US4801942A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Interferometeric lightning ranging system
Assignee: Airborne Research Associates
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Filing: 1986-08-18
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Granted: 1989-01-31
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Expires: 2006-08-18
Abstract
Abstract The lightning ranging system for determining distance between a lightning discharge and an airborne object includes a receiver on the airborne object adapted to receive electromagnetic radiation signals generated by a lightning discharge along both a direct and a surface reflected path. Signal processing apparatus is interconnected with the receiver for determining the difference in the time of arrival of the direct and reflected signals. A computer is provided to calculate the range of the lightning discharge from the difference in the time of arrival of the direct and reflected signals. In a preferred embodiment, the signal processing apparatus is digital and includes at least a 10-bit analog-to-digital converter with at least a 36 megahertz sampling rate.
Inventors
- 👤 Ralph Markson
- 👤 James W. Warwick
- 👤 Arthur Uhlir, Jr.
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 16:07
CPC Classifications
G; G01; G01S; G01S11/00; G01S11/02
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
118 words
Interferometric lightning ranging system for determining distance between a lightning discharge at a first altitude and an airborne or elevated object at a second altitude comprising: a receiver on the object adapted to receive electromagnetic radiation signals generated by a lightning discharge along both a direct and a surface reflected path, the receiver having a center frequency of at least 30 MHz; signal processing means interconnected with the receiver for determining in the frequency domain the difference in time of arrival of the direct and reflected signals from the interference pattern between the direct and reflected signals; and computing means of calculating the distance from the difference in the time of arrival of the direct and reflected signals.
Claim 2
Dependent Claim
118 words
Interferometric lightning ranging system for determining distance between a lightning discharge at a first altitude and an airborne or elevated object at a second altitude comprising: a receiver on the object adapted to receive electromagnetic radiation signals generated by a lightning discharge along both a direct and a surface reflected path, the receiver having a center frequency of at least 30 MHz; signal processing means interconnected with the receiver for determining in the frequency domain the difference in time of arrival of the direct and reflected signals from the interference pattern between the direct and reflected signals; and computing means of calculating the distance from the difference in the time of arrival of the direct and reflected signals.
Claim 3
Dependent Claim
38 words
The system of claim 1 wherein the signal processing means is adapted to analyze ripples in the spectrum of the received signal, the spacing of the ripples being an indication of the difference in the time of arrival.
Claim 4
Dependent Claim
12 words
The system of claim 2 wherein the signal processing means is digital.
Claim 5
Dependent Claim
14 words
The system of claim 3 wherein the signal processing means includes an analog-to-digital converter.
Claim 6
Dependent Claim
50 words
The system of claim 3 in which the signal processing means includes means to: (1) compute the spectrum; (2) take the logarithm of the spectrum; and (3) take the Fourier transform of the logarithm of the spectrum, the Fourier transform including sharp peaks indicating the difference in time of arrival.
Claim 7
Dependent Claim
20 words
The system of claim 4 wherein an analog signal compression operation precedes conversion to digital form in the analog-to-digital converter.
Claim 8
Dependent Claim
25 words
The system of claim 4 wherein the analog-to-digital converter has at least a 20 MHz sampling rate and a resolution of at least 10 bits.
Claim 9
Dependent Claim
15 words
The system of claim 6 wherein a memory-less logarithm amplifier performs the signal compression operation.
Claim 10
Dependent Claim
25 words
The system of claim 1 wherein the receiver has a center frequency of at least 30 MHz and a bandwidth of at least 4 MHz.
Claim 11
Dependent Claim
24 words
The system of claim 1 further including an antenna connected to the receiver, the antenna comprising a loop lying approximately in the horizontal plane.
Claim 12
Dependent Claim
21 words
The system of claim 1 further including antenna means connected to the receiver, the antenna means comprising combinations of horizontal monopoles.
Claim 13
Dependent Claim
21 words
The system of claim 1 further including antenna means connected to the receiver, the antenna means comprising combinations of horizontal dipoles.
Claim 14
Dependent Claim
33 words
The system of claim 3 in which the signal processing means includes means to compute the autocorrelation function of the received signal, variations in the autocorrelation function being indicative of the time delay.
Claim 15
Dependent Claim
30 words
The system of claim 1 including means for storing calibration data obtained by exposing the system to a signal without path difference to correct false echo indications from system imperfections.
References Cited (Backward Citations)
US3727225A
Cited
US3369240A
Cited
US3483559A
Cited
US4543580A
Cited
US4543580B1
Cited
US4684951A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-01-31 | 1992-08-01 | 1993-01-31 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-01-31 | 1996-08-01 | 1997-01-31 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-01-31 | 2000-08-01 | 2001-01-31 | $7700.00 | Window Closed / Lapsed |