RFID Phase-Based Ranging with Channel Hopping
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Solution Overview
Problem
Existing RFID systems face challenges in accurately determining the distance between an RFID reader and tag due to low location and ranging accuracy using Received Signal Strength Indicator (RSSI) and phase-based ranging (PBR) methods, which require multiple commands and decrease airtime for data communication.
Innovation Solution
Implementing phase-based ranging with channel hopping, where an RFID reader performs channel hopping between multiple carrier frequencies during a single transmission to an RFID tag, measuring phase changes at each frequency to estimate distance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase-based ranging (PBR) methods are used to improve distance estimation accuracy, then measurement precision is improved, but multiple commands are required which decreases airtime for data communication
Solution Approach 1:
The patent combines multiple phase measurements at different carrier frequencies into a single command exchange between reader and tag. The reader transmits a continuous carrier signal that hops across multiple frequencies, and the tag responds with a continuous backscatter signal, allowing the reader to collect multiple phase measurements during one communication interval rather than requiring separate commands for each measurement.
Solution Approach 2:
The patent uses continuous carrier signals and continuous backscatter signals instead of discrete pulsed measurements. The carrier signal continuously hops across multiple frequencies, and the tag continuously backscatters, enabling uninterrupted phase measurements across the frequency spectrum within a single command period, maximizing airtime efficiency.
2Measurement precision
If multiple phase measurements are taken at different carrier frequencies to improve distance estimation accuracy, then measurement precision is improved, but communication time increases
Solution Approach 1:
The patent implements dynamic frequency hopping where the carrier frequency changes continuously across multiple frequencies during a single command exchange. This dynamic approach allows the system to gather multiple phase measurements at different frequencies without extending the communication duration, as the frequency transitions occur seamlessly within the ongoing signal transmission.
Solution Approach 2:
The patent changes the carrier frequency parameter dynamically during the measurement process. By hopping across multiple carrier frequencies within a single command interval, the system obtains multiple phase measurements with different frequency parameters, improving distance estimation accuracy without proportionally increasing communication time.
3Device complexity
If RSSI method is used for ranging, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent implements a multi-functional ranging approach that combines phase-based measurements across multiple frequencies within a unified framework. The system performs both fine-grained phase measurements and coarse-grained frequency hopping in a single process, achieving high precision distance estimation while maintaining practical device complexity through integrated signal processing.
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
Enhances distance estimation accuracy and reduces communication time by obtaining multiple phase measurements in a single command, improving RFID system efficiency and accuracy.
Implementation Method 1
The tag or transponder reflects back a portion of the incident signal as a backscatter signal
Implementation Method 2
transmitting a continuous carrier signal to a Radio Frequency Identification (RFID) tag
Implementation Method 3
measuring a phase change in the backscatter signal to determine a distance between the RFID reader device and the RFID tag
Data Source
AI summary
Systems and techniques are provided for wireless communications. For example, a process can include determining a frequency hopping configuration corresponding to a plurality of frequency hops between a plurality of carrier frequencies, and transmitting a continuous carrier signal to a Radio Frequency Identification (RFID) tag, where the continuous carrier signal comprises a pilot tone transmitted on each respective carrier frequency of the plurality of carrier frequencies. A process can include receiving, from the RFID tag, a continuous backscatter signal including a corresponding reflection of the pilot tone transmitted on each respective carrier frequency of the plurality of carrier frequencies. A process can include determining an estimated distance from a wireless communication device to the RFID tag based on a plurality of measurements obtained from the continuous backscatter signal.