Circuit for removing in-band FSK signals without muting of receiver

• US 6,795,551 B1
• Filed: 01/13/2000
• Issued: 09/21/2004
• Est. Priority Date: 01/13/2000
• Status: Expired due to Term

• Current Assignee: Dialog Semiconductor B.V. (Renesas Electronics Corporation)
• Original Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Inventors: Kohlmann, Renardus Henrikus Maria, Tielens, Theo Ary Asmund
• Primary Examiner(s): Isen, Forester W.
• Assistant Examiner(s): Tran, Con P.
• Application Number:
  US09/482,380
• Time in Patent Office: 1,713 Days
• Field of Search: 379/406.01, 379/406.08, 379/142.02, 379/142.04, 379/93.23, 381/71.11, 381/71.8, 370/290, 708/322
• US Class Current: 379/406.01
• CPC Class Codes: H04M 1/573 Line monitoring circuits for detecting caller identification
• CPC Class Codes: H04M 1/6016 in the receiver circuit
• CPC Class Codes: H04M 3/002 Applications of echo suppressors or cancellers in telephonic connections in two-way loud-speaking telephone systems H04M9/08, echo suppressors or cancellers per se H04B3/20
• CPC Class Codes: H04M 3/42042 Notifying the called party of information on the calling party details within substation equipment H04M1/57, signalling details H04Q3/72
• CPC Class Codes: H04M 3/428 Arrangements for placing incoming calls on hold

Abstract

A circuit for blocking reception of in-band frequency-shift keyed (FSK) signals by the reception transducer of a telephone subscriber terminal without requiring muting of the reception transducer. The incoming telephone reception signal, which contains both voice and frequency-shift keyed (FSK) signal components, is processed, e.g., within a digital signal processor (DSP), such that the FSK signal component is substantially cancelled. The incoming telephone reception signal is processed to extract amplitude, frequency and phase information, as well as to recover the FSK data clock. This FSK signal information is then used to generate a replica FSK signal for summing with the incoming telephone reception signal to cancel the FSK signal component. Echo cancellation of the local subscriber voice can also be implemented by adaptively filtering the incoming telephone reception signal in accordance with the outgoing telephone transmission signal and subtracting the resultant signal from the incoming telephone reception signal, thereby canceling the transmission signal echo component.

Claims

1. An apparatus including a circuit for blocking reception of in-band frequency-shift keyed (FSK) signals by the reception transducer of a telephone subscriber terminal without requiring muting of said reception transducer, comprising:

a signal reception path configured to convey a telephone reception signal for conversion by a telephone reception transducer, wherein said telephone reception signal includes voice and FSK signal components; and

a FSK signal cancellation circuit, coupled to said signal reception path, configured to provide a replica FSK signal component for subtraction from said telephone reception signal to substantially cancel said FSK signal component without interrupting said conveyance of said voice signal component.

2. The apparatus of claim 1, wherein said signal reception path and said FSK signal cancellation circuit together comprise at least a portion of a digital signal processor (DSP) circuit.

3. The apparatus of claim 1, wherein:

said FSK signal cancellation circuit comprises a FSK signal detection circuit configured to receive said telephone reception signal and detect said FSK signal component and in accordance therewith provide said replica FSK signal component; and

said signal reception path includes a signal combining circuit configured to receive and substract said replica FSK signal component from said telephone reception signal and in accordance therewith provide a modified telephone reception signal in which said voice signal component substantially remains and said FSK signal component is substantially cancelled.

