Radar Interferometry Calibration for Vibration Measurement
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Solution Overview
Problem
Current radar systems for measuring displacements and vibrations of objects/structures face challenges in distinguishing reflected signals from targets at the same distance, leading to interference that distorts and attenuates measurements, and are often cumbersome, costly, and unsuitable for short-distance or vibrational motions.
Innovation Solution
A kinematic calibration system using radar interferometry that induces a known vibrational motion in the target of interest, allowing for the separation and removal of interfering contributions through signal processing, employing a calibration device with an actuator-shaker to separate vibrational motion from stationary targets and eliminate interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If radar interferometry is used to measure displacements and vibrations, then measurement precision is improved, but interference from targets at the same distance distorts and attenuates measurements
Solution Approach 1:
The system performs a preliminary calibration phase before actual measurement, during which a known vibrational motion is induced in the target to characterize the relationship between induced vibration and radar signal. This preliminary characterization enables the system to later distinguish target signals from interference signals during normal operation, resolving the contradiction by preparing the measurement system in advance to handle interference conditions.
Solution Approach 2:
The system uses periodic vibrational motion induced in the target during calibration, with the vibration frequency being known and controllable. By inducing periodic motion and analyzing the periodic response in the radar signal, the system can separate periodic target vibrations from non-periodic or differently-periodic interference signals, thereby improving measurement precision despite the presence of interference.
2Adaptability or versatility
If SAR systems are used to separate spatial contributions, then measurement capability is improved, but device complexity and cost increase
Solution Approach 1:
The invention replaces complex mechanical/SAR systems with a simpler radar interferometry approach. Instead of using large synthetic aperture radar systems that require moving the radar sensor on slides or using aeroplanes and satellites, the patent uses a stationary radar device that measures displacements and vibrations through interferometry of reflected signals, achieving spatial separation capability through signal processing rather than mechanical complexity.
Solution Approach 2:
The system introduces a calibration device with a known vibrational motion as an intermediary element. This calibration device serves as a mediator that enables the radar system to characterize and subsequently distinguish between target signals and interference signals, providing spatial separation capability without requiring complex SAR hardware. The calibration device acts as a reference that facilitates the measurement process.
3Reliability
If active systems with transponders are used, then interference problems are solved, but installation complexity and thermal drift issues increase
Solution Approach 1:
The invention extracts the transponder from the measurement system, eliminating the need for active systems with installed transponders on the target. Instead, the patent uses passive radar interferometry where the target itself reflects radar signals without requiring any installed equipment. This removes installation complexity while maintaining the ability to measure displacements and vibrations, and eliminates thermal drift issues associated with installed electronic equipment.
Solution Approach 2:
The target structure serves itself as the measurement object without requiring external active components. The radar system measures displacements and vibrations by detecting changes in the reflected signal from the target's own surface, eliminating the need for installed transponders or sensors on the target. This self-service approach reduces installation complexity and eliminates thermal drift problems while maintaining measurement capability.
4Object-affected harmful factors
If directional radar antennas are used to limit visibility, then interference is reduced, but angular aperture becomes extremely narrow
Solution Approach 1:
The invention transitions from spatial filtering in the angular domain to temporal-frequency domain filtering. Instead of using narrow angular apertures to reduce interference, the patent induces periodic vibrational motion in the target and uses Fourier analysis to separate signals in the frequency domain. This dimensionality change allows the system to achieve interference reduction without constraining the angular aperture, maintaining measurement versatility while eliminating harmful interference.
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
Enables precise, micrometric accuracy and rapid measurement of displacements and vibrations with reduced interference, achieving effective measurement even in scenarios where traditional systems fail, such as in close proximity or vibrational applications.
Implementation Method 1
using a radar interferometry technique which provides, in real time, an estimation of the displacements, deformations and vibrations of objects/structures
Implementation Method 2
measuring displacements and vibrations with a micrometric accuracy and sensitivity... using simultaneous measurements effected by one or more radar devices
Implementation Method 3
inducing, in the target of interest, a known vibrational motion, for example repetitive
Implementation Method 4
by Fourier transform of the complex signal, it is possible to identify the contribution of each target to the measured signal
Data Source
AI summary
A method and system are described for measuring displacements and vibrations of an object/structure. The method includes transmission of at least one radar wave by a single radar device positioned at a predefined distance from a receiver device applied on the object/structure, reception, by the radar device, of a complex signal consisting of the sum of the signal reflected from said receiver device and of one or more interfering signals generated by one or more corresponding targets substantially stationary and substantially positioned at the same distance from the radar device, separation of the interfering signals from the reflected signal. The separation includes calibration by induction, for a pre-determined period of time, of a vibrational motion having a known frequency and duration in the receiver device, which consequently operates as a calibration device, for obtaining an estimated value of the interfering signals.