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If I take any arbitrary M-ary phase-shift keying modulation scheme, and use some sort of "shaping" filter (perhaps a raised-cosine filter) to smoothly transition from one symbol in the constellation to another (which causes the phase also to smoothly transition), would that be a kind of continuous phase modulation?

Or does "continuous phase modulation" refer only to some frequency modulation schemes? --75.19.73.101 (talk) 04:55, 6 December 2007 (UTC)[reply]

Like you have said, the key thing for CPM is that the phase smoothly transitions at symbol boundaries. One way to think about generating a CPM signal is to imagine M-ary data symbols being convolved with a phase pulse function. Now for CPM this phase pulse must begin at 0 so there is no phase jump at the symbol boundary. (By convention the phase pulse's final value is 1/2). For full response the phase pulse transitions from 0 to 1/2 during one symbol interval. For partial response, the phase pulse lasts for multiple symbol intervals.

For CPM this phase pulse function can be anything, as long as it is continuous and starts at 0.

CPM can be thought of as frequency modulation or phase modulation. Frequency is just the integral of phase, so a linearly increasing phase is a constant frequency. Instead of describing the CPM scheme with a phase pulse, you can also equivalently describe it using a frequency pulse.

I havn't really answered your first question though.

121.72.69.231 (talk) 04:05, 14 May 2008 (UTC)[reply]

Should there be a hyphen in "continuous phase modulation" after the word "continuous"? In other words, is the adjective "continuous" describing "phase"? —Voidxor (talk) 16:30, 20 April 2010 (UTC)[reply]

As both FSK and Continuous-phase frequency-shift keying (CPFSK) are condidered a special form of frequency modulation, shouldn't FSK be mentioned in this article? What about 4-level Continuous FM (C4FM) - is this the same as CPFSK? --Dmitry _{(talk•contibs)} 09:44, 26 March 2012 (UTC)[reply]