Armms RF and Microwave Society
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Conferences

Monday 9th November to Tuesday 10th November 2015 at Wyboston Lakes, Wyboston

The November 2015 was held at Wyboston Lakeson Monday 9th and Tuesday 10th.

Young Engineer Sponsorship: Sarah Heywood of e2v and Mofei Guo of Bringham University were awarded Young Engineer sponsorship for the November 2015 meeting. The ARMMS RF & Microwave Society offers sponsorship to young engineers (28 or below) who have papers accepted for presentation. Sponsorship is £100 cash plus free attendance (including conference dinner and overnight accommodation). Potential candidates should identify themselves as eligible at time of submission and state their date of birth. This offer is limited to a maximum of 2 places per meeting.

Best Paper Award: The Steve Evans-Pughe prize for the best presenter was awarded to Rajan Bedi of Spacechips, the runner up was Jonny Lees of Cardiff University. The award is £200 for the best paper and £50 for the runner-up. The prize is sponsored by AWR.

 

VENUE

Wyboston Lakes
Great North Road
Wyboston
Bedfordshire
MK44 3AL

Tel0333 7007 667
Emailsales@wybostonlakes.co.uk
Webhttp://www.wybostonlakes.co.uk/

PROGRAMME CO-ORDINATOR

Chris Oxley
De Montfort University

Tel07808 739763
Emailchoxley@dmu.ac.uk

PAPERS

18 GHz In, 6 GHz Out Satellite Transponders Without Local Oscillators or Mixers

Dr Rajan Bedi
Spacechips Ltd

RF, satellite-transceiver technology has evolved from the traditional superhetrodyne architecture used on the Inmarsat 4 and Alphasat telecommunication payloads, to a software-defined radio approach using under-sampling, wideband ADCs to directly digitise S-band carriers and return-to-zero DACs to reconstruct the digital baseband up to almost 6 GHz. The next generation of transponder will exploit advances in analogue circuit design to directly digitise 18 GHz, communications traffic and output C-band IF/RF without the use of local oscillators or mixers.

Current, state-of-the-art, RF, transponder research is able to deliver higher performance than software-defined radio, mixed-signal transceivers by exploiting novel advances in wideband circuit design and SAW-based oscillators. The result is higher SNR and better SFDR due to improved linearity.

Future, RF transponders will be smaller, lighter, lower power consuming, higher performing, more reliable and significantly less expensive to manufacture, test and sell. Production testing and measurement will remain RF in nature, without the need to characterise traditional, individual IF stages.

All of the above benefits will allow OEMs to deliver the next generation of transceivers which will enable spacecraft operators to offer competitive Ku-band services overcoming the congested bandwidths at traditional, lower, satellite-communication frequencies.


A New Multi-passband Filter Synthesis Technique

Mofei Guo
University of Birmingham

 

This paper looks at a new design method for resonator-based multi-passband filters. The technique is able to design an arbitrary number of passbands. The design procedure is based on calculating the coupling matrix for a particular topology of coupled resonators. The physical design parameters, such as the centre frequency of each resonator, the coupling between resonators and the external Q-factors can all be analytically synthesised with the requested filter specifications. In the paper we will show designs for both Chebyshev and quasi-elliptic multi-passband filters. Theoretically, this method can obtain any number of passbands with each band shares the same shape.

Two theoretical and one practical example of filters designed through this method are given; the three examples are: (1) A 10th order even bandwidth five-passband filter with Chebyshev response; (2) A 20th order uneven bandwidth five-passband filter with quasi-elliptic response; (3) Measured results from an X-band waveguide resonator based multi-passband filter.


A Study of the Mechanism of the Nonlinear Input Capacitance on the RF Performance in GaN HEMT Devices

Mirza Rasheduzzman
University of Sheffield

The nonlinear input capacitance characteristic in GaN HEMTs affects the linearity of the output signal and limits the device performance by generating intermodulation distortion at the input of the circuit. This effect has been discussed extensively and design approach such as pre-linearization technique has also been suggested to compensate the impact. In this paper, the mechanism behind this behaviour is examined as a function of input power and frequency using a lumped element based model. An RLC circuit formed by the gate resistance, inductance and the input capacitance is considered at the input. Its response and impact on the input signal before it reaches the intrinsic current generator are observed for both linear and nonlinear input capacitance. Simulation results show that the distortion due to the harmonics created by the nonlinear capacitance is higher at large-signal and at operating frequency lower than the self-resonance frequency of the RLC circuit. At frequency much higher than the self-resonance frequency, there are no harmonics; however the signal is strongly attenuated. The results also show that the operation at self-resonance frequency must be avoided due to potential detrimental effect on the device as the output signal can become higher than the device breakdown voltage.


