The Matched Acoustic Generator

1972 ◽  
Vol 94 (1) ◽  
pp. 11-14
Author(s):  
K. Toda ◽  
G. Roffman ◽  
A. I. Talkin
Keyword(s):  
Measurement Error ◽  
Frequency Response ◽  
Transmission Lines ◽  
Acoustic Signal ◽  
Maximum Error ◽  
Power Gain ◽  
Frequency Range ◽  
Input Line ◽  
Pressure Signal ◽  
Frequency Responses

The design of a swept-frequency, acoustic generator for quickly measuring the insertion power gain and bandwidth of flueric components is described and illustrated. The generator is used to produce and measure the signal incident on flueric components without being affected by reflections from them. The components are connected to the generator by transmission lines. The output of the flueric component is measured in a line of the same diameter as the input line and long enough to attenuate reflections from the far end of the line to negligible levels. The generator produces a 17.7 × 10−3 kilopascal (2.6 × 10−3 psi) acoustic signal in a 1/8 in. (0.32 cm) line over the frequency range of 200 to 5000 Hz. The maximum error in the measurement of the incident pressure signal is approximately 5 percent. More precise construction of the generator could reduce the measurement error, but the accuracy is sufficient for many engineering purposes. The swept-frequency responses and carrier-pulse responses of several flueric amplifiers are illustrated and in particular the frequency response of certain proportional amplifiers has been shown to extend to 4000 Hz.

scholarly journals Self-Calibrated Measurement of Frequency Response for Broadband Photodetectors Based on Two-Tone Photonic Sampling

2021 ◽  
Vol 9 ◽  
Author(s):  
Mengke Wang ◽  
Ying Xu ◽  
Yutong He ◽  
Zhao Liu ◽  
Yali Zhang ◽  
...  
Keyword(s):  
Frequency Response ◽  
Wide Frequency Range ◽  
Repetition Frequency ◽  
Difference Frequency ◽  
Ultra Wideband ◽  
Center Frequency ◽  
Frequency Range ◽  
Frequency Responses ◽  
Tone Signal ◽  
Photonic Sampling

A self-calibrated method to measuring the frequency responses of broadband photodetectors (PDs) is proposed based on photonic pulse sampling of two-tone microwave signal, with the help of a mode-locked laser diode (MLLD) and a Mach-Zehnder modulator (MZM). Firstly, the repetition frequency of the optical comb from the MLLD divides the whole measuring frequency range into several segments. Then, a close-spaced two-tone signal modulates every comb tooth through the MZM and generates the sum- and difference-frequency products, working as the probing signal to extract the frequency response of the PD in every segment. Hyper-fine frequency response of the PD at any frequency point can be obtained in every segment by subtly varying the center frequency of the two-tone signal while keeping the difference frequency fixed. Finally, the whole frequency response of the PD in ultra-wide frequency range is obtained by seamlessly stitching the segmental frequency responses. In our experiment, measurement of a commercial PD is demonstrated up to 49.765 GHz with an optical comb at the repetition frequency of 9.953 GHz and a two-tone modulation up to 4.9765 GHz. The measured results are compared with those by using the traditional methods to check accuracy. Moreover, the uneven responses of the MLLD and the MZM are fully subtracted, verifying the ultra-wideband, hyperfine and self-calibrated measurement of PDs based on the two-tone photonic sampling.

New aspects of power grid facilities personnel workplaces electromagnetic environment

2020 ◽  
Vol 60 (9) ◽  
pp. 569-574
Author(s):  
Nina B. Rubtsova ◽  
Sergey Yu. Perov ◽  
Olga V. Belaya ◽  
Tatiana A. Konshina
Keyword(s):  
Transmission Lines ◽  
Power Transmission ◽  
Power Grid ◽  
Spectral Characteristics ◽  
Ground Level ◽  
Frequency Characteristics ◽  
Frequency Range ◽  
Electromagnetic Environment ◽  
Limit Values ◽  
Special Assessment

