🚀 go-pugleaf

In article <1993Jan20.233931.268@gems.vcu.edu>, hleaves@gems.vcu.edu writes:
|> I know what frequency hopping is, but what is "spread spectrum"? Are they the
|> same thing?
|> 
Frequency hopping is a form of spread spectrum that hops the carrier among
  several discrete frequencies based on some pseudo-noise (PN) sequence.

The more modern technique, especially for data, is to use "direct-sequence"
  spread spectrum in which the carrier is spread in frequency directly by the
  data.  The typical implementation is to use a high-speed clock that is some
  large (10-100X) multiple of the data rate, and use this clock to read out a PN
  sequence, XOR this PN sequence with your data, and use that
  signal to phase-shift your carrier. The occupied bandwidth of such a signal
  (how much it's spread) is a function of the rate at which the carrier is
  phase shifted.

Once you've synchronized at the receiving end [this is where spread-spectrum
  gets "interesting"], you "despread" the carrier using the same phase-shifting
  technique you used to spread it.

Good books on the Topic are "Spead Spectrum Systems", by Dixon. And the
  ARRL spread-spectrum sourcebook.

-- 
Marcus Leech, 4Y11             Bell-Northern Research  |opinions expressed
mleech@bnr.ca                  P.O. Box 3511, Stn. C   |are my own, and not
ml@ve3mdl.ampr.org             Ottawa, ON, CAN K1Y 4H7 |necessarily BNRs