[Ground-station] Operation PFB

John Ackermann N8UR jra at febo.com
Mon Jan 14 17:38:27 EST 2019


I'm on the road for a day or two but will dig them out and get them to you.

John
----

On 1/14/19 5:32 PM, Michelle Thompson wrote:
> Hi John!
> 
> Could you share them? I'm sure they have a special inner beauty that we 
> all know and love!
> 
> -Michelle W5NYV
> 
> 
> 
> 
> On Tue, Nov 20, 2018 at 10:06 AM John Ackermann N8UR via Ground-Station 
> <ground-station at lists.openresearch.institute> wrote:
> 
>     Hi Michelle --
> 
>     I've done several PFB receivers in Gnuradio Companion.  They are all
>     fairly narrow-band (FM or AM voice channels).  One is something like
>     115
>     slots to channelize the AM broadcast band.  The flowgraphs are deeply
>     ugly, but I'm happy to share them.
> 
>     73,
>     John
>     ----
> 
>     On 11/20/18 11:56 AM, Michelle Thompson via Ground-Station wrote:
>      > We've had some recent successes with some very difficult pieces
>     of the
>      > project.
>      >
>      > There is yet another one that needs some attention! :+D
>      >
>      > I'm talking about the polyphase filter bank.
>      >
>      > We have enough interest, enthusiasm, and competence to get this
>     rolling
>      > and succeed. Like LDPC, this technology has much wider
>     application and
>      > impact than just our project.
>      >
>      > This filter bank is in the payload. We call it a channelizer. The
>      > receive bandwidth is organized into channels by this filter bank.
>     From
>      > there, the communications are multiplexed into the time division
>      > downlink DVB frames.
>      >
>      > Polyphase filter bank is the exact right method to use, but it is
>     going
>      > to require a real team effort to get it working and demonstrated.
>      >
>      > We have excellent MATLAB models for several different variants of
>      > polyphase filter banks directly from fred harris. He wrote the book
>      > about multirate processing and wants us to succeed. His
>     contribution can
>      > be found in the Polyphase Filter Bank repo
>      > (https://github.com/phase4ground/polyphase-filter-bank).
>      >
>      > We have a number of volunteers that want to help with this.
>      >
>      > There is a polyphase filter bank in GNU Radio. It's used on our
>     ground
>      > station emulator flowgraphs. It's based on work by fred harris
>     and Chris
>      > Dick.
>      >
>      > There was a polyphase filter bank in RFNoC, described at GRCon17.
>      >
>      > There was an update and revision to the RFNoC work discussed at
>     GRCon18.
>      > The work appears to be ongoing. RFNoC ties you to USRPs, but the
>      > increase in efficiency and speed put it into the Phase 4 Ground
>     category.
>      >
>      > Recently, we asked for a particular working repository from a
>     particular
>      > source to be released as open source, so we could use it as a
>     codebase
>      > and adapt it for Phase 4 Ground. That request was unfortunately
>     denied.
>      > This is not the only polyphase codebase that I've campaigned to get
>      > donated, but it did feel like the most promising.
>      >
>      > I know and appreciate how difficult it can be to dive in and start
>      > working on a challenging and mathematically intimidating function
>     like
>      > multirate or polyphase.
>      >
>      > If we want to succeed, then we need to either get a fast open source
>      > implementation identified (or a proprietary one donated) that we can
>      > adapt, or write one from scratch.
>      >
>      > Here's the plan. We need eyeballs, and we need some risk takers.
>      >
>      > 1) Go find all the open source polyphase implementations that are
>      > currently out there. Report them here:
>      > https://goo.gl/forms/BTIe81jb8746PqJ23
>      >
>      > 2) Make and share a GNU Radio flowgraph that uses the polyphase
>     filter
>      > bank to receive several channels. Pick 2, or 4. Pick more if you're
>      > ambitious. Use your RTL-SDR, your Lime, your HackRF, whatever you
>     have.
>      > How far did you get? What problems did you have? What's not clear
>     in how
>      > to use it? This is a pragmatic, operator-focused experiment in
>     using a
>      > very powerful technique. We need to know where it falls down and
>     how far
>      > we can push it with today's code.
>      >
>      > 3) Write me if you want to participate but aren't currently one
>     of the
>      > members of our polyphase filter bank repository and I will add you.
>      >
>      > It goes without saying but it's always better with. You do not
>     have to
>      > be an expert to participate, contribute, and learn. You just have
>     to be
>      > willing to accidentally become one while digging in.
>      >
>      > I'm here to help make it fun and worthwhile. Want to get
>     competent in
>      > multirate and polyphase filter techniques? This is a wonderful
>      > opportunity for that. It's cutting edge and highly marketable
>     knowledge,
>      > and is also a critical component for our radio system to work. Ask
>      > questions, pick something, and publish it. The Polyphase Filter Bank
>      > repository is where our work lives. Let's light it up.
>      >
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>      >
> 
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