• Title/Summary/Keyword: grating lobe

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A Reduction of Grating Lobe By Using the Multi-element Receive Synthetic Focusing In Ultrasonic Image (초음파 영상에서 Multi-element Receive Synthetic Focusing을 이용한 그레이팅 로브 감축)

  • Lee, J.S.;Ahn, Y.B.
    • Proceedings of the KOSOMBE Conference
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    • v.1997 no.11
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    • pp.559-562
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    • 1997
  • In this paper, we propose the method that reduce the grating lobe in the ultrasound synthetic focusing images. synthetic focusing images have more larger and closer grating lobe than conventional phased array images and more lower signal to noise ratio. so, we represent the method that reduce the grating lobe by using multi element receive focusing. experimental results are showed that the proposed multi element receiving method reduce the grating lobe and increase the signal to noise ratio.

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Suppression of side lobe and grating lobe in ultrasound medical imaging system (의료용 초음파 영상 시스템에서 부엽과 격자엽의 억제)

  • Jeong, Mok Kun
    • The Journal of the Acoustical Society of Korea
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    • v.41 no.5
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    • pp.525-533
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    • 2022
  • We propose an effective method for suppressing both side and grating lobes by applying 2-dimensional Fourier Transform to the received channel data during the receive focusing process of an ultrasound imaging system. When the signal from the image point is focused, the channel signals have the same DC value across the channels. However, even after echoes from outside an imaging point are focused, they are manifested as having different spatial frequencies depending on their incident angles. Therefore, after the receive focusing delay time is applied, 2-D Fourier Transform is performed on the time-channel data to separate the DC component and other frequency components in the spectral domain, and the weighting value is defined using the ratio of the two values. The side lobe and grating lobe were suppressed by multiplying the ultrasound image by a weighting value. Ultrasound images with a frequency of 5 MHz were simulated in a 64-channel linear array. The grating lobe appearing in the ultrasound image was completely removed by applying the proposed method. In addition, the side lobe was reduced and the lateral resolution was greatly increased. Results of computer simulation on a human organ mimicking image show that the proposed method can aid in better lesion diagnosis by increasing the image contrast.

Analysis of the Ultrasonic Beam Profile Due to Variation of the Inter-Element Spacing for the Phased Array Transducer (페이즈드 어레이 트랜스듀서에 있어서 구성 압전소자의 간격 변화에 따른 초음파 빔 전파 특성 해석)

  • Choe, Sang-U;Lee, Jun-Hyeon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.4 s.175
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    • pp.972-981
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    • 2000
  • The phased array transducer has two distinct advantages. One is rapid scanning comparing with the conventional mechanical or manual scanning system. Therefore, output image is represented in real-time. The other is the dynamic focusing and the dynamic steering of ultrasonic beam. Only the delay times that are controlled electrically are used to focus and to steer beam without any lenses or wedges. In this study, the profile of the ultrasonic beam for the phased array transducer has been simulated in the Huygens principle with varying the inter-element spacing of the linear phased array transducer. From the result of this study, it was found that the ultrasonic beam spread wider as the inter-element spacing was decreased. However, the focusing effect was improved, even when the number of the element was not big. In addition, there was grating lobes that are constructed when the inter-element spacing is more than half wavelength. However, this grating lobe has lower amplitude than the main lobe.

Optimal design of a concave annular array transducer to generate high intensity focused ultrasound (고강도 집속 초음파 발생용 오목한 환상형 배열 트랜스듀서의 최적설계)

  • Choi, Euna;Roh, Yongrae
    • The Journal of the Acoustical Society of Korea
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    • v.35 no.6
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    • pp.452-465
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    • 2016
  • In this study, the structure of a concave annular array transducer was optimized to generate high intensity focused ultrasound for medical therapeutic application. The transducer has a phased array structure composed of several concentric channels that have 40 mm as the radius of curvature. We derived theoretical equations to analyze the sound field of the transducer and verified the validity of the equations by comparing the results calculated by the equations with those from finite element analyses. We also checked the possibility of dynamic focusing at around the geometric focal point. Further, the level of a grating lobe occurring at an unwanted position in the transducer sound field was confirmed to be reducible through the relation between the number of channels and the frequency of the transducer. Hence, the structure of the transducer was optimized to place the main lobe within a specific range from the zenith while systematically reducing the level of the maximum sidelobe including the grating lobe. The designed structure showed the performance better than that targeted at all the focal points.

The Effects of Various Apodization Functions on the Filtering Characteristics of the Grating-Assisted SOI Strip Waveguides

  • Karimi, Azadeh;Emami, Farzin;Nozhat, Najmeh
    • Journal of the Optical Society of Korea
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    • v.18 no.2
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    • pp.101-109
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    • 2014
  • In this paper, four apodization functions are proposed for silicon-on-insulator (SOI) strip waveguides with sidewall-corrugated gratings. The effects of apodization functions on the full width at half maximum (FWHM), the side-lobe level, and the reflectivity of the reflection spectrum are studied using the coupled-mode theory (CMT) and the transfer-matrix method (TMM). The results show that applying proposed apodization functions creates very good filtering characteristics. Among investigated apodized waveguides, the apodization functions of Polynomial and z-power have the best performance in reducing side-lobes, where the side-lobe oscillations are entirely removed. Four functions are also used for precise adjustment of the bandwidth. Simulation results show that the minimum and maximum values of the FWHM are 0.74 nm and 8.48 nm respectively. In some investigated functions, changing the apodization parameters decreases the reflectivity which is compensated by increasing the grating length.

