SAW Tag Orthogonal Frequency Coding for Multi-Sensor Identification
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Solution Overview
Problem
In multi-sensor environments, existing SAW sensors face challenges in simultaneously identifying and transmitting sensor information effectively, as they require advanced coding techniques to differentiate between multiple sensors and enhance interrogation power.
Innovation Solution
The implementation of orthogonal frequency coding (OFC) for SAW devices, which includes a transceiver with reflectors producing orthogonal frequencies, allowing for wide bandwidth, chirp interrogation, frequency and binary coding per bit, reduced compressed pulse width, and secure coding, along with the addition of pseudo noise (PN) sequences for increased code diversity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If single carrier RF frequency is used for SAW sensor, then device simplicity is maintained, but multi-sensor identification capability is lost
Solution Approach 1:
The patent segments the single carrier frequency into multiple orthogonal frequency components (f1, f2, f3, f4) that are sequentially applied to the SAW sensor. Each frequency component carries a portion of the identification and sensing information, enabling multi-sensor differentiation while maintaining a relatively simple device architecture without requiring multiple physical oscillators.
2Reliability
If spread spectrum techniques are used for SAW sensor, then processing gain and interrogation power are enhanced, but device complexity increases
Solution Approach 1:
The patent changes the frequency parameter of the interrogation signal by applying a sequence of orthogonal frequencies (f1, f2, f3, f4) to the SAW sensor. This frequency modulation approach provides spread spectrum benefits including processing gain and enhanced interrogation power, while avoiding the need for complex spread spectrum coding hardware by using systematically generated orthogonal frequency components.
3Productivity
If orthogonal frequencies are used for M-ary FSK system, then communication capability is improved, but bandwidth requirements increase
Solution Approach 1:
The patent employs periodic application of orthogonal frequencies in a time-sequential manner (f1 at t1, f2 at t2, f3 at t3, f4 at t4) rather than simultaneous transmission. This periodic time-multiplexed approach enables M-ary communication capability while reducing the required simultaneous bandwidth compared to traditional parallel FSK systems, as only one frequency component is active at any given time.
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 enables unique sensor operation and identification in multi-sensor environments, providing enhanced processing gain, secure data transmission, and reduced intersymbol interference, while allowing for simultaneous sensing and tagging with increased power and security.
Implementation Method 1
surface acoustic wave (SAW) communication, tag and sensor application
Data Source
AI summary
A secure apparatus, system, device and method for coding surface acoustic wave identification tags and sensors to enable unique sensor operation and identification for a multi-sensor environment. In an embodiment, a pseudo noise sequence is applied to the orthogonally coded signal for increased security. An orthogonal frequency coding technique is applied to the SAW tag using periodic reflector gratings for responding to an orthogonal interrogation signal to transmit the sensor identification and sensed data. A transceiver interrogates the sensor with a stepped chirp corresponding to the orthogonal frequency coded chip frequency response, receives a response from the SAW device, applies an oppositely stepped chirp to the response and then uses matched filtering to produce a compressed pulse. The orthogonal frequency coding technique has an inherent advantage of processing gain, code division multiple access, spread spectrum and security.