Apparatus and method for demodulating an angle-modulated signal

Abstract

An angle demodulator in which an FM modulated wave is converted into an IF signal (SI) in the form of digital so as the signal is supplied to a Hilbert transformer ( ) and to an outer product calculation section ( ). The Hilbert transformer ( ) allows the phase of the IF signal (SI) to shift ninety degrees and supplied it to the outer product calculation section ( ). An integrator ( ) calculates a phase of a cosine wave of an angular frequency that a frequency control unit ( ) designates. A phase converter ( ) calculates the cosine wave and an instantaneous value of a signal in which the cosine wave shifts ninety degrees out of phase so as to supply the value to the outer product calculation section ( ). The outer product calculation section ( ) supplies to the frequency control unit ( ) an outer product of a vector including a value of the IF signal and of a signal from the Hilbert transformer ( ) and a vector including a value supplied from the phase converter ( ). The frequency control unit ( ) performs a proportion integral control to the outer product so as to determine an updated value of an angular frequency, and supplies the determined value to the integrator ( ). A digital signal representing the value of the angular frequency is converted into an analog signal as a result of D/A conversion and is reproduced as a voice.