double

Cast coefficients of digital filter to double precision

Syntax

f2 = double(f1)

Description

f2 = double(f1) casts coefficients in a digital filter, f1, to double precision and returns a new digital filter, f2, that contains these coefficients.

Examples

Lowpass FIR Filter in Single and Double Precision

Use designfilt to design a 5th-order FIR lowpass filter. Specify a normalized passband frequency of $$0.2\pi$$ rad/sample and a normalized stopband frequency of $$0.55\pi$$ rad/sample.

Cast the filter to single precision and cast it back to double precision. Display the first numerator coefficient of each filter.

format long
d = designfilt("lowpassfir",FilterOrder=5, ...
               PassbandFrequency=0.2,StopbandFrequency=0.55);
e = single(d);
f = double(e);

coed = d.Numerator(1)

coed = 
   0.003947882145754

coee = e.Numerator(1)

coee = single
   0.0039479

coef = f.Numerator(1)

coef = 
   0.003947881981730

Use double to analyze, in double precision, the effects of single-precision quantization of filter coefficients.

Input Arguments

f1 — Single-precision digital filter

digitalFilter object

Single-precision digital filter, specified as a digitalFilter object. Use designfilt to generate a digital filter based on frequency-response specifications and single to cast it to single precision.

Example: f1= single(designfilt('lowpassfir','FilterOrder',3,'HalfPowerFrequency',0.5)) specifies a third-order Butterworth filter with normalized 3-dB frequency 0.5π rad/sample cast in single precision.

Output Arguments

f2 — Double-precision digital filter

digitalFilter object

Double-precision digital filter, returned as a digitalFilter object.

Version History

Introduced in R2014a