Sub-terahertz receiver array chip enables autonomous vehicles 'see' through fog and dust

February 15, 2019 //By Jean-Pierre Joosting
Sub-terahertz receiver array chip enables autonomous vehicles 'see' through fog and dust
A sub-terahertz receiving system that could help steer driverless cars see through blinding conditions, such as fog and dust has been developed by researchers at MIT.

Sub-terahertz wavelengths can be detected through fog and dust clouds with ease, whereas the infrared-based LiDAR imaging systems used in autonomous vehicles today struggle. To detect objects, a sub-terahertz imaging system sends an initial signal through a transmitter – a receiver then measures the absorption and reflection of the rebounding sub-terahertz wavelengths. That sends a signal to a processor that recreates an image of the object.

But 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 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 a lot of 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.

See also: Terahertz sensors based on indium phosphide ideal for autonomous cars

The researchers built a prototype, which has a 32-pixel array integrated on a 1.2-square-millimeter device. The pixels are approximately 4,300 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.

See also: NEC joins 5G Autonomous Cars for cross-borders digital corridors research

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