SU-8 micromachined WR-3 band waveguide bandpass filter with low insertion loss

Presented is a WR-3 band (220-325 GHz) waveguide bandpass filter, which is constructed from three offset waveguide resonators operating at TE mode. This directly coupled resonator filter with Chebyshev response is designed to have a centre frequency of 300 GHz, a fractional bandwidth of 3.3% and a passband return loss of 20 dB. This filter is fabricated using thick SU-8 photoresist micromachining technique and has been tested. The measured average passband insertion loss is as low as around 0.4 dB. The measured return loss is better than 15 dB across the whole passband.