Radar Transceiver Self-Calibration via Reciprocal Transit Time
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Solution Overview
Problem
Current geo-radar systems face challenges in accurately calibrating the temporal zero point for permanently installed devices, especially when measuring across boreholes, due to unknown material properties and the inability to temporarily position antennas in air for calibration.
Innovation Solution
The method involves reciprocal measurements between transceivers, where each transceiver acts as both a transmitter and receiver, allowing the determination of transit times through the sample without the need for calibration in air, enabling reliable calibration for permanently installed radar devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional calibration methods are used for permanently installed radar devices, then the temporal zero point can be calibrated in temporary setups, but the method cannot be applied to permanently installed devices where antennas cannot be repositioned in air
Solution Approach 1:
The patent introduces a reference signal as an intermediary element that can be transmitted through the unknown material. By comparing the phase of the reference signal with the measurement signal, the system can determine the temporal zero point without requiring the antennas to be positioned in air, thus enabling calibration for permanently installed devices.
Solution Approach 2:
The patent changes the calibration approach from relying on physical antenna positioning (spatial parameter) to relying on signal phase comparison (temporal parameter). By measuring phase differences at multiple frequencies and solving the resulting system of equations, the temporal zero point can be determined without moving the antennas.
2Measurement precision
If air-based calibration is performed, then the temporal zero point can be determined accurately, but the material properties between antennas must be known
Solution Approach 1:
The system performs self-calibration by using the measurement signals themselves as reference. The reference signal is transmitted through the same unknown material as the measurement signal, allowing the system to determine the temporal zero point based on phase comparisons without requiring external calibration standards or knowledge of the material properties.
Solution Approach 2:
The patent uses feedback from phase measurements at multiple frequencies to iteratively determine the temporal zero point. By measuring the phase difference between reference and measurement signals at different frequencies and solving the resulting equations, the system refines its knowledge of the temporal zero point based on the actual measurement conditions.
3Measurement precision
If multiple measurements at different distances are performed, then the temporal zero point can be determined via linear regression, but the measurement time increases
Solution Approach 1:
The patent uses periodic modulation of the reference signal at multiple known frequencies. By analyzing the phase response at these different frequencies, the temporal zero point can be determined from a single measurement setup without requiring multiple measurements at different distances, thus reducing the measurement time while maintaining accuracy.
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
This approach allows for accurate determination of transit times and sample properties like permittivity, eliminating the need for air-based calibration and enabling reliable results in scenarios where conventional calibration is not feasible.
Implementation Method 1
The propagation of the emitted EM waves depends on the relative dielectric permittivity ε r and the electrical conductivity σ of the substrate
Implementation Method 2
GPR systems derive the permittivity of the ground from determining the travel time and thus the speed of the EM waves in the ground
Data Source
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AI summary
The present invention relates to a method for the non-destructive testing of a sample (7) using a radar device (1), wherein the radar device (1) comprises several transceivers (2), in which - one or more reciprocal measurements are performed between pairs of transceivers (step S1), wherein a reciprocal measurement includes a forward and a return measurement, - by referring to the respective arrival time of the measurement signal at one transceiver (2) during the respective forward measurement, forward arrival time (taij), and the arrival time of the measurement signal at the other transceiver during the respective return measurement, return arrival time (taji), at least one transit time (tp, tpij) of the measurement signal between the two transceivers (2) is determined (step S2), and - from the at least one transit time (tp, tpij, tpji) is inferred properties of the sample (7) to be tested (step S3).