Microstrip comb-line antenna with inversely tapered mode transition and slotted stubs on liquid crystal polymer substrates

In recent years, millimeter-wave technology has attracted much attention in high-speed wireless communications, imaging and radar applications. Low-cost devices are very important for prevalence of the technology in consumer applications. Antennas for such applications are required to have high gain and low loss due to the high absorption in air-propagation and the high operation frequency. In this paper, a microstrip comb-line antenna constructed on liquid crystal polymer substrates is proposed. The antenna consists of 10 radiation elements and a termination element lined up like a comb and a waveguide-to-microstrip mode transition. Each radiation element has a slot and the mode transition has an inversely tapered section. The antenna realized a return loss less than -15 dB and a radiation with a maximum gain of 13 dBi and a side lobe level less than -10 dB at 60GHz. Radiation efficiency reached to about 90%.