Tunable Higher Order Mode-Based Dual-Beam CRLH Microstrip Leaky-Wave Antenna for V-Band Backward-Broadside-Forward Radiation Coverage

This article proposes a composite right-/left-handed (CRLH) dual-beam leaky-wave microstrip antenna with a tunable operating region for V-band radiation coverage. Due to wideband excitation for second higher order modes, the symmetrically formed side-by-side dual beam initially scans in one quadrant from 52.5 to 65 GHz. Further, by appropriate placement of metallic via holes, a pair of back-to-back half-modes realizes generating two symmetrical side beams in E-plane with an enhanced gain over 40-52 GHz. Mode switching is performed electronically by incorporating p-i-n diodes and proper biasing network. Finally, incorporating half-sinusoidal interdigital slot variations and periodically placed switching diodes enables CRLH media having frequency beam steering from backward-broadside-forward quadrant. Leaky bands in microstrip higher order modes were analyzed by dispersion characteristics, and the proposed antenna achieved -10 dB impedance bandwidth of 29.2%, scanning range in H-plane from -65 degrees to +69.7 degrees, and peak gain of 18.7 dBi for the unbiased state and 28%, -78 degrees to +69.6 degrees, and 18 dBi, respectively, for the biased state. The average sidelobe level and minimum cross polar level are obtained as 13.5 and 23 dB, respectively. The fabricated prototype responses closely matched theoretical predictions, verifying the proposed concept.