Airborne SAR preprocessing method based on Doppler center estimation

Abstract

The invention relates to an airborne SAR preprocessing method, in particular to an airborne SAR preprocessing method based on Doppler center estimation. The invention aims to solve the problems of SAR image two-dimensional defocusing and low processing efficiency in the existing airborne SAR imaging method. The method comprises the following steps: 1, obtaining airborne SAR echo data after distance compression; 2, initializing the number of sub-data blocks; 3, if k is less than or equal to K, executing step 4; otherwise, executing the step 10; 4, acquiring a sub-data block; 5, solving a conjugate multiplication matrix; 6, obtaining a correlation function; 7, obtaining an autocorrelation function; 8, solving a Doppler frequency estimation value of the echo; ninthly, k is made to be equal to k + 1, and the third step is executed; 10, solving a Doppler frequency theoretical value caused by the motion of the SAR platform; 11, obtaining a Doppler frequency estimation value caused by ISAR platform motion; 12, obtaining a fitting curve; and 13, obtaining an optimal imaging data segment. The method is applied to the field of airborne SAR preprocessing.

Description

technical field

[0001] The invention relates to an airborne SAR preprocessing method. Background technique

[0002] Airborne synthetic aperture radar (synthetic aperture radar, SAR) plays an important role in the field of sea area monitoring for ship target imaging on the sea surface. The SAR imaging scene is usually radar moving and the target does not move. During the imaging of the ship target on the sea, the ship target often has translation and swing motions, which makes the two-dimensional defocus of the ship image in the radar image and reduces the image quality. , affecting subsequent target classification and recognition accuracy.

[0003] The currently proposed airborne SAR imaging algorithm or combined inverse synthetic aperture radar (ISAR) processing technology can improve the image quality to a certain extent, but these algorithms only process all echo data during the observation period of the ship, so It has the following defects: (1) The echo data includes ...

Examples

specific Embodiment approach 1

[0039] Specific implementation mode one: combine figure 1 Describe this embodiment, the specific process of the airborne SAR preprocessing method based on Doppler centroid estimation in this embodiment is:

[0040] Step 1. Obtain the airborne SAR echo data, and perform range compression on the obtained airborne SAR echo data by using the range-dimension matched filter in the range-Doppler (range Doppler, RD) algorithm, and obtain the airborne SAR echo data after the range compression. SAR echo data, record the airborne SAR echo data after distance compression as s rb (m,n);

[0041] Among them, m is the pulse sequence number of the echo, n is the fast time sequence number; m=1,2,...,N a , N a is the number of pulses, n=1,2,…,N r , N r is the number of fast time sampling points;

[0042] Step 2, initialize the sub-data block sequence number k=1, set the sub-data block pulse number N a0 , 1a0 a ; The number of sub-blocks is

[0043] In the formula, is the rounding do...

specific Embodiment approach 2

[0059] Specific embodiment two: the difference between this embodiment and specific embodiment one is that the sub-data block in the step four The expression is:

[0060] subblock

[0061] Other steps and parameters are the same as those in Embodiment 1.

specific Embodiment approach 3

[0062] Specific embodiment three: the difference between this embodiment and specific embodiment one or two is that the conjugate multiplication matrix s(m 1 , n) is expressed as:

[0063]

[0064] In the formula, m 1 is the conjugate multiplication matrix s(m 1 ,t r ) pulse number, m 1 =1,2,...,N a0 -1,[·] H is a conjugate function.

[0065] Other steps and parameters are the same as those in Embodiment 1 or Embodiment 2.

technical field

[0001] The invention relates to an airborne SAR preprocessing method. Background technique

[0002] Airborne synthetic aperture radar (synthetic aperture radar, SAR) plays an important role in the field of sea area monitoring for ship target imaging on the sea surface. The SAR imaging scene is usually radar moving and the target does not move. During the imaging of the ship target on the sea, the ship target often has translation and swing motions, which makes the two-dimensional defocus of the ship image in the radar image and reduces the image quality. , affecting subsequent target classification and recognition accuracy.

[0003] The currently proposed airborne SAR imaging algorithm or combined inverse synthetic aperture radar (ISAR) processing technology can improve the image quality to a certain extent, but these algorithms only process all echo data during the observation period of the ship, so It has the following defects: (1) The echo data includes ...

Examples

specific Embodiment approach 1

[0039] Specific implementation mode one: combine figure 1 Describe this embodiment, the specific process of the airborne SAR preprocessing method based on Doppler centroid estimation in this embodiment is:

[0040] Step 1. Obtain the airborne SAR echo data, and perform range compression on the obtained airborne SAR echo data by using the range-dimension matched filter in the range-Doppler (range Doppler, RD) algorithm, and obtain the airborne SAR echo data after the range compression. SAR echo data, record the airborne SAR echo data after distance compression as s rb (m,n);

[0041] Among them, m is the pulse sequence number of the echo, n is the fast time sequence number; m=1,2,...,N a , N a is the number of pulses, n=1,2,…,N r , N r is the number of fast time sampling points;

[0042] Step 2, initialize the sub-data block sequence number k=1, set the sub-data block pulse number N a0 , 1a0 a ; The number of sub-blocks is

[0043] In the formula, is the rounding do...

specific Embodiment approach 2

[0059] Specific embodiment two: the difference between this embodiment and specific embodiment one is that the sub-data block in the step four The expression is:

[0060] subblock

[0061] Other steps and parameters are the same as those in Embodiment 1.

specific Embodiment approach 3

[0062] Specific embodiment three: the difference between this embodiment and specific embodiment one or two is that the conjugate multiplication matrix s(m 1 , n) is expressed as:

[0063]

[0064] In the formula, m 1 is the conjugate multiplication matrix s(m 1 ,t r ) pulse number, m 1 =1,2,...,N a0 -1,[·] H is a conjugate function.

[0065] Other steps and parameters are the same as those in Embodiment 1 or Embodiment 2.

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