Q: Phase-coherence vs phase-continuous

I've looked for info on this and found:

http://www.analog.com/library/analogDialogue/archives/44-11/phase_coherent.html

The article states:

Phase-coherence is preferred because the phase is remembered.
Phase-continuous is lower bandwidth.

They do not say why phase-coherence is preferred.

If one is doing FSK signaling, why is phase-coherence preferred?

Thanks.

 

Oops! This was my conclusion ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

 

If you are not continuous phase, you need more bandwidth. Noise is
proportional to the square root of the bandwidth, so I can't see phase
coherence being beneficial in performance. I suppose if you went GMSK
and reduced the bandwidth, then your point is valid.

 

CPFSK eliminates the jumps, but the author is espousing the virtues of
PCFSK, i.e. just the opposite.

 

Excellent point! I had not considered the use to two PLLs. Maybe at high
data rates that would be important.

Thanks.

 

Yes, but how do you distinguish a frequency shift using two slow PLLs?

 

Very slowly, methodically, and carefully.

Sub hertz sample rates. ;-) Hehehehehe!

 

Using a PLL to make a matched filter seems iffy. Couple
of resonant filters and a comparator sounds better to my ear. 'Course,
there's a lot of dance-management too...

 

Formal consistency check failed. Please resubmit.

?-)

 

I am fairly sure you disunderstand. Can you (or anybody here) explain the
difference CPFSK and PCFSK clearly(; and the S/N effects)?

?-)

 

Just for grins can you set up a simulation to play with? I don't quite
follow yet.

?-)