KR20050011134A - Power amplifier circuit for mobile communication terminal - Google Patents

Abstract

PURPOSE: A power amplifying circuit for mobile terminals is provided to improve linearity and amplification efficiency by reinforcing the current at a base terminal of a transistor in a power amplifier. CONSTITUTION: A power amplifying circuit for mobile terminals includes a driver amplifier(400), a power amplifier(600), and an output matching portion(800). The driver amplifier amplifies an output signal to have a power used at the terminal. The power amplifier amplifies the signal amplified at the driver amplifier to a power level adequate for transmitting/receiving at a transmitter. The output matching portion matches the amplified signal to have impedance adequate to be outputted at the output terminal. The driver amplifier includes a linear circuit for improving linearity of the output power.

Description

Power amplifier circuit for mobile communication terminal

The present invention relates to a power amplifier circuit for use in a wireless mobile communication terminal, and more particularly, to a power amplifier circuit for minimizing interference between adjacent channels by improving nonlinearity at a high output of the power amplifier.

The future means of communication are evolving from fixed to mobile, from wired to wireless, from voice to non-voice. Therefore, research on adjacent channel interference, that is, nonlinearity improvement, is being actively activated to economically use a given bandwidth while maintaining reliability of call quality.

In general, research on improving nonlinearity has attracted attention for preparing countermeasures for various interference phenomena for existing wireless communication services, and has made great efforts to develop high-speed, efficient and reliable methods for new wireless communication services. This is being invested. However, in order to provide such a service to a large number of general subscribers, bandwidth efficiency must be high and economical, but robust high quality service against various interferences is required.

In particular, the adjacent channel interference phenomenon has a great effect on the overall design and operation of the wireless communication system in terms of efficiency and reliability as well as economics.

1 and 2 illustrate a power amplifier circuit according to the prior art.

The power amplifier circuit according to the prior art amplifies the signal input from the external driving amplifier 40 to the power used in the terminal, and amplifies the signal amplified by the drive amplifier 40 to the power suitable for transmission and reception The power amplifier 50 and an output matching unit 60 to match the amplified signal to the impedance suitable for output to the output terminal.

However, in the power amplifier circuit according to the related art, only the current I1 is supplied by the transistor Q1 of the driving amplifier 40 to the base portion of the RF transistor Q2 constituting the power amplifier 50. When a high output is required as the power level of the RF input signal increases, as shown in FIG. 2, the non-linearity of the power amplifier, that is, the base and the power of the RF input signal in the RF transistor Q2 is already increased. The phenomenon that the inter-terminal voltage (Vbe) is reduced has a problem that the amplification efficiency is lowered.

The present invention has been made to solve the above-mentioned problems of the prior art, and its object is to reduce the nonlinearity that increases as the power of the RF input signal increases when amplifying and outputting the input RF signal, thereby reducing the linearity of the output power. The present invention provides a power amplification circuit which improves the voltage and thereby improves the amplification characteristic.

1 is a view showing a power amplifier circuit according to the prior art;

2 is a graph illustrating a voltage change between a base and an emitter in an RF transistor according to RF power input to an RF transistor of a power amplifier circuit according to the related art;

3 is a view showing a power amplifier circuit according to the present invention;

4 is a diagram illustrating a linearity improvement unit in a power amplifier circuit according to the present invention.

<Explanation of symbols on main parts of the drawings>

100: input terminal 200: output terminal

300: power supply 400: drive amplifier

500: linearity improvement circuit 600: output amplifier

700: linearity improvement unit 800: output matching unit

According to a feature of the power amplification circuit according to the present invention for solving the above problems, a drive amplifier for amplifying the signal input from the outside to the power used in the terminal, and the signal amplified by the drive amplifier RF (Radio Frequency) A power amplifier for amplifying the transistor to a power suitable for transmission and reception, an output matching unit for matching the amplified signal with an impedance suitable for output to an output terminal, and a nonlinearity of the output power of the power amplifier. It consists of a linearity improvement circuit.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 3, the power amplifying circuit according to the present invention includes a driving amplifier 400 for amplifying a signal input from the outside to the input terminal 100 with the power used by the terminal, and a radio frequency (RF) transistor. And a power amplifier 600 configured to amplify the signal amplified by the driving amplifier 400 to power suitable for transmission and reception, and an impedance suitable for outputting the amplified signal to the output terminal 200. It includes an output matching unit 800 and a linearity improving circuit 500 for improving the non-linearity of the output power of the power amplifier 600.

