RFID Tag Bearing Precision via Offset Beam Steering
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Solution Overview
Problem
Existing RFID systems face challenges in accurately and rapidly determining the true bearings of RFID tags in controlled areas due to limitations in the number of antenna elements, leading to imprecise and slow tracking, with bearing errors of 5 to 10 degrees and high latency, which are not tolerable in many applications.
Innovation Solution
The system employs an RFID reader with a phased array and multiple RF transceivers, utilizing a controller to steer primary and secondary receive offset beams simultaneously, processing signal strengths to determine true bearings in real-time by selecting secondary receive offset signals that provide elevation and azimuth corrections to the primary steering angle, thereby reducing beam width and increasing tracking efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of antenna elements is increased to improve bearing precision, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent replaces the mechanical approach of increasing antenna element count with a signal processing approach using secondary receive offset beams. Instead of adding more physical antenna elements, the system uses electronic beamforming with offset beams to achieve sub-degree bearing precision, resolving the contradiction between measurement precision and device complexity.
Solution Approach 2:
The patent changes the operational parameters of the existing antenna array by introducing secondary receive offset beams with different steering angles. By adjusting beamforming parameters and processing signals from multiple offset beams, the system achieves high bearing precision without increasing the number of antenna elements.
2Measurement precision
If the primary transmit beam is incrementally moved throughout the controlled area in a hunting mode to find peak RSS, then bearing determination is achieved, but time consumption increases
Solution Approach 1:
The patent performs preliminary action by simultaneously steering multiple secondary receive offset beams to cover the entire controlled area before processing. This allows the system to identify potential tag locations in advance without incremental beam movement, significantly reducing the time to find peak RSS while maintaining bearing accuracy.
Solution Approach 2:
The patent maintains continuous useful action by simultaneously processing signals from multiple secondary receive offset beams across the entire controlled area. Instead of incrementally moving beams and waiting for peak detection, the system continuously monitors all areas in parallel, eliminating idle time and reducing overall bearing determination time.
3Measurement precision
If multiple movements of the primary transmit beam and multiple samples of RSS are taken to find peak RSS, then bearing determination is achieved, but productivity decreases
Solution Approach 1:
The patent performs preliminary scanning by simultaneously steering multiple secondary receive offset beams to cover all possible tag locations before final bearing determination. This preliminary action identifies candidate tags and their approximate locations, allowing the system to process multiple tags in parallel and significantly increasing the number of tags that can be located per unit time while maintaining accuracy.
Solution Approach 2:
The patent uses partial action by focusing computational resources on processing signals from secondary receive offset beams that show peak RSS, rather than processing all possible beam positions for all tags. This selective processing approach maintains bearing accuracy for tags of interest while reducing overall processing time and increasing productivity.
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 accurate and rapid determination of RFID tag bearings with reduced latency and increased tracking capacity, achieving bearing precision of less than one degree and enabling real-time monitoring of multiple tags within a given time frame.
Implementation Method 1
positioned at a known location and oriented in a known direction, and that electronically steers a primary transmit beam over the controlled area in azimuth, e.g., over an angle of 360 degrees, and in elevation, e.g., over an angle of about 90 degrees
Implementation Method 2
Each RFID tag, which senses the interrogating RF signal, responds by transmitting a return RF signal. 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.
Implementation Method 3
receive the return RF signal as a primary receive beam from the tags
Implementation Method 4
processing the secondary receive offset signals to determine a true bearing for each tag in real-time
Data Source
AI summary
A radio frequency identification (RFID) tag reading system and method accurately and rapidly determine, in real-time, true bearings of RFID tags associated with items in a controlled area. Primary transmit and receive beams are steered over the area, and multiple secondary receive beams are substantially simultaneously steered to a plurality of bearings in the area. The highest signal strength of secondary receive signals from the secondary receive beams determines an approximate tag bearing of each tag. Two secondary receive beams at opposite sides of the approximate tag bearing in elevation are selected to obtain a pair of elevation offset signals, and two secondary receive beams at opposite sides of the approximate tag bearing in azimuth are selected to obtain a pair of azimuth offset signals. The elevation offset signals and the azimuth offset signals are processed to determine a true bearing for each tag in real-time.