JPH09232890A - Power amplifier and transmitter - Google Patents

Abstract

(57) Abstract: To provide a power amplifier which has good linearity, high power efficiency, and is small in size and inexpensive. A plurality of, for example, four field effect transistors T1 to T4 are connected in parallel, and each of the transistors T1 to T4.
An operating voltage or a non-operating voltage is input to the gate electrode of the control circuit 5 through the signal lines L1 to L4. In the M16QAM modulation method, the amplitude information of the input signal is given from the digital signal processing unit 2 to the quadrature modulator 21, but the control circuit 3 takes in this amplitude and, according to the amplitude level, the number of transistors to be activated. To control. That is, when the amplitude level is small, the transistor T
When only 1 is operated and the amplitude level increases,
The remaining transistors are sequentially operated based on a set level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power amplifier and a transmitter for mobile communication using the power amplifier.

[0002]

2. Description of the Related Art In mobile communication, 16-value QAM (Qua)
draw Amplitude Modulati
on) and π / 4 shift QPSK (Quadrature)
A modulation method such as Phase Shift Keying is used, but a communication device that requires modulation for such an amplitude component requires a power amplifier with good linearity (small distortion). In this case, for example, if the output of the power amplifier changes between 0.1 W and 20 W,
A direct current voltage must be supplied between the drain and source of the transistor so that a drain current matching the maximum output can be obtained by using a transistor capable of covering the maximum output, for example, an FET (field effect transistor). Therefore, when using a normal class A amplifier, the power efficiency is low,
Since power consumption increases, for example, in a mobile phone, there is a problem that the battery usage time is shortened.

Therefore, as the power amplifier used in the above-mentioned communication device, the one having the configuration shown in FIG. 5 is known.
In FIG. 5, 11 is a waveform generation circuit, 12 is a quadrature modulator,
Reference numeral 13 is an amplitude modulation circuit, 14 is a saturation type amplifier, 15 is a control circuit, 16 is a DC amplifier, and 17 is a detector. In this power amplifier, the control circuit 15 includes the waveform generation circuit 11
The control signal according to the level of the envelope of the input signal sent from the DC amplifier 16 is applied to the DC amplifier 16, and the DC amplifier 16 changes the drain voltage of the transistor forming the saturation amplifier based on this control signal.

That is, the drain-source voltage of the saturation type amplifier is controlled so as to be large when the level of the envelope of the input signal is high and small when the level of the input signal is low, so that the power amplifier is saturated irrespective of the envelope. I am trying to make it work at the point. According to such a power amplifier, since the voltage between the drain and the source of the transistor is changed in accordance with the amplitude level (envelope level) of the input signal, high power efficiency is obtained and extra power consumption is reduced. There is an advantage.

[0005]

However, a high-efficiency large DC / DC converter capable of controlling a large current of about several amperes flowing in the drain of a transistor is used for the DC amplifier used in the above-mentioned power amplifier. Therefore, the communication device becomes large and expensive. Furthermore, since the drain-source voltage is controlled by following the envelope level of the input signal, a complicated circuit is required.

The present invention has been made under such circumstances, and an object thereof is to provide a small-sized and inexpensive power amplifier which has good linearity and can ensure high power efficiency. is there. Another object of the present invention is to provide a small-sized transmitting device with low power consumption by using this power amplifier.

[0007]

According to the present invention, a plurality of power amplification units, for example transistors, are connected in parallel and the number of amplification units to be turned on is controlled according to the amplitude level of an input signal.
That is, when the amplitude level is low, for example, one amplification unit is turned on and the number is increased as the amplitude level increases.

Specifically, according to the present invention, an amplifier parallel circuit in which a plurality of power amplifiers are connected in parallel and a control signal for turning the amplifier on or off are provided to the amplifier. A control signal for applying to the control electrode, taking in the magnitude of the amplitude level of the input signal, and turning on the number of amplifying units corresponding to the amplitude level among the amplifying units of the amplifying unit parallel circuit. And a control unit for applying a control signal for turning off the other amplification units to turn them off.

In a power amplifier having an amplifying section composed of a transistor, an input signal is supplied between the control electrode and the cathode electrode of the transistor, and an output signal is taken out between the cathode electrode and the anode electrode. A transistor parallel circuit in which control electrodes of a plurality of transistors are commonly connected to a signal input terminal, and an anode electrode and a cathode electrode of each transistor are connected in parallel, and a control electrode of the transistor. And between the cathode electrodes, a control voltage for turning the transistor on or off is applied, and the amplitude data of the input signal is taken in, and the amplitude of the input signal among the transistors of the transistor parallel circuit is taken. Apply a control signal to turn on the number of transistors according to the level It is for which characterized by including a control unit for applying a control signal to the OFF state.

