Backscattering-Based Radiation Mode Analysis for Angle Estimation of a CRLH Leaky Wave Antenna

Abstract. This study explores the extraction of the radiation mode field from backscattering field components of a composite right/left-handed (CRLH) leaky wave antenna (LWA) to estimate the relative angle to the radiation mode field within its frequency band of operation. Two methods, transmission line delay (TLD) and impedance loading (IL), for extracting the radiation mode from backscattering field components, are employed to isolate the radiation mode field of a CRLH LWA. In the IL method, backscattered fields are measured by terminating the CRLH LWA with short and open load impedances to express the radiation mode and structure mode field components. The TLD method uses a coaxial transmission line to connect the CRLH LWA to a high-gain X-band horn antenna, enabling isolation of the radiation mode field component from the backscattered field components, using time gating. This analysis employs two measurement setups for TLD, one in which both the CRLH LWA and the horn antenna rotate along the azimuth and the other in which only the CRLH LWA rotates. The analysis shows the frequency-angle relationship of the CRLH LWA radiation mode field, which reveals the frequency-dependent features of the CRLH LWA. Additionally, an evaluation of frequency ambiguity is done to provide more insights into the effectiveness of each approach for angle estimation of CRLH LWA relative to the incident wave.