Digital Gain Control for NFC Baseband Amplifiers Without Preamble
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Solution Overview
Problem
State-of-the-art NFC reader ICs fail to meet the dynamic range demands for near field communication (NFC) due to limitations in the resolution of integrated analog to digital converters (ADCs), particularly in scenarios without a preamble for on-off keying protocols, leading to challenges in start-of-frame synchronization and gain control.
Innovation Solution
The implementation of a digital gain control (DGC) block with clipping detectors, water level monitors, and a finite state machine (FSM) to dynamically adjust gains in baseband amplifiers, coupled with a signal energy correction mechanism to manage gain updates and correct synchronization errors, ensuring robust communication in NFC devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If integrated ADCs are used in NFC reader ICs, then device integration is improved, but dynamic range capability deteriorates due to resolution limitations
Solution Approach 1:
The gain control function is segmented into multiple discrete gain stages within the baseband amplifier, allowing progressive gain adjustment in 6dB steps. This segmentation enables the system to handle a wider dynamic range by combining multiple smaller gain steps rather than relying on a single high-resolution ADC
Solution Approach 2:
The patent implements dynamic gain control through an automated gain control (AGC) loop that continuously monitors signal levels and adjusts amplifier gain in real-time. The gain control register is dynamically updated based on detected signal strength, allowing the system to adapt to varying signal conditions and maintain optimal dynamic range performance
2Ease of operation
If classical AGC regulation loops are used, then gain control is improved, but synchronization performance deteriorates for OOKWP protocols
Solution Approach 1:
The patent applies gain control adjustments during a predetermined gain adjustment period before the actual data reception begins. By completing all necessary gain updates in advance, the system establishes stable baseline conditions for synchronization algorithms, preventing gain changes from interfering with frame synchronization and bit timing detection
Solution Approach 2:
The AGC loop incorporates feedback from signal level detection to automatically adjust baseband amplifier gain. The system monitors the strength of received signals and provides feedback to the gain control register, creating a closed-loop system that maintains optimal signal levels for subsequent synchronization and data reception operations
3Adaptability or versatility
If gain updates are performed dynamically, then signal level adaptation is improved, but synchronization error increases due to NCO frequency adjustments
Solution Approach 1:
All gain updates are performed during a dedicated gain adjustment period that occurs before the actual data frame reception. This preliminary completion of gain adjustments ensures that the numerically controlled oscillator (NCO) frequency stabilizes before synchronization algorithms begin, eliminating the risk of gain changes causing synchronization errors during data reception
Solution Approach 2:
The patent introduces an intermediate gain adjustment period as a buffer between signal reception and data processing. This intermediary phase allows the system to complete all necessary gain control adjustments without directly interfering with the synchronization and data reception processes, effectively decoupling the two functions
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 configuration enhances the dynamic range of NFC receivers, enabling stable and efficient data transfer in both static and dynamic conditions, particularly for on-off keying protocols without a preamble, by effectively managing gain updates and correcting synchronization errors.
Implementation Method 1
an NFC module being adapted to generate an electromagnetic carrier signal and to modulate the carrier signal according to data to be transmitted
Implementation Method 2
an antenna coupled to and driven by said NFC module with the modulated carrier signal
Implementation Method 3
a first baseband amplifier (BBA) for amplifying in-phase signals and a second baseband amplifier (BBA) for amplifying quadrature signals
Implementation Method 4
a first analog to digital converter (ADC) coupled to said first BBA for converting in-phase signals to digital signals and a second ADC coupled to said second BBA for converting quadrature signals to digital signals
Data Source
AI summary
A device includes a near field communication (NFC) module for generating an electromagnetic carrier signal and modulating the carrier signal according to data to be transmitted, and an antenna coupled to and driven by the NFC module with the modulated carrier signal. The device includes an analog front end coupled between the NFC module and the antenna. The device further includes a digital gain control (DGC) block for controlling gains in a first and second baseband amplifiers (BBAs). The DGC block includes a first clipping detector for correlating in-phase input signals with a subcarrier pattern and a second clipping detector for correlating quadrature input signals with the subcarrier pattern, and further includes a signal energy correction block adapted to output a number of correction ticks for a numerically controlled oscillator (NCO) based on a number of gain updates performed for the first or the second BBAs.