HMD Antenna Isolation via 3D Folded Patch Design
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Solution Overview
Problem
Head-mounted display (HMD) devices face challenges in achieving adequate isolation between wireless personal area network (WPAN) and wireless local area network (WLAN) antennas due to their compact size, leading to interference issues and limited connectivity options, as conventional solutions like spatial separation or frequency separation are impractical.
Innovation Solution
The HMD device employs a directional patch antenna with a 3D ground plane and strategically positions WPAN and WLAN antennas to optimize physical distance and radiation patterns, utilizing a dual-channel MIMO WLAN antenna configuration to achieve effective antenna isolation and reduce radiation towards the user's head.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If inverted-F or monopole antennas are used for WPAN and WLAN in HMD devices, then wireless connectivity is enabled, but adequate isolation between the two antennas cannot be achieved due to compact device dimensions
Solution Approach 1:
The patent transitions from conventional planar inverted-F or monopole antennas to a three-dimensional folded patch antenna structure. This dimensional change allows the antenna to achieve adequate isolation and performance within the compact HMD form factor by utilizing vertical space and creating a folded configuration that separates radiation patterns while maintaining electrical length.
Solution Approach 2:
The patent divides the single antenna function into two separate folded patch antennas - one dedicated to WPAN and one to WLAN. This segmentation allows each antenna to be optimized for its specific frequency band and communication protocol, reducing mutual interference while maintaining compact dimensions through the folded geometry.
2Object-affected harmful factors
If antennas are separated spatially to provide isolation, then interference is reduced, but the compact HMD dimensions do not allow sufficient separation distance
Solution Approach 1:
The folded patch antenna design exploits the third dimension (vertical height) by folding the antenna elements in multiple directions. This allows the antenna to achieve the effective electrical length and isolation distance required for proper operation without increasing the planar footprint, thus maintaining compact HMD dimensions while reducing interference.
Solution Approach 2:
The folded patch antenna structure nests multiple antenna elements and ground plane layers within a compact volume. The folded geometry allows antenna elements to be positioned in three-dimensional space, effectively nesting the radiation patterns and isolation structures within the limited HMD form factor.
3Object-affected harmful factors
If time-multiplexing is used between WPAN and WLAN antennas, then isolation is achieved, but effective bandwidth of both antennas is significantly reduced
Solution Approach 1:
The patent implements spatial and spectral segmentation by providing dedicated folded patch antennas for WPAN and WLAN operations. Each antenna is optimized for its specific frequency band, allowing concurrent operation without time-multiplexing. The folded geometry and positioning create sufficient isolation to enable simultaneous transmission and reception across both bands, maintaining full effective bandwidth for each communication protocol.
Data Source
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AI summary
A head mounted display (HMD) device (102) includes a housing (106) configured to mount on a face of a user, at least one display (112) mounted in the housing, a wireless personal area network (WPAN) antenna (128) mounted in a medial region (138) of the housing, and first and second wireless local area network (WLAN) antennas (122, 124) located at respective lateral peripheries (142, 144) of the housing. The WPAN antenna includes a directional patch antenna comprising a feed line (202), a three-dimensional (3D) ground plane formed as a plurality of conductive sidewalls (208-211) and a ground plane structure (206) disposed at a first end of the sidewalls, wherein the ground plane structure is substantially perpendicular to the plurality of sidewalls. The WPAN antenna also includes a radiating surface (204) disposed at a second end of the sidewalls opposite of the first end, wherein the radiating surface includes a patch antenna structure (212) coupled to the feed line.