Synthesis and new applications of multi-port filtering networks

Lead Research Organisation: University of Greenwich
Department Name: Electronic, Electrical & Comp. Eng., FES

Abstract

Microwave filters are essential components in many wireless systems from mobile base stations to satellites. They are used to select useful signals while rejecting unwanted interferences or spurious signals. The most widely used microwave filters are formed of resonators that are electromagnetically coupled together to generate the required transmission responses between the two ports - input and output. The properties of the resonators and the couplings between them can be mathematically represented by a so-called 'coupling matrix'. Such a matrix may be found - synthesised - from the required frequency response. The synthesis of two-port filters is an established art. Recently this coupling matrix approach has been extended from two-port filters to multi-port filtering networks (MPFNs).
The fundamental difference between a filter and a MPFN is the 'junction resonators', introduced to route the signal to different ports. Such resonators serve not only as resonant poles as in a filter, but also as splitters of the signal which are traditionally achieved by non-resonant transmission lines. One of the microwave circuits that benefit most from the MPFN concept is a multiplexer, also known as a combiner or a filter bank. It basically contains multiple interconnected filters, used to combine multiple channels and feed to one antenna for transmission or reception. It is one of the most complex passive circuits in wireless base stations and satellite payloads. Conventionally all the channel filters are connected to the common port through a signal distribution network based on transmission lines. Using the MPFN concept, the transmission line network can be replaced with resonators. This significantly increases the selectivity of the multiplexer without sacrificing the circuit size, which is highly desired by industrial applications. This means the multiplexer, usually a large component, can be reduced in size and mass for a more contact system. In the case of satellites, this can be translated to a significant cost reduction. The exclusive use of resonators in a microwave circuit also enables integrating filtering function into traditional non-filtering circuit. For instance, common microwave power dividers and couplers are transmission-line based with very limited selectivity. By using the MPFN concept, all-resonator-based power dividers and couplers can be realised with embedding filtering functions. This means two circuit functions are merged into one circuit. This approach is known as 'co-design'.
Despite the significant increase in the usage of the MPFN concept and co-design approach in microwave circuit design, there are still significant challenges associated with the technique. The synthesis of the MPFNs is much more demanding than the filters. It requires a new understanding of the coupling characteristics around the junction resonators. The currently inaccessible synthesis technique impedes the take-up of the MPFN concept by microwave engineers. Also there are concerns with the bandwidth and power handling capability of the MPFN-enable devices, as the junction resonator is narrowband in nature and may be a concentration of power. This project aims to develop a robust, more accessible and applicable synthesis technique for MPFNs and to address the practical challenges in bandwidth and power handling by proposing novel junction resonators. The research will help to release the full potentials of MPFNs for industrial applications. There is no doubt the MPFN concept will lead to more innovations in microwave circuits. Built on from the synthesis technique, the project will investigate two new circuit concepts. It is expected new research directions on novel microwave circuits, opportunities for further development and commercial exploration will be generated from this project.

Planned Impact

This research has been designed to have an impact beyond the academic domain. The project aims to raise the technology readiness level of the multi-port filtering network (MPFN) techniques and demonstrate their capability. This will bring the technology closer to industrial requirements. Companies have shown a lot of interests in various aspects of the research. This is evident from the support of this project by industrial partners from different sectors - space (ESA), telecommunications (Huawei) and defence (BAE Systems). The success of the research will also lead to new and enabling device technologies which will enhance the innovative capacity and competitiveness of the industries. The application of the MPFN concept to multiplexers has attracted lots of interests. Multiplexer is one of the most complex passive circuits in wireless systems such as satellite payloads and mobile base stations. The potential reduction in size and mass offered by the MPFNs is a huge benefit to satellites, which will result in a significant cost reduction. This is highly desired for the space industry. The multiplexers used in mobile base stations present a different challenge. This project will tackle the practical challenge and demonstrate the capability to the industry. Both communications satellites and mobile base stations are becoming an important part of our daily lives, to support the ever expanding need from personal communications, data transfer to TV. The improved device technologies will not only have an economic impact but also indirectly contribute to the better quality of life. For this research work to be translated into suc h impacts, commercial development may be required. The Pathway to Impact outlines the routes for commercial exploration.
The proposed research will have a broad impact on many aspects of microwave engineering. The synthesis technique will equip engineers with a new and more accessible tool for microwave circuit design. It underpins a range of passive microwave circuits such multiplexers, power dividers, couplers and coupler networks. The users of the research will further benefit from the information and the GUI interface to the synthesis code, provided through the website of the project.
The training of people is an integral part of this project. The close cooperation with industrial partners will provide the researchers and students the needed skills. The research will raise their awareness of both the intellectual challenges and the potential for industrial applications. This has far-reaching impact on the health and competitiveness of the industry.
This research will attract R&D investment from global business. This is evident by the support of Huawei Technologies, the world largest telecommunications equipment maker with a very strong international presence. The research also has the potential to attract funding from European Space Agency, who is another project partner of this proposal.

