Abstract: An impedance matched class-F high frequency amplifier includes an input matching circuit receiving high frequency signals connected to the gate of the FET. The drain of the FET is connected to an output matching circuit which matches the fundamental frequency and the second harmonic frequency, and the output of the output matching circuit is connected to an even harmonic terminating circuit. The stray reactance componance at the output impedance of the FET is offset by the output matching circuit, and therefore the even harmonics terminating circuit can more accurately terminate the second harmonic frequencies.

Abstract: The system for measuring the spillover signal from a transmitter to a receiver in a same frequency repeater or a booster has a frequency conversion device which slightly offsets the transmission frequency from the reception frequency, and a signal detector which measures the offset frequency component in the reception signal. The offset frequency is around 100 Hz, which is higher than the fading frequency, and low enough not to affect the operation of receivers. The measured spillover level is used to control the gain of the repeater, and/or to cancel the spillover signal, so that the repeater has the maximum gain without suffering from oscillation.

Abstract: An input signal is divided equally by a divider and the equally divided outputs are applied to first and second amplifying means, respectively. A filter means, which rejects the fundamental wave component of the input signal but passes therethrough its harmonic component, is connected between the first and second amplifying means. The outputs of the first and second amplifying means are respectively connected to first and second select circuits which select the fundamental wave components of the input signal. The outputs from the first and second circuits are combined in phase with each other, by a combiner, into a composite signal.