Richard Al Hadi

A 1kpixel CMOS camera chip for 25fps real-time terahertz imaging applications

Future imaging applications in the submillimeter-Wave range (300GHz to 3THz) require RF systems that can achieve high sensitivity and portability at low power consumption levels. In particular, CMOS process technologies are attractive due to their low price tag for industrial, surveillance, scientific, and medical applications. Recently, CMOS-based detectors have shown good sensitivity up to 1THz with NEPs on the order of 66pW/√(Hz) at 1THz [1]. However, CMOS terahertz imagers developed thus far have only operated single detectors based on lock-in measurement techniques to acquire raster-scanned images with frame rates on the order of minutes [2]. To address these impediments, we present a low-power 1kpixel terahertz camera chip fully compliant with an industrial 65nm ft/fmax=160GHz/200GHz CMOS process technology. The active-pixel circuit topology is designed to accommodate the optics for wide bandwidth (0.6 to 1THz) in stand-off detection with a 40dBi Si-lens. It includes row/col select and integrate-and-dump circuitry capable of capturing terahertz images with video frame rates up to 25fps at a power consumption of 2.5μW/pixel.

Terahertz imaging detectors in a 65-nm CMOS SOI technology

Terahertz imaging detectors implemented in a 65-nm CMOS SOI technology are presented. Low-noise square-law power detection is provided by distributed self-mixing in NFET-based passive mixers with optional integrated amplifiers. The pixels of the imaging array are equipped with folded-dipole antennas designed for through-substrate illumination by an integrated silicon lens. With front-side illumination and conductor backing of the chip a maximum non-amplified responsivity (Rv) of 1.1 kV/W and a minimum noise-equivalent power (NEP) of pW/√Hz is achieved. In the intended lens-integrated backside illumination configuration a further 8-dB improvement of Rv and NEP due to the elimination of substrate modes is predicted by EM simulations.

A 0.53 THz Reconfigurable Source Module With Up to 1 mW Radiated Power for Diffuse Illumination in Terahertz Imaging Applications

This paper presents a high-power 0.53 THz source module with programmable diversity to adjust the brightness and the direction of light to obtain the desired diffuse lighting conditions in THz imaging applications. The source module consists of a single SiGe BiCMOS chip which operates an array of 16 source-pixel incoherently. Each source pixel consists of a primary on-chip ring-antenna and two triple-push oscillators locked 180° out-of-phase. The module provides a total radiated power of up to 1 mW (0 dBm) with 62.5 μW (-12 dBm) per source pixel on average and an EIRP per pixel of 25 dBm. The circuit layout is scalable in size and output power. The chip consumes up to 2.5 W from a 2.4 V supply and 3.2 mW from a digital 1.2 V supply respectively. The module includes a secondary silicon lens, is programmable through a CPLD, and supplied from a USB port. The THz radiation can be recorded with a CMOS 1 k-pixel THz video camera and represent an all silicon solution for real-time active THz imaging.

14.5 A 0.53THz reconfigurable source array with up to 1mW radiated power for terahertz imaging applications in 0.13μm SiGe BiCMOS

Recently, silicon-based THz video cameras have been demonstrated for industrial, surveillance, scientific, and medical applications in the THz range (300GHz to 3THz) [1]. Such camera implementations favor pixels with antenna-coupled direct detectors for a low power dissipation and a high pixel count. Despite this progress, they lack the required sensitivity for passive imaging and imagers are in the need of artificial illumination to provide the required image quality. The choice has been to use expensive high-power focused illumination with a single direction for the incoming beam, which seriously limits the image quality due to its specular nature. Additionally, detectors in a focal-plane array configuration share the available source power and the image SNR further drops with the camera resolution. Like imaging at visible light, where shades or reflectors are commonly used, active THz imaging would greatly benefit from incoherent artificial light sources to adjust brightness, phase/frequency, and the direction of light to obtain the desired lighting conditions.

A Terahertz Detector Array in a SiGe HBT Technology

This paper presents HBT terahertz power detectors implemented in an experimental 0.25- μm SiGe process technology with a peak fT/fmax of 280/435 GHz. Based on the nonlinearity of the HBT base-emitter junction, the detector operates as a square-law down converter, mixing terahertz frequencies directly to dc. Fifteen detectors have been arranged in a 3 × 5-pixel array with differential on-chip ring antennas. The array has been assembled with a hyper-hemispherical silicon lens. Referred to the collecting aperture of the lens, a maximum optical current responsivity RI of 1 A/W and a minimum noise equivalent power (NEP) of about 50 pW/√{Hz} have been measured at 0.7 THz with a 125-kHz chopping frequency. The detectors have been characterized from 0.65 to 1 THz.

Lens-integrated THz imaging arrays in 65nm CMOS technologies

THz CMOS imagers integrated with hyperhemispherical Si-lenses are presented and characterized. FPAs are implemented in 65nm CMOS bulk and SOI technologies. Lens-integrated detectors at 0.65 THz show an increase of 15dB and 20dB in SNR compared to front-side illumination for SOI and bulk respectively. The responsivities Rv are increased and a minimum noise-equivalent power NEP of 17pW/√Hz is measured for SOI detectors with the lens. THz Images are presented.

Terahertz detector arrays in a high-performance SiGe HBT technology

This paper presents heterojunction bipolar transistor (HBT) based terahertz power detectors implemented in a 0.25-μm SiGe process technology. The detectors have been arranged in a 3 × 5-pixel FPA and characterized at 0.65 THz. Referred to the collecting aperature of a 3-mm diameter lens, a maximum current responsivity RI of 0.79 A/W and a minimum noise equivalent power NEP of 370 pW/√Hz have been measured at a 1-kHz chopping frequency.