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Journal articles on the topic 'Directivity'

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Author: Grafiati

Published: 4 June 2021

Last updated: 1 April 2023

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1

Nakazawa, Toshiyasu, and Naoaki Shinohara. "Study on aircraft noise directivity of behind the start of takeoff roll." INTER-NOISE and NOISE-CON Congress and Conference Proceedings 263, no. 3 (August 1, 2021): 3202–8. http://dx.doi.org/10.3397/in-2021-2330.

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This paper discusses aircraft noise directivity behind the start of takeoff roll. Aircraft noise has the radiation directivity because of aircraft engine mount position and the engine noise directivity. Thus, lateral noise directivity correction is recommended in airport noise calculation guidelines such as ECAC Doc.29 and ICAO Doc9911. In these guidelines, the directivity of flyover noise and the directivity at the start of takeoff roll on ground are prepared separately. A 90-degree dipole model is used for the directivity of the flyover noise, and another similar directivity is used for the directivity behind the start of takeoff roll. It is necessary to properly evaluate the directivity behind the takeoff roll because it has a large contribution to noise calculation of the vicinity of the airport. Therefore, we measured aircraft noise behind the start of takeoff roll with sound level meters placed half-concentrically around Narita Airport in Japan. From these measurement results, various types of aircraft noise directivity behind the takeoff roll are examined and considered the effects of weather conditions such as wind direction. Finally the differences from existing models are compared.

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2

O'Donoghue, Jennifer L., and Karen R. Strobel. "Directivity and Freedom." American Behavioral Scientist 51, no. 3 (November 2007): 465–85. http://dx.doi.org/10.1177/0002764207306071.

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3

Dittberner, Andrew B. "Quantifying microphone directivity." Hearing Journal 56, no. 11 (November 2003): 22. http://dx.doi.org/10.1097/01.hj.0000292901.09293.7b.

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4

Jers, Harald. "Directivity of singers." Journal of the Acoustical Society of America 118, no. 3 (September 2005): 2008. http://dx.doi.org/10.1121/1.4785700.

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5

Johnston, James David. "Perceptual speaker directivity." Journal of the Acoustical Society of America 120, no. 4 (2006): 1763. http://dx.doi.org/10.1121/1.2372346.

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6

Zhao, Guozhu, Kaibo Shi, and Shouming Zhong. "Research on Array Structures of Acoustic Directional Transducer." Mathematical Problems in Engineering 2021 (January 2, 2021): 1–5. http://dx.doi.org/10.1155/2021/6670277.

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This paper focuses on the directivity design of array structures of acoustic directional transducers. Based on Huygens principles, the directivity formula of transducer arrays under random distribution in xyz space is derived when the circular piston transducers are used as the array element, which is used to analyze the directivity and acoustic pressure of conical transducer arrangements. In addition, a practical approach to analyze the directivity and acoustic pressure of transducer arrays under random arrangements is proposed. Findings. The conical transducer arrays show side lobes at higher frequency. Below the frequency of 2 kHz, array directivity shows rapid changes. Above the frequency of 2 kHz, array directivity varies slowly with frequency. Besides, the beam width is Θ − 3 dB ≤ 29.85 ° .

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7

Musset, S., M. Maksimovic, E. Kontar, V. Krupar, N. Chrysaphi, X. Bonnin, A. Vecchio, et al. "Simulations of radio-wave anisotropic scattering to interpret type III radio burst data from Solar Orbiter, Parker Solar Probe, STEREO, and Wind." Astronomy & Astrophysics 656 (December 2021): A34. http://dx.doi.org/10.1051/0004-6361/202140998.

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Aims. We use multi-spacecraft observations of individual type III radio bursts to calculate the directivity of the radio emission. We compare these data to the results of ray-tracing simulations of the radio-wave propagation and probe the plasma properties of the inner heliosphere. Methods. We used ray-tracing simulations of radio-wave propagation with anisotropic scattering on density inhomogeneities to study the directivity of radio emissions. Simultaneous observations of type III radio bursts by four widely separated spacecraft were used to calculate the directivity and position of the radio sources. The shape of the directivity pattern deduced for individual events is compared to the directivity pattern resulting from the ray-tracing simulations. Results. We show that simultaneous observations of type radio III bursts by four different probes provide an opportunity to estimate the radio source positions and the directivity of the radio emission. The shape of the directivity varies from one event to another and it is consistent with anisotropic scattering of the radio waves.

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8

Liu, Hong, and Guo Zhu Zhao. "Two Methods to Test Transducer Array Directivity." Advanced Materials Research 912-914 (April 2014): 1485–88. http://dx.doi.org/10.4028/www.scientific.net/amr.912-914.1485.

