Reconfigurable photonic antennas

Sharing the electromagnetic spectrum and the physical space for multiple wireless applications in commercial and military applications has resulted in large and complex integrated solutions. Traditional microwave approaches required to look for other alternatives to overcome the aerodynamics limits of front-end devices, particularly in airborne platforms. The implementation of Microwave Photonics techniques to remote microwave antennas is increasingly finding more and more application in airborne Electromagnetic Support applications. This is not only because optical fibres are excellent substitutes of bulky transmission lines (e.g., coaxial and rectangular waveguide) but also because traditional microwave signal processing techniques can also be implemented using photonic techniques.

The aim of this dissertation is to investigate the use of Microwave Photonic technologies and photonic signal processing techniques as a means of improving front-end receivers for wireless platforms, particularly for airborne Electronic Warfare applications.

This work focuses in specific on the development of a single shared aperture sensor for Electromagnetic Support applications such as early detection radar and direction finding.

The use of photonic signal processing techniques such as polarisation diversity, multiplexing and transversal techniques is proposed to control the radiation characteristics of multifunctional broadband antennas.

Major contributions made by this work include the derivation of a flexible and broadband receiving “wireless kiosk” suitable for current and future integrated multiple antenna systems. The design and development of an orthogonal mode transformer that enables the multi-mode operational characteristics of broadband frequency independent two-arm spiral antennas. The implementation of a Photonic 180° hybrid coupler that controls the radiation modes of a multi-mode two-arm spiral antenna. The implementation of a microwave photonic mode transformer using photonic signal processing techniques that substitutes complex and bulky microwave mode transformers such as microwave Butler matrices. In specific, photonic transversal techniques were used to implement 90° photonic hybrid couplers that, combined with 180° photonic hybrid couplers, controlled the radiation patterns and polarisation characteristics of a multifunctional four- arms sinuous antenna.