SU-8 micromachined cross-coupled waveguide cavity filter for sideband rejection above 300 GHz

A 300 GHz waveguide filter, designed to block the unwanted upper sideband from reaching a heterodyne mixer, is presented. This WR-3 filter is based on three cross-coupled TE101 resonators. It is designed to have a Chebyshev response, and cross-coupling between first and third resonators provides transmission zeros in the stopband. The filter is fabricated using a multilayered SU-8 micromachining process. The completed filter has a 12 GHz bandwidth with a center frequency of 298.5 GHz: in-band insertion loss is 0.45 dB, with >30 dB rejection of the unwanted sideband. Good agreement between predicted and measured transmissions is obtained.