Shared Clock Architecture for GPS-Stable Cellular AFC
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Solution Overview
Problem
Existing multi-functional cellular applications face challenges in sharing a clock reference between cellular transceiver and GPS receiver modules due to abrupt frequency changes caused by automatic frequency correction, which are not tolerated by the GPS receiver.
Innovation Solution
A system with a first clock module generating an uncorrected clock reference shared between both modules, and an integrated circuit performing automatic frequency correction to generate a second AFC-corrected clock reference, allowing both modules to operate without abrupt changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single clock reference is shared between cellular transceiver and GPS receiver, then device cost is reduced, but GPS performance deteriorates due to abrupt frequency changes from AFC correction
Solution Approach 1:
The patent segments the clock reference system into two distinct paths: an uncorrected clock reference path for GPS receiver and an AFC-corrected clock reference path for cellular transceiver. This segmentation allows each module to receive the appropriate type of clock reference, resolving the conflict between cost reduction and GPS performance.
Solution Approach 2:
The patent introduces a clock distribution module as an intermediary that receives a single clock reference and distributes differentiated versions to different modules. This mediator enables the system to provide both corrected and uncorrected clock references from a single source, achieving cost reduction without compromising GPS performance.
2Reliability
If AFC correction is applied to the clock reference, then cellular transceiver performance is improved, but GPS receiver cannot tolerate the abrupt frequency changes
Solution Approach 1:
The patent applies local quality by providing different clock reference characteristics to different modules based on their specific requirements. The GPS receiver receives an uncorrected clock reference with stable frequency, while the cellular transceiver receives an AFC-corrected clock reference with optimal frequency accuracy for its operations.
Solution Approach 2:
The patent implements dynamics by making the clock distribution system adaptive - it dynamically selects whether to apply AFC correction based on the receiving module's requirements. The system can switch between providing corrected and uncorrected clock references as needed by different modules.
3Reliability
If a second separate TCXO clock module is used for GPS receiver, then GPS performance is maintained, but device complexity increases
Solution Approach 1:
The patent achieves universality by designing a single clock distribution module that can serve multiple functions: distributing both corrected and uncorrected clock references to different modules. This multi-functional approach eliminates the need for separate TCXO clock modules while maintaining GPS performance.
Solution Approach 2:
The patent merges the functionality of multiple clock modules into a single clock distribution module. By combining the clock generation and distribution functions, the system reduces the total number of components while maintaining the ability to provide specialized clock references to each module.
Data Source
AI summary
A system includes a first clock module, a global positioning system (GPS) module, a phase-locked loop (PLL) module, a cellular transceiver, and a baseband module. The first clock module generates a first clock reference. The GPS module operates in response to the first clock reference. The WLAN module operates in response to the first clock reference. The PLL module generates a second clock reference by performing automatic frequency correction (AFC) on the first clock reference in response to an AFC signal. The cellular transceiver receives radio frequency signals from a wireless medium and generates baseband signals in response to the received radio frequency signals. The baseband module receives the baseband signals, operates in response to a selected one of the first clock reference and the second clock reference, and generates the AFC signal in response to the baseband signals.