Tone detector for use in a modem

• US 6,711,205 B1
• Filed: 09/25/1998
• Issued: 03/23/2004
• Est. Priority Date: 09/25/1998
• Status: Expired due to Fees

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Beaney, Jim
• Primary Examiner(s): DEPPE, BETSY LEE
• Application Number:
  US09/160,538
• Time in Patent Office: 2,006 Days
• Field of Search: 375/222, 375/229, 375/230, 375/232, 375/350, 375/316, 375/343, 375/368, 379/386, 379/93.26, 708/300, 708/322, 708/323
• US Class Current: 375/222
• CPC Class Codes: H04Q 1/44 using alternate current H04Q1/50 takes precedence

Abstract

A tone detector for a modem detects the presence of a tone, such as that sent during a retraining request, using a complex adaptive FIR filter of the form 1−z⁻¹. The filter will detect the tone regardless of symbol rate.

Claims

1. A modem comprising:

an adaptive tone detector to detect a plurality of tones, the adaptive tone detector comprising a complex adaptive finite impulse response filter; and

a notch filter coupled to the adaptive tone detector to detect a symbol sequence, the notch filter comprising a finite impulse response filter, the output of the notch filter being the input of the adaptive tone detector, the notch filter to be used in detecting a certain symbol sequence by comparing an energy level at an input of the notch filter to an energy level at an output of the notch filter.

2. The modem of claim 1, wherein the adaptive tone detector detects the plurality of tones at a plurality of different symbol rates.

3. The modem of claim 2, wherein the detection of the plurality of tones is performed by measuring an amplitude of a signal produced at a tap of the complex adaptive finite impulse response filter.

4. The modem of claim 3, wherein the adaptive tone detector is a complex adaptive finite impulse response filter of the form 1−

z<sup>−

1</sup>.

5. The modem of claim 4, wherein the modem implements a V.34 standard.

6. The modem of claim 5, wherein a retrain phase is initiated upon detection of one of the plurality of tones.

7. The modem of claim 1, wherein the notch filter is coupled between a receiver and the tone detector.

8. The modem of claim 7, wherein the symbol sequence has a spectrum with peaks at certain complex roots and wherein the notch filter has zeros at the frequencies corresponding to the complex roots.

9. The modem of claim 7, wherein the notch filter is a finite impulse response filter of the form 1−

z<sup>−

6</sup>.

10. The modem of claim 9, wherein a rate negotiation is initiated upon the detection of the symbol sequence.

11. A method comprising:

receiving a series of symbols;

detecting a symbol sequence in the series of symbols by filtering the series of symbols using a notch filter, the notch filter comprising a finite impulse response filter; and

a plurality of tones in the series of symbols using an adaptive tone detector, the adaptive tone detector comprising a complex adaptive finite impulse response filter, the output of the notch filter being the input of the adaptive tone detector.

12. The method of claim 11, wherein the plurality of tones are detected at a plurality of different symbol rates.

13. The method of claim 12, wherein the detection of the plurality of tones is performed by measuring an amplitude of a signal produced at a tap of the complex adaptive finite impulse response filter.

14. The method of claim 13, wherein the adaptive tone detector is a complex adaptive finite impulse response filter of the form 1−

z<sup>−

1</sup>.

15. The method of claim 14, wherein a V.34 standard is implemented.

16. The method of claim 15, further comprising initiating a retrain phase upon detection of the one of the plurality of tones.

17. The method of claim 11, wherein the symbol sequence is detected by comparing energy at an input of the notch filter to energy at an output of the notch filter.

18. The method of claim 17, wherein the symbol sequence has a spectrum with peaks at certain complex roots and wherein the notch filter has zeros at the frequencies corresponding to the complex roots.

19. The method of claim 18, wherein the notch filter is a finite impulse response filter of the form 1−

<sup>−

6</sup>.

20. The method of claim 19, further comprising initiating a rate negotiation upon the detection of the symbol sequence.

21. A machine-readable medium having stored thereon data representing sequences of instructions that, when executed by a processor, cause the processor to perform operations comprising:

receiving a series of symbols;

detecting a symbol sequence in the series of symbols, wherein detecting the symbol sequence includes filtering the series of symbols with a notch filter, the notch filter comprising a finite impulse response filter; and

detecting a plurality of tones in the series of symbols using an adaptive tone detector, the adaptive tone detector comprising a complex adaptive finite impulse response filter, the output of the notch filter being the input of the adaptive tone detector.

22. The medium of claim 21, wherein the plurality of tones are detected at a plurality of different symbol rates.

23. The medium of claim 22, wherein the detection of the one or more tones is performed by measuring an amplitude of a signal at a tap of the complex adaptive finite impulse response filter.

24. The medium of claim 23, wherein the adaptive tone detector is a complex adaptive finite impulse response filter of the form 1−

z<sup>−

1</sup>.

25. The medium of claim 24, wherein a V.34 standard is implemented.

26. The medium of claim 25, further comprising sequences of instruction that, when executed by the processor, cause the processor to perform operations comprising initiating a retrain phase upon detection of one of the plurality of tones.

27. The medium of claim 21, wherein the symbol sequence is detected by comparing energy at an input of the notch filter to energy at an output of the notch filter.

28. The medium of claim 27, wherein the symbol sequence has a spectrum with peaks at certain complex roots and wherein the notch filter has zeros at the frequencies corresponding to the complex roots.

29. The medium of claim 28, wherein the notch filter is a finite impulse response filter of the form 1−

z<sup>−

6</sup>.

30. The medium of claim 29, further comprising sequences of instruction that, when executed by the processor, cause the processor to perform operations comprising initiating a rate negotiation upon the detection of the symbol sequence.

31. A receive engine module for a modem comprising:

a receiver for demodulating received data samples to a baseband; and

an adaptive tone detector, the adaptive tone detector comprising a complex adaptive finite impulse response filter, the tone detector detecting a plurality of tones; and

a notch filter coupled to the adaptive tone detector, the notch filter comprising a finite impulse response filter, the output of the notch filter being the input of the adaptive tone detector, the notch filter being used in detecting a certain symbol sequence.

32. The receive engine module of claim 31, wherein the adaptive tone detector detects the plurality of tones at a plurality of different symbol rates.

33. The receive engine module of claim 32, wherein the detection of the plurality of tones is performed by measuring an amplitude of a signal produced at a tap of the complex adaptive finite impulse response filter.

34. The receive engine module of claim 33, wherein the adaptive tone detector is a complex adaptive finite impulse response filter of the form 1−

z<sup>−

1</sup>.

35. The receive engine module of claim 34, wherein the modem implements a V.34 standard.

36. The receive engine module of claim 35, wherein a retrain phase is initiated upon detection of one of the plurality of tones.

37. The receive engine module of claim 31, wherein the notch filter is coupled between the receiver and the tone detector.

38. The receive engine module of claim 31, wherein the symbol sequence is detected by comparing energy at an input of the notch filter to energy at an output of the notch filter.

39. The receive engine module of claim 38, wherein the symbol sequence has a spectrum with peaks at certain complex roots and wherein the notch filter has zeros at the frequencies corresponding to the complex roots.

40. The receive engine module of claim 39, wherein the notch filter is a finite impulse response filter of the form 1−

z<sup>−

1</sup>.

41. The receive engine module of claim 40, wherein a rate negotiation is initiated upon the detection of the symbol sequence.