 15, and the power after the adjustment is supplied to each power amplifying unit 12. The amplitude control unit 15 controls the on / off of the power amplification unit 12 in accordance with the input signal. The output synthesizing unit 14 synthesizes the output signals from each of the power amplifying units 12 that are operating (i.e., is on) so that they almost add up to power, and outputs them as the transmission output signals 11.

The power amplification unit 12 may be an amplification circuit using an amplification element such as FET. The input / output characteristics and efficiency characteristics are generally similar to those of the class F amplifier shown in FIG. When the saturation output power of the power amplification unit 12 is Ps, the closer the output is to the saturation power Ps, the higher the efficiency.

The amplitude control unit 15 may be a circuit including a microprocessor, and can control other circuit elements based on the information from the transmission input signal 10.

The amplitude control unit 15 is input to the on / off control of the N power amplifying units 12 and to them so that the amplitude of the transmission output signal 11 becomes a continuous function with respect to the amplitude of the transmission input signal 10. Control the power adjustment factor of the signal.

(Example 1)

4 shows a power amplifier 101 according to Embodiment 1 of the present invention. The power amplifier 101 is composed of N (N is an integer of 2 or more) power amplifying units 112, N amplitude regulators 113, a power synthesizer 114, and a controller 115. The amplitude control unit 15 is composed of N amplitude adjusters 113 and a controller 115. In this embodiment, the power of the transmission input signal 110 is adjusted by each amplitude adjuster 113, and the power after the adjustment is supplied to each power amplifying unit 112. The controller 115 controls the power adjustment coefficient of each amplitude regulator 113, and also controls the on / off of the power amplification unit 112. The power synthesizer 114 synthesizes the output signals from each of the power amplifying units 112 that are in operation (i.e., is turned on) to almost sum the power, and outputs them as the transmission output signals 111.

The power amplifier unit 112 may be, for example, an amplifier circuit using an amplifier such as a FET. The input / output characteristics and efficiency characteristics are generally similar to those of the class F amplifier shown in FIG. When the saturation output power of the power amplification unit 112 is set to Ps, the closer the output is to the saturation power Ps, the higher the efficiency.

The controller 115 may be a circuit including a microprocessor, and may control other circuit elements based on the information from the transmission input signal 110.

The amplitude adjuster 113 may be any known adjuster and adjusts the amplitude of the transmission input signal in response to a control signal from the controller 115.

The controller 115 controls the on / off of the N power amplifying units 112 and the amplitude adjuster 113 so that the amplitude of the transmit output signal 111 becomes a continuous function with respect to the amplitude of the transmit input signal 110. Control the power adjustment factor. This control will be described with reference to FIG. 8 when N = 2 without loss of generality.

In the graph shown in FIG. 8, curves a and b represent input / output characteristics of the power amplifying units 112-1 and 112-2, respectively. The relationship between the power of the transmission input signal 110 and the power of the desired transmission output signal 111 is called curve c, for example. In this case, the saturation output powers of the two power amplification units 112-1 and 112-2 are Ps ₁ and Ps ₂ (Ps ₁ <Ps ₂ ), respectively, and the corresponding input powers are Pa and Pb, respectively. Also, the power of the transmission input signal 110 is called x.

Only a predetermined input power levels P _1, P _2, and P ₃ is on, when the transmission input signal power x is within the range from x≤P _1, the power amplifying unit 112-1 is selected. Then, by adjusting the power adjustment coefficient of the amplitude adjuster 113-1, the input to the power amplifying unit 112-1 changes to 0 to Pa when x changes from 0 to P ₁ . As a result, the power amplifying unit 112-1 outputs power from 0 to Ps ₁ .

Next, the transmit input signal power x is P ₁ When in the range of <x≤P ₂ , only the power amplifying unit 112-2 is selected. Then, by adjusting the power adjustment coefficient of the amplitude adjuster 113-2, the output of the power amplifying unit 112-2 outputs the power of Ps ₁ to Ps ₂ when x changes from P ₁ to P ₂ . Adjust

In addition, the transmit input signal power x is P ₂ When in the range of <x ≦ P ₃ , both power amplification units 112-1 and 112-2 are selected, and by adjusting both amplitude adjusters 113-1 and 113-2, x is P _2. It is adjusted so as to be the sum of the output power Ps ₁ + Ps ₂ ~Ps ₂ of the power amplifying units (112-1 and 112-2) to change ~P _through.

