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Re: Proposal: SDR-DSP receiver (was: Re: Cube sat and DSPs (was Re: cube sat))

Hello Achim,

I am doing something very similar. I have designed and built a small PCB (3.5 x
3.5 in.) that contains all the components for a stand-alone SDR but will also
operate over a high-speed USB interface. I've submitted an article to QEX that
describes the board and have accepted a volunteer position with the ARRL High
Speed Multimedia Working Group to define an OFDM RF modem for use in
constructing radio-linked metropolatin area networks. We're forming a small
group to do the software development, which will be open source.

My original motive was to write software to support analog and digital amateur
satellite operation using SSB and NBFM voice and 9.6-153.6 KBPS FSK modems. I
don't know when I will be able to get to that now. Perhaps someone else could
pick up that project using the hardware that I designed.

The board was designed to support open software development using free
development software from the Free Software Foundation and Xilinx. It is
designed around a 60 MIPS ARM7-TDMI 32-bit RISC MCU from Oki Semiconductor
(ML67Q5003) and a 4,320 logic element Xilinx Spartan-3 FPGA (XC3S200). The MCU
has a mask ROM that downloads software via an RS-232 or RS-485 port for
execution from its on-chip 32KB of RAM or 512KB flash ROM. The MCU has a 16-bit
parallel interface to the FPGA to access its on-chip 216K RAM and the MCU can
configure the FPGA via its JTAG port. The FPGA also has twelve 4ns 18x18

The RF interface is a 14-bit 40MSPS ADC (AD9244) that can sample signals up to
240MHz and a dual 128MSPS 14-bit DAC (AD9767). A 16-bit 24KSPS audio codec
(PCM3501) supports audio I/O and a USB interface chip (Agere USS2X1A) supports
12MBPS or 480MBPS digital I/O. There is also a low-speed ADC input and a SPI I/O
port provided by the MCU.

The OFDM modem group is planning to use ARM7 assembly language and C for the MCU
programming and Verilog for the FPGA programming. I've ordered sample parts for
twelve boards and could provide hardware to anyone willing to do serious
development that would support AMSAT satellite users.

When production FPGAs are available (18 weeks), I should be able to provide
hardware to users for under 200 USD.

Let me know if you are interested. I can provide a copy of the QEX article if
you are able to receive multi-megabyte mail messages. The same goes for other
AMSAT members.



----- Original Message -----
From: "Achim Vollhardt" <avollhar@physik.unizh.ch>
To: "AMSAT Bulletin Board" <amsat-bb@AMSAT.Org>
Sent: Tuesday, 30 March, 2004 06:02 UTC
Subject: Proposal: SDR-DSP receiver (was: Re: [amsat-bb] Cube sat and DSPs (was
Re: cube sat))

> Hello Hams,
> This brings up a very interesting point, which I am thinking about right
> now very intensely.. but I am lacking of some support and knowledge..
> Remember the TAPR/Amsat DSP-93? I don't know it's shortcomings, but fact
> is, it is discontinued.. I would like to so a step further and design an
> all digital SDR-DSP receiver, quite similar to Moe Wheatley AE4JY and
> Pieter Ibelings (N4IP), but with a small DSP behind, so you can use it
> as a standalone receiver, rather than having to connect it to a PC.
> Proposal is to is a 65 MSPS ADC with the digital down converter and
> DSP.. so possible reception would be somwhere between 0.1 and 30 MHz.
> Perhaps direct reception of the aliased image of 144 MHz (at 14 MHz)
> would be possible as well.. a common problem like bad large signal
> performace is negligible as we deal with sat-downlinks.. we don't have
> large signals!!
> What I have:
> - a basic idea how this works
> - some sample devices
> - experience in layouting and a PCB company at hand.. :)
> What I need:
> - more people willing to join (!)
> - some techies to iron out the bumps.. ;)
> - some DSP coders.. I started digging into it but with some experience,
> things like SSB, FM, AM and CW demodulation is a piece of cake..
> - more ideas: this baby could also handle PSK31 or high speed PSK
> decoding (anybody interested in decoding the deep-space probes?),
> digital voice encoding (with forward error correction!).
> I think this is a real challenge.. when keeping all open-source, this
> could be a wonderful project pushing the limits !
> Hpoing to trigger some discussion..
> 73s, Achim, DH2VA
> > Date: Sun, 28 Mar 2004 19:12:17 -0900
> > From: "Edward R. Cole" <al7eb@acsalaska.net>
> > Subject: Re: [amsat-bb] Cube sat and DSPs (was Re: cube sat)
> >
> > At 07:27 PM 3/28/2004 -0500, Dquagliana@aol.com wrote:
> >
> >>Keith N6ORS writes:
> >
> > ***snip***
> >
> >>Now, converting the RF input down to the audio range,
> >>where the DSPx's ADC can process it, with the remaining
> >>275 milliwatts (of that 1/2 watt power budget) is left as
> >>an exercise to the reader, but should be achievable in a
> >>simple receiver.  QRP kit type receivers typically use
> >>much less than 275 milliwatts on receive.
> >>
> >></But-I-digress=ON>
> >>In addition, there are open source applications already written
> >>for the DSPx and free development tools.  If someone does launch a
> >>DSP processor, factors such as free and open tools and a known
> >>architecture will help to increase your pool of available DSP
> >>programmers from among the ranks of amateur radio operators.
> >
> > ***unsnip***
> >
> > As you speak here, a fellow in the amateur radio astronomy world has built
> > a  I-Q direct-conversion receiver for 1420 MHz with 98 KHz bw.  May not be
> > space qualified chips but didn't I just read the the Universities were
> > cobling up satellites with RS parts (or such)?  Then its the sw that does
> > the demod.  Sounds like a SDR, right?  So design a standard radio and
> > launch them and install whatever sw your heart desires.  Want to change
> > later...upload the change.
> >
> > No I do not have this expertise...but this is a college student doing this
> > if I am not mistaken.
> >
> > 73s Ed- AL7EB
> >
> >
> --
> -------------------------------------
>      Achim Vollhardt
>      Universitaet Zuerich
>      Physik Institut, 36H24
>      Winterthurerstrasse 190
>      CH-8057 Zuerich
>      tel: 0041-1-6355742
> 0041-1-6355704 (fax)
>      email: avollhar@physik.unizh.ch
> ----
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