Terahertz Input-Reflectionless Waveguide Filter

This paper presents, for the first time, the design of a terahertz waveguide input-reflectionless filter operating at WR3.4 band. The filter has filtering and matching sections, and they are combined at the input port. The filter has been designed to have three resonators in the filtering section and one resonator in the matching section. The normalized coupling values producing the return loss larger than 13 dB in both the passband and the stopband have been derived for designing the filter. For demonstration, the filter was designed based on the target center frequency and fractional bandwidth set to 275 GHz and 3%, respectively. The measured return loss is larger than 10 dB over the entire WR3.4 band from 220 GHz to 330 GHz.