A HMSIW Circularly Polarized Leaky-Wave Antenna With Backward, Broadside, and Forward Radiation

A miniaturized frequency-scanning leaky-wave antenna (LWA) with circular polarization (CP) and backward-broadside-forward radiation is presented. Half-mode substrate integrated waveguide (HMSIW) in combination with interdigital capacitors (IDCs) is utilized in order to achieve a composite right/left-handed leaky-wave structure. Ramp-shaped slots are introduced as interdigital capacitors. Using this structure, the balanced condition (in which series and shunt resonances are equal) can be obtained for the unit-cell. As a result, wide bandwidth of 7.4-13.5 GHz with continuous angular scanning of ~ -70^° to 70 ^° is achieved. The axial ratio in the direction of the main beam is lower than 3.1. The performance of the antenna is measured, and close agreement between the simulation and measurement is observed.