Impulse response of discrete-time filter System object
Plot the Impulse Response of a Lowpass Elliptic Filter
Create a discrete-time filter for a fourth-order, lowpass elliptic filter with a cutoff frequency of 0.4 times the Nyquist frequency. Use a second-order sections structure to resist quantization errors. Plot the first 50 samples of the impulse response, along with the reference impulse response.
d = fdesign.lowpass(.4,.5,1,80);
Create a design object for the prototype filter. Use
ellip to design a minimum order discrete-time biquad filter.
biquad = design(d,'ellip','Systemobject',true);
Plot the impulse response.
impz(biquad); axis([1 75 -0.2 0.35])
sysobj — Input filter
filter System object
Input filter, specified as one of the following filter System objects:
n — Number of filter coefficients
Length of the impulse response vector, specified as a positive integer.
fs — Sampling frequency
1 (default) | positive scalar
Sampling frequency used in computing the impulse response, specified as a positive scalar.
arithType — Arithmetic type
'double' (default) |
Arithmetic used in the filter analysis, specified as
'Fixed'. When the arithmetic
input is not specified and the filter System object is unlocked, the analysis tool assumes a double-precision filter. When the
arithmetic input is not specified and the System object is locked, the function performs the analysis based on the data type of
the locked input.
'Fixed' value applies to filter System objects with fixed-point
'Arithmetic' input argument is specified as
'Fixed' and the filter object has the data type of the
coefficients set to
'Same word length as input', the arithmetic
analysis depends on whether the System object is unlocked or locked.
unlocked –– The analysis object function cannot determine the coefficients data type. The function assumes that the coefficients data type is signed, has a 16-bit word length, and is auto scaled. The function performs fixed-point analysis based on this assumption.
locked –– When the input data type is
'single', the analysis object function cannot determine the coefficients data type. The function assumes that the data type of the coefficients is signed, has a 16-bit word length, and is auto scaled. The function performs fixed-point analysis based on this assumption.
To check if the System object is locked or unlocked, use the
When the arithmetic input is specified as
'Fixed' and the filter
object has the data type of the coefficients set to a custom numeric type, the object
function performs fixed-point analysis based on the custom numeric data type.
impResp — Impulse response
Impulse response, returned as an
n-element vector. If
n is not specified, the length of the impulse
response vector equals the number of coefficients in the filter.
t — Time vector
Time vector of length
n, in seconds.
t consists of
n equally spaced
points in the range
n is not specified, the function uses the number of
coefficients of the filter.