This proposal is a Platform Grant renewal. Our previous grant allowed us to develop the key characterisation facilities and enabled us to understand fully the materials that were the study of the grant. These materials were low loss microwave dielectrics, ferroelectric materials and thin films of these materials. The Platform renewal will build upon some remarkable discoveries that the team, including the key PDRAs, has made over the last 4 years and centre around functional materials for devices operating from microwave to millimetre wave or from MHz to THz. First it is important to explain the Materials Science progress that forms the underpinning technologies that will enable us to use the Platform grant to build new devices. At the heart of microwave devices are resonators that require low dielectric loss or very high Q factor and the target is to aim for very high Q dielectrics. Our previous Platform grant and indeed prior support from EPSRC allowed us to discover very low loss, high Q materials. This culminated in two significant discoveries. 1 First we were able to use low loss resonators as sensors for liquid sensing 2 Second, we demonstrated that by using a very high Q resonator we could achieve maser action at room temperature and in Earth's field - published in Nature 2012. This platform grant will enable us to build upon these discoveries. 1) Advanced Characterisation: In the first theme the aim will be to carry out a series of qualifying experiments to determine the best possible conditions and materials for sensing over the wide range of frequencies available to us (Hz to THz) 2) Microwave and mm wave sensors: The third theme takes the science to application. We will use the resonators for analysis of ions, biomolecules, proteins and cells. The sensitivity of the resonators allows nanolitre quantities to be analyzed very rapidly for possible cancer cell detection in blood and bacteria in water. 3) "UMPF" and "HEP" Cavities: In the second theme we aim to make UMPF (Ultrahigh Magnetic Purcell Factor) and "HEP" (High Electric Purcell) cavities. These are small resonant cavities with a very high Q given the very small mode volume and success here will enable us to improve electron paramagnetic sensing dramatically and enable single cell detection. Success in these new themes for the Platform would represent a remarkable step-change in technology.

The outcomes of SYnthesizing 3D METAmaterials for RF, Microwave and THz Applications (SYMETA) have the potential for significant academic, economic, societal and environmental impacts. To achieve these outcomes SYMETA will bring together leading expertise in engineering, physics and materials science from five institutions: Loughborough University, University of Exeter, University of Sheffield, Oxford University and Queen Mary, University of London together with twelve industrial partners from a range of sectors including defence and electronics manufacture. The Grand Challenge will be led by Loughborough University. SYMETA responds to Grand Challenge 3: Engineering across length scales, from atoms to applications. This Challenge area requires researchers to consider design across the scales for both products and systems looking at new approaches to bridge the meso-scale (intermediate-scale) gap and taking into consideration that many engineering systems are dynamic. SYMETA's grand vision is to deliver a palette of novel, multi-functional 3D metamaterials (synthetic composite materials with structure that exhibit properties not usually found in natural materials) using emerging additive manufacturing (AM), with the potential to support a single 'design-build' process. Our goal, to compile a palette of meta-atoms (the basic building blocks of metamaterials) and then to organise these inclusions systematically to give the desired bulk properties, opens up a plethora of new structures. This will not only improve existing applications but inspire new applications by breaking down barriers to innovation. Introducing these novel structures into the complex world of electronic design will offer a radical new way of designing and manufacturing electronics. The metamaterials will be developed to give end-users the electromagnetic responses they require, for a wide range of communication, electronics, energy and defence applications. The meta-atoms comprising the metamaterial will be micro-scale, i.e. small in comparison to the wavelength of operation, and fabricated from a range of new and existing raw materials, including the incorporation of dielectric, metallic and magnetic components. They will facilitate complex multi-component systems, incorporating elements such as inductors, capacitors, and resistors through to transmission lines and matching circuits and filters, to be created in hybrid and multi system AM - reducing waste, cost and timescales. The SYMETA project has three overarching research goals: 1. To synthesize a palette of 3D meta-atoms using suitable materials. 2. To construct designer-specified 3D arrangements of meta-atoms using process efficient AM to create metamaterials 3. To build demonstrators for applications at RF, microwave and THz frequency ranges. Supplementing these research goals SYMETA will: 4. Build a cohort of new knowledge by bringing together multi-disciplinary expertise from a number of institutions and companies and share this knowledge across academic networks. 5. Engage industry, sector relevant professional bodies and the wider academic community to ensure that the potential of this research is recognised and realised. To translate and condense the exciting science to key messages and outcomes and to communicate these to the public to boost the public understanding of science. The likely impacts of the SYMETA are manifold. It has the potential to transform manufacturing processes and to significantly shorten the time it takes for innovative new technologies to reach consumers whilst reducing waste and removing some of the more harmful processes associated with the manufacturing such as the use of harsh chemicals. This is transformation science, which could place the UK at the leading edge of engineering innovation stimulating economic growth and opening up huge potential for innovation in many sectors from consumer electronics through to defence and space.

