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The papers presented at the SJ Technologies sponsored ARMMS RF & Microwave Society conference in Corby, UK, on 5 and 6 November, covered a wide range of topics in the RF and microwaves sector. The Society is a non-profit, independent professional society comprised of electronics engineers with an interest in high frequency design and measurement. It is run by a committee of ten volunteers assembled from industry and academia.
The committee’s chairman, Roger Hopper of Roke Manor Research, opened the conference and introduced a varied range of papers from component level design of GaN HEMT power amplifiers through to calibration issues associated with precise measurement of modulation. As has become the custom, the broad range of speakers from UK Industry and academia was complemented by eminent figures from further afield in Europe. These included Francois Bore of e2v (France) who provided details of an ADC operating at 2.2 GS/s, which is believed to be world leading currently, and Dr. Stelios Tsitsos of TEI, Serres, Greece who considered an equivalent circuit approach to ceramic filter design for UMTS.
At the end of proceedings delegates voted to decide who should be awarded the Steve Evans-Pugh Memorial Prize for best paper. The winner was Dominic Fitzpatrick of Cardiff University for his paper on sampling techniques for microwave characterization. This method allows very accurate characterization of large signal devices by deriving the waveforms present at the device itself. Fitzpatrick’s paper and the other papers are outlined below and can be downloaded.
By Liam Devlin, Plextek Ltd
This paper details the design, realisation and measured performance of a set of MMICs for broadband receiver applications. Five different MMICs are described: a 0.5 to 20 GHz dual channel limiter, a 2 to 18 GHz dual channel Low Noise Amplifier, a DC to 20 GHz dual channel Single Pole Double Throw switch, a 2 to 18 GHz upconverter and a companion downconverter. The MMICs can be used to implement a compact, dual channel 2-18 GHz receiver and an example of this is also described.
Download the PDF (520 kb)
By Paul Roberts, Fluke Precision Measurement Ltd
This paper describes the digital signal processing based techniques used to measure the modulated outputs of a new RF calibration source, and explores the challenges in assessing modulation measurement uncertainties and validating the results obtained.
Download the PDF (376 kb)
By Simon W Day, Phasor Design
The Software Defined Radio notion is a radio receiver consisting of antenna, analogue to digital converter with filtering, demodulation etc., implemented either in software or software configurable logic. In this scheme the performance of the ADC is particularly important and a sufficiently large amount of digital processing power may be necessary. However the technology is slowly becoming mature and applications are appearing.
The principal means of disseminating the UK national standards of time and frequency is the MSF signal, which is provided by the National Physical Laboratory. Transmission from Anthorn in Cumbria is 24 hours a day and the carrier frequency is maintained at 60 kHz to within 2 parts in 1012. The basic symbol rate is 10 Symbol/s and so a bandwidth of 10 to 20 Hz is required. The SDR arrangement is particularly well suited to a receiver for the 60 kHz MSF time signal, which is the subject of this paper. 10 Hz low pass filters with good Gaussian pulse performance can be implemented in software, which would otherwise be a little laborious and, in addition, good stability is inherent in the SDR method
Download the PDF (488 kb)
by Dominic FitzPatrick, Cardiff University
The most commonly used method for characterising microwave components is to measure the S-parameters of the device using a vector network analyser. A problem with this method is that the VNAs are essentially narrow band down converters and cannot handle harmonic and distortion products. By directly measuring the incident and reflected waveforms on the device ports with wide bandwidth samplers and then processing these waveforms, not only can large signal S-parameters be extracted but also harmonic and compression characteristics. The flexibility offered by the direct access to the sampling heads allows for the construction of measurement systems which can, for example, directly measure the multi-port devices with all ports simultaneously excited (such as phased array elements).
This paper describes the basic waveform measurement system developed at Cardiff University, and then some of the applications to which this system has been applied including, small and large S-parameter measurement, DC-IV device characterisation, active load-pull including harmonic, and four port antenna match. The potential for 'waveform engineering' and accurate large signal device modelling is also described.
Download the PDF (384 kb)
By Francois Bore, Atmel
A high speed ADC that offers good linearity over a range of high frequency inputs is a key component for tomorrow's broadband RF transmitters using high Intermediate Frequency (IF) architectures. New architectures for ADC enable performances to be achieved that were barely conceivable a few years ago. Broadband IF Sampling ADC architectures are today capable of directly digitizing wideband signals around second or first IF zones while keeping excellent linearity performance, paving the way to Software Radio.
The architectural shift to broadband data conversion leads to increased ADC sampling rate thus creating new challenges in design, package and test methodology. A 10-bit 2.2 Gsps ADC has been developed based on a 75 GHz SiGe HBT process, including special features for better industrial test coverage. Key issues for design, test and circuit specification, together with characterization results are presented and analyzed.
