[time-nuts] WWVB New Modulation five cent demodulator / carrier regenerator ? (Dale J. Robertson)

johncroos at aol.com johncroos at aol.com
Mon Oct 22 02:16:19 EDT 2012


Dale -

To your question re BPSK and DPSK. In both modes the phase shift is 180 
degrees.
Straight PSK has the issue of determining the 1's from the 0's, at the 
receiver as there is
no phase reference.
To avoid this DPSK encodes the the serial data stream prior to the 
bi-phase modulator.
As I recall (at 1 AM) the method is like this. If the present bit to be 
sent is a 1 the phase
of the carrier is inverted. If it is a zero the phase is not inverted. 
This is easily sorted out
in the receiver using a flip flop and an XOR.

However recovery of the carrier must occur before decoding of the data 
stream and is
done the same way for both - at least in classical receivers. Squaring 
Loop or Costas Loop.

-john k6iql




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