Publications

10 25 50
 
Description (1) We have developed an optimisation-based synthesis technique to generate coupling matrices that enable the design and implementation of a new class of multi-port microwave devices. We have produced a software tool with graphic user interface in order to facilitate the take-up of the techniques by design engineers and researchers.
(2) We have demonstrated a number of devices that verified the design concept of multi-port filtering networks in diplexers/multiplexers and tackled the practical challenges of bandwidth capability and physical implementation.
(3) We have opened up a new research area of integrated filtering antennas and attracted significant interests from Satcom and 5G industries.
Exploitation Route (1) We will continue the engagement with industries to promote the developed techniques as well as to gauge requirement and shape our research. We have kept the project partners informed through interim reports and face-to-face meetings throughout the project. As a results, we have been invited to present the research outcomes three times to two partners. We have been conducting feasibility case studies based on several new industrial requirements using the techniques and concepts developed form this project.
(2) We have published a number of research papers and presented in several conferences. A few more research outputs are being peer-reviewed by journals and conferences. The PI organised one IET annual conference (2016) and one topical workshop at the European Microwave Conference (2016) which provided many networking opportunities with expert academics and researchers in the field. later this year, the PI will be presenting in one international conference as an invited speaker and one UK conference mainly to an industrial audience.
(3) One postdoc researcher funded by the grant and one PhD (not funded) were involved in the project. Two more PhD students joined the team as scholarships were secured towards the end of the project. The two students have been following on the emerging research areas identified by the project.
Sectors Aerospace, Defence and Marine,Digital/Communication/Information Technologies (including Software),Electronics

 
Description We have seen noticeable attention and take-up of the techniques and concepts developed by the project. We have received several requests to assess the feasibility of devices with written technical specifications. We have been invited to present the research outcomes three times to two companies. We have completed one case study with an application scenario defined by a company and currently undertake further studies.
Sector Aerospace, Defence and Marine,Digital/Communication/Information Technologies (including Software)
Impact Types Economic

 
Description PhD Scholarship (fee waiver; 2016 - 2019)
Amount £42,000 (GBP)
Organisation University of Greenwich 
Sector Academic/University
Country United Kingdom
Start 11/2016 
End 11/2019
 
Description REF PhD Scholarship
Amount £66,000 (GBP)
Organisation University of Greenwich 
Sector Academic/University
Country United Kingdom
Start 05/2016 
End 04/2019
 
Description Research contract with Huawei Technologies
Amount £18,000 (GBP)
Organisation Huawei Technologies 
Sector Private
Country China
Start 03/2015 
End 11/2015
 
Description CAS 
Organisation Chinese Academy of Sciences
Country China 
Sector Public 
PI Contribution Joint development of a new device technology. My team is responsible for device design and brings expertise of microwave engineering into the partnership.
Collaborator Contribution The partner is specialised in microwave dielectric materials and process. They are responsible for the fabrication of the device and process optimisation.
Impact A joint publication was submitted in Jan 2017.
Start Year 2014
 
