Optimized Architecture of E-plane Filters for High-Power Applications

The trend of modern telecommunication satellites is to accommodate different services in a single antenna feed-system. Typical examples are commercial payloads for Fixed Satellite Services (FSS) and Broadcast Satellite Services (BSS) working in the Ku/K bands or dual-use telecom payloads operating in K/Ka/Q bands . In multi-band feed-system operating in multi-carrier conditions, filters and diplexers are usually the most limiting elements due to their resonant characteristics that make them particularly susceptible to multipaction discharge and passive intermodulation products. Although a quite deep and extended literature can be found on different filter architectures, stop-band structures based on in-line resonators are usually considered the best candidates in high power applications for their compact size, low insertion losses and achievable high isolation levels. The main disadvantages of these devices are the high multi-mode interaction between the resonators, which limit the operative bandwidth, and the small size of the resonator apertures that restrict the maximum handling power. An advanced E-plane filter configuration is reported in this paper. It is based on a composite step/stub resonator that enables to maximize the "frequency x distance" product that, as well known, is directly proportional to the multipaction threshold power level. Exploiting this architecture, the design of high power filter and diplexer, working in Ku/K bands, is described. To confirm the effectiveness of the proposed architecture the measurements of a Ku-band diplexer prototype are reported.