Dynamic Compensation Filter for Sonar Absorption Loss
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Wideband energy transmission systems, such as sonar systems, face challenges in maintaining spectral flatness due to frequency-dependent absorption loss in lossy media like water, which degrades pulse compression and range-wise resolution, especially as signals propagate over longer distances.
Innovation Solution
A compensation filter with a digital filter and electronic memory that adjusts filter coefficients in real-time to compensate for absorption loss, ensuring spectral flatness across the received signal by applying different filter transfer characteristics at different times, effectively flattening the frequency spectrum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If wideband transmissions are used to improve resolution, then range-wise resolution and azimuthal resolution are improved, but frequency-dependent absorption loss degrades system performance
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the filter transfer function parameters (coefficients) based on the received signal characteristics. The filter coefficients are modified in real-time to compensate for frequency-dependent absorption loss, allowing the system to maintain spectral flatness across wideband transmissions while improving range-wise resolution.
Solution Approach 2:
The patent implements dynamics by making the filter transfer function time-varying rather than static. The filter adapts its characteristics during the received signal duration, changing its frequency response to counteract the cumulative absorption loss that varies with propagation distance and frequency, thereby maintaining optimal performance across the wideband spectrum.
2Measurement precision
If higher bandwidth pulses are used to increase range-wise resolution, then resolution is improved, but absorption loss varies across the band and degrades pulse compression
Solution Approach 1:
The patent changes the filter parameters dynamically during pulse compression to compensate for the varying absorption loss across the bandwidth. By adjusting the transfer function coefficients in real-time, the filter equalizes the frequency response, ensuring that all frequency components are properly compressed regardless of their differential absorption, thus maintaining reliable pulse compression performance.
Solution Approach 2:
The patent converts the harmful effect of frequency-dependent absorption loss into a beneficial compensation mechanism. By measuring the actual absorption characteristics through the received signal and using this information to adjust the filter transfer function, the system transforms the degradation caused by absorption into an opportunity for precise equalization and improved pulse compression.
3Device complexity
If a static filter is used for pulse compression, then system complexity is reduced, but absorption loss causes spectral coloration and degrades resolution
Solution Approach 1:
The patent transitions from a static filter to a dynamic, time-varying filter structure. The filter transfer function is continuously adjusted during the received signal duration to compensate for absorption loss, maintaining spectral flatness. This dynamic approach, while increasing complexity, is justified by the significant improvement in resolution and the relatively simple implementation using adaptive coefficient adjustment.
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 allows for improved pulse compression and maintained range-wise resolution by compensating for absorption loss, ensuring the sonar system can recover a fully pulse-compressed signal even over long ranges, enhancing detection and classification capabilities.
Implementation Method 1
frequency dependent loss characteristic... absorption loss can be highly dependent on the frequency of the energy... intensity of the sound is reduced with range due to heating of the medium associated with molecular action of the medium
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A compensation filter is operable to receive a received signal in response to a transmitted signal, the received signal having a time duration. The compensation filter is operable to generate a compensated signal. The compensation filter changes shape of an associated transfer function during the time duration of the received signal to result in the compensated signal having an improved spectral flatness throughout the time duration of the received signal. The compensation filter can be used in a sonar system. A method, which can be used in a sonar system, uses the compensation filter.