340-GHz Heterogeneously-Integrated THz Imager With 4°-Beamwidth 16×16 IPD Antenna Array for Lensless Terahertz Imaging Applications

Te-Yen Chiu,Chun-Hsing Li

doi:10.1109/access.2021.3097739

Abstract

A low-cost and planar heterogeneously-integrated 340-GHz THz imager is proposed for lensless THz imaging applications. The proposed THz imager is composed of a 16×16 antenna array realized in an integrated-passive-device (IPD) technology, an IPD-to-CMOS THz interconnect, and a power detector implemented in a 0.18- μm CMOS technology. The 16×16 IPD antenna array can provide simulated antenna gain of 23.9 dBi, antenna directivity of 30 dB, and half-power beamwidth (HPBW) of 5.6° at 340 GHz. The proposed THz interconnect utilizes a transmission line coupling technique to provide low-loss and broadband signal transition from a CMOS chip to an IPD one while occupying a small chip area. The simulated insertion loss of the THz interconnect is only 1.8 dB at 340 GHz while providing 3-dB bandwidth from 230 to 446 GHz. The power detector exploits the transistor's inherent even-order nonlinearity to rectify the input signal for power detection. The power detector can give simulated voltage responsivity R V and noise equivalent power (NEP) of 190.2 kV/W and 1.9 nW/Hz 0.5 at 340 GHz, respectively, as the chopping frequency f mod is 1 kHz. A nonlinear curve fit technique is proposed to tackle the undesired fluctuation of the measured output voltage due to a standing-wave effect. Experimental results show that the proposed heterogeneously-integrated THz imager can provide measured effective R V and NEP of 0.967 MV/W and 0.18 nW/Hz 0.5 at 328 GHz, respectively, as f mod is 1 kHz. The measured antenna directivity and HPBW can be 30 dB and 4° at 340 GHz, respectively. Such a THz imager with advantages of high antenna directivity and narrow HPBW can be employed to realize a simple, low-cost, and lensless THz imaging system. To the best of the authors' knowledge, the proposed THz imager integrates the highest number of antennas and exhibits the highest antenna directivity and the narrowest HPBW at THz frequencies reported thus far.

Highlights

INTRODUCTION THz science and technology have attracted great attention in recent years since they can be used for many useful applications, including the sixth-generation (6G) wireless communications, non-invasive biomedical and medical imaging, stand-off detection of concealed weapons and explosives, pharmaceutical, and semiconductor packaging inspection [1]–[6]
The CMOS chip is bonded to the IPD one by a flip-chip bonding machine to form the proposed heterogeneouslyintegrated THz imager using an Au-Au thermo-compressive packaging technique conducted in Taiwan Semiconductor Research Institute
The measured frequency response of RV,eff and noise equivalent power (NEP) is illustrated in Fig. 14(b) as the THz imager is biased at the optimal VGS of 0.44 V

Summary

Introduction

Hz science and technology have attracted great attention in recent years since they can be used for many useful applications, including the sixth-generation (6G) wireless communications, non-invasive biomedical and medical imaging, stand-off detection of concealed weapons and explosives, pharmaceutical, and semiconductor packaging inspection [1]–[6]. Utilizing CMOS technologies to realize THz electronic systems for the aforementioned applications is appealing because it can deliver a low-cost, compact, high-integration, and mass-producible solution. Many electronic THz imaging systems have been reported using silicon technologies [7]–[17].

Methods

Results

Conclusion