Simulation of a phased-array antenna in waveguide

TLDR

The array is modeled as an infinite array formed by imaging through waveguide walls. The method uses measurements of a few elements in waveguides to predict array performance across frequency, scan angle, and polarization. The approach, requiring only a few measured elements, was validated with five waveguide simulators that measured array impedance and reflection loss, from which an equivalent circuit and active impedance were derived, and it revealed the polarization behavior and reflection characteristics for circularly polarized excitation.

Abstract

A method has been developed for simulating a large planar phased-array antenna in order to determine the performance of its radiating elements. By simple measurements of a few elements inside of waveguides, their performance in the antenna array as a function of frequency, scan angle, and polarization may be determined. The number of elements that need to be constructed is small, and the method is well-suited to economical, empirical design of an element for an array having a very large number of elements. For this purpose, such an array is well represented by the infinite array which results from imaging by the waveguide walls. Five waveguide simulators, sampling five significant combinations of scan angle and polarization, have been developed for a particular array comprising circular elements in a square arrangement. The array impedance has been measured in the simulators, and from these measurements the reflection loss of the array has been calculated. An equivalent circuit for the element in the array has been obtained from two simple waveguide-impedance measurements, and the active impedance of the elements has been determined therefrom. Finally, these results have been employed to determine the behavior of the elements when the array is excited for circular polarization; the departure from circularity of the radiated polarization, as well as the reflection in both senses of circular polarization, have been obtained.