A step-by-step adaptive remote sensing image radio frequency interference source detection threshold setting method

Abstract

A step-by-step adaptive remote sensing image radio frequency interference source detection threshold setting method adopts an adaptive manner to adjust the detection threshold, so that it can adapt to the changes of different scenes, and can effectively detect and suppress the radio frequency interference source in the remote sensing image. First, the original scene brightness temperature image of the observed earth scene is obtained. Then, according to the larger value of the preset proportion and the preset value of the maximum value of the current scene brightness temperature, the detection threshold is determined. The brightness temperature threshold is used to detect the radio frequency interference source (RFI), and then the DFT interpolation technology is used to accurately position the position of the RFI, and the position of the maximum value is taken as the accurate position of the RFI. Next, the intensity of the RFI is estimated, and the visibility of the RFI contribution is constructed, which is subtracted from the current visibility. Then, the above threshold setting, detection, positioning and suppression steps are repeated until no RFI can be detected in the scene.

Description

Technical Field

[0001] This invention relates to a method for setting a threshold for radio frequency interference source detection in stepwise adaptive remote sensing images, belonging to the field of satellite microwave ocean remote sensing technology. Background Technology

[0002] Radio frequency interference (RFI) refers to unintentionally emitted electromagnetic energy in wireless communication systems. RFI can introduce additional noise and interference signals, compromising the accuracy and reliability of the original data. Therefore, handling RFI is crucial for improving data quality.

[0003] In existing technologies, RFI-based processing methods mainly use a constant brightness temperature threshold (350K, the brightness temperature limit of a natural radiation blackbody) to detect and process RFI. However, when using a fixed threshold to detect RFI, some detected RFIs may be generated by the superposition of sidelobes of stronger RFIs, leading to false detections. Therefore, a new RFI processing method is needed that uses an adaptively adjusted detection threshold to process the RFI in the scene step by step, thereby reducing false detections. Summary of the Invention

[0004] The technical problem solved by this invention is that existing RFI-based processing methods are prone to false detections. This invention proposes a step-by-step adaptive threshold setting method for radio frequency interference source detection in remote sensing images.

[0005] The present invention solves the above-mentioned technical problem through the following technical solution:

[0006] A method for setting a threshold for radio frequency interference source detection in stepwise adaptive remote sensing images, comprising:

[0007] Raw measurements of microwave radiation signals emitted from the Earth's surface are performed to obtain raw scene brightness temperature images of the observed Earth scene;

[0008] Determine the brightness temperature detection threshold based on the original scene brightness temperature image;

[0009] The brightness temperature of the RFI source is detected using a determined brightness temperature detection threshold. Based on the detection results, the RFI source is located by DFT interpolation, and the precise location of the RFI source is obtained.

[0010] The intensity of the RFI source is estimated based on the precise location of the RFI source, the visibility contribution of the RFI source is calculated, and the visibility after RFI suppression is calculated based on the visibility contribution of the RFI source.

[0011] Repeatedly perform RFI suppression on the brightness temperature image after RFI suppression until the brightness temperature data at each location in the selected scene brightness temperature image does not exceed the brightness temperature detection threshold.

[0012] The method for constructing the brightness temperature detection threshold is as follows:

[0013] If the preset proportion of the maximum brightness temperature value of the original scene brightness temperature image acquired in the current scene is less than the preset value, then the preset value is used as the detection threshold; otherwise, the preset proportion of the maximum brightness temperature value of the current scene is used as the detection threshold.

[0014] The method for determining the precise location of the RFI source is as follows:

[0015] The original scene brightness temperature image is processed into a grid, and brightness temperature is detected at each grid point. If the brightness temperature of the selected grid point is greater than the brightness temperature detection threshold, the selected grid point is taken as the RFI source location; if the brightness temperature of the selected grid point is less than the brightness temperature detection threshold, the selected grid point does not have an RFI source.

[0016] Centered on the RFI source location, a rectangular region is constructed with twice the distance between horizontally adjacent and vertically adjacent grid points in the current scene's field of view (Fov) as its length and width, respectively. A preset number of sampling points are then used to sample the region, and the resulting sampling points are used to reconstruct the brightness temperature inversion field of view.

[0017] For all sampling points within the current reconstructed field of view, brightness temperature inversion is performed using the visibility of the original scene brightness temperature image. Based on the obtained inverted brightness temperature, the sampling point where the maximum value of the inverted brightness temperature is located is found in the reconstructed brightness temperature inversion field of view, which is used as the precise location of the RFI source.

