Efficient wideband waveform generation and signal processing design for an active multi-beam ESA digital radar system
First Claim
1. A system for generating signals for driving the individual elements of an electronically scanned antenna array (ESA) comprising:
- a signal generator for generating a first digital signal;
a digital beamsteering unit operating on said first digital signal to produce a second digital signal for each individual element of said antenna array; and
serial memory buffers for storing said digital signals prior to conversion to analog.
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Accused Products
Abstract
An efficient digital wideband waveform generation and signal processing system for multi-beam electronically scanned antenna array (ESA) radar systems. The digital waveform generator (50) first produces a series of waveform phase angles corresponding to the phase angles of a common signal to be transmitted by the ESA. Then, for each antenna element, the waveform phase angles are adjusted to steer the beam by adding a time delay and a phase adjustment. A digital signal is then produced for each antenna element by applying a cosine function to the adjusted phase angles. In the illustrative embodiment, this is accomplished using a cosine look-up table (14). Each digital cosine wave is then stored in a serial memory buffer (16A to 16L) in preparation for conversion to digital. Each of digital signals is passed through a digital to analog converter (18A to 18L) and an RF filter (20A to 20L) at each antenna element. The resulting analog signals are each amplified by a power amplifier (22A to 22L), and then sent through a wideband circulator (24A to 24L) to an antenna element (26A to 26L). On receive, at each antenna element (26A to 26L), a wideband linear amplifier (30A to 30L) and an RF filter (32A to 32L) provide rejection of out of band signals while providing amplification and signal conditioning for the following analog to digital converter (34A to 34L). The resulting digital signals (one for each element) are sent through the (36A to 36L) which separate each digital signal into N frequency channels. A digital beam formation unit (38A to 38N) for each frequency channel then forms multiple digital simultaneous beams by combining like frequency channels from each antenna element with an added phase adjustment.
31 Citations
17 Claims
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1. A system for generating signals for driving the individual elements of an electronically scanned antenna array (ESA) comprising:
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a signal generator for generating a first digital signal;
a digital beamsteering unit operating on said first digital signal to produce a second digital signal for each individual element of said antenna array; and
serial memory buffers for storing said digital signals prior to conversion to analog. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
where {right arrow over (U)}T is a unit vector along the transmit beam, {right arrow over (x)}l is the position of antenna element l relative to the antenna array center, and c is the speed of light.
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9. The invention of claim 1 wherein said digital beamsteering unit is implemented in software.
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10. The invention of claim 1 wherein said system further includes means for generating a third digital signal for each individual element of said antenna array wherein said third digital signal is a function of said second digital signal.
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11. The invention of claim 10 wherein said function is cosine.
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12. The invention of claim 10 wherein said function is implemented through the use of a look-up table.
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13. The invention of claim 10 wherein said means for generating a third digital signal is implemented in software.
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14. The invention of claim 1 wherein said system further includes means for converting said digital signals to analog.
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15. The invention of claim 14 wherein said means for converting to analog includes a digital to analog (D/A) converter for each antenna element.
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16. The invention of claim 15 wherein said system further includes an RF filter after each D/A converter.
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17. A transmit system for an electronically scanned antenna array (ESA) radar system comprising:
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a signal generator for generating a first digital signal;
a digital beamsteering unit operating on said first digital signal to produce a second digital signal for each individual element of said antenna array;
a program for generating a third digital signal for each antenna element wherein said third digital signal is a function of said second digital signal;
a serial memory buffer for each antenna element for storing said third digital signals;
a digital to analog (D/A) converter coupled to each serial memory buffer, an RF filter coupled to each D/A;
a power amplifier coupled to each RE filter; and
a wideband circulator connecting each power amplifier to an antenna element of said antenna array.
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Specification