As a result, the range of the power of the transmission output signal 111 from 0 to (Ps ₁ + Ps _2), as shown by the curve of Figure 8, can be obtained a continuous input-output characteristics. In addition, it is possible that in the transmission input signal power x is P ₁ or more ranges, each operating a power amplifying unit (112-1 and 112-2) in the region close to the saturation output power, it is possible to obtain a high efficiency.

In general, in the configuration of this embodiment shown in Fig. 4, continuous input / output characteristics can be realized in the range of output power from 0 to ΣPs _i (Ps _i is saturated output power of each power amplifying unit 112-i). have. In addition, it is possible to obtain high efficiency in the range where the transmission input signal power x is equal to or more than Ps ₁ (for example, Ps ₁ <Ps _i , i = 2, 3,..., N). When the input / output power characteristic is a continuous function, the input / output amplitude characteristic also becomes a continuous function.

(Example 2)

5 shows a power amplifier 102 according to Embodiment 2 of the present invention. The power amplifier 102 is similar to the power amplifier 101, but in the power amplifier 102, to compensate for the nonlinearity of the power amplification unit 112, between the amplitude adjuster 113 and the power amplification unit 112. A pre-distorter (hereinafter referred to as PD) 116 is inserted. Each PD 116 and each power amplification unit 112 form N equivalent linear amplifiers 117. Each equivalent linear amplifier 117 has the same gain value G. In FIG. 9, the input / output characteristic (curve a) of each equivalent linear amplifier 117 and the input / output characteristic (curve b) of the power amplification unit 112 which are the base are shown. When the saturation output power of the power amplification unit 112 is Ps, the equivalent linear amplifier 117 may have a linear input / output characteristic in an output range of 0 to Ps. In addition, the efficiency of the equivalent linear amplifier 117 is equal to the efficiency of the power amplifying unit 112 at a specific output power (for example, P0 in FIG. 9). For this reason, the efficiency of the equivalent linear amplifier 117 becomes higher efficiency as the output is closer to the maximum output power Ps.

The controller 115 performs on / off control of the N power amplifying units 112 (that is, on / off control of the equivalent linear amplifier 117), and suitably adjusts the power adjustment coefficient of the amplitude adjuster 113. To control. This control will be described with reference to FIG. 10 in the case where N = 2 without losing generality.

The maximum output power of the two equivalent linear amplifiers 117-1 and 117-2 is Ps ₁ , Ps ₂ (Ps ₁ <Ps ₂ ), and the power of the transmission input signal 110 is x ≦ x ≦ (Ps ₁ / G), only equivalent linear amplifier 117-1 is selected. Then, the power adjustment coefficient of the amplitude adjuster 113-1 is set to one. As a result, the power of the transmission output signal 111 becomes Gx.

Next, when the transmission input signal power x is in the range of (Ps ₁ / G) <x ≤ (Ps ₂ / G), only the equivalent linear amplifier 117-2 is selected. Then, the power adjustment coefficient of the amplitude adjuster 113-2 is set to one. At this time, the power of the transmission output signal 111 also becomes Gx.

Further, when the transmission input signal power x is in the range of (Ps ₂ / G) <x ≤ [(Ps ₁ + Ps ₂ ) / G], the equivalent linear amplifiers 117-1 and 117-2 are both selected. The power adjustment coefficients of the amplitude adjusters 113-1 and 113-2 are set to Ps ₁ / (Ps ₁ + Ps ₂ ) and Ps ₂ / (Ps ₁ + Ps ₂ ), respectively. As a result, the power of the transmission output signal 111 becomes G [Ps ₁ / (Ps ₁ + Ps ₂ )] x + G [Ps ₂ / (Ps ₁ + Ps ₂ )] x = Gx. Therefore, the linear input / output characteristics of the transmission output signal 111 are maintained in the range of 0 to (Ps ₁ + Ps ₂ ). In addition, in the case where the transmission input signal power x becomes Ps ₁ / G or more, the equivalent linear amplifiers 117-1 and 117-2 operate in an area close to their respective maximum output power, which is high efficiency.

