Waveguide band-pass filter with reduced sensitivity to fabrication tolerances for Q-band payloads

Abstract

A rectangular waveguide band-pass filter with very low sensitivity to fabrication tolerances is proposed. The novel filter exploits the inherent first passband replica of commensurate-line stepped-impedance low-pass filters. Waveguide width reduction is also exploited to obtain a band-pass filter with a significant enhancement in the fabrication yield. This improvement is especially attractive for space applications in the millimeter-wave range. The validity of the novel design technique has been demonstrated with a 13th-order Chebyshev band-pass filter for Q-band payloads. The manufacturing yield of the novel filter has been dramatically improved when compared to the classical inductive-iris filter designed to fulfill the same frequency specifications (92 % vs. 8 %, for a worst-case fabrication error of ± 25 μm). A prototype has been fabricated using milling techniques showing a very good agreement between simulated and measured results.