Asymmetric Patch Antenna Array for RFID Beam Steering
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Solution Overview
Problem
RFID systems face challenges in achieving high directivity to mitigate multipath fading, which affects RF coverage, and existing phase array antennas require large sizes that are undesirable for RFID readers.
Innovation Solution
A circular antenna array with asymmetric patch elements distributed around a longitudinal axis, where each element has different sized patch elements with the same resonant frequency, optimized for beam steering and improved directivity, is used in an RFID reader to enhance RF coverage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large antenna is used to achieve high directivity, then the ability to mitigate fading due to multipath is improved, but the mounting problems and device size increase
Solution Approach 1:
The patent divides the antenna system into multiple discrete antenna elements arranged in a circular array. By segmenting the overall antenna function into multiple smaller elements that can be independently controlled with different phase and amplitude, the system achieves high directivity and fading mitigation capability without requiring a single large antenna structure.
Solution Approach 2:
The patent transitions from traditional linear or planar antenna arrangements to a three-dimensional circular array configuration. This spatial reorganization in multiple dimensions allows the antenna system to achieve superior directivity and multipath mitigation performance while maintaining a compact footprint, effectively utilizing vertical and radial dimensions rather than just horizontal expansion.
2Reliability
If beam steering techniques are used to improve RF coverage, then the ability to mitigate multipath fading is improved, but the antenna array complexity increases
Solution Approach 1:
The patent employs asymmetric antenna elements within the circular array, where individual elements have non-uniform radiation patterns and impedance characteristics. This asymmetry, when combined with appropriate phase and amplitude weighting, enables effective beam steering and multipath mitigation while reducing the overall system complexity compared to using identical symmetric elements that would require more sophisticated control algorithms.
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 improved RF coverage and reduced effects of multipath fading by controlling the amplitude and phase of signals applied to each antenna element, allowing for better beamforming and increased directivity without the need for a large antenna size.
Implementation Method 1
One factor that impairs RF coverage are the nulls that result from destructive interference caused by multipath fading. On the other hand, multipath propagation can also result in constructive interference, which can improve RF coverage and the range of an RFID reader.
Implementation Method 2
destructive interference caused by multipath fading. On the other hand, multipath propagation can also result in constructive interference
Implementation Method 3
RFID readers that employ beam steering techniques using phase array antennas typically have better RF coverage than RFID readers that use traditional antennas due to the phase array antennas' ability to steer a beam
Implementation Method 4
a first patch element disposed proximate to the first end of the asymmetric antenna element is larger than a second patch element disposed proximate to the second end of the asymmetric antenna element, and wherein a resonant frequency associated with the first patch element of the asymmetric antenna element is approximately the same as a resonant frequency associated with the second patch element disposed proximate to the second end of the asymmetric antenna element
Data Source
AI summary
An RFID reader is provided that includes an antenna array comprising multiple antenna elements circumferentially distributed around a longitudinal axis of the antenna array. Each antenna element includes multiple patch elements disposed above one or more underlying substrates, wherein the patch elements of each antenna element are disposed on an outer side of the antenna element. Further, one or more of the antenna elements is an asymmetric antenna element, wherein a first end of the asymmetric antenna element is wider than a second, opposite end of the asymmetric antenna element, wherein a first patch element disposed proximate to the first end of the asymmetric antenna element is larger than a second patch element disposed proximate to the second end of the asymmetric antenna element, and wherein a resonant frequency associated with the first patch element is approximately the same as a resonant frequency associated with the second patch element.