Synthetic Aperture Radiometer Visibility Function Calculation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Interferometric aperture synthesis radiometers face challenges in effectively detecting and suppressing interfering signals, which degrade measurement precision and lead to significant artifacts in data, especially due to the low power ratio of interfering signals to noise.
Innovation Solution
A method involving digitization, filtering, and cross-correlation matrix calculation for each reception chain, followed by detection and elimination of invalid cross-correlation matrices, allowing for improved interference detection and removal before image synthesis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If interferometric aperture synthesis radiometers are used to measure natural thermal radiation, then measurement capability for low-power signals is improved, but measurement precision deteriorates due to interfering signals from transmitters
Solution Approach 1:
The patent segments the signal processing into multiple reception chains, each processing signals from different antenna pairs. By dividing the overall measurement into separate correlation calculations for different antenna combinations, the system can identify and exclude contaminated measurements from individual chains while maintaining overall measurement capability. This segmentation allows localized interference rejection without sacrificing global measurement precision.
Solution Approach 2:
The patent introduces an intermediary processing stage that calculates correlation matrices between signals from different antenna pairs before final image reconstruction. This intermediate correlation calculation serves as a mediator that enables detection of interfering signals through statistical analysis of signal coherence patterns, allowing the system to identify and exclude contaminated data while preserving valid measurements.
2Difficulty of detecting and measuring
If signal digitization and statistical analysis are performed to detect interfering signals, then interference detection capability is improved, but processing complexity increases
Solution Approach 1:
The patent performs preliminary digitization of received signals and pre-calculates correlation matrices between antenna pairs before final image reconstruction. By conducting these statistical analyses in advance, the system prepares interference detection data structures that can be efficiently queried during processing, reducing real-time computational complexity while maintaining comprehensive interference detection capability.
Solution Approach 2:
The processing chain uses the received signals themselves to generate statistical characteristics for interference detection, rather than requiring separate dedicated detection hardware. The correlation calculations and power spectral density estimations are derived directly from the measurement data, allowing the system to self-diagnose interfering signal presence using its own operational data.
3Measurement precision
If time/frequency block decomposition is used to eliminate interfering emissions, then radiometric precision is improved, but precision degradation occurs due to elimination of valid time/frequency blocks
Solution Approach 1:
The patent applies interference rejection selectively to specific reception chains and time/frequency blocks only when interference is detected in those particular segments. By making the interference rejection quality local rather than global, the system maintains high radiometric precision for clean blocks while applying correction only where needed, minimizing information loss from valid signal blocks.
Solution Approach 2:
The patent changes the detection parameters dynamically based on the statistical characteristics of each time/frequency block. By adjusting detection thresholds and criteria according to local signal conditions, the system optimizes the balance between interference detection sensitivity and false rejection rates, thereby minimizing loss of valid signal blocks while maintaining radiometric precision.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The invention relates in particular to a method (100) for calculating visibility functions for a synthetic aperture interferometric radiometer comprising a plurality of reception chains (30) respectively associated with a plurality of antennas (31). The method comprises, for each reception chain: - digitizing (101), on a frequency band of interest, a signal received by the antenna of said reception chain, - filtering (102) the digitized signal in a plurality of frequency sub-bands so as to obtain a plurality of filtered samples in each frequency sub-band, - calculating (103), for each frequency sub-band, an intercorrelation matrix (40), each element of which is associated with a pair of antennas and takes values calculated on the basis of the filtered samples associated with said antennas and obtained over an accumulation period, - detecting (104) invalid intercorrelation matrices, - calculating (105) the visibility functions from those intercorrelation matrices that are considered to be valid.