NFC Receiver Circuit Integrating ASK Signal Peaks
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Solution Overview
Problem
Existing near field communication (NFC) systems, particularly those using ISO/IEC 14443 standards, face challenges with low-pass filtration limiting signal bandwidth and non-linear responses in high bit rate applications, making it difficult to perform equalization and recover data effectively.
Innovation Solution
A receiver circuit that integrates and samples peaks of the ASK modulated signal without low-pass filtration, using an integrate-and-dump process to preserve data information while avoiding interference, and includes a frequency divider to generate clock signals for integration and sampling, allowing for a sample-based approximation of the modulated carrier signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If low-pass filtration is used to filter interference in the received ASK signal, then interference is reduced, but signal bandwidth is limited
Solution Approach 1:
The patent extracts only the necessary filtering function to remove interference while eliminating the low-pass filter that limited bandwidth. The solution uses peak detection and integration methods that inherently reject interference without constraining the signal bandwidth, thus separating the harmful interference removal from the bandwidth-limiting filtration.
Solution Approach 2:
The patent replaces the traditional low-pass filter (analog filtering mechanism) with a digital signal processing approach using peak detection, integration, and sampling. This substitution allows interference rejection through mathematical operations rather than frequency-based analog filtering, preserving the full signal bandwidth while still eliminating interference.
2Object-affected harmful factors
If diode-rectifier with low-pass filter is used for demodulation, then interference is filtered, but non-linear response makes equalization difficult
Solution Approach 1:
The patent removes the diode-rectifier and low-pass filter combination that caused non-linear response. Instead, it uses linear integration and sampling operations that maintain signal linearity, thereby eliminating the source of non-linearity while still achieving interference rejection through the integration process.
Solution Approach 2:
The patent replaces the non-linear diode-rectifier mechanism with linear digital signal processing operations (integration and sampling). This substitution transforms the demodulation process from a non-linear analog operation to a linear digital operation, making the signal suitable for subsequent digital equalization without the distortion introduced by diode rectification.
3Loss of information
If integrated and dump process is used to sample peaks, then data information is preserved and interference avoided, but additional processing circuitry is required
Solution Approach 1:
The patent merges the detection, integration, and sampling functions into a unified integrated-and-dump process. By combining these operations into a single coherent processing stage, the patent achieves effective data recovery and interference rejection without requiring separate complex circuits for each function, thus reducing overall processing circuitry complexity.
Solution Approach 2:
The integrated-and-dump process is self-regulating, automatically identifying and sampling peak values without requiring external control signals or complex synchronization mechanisms. The integration naturally accumulates signal energy at peak points, and the dump operation automatically resets the integrator, creating a self-service system that reduces the need for additional control circuitry.
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
This approach enables efficient demodulation of NFC signals by avoiding interference and preserving data information, improving signal recovery and equalization in high bit rate applications without the need for phase locked loops or delay locked loops.
Implementation Method 1
the modulated magnetic field may induce currents/voltage in a coil antenna connected to the contactless smart card
Data Source
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AI summary
In one embodiment, an apparatus is provided that includes a first circuit (120) configured and arranged to provide a modulated carrier signal in response to a signal provided from the antenna (104). The modulated carrier signal conveys data using peaks or amplitudes of the carrier signal. A second circuit (130) is configured to rectify (132) the modulated carrier signal and integrate (134) the rectified signal in response to a first clock signal. A third circuit (140) is coupled to an output of the second circuit and is configured to sample the integrated signal values and provide therefrom a sample-based approximation of the modulated carrier signal.