Spectral distortion in pulsed class-C amplifiers

An important problem in solid-state radar transmitters using class-C pulsed amplifiers is the spectral distortion generated during the fall time of the RF pulse. The widening of the spectrum is commonly corrected with cavity filters. In this paper, the sources and the nature of such a distortion are explained. A novel technique to avoid it based on bias modulation of a low power stage at the beginning of the amplifying chain is also presented. Experimental results show that this technique eliminates the need of the output filter, thus resulting in an output power improvement of hundreds of watts