Introduction. Electromagnetic safety of power grid facilities staff requires the exclusion of electromagnetic fields (EMF) harmful effects. EMF is evaluated by 50 Hz electric and magnetic fields (EF and MF) values in the framework of working conditions special assessment, and very rarely the analysis of the electromagnetic environment (EME) is carried out in depth. The aim of the study - EME hygienic assessment of power grid EHV facilities personnel workplace with adequate 50 Hz EF and MF levels evaluation as well as the analysis of EF and MF in the frequency range from 5 Hz to 500 Hz amplitude-frequency characteristics. Materials and methods. 50 Hz EF and MF values assessment was carried out on open switchgears (S) of substations and within sanitary breaks of 500 and 750 kV overhead power transmission lines (OTL). Measurements along to OTL trasses was performed using matrix-based method. Measurements and analysis of EF and MF values in 5-500 Hz frequency range amplitude-frequency characteristics were performed in the territory of 500 and 750 kV S. Results. Power frequency 50 Hz measurements results at 500 and 750 kV S ground-level personnel workplaces showed the presence of an excess of permissible limit values by EF intensity and the absence of an excess by MF. The measured EF values within 500 and 750 kV OTL sanitary gaps require limiting the working time of linemen due to the excess of the hygienic norms for full work shift, while the MP levels were almost completely within the standard values for persons not occupationally connected with electrical installations maintenance. MF and EE frequency range from 50 Hz to 500 Hz spectral characteristics analysis showed that 3rd harmonic percentage does not exceed 2.5% for EF and 6% for MF of the main level, the level of the 5th harmonic does not exceed 1% for EF and 3.5% for MF, the level of the 7th harmonic does not exceed 0.2% for EF and 0.8% for MF. These data show despite its low levels the contribution of MF different harmonics in a possible adverse impact on humane than EF corresponding harmonics. Conclusions. There was the confirmation of the previously justified use of the "matrix" scheme for of EF and MF values measurement along OTL routes. The relevance of to EF and MF all frequency components expos ure assessing possible health risk in extremely high voltage S territories and under OTL, based on international recommendations due to the lack of sanitary regulations in the Russian Federation for >50 Hz-30 kHz EF and MF, is shown.

scholarly journals Detection and localization of multiple small damages in beam

2021 ◽  
Vol 13 (1) ◽  
pp. 168781402098732
Author(s):  
Ayisha Nayyar ◽  
Ummul Baneen ◽  
Syed Abbas Zilqurnain Naqvi ◽  
Muhammad Ahsan
Keyword(s):  
Frequency Response ◽  
Natural Frequencies ◽  
Signal To Noise Ratio ◽  
Moving Average ◽  
A Priori ◽  
Damage Index ◽  
High Signal ◽  
Frequency Range ◽  
Spatial Locality ◽  
System Frequency

Localizing small damages often requires sensors be mounted in the proximity of damage to obtain high Signal-to-Noise Ratio in system frequency response to input excitation. The proximity requirement limits the applicability of existing schemes for low-severity damage detection as an estimate of damage location may not be known  a priori. In this work it is shown that spatial locality is not a fundamental impediment; multiple small damages can still be detected with high accuracy provided that the frequency range beyond the first five natural frequencies is utilized in the Frequency response functions (FRF) curvature method. The proposed method presented in this paper applies sensitivity analysis to systematically unearth frequency ranges capable of elevating damage index peak at correct damage locations. It is a baseline-free method that employs a smoothing polynomial to emulate reference curvatures for the undamaged structure. Numerical simulation of steel-beam shows that small multiple damages of severity as low as 5% can be reliably detected by including frequency range covering 5–10th natural frequencies. The efficacy of the scheme is also experimentally validated for the same beam. It is also found that a simple noise filtration scheme such as a Gaussian moving average filter can adequately remove false peaks from the damage index profile.

scholarly journals DESIGN OF BAND-PASS FILTERS WITH NON-EQUIRIPPLE FREQUENCY RESPONSES

2019 ◽  
Vol 22 (3) ◽  
pp. 5-23
Author(s):  
Evgeniy N. Chervinskiy
Keyword(s):  
Frequency Response ◽  
Special Functions ◽  
Band Pass Filter ◽  
System Of Equations ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Frequency Responses ◽  
Band Pass ◽  
Standard Values ◽  
Circuit Elements

Introduction. Band-pass filters circuit elements can be calculated by converting low-pass filter (LPF) parameters, which is the prototype of the designed band-pass filter. The conversion causes problems in case calculated values of circuit elements (resistors and capacitors) are out of standard values determined by the GOST standard. Obviously, frequency characteristics of band-pass filters are distorted when replacing the calculated values of circuit elements by the standard ones. The number of circuit elements with values different from standard can be reduced to zero by solving an additional system of equations that connects parameters of designed and reintroduced non-equiripple frequency responses. Objective. The objective of this work is to develop a calculation method of band-pass ladder filters with values of circuit elements corresponding to standard ones. Materials and methods. The filter design process includes two stages. The first stage is a parameters calculation of a polynomial LPF prototype. The calculated parameters are determined as a system of equations solution set. The equations are formed by equating coefficients of variables raised to the same powers in transfer function (TF) expressions of designed and realized filters. Initial characteristics are the filter order and frequency response unevenness. The transition to the standard values of circuit elements can be done when solving another system of equations that connects LPF converted parameters with unknown parameters of reintroduced non-equiripple frequency response. Results. TF of LPF prototypes up to the fifth order and frequency responses of band-pass filters (BPF) and bandrejection filters up to the tenth order are presented. Analytical expressions of non-equiripple and equiripple frequency responses are used to estimate distortions of the latter when a band-pass filter center frequency is tuned by using variable inductors or capacitors. The integral quadratic function of a variable is taken as a measure of real frequency response distortions. The tenth order BPF calculation example is given. Conclusion. The presented calculation methods of band-pass filters and given example demonstrate possibilities of the filter design method based on the systems of non-linear equations solution. In contrast to approximation methods of ideal filter frequency response by using special functions and tabular filters design, the presented method allows high-order filter calculation for any initial requirements without using reference data.

