Research And Design Of THz Heterodyne Mixer In CMOS

In the electromagnetic spectrum,terahertz wave is between microwave and infrared light.Due to its unique location and advantages,terahertz has a wide range of applications in detection systems,wireless communications,biometrics and radar detection.As the core module of terahertz detection system,the performance of mixer will directly affect the detection quality.The traditional THz Schottky-based mixers have some limitations,such as low integration,high cost and no conversion gain,which make its application market smaller.CMOS technology has become a research hotspot of terahertz mixer circuit because of its small size,low cost and high integration.In this paper,a CMOS terahertz heterodyne mixer is designed aiming at the problems of low sensitivity and zero IF output of CMOS self-mixing circuit.It is innovatively proposed to integrate RF inductance and on-chip antenna,and its theoretical analysis and simulation design are carried out.The contents and methods of this paper are as follows:?1?Based on single balanced mixer,the circuit structure of heterodyne mixer is studied,the theoretical analysis of heterodyne mixer is given,and the circuit pre-simulation is carried out by Cadence.?2?The integrated model of inductance and antenna is designed and simulated respectively,and the rationality of the idea is verified by the simulation results of electromagnetic field.?3?The layout and circuit post-simulation of the heterodyne mixer are carried out,and the electromagnetic field simulation and optimization of the key transmission lines are carried out.Based on TSMC 65nm CMOS process,the heterodyne terahertz mixer is designed,and ADS,HFSS,Cadence co-simulate is used.The pre-simulation results of the heterodyne mixer circuit are as follows:the maximum conversion gain of the mixer is 14.9dB,the bandwidth is0.05¹2.47GHz;the minimum noise factor is 17dB;the compression point of 1dB is-8.4dBm,the third-order intermodulation point is 3.3dBm;and the maximum voltage response is 56kV/W.In the integrated inductance model of RF inductance and on-chip antenna,the inductance value is21.9pH and the quality factor is 2.4 at 300GHz.In the integrated antenna model of RF inductance and on-chip antenna,the bandwidth of antenna S₁₁ is 280³02GHz,the gain is-2.3dB,the radiation direction is downward,and the beam is concentrated.The overall layout of terahertz heterodyne mixer,including pad,is 550?m×475?m.The post-simulation results show that the maximum conversion gain of the mixer is 10.7dB,the bandwidth is 0.12⁷GHz,the minimum noise figure is 18.3dB,the compression point of 1dB is-11.3dBm,the third-order intermodulation point is-1.1dBm,and the maximum voltage response is 32.7kV/W.The mixer designed in this paper has the following characteristics:?1?Integrating on-chip antenna and inductance into a heterodyne mixer circuit not only eliminates the matching between antenna and mixer circuit,but also further reduces the size of the chip.?2?Using high-order harmonic mixing to break the cut-off frequency of the MOS tube,the direct mixing of the terahertz signal is realized,thereby reducing the use of the frequency doubling chain.?3?A two-stage differential common source IF amplifier is used to realize high gain and bandwidth of harmonic mixer.