Digital FM demodulator performing amplitude compensation
AssigneeMitsubishi Denki Kabushiki Kaisha
InventorsKenichi Taura, Masayuki Tsuji, Masahiro Tsujishita, Masayuki Ishida
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Abstract
A digital FM demodulator converts a digital FM input signal to a demodulated signal, detects the amplitude of the digital FM input signal, generates a corresponding amplitude signal, and adjusts the amplitude of the demodulated signal according to the amplitude signal, thereby compensating for variations in the amplitude of the digital FM input signal and removing amplitude distortion from the demodulated signal. This reduces the performance requirements of, for example, a low-pass analog filter preceding the digital FM demodulator in an FM radio broadcast receiver, permitting the analog filter to be implemented in a semiconductor integrated circuit.
Claims17
A digital FM demodulator, comprising:
- means for demodulating a digital FM input signal to obtain a demodulated signal;
- means for detecting an amplitude of the digital FM input signal and generating a corresponding amplitude signal;
- means for calculating an amplitude compensation coefficient;
- and
- means for performing amplitude compensation, said means for performing amplitude compensation operating in combination with said means for calculating an amplitude compensation coefficient to adjust an amplitude of the demodulated signal according to the amplitude signal, thereby compensating for variations in the amplitude of the digital FM input signal,
- wherein said means for demodulating delays the digital FM input signal to obtain a delayed signal, and multiplies the digital FM input signal by the delayed signal, and
- wherein said means for detecting calculates a sum of squares of the digital FM input signal and the delayed signal.
A method of demodulating a digital FM input signal, comprising the steps of:
- converting the digital FM input signal to a demodulated signal;
- detecting an amplitude of the digital FM input signal and generating a corresponding amplitude signal;
- calculating an amplitude compensation coefficient;
- and
- performing ampltiude compensation, said step of performing amplitude compensation operating in combination with said step of calculating an ampltiude compensation coefficient to adjust an amplitude of the demodulated signal according to the amplitude signal, thereby compensating for variations in the amplitude of the digital FM input signal,
- wherein said step of converting further comprises the steps of:
- delaying the digital FM input signal to obtain a delayed signal;
- and
- multiplying the digital FM input signal by the delayed signal, and
- wherein said step of detecting includes calculating a sum of squares of the digital FM input signal and the delayed signal.
A digital FM demodulator, comprising:
- a demodulating unit that demodulates a digital FM input signal to obtain a demodulated signal;
- an amplitude detector that detects an amplitude of the digital FM input signal and generates a corresponding amplitude signal;
- and
- an amplitude compensation unit and an amplitude compensation coefficient calculation unit, which in combination adjusts an amplitude of the demodulated signal according to the amplitude signal, thereby compensating for variations in the amplitude of the digital FM input signal,
- wherein said demodulating unit delays the digital FM input signal to obtain a delayed signal, and multiplies the digital FM input signal by the delayed signal, and
- wherein said amplitude detector calculates a sum of squares of the digital FM input signal and the delayed signal.
Dependencies are inferred from the claim text.