CA2488909C - Interferometric microwave radar method - Google Patents
Interferometric microwave radar method Download PDFInfo
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- CA2488909C CA2488909C CA2488909A CA2488909A CA2488909C CA 2488909 C CA2488909 C CA 2488909C CA 2488909 A CA2488909 A CA 2488909A CA 2488909 A CA2488909 A CA 2488909A CA 2488909 C CA2488909 C CA 2488909C
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/88—Radar or analogous systems specially adapted for specific applications
- G01S13/89—Radar or analogous systems specially adapted for specific applications for mapping or imaging
- G01S13/90—Radar or analogous systems specially adapted for specific applications for mapping or imaging using synthetic aperture techniques, e.g. synthetic aperture radar [SAR] techniques
- G01S13/9021—SAR image post-processing techniques
- G01S13/9023—SAR image post-processing techniques combined with interferometric techniques
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/003—Transmission of data between radar, sonar or lidar systems and remote stations
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- Engineering & Computer Science (AREA)
- Remote Sensing (AREA)
- Radar, Positioning & Navigation (AREA)
- Physics & Mathematics (AREA)
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- Computer Networks & Wireless Communication (AREA)
- General Physics & Mathematics (AREA)
- Radar Systems Or Details Thereof (AREA)
Abstract
Phase ambiguities measured in an interferometric microwave radar method are resolved by phase unwrapping in the form of analyzing two interferograms based on different wavelengths, from which a so-called delta k interferogram is obtained having a substantially greater wavelength serving as a value for estimating the absolute phase without further unwrapping. For this purpose, two trains of radar transmission pulses are generated at the transmitter end operated in separate different wavelength ranges and each pulse of which is always emitted simultaneously or sequenced in time in thus forming together a train of two- wavelength pulses. At the receiver end the received signal spectrum is split into two sub-bands each containing one of the two different wavelength ranges, and the interferograms materializing in these two sub-bands are added to result in the delta k interferogram which is then employed as the value for estimating the absolute phase and thus also the absolute distance measured value for the pixels. Applications in generating elevation models and in aerospace sensing object and flow velocities.
Description
Title:
Interferometric Microwave Radar Method The invention relates to an interferometric microwave radar method,-particularly including a synthetic aperture (SAR), wherein in phase difference analysis undertaken by coherent demodulation of the echo signals of pulse radar transmission signals received in two different positions, any resulting phase ambiguities are resolved by phase unwrapping in the form of analyzing two interferograms based on different wavelengths, from which a so-called delta k interferogram of substantially greater wavelength is obtained, serving as a value for estimating the absolute phase without further unwrapping.
In radar interferometry the phase is analyzed as measured in a radar system with coherent demodulation of the received signal. Since the distance resolution of a microwave radar is much coarser than the wavelength, although this phase furnishes highly accurate relative distance sensing between neighboring pixels, it produces no absolute values for pixel sensing. Apart from this, phase sensing is available in principle only in the range -180 to +180 , and is, in other words, ambiguous.
Practically all applications of radar interferometry suffer hitherto from this ambiguity, e.g. in generating digital terrain models, mapping geological deformations or in sensing vehicle velocities.
This ambiguity is resolved in the majority of the applications by unwrapping the phase by analyzing the gradients to the neighboring pixels.
Interferometric Microwave Radar Method The invention relates to an interferometric microwave radar method,-particularly including a synthetic aperture (SAR), wherein in phase difference analysis undertaken by coherent demodulation of the echo signals of pulse radar transmission signals received in two different positions, any resulting phase ambiguities are resolved by phase unwrapping in the form of analyzing two interferograms based on different wavelengths, from which a so-called delta k interferogram of substantially greater wavelength is obtained, serving as a value for estimating the absolute phase without further unwrapping.
In radar interferometry the phase is analyzed as measured in a radar system with coherent demodulation of the received signal. Since the distance resolution of a microwave radar is much coarser than the wavelength, although this phase furnishes highly accurate relative distance sensing between neighboring pixels, it produces no absolute values for pixel sensing. Apart from this, phase sensing is available in principle only in the range -180 to +180 , and is, in other words, ambiguous.
