Fundamental frequency

About: Fundamental frequency is a research topic. Over the lifetime, 8941 publications have been published within this topic receiving 131583 citations.

Ultrasound imaging method and system for transmit signal generation for an ultrasonic imaging system capable of harmonic imaging

Abstract: An improvement to the method for harmonic imaging including the steps of (a) transmitting ultrasonic energy at a fundamental frequency and (b) receiving reflected ultrasonic energy at a harmonic of the fundamental frequency is provided. For the improvement, the transmitting step includes the step of transmitting a uni-polar waveform or a waveform characterized by an amplitude change rate of 8 or fewer times pre carrier cycle, said waveform comprising an envelope shape rising gradually to a respective maximum value and falling gradually from the respective maximum value.

Ultrasonic actuator driving unit and ultrasonic actuator driving method

Abstract: PROBLEM TO BE SOLVED: To provide an ultrasonic actuator driving unit which can drive an ultrasonic actuator, detecting the resonance frequency of its oscillator accurately while restraining manufacture cost, using a signal of a rectangular wave as a drive signal, and is consequently efficient, and in which the duration of a battery in the case that the battery is used as a power source is long, and a method of driving the ultrasonic actuator. SOLUTION: This ultrasonic actuator is provided with a drive signal generator 3 which generates a drive signal for driving the ultrasonic oscillator 2A of the ultrasonic actuator 2, a detector 4 which detects the phase difference between a voltage and a current applied to the ultrasonic oscillator 2A, and a controller 5 which controls the frequency of the drive signal generated by the drive signal generator 3 based on the detection result of the detector 4. Moreover, the detector 4 is so constituted as to detect the component of the fundamental frequency of the current applied to the ultrasonic oscillator 2A and to detect the phase difference between the voltage and the current applied to the oscillator based on the fundamental frequency component. COPYRIGHT: (C)2006,JPO&NCIPI

Digital Filters for Fast Harmonic Sequence Component Separation of Unbalanced and Distorted Three-Phase Signals

Abstract: In this paper, two methods for determining the fundamental frequency and harmonic positive- and negative-sequence components of three-phase signals are investigated. Many aspects of the space-vector discrete Fourier transform and generalized delayed signal cancellation (GDSC) such as response time for different possible implementations, frequency adaptation schemes, stability of recursive implementation, and rounding error effects are discussed. A new design procedure for GDSC transformations is presented. New indices for characterizing three-phase unbalanced and distorted signals are proposed. Simulations and experiments are included in order to verify the performances and illustrate the theoretical conclusions.

Analysis and Calculation of DC-Link Current and Voltage Ripples for Three-Phase Inverter With Unbalanced Load

Abstract: In this paper, an analysis and calculation of the dc-link current and voltage ripples are presented for a three-phase inverter with unbalanced load. A comparison of the dc-link average and root-mean-square (rms) currents between considering and ignoring high frequency harmonics of the output current is drawn. It is shown that high frequency harmonic currents have little effect on the dc-link current, and therefore, they can be ignored. Based on the symmetrical components method, the dc-link average and harmonic rms currents are derived, and the dc-link voltage ripple is compared between the balanced and unbalanced loads. It can be found that the dc-link current and voltage ripples consist of not only high frequency harmonics but also the double fundamental frequency harmonic, and the voltage ripple is independent of the positive-sequence component and determined by the negative-sequence component, under the unbalanced load. Experimental results are shown to verify the accuracy of the theoretical analysis.