Full-Duplex Backscatter Self-Interference Cancellation
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Solution Overview
Problem
Current RFID tags have limited usefulness due to poor receive sensitivity, restricting their operation to short distances and hindering their application in scenarios requiring communication beyond this range.
Innovation Solution
A full-duplex backscatter system is developed, incorporating a transmitter, receiver, tunable impedance network, and microcontroller to achieve significant self-interference cancellation, enabling long-range communication with backscatter tags using a single antenna and reducing signal power by up to 78 dB in the analog domain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single antenna is used for both transmission and reception in a backscatter system, then device complexity is reduced and integration is simplified, but self-interference from the transmitted carrier signal degrades receive sensitivity and limits communication range
Solution Approach 1:
The patent segments the transmitted carrier signal path by using a coupler to separate the forward path (transmitter to antenna) from the reverse path (antenna to receiver). This segmentation allows the receiver to be isolated from the direct carrier signal while still enabling the antenna to transmit, thus reducing self-interference without requiring separate transmit and receive antennas.
Solution Approach 2:
The coupler acts as an intermediary device that manages signal flow between the transmitter, antenna, and receiver. It provides isolation between the transmitter and receiver while allowing the antenna to simultaneously serve both transmission and reception functions, thereby resolving the self-interference problem without increasing overall system complexity.
2Length of stationary object
If the transmitted carrier signal power is increased to extend communication range, then long-range communication is enabled, but self-interference at the receiver increases and degrades signal detection capability
Solution Approach 1:
The patent converts the harmful self-interference effect into a beneficial isolation mechanism. By using the coupler to deliberately reflect or isolate the carrier signal path, the system allows high-power transmission while protecting the receiver. The same signal path that causes interference is managed through the coupler to prevent it from reaching the receiver, thus enabling long-range communication without degradation of signal detection.
3Device complexity
If conventional RFID tags with poor receive sensitivity are used, then device simplicity and low cost are maintained, but communication is limited to short distances
Solution Approach 1:
The patent merges the transmitter and receiver functions into a single integrated backscatter reader unit that shares a common antenna. This consolidation allows the system to achieve long-range communication through coordinated transmit-receive operations and self-interference management, compensating for the simple, passive structure of the backscatter tags while extending operating distance beyond conventional RFID limitations.
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
The system allows for reliable communication with backscatter tags at distances of up to 300 feet, even in obstructed environments, and can be integrated into portable devices or drones, enhancing the range and usability of RFID systems.
Implementation Method 1
a tunable impedance network configured to reflect the single tone carrier to form a reflected signal
Implementation Method 2
backscatter data packets from one or more backscatter tags positioned in a real-world environment
Data Source
AI summary
Systems and methods for a full-duplex backscatter system. An example method includes outputting, via a transmitter of the backscatter system, a single tone carrier for transmission via an antenna of the backscatter system. A tunable impedance network is tuned via a microcontroller to reduce self-interference associated with the signal tone carrier by at least a threshold level, with the tunable impedance network including passive elements which are configured to be tuned, and with the self-interference reduction by the threshold level being in the analog domain. Backscatter data packets are received via a receiver from backscatter tags, with the backscatter data packets being associated with an offset frequency and are decoded by the receiver.