Research Of X-band And Ka-band Mixer

The super-heterodyne receiver is commonly used in modern communicationsystems. As the frequency conversion component, mixer is the essential part of thesuper-heterodyne receiver, its performance directly affects the quality of thecommunication system. System used in the electronic warfare and microwavemeasurement requires high anti-interference. In the millimeter wave communicationsystem, because of the immaturity of the millimeter signal generator, how to achievelow-cost, high-stability and high-performance mixer becomes the hotspot.To solve the problems above, high-performance mixer technology used inmicrowave and millimeter wave is discussed in this thesis. Basic theories ofbalance-mixer, image rejection mixer, sub-harmonic mixer are introduced. Designproposals are proposed, and experiments are done to prove the proposals.First, the phase-balanced image rejection mixer is proposed, the design andimplementation of an X-band image rejection mixer are introduced. The mixer unit isthe designed90degrees phase shift-type single-balance mixer using AglientHSMS-8202. RF and LO signals are fed to the two mixer units from the in-phasedivider and90degrees copper respectively, IF singal puts out from the90degreescombiner. The copper, divider, low pass filter, combiner and matching network aresimulated by the combination of ADS and HFSS. Finally, the designed mixer is testedand the result shows that:13.2dBm is the optimal LO input power, which correspondsto the minimum conversion loss. In the RF sideband9.3-9.7GHz, the conversion loss is8.8-9.9dB and17-30dB image rejection is achieved at the same time, LO-RF isolation is20-25dB,1dB input power compression point is11.6dBm. The tested result meets thedesign requirement. Improvement is discussed at last.Then, by using the2ndharmonic mixer program, a Ka-band2ndsub-harmonicmixer is designed and implemented. The anti-parallel diode pair DMK-2308is used,low conversion loss and high port isolation can be achieved by using the reflectingmicrostrip lines and filters. IF is out from the low pass filter. In this thesis, designaccuracy can be highly improved by the combination use of HFSS and ADS. The tested result shows that: when the LO input power is4dBm, the conversion loss is theminimum, which is6.6dB. In the sideband27.6-33.5GHz, conversion loss is less than10dB. LO-RF isolation is30.2-52.3dB,1dB input power compression point is-3dBm.The result meets the design requirement well.