Wireless communication systems require the translation of an information-bearing signal at higher frequencies (such as radio- or mm-wave frequencies) to allow propagation through the wireless medium (the channel). This translation is typically performed in transmitters and receivers that along with the channel form the communication system. In the transmitter, a power amplifier (PA) is used to boost the power of the signal to a level sufficient to overcome the channel's attenuation and arrive with sufficient signal strength at the receiver. Today's best PAs are capable of 60-70% efficiency when used at their maximum output power. This means that about 1/3 of the power is wasted into heat only for the purpose of amplifying at such higher frequencies. Efficiency decreases when reduced output powers are required. Modern communications standards such as 5G generate signals which present a large power variation over time (this is also described by the peak-to-average power ratio or PAPR) and this causes the PA to operate even more inefficiently with values down to 10-20%, instead of the aforementioned 60-70%. Wasting almost 90% of the DC power into heat causes additional demands on the energy supply network which may lead to an increase in carbon emissions. Higher DC power dissipations result in reduced transmitter performance (e.g. less output power and so less coverage), reduced battery lifetime, in additional weight, cost, and size because of the heatsinks and necessary cooling hardware. Heat dissipation causes the electronics within the PA to operate at higher temperatures which are known to degrade the component's reliability (ageing) and change their electrical behaviour. The goal of this project is to radically improve the RF PA efficiency by using a technique called supply modulation (SM). Unlike the 1952's envelope-tracking (ET) method, SM uses a very high-efficiency modulator to generate a number of voltage levels (Vmin, ..., Vmax) that are applied to the drain of the PA. When the RF output power in the PA is high, the PA is supplied with the maximum voltage level and so it operates at maximum efficiency. Vice-versa, when the PA output power is low, a lower voltage level is supplied to the PA drain. This change in the supply results in an efficiency improvement usually in the range of 20-30% (and so in a SM-PA efficiency of 30-50%), but most importantly, it typically reduces the DC power consumption by ~50% for the same output power. Achieving wider and wider bandwidths for high link capacities requires this SM-PA to commutate very rapidly as a consequence of a wideband signal. The current state-of-art bandwidth is ~100MHz for the SM-PA. Achieving 1GHz bandwidth, as required in multi-band and mm-wave PAs, is thus the target of this project. To achieve this, new circuit topologies combined with high figure-of-merit semiconductor technologies will be explored, with the unavoidable hardware imperfections compensated through signal processing techniques such as digital pre-distortion (DPD). The SMPA specifications and top-level design parameters will be agreed between the University of Bristol (UoB)'s team and the project's partners to ensure relevance for industrial applications. This SM-PA is firstly simulated in the SM part, then in the PA, and then co-simulated together as a complete sub-system. The fabricated prototype is then characterized in terms of linearity, efficiency, and power with the latest communication standards. The SM circuit can also be combined with existing PAs as an 'efficiency upgrade'. Results of this theoretical and experimental activity are presented at conferences and published in journals by the UoB team. Public engagement and industry impact is also ensured by the presence of an advisory board. In summary, this project is an adventurous research programme that will re-define next-generation RF transmitters amplifiers and so contribute to UK's leadership in wireless technologies.

Three-dimensional (3D) printing, also known as additive manufacturing, is now common place in many industries and is used widely. Some types of 3D printers are available for home use at modest cost. However, detailed work, together with demonstrator devices, is still in the very early stages in relation to the manufacture of microwave and terahertz circuits. These requires a level of precision and materials very different from the consumer products. This proposal is to evaluate and improve the performance of 3D printing for microwave and terahertz passive and diode circuits through measurement, design and demonstration. These high frequencies, from 10 GHz to 1000 GHz, are used for free space communications, security sensing and remote monitoring of the Earth's atmosphere. The focus will be on evaluation of 3D printed circuits at frequencies above about 50 GHz, the small feature sizes required for these frequencies allows only the best printing process to compete; enabling the project to evaluate the most advanced 3D printing approaches. This exciting project will be the most comprehensive academic study worldwide to date. A strong, experienced, national team, at the University of Birmingham and the STFC Rutherford Appleton Laboratory (RAL) will conduct the research in collaboration with several UK and international industry partners. The Communications and Sensing research group at Birmingham University have already demonstrated significant research in this area, with 3D printed devices published covering the frequency range 0.5 GHz to 100 GHz. The importance of this work has been recognised externally through prizes, invited international presentations and refereed academic publications. Birmingham's partners, the Millimetre Wave Technology Group in the RAL Space department, bring extensive expertise in precision manufacturing of conventional devices for these high frequencies, and knowledge of the demanding space and other requirements that the new 3D circuits must fulfil. RAL staff will conduct post processing of the 3D printed circuits and perform accelerated lifetime measurements under conditions of elevated temperature and humidity. 