Electronically beam-steerable array antennas (phased arrays or smart antennas) at microwave and millimetre-wave (mm-wave) frequencies are extremely important for various wireless systems including satellite communications, terrestrial mobile communications, radars, "Internet Of Things", wireless power transmission, satellite navigations and deep-space communication. Traditionally, beam steering of antenna is achieved by moving the reflector mechanically, which is slow, bulky and not reliable. Phased arrays, which integrate antennas and phase shifter circuits, are an attractive alternative to gimbaled parabolic reflectors as they offer rapid beam steering towards the desired targets and better reliability. Phase shifters are critical components in phased arrays as the beam steering is achieved by controlling phase shifters electronically. A promising research direction to create small, fast, reliable phase shifters with low insertion loss at high frequency is the use of tunable dielectric materials due to its potential of monolithic fabrication of array antennas and circuits. A breakthrough in such materials came recently when we demonstrated that Lead Niobate Pyrochlores PbnNb2O5+n gives the best combination of dielectric constant, tunability and low loss of any known thin film system. Translating these superior materials properties into actual device performance and high-performance electronically beam-steerable arrays antennas at microwave and mm-wave bands are the key aims of this project

In response to the growing demands for delivery of content-rich and delay-sensitive services, network architectures for 5th generation and beyond wireless communication systems are becoming more and more dense. This illustrated through the ever increasing deployment of small cell networks as well as machine-to-machine (M2M) communications. This trend, whilst improving network capacity, will still necessitate reuse of available resources such as frequency spectrum within smaller areas by larger number of nodes/cells, which in turn would adversely affect the quality of service. On the other hand, by allowing simultaneous transmission and reception in the same frequency band, In-band Full-Duplex Communication (IFDC) technology potentially enhances the spectral efficiency of a single point-to-point (P2P) channel by 100% over the conventional half-duplex communication. IFDC also enables the nodes, e.g. in P2P scenarios, to receive channel feedback or sense other channels whilst transmitting data, which shortens the latency compared to conventional half duplex communication with time-division-duplexing. Moreover, using full duplex relay nodes in multi-hop scenarios can potentially reduce the end-to-end latency by enabling simultaneous receiving and relaying. Practical implementation of this technology requires rigorous interference cancellation methods at each node to suppress the strong self-interference imposed on the receiver by the transmitter of the same node. The major bulk of research on IFDC has focused on self interference cancellation (SIC), and the respective state-of-the-art technology can achieve a high level of SIC at full duplex terminals; hence the IFDC technology has become closer to commercial deployment by industry. Deploying IFDC in realistic dense settings entails new range of technical challenges, and opportunities alike. IFDC can yield substantially greater network throughputs and delay reductions over half duplex networking by deploying the technology in denser networks. However, attaining such gains demands for efficient scalable resource allocation and multi-node interference control methods. This great potential of 'full-duplex dense networks' in 'scalable service provisioning' has not been addressed to date by the research community in sufficient depth. At physical-layer, new resource allocation challenges arise in IFDC networks; for instance, in the design of concurrent channel sensing and data transmission, and in adapting transmit power of the nodes to their variable self-interference. Also, using IFDC in dense scenarios will affect design of the protocols in the higher layers; for instance IFDC would entail greater chance of packet collisions and multi-node interference, which demands for new medium access control (MAC) protocols suited to the emerging dense full duplex networks. Furthermore, IFDC will enable full duplex relaying in multi-hop communication, hence requires new Forwarding-layer/Network-layer protocols to deal with the new full-duplex forwarding paradigms. For conventional half duplex scenarios it is known that network throughput and quality of services can be improved through cross-layer methods, particularly with co-design of physical and MAC layers or MAC and Network/Forwarding layers. In fact for optimal scalability of heterogeneous services in full duplex dense networks, cross-layer approaches are inevitable. This project aims to propose systematic design of resource allocation and interference suppression techniques and algorithms at physical, MAC and Forwarding layers in order to enable substantial throughput gain and delay reduction by deploying full-duplex communication in dense wireless networks. These new methods will pave the way for deploying scalable service provisioning in the emerging dense wireless networks.

Abstracts are not currently available in GtR for all funded research. This is normally because the abstract was not required at the time of proposal submission, but may be because it included sensitive information such as personal details.

Acoustic wave devices exploit the higher speed of sound in solid materials than air by converting electrical energy into acoustic energy by piezoelectricity. Devices such as Surface Acoustic Wave (SAW) devices and Bulk Acoustic Wave (BAW) devices can filter high frequencies in the acoustic domain and form the backbone of mobile telephony base stations and radar. Unfortunately, piezoelectrics do not exhibit the highest acoustic wave velocities, and high velocity materials such as diamond do not exhibit piezoelectricity. This limits incumbent SAW technologies to around 2GHz. Piezoelectrics also have very limited thermal conductivity which means that operation at high powers is not possible. There is an increasing drive to create new materials combinations to realise higher frequency devices as evidenced by Murata's "Incredibly High Performance" (IHP) SAW filter which combines the piezoelectric LiTO3 and silicon. Diamond would be a natural extension of this technology with the highest of all acoustic wave velocities as well as the highest thermal conductivity of any electrical insulator. Unfortunately, the coupling between diamond and most piezoelectrics is relatively weak which leads to high insertion loss. This project aims to alleviate this issue with a Surface Activated Wafer Bond (SAWB), which also circumvents the high temperature and harsh environment of diamond growth which can significantly damage piezoelectric materials. By bonding at room temperature, it will be possible to combine high performance piezoelectric single crystals with diamond over large areas for unrivalled performance. The superlative acoustic wave velocity of diamond provides for high frequency operation whilst the thermal conductivity simultaneously unlocks high power operation currently unavailable to any other SAW platform (piezoelectrics are inherently of low thermal conductivity). This platform will have multiple applications from 5G base station transceivers to quantum memories.

Future intelligent, autonomous platforms (autonomous vehicles, robots, satellites, ships, air planes) and portable terminals are expected to have multiple functions such as wireless communication (with satellites and/or terrestrial base stations and/or ground terminals), ultra-fast data transfer, navigation, sensing, radars, imaging and wireless power transfer. These wireless systems operate at various frequencies. As a single radio frequency (RF) system usually has a narrow bandwidth, multiple RF systems at different frequency bands are often employed, leading to a huge increase in the volume, power consumption and cost. To address this need, it requires a single-aperture ultra-wideband (UWB) phased array capable of operating over an extremely wide range of frequencies, and having a low profile, wide-angle-scanning steerable beams, high gain, high efficiency and multiple polarizations (e.g. right-hand circular polarization for navigation, dual linear polarizations for mobile communication). Such an advanced antenna system does not exist yet. This project aims to tackle the ambitious challenges of addressing this need. This multi-disciplinary research consortium, having RF/microwave/mm-wave phased array researchers working together with researchers in optical beamforming and 3D printing, are ideally placed to development a new generation of low-profile UWB phased arrays, which is expected to find wide uses for both civilian and military applications.