Design Method of Broad Flat-Top Fan-Beam Complementary Antenna for Radar Applications

Abstract

This article presents a design method of a broad flat-top fan-beam complementary antenna. This antenna superposes a finite-length dipole (FLD) and a nonsmall circular loop (NSCL). Their amplitude ratio, phase difference, and phase center spacing can be utilized to enhance the overall beamwidth and obtain a fan beam. To realize the NSCL, two symmetric inverted-F and two connected L-shaped strips are employed to generate two small loops and one large loop, respectively. For FLD, two connected parasitic strips introduce two dipole modes for superposition. To verify the design idea, a printed $1 \times 4$ E-plane antenna array is simulated, fabricated, and measured for 24-GHz applications. A measured 10-dB impedance bandwidth of 31.0% (19.2–26.2 GHz) can be obtained, with a peak measured 1-dB H-plane beamwidth of 202° at 22 GHz.