CN103389497B - Airborne thinned array antenna downward-looking three-dimensional imaging radar system and imaging method - Google Patents

Abstract

The invention discloses an airborne sparse array antenna downward-looking three-dimensional imaging radar system and an imaging method. The system includes an airborne platform, a sparse array antenna system and a distributed POS. The airborne platform is used to carry the Sparse array antenna system and distributed POS aircraft, array antennas can be arranged in the middle and both sides of the aircraft; the sparse array antenna system consists of multiple densely arranged sub-arrays in the middle and 1 or 2 Composed of sub-arrays; use the distributed POS to realize accurate measurement of the relative spatial position of the multi-phase center of the array antenna; under the looking-down mode, the scanning mode combined with the ScanSAR mode and the SweepSAR mode is used to expand the observation width; when the carrier aircraft When running at high altitude, the cross-track equivalent array is obtained by using the sparse re-passing method with Barker code as the sampling criterion to improve the cross-track resolution. The invention adopts an array antenna with a spatially sparse layout in the cross-track direction of the carrier aircraft, so as to realize high-resolution and wide-width three-dimensional imaging of the observation scene.

Description

Airborne Sparse Array Antenna Downward-Looking 3D Imaging Radar System and Imaging Method

technical field

The invention relates to the technical field of radar systems, information acquisition and processing, in particular to an airborne sparse array antenna downward-looking three-dimensional imaging radar capable of realizing high-resolution and wide-width three-dimensional imaging.

Background technique

The airborne downward-looking 3D imaging radar system is a new microwave 3D imaging radar system, and its imaging principle is shown in Figure 1. Through the movement of the carrier platform, a synthetic aperture is formed in the X direction (following the track direction), and the along-track resolution is obtained; an array antenna is used to form a real aperture in the Y direction (cross-track direction), and the cross-track resolution is obtained; The broadband signal is transmitted in the direction (elevation direction), and the range (elevation direction) resolution is obtained through pulse compression processing, so as to realize the three-dimensional imaging of the observation scene.

At present, domestic and foreign studies have been carried out on airborne down-looking 3D imaging radars. Among them, the ARTINO system of FGAN-FHR in Germany is the most typical. For the antenna, the transmitting unit is located at both ends of the array, and the receiving unit is located in the middle of the array. The equivalent full array can be obtained in the cross-track direction by using time division. Combined with the synthetic aperture formed by the movement of the carrier along the track and the broadband signal emitted, 3D imaging is realized. (See KlareJ, Weiss M, Peters O, et al. "ARTINO: A New High Resolution 3D Imaging Radar System on An Autonomous Airborne Platform", IGARSS, Colorado, USA, 2006; Klare J. "A New Airborne Radar for 3D Imaging- Simulation Study of ARTINO".)

The sparse array antenna aperture synthesis technology can greatly reduce the number of large-scale array antenna sub-arrays and their corresponding transceiver units. Applying the sparse array antenna in the cross-track direction of the carrier aircraft can greatly reduce the volume, weight and complexity of the system. The sparse array antenna is equivalent to a full array by using sub-array time-division transmission, and the same imaging results as the full array antenna can be obtained in the cross-track direction. (See HouY N, Li D J, Hong W. "The Thinned Array Time Division Multiple PhaseCenter Aperture Synthesis and Application", IGARSS, Boston, USA, 2008.)

In the above system, if the cross-track array antenna is composed of small-sized sub-arrays, its beam width is wider, so a larger observation width can be obtained, but the size of the sub-arrays is small, and the number of required sub-arrays will be A sharp increase, while increasing the complexity of the system. If the cross-track array antenna is composed of large-sized sub-arrays, it can solve the problem that too many sub-arrays increase the complexity of the system, but the observation width is limited due to the narrow beam of the sub-arrays.

Due to the limited length of the aircraft's wingspan, the length of the cross-track array antenna is limited. The cross-track resolution is related to the length of the cross-track array antenna, the operating height of the carrier platform, and the wavelength of the transmitted signal. When the carrier platform operates at high altitude, the available cross-track resolution will be reduced, which cannot meet the requirements of high resolution. The need for ground imaging.

