The Design Of W Band Sub-Harmonic Mixer

In this paper we describe the operation theory and design method of W band sub - harmonic mixer. The circuit simulation andparameter optimization have been made, and the result has beengiven. The sub- harmonic mixer consists of waveguide – to - microstriptransition, image reject band pass filter, IF low pass filter,anti-parallel diode pair and matching network. The structure ofmicrostrip probe has been chosen for well - matched Waveguide-to-microstrip transition . The simulation of S parameter has beenmade using Ansoft HFSS, and the test circuit has beenimplemented. The insertion loss is just about 1dB and the return loss is better than 15 dB between 94 and 96 GHz . Microstrip linehalf wave length edge-coupled filter has been chosen for image rejectBPF .With the Agilent ADS Momentum,the result of simulation is thatthe insertion loss is about 2dB and image rejection is larger than15dB. We also introduce a method for mixer design . Through theanalysis of the relationship between phase of S11 and mixer conversion loss ,we obtain the optimum matching network, through parameter optimization, with ADS harmonic balance simulation, the conversion loss of W band sub- harmonic mixer is about 14dB.