A Low Profile and Low Sidelobe Wideband Slot Antenna Array Feb by an Amplitude-Tapering Waveguide Feed-Network

Abstract

A low profile slot antenna array is designed to operate over a wide bandwidth with low sidelobe levels. Taylor synthesis is used to taper the power distribution among array aperture. An efficient approach to design an equal-phase but unequal-power symmetric waveguide divider is proposed for constructing an amplitude-tapering feed-network for the array. Phase differences are balanced by adjusting the waveguide phase velocities. The basic radiator is a 2 $\,\times\,$ 2 slot subarray, uniformly fed by such a waveguide divider. A 16 $\,\times\,$ 16 array is then constructed by 8 $\,\times\,$ 8 of such subarrays. A 1-to-64 way corporate-feed waveguide network is designed to excite all subarrays instead of individual slots, and the required power distribution is obtained by adopting a 30 dB Taylor $\overline N=4$ synthesis. Measured results indicate that the array can achieve a 13.8% bandwidth and a gain of more than 29.5 dBi. The first sidelobe level is $ -26.5~{\rm dB} $ in the $E$ -plane and $ -30.4~{\rm dB} $ in the $H$ -plane. The holistic sidelobe levels in both planes are better than $ -25~{\rm dB} $ with a better than $ -40~{\rm dB} $ cross-polarization.