From materials to hopping, from morphing to intent

Materials & devices
One EMRS talk described the development of a microstrip circuit technology based around world class, High Electron Mobility Transistors or 50nm mHEMPT developed by Glasgow University for mm-wave frequency  applications. The primary interest is for real-time mwave imaging systems and passive mm wave imaging for all-weather pilot aids for both rotary and fixed wing aircraft, and for security screening applications for detection of improvised explosive devices.
 
The process at Glasgow University is based on a co-planar waveguide environment, but that transmission line may make integration into imaging receivers problematic from both packaging compatability and parasitic modulation. Accordingly the Monolithic Microwave Integrate Circuit has been redeveloped as a microstrip process.  The steps involved development of backside thinning; development of a via-hole process; electroplating the backside; while additional wafer handling and die singulisation issues had to be addressed. Currently a number of active and passive test structures are being fabricated and measured.

Glasgow and Aberdeen Universities are also working on Gunn diodes where planar Gunn oscillation sources have been modelled and experimentally realised. These offer the prospect of THz operation and increased ease of integration over the more traditional vertical devices. Grown by MBE, made using EBL, devices comparable of operation beyond 108GHz are underway with integration into suitable pre-existing cavity design. Output power expects reach mW levels and bare devices have reached -22dBm.

The material battle between GaN Heterostructure Field Effect Transistor and  GaAs FETs is over, with GaN proven with more power 40GHz frequency and comparable RF noise. But, traditionally grown on expensive silicon carbide (SiC)  substrates  (100x more expensive than silicon and only now reaching  100mm wafer sizes) the current struggle is to produce GaN HFET devices on silicon. 

GaN HFET for QinetiQ. Courtesy: www.kelvinnanotechnology.com
The purchase and installation of a new growth reactor at QinetiQ to produce GaN based on HFET on 150mm Si substrates will provide layers suitable for processing trials of GaN FETs in exisiting UK foundry facilities. In situ nitride has been successfully and reproducibly deposited during MOVPE growth and incorporated
into the QinetiQ GaN HFET process, but the control current collapse and improved FR efficiency and output power still requires more than just the control of the interface chemistry and in-built strain in the structure is under consideration.

At Sheffield, studies of avalanche multiplication in InAs avalanche photodiodes (APD) includes a number of first observations and best performance results for the III-V material system, showing that InAs has material characteristics which allow excellent APDs to be made from it and in many aspects can match the theoretically optimal results until now only obtained from HgCDTe ‘electron.’ The APDs would be well suited to Focal Plane Array applications where standard III-V manufacturing requirement and good material uniformity would compliment the low voltage, extremely low noise, and sensitivity enhancing gain which has been identified.

CVD diamond in two device designs for high power FETs is being worked on by the E6 subsidiary, Diamond Microwave Devices, namely a stable FET using transfer doping to create carriers in the diamond near surface (SURFET) and an AlN/diamond heterostructure using polarisation enhancement to confine carriers near the surface (PEFET).  Work to date shows the need to realise not only a low defect diamond surface and subsurface; but surface treatment to induce time-stable transfer doping (Oxford Advanced Surfaces work) and fabrication of a SURFET once stable surface has been achieved. For the PEFET polarity control of the polar layer (Walter Schottky Institute work) is underway to find a suitable AlN on diamond material, and device fabrication and testing once the material layers have been formed.

Vision with SAR sound: high speed photon counting: underwater RF

(L) Listening. Courtesy: http://www.deafeducation.org.uk

Waterfall Solutions, Ltd, based in Parklands Surrey is working on (among other things) synthetic aperture radar (SAR) challenging to all but experience image analysts, and is targeting the use of sound for discrimination of SAR imagery, ignoring the temptation to collect treat the image as if it were an electro-optic sensor.  It shows the benefit to analysts to ‘listening’ to images and particularly applicable to high dimensional (hyperspectral) data. Sonic mappings developed to translate image features into sound and an assessment of these, show that users were able to discriminate between targets and false alarms successfully.

At Heriot-Watt University work has been on the first scanning time-of-flight system using time-correlated sing-photon counting in conjunction with data analysis algorithms to produce 3D images of scenes using very low laser power levels. The system has an xy resolution of 25cm at a distance of 1km with a depth resolution of at least that figure. More work is need on reducing the solar background with improved spatial and spectral filtering and more work will be don on optimized algorithm for low contrast return using actual experimental data.

And from Livingston based WFS (which won  £280,000 for its harbour sensing net) comes work investigating transmit antenna configuration for underwater RF communications shows that multiple transmit antennas (either array or stacked) can combine to increase transmitted magnetic moment close-in to the antenna. If this holds for far-field, then multiple transmit antenna will be more powerful and efficient than single anennas at creating magnetic flux.

