four-phase modulation

four-phase modulation

[¦fȯr ¦fāz ‚mäj·ə′lā·shən]
(communications)
Modulation in which data are encoded on a carrier frequency as a succession of phase shifts that will be 45, 135, 225, or 315°; each phase shift contains 2 bits of information called dibits, as follows: 225° represents 00, 315° is 01, 45° is 11, and 135° is 10.