Design and fabrication of a low power terahertz imager based on 180 nm CMOS process technology

Abstract

A low power terahertz imaging using CMOS detector and analog-to-digital conversion (ADC) is proposed. For terahertz detection, a CMOS cascade amplifier, biased near the threshold voltage of a MOSFET, is utilized. A 16 x 16 pixel imaging array with the 256 column ADCs is designed using 180 nm CMOS process technology. Measured result for the pixel circuit is presented. The imaging pixel consists of a microstrip patch antenna, an impedance-matching circuit, and a direct detector. It achieves a responsivity of 51.9 kV/W at 0.915 THz and noise equivalent power (NEP) of 358 pW/Hz1/2 at modulation frequency of 31 Hz. NEP is estimated to be reduced to 42 pW/Hz1/2 at 100 kHz. The detector only draws about 3 µA from a power supply (Vdd) of 1.5 V.