In general, in the configuration of this embodiment shown in Fig. 5, continuous input / output characteristics can be realized in the range of output power from 0 to ΣPs _i (Ps _i is the saturation output power of each equivalent linear amplifier 117-i). Can be. In addition, it is possible to obtain high efficiency in a power range in which the transmission input signal power x is equal to or more than Ps ₁ / G (for example, Ps ₁ <Ps _i , i = 2, 3,..., N).

On the other hand, when the transmission input signal 110 is a non-uniform signal, the controller 115 selects the equivalent linear amplifier 117 and the amplitude adjuster 113 as described above according to the instantaneous power of the transmission input signal 110. By performing the control, linear amplification can be achieved.

(Example 3)

6 shows a power amplifier 103 according to Embodiment 3 of the present invention. The power amplifier 103 is similar to the power amplifier 102, but in the power amplifier 103, the function of the PD 116 to compensate for the nonlinearity of the power amplifying unit 112 is performed by the amplitude adjuster 113. It is different in that it becomes. The power adjustment amount of the amplitude adjuster 113 in this embodiment includes a first adjustment amount for configuring the equivalent linear amplifier 119 that compensates for the nonlinearity of the power amplification unit 112, and the transmission input signal 110. Is made up of two parts of the second adjustment amount for adjusting the power of the power amplifier within the input range of the equivalent linear amplifier 119.

Each of the amplitude regulators 113 is assumed to have an equivalent linear amplifier 119 having a gain of G and a maximum output of Ps. First, the second adjustment amount is set in the same manner as in the second embodiment shown in FIG. . The power of the transmission input signal 110 after being adjusted by this second adjustment amount is set to x ₁ in FIG. 11. Next, since the desired output power 111 corresponding to x ₁ is Gx ₁ , the regulator 113 adjusts x ₁ back to x ₂ so that the power amplifying unit 112 outputs Gx ₁ . The total power adjustment amount of the amplitude adjuster 113 is a product of the first adjustment amount and the second adjustment amount.

(Example 4)

In the configuration shown in Fig. 5 or 6, the maximum output power of each equivalent linear amplifier 117, 119 may be set equally. In this case, the controller 115 can control the power amplifying unit 112 and the amplitude adjuster 113 as follows. That is, the maximum output power of each equivalent linear amplifier 117, 119 is set to Ps, and r is an integer from 1 to N. When the power x of the transmission input signal 110 is at [(r-1) Ps / G] <x ≤ (rPs / G), r power amplification units 112 are selected, and corresponding amplitude adjusters are respectively. The power control coefficient of 113 is set to 1 / r. Thereby, since the equivalent linear amplifiers 117 and 119 operating respectively output the power of G (1 / r) x, the power of the transmission output signal 111 becomes Gx.

Further, in the range of x, the output powers of the equivalent linear amplifiers 117 and 119 respectively operating are in the range of [Ps (r-1) / r] to Ps. Except when r = 1 (that is, x is equal to or greater than Ps / G), the equivalent linear amplifiers 117 and 119 that operate respectively are highly efficient because they operate within an area close to the maximum output power. This high efficiency amplification range is 10log (N) (dB).

