Archives - Antennas Research Ltd

Antennas Research
Arthur is the name of a huge reflector antenna at Goonhilly, Cornwall
Antennas Research Ltd.     2024
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1.  University of Oxford
Between 1996 and 2000 I worked for the University of Oxford as a research assistant in the communications research group at the Department of Engineering Science.  I  completed a doctoral thesis on passive microwave transponders for the Open University in 2002.
In 2000 I moved to the post of Research Fellow at the University of York.
Modulated radar reflectors / radar transponders
I designed various printed circuits which I used to make retro-reflective transponders as part of my PhD while working at University of Oxford in the late 1990s. These were based on variants of the Van Atta Array, but with pin diode modulators integrated into the interconnecting transmission lines. This technology gives rise to two effects which in combination have very useful properties:

  • Incident microwave energy is reflected back in the direction it originated from (retro-reflectivity)
  • The reflected signal is modulated with a code, so that it is distinguishable from clutter (passive  transponder)

The microwave energy is not amplified, hence the term passive. To increase the magnitude of the reflected power, the array may be made larger. Eventually, internal losses diminish the increase in array gain (see 3rd paper listed below).
I published details of a very accurate FM radar technique which woked elegantly with the transponder. The work later evolved into a commercial product under a license agreement.

Above: PCB design circa 1999. Here, we used ADS Momentum, in those days called a '2.5D' solver.
These printed circuits are for x-band antennas

Modulated retro-reflector prototype.                ‘RADASCAN’ system used on Shell Oil’s dynamic positioning vessels.

  • J. Thornton and D. J. Edwards, "Modulating Retroreflector as a Passive Radar Transponder", Electronics Letters, Vol 34, No. 19 September 1998, p.1880
  • J. Thornton and D. J. Edwards, "Range measurement using modulated retro-reflectors in FM radar system", IEEE Microwave and Guided Wave Letters, Vol.10, no.9, Sept. 2000, pp.380-2
  • J. Thornton, "Dimensioning a Retro-directive Array for Communications via a Stratospheric Platform, ETRI Journal,  Vol 24, No.2, April 2002, pp. 153 - 160  .
2.   University of York,  2000-2010
  • European HeliNet programme.   This consortium-led project ran from 2000 - 2003 and was funded by the EU 5th Framework Programme. It investigated broadband wireless communication to solar powered High Altitude Platforms (HAPs) using muti-beam Ka band antenna payload.
  • V-band study for British National Space Centre.  This examined use of 47-50 GHz band for sharing by satellite and HAPs
  • European project CAPANINA , another HAPs study funded under the EU 6th Framework Programme, 2003-2006
  • 'Advanced Components for the HYLAS User Segment', which concerned multi-beam user antennas for satcoms.
  • ‘MULTISCAN’ - Multi-beam Scanning Antenna for Satellite Communications, sponsored by European Space Agency.   2007 – 2009.
  • WIMAX from aerial platforms, funded under the Enabling Secure Information Infrastructure (ESII) programme of the UK’s Ministry of Defence. A short study on the critical issues for deploying WIMAX in the low GHz bands from an aerial platform or HAP (January - July 2008)

30GHz scanning lens                     low sidelobe multi-beam lens          waveguide measurements           60cm Luneburg lens for satcoms.
Antennas for high altitude platforms.  
For a 5th Framework project investigating communications from stratospheric platforms (very high aircraft) low sidelobe antennas were developed for 30 GHz. The first photo shows a dielectric lens illuminated by a corrugated horn, being measured in the anechoic chamber.

   Lens antenna with corrugated horn, 30GHz carrier frequency                    Lens-reflector. A harmonic mixer is seen at the primary feed.

This theme was also continued in the 6th Framework project ‘CAPANINA’ where I lead a work package on scanning antennas for vehicles. I published several papers in this area. I became quite intrigued by the properties of spherical dielectric lenses and built a prototype for 30 GHz. This was very successful and lead to the next activity...

Scanning Antenna for Satellite Communications. (Sponsored by European Space Agency)

I managed this project from the submission of the proposal to ESA to the final presentation, and lead a team of five in working out its design and construction. The project is more fully described in an article in Microwave Journal (August 2009).

Two primary feeds scan independently in azimuth and elevation. This allows two satellites to be tracked from one antenna. In the configuration shown above, one feed is used for two way communications at Ka band, while the other is a Ku band receive-only feed.

       A view of the elevation control arm                                     Receiving satellite TV with the lens antenna

The lens has half the height of an equivalent dish - ideal for low profile antenna.

WiMAX and Propagation studies.

We evaluated equipment for long range WiMAX links, and later developed a payload for a high altitude plane We achieved a throughput of 8 Mbits/s over a 30 km distance.  The payload was tested on a helicopter flight in Switzerland (my colleague flew - I did not !)

Antennas pointing over the Vale of York             A portable WIMAX base station                      The flight-ready WIMAX payload

A local company approached me to advise on the feasibility of point-to-point links for wireless  provision of broadband to rural areas in North Yorkshire.

Microwave signal strength coverage.                             Modelling terrestrial propagation.
Antennas Research Ltd.
A Company registered in England and Wales.  Company number 11118264.  Incorporated 2017.
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