RFID Tag Bearing Determination Using Phased Array Beam Steering
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Solution Overview
Problem
Existing RFID systems face challenges in accurately determining the true bearings of RFID tags due to the practical limit on the number of antenna elements, resulting in broad beam widths and slow processing times for multiple secondary receive beams, which are not tolerable in many applications.
Innovation Solution
The system employs a phased array of antenna elements with a controller that steers a primary transmit beam and primary receive beam, and simultaneously or sequentially steers multiple secondary receive beams over a single inventory round to determine true bearings, reducing processing time and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of antenna elements is increased to improve bearing accuracy, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent divides the bearing measurement process into two stages: a first pass using a primary receive beam for initial tag identification, and a second pass using multiple secondary receive beams for precise bearing determination. This segmentation allows accurate bearing measurement without requiring a large number of antenna elements, as the secondary beams focus computational resources only on tags that need precise bearing information.
Solution Approach 2:
Instead of using multiple secondary receive beams for all tags from the beginning, the patent applies partial action by first identifying tags with the primary beam, then applying the more resource-intensive secondary beam processing only to those specific tags. This reduces the overall computational burden and allows accurate bearing measurement without requiring excessive antenna elements or processing power for the entire system.
2Measurement precision
If multiple secondary receive beams are used to improve bearing accuracy, then measurement precision improves, but processing time increases
Solution Approach 1:
The patent performs preliminary tag identification using the primary receive beam before initiating the more time-consuming secondary beam processing. By pre-identifying which tags are present and need bearing measurement, the system avoids wasting time processing secondary beams for all possible tags, thereby reducing total processing time while maintaining bearing accuracy for the relevant tags.
Solution Approach 2:
The bearing measurement process is segmented into two distinct passes: a quick initial pass with the primary beam to identify tags, followed by a focused second pass with secondary beams only for tags requiring precise bearing information. This time segmentation allows the system to achieve accurate bearing measurements without the prohibitive processing time that would result from applying secondary beam processing to all tags simultaneously.
3Area of stationary object
If broad beam widths are used to cover more area, then coverage area increases, but bearing accuracy deteriorates
Solution Approach 1:
The patent employs dynamic beam steering to electronically adjust the direction and focus of receive beams without physically moving antenna elements. The primary beam provides broad coverage for initial tag detection, while secondary beams are dynamically steered to specific angular positions for precise bearing measurement. This dynamic capability allows the system to maintain broad coverage area while achieving high bearing accuracy through selective beam focusing.
Solution Approach 2:
The patent transitions from a single broad beam approach to a multi-dimensional beam strategy, using both a primary beam for wide-area coverage and multiple secondary beams at different angular positions for precise bearing determination. By adding the dimensional aspect of angular positioning with secondary beams, the system achieves accurate bearing measurements while maintaining the broad coverage capability of the primary beam.
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
This approach allows for rapid and accurate determination of true bearings, enabling more tags to be read within a given time period and improving the quality of bearing measurements, with potential bearing errors reduced to less than one degree.
Implementation Method 1
Each RFID reader transmits an RF interrogating signal, and each RFID tag, which senses the interrogating RF signal, responds by transmitting a return RF signal
Implementation Method 2
The RFID tag either generates the return RF signal originally, or reflects back a portion of the interrogating RF signal in a process known as backscatter
Data Source
AI summary
An RFID tag reading system and method accurately and rapidly determine true bearings of RFID tags associated with items in a controlled area. An RFID reader has an array of antenna elements and a plurality of RF transceivers. A controller controls the transceivers by steering a primary transmit beam over the controlled area to each tag, by steering a primary receive beam at a primary steering angle from each tag, by steering a plurality of secondary receive beams at different secondary steering angles that are offset from the primary steering angle by receiving secondary receive signals from each tag, and by processing the secondary receive signals to determine a true bearing for each tag. Bidirectional communication between the reader and a tag is conducted over a single inventory round in which the tag is read a plurality of times by the primary and the secondary receive beams.