$Ku$ -Band Channel Aggregation Waveguide Filters by RF MEMS-Based Detuning

By switching high Q-factor 3-D waveguide bandpass filters with planar radio frequency micro-electromechanical system (RF MEMS)-based elements, a channel aggregation technique is developed in this article. These planar elements play the role of generating an effective phase shift when activated, detuning the resonant cavities of the bandpass filter, and contributing minimal insertion loss when deactivated. The proposed detuning system also has the advantage of not affecting the other operating filter channels connected to manifolds in a switchable waveguide filter bank. A two-channel prototype, based on the Australian satellite Ku-band, with 500-MHz bandwidth, at 14.25GHz (CH1) and 16.25-GHz (CH2) frequencies, is designed, fabricated, and measured demonstrating the channel aggregation operation. When using only two waveguide bandpass filters with no external switches, four different passband states are implemented, e.g., both channels disable (00), channel 2 enables only (01), channel 1 enables only (10), and both channels enable (11). The system provides excellent channel isolation of better than 35 dB over the disabled channels. For the enabled channels, the filters maintain a measured Q-factor of over 800, and better than 15 dB return loss. The measurements confirm that the detuning elements have a minimal impact on the manifolds and other channel filters, regardless of the operating states.