Contents of the invention

(1) Technical problems to be solved

The technical problem to be solved by the present invention is that there are two deficiencies in the existing airborne array antenna downward looking three-dimensional imaging radar system: one, if the cross-track array antenna is composed of small-sized sub-arrays, its beam width is relatively wide, so A larger observation width can be obtained, but the size of the sub-array is small, the number of required sub-arrays will increase sharply, and the complexity of the system will be increased at the same time. If the cross-track array antenna is composed of large-sized sub-arrays, it can solve Too many sub-arrays increase the complexity of the system, but the observation width is limited due to the narrow beam of the sub-arrays; The length of the antenna is limited by the wingspan of the carrier aircraft. When the carrier aircraft is operating at high altitude, the cross-track resolution will be reduced, which cannot meet the needs of high-resolution earth observation.

(2) Technical solution

In order to solve the above technical problems, the present invention proposes an airborne sparse array antenna downward-looking three-dimensional imaging radar system, which includes an airborne platform, a sparse array antenna system, and a distributed POS. The airborne platform is used to carry the sparse An array antenna system and a distributed POS aircraft, array antennas can be arranged in the middle and both sides of the aircraft; the sparse array antenna system is composed of multiple sub-arrays, and the multiple sub-arrays are distributed on three sides of the carrier platform. area, the three areas are distributed in the middle and both sides of the carrier platform.

According to a specific embodiment of the present invention, the three areas are a main area and two sub-areas, the main area is located in the middle of the carrier platform, and the sub-areas are located on both sides of the carrier platform , and an array antenna arranged by a plurality of sub-arrays is installed in the main area, and one or two sub-arrays are installed in the sub-area, and the array antennas in the three areas constitute the sparse array antenna system.

According to a specific embodiment of the present invention, the carrier platform is an aircraft, the main area is located at the belly of the aircraft, and the two auxiliary areas are respectively located in the pods under the two wings of the aircraft .

According to a specific implementation manner of the present invention, the multiple sub-arrays are all two-dimensional phase-scan active arrays.

According to a specific embodiment of the present invention, the distributed POS is distributed in the three areas, and is used for accurate measurement of the polyphase center of the sparse array antenna system.

According to a specific embodiment of the present invention, the cross-rail size of the sub-arrays is 0.25m, the main area has 8 sub-arrays, and each sub-area has 2 sub-arrays.

The present invention also proposes an airborne sparse array antenna downward-looking three-dimensional imaging method. An array antenna composed of 1 or 2 sub-arrays, distributed POS at each sub-array position, the method includes the following steps: using the distributed POS to measure the relative spatial position of the polyphase center of the sparse array antenna ; With the DBF pattern of the array antenna in the main area as a weighting function, weighting is performed on the sparse array pattern formed by the equivalent phase center for each of the sub-arrays, so as to improve its peak side lobe ratio and integral side lobe ratio. lobe ratio; the sub-array of the sparse array antenna adopts a two-dimensional phase-sweep active array, and in the working mode of looking directly down, adopts the scanning mode combining the ScanSAR mode and the SweepSAR mode to expand the observation imaging width; According to the flight mode, an equivalent array antenna with a longer length than the sparse array antenna is obtained in the cross-track direction to improve the resolution in the cross-track direction; according to the echo signals obtained in the above steps, three-dimensional imaging of the observation scene is performed.

According to a specific embodiment of the present invention, the Barker code is used as the sampling criterion for re-passing.

According to a specific embodiment of the present invention, in the step of performing three-dimensional imaging, a three-dimensional wavenumber domain algorithm is used, and the measured value of the relative spatial position of the equivalent phase center by the distributed POS and the weighting method of the pattern are introduced.

According to a specific embodiment of the present invention, the cross-track dimension of the sub-arrays is 0.25m, the main area has 8 sub-arrays, and each sub-area has 2 sub-arrays.