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An array which possess more array element number and whose frequency of the drive signal can be as large as possible in a range, directivity will be more preferable. On the other hand, when the structure of the sound radiating surface of the transducer or array layout is symmetrical, the corresponding directivity pattern will be symmetrical. In order to test transducer directivity, two methods are designed. The one is to measure the ultrasonic sound pressure level by instruments. The sound pressure level is measured at multiple points to deduce the directivity angle of the acoustic transducer array. The beam width of the 3×3 array is about at 23kHz, and the directivity acute angle is about 10°; higher frequencies will lead to the side lobes, but it can be negligible when compared to the main lobe. The other method is using the frequency analyzer to test transducer directivity in a silencer chamber. The sound pressure level can be read out from frequency response diagrams. The angle between the sound pressure value that decreasing 3db from the max value 111.7db and the max value is about 11°. So the directivity acute angle is about 11°. It should be noticed that, as the directivity diagram can not be directly attributed, there is some deviation in the conclusion.

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9

Zhao, Guo Zhu, and Li Xuan Ma. "Research on the High-Power Directional Acoustic Transducer." Advanced Materials Research 912-914 (April 2014): 753–56. http://dx.doi.org/10.4028/www.scientific.net/amr.912-914.753.

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Through studying how to affect acoustic directivity with MATLAB software, it show that selection of a relatively larger surface of the transducer and a relatively closer transducer interval will be more preferable for directivity. While an array which possess more array element number and whose frequency of the drive signal can be as large as possible in a range, directivity will be more preferable. On the other hand, when the structure of the sound radiating surface of the transducer or array layout is symmetrical, the corresponding directivity pattern will be symmetrical. At a frequency of 10kHz, the individual rare earth magnetostrictive transducers its first point of the simulation carried out before the test. Sounding board with aluminum by the method used to improve the sound source diameter. With the sound plate diameter incrementing, the smaller the angle of the directivity. The beam width of the 3×3 array is about at 23kHz, and the directivity acute angle is about 10°, with a sounding board by the method used to improve their the diameter of the sound source, so as to realize the sound has directivity is feasible.

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10

Bellows, Samuel D., and Timothy W. Leishman. "Modeling musician diffraction for artificially excited clarinet directivity measurements." Journal of the Acoustical Society of America 151, no. 4 (April 2022): A157. http://dx.doi.org/10.1121/10.0010960.

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Directivity measurements of musical instruments have many applications in musical, audio, and architectural acoustics. Typical measurement methods include artificially excited instruments and instruments played by live musicians. While recent advances in directivity measurement techniques enable higher resolutions for played instruments, the results are still limited in bandwidth and repeatability compared with directivity results from artificially excited instruments. However, artificially excited instruments typically neglect musician diffraction and absorption. This work compares possible approaches for representing musician diffraction in artificially excited clarinet measurements to improve their directivity results for room simulations or auralizations.

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11

Spudich, Paul, Badie Rowshandel, Shrey K. Shahi, Jack W. Baker, and Brian S. J. Chiou. "Comparison of NGA-West2 Directivity Models." Earthquake Spectra 30, no. 3 (August 2014): 1199–221. http://dx.doi.org/10.1193/080313eqs222m.

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Five directivity models have been developed based on data from the NGA-West2 database and based on numerical simulations of large strike-slip and reverse-slip earthquakes. All models avoid the use of normalized rupture dimension, enabling them to scale up to the largest earthquakes in a physically reasonable way. Four of the five models are explicitly “narrow-band” (in which the effect of directivity is maximum at a specific period that is a function of earthquake magnitude). Several strategies for determining the zero-level for directivity have been developed. We show comparisons of maps of the directivity amplification. This comparison suggests that the predicted geographic distributions of directivity amplification are dominated by effects of the models’ assumptions, and more than one model should be used for ruptures dipping less than about 65 degrees.

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12

Zhou, R., and L. Shafai. "Directivity enhancement by layered radomes." Canadian Journal of Physics 73, no. 7-8 (July 1, 1995): 444–51. http://dx.doi.org/10.1139/p95-064.

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Single and layered radomes are often used to protect radiating elements. A two-dimensional analysis is used to investigate their influence on the antenna directivity and radiation patterns. Image-theory and integral-equation methods are used to formulate the problem for a line source and layered dielectrics of finite length over a ground plane, and solved numerically using the moment method. It is shown that, for a sufficiently long single-layer slab, the directivity enhancement is approximately equal to the square root of its relative permittivity. Properly truncating the slab can even improve the directivity. The optimum length of a finite dielectric slab is determined to maximize the directivity. For multilayer slabs, the directivity enhancement is much greater and they can be used with low-permittivity dielectrics to simulate a single-layer one of higher permittivity. Frequency dependency of the enhanced gain is also studied. Useful information for how to incorporate the radome parameters into the antenna design and use it for gain or directivity enhancement is provided.

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13

Pörschmann, Christoph, and Johannes M. Arend. "Effects of hand postures on voice directivity." JASA Express Letters 2, no. 3 (March 2022): 035203. http://dx.doi.org/10.1121/10.0009748.

