[Ground-station] Operation PFB

[Michelle Thompson]

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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