A 250-GHz microshield bandpass filter

A four-section, planar bandpass filter has been designed, fabricated and tested at 130-360 GHz. The filter is based on the microshield line, a half-shielded transmission line in which the conducting lines are supported on a 1.4-μm-thick dielectric membrane. The insertion loss of the filter is less than 1.5 dB with a 58% relative bandwidth at 250 GHz, demonstrating the excellent performance of the microshield geometry. Also, a Monte Carlo routine was developed in conjunction with a semi-empirical/semi-analytical model to allow the S-parameters of the filter to be derived from scalar power measurements.