Metamaterial based CMOS terahertz integrated circuits
Date of Issue2015
School of Electrical and Electronic Engineering
Terahertz (THz) radiation (0.1-30 THz) fills the gap between electronics and photonics with unique spectroscopic properties. A great deal of attention has been paid to THz imaging system with application of biomedical and security due to the moderate wavelength of THz signal to leverage advantages of both microwave and optics, such as high spatial resolution, good penetration depth to dielectric material or human tissue with no harmful ionization. However, the current optics based THz imaging systems are bulky, expensive, lack of portability with low detection resolution by electro-optic sampling techniques. With the rapid scaling of CMOS technology, it has become feasible to realize integrated circuits with standard CMOS process in THz regime towards low cost, portable and large-arrayed THz imaging system on a chip. However, it is challenging to deal with the generation, transmission and detection of THz signal by single CMOS transistor due to substrate loss and low device gain with huge path propagation loss. One needs to figure out solutions from all perspectives such as high output power transmitters, high gain antennas, and high sensitivity receivers. This PhD thesis has explored the use of metamaterial to integrate a number or array of CMOS transistors with significantly improved performance of THz signal generation, detection and transmission. New metamaterial based THz imaging systems have been demonstrated at 140GHz and 280GHz, respectively. For CMOS THz signal generation, the target is to improve the output power and power efficiency with wide frequency tuning range (FTR) as well as compact size. By coupling N oscillators in-phase, coupled oscillator network (CON) can effectively achieve an N times higher output power but also an N times less phase noise. The conventional on-chip coupling network by length of λ/2 or λ transmission-line is too bulky and lossy with difficulty for phase synchronization. Non-resonant-type metamaterial such as magnetic plamson waveguide (MPW) with zero-phase-shift property is applied to achieve in-phase low loss coupling with compact size, which enables the design of signal source with high power density and high efficiency. For CMOS THz signal detection, the target is to improve the receiver sensitivity with compact size. The use of resonant-type metamaterial: transmission line (T-line) loaded with split ring resonator (TL-SRR) or complementary split ring resonator (TLCSRR) can significantly improve both high-Q oscillation and oscillatory amplification within compact area. As such, one can achieve low phase noise oscillator for the design of high sensitivity super-regenerative receiver (SRX) with quench control. For CMOS THz signal transmission, the target is to design wide band, high gain onchip antennas with compact chip area as well as high efficiency. Substrate integrated waveguide (SIW) has been recently explored for the design of high quality factor (Q) passive devices from mm-wave to THz, which enables an on-chip antenna design that can leverage the advantages of both planar transmission line and non-planar waveguide with lower loss and wide band performance in a miniaturized cavity. Moreover, nonresonant-type metamaterial such as composite-right-left-handed (CRLH) T-line with nonlinear phase-to-length relationships enables more compact antenna design with even higher gain and efficiency. Finally, with the proposed transmitter and receiver designs, both narrow and wide band THz imager can be demonstrated at 135GHz and 280GHz, respectively. In summary, a metamaterial based CMOS transceiver for THz imaging is proposed with significantly improved performance in THz signal generation, transmission and detection. For THz signal generation, non-resonant-type metamaterial such as MPW can be applied for high power signal source designs; for THz signal transmission, nonresonant-type metamaterial such as CRLH T-line can be applied for the high gain antenna designs; for THz signal detection, resonant-type metamaterial such as DTLSRR or DTL-CSRR can be applied in the high sensitivity receiver designs. The component designs are supported by chip demonstration with measurement results. The system performance is also evaluated after integration by post-layout simulations.