Rear-Facing Patch Antenna Layout Isolated From Charging Coil
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Solution Overview
Problem
There is a challenge in designing compact electronic devices with wireless circuitry that balances antenna efficiency bandwidth with the need to minimize interference from other components, particularly in devices where space is limited, such as wristwatches.
Innovation Solution
The design incorporates a housing with conductive sidewalls and a rear wall featuring a patch antenna element separated from the antenna ground by an antenna volume, where the patch element includes conductive traces on both the rear wall and a sensor board connected by a conductive interconnect structure, with the coil structure positioned outside the antenna volume to maximize antenna volume and minimize interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the antenna volume is increased to improve efficiency bandwidth, then antenna performance is improved, but the device size and complexity increase
Solution Approach 1:
The patent utilizes the third dimension (depth) by positioning the coil structure in a cavity below the antenna assembly, allowing the antenna to achieve larger effective volume and better performance without increasing the device's external footprint. The antenna elements are arranged in stacked configurations across multiple layers, maximizing space utilization in the vertical dimension.
Solution Approach 2:
The coil structure is nested within a cavity formed by dielectric portions of the housing, while the antenna elements are positioned in the space above the coil. This nested arrangement allows both the charging coil and antenna to coexist in a compact configuration, with each component occupying its own designated space without significant interference.
2Device complexity
If the coil structure is positioned closer to the antenna, then device complexity is reduced, but the coil interferes with antenna performance
Solution Approach 1:
The coil structure is extracted from the antenna volume and positioned in a separate cavity below the antenna assembly. This separation removes the source of electromagnetic interference from the antenna's operating space, allowing the antenna to function without degradation while maintaining a compact overall device structure.
Solution Approach 2:
Dielectric portions of the housing are positioned between the coil structure and the antenna elements, serving as electromagnetic shields that prevent interference from the coil from affecting antenna performance. These dielectric barriers allow close proximity positioning while maintaining signal integrity.
3Volume of stationary object
If the antenna elements are distributed across multiple surfaces, then antenna volume is maximized, but manufacturing complexity increases
Solution Approach 1:
The antenna is segmented into multiple discrete elements positioned on different surfaces and layers within the device housing. Each element can be independently fabricated and tested, allowing for modular assembly and simplifying the manufacturing process despite the distributed configuration across multiple surfaces.
Solution Approach 2:
The housing structure serves multiple functions: it provides mechanical support, contains dielectric shielding material, and acts as the mounting substrate for antenna elements. This multi-functionality reduces the need for separate components and simplifies the overall manufacturing process while maintaining the distributed antenna configuration.
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 enhances antenna efficiency across a wide range of frequencies, optimizing wireless performance while maintaining a compact device form factor and preventing coil interference with the antenna.
Implementation Method 1
The coil structure may be used to receive wireless charging signals through the rear wall
Implementation Method 2
The electronic device may include an antenna that radiates through the rear wall
Data Source
AI summary
An electronic device may have conductive sidewalls and a rear wall. The rear wall may have a first portion mounted to the sidewalls and a second portion protruding away from the first portion to define a cavity. A sensor board may be mounted within the cavity. A coil structure may be mounted within the cavity and surrounding the sensor board. An antenna may have an antenna ground separated from a patch element by an antenna volume. The patch element may include a first conductive trace on the first portion of the rear wall, a second conductive trace on the sensor board, and a conductive interconnect structure that couples the first conductive trace to the second conductive trace. The coil structure may be disposed outside of the antenna to minimize impact of the coil structure on performance of the antenna.