A transmitting device to which such a power amplifier is applied is based on a signal processing section for creating amplitude data based on a digital signal which is transmission data, and on the basis of the amplitude data from this signal processing section. And a power amplifier described above connected to the output side of the modulation unit. In this case, the control unit controls the amplitude data of the input signal from the signal processing unit. Will be taken in.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION A power amplifier according to the present invention has an M16 value Q.
An embodiment applied to an AM (16-valued quadrature amplitude modulation) transmitter will be described. In FIG. 1, reference numeral 2 is a digital signal processing unit, which creates amplitude and phase data based on digital data to be transmitted. In the case of M16 value QAM, the relationship between the digital data and the modulation signal is 3.2 ^1/2 sin (ωt + 45 °) when “0000”,
In “0111”, the allocation is 2 ^1/2 sin (ωt + 135 °) and the M16 value QAM.
In this case, since there are as many sub-carriers as possible, the digital signal processing unit 2 calculates the amplitude information and phase information of the corresponding modulated signal from the memory based on the input digital data. 21 is output.

The quadrature modulator 21 creates a modulation signal based on the amplitude information and the phase information and outputs it to the voltage controlled variable attenuator 22. The voltage control variable attenuator 22 adjusts the amplitude of the input signal input to the amplifier 3 based on the detected value of the amplitude of the output signal of the power amplifier 3 in the subsequent stage, and keeps the gain of the amplifier 3 constant in all states. It is for. That is, the output signal of the power amplifier 3 is detected by the detector 41,
It is returned to the digital signal processing unit 2 via the feedback amount adjuster 42, and the phase is adjusted in the digital signal processing unit 2 so that the output signal has a predetermined phase.
Regarding the amplitude, the attenuator control circuit 43 converts the digital adjustment signal from the digital signal processing unit 2 into an analog signal and supplies the analog signal to the voltage control variable attenuator 22, whereby the output signal has a predetermined amplitude. Is adjusted.

The power amplifier 3 in the latter stage of the voltage controlled variable attenuator 22 is a characteristic part of this embodiment, and is an amplifying element which is four amplifying parts, for example, a field effect transistor T1.
To T4 are connected in parallel, and control signal lines L1 to L4 for applying a control voltage are connected to gate electrodes which are control electrodes of the transistors T1 to T4. One ends of these control signal lines L1 to L4 are connected to a control circuit 5 that is a control unit that controls the transistors T1 to T4.

The power amplifier 3 will be described with reference to FIG. 2. The output end of the voltage controlled variable attenuator 22 is branched into four, which are respectively connected to the gate electrodes of the transistors T1 to T4 via the capacitor C1. Therefore, an input signal is supplied from the voltage control variable attenuator 22 between the gate electrodes G of the transistors T1 to T4 and the source electrode S which is a cathode electrode. In addition, in order to avoid complication of symbols, common symbols are used for capacitors and resistors connected to the transistors T1 to T4.

The drain electrodes D, which are the anode electrodes of the transistors T1 to T4, are connected in common, and their connection ends 3
0 is +8 via the λ / 4 microstrip line M1
It is connected to a V DC power supply 31. Transistor T1
Source electrodes S of T4 to T4 are grounded, and a DC voltage from the DC power supply 31 is applied between the drains of the transistors T1 to T4 and the source electrodes D and S. The connecting end 30 is connected to an antenna (not shown) via a capacitor C2.

The gate electrodes G of the transistors T1 to T4 are connected to the other end of a resistor R1 whose one end is grounded. Further, the gate electrodes G of the transistors T1 to T4
Is a resistor R2 and a λ / 4 microstrip line M
It is connected to the control circuit 5 via the control signal lines L1 to L4 described above. The control circuit 5 has a function of fetching the amplitude information of the input signal from the digital signal processing unit 2 and controlling the voltage output to the control signal lines L1 to L4 based on the amplitude information. That is, the control circuit 5 is, for example, M16.
In the case of the modulation method of the value QAM, the amplitude values that the modulated signal can take can be represented by a combination of three types and the number of multi-subcarriers, and therefore, each amplitude value and information as to which of the transistors T1 to T4 is to be operated is provided. For example, -4 is provided for the signal lines L (L1 to L4) associated with the transistors T (T1 to T4) that are brought into the ON state (operating state) based on the captured amplitude value. .5V
Control voltage lines L (L1 to L4) related to the transistors T (T1 to T4) that bring the operating voltage of
For example, a voltage of -6.5 V is supplied to L4).

