RFID Reading Device Antenna Spatial Resolution
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Solution Overview
Problem
Current RFID systems in logistics face challenges in accurately localizing and assigning RFID transponders due to large detection areas, leading to ambiguities and errors, especially in conveyor systems where spatial resolution is insufficient and multiple sources of error disrupt accuracy.
Innovation Solution
An RFID reading device with two transmission antennas spaced at λ/2 apart in the conveying direction transmits quadrature amplitude-modulated signals as in-phase and quadrature components separately, ensuring only transponders in a central plane can respond, allowing precise assignment to objects on a conveyor belt.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single transmission antenna is used for RFID reading, then the device complexity is reduced, but the spatial resolution and localization accuracy deteriorate due to large detection area
Solution Approach 1:
The single transmission antenna is segmented into two separate transmission antennas spaced apart in the conveying direction. Each antenna transmits a quadrature component (in-phase or quadrature) of the transmission signal, enabling directional control and spatial resolution through the relative positioning and phase relationship between the two antennas.
Solution Approach 2:
The patent introduces a spatial dimension by positioning two antennas at a specific distance apart in the conveying direction. This dimensional arrangement creates a central plane where only transponders at this specific location can receive both quadrature components properly, thereby achieving localization without significantly increasing overall system complexity.
2Length of stationary object
If transmission power is increased to extend detection range, then the reading distance is improved, but multiple scattering and echoes increase causing localization accuracy to deteriorate
Solution Approach 1:
Instead of uniformly increasing transmission power across the entire detection area, the patent concentrates the transmission energy locally by using two antennas spaced apart. The quadrature amplitude modulation ensures that the transmission signal is effectively confined to a central plane region, providing sufficient power for extended reading distance while limiting the spread to reduce multiple scattering and echoes.
3Device complexity
If conventional RFID reading is used on conveyor systems, then the system simplicity is maintained, but assignment accuracy deteriorates due to large detection area and multiple errors
Solution Approach 1:
The patent employs dynamic quadrature amplitude modulation where the transmission signal varies in phase between the two antennas. This dynamic signal structure enables the system to adaptively control the transmission pattern, ensuring that only transponders in the central plane can properly receive and respond to the signal, thereby improving assignment accuracy while maintaining relative system simplicity.
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 enhances the spatial resolution and accuracy of RFID transponder assignment, reducing errors and ambiguities by ensuring only one transponder can transmit from the central plane, facilitating precise object identification in logistics.
Implementation Method 1
A transmission unit (20, 22) transmits a quadrature amplitude modulated transmission signal, i.e. with an in-phase component (I component) and a quadrature component (Q component), to the transponder
Implementation Method 2
RFID information of a frequency in a baseband is modulated onto a carrier signal by backscatter modulation
Data Source
Figure 1~2
AI summary
The invention relates to an RFID reading device according to the invention for reading RFID information from an RFID transponder and to a reading and assignment method. The reading device is stationary and mounted on a conveyor system. The RFID information is read by generating a transponder signal during a reading process. For this purpose, RFID information of a frequency in a baseband is modulated onto a carrier signal by backscatter modulation. A transmitter unit sends a quadrature amplitude modulated transmission signal, i.e., with an in-phase component (I component) and a quadrature component (Q component), to the transponder, and a receiver unit receives the transponder signal from the RFID transponder. An evaluation unit reads the RFID information from the transponder signal.According to the invention, the transmitting unit has two transmitting antennas spaced apart in the conveying direction, wherein the transmitting signal of one transmitting antenna represents the in-phase component and the transmitting signal of the other transmitting antenna represents the quadrature component of the quadrature amplitude modulated transmitting signal, so that when the in-phase and quadrature components are emitted, they are superimposed additively in a plane extending transversely over the conveying device to form the complete quadrature amplitude modulated transmitting signal.