E-band Transceiver Design at Filtronic

Chris Buck
Filtronic Components

The massive growth in mobile data is making increasing demands on backhaul capacity. Existing point to point links make use of ~15GHz of total bandwidth distributed in narrow licenced bands between 6 to 42GHz. These are already running close to capacity and more bandwidth is urgently needed to keep pace with the forecast growth in mobile data. An additional 21GHz of bandwidth has been allocated in V, E and W bands (57 to 95GHz), and is now coming into use. These frequencies offer opportunities to use much wider channels, up to ~2GHz, and the potential for data rates up to ~10Gbps.This paper will deal with some of the design challenges presented in making low cost, high performance transceivers at these frequencies, particularly in the areas of MMIC technology. Considerations will be made of manufacturing tolerances and process variation, operation over a specified temperature range, reliability and stability, integration into transceivers and testability. The relevant microwave parameters simulated will be presented and will show good agreement with actual measurements.


GaN Microwave Transistors: How the Reliability Challenges Have Been Solved

Prof Mike Uren
University of Bristol

Microwave transistors based on GaN can deliver outstanding performance because of basic material advantages of high breakdown voltage, high carrier density and good mobility. They now deliver unmatched lifetime and robustness, are space qualified, and are displacing traditional solid-state technologies in numerous applications.  However, this performance did not come without a struggle. The primary problem areas which have impacted the performance and reliability of GaN microwave devices will be identified, and the techniques discussed which have been used to control or mitigate their impact. The talk will highlight the control of current-collapse from surface and bulk traps, the suppression of high-temperature reverse-bias gate edge breakdown, and the impact of the epitaxial growth approach on the crucial parameter for reliability - thermal resistance.


Heterodyne Mixing of Acoustic and Microwave Signals Using a Beam-lead Schottky Diode

Sarah Heywood
E2v

This paper looks at the use of a microwave (W-band) beam-lead Schottky diode for heterodyne detection of acoustic waves with frequencies up to about 100 GHz.  A W-band reference frequency, (local oscillator, LO) for the detector is provided by a 94 GHz Gunn diode oscillator coupled to the Schottky diode via a waveguide. Coherent acoustic waves are generated in the GaAs substrate of the device using a femtosecond pulsed laser. The electrical output is detected from the Schottky diode at the difference frequency between the Gunn oscillator and the acoustic signal, which was in the 0 – 12.5 GHz range, using a high-bandwidth digitizing oscilloscope. The idea of using an integrated acoustic LO in a down -conversion mixer will be examined.


Investigation of GaN FET Optimal Harmonic Terminations Using a Simplified Compact Large Signal Model

Dr Jonathan Leckey
MACOM, Belfast

There remains ongoing debate in the high frequency PA community as to which class of operation eg Class J Class F, Class Inverse-F etc is most suitable for optimizing the efficiency of the GaN FET PA. While active load pull measurements can be useful in observing actual termination sensitivities they do not necessarily explain the class of operation at the intrinsic current generator plane, without significant de-embedding, or reveal more subtle effects of device non linearity.  A simplified compact large signal model was developed with emphasis on low number of parameters and robust, fast convergence under high harmonic reflection coefficient. The model has been constructed in a piecewise fashion to enable the effect of each of the intrinsic nonlinearities for example gate-source charge, to be easily disabled or examined. The model includes a thermal sub-circuit, while trapping effects have been neglected in the first instance.  The model has been used to examine harmonic terminations and waveforms at the intrinsic current generator plane.


Microwave and RF Measurements in Astrophysics and Cosmology - an Overview of Applications and its Technology Drivers

Dr Giorgio Savini
University College, London

The Cosmic Microwave Background radiation has been object of increasingly detailed measurements from the ground and in space for the past 5 decades. Together with a number of galactic and extra-galactic signals which present themselves as impairing foregrounds for cosmology but which carry significant astrophysical significance of their own, the astronomy instrumentation community has been developing microwave and RF receivers of increased complexity to achieve greater precision and accuracy in their measurements in order to advance the knowledge of this field.

In this talk I will attempt to give an overview of the astrophysical and cosmological signals to be measured and the drive in technology development which they triggered.