Practically all applications of radar interferometry suffer hitherto from this ambiguity, e.g. in generating digital terrain models, mapping geological deformations or in sensing vehicle velocities.
This ambiguity is resolved in the majority of the applications by unwrapping the phase by analyzing the gradients to the neighboring pixels.
Most of the known phase unwrapping techniques attempt to achieve a consistently correct solution solely from ambiguously sensed values, basically making it impossible to come to a physically unambiguous correct solution. The reason for this is that various physical constellations can produce the same sensed values, experience having shown that such problematic constellations materialize not only in theory but often also in nature.
The sole alternative is accordingly to take into account external prior knowledge in the process of phase unwrapping. This necessitates being previously aware of the sensing parameter with the accuracy of the wavelength X, as is, however, only very seldom the case.
One possibility of establishing at least a constant phase offset of the full image reads from the paper by S.N.
Madsen: "On absolute phase determination techniques in SAR
interferometry", SPIE Conference on Radar Sensor Technology, April 19-21, 1995, pages 393-401. To compute the absolute distance between the radar sensor and a backscatter object with wavelength accuracy, use is made of the minimally different wavelengths within the radar frequency spectrum. Referring now to FIG. 1 there is illustrated how for this purpose an interferogram is formed in each case from the upper and lower sideband, a so-called delta k interferogram being obtained from these two interferograms fl and f2. This delta k interferogram corresponds to an interferogram having the substantially greater wavelength 1(1/X1-1/X2) which can serve as a value for estimating the absolute phase in broad ranges without further phase unwrapping by scaling with the ratio of the carrier frequency fo to the distance of the frequency bands B/2. For radar sensors as used nowadays this ratio is a very large number between 1000 and 3000, this being the reason why the error in the estimate is correspondingly high. It is because of this that the relative unwrapped phase is subtracted from the interferogram fa and the difference is averaged over the full image, i.e. over several million pixels.
One indication of being able to derive even the absolute phase of single pixels by this known technique reads from the paper by Engen, G., Guneriussen, T., Overein O.; "New Approach for Snow Water Equivalent (SWE) estimation using repeat pass interferometric SAR", IGARSS 2003.
Unfortunately, because of the small differences in wavelength this known interferometric technique is highly prone to error, is seldom mentioned in pertinent literature and also finds hardly any application in actual practice.
Techniques for phase unwrapping as known hitherto in interferometric radar are thus unreliable and in general no measure of the error can also be stated. Although the value as measured in the interferogram is precise to a millimeter, the real value may be imprecise by multiples of the wavelength, i.e. centimeters or even several meters.
Accordingly, making use of the delta k interferometric technique for phase unwrapping has hitherto been a failure for lack of accuracy, it finding mention hitherto only for establishing the constant absolute phase offset value of the image as a whole (Madsen) as well as the absolute phase of discrete, very strong single point scatterers (G. Engen et al.).
The invention is thus based on the objective of reliably resolving the phase ambiguities with zero error in interferometric radar techniques as correctly indicated for each and every pixel of an image without undue additional complication technically.
In accordance with the invention there is provided an interferometric microwave radar method with a synthetic aperture (SAR), wherein, upon a phase difference analysis performed after a coherent demodulation of echo signals of a pulsed radar transmission signal transmitted from a transmitter end, said echo signals being received with their spectrum at a receiver end at two different positions resulting in two received signals, any occurring phase ambiguities are resolved by phase unwrapping realized by analyzing two interferograms formed in different wavelength ranges, from which a so-called delta-k-interferogram of a substantially greater wavelength is obtained, which, without any further unwrapping serves as an absolute phase estimate, the spectrum of the received signal therefore being split into two sub-bands, each including a respective one of the two different wavelength ranges, and the interferograms occurring in those two sub-bands being calculated to obtain said delta-k-interferogram, comprising following steps of:
generating two separate radar transmission pulse trains on the transmitter end when forming the pulsed radar transmission signal, said two radar pulse transmission trains being driven in separate different wavelength ranges within a predetermined band width range and each pulse of which is always emitted simultaneously and in 4a parallel or sequenced in time in thus forming together a train of two-wavelength pulses, and employing the delta-k-interferogram calculated at the receiver end as an estimate of absolute phase and thus also as an absolute measured value of distance sensed for pixels.
