Switchable Patch Antenna for RFID Shelf Reader Null Zone Elimination
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Solution Overview
Problem
Existing RFID shelf reader antennas often have null zones or weak fields in the near field, radiating near field, and far field regions, making them unreliable for detecting RFID labels or deactivating EAS tags across various orientations and distances.
Innovation Solution
A switchable patch antenna with two orthogonal feed lines and a switch that sequentially selects between them to create an electric field with consistent orientations in all three regions, ensuring strong field presence regardless of tag orientation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a linear polarized antenna is used, then the antenna structure is simple and manufacturing is easy, but the antenna creates null fields in orthogonal directions and cannot detect RFID labels of all orientations
Solution Approach 1:
The patent applies dynamics by making the antenna polarization switchable between linear and circular modes. The antenna transitions from a static linear polarized configuration to a dynamic system that can change its radiation pattern based on the orientation of RFID tags, thereby achieving both structural simplicity and adaptability to all tag orientations.
Solution Approach 2:
The patent changes the polarization parameter of the antenna from fixed linear to switchable between linear and circular polarization. By controlling the phase difference between orthogonal feed lines, the antenna can adjust its radiation characteristics to match different tag orientations, resolving the contradiction between simplicity and versatility.
2Adaptability or versatility
If a circularly polarized antenna is used, then the antenna can detect RFID labels of all orientations, but the antenna creates weak fields and null zones in the near field and radiating near field regions
Solution Approach 1:
The patent makes the antenna polarization dynamic and switchable. Instead of using fixed circular polarization which creates near-field null zones, the system can switch between linear and circular polarization modes. When a tag is detected in a null zone, the system switches to an appropriate linear polarization mode that provides strong field coverage for that specific orientation.
Solution Approach 2:
The patent employs periodic switching between different polarization modes to systematically cover all possible tag orientations. By periodically alternating between linear polarizations in different directions and circular polarization, the antenna ensures continuous detection capability without leaving persistent null zones in any particular direction.
3Device complexity
If a single polarization mode is used, then the antenna operation is simple and energy consumption is low, but the antenna cannot reliably detect RFID labels with random orientations in near field, radiating near field, and far field regions
Solution Approach 1:
The patent introduces dynamic polarization switching capability to the antenna system. The antenna can transition between different polarization states (linear and circular) based on the detected tag orientation and field region, achieving high adaptability while maintaining relatively simple operation through automated switching control.
Solution Approach 2:
The patent creates a universal antenna system that can handle all RFID tag orientations and all field regions (near field, radiating near field, and far field) with a single antenna structure. The multi-functional capability is achieved through polarization switching that adapts to different detection scenarios, eliminating the need for multiple specialized antennas.
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 switchable patch antenna provides a well-behaved electric field in the near field, radiating near field, and far field, enabling reliable detection and communication with RFID labels and simultaneous deactivation of EAS tags across all orientations and distances.
Implementation Method 1
A switchable patch antenna with two orthogonal feed lines and a switch that sequentially selects between them to create an electric field with consistent orientations in all three regions
Data Source
AI summary
A switchable patch antenna includes a ground plane, a metal patch, at least two feed lines and a switch. The metal patch is positioned adjacent, but not in contact with, the ground plane. Each feed line is electrically connected to the metal patch. Each feed line is substantially orthogonal to at least one other feed line. The switch is electrically connected to the at least two feed lines. The switch is operable to sequentially select between the at least two feed lines for exciting the switchable patch antenna.