A Reactive Fourth-Harmonic Filter Operating at 400-kW CW

A reactive fourth-harmonic filter operating at a fundamental power level of 400-kW CW is described. The filter, used in the NASA Deep Space Instrumentation Facilities, operates in an S-band (WR-430) waveguide run and it effectively attenuates the fourth harmonic of the fundamental transmit frequency near 2.1 GHz by a minimum of 40 dB. The design approach including power handling capability considerations is presented. Also included are some details of mechanical construction, tuning procedures, and results achieved.