Microwave Power Amplifiers, Resonant Structures and the Rapid Diagnosis of C-difficile and other Antibiotic Resistant Bacteria

Dr Jonny Lees
Cardiff University

The spread of antibiotic resistance is a growing threat to our ability to treat infectious disease, due largely to the “blind” prescribing of antibiotics, and is in part a consequence of our inability to determine the antibiotic susceptibility of the infecting bacteria in real time.  Current bacterial detection methods take typically several hours and sometimes days to produce accurate results and as a result, tend to be used to confirm rather than to prevent infection. This talk describes how high-efficiency microwave amplifiers and microwave resonant cavities are enabling a prototype bacterial DNA detection system that is able to identify specific pathogens within minutes; a change that promises to reduce patient suffering and morbidity, and help extend the utility of the remaining effective antibiotics.


Microwave-enhanced Heterogeneous Catalytic Decomposition of Carbetamide and Chloroluron

Dr George Chi Tangyie
De Montfort University

Growing population and industrial activities mean that fresh and potable water resources are declining at an alarming rate with the generation of vast amounts of wastewater and subsequent release of contaminants in to water courses. Heterogeneous advanced oxidation processes constitute a promising technology for the treatment of wastewaters containing non-easily removable organic compounds.

However, some reactions rates are very slow, thereby limiting the scope of application especially with regards to throughput. In this paper we report a method for the treatment of toxic and recalcitrant contaminants such as carbetamide and chlortoluron in wastewater by enhancing the rate of a heterogeneous catalytic treatment process using microwave energy.

The use of 80W CW microwave power (2.45GHz) in a multimode cavity under atmospheric pressure increased the rate of decomposition of the organic pollutants (100mL of 20mg/L carbetamide and chlortoluron solutions, pH 4.6, 300mg/L H2O2, and 4g catalyst) by 2.6 folds in comparison to conventional isothermal reactions performed at 32oC. Most significantly, a 32% rate improvement was observed when microwaves were used in comparison to conventional heating under the same temperature profile.


Microwave-to-Terahertz Properties and Applications of Graphene

Prof Klein Norbert
Imperial College

The unique electronic properties of graphene are attractive for a variety of device applications in microwave-to-terahertz technology. For frequencies up to several 100 GHz, graphene behaves like a dispersion-free resistive sheet, the value of its sheet resistance can be controlled by an external gate voltage. This property enables the realization of electrically controllable attenuators, fast switches and modulators for frequencies up to the terahertz range. Due to hot electrons in graphene, highly sensitive and ultrafast graphene THz detectors have been demonstrated, which have a strong potential to outperform other detector types operated at room temperature. In the terahertz-to-mid-infrared range, the excitation of plasmon type surface waves enables promising application as label free electromagnetic biosensor devices.

In this presentation, a realistic overview about microwave-to-terahertz applications of graphene will be given, and the application potential in context with the state-of-the art of graphene technology will be discussed.


Millimetre-Wave and Terahertz System-on-Substrate Technology: Prospects and Challenges

Prof Ian Robertson
University of Leeds

The millimetre-wave frequency range has received renewed interest for 5G+ wireless networks, including machine-to-machine (m2m), body area networks and the Internet of Things (IoT). System-in-package (SiP) or system-on-substrate technology is vital for the realisation of miniature millimetre-wave systems, especially some of the very advanced massive MIMO antennas that have been proposed. SoS technology provides a multi-technology platform by which integrated circuits, devices and components from any technology (Si/SiGe, GaAs, GaN, InP, etc.) can be integrated to form a system alongside high performance passive components. There remain significant challenges to address. On the one hand, there is an urgent need to push down the cost of millimetre-wave systems. On the other, there is a significant technical challenge to be overcome in order to push the performance envelope so that SoS solutions can be employed for systems beyond 100 GHz, including terahertz systems - as and when the necessary devices become commercially available. System-on-substrate technology will be a key enabler for the explosion in applications of the millimetre-wave bands for applications such as 5G+, IoT, m2m communications, biosensing, imaging, security screening, etc.


Re-Assessment of the 450 Heat-spreading Approximation used in the Calculation of the Thermal Resistance of RF Power Transistors

J.L.B. Walker
Integra Technologies, Inc.

The original paper in which the 450 heat-spreading approximation was first proposed showed that in the worst case the error was around 10% for a device mounted on a semi-infinite heatsink. It will be shown in this paper that when applied to the calculation of the thermal resistance of an RF power transistor that it can under-estimate the thermal resistance by up to 30%. The effect of using smaller heat-spreading angles in an attempt to improve the accuracy is also investigated.


