Signal extraction method and apparatus

• US 6,088,403 A
• Filed: 11/19/1999
• Issued: 07/11/2000
• Est. Priority Date: 03/16/1999
• Status: Expired due to Term

• Current Assignee: International Automated Systems
• Original Assignee: International Automated Systems
• Inventors: Johnson, Neldon P.
• Primary Examiner(s): Bocure, Tesfaldet
• Application Number:
  US09/443,905
• Time in Patent Office: 235 Days
• Field of Search: 375/260, 375/340, 375/316, 375/360, 375/350, 375/259, 375/268, 375/320, 375/285, 375/346, 329/347, 329/349, 329/363
• US Class Current: 375/340
• CPC Class Codes: H04J 1/06 Arrangements for supplying the carrier waves ; Arrangements for supplying synchronisation signals synchronisation in general H03B; frequency multiplication H03B19/00, H03B21/00; mixing H03D7/00, H03D9/00; carrier supply H04L5/10
• CPC Class Codes: H04J 9/00 Multiplex systems in which each channel is represented by a different type of modulation of the carrier
• CPC Class Codes: H04L 5/06 the signals being represented by different frequencies combined with time-division multiplexing H04L5/26
• CPC Class Codes: H04L 7/046 using a dotting sequence

Abstract

A method and apparatus for separating multiple frequency information signals. This invention provides a method and apparatus for separating a communications signal, which is comprised of multiple component information waves of distinct frequencies, into its component waves for demodulation. The extraction of the component information waves is accomplished by determining the mid-cycle zero crossing points of the component information waves by reference to a reference wave, determining the amplitude of the combined wave at these zero crossing points and generating amplitude equations for each of these zero crossing points. These amplitude equations are solved to determine the amplitude coefficients of the component information waves, thereby extracting the transmitted information.

Claims

1. Method for extracting component information waves from a combined information wave, said combined information wave comprising two or more component information waves of known and distinct frequencies and known wave forms and relative phases, one half cycle of each component information wave, an information segment, having its amplitude determined as a function of the information carried and the other half cycle, a calibration segment, having a known calibration amplitude, said method comprising:

a) a step of determining an amplitude of the combined information wave at the mid-cycle zero crossing point of each of the component information waves;

b) a step of generating amplitude equations, one of the amplitude equations corresponding to each of the mid-cycle zero crossing points, with the sum of the unknown or known amplitude coefficients of each of the non-zero component information waves, as adjusted by the phase factor for the corresponding component information wave, being equal to the measured amplitude of the combined information wave at the mid-cycle zero crossing point;

c) a step of solving the amplitude equations to determine the amplitude coefficients of each of the component information waves;

d) a step of generating a calibration amplitude equation for one or more selected points on the combined information wave, at which points each of the component information waves has a known amplitude, and the sum of the products of the known amplitude coefficients of the respective component information waves, as adjusted by the known phase factor for the corresponding component information wave, multiplied by the respective known amplitudes of corresponding component information waves being equal to the amplitude of the combined information wave at the selected points; and

e) a step of computing the amplitude of the combined information wave through use of the calibration amplitude equations, comparing the computed amplitude with the measured amplitude at each of the calibration points, and calibrating the amplitude coefficients determined above for each of the component information waves.

2. Method as recited in claim 1 wherein the combined information wave further comprises one or more reference waves of known amplitude, frequency and phase, and wherein the component information waves are synchronized by reference to the reference waves, and the method further comprises a step of dividing the combined information wave into a number of divided information waves, the number of divided information waves matching the number of the reference waves, and passing the divided waves through narrow bandwidth filters, one filter being frequency matched to each of the reference waves, thereby extracting each of the reference waves from the combined information wave, a step of determining zero crossing points of each of the reference waves, and a step of determining the mid-cycle zero crossing points of the component information waves by reference to one or more of the reference waves.

3. Method as recited in claim 1 wherein the combined information wave is amplitude adjusted to a selected amplitude.

4. Method as recited in claim 2 wherein the combined information wave is amplitude adjusted to a selected amplitude.

5. Method as recited in claim 2 wherein the ratio of the amplitude of each component information segment to the amplitude of one or more of the reference waves, is a function of the information transmitted by the component information wave.

6. Method as recited in claim 4 wherein the ratio of the amplitude of each component information segment to the amplitude of one or more of the reference waves, is a function of the information transmitted by the component information wave.

7. Method as recited in claim 2 further comprising a step of readjusting the phases of the extracted reference waves to correct for the phase shift imposed by the narrow bandwidth filters, thereby restoring the phase relationship between the extracted reference waves and the component information waves.