Download the PDF (824 kb)
By Dr. Stelios Tsitsos, Technological and Educational Institute (T.E.I.) of Serres, Greece
The rapid development of today's mobile communication systems has produced a huge number of compact and inexpensive handheld communication sets. Very small sized filters suitable for GSM, DCS, UMTS and other technologies have been produced by utilising high dielectric constant and low loss ceramic materials. A common problem during the manufacturing process of such components is the considerable amount of time spent during the trimming process to achieve the desired frequency response. An improved design method is presented and can be employed to provide reliable components ‘straight out of the box’. Computer-aided analysis techniques of ceramic filters have been presented and in this paper an accurate approach for the design of ceramic monoblock filters is presented. This technique makes use of an equivalent circuit as the basic design and tuning tool. This equivalent circuit is based on the extraction of equivalent circuit parameters from first electromagnetic principles and provides an accurate model for the ceramic monoblock structures.
Download the PDF (284 kb)
By Ivan Boshnakov, Aerial Facilities Ltd
In the recent years wide band gap transistors (SiC MESFETs and GaN HEMTs) have appeared on the market for high power RF/microwave transistors. They offer higher power density and higher voltage operation, which in turn are associated with much lower parasitic capacitances and much higher load-line dynamic resistance, and hence wider bandwidth applications. Of the two kinds the GaN HEMTs offer higher gain performance. This paper compares the performance of a 10 W GaAS MESFET which has been very popular for years and a new 10 W GaN HEMT by describing the practical design of 10 W Class A amplifier stages with the two transistors.
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By S.V. Potter, EADS Astrium (UK) Ltd
Some communication satellites have an antenna that consists of a fixed parabolic reflector that is fed by an array. Such antenna systems can be programmed to produce a variety of fixed beams in response to traffic demands and can be built so that each array element is fed by its own high power amplifier. However, benefits can accrue if the amplifiers are incorporated in Multiport Power Amplifiers. Ideally all the MPA inputs are divided equally between all amplifiers and there is a one to one correspondence between the MPA feed ports and the MPA array ports. Due to imperfections in the INET and the ONET, and differences between the amplifiers, the ideal behaviour is never realized in practice.
To optimize the performance of any manufactured MPA a deliberate offset in the gain and phase shift of each amplifier has to be introduced to compensate for the imperfections introduced by the INET, the ONET and their associated cabling. This paper shows how the RF modelling of an MPA has been performed by computer modelling using the Agilent ADS software.
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Andy Pienkowski, Innovision Research & Technology Plc
In the world of passive RFID, fast returns on investment in an extremely high volume industry are only possible if testing costs are minimised. This pushes the limits of traditional testers beyond their standard digital and parallel test capability. Reliable techniques must be found, therefore, to adapt standard testers to suit the RFID purpose: such techniques are the subject of this paper.
Download the PDF (864 kb)
Roscoe W.S. Harrison, Roke Manor Research Ltd
Roke Manor Research has developed Wavedancer 400, an ultra-low-power ISM band transceiver integrated circuit. It utilises low cost direct conversion architecture with class leading power consumption and receiver sensitivity. The chip offers two selectable bandwidths in both transmit and receive modes allowing either high data rates or maximum receiver sensitivity. These features mean it is ideally placed for use in a variety of applications such as telemetry, remote location deployment and ranged tagging.
Download the PDF (864 kb)
Andrew Wallace, Applied Wave Research Ltd
ACE™ automated circuit extraction technology from Applied Wave Research, Inc. is an innovative approach to avoid the over dependence of EM analysis as a design tool. ACE software automates modelling of complex interconnect structures defined by paths by assembling their equivalent electrical models on the fly using the very same network representation designers themselves would make use of if they had the time and patience to do so. The simulation of the equivalent circuit is done in a fraction of the time that it would take EM tools to create S-parameters. The speed, accuracy, and parametric nature of ACE software enable engineers to return to real design by exploring design alternatives and changes in seconds. It enables engineers to once again design rather than analyze, even on many of the most challenging RF/microwave designs.
Download the PDF (3.6 Mb)
As well as the conference, the tabletop exhibition, organized by John Kitchen of SJ Technologies, provided a useful contribution by enhancing the discussion periods between talks. Demonstrations of spectrum analyzers and receiver systems were made along with EDA tools and the display of microwave and RF components.
ARMMS SPRING 2008
The next ARMMS RF & Microwave Society conference will be sponsored by Plextek Ltd and will be held on 7 and 8 April 2008, at Milton Hill House near Oxford, UK. As always it will be accompanied by a small commercial exhibition and the Call for Papers has now gone out.
Call for Papers
Contributions are invited with an emphasis on RF and microwave design, testing and associated subjects. Papers will be printed in the society digest and distributed to delegates at the meeting. Presentations are generally in the form of an informal talk with PowerPoint or OHP illustrations. Alternative methods of presentation are welcome. Contributors are requested to submit the title and a one-page abstract of their paper by 1 February 2008.
Anyone interested in submitting a paper for presentation at this conference should contact the technical co-ordinator, Matthew Harper, with a prospective title:
Telephone: +44 (0) 20 8943 6849
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