Doppler Shift Extraction for Surface Impedance Testing
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Solution Overview
Problem
Existing methods for testing radioelectric surface homogeneity are limited by their inability to detect localized impedance discontinuities effectively, especially at higher frequencies, and are often sensitive to external environments, requiring expensive and complex setups like anechoic enclosures.
Innovation Solution
A non-destructive testing device that moves tangentially across the surface, using a transmitter and receiver with an extraction unit to isolate a shifted frequency component from the Doppler shift, allowing for sensitive detection of local impedance variations and displaying them as a variable intensity signal, while being portable and less sensitive to external factors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If radar techniques are used to obtain good spatial resolution, then measurement precision is improved, but device complexity and cost increase due to requirement of anechoic enclosures and wide frequency bands
Solution Approach 1:
The invention extracts the Doppler-shifted frequency component from the reflected signal using a mixer and frequency selector. This extraction of the specific frequency component containing defect information allows achieving good spatial resolution without requiring complex anechoic enclosures or wide frequency bands, thus resolving the contradiction between measurement precision and device complexity
Solution Approach 2:
The invention introduces a mixer as an intermediary device that combines the reflected signal with a reference signal at the transmission frequency. This intermediary process enables isolation of the Doppler-shifted component through frequency mixing, achieving precise defect detection without requiring the complex radar setup with anechoic enclosures
2Measurement precision
If measurement frequency band is widened to improve spatial resolution, then measurement precision is improved, but measurement time increases significantly
Solution Approach 1:
The invention changes the frequency parameter by detecting the Doppler shift caused by relative motion between the device and surface defects. Instead of using a wide frequency band to achieve spatial resolution, the invention uses the frequency shift induced by motion, allowing precise defect localization with a narrow frequency band and thus reducing measurement time
3Ease of operation
If coils are used as sensors for testing, then ease of operation is improved, but measurement precision deteriorates at frequencies above 300 MHz due to spatial radiation and sensitivity to outside echoes
Solution Approach 1:
The invention replaces the coil-based electromagnetic sensing system with a transmitter-receiver system that uses Doppler frequency shift detection. This substitution eliminates the spatial radiation problem and sensitivity to outside echoes that plague coil-based systems at high frequencies, while maintaining ease of operation through a similar handheld device configuration
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 device provides sensitive detection of small defects and impedance variations, is usable over a wide frequency range, and can be easily operated, offering improved spatial resolution and reduced environmental sensitivity compared to existing techniques.
Implementation Method 1
a transmitter (22) supported by the holder (20), the transmitter (22) being able to transmit an electromagnetic signal to the surface (12) at a transmission frequency
Implementation Method 2
a receiver (26) for receiving a signal reflected on the surface (12)
Implementation Method 3
an extraction unit for extracting a shifted frequency component of the transmission frequency resulting from a local impedance variation of the surface (12) in the signal received by the receiver (26)
Data Source
AI summary
A device including a holder and a transmitter supported by the holder is provided. The transmitter is capable of transmitting an electromagnetic signal toward the surface any transmission frequency (Fe). The device also includes a receiver for receiving a signal reflected on the surface. The device also includes a guide assembly for guiding the movement of the holder to move the transmitter and the receiver across from the surface, tangentially relative to the surface. The device also includes an extraction unit for extracting, in the signal received by the receiver, a shifted frequency component of the transmission frequency resulting from a local impedance variation of the surface. The extraction unit produces an extracted signal representative of the state of the surface from the shifted frequency component.