Blind Signal Detection Using a Linear Antenna Array: An Experimental Approach

An experimental investigation is reported on the use of a linear antenna array to perform blind signal detection. A software-defined-radio (SDR)-based receiver system is used to capture signals received by an antenna array while ensuring time and frequency synchronization across the radio-frequency (RF) front ends. The antenna array is moved in circular and linear paths to cause variation in received signal strength and to cause variation in the incident angles of the incoming waves. Covariance-based detection (CBD) algorithms are applied to the received signals to perform blind signal detection. Multiple antennas serve to enhance the received signal correlation, thereby causing an improvement in the detection performance of the CBD algorithms. In the presence of noise calibration error (which is inevitable in a practical system), the maximum eigenvalue of the correlation matrix (MEC), Hadamard ratio test (HRT), and covariance absolute value (CAV) algorithms exhibit a significant improvement in detection performance as the number of antennas is increased, whereas the eigenvalue-based detection (EBD) algorithms show no improvement. This paper also investigates the effect of varying the antenna spacing on the received signal correlation and its subsequent effect on the detection performance. It is observed that the detection performance of the linear array is directly related to the mean signal cross-correlation achieved by the array. A significant improvement in detection performance was observed for an antenna spacing of 0.1λ; however, to avoid degradation of antenna efficiency at such close spacing, proper impedance matching must be performed.