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In this paper three different monolithic disvibuted mixers have been characterized in detail in order to identify the dominant operating modes and mixing mechanisms. The first chip is a cascode mixer. using two FETs to mimic the dual-gate FET mixer. The second chip is a novel matrix mixer. which draws on the matrix distributed amplifier concept. The third circuit is a balanced mixer using common-source and common-gate FET pairs. All three circuits operate over 1 to 14 GHz.

In this paper. the accurate characterization of an ultra-wideband monolithic CPW-to-Slotline transition is described. An accurate model for this transition is presented which gives excellent agreement with the measured data by incorporating dispersion in both the CPW and slotline. junction pamsitics. and frequency dependence of the transformer turns ratio from the classical transition model.

A MMIC balun has been realised using spiral transformers in a Marchand configuration. This arrangement results in a simple, compact design with good performance. Using standard foundry processing, amplitude balance of 0.2 dB and phase balance of 10/spl deg/ was achieved from 2 to 6 GHz.

This paper describes a sub-harmonically pumped single chip resistive mixer consisting of two pHEMTs, a LO Marchand balun and RF/IF filters. The balun achieves 0.2 dB and 5/spl deg/ of amplitude and phase balance from 17 to 34 GHz. This provides the mixer with over 30 dB of LO rejection and a minimum conversion loss of 9.5 dB over a 34 to 40 GHz RF bandwidth with only 5 dBm of LO power.

The design and measured performance of a GaAs FET amplifier developed for use onboard an experimental digital mobile satellite system are presented. The required 20 W output power is achieved with 26% power-added efficiency and 0.3 degrees/dB AM-to-PM conversion coefficient. The power spectrum of a bandlimited QPSK (quaternary-phase-shift keying) signal measured at the output of the amplifier shows an acceptable restoration of the filtered sidelobes. The bit error rate performance of the system obtained by computer simulation shows a very small E/sub b//N/sub 0/ degradation due to the high-power amplifier nonlinearities. >

In a joint EPSRC project, King's College London, the University of Leeds, and the Queens University of Belfast are addressing the problems involved with the large-signal characterisation and design of millimetre-wave integrated circuits. The circuit functions of particular interest are LNAs, mixers and modulators (King's), power amplifiers (Leeds) and oscillators (Belfast). A 38 GHz communications transmitter-receiver is the target of the work, and GEC-Marconi's new H40 pHEMT MMIC process is being used. A wide range of demonstrator circuits has recently been tested and some early results are presented.

The performance of five key single-ended monolithic millimetre wave amplifier topologies is compared with design, fabrication and measurements. This is the first such extensive comparative study of the special problems encountered when designing millimetre-wave amplifiers. The five different circuit topologies have been applied to the design of two-stage amplifiers using the same AlGaAs-GaInP PHEMT foundry process in order to arrive at meaningful conclusions. The topologies included are the reactive matching technique, voltage shunt feedback, series feedback, lossy matching and a resonator type topology. Each one has shown its distinctive behaviour at millimetre-wave frequencies. The comparison has been performed with simulations and verified through measurements.

A novel programmable switch design technique is presented. The design uses an analog reflection topology with PHEMT reflection terminations. The programmable switch provides a maximum of 60 dB isolation with a programmable frequency range of 40 to 57 GHz.

Advancement in thick-film technology has allowed smaller, more compact and high quality circuits to be designed. This is partly attributed to the use of the novel thick-film conductor and dielectric pastes, i.e. photoimageable thick-film pastes. In this paper, the technology is used to fabricate dielectric filled rectangular waveguide and H-plane offset rectangular waveguide filters. Data are presented over the frequency range >60 GHz to show that the technology can realise non-planar structures for future technology integration and millimetre-wave interconnections. (4 pages)

This paper suggests the use of short tapered slot antennas (TSAs) as a flexible antenna element in realising sectored antennas for high speed, increased capacity wireless LANs operating in the high microwave and millimeter wave regions. Design guidelines, typical radiation characteristics, and sectored antenna topologies based on this antenna element are presented.

