Circularly Polarized Beam-Steering Microstrip Leaky-Wave Antenna Based on Coplanar Polarizers

A periodic frequency-scanning one-dimensional microstrip leaky-wave antenna with circular polarization is proposed in this letter. The introduction of the novel square patch and stub, which are printed on the same layer of the microstrip array, can effectively transform the polarization type into left-handed circular polarization (CP). The two parasitic elements in each unit cell can he excited by the host meandering microstrip line without extra feeding networks, which introduce one orthogonal polarized wave to satisfy the condition of CP radiation. A prototype includes nine modified unit cells is fabricated and measured. The designed antenna covers an impedance bandwidth over 26.1% with vertical bar S-11 vertical bar < -10 dB and a CP bandwidth over 11.2% with vertical bar AR vertical bar.< 3 dB in the measurement. The main beam scans from -4 degrees to 18 degrees in the yoz plane (beam scanning plane) through broadside direction (0 degrees) while maintaining good CP property.