Systems and methods for spectral corrected lightning detection

• US 6,735,525 B1
• Filed: 03/24/2003
• Issued: 05/11/2004
• Est. Priority Date: 03/24/2003
• Status: Expired due to Term

• Current Assignee: Vaisala Oyj
• Original Assignee: Vaisala Oyj
• Inventors: Murphy, Martin J.
• Primary Examiner(s): McElheny, Jr., Donald E.
• Application Number:
  US10/395,808
• Time in Patent Office: 414 Days
• Field of Search: 702/2-4, 342/460, 342/26, 324/72
• US Class Current: 702/4
• CPC Class Codes: G01R 29/0842 Measurements related to lightning, e.g. measuring electric disturbances, warning systems
• CPC Class Codes: G01W 1/16 Measuring atmospheric potential differences, e.g. due to electrical charges in clouds measuring potentiels in general G01R

Abstract

A lightning detection system provides an estimated location of a lightning stroke. The system includes sensors and an analyzer. Each sensor within range of a lightning event provides messages to the analyzer. Each sensor includes a waveform engine that converts a signal received from the lightning event to a series of frequency domain components having respective magnitude and phase. The waveform engine adjusts magnitudes and phases of the frequency components, for example, to mitigate the effects of terrain conductivity where the received signal traveled across terrain. The adjusted frequency components are then converted by the waveform engine into a second time domain signal that is described in a message to the analyzer. Each message includes sensor identification, peak amplitude, and time of detecting the lightning event. The analyzer provides an estimated location of the lightning stroke and an estimated peak current of the lightning stroke in accordance with messages received from sensors.

Claims

1. A method for providing a description of a signal received from a lightning event, the signal having been modified by travel through a medium, the method comprising:

a step for determining a plurality of frequency domain components of the signal;

a step for determining a plurality of adjusted magnitudes for a multiplicity of the frequency domain components of the plurality; and

a step for providing a description of a time domain signal corresponding to at least the plurality of adjusted magnitudes for the multiplicity of frequency domain components.

2. The method of claim 1 further comprising:

a step for determining whether the signal has traveled over terrain; and

a step for determining the plurality of adjusted magnitudes in accordance with whether the signal has traveled over terrain.

3. The method of claim 2 wherein adjusted magnitudes are determined in accordance with a filter function of frequency and conductivity when it is determined that the signal has traveled over terrain.

4. The method of claim 1 wherein applied adjustments mitigate an effect of conductivity of terrain.

5. The method of claim 1 wherein the description comprises a peak amplitude.

6. The method of claim 1 wherein the description comprises a rise time.

7. The method of claim 1 wherein adjusted magnitudes are determined in accordance with a first function of frequency and conductivity.

8. The method of claim 7 wherein the method further comprises:

a step for determining conductivity as a second function of frequency; and

a step for determining an adjusted magnitude in accordance with the first function and a result of the second function.

9. The method of claim 8 wherein the step for determining the conductivity comprises:

a step for determining a magnitude breakpoint frequency in the multiplicity of frequency domain components; and

a step for determining the conductivity in accordance with the breakpoint frequency.

10. The method of claim 9 wherein the step for determining the conductivity in accordance with the breakpoint frequency comprises computing a square root of the break point frequency.

11. The method of claim 1 wherein:

a. the method further comprises a step for determining a plurality of adjusted phases for the multiplicity of frequency domain components of the plurality; and

b. the step for providing the description comprises a step for providing the description of the time domain signal further corresponding to at least the plurality of adjusted phases for the multiplicity of frequency domain components.

12. A sensor that provides a description of a signal received from a lightning event, the signal having been modified by travel through a medium, the sensor comprising:

means for determining a plurality of frequency domain components of the signal;

means for determining a plurality of adjusted magnitudes for a multiplicity of the frequency domain components of the plurality; and

means for providing a description of a time domain signal corresponding to at least the plurality of adjusted magnitudes for the multiplicity of frequency domain components.

13. The sensor of claim 12 further comprising:

means for determining whether the signal has traveled over terrain; and

means for determining the plurality of adjusted magnitudes in accordance with whether the signal has traveled over terrain.

14. The sensor of claim 13 wherein adjusted magnitudes are determined in accordance with a filter function of frequency and conductivity when it is determined that the signal has traveled over terrain.

15. The sensor of claim 12 wherein applied adjustments mitigate an effect of conductivity of terrain.

16. The sensor of claim 12 wherein the description comprises a peak amplitude.

17. The sensor of claim 12 wherein the description comprises a rise time.

18. The sensor of claim 12 wherein the means for adjusting magnitudes further determines each adjusted magnitude in accordance with a first function of frequency and conductivity.

19. The sensor of claim 18 further comprising:

means for determining conductivity as a second function of frequency; and

means for determining an adjusted magnitude in accordance with the first function and a result of the second function.

20. The sensor of claim 19 wherein the means for determining the conductivity comprises:

means for determining a magnitude breakpoint frequency in the multiplicity of frequency domain components; and

means for determining the conductivity in accordance with the breakpoint frequency.

21. The sensor of claim 20 wherein the means for determining the conductivity in accordance with the breakpoint frequency comprises means for computing a square root of the break point frequency.

22. The sensor of claim 12 wherein:

a. the sensor further comprises means for determining a plurality of adjusted phases for the multiplicity of frequency domain components of the plurality; and

b. the means for providing the description comprises means for providing the description of the time domain signal further corresponding to at least the plurality of adjusted phases for the multiplicity of frequency domain components.

23. A lightning detection system that provides an estimated location of a lightning event, the system comprising:

a. analyzer means for providing the estimated location of the lightning event in accordance with a plurality of messages; and

b. a plurality of sensor means providing a message of the plurality respectively comprising sensor identification and a time of detecting the lightning event;

each sensor means comprising;

(1) means for receiving an event and for providing a first time-domain signal in response to the lightning event;

(2) waveshaping means comprising;

(a) means for determining a frequency component of the first signal;

(b) means for adjusting at least one of the magnitude and phase of the component to provide an adjusted component; and

(c) means and for determining a second time-domain signal in accordance with the adjusted component; and

(3) means for transmitting and for providing the message in accordance with the second time-domain signal.

24. The system of claim 23 wherein the waveshaping means further comprises:

a. means for determining a plurality of frequency components of the first signal;

b. means for adjusting a multiplicity of the frequency components of the plurality to provide a plurality of adjusted components; and

c. means for determining a second time-domain signal in accordance with the plurality of adjusted components.

25. The system of claim 24 wherein the waveshaping engine further comprises means for adjusting frequency components of the multiplicity to provide a series of adjusted components having magnitudes that exhibit in log frequency domain a slope that is inversely proportional to frequency.

26. The system of claim 25 wherein the slope in log frequency is 1/f where f is frequency in Hertz.

27. The system of claim 24 wherein each component of the multiplicity corresponds to a respective frequency above 50 KHz.

28. The system of claim 24 wherein each component of the multiplicity corresponds to a respective frequency above 100 KHz.