fdesign.parameq - Parametric equalizer filter specification

Syntax

d = fdesign.parameq(spec, specvalue1, specvalue2, ...) d = fdesign.parameq(... fs)

Description

d = fdesign.parameq(spec, specvalue1, specvalue2, ...) constructs a parametric equalizer filter design object, where spec is a non-case sensitive specification string. The choices for spec are as follows:

'F0, BW, BWp, Gref, G0, GBW, Gp' (minimum order default)
'F0, BW, BWst, Gref, G0, GBW, Gst'
'F0, BW, BWp, Gref, G0, GBW, Gp, Gst'
'N, F0, BW, Gref, G0, GBW'
'N, F0, BW, Gref, G0, GBW, Gp'
'N, F0, Fc, Qa, G0'
'N, F0, Fc, S, G0'
'N, F0 ,BW, Gref, G0, GBW, Gst'
'N, F0, BW, Gref, G0, GBW, Gp, Gst'
'N, Flow, Fhigh, Gref, G0, GBW'
'N, Flow, Fhigh, Gref, G0, GBW, Gp'
'N, Flow, Fhigh, Gref, G0, GBW, Gst'
'N, Flow, Fhigh, Gref, G0, GBW, Gp, Gst'

where the parameters are defined as follows:

BW — Bandwidth
BWp — Passband Bandwidth
BWst — Stopband Bandwidth
Gref — Reference Gain (decibels)
G0 — Center Frequency Gain (decibels)
GBW — Gain at which Bandwidth (BW) is measured (decibels)
Gp — Passband Gain (decibels)
Gst — Stopband Gain (decibels)
N — Filter Order
F0 — Center Frequency
Fhigh - Higher Frequency at Gain GBW
Flow - Lower Frequency at Gain GBW
Qa-Quality Factor
S-Slope Parameter for Shelving Filters

Regardless of the specification string chosen, there are some conditions that apply to the specification parameters. These are as follows:

Specifications for parametric equalizers must be given in decibels
To boost the input signal, set G0 > Gref; to cut, set Gref > G0
For boost: G0 > Gp > GBW > Gst > Gref; For cut: G0 < Gp < GBW < Gst < Gref
Bandwidth must satisfy: BWst > BW > BWp

d = fdesign.parameq(... fs) adds the input sampling frequency. Fs must be specified as a scalar trailing the other numerical values provided, and is assumed to be in Hz.

Examples

Design a Chebyshev Type II parametric equalizer filter that cuts by 12 dB:

 d = fdesign.parameq('N,Flow,Fhigh,Gref,G0,GBW,Gst',...
       4,.3,.5,0,-12,-10,-1);
 Hd = design(d,'cheby2');
 fvtool(Hd)

Design a 4th order audio lowpass (F0 = 0) shelving filter with cutoff frequency of Fc = 0.25, quality factor Qa =10, and boost gain of G0 = 8 dB:

d = fdesign.parameq('N,F0,Fc,Qa,G0',4,0,0.25,10,8);
Hd = design(d);
fvtool(Hd)

Design 4th-order highpass shelving filters with S=1.5 and S=3:

N=4;
F0 = 1;  
Fc = .4; % Cutoff Frequency
G0 = 10;
S = 1.5;
S2=3;
f = fdesign.parameq('N,F0,Fc,S,G0',N,F0,Fc,S,G0);
h1 = design(f);
f.S=3;
h2=design(f);
hfvt=fvtool([h1 h2]);
set(hfvt,'Filters',[h1 h2]);
legend(hfvt,'S=1.5','S=3');

fdesign.parameq - Parametric equalizer filter specification

Syntax

Description

Examples

See Also