DESCRIPTION
In an FM signal, the modulation is the deviation of a carrier from its nominal frequency. The conventional method to demodulate this signal is to convert frequency deviation to phase and detect the change of phase. In the quadrature demodulator, the modulated carrier is passed through an LC tank circuit that shifts the signal by 90° at the center frequency. This phase shift is either greater or less than 90° depending on the direction of deviation. A phase detector compares the phase-shifted signal to the original to give the demodulated baseband signal. You use quadrature demodulators not only for frequency modulation, but also with digital modulation schemes such as FSK (frequency shift keying) and GFSK (Gaussian frequency shift keying).

PREREQUISITES
NA