![]() ![]() However, if you need to choose between short traces and few bends, always choose the length of the trace and use vias to jump over traces in the way. Bends and corners in traces can create reflections and help with EM emissions so removing these if possible is usually a good idea. One other trick to prevent stray emissions is to keep the trace as straight as possible. This is one of the reasons why high-frequency ICs such as microcontrollers and memory chips are placed so close to each other. Traces and wires that carry signals which may be prone to EM emissions should be kept as short as possible. The opposite applies to circuits that are prone to EM emissions. Series resistors help to limit current and therefore help with the smoothing of square waves.Ī radio that has poor reception can significantly be improved by increasing the length of the aerial. However, care must be taken when smoothing square waves as circuits based on CMOS technology will respond unexpectedly during intermittent voltages. ![]() Typical capacitor values range from 10pF to 47pF for such circuits. One example of such smoothing can be found on many USB and other serial communication lines. This is easily done with a capacitor and series resistor. One method for reducing EM radiation from switching circuits is by increasing the rise and fall times. This is why spectrum analyzers are so important when trying to comply with EMC regulations (showing detected signals at different frequencies). Therefore, square waves have a tendency to emit radio waves not just on the frequency of the switching circuit but at many other frequencies as well. A square wave, however, is made up of a singular sine wave and an infinite number of sine waves at odd harmonic frequencies. A sine wave signal in a wire will mostly emit EM radiation whose frequency is equal to the frequency of the sine wave. The issue does not usually come from the switching frequency itself but from the rise and fall times from the signals. Switching circuits and circuits that involve data/clock signals can cause serious problems when it comes to emission. Typically, it is easier to remove emissions and mediums than it is to remove receivers since most electronic circuits that exist on the market comply with receiver regulations (circuits inside products must not be susceptible to standard emissions from sources such as WiFi, Mobile phones, and other radio equipment). The Receiver – Something must be receiving EM emissions and be failing as a resultĮMC issues can be solved by removing one of the three areas above and some techniques apply to more than one area shown above.The Medium – Something must be carrying the EM emissions.The Emitter – Something must be creating EM emissions (possibly at unacceptable levels).Therefore, these emissions must be reduced as much as possible for a circuit to pass FCC and CE regulations (which is required when selling a product).Īll EM emission related problems come down to three main areas: However, many circuits containing microcontrollers and/or switching circuits produce EM emissions which can cause serious problems with other nearby circuits. This example of EM emission demonstrates intentional EM emission (since the goal is to send information over radio waves). ![]() A classic example of EM emission is an RF transmitter circuit that generates a high-frequency oscillation which in turn creates photons with a frequency equal to the frequency of the oscillator (these EM emissions can then be detected by a radio receiver). All circuits that switch or change voltage polarity emit EM radiation which can potentially be detected by a receiver. What Is EMC?ĮMC stands for electromagnetic compatibility and it is concerned with circuit EM emissions and susceptibility to EM emissions. However, strict rules and regulations surround electronic devices on the market mainly involving EMC considerations, so in this article, we will look into what EMC is and some small tips on how to improve the EMC performance of a circuit. Creating projects for hobby reasons rarely calls on electromagnetic compatibility (EMC), but it is not unheard of when a hobby project becomes a commercial product. ![]()
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