[0018] The method for determining the visibility after RFI suppression is as follows:

[0019] The intensity of the RFI source is determined by the average brightness temperature of the scene around each RFI source location.

[0020] Calculate the visibility of RFI source contributions;

[0021] The visibility after RFI suppression is calculated using the original visibility of the original scene brightness temperature image.

[0022] The method for calculating the RFI source strength is as follows:

[0023]

[0024] In the formula, I RFI It is to estimate the intensity of RFI, (ξ) RFI ,η RFI T represents the precise location estimated by the RFI obtained from the localization. SceneAverage Average brightness temperature for representative scenes.

[0025] The average brightness temperature T of the scene SceneAverage By analyzing (ξ) RFI ,η RFIThe average brightness temperature of each grid point within the surrounding square area was calculated, with 11×11 grid points selected for the square area.

[0026] The method for calculating the visibility of the RFI source contribution is as follows:

[0027] V RFI =I RFI ·V 1K (ξ RFI ,η RFI )

[0028] In the formula, V 1K (ξ RFI ,η RFI ) is the position (ξ) RFI ,η RFI The visibility generated by the 1K point source at ().

[0029] The scene visibility after RFI suppression is obtained by subtracting the visibility contributed by the RFI source from the original visibility of the original scene brightness temperature image. The calculation method is as follows:

[0030] V mitigated (ξ,η)=V raw (ξ,η)-I RFI ·V 1K (ξ RFI ,η RFI )

[0031] In the formula, V mitigated This is the visibility after RFI suppression.

[0032] The preset ratio and preset value of the maximum brightness temperature of the original scene brightness temperature image are determined based on the selected location of the observed Earth scene.

[0033] Repeatedly perform RFI suppression on the brightness temperature image after RFI suppression is completed until the brightness temperature data of each grid point in the selected scene brightness temperature image does not exceed the brightness temperature detection threshold. At this point, RFI suppression is complete and no RFI source can be detected in the current scene brightness temperature image.

[0034] The advantages of this invention compared to the prior art are:

[0035] This invention provides a step-by-step adaptive threshold setting method for radio frequency interference (RFI) detection in remote sensing images. By using adaptive threshold detection (RFI), the threshold can be automatically adjusted according to the actual environment and data characteristics to adapt to different interference levels and signal strength variations. This makes it more adaptable and flexible, capable of handling complex interference situations. Furthermore, adaptive threshold detection (RFI) can more accurately identify and locate interference signals, thereby reducing false alarms and false negatives and obtaining more precise RFI detection results. Attached Figure Description

[0036] Figure 1 A flowchart of a step-by-step radio frequency interference processing method provided for the invention;

[0037] Figure 2 The BT snapshot image reconstructed using the standard HFFT (hexagonal star fast Fourier transform) is provided for the invention.

[0038] Figure 3 The original brightness temperature scene image provided for the invention, incorporating RFI simulation;

[0039] Figure 4 The original brightness temperature scene image provided for the invention, incorporating RFI simulation;

[0040] Figure 5 Brightness temperature scene image after radio frequency interference processing provided for the invention;

[0041] Figure 6 The brightness temperature residual between the scene after radio frequency interference processing and the original scene provided for the invention; Detailed Implementation

[0042] A step-by-step adaptive remote sensing image radio frequency interference (RFI) detection threshold setting method first acquires the original scene brightness temperature image of the observed Earth scene. Then, a detection threshold is determined based on a preset proportion of the current scene brightness temperature maximum value and the larger of the preset values. The brightness temperature threshold is used to detect radio frequency interference (RFI), and then DFT interpolation technology is used to accurately locate the RFI, taking the location of the maximum value as the accurate location of the RFI. Next, the intensity of the RFI is estimated, and the visibility contributed by the RFI is constructed and subtracted from the current visibility. Then, the above threshold setting, detection, localization, and suppression steps are repeated until the RFI is no longer detectable in the scene. The specific process is as follows:

[0043] Raw measurements of microwave radiation signals emitted from the Earth's surface are performed to obtain raw scene brightness temperature images of the observed Earth scene;

[0044] Determine the brightness temperature detection threshold based on the original scene brightness temperature image;

[0045] The brightness temperature of the RFI source is detected using a determined brightness temperature detection threshold. Based on the detection results, the RFI source is located by DFT interpolation, and the precise location of the RFI source is obtained.

[0046] The intensity of the RFI source is estimated based on the precise location of the RFI source, the visibility contribution of the RFI source is calculated, and the visibility after RFI suppression is calculated based on the visibility contribution of the RFI source.

