Measurement Group Meets On Test/Modeling Issues

The most recent meeting of the ARMMS RF and Microwave Society featured technical presentations on optimum use of CAE simulation tools and precision test equipment.

Simulation and measurement results should agree closely under ideal conditions. Although such conditions are often not met, the most recent meeting of the ARMMS RF and Microwave Society Meeting focused on coordinating design efforts with computer-aided-engineering tools and accurate measurement techniques with microwave test equipment for the improvement of both commercial and military designs. Coordinated by Roger Hopper of Roke Manor Research Ltd. (Roke Manor, Romsey, Hamshire, England), the ARMMS RF and Microwave Society Meeting was held November 3-4, 2003 in the Hotel Elizabeth (Rockingham, Corby, Northamptonshire, England).

The two-day meeting offered modeling and measurement solutions for both commercial and military applications. The opening report, for example, by Malcolm Edwards of AWR Ltd. (Hitchin, Hertsfordshire, England), reviewed the differences among the major wireless-local-area-network (WLAN) standards, such as IEEE 802.11a/b/g, and some of the approaches used to design WLAN radios, including as integrated multichip modules and single-chip receivers. His presentation included a discussion on orthogonal frequency division multiplexing (OFDM), which is designed to reduce crosstalk between channels and minimize the effect of multipath distortion, and important parameters for testing WLANs, such as adjacent-channel-ratio (ACPR) and error-vector magnitude (EVM).

Edwards' presentation was followed by Kelvin Clarke of Ansoft UK who explained how many complex design problems could be broken down into constituent parts. This "divide and conquer" strategy can lead to very efficient and accurate solutions. The basic approach involves deciding how to best subdivide large problems and solve the constituent problems parametrically and then construct models from constituent parts. The availability of parametric three-dimensional (3D) models enables fast design and optimization of very large structures. Software based on finite-element (FE) analysis solves Maxwell's equations for the volume of arbitrary 3D structures. The FE method can also be applied to solve transfinite-element problems to determine the two-dimensional field solution at a given port of a "black box" design.

Chris Mann of Flann Microwave Ltd. (Bodmin, Cornwall, England) spoke on using the HFSS 3D field solver from Ansoft Corp. (Pittsburgh, PA), his report was inspired by the high cost of fabricating millimeter-wave waveguide components. HFSS provides an engineering environment in which engineers can experiment without cutting metal or operating expensive computer-controlled machinery. The report offered several design examples, including modification of a broadband dual polar horn antenna that operates from 2.5 to 18.0 GHz to cover a new frequency range of 18 to 40 GHz. Eventually, the software was used to optimize the design for a frequency range of 6 to 50 GHz. The software was also used to improve a 59-to-64-GHz omnidirectional antenna for WLAN use in the unlicensed 60-GHz band and to optimize an extremely compact Gaussian antenna.

Well-known design consultant, lecturer, and amplifier guru Steve Cripps offered a report on a high-efficiency Class F amplifier using a Chireix power combiner. Amidst lectures on advanced computer-aided-engineering (CAE) tools, Cripps explained how the amplifier, designed for a WLAN chip set from IceFyre (Kanata, Ontario, Canada), was created as a breadboard design built on hand-milled FR4 Test results revealed efficiency of better than 70 percent.

John Birkbeck of Roke Manor Research Ltd. covered issues associated with the design of RF and DC circuits for a custom heterojunction-bipolar-transistor (HBT) MMIC amplifier in parallel with packaging and thermal design. Design approaches must consider reducing the amplifier's sensitivity to process, temperature, and supply rail variations.

Nick Long of Great Circle Design (Somerset, England) explored a technique for detecting and measuring imperfections in I/Q signal processing systems. The technique can be used for fault analysis, design evaluation, and for alignment and calibration of systems.

Guy Purchon of Anritsu Ltd., European Measurement Division (Rutherford Close, Stevenage, Hertsfordshire, England) described the design and measurement principles for a new-high speed dual display channel power meter capable of detecting and displaying modulated signals. He explained how the tool could be used for commercial (WCDMA, WLAN) and military (radar) applications.

Kevin Lees and Stephen Protheroe of National Physics Laboratory (NPL, Teddington, England) discussed a traceable radiometer for calibration of noise sources below 10 MHz. They showed typical calibration results for a commercial noise source at 0.784 MHz and noted that their lowest traceable frequency was 100 kHz.

The next ARMMS meeting is scheduled March 29-30, 2004 at the Milton Hill House (Milton Hill, Steventon, Oxfordshire, England). For more information about ARMMS, visit the web site at, or contact JJ Heath-Caldwell, marketing coordinator, at 01962-761-565 (e-mail: [email protected]) or Duncan McIntosh, secretary (e-mail: [email protected]).

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