Electromagnetic Performance Optimisation of Passive and Dynamic Linear to Circular Polarisation Converters


  • Electromagnetic Performance Optimisation of Passive and Dynamic Linear to Circular Polarisation Converters

Electromagnetic Performance Optimisation of Passive and Dynamic Linear to Circular Polarisation Converters

Principal Supervisor: Dr. Robert Cahill

Second Supervisor: Prof. Vincent Fusco

+ Project Description

Microwave linear to circular polarisers have received significant historical development stretching back to late 1950’s where methods from the optical domain were implemented using anisotropic dielectric layers. Other methods using meander lines arranged in a multilayer sandwich construction followed. More recently, in 2009, QUB developed a linear to circular polarisation transformer based on two FSS screens with unit cells composed of nested annular split slots. This was shown to exhibit low insertion loss when operated in transmission mode. In 2012 QUB developed for the first time, a single layer anisotropic impedance surface that works in reflection mode and exhibits a wide operating bandwidth, low reflection loss, and high angular stability, providing a significant improvement over previously reported polarisers. In addition the latter arrangement exhibited dual band functionality; for the same structure and polarization of the incident field, different output polarizations are achieved for different frequencies. The proximity of these frequencies can be tuned by the geometry of the structure. The simplicity of manufacturing is appealing, having only two metal layers (including the ground plane). Further recent publications on the concept advanced the design, and established its potential for operation in K/Ka Band satellite based antenna systems. A further interesting and more recent development of the concept is a new class of electronic reflection polarisers which provide dynamic polarisation agility. This is a desirable feature which can be deployed to reduce mechanical complexity, volume/mass/power budget, and simplify the instrumentation design of next generation radar, wireless and satellite telecommunications systems, many of which commonly require dedicated receive and transmit chains for each polarization state. The purpose of this project is to assess the current state-of-the art in active and passive transmission and reflection polarizers, and identify new opportunities to employ this technology in future space and terrestrial wireless systems. Current limitations in the technology shall be identified by considering the demanding electromagnetic performance specifications imposed on wave propagation in modern microwave systems. New design and manufacturing strategies will be developed to achieve the required bandwidth, polarisation purity, angular sensitivity and channel separation in orthogonal polarized systems. Numerical analysis and design using computational analysis programmes will be validated experimentally in a state of the art microwave laboratory.

+ How to Apply

Applicants should apply electronically through the Queen’s online application portal at: https://dap.qub.ac.uk/portal/

+ Contact Details

Supervisor Name: Dr Robert Cahill     

Queens University of Belfast
School of EEECS
Centre for Wireless Innovation (CWI)
NI Science Park
Queens Road,




+44 (0)28 9097 1851