[0047] Repeatedly perform RFI suppression on the brightness temperature image after RFI suppression until the brightness temperature data at each location in the selected scene brightness temperature image does not exceed the brightness temperature detection threshold.

[0048] The method for constructing the brightness temperature detection threshold is as follows:

[0049] If the preset proportion of the maximum brightness temperature value of the original scene brightness temperature image acquired in the current scene is less than the preset value, then the preset value is used as the detection threshold; otherwise, the preset proportion of the maximum brightness temperature value of the current scene is used as the detection threshold.

[0050] The method for determining the precise location of the RFI source is as follows:

[0051] The original scene brightness temperature image is processed into a grid, and brightness temperature is detected at each grid point. If the brightness temperature of the selected grid point is greater than the brightness temperature detection threshold, the selected grid point is taken as the RFI source location; if the brightness temperature of the selected grid point is less than the brightness temperature detection threshold, the selected grid point does not have an RFI source.

[0052] Centered on the RFI source location, a rectangular region is constructed with twice the distance between horizontally adjacent and vertically adjacent grid points in the current scene's field of view (Fov) as its length and width, respectively. A preset number of sampling points are then used to sample the region, and the resulting sampling points are used to reconstruct the brightness temperature inversion field of view.

[0053] For all sampling points within the current reconstructed field of view, brightness temperature inversion is performed using the visibility of the original scene brightness temperature image. Based on the obtained inverted brightness temperature, the sampling point where the maximum value of the inverted brightness temperature is located is found in the reconstructed brightness temperature inversion field of view, which is used as the precise location of the RFI source.

[0054] The method for determining the visibility after RFI suppression is as follows:

[0055] The intensity of the RFI source is determined by the average brightness temperature of the scene around each RFI source location.

[0056] Calculate the visibility of RFI source contributions;

[0057] The visibility after RFI suppression is calculated using the original visibility of the original scene brightness temperature image.

[0058] The method for calculating RFI source strength is as follows:

[0059]

[0060] In the formula, I RFI It is to estimate the intensity of RFI, (ξ) RFI ,η RFI T represents the precise location estimated by the RFI obtained from the localization. SceneAverage Average brightness temperature of representative scenes;

[0061] Scene average brightness temperature TSceneAverage By analyzing (ξ) RFI ,η RFI The average brightness temperature of each grid point within the surrounding square area was calculated, with 11×11 grid points selected for the square area.

[0062] The method for calculating the visibility of RFI source contributions is as follows:

[0063] V RFI =I RFI ·V 1K (ξ RFI ,η RFI )

[0064] In the formula, V 1K (ξ RFI ,η RFI ) is the position (ξ) RFI ,η RFI The visibility generated by the 1K point source at ().

[0065] The scene visibility after RFI suppression is obtained by subtracting the visibility contributed by the RFI source from the original visibility of the original scene brightness temperature image. The calculation method is as follows:

[0066] V mitigated (ξ,η)=V raw (ξ,η)-I RFI ·V 1K (ξ RFI ,η RFI )

[0067] In the formula, V mitigated This is the visibility after RFI suppression.

[0068] The preset ratio and preset value of the maximum brightness temperature of the original scene brightness temperature image are determined based on the selected location of the observed Earth scene.

[0069] Repeatedly perform RFI suppression on the brightness temperature image after RFI suppression is completed until the brightness temperature data of each grid point in the selected scene brightness temperature image does not exceed the brightness temperature detection threshold. At this point, RFI suppression is complete and no RFI source can be detected in the current scene brightness temperature image.

[0070] The following description, in conjunction with the accompanying drawings and preferred embodiments, provides further details:

[0071] In the current embodiment, such as Figure 1 As shown, a step-by-step adaptive remote sensing image radio frequency interference source detection threshold setting method specifically includes the following steps:

[0072] S1. Obtain the scene brightness temperature image from visibility inversion;

[0073] S2. Set the brightness temperature threshold to the greater of 70% of the current scene's maximum brightness temperature and 350K;

[0074] S3. RFI detection and localization based on brightness temperature threshold.

[0075] S4. Perform RFI suppression based on the RFI location obtained from the localization.

[0076] S5. Invert the suppressed visibility into brightness temperature as the brightness temperature image of the current scene, and repeat S2 to S5 until no RFI can be detected in the current scene;

[0077] The following is an example, combined with Figures 2-6 This invention describes a method for locating radio frequency interference by combining brightness temperature images and subspace.

