Assessment of Performance Limitations of PON Retrodirective Arrays

We examine the behavioral characteristics of Pon type heterodyne retrodirective arrays (RDAs) (see Pon, C.Y., IEEE Trans. Antenna Propagat., vol.12, p.176-80, 1966) and provide a simple, yet comprehensive, modeling equation that allows the retransmission response of the RDA to be determined. Using this modeling philosophy, the optimum array size required for a prespecified beam pointing error is determined. Then, deleterious effects, such as mixer-leakage, phase-conjugate circuit gain imbalance and cable phase error, that occur due to the presence of real components, are quantified experimentally for a four-element RDA. These are then correlated with theory. Specific recommendations on the permissible tolerances allowable for these parameters are given in order to assist design specification adherence. In addition, it is shown in theory, and confirmed by measurement, how radiation element aberration due to diffraction and mutual coupling can be used to enhance the azimuthal tracking response of the array. This paper allows the first comprehensive, practical, and theoretical appraisal of the design limitations that exist for this type of array. The insights provided by this paper should be of value to practicing antenna engineers.