Design of Low-Sidelobe Circularly Polarized Loop Linear Array Fed by the Slotted SIW

A novel loop linear array for circularly polarized (CP) radiation with low sidelobe levels (SLLs) and high gains is proposed in this letter. The resonant element consists of a pair of loops fed by a slot. Moreover, two square patches are added on the opposite corners of both loops to implement circular polarization. Fed by the slotted substrate integrated waveguide, a 10-element linear array with Taylor distribution is then designed, manufactured, and measured. Measured results show that the fabricated array has bandwidths of 350 MHz (9.76-10.11 GHz) with the reflection coefficients better than -10 dB and 280 MHz (9.82-10.10 GHz) with the axial ratios (ARs) less than 3 dB, respectively. In addition, -22 dB peak SLL, 15.4 dBic gain, -29.6 dB cross-polarization level, namely 0.57 dB AR at the boresight, and 65% aperture efficiency are experimentally obtained at the center frequency.