Segmented HMD Chassis Antennas Using Notch Filters as Common Ground
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Solution Overview
Problem
Multi-band antenna configurations in head-mounted devices (HMDs) require active switches and shields to manage different frequency bands, leading to reduced power efficiency, increased size, cost, and weight due to power consumption and physical footprint, as well as signal interference issues.
Innovation Solution
A segmented metal chassis with physically separate RF antennas corresponding to different head regions, each connected to a distributed RF transceiver and notch filter circuits that attenuate signals within the resonant frequency band, allowing the chassis to function as a common ground plane, eliminating the need for active switches and shields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multi-band antenna configurations are used in HMDs, then various communication and sensing functionality is provided, but power efficiency is reduced due to active switches and shields
Solution Approach 1:
The antenna system is divided into multiple physically separate RF antennas, each dedicated to a specific frequency band and head region. This segmentation eliminates the need for active switches to toggle between bands, as each antenna operates independently at its resonant frequency, thereby improving power efficiency while maintaining multi-band functionality.
Solution Approach 2:
Notch filter circuits are introduced as intermediary components connected to each RF antenna. These filters selectively attenuate signals within the resonant frequency band of each antenna while passing other frequency bands, enabling frequency isolation without requiring active switches or shields, thus improving power efficiency.
2Object-generated harmful factors
If active switches and shields are used to manage different frequency bands, then signal interference is controlled, but device size and weight increase
Solution Approach 1:
Passive notch filter circuits serve as intermediary components that provide frequency-selective signal isolation. These filters attenuate signals within each antenna's resonant band while allowing other frequencies to pass, controlling signal interference without requiring heavy active shields, thus reducing device weight.
Solution Approach 2:
The design uses simple, lightweight passive notch filter circuits instead of complex, heavy active shield systems. The notch filters are inexpensive passive components that effectively isolate frequency bands without adding significant weight to the HMD.
3Adaptability or versatility
If active switches and shields are implemented for multi-band management, then frequency band control is achieved, but device cost increases
Solution Approach 1:
The patent employs inexpensive passive notch filter circuits instead of costly active switch and shield assemblies. These simple passive filters are easy to manufacture and integrate, significantly reducing bill of materials costs while maintaining effective frequency band control for multi-band operation.
Solution Approach 2:
The design extracts and eliminates the expensive active switch and shield components from the system. By using only passive notch filters for frequency isolation, the patent removes the need for complex active management hardware, thereby reducing device cost while preserving frequency band control capabilities.
4Measurement precision
If physically separate RF antennas are used for different head regions, then proximity sensing accuracy is improved, but device complexity increases
Solution Approach 1:
The antenna system is segmented into multiple physically separate RF antennas, each positioned near a specific head region (e.g., left cheek, right cheek, nose, jaw). This segmentation enables each antenna to independently sense proximity in its local region with high accuracy, while the overall system complexity is managed through the use of simple, identical notch filter circuits for each antenna.
Solution Approach 2:
Each RF antenna is optimized for its specific local head region, providing localized proximity sensing accuracy. The notch filters are tuned to the resonant frequency of their associated antenna, creating locally optimized frequency isolation. This local quality approach improves sensing precision while keeping the overall system architecture simple and repetitive.
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 design enhances power efficiency, reduces cost and weight, improves industrial design, and increases electro-static discharge (ESD) robustness and signal-to-noise ratio (SNR) by providing a common ground path for built-up charge and reflecting waves radiated by RF antennas.
Implementation Method 1
the segmented metal chassis functions as a common ground plane
Implementation Method 2
Each notch filter is configured to attenuate signals at frequencies within the resonant frequency band of the corresponding RF antenna
Implementation Method 3
Each RF transceiver is configured to drive the corresponding RF antenna with a drive signal at a frequency within a resonant frequency band
Data Source
AI summary
A head-mounted device (HMD) has a segmented metal chassis including a plurality of physically separate radio frequency (RF) antennas corresponding to different head regions. The HMD further includes a plurality of RF transceivers, each electrically connected to a corresponding RF antenna. Each RF transceiver is configured to drive the corresponding RF antenna with a drive signal at a frequency within a resonant frequency band of the corresponding RF antenna and sense a frequency response to the drive signal. The HMD further includes a plurality of notch filter circuits, each electrically connected in series with a corresponding RF antenna. Each notch filter is configured to attenuate signals at frequencies within the resonant frequency band of the corresponding RF antenna and pass signals at frequencies outside of the resonant frequency band, such that the segmented metal chassis functions as a common ground plane.