Ultrasonic Measuring Apparatus Interference Cancellation
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Solution Overview
Problem
In ultrasonic measuring systems, interference from multiple ultrasonic waves encoded with different M-sequence discrete spread spectrum codes leads to decreased peak correlation values, making it difficult to accurately determine the propagation time and measure distances, especially when overlap between signals is significant, and predicting the effect of interfering waves is challenging due to varied environments.
Innovation Solution
The method involves receiving ultrasonic waves at multiple receivers, despreading signals with codes other than the desired one to extract interference signals, spreading and removing these signals, and then despreading with the desired code to calculate maximum correlation values, allowing for accurate estimation of propagation distance and azimuth without relying on propagation path profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple ultrasonic measuring apparatuses transmit ultrasonic signals simultaneously using spread spectrum codes, then the system can operate in parallel without time coordination, but the ultrasonic signals interfere with each other causing decreased peak correlation values and measurement errors
Solution Approach 1:
The patent extracts and removes interference signals from the received ultrasonic signal by despreading with other apparatuses' codes and identifying interference components. This allows the desired signal to be separated from the mixed signals, maintaining measurement precision while enabling parallel operations of multiple apparatuses
Solution Approach 2:
The patent converts the harmful interference signals into useful information by despreading them with their respective codes to identify and characterize the interference. This extracted interference information is then used to cancel out the interference effects, turning the harmful multi-apparatus interference into a manageable and correctable problem
2Reliability
If ultrasonic signals are encoded with different M-sequence codes to distinguish between apparatuses, then signal identification is improved, but the overlap between signals causes decreased peak correlation values making it difficult to determine propagation time
Solution Approach 1:
The patent employs feedback mechanisms where the received signal is processed through multiple despreading operations with different codes, and the results are used to iteratively improve the interference cancellation. This feedback loop allows continuous refinement of the signal separation, maintaining both identification reliability and measurement precision
Solution Approach 2:
The patent performs preliminary despreading operations with codes of other apparatuses before final signal extraction. This preliminary action identifies and isolates interference components early in the processing chain, preventing them from degrading the peak correlation values of the desired signal
3Measurement precision
If time-division transmission is used to avoid signal interference, then measurement accuracy is maintained, but it requires coordination between apparatuses which is difficult to achieve in independent systems
Solution Approach 1:
Each ultrasonic measuring apparatus independently performs self-service by despreading received signals with all known codes to identify its own signal and cancel interference. This self-service approach eliminates the need for inter-apparatus timing coordination while maintaining measurement accuracy, as each apparatus autonomously manages its own signal extraction
4Measurement precision
If interference cancellation is performed by despreading with multiple codes, then interference signals can be identified and removed, but the processing complexity increases significantly
Solution Approach 1:
The patent segments the signal processing into distinct stages: despreading with each possible code to identify interference components, extracting interference signals based on threshold criteria, and then removing these identified interferences. This segmentation makes the complex interference cancellation process more manageable and efficient
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 effectively cancels mutual interference in ultrasonic measuring systems, enabling accurate distance measurement even in environments with multiple ultrasonic devices, without requiring prior knowledge of the propagation path profiles, thus improving measurement precision across various settings.
Implementation Method 1
a transmitter 8 to send out an ultrasonic wave and a receiver 9 to receive the ultrasonic wave
Implementation Method 2
estimate the distance between an object and the ultrasonic measuring apparatus itself by the amount of time it has taken for an ultrasonic wave, sent out from the transmitter, to reach the object, get reflected by the object and then get received at the receiver
Implementation Method 3
the correlation between the received signal and the pseudo random code is calculated, thereby identifying a signal component of the ultrasonic wave transmitted by the ultrasonic measuring apparatus
Data Source
AI summary
An ultrasonic measuring method includes the steps of: receiving ultrasonic waves, which have been transmitted by a spread spectrum technique using mutually different codes, at first and second receivers, thereby generating first and second received signals, respectively; generating interference signals, of which the amplitudes are equal to or greater than respective threshold values, from the first and second received signals that have been despread with a code that has been used to spread any of the ultrasonic waves other than a desired one; removing the spread interference signals from the first and second received signals; calculating maximum correlation values between the first and second despread received signals for the respective threshold values; selecting one of the threshold values, at which the greatest one of the maximum correlation values has been obtained, as a threshold value for canceling interference; and calculating the propagation distance or propagation azimuth of the desired ultrasonic wave by the amount of time it has taken for the first and second received signals to arrive.