Multi-Loop Antenna Far-Field Radiation Cancellation
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Solution Overview
Problem
Conventional RFID systems face limitations in operating range due to proportional increases in far-field radiation, which violate FCC radiation regulations when attempting to enhance range, necessitating a solution that increases near-field radiation while reducing far-field radiation.
Innovation Solution
An antenna system with adjuster elements and transformers is used to control the size and current flow through multi-looped antenna configurations, ensuring equal and opposite phase center points and enclosed areas to cancel far-field radiation while maintaining near-field radiation, thereby extending the operating range while adhering to regulatory limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If input power is increased to extend RFID system range, then near-field radiation is improved, but far-field radiation increases and violates FCC regulations
Solution Approach 1:
The antenna system is divided into multiple loops (first loop, second loop, third loop) with different enclosed areas. Each loop contributes to near-field radiation while the segmented structure enables differential current control to cancel far-field radiation components.
Solution Approach 2:
Different loops are assigned different current polarities and relative current magnitudes based on their specific enclosed areas. The current distribution is locally optimized for each loop to achieve constructive interference in near-field regions and destructive interference in far-field regions.
2Object-generated harmful factors
If multi-looped antenna configuration is used with adjusted enclosed areas, then far-field radiation is canceled, but near-field radiation must be maintained
Solution Approach 1:
The system adjusts the relative current flowing through each loop based on the ratio of their enclosed areas. By changing current parameters (magnitude and polarity) rather than physical structure, the system achieves far-field cancellation while maintaining near-field effectiveness.
Solution Approach 2:
The antenna loops have asymmetric enclosed areas (first loop has first enclosed area, second loop has second enclosed area, third loop has third enclosed area). This asymmetric configuration, combined with asymmetric current distribution, enables selective cancellation of far-field radiation while preserving near-field radiation patterns.
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 antenna system effectively reduces or cancels far-field radiation, maintaining near-field radiation strength, thus enhancing the operating range of RFID systems while complying with RF radiation regulations.
Implementation Method 1
antenna systems have near-field and far-field radiation regions... the far-field region is where radiation from the antenna is said to occur
Implementation Method 2
far-field radiation from the antenna can be reduced, minimized and/or substantially canceled... the far-field radiation generated by each of the loops is out-of-phase and coincident and so tends to cancel out
Data Source
AI summary
An antenna includes a first loop defining a first enclosed area and having a first phase center point, a second loop coupled to the first loop and disposed substantially parallel to the first loop, the second loop defining a second enclosed area, and a third loop coupled to the first loop and the second loop and substantially parallel to the first loop, the third loop defining a third enclosed area with a plurality of adjuster elements coupled to at least one of the first loop, the second loop, or the third loop to provide an adjustable loop and configured to expand or contract the enclosed area of the adjustable loop.