High frequency characteristics of the two wire rhombic illuminator

The high frequency performance characteristics of a two-wire rhombic illuminator under common-mode excitation are studied using the Numerical Electromagnetics Code (NEC-2). The electrical length of the overwall wire structure ranges from approximately 700 wavelengths at 500 MHz to approximately 1400 wavelengths at 1 GHz. Efficient segmentation schemes are required to extend the analysis up to 1 GHz. The rhombic illuminator radiates more effectively as the frequency of operation is increased from 500 MHz to 1 GHz. Based on the resulting damping characteristic of the rhombic illuminator wire current at these frequencies, only a portion of the wire structure must be modeled. This technique allows one to analyze such a structure efficiently at very high frequencies. The general characteristics of the antenna impedance, wire currents, and radiated fields are discussed