Error performance of a duplex retrodirective array system

A retrodirective antenna array has the property that it is capable of independently phasing the array elements so that it provides an improved link gain in the direction of the incoming signal without prior knowledge of the position of the source radiator. Many schemes have been proposed to achieve the retrodirectivity including the use of digital signal processing techniques. However, the diverse digital RF communication schemes pose a considerable challenge when it comes to quantitatively measuring the quality of a retrodirective system. Therefore, it becomes necessary to perform the analysis in time, frequency and modulation domains in order to obtain an insight into the RF system performance. Error vector magnitude (EVM) measurements by virtue of their ability to process the signals in full vector (magnitude and phase), provides us with a quantitative figure-of-merit for a digitally modulated signal. This paper presents the simulation model of a retrodirective communication system and its error performance in terms of EVM. The simulation and EVM measurements were performed for the first time on a DSP based half duplex retrodirective system.