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While speaking, hand postures, such as holding a hand in front of the mouth or cupping the hands around the mouth, influence human voice directivity. This study presents and analyzes spherical voice directivity datasets of an articulated [a] with and without hand postures. The datasets were determined from measurements with 13 subjects in a surrounding spherical microphone array with 32 microphones and then upsampled to a higher spatial resolution. The results show that hand postures strongly impact voice directivity and affect the directivity index by up to 6 dB, which is more than variances caused by phoneme-dependent differences.

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14

KOYAMA, Junji. "Short Period Seismic Directivity." Zisin (Journal of the Seismological Society of Japan. 2nd ser.) 40, no. 3 (1987): 397–404. http://dx.doi.org/10.4294/zisin1948.40.3_397.

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15

Oyaba, Takashi. "Speaker system having directivity." Journal of the Acoustical Society of America 93, no. 3 (March 1993): 1680. http://dx.doi.org/10.1121/1.406748.

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16

Oyaba, Takashi. "Speaker system having directivity." Journal of the Acoustical Society of America 91, no. 2 (February 1992): 1200. http://dx.doi.org/10.1121/1.402556.

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17

Harrell, Jefferson A., and Elmer L. Hixson. "Constant directivity loudspeaker arrays." Journal of the Acoustical Society of America 91, no. 4 (April 1992): 2326. http://dx.doi.org/10.1121/1.403523.

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18

Williams, J. Michael, Michael D. Cerna, and Elmer L. Hixson. "Constant directivity receiving arrays." Journal of the Acoustical Society of America 91, no. 4 (April 1992): 2325. http://dx.doi.org/10.1121/1.403546.

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19

Chu, Wing T., Alf Warnock, and Jean‐Charles Guy. "Directivity of human talkers." Journal of the Acoustical Society of America 110, no. 5 (November 2001): 2664. http://dx.doi.org/10.1121/1.4777091.

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20

Leishman, Timothy W., and Samuel D. Bellows. "Musical instrument directivity measurements." Journal of the Acoustical Society of America 146, no. 4 (October 2019): 2822. http://dx.doi.org/10.1121/1.5136777.

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21

Pozar, D. "Directivity of omnidirectional antennas." IEEE Antennas and Propagation Magazine 35, no. 5 (October 1993): 50–51. http://dx.doi.org/10.1109/74.242180.

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22

Schejbal, V., J. D. Mahoney, and N. McDonald. "Directivity of planar antennas." IEEE Antennas and Propagation Magazine 41, no. 2 (April 1999): 60–65. http://dx.doi.org/10.1109/74.769693.

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23

Bulgakovа, A. A., N. N. Gorobets, V. A. Katrich, and V. A. Lyashchenko. "DIRECTIVITY OF ANTENNA ARRAYS." Radio physics and radio astronomy 21, no. 4 (December 5, 2016): 285–97. http://dx.doi.org/10.15407/rpra21.04.285.

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24

Bodley, Martin Reed. "High directivity microphone array." Journal of the Acoustical Society of America 113, no. 6 (2003): 2957. http://dx.doi.org/10.1121/1.1588802.

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25

Bodley, Martin Reed. "High directivity microphone array." Journal of the Acoustical Society of America 116, no. 6 (2004): 3246. http://dx.doi.org/10.1121/1.1852937.

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26

Bodley, Martin Reed. "High directivity microphone array." Journal of the Acoustical Society of America 120, no. 1 (2006): 18. http://dx.doi.org/10.1121/1.2227659.

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27

Murphy, David John. "Constant directivity acoustic horn." Journal of the Acoustical Society of America 121, no. 1 (2007): 14. http://dx.doi.org/10.1121/1.2434265.

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28

Hansen, R. C. "Directivity of ring arrays." Microwave and Optical Technology Letters 18, no. 6 (August 20, 1998): 370–75. http://dx.doi.org/10.1002/(sici)1098-2760(19980820)18:6<370::aid-mop2>3.0.co;2-a.

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29

Pezzoli, Mirco, Antonio Canclini, Fabio Antonacci, and Augusto Sarti. "A comparative analysis of the directional sound radiation of historical violins." Journal of the Acoustical Society of America 152, no. 1 (July 2022): 354–67. http://dx.doi.org/10.1121/10.0012577.

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The directivity pattern of a musical instrument describes the sound energy radiation as a function of frequency and direction of emission. Violins exhibit a rather complex directivity pattern, which is known to show rapid variations across frequencies, and whose behavior cannot be easily predicted except in the lowest frequency range. The acoustic behavior of the violin is a fascinating research topic that has prompted numerous published works, but a thorough, comprehensive, and comparative analysis of violin directivity patterns is long overdue. In this article, we propose a set of metrics for characterizing the radiative behavior of musical instruments and, in particular, for comparing their directivity patterns. We apply such metrics for a comparative analysis of the directivity patterns of some of the most prestigious historical violins ever made, including grand masters such as Antonio Stradivari, Giuseppe Guarneri “del Gesú” and members of the Amati family. The instruments are preserved in the Violin Museum of Cremona, Italy, where our lab is located. The analysis methodology introduced in this work allowed us to quantitatively evaluate the similarity of directivity patterns of such extraordinary instruments and draw some interesting conclusions.