(Example 5)

In the configuration shown in FIG. 5 or 6, the i (i = 1, 2, ... N) th maximum output power of each equivalent linear amplifier 117, 119 can be set to 2 ^(i-1) Ps. In this case, the controller 115 can control the power amplifying unit 112 and the amplitude adjuster 113 as follows. That is, if r is an integer from 1 to (2N-1), when power x of the transmission input signal 110 is at [(r-1) Ps / G] <x≤ (rPs / G), r Is represented by an N-digit binary number, and the equivalent linear amplifiers 117 and 119 corresponding to the number of digits to be 1 in the binary number (where LSB is the first digit and MSB is the N digit). Operate. Then, the power adjustment coefficient of the amplitude adjuster 113 corresponding to the i-th operating equivalent linear amplifiers 117 and 119 is set to 2 (i-1) / r. As a result, the equivalent linear amplifiers 117 and 119 operating in the i &lt; th &gt; output G [2 (i-1) / r] x power, and the power of the transmission output signal 111 is? {G [2 (i -1) / r] x} (i is the number of equivalent linear amplifiers in operation), and Σ2 ^(i-1) = r, so that the power of the transmission output signal 111 becomes Gx as a result.

The output powers of the equivalent linear amplifiers 117 and 119 respectively operating in the range of x are in the range of [Ps (r-1) / r] to Ps. Except for r = 1 (that is, x is equal to or more than Ps / G), the equivalent linear amplifiers 117 and 119 that operate respectively are highly efficient because they operate within an area close to the maximum output power. The range of output power that can be amplified with this high efficiency is 10log (2 ^N- 1) (dB).

(Example 6)

In any of the embodiments described above, the controller 115 may set the power adjustment amount α for the amplitude adjuster 113 based on the average power of the desired transmission output signal 111. That is, the controller 115 may provide to each amplitude adjuster 113 a product of the power adjustment coefficient set according to the instantaneous power of the transmission input signal 110 shown in the above-described embodiment and the power adjustment amount α. The power adjustment amount α can be set according to the average power of the desired transmission output signal 111. When the present embodiment is applied to the above-described embodiment, transmission power control in a continuous power range can be performed for a constant amplitude signal. In addition, when the present embodiment is applied to Embodiments 2 to 5, transmission power control in a continuous power range can be performed on an amplitude signal that is not fixed.

(Example 7)

7 shows a power amplifier 104 according to Embodiment 7 of the present invention. The power amplifier 104 is similar to the power amplifier 101 shown in FIG. 4, but in the linear power amplifier 104, the transmission input signal 110 is transmitted to each amplitude regulator 113 through an amplitude regulator 118 for transmission power control. ) Is characterized in that it is supplied. The controller 115 can set the constant power adjustment amount α to the amplitude adjuster 118 for transmission power control in accordance with the average power of the desired transmission output signal 111.

7 shows an example in which the transmission power control amplitude adjuster 118 is provided in the configuration of FIG. 6, the transmission power control amplitude adjuster 118 can also be provided in the configuration of the embodiments shown in FIGS. 4 and 5. have.

Hereinafter, an embodiment in the case where the present invention is applied to a high efficiency transmission signal generator will be described. However, the present invention is not limited to the transmission signal generator but can be applied to so-called various power amplifiers.

(Example 8)

12 shows a high efficiency transmission signal generator 210 according to Embodiment 8 of the present invention. The high efficiency transmission signal generator 210 is composed of a constant amplitude local oscillator 121, N (N is an integer of 2 or more) saturation amplifying units 212, an output synthesis circuit 214, and an amplitude control unit 215. The amplitude control unit 15 is constituted by the amplitude control unit 215, and the power amplification unit 12 is constituted by the saturation amplification unit 212. As the output synthesizing circuit 214, one capable of synthesizing the output of each saturation amplifying unit 212 operating almost losslessly is preferably used. The saturation amplification unit 212 can use, for example, a class-F amplification circuit using a FET. The saturated output power of each saturation amplifying unit 212 may be set to be substantially the same, or may be set to different saturated output powers.

In the configuration of FIG. 12, local oscillator 212 outputs a constant amplitude sinusoidal cos (ω _c t + φ ₀ ). Here, ω _c = 2πf _c , f _c is a predetermined frequency, and φ ₀ is an initial phase. Since there is no loss of generality, assuming that φ ₀ = 0, there is no problem even if the output of the local oscillator 212 is cos (ω _c t). Let the modulation signal 210 be a (t). The amplitude control unit 215 controls the number of saturation amplifying units 212 that are turned on in accordance with the instantaneous value of the modulation signal a (t). Thus, the number n of saturated amplifying units 212 that are turned on is a function of the modulated signal a (t).

