Quad-pol SAR Range Ambiguity Suppression via Orthogonal Nonlinear FM
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Solution Overview
Problem
The quad-pol SAR system faces range ambiguity issues due to interference from co-polarimetric signals, which degrades the quality of radar images by mixing external echo energy with intended echo energy within the swath region.
Innovation Solution
The method involves determining a pulse timing relationship and using orthogonal nonlinear frequency modulation signals to modulate transmission signals, which are then transmitted and processed to generate images based on a polarization scattering matrix, effectively separating and suppressing range ambiguity energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If a quad-pol SAR system is used to detect abundant scattering information, then the detection capability is improved, but the cross-pol channel is interfered by co-pol range ambiguity signals which degrades image quality
Solution Approach 1:
The patent segments the transmitted signal into orthogonal nonlinear frequency modulation signals with distinct frequency characteristics. By assigning different frequency modulation patterns to different polarization channels, the system can separate and identify signals from different ranges, effectively segmenting the range ambiguity problem and allowing the cross-pol channel to reject co-pol ambiguity interference while preserving scattering information detection capability.
Solution Approach 2:
The patent changes the frequency modulation parameters of the transmitted signals using orthogonal nonlinear frequency modulation. By varying the frequency characteristics of signals transmitted in different polarization channels, the system creates distinguishable signal signatures that enable the receiver to differentiate between intended echoes and range ambiguity signals, thus resolving the interference problem while maintaining enhanced detection capability.
2Area of stationary object
If the antenna beam width is increased to cover the swath, then the coverage area is improved, but echo energy from outside the swath region mixes with the intended echo energy, reducing image quality
Solution Approach 1:
The patent employs periodic pulse transmission with orthogonal nonlinear frequency modulation patterns. By using periodic signaling with distinct frequency characteristics for different channels, the system can identify and separate echoes from different range intervals, allowing the antenna to maintain wide beam coverage while the signal processing selectively extracts only the desired swath region echoes, preventing contamination from out-of-swath energy.
Solution Approach 2:
The patent changes the frequency modulation parameters of transmitted pulses to create orthogonal signals with unique spectral signatures. This allows the receiver to distinguish between echoes from different spatial locations based on their frequency characteristics, enabling the system to maintain wide beam coverage for adequate swath area while selectively processing only the intended echo energy and rejecting range ambiguity energy from outside the swath.
Data Source
AI summary
A method and device for suppressing range ambiguity and a computer readable storage medium are provided. The method includes: determining a pulse timing relationship of a transmission signal; determining orthogonal nonlinear frequency modulation signals; modulating the transmission signal by using the orthogonal nonlinear frequency modulation signals; transmitting the modulated transmission signal according to the pulse timing relationship, and determining echo data of the modulated transmission signal; and generating an image according to a polarization scattering matrix for the echo data of the modulated transmission signal.