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Topic Name: Researchers at Chalmers have succeeded in combining integrated receiver for high frequency applications

Category: Electronics

Research persons: Chalmers Research Team

Location: Chalmers University of Technology, Sweden

Details

As the first research group in the world, researchers at Chalmers have succeeded in combining a receiver for high frequencies with an antenna on a small chip.

The receiver is just a few square millimetre and is suitable for new safety systems, image sensors, and radio communication for high bitrates. The receiver is an electronic circuit including antenna, low noise amplifier, and frequency converter monolithically integrated on gallium arsenide.

"This is a breakthrough in our research. Our result opens the possibility to manufacture systems for very high frequencies within the so called 'THZ-electronics' area, to a relatively low cost. In the next phase of this project even more functions can be integrated on the same chip", according to Herbert Zirath, professor at the department of Microwave Electronics.

This circuit can for instance be used in radiometer systems in future safety systems looking for concealed weapons without personal visitation. Other applications for this circuit are imaging sensors that can look through darkness, smoke or fog. This is an important safety function for vehicles such as cars and aircrafts.

"Thanks to this technology, we now have the possibility of integrating imaging sensors by using circuits of a few square millimetre which is much smaller that the present technology at a lower cost. For automotive applications such as cars, aircrafts and satellites, the size and weight is of utmost importance. The present systems consist of many pieces and demands several cubic decimetres volume", says Herbert Zirath.

The new circuit is designed to work at the frequency of 220 gigahertz, but this is not an upper limit. According to professor Zirath, the technology can be used up to and above 300GHz in a near future.

The technology is also interesting for wireless data communication because, due to the very high bandwidth, data rate well above 10 Gbit/s is possible to realize in future radio links. Together with Omnisys Instruments in Gothenburg, we are also implementing receivers for future earth observation satellites for environmental studies and weather forecasts at frequencies 118 and 183 GHz, using the same technology.

Note for Image sensor

An image sensor is a device that converts a visual image to an electric signal. It is used chiefly in digital cameras and other imaging devices. It is usually an array of charge-coupled devices (CCD) or CMOS sensors such as active-pixel sensors.
There are several main types of color image sensors, differing by the means of the color separation mechanism:

Bayer sensor, low-cost and most common, using a Bayer filter that passes red, green, or blue light to selected pixels, forming interlaced grids sensitive to red, green, and blue. The image is then interpolated using a demosaicing algorithm.

Foveon X3 sensor, using an array of layered sensors where every pixel contains three stacked sensors sensitive to the individual colors.

3CCD, using three discrete image sensors, with the color separation done by a dichroic prism. Considered the best quality, and generally more expensive than single-CCD sensors.

Note for Low noise amplifier

The low noise amplifier (LNA) is a special type of electronic amplifier or amplifier used in communication systems to amplify very weak signals captured by an antenna. It is often located very close to the antenna. If the LNA is located close to the antenna, then losses in the feedline become less critical. This "active antenna" arrangement is frequently used in microwave systems like GPS, because coaxial cable feedline is very lossy at microwave frequencies.

It is a key component, which is placed at the front-end of a radio receiver circuit. Per Friis' formula, the overall noise figure of the receiver front-end is dominated by the first few stages.
Using a LNA, the noise of all the subsequent stages is reduced by the gain of the LNA and the noise of the LNA is injected directly into the received signal. Thus, it is necessary for a LNA to boost the desired signal power while adding as little noise and distortion as possible so that the retrieval of this signal is possible in the later stages in the system.

Note for Frequency converter

A frequency changer or frequency converter is an electronic device that converts alternating current (AC) of one frequency to alternating current of another frequency. The device may also change the voltage, but if it does, that is incidental to its principal purpose.
Traditionally, these devices were built out of electromechanical components such as motor-generator sets or rotary converters. But with the advent of solid state electronics, it has become possible to build completely electronic frequency changers. These devices usually consist of a rectifier stage (producing direct current) which is then inverted to produce ac of the desired frequency. The inverter may use thyristors or IGBTs. If voltage conversion is desired, a transformer will usually be included in either the ac input or output circuitry and this transformer may also provide galvanic isolation between the input and output ac circuits. A battery may also be added to the dc circuitry to improve the converter's ride-through of brief outages in the input power.

About Researcher

Professor Herbert Zirath, Microwave Electronics Laboratory, Department of Micro technology and Nanoscience MC2, Chalmers University of Technology
Tel: +46 31-772 18 52

This work is the results of a co-operation between Chalmers, Saab Microwave Systems, Omnisys Instruments AB, FOI, The Fraunhofer Institute IAF in Freiburg and FGAN, Germany, within the project "nanoComp".