Analysis of Arrayed Waveguide Grating Waveglength Filter using Wide Angle Beam Propagation Method (Wide Angle BPM 을 이용한 광도파로열 격자 파장 필터의 해석)

  • Park, Jun-O;Jeong, Yeong-Cheol
    • Journal of the Institute of Electronics Engineers of Korea SD
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    • v.39 no.2
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    • pp.46-55
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    • 2002
  • The key component to accomplish the WDM all optical network is an Arrayed Waveguide Grating(AWG) wavelength filter Numerical analysis is necessary for design and analysis of optical components like AWG wavelength filter. Beam Propagation Method(BPM) is the most widely-used method. In this paper, we analyze the difference between the paraxial BPM and the WA-BPM when they are applied to the analysis of InP/InGaAsP/InP AWG wavelength filter. The paraxial BPM is based on paraxial approximation, and the WA-BPM is based on the low order Pade approximant. The side lobe level(SLL) and insertion loss calculated from both methods are compared. The high order Pade approximant will to used to more accurate design and analysis of AWG.

A Study on the Beam-forming of the Linear Array Antenna using Grating Lobe (Grating Lobe를 이용한 선형 배열 안테나의 Beam-forming에 관한 연구)

  • 신정록;송우영
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.11 no.5
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    • pp.806-812
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    • 2000
  • In this paper, we theoretically studied on the large antenna array whose element had wider than one wavelength. And we also verified the adaptedness through the experiments. Using grating lobes, we could make antenna have sharp HPBW. Not only HPBW but also SLL could be controlled by giving optimal space for antenna array. In order to verify this method, we designed 4 horn antenna array and measured the radiation patterns at 9 GHz. Each horn antenna has the dimension of 64.3$\times$82.5$\textrm{mm}^2$ and HPBW of 27$^{\circ}$. The space between antennas is longer than one wavelength so that it may have the grating lobes in visible region. As a result of experiments, we could get HPBW of 4.3$^{\circ}$, 3.3$^{\circ}$ and 1.7$^{\circ}$when giving 2.5λ, 2.7λ and 3.0λ of the spacing respectively. We concluded this could be useful making the antenna with narrow HPBW.

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Scan Performance Analysis by Mutual Coupling Effects in Fabry-Perot Cavity Antennas (패브리 패롯 공진기형 안테나에서 뮤츄얼 커플링에 의한 스캔특성 분석)

  • Kim, Jong-Sung
    • Journal of the Institute of Electronics and Information Engineers
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    • v.51 no.10
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    • pp.21-25
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    • 2014
  • Scan capabilities of Fabry-Perot cavity (FPC) antennas are investigated for the case of a $4{\times}1$ thinned array placed inside the cavity. The FPC array antenna has higher maximum gain and lower sidelobe level (SLL), but the maximum scan angle of the thinned array is 14-17% lower than the patch array alone, due to increased mutual coupling in the FPC structures. However, unlike the bare thinned array, the SLL of FPC array does not suffer from the grating lobe problem even though it has a relative large element spacing of more than $1.0{\lambda}_0$.

Analysis of Ultrasound Synthetic Transmit Focusing Using Plane Waves (평면파를 이용한 초음파 합성 송신 집속 기법의 해석)

  • Lee, Jong Pil;Song, Jae Hee;Song, Tai-Kyong
    • The Journal of the Acoustical Society of Korea
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    • v.33 no.3
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    • pp.200-209
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    • 2014
  • In this paper, we present a general model for synthetic transmit focusing method using plane waves (STF-PW) of which the properties are investigated through mathematical analysis and compared with those of the conventional focusing method. The analysis results show that STF-PW produces non-diffracting beams in the sense that their main lobe widths do not change with depth. We also present a method for synthesis of plane waves to obtain a desired main lobe width while preventing grating lobe generation and a method for broadening the region over which the non-diffracting property is maintained. The proposed model and analysis results were validated through computer simulations.

Comparative Study of Optimization Algorithms for Designing Optimal Aperiodic Optical Phased Arrays for Minimal Side-lobe Levels (비주기적 광위상배열에서 Side-lobe Level이 최소화된 구조 설계를 위한 최적화 알고리즘의 비교 연구)

  • Lee, Bohae;Ryu, Han-Youl
    • Korean Journal of Optics and Photonics
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    • v.33 no.1
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    • pp.11-21
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    • 2022
  • We have investigated the optimal design of an aperiodic optical phased array (OPA) for use in light detection and ranging applications. Three optimization algorithms - particle-swarm optimization (PSO), a genetic algorithm (GA), and a pattern-search algorithm (PSA) - were employed to obtain the optimal arrangement of optical antennas comprising an OPA. The optimization was performed to obtain the minimal side-lobe level (SLL) of an aperiodic OPA at each steering angle, using the three optimization algorithms. It was found that PSO and GA exhibited similar results for the SLL of the optimized OPA, while the SLL obtained by PSA showed somewhat different features from those obtained by PSO and GA. For an OPA optimized at a steering angle <45°, the SLL value averaged over all steering angles increased as the angle of optimization decreased. However, when the angle of optimization was larger than 45°, low average SLL values of <13 dB were obtained for all three optimization algorithms. This implies that an OPA with high signal quality can be obtained when the arrangement of the optical antennas is optimized at a large steering angle.