A Novel High-Gain Low-Profile Circularly Polarized Endfire Leaky-Wave Antenna With Binary Codification

In this letter, a novel high-gain low-profile circularly polarized endfire leaky-wave antenna with binary codification is proposed. The antenna is based on the double-sided parallel strip line (DSPSL), which loads periodic metal vias for endfire vertically polarized radiation and pairs of horizontal stubs for endfire horizontally polarized radiation. To balance the amplitude ratio and phase difference between horizontal polarization and vertical polarization, the strip of DSPSL in one period is divided into 16 × 8 grids. Each grids has two states. By optimizing the state of each grid, the amplitude ratio is close to 1, and the phase difference is close to 90°, and then, excellent endfire radiation with circular polarization is realized. The proposed antenna is fabricated, and the measured impedance bandwidth is from 5.6 GHz to 6.2 GHz with reflection coefficient being less than −11.9 dB and 3 dB axial ratio bandwidth is from 5.61 GHz to 5.92 GHz. The size of the antenna is 5.88<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda _{0}\times$</tex-math></inline-formula> 0.83<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda _{0}\times$</tex-math></inline-formula> 0.077<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda _{0}$</tex-math></inline-formula>, and the peak gain is 11.5 dBi.