July 24, 2008 -- It is well-known that, during system development, critical signal-integrity and EMI (electromagnetic-interference) simulations are difficult, time-consuming, and error-prone due to their reliance on hard-to-predict models and parameter extractions. This situation worsens with every new product generation due to steadily increasing clock speeds and decreasing supply voltages, resulting in reduced noise margins. These problems, coupled with the shorter product-development periods that shorter product-life cycles require, hinder the ability of designers to bring their products to market fast enough to meet market demand. The ever-increasing expectations of the end user or the consumer require approaches to such problems that interfere with a company’s ability to expeditiously manufacture quality products at high volumes and to outpace dwindling product life spans in the market.

Although simulating electronics systems to predict EMI levels is a difficult and time-consuming task, understanding the fundamental causes of electromagnetic radiation is simple. Any charge moving in an electrical field or change in a field emits electromagnetic radiation. The strength of radiation is directly proportional to the rate of change. The sources of electromagnetic emissions can be intentional transmitters, such as cellular phones. But digital systems, such as PCs, PDAs (personal digital assistants), printers, and scanners, emit unintentional radiation. In digital systems, periodic clock signals are the major causes of EMI radiation. In addition, control and timing signals, address and data buses, interconnect cables, and connectors also contribute to EMI emissions.

By Cavit Ozdalga. (Ozdalga is director of marketing at SpectraLinear.)