Design of a Lock-in Amplifier For Terahertz Detector And Imager Arrays on Monolithic CMOS

This work describes the design and integration of a lock-in amplifier with a terahertz detector array. Research in the terahertz region, which lies between the microwave and infrared portion of the electromagnetic spectrum, has been on the rise due to its potential applications as a biologically-safe replacement for X-Ray imaging and other non-invasive applications such as spectroscopy. Cryogen-cooled bolometers and devices based on compound semiconductors such as Gallium-Arsenide are currently the industry-standard for terahertz detection. However, these devices have major drawbacks such as the use of cryogenics, high cost, and inability to realize a large array. CMOS-based (complementary metal oxide semiconductor) detectors have none of those drawbacks, however the detector noise exceeds that of the industry-standard. This project combines the advantages of both the industry-standard and CMOS-based detectors into one monolithic CMOS chip. A specially designed lock-in amplifier is integrated with the CMOS-based detectors to improve the signal-to-noise ratio. The chip was successfully designed and simulation confirms that it has the ability to attenuate unwanted frequencies while providing gain of 70dB on the desired detected signal. The chip has recently been fabricated in United Microelectronics Corporation's (UMC) 130nm logic/mixed-mode1.2V RF CMOS process and is expected to be ready for testing by mid-December.