Two-Point PLL Channel Scanning Without Re-Locking Delays
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Solution Overview
Problem
Conventional Bluetooth channel scanning techniques are restrictive due to the need for frequent re-locking of the phase-locked loop at each channel frequency, resulting in significant delays and increased channel contention, especially in congested ISM bands with high wireless traffic.
Innovation Solution
A two-point modulation scheme for the phase-locked loop allows the PLL to remain locked while scanning multiple channels, eliminating the need for re-locking at each frequency, thereby reducing scan times and enabling faster adaptation of frequency hopping to avoid interfered channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional Bluetooth channel scanning uses a phase-locked loop that re-locks at each channel frequency, then frequency accuracy is maintained, but scan time increases significantly causing delays in detecting congested channels
Solution Approach 1:
The system performs preliminary channel scanning using a frequency synthesizer that can rapidly tune across channels without full phase-locked loop re-locking. The frequency synthesizer pre-establishes frequency references that allow quick channel assessment, and only channels showing potential interference trigger a full PLL re-lock for confirmation, thus reducing overall scan time while maintaining detection accuracy
Solution Approach 2:
The patent implements a dynamic scanning approach where the phase-locked loop operates in different modes depending on the scanning phase. During initial channel assessment, the system uses a faster frequency synthesis mode with relaxed locking requirements. When a congested channel is detected, the system dynamically switches to full PLL re-locking mode for that specific channel to ensure accurate frequency measurement and interference detection
2Stability of the object's composition
If the phase-locked loop re-locks at each channel frequency during scanning, then frequency stability is ensured, but the ability to rapidly adapt to congested channels deteriorates
Solution Approach 1:
The frequency synthesizer performs preliminary frequency establishment and channel identification before full PLL engagement. This preliminary action allows the system to quickly identify potentially congested channels and only engage the stable PLL re-locking mechanism when necessary, thus maintaining frequency stability for critical measurements while improving overall channel assessment rate
Solution Approach 2:
The system implements periodic scanning with alternating phases: a fast scanning phase using frequency synthesis for routine channel assessments, and a verification phase using full PLL re-locking for channels that require confirmed frequency stability. This periodic alternation between fast and stable modes maintains frequency stability where needed while improving overall productivity
3Adaptability or versatility
If frequent channel scanning is performed to detect congested channels, then adaptability to changing radio conditions improves, but firmware resource allocation and time management become more complex
Solution Approach 1:
The frequency synthesizer performs preliminary channel identification and basic signal strength measurement before triggering full PLL-based analysis. This preliminary filtering reduces the number of channels that require complex firmware processing and time resource allocation, allowing frequent scanning to be performed with reduced computational overhead while maintaining adaptability to congested channels
Solution Approach 2:
The scanning process is segmented into multiple stages: initial fast frequency synthesis-based channel identification, intermediate signal strength filtering, and final PLL-based verification only for suspect channels. This segmentation divides the complex scanning task into manageable stages with decreasing resource requirements, enabling frequent scanning while simplifying firmware time resource allocation at each stage
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
The two-point modulation technique significantly reduces scan times and improves the ability to rapidly detect and adapt to congested channels, enhancing radio performance and data transfer efficiency by allowing more frequent and timely channel assessments.
Implementation Method 1
a phase-locked loop configured to generate a local oscillator signal responsive to a two-point modulation
Implementation Method 2
modulating a frequency gain of an oscillator in a phase-locked loop to equal a first frequency gain
Implementation Method 3
a mixer configured to mix a radio frequency signal with the local oscillator signal to produce a down-converted signal
Data Source
AI summary
A receiver is provided having a two-point-modulated phase-locked loop for the rapid scanning of the signal strength of a plurality of frequency channels. The two-point modulation includes a modulation of a frequency gain by an oscillator in the phase-locked loop and a modulation of a frequency division by a divider in the phase-locked loop.