W-Band E-Plane Waveguide Filter Using Compact Beeline Resonator

This letter presents a novel but very simple W-band E-plane waveguide bandpass filter (BPF) using just one compact beeline resonator (CBR), which leads to multiple transmission zeros (TZs). The proposed filter with low insertion loss (IL) and high selectivity is only 3.21 mm in length of the E-plane substrate. For further demonstration, a filter example with center frequency at $f_{0} =$ 88.55 GHz is implemented with generation of three TZs for theoretically calculated certification. Moreover, the measured minimum IL is only 1.15 dB. Good agreement between simulations and measurements validates the design method.