RFID Interrogator Frequency Hopping Matrix Design
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Solution Overview
Problem
In RFID systems, frequency hopping patterns that do not follow the (prime number)−1 format can lead to interference between adjacent interrogators, as they may continuously use the same frequency for a long period, especially when the number of frequencies used is not a prime number minus one.
Innovation Solution
The implementation of an interrogator that uses a frequency hopping pattern setting mechanism to ensure all integers from 1 to the number of frequencies appear only once, with additional offsets applied to elements of a circulant matrix, allowing for the generation of frequency hopping codes that prevent continuous use of the same frequency, thereby minimizing interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a frequency hopping pattern using (prime number)−1 frequencies is used, then interference between adjacent interrogators is reduced, but not all allocated frequencies can be used efficiently
Solution Approach 1:
The patent changes the parameter of frequency pattern structure from traditional (prime number)−1 format to a matrix-based format where all integers from 1 to the number of frequencies appear only once. This allows flexible adaptation to different frequency allocations (e.g., 9 frequencies in Japan) while maintaining interference reduction through systematic distribution of frequency usage across time slots.
Solution Approach 2:
The frequency hopping pattern is segmented into a matrix structure with rows and columns, where each element represents a frequency index. This segmentation allows systematic control of frequency assignment, ensuring that adjacent interrogators using phase-shifted patterns will not continuously collide on the same frequency, thus reducing interference while accommodating any number of frequencies.
2Adaptability or versatility
If adjacent interrogators use the same frequency hopping pattern with phase shifting, then frequency diversity is achieved, but they may continuously use the same frequency at the same time causing interference
Solution Approach 1:
The patent introduces a temporal dimension to frequency assignment by using a matrix structure where frequency selection depends on both the row (base pattern) and column (time slot). This dimensional approach ensures that even with phase shifting, adjacent interrogators will not continuously collide because the frequency assignment evolves systematically over time slots, transforming a 1D frequency sequence into a 2D matrix-based hopping pattern.
3Ease of manufacture
If the number of frequencies is limited to (prime number)−1, then a systematic frequency hopping pattern can be formed, but the pattern cannot adapt to regional frequency allocations
Solution Approach 1:
The patent creates a universal frequency hopping pattern matrix that can function with any number of frequencies by using 1-based indexing for all frequency elements. The matrix structure with offset addition is universally applicable whether there are 5, 9, or any other number of frequencies, making the system adaptable to different regional allocations (e.g., 952-954 MHz in Japan) while maintaining systematic pattern formation through the same mathematical approach.
Data Source
AI summary
A hopping pattern setting section sets, as a frequency hopping pattern code, elements of a matrix in which all integers of “1” to “the number of frequencies to be used” appear only once and which is obtained by adding, as an offset, any one of integers of “0” to “(the number of frequencies to be used)−1” to each of elements of a matrix obtained by excluding integers larger than the number of frequencies to be used from a matrix in which all integers of “1” to “(prime number larger than the number of frequencies to be used)−1” appear only once. A frequency oscillation section converts the frequency hopping pattern code into the frequencies to be used to output unmodulated signals of the frequencies to a transmission section and a reception section.