Radar Wave Field Measurement Using Phase-Corrected Doppler Processing
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Solution Overview
Problem
Ship-based or ground-based radar systems face challenges in measuring water waves at low grazing angles and extensive ranges, complicating the inversion of electromagnetic measurements into sea wave information due to surface scattering physics.
Innovation Solution
A system using a radiation source and antenna to transmit RF signals with phase offsets, receiving backscattered signals, and processing them to determine wave velocity and height through Doppler processing, while identifying and removing bad data to improve measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If ship-based or ground-based radar systems are used to measure water waves at extensive ranges, then the measurement distance is increased, but the low grazing angle complicates the surface scattering physics and makes inversion of electromagnetic measurements difficult
Solution Approach 1:
The patent changes the measurement parameters by using X-band radar frequency (3-12 GHz) specifically optimized for ocean wave measurements. This frequency range provides optimal balance between penetration through atmospheric conditions and sensitivity to surface wave scattering, enabling accurate measurements at extensive ranges while maintaining invertibility of the electromagnetic measurements into wave parameters
Solution Approach 2:
The patent introduces an intermediary processing system that includes signal averaging, spectral analysis, and iterative inversion algorithms. This intermediary layer transforms the raw electromagnetic measurements into meaningful wave parameters by compensating for the low grazing angle effects and surface scattering complexities, making the inversion process tractable even at extensive measurement ranges
2Length of stationary object
If radar measurements are performed at low grazing angles, then the measurement range is extended, but the surface scattering process becomes more complex
Solution Approach 1:
The patent utilizes X-band radar frequencies that are specifically suited for low grazing angle measurements over the ocean surface. This frequency range optimizes the interaction between electromagnetic waves and surface waves, providing sufficient backscatter signal strength even at low grazing angles while maintaining manageable scattering physics that can be modeled and inverted
Solution Approach 2:
The patent employs periodic pulse transmission with coherent integration over multiple pulses. By transmitting periodic radar pulses and coherently integrating the returned signals, the system enhances the weak backscatter signals from low grazing angle measurements while averaging out random noise and simplifying the effective scattering model through statistical processing
3Measurement precision
If phase offset is introduced in RF signals, then measurement accuracy is improved through phase correction, but signal processing complexity increases
Solution Approach 1:
The patent implements self-service phase correction where the radar system uses its own transmitted signal as a reference. By comparing the phase of the transmitted signal with the received backscatter signal, the system automatically determines and corrects for phase offsets introduced by the radiation source and transmission path, eliminating the need for external phase reference equipment
Solution Approach 2:
The patent employs feedback mechanisms where the processed wave field measurements are used to refine the phase correction parameters for subsequent measurements. The system continuously adjusts its phase offset compensation based on the consistency and quality of the measured wave parameters, improving measurement precision while adapting the processing complexity to the actual sea state conditions
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
The system effectively characterizes wave fields by correlating backscattered energy with wave height and velocity, enabling accurate modeling of future ship motion and improving robustness in wave measurement across various ranges.
Implementation Method 1
The antenna can receive backscattered signals from the wave field
Implementation Method 2
The local oscillator can be coupled with the antenna and can downconvert the backscattered signals into baseband signals
Implementation Method 3
determine a relative velocity of each of the one or more waves of the wave field based on Doppler processing using the phase corrected returns
Data Source
AI summary
This disclosure relates to systems and methods for measuring wave fields of a body of water. A system can include a radiation source and an antenna that can cooperate with the radiation source to transmit a radio frequency (RF) signal to a wave field having one or more waves. The antenna can receive backscattered signals from the wave field. The system can include a local oscillator and a processor. The local oscillator downconverts the backscattered signals into baseband signals and the processor can process the baseband signals to determine a relative velocity of each of the waves of the wave field. The processor can further be programmed to identify an observed portion of the backscattered signals as bad data and remove the bad data from further processing.