Multi-band Antenna with Variable Loading for SAR Control
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Solution Overview
Problem
The challenge in designing cellular communications devices is to create antennas that provide desired operating characteristics within the limited space available, while also ensuring compliance with SAR and HAC requirements, especially as devices become smaller and internal antennas are placed closer to the user's ear, making it difficult to achieve desired signal characteristics and radiation exposure control.
Innovation Solution
A mobile wireless communications device with a multi-band antenna system that includes both internal and external antennas, using a controller to selectively switch between wireless transceivers and antennas, and connect/disconnect them to loads, allowing for variable loading and operation across different frequency bands, thereby optimizing antenna performance and reducing radiation exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If internal antennas are used to reduce device size, then device portability is improved, but radiation exposure to user increases making SAR compliance difficult
Solution Approach 1:
The antenna system is segmented into multiple antenna elements distributed across different locations on the device housing. This segmentation allows the radiation to be distributed spatially, reducing the concentration of electromagnetic energy near the user's head while maintaining compact device dimensions.
Solution Approach 2:
Parasitic antenna elements are introduced as intermediaries between the active antenna elements and the user's head. These parasitic elements redirect and shape the radiation pattern away from the user, acting as a mediator that reduces SAR exposure without requiring larger device form factors.
2Object-affected harmful factors
If external antennas are used to reduce radiation exposure, then SAR compliance is improved, but device durability worsens due to susceptibility to damage
Solution Approach 1:
The antenna system employs a nested structure where parasitic antenna elements are positioned within or adjacent to the housing structure, protecting them from external damage while maintaining their radiation-shaping function. The active antenna elements are integrated into the device interior, shielded from environmental exposure.
3Volume of moving object
If limited space is used for antenna design, then device compactness is improved, but achieving desired signal characteristics becomes difficult
Solution Approach 1:
The antenna system incorporates variable loading mechanisms that dynamically adjust the electrical characteristics of the antenna elements based on operating conditions. This allows the antenna to adapt its impedance and radiation pattern to maintain optimal signal characteristics across different frequency bands and operating scenarios, despite limited physical space.
Solution Approach 2:
The system changes electrical parameters such as loading impedance and element excitation amplitudes to optimize signal characteristics. By adjusting these parameters rather than relying solely on fixed physical dimensions, the antenna achieves desired performance in compact form factors.
4Adaptability or versatility
If multi-band operation is implemented, then communication versatility is improved, but antenna design complexity increases
Solution Approach 1:
The antenna elements are designed with multi-functionality to operate across multiple frequency bands. The same physical antenna structure serves multiple communication standards (EDGE, CDMA, WCDMA) by adjusting electrical parameters and loading conditions, eliminating the need for separate dedicated antennas for each band and reducing overall system 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
The solution provides a high-performance multi-band antenna system that achieves wide bandwidth and high system antenna gain, while maintaining compliance with SAR and HAC requirements by using a variable loading mechanism that adjusts antenna performance based on frequency bands and radiation exposure considerations.
Implementation Method 1
electromagnetic radiation generated by the first in-built driven antenna element is enhanced in a direction away from a side of the casing intended to be facing a user
Data Source
AI summary
A mobile wireless communications device may include a plurality of antennas, a plurality of wireless transceivers, and signal processing circuitry. The device may further include a controller for selectively switching the signal processing circuitry to a desired one of the wireless transceivers, and for selectively switching a desired one of the antennas to the desired one of the wireless transceivers. Moreover, the controller may also be for selectively connecting and disconnecting the at least one other one of the antennas to an unused one of the wireless transceivers.