Biography
Enrollment Date: 2011
Graduation Date：2016
Degree：Ph.D.
Defense Date：2016.12.19
Advisors：Zhihua Wang
Department：Institute of Microelectronics，Tsinghua University
Title of Dissertation/Thesis：Research on Key Techniques of CMOS Terahertz Wireless Tranceivers
Abstract:
Terahertz technology has wide application prospects in wireless communication, nondestructive detection, biomedicine, anti-terrorism security and astronomical atmosphere. Especially in the field of communication, the wide spectrum resources of terahertz wave greatly enhance the attraction of terahertz communication. Furthermore, silicon-based CMOS technology scaling is a strong guarantee for the low-cost and widespread use of THz wireless transceivers in the future. In this thesis, the key technology of silicon-based THz communication system is studied.
In this thesis, a scheme of de-embedding scheme based on transmission line structure is proposed to solve the problem that the de-embedding scheme of discrete model is not accurate in terahertz frequency band. The de-embedding scheme can be used to perform accurate de-embedding of the on-chip passive components and the two-port network in which the active components are mixed with the passive components. The simulation shows that by optimizing the length of the de-embedding transmission line, the component de - embedding error in the frequency range of 140 GHz to 180 GHz can be controlled within 5%. Moreover, the distributed model can accurately decouple two-port networks consist of active circuits and passive circuits in the frequency range of 140 GHz to 180 GHz.
This paper presents a GS-GP model for non-feed back passive two-port networks. Based on this model, the impedance matching and the phase shift characteristics of the two-port network can be accurately and quickly analyzed. On this basis, this paper presents a small signal oscillator design method, which can boost the oscillator loop gain to the G_MAG of the corresponding open loop network. The simulation results show that the improved cross - coupled oscillator can obtain higher oscillation frequency and higher output signal swing than the conventional cross - coupled oscillator. Based on this theory, a fundamental frequency oscillator is designed using 65nm CMOS process. Test results show that the oscillator oscillates at 192.3GHz frequency with -10dBm output power. The fundamental oscillation frequency and the maximum oscillation frequency ratio of the process were 71.3%. This index ranks second of all the fundamental frequency oscillators for all processes in the world (CMOS, SiGe, GaAs, InP).
Aiming at the shortcomings of low gain and high loss silicon-based terahertz amplifier, a neutralizing schematic based on mutual inductance is proposed. In the schematic, one inductance is inserted into the feedback loop to balance the quality factor of the input and the output. The dc level of the gate and the drain of the transistor in the schematic can be controlled separately, thus ensuring that the transistor can operate in the optimum current density. Based on this technique, a four-stage amplifier with a gain of 18.5 dB at 142 GHz is implemented in a 65 nm CMOS process. The technology can be widely used in low-noise amplifier, power amplifier, output buffer design to achieve high-gain characteristics in the terahertz band.
In this thesis, two voltage-controlled oscillators (VCOs) based on the wide tuning range colpitts structure are designed to overcome the small tuning range shortcoming of the conventional THz-band VCO. The two VCOs are implemented based on 65 nm CMOS process. The first voltage-controlled oscillator proposed a high-quality-factor tuning scheme by analyzing the small-signal parasitics of the colpitts oscillator in the terahertz band. The test results show that the VCO has a tuning range of 2.3% and a -13.15 dBm output power. The second voltage-controlled oscillator effectively increases the tuning range of the VCO by adding a high-quality factor switching inductor. The test results show that the VCO has a tuning range of 6.9 % and an output power of -8.2 dBm.
Based on the above-mentioned innovative circuit technology, a 150 GHz On-Off Keying (OOK) transmitter and a 150 GHz OOK receiver were realized based on the 65 nm CMOS process. This thesis first introduced a high speed switch power amplifier based on neutralization technique which improves the signal to noise ration of the OOK signal. The signal source of the transmitter first took the single-loop double-loop transformer structure to enhance the second harmonic signal power and the DC-RF efficiency of the signal source. Based on the innovative techniques, the transmitter achieves 39.3 dB measured on-off power ratio and 3.1 dBm output power. The transmitter and receiver system realized 12 Gbps bit rate data communication based on bond wire signal path.