A Power Combiner for Step Level High Power UHF Solid State Transmitters

Abstract

A combining network is described which satisfies the requirements of low loss, compact size and input port selection capability. This power combiner, which follows a basic network scheme suggested by E. J. Wilkinson, uses helical wound quarter wave lines for impedance matching, relays for switching inputs in or out, and thick film resistors in the isolation network. The combiner was designed for a UHF solid-state transmitter for a communications satellite. The power level is in excess of 300 watts. From 8 to 16 inputs, from coherently driven power amplifiers, can be selected by command. This step level feature provides a very useful means to achieve maximum utilization of prime power as well as an improvement in reliability through redundancy. Design equations are given for the units. The results of a computer study of losses due to unequal input phases and amplitudes are presented. The equivalent circuit of the network, including parasitics, is described and the compensating elements are discussed. Tests have been made on the completed flight unit, and these results are plotted and discussed.