Study And Design Of Multi-information Terahertz Detector

The unique properties of THz wave make it more excellent than traditional application equipment in many specific occasions.With the development of semiconductor technology,it is possible to realize a portable compact terahertz detection system which can work at room temperature.As an important part of THz detection system,THz detector developed in the form of integrated circuit in the early stage mostly works in direct detection mode.However,it can only obtain the amplitude information of THz signal,which lead to the sensitivity and imaging accuracy of direct detector are not high.We focus on the matter of less information and low sensitivity of THz direct detector,based on the study of the THz detection principle of field effect transistor.This paper adopts heterodyne mixing combined with on-chip orthogonal polarization antenna to realize the orthogonal heterodyne THz detector based on CMOS technology,which can obtain the amplitude,phase and polarization information of THz signal,so as to get more information and higher sensitivity of THz detector.What have been done as show as below:Firstly,the principle of THz direct detection based on field effect transistor is studied.A300GHz direct detector with integrated on-chip antenna and cascode amplifier is fabricated based on 40nm CMOS process.The test results show that under 0.4V bias,the maximum R_v and the NEP of detector are 40k V/W and 62.5p W/Hz^1/2,respectively.It can be seen that the responsivity of THz detector is effectively improved by the on-chip amplifier,but the noise inevitably worsens the noise equivalent power.Secondly,the principle of THz heterodyne detection based on field effect transistor is studied.Two 150GHz quadrature heterodyne detectors with single balance cell and double balance cell respectively are designed in 40nm CMOS technology.The simulation results show that the heterodyne detector combined with orthogonal polarization on-chip antenna can obtain the amplitude,phase and polarization information of THz radiation signal,and the detector with double balanced structure has better orthogonality and higher isolation than that with single balanced structure.Thirdly,in order to distribute the LO power reasonably,the principle of power divider is studied.Taking full advantage of the characteristics of multilayer metal in CMOS process,the150GHz 1:4 and 1:8 on-chip power dividers are designed based on the structure of stacked transformer.The electromagnetic simulation of Momentum with ADS shows that the actual insertion loss of the two power dividers is about 5d B and the output waveform is consistent.The LO power distribution of heterodyne array detectors can be realized.The orthogonal heterodyne THz detector circuit designed in this paper combined with orthogonal polarization on-chip antenna solves the problem of single information of traditional THz direct detector,increases the information acquisition of THz signal,and effectively improves the sensitivity of the detector.