8. Method for extracting component information waves from a combined information wave, said combined information wave comprising one or more reference waves and one or more component information waves, the reference waves and each of the component information waves having known wave forms, known and distinct frequencies, and known relative phases, one half cycle of each component information wave, an information segment, having its amplitude determined as a function of the information carried and the other half cycle, a calibration segment, having a known calibration amplitude, the reference waves each having a known amplitude, and the component information waves being synchronized by reference to the reference waves, said method comprising:

a) a step of dividing the combined information wave into a number of divided information waves, the number of divided information waves matching the number of the reference waves, and passing the divided waves through narrow bandwidth filters, one filter being frequency matched to each of the reference waves, thereby extracting each of the reference waves from the combined information wave;

b) a step of determining one or more zero crossing points of each of the reference waves;

c) a step of determining mid-cycle zero crossing points of each of the component information waves by reference to one or more of the reference waves;

d) a step of determining an amplitude of the combined information wave at the mid-cycle zero crossing point of each of the component information waves;

e) a step of generating amplitude equations, one of the amplitude equations corresponding to each of the mid-cycle zero crossing points of the component information waves with the sum of the unknown or known amplitude coefficients of each of the non-zero component information waves, as adjusted by the phase factor for the corresponding component information wave, being equal to the measured amplitude of the combined information wave at the mid-cycle zero crossing point;

f) a step of solving the amplitude equations to determine the unknown amplitude coefficients of each of the component information waves;

g) a step of generating a calibration amplitude equation for one or more selected points on the combined information wave, at which points each of the component information waves has a known amplitude, and the sum of the products of the known amplitude coefficients of the respective component information waves, as adjusted by the known phase factor for the corresponding component information wave, multiplied by the respective known amplitudes of corresponding component information waves being equal to the amplitude of the combined information wave at the selected points; and

h) a step of computing the amplitude of the combined information wave through use of the calibration amplitude equations, comparing the computed amplitude with the measured amplitude at each of the calibration points, and calibrating the amplitude coefficients determined above for each of the component information waves.

9. Method as recited in claim 8 wherein the combined information wave is amplitude adjusted to a selected amplitude.

10. Method as recited in claim 8 wherein the ratio of the amplitude of each component information segment to the amplitude of one or more of the reference waves, is a function of the information transmitted by the component information wave.

11. Method as recited in claim 9 wherein the ratio of the amplitude of each component information segment to the amplitude of one or more of the reference waves, is a function of the information transmitted by the component information wave.

12. Method as recited in claim 8 further comprising a step of readjusting the phase of each of the extracted reference waves to correct for the phase shifts imposed by the narrow bandwidth filters, thereby restoring the phase relationship between the extracted reference waves and the component information waves.

13. Method for digital information transfer comprising:

a) a step of generating one or more reference waves of selected wave forms, amplitudes, frequencies and phases;

b) a step of generating one or more component information waves of a selected wave form, the frequency of each component information wave being distinct from each of the other component information waves and from the reference waves, one half cycle of each component information wave, an information segment, having its amplitude determined as a function of the information carried, and the other half cycle, a calibration segment, having a known calibration amplitude, and the amplitude of successive information segments of each component information wave being a function of successive magnitudes of a corresponding source digital signal;

c) a step of combining the reference waves and the component information waves to form a combined information wave, the phase relationship between the reference waves and the component information waves being selected to provide for synchronization of the component information waves with the reference waves;

d) a step of transmitting the combined information wave;

e) a step of receiving the combined information wave;

f) a step of dividing the combined information wave into a number of divided information waves, the number of divided information waves matching the number of the reference waves, and passing the divided waves through narrow bandwidth filters, one filter being frequency matched to each of the reference waves, thereby extracting each of the reference waves from the combined information wave;

g) a step of determining one or more zero crossing points of each of the reference waves;

h) a step of determining mid-cycle zero crossing points of each of the component information waves by reference to one or more of the reference waves;

i) a step of determining an amplitude of the combined information wave at the mid-cycle zero crossing point of each of the component information waves;

j) a step of generating amplitude equations, one of the amplitude equations corresponding to each of the mid-cycle zero crossing points of the component information waves with the sum of the unknown or known amplitude coefficients of each of the non-zero component information waves, as adjusted by the phase factor for the corresponding component information wave, being equal to the measured amplitude of the combined information wave at the mid-cycle zero crossing point;

k) a step of solving the amplitude equations to determine the unknown amplitude coefficients of each of the component information waves;

l) a step of generating a calibration amplitude equation for one or more selected points on the combined information wave, at which points each of component information waves has a known amplitude, and the sum of the known amplitude coefficients of each of the component information waves, as adjusted by the known phase factor for the corresponding component information wave, being equal to the amplitude of the combined information wave at the selected points; and

m) a step of computing the amplitude of the combined information wave through use of the calibration amplitude equations, comparing the computed amplitude with the measured amplitude at each of the calibration points, and calibrating the amplitude coefficients determined above for each of the component information waves.

