NFC Clock Recovery Circuit for Low-Power Tag Detection

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Solution Overview

Problem

NFC circuits face high power consumption when maintaining a reader mode, necessitating efficient detection methods for NFC tags in low power standby mode to reduce unnecessary energy usage.

Innovation Solution

The NFC circuit includes a transmitter, clock recovery circuit, phase detector, and controller that generate and transmit a reference clock signal, recover and detect phase changes in the detection signal to determine the presence of an NFC tag, allowing for efficient switching between standby and reader modes to minimize power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the NFC circuit continuously maintains a reader mode to detect NFC tags, then the detection performance is improved, but the power consumption increases

Engineering Contradiction:

Improvedetection performanceVSAvoidpower consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The NFC circuit dynamically switches between standby mode and reader mode based on detection needs. The system transitions from a static continuous reader mode to a dynamic state where it alternates between low-power standby and active detection modes, optimizing both power consumption and detection performance

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system employs periodic detection cycles where the NFC circuit periodically activates in reader mode to detect tags and then returns to standby mode. This periodic activation pattern reduces overall power consumption while maintaining adequate detection coverage through scheduled monitoring intervals

Inventive Principle:

Principle #19Periodic action

2Use of energy by moving object

If the NFC circuit switches to standby mode to reduce power consumption, then the power consumption is reduced, but the ability to detect NFC tags deteriorates

Engineering Contradiction:

Improvepower consumptionVSAvoiddetection capability

Core Design Contradiction:

Use of energy by moving objectVSMeasurement precision

Solution Approach 1:

Before fully entering standby mode, the system performs preliminary detection actions by periodically activating the reader mode to check for nearby NFC tags. This preliminary check ensures that the system maintains awareness of tag presence while minimizing time spent in high-power mode

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system uses feedback from periodic detection cycles to determine whether to remain in standby mode or transition to reader mode. When tags are detected during periodic checks, the system receives feedback to activate full reader mode; otherwise, it continues in low-power standby, optimizing the balance between detection capability and power consumption

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS10911104B2Near-field communication circuit and operation method of the same

Publication Date: 2021.02.02 SAMSUNG ELECTRONICS CO LTD

AI summary

A near-field communication (NFC) circuit includes a transmitter that generates a transmission signal based on a reference clock signal and transmits the transmission signal through an antenna; a clock recovery circuit that receives a detection signal through the antenna responsive to the transmission signal and recovers a recovered clock signal from the detection signal; a phase detector that detects a phase change of the recovered clock signal; and a controller that determines, based on the phase change of the recovered clock signal, whether an NFC tag external to the NFC circuit is located within a communication range of the NFC circuit.