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30

Xie, Junju. "Strong‐Motion Directionality and Evidence of Rupture Directivity Effects during the Chi‐Chi Mw 7.6 Earthquake." Bulletin of the Seismological Society of America 109, no. 6 (October 29, 2019): 2367–83. http://dx.doi.org/10.1785/0120190087.

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Abstract This article investigates the spatial distribution, predominant direction, and variations in the intensity measures (IMs) with orientation for classified pulse‐like and nonpulse motions during Chi‐Chi Mw 7.6 earthquake. The results show evidence of high polarization for long‐period spectral accelerations at relatively large source‐to‐site distances (50–100 km) north of the Chelungpu fault. The polarization of long‐period motions shows a clear correlation with the directivity parameters’ isochrone directivity predictor and ξ, indicating a connection between directionality and rupture directivity. The variation in strong‐motion directionality with the period is also studied. The discrepancy in directionality caused by strong directivity increases with the period from 1 to 10 s, which confirms a clear correlation of period‐dependent directionality with directivity effects. This study finds stronger directionality of pulse‐like motions than nonpulse motions for long periods over 3 s with higher maximum‐to‐median and maximum‐to‐minimum IM ratios. For periods over 3 s, the maximum‐to‐median ratios of pulse‐like motions are higher than the mean prediction of the Shahi and Baker (2014a) model, whereas those of nonpulse motions are lower than the prediction. However, this study does not find simple and clear results for the directions of the maximum component at different periods for pulse‐like and nonpulse motions. Despite clear differences between the unidirectional fling‐step and bidirectional forward directivity pulses, the effects of fling‐step and forward directivity are actually coupled in the waveforms.

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31

Brandner, Manuel, Matthias Frank, and Alois Sontacchi. "Horizontal and Vertical Voice Directivity Characteristics of Sung Vowels in Classical Singing." Acoustics 4, no. 4 (October 1, 2022): 849–66. http://dx.doi.org/10.3390/acoustics4040051.

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Singing voice directivity for five sustained German vowels /a:/, /e:/, /i:/, /o:/, /u:/ over a wide pitch range was investigated using a multichannel microphone array with high spatial resolution along the horizontal and vertical axes. A newly created dataset allows to examine voice directivity in classical singing with high resolution in angle and frequency. Three voice production modes (phonation modes) modal, breathy, and pressed that could affect the used mouth opening and voice directivity were investigated. We present detailed results for singing voice directivity and introduce metrics to discuss the differences of complex voice directivity patterns of the whole data in a more compact form. Differences were found between vowels, pitch, and gender (voice types with corresponding vocal range). Differences between the vowels /a:, e:, i:/ and /o:, u:/ and pitch can be addressed by simplified metrics up to about d2/D5/587 Hz, but we found that voice directivity generally depends strongly on pitch. Minor differences were found between voice production modes and found to be more pronounced for female singers. Voice directivity differs at low pitch between vowels with front vowels being most directional. We found that which of the front vowels is most directional depends on the evaluated pitch. This seems to be related to the complex radiation pattern of the human voice, which involves a large inter-subjective variability strongly influenced by the shape of the torso, head, and mouth. All recorded classical sung vowels at high pitches exhibit similar high directionality.

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32

Pinchera, Daniele. "On the Trade-Off between the Main Parameters of Planar Antenna Arrays." Electronics 9, no. 5 (April 30, 2020): 739. http://dx.doi.org/10.3390/electronics9050739.

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The aim of this paper is two-fold. First, the trade-off between directivity, beam-width, side-lobe-level, number of radiating elements, and scanning range of planar antenna arrays is reviewed, and some simple ready-to-use formulas for the preliminary dimensioning of equispaced planar arrays are provided. Furthermore, the synthesis of sparse planar arrays, and the issue of their reduction in directivity, is analyzed. Second, a simple, yet effective, novel approach to overcome the directivity issue is proposed. The presented method is validated by several synthesized layouts; the examples show that it is possible to synthesize sparse arrays, able to challenge with equispaced lattices in terms of directivity, with a significant reduction of the number of radiators.

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33

Xu, Long Jun, and Sheng Chao Yang. "Near-Fault Directivity Spectrum for Nuclear Structure Design on Rock Site." Advanced Materials Research 243-249 (May 2011): 3820–23. http://dx.doi.org/10.4028/www.scientific.net/amr.243-249.3820.

