Full duplex speakerphone for radio and landline telephones
First Claim
1. Hands-free telephone circuitry for providing cancellation of undesired signal coupling, including a speaker transducing a modified first signal produced from a first signal received from a communications channel and a microphone transducing a second signal for modification and transmissing as a modified second signal on a communication channel simultaneous with the first signal, comprising:
- means for detecting the modified first signal;
a first adaptive filter having coefficient determining means enabled by said modified first signal detecting means;
means including said first adaptive filter for substracting at least a portion of the modified first signal from the second signal, thereby producing the modified second signal with coupling from the modified first signal essentially cancelled;
means for detecting the modified second signal;
a second adaptive filter having coefficient determining means enabled by said modified second signal detecting means; and
means including said second adaptive filter for substracting at least a portion of the modified second signal from the first signal, thereby producing the modified first signal with coupling from the modified second signal essentially cancelled.
1 Assignment
0 Petitions
Accused Products
Abstract
A full duplex speakerphone employing adaptive filters and having application in radiotelephone systems is disclosed. To cancel acoustic feedback echo of the receive signal, a representation of the receive signal is subtracted from the transmit signal generated by the speakerphone microphone. The adaptive filter receive signal representation coefficents are modified when the receive signal is detected. Likewise, to cancel electronic echo of the transmit signal, a representation of the transmit signal is subtracted from the receive signal. The adaptive filter transmit signal representation coefficients are modified when the transmit signal is detected.
141 Citations
24 Claims
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1. Hands-free telephone circuitry for providing cancellation of undesired signal coupling, including a speaker transducing a modified first signal produced from a first signal received from a communications channel and a microphone transducing a second signal for modification and transmissing as a modified second signal on a communication channel simultaneous with the first signal, comprising:
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means for detecting the modified first signal; a first adaptive filter having coefficient determining means enabled by said modified first signal detecting means; means including said first adaptive filter for substracting at least a portion of the modified first signal from the second signal, thereby producing the modified second signal with coupling from the modified first signal essentially cancelled; means for detecting the modified second signal; a second adaptive filter having coefficient determining means enabled by said modified second signal detecting means; and means including said second adaptive filter for substracting at least a portion of the modified second signal from the first signal, thereby producing the modified first signal with coupling from the modified second signal essentially cancelled. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. Hands-free radiotelephone circuitry for providing cancellation of undesired baseband signal coupling, including a receiver for receiving a first signal, a speaker for transducing a modified first signal, a microphone for transducing a second signal, and a transmitter for transmitting a modified second signal simultaneous with receiver reception, comprising:
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means for detecting the modified first signal; means for creating a representation of the modified first signal when the modified first signal is detected; means for subtracting said representation of the modified first signal from the second signal, thereby producing the modified second signal with coupling from the modified first signal essentially cancelled; means for increasing the level of the modified first signal transduced by the speaker when the modified first signal is detected; means for detecting the modified second signal; means for creating a representation of the modified second signal when the modified second signal is detected; means for subtracting said representation of the modified second signal from the first signal, thereby producing the modified first signal with coupling from the modified second signal essentially cancelled; and means for increasing the level of the modified second signal transmitted by the transmitter when the modified second signal is detected. - View Dependent Claims (10, 11, 12, 13)
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14. A method for providing cancellation of undesired signal coupling in a hands-free telephone having a speaker, which transduces a modified first signal produced from a first signal received from a communications channel, and a microphone, which transduces a second signal for modification and transmission as a modified second signal on a communications channel simultaneous with the first signal, comprising the steps of:
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detecting the modified first signal; enabling coefficient determining means of a first adaptive filter in response to said detection of the modified first signal; subtracting at least a portion of the modified first signal from the second signal, thereby producing the modified second signal with coupling from the modified first signal essentially cancelled; detecting the modified second signal; enabling coefficient determining means of a second adaptive filter in response to said detection of the modified second signal; and subtracting at least a portion of the modified second signal from the first signal, thereby producing the modified first signal with coupling from the modified second signal essentially cancelled. - View Dependent Claims (15, 16, 17, 18, 19)
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20. A method for providing cancellation of undesired baseband signal coupling in a hands-free radiotelephone which includes a receiver for receiving a first signal, a speaker for transducing a modified first signal, a microphone for transducing a second signal, and a transmitter for transmitting a modified second signal simultaneous with receiver reception, comprising the steps of:
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detecting the modified first signal; creating a representation of the modified first signal when the modified first signal is detected; subtracting said representation of the modified first signal from the second signal, thereby producing the modified second signal with coupling from the modified first signal essentially cancelled; increasing the level of the modified first signal transduced by the speaker when the modified first signal is detected; detecting the modified second signal; creating a representation of the modified second signal when the modified second signal is detected; subtracting said representation of the modified second signal from the first signal, thereby producing the modified first signal with coupling from the modified second signal essentially cancelled; and increasing the level of the modified second signal transmitted by the transmitter when the modified second signal is detected. - View Dependent Claims (21, 22, 23, 24)
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Specification