Development of an error vector testbed for a DSP based half-duplex retrodirective multi-antenna system

Ever-increasing demand for wireless communication devices and services puts unprecedented pressure on the use of the available wireless spectrum. As wireless device manufacturers try to cram more functionalities into their devices, the need for more power efficient wireless transmission techniques also arise. As the communication modulation schemes go digital, researchers around the world have come up with coding and compression schemes that strive to meet these requirements of spectral efficiency and low power operation. In the recent past, antenna techniques have come to the forefront of research interest due to their ability to provide low-cost and efficient solutions to the above mentioned problems. Retrodirective antenna array techniques have generated considerable interest among research circles as well as in the wireless industry due to its ability to exploit the spatial dimension of wireless communications. The advantage of such techniques is that it is possible to direct radio transmission towards the intended recipient, which allows for more efficient use of the spectrum. Retrodirective techniques are also computationally less intensive compared to beam-forming techniques, which translates to low-power implementations.; Many schemes have been proposed to achieve retrodirectivity including the use of digital signal processing techniques. However, the diverse digital wireless 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 wireless 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. EVM measurements provide us with valuable insight into the wireless system performance and offer us with the knowledge to troubleshoot wireless systems. This thesis presents a versatile and reconfigurable vector error measurement test setup, which is used to analyze the error performance of a retrodirective system in terms of its EVM and Bit Error Rate (BER). The retrodirective advantage is quantified and is compared with that of a conventional non-retrodirective antenna array.