RF repeateris an important part of various wireless transmitters. In the pre-stage circuit of the transmitter, the RF signal power generated by the modulation oscillation circuit is very small, it needs to go through a series of amplification a buffer stage, intermediate amplification stage, the final power amplification stage, to obtain enough RF power later, in order to feed to the antenna radiation out. In order to obtain a large enough RF output power, must use RF power amplifier.

RF repeater operating frequency is very high, but the relative frequency band is narrow, RF power amplifier are generally used to select the frequency network as a load loop. RF power amplifier can be divided into A (A), B (B), C (C) three types of working states according to the different current conduction angle. Class A amplifier current conduction angle is 360°, which is suitable for small signal low power amplification, Class B amplifier current conduction angle is equal to 180°, and Class C amplifier current conduction angle is less than 180°. Both Class B and Class C are suitable for high-power operation, and the output power and efficiency of Class C operation is the highest among the three operation states. Most RF power amplifiers work in Class C, but the distortion of the current waveform of Class C amplifiers is too large and can only be used to amplify the resonant power using a tuned loop as a load. Due to the filtering capability of the tuned loop, the loop current and voltage are still close to the sinusoidal waveform, and the distortion is very small.