Terahertz Band Sub-harmonic Mixer

Terahertz (THz) electromagnetic radiation (from 100GHz to 10THz) that lies in the boundary region between light and radio waves has attracted a great deal of attention in the academic world in recent years. In THz solid-state radar and communication systems, mixers serve as the first stage of receivers due to the lack of low noise amplifiers so that the level of the mixer plays a significant role in the performance of the overall system. The sub-harmonic mixer is an effective alternative to conventional fundamental mixers in THz band for the reason that the local oscillator requirements are easier to meet.In this dissertation, the development tendency and the basic theory of sub-harmonic mixers based on the Schottky anti-parallel diodes pair were introduced. The research firstly focused on the topology of sub-harmonic mixers, device modeling of Schottky diodes, the 3D electromagnetic analysis of passive circuits and the mixer circuitry for optimum performance. On this basis, the fabrication and experimental measurement of a 118GHz sub-harmonic mixer was carried out. Through the extraction and correction of the diode parameters and the optimization of the circuit matching network, the best measured performance of the mixer exhibits a conversion loss with a fixed LO frequency lower than 10dB over the range from 103GHz to 133GHz and the lowest conversion loss below 5dB, which is in accord with the simulation prediction and approaching the state-of-the-art results, while with a fixed IF frequency, the bandwidth of the conversion loss below 10dB is from 98GHz to 138GHz. A 220GHz sub-harmonic mixer was also developed. The simulation result shows that the conversion loss is below 8dB over the range from 205GHz to 245GHz.The achievements in this dissertation make a contribution to the development in the THz sub-harmonic mixing and THz solid-state circuit technology and also lay a theoretical and technological foundation for the further research and applications.