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This study is aimed at evaluating the safety implications of near-fault directivity effect on nuclear structure and facilities designed according to the Chinese code. To this end, a set of near-fault ground motions at rock site with typical forward-directivity effect is examined with emphasis on several key parameters and response spectra. The bi-normalized response spectra in terms of different corner periods are utilized to derive nuclear design spectra. It was concluded that nuclear design spectra on rock site derived from typical directivity records are significantly influenced by both magnitude and distance. The nuclear design spectra specified in the code need to be adjusted to reflect the near-fault directivity effect of large earthquakes.

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34

W.A., Al-lami. "Systematic Directivity for Selecting Special Javelin Throw Exercises." International Journal of Psychosocial Rehabilitation 24, no. 4 (February 28, 2020): 4046–52. http://dx.doi.org/10.37200/ijpr/v24i4/pr201517.

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35

Seo, Min-Seong, Won-Young Kim, and YoungHee Kim. "Rupture Directivity of the 2021 ML 2.2 Gwangyang, Korea, Microearthquake: Toward Resolving High-Resolution Rupture Process of a Small Earthquake." Seismic Record 2, no. 4 (October 1, 2022): 227–36. http://dx.doi.org/10.1785/0320220030.

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Abstract Moderate-to-large earthquakes (M>6) frequently show clear rupture directivity. Recent studies revealed that a substantial percentage of small-sized earthquakes (M<∼5) display rupture directivity as well, owing to enhanced seismic monitoring. Is rupture directivity a common feature for earthquakes of all sizes? In this study, we investigated the rupture directivity of the 27 August 2021 ML 2.2 Gwangyang microearthquake that occurred at the southern tip of the Korean Peninsula by utilizing data from a recently expanded dense seismic network. The mainshock had two foreshocks and three aftershocks, which enabled us to define the fault plane from precise relative event locations and a well-constrained focal mechanism. Analysis of apparent source time functions obtained with the empirical Green’s function technique reveals that the mainshock ruptured unilaterally toward the east. A detailed analysis of the source pulse leaving the focal sphere in 3D indicates that rupture directivity is consistent with the fault geometry and slip direction. Our study demonstrates that we can resolve rupture directivity of unilaterally rupturing microearthquakes (M<∼3) given adequate azimuthal coverage, and that this will lead to an improved understanding of the seismogenic processes in regions of low seismicity worldwide.

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36

Zhong, Jiaxin, Haishan Zou, Jing Lu, and Dong Zhang. "A modified convolution model for calculating the far field directivity of a parametric array loudspeaker." Journal of the Acoustical Society of America 153, no. 3 (March 2023): 1439–51. http://dx.doi.org/10.1121/10.0017361.

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The far field directivity is a straightforward indicator to describe the radiation pattern of the audio sound generated by a parametric array loudspeaker (pal), but its accurate and computationally efficient prediction is still challenging at present. This paper derives two-dimensional (2D), three-dimensional (3D), and 3D axisymmetric convolution models for calculating the far field directivity based on the quasilinear solution of Westervelt equation. The obtained expressions are expressed as linear and spherical convolutions of the ultrasound directivity and Westervelt directivity for 2D and 3D models, respectively. To improve prediction accuracy, the obtained expression is multiplied by an effective directivity resulted from the aperture factor of audio sound. The calculated directivities are compared against the exact solution obtained using the cylindrical and spherical wave expansions for 2D and 3D models, respectively. Numerical results with piston, apodized, and steerable profiles in both 2D and 3D models show that the proposed modified convolution model agrees well with the exact solution. It is also found that sidelobes appear in the audio sound directivity at large aperture sizes and high audio frequencies due to the aperture factor of audio sound, which can be predicted with the proposed method with a relatively low computational expenditure.

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37

Shrestha, Sujan, Hijab Zahra, Muhammad Ali Babar Abbasi, Mohsen Asadnia, and Syed Muzahir Abbas. "Increasing the Directivity of Resonant Cavity Antennas with Nearfield Transformation Meta-Structure Realized with Stereolithograpy." Electronics 10, no. 3 (February 1, 2021): 333. http://dx.doi.org/10.3390/electronics10030333.

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A simple, nearfield transformation meta-structure is proposed to increase the directivity of resonant cavity antennas (RCA). The meta-structure is comprised of 14 × 14 meta-atoms or so called “unit-cells”, adding localized phase delays in the aperture of the RCA and thus increasing its broadside directivity. A prototype of the meta-structure is additively manufactured using the stereolithograpy process and has a profile of 0.56λ. With the meta-structure integrated with the RCA, it demonstrates a measured broadside directivity of 20.15 dBi without affecting its half-power directivity bandwidth. Benefiting from additive manufacturing, the proposed approach is a simple, light-weight, low-cost, and planar approach that can be tailored to achieve medium-to-high gains with RCAs.

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38

Song, Zhongchang, Chuang Zhang, Weijie Fu, Zhanyuan Gao, Wenzhan Ou, Jinhu Zhang, and Yu Zhang. "Investigation on whistle directivity in the Indo-Pacific humpback dolphin (Sousa chinensis) through numerical modeling." Journal of the Acoustical Society of America 151, no. 6 (June 2022): 3573–79. http://dx.doi.org/10.1121/10.0011513.

