Linearly tapered slot antenna impedance characteristics

The linearly tapered slot antenna (LTSA) is a very useful antenna. Previous experimental studies emphasized the dependance of the beam width, directivity and gain on the flare length and angle of the LTSA. In addition Simons et al. (1992) demonstrated several novel techniques to feed an LTSA. Simons and Lee (1993) also studied the effect of a dielectric overlay on the LTSA beam width and gain. In all of the above investigations, the input impedance of the LTSA has been approximated to be the same as that of an equivalent biconical fin antenna. This approximation is valid only over a certain frequency band. The present paper demonstrates for the first time an accurate technique to determine the input impedance of an LTSA using a microwave wafer probe and a set of on-wafer thru-reflect-Line (TRL) slot line calibration standards. Experimental results are presented which show the variation of the input impedance as a function of the frequency with the semi-flare angle and flare length as parameters.