Matlab filter常用函数_IT分享知识网

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Filtering and Analysis Functions

Filtering

Function	Description
fftfilt	Filters a signal with a `digitalFilter` using an FFT-based overlap-add method
filter	Filters a signal using a `digitalFilter`
filtfilt	Performs zero-phase filtering of a signal with a `digitalFilter`

Filter Analysis

Function	Description
double	Casts the coefficients of a `digitalFilter` to double precision
filt2block	Generates a Simulink® filter block corresponding to a `digitalFilter`
filtord	Returns the filter order of a `digitalFilter`
firtype	Returns the type (1, 2, 3, or 4) of an FIR `digitalFilter`
freqz	Returns or plots the frequency response of a `digitalFilter`
fvtool	Opens the Filter Visualization Tool and displays the magnitude response of a `digitalFilter`
grpdelay	Returns or plots the group delay response of a `digitalFilter`
impz	Returns or plots the impulse response of a `digitalFilter`
impzlength	Returns the length of the impulse response of a `digitalFilter`, whether actual (for FIR filters) or effective (for IIR filters)
info	Returns a character array with information about a `digitalFilter`
isallpass	Returns `true` if a `digitalFilter` is allpass
isdouble	Returns `true` if the coefficients of a `digitalFilter` are double precision
isfir	Returns `true` if a `digitalFilter` has a finite impulse response
islinphase	Returns `true` if a `digitalFilter` has linear phase
ismaxphase	Returns `true` if a `digitalFilter` is maximum phase
isminphase	Returns `true` if a `digitalFilter` is minimum phase
issingle	Returns `true` if the coefficients of a `digitalFilter` are single precision
isstable	Returns `true` if a `digitalFilter` is stable
phasedelay	Returns or plots the phase delay response of a `digitalFilter`
phasez	Returns or plots the (unwrapped) phase response of a `digitalFilter`
single	Casts the coefficients of a `digitalFilter` to single precision
ss	Returns the state-space representation of a `digitalFilter`
stepz	Returns or plots the step response of a `digitalFilter`
tf	Returns the transfer function representation of a `digitalFilter`
zerophase	Returns or plots the zero-phase response of a `digitalFilter`
zpk	Returns the zero-pole-gain representation of a `digitalFilter`
zplane	Displays the poles and zeros of the transfer function represented by a `digitalFilter`

1.zero,pole–>transfer function form

[b,a] = zp2tf(zer,pol,1);
fvtool(b,a)

Matlab filter常用函数

2.transform function–>zero/polo

fvtool(b,a,'Analysis','polezero')

Matlab filter常用函数

zplane(b,a)

Matlab filter常用函数

3.Z-transform frequency response of a digital filter.

[h,w] = freqz(b,a,p)

returns the p-point complex frequency response, H(ejω), of the digital filter.

For example, a ninth-order Butterworth lowpass filter with a cutoff frequency of 400 Hz, based on a 2000 Hz sampling frequency, is

[b,a] = butter(9,400/1000);

To calculate the 256-point complex frequency response for this filter, and plot the magnitude and phase with freqz, use

freqz(b,a,256,2000)

Matlab filter常用函数

4.filter

Use filter in the form y = filter(d,x) to filter an input signal, x, with a digitalFilter, d, and obtain output data, y.

5.designfilt(https://ww2.mathworks.cn/help/signal/ref/designfilt.html)

Use designfilt in the form d = designfilt(resp,Name,Value) to design a digital filter, d, with response type resp. Specify the filter further using a set of Name,Value pairs.

Type d.Coefficients to obtain the coefficients of a digitalFilter, d. For IIR filters, the coefficients are expressed as second-order sections.

Lowpass IIR Filter

Design a lowpass IIR filter with order 8, passband frequency 35 kHz, and passband ripple 0.2 dB. Specify a sample rate of 200 kHz. Visualize the magnitude response of the filter. Use it to filter a 1000-sample random signal.

lpFilt = designfilt('lowpassiir','FilterOrder',8, ...
         'PassbandFrequency',35e3,'PassbandRipple',0.2, ...
         'SampleRate',200e3);
fvtool(lpFilt)

Matlab filter常用函数

dataIn = randn(1000,1);
dataOut = filter(lpFilt,dataIn);

Output the filter coefficients, expressed as second-order sections.

sos = lpFilt.Coefficients

sos = 4×6

    0.2666    0.5333    0.2666    1.0000   -0.8346    0.9073
    0.1943    0.3886    0.1943    1.0000   -0.9586    0.7403
    0.1012    0.2023    0.1012    1.0000   -1.1912    0.5983
    0.0318    0.0636    0.0318    1.0000   -1.3810    0.5090

Bandpass FIR Filter

Design a 20th-order bandpass FIR filter with lower cutoff frequency 500 Hz and higher cutoff frequency 560 Hz. The sample rate is 1500 Hz. Visualize the magnitude response of the filter. Use it to filter a random signal containing 1000 samples.

bpFilt = designfilt('bandpassfir','FilterOrder',20, ...
         'CutoffFrequency1',500,'CutoffFrequency2',560, ...
         'SampleRate',1500);
fvtool(bpFilt)

Matlab filter常用函数

dataIn = randn(1000,1);
dataOut = filter(bpFilt,dataIn);

Output the filter coefficients.

b = bpFilt.Coefficients

b = 1×21

   -0.0113    0.0067    0.0125   -0.0445    0.0504    0.0101   -0.1070    0.1407   -0.0464   -0.1127    0.1913   -0.1127   -0.0464    0.1407   -0.1070    0.0101    0.0504   -0.0445    0.0125    0.0067   -0.0113 ⋯

6.fvtool

fvtool(b,a)
fvtool(sos)
fvtool(d)
fvtool(b1,a1,b2,a2,…,bN,aN)
fvtool(sos1,sos2,…,sosN)
fvtool(Hd)
fvtool(Hd1,Hd2,…,HdN)
h = fvtool(…)

Use fvtool to visualize a digitalFilter, d.

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Matlab filter常用函数

Filtering and Analysis Functions

Lowpass IIR Filter

Bandpass FIR Filter

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