Greetings: There is so much good stuff on RF Cafe that there is no way to list or link to
all of it here. Please use the Search box or the Site Map
to find what you want - there is a good chance I have it here. Thanks!
Filter Equivalent Noise Bandwidth
A filter's equivalent noise bandwidth (EqNBW) is the bandwidth that an ideal filter (infinite rejection in the stopband) of the same bandwidth would have. EqNBW is calculated by integrating the total available noise power under the response curve from 0 Hz to infinity Hz. In practice, integration only needs to be carried out to about the point of thermal noise. The steeper the filter skirts (higher order), the narrower the range of integration needed to get an acceptable approximation. Integration needs to be done in linear terms of power (mW, W, etc.) rather than in dB. The values in the following table are for normalized lowpass filter functions with infinite Q and exact conformance to design equations. If you need a better estimation than what is presented here, then a sophisticated system simulator is necessary.