4 is a diagram separately illustrating the linearity improving unit 700 including the linearity improving circuit 500 and the power amplifier 600. As shown in FIG. 4, the linearity improver 700 is formed by connecting an emitter of a current driver transistor Q3 that reinforces and supplies a current to a base of an RF transistor Q2 of the power amplifier 600. .

Looking at the operation of the power amplifier circuit according to the present invention configured as described above are as follows.

First, when a signal is input from the outside through the input terminal 100, the driving amplifier 400 amplifies the input signal by the power supplied from the power supply unit 300, and the amplified input signal is the power amplifier. Is entered at 600.

The input signal input to the power amplifier 600 is amplified according to the set amplification factor and then input to the output matching unit 800 and the amplified input signal input to the output matching unit 800 is the output terminal ( The impedance is matched to 200 so that it can be output without loss of signal.

As shown in FIG. 1, in the driving amplifier 40 of the power amplifier circuit according to the related art, a current is generated by the transistor Q1.I1Only Current in the base portion of the RF transistor (Q2) of the power amplifier 50I3Is supplied.

In this case, in the conventional circuit illustrated in FIG. 2, when a high output is required as the RF input power level is increased, if only the current I1 is supplied to the base of the RF transistor Q2 by the transistor Q1, the power amplifier is nonlinear. That is, the voltage Vbe between the base and the emitter decreases as the RF input power increases in the RF transistor Q2. In addition, if the voltage Vbe between the base and the emitter of the RF transistor Q2 is reduced, the output of the collector is reduced, thereby reducing the amplification efficiency.

However, as shown in FIG. 3, the power amplification circuit according to the present invention has a linearity improvement circuit 500 formed of a current driver transistor Q3 in addition to the current I1 of the transistor Q1 according to the existing invention on the base of the RF transistor Q2. Reinforce and supply current I2 with).

Therefore, the power amplifier circuit of the present invention reinforces a corresponding current even when a high output is required, thereby reducing the voltage Vbe between the base and emitter according to the RF input power in the RF transistor Q2. To improve linearity and amplification efficiency.

As described above, the power amplification circuit according to the present invention has been described with reference to the illustrated drawings, but the present invention is not limited by the embodiments and drawings disclosed herein, and various circuits by those skilled in the art within the scope of the technical idea of the present invention. Of course, modifications can be made.

The power amplifier circuit according to the present invention configured as described above has a linearity improvement circuit formed of a current driver transistor for reinforcing and supplying current to the base of the RF transistor of the power amplifier. By improving the linearity and amplification efficiency by preventing the voltage (Vbe) between the emitters from being reduced, improved power amplifier characteristics can be obtained without a special additional circuit, and because the design area is not required, MMIC (Microwave Monolithic Integrated) Circuit) It is easy to design.

Claims (3)

A driving amplifier for amplifying an externally input signal with power used by a terminal, a power amplifier for amplifying the signal amplified by the driving amplifier with power suitable for transmission / reception by a radio frequency (RF) transistor, and the amplified signal In the power amplification circuit for a mobile communication terminal comprising an output matching unit to be matched to the impedance suitable to be output to the output terminal, And the driving amplifier includes a linearity improvement circuit for improving nonlinearity of output power. The method of claim 1, The linearity improvement circuit includes a current driver transistor having an emitter connected to the base of the RF transistor to supply a current. The method of claim 2, And the current driver transistor reinforces a current in the base of the RF transistor to increase linearity by increasing the collect output of the RF transistor.