The invention thus involves precisely optimizing an interferometric radar method for delta k interferometry.
The technical means for achieving this are modest and can be easily supplemented in interferometric radar sensors.
The method in accordance with the invention will now be detailed with reference to the drawings in which:
FIG. 1 is a block diagram of an assembly for 5 implementing the interferometric radar technique with delta k interferometry as known from the aforementioned paper by S.N.Madsen:
FIG. 2 is a graph showing the frequency spectrum of a parallel two-frequency pulse as a function of time for the improved delta k interferometry by the method in accordance with the invention;
FIG. 3 is likewise a graph showing the frequency spectrum of a sequential two=frequency pulse as a function of time for the improved delta k interferometry by the method in accordance with the invention;
FIG. 4 is a rough block diagram of an interferometric radar system for implementing the invention with a SAR processor, the optimizations achieved by the invention for the delta k interferometry being highlighted shaded;
FIG. 5 is a diagram showing the receiver spectrum of the radar signal with 1/6 of the total bandwidth in the sub-bands;
FIG. 6 is a diagram showing the receiver spectrum of the radar signal decimated by the factor 3, the repetition spectra being highlighted heavily shaded, and FIG. 7 is a block diagram of a circuit for implementing processing of the interferometric radar data in the method in accordance with the invention, the phase constant n being derived from interferometric delta k processing.
In the interferometric radar method in accordance with the invention the conventional radar transmitter is modified into a two-frequency transmitter by modulating the carrier signal with a two-frequency chirp. As compared to prior art as explained at the outset, this achieves, for the same channel bandwidth, a substantially greater spacing of the frequency channels in thus significantly enhancing the accuracy of the delta k interferometry method.
Concentrating the transmitter power to a narrow bandwidth improves the signal-to-noise ratio.
Referring now to FIG. 2 there is illustrated as a function of time the frequency spectrum of a parallel two-frequency pulse, i.e. existing simultaneously with its single pulses, as emitted by the radar transmitter. For each single pulse of the two parallel pulse trains a linear modulated chirp is used over the pulse duration, for example. With the one single pulse the frequency linearly increases during the pulse duration about the frequency fl whereas with the other pulse the linear increase is about the higher frequency f2.
Even larger differences in frequency are achievable as long as the electronic modules used in common permit. Thus, common reflector antennas can be used, for example, signalled with horns in different frequency bands, for instance X-band and Ku-band.
Referring now to FIG. 3 there is illustrated how likewise the two single pulses of the two pulse trains can be transmitted one after the other in time, as evident from the frequency spectrum graph as a function of time.
The conventional radar receiver is modified in application of the interferometric radar method in accordance with the invention into a two-frequency receiver having a common arialog/digital conversion followed by a sub-sampler.
Referring now to FIG. 4 there is illustrated in a diagrammatic circuit diagram a radar system working with a synthetic aperture (SAR) for implementing the method in accordance with the invention with the modules modified for improved delta k interferometry, indicated shaded. FIG. 5 shows in addition the spectrum of the received radar signal.
Using two separate sub-band filters in the receiver makes for an improved signal-to-noise ratio as compared to use of a wideband filter as employed in prior art should decimation in the analog/digital conversion of the interferometric signal be provided. Decimation to the effectively used bandwidth of the channels is possible when the width and spacing of the channels as well as the decimation ratio are suitably selected.
Referring now to FIG. 6 there is illustrated in this case how the signal of a wideband receiver, but also how the sum of two narrow band receivers can be decimated by a factor of 3 without the repetition spectra (shown heavily shaded) overlapping. This decimation is a major advantage over prior art delta k interferometry as aforementined since the data rate is reduced to a fraction for the same total bandwidth. This data reduction is very important especially when radar interferometry is employed in satellite systems.
If use is made of various frequency bands with a difference of more than a few hundred MHz, it is of advantage to sample the analog data separately. Mixing the two channels in this case is done digitally in capturing the data stream, in thus enhancing the signal quality whilst facilitating separating the frequency channels in processing.
