JPH03101511A - Power amplifier - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a power amplification device, and more particularly to a power amplification device that has a multi-stage power amplifier and whose output power can be controlled.

In recent years, with the expansion of the mobile communication market, there has been a demand for lower power consumption for long-duration calls, especially in wireless devices such as mobile phones. Therefore, in radio equipment, it is necessary to improve the efficiency of the transmission power amplifier, which has a high power consumption rate.

[Conventional technology]

Elements that perform power amplification in the communication field, for example in the digital wireless field, include silicon bipolar transistors and invat diodes, and recently GaAs
Field-effect transistors using Invat diodes can obtain a relatively large output in the microwave band, but because of their large thermal noise, they are mainly used as transmitting elements, and are currently used in 5 GHz and 11 GHz.
z, 15GHz.

1.4W, 0.6W, respectively in 20GHz band
Types with outputs of 0.2W and 0.15W are in practical use.

In conventional power amplifiers used in the communication field, an operation method called class B, class C, or class F is adopted in order to increase efficiency at maximum output. However, due to the system nature of the radio device, it is necessary to constantly control the output in four to six steps, and in this case, only the bias power source of the power amplifier is varied to control the output.

Specifically, as shown in FIG. 5, when the power amplifier 21 has transistors 22 to 24 in each stage and amplifies the signal from the input signal terminal 25 in three stages and outputs it from the output signal terminal 26, The voltages supplied to the power supply terminals 22a to 24a of each stage are variably controlled. For example, transistor 2 in each stage
When performing output control when 2 to 24 are FETs, the 6th
As shown in the figure, the output power is suppressed by lowering the drain voltage v0 of each stage, or by lowering the drain current by increasing the gate voltage 6 of each stage as shown in FIG. 7, thereby suppressing the output. -For boat fishing, the first stage transistor 22 or the first stage middle stage transistor 22.
Power control is performed only for 24. Note that each stage is an FET.
In the case of a transistor instead, power control is performed by changing the collector voltage or base voltage.

[Problem to be solved by the invention]

However, in such conventional power amplification devices, when the output of a power amplifier that is matched to maximize efficiency near the maximum output is controlled by a bias power supply, for example, when the output is controlled by a bias power supply, approximately 3 In the case where the output is lowered by ~1 OdB, there is a problem that the matching circuit of the fixed amplifier, especially the output circuit, cannot achieve sufficient matching, resulting in a significant decrease in efficiency.

Therefore, an object of the present invention is to provide a power amplification device that can control output power without reducing efficiency.

[Means to solve the problem]

In order to achieve the above object, the power amplification device 101 according to the present invention, as shown in the principle block diagram in FIG. In a power amplification device 101 that controls power and includes an output matching circuit 103 in the final stage or at least one of each stage, a capacitive active element 104 is provided in the output matching circuit 103, and the bias of the active element 104 is controlled. The output power is controlled by changing the biases of the amplifier circuits 102a to 102n while matching the circuits by changing the biases of the amplifier circuits 102a to 102n.

[Effect]

In the present invention, when controlling the output, the capacitive active element 104
The bias of the amplifier circuits 102a to 102n is changed, thereby changing the capacitance component and matching of the output matching circuit 103, and at the same time changing the bias of the amplifier circuits 102a to 102n.

Therefore, the impedance of the output matching circuit 103 and the power supply voltage of each stage are linked to control power, and a decrease in efficiency is prevented.

〔Example〕

Hereinafter, the present invention will be explained based on the drawings.

FIG. 2.3 is a diagram showing an embodiment of the power amplifying device according to the present invention. Figure 2 is a circuit diagram of a power amplifier. In this figure, 1.2 is an FET, 3.4 is a choke coil, and 5 to 12 are chip-type capacitors, among which capacitors 5, 6, 7, and 8 are Capacitor 9.11 is used for output matching with choke coil 3.4, and 13 is a variable capacitance diode (capacitive active element). This is an example of two-stage amplification. Further, regarding power supply relations, VGI and vG□ are gate bias power supplies for FETI 2, respectively, V p 1 and V Dz are drain bias power supplies for FET 1.2, respectively, and VO2 is a diode power supply for the variable capacitance diode 13 .

