JPH0326561B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a high efficiency power amplifier circuit.

(Prior Art) As a conventional circuit of this type, there is a circuit called a class F amplifier circuit shown in FIG. (Here, a class F amplifier circuit mainly refers to one that is composed of a transistor that functions as a current source and a load circuit that has a specific harmonic impedance.) In the figure, 1 is a transistor that functions as a current source and a switch, and 2 is a transistor that functions as a current source and a switch. A 1/4 wavelength transmission line with a length of 1/4 wavelength, 3 is an output terminal, and 4 is a parallel resonant circuit. The basic operation of this circuit is to short-circuit one end of the 1/4 wavelength transmission line 2, open the other end for odd harmonics, and short-circuit even harmonics, thereby achieving high efficiency. However, since the short circuit at one end uses the capacitor of the parallel resonant circuit 4, it cannot be a complete short circuit, and the parallel resonant circuit has a high impedance for the fundamental wave. Therefore, there was a drawback that the other end could not ideally be an open circuit for odd numbers and a short circuit for even numbers.

(Object of the invention) The object of the present invention is to solve the drawbacks of the above-mentioned prior art,
The present invention provides a power amplifier circuit that can completely short-circuit both ends of a single-wavelength transmission line to obtain a highly efficient fundamental wave output from an open position for odd-numbered harmonics,
This will be explained in detail below.

(Structure of the Invention) The present invention includes a transmission line having a length equal to one wavelength and having both ends short-circuited with high frequency, and a transmission line connected to a point 1/4 wavelength from one end of the transmission line and functioning as a current source and a switch. A power amplification circuit characterized in that it is comprised of an amplification element and a series resonator that obtains fundamental wave signal power from a location 1/4 wavelength from the other end of the transmission line.

(Embodiment) Fig. 2 is a circuit diagram showing an embodiment of the power amplifier circuit according to the present invention, in which 5 is a transmission line having a length of one wavelength bent into a rectangular shape and both ends a and b are set at the same point. a high-frequency short-circuited one-wavelength transmission line, 6 a gallium arsenide field effect transistor (hereinafter referred to as GaAsFET) that functions as a current source and a switch;
7 is a series resonator for extracting the fundamental wave signal power;
8 is an output terminal. One end a of the one-wavelength transmission line 5
Connect to the drain of the GaAsFET 6 at a point c that is 1/4 wavelength from the point c, and connect one end of the series resonator 7 at a point d that is 1/2 wavelength from the point c, and connect the other end of the series resonator 7 to the output terminal 8. is connected to. When a fundamental wave signal is input to the GaAsFET 6, voltages such as a fundamental wave A, a double wave B, etc. are distributed on the line of the one-wavelength transmission line 5 as shown in FIG. Each of a, b, c, and d in Fig. 3 corresponds to Fig. 2, and the connection point c with the GaAsFET 6 of the one-wavelength transmission line 5 and the connection point d with the direct resonator 7 are connected to the fundamental wave A. For the second harmonic wave B, it is open, and for the second harmonic B, it is short-circuited. Similarly, for harmonics of 3rd order or higher, points c and d are open for all odd harmonics, and shorted for all even harmonics.

The impedance with these characteristics is GaAsFET.
6, the voltage waveform at the drain is a rectangular wave, the current is a half-wave rectified sine wave, and the so-called class F operation mode (for class F amplifiers and class F operation, see Nikkei Electronics
1976, 8.28), the desired fundamental wave is the series resonant circuit 7 connected to point d.
Through this process, highly efficient output can be obtained on the load side.

That is, in the basic circuit shown in Fig. 2,
When a fundamental wave signal is input to GaAsFET6, a rectangular wave voltage appears on the drain side because it is in class F operation mode, but since the rectangular wave consists of odd number harmonic components, the desired fundamental wave is an odd number. It can be obtained from the open part of the next harmonic through a series resonant circuit. Moreover, in this circuit, since both ends of the one-wavelength transmission line can be completely short-circuited at high frequency, the open points of the odd-numbered harmonics become clear, and a highly efficient fundamental wave output can be obtained.

In this embodiment, GaAsFET is used as the amplification element for GHz band frequencies, but transistors such as MOSFETs can also be used for other frequency bands.

Further, in this embodiment, a case has been described in which both ends of the one-wavelength transmission line 5 are short-circuited at the same point, but the same effect can be obtained by short-circuiting the high-frequency waves at both ends separately.

(Effects of the Invention) As explained above, the present invention provides a one-wavelength transmission line 5 having a length of one wavelength and a series resonant circuit 7,
Since both ends of the wavelength transmission line 5 are completely short-circuited for high frequency (in the above embodiment, both ends are short-circuited for high frequency at the same point), the short-circuited and open points on the line are clear, and the connection point of the amplification element is The odd harmonics can be opened and the even harmonics can be shorted. In other words, the power amplifier circuit according to the present invention is in an ideal class F operation mode, and a highly efficient fundamental wave output can be obtained from the odd harmonic open portion through the series resonant circuit.

Therefore, when the power amplifier circuit according to the present invention is used in a portable radio device or the like, it has advantages such as being able to reduce the size of the heat sink and battery.

[Brief explanation of drawings]

FIG. 1 is a basic circuit diagram of a conventional class F amplifier circuit, FIG. 2 is a basic circuit diagram of a power amplifier circuit according to an embodiment of the present invention, and FIG. 3 is a voltage distribution diagram on a one-wavelength transmission line. 5... Single wavelength transmission line, 6... Gallium arsenide field effect transistor (GaAsFET), 7... Series resonator, 8... Output terminal.

Claims (1)

[Claims] 1. A transmission line having a length equal to one wavelength of the fundamental wave and having both ends short-circuited at high frequency, and a transmission line connected to a point 1/4 wavelength from one end of the transmission line and functioning as a current source and a switch. A power amplification circuit comprising an amplification element and a series resonator that obtains fundamental wave signal power from a point 1/4 wavelength from the other end of the transmission line. 2. The power amplification circuit according to claim 1, characterized in that a gallium arsenide field effect transistor is used as the amplification element. 3. The power amplifier circuit according to claim 1, wherein both ends of the transmission line are high-frequency short-circuited at the same point.