Referring now to FIG. 7 there is illustrated how the data is processed in a block diagram, whereby the same as in FIG. 4 SLC stands for "single look complex image", in other words the focussed image product as usual in a complex visualization. To make for a better understanding, deriving the phase constant n from interferometric delta k processing is illustrated here merely incompletely and in a simplified way, it being somewhat more complicated in the embodiment as actually achieved.
For the improved interferometric radar method in accordance with the invention there exists a whole series of applications of considerable potential as regards marketing and scientific importance.
Thus, highly accurate digital elevation models even of difficult mountainous areas in which hitherto the phase ambiguity was non-resolvable can now be produced by space satellites.
It can also be used for aerospace sensing the velocity of traffic, glaciers and ocean currents, it being particularly in the case of single vehicles that even higher velocities outside of the ambiguity interval can now be resolved by application of the interferometric radar method in accordance with the invention.
It will be appreciated that the method as described can be put to use, of course, not only on satellites but also in aircraft.
The sole alternative is accordingly to take into account external prior knowledge in the process of phase unwrapping. This necessitates being previously aware of the sensing parameter with the accuracy of the wavelength X, as is, however, only very seldom the case.
One possibility of establishing at least a constant phase offset of the full image reads from the paper by S.N.
Madsen: "On absolute phase determination techniques in SAR
interferometry", SPIE Conference on Radar Sensor Technology, April 19-21, 1995, pages 393-401. To compute the absolute distance between the radar sensor and a backscatter object with wavelength accuracy, use is made of the minimally different wavelengths within the radar frequency spectrum. Referring now to FIG. 1 there is illustrated how for this purpose an interferogram is formed in each case from the upper and lower sideband, a so-called delta k interferogram being obtained from these two interferograms fl and f2. This delta k interferogram corresponds to an interferogram having the substantially greater wavelength 1(1/X1-1/X2) which can serve as a value for estimating the absolute phase in broad ranges without further phase unwrapping by scaling with the ratio of the carrier frequency fo to the distance of the frequency bands B/2. For radar sensors as used nowadays this ratio is a very large number between 1000 and 3000, this being the reason why the error in the estimate is correspondingly high. It is because of this that the relative unwrapped phase is subtracted from the interferogram fa and the difference is averaged over the full image, i.e. over several million pixels.
One indication of being able to derive even the absolute phase of single pixels by this known technique reads from the paper by Engen, G., Guneriussen, T., Overein O.; "New Approach for Snow Water Equivalent (SWE) estimation using repeat pass interferometric SAR", IGARSS 2003.
Unfortunately, because of the small differences in wavelength this known interferometric technique is highly prone to error, is seldom mentioned in pertinent literature and also finds hardly any application in actual practice.
Techniques for phase unwrapping as known hitherto in interferometric radar are thus unreliable and in general no measure of the error can also be stated. Although the value as measured in the interferogram is precise to a millimeter, the real value may be imprecise by multiples of the wavelength, i.e. centimeters or even several meters.
Accordingly, making use of the delta k interferometric technique for phase unwrapping has hitherto been a failure for lack of accuracy, it finding mention hitherto only for establishing the constant absolute phase offset value of the image as a whole (Madsen) as well as the absolute phase of discrete, very strong single point scatterers (G. Engen et al.).
The invention is thus based on the objective of reliably resolving the phase ambiguities with zero error in interferometric radar techniques as correctly indicated for each and every pixel of an image without undue additional complication technically.
In accordance with the invention there is provided an interferometric microwave radar method with a synthetic aperture (SAR), wherein, upon a phase difference analysis performed after a coherent demodulation of echo signals of a pulsed radar transmission signal transmitted from a transmitter end, said echo signals being received with their spectrum at a receiver end at two different positions resulting in two received signals, any occurring phase ambiguities are resolved by phase unwrapping realized by analyzing two interferograms formed in different wavelength ranges, from which a so-called delta-k-interferogram of a substantially greater wavelength is obtained, which, without any further unwrapping serves as an absolute phase estimate, the spectrum of the received signal therefore being split into two sub-bands, each including a respective one of the two different wavelength ranges, and the interferograms occurring in those two sub-bands being calculated to obtain said delta-k-interferogram, comprising following steps of:
generating two separate radar transmission pulse trains on the transmitter end when forming the pulsed radar transmission signal, said two radar pulse transmission trains being driven in separate different wavelength ranges within a predetermined band width range and each pulse of which is always emitted simultaneously and in 4a parallel or sequenced in time in thus forming together a train of two-wavelength pulses, and employing the delta-k-interferogram calculated at the receiver end as an estimate of absolute phase and thus also as an absolute measured value of distance sensed for pixels.
