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# What does "freqz()" in matlab mean?

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#### leoren_tm

what does "freqz()" in matlab mean????

im doing a filter design...
pls help me..
in the figure..how can i determine the response using that funtion??

#### standardon

##### Junior Member level 2
writing polynomials in matlab

what is new in matlab 2006a?

#### Zahedpoor

##### Newbie level 6
matlab help documents

Hi ,

I think make a mistake in writing command.

there isnt any command like fregz.

In matlab 7 sp3 if you write this Help freqz , no answer be seen.

regrds

#### saberbf

##### Member level 1
denominator and numertor

this function reflects to you the frequency response of a filter (or generally, a TF).
to solve the second part of question at 1st write the filter TF and then feed it to freqz() function.
doc freqz

#### louisnells

##### Full Member level 4
freqz function in matlab

freqz is used to get or plot the frequency response of a digital system.
It can be used to get the frequency response of the filters.
To design the filters you have to first create the transfer function of the filter (ie: H(z)). Then pass the numerator and de-numerator to freqz().
Because you have the transfer function create polynomials of numertor and denominator and apply them to freqz().

It is also possible to create a transfer function of filter using "control system" functions and then use bode(). bode plot is much easier to handle.

#### leoren_tm

matlab help 2006

Zahedpoor said:
Hi ,

I think make a mistake in writing command.

there isnt any command like fregz.

In matlab 7 sp3 if you write this Help freqz , no answer be seen.

regrds
it,s freqz not fregz

louisnells said:
freqz is used to get or plot the frequency response of a digital system.
It can be used to get the frequency response of the filters.
To design the filters you have to first create the transfer function of the filter (ie: H(z)). Then pass the numerator and de-numerator to freqz().
Because you have the transfer function create polynomials of numertor and denominator and apply them to freqz().

It is also possible to create a transfer function of filter using "control system" functions and then use bode(). bode plot is much easier to handle.
thnks...
how can i transform that figure into a TF????
then using matlab to generate the filter...??

saberbf said:
this function reflects to you the frequency response of a filter (or generally, a TF).
to solve the second part of question at 1st write the filter TF and then feed it to freqz() function.
doc freqz

when i type "doc freqz" it say
Code:
  Warning - Documentation Files Not Found
MATLAB is unable to find the HTML help documents, based on your current
Documentation location setting. Some possible reasons for this are as follows:

The Documentation location is set to your CD-ROM drive, but the Documentation
CD-ROM is not in the drive.
The setting is no longer valid, because the help files have been moved or
deleted.
The setting is incorrect, perhaps mistyped.

To view or change the location where MATLAB expects to find the help documents, click
here to bring up the Preferences window showing the Help Preferences. The
Documentation Location field shows the location of the help documents.

You can set your documentation location to any of the following alternatives (listed with
examples):

CD-ROM drive

Z:\help

Installed in the \$MATLABROOT directory, or in
another location on your hard disk.

C:\MATLAB\HELP

Installed in a network location

\\CampusServer\Matlab\Help

#### louisnells

##### Full Member level 4
matlab freqz

The freqz() is even available with Matlab v6.1 (Linux). But bode() is more comfortable.

Reffer polynomials in matlab. You can create a polynomial from its co-efficients. So create the polynomials for numerator and denominator. Then pass it to freqz().

To create TF from the above reffer control system toolbox functions.

#### leoren_tm

matlab freqz low pass filter

can you give me a clue on that figure???

y=..????????

#### louisnells

##### Full Member level 4
matlab freqz with filter of image

The transfer function is attached

### leoren_tm

Points: 2

#### leoren_tm

matlab doc user-created html

thx for that...but can i have it in standard form???
in this one???
Code:
           jw               -jw              -jmw
jw  B(e)    b(1) + b(2)e + .... + b(m+1)e
H(e) = ---- = ------------------------------------
jw               -jw              -jnw
A(e)    a(1) + a(2)e + .... + a(n+1)e
thx sOOOOoo much.....
mwahhhhhhhhhhhhhhhhh............................

#### louisnells

##### Full Member level 4
doc tf matlab

For Matlab you need it in the Z-transform way.

leoren_tm said:
thx for that...but can i have it in standard form???
in this one???
Code:
           jw               -jw              -jmw
jw  B(e)    b(1) + b(2)e + .... + b(m+1)e
H(e) = ---- = ------------------------------------
jw               -jw              -jnw
A(e)    a(1) + a(2)e + .... + a(n+1)e
thx sOOOOoo much.....
mwahhhhhhhhhhhhhhhhh............................

#### leoren_tm

simple low pass filter in matlab using tf command

aw..ok...
im implementing it in matlab.....
can you help me??
and what filter would that be??

#### louisnells

##### Full Member level 4
help freqz log

The TF looks like an IIR filter.

leoren_tm said:
aw..ok...
im implementing it in matlab.....
can you help me??
and what filter would that be??

#### leoren_tm

location for matlab help files

hmm...thanks...
low pass or high pass??

#### lxtommy

##### Newbie level 1
matlab freqz 48

sorry, i have the presentation by using the matlab of the subject
- image processing
- wavelets
- DSP (digital signal processing)
so, if who has any the material of these subject, you can help me.
my mailL lxtommy@yahoo.com

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