A fast Fourier transform based method to estimate frequency response mismatches in time interleaved systems

2021 ◽  
Vol 92 (5) ◽  
pp. 054709
Author(s):  
Kuojun Yang ◽  
Zhixiang Pan ◽  
Peng Ye ◽  
Jiali Shi ◽  
Yu Zhao ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Fast Fourier Transform ◽  
Frequency Response ◽  
Estimate Frequency ◽  
Time Interleaved

scholarly journals The effect of fuel mixture on engine vibrations

2019 ◽  
Vol 177 (2) ◽  
pp. 136-138
Author(s):  
Radosław WRÓBEL ◽  
Łukasz ŁOZA ◽  
Piotr HALLER ◽  
Radosław WŁOSTOWSKI
Keyword(s):  
Fourier Transform ◽  
Comparative Analysis ◽  
Data Acquisition ◽  
Fast Fourier Transform ◽  
Frequency Response ◽  
Fuel Mixture ◽  
Graphical Form

In the article, the authors analyze the effect of a fuel mixture (iso-octane, butanol and ethanol) on the generation of engine vibrations. The paper presents the results in the form of frequency response (using the Fast Fourier Transform – FFT) for three mixtures of different proportions. The measurements were made with the use of accelerometers and data acquisition cards, conditioning the received signal. The vibration component, in the form of acceleration, will be subjected to a FFT and presented in graphical form (periodogram). The authors put a special emphasis on a comparative analysis, indicating changes in harmonics, which may be a potential cause of engine degradation.

scholarly journals USING WAVELETS WITH A RECTANGULAR AMPLITUDE-FREQUENCY RESPONSE TO FILTER SIGNALS

2021 ◽  
Author(s):  
Vladimir Semenov ◽  
Aleksandr Shurbin
Keyword(s):  
Fourier Transform ◽  
Wavelet Transform ◽  
Fast Fourier Transform ◽  
Frequency Response ◽  
Frequency Domain ◽  
Digital Filters ◽  
Bandpass Filter ◽  
Amplitude Frequency Response

The wavelet transform is the transmission of a signal through a bandpass filter. The design of wavelets with a rectangular amplitude-frequency response makes it possible to obtain almost ideal digital filters. The wavelet transform is calculated in the frequency domain using the fast Fourier transform.

Studying Contact Stress Fields Caused by Surface Tractions With a Discrete Convolution and Fast Fourier Transform Algorithm

2001 ◽  
Vol 124 (1) ◽  
pp. 36-45 ◽  
Author(s):  
Shuangbiao Liu ◽  
Qian Wang
Keyword(s):  
Fourier Transform ◽  
Fast Fourier Transform ◽  
Frequency Response ◽  
High Efficiency ◽  
Contact Stresses ◽  
Influence Coefficient ◽  
Response Functions ◽  
Frequency Response Functions ◽  
Discrete Convolution ◽  
Influence Coefficients

The knowledge of contact stresses is critical to the design of a tribological element. It is necessary to keep improving contact models and develop efficient numerical methods for contact studies, particularly for the analysis involving coated bodies with rough surfaces. The fast Fourier Transform technique is likely to play an important role in contact analyses. It has been shown that the accuracy in an algorithm with the fast Fourier Transform is closely related to the convolution theorem employed. The algorithm of the discrete convolution and fast Fourier Transform, named the DC-FFT algorithm includes two routes of problem solving: DC-FFT/Influence coefficients/Green’s function for the cases with known Green’s functions and DC-FFT/Influence coefficient/conversion, if frequency response functions are known. This paper explores the method for the accurate conversion for influence coefficients from frequency response functions, further improves the DC-FFT algorithm, and applies this algorithm to analyze the contact stresses in an elastic body under pressure and shear tractions for high efficiency and accuracy. A set of general formulas of the frequency response function for the elastic field is derived and verified. Application examples are presented and discussed.

An Eigenvalue Based Acoustic Impedance Measurement Technique

1991 ◽  
Vol 113 (2) ◽  
pp. 250-254 ◽  
Author(s):  
A. J. Hull ◽  
C. J. Radcliffe
Keyword(s):  
Fourier Transform ◽  
Fast Fourier Transform ◽  
Frequency Response ◽  
Measurement Technique ◽  
Acoustic Impedance ◽  
Laboratory Tests ◽  
Impedance Measurement ◽  
Wave Pattern ◽  
Impedance Tube ◽  
One Dimensional

A method is developed for measuring acoustic impedance. The method employs a one-dimensional tube or duct with excitation at one end and an unknown acoustic impedance at the termination end. Microphones placed in the tube are then employed to measure the frequency response of the system from which acoustic impedance of the end is calculated. This method uses fixed instrumentation and takes advantage of modern Fast Fourier Transform analyzers. Conventional impedance tube methods have errors resulting from movement of microphones to locate the maxima and minima of the wave pattern in the impedance tube or require phase matched microphones with specific microphone spacing. This technique avoids these problems by calculating the acoustic impedance from measured duct eigenvalues. Laboratory tests of the method are presented to demonstrate its accuracy.

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