The transistor has an operating voltage of -4.5V.
Is applied to L1 to L4, class A operation is performed, and when a non-operating voltage of −6.5 V is applied, class C operation is performed. That is, depending on the level of the input signal, a linear amplifier (transistor)
By independently controlling the gate voltage of each of the transistors, each transistor is switched from class A operation to class C operation.

As an example, the amplitude value of the input signal is 2
If it is 6.5 dBm or less, only the transistor T1 is turned on, the transistors T1 and T2 are turned on up to 29.5 dBm over 26.5 dBm, and the transistors T1, T2 and T3 are turned on up to 31.3 dBm over 29.5 dBm. The control circuit 5 sets the number of transistors so that all the transistors T1 to T4 are turned on when the power is turned on and exceeds 31.3 dBm.

Next, the operation of the above-mentioned transmitter will be described. First, when the digital data to be transmitted is input to the digital signal processing unit 2, the corresponding amplitude information and phase information are given to the quadrature modulator 21, from which the modulated signal is transmitted via the voltage control variable attenuator 22 to the power amplifier. Input to 3. Here, FIG. 3 shows the amplitude level of the input signal (input power) on the input side of the voltage controlled variable attenuator 22, each transistor T
1 to T4 state (on / off state distinction), DC power supply 3
FIG. 3 is a diagram showing the relationship between the consumption current flowing from 1 to the transistors T1 to T4, the amplitude level of the output signal (output power), and the power efficiency. The setting of which transistor is in operation when the amplitude level of the input signal is
This is the same as the specific example described above. A curve a shown as a solid line as an input signal is an envelope of the M16QAM modulation signal.

The modulation method of the transmitter according to this example is M1.
Since it is 6QAM, the deviation of the amplitude level of the input power is
25 dBm to 32.5 dBm (0.316W to 1.77)
8W) and the deviation of the input voltage is 3.975V to 9.4V.
It is 29 V (input impedance 50 Ω). As can be seen from FIG. 3, when the amplitude level of the input voltage is small, for example, 25 dBm, the amplitude information is given from the digital signal processing unit 2 to the control circuit 5, so that the control circuit 3
The operating voltage of -4.5 V is output from the signal line L1 and the non-operating voltage of -6.5 V is output to the other signal lines L2 to L4, and only the transistor T1 is in the operating state.

Then, as the amplitude level of the input signal increases, the control circuit 3 sequentially causes the transistors T2, T
An operating voltage is supplied to the gate electrodes of T3, T4, and these transistors T2, T3, T4 are put into an operating state. At this time, the consumption current flowing from the DC power supply 31 into the transistor,
That is, the total value of the currents between the drain and the source of each of the transistors T1 to T4 is about 1 A when only the transistor T1 is in the operating state as shown by the solid line b1, but the transistors T2, T3 and T4 are sequentially in the operating state. As the number of transistors T1 to T4 becomes operational, it becomes about 4 A. That is, when the amplitude level of the input power increases, the number of transistors commensurate with the amplitude is activated, and the parallel circuit of these transistors causes class A operation as a whole.

Therefore, the amplitude level of the output power becomes linear as shown by the solid line c, and its deviation is 35 dBm.
~ 42.5 dBm (3.162 W ~ 17.782 W), the output voltage deviation is 12.573 V ~ 29.817.
V (output impedance 50Ω). In the middle of the graph showing the amplitude level of the output power, as a comparative example, regardless of the amplitude of the input power, only the transistor T1 is in the operating state, the transistors T1 and T2 are in the operating state, and the transistor T1 is in the operating state. The respective amplitude levels when T3 to T3 are activated are shown.

As described above, according to the power amplifier described above, good linearity is obtained, and since the number of operating transistors is controlled according to the amplitude level of the input power, high power efficiency can be obtained. . The solid line b2 in FIG. 3 indicates that the four transistors T are independent of the level of the amplitude of the input power.
The consumption currents flowing into the transistors when 1 to T4 are all in the operating state, and the dotted lines d1 and d2 indicate the numbers of transistors respectively (in the embodiment of the present invention)
It shows the power efficiency with and without.

The power efficiency is defined by input power, output power Pi,
Let Po be the drain current and gate current of the transistor be Id and Ig, and the drain-source voltage and the gate-source voltage of the transistor be Vds and Vgs.

Efficiency = (Po-Pi) / (Vds × Id) + (Vgs × Ig) (1) However, since Ig is so small that it can be ignored as compared with Id, it is eventually expressed by equation (2).

