NFC I/Q Signal Extraction Using Lookup Tables
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Solution Overview
Problem
Near field communication (NFC) devices face challenges in reducing size, cost, and power consumption due to the complexity of analog and digital circuits required for extracting in-phase and quadrature-phase signals, which are necessary for data demodulation.
Innovation Solution
The NFC device incorporates a matching circuit, local oscillators, mixers, low-pass filters, analog-to-digital converters, and a digital signal extractor using look-up tables to simplify the extraction of in-phase and quadrature-phase signals, reducing the need for complex phase calculations and thereby minimizing circuit size, complexity, and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If large analog circuit or complicated digital circuit is used to calculate amplitude and phase, then signal extraction accuracy is improved, but device size, cost, and power consumption increase
Solution Approach 1:
The patent extracts only the essential information needed for signal detection by comparing in-phase and quadrature-phase signals directly, rather than calculating full amplitude and phase values. This selective extraction approach maintains detection accuracy while eliminating unnecessary computational complexity.
Solution Approach 2:
Instead of using complex amplitude and phase calculation methods, the patent inverts the approach by directly comparing signal components and using look-up tables to determine signal presence. This reverse engineering of the signal processing path simplifies the circuit architecture significantly.
2Measurement precision
If large analog circuit or complicated digital circuit is used to calculate amplitude and phase, then signal extraction accuracy is improved, but power consumption increases
Solution Approach 1:
The patent extracts only the essential information needed for signal detection by comparing in-phase and quadrature-phase signals directly, rather than calculating full amplitude and phase values. This selective extraction approach maintains detection accuracy while eliminating unnecessary computational complexity.
Solution Approach 2:
The patent uses look-up tables stored in memory that can be quickly queried and discarded or refreshed, replacing complex real-time calculations. This approach uses simple memory access operations instead of power-intensive computational operations.
3Measurement precision
If complex phase calculation circuit is used, then signal demodulation accuracy is improved, but device size increases
Solution Approach 1:
The patent extracts only the essential information needed for signal detection by comparing in-phase and quadrature-phase signals directly, rather than calculating full amplitude and phase values. This selective extraction approach maintains detection accuracy while eliminating unnecessary computational complexity.
Solution Approach 2:
The patent uses look-up tables that store pre-calculated signal characteristics, replacing the need for complex real-time calculation circuits. This copying approach allows simple memory-based lookups instead of power-intensive computational operations.
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 NFC devices with reduced size, cost, and power consumption while maintaining effective data extraction and demodulation, improving communication reliability and accuracy by simplifying signal processing.
Implementation Method 1
a matching circuit connected to an antenna, and including at least one from among a capacitor and an inductor
Implementation Method 2
a local oscillator configured to generate a first oscillation signal and a second oscillation signal that is 90 degrees out of phase with the first oscillation signal
Implementation Method 3
a first mixer configured to receive a signal from the antenna through the matching circuit, to receive the first oscillation signal from the local oscillator, and to generate a first in-phase signal by multiplying the signal with the first oscillation signal
Data Source
AI summary
A near field communication device configured to receive a signal from an antenna and to generate a first in-phase signal and a first quadrature-phase signal by multiplying the signal with a first oscillation signal and a second oscillation signal; a first and second low-pass filter configured to generate a second in-phase signal and a second quadrature-phase signal; a first and second analog-to-digital converter configured to generate a third in-phase signal and a third quadrature-phase signal; a digital signal extractor configured to generate a first signal and a second signal based on the third in-phase signal, the third quadrature-phase signal, a first look-up table, and a second look-up table, select one from among the first signal and the second signal based on a signal pattern, and output the selected one as an extraction signal; and a modem configured to receive the extraction signal and to demodulate the extraction signal.