(3) Beneficial effects

As can be seen from the foregoing technical solutions, the present invention has the following beneficial effects:

1. In the cross-track direction, the present invention adopts a sparse array structure combining sub-arrays on both sides and a large array in the middle, and realizes resolution in the cross-track direction with a relatively small number of sub-arrays.

2. For the cross-track array antenna structure, the present invention adopts the distributed position and attitude measurement system POS to realize high-precision measurement of the relative spatial position of the multi-phase center of the array antenna, thereby realizing high-precision motion compensation and improving imaging quality.

3. The present invention adopts the scanning mode combining SweepSAR scanning mode and SweepSAR mode, which expands the imaging width.

Description of drawings

Figure 1 is a schematic diagram of the imaging geometry of the airborne downward-looking 3D imaging radar system;

Fig. 2 is a schematic plan view of the installation position of the cross-track array antenna of the present invention on the carrier platform;

Fig. 3 is a schematic diagram of the installation position of the cross-track array antenna of the present invention on an aircraft;

Fig. 4 is a schematic diagram of the position of the equivalent phase center that can be obtained in the cross-track direction when each sub-array transmits and receives multiple times according to the principle of the equivalent phase center of the present invention;

Figure 5 is the positional relationship between the equivalent phase center and the transceiver sub-array;

Fig. 6 is the flowchart of the airborne sparse array down-looking radar three-dimensional imaging method of the present invention;

Fig. 7a is the direction diagram of the 0.25m sub-array of the embodiment of the present invention;

Fig. 7b is the array factor of the cross-track sparse array antenna according to the embodiment of the present invention;

Fig. 7c is a direction diagram of a cross-track sparse array antenna according to an embodiment of the present invention;

Fig. 7d is the DBF direction diagram of the belly phalanx of the embodiment of the present invention;

Fig. 7e is a synthetic pattern after weighting the cross-track direction sparse array antenna pattern with the DBF pattern of the belly phalanx as the weight according to the embodiment of the present invention;

FIG. 8 is a schematic diagram of a scanning mode in which the ScanSAR mode and the SweepSAR mode are combined in an embodiment of the present invention;

Fig. 9 is a geometrical schematic diagram of sparse heavy-flying flight imaging according to an embodiment of the present invention;

Fig. 10 is the autocorrelation function of the 13-bit Barker code sequence ([1 1 1 1 0 0 1 1 0 1 0 1]) of the embodiment of the present invention;

Fig. 11a is a cross-orbit sparse array antenna pattern obtained during a random sparse re-overflight flight using 13-bit Barker codes as a sampling criterion according to an embodiment of the present invention;

Fig. 11b is a synthetic pattern obtained by weighting the cross-orbit sparse array antenna pattern obtained by sparse re-passing with the belly phalanx DBF pattern as a weight according to the embodiment of the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

For the airborne downward-looking three-dimensional imaging radar system shown in Figure 1, the present invention designs it from the perspective of analyzing its cross-track array layout, so as to realize high-resolution and wide-width imaging of the observation scene.

Specifically, the airborne sparse array downward-looking three-dimensional imaging radar system of the present invention includes an airborne platform, a sparse array antenna system, and a distributed POS (Position and Orientation System).

The airborne platform is an aircraft for carrying the sparse array antenna system and distributed POS. The aircraft can be equipped with array antennas in the middle and both sides, and can fly stably at an altitude of 1-3 km.

The sparse array antenna system of the present invention is composed of multiple sub-arrays, and the multiple sub-arrays are distributed in three areas of the airborne platform, ie a main area and two sub-areas. The main area is distributed in the middle of the carrier platform, and the two sub-regions are respectively located on both sides of the carrier platform.

According to the present invention, an array antenna densely arranged with a plurality of sub-arrays is installed in the main area, and one or two sub-arrays are installed in the sub-area, and the array antennas in the three areas form a larger sparse array antenna . The size of the sub-array in the cross-track direction may be 0.25m, and the size in the along-track direction may be determined according to the actually required resolution in the along-track direction.