Efficiency = (Po-Pi) / Vds × Id (2) As can be seen by comparing the solid lines b1 and b2, the dotted lines d1 and d2
As can be seen by comparing d2, according to the embodiment of the present invention, the current consumption is small and high power efficiency can be obtained.

Since the number of transistors to be activated is controlled instead of dynamically changing the drain current of the transistors according to the amplitude level as in the conventional case, the control circuit 5 has a function of switching the number. Since it is sufficient to have it, a complicated circuit is not required. Further, the advantage of this embodiment is that since the gate voltage of the transistor is controlled, the control signal lines (L1 to L1) for the gate voltage are controlled.
The current flowing in 4) is as small as a few mA (the drain current is controlled in the conventional example, so a large current of about several A has to be controlled). Therefore, since a small signal switching circuit may be incorporated, The device can be downsized and the price can be reduced, and is suitable as a portable transmission device such as a digital mobile phone.

Here, in the above-mentioned embodiment, one amplifying section is formed by one transistor, and four amplifying sections of these amplifying sections are provided.
Although the number of amplifiers is connected in parallel, the number of amplifiers is not limited to four. Further, in the present invention, one amplifying section may be composed of a plurality of transistors. For example, as shown in FIG. 4, two transistors T1 and T2 are connected in parallel to form one amplifying section. Four amplifiers A1 to A4
May be connected in parallel to form a power amplifier. In this case, the two transistors T11 and T12 are connected to the signal line L1.
The control voltage from L1 and L12 simultaneously sets the operating state and the non-operating state.

Furthermore, as a transistor, a bipolar
Alternatively, a transistor may be used. The power amplifier of the present invention can be applied to a transmitter that requires modulation for amplitude components such as π / 4 shift QPSK in addition to M16QAM, but is not limited to such a transmitter and has a receiver input voltage. Transmission power control when the value exceeds the value, and the conventional A
It can also be applied to M and SSB analog modulation systems.

[0030]

According to the present invention, a highly efficient linear amplifier, which is small and inexpensive, can be obtained. For example, the transmitter can be downsized and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a main part of an embodiment of the present invention.

FIG. 3 is an operation characteristic diagram showing the operation of the embodiment of the present invention.

FIG. 4 is a circuit diagram schematically showing another embodiment of the present invention.

FIG. 5 is a block diagram showing a conventional power amplifier.

[Explanation of symbols]

2 Digital Signal Processing Unit 21 Quadrature Modulator 22 Voltage Controlled Variable Attenuator 3 Power Amplifier T1 to T4, T11, T12 Transistor L1 to L4 which is an Amplifying Unit Signal Line of Control Voltage 31 DC Power Supply 5 Control Circuit

Claims (3)

[Claims] 1. An amplifier parallel circuit, which is formed by connecting a plurality of power amplifiers in parallel, and a control signal for turning the amplifier on or off is applied to a control electrode of the amplifier. Taking in the magnitude of the amplitude level of the input signal and applying a control signal for turning on the number of the amplification units of the amplification unit parallel circuit corresponding to the amplitude level to the other amplification units. And a control unit that applies a control signal for turning off the power amplifier. 2. A power amplifier for supplying an input signal between a control electrode and a cathode electrode of a transistor to extract an output signal from between the cathode electrode and the anode electrode. A transistor parallel circuit that is commonly connected to the signal input terminal and that is connected in parallel between the anode electrode and cathode electrode of each transistor, and the transistor between the control electrode and cathode electrode of the transistor. A control voltage for turning on or off is applied, and the amplitude data of the input signal is taken in, and among the transistors of the transistor parallel circuit, the number of transistors corresponding to the amplitude level of the input signal is applied. A control unit that applies a control signal for turning on and a control signal for turning off other transistors. , Power amplifier and characterized in that it comprises a. 3. A signal processing section for creating amplitude data based on a digital signal which is transmission data, and a modulation section for modulating an amplitude component based on the amplitude data from this signal processing section. A power amplifier connected to the output side of this modulator,
Wherein the power amplifier is a power amplifier that supplies an input signal between a control electrode and a cathode electrode of a transistor to extract an output signal from between the cathode electrode and the anode electrode, A transistor parallel circuit in which the control electrodes of the transistors are commonly connected to the signal input terminal, and the anode electrodes and cathode electrodes of the respective transistors are connected in parallel, and the control electrodes and cathode electrodes of the transistors In between, a control voltage for turning the transistor on or off is applied, and the amplitude data of the input signal is fetched from the signal processing unit, and the amplitude of the input signal among the transistors in the transistor parallel circuit is input. Apply a control signal to turn on the number of transistors corresponding to the level and turn off the other transistors. Transmitting apparatus characterized in that it comprises a control unit applying a control signal for.