Multi-Antenna System for Metal-Back Mobile Handsets
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Solution Overview
Problem
The challenge in designing antennas for slim, stylish mobile devices with metal backs is maintaining high performance while avoiding signal loss when the phone is held in certain ways, particularly in accommodating LTE frequency bands within tight internal spaces.
Innovation Solution
A multi-antenna system with four antennas, including two cap-monopole antennas for low-band coverage on the exterior and two inverted-L or PIFA antennas for mid and high-band coverage inside, integrated with a non-conducting chassis and a parasitic ground plane to maintain signal integrity and aesthetic appeal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a metal back is used for aesthetic appeal and slim design, then the device appearance and form factor are improved, but antenna performance deteriorates and signal reception is lost when held in certain ways
Solution Approach 1:
The back cover is segmented into multiple regions: a non-conducting portion for antenna placement and a metal portion for aesthetic appeal. This segmentation allows the antenna to be isolated from the metal back, preventing signal degradation while maintaining the desired aesthetic appearance and slim profile.
Solution Approach 2:
The antenna is extracted from the metal back region and placed on a non-conducting portion of the back cover. This extraction removes the harmful interaction between the metal back and antenna, eliminating signal loss issues while preserving the overall metal aesthetic of the device.
2Weight of moving object
If the device is made slim and lighter, then portability and aesthetics are improved, but internal space for antennas is reduced
Solution Approach 1:
The antenna design utilizes the surface area of the back cover in a different dimensional approach. By placing the antenna on the non-conducting portion of the back cover and using microstrip lines on the inner surface, the design maximizes the use of available surface area rather than requiring deep internal volume, enabling slim device profiles while accommodating functional antenna elements.
3Reliability
If LTE antennas with larger electrical size are used for low-frequency bands, then LTE signal reception is improved, but device thickness increases
Solution Approach 1:
The antenna incorporates microstrip lines on the inner surface of the back cover, utilizing the thin film structure of the back cover itself as part of the antenna system. This approach allows LTE-frequency antennas to achieve their required electrical length along the surface of the thin back cover rather than requiring thick internal space, maintaining both slim device profile and effective LTE reception.
Data Source
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AI summary
A device with a predominantly metal back side is provided. The device comprises: a nonconducting chassis having an interior and an exterior; at least one exterior radiating arm on the exterior of the chassis and a respective microstrip line located on the interior of the chassis, the exterior radiating arm and the microstrip electrically connected through the chassis, the exterior radiating arm and microstrip configured to resonate together in a first frequency range; and, at least one interior radiating arm located, and configured to resonate in one or more second frequency ranges higher than the first frequency range; a ground plane located on the exterior of the chassis, each of the exterior radiating arms and the ground plane being electrically separated from each other on the exterior of the chassis; and, one or more antenna feeds configured to connect to each of the microstrips and interior radiating arms.