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Ericsson CH388 Personal Communication Services (PCS) Phone Ericsson, Inc., a leading manufacturer of cellular and PCS consumer electronics chose VisSim/Comm, a Windows® -based modelling and simulation package, for the rapid prototyping of new transceiver architectures for its next generation products. VisSim/Comm uses a block diagram-based approach for the modelling and simulation of end-to-end communication systems at the signal or physical level. With a full complement of communication blocks and powerful, time-domain simulation engine, VisSim/Comm provides fast and accurate solutions for analogue, digital and mixed-mode communication system designs.

The goal of its RF Advanced Development Group in Research Triangle Park, North Carolina is to evaluate and implement new technologies that will reduce cost, size and power consumption in future products. A system-level simulation tool such as VisSim/Comm allows engineers to investigate new concepts and provide first-order results to upper management before committing to a more costly hardware prototype phase.

Critical to the design of a new digital modulation synthesiser was a novel approach employing a modified phase locked loop (PLL) circuit. The new concept involved generating the desired digital modulation at the output of the synthesiser’s voltage controlled oscillator (VCO) by appropriately manipulating the phase within the PLL’s feedback loop. This approach would eliminate the need for a subsequent I/Q modulator stage, thus resulting in cost and board real estate savings.

The challenge was to prove the feasibility of this new synthesiser design without an extensive hardware prototype development cycle. What was needed was a system-level tool that would allow the creation of a block diagram model of the modulation synthesizer and predict its theoretical performance mathematically through appropriate simulations. “If it doesn’t work mathematically, it won’t work on the bench! Using VisSim/Comm, we designed a new modulation synthesiser much faster than if we had followed the conventional hardware prototype cycle for proof-of-concept. We were able to validate our approach in a matter of days as opposed to the several weeks required to design, assemble, and test a breadboard,” said Charles Gore, R & D Engineer, Ericsson.

Among the applications considered was the VisSim/Comm rapid prototyping tool. VisSim/Comm proved to be the perfect choice for the task at hand. Initial evaluations proved that it was not only easy to use, but also powerful enough to model and simulate the behaviour of a system involving complex feedback loops. Its intuitive graphical interface provided an easy way to develop communication system models, enabling users to quickly manipulate transceiver elements and achieve the desired results without having to build a hardware prototype.

They started by modelling the synthesiser using a standard second order PLL. During the simulation they were able to adjust all the key PLL parameters to achieve the desired transient behaviour and produce the desired modulated output. Based on the simulation results, they immediately moved on to a successful hardware implementation with a minimum of tweaking required.

Future plans now include implementation of the approach in an ASIC, which could easily be used in millions of digital cellular phones. They have also applied for a patent for this new design.

“Much of the success for this project we owe to VisSim/Comm. Using VisSim/Comm, we designed the new modulation synthesiser much faster than if we had followed the conventional hardware prototype cycle for proof-of-concept. We were able to validate our approach in a matter of days as opposed to the several weeks required to design, assemble and test a breadboard. VisSim/Comm makes it easier for us to develop innovative architectures for the next generation of Ericsson transceiver products. We keep finding new applications for this useful tool. Most recently, we have been using VisSim/Comm to investigate how to compensate for the effects of nonlinearities in certain receiver architectures,” said Charles Gore. “In addition, the task of convincing upper management to pursue this innovative approach would have been much more difficult without the results obtained from the VisSim/Comm simulations.Overall, using VisSim/Comm shortened our design cycle and simplified the development of new and innovative architectures for the next generation of Ericsson transceiver products.”

VisSim is supplied and supported in the UK and Ireland by Adept Scientific plc, Amor Way, Letchworth, Herts. SG6 1ZA; telephone (01462) 480055, fax (01462) 480213, email vissim@adeptscience.co.uk; or see Adept’s World Wide Web site http://www.adeptscience.co.uk/. Adept Scientific is one of the world’s leading suppliers of software and hardware products for research, scientific, engineering and technical applications on desktop computers.

With offices in the UK, USA, Germany and throughout the Nordic region, Adept Scientific is one of the world’s leading suppliers of software and hardware products for research, scientific, engineering and technical applications on desktop computers.