Contactless Circuit Testing via Resonant Frequency Analysis
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Solution Overview
Problem
Existing methods for testing contactless data communication circuits, such as those in RFID or NFC modules, are complex, non-reproducible, and fail to accurately detect faults like conductor breaks or short circuits in antenna coils due to their reliance on direct current resistance measurements and phase/impedance analysis, which are influenced by external magnetic fields.
Innovation Solution
A method involving the excitation of the circuit with an energy pulse and evaluation of the resulting oscillation, specifically accounting for the natural resonant frequency and quality in a controlled alternating magnetic field, allowing for precise and reproducible testing of circuit properties by distinguishing between intact and faulty antenna coils.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If DC resistance measurement is used to test antenna coils, then the testing process is simple, but it can only detect certain faults and cannot identify breaks or short circuits in coil windings
Solution Approach 1:
The patent replaces direct electrical contact measurement (DC resistance) with contactless electromagnetic induction measurement. By using a measuring antenna that generates an alternating magnetic field to induce current in the test antenna, the system achieves both contactless operation and comprehensive fault detection capability, resolving the contradiction between simplicity and reliability.
Solution Approach 2:
The patent changes the measurement parameter from DC resistance to resonant frequency and quality factor under alternating magnetic field conditions. This parameter transformation enables detection of various fault types (breaks, short circuits, soldering issues) that are invisible to DC resistance measurement, while maintaining operational simplicity through automated frequency sweeping and Q-factor calculation.
2Measurement precision
If phase and impedance analyzer is used to determine resonant frequency contactlessly, then more informative test results are obtained, but the procedure becomes complex and time-consuming
Solution Approach 1:
The patent introduces a measuring antenna as an intermediary between the test antenna and the evaluation system. This measuring antenna generates the alternating magnetic field and induces current in the test antenna, enabling contactless measurement of resonant frequency and Q-factor without requiring complex phase and impedance analyzers, thus reducing device complexity while maintaining measurement precision.
Solution Approach 2:
The patent creates a simplified measurement system that copies the essential functionality of phase and impedance analyzers. By using a measuring antenna to generate known alternating magnetic fields and measuring the induced current amplitude and phase, the system replicates impedance analysis capabilities with simpler, more accessible equipment.
3Reliability
If resonant frequency and quality factor are measured contactlessly, then comprehensive circuit functionality is tested, but the measurement is influenced by external magnetic fields and lacks reproducibility
Solution Approach 1:
The patent applies preliminary anti-action by deliberately applying a controlled alternating magnetic field before measurement and compensating for its effects. The system measures the test antenna's response to this known field and uses the field strength information to correct the resonant frequency and Q-factor values, eliminating the harmful influence of external magnetic fields and achieving reproducible results.
Solution Approach 2:
The patent implements feedback by measuring the alternating magnetic field strength during the test and using this information to compensate for its influence on the resonant frequency and quality factor measurements. The system continuously monitors field conditions and adjusts the evaluation accordingly, ensuring reproducible results regardless of external magnetic environment variations.
4Measurement precision
If manual sampling testing is performed with complex analyzers, then production release verification is achieved, but the testing time is several seconds per sample
Solution Approach 1:
The patent uses periodic action by automatically sweeping through a frequency range to find the resonant frequency and measuring the quality factor at that frequency. This automated periodic frequency sweeping, combined with rapid field strength measurement and compensation, reduces testing time from several seconds to a fraction of a second while maintaining production verification accuracy, enabling high-speed automated testing.
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 quick, easy, and cost-effective testing of contactless data communication circuits, allowing for the detection of faults and differentiation between types of defects, with precise measurement of resonant frequency and quality under standardized conditions, facilitating testing during production and reducing variability from external magnetic fields.
Implementation Method 1
a transmitting antenna 210 is arranged coaxially to the antenna 22 of the circuit 20 under test. By means of the transmitter 200 and the transmitting antenna 210, an alternating magnetic field of adjustable field strength H can be generated
Implementation Method 2
the circuit 20 is excited by means of an energy pulse. In a further step, an oscillation of the circuit in response to the excitation of the circuit by the energy pulse is detected. The detected oscillation of the circuit is finally evaluated, in particular with regard to a self-resonant frequency of the circuit
Data Source
Figure 1
Figure 2A~2C
Figure 3~4
AI summary
A method for testing a circuit (20) designed for contactless data communication, which comprises an antenna (22) and an electronic component (24) coupled to the antenna (22), therefore comprises the following steps: generation (S1) of a magnetic alternating field of a field strength and arrangement (S2) of the circuit (20) within the alternating field range. The electronic circuit (20) is then excited by means of an energy pulse (S3). In a further step, an oscillation of the circuit (20) in response to the excitation of the circuit by the energy pulse is detected (S4). The detected oscillation of the circuit (20) is finally evaluated (S5), in particular with regard to a self-resonant frequency of the circuit (20).