Code-modulated phased-array interferometric imaging
Embodiments of a code modulated phased-array interferometer are described. In one embodiment, a code modulated phased-array interferometer includes a phased array having a plurality of receiver elements that receive a plurality of received signals. A code multiplexer multiplexes each of the plurality of received signals to generate a plurality of code multiplexed signals, and a combiner combines the plurality of code multiplexed signals into a combined signal. After other processing for signal reception, a code demultiplexer demultiplexes the combined baseband signal, and a complex correlator correlates unique pairs of baseband signals to generate a plurality of visibility products. Finally, the plurality of visibility products are transformed to generate an image. The concepts described herein may be relied upon to reconfigure or repurpose a phased-array receiver to achieve imaging.
1. A code-modulated phased-array interferometer, comprising:
a phased array comprising a plurality of receiver elements configured to receive a plurality of signals;
a code multiplexer configured to multiplex the plurality of signals to generate a plurality of code multiplexed signals;
a combiner configured to combine the plurality of code multiplexed signals into a combined signal; and
a code demultiplexing image processor configured to:
half-demultiplex a plurality of baseband signals from the combined signal;
correlate unique pairs of the plurality of baseband signals to generate a plurality of visibility products; and
Fourier transform the plurality of visibility products to generate an image.
2. The interferometer according to claim 1 , further comprising a downconverter configured to downconvert the combined signal to a lower-frequency combined signal.
3. The interferometer according to claim 1 , wherein the code multiplexer is configured to phase shift each of the plurality of signals according to a respective code to generate the plurality of code multiplexed signals.
4. The interferometer according to claim 1 , wherein the code multiplexer is configured to phase shift each of the plurality of signals with a respective code from a code-set which has balanced orthogonal code products (BOCPs).
5. The interferometer according to claim 4 , wherein the code-set has a chip rate selected based on a rate of scene changes in the image.
6. The interferometer according to claim 1 , wherein the interferometer is configured to generate the image using ambient illumination.
7. The interferometer according to claim 1 , further comprising:
an active illumination source, wherein the interferometer generates the image using active illumination provided by the active illumination source.
8. The interferometer according to claim 7 , wherein the active illumination source comprises at least one of a narrowband frequency transmitter or a broadband frequency transmitter.
9. The interferometer according to claim 7 , wherein the active illumination source comprises a compact florescent illumination source.
10. A code modulated phased-array interferometer process, comprising:
receiving, with a phased-array receiver, a plurality of signals;
multiplexing, with the phased-array receiver, the plurality of signals to generate a plurality of code multiplexed signals;
combining, with the phased-array receiver, the plurality of code multiplexed signals into a combined signal;
half-demultiplexing, with a code demultiplexing image processor, a plurality of baseband signals from the combined signal;
correlating, with the code demultiplexing image processor, unique pairs of the plurality of baseband signals to generate a plurality of visibility products; and
transforming, with the code demultiplexing image processor, the plurality of visibility products to generate an image.
11. The process according to claim 10 , wherein the multiplexing comprises multiplexing each of the plurality of signals according to a respective code to generate the plurality of code multiplexed signals.
12. The process according to claim 10 , wherein the multiplexing comprises multiplexing each of the plurality of signals with a respective code from a code-set which has balanced orthogonal code products (BOCPs).
13. The process according to claim 12 , wherein the code-set has a chip rate selected based on a rate of scene changes in the image.
14. The process according to claim 10 , further comprising illuminating the image with an active illumination source.
15. The process according to claim 14 , wherein the active illumination source includes at least one of a narrowband frequency transmitter or a broadband frequency transmitter.
16. A code-modulated phased-array interferometer, comprising:
a phased array comprising a plurality of receiver elements configured to receive a plurality of signals;
a code multiplexer configured to multiplex the plurality of signals to generate a plurality of code multiplexed signals;
a combiner configured to combine the plurality of code multiplexed signals into a combined signal;
a downconverter configured to downconvert the combined signal to a lower-frequency combined signal; and
a code demultiplexing image processor configured to:
half-demultiplex a plurality of baseband signals from the lower-frequency combined signal;
correlate unique pairs of the plurality of baseband signals to generate a plurality of visibility products; and
Fourier transform the plurality of visibility products to generate an image.
17. The interferometer according to claim 16 , wherein the code multiplexer is configured to phase shift each of the plurality of signals according to a respective code to generate the plurality of code multiplexed signals.
18. The interferometer according to claim 16 , wherein the code multiplexer is configured to phase shift each of the plurality of signals with a respective code from a code-set which has balanced orthogonal code products (BOCPs).
19. The interferometer according to claim 18 , wherein the code-set has a chip rate selected based on a rate of scene changes in the image.
20. The interferometer according to claim 16 , wherein the interferometer generates the image using at least one of ambient illumination or active illumination provided by an active illumination source.