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# filternorm() - Signal Processing

### Syntax

### Example

### Output / Return Value

### Limitations

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### Reference

A typical use for filter norms is in digital filter scaling to reduce quantization effects. Scaling often improves the signal-to-noise ratio of the filter without resulting in data overflow. You also can use the 2-norm to compute the energy of the impulse response of a filter.L = filternorm(b,a) computes the 2-norm of the digital filter defined by the numerator coefficients in b and denominator coefficients in a.L = filternorm(b,a,pnorm) computes the 2- or infinity-norm (inf-norm) of the digital filter, where pnorm is either 2 or inf. L = filternorm(b,a,2,tol) computes the 2-norm of an IIR filter with the specified tolerance, tol. The tolerance can be specified only for IIR 2-norm computations. pnorm in this case must be 2. If tol is not specified, it defaults to 10–8.

L = filternorm(b,a)L = filternorm(b,a,pnorm)L = filternorm(b,a,2,tol)

Filter NormsOpen This Example Compute the 2-norm of a Butterworth IIR filter with tolerance . Specify a normalized cutoff frequency of rad/s and a filter order of 5. [b,a] = butter(5,0.5); L2 = filternorm(b,a,2,1e-10) L2 = 0.7071 Compute the infinity-norm of an FIR Hilbert transformer of order 30 and normalized transition width rad/s.b = firpm(30,[.1 .9],[1 1],'Hilbert'); Linf = filternorm(b,1,inf) Linf = 1.0028