Design Of Terahertz Oscillator Based In CMOS

Terahertz waves are located in the transitional region of the electromagnetic spectrum between the classic electronics area(radio,microwave,and millimeter wave)and the photonics area(infrared,visible,ultraviolet,and X-ray).The characteristics of terahertz waves such as high penetration,strong spectral resolution and non-ionization make terahertz wave technology have wide research value in the fields of biomedical imaging,spectral analysis,human body safety inspection,communication and other fields.The terahertz oscillator is a key module of the terahertz transmitting and receiving system,and its performance index affects the stability of the system.Therefore,the research and application of terahertz oscillators have become one of the hotspots in the frontier scientific research of terahertz.In recent years,with the gradual shrinking of the transistor process size and the gradual increase of the cutoff frequency,it has become possible to design a terahertz oscillator using a CMOS process.The CMOS process has low cost and high integration,but as the operating frequency increases,the transistor gain decreases,and the quality factors of passive devices such as capacitors and inductors become the difficulties in the design of terahertz oscillators.Based on the 40 nm CMOS process,this paper designs an improved Push-Push structure high output power terahertz voltage controlled oscillator.The output of the second harmonic 300 GHz signal breaks through the MOS tube cutoff frequency limit,and the frequency tuning purpose is achieved by controlling the transistor substrate bias voltage.The following lists the specific research content and results:(1)Based on the traditional cross-coupled Push-Push oscillator,an improved Push-Push oscillator is proposed.The gate swing inductance is increased to increase the voltage swing to increase the output power.The control of the MOS tube substrate voltage is used for frequency tuning to avoid the loss caused by the introduction of a tunable varactor tube.(2)The electromagnetic field simulation of the on-chip inductance of the key components of the oscillator is carried out.The on-chip inductor is designed as a symmetrical structure with the top metal,and its quality factors are all above 10.Then the pre-simulation analysis and post-simulation analysis of the oscillator circuit are done.The post-simulation results are: fundamental frequency is 154.5GHz,output second harmonic is 309.0GHz,output power of second harmonic can reach-3.0dBm,phase noise is-79.5dBc/Hz@1MHz,power consumption is 28.6mW,the frequency tuning range is 303.5GHz-315.4GHz.Draw the on-chip testable oscillator layout,and design a single rectangular slot antenna oscillator and a T-slot antenna 1 × 2 array oscillator based on the core oscillator.(3)In order to test the oscillator chip,an integrated terahertz chip test platform is designed,which mainly includes a signal generating module,a cavity module,a silicon lens module and a signal receiving module,so as to realize the miniaturized design of the terahertz test platform.Finally,the test results of the integrated test platform and the test results of the terahertz measuring instrument are given.The maximum voltage responsiveness of the self-mixing terahertz detector chip tapped on the same period to the array oscillator designed this time is 495 kV / W;the radiation power of the array oscillator measured by the terahertz measuring instrument is-9.75 dBm.The terahertz oscillator designed in this paper has the following characteristics:(1)Based on the traditional cross-coupled Push-Push oscillator,an improved Push-Push oscillator is proposed,which increases the voltage swing by increasing the gate interconnection inductance to increase the output power,and outputs the second harmonic signal,breaking through the transistor cut-off frequency limit.(2)Abandon the traditional on-chip variable capacitor tuning method,and adjust the MOS tube substrate voltage to change the gate parasitic capacitance of the MOS tube to achieve frequency tuning.(3)A terahertz test platform integrating source and detection is proposed to realize the miniaturized design of the terahertz test platform.