The following papers are associated with or a direct result of SYMETA's research.

“Fused deposition modelling for microwave circuits & antennas”

Cadman D.A., Zhang S., Vardaxoglou J.C.,

International Symposium on Antennas and Propagation (ISAP): 418-419 (2 pages). 24 Oct 2016


Additive Manufacturing, or 3D printing, is moving from the research labs and into both consumer and commercial manufacturing markets. As the systems, processes and materials available are becoming more mature we are seeing them being tested for new application areas such as electronics. In this paper we review how fused deposition modelling (FDM) is being explored for creating microwave circuits and componentry, their RF performance and the materials challenges faced. In recent years such microwave circuits and components have included antennas, lenses, anti-reflective coatings, transmission lines and planar circuits, waveguide terminations, performing at frequencies ranging from low GHz up to tens of GHz. Additive manufacture of such objects allows new, novel and complex structures to be fabricated with lower impact on the environment relative to current manufacturing processes, plus the rapid prototyping of circuits. Additionally it currently offers reasonable RF performance that can be competitive through further advances in manufacturing processes and materials.


Rapid protoyping of waveguide and horn antennas

Cadman D.A., Zhang S., Vardaxoglou J.C.,

European Conference on Antennas and Propagation, Paris, 19 Mar 2017 - 24 Mar 2017. (Presentation)


In this paper we review how fused deposition modelling (FDM) can be deployed for the rapid prototyping of microwave waveguide componentry and antennas. Additive manufacture of such objects allows new, novel and complex structures to be fabricated with lower impact on the environment relative to current manufacturing processes, plus the fast turnaround of design to manufacture and test. Additionally while the resulting physical antenna properties may not be perfect compared to the design or what can be machined, their RF/microwave performance can be quite forgiving thereby allowing the antenna design engineer to fully exploit the rapid prototyping concept.

The University of Oxford and Loughborough University presented these related papers at 10th International Congress on Advanced Electromagnetic Materials in Microwaves and Optics – Metamaterials 2016 Crete, Greece, 17-22 September 2016

"Experimental Demonstration of Superdirectivity for Coupled Dimers of Meta-Atoms" (Invited)

Anna Radkovskaya, M. V. Lomonosov Moscow State University, Russia, Andrea Vallecchi, Lianbo Li, Grahame Faulkner, Chris Stevens, Ekaterina Shamonina, University of Oxford, UK


A century-long quest for realizing superdirective antennas has got a new lease of life with the advent of metamaterials: Arrays of coupled meta-atoms capable of carrying slow short-wavelength magneto-inductive waves were shown to be promising candidates for realizing rapidly varying current distributions required for superdirectivity. This paper provides an overview of our work towards realizing a genuine superdirective meta-array, with only one element being driven. In particular, we report on our most recent experimental, numerical and analytical results, which, for the first time to our knowledge, confirm superdirective end-fire directivity reaching the maximum theoretical value. We formulate the conditions for superdirectivity in terms of shape and size of the meta-atoms and discuss implications of our results for future work on superdirective metamaterials.


"Programmable Magnetoinductive Devices"

Jan Paszkiewicz, UK Ekaterina Shamonina, UK Christopher Stevens, University of Oxford, UK


A design for a programmable magnetoinductive waveguide where the impedance of each cell can be set to one of two values by an electronic signal is presented. A 1D magnetoinductive waveguide using such cells is verified experimentally and used to demonstrate an electronically programmable transfer function. Extension of the concept to 2D devices and creating programmable RF systems is discussed.

"Impact of a Conducting Medium on the Coupling of Meta-Atoms"

Andrea Vallecchi, Son Chu, Chris Stevens, Ekaterina Shamonina, University of Oxford, UK


We have studied analytically, numerically and experimentally the effect of conducting material upon the mutual inductance between two coils yielding thereby the attenuation of magnetoinductive (MI) waves. It is shown among others that the expression for plane wave attenuation, used in the literature, has only limited validity. Our results will be relevant for the design and optimisation of MI waveguide links in conducting media in general and particularly when the attenuation is caused by soil conductivity. The results will also help medical diagnosis in problems where parts of the human body are imaged.

"3D-Printed Metamaterials with Periodic Metallic Elements"

S. Zhang, W.G. Whittow, J.C. Vardaxoglou Loughborough University


This paper presents a study on artificial heterogeneous metamaterials that were synthesized by adding metallic rectangular cuboid inclusions (meta-atoms) into a dielectric host material. Multi-layered metamaterial substrates were fabricated using the addictive manufacturing technique. Varying the space between the metallic inclusions in the material affects its effective electromagnetic properties including the relative permittivity, permeability and loss tangent

"Frequency Tunable Metasurface for GNSS"

Y. F. Cao 1, John (Yiannis) C. Vardaxoglou 2, S. W. Cheung 1, and T. I. Yuk 1

1The University of Hong Kong, Department of Electrical and Electronic Engineering, Pokfulam Road, HK 2 Loughborough University, Department of Electronic and Electrical Engineering


A compact frequency tunable MetaSurface (MS) for GNSS is proposed in this paper. The MS comprised of a double layer array with square conducting patches on one layer and meander line slots on the other. The unit cell has a total volume of 0.15λg×0.15λg×0.01λg (λg is the guided wavelength) where four varactor diodes are placed symmetrically across the meandered slot on the ground plane to achieve the frequency tunability. Because the meandered slot on the other side of the substrate is inductive, the operating frequency is reduced and the operating bandwidth is increased. A very efficient biasing circuit has been designed to control all the varactors where simulation results show that, by tuning the varactors from 4.08 pF to 0.95 pF, the operating frequency of the MS can be tuned from 1.08 to 1.61 GHz.

"Artificial Dielectrics Metamaterials for Antenna Applications"

Shiyu Zhang, Yiannis Vardaxoglou, Will Whittow, Wolfson School of Mechanical, Electrical and Manufacturing Engineering, Loughborough University and Raj Mittra EMC Laboratory, University of Central Florida, Florida, USA & EE Department, KAU, Saudi Arabia