On the characteristic impedance of TEM horn antennas

We have built several TEM horn antennas, measured their performance and compared this to calculations made using the finite-difference time-domain (FDTD) method. All of the horns were of the image equivalent design shown, were driven from a coaxial line (APC-7) with the characteristic impedance Z/sub 0/=50/spl Omega/, and had the angle /spl beta//2=160/spl deg/. During the course of these investigations, we noticed that Carrel's (1958) formula and graph did not agree with our measurements or FDTD calculations; this observation prompted the study which we present.

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