Golay Code Ultrasound Doppler Sidelobe Filtering
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Solution Overview
Problem
The ultrasound Doppler detection system with Golay coded excitation struggles to effectively inhibit sidelobe signals when observing fast-moving objects, limiting its application to only slow-moving objects due to weakened sidelobe inhibition and resulting residual sidelobe signals.
Innovation Solution
The method involves transmitting two Golay coded signals every pulse repetition interval, followed by low-pass filtering in the Doppler frequency domain of slow-time to filter out sidelobes, allowing for the detection of both slow and fast-moving objects by maintaining the strength of mainlobes and resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Golay code is used for code excitation in ultrasound Doppler detection, then the energy of mainlobe is improved and sidelobe signals are inhibited, but the ability to inhibit sidelobe signals is greatly weakened when observing fast-moving objects, resulting in residual sidelobe signals that affect detection precision
Solution Approach 1:
The patent segments the Doppler frequency spectrum into different components (mainlobe and sidelobe) and applies selective filtering to separate them. By dividing the frequency domain and applying a filter with specific cut-off frequency, the system can independently process mainlobe signals (for detecting fast-moving objects) while removing sidelobe artifacts, thus resolving the contradiction between detection precision and sidelobe inhibition.
Solution Approach 2:
The patent extracts and removes the harmful sidelobe signals from the processed ultrasound data by applying a filter in the Doppler frequency domain. The filter is designed to pass the mainlobe frequencies while blocking the sidelobe frequencies, effectively taking out the harmful components that cause artifacts and affect detection precision for fast-moving objects.
2Measurement precision
If code excitation is used to improve SNR, then the SNR and resolution of Doppler detection are improved, but sidelobe signals cause artifacts that affect the result of Doppler detection
Solution Approach 1:
The patent converts the harmful sidelobe artifacts into a manageable problem by using the known frequency characteristics of sidelobes (which are predictable and located at specific frequencies) to design a filter that selectively removes them. The harmful sidelobe signals, instead of being accepted as unavoidable, are used to inform the filter design, transforming them from a problem into a solution for improving signal quality.
Solution Approach 2:
The patent introduces a filter as an intermediary component between the code excitation system and the final Doppler detection output. This filter mediates the interaction by allowing the beneficial mainlobe signals to pass through while blocking the harmful sidelobe artifacts, thus protecting the detection system from the harmful effects of code excitation without sacrificing its benefits.
3Adaptability or versatility
If Golay code is applied to Doppler detection, then the system can detect slow-moving objects, but it cannot effectively detect fast-moving objects such as high speed moving blood flow due to weakened sidelobe inhibition
Solution Approach 1:
The patent makes the system adaptive by dynamically adjusting the filter parameters based on the detected Doppler frequency range. The filter cut-off frequency is set to a quarter of the pulse repetition frequency, which allows the system to adapt to different flow speeds. This dynamic adjustment enables the system to maintain effective sidelobe inhibition across both slow and fast moving objects, expanding the detection range while preserving measurement precision.
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 the use of Golay code in Doppler detection systems for high-speed blood flow, preserving the precision of flow information such as speed and direction, by filtering out sidelobes and enhancing the Signal-to-Noise Ratio.
Implementation Method 1
the Doppler effect is utilized to determine whether a certain structure (usually blood flow) moves toward or away from a probe, to calculate its relative speed
Implementation Method 2
Coded waves are designed with longer transmission time and averagely low sound pressure. A result of short and high sound pressure is obtained after the coded waves are received, decoded and compressed
Implementation Method 3
a filter with a cut-off frequency of a quarter of a pulse repetition frequency (PRF) is designed in a Doppler frequency domain of a slow-time; and the filter filters out reflected Golay coded signals in slow-time
Implementation Method 4
The signals are received at the receiving end and compressed via corresponding matched filter so as to remove sidelobe and enhance the strength of mainlobe
Data Source
AI summary
An ultrasound Doppler detection method with Golay-encoded excitation is used to obtain the flow information of a moving object. A first Golay code is transmitted to the moving object for a reflection signal of the first Golay code and a second Golay code is transmitted to the moving object for a reflection signal of the second Golay code after waiting for a pulse repetition interval. The received reflection signals are match-filtered to generate a first and a second wave. The above steps are repeated several times. Then, a slow-time filter in the Doppler frequency domain whose low-pass cut-off frequency is a quarter of the pulse repetition frequency is used to filter out the first sidelobes of the first waves and the second sidelobes of the second waves. Finally, the ultrasound Doppler detection is formed according to the first mainlobes of the first waves and the second mainlobes of the second waves.