The invention thus involves precisely optimizing an interferometric radar method for delta k interferometry.
The technical means for achieving this are modest and can be easily supplemented in interferometric radar sensors.
The method in accordance with the invention will now be detailed with reference to the drawings in which:
FIG. 1 is a block diagram of an assembly for 5 implementing the interferometric radar technique with delta k interferometry as known from the aforementioned paper by S.N.Madsen:
FIG. 2 is a graph showing the frequency spectrum of a parallel two-frequency pulse as a function of time for the improved delta k interferometry by the method in accordance with the invention;
FIG. 3 is likewise a graph showing the frequency spectrum of a sequential two=frequency pulse as a function of time for the improved delta k interferometry by the method in accordance with the invention;
FIG. 4 is a rough block diagram of an interferometric radar system for implementing the invention with a SAR processor, the optimizations achieved by the invention for the delta k interferometry being highlighted shaded;
FIG. 5 is a diagram showing the receiver spectrum of the radar signal with 1/6 of the total bandwidth in the sub-bands;
FIG. 6 is a diagram showing the receiver spectrum of the radar signal decimated by the factor 3, the repetition spectra being highlighted heavily shaded, and FIG. 7 is a block diagram of a circuit for implementing processing of the interferometric radar data in the method in accordance with the invention, the phase constant n being derived from interferometric delta k processing.
In the interferometric radar method in accordance with the invention the conventional radar transmitter is modified into a two-frequency transmitter by modulating the carrier signal with a two-frequency chirp. As compared to prior art as explained at the outset, this achieves, for the same channel bandwidth, a substantially greater spacing of the frequency channels in thus significantly enhancing the accuracy of the delta k interferometry method.
Concentrating the transmitter power to a narrow bandwidth improves the signal-to-noise ratio.
Referring now to FIG. 2 there is illustrated as a function of time the frequency spectrum of a parallel two-frequency pulse, i.e. existing simultaneously with its single pulses, as emitted by the radar transmitter. For each single pulse of the two parallel pulse trains a linear modulated chirp is used over the pulse duration, for example. With the one single pulse the frequency linearly increases during the pulse duration about the frequency fl whereas with the other pulse the linear increase is about the higher frequency f2.
Even larger differences in frequency are achievable as long as the electronic modules used in common permit. Thus, common reflector antennas can be used, for example, signalled with horns in different frequency bands, for instance X-band and Ku-band.
Referring now to FIG. 3 there is illustrated how likewise the two single pulses of the two pulse trains can be transmitted one after the other in time, as evident from the frequency spectrum graph as a function of time.
The conventional radar receiver is modified in application of the interferometric radar method in accordance with the invention into a two-frequency receiver having a common arialog/digital conversion followed by a sub-sampler.
Referring now to FIG. 4 there is illustrated in a diagrammatic circuit diagram a radar system working with a synthetic aperture (SAR) for implementing the method in accordance with the invention with the modules modified for improved delta k interferometry, indicated shaded. FIG. 5 shows in addition the spectrum of the received radar signal.
Using two separate sub-band filters in the receiver makes for an improved signal-to-noise ratio as compared to use of a wideband filter as employed in prior art should decimation in the analog/digital conversion of the interferometric signal be provided. Decimation to the effectively used bandwidth of the channels is possible when the width and spacing of the channels as well as the decimation ratio are suitably selected.
Referring now to FIG. 6 there is illustrated in this case how the signal of a wideband receiver, but also how the sum of two narrow band receivers can be decimated by a factor of 3 without the repetition spectra (shown heavily shaded) overlapping. This decimation is a major advantage over prior art delta k interferometry as aforementined since the data rate is reduced to a fraction for the same total bandwidth. This data reduction is very important especially when radar interferometry is employed in satellite systems.
If use is made of various frequency bands with a difference of more than a few hundred MHz, it is of advantage to sample the analog data separately. Mixing the two channels in this case is done digitally in capturing the data stream, in thus enhancing the signal quality whilst facilitating separating the frequency channels in processing.
