A compact pattern reconfigurable antenna with low correlation for wireless sensor networks in harsh environments

A compact pattern reconfigurable antenna, capable of generating twelve uncorrelated radiation patterns, is proposed. It comprises two components: eight spatially distributed elements (four inverted-F and four quarter-wavelength slot antennas) arranged along the ground-plane edges for spatial diversity, and a central shorted patch surrounded by PIN-diode-controlled T-shaped parasitic elements that produce four states for temporal diversity. The antenna occupies a compact volume of 0.5λ0 × 0.5λ0 × 0.08λ0 at 2.4 GHz. Measured and simulated reflection coefficients and radiation patterns confirm effective multi-pattern operation, with impedance bandwidths up to 135 MHz and peak realized gains of 2.5-4.1 dBi. The worst-case envelope correlation coefficient (ECC) is 0.15, and the diversity gain reaches 9.4. These results demonstrate reliable performance in multipath environments, making the antenna well suited to space-constrained, harsh settings such as wireless sensor networks in autonomous train control systems.