The art of delaying (discrete)

Hi everyone

Simple newbi question on discrete signals. How can a discrete signal of sample time T can be delayed by a delay = T/4 ?

I am trying to use the delay block but I can only delay by an integer of the sample time. I am afraid my vision of "delay" is not correct.

Thank you very much for any kind of help on that.

Answer 1

[Guy Rouleau]

Sample Time Offset:

http://blogs.mathworks.com/seth/2011/11/20/sample-time-offset/

[Azzi Abdelmalek]

I was not aware of that. Good to know

[Greg]

Hey! Thanks a lot for your answer, it seems it is exactly what I am looking for.

I just had some trouble until I realized that this option has to be unchecked into the Rate Transition block (!):

"Ensure deterministic data transfert (maximum delay)"

Thanks again Guy :-) !

Answer 2

[Azzi Abdelmalek]

Set the sample time of your unit delay block to T/4, you will get a signal containing 4x number of original samples, delayed with T/4

[Greg]

Hi! Thanks for your answer! I just tried it, but unfortunately it is still delaying by T and not by a fraction of it.

Here is the test: I have a discrete signal of sample time = 1 seconde. And I am using a Unit Delay block with a specified value of 1/4 seconde.

Output: the first outputed value is zero until 1 second, and then it is outputting the input signal with a delay of 1 second.

I am doing something wrong?

[Azzi Abdelmalek]

Suppose you have signal y1 with sample time 1 ans time simulation is 0 to 10, that means you have 11 samples

When you pass a signal y1 through a unit delay block with T/4 you will get a signal y2 with 41 sample. which means:

The second sample of y1 corresponds to 1 sec

The second sample of y2 corresponds to 0.25 sec

If you want to check the result you should compare the signal y2 with the signal y3 which is obtained by passing y1 through a zoh block with sample time=T/4