Broadband circularly polarized periodically modulated leaky-wave antenna with open-stopband suppression and sidelobe control.

This paper presents a single-layer circularly polarized leaky-wave antenna (CPLWA) based on substrate-integrated waveguide (SIW) technology, simultaneously featuring open-stopband (OSB) suppression and sidelobe-level (SLL) control. The proposed LWA consists of 21 periodically modulated unit cells. To suppress the OSB effect, a CP unit cell with optimized impedance matching is proposed. An equivalent lumped-element circuit is then derived to theoretically investigate the underlying physical mechanisms of the unit cell. Then, to control the SLL, a Taylor-tapered aperture distribution is implemented by precisely tailoring the leakage constant of each unit cell. Numerical analysis and full-wave simulations are conducted to evaluate the performance across uniform and Taylor-tapered array configurations. Finally, a prototype is fabricated and measured. Experimental results demonstrate a 3-dB axial ratio (AR) bandwidth of 30% over 23.3-31.5 GHz, enabling a continuous beam-scanning range of 50° from -19° to 31°. A suppressed SLL of -23.9 dB is achieved at 28 GHz. Owing to its broadband CP radiation, continuous beam scanning, and low SLL, the proposed antenna could serve as a promising candidate for next-generation wireless sensing and communication applications.