Reply by Predrag Valozic●February 25, 20032003-02-25
Hi Katrina!
It is all about a LFSR(4) sequence (I suppose) that (theoretically)
has properties you are describing:
normalized ACF(0) = 1, ACF(<>0) = 0.
But it is only for bipolar sequence of infinit length.
If the sequence is bipolar, length N then normalized ACF(<>0) = -1/N.
If ACF(0) <> 1, then you have to normalize it.
Predrag
----- Original Message -----
From: <>
To: <>
Sent: 2003. velja 22 20:24
Subject: [matlab] autocorrelation problem
> Hi everyone,
>
> I need help in autocorrelation. I have generated a particular
> sequence code, C of period 15 and need to find its autocorrelation.
> I need to get the values at given lags from i = 0 to i = 15. For
> example when i = 0, it's a perfect autocorrelation (no lag) so I
> should get the peak value of the autocorrelation here.
> Theoretically, this value should be equal to 1. But what I got was
> more that. Subsequently, I got a constant value (which was lower
> than the peak) when there is lag. Theoretically, I should be
> getting a constant 0 value...
>
> What I did was multiply C by a cyclic shift of it for each lag.
> What did I do wrong or forgot? Really need suggestions....
>
> Thanks in advance!
> Kat~
>
> _____________________________________
> Note: If you do a simple "reply" with your email client, only the
author of this message will receive your answer. You need to do a "reply
all" if
you want your answer to be distributed to the entire group. >
> _____________________________________
> About this discussion group:
>
> To Join:
>
> To Post:
>
> To Leave:
>
> Archives: http://www.yahoogroups.com/group/matlab
>
> More DSP-Related Groups: http://www.dsprelated.com/groups.php3
>
> ">http://docs.yahoo.com/info/terms/
>
>
Reply by ●February 24, 20032003-02-24
I'm just guessing here, but it sounds as if you have a non-zero average
value in
C when you expected C to be zero-mean.
Is the constant value at lags not equal to zero positive or negative?
Sincerely,
Glen Ragan
From: "t_katrina <>" <t_katrina on 02/22/2003 01:24 PM
To:
cc:
Subject: [matlab] autocorrelation problem
Hi everyone,
I need help in autocorrelation.
I have generated a particular
sequence code, C of period 15 and need to find its autocorrelation.
I need to get the values at given lags from i = 0 to i = 15. For
example when i = 0, it's a perfect autocorrelation (no lag) so I
should get the peak value of the autocorrelation here.
Theoretically, this value should be equal to 1. But what I got was
more that. Subsequently, I got a constant value (which was lower
than the peak) when there is lag. Theoretically, I should be
getting a constant 0 value...
What I did was multiply C by a cyclic shift of it for each lag.
What did I do wrong or forgot? Really need suggestions....
_____________________________________
Note: If you do a simple "reply" with your email client, only the
author of this
message will receive your answer. You need to do a "reply all" if you
want your
answer to be distributed to the entire group.
_____________________________________
About this discussion group:
Reply by Sergio Dominguez●February 24, 20032003-02-24
Hi katrina,
I do not really understand what you mean (my English is no that good). Could
you send the sequence and describe a little more what you intend to do? What
kind of process is it and what are you using to calculate the autocorrelation?
I
guess you are using xcorr, or have you done your own code?
Sergio
A las 07:24 del 22 de Feb de 2003, t_katrina <>
<> dijo: > Hi everyone,
>
> I need help in autocorrelation. I have generated a particular
> sequence code, C of period 15 and need to find its autocorrelation.
> I need to get the values at given lags from i = 0 to i = 15. For
> example when i = 0, it's a perfect autocorrelation (no lag) so I
> should get the peak value of the autocorrelation here.
> Theoretically, this value should be equal to 1. But what I got was
> more that. Subsequently, I got a constant value (which was lower
> than the peak) when there is lag. Theoretically, I should be
> getting a constant 0 value...
>
> What I did was multiply C by a cyclic shift of it for each lag.
> What did I do wrong or forgot? Really need suggestions....
>
> Thanks in advance!
> Kat~
>
> _____________________________________
> Note: If you do a simple "reply" with your email client, only the
author of this message will receive your answer. You need to do a "reply
all" if you want
your answer to be distributed to the entire group. >
> _____________________________________
> About this discussion group:
>
> To Join:
>
> To Post:
>
> To Leave:
>
> Archives: http://www.yahoogroups.com/group/matlab
>
> More DSP-Related Groups: http://www.dsprelated.com/groups.php3
>
> ">http://docs.yahoo.com/info/terms/
>
--
Did you ever notice that everyone in favour of birth control has already
been born?
-- Benny Hill
Reply by t_katrina●February 22, 20032003-02-22
Hi everyone,
I need help in autocorrelation. I have generated a particular
sequence code, C of period 15 and need to find its autocorrelation.
I need to get the values at given lags from i = 0 to i = 15. For
example when i = 0, it's a perfect autocorrelation (no lag) so I
should get the peak value of the autocorrelation here.
Theoretically, this value should be equal to 1. But what I got was
more that. Subsequently, I got a constant value (which was lower
than the peak) when there is lag. Theoretically, I should be
getting a constant 0 value...
What I did was multiply C by a cyclic shift of it for each lag.
What did I do wrong or forgot? Really need suggestions....