Floating-Point to Fixed-Point Conversion of IIR Filters

I am trying to run this official example https://fr.mathworks.com/help/dsp/ug/floating-point-to-fixed-point-conversion-of-iir-filters.html . But when I copy the first line

biquad = design(fdesign.lowpass('Fp,Fst,Ap,Ast',0.4,0.45,0.5,80),'ellip',FilterStructure='df1sos', SystemObject=true, UseLegacyBiquadFilter=true);

it triggers an error :

Error: Incorrect use of '=' operator. To assign a value to a variable, use '='. To compare values for equality, use '=='.

I run this version of matlab

-----------------------------------------------------------------------------------------------------
MATLAB Version: 9.9.0.1857802 (R2020b) Update 7
MATLAB License Number: 
Operating System: Microsoft Windows 10 Pro Version 10.0 (Build 19044)
Java Version: Java 1.8.0_202-b08 with Oracle Corporation Java HotSpot(TM) 64-Bit Server VM mixed mode
-----------------------------------------------------------------------------------------------------
MATLAB                                                Version 9.9         (R2020b)
Control System Toolbox                                Version 10.9        (R2020b)
DSP System Toolbox                                    Version 9.11        (R2020b)
Fixed-Point Designer                                  Version 7.1         (R2020b)
Instrument Control Toolbox                            Version 4.3         (R2020b)
Parallel Computing Toolbox                            Version 7.3         (R2020b)
RF Toolbox                                            Version 4.0         (R2020b)
Signal Processing Toolbox                             Version 8.5         (R2020b)
Statistics and Machine Learning Toolbox               Version 12.0        (R2020b)

How can I run this example on my computer ?

Answer 1

[Les Beckham]

The Name=Value syntax for name/value pairs of function arguments only works in r2021a and above.

So, changing this:

biquad = design(fdesign.lowpass('Fp,Fst,Ap,Ast',0.4,0.45,0.5,80),'ellip',FilterStructure='df1sos', SystemObject=true, UseLegacyBiquadFilter=true);

to this:

biquad = design(fdesign.lowpass('Fp,Fst,Ap,Ast',0.4,0.45,0.5,80), 'ellip', 'FilterStructure', 'df1sos', 'SystemObject', 1, 'UseLegacyBiquadFilter', 1);

should get rid of the "Incorrect use of '=' operator" error. I'm not familiar with this filter design process so I don't know if no error means that it is working correctly.

[Stephane DAVID-GRIGNOT]

awesome, thanks for your answer

[Les Beckham]

You are quite welcome.

Answer 2

[Andy Bartlett]

Hi,

Examples often depend on supporting files. To successfully run these examples, all the files needed by the example need to be on the MATLAB path. The help page for an example will have a big blue button labelled "Open Live Script." Clicking that button will make sure that copies of all the needed files are put on the current MATLAB path. Often the files are copied to a directory and the current directory is changed to that folder. These files can then be found by the commands in the example.

In contrast, if you do not click the big blue "Open Live Script" button, and copy commands from the help text and past them into MATLAB command window, then those commands can fail do to missing dependencies.

Please try clicking the "Open Live Script" button from the examples help page. Then try to repeat the individual commands, and see if that resolves the issues.

Andy

[Stephane DAVID-GRIGNOT]

Thank you very much for your answer.

I can't see the blue "Open Live Script" button . The web page only offers to "Open in Matlab Online" (cf image). Once I open it online, the example works, but I did not find how to download the files from the online matlab to my computer. Is there a solution for running the example localy on my computer ?

thank you again

Stéphane

[Stephane DAVID-GRIGNOT]

I have found how to dowload the example folder from matlab online. However the error is still triggered even when operating in the example folder. What am I doing wrong ?

thank you again