A method of setting the number n of the saturated amplifying units 212 to be turned on will be described with reference to FIG. 21. In FIG. 21, as an example, the number N of saturation amplifying units 212 is 4. 21A shows an example of a waveform of the modulated signal a (t). The modulation range of the modulated signal a (t) is between 0 and a ₀ as shown. The number n of saturation amplifying units 212 to be turned on is set as follows.

The saturated amplifying unit 212 that is turned on amplifies the output signal of the local oscillator 212 and outputs b ₀ cos (ω _c t). Where (1/2) b ₀ ² is the saturated output power. When the transmission output signal 211 is represented by s (t) and n saturated amplification units 212 are turned on, s (t) = nb ₀ cos (ω _c t) = b (t) cos (ω _c t). Where b (t) = nb _o is the envelope of s (t). The waveform of b (t) is shown in FIG.21 (b). The waveform c (t) in FIG. 21B is obtained by multiplying the modulated signal a (t) shown in FIG. 21A by (4b ₀ ) / a ₀ times, and the desired s (t) is the envelope. In the following, c (t) cos (ω _c t) is referred to as the desired transmission output. On the other hand, b (t) is a quantized c (t). Here, if e (t) = b (t) -c (t), e (t) is an error component and | e (t) | ≦ (1/2) b ₀ . b (t) is the sum of c (t) and e (t). When the maximum value of c (t), that is, (Nb ₀ ) is determined in advance, by increasing N, b ₀ can be set small, so that the error component e (t) can be suppressed small.

In the above description, the saturation output of each saturation amplifying unit 212 is the same, but the saturation output power is set to b ₀ , 2b _o , 4b ₀ ,. , 2 ^N-1 Like b ₀ , it can also be set to a power of two. In this case, 0, b ₀ , 2 b _o , 3 b ₀ ,... , 2 ^N-1 We can get the level of b (t) which is b ₀ . Also in this case, the maximum amplitude of the required transmission output signal s (t), that is, (2 ^N -1) When b ₀ is determined, by setting N sufficiently large and b ₀ small, the power of the noise component e (t) can be suppressed to below the prescribed value.

In the configuration of Fig. 12, each saturation amplifying unit 212 operates at the saturation point when it is turned on, and therefore is highly efficient. If each saturation amplifying unit 212 has the same efficiency η, the efficiency η _T of the entire structure of Fig. 12 is expressed by the following expression (12), which is high efficiency.

In Equation 2, P _i represents the output power of the saturated amplifying unit 212 to be turned on.

12, the transmission output signal 211 is an amplitude modulated wave (AM wave) modulated by the modulated signal 210. In FIG.

(Example 9)

13 shows a high efficiency transmission signal generator 202 according to Embodiment 9 of the present invention. In Embodiment 9, the high efficiency transmission signal generator 202 includes a constant amplitude local oscillator 212, N (N is an integer of 2 or more) saturation amplification units 212, an output synthesis circuit 214, and an amplitude control unit 215. And a polar coordinate modulation processor 216 and a phase modulator 217. Compared with the configuration of the eighth embodiment of FIG. 12, in the ninth embodiment, the polar coordinate modulation processing unit 216 and the phase modulation unit for decomposing and outputting the modulated signal 210 into the amplitude component 218 and the phase component 219. 217 is newly installed.

The modulated signal 210 is a complex signal, represented by a (t) exp (jφ (t)). Here, a (t) and φ (t) are amplitude components and phase components of the modulation signal 210, respectively. The polar modulation processing unit 216 separates the modulation component 218 and the phase component 219 of the modulated signal 210 and outputs an amplitude component a (t) and a phase component φ (t). In the phase modulator 217, the output signal cos (ω _c t) of the local oscillator 212 is phase-modulated by φ (t) to output a phase modulated wave cos (ω _c t) + φ (t). . This phase modulated wave is amplitude by a (t) by the saturation amplifying unit 212, the output synthesis circuit 214, and the amplitude control part 215 similarly to the process demonstrated in Example 8 of FIG. Modulation is performed. As a result, the transmission output signal 211 has a modulated wave a (t) cos (ω _c t + φ (t)) amplitude-phase modulated by the modulated signal 210, that is, a quadrature amplitude modulated wave (QAM wave). do.

