Ka-band Phemt Mixer

The project is from military microelectronics project "Development of Millimeter Wave Hybrid Integrated Circuit". The objective of the project is to develop a mixer with three-terminal device. The request is that: RF 35 ?GHz, LO 30?2GHz, IF 5 ?.5 GHz, Conversion gain>2dB; RF and LO are fed via BJ320 waveguide, the output IF is through a SMA port.The mechanism of the three-terminal-device mixer is studied. The unit PHEMT drain mixer is chosen as the target. Firstly, with the I-V curve and S parameters of the PHEMT, it's nonlinear equivalent circuit is fitted. The transition from the waveguide to microstrip is simulated using finite-element method. The EF low-pass filter and the LO band-pass filter is optimized. The conversion gain and noise figure are calculated. After selected the topology of the mixer, using nonlinear circuit analysis theory we simulate and optimize the mixer circuit. Finally the mixer is fabricated on RT/Duroid5880 and is tested as well.The Modified-Materka model is chosen as the PHEMT equivalent circuit. The passive part of the circuit is simulated with finite-element method. Simplified the embedded network, using large and small signal method - harmonic balance and conversion matrix method we analyze and optimize the mixer. The noise figure of the mixer is analyzed with using square mean values we get the noise figure .The testing result is that: RF: 33^7GHz, LO:10dBm, IF: 4.5-5. 5GHz, Conversion gain is IdB.The conversion gain versus DC bias and LO power is also tested.The mixer has good performance and the test result is consistent with the theoretic result. The study about the mixer including nonlinear circuit model and the analysis method is necessary attempt. All of that can provide important experience for later research on it. As a key component of the receive system, advanced mixer canimprove the performance of the system. Therefore in practice, no matter in military field and commercial field, the work is of high importance.