Researchers at MIT have developed a sub-terahertz-radiation receiving system that could help steer driverless cars when traditional methods, such as light-based image sensors, fail. However, implementing sub-terahertz sensors into driverless cars is challenging. Sensitive, accurate object-recognition requires a strong output baseband signal from receiver to processor. Traditional systems, made of discrete components that produce such signals, are large and expensive. Smaller, on-chip sensor arrays exist, but they produce weak signals. In a paper published online on Feb. 9 by the IEEE Journal of Solid-State Circuits, the researchers describe a two-dimensional, sub-terahertz receiving array on a chip that is orders of magnitude more sensitive, meaning it can better capture and interpret sub-terahertz wavelengths in the presence of high signal noise. To achieve this, they implemented a scheme of independent signal-mixing pixels—called “heterodyne detectors”—that are usually very difficult to densely integrate into chips. The researchers drastically shrank the size of the heterodyne detectors so that many of them can fit into a chip. The trick was to create a compact, multipurpose component that can simultaneously down-mix input signals, synchronize the pixel array, and produce strong output baseband signals. The researchers built a prototype, which has a 32-pixel array integrated on a 1.2-mm² device. The pixels are approximately 4300 times more sensitive than the pixels in today’s best on-chip sub-terahertz array sensors. With a little more development, the chip could potentially be used in driverless cars and autonomous robots, playing a complementary role to LiDAR for when the environment is rough.

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