Study On Thz Subharmonic Mixer Based On The Schottky Diode

Terahertz wave generally refers to electromagnetic wave with frequencies between 0.1 THz-10 THz,that is between millimeter wave and light wave.With the development of technology and the increasing shortage of millimeter wave spectrum resources,the advantages of terahertz wave in many fields are gradually revealed.Therefore,terahertz spectrum resources have become an invisible battleground.Terahertz technology has caught the attention of researchers.Terahertz mixer is one of core devices of solid state THz transceiver front-end,which has important applications in THz communication,imaging and so on.Based on the planar schottky diode,the principle,structure and design method of the mixer are discussed and studied in this thesis.Two with center frequency 560 GHz sub-harmonic mixers and with center frequency 500 GHz sub-harmonic mixer are designed by different methods.Specific research work are as follows:(1)Research on model of Schottky diode.The physical structure and mechanism of Schottky diode are introduced,and the general intrinsic SPICE model cannot accurately characterize the complete characteristics of the diode in terahertz frequency band.In order to complement and improve the traditional modeling method,the linear part of the diode is modeled separately from the nonlinear part,and then combined in ADS.This model can basically represent the characteristics of the diodes in terahertz frequency band when the signal is small.(2)Mixer design method.The design method of mixer is discussed in details,and its advantages and disadvantages are analyzed.To solve the problems of small optimization space of the traditional partial design method and poor portability of the whole design method,the semi-whole method is used.In the actual design,two 560 GHz sub-harmonic mixer are designed using the above method of partial design and overall design,respectively.A 500 GHz sub-harmonic mixer is designed by using semi-integral method.These three design methods are verified.The applicability,advantages and disadvantages of the three methods are discussed.(3)Research on terahertz mixer circuit structure.The structure and principle of the traditional mixer are studied and discussed deeply,and the structure of the mixer is appropriately innovated.In order to solve the problem that the high aspect ratio of the traditional structure mixer in high frequency band makes the quartz substrate bend and warp,which leads to the instability of the physical structure.Two design ideas of waveguide matched filter to replace the microstrip matched filter structure and without local oscillator filter structure are proposed and applied to mixer design.A 560 GHz sub-harmonic mixer is designed using the waveguide filter matched structure and a 500 GHz sub-harmonic mixer with no local oscillator filter is designed in the thesis,which verify the feasibility of these two structures.