Professor Kenneth KO and his colleagues at the University of Texas at Dallas and the University of Oklahoma have developed an innovative and affordable terahertz image microchip that can allow devices to detect objects and create images through obstacles that include fog, smoke, dust and snow.
Technical summaries: What started you in this field of study?
Professor Kenneth CO: For 15 years, my research team has been trying to discover new opportunities for the silicon integrated circuit industry. When we started, although we were working on terahertz applications, our main focus was on 77 GHz radar.
Technical summaries: What are some differences between your terahertz image and 77 GHz radar?
About: The main difference is only in the frequency – it is a factor approximately five times higher – so the wavelength is about five times smaller. This means that an image device with the same form factor can give five times better resolution by switching to 430 GHz. Our system is essentially made up of pixel arrays of 430 GHz radar. But the performance of these pixels is worse than at 77 GHz. So to solve this problem, we designed the chips to work with a reflector. With the help of the reflector, we can potentially achieve the same type of range – about 200 meters – as radar operating at 77 GHz.
Technical summaries: How does it contribute to power reduction?
About: You can think of it as a lens – it focuses the signal and sends it to a certain point in space. Therefore, all the power emitted by the pixel is focused on this point, instead of scattering as it propagates.
Technical summaries: How does your radar cope with the frequency limitations of CMOS technology?
About: The problem is that we can’t use CMOS amplifiers to provide amplification for terahertz receivers. So, we use frequency multiplication to generate an RF signal and we also use a technique called harmonic mixing to convert the signal down without an amplifier in front. This impairs the sensitivity of the receiver, so we have to overcome it. These are two challenges in raising higher frequencies compared to 77-GHz radar.
Technical summaries: So you’re saying that somehow you need more amplification to increase the amplitude of the reflected signal?
About: Yes exactly. We need to make sure that the signal we are transmitting is racketeering the target we are trying to find, and that the level of signal power that reaches the targets is the same as at 77 GHz. The way we do this is by using the reflector together with our focal plane grating. This reflector gives us this gain in power and then reflects back and again gives us a gain for the receiver. So, even with poor sensitivity, we can still detect the reflected signal.
Technical summaries: You said that this radar could penetrate atmospheric obstacles such as snow, dust and fog. But these are all particles; can it penetrate solid particles?
About: some. May penetrate non-conductive materials such as plastic containers. Industrial applications include tracking the dryness of printing on paper and fabrics. You can also think of industrial settings where you have a steam environment. You have to watch what is behind the steam. A really important app is seeing through smoke and fire – an amazing app for firefighters to help them look for people.
An edited version of this interview appeared in Tech Briefs edition of May 2022 .