NFC Dithering Circuit Reduces Noise Frequency Energy
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Solution Overview
Problem
NFC devices are vulnerable to noise interference from other electromagnetic devices due to parasitic couplings and intrinsic nonlinearity, leading to distortion and incorrect operation, with existing EMC filters only reducing the aggressiveness of NFC devices and not addressing noise from other devices.
Innovation Solution
Applying synchronous dispersion (dithering) on both the transmitter and receiver sides to attenuate noise without affecting the desired signal, using structurally identical circuits with pseudo-random binary sequence generators and delay means to generate dispersed signals, ensuring noise reduction without filtering the desired signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If synchronous dispersion (dithering) is applied on both transmitter and receiver sides, then noise frequency energy is reduced, but the desired signal is also dispersed and requires complex synchronous processing
Solution Approach 1:
The receiver uses feedback from the known transmission dithering sequence to generate an identical dithering sequence for synchronous processing. This feedback mechanism allows the receiver to correlate and despread the desired signal while canceling out the dispersed noise, resolving the contradiction between noise reduction and processing complexity
Solution Approach 2:
A pseudo-random dithering sequence acts as an intermediary between transmission and reception. This intermediary sequence is applied at both ends and serves as a key for selective signal recovery, enabling noise attenuation without requiring complex adaptive processing at the receiver
2Object-affected harmful factors
If dithering is applied to disperse noise, then noise emissions are attenuated, but the desired signal spectrum is also spread requiring wider bandwidth
Solution Approach 1:
The dithering sequence is applied periodically with a known pattern at both transmitter and receiver. This periodic application allows the signal to be spread during transmission but recovered by correlating with the same periodic sequence at reception, effectively reducing noise without permanently increasing bandwidth requirements
3Object-generated harmful factors
If EMC filters are used to reduce NFC device aggressiveness, then electromagnetic coupling to other devices is reduced, but noise from other devices attacking NFC victim is not reduced
Solution Approach 1:
Instead of filtering noise at the source (traditional EMC approach), the invention applies dithering at the receiver to selectively recover the desired signal from the noisy environment. This inverted approach addresses the victim's vulnerability rather than the aggressor's emissions, protecting NFC devices from external noise sources
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
Effectively reduces noise frequency energy in side harmonics containing the useful signal, filtering noise emissions without filtering the desired signal, thereby improving the reliability of NFC communications.
Implementation Method 1
generation, from this stream and an application of a first dithering, of a first amplitude-modulated and dithered signal at the antenna of the first device
Implementation Method 2
a frequency transposition of a second dithered amplitude-modulated signal from the first signal, with the application of a second dithering synchronous with said first dithering
Implementation Method 3
two NFC devices, each having two antennas intended to be coupled by a near magnetic field
Data Source
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Figure 2
Figure 3
AI summary
Contactless communication system for information between a first device (1, 2) and a second device (2, 1) having respectively two antennas (11, 21) intended to be coupled by a near magnetic field, comprising within the first device (1, 2), a transmission chain (12, 22) having first means configured to generate a stream of digital data corresponding to the information to be transmitted and second means configured to generate, from this stream and an application of a first dispersion, a first amplitude-modulated signal dispersed at the antenna of the first device, within the second device (2, 1), a reception chain (23, 13) having third means configured to perform a frequency transposition of a second amplitude-modulated and dispersed signal, from the first signal, with application of a second synchronous dispersion of said first dispersion.