Moreover, since each saturation amplification unit 212 operates at the saturation point when it is turned on, it is highly efficient. The efficiency η _T of the entire structure of FIG. 13 is represented by the same expression (2), and since η _T = η, high efficiency is achieved.

(Example 10)

14 shows a high efficiency transmission signal generator 203 according to Embodiment 14 of the present invention. As compared with the configuration of the eighth embodiment shown in Fig. 12, in the tenth embodiment, the amplitude modulation unit 220 and the linear amplifying unit 221 are newly installed. This embodiment will be described with reference to FIG. 21. In the configuration of FIG. 14, if the output of the linear amplifying unit 221 is not taken into consideration, for example, the amplitude of the transmission output signal 211 becomes b (t) shown in FIG. 21B. The gain of the linear amplification unit 221 is k. The amplitude control unit 215 provides the above-mentioned e (t) = b (t) .c (t) to the amplitude modulation unit 220 in the form of-(1 / k) e (t). The amplitude modulator 220 performs amplitude modulation on the output of the local oscillator 212 by-(1 / k) e (t) to obtain-(1 / k) e (t) cos (ω _c t). Output For this purpose, the linear amplification unit 221 outputs -e (t) cos (ω _c t). Taking this into account, the amplitude of the transmission output signal 211 becomes -e (t) + b (t) = c (t). Here, c (t) is the envelope of the desired s (t) described above. Therefore, in the structure of Example 10 shown in FIG. 14, the transmission output signal 211 becomes a desired transmission output.

The efficiency η _T of the entire configuration in FIG. 14 becomes η _T = {P _s (t) / (P _DC1 + P _DC2 )}. Where P _s (t) = (1/2) c ² (t), P _DC1 is the DC power consumed in the linear amplifier 21, and P _DC2 is consumed in each saturated amplifying unit 212 that is turned on. Is the sum of the direct current powers. P _DC2 when the efficiency of each saturation amplifying unit 212 is equal to η = (1/2) b ² (t) / η ≒ P _s (t) / η. Thereby, η _T is

Becomes In Equation 3, since P _s (t) changes in time, η _T also changes in time, but the time average η _T (time average) is

Becomes In general, although the efficiency of the linear amplifier is low, by increasing the number N of the saturation amplifying units 212 as described in the eighth embodiment shown in Fig. 12, e (t) can be suppressed to be small. The output signal of the amplifying unit 221 can be made very small. In this case, even if the efficiency of the linear amplification unit 221 is low, P _DC1 is very small. Therefore, in Equation 4, η _T (time average)) η is obtained. Therefore, on average, the efficiency of the whole structure of Example 10 of FIG. 14 becomes high efficiency.

(Example 11)

15 shows a high efficiency transmission signal generator 204 according to Embodiment 11 of the present invention. Compared with the configuration of the ninth embodiment shown in FIG. 13, the eleventh embodiment differs from the newly installed amplitude modulator 220 and the linear amplification unit 221. In addition, in comparison with the configuration of the tenth embodiment shown in FIG. 14, in the eleventh embodiment, each of the saturation amplifying units 212 has been subjected to a phase modulation of the output signal from the local oscillator 212 by the phase modulator 217. And the point supplied to the amplitude modulator 220 is different. Operations of the amplitude modulator 220 and the linear amplification unit 221 are the same as in the tenth embodiment of FIG. 14.

In the present embodiment, the linear amplification unit 221 outputs -e (t) cos (ω _c t + φ (t)), and the transmission output signal 211 transmits c (t) cos (ω _c t + φ (t)), which is a desired transmission output. Similarly to the reason explained in the tenth embodiment shown in FIG. 14, the efficiency of the entire structure of FIG. 15 is, on average, highly efficient.

