Ultrasonic Measurement Device Interference Removal via Code Division
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Solution Overview
Problem
Ultrasonic measurement devices face challenges in accurately measuring propagation distance and direction in environments with multiple devices due to interference from overlapping ultrasonic waves, where existing methods are inadequate in handling significant amplitude variations and noise from relative movement between devices and objects.
Innovation Solution
The method involves receiving and de-spreading ultrasonic waves with different codes, determining amplitude ratios, extracting interfering signals based on threshold values, and removing them to produce clear de-spread signals for accurate distance and direction calculation, using a storage-based approach to optimize S/N ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ultrasonic waves are transmitted simultaneously from multiple ultrasonic measurement devices, then the productivity of the system is improved, but the measurement precision deteriorates due to interference between ultrasonic waves
Solution Approach 1:
The patent applies spread spectrum modulation to ultrasonic waves, transforming the transmission parameters by modulating the ultrasonic carrier wave with pseudo-random binary sequences. This allows multiple devices to transmit simultaneously without interference, as each device's signal is distinguished by its unique code rather than time slot, resolving the contradiction between simultaneous transmission capability and measurement accuracy
Solution Approach 2:
The patent introduces code division as an intermediary mechanism to separate multiple ultrasonic signals. By assigning unique spreading codes to each device and using correlation detection at the receiver, the system can distinguish between simultaneous transmissions from different devices, enabling both high productivity and maintained measurement precision
2Measurement precision
If time division transmission is used to prevent interference between ultrasonic waves, then the measurement precision is improved, but the productivity of the system deteriorates due to sequential operation
Solution Approach 1:
The patent employs periodic spreading codes (M-sequences) that repeat at regular intervals. This periodic structure enables the receiver to identify and correlate with the transmitted code patterns, allowing simultaneous transmissions to be distinguished through code synchronization rather than time division, thus maintaining precision while improving productivity
Solution Approach 2:
By changing from time-based separation to code-based separation, the system transforms the fundamental parameter used for signal differentiation. This allows multiple devices to operate simultaneously with unique codes, eliminating the productivity limitation of sequential time division while maintaining measurement accuracy through code correlation
3Adaptability or versatility
If pseudo-random signals with different codes are used for ultrasonic wave transmission, then the adaptability of the system is improved, but the device complexity increases due to encoding and decoding requirements
Solution Approach 1:
The patent uses identical hardware configurations for all ultrasonic measurement devices, with each device copying the same transmitter and receiver design. The only differentiation is the assigned spreading code, which simplifies manufacturing and reduces per-device complexity while maintaining multi-device adaptability through code diversity
Solution Approach 2:
The ultrasonic measurement device is designed with universal functionality to handle both transmission and reception of spread spectrum signals. The same device can transmit with its assigned code and receive signals from any other device in the network, reducing overall system complexity through functional consolidation while maintaining high adaptability
4Reliability
If M-sequence pseudo-random signals are used for ultrasonic wave transmission, then the reliability of measurement is improved, but the loss of information increases due to correlation noise from overlapping signals
Solution Approach 1:
The patent applies correlation detection to extract the intended signal from the composite received signal. By correlating the received signal with the known spreading code, the receiver extracts the desired ultrasonic wave information while suppressing interference from other codes, thus maintaining reliability without significant information loss
Solution Approach 2:
The patent transforms the harmful effect of overlapping signals into a beneficial feature. The unique correlation properties of M-sequences cause interfering signals to appear as low-level noise rather than coherent interference, and the spreading code structure actually enhances the signal-to-noise ratio through processing gain, converting potential harm into measurement reliability
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 precise measurement of propagation distance and direction by effectively removing interference, maintaining high S/N ratios, and adapting to varying environmental conditions.
Implementation Method 1
An ultrasonic measurement device includes a wave-transmitter for transmitting an ultrasonic wave and a wave-receiver for receiving an ultrasonic wave
Data Source
AI summary
An ultrasonic measurement method, including: receiving a plurality of ultrasonic waves that have been spectrum-spread with different codes by first and second wave-receivers; de-spreading the first and second receive signals respectively with a selected code and a non-selected code; obtaining an amplitude ratio between the produced selected de-spread signal and the non-selected de-spread signal; determining a threshold value based on the amplitude ratio; extracting a signal having an amplitude greater than or equal to the threshold value from the non-selected de-spread signal to thereby produce an interfering signal; spreading the interfering signal with a corresponding non-selected code and then removing the interfering signal from the first and second receive signals to thereby produce first and second receive signals from which the interfering signal has been removed; de-spreading the first and second receive signals from which the interfering signal has been removed each with the selected code to thereby obtain first and second de-spread signals from which the interfering signal has been removed; and calculating the propagation distance and the propagation direction of the selected ultrasonic wave based on points in time at which the first and second de-spread signals arrive at the first and second wave-receivers.