The distributed POS of the present invention is distributed in the sub-array positions of the sparse array antenna, and is used to realize high-precision measurement of the relative positions of the multi-phase centers of the array antenna.

A specific embodiment of the present invention will be described below with reference to FIG. 2 .

In an embodiment of the present invention, the aircraft carrier platform is an aircraft as shown in FIG. 2 , such as a transport aircraft. However, according to the present invention, the carrier platform can be any aircraft that can be equipped with array antennas in the middle and both sides, and can fly stably at an altitude of 1-3 km above the ground.

As mentioned above, the airborne platform of the present invention is used to carry the sparse array antenna and distributed POS, so there should be a location and area where the sparse array antenna and distributed POS are arranged.

In this embodiment, position 1 shown in Figure 2 is the belly of the aircraft, which is the main area where the sparse array antennas are distributed, and 8 closely arranged sub-arrays are installed along the cross-track direction in the main area to form a length 2m array antenna. Position 2 shown in Figure 2 is the position where the pods are mounted on the wings on both sides of the aircraft, which are the two sub-regions where the sparse array antenna is distributed. The distance between the two sub-regions is about 9m. Two sub-arrays are installed in the rail direction to form a 0.5m array antenna. The sub-arrays distributed in three areas form a sparse array antenna with a length of about 9.6m.

In Fig. 3, take Yun 12IV type aircraft as a specific example of a carrier platform, showing the specific positions of the belly and wing pods on the carrier platform.

Each subarray of the sparse array antenna transmits frequency-division quadrature signals at the same time, and the distribution of the equivalent phase centers that can be obtained is shown in FIG. 4 by using the principle of multi-phase central aperture synthesis. The equivalent phase center is the virtual phase center generated in the middle of the transceiver sub-array when the transceiver sub-arrays are separated. The positional relationship between the equivalent phase center and the transceiver sub-array is shown in Fig. 5 .

The sub-array adopts a two-dimensional phase-scanning active array, that is, its beam can be scanned in two directions (following the track and crossing the track), especially when the cross-tracking beam needs to be scanned to expand the imaging width. The phase sweep refers to changing the excitation phase of each sub-array by controlling the phase shift amount of the phase shifter on the array antenna, so as to realize beam scanning.

The distributed POS is distributed in the sub-array positions of the sparse array antennas in the three regions, and realizes accurate measurement of the multi-phase centers of the array antennas in a distributed spatial structure, thereby realizing precise motion compensation and improving imaging quality.

Referring to FIG. 6 , the method for realizing high-resolution and wide-range three-dimensional imaging of the observation scene by using the airborne sparse array downward-looking three-dimensional imaging radar system of the present invention is described below.

First, for a sparse array antenna composed of multiple sub-arrays in the cross-track direction, the distributed POS distributed in each sub-array position is used to measure the relative spatial position of the multi-phase center of the array antenna, so that high-precision motion compensation processing can be realized.

Then, using the DBF (Digital Beamforming) pattern of the array antenna in the main area as a weighting function, the sparse array pattern formed by multiple transmission and multiple reception of the sub-arrays to obtain the equivalent phase center is weighted to improve its peak value. lobe ratio and integral sidelobe ratio.

According to the pattern product principle, the array pattern F(θ) is obtained by multiplying the subarray pattern F _e (θ) and the array factor S(θ), namely

F(θ)＝F _e (θ)S(θ)

The array factor of an equally spaced linear array antenna composed of N subarrays with a spacing of d and a beam pointing to θ ₀ is

$\mathrm{<span\; class="notranslate">\; S</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; e</span>}}^{\mathrm{<span\; class="notranslate">\; jkd</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; sin</span>}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; e</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; kd</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; sin</span>}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; e</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; kd</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; sin</span>}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>}$

$<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; Nkd</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; sin</span>}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; ]</span>}{\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; kd</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; sin</span>}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; ]</span>}$