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Odontocetes have evolved special acoustic structures in the forehead to modulate echolocation and communication signals into directional beams to facilitate feeding and social behaviors. Whistle directivity was addressed for the Indo-Pacific humpback dolphin ( Sousa chinensis) by developing numerical models in the current paper. Directivity was first examined at the fundamental frequency 5 kHz, and simulations were then extended to the harmonics of 10, 15, 20, 25, and 30 kHz. At 5 kHz, the –3 dB beam widths in the vertical and horizontal planes were 149.3° and 119.4°, corresponding to the directivity indexes (DIs) of 4.4 and 5.4 dB, respectively. More importantly, we incorporated directivity of the fundamental frequency and harmonics to produce an overall beam, resulting in −3 dB beam widths of 77.2° and 62.9° and DIs of 8.2 and 9.7 dB in the vertical and horizontal planes, respectively. Harmonics can enhance the directivity of fundamental frequency by 3.8 and 4.3 dB, respectively. These results suggested the transmission system can modulate whistles into directional projection, and harmonics can improve DI.

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39

Sonasang, Somchat, and Niwat Angkawisittpan. "Design of Microstrip Parallel-Coupled Lines with High Directivity using Symmetric-Centered Inductors." Applied Computational Electromagnetics Society 36, no. 6 (August 6, 2021): 657–63. http://dx.doi.org/10.47037/2020.aces.j.360606.

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A technique for directivity improvement of the microstrip parallel-coupled lines using symmetric-centered inductors is presented in this paper. The design procedure of the symmetric-centered inductors using the closed-form equations is given. The proposed technique was performed with a design at the operating frequency of 0.9 GHz on an FR4 substrate. Validity of the proposed technique is verified by simulations and measurements in comparisons with conventional parallel-coupled lines. The measured results exhibit the isolation of -30.10 dB and directivity of 19.28 dB at the operating frequency of 0.9 GHz. The directivity from the measured results is improved by more than 4 dB at 0.9 GHz and more than 6 dB at 1.05 GHz compared with the conventional parallel-coupled lines. In addition, the proposed technique for the microstrip parallel-coupled line can achieve a high directivity with the compact size (21.0 mm x 4.70 mm). The novelty of this paper is by introducing the proposed and closed-form design equations for the compact symmetric-centered inductors with high directivity.

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40

Zhang, Wen, Hui Zhang, Shijiu Jin, and Zhoumo Zeng. "A Two-Dimensional CMUT Linear Array for Underwater Applications: Directivity Analysis and Design Optimization." Journal of Sensors 2016 (2016): 1–8. http://dx.doi.org/10.1155/2016/5298197.

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Capacitive micromachined ultrasonic transducers (CMUTs) are one of the promising MEMS devices. This paper proposed an integrated vibration membrane structure to design a two-dimensional CMUT linear array for underwater applications. The operation frequencies for different medium have been calculated and simulated, which are 2.5 MHz in air and 0.7 MHz in water. The directivity analyses for the CMUT cell, subarray, and linear array have been provided. According to the product theorems, the directivity function of the complex array is obtained using a combination of the directivity functions of certain simple structures. Results show that the directivity of a CMUT cell is weak due to the small size, but the directivity of the designed linear array is very strong. Influential parameters of the linear array have been discussed, including the cell numbers, the adjacent distance, and the operation medium. In order to further suppress the side lobe interference and improve the resolution and the imaging quality of the imaging system, several weighting methods are used for optimization and comparison. Satisfactory side lobe suppression results are obtained, which can meet the actual requirements.

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Pörschmann, Christoph, and Johannes M. Arend. "Investigating phoneme-dependencies of spherical voice directivity patterns II: Various groups of phonemes." Journal of the Acoustical Society of America 153, no. 1 (January 2023): 179–90. http://dx.doi.org/10.1121/10.0016821.

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The substantial variation between articulated phonemes is a fundamental feature of human voice production. However, while the spectral and temporal aspects of the phonemes have been extensively studied, few have investigated the spatial aspects and analyzed phoneme-dependent differences in voice directivity. This paper extends our previous research focusing on the directivity patterns of selected vowels and fricatives [Pörschmann and Arend, J. Acoust. Soc. Am. 149(6), 4553–4564 (2021)] and examines different groups of phonemes, such as plosives, nasals, voiced alveolars, and additional fricatives. For this purpose, full-spherical voice directivity measurements were performed for 13 persons while they articulated the respective phonemes. The sound radiation was recorded simultaneously using a surrounding spherical microphone array with 32 microphones and then spatially upsampled to a dense sampling grid. Based on these upsampled datasets, the spherical voice directivity was studied, and phoneme-dependent variations were analyzed. The results show significant differences between the groups of phonemes. However, within three groups (plosives, nasals, and voiced alveolars), the differences are small, and the variations in the directivity index were statistically insignificant.

