Chirping Techniques to Maximize the Power-Handling Capability of Harmonic Waveguide Low-Pass Filters

摘要

A novel chirping technique is applied to the designof very high-power waveguide harmonic low-pass filters. Thetechnique could be used, for instance, to avoid multipactortesting in multicarrier systems such as the output multiplexerof a communications satellite. The novel chirped filter showslow insertion loss, all higher order mode suppression, and broadstopband rejection up to the third harmonic. This paper focuseson the maximization of the filter power-handling capabilitywithout affecting its excellent frequency behavior. Given a certainfrequency response, the E-plane mechanical gap of the structureand the length (in the propagation direction) of the waveguidesections between its constituent bandstop elements can be consideredto improve the high-power behavior. However, the powerperformance may not be sufficient yet in some applications ifwe wish, for instance, multipactor testing to be avoided. Thisbecomes feasible by chirping the length (in the propagationdirection) of the bandstop elements. An example for Ku band isdiscussed for relevant frequency specifications. An improvementfrom ∼8 kW (non-chirped filter) to more than 100 kW (chirpedfilter) is obtained. As a reference, the equivalent waffle-iron filtercan handle only 0.15 kW. Such high-power threshold levels havenever been reported before for such kind of filters.