(Example 12)

16 shows a high efficiency transmission signal generator 205 according to Embodiment 12 of the present invention. As compared with the configuration of the eighth embodiment shown in Fig. 12, in the twelfth embodiment, a band limiting filter 230 is newly installed at the rear end of the output synthesis circuit 214, and the transmission output signal from the band limiting filter 230 is Is different.

In the configuration of the twelfth embodiment, the band limiting filter 230 smoothes the envelope of the transmission output signal 211 by removing the frequency component of the aforementioned error component e (t) outside the transmission signal band. The high frequency component output from the saturation amplifying unit 212 is removed. Similar to the configuration of the twelfth embodiment, the smoothing filter 230 can be provided at the rear end of the output synthesizing circuit 214 in the configuration of the ninth embodiment of FIG. 13.

The smoothing filter or the band limiting filter 230 can also be provided at the rear end of the output synthesis circuit 214 also in the configurations of the tenth and eleventh embodiments shown in FIGS. 14 and 15. In these cases, the band limiting filter 230 removes the high frequency component output from the saturation amplifying unit 212.

(Example 13)

17 shows a high efficiency transmission signal generator 206 according to Embodiment 13 of the present invention. Compared with the configuration of the eighth embodiment shown in FIG. 12, in the thirteenth embodiment, the output synthesizing circuit 214 is controlled by the amplitude control unit 215.

In the configuration of the thirteenth embodiment, the amplitude control unit 215 adjusts the electrical characteristics of the output synthesis circuit 214 in accordance with the on / off of each saturation amplifying unit 212, and the power loss in the output synthesis circuit 214 Suppress very small.

(Other Examples)

18 shows an example of an output synthesis circuit used in the high efficiency transmission signal generator according to another embodiment of the present invention. In any of the eighth to eleventh embodiments, the output synthesizing circuit 214 can use, for example, the configuration shown in FIG. 18A. The output synthesizing circuit 214 shown in FIG. 18A is a current synthesizing circuit that simply connects and outputs the output from each saturation amplifying unit 212.

18B illustrates another example of the configuration of the output synthesis circuit 214. The output synthesizing circuit 214 shown in FIG. 18B connects and synthesizes the outputs from the respective saturation amplifying units 212 and then outputs them through the output matching circuit 280.

FIG. 18C shows another configuration example of the output synthesis circuit 214. In any of the eighth to eleventh embodiments, the output synthesizing circuit 214 can use the configuration shown in Fig. 18C. The output synthesizing circuit 214 shown in FIG. 18C connects and synthesizes the outputs from the respective saturation amplifying units 212 and then outputs them through the variable output matching circuit 281. The variable output matching circuit 281 controls power loss in the output synthesizing circuit 214 by controlling its electrical characteristics according to the on / off of each saturation amplifying unit 212 by the control from the amplitude control unit 215. Keep it small.

FIG. 19 shows an example of a configuration of the variable output matching circuit 281 shown in FIG. The variable output matching circuit 281 shown in FIG. 19 is composed of a plurality of open or ground reactances 282 provided in parallel. The switching of the open or ground state of the reactance 282 is performed by switching the switch 283 controlled by the amplitude control unit 215. The electrical characteristics of the variable output matching circuit 281 are adjusted by the change in the number of parallel reactances 282 grounded.

20 shows an example of a specific configuration for controlling the on / off of the saturation amplifying unit 212 by the amplitude control unit 215 in any of the above embodiments. For example, in the configuration shown in FIG. 20A, the saturation amplifying unit 212 includes a saturation amplifier 300 and an RF switch 301 provided on the RF input side thereof. The amplitude control unit 215 controls the on / off of the RF switch 301 through the amplitude control input terminal of the RF switch 301. Thereby, on / off of the saturation amplifying unit 212 is achieved.

In another configuration shown in FIG. 20B, the saturation amplifying unit 212 includes a saturation amplifier 300 and a bias control circuit 302. The amplitude control unit 215 controls ON / OFF of the saturation amplifying unit 212 by controlling the state of the bias control circuit 302 through the amplitude control input terminal of the bias control circuit 302.