The use of suitable antenna techniques ranging from the less intelligent ones (diversity) to the most complex ones (adaptive array techniques) can significantly contribute in optimising the air interface of wireless local area networks (WLANs) able to support high bit rate services such as multimedia applications. In this paper we review some of the most important antenna techniques and the improvements they can provide against channel limitations, and including the ones which are more likely to be adopted in future broadband WLANs. Active research fronts are addressed. The wireless part of the network is assumed to be of microcellular or/and picocellular configurations with indoor wireless networking being a major part of the infrastructure. The general infrastructure of such a network including the fixed network is shown.

Analogue MMIC amplitude and phase control circuits have been designed, fabricated and tested. These reflection-type analogue control devices are intended for direct carrier modulation in 17/18 GHz indoor radio LAN applications. The circuits were fabricated on the GMMT F20 standard foundry. The phase shifter uses varactor diodes and four 90/spl deg/ phase shifter sections were cascaded to achieve 360/spl deg/ for direct QPSK modulation. The attenuator uses cold-FETs as variable resistance elements. At 18 GHz the parasitic reactance is found to lead to very high phase variations. To combat this a simple symmetrical control method is presented for a two-stage attenuator.

This paper focusses on new applications of the sectored antenna system with optimum combining in order to accommodate the high data rate. It investigates the required Tx power for a TDMA system application and describes a reference signal generation. For example, the proposed configuration, with minimal ratio analysis requires only 15.9 dBm transmitter power in a 100 ft office (30 ns RMS delay) to reach the minimum 30 Mbps data rate at 10/sup -4/ uncoded BER with a 4 element antenna system, and a 51 Mbps data rate with a 6 element antenna system at 10/sup -2/ outage rate. In the case of optimum combining, only 6 dBm Tx power is required to get the same performance. Furthermore, compared with selective diversity systems, the proposed system can be adapted for any element location as well as a wide range of frequencies.

A microstrip hybrid based QPSK demodulator operating with a 4GHz I.F., for simplified VSAT receive terminals, is presented. The design features independent inphase and quadrature RF arm phase trimming. Implementation is based on varactor tuned phase shifters and single balanced mixers, contained within a substrate dimension of 50 × 55mm. The approach demonstrates that accurate constellation responses can be achieved with a low tolerance assembly, constructed in a conventional microstrip form.

The paper discusses the application of ICA techniques within the Sunderland and South Shields Water Company, with particular reference to the Lumley Treatment Works. The need for a control strategy for the river abstraction works is discussed and the steps taken in modelling the works and the resulting control algorithms outlined. The design and development of the Company's own intelligent outstation is described and its role in integrated PC based telemetry and control systems, including alarm annunciation, filter washing, coagulation control and clarification tank desludging. Based on the experience gained, general criteria for further ICA developments and conclusions are given.

An investigation of the variation of measured and simulated nonlinear characteristics of a MESFET with bias and load resistance is reported. A discrete MESFET exhibits simultaneous low 2nd and 3rd order intermodulation distortion while yielding high gain and operating in its low noise region.

The authors discuss the problem of power limitation in on-board satellite communications systems. They consider the nonlinear characteristics of on-board high-power amplifiers and corresponding linearisation techniques. It is shown that, with the recent development of solid-state high-power amplifier designs and linearisation techniques for travelling wave-tube amplifiers, it is now possible to operate on-board amplifiers near to saturation without increasing their nonlinear effects.

Extract Madam:– I wish to advise of the recent isolation of Streptococcus suis 1 and 2 from pigs in New Zealand. Type 1 was isolated from brain and joint swabs from a three-week-old piglet. The piglet had meningitis, was laterally recumbent, paddling and had arthritis with grossly swollen joints. Type 2 was isolated from tonsils collected from apparently normal bacon pigs slaughtered at a meat works. Isolates were confirmed as either Streptococcus suis type 1 or 2 on the basis of biochemical characteristics(4) and Lancefield precipitin tests using Sand R antisera as originally used by De Moor.(2)