High coupling radiating element using impedance transform stub for microstrip comb-line antennas in the millimeter-wave band

A novel high coupling radiating elements using an impedance transform stub are developed for microstrip comb-line antennas. In the design of low-sidelobe microstrip comb-line antennas with small numbers of element, array element with large coupling of the antenna around the input port is required. The radiating edge impedance of the rectangular microstrip antenna is transformed to adequate low impedance around the input port by the impedance transform stub. Then, high coupling is achieved. The coupling power is controlled from 6 % to 70 %. The performance of low-sidelobe 6-elements comb-line antenna with our proposed high coupling radiating element using impedance transform stub was demonstrated in this paper.