The cross-track dimension of the sub-array is 0.25m. If the wavelength of the transmitted signal is 0.02m, the sub-array of 0.25m can be composed of 25 omni-directional antenna elements (i.e. F _e (θ)=1) spaced at a half-wavelength , and its orientation diagram is shown in Figure 7a. Since each sub-array transmits and receives more, 39 equivalent phase centers will be formed in the cross-track direction, as shown in FIG. 3 . The normalized array factor of a sparse array composed of equivalent phase centers is shown in Figure 7b, and its pattern is obtained by multiplying the subarray pattern and the array factor, as shown in Figure 7c.

Since the array is sparsely distributed, its peak side lobe ratio and integral side lobe ratio are relatively high. Through the DBF pattern of the array formed by the 8 sub-arrays in the distribution main area (as shown in FIG. 7d ), the result of weighting the above pattern is shown in FIG. 7e. The peak sidelobe ratio and integral sidelobe ratio of the sparse array antenna can be improved through pattern weighting.

The pattern of the array antenna corresponds to the imaging result, and the method of weighting the pattern can be introduced in the imaging algorithm to improve the imaging quality.

Then, the sparse array antenna sub-array adopts a two-dimensional phase-scanning active array, and in the looking-down working mode, adopts a scanning mode combining ScanSAR mode and SweepSAR mode to expand the observation imaging width.

The ScanSAR mode and the SweepSAR mode are two commonly used beam scanning methods. The ScanSAR mode expands the observation width at the cost of reducing the along-track resolution, and the SweepSAR mode expands the observation width at the cost of increasing the system pulse repetition frequency. Width. The scanning mode combined with ScanSAR mode and SweepSAR mode can take into account the pulse repetition frequency and along-track resolution of the system.

Fig. 8 shows a specific embodiment of a scanning method combining ScanSAR mode and SweepSAR mode, using 3 SweepSAR mode wave standing positions to form a ScanSAR mode sub-strip, and the total observation width is composed of 5 such ScanSAR mode sub-strips band composition. Assuming that when the beam is not scanning, the pulse repetition frequency of the system is 4kHz, and the along-track resolution is 0.2m. In the scanning mode, the pulse repetition frequency of the system will be increased to 12kHz, and the along-track resolution will be reduced to 1m. The observation width can be enlarged by 15 times.

Then, when the airborne platform is running at high altitude, a sparse and heavy-passing flight mode is adopted to obtain an equivalent array antenna with a larger length in the cross-track direction to improve the resolution of the cross-track direction.

The expression of the cross-track resolution of the airborne sparse array downward-looking 3D imaging system is

${\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&lambda;R</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; L</span>}}$

It can be seen that the cross-track resolution is related to the transmitted signal wavelength λ, the slant distance R and the effective length L of the cross-track array.

For a given transmission signal, when the flight altitude of the carrier aircraft is increased, if we want to improve the cross-track resolution, we can only increase the length of the cross-track array, and the length of the cross-track array is limited by the wingspan of the carrier aircraft. increase arbitrarily. By adopting the method of re-passing, a longer array antenna can be obtained in the cross-track direction, so as to improve the resolution of the cross-track direction.

The schematic diagram of the airborne sparse array down-looking 3D imaging radar overflight is shown in Figure 9.

In order to reduce the number of re-passing flights, a sparse re-passing scheme is considered. The Barker code is a random signal with equal sidelobe characteristics, which can be used as a sampling criterion for sparse re-passing.

Figure 10 shows the autocorrelation function of the 13-bit Barker code sequence ([1 1 1 1 0 0 1 1 0 1 0 1]), it can be seen that the sidelobe values are all equal. Figure 11a shows the pattern of the array obtained when the 13-bit Barker code is used as the sampling criterion for random sparse heavy-passing flight, and the DBF pattern of the array composed of 8 sub-arrays in the main distribution area (as shown in Figure 7d ), the result of weighting the above direction diagram is shown in Fig. 11b.

