A W‐Band Bandpass Filter With Two Controllable Transmission Zeros Based on Rectangular Resonators

ABSTRACT In this paper, an improved W‐band bandpass filter for the W‐band synthetic aperture radar (SAR) system with a center frequency of 96 GHz is designed and implemented. Compared with the conventional rectangular waveguide resonator filters, two specially designed oversized rectangular waveguide cavities are combined in the structure to create two transmission zeros (TZs), which improves the sharp cutoff rate of the filter and remains the simplicity of the structure. Meanwhile, the position of each TZ is independently controlled by the dimensions of one specific oversized rectangular resonator, which makes it easier to realize a flexible and accurate design. The improved structure is analyzed, modeled and optimized to obtain a better transmission characteristic. The measured results show that the return loss of the improved W‐band bandpass filter is less than −8 dB and the insertion loss is less than 1.4 dB within the passband. Additionally, the two TZs are located at 89.17 GHz and 103 GHz, respectively. These results verify the feasibility of the improved bandpass filter structure.