According to the power amplifier according to the present invention, the output power can be a continuous function with respect to the input power, and as a result, the transmission power control can be performed in a continuous power range and with high efficiency.

According to the power amplifier according to an embodiment of the present invention, an equivalent linear amplifier is configured by compensating for the nonlinearity of the input / output characteristics of each power amplifying unit, and by combining the equivalent linear amplifier according to the instantaneous power of the input signal, it is linear and high efficiency. The power amplifier of can be configured. This makes it possible to achieve a high efficiency and linear amplitude even with a transmission input signal having a constant amplitude. In the case of using N power amplification units, by increasing N, the high efficiency and amplifiable input / output power range can be expanded. This feature is particularly advantageous when amplifying non-uniform amplitude signals with large peak-to-average power. In this case, the average power of the output signal can be continuously controlled by adjusting the average power of the input signal.

Further, according to the power amplifier according to another embodiment of the present invention, by controlling the number of saturation amplification units operating in accordance with the amplitude of the modulated signal, it is possible to generate the transmission output signal of the AM modulated wave or QAM modulated wave. In addition, since each saturation amplification unit amplifies only a constant amplitude signal from the local oscillator, it operates with high efficiency. Therefore, the whole structure of the embodiment of the present invention is also highly efficient. Further, by providing a sufficient number of saturation amplifying units or by providing a linear amplifying unit for compensating for error components, an output signal with less distortion in the transmission band can be generated.

 Industrial availability

The power amplifier according to the present invention can be used, for example, in a base station of a mobile telephone system, a transmitter in a mobile station, or a high efficiency signal generator, and can be used in a technical field requiring various various power amplifiers.

Claims (7)

In a power amplifier which inputs a modulated signal 210 as an input signal and outputs a signal corresponding to the amplified signal of this modulated signal as an output signal 211: (FIG. 12) A local oscillator 222 for outputting a signal of a constant amplitude; N saturation amplifying units (212) connected in parallel to amplify the output signal from the local oscillator in response to the modulation signal (210); An output synthesizing unit 214 for synthesizing the respective signals from the N saturation amplifying units 212 and outputting the synthesized signals as output signals 211 of the power amplifier via a variable output matching circuit 281 (Fig. 18). ); And An amplitude control unit (215) for on / off controlling each of the N saturation amplification units in accordance with the amplitude of the modulation signal (210); Including; Wherein said variable output matching circuit is configured by a plurality of parallel reactances (282) in which the state of open or ground is controlled by said amplitude control unit (FIG. 19). The method of claim 1, A polar coordinate modulation processor for dividing the received modulated signal into an amplitude component and a phase component and outputting the amplitude component to the amplitude control unit; A phase modulator for inputting said phase component from said polar modulation processor, performing phase modulation on said output signal from said local oscillator by said phase component, and outputting a phase modulated signal to said plurality of saturated amplifying units; Power amplifier. The method of claim 1, An amplitude modulation unit that performs amplitude modulation on an output signal from the local oscillator, under control of the amplitude control unit, And a linear amplifying unit for linearly amplifying the output signal from the amplitude modulation unit and outputting the linearly amplified unit to the output synthesizing unit. The method of claim 2, An amplitude modulator for performing amplitude modulation on the output signal from the phase modulator under the control of the amplitude control unit; And a linear amplifying unit for linearly amplifying the output signal from the amplitude modulation unit and outputting the linearly amplified output signal to the output synthesizing unit. The power amplifier as set forth in claim 1, further comprising a band limiting filter installed at a rear end of said output synthesizing unit. The power amplifier as set forth in claim 1, wherein the electrical characteristic of said output synthesizing unit is also controlled by said amplitude control unit. The method of claim 1, wherein each saturation amplification unit A saturation amplifier that performs saturation amplification, Is provided at an input side of the saturation amplifier, and an on / off state of the RF switch controlled by the amplitude control unit or a bias voltage state supplied to the saturation amplifier includes a bias control circuit controlled by the amplitude control unit. Characterized by power amplifier.

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