3D printed microwave and terahertz circuits will have an important beneficial economic impact on UK industry, not only because complex circuits become possible at low cost, but because new design approaches emerge because of the unique manufacturing. The applicants will both work on their own ideas, and closely with industrial partners, during the project. There are a number of hurdles to overcome before the technology becomes mainstream: this proposal tackles these challenges. The advantages of 3D printing include the availability to rapidly generate novel circuits with complex shapes and multiple functions using low material volumes in a lightweight form. This enables reliable, low cost, superior performance circuits with less waste and reductions in lead time. Considerations to be addressed include the metal coating of polymer circuits which adds an extra step in the production, as well as potentially lower thermal stability and power handling of such circuits. If the polymer is used as a microwave dielectric, power loss may be a problem. For metal 3D printed circuits, power handling and thermal stability is good, but surface roughness may reduce device performance. These problems and others are addressed in the proposal with a methodical investigation based on the measurement of resonant waveguide cavities, the microwave equivalent of a tuning fork. Changes to the frequency and decay time indicate the quality of manufacture. The project will inform industry and academia through a widely distributed technology development roadmap and external collaborative projects, as well as the provision of advice and guidance. Our finding will also be communicated to national and international colleagues through academic publications, and presentations at relevant conferences.

The extraordinary increase of wireless data traffic by smartphones and laptops, virtual reality, billions of IoTs or Industry 4.0 infrastructure need 5G, small cell densification and reduction of digital divide. High throughput connectivity everywhere is a fundamental requirement to support the growing data demand and the evolution of future wireless communication market. Affordable wireless networks with fibre data rate are needed. Wireless links with multi-gigabit (Gb/s) distribution at millimetre waves have been demonstrated up to 400 GHz. However, the strong atmosphere attenuation at the increase of frequency and limitations of the present semiconductor-based millimetre wave technology limit their potentiality. E-band wireless links with 2 GHz bandwidth and theoretical few Gb/s are already in the market, but large antenna footprint and low transmission power are probably preventing wider adoption. The portion of the spectrum above 100 GHz includes numerous wide bands which are presently unused, and could support tens of Gb/s, if adequate millimetre wave technology were available. In particular, the D-band (141 - 174.8) has about 28 GHz split in three sub-bands. The DLINK project aims to bring the UK at the forefront of millimetre wave wireless technology through the realisation of the first high capacity link at D-band with unprecedented performance, to provide 45Gb/s, over 1 km range, and with 99.99% availability in ITU rain zone K (typical of UK and Europe). The DLINK system includes a high power vacuum traveling wave tube (TWT) of new generation driven by a novel resonant tunnelling diode (RTD) transmitter with an integrated vector modulator. The system will be demonstrated in Frequency Division Duplex (FDD), with two bands of 10 GHz each to provide about 45 Gb/s data rate. The high performance of DLINK is enabled by traveling wave tubes as amplifiers, with about 10W output power, which is more than one order of magnitude than solid state amplifiers at the same frequency. The TWT working mechanism is based on the transfer of energy from a high energy electron beam, flowing in a waveguide with high level of vacuum, to the electric field generated by the input signal. No D-band TWTs are available in the market. Substantial challenges must be solved for an affordable microfabrication of mm-wave waveguides, due to small dimensions and three dimensional shapes. The transmitter will be an RTD oscillator with very low phase noise to support QAM modulation generated by an on-chip PIN diode vector modulator. The DLINK system includes two transmitters, one for each FDD channel, integrating a RTD oscillator/transmitter, a TWT and an antenna. For the first time, the property of a transmission link with 20 GHz bandwidth above 100 GHz will be investigated by field tests at BT. The DLINK project has a strong industry focus. It is a collaboration between Lancaster and Glasgow Universities with the strategic support of the wireless communication industry full chain, from devices to end users: IQE (semiconductor wafers), Filtronic (mm-wave links), Teledyne e2v (mm-wave TWT), Nokia (system manufacturer), Intel (chip manufacturer), BT (UK main network operator and end user). The high impact of the project will enable new architectures of wireless high capacity networks by mesh of high data rate links at mm-waves. The DLINK project has the ambition to fully contribute to "Connected Nation", one of the four Prosperous Outcomes and to benefit other numerous ambitions of the Prosperous Nation outcomes. DLINK involves researchers and PhD students of two leading research groups and a number of industry partners that will work together for the success of the project, with a long term strategy for future industry exploitation. A particular attention is devoted to growth of talent, improving the gender balance in the millimetre wave technology sector highlighting role models in the Lancaster and Glasgow teams.