US5148174A
Expired / Lapsed
US
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Selective reception of carrier-free radar signals with large relative bandwidth
Assignee: GEOPHYSICAL SURVEY SYSTEMS Inc 13 KLEIN DRIVE NORTH SALEM NH 03073-0097 A MA CORP
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Filing: 1991-02-13
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Granted: 1992-09-15
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Expires: 2011-02-13
Abstract
Abstract A method for generating a sequence of short radar pulses and a method plus apparatus for detecting those same short pulses when backscattered, even though they are heavily distorted by a target and have additive noise and unwanted signals superimposed on them. The method applies to pulses of long or short duration, including durations of 1 nanoseconds (1 ns) or less. The pulses are transmitted without the fine structure marking of a sinusoidal wave carrier, but organized into a coarse structure that results from incorporating them within a highly unconventional type of character, wherein a plurality of positive-going and negative-going pulses are transmitted such that each pulse is spaced apart from its neighbors. Each pulse is short, so the return signal is highly distorted. The sequence of positive-going and negative-going pulses are organized into a pattern of non-contiguous pulses that constitute a new type of "character", which may be thought of as a "spaced-apart-character". This "spaced-apart-character" is organized into a large coarse structure marking, so that a) the total transmitted energy is large, b) a receiver can selectively distinguish the wanted return signal from noise and unwanted signals, and c) reflections from targets longer than L=Δtc/2 are rejected.
Inventors
- 👤 Henning F. Harmuth
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 10:24
CPC Classifications
G; G01; G01S; G01S13/00; G01S13/02; G01S13/06; G01S13/08; G01S13/10; G01S13/106; G01S13/0209; G01S13/30; G01S7/00; G01S7/02; G01S7/28; G01S7/285; G01S7/292
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
78 words
In a radar transmission system having means for transmitting into a medium an electromagnetic signal comprising a plurality of positive-going and negative-going pulses, without a sinusoidal carrier as a fine structure marking, in a pattern of pulses that form a signal with coarse structure marking which is long compared to each of said pulses, the improvement comprising: means for supplying to the means for transmitting, a sequence of positive-going and negative-going pulses in a pattern of non-continguous pulses.
Claim 2
Dependent Claim
78 words
In a radar transmission system having means for transmitting into a medium an electromagnetic signal comprising a plurality of positive-going and negative-going pulses, without a sinusoidal carrier as a fine structure marking, in a pattern of pulses that form a signal with coarse structure marking which is long compared to each of said pulses, the improvement comprising: means for supplying to the means for transmitting, a sequence of positive-going and negative-going pulses in a pattern of non-continguous pulses.
Claim 3
Dependent Claim
33 words
The radar transmission system of claim 1 comprising: means for transmitting a first pattern of non contiguous pulses; and means for transmitting a second pattern of non contiguous pulses after the first pattern.
Claim 4
Dependent Claim
21 words
The radar system of claim 2 wherein the first and second patterns transmitted in sequence separated by an interval without transmission.
Claim 5
Dependent Claim
20 words
The radar transmission system of claim 2 wherein the second pattern is a complementary code pattern of the first pattern.
Claim 6
Dependent Claim
73 words
The radar transmission system of either claim 3 or claim 4 wherein the interval is selected such that a delay time from the start of the transmission of the first pattern to the start of the transmission of the second pattern is at least as large as 2L/c, where L is the largest linear dimension of all targets of interest, and c is the speed of light as measured in the transmission medium.
Claim 7
Dependent Claim
40 words
The radar transmission system of claim 1 wherein the total energy of all the non-contiguous pulses that form the signal with coarse structure marking is large enough to assure good all-weather radar transmission with reception at distances exceeding 20 km.
Claim 8
Independent Claim
78 words
A method of forming a radar signal comprising the steps of: generating positive-going and negative-going pulses without a sinusoidal carrier as a fine structure marking; generating a first pattern using said pulses to generate a first sequence of non-contiguous positive-going and negative-going pulses; generating a second pattern using said pulses to generate a second sequence of non-continguous positive-going and negative-going pulses; and transmitting the first pattern and then after a predetermined interval of time, transmitting the second pattern.
Claim 9
Independent Claim
78 words
A method of forming a radar signal comprising the steps of: generating positive-going and negative-going pulses without a sinusoidal carrier as a fine structure marking; generating a first pattern using said pulses to generate a first sequence of non-contiguous positive-going and negative-going pulses; generating a second pattern using said pulses to generate a second sequence of non-continguous positive-going and negative-going pulses; and transmitting the first pattern and then after a predetermined interval of time, transmitting the second pattern.
Claim 10
Dependent Claim
23 words
The method of forming the radar signal of claim 7 wherein the second pattern is a complementary code pattern of the first pattern.
Claim 11
Dependent Claim
70 words
The method of forming a radar signal of either claim 7 or claim 8 wherein the interval is selected such that a delay time between the start of the second pattern and the start of the first pattern is at least as large as 2L/c, where L is the largest linear dimension of all targets of interest, and c is the speed of light as measured in the transmission medium.
Claim 12
Dependent Claim
50 words
The method of forming the radar signal of claim 9 in the transmitter, and further comprising a receiver, wherein the delay between the first and second patterns is sufficient to enable the receiver to selectively suppress clutter in a received signal returned from all targets greater in length than L.
Claim 13
Dependent Claim
31 words
The method of claim 7 wherein each pattern is long enough to assure that the total radiated energy is sufficient to assure good all-weather radar transmission for distances exceeding 20 km.
Claim 14
Dependent Claim
156 words
A radar receiving system comprising: means for selectively receiving a first pattern of non-contiguous positive-going and negative-going pulses as a radar signature, without a sinusoidal carrier as a fine structure marking, including means for producing an auto-correlation function of the first pattern to enhance detection of the radar signature and suppress unwanted signals and noise; means for receiving selectively a second pattern of non-continguous positive-going and negative-going pulses as a radar signature, without a sinusoidal carrier as a fine structure marking, including means for producing an auto-correlation function of the second pattern to enhance detection of the radar signature while simultaneously suppressing unwanted signals and noise; and means for summing the auto-correlation function of the first pattern with the auto-correlation function of the second pattern to produce an output signal with a ratio of the radar signature signal to the unwanted signals and noise that is greater than the received signal and auto-correlation functions taken individually.
Claim 15
Dependent Claim
156 words
A radar receiving system comprising: means for selectively receiving a first pattern of non-contiguous positive-going and negative-going pulses as a radar signature, without a sinusoidal carrier as a fine structure marking, including means for producing an auto-correlation function of the first pattern to enhance detection of the radar signature and suppress unwanted signals and noise; means for receiving selectively a second pattern of non-continguous positive-going and negative-going pulses as a radar signature, without a sinusoidal carrier as a fine structure marking, including means for producing an auto-correlation function of the second pattern to enhance detection of the radar signature while simultaneously suppressing unwanted signals and noise; and means for summing the auto-correlation function of the first pattern with the auto-correlation function of the second pattern to produce an output signal with a ratio of the radar signature signal to the unwanted signals and noise that is greater than the received signal and auto-correlation functions taken individually.
Claim 16
Dependent Claim
31 words
The radar receiver of claim 12, wherein the output signal is supplied as an input to a Doppler processor means for further eliminating unwanted signals and noise in the return signal.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1995-09-15 | 1996-03-16 | 1996-09-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1999-09-15 | 2000-03-16 | 2000-09-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2003-09-15 | 2004-03-16 | 2004-09-15 | $7700.00 | Window Closed / Lapsed |