14. Method as recited in claim 13 wherein the amplitude of the combined information wave is adjusted to a selected amplitude prior to transmission.

15. Method as recited in claim 13 wherein the ratio of the amplitude of each cycle of each component information segment to the amplitude of one or more of the reference wave, is a function of the magnitude of a corresponding source digital signal.

16. Method as recited in claim 14 wherein the ratio of the amplitude of each cycle of each component information segment to the amplitude of one or more of the reference wave, is a function of the magnitude of a corresponding source digital signal.

17. Method as recited in claim 13 further comprising a step of readjusting the phase of each of the extracted reference waves to correct for the phase shift imposed by the narrow bandwidth filters, thereby restoring the phase relationship between the extracted reference waves and the component information waves.

18. Method for extracting a component information wave from a combined information wave, said combined information wave comprising two reference waves, a first reference wave and a second reference wave, and one component information wave, the reference waves and the component information wave having known wave forms and frequencies, the second reference wave and the component information wave having the same frequency and being ninety degrees out of phase, the phase relationship between the first reference wave and the second reference wave and the component information wave being known, each half cycle of each component information wave having the ratio of its amplitude to the amplitude of the second reference wave determined as a function of the information carried, the reference waves each having a known amplitude, and the second reference wave and the component information wave being synchronized by reference to the first reference wave, said method comprising:

a) a step of dividing the combined information wave into a first divided information wave and a second divided information wave and passing the first divided information wave through a narrow bandwidth filter, thereby extracting the first reference wave;

b) a step of determining one or more zero crossing points of the first reference wave;

c) a step of subtracting the first reference wave from the second divided information wave, thereby generating a resultant wave;

d) a step of determining a zero crossing point for the second reference wave and a zero crossing point for the component information wave by reference to a zero crossing point of the first reference wave;

e) a step of determining the amplitude of the second reference wave as the measured amplitude of the resultant wave at the zero crossing point of the component information wave, and determining the amplitude of the component information wave as the measured amplitude of the resultant wave at the zero crossing point of the second reference wave;

f) a step of extracting information carried by the component information wave as a function of the ratio of the amplitude of the component information wave to the amplitude of the second reference wave.

19. Method as recited in claim 18 further comprising a step of correcting the extracted first reference wave for the phase shift imposed by the narrow bandpass filter, thereby more accurately locating the first reference wave zero crossing points.

20. Method as recited in claim 18 wherein the ratio of the amplitude of the first reference wave to the amplitude of the second reference wave is a known value and the extracted amplitude of the second reference wave is adjusted by comparing the ratio of the amplitudes of the first reference wave to the second reference wave as transmitted to the ratio of the amplitude of the first reference wave to the amplitude of the second reference wave as extracted.

21. Apparatus for extracting component information waves from a combined information wave, said combined information wave comprising two or more component information waves of known and distinct frequencies and known wave forms and phases, one half cycle of each component information wave, an information segment, having its amplitude determined as a function of the information carried and the other half cycle, a calibration segment, having a known calibration amplitude, said apparatus comprising:

a) means for determining an amplitude of the combined information wave at the mid-cycle zero crossing point of each of the component information waves;

b) means for generating amplitude equations, one of the amplitude equations corresponding to each of the mid-cycle zero crossing points, with the sum of the unknown or known amplitude coefficients of each of the non-zero component information waves, as adjusted by the phase factor for the corresponding component information wave, being equal to the measured amplitude of the combined information wave at the mid- cycle zero crossing point;

c) means for solving the amplitude equations to determine the amplitude coefficients of each of the component information waves;

d) means for generating a calibration amplitude equation for one or more selected points on the combined information wave, at which points each of component information waves has a known amplitude, and the sum of the known amplitude coefficients of each of the component information waves, as adjusted by the known phase factor for the corresponding component information wave, being equal to the amplitude of the combined information wave at the selected points; and

e) means for computing the amplitude of the combined information wave through use of the calibration amplitude equations, comparing the computed amplitude with the measured amplitude at each of the calibration points, and calibrating the amplitude coefficients determined above for each of the component information waves.

