Modulation Device, Modulation Method, Demodulation Device, and Demodulation Method

• US 20080243491A1
• Filed: 10/02/2006
• Published: 10/02/2008
• Est. Priority Date: 10/07/2005
• Status: Active Grant

• Current Assignee: NTT Docomo Incorporated (Nippon Telegraph and Telephone Corporation)
• Original Assignee: NTT Docomo Incorporated (Nippon Telegraph and Telephone Corporation)
• Inventors: Matsuoka, Hosei
• Granted Patent: US 8,498,860 B2
• Time in Patent Office: Days
• US Class Current: 704/201
• CPC Class Codes: H04B 11/00 Transmission systems employing sonic, ultrasonic or infrasonic waves
• CPC Class Codes: H04L 1/004 by using forward error control H04L1/0618 takes precedence; coding, decoding or code conversion, for error detection or correction H03M13/00
• CPC Class Codes: H04L 27/2602 Signal structure
• CPC Class Codes: H04L 27/2627 Modulators
• CPC Class Codes: H04L 27/2649 Demodulators
• CPC Class Codes: H04R 5/04 Circuit arrangements, e.g. for selective connection of amplifier inputs/outputs to loudspeakers, for loudspeaker detection, or for adaptation of settings to personal preferences or hearing impairments combinations of amplifiers H03F3/68; stereophonic systems H04S

Abstract

A modulation device including: a modulation unit for modulating a carrier in an audible sound range by an encoded transmission signal to generate a modulated signal; a masker sound generation unit for generating a masker signal outputted as a masker sound for making the modulated signal harder to hear when transmitted with the modulated signal; and an acoustic signal generation unit for inserting the masker signal in the modulated signal to generate an acoustic signal.

Claims

1. A modulation device comprising:

modulation means for modulating a carrier in an audible sound range by a baseband signal to generate a modulated signal;

masker sound generation means for generating a masker signal outputted as a masker sound for making the modulated signal harder to hear when transmitted with the modulated signal; and

acoustic signal generation means for attaching the masker signal to the modulated signal to generate an acoustic signal.

2. The modulation device according to claim 1, wherein the masker sound generation means composes each said masker signal inserted in the modulated signal, of a sine wave, and selects a frequency of the masker signal so that frequencies of at least a partial series of masker sounds among the masker sounds constitute a predetermined pattern.

3. A modulation device comprising:

modulation means for matching an amplitude of a carrier in an audible sound region with a spectrum envelope of an acoustic signal and for modulating the carrier by a baseband signal to generate a modulated signal; and

acoustic signal generation means for replacing a component in a frequency band of the carrier in the acoustic signal with the modulated signal generated by the modulation means, to generate a synthetic acoustic signal.

4. The modulation device according to claim 3, wherein when there is a frequency less than a predetermined threshold based on an audible level in the spectrum envelope of the acoustic signal, the modulation means amplifies a power of a spectrum at the frequency to the threshold.

5. A demodulation device comprising:

coupling means for making a copy of a signal frame of a transmission signal modulated by frequency division multiplexing and for coupling a plurality of signal frames including the signal frame copy and the transmitted signal frame;

demodulation means for Fourier-transforming the plurality of signal frames coupled by the coupling means, to demodulate the signal frames;

detection means for detecting a deviation of a carrier frequency of the transmission signal in the plurality of signal frames Fourier-transformed by the demodulation means; and

correction means for correcting the carrier frequency of the transmission signal on the basis of the deviation of the carrier frequency detected by the detection means.

6. A demodulation device for demodulating an acoustic signal containing a modulated signal, and a masker signal outputted as a masker sound for making the modulated signal harder to hear when transmitted with the modulated signal, said demodulation device comprising:

removal means for removing the masker signal from the acoustic signal; and

demodulation means for demodulating the acoustic signal from which the masker signal was removed by the removal means.

7. A demodulation device for demodulating an acoustic signal containing a modulated signal, and a masker signal composed of a frequency associated with a frequency band of a carrier and outputted as a masker sound for making the modulated sound harder to hear when transmitted with the modulated signal, said demodulation device comprising:

storage means for storing the frequency band of the carrier and the frequency of the masker signal in association with each other;

detection means for Fourier-transforming the masker signal to detect the frequency of the masker signal; and

demodulation means for demodulating the acoustic signal in the frequency band stored by the storage means in association with the frequency of the masker signal detected by the detection means.

8. A modulation method comprising:

a modulation step wherein modulation means modulates a carrier in an audible sound range by a baseband signal to generate a modulated signal;

a masker sound generation step wherein masker sound generation means generates a masker signal outputted as a masker sound for making the modulated signal harder to hear when transmitted with the modulated signal; and

an acoustic signal generation step wherein acoustic signal generation means attaches the masker signal to the modulated signal to generate an acoustic signal.

9. A modulation method comprising:

a modulation step wherein modulation means matches an amplitude of a carrier in an audible sound region with a spectrum envelope of an acoustic signal and modulates the carrier by a baseband signal to generate a modulated signal; and

an acoustic signal generation step wherein acoustic signal generation means replaces a component in a frequency band of the carrier in the acoustic signal with the modulated signal generated in the modulation step, to generate a synthetic acoustic signal.

10. A demodulation method comprising:

a coupling step wherein coupling means makes a copy of a signal frame of a transmission signal modulated by frequency division multiplexing and couples a plurality of signal frames including the signal frame copy and the transmitted signal frame;

a demodulation step wherein demodulation means Fourier-transforms the plurality of signal frames coupled in the coupling step, to demodulate the signal frames;

a detection step wherein detection means detects a deviation of a carrier frequency of the transmission signal in the plurality of signal frames Fourier-transformed in the demodulation step; and

a correction step wherein correction means corrects the carrier frequency of the transmission signal on the basis of the deviation of the carrier frequency detected in the detection step.