Re: How to downsample this signal?

From	Piotr Wyderski <peter.pan@neverland.mil>
Newsgroups	comp.dsp
Subject	Re: How to downsample this signal?
Date	2017-05-15 00:42 +0200
Organization	ATMAN - ATM S.A.
Message-ID	<ofamgn$bbs$1@node1.news.atman.pl> (permalink)
References	<of6c98$vve$1@node1.news.atman.pl> <878tm0puch.fsf@digitalsignallabs.com>

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Thank you all for your input.

Randy Yates wrote:

> What I don't understand is why, with the sledgehammer processor
> you have, you don't do a decent polyphase filter with a good
> FIR?

It is a hobby project and I had 15 years of break with any form
of DSP, at least understood as *signal* processing. I believe
I still understand the math behind it, but I know only a limited
number of "tricks". Polyphase representation is totally new to
me, so are its applications to decimation/interpolation.

The FIR filter has many advantages, e.g. maintaining linear phase
will be easy, but the "direct" approach implied a FIR of insanely
high order, so I didn't pursue the idea and drifted towards IIR,
with which I had some positive experience, especially with CICs
used in my SDR project.

As far as I can see, the polyphase FIR approach should be the right
choice for me. I am still not sure whether I am able to design a
filter in this topology correctly, but well, it's what we call
"learning". Thank you for bringing it to my attention.

BTW, the processor is not as sledgehammer as it may sound, especially
due to the very limited RAM resources available to the DSP unit (2 banks
of 128 24-bit words each, period.). The main processor (an ARM) has
everything needed to the job, except of low latency guarantees, which
is enough to kick it out of the scene. Whatever I can do, I must do
using the DFB block. Currently the unknown is the definition of
"whatever", but I'm aiming at saturating the block.

	Best regards, Piotr

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Thread

How to downsample this signal? Piotr Wyderski <peter.pan@neverland.mil> - 2017-05-13 09:23 +0200
  Re: How to downsample this signal? Evgeny Filatov <filatov.ev@mipt.ru> - 2017-05-13 15:42 +0300
  Re: How to downsample this signal? bitterlemon40@yahoo.ie - 2017-05-13 07:53 -0700
  Re: How to downsample this signal? rickman <gnuarm@gmail.com> - 2017-05-13 11:48 -0400
  Re: How to downsample this signal? Randy Yates <yates@digitalsignallabs.com> - 2017-05-13 12:58 -0400
    Re: How to downsample this signal? rickman <gnuarm@gmail.com> - 2017-05-13 16:04 -0400
      Re: How to downsample this signal? Randy Yates <yates@digitalsignallabs.com> - 2017-05-14 14:19 -0400
    Re: How to downsample this signal? Piotr Wyderski <peter.pan@neverland.mil> - 2017-05-15 00:42 +0200
      Re: How to downsample this signal? rickman <gnuarm@gmail.com> - 2017-05-15 00:46 -0400
        Re: How to downsample this signal? Piotr Wyderski <peter.pan@neverland.mil> - 2017-05-15 07:21 +0200
          Re: How to downsample this signal? rickman <gnuarm@gmail.com> - 2017-05-15 10:51 -0400
            Re: How to downsample this signal? Randy Yates <randyy@garnerundergroundinc.com> - 2017-05-15 11:49 -0400
              Re: How to downsample this signal? Randy Yates <randyy@garnerundergroundinc.com> - 2017-05-15 17:20 -0400
              Re: How to downsample this signal? rickman <gnuarm@gmail.com> - 2017-05-16 02:59 -0400
                Re: How to downsample this signal? eric.jacobsen@ieee.org - 2017-05-16 15:59 +0000
                Re: How to downsample this signal? rickman <gnuarm@gmail.com> - 2017-05-16 15:36 -0400
                Re: How to downsample this signal? Randy Yates <randyy@garnerundergroundinc.com> - 2017-05-16 13:11 -0400
                Re: How to downsample this signal? eric.jacobsen@ieee.org - 2017-05-16 18:08 +0000
                Re: How to downsample this signal? Randy Yates <randyy@garnerundergroundinc.com> - 2017-05-16 15:35 -0400
                Re: How to downsample this signal? Randy Yates <randyy@garnerundergroundinc.com> - 2017-05-16 15:45 -0400
                Re: How to downsample this signal? Randy Yates <randyy@garnerundergroundinc.com> - 2017-05-16 15:50 -0400
                Re: How to downsample this signal? rickman <gnuarm@gmail.com> - 2017-05-16 21:36 -0400
                Re: How to downsample this signal? rickman <gnuarm@gmail.com> - 2017-05-16 15:35 -0400
                Re: How to downsample this signal? Randy Yates <randyy@garnerundergroundinc.com> - 2017-05-16 15:36 -0400
                Re: How to downsample this signal? Randy Yates <randyy@garnerundergroundinc.com> - 2017-05-16 15:40 -0400
                Re: How to downsample this signal? rickman <gnuarm@gmail.com> - 2017-05-16 22:06 -0400
                Re: How to downsample this signal? Randy Yates <yates@digitalsignallabs.com> - 2017-05-17 01:25 -0400
      Re: How to downsample this signal? Evgeny Filatov <filatov.ev@mipt.ru> - 2017-05-15 14:51 +0300
      Re: How to downsample this signal? Randy Yates <randyy@garnerundergroundinc.com> - 2017-05-15 10:37 -0400
  Re: How to downsample this signal? makolber@yahoo.com - 2017-05-15 06:27 -0700
    Re: How to downsample this signal? Piotr Wyderski <peter.pan@neverland.mil> - 2017-05-15 20:39 +0200

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