An Electrically Controlled CRLH-Inspired Circularly Polarized Leaky-Wave Antenna

An electrically controlled beam-scanning circularly polarized leaky-wave antenna is presented by cascading multiple unit cells of a composite right/left-handed transmission line (CRLH-TL) structure. The CRLH-TL unit cell consists of two parts: varactor diodes (two series ones and a shunt one), which enable beam electrically steerable at a fixed frequency, and a subwavelength (0.2 λ
_g
 × 0.2 λ
_g
) square-shaped patch that is perturbed to stimulate circular polarization radiation. Moreover, a single-voltage bias circuit, which allows all the unit cells to be simply controlled by a single uniform bias voltage, is introduced to steer the beam direction. The proposed antenna operates at 2.4 GHz and beam scans from +40° to –17° continuously. The axial ratio remains below 3.5 dB at different bias voltages.