Design and Implementation of a Switched Back-to-Back E-Slotted Antenna for Bidirectional Wireless Relay Applications

This paper presents the design, fabrication, and experimental validation of a switched back-to-back E-slotted antenna system for bidirectional wireless relay applications. The proposed antenna integrates two identical E-slotted microstrip patches placed on opposite sides of a single-layer FR4 substrate, together with a PIN diode-based SPDT switching circuit. The switching circuit dynamically routes the RF signal to either antenna element, enabling controllable bidirectional beam switching without additional structural layers. A prototype was fabricated and its performance was verified using a vector network analyzer and a custom-built outdoor radiation pattern measurement setup. The measured resonant frequencies of 2410 MHz and 2418 MHz for the two switching states show good agreement with the simulated value of 2420 MHz. The antenna achieves a measured impedance bandwidth of 3.68% and a simulated peak gain of 5.6 dBi, outperforming several comparable designs reported in the literature. The measured radiation patterns also closely match the simulation results. To demonstrate practical applicability, the antenna was integrated into an active relay node and tested in a non-line-of-sight environment. The system achieved average packet delivery ratios of 89.88% and 86.94% for the short-range and long-range scenarios, respectively. These results confirm that the proposed switched back-to-back antenna system offers a compact, cost-effective, and reliable solution for bidirectional wireless relay applications.