Study Of 220GHz Subharmonic Mixer Based On Schottky Diode

Terahertz(Terahertz, THz) wave in the spectrum lies between infrared and millimeter waves, whose frequency range typically is 100 GHz ~ 10 THz. In the solid-state terahertz communication systems, terahertz mixer as a key technology of the accepted front-end, it completes the relocation of the operating frequency, and converts radio frequency signal of terahertz frequency to a low frequency band IF signal. In addition, due to the requirement of high power of the local oscillator for the fundamental terahertz frequency mixer, the local oscillator is difficult to obtain. The harmonic mixer frequency requires low frequency of local oscillator, just half of the fundamental frequency mixer, which can be a good solution to this problem.This thesis describes the developments at home and abroad of the solid-state THz mixer based on Schottky diode firstly, and give a detailed description of the working mechanism based on planar Schottky diodes and Schottky barrier diode harmonic mixer works and its unique advantages. what’s more the thesis discuss a complete diode model for designing 220 GHz harmonic mixer which primarily create internal ports through 3D model of the Schottky diode chip, and extract S-parameters to characterize the high frequency parasitic parameters. On this basis, respectively 220 GHz mixer’s topology, passive circuit design and simulation to optimize the overall performance of the mixer are systematically introduced, and 220 GHz harmonic mixers of processed and assembled were tested. The test results of the first edition show that in near range of 20 GHz centered at 220 GHz frequency, the average conversion loss is about 12 dB, and the optimal conversion loss is 6.7dB. However, the test results has a big gap compared with the simulation results. Based on the detailed analysis of the first edition of tolerance and on the basis of the model accuracy, diode model is improved, mainly according to the characteristics of the HFSS simulation software the new model has adjusted to the position of the model of internal port, redesigned the second edition 220 GHZ sub harmonic mixer. The test results show that the frequency- invert performance of the second edition has a substantial increase and narrows the gap between the test results and simulation results and it shows in the near 20 GHz bandwidth achieves an average performance of approximately 10 dB conversion loss, the minimum conversion loss is 6.4dB, and illustrates the accuracy and feasibility of the improved model’s method.Results of this study will provide reference for research of terahertz subharmonic mixer which has more excellent feature and works in higher frequency..