Reference Frequency Conversion for Crystal Oscillator Synchronization
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Solution Overview
Problem
Existing radio communication devices face challenges in generating a stable reference frequency due to variations in crystal oscillators and require additional control circuitry for frequency correction, leading to increased cost, space requirements, and reduced reliability.
Innovation Solution
A synchronization apparatus and method that uses a frequency conversion unit to convert an uncorrected reference frequency to an exact reference frequency using correction control information, eliminating the need for external control means and achieving a linear control characteristic, allowing for fast synchronization across channels without altering the reference oscillator frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a crystal oscillator is used as a reference oscillator to provide a reference frequency, then the radio terminal can function with a basic frequency reference, but the output frequency varies over temperature and cannot meet the frequency stability requirements
Solution Approach 1:
The patent implements an automatic frequency control mechanism where the frequency error detector continuously monitors the frequency deviation of the local oscillator and generates a correction signal through the loop filter to adjust the crystal oscillator, creating a closed-loop feedback system that maintains frequency stability despite temperature variations
Solution Approach 2:
The patent changes the operating parameters of the crystal oscillator by applying a DC control voltage from the loop filter that adjusts the oscillator frequency in response to detected errors, allowing the system to adapt the frequency parameter dynamically to maintain accuracy under varying conditions
2Manufacturing precision
If an automatic frequency control mechanism with analog control circuitry is used to correct frequency deviations, then the radio transceiver operating frequency can be centered onto the counterpart station channel frequency, but additional cost, space, and reduced reliability result from the extensive decoupling network and control circuitry
Solution Approach 1:
The patent replaces the traditional analog control circuitry with a digital implementation where the frequency error detector and loop filter operate in the digital domain, eliminating the need for extensive analog decoupling networks and reducing hardware complexity while maintaining frequency correction capability
Solution Approach 2:
The patent introduces a digital signal processing intermediary that processes frequency error information and generates correction signals through digital filtering and computation, acting as a mediator between the frequency error detector and the crystal oscillator control to reduce the complexity of direct analog control paths
3Manufacturing precision
If the reference oscillator frequency is altered using external control means to achieve frequency synchronization, then the frequency accuracy can be improved, but the device complexity and space requirements increase
Solution Approach 1:
The patent merges the frequency correction function with the existing phase-locked loop architecture by integrating the frequency error detector and digital loop filter within the same circuit block, eliminating the need for separate external control circuitry and reducing the overall area required for frequency synchronization
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 solution reduces current consumption, eliminates the need for additional control circuitry, and ensures precise frequency synchronization, enhancing spectral purity and reducing costs and space requirements while maintaining reliability.
Implementation Method 1
This analog control signal is applied to a varactor diode which changes its capacitance in dependence of the applied voltage and therefore the frequency of the crystal oscillator changes, when the capacitance, that builds the resonance circuit varies
Data Source
AI summary
The present invention relates to an apparatus and method for providing synchronization of an output signal to a synchronization information. The synchronization is accomplished by providing coupling of a correction control information that controls a signal generating means, e.g. a phase locked loop arrangement (30) or a direct digital synthesis arrangement, to its exact frequency to a frequency conversion unit (90) that converts an uncorrected reference frequency to a correct or exact reference frequency. Thereby, the uncorrected reference frequency for the signal generating means (30) can be provided by a simple crystal oscillator (2) without any means for frequency control. The setting of the signal generating means (30) and the frequency conversion unit (90) can be done in a predetermined sequence which enables a user equipment to synchronize its reference frequency to the synchronization information emitted by a communication network.