CHARACTERISTIC ANALYSIS AND TEST VERIFICATION OF TAPERED WAVE-GUIDES WITH FINITE WALL SURFACE-RESISTANCE

The detail behavior of tapered waveguide circuits with finite wall sur face resistance used at or close to the cutoff frequency is investigat ed. The analytical method used is based on a generalized waveguide tra nsmission equation applied to the TE(10) mode of a square waveguide wi th finite inner wall surface resistance. An equation suitable for nume rical calculations is derived. Further, in the case of waveguides of f inite wall surface resistance, the equivalent characteristic impedance and the propagation constant are also derived. The equations derived herein (imposed to a uniform waveguide) are in agreement with the freq uently used approximate equations in the frequency range far from the cutoff. Two types of taper waveguide circuits are devised for uses aro und the cutoff frequency. The shapes of the measured frequency charact eristics of the return losses of these circuits cue in agreement with those of the theoretical ones. Further, it is confirmed that if the ef fective value of the conductivity of the wall surface is taken to be o ne-half that of the nominal one, there is good agreement between the t heoretical and experimental results.