Design Of W - Band Harmonic Mixer

W band is defined as the electromagnetic wave whose frequency is in the range of 75-110GHz, W band is the important "window frequency" in the millimeter wave, the center frequency lies in 94GHz atmospheric window of the millimeter wave, so that the W band is applied widely in the area of communication and remote sensing. As a key device in the system, the index of the mixer greatly affects the overall performance of the system, the sub harmonic technology is widely used because of reducing the requirements of local oscillator source.Firstly this paper introduces the development dynamics of sub harmonic mixer based on Schottky diode at home and abroad, on this basis, the theory and design method of Schottky diode applied to harmonic mixer is studied. In the W band, because of the influence of Schottky diode package parasitic parameters on the performance of mixer has been very significant, the parameters of W band Schottky antiparallel diode pair of VDI company R23C15 is analysed in the use of lumped equivalent circuit method, a relatively accurate antiparallel diode pair equivalent model is established under the consideration of package parasitic parameters. Traditional design method of harmonic mixer is based on discrete devices simulation, which is difficult to get the optimal conversion loss, in order to overcome the shortcomings, a global simulation optimization method of system level is used basing on the discrete device modeling, the key parameters which affect harmonic mixer performance significantly is optimized. Under the condition of a fixed LO frequency, the best simulation performance of the W band sub harmonic mixer exhibits a conversion loss lower than 9.4dB over the range from 80 to 100GHz, while the fourth harmonic mixer exhibits a conversion loss lower than 11.2dB over the range from 84 to 96GHz, the fourth harmonic mixer is fabricated and measured, the best measured performance exhibits a conversion loss lower than 14dB over the range from 82 to 94GHz. The antiparallel diode pair equivalent model is proved to be accurate and reasonable, thus an effective method for the design of harmonic mixer is established.