getBandwidth

Get 3 dB bandwidth

Syntax

BW = getBandwidth(npFilter)

Description

BW = getBandwidth(npFilter) returns the 3 dB bandwidth for the notch peak filter. If the Specification property is set to 'Quality factor and center frequency', the 3 dB bandwidth is determined from the quality factor value. If the Specification property is set to 'Coefficients', the 3 dB bandwidth is determined from the BandwidthCoefficient value and the sample rate.

Examples

Get 3 dB Bandwidth of Notch Peak Filter

Create a dsp.NotchPeakFilter object. Set the Specification property to 'Quality factor and center frequency' and the NormalizedFrequency property to true. The default quality factor Q is 5, and the center frequency Fc is 0.5 in normalized units.

np = dsp.NotchPeakFilter(Specification='Quality factor and center frequency',...
    NormalizedFrequency=true)

np = 
  dsp.NotchPeakFilter with properties:

          Specification: 'Quality factor and center frequency'
          QualityFactor: 5
        CenterFrequency: 0.5000
    NormalizedFrequency: true

Compute the 3 dB bandwidth of the notch peak filter using the getBandwidth function. The function computes the bandwidth as the ratio of the center frequency and the quality factor, $\frac{\mathrm{Fc}}{\mathit{Q}}$. Since Fc is in normalized units, the function computes the 3 dB bandwidth in normalized units.

getBandwidth(np)

ans = 
0.1000

Visualize the filter response.

filterAnalyzer(np)

Input Arguments

npFilter — Notch peak filter

dsp.NotchPeakFilter

Notch peak filter whose 3 dB bandwidth is measured, specified as a dsp.NotchPeakFilter object.

Output Arguments

BW — 3 dB bandwidth

scalar

3 dB bandwidth of the filter, returned as a scalar.

Data Types: double

Version History

Introduced in R2014a

R2024a: Support for normalized frequencies

In the dsp.NotchPeakFilter object, you can now specify the 3-dB bandwidth and center frequency values in normalized frequency units (0 to 1). To enable this functionality, set the NormalizedFrequency property of the object to true.