www.gusucode.com > signal 工具箱matlab源码程序 > signal/@dfilt/noisepsd.m
function noisepsd(this) %NOISEPSD Power spectral density of filter output due to roundoff noise. % Hpsd = NOISEPSD(Hd,L) computes the power spectral density (PSD) at the % output of filter Hd due to roundoff noise produced by quantization % errors within the filter. L is the number of trials used. The PSD is % computed from an average over the L trials. The more trials the better % the estimate (at the expense of longer computation). If L is not % specified, it defaults to 10 trials. % % Hpsd is a PSD data object. The PSD vector can be extracted from Hpsd by % GET(Hpsd,'Data'). It can be plotted using PLOT(Hpsd). The average power % of the output noise (the integral of the PSD) can be computed with % AVGPOWER(Hpsd). % % Hpsd = NOISEPSD(Hd,L,P1,V1,P2,V2,...) specifies optional parameters via % parameter-value pairs. Valid pairs are: % Parameter Default Description/Valid values % --------------------- ----------- ---------------------------------- % 'NFFT' 512 Number of FFT points. % 'NormalizedFrequency' true {true,false} % 'Fs' 'Normalized' Sampling frequency. Only used when % 'NormalizedFrequency' is false. % 'SpectrumType' 'Onesided' {'Onesided','Twosided'} % 'CenterDC' false {true,false} % % NOISEPSD(Hd,L,OPTS) uses an options object to specify the optional % parameters in lieu of specifying parameter-value pairs. The OPTS object % can be created with OPTS = NOISEPSDOPTS(Hd). Settings can be changed in % OPTS before calling NOISEPSD, e.g. set(OPTS,'Fs',48e3); % % % Example: Compute the PSD of the output noise due to quantization in a % % fixed-point FIR filter implemented in direct-form. % f = fdesign.lowpass('N,Fp,Fst',27,.4,.6); % h = design(f,'equiripple','FilterStructure','dffir'); % h.Arithmetic = 'fixed'; % specifyall(h); h.OutputFracLength=15; % Hpsd = noisepsd(h); % plot(Hpsd) % % See also DFILT/NOISEPSDOPTS, DFILT/FREQRESPEST, DFILT/SCALE, % DFILT/FUNCTIONS, DSPDATA/PSD. % Author(s): R. Losada % Copyright 1988-2006 The MathWorks, Inc. % [EOF]