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Filter Equivalent Noise Bandwidth |
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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.
Reference: Filter Design, by Steve Winder Related Pages on RF Cafe - Butterworth Filter Equations for Magnitude, Phase, and Group Delay - Chebyshev Filter Equations for Magnitude, Phase, and Group Delay - Butterworth Lowpass Filter Gain, Phase, and Group Delay Equations - Butterworth Highpass, Bandpass, & Bandstop Filter Gain, Phase, and Group Delay Equations - How to Use Filter Equations in a Spreadsheet - Filter Equivalent Noise Bandwidth - Filter Prototype Denormalization - Bessel Filter Prototype Element Values - Butterworth Lowpass Filter Poles - Butterworth Filter Prototype Element Values - Chebyshev Lowpass Filter Poles - Chebyshev Filter Prototype Element Values - Monolithic Ceramic Block Combline Bandpass Filters Design - Coupled Microstrip Filters: Simple Methodologies for Improved Characteristics |
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