filtering a special frequency in Matlab

Hi everyone!

I am currently working on a simulation of a 16 QAM transmission and have some problems attenuating a specific frequency!
The Transmitter is fine, transmission over air interface works also fine! After that I bring the signal back to the baseband representation and now want to filter it by a Lowpass of third order.
I know how to programme a lowpass in Matlab but I don´t know how to filter the signal!
For example I transmit about 128000 bits at a carrier frequency of 440Hz. So after bringing the signal back to baseband, I have also components in there with 880Hz (which should be surpressed)

My problem is that I don´t understand how to handle the filter, because on the one hand I have a vector with 128000 elements then "multiply" it with a lowpass transfer function and on the other hand I should use a vector with different frequencies so that the higher frequencies are attenuated?? I am so confused ...

Thanks

Maybe I'm not understanding your question, but have you looked at the filter function?

yes but this is not the function i need
I programmed a Lowpass filter as follows:


So my question is: how to apply this filter on a data-vector with 128000 elements? I cannot just multiply my data vector with that transfer function ...

you can use the 'filter' function in matlab! just type 'help filter' to see the parameters.

I hope it helps!

nein nicht wirklich, leider
aber ich arbeite gerade an der Lösung die vielversprechend aussieht!