Coherent Echo Summation for Wireless Sensor SNR
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Solution Overview
Problem
Passive wireless sensor platforms face limitations in reading range and accuracy due to low signal-to-noise ratio (SNR) caused by multi-path propagation and interference from nearby antennas, particularly in the 2.4 GHz-2.5 GHz frequency range.
Innovation Solution
The technique involves identifying and summing multiple echoes coherently, which share unique characteristics specific to the wireless sensor node, to improve the SNR by time delaying and phase shifting the echoes to align them in time and phase, thereby enhancing the determination of environmental or physical conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multiple interrogation pulses are transmitted to the sensor node, then more echoes are available for analysis, but the signal-to-noise ratio deteriorates due to multi-path propagation and interference
Solution Approach 1:
The patent combines multiple echoes into a single coherent response signal by summing them together after time-delaying and phase-shifting. This merging process integrates the information from multiple interrogation pulses while maintaining signal integrity, resolving the contradiction by transforming multiple individual echoes into one enhanced signal that improves SNR rather than deteriorating it.
Solution Approach 2:
The patent applies time-delaying and phase-shifting operations to the echoes before summation. These preliminary actions align the echoes in time and phase, ensuring that when they are summed, their amplitudes constructively interfere. This preliminary processing prepares the echoes for coherent summation, transforming what would be noisy individual signals into a coherent signal with improved SNR.
2Device complexity
If echoes are summed incoherently, then the processing is simpler, but the signal amplitude does not increase and SNR improvement is limited
Solution Approach 1:
The patent applies time-delaying and phase-shifting operations to align echoes before summation. These preliminary actions ensure that when the echoes are summed, their phases are matched, allowing for constructive interference and amplitude enhancement. This preliminary processing is what enables coherent summation to work, transforming simple arithmetic addition into a process that leverages phase alignment for signal enhancement.
Solution Approach 2:
The patent changes the temporal and phase parameters of the echoes through time-delaying and phase-shifting operations. By adjusting these parameters, the system transforms the echoes into a coherent state where their phases are aligned. This parameter transformation enables the echoes to add constructively, increasing the signal amplitude beyond what would be achieved through simple incoherent summation.
3Length of stationary object
If the reading range is increased, then more distant sensor nodes can be detected, but the signal-to-noise ratio decreases due to attenuation
Solution Approach 1:
The patent combines multiple echoes from distant sensor nodes into a single coherent response signal. By summing the echoes coherently after time-delaying and phase-shifting, the system enhances the signal amplitude, compensating for the attenuation that occurs over long distances. This merging process allows the system to maintain adequate SNR even when detecting distant nodes, effectively extending the reading range.
Solution Approach 2:
The patent continuously processes multiple echoes through time-delaying, phase-shifting, and summation operations. This continuous processing of echo signals allows the system to accumulate signal energy over time, maintaining a coherent response signal even from distant nodes. The continuous action of aligning and summing echoes ensures that the useful signal information is preserved and enhanced throughout the measurement process.
Data Source
AI summary
Described herein are techniques for improving the signal-to-noise ratio of a wireless sensor platform. The device that interrogates a wireless sensor node (an interrogator) may be configured to determine the quantity to be measured by extracting information from multiple echoes produced in response to multiple interrogation pulses or produced due to multi-path propagation. Although different echoes may have been transformed to different extents, the echoes may share unique characteristics that are specific to the wireless sensor node that produced them. Accordingly, the SNR may be improved by keeping only portions of the received signal that exhibit such characteristics. The SNR may be further improved by summing the echoes together. In some embodiments, the echoes may be summed together in a coherent fashion, thereby producing an echo having an amplitude greater than the amplitude of each of the received echoes.