A novel spatial interference suppression algorithm has been proposed to address the challenges of conventional beamforming(CBF) methods, such as wide main lobes, high sidelobes, low resolution, and inadequate interference suppression capability. The algorithm combines the reconstruction of covariance matrices with functional beamforming method. Firstly, virtual interference sources are artificially introduced in the interference area to reconstruct the covariance matrix with added noise, leveraging the principle of automatic nulling in Minimum Variance Distortionless Response (MVDR), which suppresses strong interferences effectively. Subsequently, the reconstructed covariance matrix is subjected to eigenvalue decomposition and integrated with the functional beamforming approach. The eigenvalue matrix is raised to the power of v-1 to obtain refined weight vectors, which are then employed for beamforming. The beamformed results are raised to the power of v to restore the information of source distribution, thereby enhancing beam resolution. The algorithm demonstrates its capability to effectively suppress sidelobe interference in intense noise environments and achieve high-resolution beamforming through simulation and experimental validation.
KEYWORDS: Transducers, Ultrasonics, Time metrology, Optimization (mathematics), Systems modeling, Mathematical modeling, Chemical elements, Nonlinear optics, Radar, Data modeling
The SBF (short baseline framework) is commonly used in ultrasonic parameter measurement, and ToF (time of flight) of which is essential in sound velocimeter and other applications. Different from general ultrasonic measurement research work mainly on ToF estimation method, this paper studies the criterion and way of establishing the optimum signal. For given transducers, the optimum signal achieves the most accuracy, and the pulsed form signal is stress here. To find the optimum signal, firstly, the transmitting is illustrated in its Fourier series form, which establishes the waveform, and the problem of transmitting wave design is converted into finding the optimum Fourier series. Secondly, as the accuracy is in inverse ratio to the sensitivity of the measured signal, the problem of finding the optimum Fourier series is equivalent to maximizing the sensitivity, resulting into a form of nonlinear optimization problem. For optimum parameter derivation, the sensitivity is expressed in form of vector and matrix, and a novel method based on SCHUR decomposition on the matrix is proposed to solve the nonlinear optimization problem. Simulation with a typical narrowband system testifies that the proposed method can synthesize transmitting waveform efficiently.
KEYWORDS: Transducers, Temperature metrology, Calibration, Acoustics, Electronics, Signal processing, Prototyping, Technetium, Field programmable gate arrays, Signal detection
The short baseline framework is commonly used in ultrasonic parameter measurement, and ToF (time of flight) of which is essential in sound velocimeter and other applications. Different from conventional steady-state and transient methods, this paper proposed a new method using DSSS (Direct Sequence Spread Spectrum) signal to extract the ToF. DSSS signal possesses excellent auto-correlation features, thus it does not need to adjust path-length or the acoustic frequency, nor avoid the impact of the multiple echoes. The DSSS signal and measurement system are modeled and the detailed theoretical process of ToF estimation is derived to demonstrate the measurement principles, and the principles of echoesresistance are analyzed. Measurement experiments are carried out using distilled water at ambient pressure with temperature ranging from 19°C to 30°C. The test results indicate that the relative precision of ToF is in bounds of 2 ppm and the bias of sound speed derived is within 0.06m/s compared to Del Grosso's equation.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.