RFID Apparatus Calibration for Antenna Boresight Alignment
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Solution Overview
Problem
RFID inventory systems face challenges in accurately determining the alignment between the motion sensing device frame of reference and the RFID reading device antenna boresight, leading to incorrect depiction of the RFID tag read path, especially in retail floor inventory operations where user grip and antenna polarization affect the reading device's radiation pattern.
Innovation Solution
A method involving calibration of the RFID apparatus by positioning it near an RFID tag array with a visible reference mark, using motion sensing and visual data to align the device, acquire RFID tag information, and compute calibration values to determine alignment differences between the motion sensing device frame and the RFID reader antenna boresight, adjusting the scan path data to accurately depict the RFID tag reading path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the RFID apparatus is used without calibration, then the device can operate immediately, but the depicted motion path is incorrect and may mislead the user
Solution Approach 1:
The patent implements a calibration process that must be performed before normal RFID inventory operations. During calibration, the user positions the RFID apparatus at a known location relative to an RFID tag array with visible reference marks, allowing the system to determine the alignment between the motion sensing device frame of reference and the RFID reader antenna boresight. This preliminary calibration action ensures that subsequent motion path depictions are accurate.
Solution Approach 2:
The patent introduces visible reference marks on the RFID tag array as an intermediary element during calibration. These reference marks serve as a mediator between the motion sensing device and the RFID antenna boresight, allowing the system to compute alignment differences. The reference marks enable the user to align the apparatus visually while the system calculates the transformation between coordinate systems.
2Reliability
If the user performs multiple inventory passes to increase coverage, then more items may be inventoried, but the process becomes quite time consuming
Solution Approach 1:
The patent implements feedback mechanisms that provide the user with real-time information about the RFID tag read path and inventory status. The system depicts the actual path over which RFID tags are read based on calibrated motion sensing data, allowing users to see which areas have been scanned and which require additional passes. This feedback enables more efficient inventory operations by reducing unnecessary repasses.
3Device complexity
If the RFID reading device antenna radiation pattern is invisible, then the device design is simpler, but the user is unable to correlate the motion of the RFID apparatus with the path of the RFID antenna boresight
Solution Approach 1:
The patent uses visible reference marks on the RFID tag array as an intermediary to bridge the gap between the invisible antenna radiation pattern and the user's visual perception. During calibration, the user aligns the apparatus with these visible marks, and the system uses this alignment information to compute the relationship between the motion sensing device frame and the antenna boresight. This allows the invisible boresight path to be accurately depicted without making the radiation pattern itself visible.
4Ease of manufacture
If the motion sensing device frame of reference is not aligned with the RFID reader antenna boresight, then the devices can be manufactured independently, but the depicted motion path does not properly indicate the RFID tag read path
Solution Approach 1:
The patent implements a self-calibration process where the RFID apparatus determines its own alignment parameters during the calibration routine. The system uses the motion sensing device to track the position and orientation of the apparatus relative to the visible reference marks on the RFID tag array, and automatically computes the calibration values needed to align the depicted motion path with the actual RFID tag read path. This self-service approach eliminates the need for precision alignment during manufacturing.
Data Source
AI summary
Calibrating an RFID apparatus includes: positioning the RFID apparatus within a distance of an RFID tag array, the RFID apparatus having an RFID antenna to detect RFID tags and at least one motion sensing device; aligning the RFID apparatus with the RFID tag array using the motion sensing device; acquiring (i) RFID tag information including signal strength using the RFID antenna to generate an RFID antenna radiation pattern that includes a region of at least one RFID tag exceeding a signal strength, and (ii) position information of the RFID tag in the RFID tag array; and determining calibration values of the RFID apparatus based on a one or more alignment differences between the acquired region of the RFID tag information and the position information of the motion sensing device; adjusting the RFID apparatus scan path data acquired from the at least one motion sensing device using the determined calibration values.