AN ALTERNATIVE APPROACH TO IMPROVING THE EFFICIENCY OF HIGH-POWER RADIO-FREQUENCY AMPLIFIERS

This paper introduces the concept of using fourth harmonic rather than third harmonic resonant circuits in the tuned plate circuits of high power radio frequency amplifiers to improve operating efficiency. The advantages are circuit simplicity, greater stability, and simpler adjustment than with third harmonic enriched amplifiers because the grid excitation voltage can be sinusoidal. Improvements in plate efficiency, envelope distortion, and carrier shift characteristics are comparable to those achieved with third harmonic designs; however, implementation is simpler and the amplifier more stable because the requirement to maintain a constant grid current under conditions of plate modulation becomes less critical.