Radio-Controlled Timepiece Oscillator Frequency Adjustment
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Solution Overview
Problem
Radio-controlled timepieces face challenges in optimizing reception sensitivity and frequency adjustment due to the use of a singular reference frequency for both local oscillation and time measurement, leading to increased complexity and cost, particularly when receiving multiple frequencies.
Innovation Solution
A radio-controlled timepiece with a control unit that adjusts the oscillation conditions of the timepiece measuring circuit based on reception status, using a frequency divider circuit and logic variation circuit to correct time measurement drift and optimize load capacitance for improved reception sensitivity and reduced frequency adjustment range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a 32768Hz crystal oscillator is used as the reference frequency for the local oscillator circuit, then the timepiece can use a single oscillator for both time measurement and frequency reference, but the selection of comparison frequency becomes difficult and reception sensitivity deteriorates
Solution Approach 1:
The patent introduces a frequency adjusting unit that dynamically changes the oscillation frequency of the crystal oscillator based on the received signal frequency. When receiving 60kHz signals, the oscillator frequency is adjusted to 30000Hz; when receiving 40kHz signals, it is adjusted to 20000Hz. This dynamic adjustment allows the system to maintain optimal reception sensitivity for different frequency standards while still using a single crystal oscillator, thus resolving the contradiction between device simplicity and reception reliability.
2Reliability
If the oscillation frequency of the crystal oscillator is changed to optimize local oscillator performance, then reception sensitivity improves, but the frequency adjustment range becomes excessively large and timing signals become inaccurate
Solution Approach 1:
The patent changes the oscillation frequency parameter of the crystal oscillator from the standard 32768Hz to alternative values (30000Hz or 20000Hz) depending on the received signal frequency. This parameter change enables the local oscillator to achieve optimal reception sensitivity for different frequency standards while the frequency adjusting unit compensates for timing drift, thus resolving the contradiction between reception sensitivity and timing accuracy.
3Measurement precision
If a specialized high-accuracy oscillator circuit is used for the reference signal, then local oscillator accuracy improves, but power consumption increases and device size increases
Solution Approach 1:
The patent makes the crystal oscillator serve multiple functions: it acts as both the timekeeping reference and the frequency reference for the local oscillator circuit. By adjusting the oscillator frequency based on the received signal, a single oscillator replaces what would traditionally require separate specialized oscillators, thereby reducing power consumption and device size while maintaining local oscillator accuracy.
Data Source
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AI summary
A radio-controlled timepiece (1) includes an oscillator circuit (22) of which an oscillation condition can be varied by an oscillation condition adjustment circuit (23) that adjusts an oscillation frequency fref, a frequency divider circuit (24) that divides the oscillation frequency fref and generates a time measurement reference timing signal F1, a frequency adjustment circuit (25) that adjusts the period of time measurement reference timing signal F1, a local oscillator circuit (33) that uses the oscillation frequency fref as a reference frequency and outputs a local oscillation frequency fLO, and a control circuit (26). The control circuit (26), when the radio-controlled timepiece (1) is performing reception operations, causes the oscillation condition adjustment circuit (23) to operate whereby the oscillation frequency fref is adjust to an optimal frequency for the local oscillator circuit (33) and the variation setting value of the frequency adjustment circuit (25) is set such that time measurement reference timing signal F1 has a fixed period for normal operations and for reception operations.