Researchers at Chalmers University of Technology in Sweden have demonstrated an integrated amplifier that offers new possibilities for detecting the faintest electromagnetic radiation.
A fundamental property for the first microwave amplifier in the radio receiver is its noise figure, which is normally given in decibels (dB). A typical noise figure for low-noise amplifiers in mobile communication systems is tenths of a decibel.
Last year, Chalmers reported a world record for a low-noise amplifier in the journal Electron Device Letters. The amplifier exhibited a minimum noise figure of 0.018dB across a bandwidth of 4-8GHz. However, since the low-noise amplifier was designed in a hybrid solution, scaling up to larger quantities turned out to be difficult.
Chalmers, in collaboration with a company called Low-Noise Factory, has now published an article on an integrated ultra-low-noise amplifier.
According to Chalmers, the scientists have developed an indium phosphide-based process for high electron mobility transistors (HEMT). Transistors and other semiconductor components have been fabricated on a monolithic chip on an indium phosphide wafer. All parts of the design such as semiconductor layers, components, process and circuit design have been optimised for the lowest noise performance.
As a result, an integrated 2.0 x 0.75mm amplifier with an ultra-low-noise figure of 0.045dB has been demonstrated. The amplifier has a very large bandwidth of 0.5-13GHz and a high gain exceeding 38dB across the frequency band. In order to show such extreme performance, the amplifier was cooled to minus 260 degrees of Celsius.
‘The combination of high gain, large bandwidth and ultra-low-noise figure makes this circuit very attractive for large multipixel arrays containing thousands of antennas,’ said Jan Grahn, research group leader at Chalmers.
‘The integrated ultra-low-noise process enables the fabrication of thousands of amplifiers with identical performance. One potential future application is in the world’s largest radio telescope SKA (Square Kilometer Array) that is being planned, an international project where the Onsala Space Observatory at Chalmers is one of the acting members.
‘In huge applications such as the SKA, even a small noise-figure reduction in the first low-noise amplifier in the receiver chain may potentially bring about major savings in the final system design.’