A Micromachined Millimeter-Wave Radar Technology for Indoor Navigation

A compact, light-weight, low-power MMW radar system operating at 240 GHz is introduced to enable autonomous navigation of micro robotic platforms in complex environments. The short wavelength at the operating frequency band (1.25mm @ 240 GHz) enables implementation of the radar front-end components on a silicon wafer stack using micromachining techniques. This work presents the design, fabrication technology, and measurement methodology of components for the micromachined MMW radar and the phenomenology of such radars in indoor environments. Novel passive structures are developed to realize a fully micromachined radar front-end. Low loss cavity-backed CPW (CBCPW) lines (0.12 dB/mm @ 240 GHz), broadband transitions from the CBCPW line to rectangular waveguide (IL13 dB; BW: 39%), MMIC chip integration transitions, and waveguide directional couplers are designed to fully integrate active and passive components of the radar. Also a membrane-supported miniaturized-element FSS image-reject filter (IL25 dB in the stopband) is developed for MMW radar applications. The structures are designed compatible with micromachining technology and optimized for minimum insertion loss. The designed components are then realized over a two layer stack of silicon wafers. Multi-step structures are realized on one of the wafers and the membrane-supported features are implemented on the other wafer. A novel multistep DRIE technique is utilized to enhance the profile quality of the fabricated structures. Measurement techniques are developed to enable accurate and repeatable characterization of the on-wafer components at MMW and higher frequency bands. A novel waveguide probe S-parameter measurement technique is introduced for non-contact characterization of the multi-port components using a two-port network analyzer. To examine the utilization of the proposed 240 GHz radar for collision avoidance and building interior mapping applications, the interaction of electromagnetic waves with objects in the indoor environments is investigated. An instrumentation radar is utilized to collect backscatter data from corridors in an indoor setting. The collected data is used to form radar images for obstacle detection. The radar images are co-registered in a global coordinate matrix to form a complete map of the interior layout. Image processing techniques are used to enhance the final layout map.PhDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/107273/1/moallem_1.pd

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