scholarly journals Frequency Response Stabilization and Comparative Studies of MET Hydrophone at Marine Seismic Exploration Systems

Sensors ◽  
2020 ◽  
Vol 20 (7) ◽  
pp. 1944 ◽  
Author(s):  
Egor Egorov ◽  
Anna Shabalina ◽  
Dmitry Zaitsev ◽  
Sergey Kurkov ◽  
Nikolay Gueorguiev
Keyword(s):  
Frequency Response ◽  
Field Tests ◽  
High Sensitivity ◽  
Seismic Exploration ◽  
Joint Stock Company ◽  
Experimental Sample ◽  
Frequency Range ◽  
Stock Company ◽  
Low Frequencies ◽  
Marine Seismic

Low frequency hydrophone with a frequency range of 1−300 Hz for marine seismic exploration systems has been developed. The operation principle of the hydrophone bases on the molecular electronic transfer that allows high sensitivity and low level self-noise at low frequencies (<10 Hz) to be achieved. The paper presents a stabilization method of the frequency response within the frequency range at a depth up to 30 m. Laboratory and marine tests confirmed the stated characteristics as well as the possibility of using this sensor in bottom marine seismic systems. An experimental sample of the hydrophone successfully passed a comparative marine test at Gelendzhik Bay (Black Sea) with the technical support of Joint-Stock Company (JSC) “Yuzhmorgeologiya”. One of the main results is the possibility of obtaining high-quality information in the field of low frequencies, which was demonstrated in the course of field tests.

Data-Driven Modeling Techniques to Estimate Dispersion Relations of Structural Components

2018 ◽  
Author(s):  
Vijaya V. N. Sriram Malladi ◽  
Mohammad I. Albakri ◽  
Pablo A. Tarazaga ◽  
Serkan Gugercin
Keyword(s):  
Frequency Response ◽  
Dispersion Relations ◽  
Data Driven ◽  
Response Functions ◽  
Structural Components ◽  
Frequency Range ◽  
Frequency Response Functions ◽  
Material Inhomogeneity ◽  
Modeling Techniques ◽  
Data Driven Modeling

Dispersion relations describe the frequency-dependent nature of elastic waves propagating in structures. Experimental determination of dispersion relations of structural components, such as the floor of a building, can be a tedious task, due to material inhomogeneity, complex boundary conditions, and the physical dimensions of the structure under test. In this work, data-driven modeling techniques are utilized to reconstruct dispersion relations over a predetermined frequency range. The feasibility of this approach is demonstrated on a one-dimensional beam where an exact solution of the dispersion relations is attainable. Frequency response functions of the beam are obtained numerically over the frequency range of 0–50kHz. Data-driven dynamical model, constructed by the vector fitting approach, is then deployed to develop a state-space model based on the simulated frequency response functions at 16 locations along the beam. This model is then utilized to construct dispersion relations of the structure through a series of numerical simulations. The techniques discussed in this paper are especially beneficial to such scenarios where it is neither possible to find analytical solutions to wave equations, nor it is feasible to measure dispersion curves experimentally. In the present work, actual experimental data is left for future work, but the complete framework is presented here.

Coupled microstrip filters on multilayered dielectric media

2002 ◽  
Vol 80 (6) ◽  
pp. 675-685
Author(s):  
Ar. Koufogiannidis ◽  
K Siakavara
Keyword(s):  
Frequency Response ◽  
Transmission Lines ◽  
Insertion Loss ◽  
Design Procedure ◽  
Multiconductor Transmission Lines ◽  
Microstrip Lines ◽  
Dielectric Media ◽  
Microstrip Filters ◽  
Loss Method ◽  
Good Agreement

The work presented in this paper is an attempt to design filters with coupled microstrip lines on multilayered dielectric media using methods employed in other applications. A procedure was formulated for designing filters with the desired frequency response and smaller size using insertion loss method combined with the theory of multiconductor transmission lines. The frequency response was verified by considering that the filters act as cascaded four-port networks. The results were in a very good agreement with those expected from the theoretically design procedure. PACS No.: 84.40D

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