• Title/Summary/Keyword: directivity

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A Study on the Incident Angle Estimation Method of Target at Coherent Interference (상관성 간섭에서 표적의 입사각 추정 방법에 대한 연구)

  • Shin, Ho-Sub
    • Journal of the Korea Society of Computer and Information
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    • v.15 no.5
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    • pp.75-81
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    • 2010
  • Adaptive array antenna system estimates target signal, as making a null pattern toward the interference signal. However, receiving a coherent interference signal at adaptive array antenna system, as target signal is regarded as interference signal, the performance of system rapidly decreases. The main beam does not direct an incidence direction of target signal due to sensitivity in directivity error. This paper proposes beamforming algorithm which combines high order limit condition and directivity error modify method. And it minimizes degree of freedom and decreases interference signal and directivity error using proposed algorithm. This paper compares and analyzes the performance of proposed algorithm and general algorithm using simulation. In this paper, the proposed algorithm correctly estimates an incident angle, but general algorithm occurs an error of about $0.8^{\circ}$.

Optimal Directivity Synthesis of Ultrasonic Transducers Using a Combined Algorithm (조합 알고리즘에 의한 초음파 트랜스듀서의 최적 지향성합성)

  • ;Takao Tsuchiya;Yukio Kagawa
    • The Journal of the Acoustical Society of Korea
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    • v.19 no.1
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    • pp.25-31
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    • 2000
  • In this paper, we proposed an algorithm that used a direct method to set an initial value of Broydon-Fletcher-Goldfarb-Shanno(BFGS) method and, accordingly, conducted an experiment in optimal directivity synthesis of adaptive ultrasonic transducer by point source array. To certify the efficiency of this method, quasi-ideal beam with arbitrary beam width, rotating beam, and multi beam, all with the limited side lobe level -30dB, were chosen to check the problem of directivity synthesis that was formed by point source array in the second dimensional sound field. The numerical calculation results showed that the proposed method performed the directivity synthesis faster than the BFGS method did. In addition, the proposed method showed a good error correction for directivity synthesis, and did not demand the choice of initial value. Finally, it is also shown that the proposed method can be used for the adaptive control that was not possible with the direct method alone.

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A Design of Microstrip Directional Coupler with the Improved Directivity Characteristic (개선된 지향성을 갖는 마이크로스트립 방향성 결합기 설계)

  • Kim, Chul-Soo;Lim, Jong-Sik;Kim, Dong-Joo;Ahn, Dal
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.15 no.6
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    • pp.548-553
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    • 2004
  • In this paper, single, two, and three-section microstrip directional couplers are implemented for realizing the high directivity characteristics. The achievement of the high directivity with microstrip configuration is carried out by the distributed capacitor to decrease the even and odd mode phase difference. Capacitive compensation is performed by gap coupling of open stub formed in sub-coupled line. Therefore, insertion loss and power handling capability are not affected by the gap coupling. The proposed structure is easy to fabricate and incorporate another microwave device due to the planner microstrip. We designed and fabricated single, two, and three-section directional coupler with 20 ㏈ coupling. In spite of microstrip structure, the capacitive compensation structure shows 30 ㏈, 27 ㏈, and 25 ㏈ of directivity in single, two, and three-section directional couplers, respectively.

Radiational characteristics of speaker directivity using active control (능동제어를 이용한 스피커 지향성의 방사특성)

  • Lee, Chai-Bong;Lee, Chang-Young
    • The Journal of the Korea institute of electronic communication sciences
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    • v.7 no.1
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    • pp.27-31
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    • 2012
  • In this paper, we constructed an array of speaker system with directivity by using FXLMS(Filtered-X LMS) algorithm and confirmed its directivity. The front $0^{\circ}$ characteristics of the controlled speaker was suppressed by interfering it with the control signal produced with filter coefficients optimized with respect to the $180^{\circ}$ characteristics of the rear speakers. The directivity of the array of rear speakers was measured and the damping effect of the signal from the front speaker array was confirmed. The frequency characteristics and directivity was investigated by using the adaptive filter coefficients on damping, the damping on the control point was verified in all the frequency range. In 100Hz, 200Hz, 1000Hz regime, the damping effect was observed in the range of front $60^{\circ}{\sim}100^{\circ}$.

The Effect of Directivity of Antenna for the Evaluation of Abnormal Area Using Ground Penetrating Radar (지하투과레이더를 이용한 이상구간 평가 시 안테나 지향성의 영향)