4. An apparatus including a circuit for blocking reception of in-band frequency-shift keyed (FSK) signals by the reception transducer of a telephone subscriber terminal without requiring muting of said reception transducer, comprising:

a signal reception path configured to convey a telephone reception signal for conversion by a telephone reception transducer, wherein said telephone reception signal includes voice and FSK signal components; and

a FSK signal cancellation circuit, coupled to said signal reception path, configured to substantially cancel said FSK signal component without interrupting said conveyance of said voice signal component;

wherein

said FSK signal cancellation circuit comprises a FSK signal detection circuit configured to receive said telephone reception signal and detect said FSK signal component and in accordance therewith provide a FSK cancellation signal,

said signal reception path includes a signal combining circuit configured to receive and combine said FSK cancellation signal and said telephone reception signal and in accordance therewith provide a modified telephone reception signal in which said voice signal component substantially remains and said FSK signal component is substantially cancelled, and

said FSK signal detection circuit comprises

a signal parameter detection circuit configured to receive said telephone reception signal and detect said FSK signal component and in accordance therewith provide FSK signal information, and

a signal generator circuit, coupled to said signal parameter detection circuit, configured to receive said FSK signal information and in accordance therewith provide a replica FSK signal as said FSK cancellation signal.

5. The apparatus of claim 4, wherein said signal parameter detection circuit comprises:

a FSK amplitude detection circuit configured to detect an amplitude of said FSK signal component and in accordance therewith provide FSK signal component amplitude information as a first portion of said FSK signal information;

a FSK clock recovery circuit configured to recover a clock signal related to said FSK signal component and in accordance therewith provide FSK signal component clock information as a second portion of said FSK signal information;

a FSK frequency detector circuit configured to detect a frequency of said FSK signal component and in accordance therewith provide FSK signal component frequency information as a third portion of said FSK signal information; and

a FSK phase detection circuit configured to detect a phase of said FSK signal component and in accordance therewith provide FSK signal component phase information as a fourth portion of said FSK signal information.

6. An apparatus including a circuit for blocking reception of in-band frequency-shift keyed (FSK) signals by the reception transducer of a telephone subscriber terminal without requiring muting of said reception transducer, comprising:

a signal reception path configured to convey a telephone reception signal for conversion by a telephone reception transducer, wherein said telephone reception signal includes voice and FSK signal components; and

a FSK signal cancellation circuit, coupled to said signal reception path, configured to substantially cancel said FSK signal component without interrupting said conveyance of said voice signal component;

wherein

said FSK signal cancellation circuit comprises a FSK signal detection circuit configured to receive said telephone reception signal and detect said FSK signal component and in accordance therewith provide a FSK cancellation signal,

said signal reception path includes a signal combining circuit configured to receive and combine said FSK cancellation signal and said telephone reception signal and in accordance therewith provide a modified telephone reception signal in which said voice signal component substantially remains and said FSK signal component is substantially cancelled, and

said signal combining circuit comprises

a signal delay circuit configured to receive and delay said telephone reception signal and in accordance therewith provide a delayed telephone reception signal, and

a signal summing circuit, coupled to said signal delay circuit, configured to receive and sum said delayed telephone reception signal and said FSK cancellation signal and in accordance therewith provide said modified telephone reception signal.

7. An apparatus including a circuit for blocking reception of in-band frequency-shift keyed (FSK) signals by the reception transducer of a telephone subscriber terminal without requiring muting of said reception transducer, comprising:

a signal reception path configured to convey a telephone reception signal for conversion by a telephone reception transducer, wherein said telephone reception signal includes voice and FSK signal components and a transmission signal echo component;

a FSK signal cancellation circuit, coupled to said signal reception path, configured to substantially cancel said FSK signal component without interrupting said conveyance of said voice signal component;

a signal transmission path configured to convey a telephone transmission signal originating from a telephone transmission traducer; and

an echo signal cancellation circuit, coupled between said signal transmission and reception paths, configured to receive said telephone transmission signal and said telephone reception signal and in accordance therewith substantially cancel said transmission signal echo component from said telephone reception signal conveyed via said signal reception path.

8. The apparatus of claim 7, wherein:

said echo signal cancellation circuit comprises an adaptive filter circuit configured to receive said telephone transmission signal and in accordance herewith receive and process said telephone reception signal and in accordance therewith provide an echo cancellation signal; and

said signal reception path includes a signal combining circuit configured to receive and combine said echo cancellation signal and said telephone reception signal and in accordance therewith provide a modified telephone reception signal in which said voice and FSK signal components substantially remain and said transmission signal echo component is substantially cancelled.

