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@article{Allen2019,
   abstract = {This paper evaluates the performance of three-dimensionally (3D) printed spiral phase plates (SPPs) for enabling an orbital angular momentum (OAM) multiplexed radio system. The design and realization of the SPPs by means of additive manufacturing exploiting a high-permittivity material is described. Modes 1 and 2 SPPs are then evaluated at 15 GHz in terms of 3D complex radiation pattern, mode purity and beam collimation by means of a 3D printed dielectric lens. The results with the lens yield a crosstalk of −8 dB for between modes 1 and −1, and −11.4 dB for between modes 2 and −2. We suggest a mode multiplexer architecture that is expected to further reduce the crosstalk for each mode. An additional loss of 4.2 dB is incurred with the SPPs inserted into the communication link, which is undesirable for obtaining reliable LTE-based communications. Thus, we suggest: using lower loss materials, seeking ways to reduce material interface reflections or alternative ways of OAM multiplexing to realize a viable OAM multiplexed radio system.},
   author = {B. Allen and T. Pelham and Y. Wu and T. Drysdale and D. Isakov and C. Gamlath and C. J. Stevens and G. Hilton and M. A. Beach and P. S. Grant},
   doi = {10.1098/rsos.191419},
   issn = {20545703},
   issue = {12},
   journal = {Royal Society Open Science},
   keywords = {Orbital angular momentum multiplexing,Spiral phase plates,Wireless communications},
   month = {12},
   pages = {191419},
   title = {Experimental evaluation of 3D printed spiral phase plates for enabling an orbital angular momentum multiplexed radio system},
   volume = {6},
   url = {https://royalsocietypublishing.org/doi/abs/10.1098/rsos.191419 https://royalsocietypublishing.org/doi/10.1098/rsos.191419},
   year = {2019},
}
@article{Pelham2017,
   abstract = {Conformal antenna arrays are becoming increasingly attractive for aerospace, medical imaging, and 5G communications. While developments in electromagnetic solvers allows accurate conformal array analysis, this study presents a method for predicting the maximum gain pattern for conformal antenna arrays using Standard Triangular/Tessellation Language models for aperture and obstruction geometry. Using raycasting techniques, the aperture model allows the prediction of the maximum gain pattern in the presence of obstructions. The maximum gain patterns are shown for a conformal antenna array integrated into the curved corner of a building, and a conformal antenna array integrated into the wing leading edge of an aircraft. This technique presents an invaluable tool to assess the viability of a conformal aperture on a structure, while allowing for variation of the structure to assess performance implications for the conformal antenna array. This study shows the increase in maximum beam steering angle of 13° from a purely planar array for the array integrated into a building, and the aeroplane wing leading edge is shown to produce a maximum achievable gain of 41.7 dB, which is 1.7 dB higher than a conventional nose-mounted planar array could be expected to achieve with a greatly increased field of view.},
   author = {Timothy Pelham and Geoffrey Hilton and Evangelos Mellios and Rob Lewis},
   doi = {10.1109/LAWP.2016.2600403},
   issn = {15361225},
   journal = {IEEE Antennas and Wireless Propagation Letters},
   keywords = {Aerospace,antenna arrays,antenna theory,conformal antenna arrays,mobile communications,ray tracing},
   pages = {700-703},
   publisher = {IEEE},
   title = {Predicting Conformal Aperture Gain from 3-D Aperture and Platform Models},
   volume = {16},
   url = {https://ieeexplore.ieee.org/document/7562524/},
   year = {2017},
}

