Full Metal Wideband Cosecant Squared Pattern Antenna With a Highly Compact Hybrid Feed Network

This article presents a full metal wideband high-performance cosecant squared (CSC2) pattern antenna. A highly compact structure is achieved by a convoluted feeding network routed in multiple layers. Double metal ridges are added to the flared radiation slot to reduce the aperture size of the antenna element. A line of 40 such elements are excited by a full-corporate feed network arranged longitudinally, so as to form a phased array in the future. A hybrid of single-ridge waveguide and coaxial line in a sandwich structure is used to construct the feed network. The absorbing wedge loaded coupler and magic-T are incorporated into the feed network to achieve high isolation and large power-division ratio, thereby improving the stability of the amplitude and phase distribution. This ensures the desired CSC2 patterns over a wide frequency band. A prototype operating at C-band is designed, fabricated, and measured. Experimental results show that the antenna has an impedance bandwidth (
$\vert \text{S}_{11}\vert < -13.1$
dB) from 6 to 7.4 GHz. Stable CSC2 patterns in the E-plane with the peak gain of over 16.5 dB and sidelobe level (SLL) of less than −17.5 dB are observed across the same frequency band.