Development of new planar retarding surfaces for mm- and sub-mm wave applications

This proposal is to design planar metal mesh retarding surfaces, based on sub-wavelength periodic or quasi-periodic structures, which selectively retard EM radiation in the microwave (GHz) to sub-mm wave (THz) regions of the spectrum. The surfaces act as artificial birefringent materials, to provide excellent polarization selectivity, or spatially varying artificial dielectrics to act as lenses. Because they are compact, robust, lightweight and exhibit favourable properties of low-loss and high predictability of performance these surfaces have the potential of altering the basic designs of a variety of instruments operating in the microwave to sub-mm wave regions of the spectrum. Examples include: telecommunications systems, radar systems, millimetre wave imaging, satellite communications, Earth observations and space science, industrial non-destructive testing and inspection, biological investigation, remote sensing, security, laboratory testing facilities and astronomical instrumentation.The new surfaces are more complex realizations of the metal grid techniques used in frequency selective surfaces (FSS). As with FSS they can be made by means of copper evaporation onto plastic substrates with the geometrical structures defined by standard photolithographic techniques. The manufacturing costs are therefore low. The innovations are: i) the design of large-scale spatially-invariant geometrical anisotropies to provide different behaviour for orthogonal polarization states; ii) the design of spatially-variant geometries-resulting in gradients in effective refractive. These innovations are based on: i) a deep physical understanding of the physics of the interaction of EM waves with lumped complex impedance elements; ii) the use of standard software (HFSS) to extract the lumped element characteristics-normally inferred empirically; iii) the ability accurately to model complex structures with large numbers of elements-beyond the capabilities of current commercial codes running on PCs.The PI works within the Manchester Radio Technology Group within the Jodrell Bank Centre for Astrophysics. The expertise, the processing and the testing facilities of the RTG group will greatly facilitate the successful completion of the research programme. The success of this grant application will be a key step in transferring considerable knowledge from the area of radioastronomy to solve real needs in the broader technological arena.

This is an innovative basic research programme aimed at producing lightweight, low-cost but high performance metal mesh surfaces able to provide excellent polarization selectivity or powerful focusing of radiation; they have the potential to alter the basic designs of instruments operating in the microwave to sub-mm wave regions of the spectrum. The new surfaces will provide new capabiliites to systems designers - cheap high quality polarization discrimination will allow new modalities for imaging/inspection while planar lenses will allow new ways to design lightweight large aperture radiation collectors. There is a wide diversity of applications on which the new devices can have an impact: telecommunications and radar systems, millimetre wave imaging, satellite communications, Earth observations and space science, industrial non-destructive testing and inspection, biological investigation, remote sensing, security, laboratory testing facilities and astronomical instrumentation. This list emphasizes the ubiquity of the radio spectrum for society and hence the commercial private sector, the public sector and the pure science sector will benefit from the research outcomes. The programme will have impact on health, culture and wealth - all of which are intimately linked since any new instrumentation will be constructed by the commercial sector. For the health and quality of life impacts one can point to the potential use of the outputs in the security screening sector and a range of material and biological investigations from GHz to THz. The Feb 2009 meeting on Terahertz Systems and Industrial Applications at the Royal Society involved non-destructive testing, imaging and substance identification in industries as diverse as military, aerospace, pharmaceutical, healthcare, food & drink. The whole telecommunications arena is also a major contributor to the quality of everyday life. In terms of culture one can point to the roles of these new devices in systems aimed knowledge-based investigations - for example space science and astronomy/cosmology - in which the public and hence the media show a continuing interest. The timescales to demonstrate fully the capabilities of the devices are simply the two years of the proposed programme since the basic metal mesh construction methodology is well proven - the innovation will be in terms of software for efficiently calculating the collective properties of large area surfaces from a knowledge of their local area (lumped) properties. The timescale for the take-up of this technology depends on making the new capabilities clear to systems designers. Communication will be via the standard academic routes of publication in journals and presentations at high impact conferences which will involve potential industrial partners. Engagement with industry will build on existing partnerships and linkages built up with UK companies via existing microwave and mm-wave imaging programmes in Manchester, including colleagues in the Microelectronics and Nanostructures group in the School of Electrical & Electronic Engineering. Manchester academics have also developed a close linkage with the Electronics Knowledge Transfer Network (eKTN) to identify and pursue industrial partnerships for the Square Kilometre Array programme and one of them is on the eKTN Board. The PI is therefore very well placed to develop existing company links established by close colleagues and to use their experience of Knowledge Transfer programmes. The programme is aimed at the forefront on EM technology - and staff working on the programme will, perforce, become skilled in basic EM physics and able to translate this into effective use of commercial software. The innovative stage is the production of new specialized software able to make large area calculation of collective surface properties feasible on PC-level hardware. These high-level skills are generic and of immediate interest to UK industry.