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Makino, Yusuke, and Yasushi Takano. "Sound source directivity considering source movement." INTER-NOISE and NOISE-CON Congress and Conference Proceedings 265, no. 4 (February 1, 2023): 3579–89. http://dx.doi.org/10.3397/in_2022_0505.

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When the source moves, frequency modulation (Doppler effect) occurs in the radiated sound, and the directivity of source changes. In addition, the source can be not located in a direction from the direction of arrival of radiated sound. Therefore, the sound pressure directivity may differ depending on whether the source is static or moving. There are two types of wave equations, one that describes sound pressure as a variable and one that describes velocity potential as a variable. When the sound source moves at a constant velocity and the equation is solved assuming that the source strength is constant with respect to the velocity, the sound pressure directivity of the radiated sound changes depending on the description method of the wave equation. The sound pressure was obtained by solving the wave equations where a single monopole source and a dipole source are moving at a constant velocity. From the results, we showed the difference of sound pressure directivity when source is moving from the directivity of static source.

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Tsaliev, T. A., and A. O. Vakarchuk. "CHARACTERISTICS OF VIBRATOR ARRAYS DIRECTIVITY ON HARMONICS OF MAIN FREQUENCY." Proceedings of the O.S. Popov ОNAT 1, no. 2 (December 31, 2020): 40–49. http://dx.doi.org/10.33243/2518-7139-2020-1-2-40-49.

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Antenna patterns representing dependences of the directivity factor (DF) on angular coordinates for arrays formed from Yagi-Uda aerials are considered and discussed. The results of computer modelling are based on the decision of integral equations by the method of moments. Patterns that represent dependences of the coefficient of the directivity factor (DF) for an array and her elements from angular coordinates are counted on fundamental frequency and four harmonics. The data obtained confirmed the validity of the assumptions that the directivity properties of vibrator antenna arrays can significantly affect the EMC conditions for harmonics of the fundamental frequency. At these frequencies, several main maxima appear in the radiation patterns, the level of directivity in which may even exceed the maximum directivity in the main lobe at the fundamental frequency. The DF patterns shown in the article refer to the case of in-phase excitation of the active elements of the array (without supply lines). However, in the presence of such lines with sequential or mixed power supply circuits, the dependence of the directivity on the angular coordinates can change significantly. The presence of bandpass filters in the input and output stages of the radar will make it possible to largely suppress the levels of harmonic interference, however, if these filters are made on the basis of transmission line segments, their parameters at harmonic frequencies may be insufficient. Further research can be aimed at studying the spatial characteristics and directivity of vibrator antenna arrays based on wave channel antennas with an increased number of passive vibrators, as well as with various power supply and filtering schemes.

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Qin, Lei, Chuan Xin Gu, Li Kun Wang, Chao Zhong, Jing Jing Liu, Bin Zhang, and Dan Long. "The Study on Broad Directivity Characteristic of Piston Transducer with Finite Baffle." Applied Mechanics and Materials 670-671 (October 2014): 1233–37. http://dx.doi.org/10.4028/www.scientific.net/amm.670-671.1233.

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Transducer with large directivity and high transmitting sensitivity is designed and fabricated. It is a sandwich transducer with composite horn and it has a finite baffle. A novel model considering the dimension of baffle is deduced, the directivity of transducers are calculated under different conditions. The computations of models agree with the experimental data well. The maximum transmitting voltage response level of the sandwich transducer is 143dB (1V/μPa) and the directivity is up to 99°(-3dB) at the resonance frequency of 75.6kHz.

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Xiong, Hong Jin, Bing Cheng Yuan, Hao Ke Zhan, Yin Bo Luo, and Long Long Fan. "Research on Simulation of Array Directivity Based on MATLAB." Advanced Materials Research 694-697 (May 2013): 2360–63. http://dx.doi.org/10.4028/www.scientific.net/amr.694-697.2360.

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According to the theory of underwater acoustic spread and circular piston transducer array, the mathematical model for the directivity of array is created. By means of MATLAB, the accurate expression method for the figure of array directivity is studied, and the characteristic and difference of the simulation curve in various direction are analyzed. It is shown by the application that, to a certain extent, the conclusion has practical value and guide meaning for the directivity simulation and design of the array.

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Lee, Donghyun, Haengseon Lee, Sunmook Hwang, and Jaewoon Ahn. "Design of an Impulse Radiating Antenna Using a Curved TEM-Wire Fed Parabola." International Journal of Antennas and Propagation 2012 (2012): 1–9. http://dx.doi.org/10.1155/2012/341206.

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A design procedure for a TEM-wire fed parabolic antenna is given for impulse radiation, which is suitable for low cost fabrication. A simple wire-type TEM horn and a parabolic reflector are used to achieve ultra-wide bandwidth and high directivity at the same time. Equations for parametric curves of a TEM-wire horn are presented and are used to investigate the relation among their shapes, bandwidth, and directivity. It is also found that wire separation near the focal point limits the high frequency directivity.

