| Abstract [eng] |
The aim of this final master's project is to analyze the possibilities of implementing a wideband ultrasound generator using signal generation and processing methods in standard microprocessors. The project objectives are as follows: examine existing real-time signal generation and processing methods used in standard microprocessors, describe the algorithm for generating sinusoidal signals in a standard processor, present a mathematical model of a wideband ultrasound generator with an amplifier operating in resonant mode, provide amplitude-frequency characteristics (ADCH) of the wideband ultrasound generator, compare the results of modeling the amplitude-frequency characteristics with experimental measurements. The following software tools were used in the project: Arduino IDE, LTspice, REW, MATLAB, SigmaStudio. The analytical part includes a review of scientific literature on signal generation and processing methods used in standard microprocessors. In the experimental part, a sinusoidal signal generator was created using a standard microprocessor (ESP32). A model of a wideband ultrasound generator with a Class D amplifier and an LC filter at the output was developed for testing purposes. In the research part, experiments were conducted with a real wideband ultrasound generator that uses 16 coils. The results of the experiments were compared with the modeling results. Results of the project: 1. The analysis of scientific literature revealed that various algorithms and transformations are used for real-time signal processing and generation in digital microprocessors, such as FFT, DFT, SWFT, DTFT, CZT, DWT, Fourier transformation, and filters like high-pass, low-pass, bandpass, infinite and finite impulse response filters, which facilitate signal processing. Signal generation relies on various libraries and internal microprocessor registers, allowing for high frequencies (90 kHz and above). 2. By implementing and testing the algorithm for a sinusoidal signal generator on a standard processor (ESP32), a signal ranging from 1 Hz to 90 kHz was obtained. Beyond 90 kHz, the sine waveform starts to deform due to the limited performance of the integrated digital-to-analog converter in the controller. 3. By developing a mathematical model of a wideband ultrasound generator with a resonant mode amplifier, and calculating the inductance values (1895 µH, 1585 µH, 1345 µH, 1105 µH, 900 µH, 725 µH, 582 µH, 460 µH, 370 µH, 303 µH, 253 µH, 212 µH, 183 µH, 159 µH, 139 µH, 123 µH) for the LC filter at the output of the Class D amplifier, resonance amplification across the entire specified frequency range (20–85 kHz) was achieved. 4. By measuring the amplitude-frequency characteristics (ADCH) of the wideband ultrasound generator, it was determined that the theoretical measurements allow for resonance amplification across the entire frequency range (20–85 kHz), and the unevenness of the characteristics does not exceed 6 dB (4.18 dB during the first test, 4.1 dB during the second test), which is an acceptable value in audio engineering. 5. Comparing the experimental measurements of the amplitude-frequency characteristics (ADCH) of the wideband ultrasound generator with the modeling results, a strong correlation was found between the tests and theoretical calculations (0.7998 for the first test, 0.7807 for the second test). |