9. The apparatus of claim 8, wherein said adaptive filter circuit comprises:

a finite impulse response filter circuit configured to receive an error signal and in accordance therewith receive and process said telephone reception signal and in accordance therewith provide said echo cancellation signal; and

another signal combining circuit, coupled to said finite impulse response filter circuit, configured to receive and combine said telephone transmission signal and said echo cancellation signal and in accordance therewith provide said error signal.

10. An apparatus including a signal processor for blocking reception of in-band frequency-shift keyed (FSK) signals by the reception transducer of a telephone subscriber terminal without requiring muting of said reception transducer, comprising:

signal reception means for conveying a telephone reception signal for conversion by a telephone reception transducer, wherein said telephone reception signal includes voice and FSK signal components; and

FSK signal cancellation means for generating a replica FSK signal component for subtraction from said telephone reception signal to substantially cancel said FSK signal component without interrupting said conveyance of said voice signal component.

11. The apparatus of claim 10, wherein:

said FSK signal cancellation means comprises FSK signal detection means for receiving said telephone reception signal and detecting said FSK signal component and in accordance therewith providing a FSK cancellation signal; and

said signal reception means includes signal combining means for receiving and combining said FSK cancellation signal and said telephone reception signal and in accordance therewith providing a modified telephone reception signal in which said voice signal component substantially remains and said FSK signal component is substantially cancelled.

12. An apparatus including a signal processor for blocking reception of in-band frequency-shift keyed (FSK) signals by the reception transducer of a telephone subscriber terminal without requiring muting of said reception transducer, comprising:

signal reception means for conveying a telephone reception signal for conversion by a telephone reception transducer, wherein said telephone reception signal includes voice and FSK signal components; and

FSK signal cancellation means for substantially canceling said FSK signal component without interrupting said conveyance of said voice signal component;

wherein

said FSK signal cancellation means comprises FSK signal detection means for receiving said telephone reception signal and detecting said FSK signal component and in accordance therewith providing a FSK cancellation signal,

said signal reception means includes signal combining means for receiving and combining said FSK cancellation signal and said telephone reception signal and in accordance therewith providing a modified telephone reception signal in which said voice signal component substantially remains and said FSK signal component is substantially cancelled, and

said FSK signal detection means comprises

signal parameter detector means for receiving said telephone reception signal and detecting said FSK signal component and in accordance therewith providing FSK signal information, and

signal generator means for receiving said FSK signal information and in accordance therewith providing a replica FSK signal as said FSK cancellation signal.

13. The apparatus of claim 12, wherein said signal parameter detector means comprises:

FSK amplitude detector means for detecting an amplitude of said FSK signal component and in accordance therewith providing FSK signal component amplitude information as a first portion of said FSK signal information;

FSK clock recovery means for recovering a clock signal related to said FSK signal component and in accordance therewith providing FSK signal component clock information as a second portion of said FSK signal information;

FSK frequency detector means for detecting a frequency of said FSK signal component and in accordance therewith providing FSK signal component frequency information as a third portion of said FSK signal information; and

FSK phase detector means for detecting a phase of said FSK signal component and in accordance therewith providing FSK signal component phase information as a fourth portion of said FSK signal information.

14. An apparatus including a signal processor for blocking reception of in-band frequency-shift keyed (FSK) signals by the reception transducer of a telephone subscriber terminal without requiring muting of said reception transducer, comprising:

signal reception means for conveying a telephone reception signal for conversion by a telephone reception transducer, wherein said telephone reception signal includes voice and FSK signal components; and

FSK signal cancellation means for substantially canceling said FSK signal component without interrupting said conveyance of said voice signal component;

wherein

said FSK signal cancellation means comprises FSK signal detection means for receiving said telephone reception signal and detecting said FSK signal component and in accordance therewith providing a FSK cancellation signal,

said signal reception means includes signal combining means for receiving and combining said FSK cancellation signal and said telephone reception signal and in accordance therewith providing a modified telephone reception signal in which said voice signal component substantially remains and said FSK signal component is substantially cancelled, and

said signal combining means comprises

signal delay means for receiving and delaying said telephone reception signal and in accordance therewith providing a delayed telephone reception signal, and

signal summing means for receiving and summing said delayed telephone reception signal and said FSK cancellation signal and in accordance therewith providing said modified telephone reception signal.

