Reduction of Off-Boresight Fields for a TEM Horn Antenna

This research involves the design, modeling, and testing of both tapered periodic surfaces (TPS) and transverse electromagnetic (TEM) horns. The goal is to reduce the off-boresight fields for a TEM horn and increase the peak-to-peak field levels on boresight. This is accomplished by applying a TPS to the free space end. Two tapers are designed - one that approximates an exponential impedance function and one that approximates a triangular impedance function. Both reduce the off-boresight fields of the TEM horn. In most cases the exponential taper reduces the field levels further than the triangular taper. This research shows that a TPS is an effective method of reducing diffraction. A procedure for designing a TPS to approximate a specific impedance function is presented. A two-dimensional finite difference time domain (FDTD) model predicts the tapers will reduce the diffraction. Experimental results verify the TPS\u27s ability to reduce the peak off-boresight fields for a TEM horn antenna