Electronic Watch Antenna Layout for Conductive Case Interference
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Solution Overview
Problem
In electronic watches with built-in antennas, the use of conductive materials in the watch case can deteriorate reception sensitivity due to interference with radio wave reception.
Innovation Solution
The electronic watch design incorporates a case with electrical conductivity, a cover member made of a material that shortens radio wave wavelength, and a recessed portion with a decorative plate of non-conductive material, ensuring a specific distance and alignment to enhance antenna performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a conductive material is used for the watch case, then structural strength and aesthetics are improved, but reception sensitivity deteriorates due to interference with radio wave reception
Solution Approach 1:
The watch case is divided into two distinct parts: a conductive case body providing structural strength, and a non-conductive facing surface (bezel) that interfaces with the cover member. This segmentation allows each part to fulfill its primary function without interfering with the other - the conductive case maintains durability while the non-conductive facing surface prevents radio wave interference
Solution Approach 2:
Different materials with different electrical conductivity properties are assigned to different locations of the watch case. The case body uses conductive material for strength, while the facing surface uses non-conductive material for antenna performance. This local differentiation of material properties resolves the contradiction between structural requirements and radio wave reception requirements
2Reliability
If the cover member is made of a material that shortens wavelength, then antenna performance is improved, but the distance requirement between the case and cover member becomes more critical
Solution Approach 1:
The non-conductive facing surface acts as an intermediary element between the conductive case and the wavelength-shortening cover member. This intermediary maintains the necessary electromagnetic isolation and distance relationship, enabling the cover member to provide antenna performance enhancement without direct contact with the conductive case that would cause interference
3Reliability
If a recessed portion with decorative plate is added, then reception sensitivity is improved, but manufacturing complexity increases
Solution Approach 1:
The facing surface is designed to serve multiple functions simultaneously: it provides the non-conductive barrier for antenna performance, creates the recessed portion structure for optimal spacing, and offers a decorative plate mounting surface for aesthetics. By combining these functions into a single structural element, the design achieves reception sensitivity improvement without proportionally increasing manufacturing complexity
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 configuration improves reception sensitivity and antenna performance by minimizing interference and enhancing electromagnetic coupling, while maintaining design aesthetics.
Implementation Method 1
the cover member is made of a material that shortens a wavelength of the radio wave
Data Source
AI summary
An electronic watch includes a case having electrical conductivity, a cover member attached to the case, a hand, a hand shaft to which the hand is attached, and an antenna disposed to overlap the cover member in plan view from a first direction, the antenna being configured to receive a predetermined radio wave, the cover member is made of a material that shortens a wavelength of the radio wave, the case includes a facing surface facing a side surface of the cover member, the facing surface being located within a predetermined dimension from the side surface, and in the first direction, a height dimension from an end portion of the facing surface positioned farthest from the antenna to a farthest portion of the cover member positioned farthest from the antenna is equal to or greater than 1/60 of the wavelength shortened by the cover member.