dsp.HighpassFilter
FIR or IIR highpass filter
Description
The dsp.HighpassFilter
System object™ independently filters each channel of the input over time using the given design
specifications. You can set the FilterType property of
dsp.HighpassFilter to 'FIR' or 'IIR'
to implement the object as an FIR or IIR highpass filter.
To filter each channel of your input:
Create the
dsp.HighpassFilterobject and set its properties.Call the object with arguments, as if it were a function.
To learn more about how System objects work, see What Are System Objects?.
Creation
Description
HPF = dsp.HighpassFilterHPF, with the default filter settings.
Calling the object with the default property settings filters the input data with a
stopband frequency of 8 kHz, a passband frequency of
12 kHz, a stopband attenuation of 80 dB, and a
passband ripple of 0.1 dB.
HPF = dsp.HighpassFilter(Name,Value)Name,Value pair arguments. Name is the
property name and Value is the corresponding value.
Name must appear inside single quotes (' '). You can specify
several name-value pair arguments in any order as
Name1,Value1,...,NameN,ValueN.
Properties
Usage
Syntax
Description
Input Arguments
Output Arguments
Object Functions
To use an object function, specify the
System object as the first input argument. For
example, to release system resources of a System object named obj, use
this syntax:
release(obj)
Examples
Impulse and Frequency Response of FIR and IIR Highpass Filters
Create a minimum order FIR highpass filter for data sampled at 44.1 kHz. Specify a passband frequency of 12 kHz, a stopband frequency of 8 kHz, a passband ripple of 0.1 dB, and a stopband attenuation of 80 dB.
Fs = 44.1e3; filtertype = 'FIR'; Fpass = 12e3; Fstop = 8e3; Rp = 0.1; Astop = 80; FIRHPF = dsp.HighpassFilter('SampleRate',Fs,... 'FilterType',filtertype,... 'PassbandFrequency',Fpass,... 'StopbandFrequency',Fstop,... 'PassbandRipple',Rp,... 'StopbandAttenuation',Astop);
Design a minimum order IIR highpass filter with the same properties as the FIR highpass filter. Use clone to create a system object with the same properties as the FIR Highpass filter. Change the FilterType property of the cloned filter to IIR.
IIRHPF = clone(FIRHPF);
IIRHPF.FilterType = 'IIR';Plot the impulse response of the FIR highpass filter. The zeroth order coefficient is delayed by 19 samples, which is equal to the group delay of the filter. The FIR highpass filter is a causal FIR filter
fvtool(FIRHPF,'Analysis','impulse')
Plot the impulse response of the IIR highpass filter.
fvtool(IIRHPF,'Analysis','impulse')
Plot the magnitude and phase response of the FIR highpass filter.
fvtool(FIRHPF,'Analysis','freq')
Plot the magnitude and phase response of the IIR highpass filter.
fvtool(IIRHPF,'Analysis','freq')
Calculate the cost of implementing the FIR highpass filter.
cost(FIRHPF)
ans = struct with fields:
NumCoefficients: 39
NumStates: 38
MultiplicationsPerInputSample: 39
AdditionsPerInputSample: 38
Calculate the cost of implementing the IIR highpass filter. The IIR filter is more efficient to implement than its FIR counterpart.
cost(IIRHPF)
ans = struct with fields:
NumCoefficients: 18
NumStates: 14
MultiplicationsPerInputSample: 18
AdditionsPerInputSample: 14
Calculate the group delay of the FIR highpass filter.
grpdelay(FIRHPF)
Calculate the group delay of the IIR highpass filter. The FIR filter has a constant group delay (linear phase) while its IIR counterpart does not.
grpdelay(IIRHPF)
Filter White Gaussian Noise with an IIR Highpass filter
Note: This example runs only in R2016b or later. If you are using an earlier release, replace each call to the function with the equivalent step syntax. For example, myObject(x) becomes step(myObject,x).
Set up the IIR highpass filter. The sampling rate of the white Gaussian noise is 44,100 Hz. The passband frequency of the filter is 12 kHz, the stopband frequency is 8 kHz, the passband ripple is 0.1 dB, and the stopband attenuation is 80 dB.
Fs = 44.1e3; filtertype = 'IIR'; Fpass = 12e3; Fstop = 8e3; Rp = 0.1; Astop = 80; hpf = dsp.HighpassFilter('SampleRate',Fs,... 'FilterType',filtertype,... 'PassbandFrequency',Fpass,... 'StopbandFrequency',Fstop,... 'PassbandRipple',Rp,... 'StopbandAttenuation',Astop);
View the magnitude response of the highpass filter.
fvtool(hpf)
Create a spectrum analyzer object.
sa = dsp.SpectrumAnalyzer('SampleRate',44.1e3,... 'PlotAsTwoSidedSpectrum',false,'ShowLegend',true,'YLimits',... [-150 30],... 'Title',... 'Input Signal and Output Signal of IIR Highpass Filter'); sa.ChannelNames = {'Input','Output'};
Filter the white Gaussian noisy input signal. View the input and output signals using the spectrum analyzer.
for k = 1:100 Input = randn(1024,1); Output = hpf(Input); sa([Input,Output]); end
Measure Frequency Response Characteristics of Highpass Filter
Measure the frequency response characteristics of a highpass filter. Create a dsp.HighpassFilter System object with default properties. Measure the frequency response characteristics of the filter.
HPF = dsp.HighpassFilter
HPF =
dsp.HighpassFilter with properties:
FilterType: 'FIR'
DesignForMinimumOrder: true
StopbandFrequency: 8000
PassbandFrequency: 12000
StopbandAttenuation: 80
PassbandRipple: 0.1000
SampleRate: 44100
Show all properties
HPFMeas = measure(HPF)
HPFMeas = Sample Rate : 44.1 kHz Stopband Edge : 8 kHz 6-dB Point : 10.418 kHz 3-dB Point : 10.8594 kHz Passband Edge : 12 kHz Stopband Atten. : 81.8558 dB Passband Ripple : 0.08066 dB Transition Width : 4 kHz
Algorithms
References
[1] Shpak, D.J., and A. Antoniou. "A generalized Remez method for the design of FIR digital filters." IEEE® Transactions on Circuits and Systems. Vol. 37, Issue 2, Feb. 1990, pp. 161–174.
[2] Selesnick, I.W., and C. S. Burrus. "Exchange algorithms that complement the Parks-McClellan algorithm for linear-phase FIR filter design." IEEE Transactions on Circuits and Systems. Vol. 44, Issue 2, Feb. 1997, pp. 137–143.