15. An apparatus including a signal processor for blocking reception of in-band frequency-shift keyed (FSK) signals by the reception transducer of a telephone subscriber terminal without requiring muting of said reception transducer, comprising:

signal reception means for conveying a telephone reception signal for conversion by a telephone reception transducer, wherein said telephone reception signal includes voice and FSK signal components and a transmission signal echo component;

FSK signal cancellation means for substantially canceling said FSK signal component without interrupting said conveyance of said voice signal component;

signal transmission means for conveying a telephone transmission signal originating from a telephone transmission transducer; and

echo signal cancellation means for receiving said telephone transmission signal and said telephone reception signal and in accordance therewith substantially canceling said transmission signal echo component from said telephone reception signal conveyed via said signal reception means.

16. The apparatus of claim 15, wherein:

said echo signal cancellation means comprises adaptive filter means for receiving said telephone transmission signal and in accordance therewith receiving and processing said telephone reception signal and in accordance therewith providing an echo cancellation signal; and

said signal reception means includes signal combining means for receiving and combining said echo cancellation signal and said telephone reception signal and in accordance therewith providing a modified telephone reception signal in which said voice and FSK signal components substantially remain and said transmission signal echo component is substantially cancelled.

17. The apparatus of claim 16, wherein said adaptive filter means comprises:

finite impulse response filter means for receiving an error signal and in accordance therewith receiving and processing said telephone reception signal and in accordance therewith providing said echo cancellation signal; and

further signal combining means for receiving and combining said telephone transmission signal and said echo cancellation signal and in accordance therewith providing said error signal.

18. An apparatus including a signal processor programmed for blocking reception of in-band frequency-shift keyed (FSK) signals by the reception transducer of a telephone subscriber terminal without requiring muting of said reception transducer, said signal processor programmed to perform the steps of:

conveying a telephone reception signal for conversion by a telephone reception transducer, wherein said telephone reception signal includes voice and FSK signal components; and

generating a replica FSK signal component for substraction from said telephone reception signal to substantially cancel said FSK signal component without interrupting said conveyance of said voice signal component.

19. The apparatus of claim 18, wherein:

said signal processor is programmed to perform said step of substantially canceling said FSK signal component without interrupting said conveyance of said voice signal component by receiving said telephone reception signal and detecting said FSK signal component and in accordance therewith providing a FSK cancellation signal; and

said signal processor is programmed to perform said step of conveying a telephone reception signal for conversion by a telephone reception transducer by receiving and combining said FSK cancellation signal and said telephone reception signal and in accordance therewith providing a modified telephone reception signal in which said voice signal component substantially remains and said FSK signal component is substantially cancelled.

20. An apparatus including a signal processor programmed for blocking reception of in-band frequency-shift keyed (FSK) signals by the reception transducer of a telephone subscriber terminal without requiring muting of said reception transducer, said signal processor programmed to perform the steps of:

conveying a telephone reception signal for conversion by a telephone reception transducer, wherein said telephone reception signal includes voice and FSK signal components; and

substantially canceling said FSK signal component without interrupting said conveyance of said voice signal component;

wherein

said signal processor is programmed to perform said step of substantially canceling said FSK signal component without interrupting said conveyance of said voice signal component by receiving said telephone reception signal and detecting said FSK signal component and in accordance therewith providing a FSK cancellation signal,

said signal processor is programmed to perform said step of conveying a telephone reception signal for conversion by a telephone reception transducer by receiving and combining said FSK cancellation signal and said telephone reception signal and in accordance therewith providing a modified telephone reception signal in which said voice signal component substantially remains and said FSK signal component is substantially cancelled, and

said signal processor is programmed to perform said step of receiving said telephone reception signal and detecting said FSK signal component and in accordance therewith providing a FSK cancellation signal by

receiving said telephone reception signal and detecting said FSK signal component and in accordance therewith providing FSK signal information, and

receiving said FSK signal information and in accordance therewith providing a replica FSK signal as said FSK cancellation signal.

