Millimeter Wave High Harmonic Mixing Technology Based On Avalanche Device

A mixer is a key circuit in a millimeter wave receiver. As the increase of theoperational frequency, the LO sources of mm-Wave mixers are becoming expensive andhard-to-get, which is bad for the application of mm-Wave mixers.The2ndor4thharmonic of the LO frequency, however, could be exploited todown-conversion with mm-Wave RF signals as harmonic mixers emerged, which wouldeffectively reduce the required LO frequency and then enhance the performance andstability of the LO sources. Given that higher harmonic mixing usually lead to highconversion loss and make mixers unsuitable for application in systems, harmonicmixers are typically limited to achieve the2ndand4thharmonics mixing.The IMPATT(Impact Avalanche Transit Time) diodes have a markedly fiercenonlinear-inductance characteristics when they are under the avalanche-breakingcondition, which could multiply a microwave band frequency up to the upper mm-Waveband. The IMPATT diodes then have a natural talent to achieve mm-Wave higherharmonic mixing because of their sufficient energy of higher harmonics.In the project, the generation mechanism of high harmonics in IMPATT diodes andtheir frequency-conversion effect have been studied. Based on a nonlinear circuit modelof the IMPATT, a W band IMPATT high order harmonic mixer has been developed,which is of high performance.In this article, a nonlinear model of IMPATT has been firstly built up by analysis inthe multiplication and transmission characteristics of carriers and thefrequency-conversion effect of IMPATT has been studied in the relevant simulationplatform. Secondly, the design proposal of the high order harmonic mixer has beendiscussed in detail, and the passive matching, bias and transition circuits have beendesigned respectively. Finally, the whole mixer circuit is simulated, fabricated andmeasured.Both the simulated and measured results have demonstrated that IMPATT highorder harmonic mixer could employ the14th、15thand16thharmonics of LO effectivelyto down-conversion with W band signals. According to the test results, the mixer could achieve the best conversion loss down to about15dB.