Referring now to FIG. 7 there is illustrated how the data is processed in a block diagram, whereby the same as in FIG. 4 SLC stands for "single look complex image", in other words the focussed image product as usual in a complex visualization. To make for a better understanding, deriving the phase constant n from interferometric delta k processing is illustrated here merely incompletely and in a simplified way, it being somewhat more complicated in the embodiment as actually achieved.
For the improved interferometric radar method in accordance with the invention there exists a whole series of applications of considerable potential as regards marketing and scientific importance.
Thus, highly accurate digital elevation models even of difficult mountainous areas in which hitherto the phase ambiguity was non-resolvable can now be produced by space satellites.
It can also be used for aerospace sensing the velocity of traffic, glaciers and ocean currents, it being particularly in the case of single vehicles that even higher velocities outside of the ambiguity interval can now be resolved by application of the interferometric radar method in accordance with the invention.
It will be appreciated that the method as described can be put to use, of course, not only on satellites but also in aircraft.
Claims (6)
1. An interferometric microwave radar method with a synthetic aperture (SAR), wherein, upon a phase difference analysis performed after a coherent demodulation of echo signals of a pulsed radar transmission signal transmitted from a transmitter end, said echo signals being received with their spectrum at a receiver end at two different positions resulting in two received signals, any occurring phase ambiguities are resolved by phase unwrapping realized by analyzing two interferograms formed in different wavelength ranges, from which a so-called delta-k-interferogram of a substantially greater wavelength is obtained, which, without any further unwrapping serves as an absolute phase estimate, the spectrum of the received signal therefore being split into two sub-bands, each including a respective one of the two different wavelength ranges, and the interferograms occurring in those two sub-bands being calculated to obtain said delta-k-interferogram, comprising following steps of:
generating two separate radar transmission pulse trains on the transmitter end when forming the pulsed radar transmission signal, said two radar pulse transmission trains being driven in separate different wavelength ranges within a predetermined band width range and each pulse of which is always emitted simultaneously and in parallel or sequenced in time in thus forming together a train of two-wavelength pulses, and employing the delta-k-interferogram calculated at the receiver end as an estimate of absolute phase and thus also as an absolute measured value of distance sensed for pixels.
generating two separate radar transmission pulse trains on the transmitter end when forming the pulsed radar transmission signal, said two radar pulse transmission trains being driven in separate different wavelength ranges within a predetermined band width range and each pulse of which is always emitted simultaneously and in parallel or sequenced in time in thus forming together a train of two-wavelength pulses, and employing the delta-k-interferogram calculated at the receiver end as an estimate of absolute phase and thus also as an absolute measured value of distance sensed for pixels.
2. The interferometric microwave radar method as set forth in claim 1 wherein a data reduction in the sub-bands is obtained by decimating the received signals from an analog/digital conversion performed in a process of interferogram data processing.
3. The interferometric microwave radar method as set forth in claim 2 comprising use of two separate filters on the receiving end for a signal filtering of the two sub-bands, each comprising a respective one of the two different wavelength ranges.
4. The interferometric microwave radar method as set forth in claim 1 wherein in generating the train of two-wavelength pulses a carrier at the transmitter end is modulated with a two frequency chirp in each single pulse.
5. The interferometric microwave radar method as set forth in claim 4 wherein for each single pulse of the train of two-wavelength pulses a linear frequency modulated chirp is employed.