@InProceedings{Pelham2015c,
  author    = {Timothy Pelham and Geoffrey Hilton and Evangelos Mellios and Rob Lewis and Evangelos Mellios and Geoffrey Hilton},
  title     = {Predicting conformal aperture directivity for arbitrary curved surfaces},
  booktitle = {Wideband and Multi-Band Antennas and Arrays for Civil, Security and Military Applications},
  year      = {2015},
  volume    = {1},
  pages     = {1-3},
  publisher = {Institution of Engineering and Technology},
  abstract  = {Conformal Antenna Arrays offer many advantages for aerospace platforms, especially if selected early in the platform design cycle. To this end a Conformal antenna array directivity equation is presented, allowing the benefits of a conformal antenna array to be explored and design trade-offs considered at an early stage. The Conformal Directivity equation is an extension of Hannan's equation for the maximum achievable directivity of a planar aperture within an infinite antenna array, and when compared to a uniform illumination model for a planar aperture for aperture areas above 0.5λ2 there is a maximum difference of 0.87dBi, and a mean difference of 0.49dBi.},
  doi       = {10.1049/ic.2015.0147},
  isbn      = {9781785610103},
  issn      = {1536-1225},
  issue     = {9},
  journal   = {IET Seminar Digest},
  url       = {http://digital-library.theiet.org/content/conferences/10.1049/ic.2015.0147 http://ieeexplore.ieee.org/document/7562524/},
}
@article{Pelham2021,
   abstract = {Conformal antenna arrays have long represented an attractive solution to challenges imposed by an electromagnetic aperture on an aerospace platform. This allows designers to trade between array positioning and geometry, and avoids the significant aerodynamic drag of a planar array. This is hampered by the expense of the design and computational modelling required to ensure that a conformal array w...},
   author = {Timothy G. Pelham and Geoff Hilton and Evangelos Mellios and Rob Lewis},
   journal = {IEEE Access},
   publisher = {IEEE},
   title = {Conformal Antenna Array Design Using Aperture Synthesis and On-Platform Modeling},
   volume = {9},
   url = {https://ieeexplore.ieee.org/document/9408625/},
   year = {2021},
}

@InProceedings{Pelham2021a,
  author    = {T. G. Pelham and A. Loaiza Freire and G. Hilton and M. Beach},
  title     = {Polarimetric Scattering with Discrete Raytracing for OTA Analysis},
  booktitle = {EuCAP 2021},
  year      = {2021},
  publisher = {IEEE},
  abstract  = {The use of millimetre waves (mmWave) requires the development of novel, robust over the air (OTA) test methods. One low-cost OTA method is based upon an elliptical arrangement of reflectors, to allow conformance testing of devices at mmWave. A discrete ray model is used to predict the influence of reflector shape and arrangement on scattering at 24GHz for two reference surfaces of differing size and a substrate reflector. The model shows a correlation of 0.99 between the predicted and measured scattering for the larger reference surface, and root mean square (RMS) error of -69dB, while for the smaller reference surface the model achieved a correlation of 0.98 between the predicted and measured scattering, and an RMS error of -69dB.},
  doi       = {10.23919/eucap51087.2021.9410981},
  isbn      = {9788831299022},
  journal   = {15th European Conference on Antennas and Propagation, EuCAP 2021},
  keywords  = {antenna,electromagnetic,measurements,propagation},
  url       = {https://ieeexplore.ieee.org/document/9410981/},
}
@article{Hannan1964,
   abstract = {In a phased-array antenna with a very large number of regularly-spaced radiating elements, the gain realized at the beam peak is equal to the number of elements times the gain realized in the same direction when only one typical element is excited. The ideal radiation pattern of one such element in a large planar array has a cosine variation of gain with angle when the elements are closely spaced, and has a peak value of gain equal to 4?rA/X2 where A is the area allotted to each element The active impedance of each element in a practical phased array varies with scan angle, becauseof mutual coupling between the elements. The associated mismatch causes power to be returned to the generators, thereby reducing the gain realized by the array and by the element. The element pattern, measured in the proper environment of surrounding elements, deviates from the ideal pattern in proportion to this effect. Mutual coupling is inherently unavoidable in a closely-spaced infinite array of elements; for example, in a square array with less than X / ⊡2 spacing. There is a loss of element efficiency caused by the coupling, and since coupling increases with closer spacing, this accounts for the lower gain expected from ideal elements with reduced allotted area. Grating lobes can exist when the elements are not closely spaced; for example, in a square array with more than X/2 spacing. In this case, the ideal pattern is truncated to discriminate against grating lobes; this gives the higher gain expected from ideal elements with larger allotted area It isc oncluded that in ap hased-array antenna having a very large number of regularly-spaced radiating elements, perfect impedance match for all scan angles can be postulated for every typical element without encountering any real discrepancy in the determination of element gain. In the absence of grating lobes, such an antennaw ould realize the greatest possible gain for all scan angles. © 1964, IEEE. All Rights Reserved.},
   author = {Peter W. Hannan},
   doi = {10.1109/TAP.1964.1138237},
   issn = {15582221},
   issue = {4},
   journal = {IEEE Transactions on Antennas and Propagation},
   keywords = {Antenna array mutual coupling,Antenna arrays,Antenna radiation patterns,Directive antennas,Gratings,Impedance,Mutual coupling,Phased arrays,Planar,Planar arrays,Power generation,Radio access networks},
   month = {7},
   pages = {423-433},
   title = {The Element-Gain Paradox for a Phased-Array Antenna},
   volume = {12},
   url = {http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=1138237},
   year = {1964},
}

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