Electronic Watch Antenna Sensitivity via Ferrite Bead Damping
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Solution Overview
Problem
Existing electronic watches face challenges in improving the reception sensitivity of their antennas when receiving radio waves, particularly satellite signals, due to resonant phenomena induced by conduction members like coil springs during high-frequency signal reception.
Innovation Solution
Incorporating circuit elements such as ferrite beads in series with the wiring lines of the antenna, which increase electrical resistance during alternating current flow, thereby suppressing the cancellation current and enhancing antenna sensitivity, while maintaining low resistance for direct current flow to ensure accurate hand position detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conduction members like coil springs are used to electrically couple substrates, then electrical connection is achieved, but resonant phenomena occur during high-frequency signal reception that reduce antenna sensitivity
Solution Approach 1:
A damping member (ferrite bead) is introduced as an intermediary element in the wiring line between the antenna and the light-receiving element. This damping member absorbs high-frequency alternating currents generated during satellite signal reception, preventing resonant phenomena that would otherwise reduce antenna sensitivity, while maintaining electrical connection functionality.
Solution Approach 2:
The electrical resistance characteristic of the wiring line is modified by adding a damping member that changes resistance based on current frequency. The wiring line exhibits low resistance for direct current (enabling normal operation) and high resistance for alternating current (suppressing resonant phenomena during radio wave reception), thus adapting parameters to different operational states.
2Reliability
If the wiring line resistance is increased to suppress alternating currents, then antenna sensitivity improves, but direct current flow to the light-receiving element is impeded
Solution Approach 1:
The wiring line's electrical resistance is made frequency-dependent through the damping member. During satellite signal reception, the high-frequency alternating current encounters high resistance, suppressing resonant phenomena and improving antenna sensitivity. During normal operation, direct current encounters low resistance, ensuring adequate power supply to the light-receiving element for hand position detection.
Solution Approach 2:
The system operates in different modes with distinct current characteristics: periodic high-frequency alternating current during satellite signal reception (where high resistance is beneficial) and direct current during normal hand position detection (where low resistance is beneficial). The damping member automatically adapts resistance based on the current type, optimizing performance for each operational mode.
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 solution improves antenna gain by approximately 1.6 dB and maintains hand position detection accuracy by reducing the impact of alternating currents on the antenna, while streamlining assembly and reducing the watch's size and thickness.
Implementation Method 1
a circuit element coupled in series halfway at least one wiring line of the first wiring line and the second wiring line, and increasing, compared to electrical resistance when a direct current flows in the wiring line, electrical resistance when an alternating current generated by a radio wave received by the antenna flows in the wiring line
Implementation Method 2
the circuit element is one of a ferrite bead
Data Source
AI summary
An electronic watch includes a time display, an antenna, a first substrate including a light-emitting element, a second substrate including a light-receiving element, a gear including a through hole passing light from the light-emitting element therethrough, the gear being disposed between the first and second substrates, and first and second conduction members electrically coupling the first and second substrates. The second substrate includes a first wiring electrically coupled to the first substrate via the first conduction member, and a second wiring electrically coupled to the second substrate via the second conduction member. Halfway on at least one of the first and second wirings, a circuit element is coupled in series that, compared to electrical resistance when a direct current flows in the wiring, increases electrical resistance when an alternating current generated by a radio wave received by the antenna flows in the wiring.