Gain‐Enhanced and Size Reduction Endfire Periodic Antenna Array With Multiple DSPSL‐Based Loop Resonant Element

ABSTRACT A compact high‐gain endfire loop antenna array based on a double‐sided parallel stripline (DSPSL) structure is proposed in this letter. The proposed design achieves radiation mode transformation by deforming the DSPSL into two half‐loops positioned on opposite sides of the substrate. A single feed port is employed, while the other port is terminated with a metal pin for impedance matching. By integrating a parasitic circular patch within the loop structure, the design effectively suppresses sidelobes and significantly enhances directionality. Furthermore, the endfire gain is further improved by incorporating a reflector behind the first radiating element. A prototype was fabricated and measured, demonstrating excellent agreement between simulated and experimental results. The measured peak gain reaches 13.57 dBi within the operating bandwidth, while maintaining a compact overall volume of only 0.19.