COMMUNICATION SYSTEM, RECEIVING APPARATUS AND COMMUNICATION METHOD
The present invention provides a communication system. When the audio signal in the wide band is input to a wireless microphone, the wireless microphone performs a balanced modulation processing to invert the frequency spectrum of the audio signal and transmits the audio signal with the inverted frequency. When a speaker apparatus receives the audio signal transmitted from the wireless microphone, the speaker apparatus cuts off a frequency component of the received audio signal in the frequency band of the infrared radiation noise produced by the external apparatus (infrared radiation noise band), performs a reverse balanced modulation processing to invert again the frequency spectrum of the audio signal having the frequency component in the infrared radiation noise band cut off, and outputs the audio signal with the frequency spectrum inverted again.
1 . A communication system, comprising:
a transmitting apparatus that transmits an audio signal in a wide band including a frequency band higher than a voice band; and
a receiving apparatus that receives the audio signal from said transmitting apparatus,
wherein said transmitting apparatus comprises:
an audio input portion to which said audio signal in the wide band is input;
a balanced modulation portion that inverts a frequency spectrum of the audio signal input to said audio input portion; and
a transmitting portion that transmits the audio signal having the frequency spectrum inverted by said balanced modulation portion, and
said receiving apparatus comprises:
a receiving portion that receives the audio signal transmitted from said transmitting apparatus;
a filter portion that cuts off a frequency component in a frequency band of infrared radiation noise of the audio signal received by said receiving portion;
a reverse balanced modulation portion that inverts again the frequency spectrum of the audio signal having the frequency component in the frequency band of the infrared radiation noise cut off by said filter portion; and
an audio output portion that outputs the audio signal having the frequency spectrum inverted again by said reverse balanced modulation portion.
2 . The communication system according to claim 1 , wherein said transmitting apparatus further comprises:
a first infrared radiation noise detecting portion that detects infrared radiation noise equal to or higher than a predetermined threshold in a vicinity of said transmitting apparatus; and
a balanced modulation controlling portion that controls said balanced modulation portion to invert the frequency spectrum of said audio signal in a case where said first infrared radiation noise detecting portion detects the infrared radiation noise equal to or higher than said predetermined threshold, and
said receiving apparatus further comprises:
a filter controlling portion that, in the case where said first infrared radiation noise detecting portion detects said infrared radiation noise, controls said filter portion to cut off a frequency component in the frequency band of said infrared radiation noise; and
a reverse balanced modulation controlling portion that, in the case where said first infrared radiation noise detecting portion detects said infrared radiation noise, controls said reverse balanced modulation portion to invert again the frequency spectrum of the audio signal having the frequency component in the frequency band of said infrared radiation noise cut off by said filter portion.
3 . The communication system according to claim 2 , wherein said transmitting apparatus further comprises:
a signal superimposing portion that, in the case where said first infrared radiation noise detecting portion detects said infrared radiation noise, superimposes a noise detection signal that indicates occurrence of said infrared radiation noise on the audio signal to be transmitted from said transmitting portion,
said receiving apparatus further comprises:
a signal extracting portion that extracts said noise detection signal from the audio signal received at said receiving portion, and
in a case where said signal extracting portion detects said noise detection signal, said filter controlling portion activates said filter portion, and said reverse balanced modulation controlling portion activates said reverse balanced modulation portion.
4 . The communication system according to claim 3 , wherein said noise detection signal superimposed on said audio signal includes a predetermined tone signal, and
in a case where said signal extracting portion extracts said tone signal included in said noise detection signal from the audio signal received at said receiving portion, said filter controlling portion activates said filter portion, and said reverse balanced modulation controlling portion activates said reverse balanced modulation portion.
5 . The communication system according to claim 1 , wherein said receiving apparatus further comprises:
a second infrared radiation noise detecting portion that detects infrared radiation noise equal to or higher than a predetermined threshold in a vicinity of said receiving apparatus;
a filter controlling portion that, in a case where said second infrared radiation noise detecting portion detects said infrared radiation noise, controls said filter portion to cut off a frequency component in the frequency band of said infrared radiation noise; and
a reverse balanced modulation controlling portion that, in the case where said second infrared radiation noise detecting portion detects said infrared radiation noise, controls said reverse balanced modulation portion to invert again the frequency spectrum of the audio signal having the frequency component in the frequency band of said infrared radiation noise cut off by said filter portion.
6 . A receiving apparatus that receives an audio signal in a wide band including a frequency band higher than a voice band, comprising:
a receiving portion that receives said audio signal;
a filter portion that cuts off a frequency component in a frequency band of infrared radiation noise of the audio signal received by said receiving portion;
a reverse balanced modulation portion that inverts again a frequency spectrum of the audio signal having the frequency component in the frequency band of said infrared radiation noise cut off by said filter portion; and
an audio output portion that outputs the audio signal having said frequency spectrum inverted again by said reverse balanced modulation portion.
7 . A communication method performed in a communication system comprising a transmitting apparatus that transmits an audio signal in a wide band including a frequency band higher than a voice band and a receiving apparatus that receives the audio signal from said transmitting apparatus, the method comprising the steps of:
said transmitting apparatus
inverting a frequency spectrum of the input audio signal; and
transmitting the audio signal having the frequency spectrum inverted to said receiving apparatus; and
said receiving apparatus
receiving the audio signal transmitted from said transmitting apparatus;
cutting off a frequency component in a frequency band of infrared radiation noise of the received audio signal;
inverting again the frequency spectrum of the audio signal having the frequency component in the frequency band of said infrared radiation noise cut off; and
outputting the audio signal having the frequency spectrum inverted again.