6. A device for performing the interferometric microwave radar method of claim 1 comprising separate microwave assemblies adapted to realize the two different wavelength ranges, said assemblies sharing transmission and receiving antennas.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE10356351.2 | 2003-11-28 | ||
| DE10356351A DE10356351A1 (en) | 2003-11-28 | 2003-11-28 | Interferometric microwave radar method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2488909A1 CA2488909A1 (en) | 2005-05-28 |
| CA2488909C true CA2488909C (en) | 2010-07-27 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA2488909A Active CA2488909C (en) | 2003-11-28 | 2004-11-26 | Interferometric microwave radar method |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP1536247B1 (en) |
| CA (1) | CA2488909C (en) |
| DE (2) | DE10356351A1 (en) |
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10230925B2 (en) | 2014-06-13 | 2019-03-12 | Urthecast Corp. | Systems and methods for processing and providing terrestrial and/or space-based earth observation video |
| US10615513B2 (en) | 2015-06-16 | 2020-04-07 | Urthecast Corp | Efficient planar phased array antenna assembly |
| US10871561B2 (en) | 2015-03-25 | 2020-12-22 | Urthecast Corp. | Apparatus and methods for synthetic aperture radar with digital beamforming |
| US10955546B2 (en) | 2015-11-25 | 2021-03-23 | Urthecast Corp. | Synthetic aperture radar imaging apparatus and methods |
| US11378682B2 (en) | 2017-05-23 | 2022-07-05 | Spacealpha Insights Corp. | Synthetic aperture radar imaging apparatus and methods for moving targets |
| US11506778B2 (en) | 2017-05-23 | 2022-11-22 | Spacealpha Insights Corp. | Synthetic aperture radar imaging apparatus and methods |
| US11525910B2 (en) | 2017-11-22 | 2022-12-13 | Spacealpha Insights Corp. | Synthetic aperture radar apparatus and methods |
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|---|---|---|---|---|
| CN108594222B (en) * | 2018-03-21 | 2020-05-08 | 中国科学院电子学研究所 | Elevation reconstruction method and device for dual-frequency interference synthetic aperture radar |
| CN109357624B (en) * | 2018-09-29 | 2021-02-23 | 北京信息科技大学 | Strain measurement method and device based on absolute phase |
| CN111638516B (en) * | 2019-03-01 | 2022-02-18 | 中国科学院电子学研究所 | Terahertz frequency band SAR motion compensation algorithm based on double-frequency conjugate processing technology |
| CN109884634B (en) * | 2019-03-20 | 2020-08-04 | 中南大学 | InSAR phase unwrapping method and system based on hierarchical network construction mode |
| CN109901151B (en) * | 2019-03-21 | 2021-04-20 | 西安交通大学 | Cyclic transformation detection method based on composite radar |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4630051A (en) * | 1985-03-01 | 1986-12-16 | Holodyne Ltd., 1986 | Imaging doppler interferometer |
-
2003
- 2003-11-28 DE DE10356351A patent/DE10356351A1/en not_active Withdrawn
-
2004
- 2004-11-22 DE DE502004007353T patent/DE502004007353D1/en active Active
- 2004-11-22 EP EP04027663A patent/EP1536247B1/en active Active
- 2004-11-26 CA CA2488909A patent/CA2488909C/en active Active
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10230925B2 (en) | 2014-06-13 | 2019-03-12 | Urthecast Corp. | Systems and methods for processing and providing terrestrial and/or space-based earth observation video |
| US10871561B2 (en) | 2015-03-25 | 2020-12-22 | Urthecast Corp. | Apparatus and methods for synthetic aperture radar with digital beamforming |
| US10615513B2 (en) | 2015-06-16 | 2020-04-07 | Urthecast Corp | Efficient planar phased array antenna assembly |
| US10955546B2 (en) | 2015-11-25 | 2021-03-23 | Urthecast Corp. | Synthetic aperture radar imaging apparatus and methods |
| US11754703B2 (en) | 2015-11-25 | 2023-09-12 | Spacealpha Insights Corp. | Synthetic aperture radar imaging apparatus and methods |
| US11378682B2 (en) | 2017-05-23 | 2022-07-05 | Spacealpha Insights Corp. | Synthetic aperture radar imaging apparatus and methods for moving targets |
| US11506778B2 (en) | 2017-05-23 | 2022-11-22 | Spacealpha Insights Corp. | Synthetic aperture radar imaging apparatus and methods |
| US11525910B2 (en) | 2017-11-22 | 2022-12-13 | Spacealpha Insights Corp. | Synthetic aperture radar apparatus and methods |
Also Published As
| Publication number | Publication date |
|---|---|
| DE502004007353D1 (en) | 2008-07-24 |
| DE10356351A1 (en) | 2005-06-30 |
| CA2488909A1 (en) | 2005-05-28 |
| EP1536247A1 (en) | 2005-06-01 |
| EP1536247B1 (en) | 2008-06-11 |
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