3 Mm Subharmonic Mixer Is Designed

The mixer is widely used in microwave communications, radar and other systems in the receiver, in addition to the measurement of the microwave equipments, it also plays an increasingly important role. In the mixer, RF and LO signal are put on the nonlinear element, and RF will be converted into a low-frequency IF signal, which will be easy to be amplification, demodulation, magnitude attenuation, phase-shifting or other processing.The3mm band is one of the most important atmospheric windows in millimeter wave band, which occupies an irreplaceable position either in the military or civil usage. In millimeter wave communication system, the mixer usually serves as the first stage of receivers so that it plays a significant role in the performance of the whole system. With the increment of the local oscillator frequency, some problems highlighted, such as technical difficulty and high cost. Sub-harmonic mixer, which uses2nd or higher term of LO frequency mixed with RF, can be a good solution to this problem.In this thesis the designs of3mm second sub-harmonic mixer and a fourth sub-harmonic mixer are proposed. At first, many types of mixer and its main technical parameters, the working principle as well as design methods of the sub-harmonic mixer are discussed, and then the designs of the sub-unit circuits are given respectively with the help of Agilent circuit simulation software ADS and An-soft three-dimensional electromagnetic simulation software HFSS, including an IF low-pass filter, the LO band-pass filter, the matching network of three end, and the open circuit terminal or short circuit terminal that for absorb useless harmonic signals. In addition, the design of a transition structure of the U-band and3mm waveguide to micro-strip probe is also presented. Finally, optimization simulation of the whole circuit is done. A sample of the3mm2nd sub-harmonic mixer has been made, and the measuring conversion loss is approximately12.77dB, and it performs well.