An unbiased subharmonic mixing antenna for wireless receivers

In this paper, an unbiased mixing antenna for wireless receiver applications is proposed. Thanks to the proper integration of a resistive subharmonic mixer in a five-patch series arrangement, a -4.47 dB isotropic conversion losses was obtained without the need for batteries. The selected printed structure behaves not only as a 1850 MHz band antenna, but also as a stepped-impedance low-pass filter, rejecting the LO component while allowing the IF signal extraction. Unbiased operation is assured taking advantage of the low positive threshold voltage of Enhancement-mode PHEMT devices. Experimental results show the validity of the proposed solution for low cost and compact wireless reception.