  • Kang, Seonghun;Lee, Jong-Sub;Lee, Sung Jin;Park, Young-Kon;Hong, Won-Taek
    • Journal of the Korean Geotechnical Society
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    • v.33 no.11
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    • pp.21-34
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    • 2017
  • The ground penetrating radar (GPR) signal can be measured with different amplitudes according to the directivity, so the directivity of the antenna should be considered. The objective of this study is to investigate the directivity of antenna by analyzing the reflection characteristics of electromagnetic waves radiated from the antenna, and to evaluate effective range of angle that can inspect an abnormal area according to the directivity of antenna. For the measurement of the directivity, a circular metal bar is used as reflector and the signals are measured by changing the angle and the distance between reflector and antenna in the E- and H-plane. The boundary distance between the near field and the far field is determined by analyzing the amplitudes of reflected signals, and two points with different distances from each of near and far fields are designated to analyze radiation patterns in near and far fields. As a result of radiation pattern measurement, in the near field, minor lobes are observed at angle section at more than $50^{\circ}$ in both E- and H-plane. Therefore, antenna has the directivity for the direction of main lobe and minor lobes in near field. In the far field, antenna has the directivity for a single direction of main lobe because minor lobes are not observed. The amplitude of the signal reflected from the near field is unstable, but it can be distinguished from noise. Therefore, in the near field, the ground anomaly can be detected with high reliability. On the other hand, the amplitude of the signal reflected from the far field is stable, but it is hard to distinguish between reflected signal and noise because of the excessive loss of electromagnetic wave. The analyses of directivity in the near and the far fields performed in this study may be effectively used to improve the reliability of the analyses of abnormal area.

Development of Directional Digital Hearing Aid Performance Testing System (지향성 디지털 보청기의 성능 검사 장치 개발)

  • Jarng, Soon-Suck;Kwon, You-Jung;Lee, Je-Hyeong
    • Proceedings of the IEEK Conference
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    • 2005.11a
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    • pp.411-414
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    • 2005
  • The most recent trend on digital hearing aid is to increase the ratio of signal to noise by directivity or to develop noise reduction algorithm inside DSP IC chip. This paper designed, fabricated and tested a digital hearing aid directivity testing device in which a micro-mouse-like the stepping motor with a speaker rotates around an examinant. Both ears of the examinant were fixed with ITE hearing aids in order to response to receiving sound. The diameter of the directivity testing device was 2 [m] and the micro-mouse was precisely controlled by PICBASIC micro processor.

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Jet-Edge Interaction and Sound Radiation in Edgetones (쐐기소리에서 분류-쐐기의 상호작용과 소리의 방사)

  • ;Powell A.
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.3
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    • pp.584-590
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    • 1994
  • A theoretical model has been developed to analyze the jet-edge interaction and the sound radiation. The edge responding to the sinuous impinging jet is regarded as an array of dipoles and their strength is determined by the boundary condition on the edge surface. The surface pressure distribution and the edgeforce are estimated using these dipoles. Then the pressure amplitude and directivity of the sound field is obtained by summing the radiating sounds from the dipole sources. It is found that the effective source is located a little distance downstream from the edge tip. And the directivity of the sound radiation is cardioid pattern near the edge but dipole pattern far from the edge. The theoretical model is confirmed by comparing the theoretical prediction of the edgeforce and sound pressure level with available experimental data.

A PVDF Acoustic Sensor for Identifying Sound Source Frequencies (음원주파수 판별을 위한 PVDF 음향센서)

  • 이용국;최용일;송유리;안형근;한득영
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 1995.11a
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    • pp.202-204
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    • 1995
  • An acoustic sensor using PVDF film is proposed in this paper. And its properties, such as sensitivity level, identification of sound source frequencies. and directivity, were experimented. Sensitivity level measured at the distance of 1[m] was limited in the range of ${\pm}$10dB. Adjacent three frequencies were also tested to identify the frequency of sound sources. In the range of audible frequencies, it could distinguish the frequencies of a complex sound. In addition, it was found that the sensor outputs were maximum in the coincided direction with a source, when directivity was experimented with three sound sources and FFT. The proposed PVDF film sensor has good characteristics of directivity and identifying ability as an acoustic sensor.

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An Experimental Study on the Propagation of Impulse Noise in the Far Sound Field (원음장에서의 충격성 소음전파에 관한 실험적 연구)

  • 송화영;제현수;이주원;이성태;이동훈
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2004.05a
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    • pp.852-855
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    • 2004
  • This experimental study describes the propagation characteristics of the impulse noise emitted from the exit of a straight pipe attached to the open end of a simple shock tube. The sound pressure level and directivity of the impulse noise propagating from the exit of pipe with several different diameters are measured in the far sound fold for the range of the incident shock wave Mach number between 1.07 and 1.26. The experimental results showed that the peak values of impulse noises had a strong dependance on the exit diameter of a pipe and the shock wave Mach number. The impulse noise had the directivity propagating toward to the pipe axis and the characteristics of inverse square law of propagation distance. Moreover, it was shown that the one-third octave band SPL of impulse noise was almost constant regardless of the frequency band.

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Non-Cavitation Noise from Large Scale Marine Propeller (대형 선박용 프로펠러의 비공동소음 예측)

  • Ryu, Ki-Wahn;Kim, Bong-Ki;Yoo, Yong-Joo
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2012.10a
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    • pp.562-567
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    • 2012
  • Noises from the large scale marine propeller are calculated numerically on non-cavitation condition. The hydrodynamic analysis are carried out by potential based panel method with time marching free wake approach. The distribution of hyrodynamic loads on the propeller surface and noise signals are obtained using the unsteady Bernoulli's equation and the Farasssat formula respectively. It turns out that the noise signal shows strong peak at the blade passage frequency. Noise signals and directivity patterns for both the thickness and the loading noise are compared with each other. The directivity pattern for the loading noise shows minor lobe at the backward side of the rotating disc plane.

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