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Terahertz heterodyne receiver components for future European space missions

Final Report Summary - TERACOMP (Terahertz heterodyne receiver components for future European space missions)


Executive Summary:

In TeraComp, a state of the art 557-GHz receiver has successfully been developed and evaluated for space applications. The receiver technology is instrumental for both environmental monitoring e.g. of our atmosphere, and in planetary missions. The receiver has a measured record low noise temperature of 1300 K at room temperature, which makes it a sensitive receiver for applications where cryogenic cooling can’t be used.

The sub-harmonic mixer is based on Schottky diode and GaAs membrane technology. The local oscillator signal is provided to the mixer by a chain consisting of a x6 MMIC W-band multiplier and a two-stage W-band amplifier based on mHEMT technology, followed by a x3 HBV diode 278 GHz multiplier.

The receiver is a direct result of collaboration between European universities, institutes and SMEs, funded by the European Commission.

Project Context and Objectives:

The project aim is to demonstrate a compact and integrated terahertz receiver, based on European components, suitable for a number of future earth observation and space science missions. Sub-millimetre wave or terahertz heterodyne receivers are key instruments for many space applications. For example, they are required for monitoring of the earth’s atmosphere or detection of molecules that might be tracers of life on other planets or moons.

TeraComp addresses strategic technology for space terahertz instrumentation and aim to develop European industrial capability to design and manufacture terahertz components and electronics based on high frequency Schottky diodes, Heterostructure Barrier Varactor (HBV) diodes and mHEMT MMICs. Within the project, the prototype components were integrated in a compact 557 GHz heterodyne receiver and evaluated for space instrument applications.

In the long-term, the outcome of TeraComp will play a role in gaining knowledge of the earth's atmosphere, the climate system and understanding of the universe. Terahertz electronics will also find dual use applications in ground-based systems and open up for new markets.

Project Results:

The remote analysis of gases and vapours by heterodyne spectroscopy is a powerful tool in environmental monitoring, astronomy, and planetary research. Particularly in space applications compact, lightweight, and robust heterodyne spectrometers are necessary. In a joint European effort we have developed a heterodyne receiver, which satisfies the requirements set by space missions. This is achieved by minimising the number of components in the local oscillator (LO) of the receiver and a high degree of integration of all of its subcomponents.

The receiver is optimized for the frequency band from 520 to 590 GHz, because in this range H2O and a number of other important atmospheric trace gases have significant spectral lines.

The project started with main emphasis on finding the technical specifications, process development and initial design work of individual components. The sub-harmonic mixer is based on Schottky diode and GaAs membrane technology. An accurate Schottky device model has been developed, and used for device optimisation and in circuit simulations. The local oscillator signal is provided to the mixer by a chain consisting of a x6 MMIC W-band multiplier and a two-stage W-band amplifier based on mHEMT technology, followed by a x3 HBV diode 278 GHz multiplier. The whole LO chain has been optimised for a high DC-to-RF efficiency and bandwidth as well as weight and size.

A THz Schottky diode process line enabling monolithically integrated membrane circuits was developed within the project at Chalmers. In this process several batches of monolithically integrated 557 GHz subharmonic
membrane Schottky diode mixers have been successfully fabricated. The Chalmers diode process is based on electron beam lithography, with a beam spot of less than 5 nm, allowing precise anode and airbridge formation.

RF test of the receiver shows state-of-the-art performance with an optimum receiver noise temperature below 1300 K DSB and an estimated mixer DSB conversion loss and mixer DSB noise temperature of 9 dB and 1100 K respectively, including all losses.

For characterization of the heterodyne receiver noise temperature measurements using the Y-factor method and measurements of the Allan stability time were performed. The antenna profile was measured with a point-like radiation source (a Hg-lamp), which was mounted on a x-y stage and scanned across the antenna beam. An end-to-end test of the system was performed by measuring the spectrum of CH3OH and H2O at various pressures. For these measurements a dedicated absorption cell with a length of 56 cm and Brewster windows from high-density polyethylene was used. Then hot (296 K) and cold (78 K) blackbody sources were placed behind the absorption cell and the spectrum was measured across the IF frequency range from 0.1 to 1.5 GHz. To characterize the sideband gain, a strong H2O absorption line at 557 GHz was measured.

In summary, the results demonstrate that the receiver is very well suited for remote sensing of atmospheres and astronomical objects. Due to its small mass and input power the receiver is particularly suited for planetary missions such as ESA’s Juice (Jupiter icy moons) mission.

Potential Impact:

Sub-millimetre wave or terahertz heterodyne receivers are key instruments for many space applications. For example, they are required for monitoring of the earth's atmosphere or detection of molecules that might be tracers of life on other planets or moons. However, key components of these systems have been supplied from outside Europe and performance as well as mass and power requirements often prohibit the implementation. The TeraComp project aims at developing European industrial level capability to design and manufacture terahertz front-end electronics based on high frequency Schottky diodes, Heterostructure Barrier Varactor (HBV) diodes and mHEMT MMICs for space and other applications.

During the project, these critical components were integrated in a compact 557 GHz heterodyne receiver and evaluated for space instrument applications. Due to its small mass and input power the receiver is particularly suited for planetary missions such as ESA’s JUICE (JUpiter ICy moons Explorer) mission. Moreover, the technology developed in TeraComp can be scaled for receiver applications ranging from 300 GHz up to 1200 GHz and hence meet a wide range of planned European missions (SWI for JUICE, STEAM-r, CIWSIR, MetOp etc.)

In the long-term, the outcome of TeraComp will play a role in gaining knowledge of the earth's atmosphere, the climate system and understanding of the universe. Terahertz electronics will also find dual use applications in ground-based systems and open up for new markets. Thanks to the technology developed and successfully demonstrated in TeraComp, European SMEs and institutes can now take a larger role in future international space projects requiring sub-millimetre wave instrumentation.

Finally, the outcome from TeraComp project has generated more than 17 scientific journal and conference papers. The project has been visible at major international conferences and workshops. A press release is scheduled for summer 2013, aiming to disseminate the final outcome of this joint European effort.

List of Websites:
www.fp7-teracomp.eu

Prof. Jan Stake
Project Leader
jan.stake@chalmers.se
+46 31 772 18 36

Adress:
Chalmers University of Technology
Department of Microtechnology and Nanoscience - MC2
SE-412 96 Göteborg
Sweden