MEMS IR laser control, 3D IR vision,  LWIR
Compact lower operating power optical scanners using MEMS technology are capable of deflecting 1W IR laser radiation generated from erbium fibre lasers in two axes with mirror tilt angles of up to +/-13o comes from  the University of Strathclyde Centre for Microsystems and Photonics, The scanners can be used in application requiring rapid scanning of wide fields of view and offer advantages of compact volume and low power requirements.

R: Intelligent cameras Roke Manor
Courtesy: https://www.ct.siemens.com/de
Roke Manor work has been on 3D computer vision techniques applied to Infra-red imagery, where, a 3D vision system DROID and VMAD an event detection system, both are based on detection and tracking of point features.
While not recommending generic vision processing research based on IR data (as the work would be taken up in addressing sensor issue) the results recommend that future work address specific applications of existing sensors as likely to achieve a more rapid pull through of research into exploitation.

Thales, celebrating its founding by Professor Archibald Barr and Dr William Stroud 120 years ago this month in Glasgow, has been working on a LWIR polarization sensitive camera which has been built, tested and trialled and work is underway on another camera incorporating simultaneous polarisation and wavelength discrimination in the LWIR. Its Polarimetric camera is capable of being switched to high resolution, non polarimetric mode and provides good polarisation and thermal sensitivity and useful imagery. Signatures allow targets to be discriminated as being man-made.

FPGA productivity with Owen
The evolution of Field Programmable Gate Array (FPGA) devices to the current System on Chip (SOC) devices poses considerable problems in terms of ensuring design productivity in deploying high and military signal processing applications to these devices.  Queen’s University Belfast has work on  the productivity improvement capabilities offered by Owen, an MDA-compliant design tool for FPGA centric embedded systems,  which significantly cuts design time to translate DSP algorithms specified in graphical modelling languages such as Labview into source files for vendor specific programming tools such as Xilinx EDK.

Hopping, morphing and fuel
Among the more curious papers from the SEAS side of life came one from Bristol Robotics Laboratory, working on compliant limb UGVs as a more versatile platform for fast locomotion over rough terrain, compared to wheels. Intriguing topics include determinant of performance for hopping vehicles; the relationship between power, weight and performance, and the power required for running.

Design of morphing wing structures is part of research at Imperial College where two current actuator concepts are researched using shape memory NiTi wires and an electroactive elastomer concept, the latter showing very high power density.  The conclusion is that the concept of morphing wings for flight control more appropriately meets flight control requirements if it consist of a compliant deformable trailing edge, with small materials embedded into the skin. The morphing system should keep the deformed shape without a continuous supply of power, working basically as a capacitor.

R Underwater autonomous vehicle. Curtesy:http://krapp.org/
Imperial and Porton Down reported on hybrid fuel cell/battery power system for a lightweight underwater vehicles. The conclusion is the hybrid fuel cell/battery system has significant advantages over a purely battery power design in terms of extended mission duration. Hydrogen storage is a problem. In the form of NH2BH2 it is identified as having high storage density, but there is no commercial product available, so liquid hydrogen stored in cyrogenic tanks provides the most promising performance.

SLAM gets attention
Adaptive Navigation, combining the Simultaneous Localisation and Mapping (SLAM) and Receding Horizon Control (RHC) to solve the problem of navigation in uncertain, GPS denied urban environment has been worked on at Bristol University. Trials show initial implementatio of the navigation system achieved a 68% success rate in reaching specified goals. Future work is needed to ptimise the system performance, and more advance SLAM algorithms incorporated. Roke Manor Research are also working on passive urban surveillance using signals of opportunity. Given favourable deployment geometry and appropriate measures to minimize the effects of transmitter breakthrough, it should be possible to detect a moving person at ranges up to 100m with a resolution of about 17m.

Inertial 3D simultaneous localization and mapping involving SLAM with Strap-down Inertial Navigation Systems (SINS) extends SLAM to underwater applications and the potential has been demonstrated. The work done so far has been based on the assumption that inertial sensors are affected by white noise, but real IMU readings themselves will drift with time. Next start research focuses on building a new SINS error model including scale factor and bias errors in the IMU reading and integrating that with SLAM.

Cooperation and intent
Finally In SEAS there’s modelling cooperative management in a mine search problem  (Warwick) and work toward autonomous systems that collaborate (Bath) which also scrutinises intentionality in human-machine interaction from a human perspective  “as intention and collaboration needs to understand how to support the individual in inferring intent.” Intent is a magic focus of the MoD, and one unusual area where researchers have already won an award in the Competition of Ideas.

R Intent: Courtesy: http://www.optimizeandprophesize.com

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