Resonant Tunnelling Diode Terahertz Sources for Broadband Wireless Communications

Dr Edward Wasige
University of Glasgow

The terahertz (THz) frequency range (0.1 THz to 3 THz) has been receiving considerable attention recently because of the inherent advantages it offers, e.g. wider bandwidths, improved spatial resolutions compared to RF electronics, and the new sensing opportunities such as inspection of sealed packages, concealed weapons detection, chemical and biological agents detection, medical diagnostics, etc. The opportunities are clear, but there is a distinct lack of compact, robust, efficient and all solid-state sources offering powers greater than 1 mW, that operate at room temperature in this frequency range.  In this talk we will review such sources that are based on resonant tunnelling diodes (RTDs). RTDs are the fastest purely electronic solid-state devices, and RTD oscillators have achieved record fundamental oscillations at 712 GHz (over 25 years ago ) and 1.55 THz recently, though with very low output power, tens of micro-Watts, respectively. These oscillation frequencies are currently beyond the highest frequency transistor oscillators built to date. Detection experiments have demonstrated that the negative resistance responsible for these oscillations may persist to frequencies as high as 2.5THz, indicating the potential of RTDs as a technology platform for THz electronics. Our work at the University of Glasgow on this topic has achieved W-band (75 - 100 GHz) and D-band (110 – 170 GHz) oscillators with around 1mW and 0.5mW output powers, respectively. The designs are being revised for higher output powers and now also being scaled into the terahertz frequency range. We will discuss the design approaches to realising such milli-Watt RTD-based THz sources and also preview work that is being done within the European Commission H2020 project, iBROW, work that addresses the last mile challenge/networks and that is based on integration of the RTD device technology with laser diodes and photo-detectors to pursue the development of a unified technology that can be integrated into both ends of the wireless link, namely consumer portable devices and fibre-optic supported base-stations to enable its deployment in 10 Gbps short-range wireless communication devices in the short term and paving the way for 100 Gbps in the long term for both the millimetre-wave and THz frequency bands, seamlessly integrated with optical fibre networks.


RF in Healthcare-Friend or Foe

Dr Peter Jarritt
Cambridge University Hospitals NHS Foundation Trust

The application of radiation in healthcare of whatever frequency is governed by the interaction of the radiation with tissue and the balance of risk and benefit in the delivery of patient benefit. For ionizing radiation this is well understood, however for non-ionizing radiation across the RF spectrum the balance of risk and benefit is less well understood. This is primarily due to the fact that the interaction with tissue is poorly understood except in higher power applications. The continuing concern that mobile phone use has the potential to mediate brain tumours is an exemplar of the lack of clear evidence and understanding. The application of RF in healthcare environments is further complicated by the potential for adverse interactions between electrical and electronic systems. It is not often possible to test all potential interactions of devices in the healthcare context and thus regulation tends to restrict technology adoption especially where there is documented potential for patient harm.

Within this context the application of RF in healthcare can be divided into a number of discrete classes. Firstly, communications and identification technologies where applications such as the management of medical devices and the asset base using RFID and radio communications are slowly being adopted. Healthcare will not be immune from the technology supporting ‘the internet of things’. This application has the potential to greatly increase the efficiency and safety of use of medical devices. Secondly, the generation of heating within tissues to deliver the ability to kill tumour cells whilst preserving normal tissues – hyperthermia or, at higher power, direct tissue ablation and destruction. This is used in surgery through diathermy to cauterize tissues during surgery and prevent excessive bleeding. One of the most important applications of RF in healthcare is in the development of MRI imaging. This has become one of the highest resolution’s, in-vivo imaging technologies with the growing potential to provide quantitative, functional discrimination of tissues, however the increase in magnetic field strength has led to safety concerns due to induced currents and heating within the body.  The application of NMR in-vitro is an established technique. More recently there have been developments in the application of multi-spectral RF technologies to characterize tissues. This is being commercialized to provide a method to monitor cerebral blood volume and changes through intra-cerebral bleeds or stroke. This has the potential to significantly change clinical practice in the management of traumatic brain injury.

This paper will provide a review of these key applications, the physical interactions that are exploited and often limit the application and the risks and benefits in the healthcare environment. The regulatory framework that needs to be applied will be highlighted.



EXHIBITION

Companies booking two or more delegate places are able to take part in the commercial exhibition that accompanies the conference. Please note: there is a maximum of 20 exhibition tables at each meeting, these are offered on a first come basis. Booking two delegate places does not guarantee an exhibition spcae, please email exhibition@armms.org to check availability and reserve and exhibition space.


SPONSORSHIP

The ARMMS RF & Microwave Society thanks Keysight for sponsoring the November 2015 meeting:


CALL FOR PAPERS

Contributions are invited with an emphasis on RF and microwave design, research, testing and associated subjects. An oral presentation will be made at the meeting and a written paper will be required for publication in the society digest, which is distributed to delegates at the meeting. Prospective speakers are requested to submit a title and a short abstract to the technical coordinator (see above) as soon as possible.

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