Doctoral Thesis: High Angular Resolution Beam Steering THz Antenna Arrays for Imaging Applications

Nathan M. Monroe

Abstract:
Terahertz antenna arrays are capable of producing Terahertz electromagnetic waves that can be focused and steered by electronic control. They are a promising emerging technology for many applications, including THz imaging, radar, communications and other sensing applications due to bandwidth availability, ability to penetrate dielectric materials, and short wavelength, allowing for smaller structures. There is particular application in automotive radar imaging, where a narrow FMCW radar beam is swept across a scene to produce a depth image which, unlike LIDAR, is tolerant to environmental conditions such as rain and snow. However, challenges exist in the design of large dense THz arrays, limiting demonstrations to hundreds of antennas, a fraction of the size and directivity required for high-resolution imaging. This is due to a number of challenges including THz phase shifters which are high-loss and too large for dense integration, consume large DC power, and introduce amplitude and phase errors. In addition, challenges exist with high-loss on-chip RF power distribution, array scalability and phase control.

The approaches taken in this work address these issues, enabling a 98 x 98 antenna array at 265GHz which employs passive one bit phase shifters based on two MOSFET switches. These phase shifters are low-loss, low-area and consume no DC power. A reflector array (reflectarray) architecture and in-unit memory address RF distribution and digital control challenges, and a scalable design allows for arbitrary array sizes. In-unit memory additionally enables performance-enhancing algorithms to mitigate beam squint and radiation sidelobes which improve effective resolution of a wideband FMCW radar image and enable radiation performance approaching that of ideal phase shifters. The concepts are demonstrated on-chip in a 22nm FinFET CMOS process, with a 4x4mm2 chip containing a dense 7×7 antenna array. An on-PCB tiling of 14×14 chips produces a 98×98 antenna array, which demonstrates electronic steering over a 120 degree window of a 1×1 degree THz beam with 42dBi of directivity, and is further enhanced by algorithmic approaches. The antenna array is employed in a radar imaging application where the high-directivity beam is used to produce 90×90 pixel radar images. This represents the largest beam-steering THz antenna array demonstrated to date, and a step towards practical solid-state THz imaging.

Details

• Date: Friday, December 10
• Time: 11:00 am
• Category: Thesis Defense
• Location: via zoom

Additional Location Details:

Thesis Supervisor(s): Prof. Ruonan Han

To attend this defense via Zoom, please contact the doctoral candidate at monroe@mit.edu