Low-noise monolithic millimeter-wave integrated circuits and a radiometric imaging system: Dissertation

This thesis focuses on design and characterization of low-noise millimeter-wave devices and circuits, especially for radiometers. In addition, a millimeter-wave imaging system based on a radiometer is presented. The thesis is based on seven scientific articles and an overview of the research area including a summary of the main results of the work. An automated measurement system for wideband on-wafer noise parameter determination of transistors has been developed for 50-75 GHz. The system can be utilized to develop and verify noise models of integrated transistors regardless the manufacturing technology. Noise parameters of a passive and an active circuit are presented. Noise parameters F_min = 2.65 dB, r_n = 0.25, and Γ_opt = 0.57∠121° have been measured for an indium phosphide high electron mobility transistor. Active cold loads based on monolithic millimeter-wave integrated circuits have been developed for millimeter-wave frequencies. The active cold loads have been realized using MHEMT technology and their suitability for radiometer calibration have been demonstrated. Noise temperatures of 75 K and 141 K are achieved at 31.4 GHz and 50-54 GHz, respectively. Monolithic millimeter-wave integrated circuit low-noise amplifiers for millimeter-wave operation have been designed and characterized. The amplifiers have been manufactured using the metamorphic high electron mobility transistor technology and they cover specific frequency bands within 75-200 GHz. Noise figures of 3.0-3.5 dB, 5.2 dB, and 7.5 dB are achieved with the 100 nm process at 94 GHz, 153 GHz, and 183 GHz, respectively. With the 50 nm process, the noise figure of 5.2 dB is achieved at 165 GHz. All amplifiers have more than 18 dB of gain. A millimeter-wave imaging system has been designed and realized. The system is capable to produce images of noise temperature variation using a single radiometer and a mechanically scanned antenna. The feasibility of millimeter-wave imaging for security and surveillance applications is demonstrated by millimeter-wave images taken with the system.