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From: sus on 16 Feb 2006 08:11
Hello,

I'm supposed to design a transmit chain with a root-raised cosine pulse
shaping filter followed by some interpolation stages.

The RRC-filter shall interpolate by 2, and its output shall be
interpolated by 8, resulting in a total interpolation of 16.

I'm told that the total characteristics of the RRC-filter + interpolation
chain shall resemble a root-raised cosine response.

I'm new to pulse shaping and interpolation and therefore needs some help:

1) What type of interpolation filters shall I use not to destroy the RRC
shape from the pulse shaping filter, and how do I dimension them (i.e. get
their coefficients)?

2) What kind of architecture do you suggest for implementation of the
RRC-filter and interpolation filters? I've heard about polyphase filters,
are these a good choise here?

3) Can you suggest a good book that covers pulse shaping, interpolation
and filter design?

Any help would be very appreciated!
SM





From: Fred Marshall on 16 Feb 2006 09:10

"sus" <mats.olsson(a)se.flextronics.com> wrote in message
news:2oidnV_PA_2O52nenZ2dnUVZ_tWdnZ2d(a)giganews.com...
> Hello,
>
> I'm supposed to design a transmit chain with a root-raised cosine pulse
> shaping filter followed by some interpolation stages.
>
> The RRC-filter shall interpolate by 2, and its output shall be
> interpolated by 8, resulting in a total interpolation of 16.
>
> I'm told that the total characteristics of the RRC-filter + interpolation
> chain shall resemble a root-raised cosine response.
>
> I'm new to pulse shaping and interpolation and therefore needs some help:
>
> 1) What type of interpolation filters shall I use not to destroy the RRC
> shape from the pulse shaping filter, and how do I dimension them (i.e. get
> their coefficients)?
>
> 2) What kind of architecture do you suggest for implementation of the
> RRC-filter and interpolation filters? I've heard about polyphase filters,
> are these a good choise here?
>
> 3) Can you suggest a good book that covers pulse shaping, interpolation
> and filter design?
>

"Multirate Signal Processing for Communication Systems" fredric j harris



From: quadtree on 13 Mar 2006 03:15
When it comes to interpolation filter design, polyphase filter is often
used because it uses less resource (memory) compared to
direct-implementation. However, it's only different implementation, so
required specification of filter doesn't change at all, so the way of
"designing filter, calculating the coefficients" doesn't change.

So, first just design the filter (calculates the coefficients) and
implement the filter in polyphase structure with those coefficients.

About RRC, root raised cosine filter, and following interpolation filter,
I guess, you need to understand what the purpose of the interpolation
after RRC. Eventually, this upsamling is compensated by downsampling at
the receiver side, and the receiver side RRC has the same rate of TX side
RRC, so they make Raised Cosine Channel shape, after all.

The specification of RRC filter is available in many wireless phy-layer
standard, i.e. cdma, wcdma,,, etc. And you need to implement that equation
into your system according to your system's sampling rate.

About polyphase filter, there are many dsp text books, Discrete time
signal processing (Oppenheim&Schaffer's) also has one section of
polyphase, and it would be a good starting point to understand polyphase
decomposition. And for the advanced understanding about polyphase
structure of filters, Multirate signal processing(?) (Vadiyanathan) would
show you the way of how to implement all these filter banks. Eventually,
these things are all related to wavelet theory.


>Hello,
>
>I'm supposed to design a transmit chain with a root-raised cosine pulse
>shaping filter followed by some interpolation stages.
>
>The RRC-filter shall interpolate by 2, and its output shall be
>interpolated by 8, resulting in a total interpolation of 16.
>
>I'm told that the total characteristics of the RRC-filter +
interpolation
>chain shall resemble a root-raised cosine response.
>
>I'm new to pulse shaping and interpolation and therefore needs some
help:
>
>1) What type of interpolation filters shall I use not to destroy the RRC
>shape from the pulse shaping filter, and how do I dimension them (i.e.
get
>their coefficients)?
>
>2) What kind of architecture do you suggest for implementation of the
>RRC-filter and interpolation filters? I've heard about polyphase
filters,
>are these a good choise here?
>
>3) Can you suggest a good book that covers pulse shaping, interpolation
>and filter design?
>
>Any help would be very appreciated!
>SM
>
>
>
>
>
>


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