NRI-TL Metamaterial Leaky-Wave Antenna With Off-Broadside Zero Beam-Squinting

Presented is the analysis and design of a leaky-wave antenna (LWA) that radiates an off-broadside beam with zero beam-squinting (ZBS), operating at a frequency of 5.5 GHz. A general design methodology is presented, which can be used to design any fixed-beam leaky-wave antenna with different design requirements. Two oppositely-directed branches of LWAs utilizing negative-refractive-index transmission-line (NRI-TL) metamaterials are employed in the design. To achieve off-broadside radiation with zero beam-squinting, it is necessary for one branch to operate within the left-handed region, while the other branch to operate within the right-handed region. A 50-ohm microstrip line is used to feed the two NRI-TL LWAs which radiate two appositively directed beams whose combination results in a wideband off-broadside beam. The antenna was validated experimentally, and its fixed-beam operation was achieved for approximately a 20% fractional bandwidth.