A High Performance Micromachined Sub-Millimeter-Wave Radar Technology

Motivated by the recent interest in high millimeter-wave (MMW) and sub-MMW radar sensors for applications ranging from navigation and mapping in autonomous systems to public safety and standoff detection of concealed weapons, this work presents the technology in support of a novel sub-MMW radar with minimal Size, Weight, and Power consumption (SWaP). This includes development of novel design, microfabrication, and measurement methods and techniques to develop the passive RF front-end of the radar system operating at 240 GHz. The sub-MMW radar system is designed for navigation and mapping applications in autonomous systems. The salient features of the proposed radar are its ultra-lightweight (less than 5 grams), compact form factor (2 cm3), low power consumption (6.7 mW for 1 fps), and ease of scalability to higher frequencies (up to 1 THz). This work introduces novel components and sub-systems for the RF front-end of the radar system. This includes developing high performance radar antenna systems as well as the chip packaging and integration technology with the associated transitions for realization of the radar system. In order to satisfy the requirements for high resolution and wide field of view for this imaging and navigation radar sensor, frequency scanning beam-steering antennas are developed to achieve ±25˚ of beam steering with a very narrow beam of 2.5˚ in the direction of scan. The designed array antenna has over 600 radiating elements and exhibits a radiation efficiency of over 55% and a gain of over 30 dBi over the entire operation frequency range. Additionally, for polarimetry applications, two versions of the antenna with both co- and cross-polarizations are developed to allow full-polarimetry imaging at sub-MMW frequencies. Another contribution of this work is development of a novel chip packaging methodology with the associated biasing network for sub-MMW integration of active and passive MMICs in the RF front-end. The packaging method offers a compact, low-loss, and wideband integration solution in the sub-MMW to terahertz (THz) frequency band which can be standardized for reliable and repeatable integrations at such frequencies. Due to the small wavelength at MMW to THz frequency band, fabrication of sub-MMW components requires high fabrication tolerances and accuracies, which is costly and hard to achieve with the standard machining techniques. To overcome this problem, in this work novel silicon micromachining methods are developed to enable reliable fabrication of complex structures, such as the radar RF front end, with low mass and low cost. The fabrication method allows seamless realization of the entire radar RF front-end on a single silicon block with a compact form factor and high level of integration. Repeatable and reliable characterization of sub-MMW components and sub-systems is a very challenging task and one major contribution of this dissertation pertains to development of novel measurement techniques to enable reliable on-wafer characterization of such devices in the MMW to THz band. This includes development of a novel waveguide probe measurement technique along with specially designed probes and the associated transitions for on-wafer S-parameter measurements at sub-MMW frequencies. Additionally, a novel on-wafer near-field measurement method is developed to allow pattern and power characterization of the antennas at sub-MMW frequencies. These methods are employed to perform full on-wafer characterization of the micromachined RF front-end components, including the antennas as well as the chip packaging, where excellent agreement of designed and measured results are shown.PHDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/140879/1/arminjam_1.pd