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Chen, Yu-Chi, Wen-Ching Ko, Han-Lung Chen, Hsu-Ching Liao, Wen-Jong Wu, Pei-Zen Chang, and Chih-Kung Lee. "Modeling and experimental verification on directivity of an electret cell array loudspeaker." Journal of Intelligent Material Systems and Structures 24, no. 3 (June 19, 2012): 326–33. http://dx.doi.org/10.1177/1045389x12451192.

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We propose a model to give us a method to investigate the characteristic three-dimensional directivity in an arbitrarily configured flexible electret-based loudspeaker. In recent years, novel electret loudspeakers have attracted much interest due to their being lightweight, paper thin, and possessing excellent mid- to high-frequency responses. Increasing or decreasing the directivity of an electret loudspeaker makes it excellent for adoption to many applications, especially for directing sound to a particular area or specific audio location. Herein, we detail a novel electret loudspeaker that possesses various directivities and is based on various structures of spacers instead of having to use multichannel amplifiers and a complicated digital control system. In order to study the directivity of an electret loudspeaker based on an array structure which can be adopted for various applications, the horizontal and vertical polar directivity characteristics as a function of frequency were simulated by a finite-element analysis model. To validate the finite-element analysis model, the beam pattern of the electret loudspeaker was measured in an anechoic room. Both the simulated and experimental results are detailed in this article to validate the various assertions related to the directivity of electret cell-based smart speakers.

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Chang, Won Il, Mahn Jea Chung, and Chul Soon Park. "Compact High-Directivity Contra-Directional Coupler." Electronics 11, no. 24 (December 9, 2022): 4115. http://dx.doi.org/10.3390/electronics11244115.

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This paper presents a novel design of a compact contra-directional coupler with high directivity for high-power monitoring in high frequency. Microstrip parallel coupled lines are widely used for directional couplers; however, they show poor directivity inherently. Their directivity has been improved by many works. However, the suggested approaches often result in other limitations, such as a weak structure for high-power monitoring, or a larger size to be integrated with other circuits. The design approach proposed in this study starts from a ring-type four-port network to avoid weak components that are vulnerable to high power, and uses a 60° electrical length of coupled line for a compact size. The design equations for the initial dimensions are derived from the ring-type four-port network model. The weak coupling of the 20 dB coupler was designed and measured. The measurement shows 20 dB directivity from 12.8 GHz to 14.8 GHz, covering the Ku-band satellite uplink communication and peak directivity of about 45 dB. The coupler’s active area is 4 mm by 5.5 mm; this is a compact size compared with other works.

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Liu, Haixia, Shuo Lei, Xiaowei Shi, and Long Li. "Study of Antenna Superstrates Using Metamaterials for Directivity Enhancement Based on Fabry-Perot Resonant Cavity." International Journal of Antennas and Propagation 2013 (2013): 1–10. http://dx.doi.org/10.1155/2013/209741.

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Metamaterial superstrate is a significant method to obtain high directivity of one or a few antennas. In this paper, the characteristics of directivity enhancement using different metamaterial structures as antenna superstrates, such as electromagnetic bandgap (EBG) structures, frequency selective surface (FSS), and left-handed material (LHM), are unifiedly studied by applying the theory of Fabry-Perot (F-P) resonant cavity. Focusing on the analysis of reflection phase and magnitude of superstrates in presently proposed designs, the essential reason for high-directivity antenna with different superstrates can be revealed in terms of the F-P resonant theory. Furthermore, a new design of the optimum reflection coefficient of superstrates for the maximum antenna directivity is proposed and validated. The optimum location of the LHM superstrate which is based on a refractive lens model can be determined by the F-P resonant distance.

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Толкачёв, А. И., В. Н. Капшай, and А. А. Шамына. "Генерация второй гармоники-суммарной частоты в тонком сферическом слое. II. Анализ диаграмм направленности." Оптика и спектроскопия 129, no. 12 (2021): 1547. http://dx.doi.org/10.21883/os.2021.12.51743.2386-21.

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The solution to the problem of second harmonic–sum frequency generation by two coherent plane electromagnetic waves with elliptical polarizations and equal frequencies in a thin spherical layer is analyzed graphically. Asymmetries are introduced that quantitatively describe the shape of three-dimensional directivity patterns (spatial distribution of the power density of second harmonic–sum frequency radiation). Three-dimensional directivity patterns and asymmetries are analyzed for various combinations of the parameters: ratio of the complex amplitudes of the incident waves, angle between the wave vectors of the incident waves (the opening angle), ellipticities, orientations of polarization ellipses, spherical particle size. It is found that, at small particle sizes, each anisotropy type corresponds to its own individual directivity pattern. It is revealed that, for one of the anisotropy types, the shape of the directivity pattern almost does not change for nearly all possible ranges of the above parameters.

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