A Design Methodology of Broadband Millimeter-Wave Conical Radiating Antenna Based on Ring-Shaped Microstrip Line

A design methodology based on ring-shaped microstrip antenna for wideband conical radiating antenna is presented in this letter. This design approach allows for flexible antenna beam pointing while maintaining broadband characteristics. The enhanced bandwidth is based on dual-mode resonance. One resonance mode is evolved from TE_{{\text{1}}} mode of the microstrip line, the other one is achieved by disrupting the quasi-TEM mode with asymmetric excitation. The ring-shaped microstrip lines of different sizes can be excited to work at the same required frequency band by adjusting the number of excitation points, to realize the adjustment of the antenna radiation beam pointing. In this letter, three different antennas are analyzed in detail, and a case with seven feeding points is tested and verified. The measured results show that a bandwidth of 13.4% (32.1-36.7 GHz) is achieved on a single-layer substrate with a conical radiation gain greater than 10 dBi.