Or, imagine 10, 20 or 50 of these operating in
parallel (to get an idea of what lies ahead
if you in the way of a 'design task'):


COM-1018 DIRECT SEQUENCE SPREAD-SPECTRUM DEMODULATOR 20 Mchip/s

Key Features
  Direct sequence spread-spectrum demodulator.
  Variable chip rate up to 20 Mchips/s.
  Spreading codes:
o Gold sequences (up to 223-1 chips)
o Maximal length sequences, (max length 223-1 chips)
o Barker codes (length 11, 13)
o GPS C/A codes.
  BPSK, QPSK selectable.
  Demodulation performances: within 1.5 dB from theory at threshold SNR of 5
dB.
  Sequential code search.
  4-bit soft-quantized demodulated bits.
  Extensive monitoring:
o Receiver lock
o Carrier frequency error
  Connectorized 3 x 3  module for ease of prototyping.
  Standard 40 pin 2mm dual row connectors (left, right, bottom).
  Single 5V supply.
  Interfaces with 5V and 3.3V logic.

Electrical Interface:

Demodulator Inputs / Outputs
DATA_I_IN[9:0]
CLK +5V GND
DATA_I_OUT[3:0]


http://www.comblock.com/download/com1018.pdf


RF Jim

----- Original Message -----
From: "Jonathan Johnson" <jonathan@OUTEREDGE.NET>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Tuesday, November 12, 2002 6:39 AM
Subject: [EE] Spread spectrum receiver/DSP problem


> Does anyone on list know how one would go about decoding multiple channels
> on a spread spectrum receiver? with different spreading codes for each
> channel but all being decoded by the one receiver?
> e.g. for a system that has  lets say 50 available spreading codes to be
used
> for diff channels, I want a receiver to be able to decode a number of
these
> simultaneously for instance channels 3,7,23,32,47.(not necessarily 5
> channels)
> The data for each channel could be output in a number of ways either with
> each packed added a channel id number to the end of it or thru different
I/O
> lines.
> I imagine this would entail some MAJOR signal processing. I don't know
> personally but this sort of  sounds like what a cellular base station does
> with multiple channels.
>
> You used to be a cellular guy didn't you Jim? have you any pointers etc
> where I could learn a bit about the techniques involved?
>
> No pointers or info will be turned down, I have no idea other than what I
> described above.
>
>
> Cheers
>
> Jonathan
>
> --
> http://www.piclist.com hint: To leave the PICList
> mailto:piclist-unsubscribe-request@mitvma.mit.edu
>
>

--
http://www.piclist.com hint: To leave the PICList
mailto:piclist-unsubscribe-request@mitvma.mit.edu