When the flight altitude of the carrier aircraft is low, the short-length Barker code can be used as the sampling criterion to realize random sparse sampling of heavy-passing flights, and a cross-track array antenna that meets the conditions can be obtained by using a small number of heavy-passing flights.

Finally, according to the echo signal obtained in the above steps, the three-dimensional wavenumber domain algorithm is used, and the measured value of the relative spatial position of the equivalent phase center by the distributed POS and the method of weighting the pattern can be implemented. 3D imaging of observed scenes.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention, and are not intended to limit the present invention. Within the spirit and principles of the present invention, any modifications, equivalent replacements, improvements, etc., shall be included in the protection scope of the present invention.

Claims (5)

1. look a three-dimensional imaging radar system under airborne thinned array antenna, comprise carrier aircraft platform, thinned array antenna system and distributed POS, it is characterized in that:

Described carrier aircraft platform is that array antenna can be laid in the middle part of this aircraft and both sides for carrying described thinned array antenna system and the aircraft of distributed POS;

Described thinned array antenna system is made up of multiple submatrix, and described multiple submatrix is bidimensional and sweeps Active Phased Array mutually;

Described multiple submatrixs are distributed in three regions of described carrier aircraft platform, described three areal distribution are in the middle part of described carrier aircraft platform and both sides, described three regions are a main areas and two sub areas, described main areas is positioned at the middle part of described carrier aircraft platform, between sub area be positioned at the both sides of described carrier aircraft platform, and in described main areas, an array antenna of being arranged by multiple submatrix is installed, install 1 or 2 submatrixs at described sub area, described trizonal array antenna forms described thinned array antenna system;

Described carrier aircraft platform is an aircraft, consider the actual position should laying antenna of described carrier aircraft platform, described main areas is laid in the ventral of described aircraft, gondola below two wings described two sub areas being laid in respectively described aircraft, the array antenna of described main areas and described sub area on the same line.

2. look three-dimensional imaging radar system under airborne thinned array antenna as claimed in claim 1, it is characterized in that, described distributed POS is distributed in described three regions, for the heterogeneous centrical accurate measurement to described thinned array antenna system.

3. look three-D imaging method under an airborne thinned array antenna, described thinned array antenna in cross rail to comprising the array antenna of being arranged by multiple submatrix being positioned at a main areas, with each array antenna be made up of 1 or 2 submatrixs being positioned at two sub areas, distributed POS is had in each submatrix position distribution, it is characterized in that, described method comprises the steps:

Described distributed POS is utilized to measure the heterogeneous centrical relative tertiary location of described thinned array antenna;

Using the DBF directional diagram of the array antenna of described main areas as weighting function, the thinned array directional diagram described each submatrix MIMO (Multiple-Input Multiple-Out-put) being obtained to displaced phase center formation is weighted process, improves its peak sidelobe ratio and integration secondary lobe ratio;

The submatrix of described thinned array antenna adopts bidimensional to sweep Active Phased Array mutually, under looking mode of operation just down, adopts the scan mode that ScanSAR pattern and SweepSAR pattern combine, and expands observation imaging fabric width;

Adopt the flying method heavily crossing boat, in cross rail to obtaining the equivalent array antenna longer compared to this thinned array antenna length, to improve cross rail to resolution;

Adopt above-mentioned steps to process the observation scene echoed signal obtained during described airborne thinned array antenna MIMO (Multiple-Input Multiple-Out-put), realize the three-dimensional imaging to observation scene.

4. look three-D imaging method under airborne thinned array antenna as claimed in claim 3, it is characterized in that, utilize Barker code as the sampling criterion heavily crossing boat.

5. look three-D imaging method under airborne thinned array antenna as claimed in claim 3, it is characterized in that, in the step of carrying out three-dimensional imaging, adopt three-dimensional Wavenumber Domain Algorithms, and introduce described distributed POS to the measured value of displaced phase center relative tertiary location and described directional diagram weighting.