S. Withington et G. Yassin, SPECTRAL-DOMAIN ANALYSIS OF SUBMILLIMETER-WAVE MICROSTRIP FILTERS, International journal of infrared and millimeter waves, 14(10), 1993, pp. 1975-1984
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.