A Wideband Diplexer for Ka-Band Passive Intermodulation Measurement
In this paper we propose a novel Ka-band waveguide diplexer for passive intermodulation (PIM) measurements. Due to the higher operating frequency, this type of measurement setup usually requires wide band filters. In addition, due to the very large separation between satellite uplink and downlink bands, the PIM measurement diplexer unit must operate over a very wide frequency band. To satisfy such wide bandwidth requirements, the proposed topology is based on a band-reject filter for the downlink frequency band which is designed to provide, at the same time, the optimal passband performance for the downlink, and the optimal equiripple rejection over the PIM band. For the PIM channel, a band-pass filter combined with a high-pass section has been used. To validate the design, a prototype has been designed and manufactured. Very good agreement is shown between simulations and measurements, thereby fully validating the proposed solution.