The coupling capacitor 7, coupling capacitor 8, output matching capacitor 12, and variable capacitance diode 13 constitute an output matching circuit 14.

In the above configuration, the drain in each stage of FBTI 2 is positively biased with respect to the source, and electrons, which are majority carriers, flow from the source to the drain in the n-type operating layer. The gate electrode and the n-type active layer form a Schottky junction (rectifying junction), and the depletion layer changes depending on the gate voltage, so the drain current changes depending on the signal applied to the gate (
INPUT). In other words, the gate operates as a current control valve, but the power consumed by the gate is small (i.e., large changes in drain current can be controlled by 0UTP).
Since it can be taken out as a UT, FET 1.2 performs a power amplification action.

Here, when performing output control, the variable capacitance diode 13
By changing the bias V113 for the variable capacitance diode 13, the capacitance component of the variable capacitance diode 13 is changed. Thereby, the output matching circuit 14 is optimized during output control. This is achieved by increasing the impedance at point A (corresponding to high output) by increasing the capacitance component of the variable capacitance diode 13 connected in parallel to the amplifier circuit, as shown in the Smith chart in Figure 3. This corresponds to moving to a certain point B. In FIG. 3, the solid line is a circle with constant efficiency, and the broken line is a circle with constant output. Therefore, by moving from point A to point B, the output goes from 33 dBm to 28 dBm.
Efficiency is 4-6 dBm at around 80% while lowering to about dBm
Although the level is reduced, it is not significantly reduced. Also,
If the output has been lowered sufficiently, lower the drain bias ■, and perform the same operation.

Although the above embodiment is a two-stage amplification with one output matching circuit, the present invention is not limited to this, and the present invention can be applied to amplifiers with other stages. It can be applied even if a matching circuit is provided. Specifically, for example, the fourth
As shown in the figure, each stage of the amplifier 202a of the amplifier device 201
202n are provided with output matching circuits 203a to 203n, each output matching circuit 203a to 203n is provided with capacitive active elements 204a to 204n, and the bias of each of these active elements 204a to 204n is changed. While performing circuit matching, the amplifiers 202a~
The output power may be controlled by changing the bias of 202n.

〔Effect of the invention〕

According to the present invention, it is possible to control the output power of the power amplifier circuit without significantly reducing efficiency. As a result, for example, by applying the present invention, the transmission time of portable wireless devices that require power control can be significantly extended.

[Brief explanation of drawings]

Fig. 1 is a principle block diagram of the present invention, Fig. 2.3 is a diagram showing an embodiment of the power amplifier according to the present invention, Fig. 2 is its circuit diagram, and Fig. 3 is its output and efficiency. FIG. 4 is a block diagram of another embodiment of the power amplifier according to the present invention; FIGS. 5 to 7 are diagrams showing conventional power amplifiers; FIG. 5 is a block diagram thereof; FIG. 6 is a diagram explaining the change in the bias voltage, and FIG. 7 is a diagram explaining other changes in the bias voltage. 1, 2...FET. 3.4...Choke coil, 5-12...Capacitor, 13...Variable capacitance diode (capacitive active element) 14.103.203a-203n... ...Output matching circuit, 101.201...Power amplifier device, 102a-102n...Amplification circuit, 1048
~l04n, 204a~204n...capacitive active element, 202a~202n...amplifier,
VGl, VO2... Gate bias power supply,
VD I + V D 2...Drain bias power supply, VDs...Diode power supply. -11ゎ1111'' 4 Lower the circuit diagram of one embodiment in Figure 2 (■), and (■). lower. Figure 6 for explaining changes in bias voltage in the conventional example. Figure 7 for explaining changes in other bias voltage in the conventional example.

Claims (1)

[Scope of Claims] A power amplifier device that performs power amplification using an amplifier circuit including multi-stage transistors, controls the output power by changing its bias, and has an output matching circuit in the final stage or at least one of each stage. , characterized in that the output matching circuit is provided with a capacitive active element, and the output power is controlled by changing the bias of the amplifier circuit while matching the circuit by changing the bias of the active element. A power amplification device.