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group delay filter modeling matlab

group delay filter modeling matlab

group delay filter modeling matlab

(OP)
Hello everyone,
I have the measurements of filter’s Group delay and S-parameters.
The S-parameters are of the following form presented in a touchstone file
!Agilent Technologies,N5242A,MY49421489,A.09.33.09
!Agilent N5242A: A.09.33.09
!Date: Thursday, March 22, 2012 19:50:06
!Correction: S11(Full 2 Port(1,2))
!S21(Full 2 Port(1,2))
!S12(Full 2 Port(1,2))
!S22(Full 2 Port(1,2))
!S2P File: Measurements: S11, S21, S12, S22:
# Hz S dB R 50
1450000000 -0.44925556 132.79056 -43.664959 42.970737 -43.609634 45.291161 -0.41757283 131.60133
1450100050.025 -0.44976574 132.81039 -43.738403 42.790764 -43.597622 44.620411 -0.40801486 131.61304
1450200100.05 -0.45033455 132.82925 -43.531742 44.20499 -43.862129 44.206757 -0.40980196 131.49973
(The S-parameters are of the following format S11,angle(db), S21,angle(db), S12,angle(db), S22,angle(db))
The filter’s Group delay data are like the demonstrated bellow:
!CSV A.01.01
!Agilent Technologies N5242A MY49421489 A.09.33.09
!Agilent N5242A: A.09.33.09
!Date: Thursday March 22 2012 19:57:00
!Source: Standard
BEGIN CH1_DATA
Freq(Hz) S21 Delay(s)
1.45E+09 -2.02E-08
1.45E+09 -1.32E-08
1.45E+09 -1.77E-08
1.45E+09 -1.70E-08
1.45E+09 -1.56E-08
1.45E+09 -1.36E-08
1.45E+09 -1.20E-08

That i want to do is to simulated the impact that the group delay will have on a particular waveform using MATLAB.
I tried to use the fdesign.arbgrpdelay in order to insert my group delay data and somehow observe how that would impact on a waveform but i am getting the following error:
Error using fdesign.abstracttype/superdesign (line 96)
Design options must be specified as a structure or as parameter-value
pairs.

Error in fdesign.abstracttype/design (line 11)
varargout{1} = superdesign(this, varargin{:});

Error in allpassfilterarbitrarygrpdly (line 413)
Hgd = design(hgd,'iirlpnorm','Weights','MaxPoleRadius',0.95);

I also tried to use fdatool but i couldn't find a way of designing a filter by changing its group delay.The group delay was flat in all the available designs.












RE: group delay filter modeling matlab

Frankly I'd use simulink for this job. Failing that did you read through the examples on filter design and simulation? I am no expert but it looks to me like you didn't structure your data correctly.

Cheers

Greg Locock


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RE: group delay filter modeling matlab

(OP)
Hello and thank you fro your reply,
I know that it could be better modelled on Simuling but it should be bone on MATLAB.
The frequencies used are scaled from 0 to one,it is the default method for the fdesign.arbgrpdelay.So that it must me done is the group delay to be inserted.@hacksaw Can you expand a bit more on that you suggested me?
Thank you in advance for your reply.

RE: group delay filter modeling matlab

your data shows that the group delay is anything but constant
here it is in tabular form

frequency time delay
1450000000 -2.02E-08
1450100050 -1.32E-08
1450200100 -1.77E-08
1450300100 -1.70E-08
1450400100 -1.56E-08
1450500100 -1.36E-08
1450600100 -1.20E-08

beyond that only an ideal transmission line will show a constant group delay, not a filter where the phase shift and the group delay is frequency dependent

good luck

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