Doppler Radar Vibration Neutralization via Phase Shift Compensation
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Solution Overview
Problem
Rotary-wing aircraft vibrations significantly impact Doppler radar operations, particularly in coherent processing, requiring precise platform movement compensation to separate ground and sea return signals, which is challenging without inertial navigation units and is sensitive to antenna installation and mechanical coupling.
Innovation Solution
An active neutralization method using three-dimensional vibration sensors to measure and compensate for antenna movements, allowing for vibration mode extrapolation, movement estimation, and phase shift compensation in the radar transmission or reception chains, eliminating the need for inertial navigation units and improving antenna coupling control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If inertial navigation units are used to compensate for platform movements, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent extracts the vibration measurement function from the complex inertial navigation unit and implements it directly through vibration sensors coupled to the radar antenna. This separation allows precise vibration measurement without requiring the full complexity of an inertial navigation system, as the vibration sensors only need to measure the specific vibratory movements of the antenna phase center.
Solution Approach 2:
The patent introduces vibration sensors as an intermediary device between the radar antenna and the compensation system. These sensors directly measure the vibratory movements of the antenna phase center and provide this information to the compensation algorithm, eliminating the need for complex inertial navigation units while maintaining measurement precision.
2Reliability
If radar antennas are installed in areas with good mechanical coupling, then reliability is improved, but adaptability deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where vibration sensors continuously measure the actual vibratory movements of the antenna phase center, and this measurement information is fed back to the compensation algorithm. This allows the system to adapt to different installation locations and mechanical coupling conditions, as the compensation is based on actual measured vibrations rather than assumed mechanical characteristics.
Solution Approach 2:
The patent changes the approach from relying on fixed mechanical coupling parameters to using dynamically measured vibration parameters. By measuring the actual vibratory movements and using these measurements to drive the compensation, the system becomes adaptable to different installation locations without requiring optimal mechanical coupling in specific areas.
3Measurement precision
If integration time is increased to improve velocity resolution, then measurement precision is improved, but stability deteriorates
Solution Approach 1:
The patent applies preliminary action by compensating for antenna movements caused by vibrations before the Doppler processing is performed. The vibration compensation is applied to the radar signals prior to coherent integration, which prevents the accumulation of phase errors during long integration periods and maintains phase coherence stability even when integration time is increased for better velocity resolution.
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
Effectively neutralizes the impact of aircraft vibrations on Doppler radar, enhancing velocity resolution and target detection by accurately compensating for antenna movements, thereby improving image reconstruction and reducing parasitic effects in synthetic aperture radar processing.
Implementation Method 1
a three-dimensional vibration sensor for each radar antenna, fixed to said antenna and near its phase centre
Implementation Method 2
compensating for the expected movements of the radar antenna(s) in the transmission chain or in the reception chain
Implementation Method 3
The present invention relates to a method and system for neutralizing the effect of vibrations in a rotary-wing aircraft for airborne Doppler radar
Data Source
AI summary
A method for active neutralization of the effect of the vibrations of a rotary-wing aircraft for a monostatic Doppler radar includes a first step of measuring and temporally extrapolating the vibration modes at the transmitting-receiving radar antenna, using a 3-axis vibration sensor, fixed to the antenna and near the phase centre of the antenna; then a second step of estimating the expected movements of the transmitting-receiving antenna or of the first transmitting antenna and the second receiving antenna; then a third step of compensating the expected movements of the transmission radar antenna in the transmission chain or in the reception chain of the radar transmitter, wherein the projection of the movement vector of the phase centre O on an aiming direction is calculated to determine the value of the compensation phase shift to be applied.