Full-Duplex Analog Relay for RFID Signal Extension
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Solution Overview
Problem
Conventional passive RFID systems have limited communication range and suffer from destructive interference and orientation misalignment, leading to a significant percentage of RFID tags remaining in blind spots, making inventory control in warehouses inefficient.
Innovation Solution
An analog relay is introduced, which is full-duplex and bi-directional, capable of extending the communication range by providing power to passive RFID tags from a distance, while preserving phase and timing of the signals, and reducing self-interference, allowing for effective localization of tags even in non-line-of-sight environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a conventional reader transmits a continuous wave to power passive RFID tags, then the tags can be powered up and communicate, but the communication range is limited to about 3-6 meters due to power delivery constraints
Solution Approach 1:
An analog relay is introduced as an intermediary device between the reader and the passive RFID tag. The relay receives the continuous wave from the reader, amplifies it, and retransmits it to the tag, enabling power delivery over extended distances beyond the conventional 3-6 meter limit while maintaining the ability to power and communicate with tags at longer ranges
2Reliability
If readers are deployed densely throughout a warehouse to eliminate blind spots, then tag detection coverage improves, but the system complexity and infrastructure cost increase significantly
Solution Approach 1:
Instead of deploying multiple readers throughout the warehouse, a single reader combined with mobile analog relays is used. The relays act as intermediaries that extend the reader's reach throughout the warehouse space, eliminating blind spots without requiring a dense infrastructure of multiple readers, thus reducing system complexity while maintaining reliable tag detection coverage
Solution Approach 2:
The system employs mobile relays that can be moved to different locations within the warehouse rather than deploying fixed readers throughout. This dynamic approach allows a single reader to serve multiple areas sequentially, reducing the need for extensive permanent infrastructure while maintaining comprehensive tag detection coverage
3Length of stationary object
If the relay transmits and receives signals simultaneously in the same frequency band, then full-duplex operation extends communication range, but self-interference from the relay's own transmitted signal degrades reception
Solution Approach 1:
The system employs periodic switching between transmission and reception modes in the relay, using time-division techniques to separate the full-duplex operation. By rapidly alternating between transmitting amplified signals to tags and receiving signals from tags in different time slots, the relay achieves extended communication range while minimizing self-interference through periodic action rather than continuous simultaneous operation
Data Source
AI summary
A method may comprise relaying a wireless signal via a bi-directional, full-duplex relay. The relay may comprise an analog uplink relay and an analog downlink relay, and may relay signals between a transmitter and a backscatter node. The spectrum of the downlink signal transmitted by the downlink relay may be different than the spectrum of the uplink signal received by the uplink relay. Filtering may attenuate leakage from the downlink relay to the uplink relay, and vice versa. The uplink relay may create a phase offset that is opposite in sign and substantially equal in magnitude to the phase offset created by the downlink relay. The downlink and uplink relays, taken together, may create a substantially constant net phase offset. The full-duplex relay may be housed in a vehicle that moves, and may be used to determine spatial coordinates of backscatter sources that are located in the relay's environment.