Study about TEM horn size reduction for ultrawideband radar application

Different kinds of traveling wave transverse electromagnetic (TEM) horn antennas with exponentially tapered flares for ultra-wideband radar application are studied. With respect to radar sensor application compact antenna design is desirable. Therefore, firstly, the influence of simple shortening of the standard exponentially tapered TEM horn on the electrical properties of the antenna is analyzed. Subsequently, the shorted exponential TEM horn is provided with a cylindrical aperture termination. It is shown that the modified antenna can be reduced in length and aperture size by approximately 18 and 35 percent, respectively, with respect to the standard exponential TEM horn with comparable figures of merit. The bandwidth and peak gain is 0.25-1.7 GHz and 3-12 dBi, respectively. Simulation and measurement of the antenna are in very good agreement. The modified TEM horn antenna has been implemented in a UWB radar sensor. Preliminary measurements are discussed.