Reply by Eric Jacobsen ●September 30, 20132013-09-30
On Mon, 30 Sep 2013 07:25:34 -0500, "zzp6682" <93580@dsprelated>
wrote:


>Anyone know how to implement polyphase filter of the RRC? The RRC filter is
>designed with 17 taps. After modulation, the symbole rate is up 1Gsps, we
>have to us polyphase structure to implement filter?
>
>How to do this ?


Is the symbol rate 1Gsps or the sample rate?   If it is the symbol
rate, what is the sample rate?

It's going to be challenging to implement a polyphase filter at symbol
rates that high.   Is the symbol rate fixed or flexible?


Eric Jacobsen
Anchor Hill Communications
http://www.anchorhill.com
Reply by mnentwig ●September 30, 20132013-09-30
yes, simply design the FIR filter at the high output rate.
Analytic expression works - see wikipedia. 
You can squeeze a little more performance out if you optimize the finite
number of taps, for example here (see demo("RRC") section) for an iterative
reweighted least-squares method:
http://www.dsprelated.com/showcode/210.php

A polyphase filter is probably not the computationally most efficient way.
If given the choice, do the filtering at the lowest possible sample rate,
then use efficient upsampling techniques (such as CIC or haflband) and
equalize the passband with the low-rate filter. But, polyphase will do, if
you can manage the high number of coefficients. 	 

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Reply by ●September 30, 20132013-09-30
On Monday, September 30, 2013 8:25:34 AM UTC-4, zzp6682 wrote:

> Anyone know how to implement polyphase filter of the RRC? The RRC filter is
> 
> designed with 17 taps. After modulation, the symbole rate is up 1Gsps, we
> 
> have to us polyphase structure to implement filter?
> 
> 
> 
> How to do this ?
> 
> 
> 
> 
> 
> 	 
> 
> 
> 
> _____________________________		
> 
> Posted through www.DSPRelated.com


Since the impulse response for an RRC has an analytic form (closed form as an equation), you may sample it anywhere you like to create any phase you wish.

IHTH,
Clay
Reply by zzp6682 ●September 30, 20132013-09-30
Anyone know how to implement polyphase filter of the RRC? The RRC filter is
designed with 17 taps. After modulation, the symbole rate is up 1Gsps, we
have to us polyphase structure to implement filter?

How to do this ?


	 

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