The shifting or translation of a signal from one frequency
band to another is accomplished by the process of modulation. In this process, the baseband signal is impressed
in some way on a carrier signal at a higher
frequency such that one or more of the characteristics of
the carrier signal are altered. In this manner, baseband frequencies
are translated in frequency up to the carrier frequency. The
three characteristics of the carrier signal that can be altered
are the amplitude, the frequency and the phase.
There are three
basic types of digital modulation:
frequency shift keying (FSK)
phase
shift keying (PSK)
amplitude shift keying (ASK)
CDMA uses phase shift keying.
Other topics in our resources on CDMA related to Modulation include: