Design of high-gain and wideband sub-THz amplifiers

Abstract

This dissertation reports the design of THz amplifiers using the concept of Maximum Achievable Gain ($G_{max}$) of a transistor embedded in a linear, lossless, reciprocal network for signal amplification at 200-300GHz sub-terahertz band. In order to overcome the limitations of low gain, narrow band, and single band operating characteristics of the previously reported amplifiers, this dissertation describe the design of three types of amplifiers incorporating the concept of maximum achievable gain in 65nm CMOS process. Firstly, a dual-peak $G_{max}$core design technique in a single transistor to achieve high gain over wide frequency range is proposed. The gain of transistor can be boosted over wide frequency range by satisfying the optimum condition for achieving $G_{max}$ at two different frequencies simultaneously, with the same size set of lumped elements for a linear, lossless, reciprocal embedding network. Secondly, the design technique of optimized $G_{max}$-core is proposed which not only amplifies the intrinsic gain of transistor to $G_{max}$ but also takes into account the inter-stage matching. Adopting the optimized $G_{max}$-core, matching loss and chip area are reduced, which result in high gain. Thirdly, the design technique of dual-band amplifier adopting dual-peak $G_{max}$-core and dual-band matching is proposed. This amplifier demonstrated dual-band operation for the first time among other amplifiers operating above 200GHz.