SPECTRAL-DOMAIN ANALYSIS OF SUBMILLIMETER-WAVE MICROSTRIP FILTERS

We consider the cut-off frequencies of high-order modes in boxed submi llimetre-wave microstrip filters. It is shown that many of the filters in use at the present time are not cut off in the way that the design ers imagine. It is also shown that for ease of manufacture the height of the microstrip channel should be 0.7 times the width and the thickn ess of the quartz substrate should be 0.5 times the width. This optimu m geometry suggests that the upper frequency limit of conventional wav eguide components is 1 THz.