Card Detector Using Adjustable Reference Voltage and Time Delay Analysis
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Solution Overview
Problem
Conventional card detectors are limited in their ability to function across multiple frequencies, making them incompatible with different card readers, and they struggle to accurately detect cards due to variations in capacitance caused by manufacturing processes and noise.
Innovation Solution
A card detector system comprising a first and second comparator, an adjustable capacitor, and a decision circuit that compares voltage comparison results at different time points to determine card proximity, using buffered results and phase detection to adjust the reference voltage and ensure accurate detection across various frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional card detector is designed to work at a single frequency, then the device complexity is reduced, but the adaptability to different card readers deteriorates
Solution Approach 1:
The card detector is designed with multiple comparators (first comparator, second comparator, third comparator) that can operate at different frequencies simultaneously. Each comparator can detect cards at its designated frequency, making the detector universal and compatible with various card readers operating at different frequencies without requiring multiple separate detectors.
2Device complexity
If the reference voltage is fixed, then the device complexity is reduced, but the measurement precision deteriorates due to capacitance variations
Solution Approach 1:
The reference voltage is made adjustable through an adjustable capacitor connected to the second comparator. This dynamic adjustment capability allows the reference voltage to be tuned to compensate for capacitance variations caused by manufacturing processes and noise, thereby improving card detection accuracy without significantly increasing device complexity.
3Device complexity
If single time point comparison is used, then the device complexity is reduced, but the measurement precision deteriorates due to noise interference
Solution Approach 1:
The detection method employs periodic sampling at multiple time points (first time point and second time point) rather than a single time point. By comparing results from multiple periodic measurements, the system can identify consistent patterns and filter out noise interference, thereby improving detection accuracy without excessive complexity increase.
4Device complexity
If no adjustable capacitor is used, then the device complexity is reduced, but the adaptability to different frequencies deteriorates
Solution Approach 1:
The adjustable capacitor enables changing the reference voltage parameter to match different operating frequencies of various card readers. By adjusting the capacitor value, the detector can adapt its reference voltage to correspond with the frequency characteristics of different card readers, thereby expanding frequency range compatibility.
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 system effectively wakes up the card reader by accurately detecting card proximity through time delay analysis, reducing errors caused by capacitance variations and noise, and ensuring compatibility with multiple frequency card readers.
Implementation Method 1
a first comparator configured to output periodically a first comparison result by comparing a voltage for a device under test (DUT) received by a positive input port of the first comparator with a first reference voltage received by a negative input port of the first comparator
Implementation Method 2
a second comparator configured to output periodically a second comparison result by comparing a second reference voltage received from a positive input port of the second comparator, with the first reference voltage received by a negative input port of the second comparator
Implementation Method 3
an adjustable capacitor is configured to adjust the second reference voltage
Implementation Method 4
a decision circuit communicatively coupled to both the first comparator and the second comparator, and configured to decide whether a card is in proximity to the card detector by comparing a time delay relationship between the first comparison result and the second comparison result respectively at a first time point and a second time point different from the first time point
Data Source
AI summary
A card detector configured to be communicatively coupled to a card reader comprises: a first comparator configured to output periodically a first comparison result by comparing a voltage for a device under test with a first reference; a second comparator outputs periodically a second comparison result by comparing a second reference voltage with the first reference voltage, wherein the second reference voltage is adjustable; a decision circuit communicatively coupled to both the first comparator and the second comparator, and decides whether a card is in proximity to the card detector by comparing the time delay relationship between the first comparison result and the second comparison result respectively at a first time point and a second time point different from the first time point, and further wakes up the card reader if the decision circuit decides that the card is in proximity to the card detector.