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Three Things an Engineer Needs to Be Aware of When Selecting an Anti-alias Filter

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One of the biggest issues that electronic engineers face when designing analog to digital conversion circuitry is the noise levels that interfere with a good and accurate sampling of the analog signal. For this reason, it is critical to have an anti-alias filter before the sampling of the signal. There are many considerations in the process of choosing the best anti-alias filter for your design. The following are a few of them.

You need to compute the Nyquist frequency

The Nyquist frequency is where your data conversion will not see an alias signal and is simply half the frequency of the analog-digital converter's sampling rate. Ideally, you want to keep your data sampling below this frequency, but this is not always possible. When you go beyond the Nyquist frequency, you will want to use an anti-alias filter to solve the problem of sampling error. Once you know this frequency, it will be the starting point of finding the right filter.

There are three main filter types to choose from

The most used filters by engineers are the Bessel, Butterworth, and Chebyshev. Each filter is designed with a different configuration of poles. This is simply the configuration of capacitors and inductors. However, the differences in these configurations produce pronounced differences in signal response. In addition, the response can be further refined by a greater number of poles. Learn more about your options by contacting companies that supply Bessel anti-alias filters. 

There is a trade-off between step-response and frequency

Because of this trade-off, you need to decide where your emphasis will be with your filter response. If your signal will be encoded for time domain, then your choice will be a Bessel filter, as the characteristics of step-response are vastly superior to those of the Butterworth and Chebyshev. However, if your design will be for frequency domain encoding, you should focus on either the Butterworth or the Chebyshev filters. The latter filter has a sharper frequency cut-off than the Butterworth filter, but there is a greater settling time of the signal after the cut-off frequency.

If you are an electronic engineer who is designing an analog to digital conversion circuit, the key to an accurate sampling of the analog signal is eliminating any alias signal. Of course, if you can sample within the parameters of the ADC, there will be no problem, but if you exceed the Nyquist frequency, you will have an issue with an alias signal. You can use a filter to get an accurate sampling of the analog signal. Learn more by contacting anti-alias filter companies.