W-band Braodband Sub-harmonic Mixer

Mixer is one of the key components of millimeter-wave transceiver system. The bandwidth and conversion loss of the mixer have a significant impact on the performance of the transceiver system. It is important to develop the wideband radio frequency mixer as to expand the bandwidth of the receiver. At the same time, compared to the fundamental wave mixer, the working frequency of LO signal of the sub-harmonic(SHM) mixer is only a half, one third or a quarter of the one of RF signal, which can reduce the difficulty of the development of the source for local oscillator. Because the source for LO signal doesn’t need to operate on the range of RF frequency, and in this case, the development of the wide-band SHM mixer becomes very significant.In this dissertation, the design of W band sub-harmonic mixer is realized by anti-parallel diode structure which is connected with the microstrip and the metallized via connected to ground. The diode is the DBES105 a Schottky barrier diode provided by UMS corperation. The RF and LO signals are fed to the microstrip through the transition structure of the waveguide to microstrip. The isolation of LO port is realized by the cut-off chararcteristic of the RF waveguide, which the isolation of RF port to LO port is achieved by Compact Microstrip Resonating Cell(CMRC) low-pass filter. The impedance matching of RF port is realized by the radial microstrip stub, and the impedance of LO port is achieved by the phase-shift structure of CMRC LPF. The IF signal passes through the low-pass filter, which is made of radial microstrip stub, and then transmitts to the K connector to output.Based on analyzing the structure of Schottky diode and comparing with the conventional methods of building diode model, this dissertation created a simplified 3D model of DBES105 a diode by the quasi-linear equivalent method in HFSS. By comparing the simulated and measured S-parameter results, the RF and LO parameters of the core of the diode are acquired, respectively. By the means of iteration of the two sets of parameters, the impedance matching of LO and RF ports are achieved, respectively. With the simulation and optimization in HFSS, the return loss of RF port can achieve better than 10 dB within 75~110GHz W-band full band, and the return loss of LO port return loss can achieve better than 10 dB within 40~50GHz.By utilizing the CHX2193, AMMC 5040, M4AE1317 and TGA4522 chips, a U-band eight times frequency multiplier is designed and measured. At last, the measured conversion loss of the fabracted mixer is less than 15 dB from 75 GHz to 108 GHz and less than 11 dB from 88 GHz to 102 GHz, when the input power of the LO port is appointed to 9dBm at 46.25 GHz.