Although many directive antennas operating in a narrow band of millimeter (mm) waves were reported, e.g., antennas for 60GHz wireless local area network (WLAN), their wideband counterparts are still unpopular. Cavity-backed antennas (CBAs) are widely developed and reported in microwave frequency bands, but handful of literatures can be found about mm-wave CBAs in spite that their many propertie...
