SAR Sub-pulse Phase Coding for Interference Suppression
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Solution Overview
Problem
Existing synthetic aperture radar systems face interference issues with sub-pulses due to digital beamforming, which affects the quality of radar images obtained from the earth's surface.
Innovation Solution
The method involves phase coding and decoding of sub-pulses, where each sub-pulse is assigned a unique coding phase and decoding phase, ensuring that the residual phase remains constant for comparable sub-pulses while varying between sub-pulses to suppress interference, allowing for efficient suppression of interference without requiring digital beam shaping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If digital beamforming is used to separate sub-pulses, then sub-pulses can be received from different directions, but interference from other sub-pulses still remains
Solution Approach 1:
The patent applies parameter changes by modifying the phase characteristics of sub-pulses. Each sub-pulse is assigned a unique residual phase value that varies across pulse repetition intervals, allowing the receiving system to distinguish and separate sub-pulses based on their phase parameters while suppressing interference from other sub-pulses
Solution Approach 2:
The patent segments the radar signaling into multiple sub-pulses with distinct phase characteristics. By dividing the transmitted signal into separate sub-pulses, each with identifiable phase markers, the system can process and separate them individually at the receiver, reducing mutual interference
2Adaptability or versatility
If multiple sub-pulses are transmitted in successive pulse repetition intervals, then broad swath or interferometric imaging is enabled, but interference between sub-pulses degrades image quality
Solution Approach 1:
The patent modifies the phase parameter of each sub-pulse to include a unique residual phase that changes across pulse repetition intervals. This parameter differentiation allows the system to maintain multiple imaging modes (broad swath, interferometric) while suppressing interference through phase-based discrimination
Solution Approach 2:
The system employs feedback mechanisms where the transmitted sub-pulse phase information is known and used at the receiver to correlate and separate incoming echoes. The receiver uses the predetermined phase relationships to identify and eliminate interference from other sub-pulses, ensuring reliable image quality
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively reduces interference between sub-pulses, improving the signal-to-interference ratio and enabling clearer radar images, particularly in broad swath and interferometric modes, with interference suppression values reaching up to -20 dB, enhancing the overall performance of synthetic aperture radar systems.
Implementation Method 1
detecting radar pulses reflected on the earth's surface, which are emitted by a radar device
Implementation Method 2
each sub-pulse is coded before it is sent out via the transmission device by being provided with a coding phase. Similarly, each received encoded sub-pulse is decoded by providing the sub-pulse with a decoding phase
Data Source
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AI summary
The invention relates to a synthetic aperture radar method for remote sensing of the earth's surface via a radar device (1) which moves across the earth's surface in an azimuth direction (x), wherein the radar device (1) comprises a transmission device (2, 3) for emitting radar pulses and a receiving device (4) for receiving radar echoes of the radar pulses in a range direction (y) perpendicular to the azimuth direction (x), wherein in consecutive pulse repetition intervals (PRI) several sub-pulses are respectively emitted by the transmission device (2, 3) and received by the receiving device (4). The sub-pulses (SP1, SP2) in a pulse repetition interval (PRI) are thereby distinguished using different designations, wherein identical sub-pulses (SP1, SP2) in different pulse repetition intervals have the same designation. In the method according to the invention, a respective sub-pulse (SP1, SP2) is encoded prior to emission, in that it is provided with an encoding phase (ϕen) and a respectively received encoded sub-pulse (SP1, SP2) is decoded, in that it is provided with a decoding phase (ϕde), wherein the addition of the encoding phase (ϕen) and decoding phase (ϕde) for each sub-pulse (SP1, SP2) remains constant in the respective pulse repetition interval (PRI) and across the pulse repetition interval (PRI), and wherein for each pair of a sub-pulse (SP1, SP2) with a designation and a sub-pulse (SP1, SP2) with another designation, the addition of the decoding phase (ϕde) for the sub-pulse (SP1, SP2) with the designation and the encoding phase (ϕen)) for the sub-pulse (SP1, SP2) with the other designation varies from one pulse repetition interval (PRI) to the next.