A 340-GHz Heterodyne Receiver Front End in 40-nm CMOS for THz Biomedical Imaging Applications

A low-power and high-performance 340-GHz heterodyne receiver front end (RFE) optimized for terahertz (THz) biomedical imaging applications is proposed in this paper. The THz RFE consists of an on-chip patch antenna, a single-balanced mixer, and a triple-push harmonic oscillator. The oscillator adopts a proposed harmonic oscillator architecture which can provide differential output by extracting output signals from the same current loop without any additional balun required. The mixer biased in the subthreshold region is designed not only to have high conversion gain and low noise figure by choosing the output intermediate frequency well above the flicker-noise corner frequency, but the required local oscillator (LO) power can also be as low as -11 dBm. Such a low demand on the LO power makes the proposed mixer very suitable for THz applications in which the achievable LO power is very limited. The impact of unavoidable slots for passing design rule checks on the performance of an on-chip patch antenna is also presented. The proposed THz RFE is implemented in a 40-nm digital complementary metal-oxide-semiconductor technology. The measured voltage conversion gain is -1.7 dB at 335.8 GHz, while the mixer and the oscillator only consume 0.3 and 52.8 mW, respectively, from a 1.1 V supply. The proposed THz RFE is employed to set up a THz transmissive imaging system which can provide spatial resolution of 1.4 mm.

I. Introduction

Terahertz (THz) science and technology have drawn great attention in recent years because of many useful applications [1]– [12]. THz biomedical imaging is especially appealing since it can be used to implement many powerful sensors for skin imaging which has potential on the determination of skin burning severity [5], [6], detection of dental caries [5], identification of healthy and cancerous tissues for skin and breast cancers detection [8]–[10] , etc. Moreover, THz wave is nonionizing, very safe technology as compared to the X-ray.