22. Apparatus as recited in claim 21 wherein the combined information wave further comprises one or more reference waves of known amplitudes, frequencies and phases, and wherein the component information waves are synchronized by reference to one or more of the reference waves, and the apparatus further comprises means for dividing the combined information wave into a number of divided information waves, the number of divided information waves matching the number of the reference waves, means for passing the divided waves through narrow bandwidth filters, one filter being frequency matched to each of the reference waves, thereby extracting each of the reference waves from the combined information wave, means for determining one or more zero crossing points of each of the reference waves, and means for determining the mid-cycle zero crossing points of the component information waves by reference to one or more of the reference waves.

23. Apparatus as recited in claim 21 wherein the combined information wave is amplitude adjusted to a selected amplitude.

24. Apparatus as recited in claim 22 wherein the combined information wave is amplitude adjusted to a selected amplitude.

25. Apparatus as recited in claim 22 wherein the ratio of the amplitude of each component information segment to the amplitude of one or more of the reference waves, is a function of the information transmitted by the component information wave.

26. Apparatus as recited in claim 24 wherein the ratio of the amplitude of each component information segment to the amplitude of one or more of the reference waves, is a function of the information transmitted by the component information wave.

27. Apparatus as recited in claim 22 further comprising means for readjusting the phase of each of the extracted reference waves to correct for the phase shift imposed by the narrow bandwidth filters, thereby restoring the phase relationship between the extracted reference waves and the component information waves.

28. Apparatus for extracting component information waves from a combined information wave, said combined information wave comprising one or more reference waves and one or more component information waves, the reference waves and each of the component information waves having known wave forms, known and distinct frequencies, and known relative phases, one half cycle of each component information wave, an information segment, having its amplitude determined as a function of the information carried and the other half cycle, a calibration segment, having a known calibration amplitude, each of the reference waves having a known amplitude, and the component information waves being synchronized by reference one or more of the reference waves, said method comprising:

a) means for dividing the combined information wave into a number of divided information waves, the number of divided information waves matching the number of the reference waves, and passing the divided waves through narrow bandwidth filters, one filter being frequency matched to each of the reference waves, thereby extracting each of the reference waves from the combined information wave;

b) means for determining one or more zero crossing points of each of the reference waves;

c) means for determining mid-cycle zero crossing points of each of the component information waves by reference to one or more of the reference waves;

d) means for determining an amplitude of the combined information wave at the mid-cycle zero crossing point of each of the component information waves;

e) means for generating amplitude equations, one of the amplitude equations corresponding to each of the mid-cycle zero crossing points of the component information waves with the sum of the unknown or known amplitude coefficients of each of the non-zero component information waves, as adjusted by the phase factor for the corresponding component information wave, being equal to the measured amplitude of the combined information wave at the mid-cycle zero crossing point;

f) means for solving the amplitude equations to determine the unknown amplitude coefficients of each of the component information waves;

g) means for generating a calibration amplitude equation for one or more selected points on the combined information wave, at which points each of component information waves has a known amplitude, and the sum of the known amplitude coefficients of each of the component information waves, as adjusted by the known phase factor for the corresponding component information wave, being equal to the amplitude of the combined information wave at the selected points; and

h) means for computing the amplitude of the combined information wave through use of the calibration amplitude equations, comparing the computed amplitude with the measured amplitude at each of the calibration points, and calibrating the amplitude coefficients determined above for each of the component information waves.

29. Apparatus as recited in claim 28 wherein the combined information wave is amplitude adjusted to a selected amplitude.

30. Apparatus as recited in claim 28 wherein the ratio of the amplitude of each component information segment to the amplitude of one or more of the reference waves, is a function of the information transmitted by the component information wave.

31. Apparatus as recited in claim 29 wherein the ratio of the amplitude of each component information segment to the amplitude of one or more of the reference waves, is a function of the information transmitted by the component information wave.

32. Apparatus as recited in claim 28 further comprising means for readjusting the phase of each of the extracted reference waves to correct for the phase shift imposed by the narrow bandwidth filters, thereby restoring the phase relationship between the extracted reference waves and the component information waves.