21. The apparatus of claim 20, wherein said signal processor is programmed to perform said step of receiving said telephone reception signal and detecting said FSK signal component and in accordance therewith providing FSK signal information by:

detecting an amplitude of said FSK signal component and in accordance therewith providing FSK signal component amplitude information as a first portion of said FSK signal information;

recovering a clock signal related to said FSK signal component and in accordance therewith providing FSK signal component clock information as a second portion of said FSK signal information;

detecting a frequency of said FSK signal component and in accordance therewith providing FSK signal component frequency information as a third portion of said FSK signal information; and

detecting a phase of said FSK signal component and in accordance therewith providing FSK signal component phase information as a fourth portion of said FSK signal information.

22. An apparatus including a signal processor programmed for blocking reception of in-band frequency-shift keyed (FSK) signals by the reception transducer of a telephone subscriber terminal without requiring muting of said reception transducer, said signal processor programmed to perform the steps of:

conveying a telephone reception signal for conversion by a telephone reception transducer, wherein said telephone reception signal includes voice and FSK signal components; and

substantially canceling said FSK signal component without interrupting said conveyance of said voice signal component;

wherein

said signal processor is programmed to perform said step of substantially canceling said FSK signal component without interrupting said conveyance of said voice signal component by receiving said telephone reception signal and detecting said FSK signal component and in accordance therewith providing a FSK cancellation signal,

said signal processor is programmed to perform said step of conveying a telephone reception signal for conversion by a telephone reception transducer by receiving and combining said FSK cancellation signal and said telephone reception signal and in accordance therewith providing a modified telephone reception signal in which said voice signal component substantially remains and said FSK signal component is substantially cancelled, and

said signal processor is programmed to perform said step of receiving and combining said FSK cancellation signal and said telephone reception signal and in accordance therewith providing a modified telephone reception signal in which said voice signal component substantially remains and said FSK signal component is substantially cancelled by

receiving and delaying said telephone reception signal and in accordance herewith providing a delayed telephone reception signal, and

receiving and summing said delayed telephone reception signal and said FSK cancellation signal and in accordance therewith providing said modified telephone reception signal.

23. An apparatus including a signal processor programmed for blocking reception of in-band frequency-shift keyed (FSK) signals by the reception transducer of a telephone subscriber terminal without requiring muting of said reception transducer, said signal processor programmed to perform the steps of:

conveying a telephone reception signal for conversion by a telephone reception transducer, wherein said telephone reception signal includes voice and FSK signal components and a transmission signal echo component;

substantially canceling said FSK signal component without interrupting said conveyance of said voice signal component;

conveying a telephone transmission signal originating from a telephone transmission transducer; and

receiving said telephone transmission signal and said telephone reception signal and in accordance therewith substantially canceling said transmission signal echo component from said conveyed telephone reception signal.

24. The apparatus of claim 23, wherein:

said signal processor is programmed to perform said step of receiving said telephone transmission signal and said telephone reception signal and in accordance therewith substantially canceling said transmission signal echo component by receiving said telephone transmission signal and in accordance therewith adaptively filtering said telephone reception signal and in accordance therewith providing an echo cancellation signal; and

said signal processor is programmed to perform said step of conveying a telephone transmission signal originating from a telephone transmission transducer reception by receiving and combining said echo cancellation signal and said telephone reception signal and in accordance therewith providing a modified telephone reception signal in which said voice and FSK signal components substantially remain and said transmission signal echo component is substantially cancelled.

25. The apparatus of claim 24, wherein said signal processor is programmed to perform the step of receiving said telephone transmission signal and in accordance therewith adaptively filtering said telephone reception signal and in accordance therewith providing an echo cancellation signal by:

receiving an error signal and in accordance therewith receiving and filtering said telephone reception signal in accordance with a finite impulse response function and in accordance therewith providing said echo cancellation signal; and

receiving and combining said telephone transmission signal and said echo cancellation signal and in accordance therewith providing said error signal.