Spread-spectrum detection system for a multi-element antenna
First Claim
1. A system for detecting spread-spectrum signals in the antenna-element outputs of a plurality of antenna elements in a multi-element antenna array, the system comprising:
- A. a two-dimensional compressive receiver comprising;
i. a plurality of input ports, each of which is associated with a different antenna element and connected to receive the antenna-element output from its associated antena element;
ii. at least one output port;
iii. a linearly sweeping local oscillator for produciing a chirp signal;
iv. at least one mixer, each associated with a different input port, and connected to receive the chirp signal and the antenna element output associated with an input port, thereby providing a plurality of chirped input signals;
v. a plurality of weighting filters, each associated with a different mixer and connected to receive as an input the chirped input signal, thereby providing a plurality of weighted output signals;
vi. two-dimensional dispersive delay line means including a common delay-line medium through which the weighted output signals propagate to produce at the at least one output port a compressed output in which components that result from antenna-element output components of a given frequency within a compressive-receiver frequency band are compressed together in time and in which components that result from antenna-element components of different frequencies in the band are separated in time, all the signals in the two-dimensional dispersive delay line means being superimposed in propagating through the common delay-line medium to the at least one output port;
B. a limiter circuit associated with each of the at least one output port of the two-dimensional compressive receiver and connected to receive the compressed output of its associated output port, each limiter circuit producing a limiter output in which any portion of the received compressed signal above a threshold amplitude is eliminated, the contributions of strong narrow-band antenna-output components to each limiter-circuit output thereby being reduced from their contributions to the associated compressive-receiver output throughout the compressive-receiver frequency band; and
C. a spread-spectrum processor circuit for detecting the results of antenna-element spread-spectrum signals in the at least one limiter output.
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Abstract
In a spread-spectrum direction-finding system, the outputs of the several antenna elements (10a-d) are progressively translated in frequency by a chirped local oscillator (14) and mixers (12a-d) and applied to a two-dimensional dispersive filter (18), which time compresses the results of single-frequency components in the antenna-element outputs to narrow pulses. Limiters (24a-d) remove any strong narrow-band components that are compressed by the dispersive delay line (18) so that further processing to detect a spread-spectrum signal is not degraded by the presence of narrow-band signals. The use of a common two-dimensional delay line (18) to provide the time compression avoids the need to maintain phase tracking among a plurality of separate parallel one-dimensional dispersive delay lines.
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Citations
14 Claims
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1. A system for detecting spread-spectrum signals in the antenna-element outputs of a plurality of antenna elements in a multi-element antenna array, the system comprising:
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A. a two-dimensional compressive receiver comprising; i. a plurality of input ports, each of which is associated with a different antenna element and connected to receive the antenna-element output from its associated antena element; ii. at least one output port; iii. a linearly sweeping local oscillator for produciing a chirp signal; iv. at least one mixer, each associated with a different input port, and connected to receive the chirp signal and the antenna element output associated with an input port, thereby providing a plurality of chirped input signals; v. a plurality of weighting filters, each associated with a different mixer and connected to receive as an input the chirped input signal, thereby providing a plurality of weighted output signals; vi. two-dimensional dispersive delay line means including a common delay-line medium through which the weighted output signals propagate to produce at the at least one output port a compressed output in which components that result from antenna-element output components of a given frequency within a compressive-receiver frequency band are compressed together in time and in which components that result from antenna-element components of different frequencies in the band are separated in time, all the signals in the two-dimensional dispersive delay line means being superimposed in propagating through the common delay-line medium to the at least one output port; B. a limiter circuit associated with each of the at least one output port of the two-dimensional compressive receiver and connected to receive the compressed output of its associated output port, each limiter circuit producing a limiter output in which any portion of the received compressed signal above a threshold amplitude is eliminated, the contributions of strong narrow-band antenna-output components to each limiter-circuit output thereby being reduced from their contributions to the associated compressive-receiver output throughout the compressive-receiver frequency band; and C. a spread-spectrum processor circuit for detecting the results of antenna-element spread-spectrum signals in the at least one limiter output. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A system for detecting spread-spectrum signals comprising:
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A. a plurality of antenna elements arranged as an antenna array, which generated at antenna element outputs, a plurality of antenna element output signals; B. a two-dimensional compressive receiver operably connected to the antenna element outputs at a plurality of input ports, each input port associated with one of the antenna element outputs, for generating a plurality of time compressed signals at a plurality of two-dimensional compressive receiver output ports, the number of compressive receiver input ports not necessarily equal to the number of compressive reciver output ports; C. a plurality of limiter circuits, each associated with one of the compressive receiver output ports, for generating a plurality of limiter outputs in which any portion of a compressive receiver output above a threshold amplitude is eliminated; and D. a spread-spectrum processor circuit for detecting the spread spectrum signals present in at least one of limiter the outputs. - View Dependent Claims (13, 14)
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Specification