220GHz Sub-harmonic Mixer Research

Terahertz (THz) wave, which is one of the important parts of electromagnetic wave, is the region of transition from classical theory to quantum theory, and also is the intersection region of electronics and optoelectronics. It can achieve very high signal noise rate due to its small energy of quanta. And the THz wave devices possess of the advantages of wideband application and cover the frequency range of oscillate frequency of organically, such as protein etc. As a result, THz wave plays a great part in modern society.Mixers are the vital components in the microwave-millimeterwave telemetry system. Electromagnetic wave at the frequency of220GHz nearby can be used in the communication security because of its small transmission attenuation. So220GHz frequency mixing technology research has important significance.Two kinds of sub-harmonic mixer using schottky diodes and suspended-microstrip structure are presented in this thesis. The first one without biased has five parts:RF input circuit, LO input circuit, LO low pass filter, IF low pass filter and IF output circuit. Compared with the first one, the biased mixer has an extra biased circuit. The radio frequency (RF) signal passes through the waveguide-to-suspended microstrip probe transition from the standard waveguide WR4to the suspended microstrip circuit, and the local oscillator (LO) signal passes through from the high-reduced waveguide WRIO to the circuit. Finally the conversion loss was reduced by optimizing the matching circuit which based on the schottky barrier diode parasitic parameters and nonlinear parameters.The measured results show that the first mixer gets its best conversion loss27dB at100GHz LO frequency and224.5GHz RF frequency; the second mixer gets its best conversion loss28.6dB at the same LO and RF frequency compared to the first one. In this paper, the220GHz mixers design is introduced, and the measured result is analyzed. It has positive promotion to the development of domestic terahertz mixers.