[0078] Example: Testing based on simulation data

[0079] Simulations were performed using parameters from the SMOS (Soil Moisture and Ocean Salinity) satellite radiometer system. Figure 2 The image shown is a reconstructed BT image of a scene on Earth. Figure 2 Adding two RFIs yields the original brightness temperature image obtained from the simulation, as shown below. Figure 3 , Figure 4 As shown. The scene brightness and temperature image obtained after processing using this invention is as follows. Figure 5 As shown, the brightness temperature residual image is obtained by subtracting the processed image from the original brightness temperature image. Figure 6 As shown.

[0080] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

[0081] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A method for setting a threshold for radio frequency interference source detection in stepwise adaptive remote sensing images, characterized in that... include: Raw measurements of microwave radiation signals emitted from the Earth's surface are performed to obtain raw scene brightness temperature images of the observed Earth scene; Determine the brightness temperature detection threshold based on the original scene brightness temperature image; The brightness temperature of the RFI source is detected using a determined brightness temperature detection threshold. Based on the detection results, the RFI source is located by DFT interpolation, and the precise location of the RFI source is obtained. The intensity of the RFI source is estimated based on the precise location of the RFI source, the visibility contribution of the RFI source is calculated, and the visibility after RFI suppression is calculated based on the visibility contribution of the RFI source. Repeatedly perform RFI suppression on the brightness temperature image after RFI suppression until the brightness temperature data at each point in the selected scene brightness temperature image does not exceed the brightness temperature detection threshold. The method for constructing the brightness temperature detection threshold is as follows: If the preset proportion of the maximum brightness temperature value of the original scene brightness temperature image acquired in the current scene is less than the preset value, then the preset value is used as the detection threshold; otherwise, the preset proportion of the maximum brightness temperature value of the current scene is used as the detection threshold. The method for determining the precise location of the RFI source is as follows: The original scene brightness temperature image is processed into a grid, and the brightness temperature of each grid point is detected. If the brightness temperature of the selected grid point is greater than the brightness temperature detection threshold, the selected grid point is taken as the RFI source location. If the brightness temperature of the selected grid point is less than the brightness temperature detection threshold, then the selected grid point does not contain an RFI source. Centered on the RFI source location, a rectangular region is constructed with twice the distance between horizontally adjacent and vertically adjacent grid points in the current scene's field of view (Fov) as its length and width, respectively. A preset number of sampling points are then used to sample the region, and the resulting sampling points are used to reconstruct the brightness temperature inversion field of view. For all sampling points within the current reconstructed field of view, brightness temperature is inverted using the visibility of the original scene brightness temperature image. Based on the obtained inverted brightness temperature, the sampling point where the maximum value of the inverted brightness temperature is located is found in the reconstructed brightness temperature inversion field of view, which is used as the precise location of the RFI source. The method for determining the visibility after RFI suppression is as follows: The intensity of the RFI source is determined by the average brightness temperature of the scene around each RFI source location. Calculate the visibility of RFI source contributions; Calculate the visibility after RFI suppression using the original visibility of the original scene brightness temperature image; The method for calculating the RFI source strength is as follows: In the formula, It is to estimate the intensity of RFI. This indicates the precise location estimated by the RFI obtained from the localization process. Average brightness temperature for representative scenes.

2. The method for setting a threshold for radio frequency interference source detection in a step-by-step adaptive remote sensing image according to claim 1, characterized in that: The average brightness temperature of the scene Through the The average brightness temperature of each grid point within the surrounding square area was calculated, with 11×11 grid points selected for the square area.

3. The method for setting a threshold for radio frequency interference source detection in a step-by-step adaptive remote sensing image according to claim 2, characterized in that: The method for calculating the visibility of the RFI source contribution is as follows: In the formula, For position The visibility generated by the 1K point source at that location.

4. The method for setting a threshold for radio frequency interference source detection in a step-by-step adaptive remote sensing image according to claim 3, characterized in that: The scene visibility after RFI suppression is obtained by subtracting the visibility contributed by the RFI source from the original visibility of the original scene brightness temperature image. The calculation method is as follows: In the formula, This is the visibility after RFI suppression.

5. The method for setting a threshold for radio frequency interference source detection in a step-by-step adaptive remote sensing image according to claim 4, characterized in that: The preset ratio and preset value of the maximum brightness temperature of the original scene brightness temperature image are determined based on the selected location of the observed Earth scene.

6. The method for setting a threshold for radio frequency interference source detection in a step-by-step adaptive remote sensing image according to claim 5, characterized in that: Repeatedly perform RFI suppression on the brightness temperature image after RFI suppression is completed until the brightness temperature data of each grid point in the selected scene brightness temperature image does not exceed the brightness temperature detection threshold. At this point, RFI suppression is complete and no RFI source can be detected in the current scene brightness temperature image.

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