33. Apparatus for digital information transfer comprising:

a) means for generating one or more reference waves of a selected wave form, amplitude, frequency and phase;

b) means for generating one or more component information waves of a selected wave form, the frequency of each component information wave being distinct from each of the other component information waves and from the reference waves, one half cycle of each component information wave, an information segment, having its amplitude determined as a function of the information carried, and the other half cycle, a calibration segment, having a known calibration amplitude, and the amplitude of successive information segments of each component information wave being a function of successive magnitudes of a corresponding source digital signal;

c) means for combining the reference waves and the component information waves to form a combined information wave, the phase relationship between the reference waves and the component information waves being selected to provide for synchronization of the component information waves with the reference waves;

d) means for transmitting the combined information wave;

e) means for receiving the combined information wave;

f) means for dividing the combined information wave into a number of divided information waves, the number of divided information waves matching the number of the reference waves, and passing the divided waves through narrow bandwidth filters, one filter being frequency matched to each of the reference waves, thereby extracting each of the reference waves from the combined information wave;

g) means for determining one or more zero crossing points of each of the reference waves;

h) means for determining mid-cycle zero crossing points of each of the component information waves by reference to one or more of the reference waves;

i) means for determining an amplitude of the combined information wave at the mid-cycle zero crossing point of each of the component information waves;

j) means for generating amplitude equations, one of the amplitude equations corresponding to each of the mid-cycle zero crossing points of the component information waves with the sum of the unknown or known amplitude coefficients of each of the non-zero component information waves, as adjusted by the phase factor for the corresponding component information wave, being equal to the measured amplitude of the combined information wave at the mid-cycle zero crossing point;

k) means for solving the amplitude equations to determine the unknown amplitude coefficients of each of the component information waves;

l) means for generating a calibration amplitude equation for one or more selected points on the combined information wave, at which points each of component information waves has a known amplitude, and the sum of the known amplitude coefficients of each of the component information waves, as adjusted by the known phase factor for the corresponding component information wave, being equal to the amplitude of the combined information wave at the selected points; and

m) means for computing the amplitude of the combined information wave through use of the calibration amplitude equations, comparing the computed amplitude with the measured amplitude at each of the calibration points, and calibrating the amplitude coefficients determined above for each of the component information waves.

34. Apparatus as recited in claim 33 wherein the amplitude of the combined information wave is adjusted to a selected amplitude prior to transmission.

35. Apparatus as recited in claim 33 wherein the ratio of the amplitude of each cycle of each component information segment to the amplitude of one or more of the reference waves, is a function of the magnitude of a corresponding source digital signal.

36. Apparatus as recited in claim 34 wherein the ratio of the amplitude of each cycle of each component information segment to the amplitude of one or more of the reference waves, is a function of the magnitude of a corresponding source digital signal.

37. Apparatus as recited in claim 33 further comprising means for readjusting the phase of the extracted reference wave to correct for the phase shift imposed by the narrow bandwidth filter, thereby restoring the phase relationship between the extracted reference wave and the component information waves.

38. Apparatus for extracting a component information wave from a combined information wave, said combined information wave comprising two reference waves, a first reference wave and a second reference wave, and one component information wave, the reference waves and the component information wave having known wave forms and frequencies, the second reference wave and the component information wave having the same frequency and being ninety degrees out of phase, the phase relationship between the first reference wave and the second reference wave and the component information wave being known, each half cycle of each component information wave having the ratio of its amplitude to the amplitude of the second reference wave determined as a function of the information carried, the reference waves each having a known amplitude, and the second reference wave and the component information wave being synchronized by reference to the first reference wave, said apparatus comprising:

a) means for dividing the combined information wave into a first divided information wave and a second divided information wave and passing the first divided information wave through a narrow bandwidth filter, thereby extracting the first reference wave;

b) means for determining one or more zero crossing points of the first reference wave;

c) means for subtracting the first reference wave from the second divided information wave, thereby generating a resultant wave;

d) means for determining a zero crossing point for the second reference wave and a zero crossing point for the component information wave by reference to a zero crossing point of the first reference wave;

e) means for determining the amplitude of the second reference wave as the measured amplitude of the resultant wave at the zero crossing point of the component information wave, and determining the amplitude of the component information wave as the measured amplitude of the resultant wave at the zero crossing point of the second reference wave;

f) means for extracting information carried by the component information wave as a function of the ratio of the amplitude of the component information wave to the amplitude of the second reference wave.

39. Apparatus as recited in claim 38 further comprising means for correcting the extracted first reference wave for the phase shift imposed by the narrow bandpass filter, thereby more accurately locating the first reference wave zero crossing points.

40. Apparatus as recited in claim 38 wherein the ratio of the amplitude of the first reference wave to the amplitude of the second reference wave is a known value, further comprising means for adjusting the extracted amplitude of the second reference wave by comparing the ratio of the amplitudes of the first reference wave to the second reference wave as transmitted to the ratio of the amplitude of the first reference wave to the amplitude of the second reference wave as extracted.