Mobile radar for visualizing topography
A mobile radar system for visualizing forward looking topography is configured with at least two phased-array antennas to form a forwarding looking phased-array interferometer.
1. A mobile radar apparatus comprising:
a first radar sub-array including at least one transmitter and a plurality of receivers;
a second radar sub-array including a plurality of receivers;
each of said sub-arrays being configured to continuously illuminate a topographical area along a directional heading traveled by said mobile radar apparatus, to receive a backscatter profile of said illuminated topographical area and to generate 2D topographic image data of said topographical area,
each of said sub-arrays being spaced by a predetermined baseline distance B;
a processor configured to receive respective 2D topographic image data from each of said first and second sub-arrays and apply single-pass interferometric processing to measure a height of the topography at each pixel within said 2D image data,
said processor being further configured to generate from said 2D topographic image data and said interferometric processing, 3D topographic image data having the position and height of each topographical feature,
wherein each sub-array includes a digital beam former configured to process said backscatter profiles using a multi-plane digital beam forming process to establish multiple digital beam forming processing planes within each sub-array.
2. The mobile radar apparatus of claim 1 wherein each sub-array is further configured to implement a frequency hopping process in combination with said multi-plane digital beam forming process.
3. The mobile radar apparatus of claim 1 wherein each sub-array is further configured to implement a frequency hopping process with phase modulation for frequency sub channel spectral leakage suppression with said multi-plane digital beam forming process.
4. The mobile radar apparatus of claim 1 wherein each sub-array is further configured to implement a Doppler shift correction using a two-step Doppler corrected digital beam forming process comprising a step of correcting for average Doppler shift and correcting for residual Doppler errors arising from variations in azimuth beam and range gating.
5. The radar apparatus of claim 1 wherein said second radar sub-array includes at least one transmitter and said processor is configured to cause said transmitters of said sub-arrays to alternately transmit pulses or simultaneously transmit pulses at offset frequencies and to receive with all receivers thereby creating an interferometric Ping Pong mode that increases the electric baseline distance.
6. A mobile radar apparatus comprising:
a first radar sub-array including at least one transmitter and a plurality of receivers;
a second radar sub-array including a plurality of receivers;
each of said radar sub-arrays comprising a transmitter gain calibration loop interposed between said transmitter and said receivers,
each of said sub-arrays being configured to continuously illuminate a topographical area along a directional heading traveled by said mobile radar apparatus, to receive a backscatter profile of said illuminated topographical area and to generate 2D topographic image data of said topographical area,
each of said sub-arrays being spaced by a predetermined baseline distance B;
a processor configured to receive respective 2D topographic image data from each of said first and second sub-arrays and apply single-pass interferometric processing to measure a height of the topography at each pixel within said 2D image data,
said processor being further configured to generate from said 2D topographic image data and said interferometric processing, 3D topographic image data having the position and height of each topographical feature,
wherein said calibration loop includes a phase modulator coupled to said transmitter, an attenuator and an N-way divider configured to output a calibration signal to each of said plurality of receivers, wherein said phase modulator is configured to transition between a first state which applies a phase shift of 0 degrees and a second state which applies a phase shift of 180 degrees.
7. The radar apparatus of claim 6 wherein attenuator comprises a switchable attenuator.
8. The radar apparatus of claim 6 wherein said attenuator comprises a fixed attenuator.
9. A mobile radar apparatus comprising:
a first radar sub-array including at least one transmitter and a plurality of receivers;
a second radar sub-array including a plurality of receivers;
each of said radar sub-arrays comprising a transmitter gain calibration loop interposed between said transmitter and said receivers,
each of said sub-arrays being configured to continuously illuminate a topographical area along a directional heading traveled by said mobile radar apparatus, to receive a backscatter profile of said illuminated topographical area and to generate 2D topographic image data of said topographical area,
each of said sub-arrays being spaced by a predetermined baseline distance B;
a processor configured to receive respective 2D topographic image data from each of said first and second sub-arrays and apply single-pass interferometric processing to measure a height of the topography at each pixel within said 2D image data,
said processor being further configured to generate from said 2D topographic image data and said interferometric processing, 3D topographic image data having the position and height of each topographical feature,
wherein said calibration loop includes a switchable attenuator coupled to said transmitter and an N-way divider configured to output a calibration signal to each of said plurality of receivers, wherein said switchable attenuator is configured to transition between a first state which applies low attenuation and a second state which applies a high attenuation.
10. The radar apparatus of claim 9 further comprising a phase modulator coupled to said transmitter.
11. A mobile radar apparatus comprising:
a first radar sub-array including at least one transmitter and a plurality of receivers;
a second radar sub-array including a plurality of receivers;
each of said sub-arrays being configured to continuously illuminate a topographical area along a directional heading traveled by said mobile radar apparatus, to receive a backscatter profile of said illuminated topographical area and to generate 2D topographic image data of said topographical area,
each of said sub-arrays being spaced by a predetermined baseline distance B;
a processor configured to receive respective 2D topographic image data from each of said first and second sub-arrays and apply single-pass interferometric processing to measure a height of the topography at each pixel within said 2D image data,
said processor being further configured to generate from said 2D topographic image data and said interferometric processing, 3D topographic image data having the position and height of each topographical feature; and
a digital terrain map data source storing DTM data,
said processor being further configured to utilize interferometric phase directly in a slant-range plane to compare said 3D topographic image data having the position and height of each topographical feature with said DTM data and to thereby detect height anomalies in the topographic field of view.