An Image-Rejection Active Integrated Antenna Utilizing Dual-Feed Circularly Polarized Antenna

This paper proposes a down-conversion active integrated antenna having an image rejection function, and the performance is evaluated by using a prototype antenna. A dual-feed circularly polarized (CP) antenna is effectively used to realize an image-rejection mixer (IRM) without a radio frequency (RF)-band 90° coupler. The measured conversion loss to the intermediate frequency (IF) signal and image rejection ratio are respectively 5.3 dB and 23.2 dB in the 5.8-GHz band when the RF signal power is −30 dBm and local oscillator (LO) power is 5 dBm.