Shielded-Loop Resonator Gradiometer Probe Near-Field Detection
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Solution Overview
Problem
Conventional coil-based gradiometers are ineffective in the near field due to varying exposure to electromagnetic fields, leading to unreliable signal measurements, and are prone to radio frequency interference (RFI) noise, especially when detecting weak signals from objects close to the probe.
Innovation Solution
A shielded-loop-resonator based gradiometer probe using coaxial cables to form shielded loop resonators and a tuning circuit, which allows the probe to operate at distances comparable to its size, providing improved sensitivity and immunity to nearby objects and RFI noise by using a balun transformer and adjustable capacitors for tuning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If coil-based gradiometers are used to detect electromagnetic fields, then the gradiometer can measure gradient in the far field, but it cannot operate effectively in the near field where the source is close to the gradiometer
Solution Approach 1:
The patent transforms the gradiometer probe into a resonant structure by introducing capacitive loading and adjusting its electrical parameters (inductance, capacitance, resonant frequency) to operate in the near field. The probe's impedance and resonant characteristics are tuned to match near-field conditions, enabling effective operation at distances comparable to the probe size rather than requiring far-field conditions.
Solution Approach 2:
The patent employs adjustable capacitors and tuning circuits that allow dynamic adjustment of the probe's electrical characteristics. This enables the probe to adapt its resonant frequency and impedance matching according to the specific near-field detection requirements, providing versatility across different operating conditions and distances.
2Measurement precision
If conventional gradiometer probes are used in near-field detection, then the probe can detect objects close to it, but the probe becomes highly susceptible to radio frequency interference (RFI) noise
Solution Approach 1:
The patent converts the harmful RFI noise into a beneficial effect by using the same resonant principle to reject interference. The probe is designed with specific resonant characteristics that allow it to resonate at the desired detection frequency while maintaining low impedance at interfering frequencies (such as AM radio bands), thereby converting potential noise sources into rejected signals through impedance mismatch.
Solution Approach 2:
The patent implements preliminary noise rejection by designing the probe's resonant circuit to inherently suppress RFI before detection. The tuning circuit and capacitive loading are configured in advance to create impedance barriers against known interference frequencies, preventing RFI from coupling into the detection circuit rather than attempting to filter it afterward.
3Adaptability or versatility
If the gradiometer probe size is increased to improve near-field detection capability, then the probe can detect objects at comparable distances, but the probe becomes more susceptible to detuning by nearby objects
Solution Approach 1:
The patent employs adjustable capacitors and tuning circuits that allow dynamic adjustment of the probe's electrical characteristics. This enables the probe to adapt its resonant frequency and impedance matching according to the specific near-field detection requirements, providing versatility across different operating conditions and distances.
Solution Approach 2:
The patent transforms the gradiometer probe into a resonant structure by introducing capacitive loading and adjusting its electrical parameters (inductance, capacitance, resonant frequency) to operate in the near field. The probe's impedance and resonant characteristics are tuned to match near-field conditions, enabling effective operation at distances comparable to the probe size rather than requiring far-field 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 shielded-loop-resonator gradiometer probe enhances object scanning performance by maintaining sensitivity and stability despite nearby metallic objects and RFI, effectively detecting near-field objects and signals with reduced noise interference.
Implementation Method 1
shielded-loop-resonator based gradiometer probe that operates at distances comparable with the size of the probe
Implementation Method 2
When a plane radio frequency (RF) wave reaches a gradiometer, a zero reading is produced. However, when the front of the RF wave that reaches the gradiometer is curved, the value of the electrical field near the gradiometer is not constant and has a gradient.
Implementation Method 3
a tuning circuit for tuning the probe... using a balun transformer and adjustable capacitors for tuning
Implementation Method 4
A major concern in systems that use near-field probes and related technologies... is suppression of radio frequency interference (RFI)... shielded-loop-resonator based gradiometer probe
Data Source
AI summary
A noise cancelling gradiometer probe includes an insulating material having a first side and a second side; a first, second, third and fourth coaxial cables forming a first, second, third and fourth loops, respectively, where a portion of each of the first, second, third and fourth loops is locating on the first side of the insulating material and a portion of the first, second, third and fourth loops is locating on the second side of the insulating material.