Detection of radar signals with large radar signatures
First Claim
1. A radar transmission system comprising:
- means for generating positive going and negative going pulses, without a sinusoidal carrier as a fine structure marking;
means for generating a first character by placing said positive going and negative going pulses together in a pattern of contiguous pulses;
means for generating at least one additional character, each said additional character being a time delayed replication of the first character;
means for summing selected characters from among the plurality of characters, to form a signal with coarse structure marking which is long compared to said pulses; and
means for transmitting said signal with coarse structure marking as a radar signal.
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Accused Products
Abstract
Method and apparatus for generating and receiving carrier-free radar pulses that can be detected even though they are heavily distorted by a target and have additive noise superimposed on them, or are in an environment of unwanted signals. The method is especially applicable to signals that are based on pulses with a duration of 1 nanosecond (ns) or less. The radar signature of typical targets from such signals is very large, which makes it hard to selectively receive return signals unless they are marked. Fine structure marking is not effective for such short duration pulses. A method for organizing the signal with coarse structure marking is described that allows the radar receiver to discriminate heavily distorted wanted signals from unwanted signals and noise without requiring large peak power at the transmitter. The disclosed method involves placing positive-going and negative-going pulses together in a pattern of contiguous pulses to form a character. Generating one or more time-delayed replicas of the character and summed selected ones together to form a signal with coarse structure marking. The delay time of each replica may vary and some replicas may have their polarity reversed before summing, but all are based on pulses that are short enough to imply that most return pulses would not be recognized by a receiver. However, the coarse structure of this invention marks the signal for selective reception. It renders the characters within it recognizable, and thereby enables the transmission of pulses without a fine structure marking which might otherwise be absorbed by the atmosphere.
79 Citations
21 Claims
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1. A radar transmission system comprising:
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means for generating positive going and negative going pulses, without a sinusoidal carrier as a fine structure marking; means for generating a first character by placing said positive going and negative going pulses together in a pattern of contiguous pulses; means for generating at least one additional character, each said additional character being a time delayed replication of the first character; means for summing selected characters from among the plurality of characters, to form a signal with coarse structure marking which is long compared to said pulses; and means for transmitting said signal with coarse structure marking as a radar signal. - View Dependent Claims (3, 4, 5, 7)
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2. A radar transmission system comprising:
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means for generating positive going and negative going pulses, without a sinusoidal carrier as a fine structure marking; means for generating a first character by placing said positive going and negative going pulses together in a pattern of contiguous pulses; means for generating at least one additional character, each said additional character being a time delayed replication of the first character; means for reversing the polarity of any of said delayed characters and said first character; means for summing selected characters from among the plurality of characters, to form a signal with coarse structure marking which is long compared to said pulses; and means for transmitting said signal with coarse structure marking as a radar signal.
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6. A method of forming a radar signal, comprising the steps of:
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generating positive going and negative going pulses without a sinusoidal carrier as a fine structure marking; generating a first character by placing said positive-going and negative going pulses together in a pattern of contiguous pulses; generating at least one additional character, each said additional character being a time delayed replication of the first character; summing selected characters from among the plurality of characters to form a signal with coarse structure marking that is long compared to said pulses. - View Dependent Claims (8, 9, 10)
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11. A radar transmission system comprising:
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means for generating positive going and negative going pulses, without a sinusoidal carrier as a fine structure marking; means for generating a plurality of characters by placing said positive going and negative going pulses in a pattern of contiguous pulses to form a signal with coarse structure marking which is long compared to said pulses; and means for transmitting said signal with coarse structure marking as a radar signal.
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12. A method of forming a radar signal, comprising the steps of:
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generating positive-going and negative-going pulses without a sinusoidal carrier as a fine structure marking; generating a sequence of characters by placing said positive-going and negative-going pulses in a pattern of contiguous pulses; and summing selected characters from among the plurality of characters to form a signal with coarse structure marking that is long compared to said pulses.
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13. A radar receiver for selective reception of received radar signals transmitted with a coarse structure marking and without a sinusoidal carrier as a fine structure marking, comprising:
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delay circuits means for generating at least one delayed replica of a received signal; and at least one summing circuit means for summing the received signal and delayed replicas, thereby generating an enhanced received signal. - View Dependent Claims (15)
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14. A radar receiver for selective reception of received radar signals transmitted with a coarse structure marking and without a sinusoidal carrier as a fine structure marking, comprising:
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delay circuits means for generating at least one delayed replica of a received signal; inverter means for inverting selected ones of said delayed replicas; and at least one summing circuit means for summing selected signals from among the received signal and delayed and inverted delayed replicas, thereby generating an enhanced received signal.
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16. A carrier free radar transmission system capable of generating positive going and negative going pulses and a contiguous pattern of said pulses to form a character, comprising:
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means for generating a plurality of characters each starting after the preceding character by a predetermined interval; and means for transmitting said plurality of characters as a signal wherein said predetermined intervals define a delay time of each character to a first character of the signal, thus generating a signal with a coarse structure marking. - View Dependent Claims (17, 18, 19, 20)
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21. A radar receiver for selective reception of a received signal with a coarse structure marking and without a sinusoidal carrier as a fine structure marking, comprising:
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means for delaying the received signal by a plurality of delay times to form a plurality of delayed received signals; means for inverting selected delayed received signals from among the plurality of delayed received signals to form a plurality of inverted delayed received signals; and at least one summing circuit means for summing the inverted delayed received signals together with the received signal and selected delayed received signals to selectively receive a transmitted signal with coarse structure marking.
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Specification