Description CTTC Spain 
Organisation Telecommunications Technology Centre of Catalonia
Country Spain 
Sector Charity/Non Profit 
PI Contribution Conduct theoretical work in a joint device design and perform measurements.
Collaborator Contribution Conduct CAD design and perform measurements
Impact Joint publication and joint grant application are expected.
Start Year 2014
 
Description Ningbo University 
Organisation Ningbo University
Country China 
Sector Academic/University 
PI Contribution Idea development and paper co-authoring
Collaborator Contribution Idea development and paper co-authoring
Impact Joint publications; Involvement in grant application.
Start Year 2016
 
Description University of Kent 
Organisation University of Kent
Department School of Engineering and Digital Arts
Country United Kingdom 
Sector Academic/University 
PI Contribution Collaboration on filter and antenna integration and co-design. Co-supervise a PhD student and advise on his research work especially in relation to the filter design aspect; Provide measurement facility.
Collaborator Contribution Supervise the PhD student; Provide expert advice on the antenna design work to my research team; Advise on research project management.
Impact Joint publications.
Start Year 2015
 
Title Software tool with GUI for the synthesis of multi-port filtering networks 
Description A software tool with GUI has been developed for the synthesis of multi-port filtering networks such as filters, multiplexers, filtering power dividers and some other generic multi-port resonator-based coupling networks. 
Type Of Technology New/Improved Technique/Technology 
Year Produced 2016 
Impact (1) This tool has sped up the take-up of the techniques by research students in their research work. (2) This tool has been used to provide a number of coupling matrices to collaborators for their circuit design and development. (3) This tool has been provided to an industrial partner for evaluation and review which helped the company to appreciate the technology. 
 
Description Host of the Annual IET Active and Passive RF Devices Seminar 2016 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Postgraduate students
Results and Impact Hosted the annual seminar at University of Greenwich London campus with 50 attendees, which sparked questions and discussions.
Year(s) Of Engagement Activity 2016
URL https://communities.theiet.org/communities/events/item/41/75/10295
 
Description Invited talks in 4 universites/institutions (2016 summer) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact Given 4 invited talks in four universities and research institutions during the summer visit in China, which resulted in research collaboration and joint grant applications.
Year(s) Of Engagement Activity 2016
 
Description Organisation of a workshop in European Microwave Week 2016 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Organised and chaired a workshop dedicated to 'Microwave Passive and Active Devices with Integrated Filtering Functions' with over 30 attendees, which led to questions, discussions and enquiries from industries.
Year(s) Of Engagement Activity 2016
URL http://www.eumweek.com/
 
Description PhD student attending Loughborough Antennas and Propagation Conference 2016 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Postgraduate students
Results and Impact PhD student presented a poster, which led to a collaboration with another university on antenna project.
Year(s) Of Engagement Activity 2016
URL http://www.lapconf.co.uk/
 
Description PhD students and RA presenting at European Microwave Conference 2016 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Presented three research papers - one oral presentation and two posters by PhD students.
Year(s) Of Engagement Activity 2012,2016
URL http://www.eumweek.com/
 
Description Presenting at 37th PIERS, Shanghai 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Presented two papers, leading to discussions and request of further information.
Year(s) Of Engagement Activity 2016
URL http://www.piers.org/piers2016Shanghai/
 
Description UK ARMMS conference (3rd April) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact Dr Yi Wang will give a talk based on the outcomes of the EPSRC grant. This is to promote the techniques developed from this project and engage with UK industries.
Year(s) Of Engagement Activity 2017
URL http://www.armms.org/conferences/
 
Description Visit to project partner (Huawei) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact Visited the project partner at their RD centre, presenting research work and discussing collaboration opportunities.
Year(s) Of Engagement Activity 2015
 
Description Visits to project partner (BAE) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact Presented research work during the first visit, which led to the identification of several cases of interests. The results of the following feasibility studies were reported back in the second visit, which led to further feasibility case studies.
Year(s) Of Engagement Activity 2016