Wideband X-Band Microstrip Image Rejection Balanced Mixer

This paper describes a wideband X-band image rejection mixer constructed in microstrip using a thin-glazed alumina substrate. This mixer has a 10 to 11.3 dB noise figure and over 20-dB image rejection over an 8 to 12 GHz frequency band. Image rejection is achieved by using a pair of balanced mixers with signal and LO voltages fed in quadrature and in phase, respectively. Such circuits have been previously constructed in waveguide and conventional strip transmission line; the microstrip mixer described herein achieves comparable electrical performance in a much smaller volume and weight than X-band designs developed in these other transmission media.