Miniaturised helical antennas for superdirectivity
Prof J R Sambles
Prof A P Hibbins
No more applications being accepted
Funded PhD Project (European/UK Students Only)
Beginning from fundamental physics, over a century ago, Marconi pioneered radio communication. He could surely never have imagined Jodrell Bank or the country strewn with antennas of numerous designs and functionality required for everything from wireless key fobs, to WiFi communication, TV reception and radar, but that is where we now are. Such devices often need to collect a weak signal or in the case of transmitters provide highly directed signals from ground, up to satellites. There is however one way this use of cumbersome dishes may be overcome, using the phenomenon of superdirectivity. Unlike conventional cumbersome phased arrays that provide high directivity by means of constructive interference, superdirective antennas are based on destructive interference that suppresses radiation in all directions. However for a suitable design in one specific direction this destructive interference is minimised and hence the radiation in that chosen direction is a relative maximum. This, in theory, makes it possible to obtain an arbitrarily sharp beam which may readily be steered to a chosen receiver.
Recently at Exeter we have demonstrated a novel superdirective dimer arrangement consisting simply of two metallic helices placed a suitable distance apart. This very small structure, much less than a wavelength in size unlike the large dishes normally used, gives very high directivity for low GHz frequency microwaves.
This research project seeks to take this superdirective work to a new level.
Firstly the researcher will explore the use of combining the superdirective dimers with ‘magnetic mirrors’ formed of arrays of resonant helices (we have already demonstrated their effectiveness for a bow-tie antenna.). This will allow this newly developed miniaturised microwave source to be used in proximity to conducting objects.
Secondly they will explore even stronger superdirectivity using 3 or more helical antennas.
Thirdly they will pioneer studies of concentric arrangements of helices, possibly of opposite handedness, to even further miniaturise the source, making it even lighter and smaller while still maintaining high directivity.
In all three cases we shall begin by modelling based around our previous experience and then move on to sample fabrication and characterisation.
The work forms part of a very strong collaboration with, and is fully sponsored by, the UK Government agency, Defence Science and Technology Laboratories (Dstl).
The work involved ranges from very fundamental physics, through modelling and on to device design, fabrication and testing. The successful applicant must have a very good degree in Physics or Electrical Engineering and be a UK or EU National.
The 4 year studentship is fully funded by the Defence and Security Technoly Laboratory (Dstl). It is of value around £129,000, which includes £15,000 towards the research project (travel, consumables, equipment etc.), tuition fees, and an annual, tax-free stipend of approximately £18,200 per year for UK/EU students.
Eligible candidates: UK/EU nationals only due to industry sponsor requirements.
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FTE Category A staff submitted: 40.20
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