• Title/Summary/Keyword: Broadband Pulse

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Computer-Aided Crafting of Pulse Shapes for Broadband Heteronuclear Decoupling in the presence of Homonuclear Coupling

  • Lee, Chang-Jae
    • Journal of the Korean Magnetic Resonance Society
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    • v.3 no.1
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    • pp.36-43
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    • 1999
  • We present a pulse shape tailored for broadband decoupling for a system of spin-1/2's with scalar couplings as well. In crafting the pulse shape Coherent Averaging Theory and Fourier expansion method are used. The Fourier expansion coefficients are optimized numerically by applying the Simulated Annealing Method. The decoupling performance of the shaped pulse thus designed is then compared with the well-known composite pulse sequence, DIPSI-2. It is shown that the shaped pulse performs well even at the conditions where the DIPSI sequence begins to fail.

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Analysis and Classification of Broadband Acoustic Echoes from Individual Live Fish using the Pulse Compression Technique (펄스압축기법을 이용한 활어 개체어에 대한 광대역 음향산란신호의 분석 및 식별)

  • Lee, Dae-Jae;Kang, Hee-Young;Kwak, Min Son
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.48 no.2
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    • pp.207-220
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    • 2015
  • This study identified the species-specific, frequency-dependent characteristics of broadband acoustic scattering that facilitate classifying fish species using the pulse compression (PC) technique. Controlled acoustic scattering laboratory experiments were conducted with nine commercially important fish species using linear chirp signals (95-220 kHz) over an orientation angle range of ${\pm}45^{\circ}$ in the dorsal plane at approximately $1^{\circ}$ increments. The results suggest that the angular-dependent characteristics of the broadband echoes and the frequency-dependent variability in target strength (TS) were useful for inferring the fish species of interest. The scattering patterns in the compressed pulse output were extremely complex due to morphological differences among fish species, but the x-ray images strongly suggested that spatial separation correlated well with scattering for the head, skeleton, bone, otoliths, and swim bladder within each specimen.

π/2 Pulse Shaping via Inverse Scattering of Central Potentials

  • 이창재
    • Bulletin of the Korean Chemical Society
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    • v.17 no.2
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    • pp.188-192
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    • 1996
  • It is shown that the inversion of the undamped Bloch equation for an amplitude-modulated broadband π/2 pulse can be precisely treated as an inverse scattering problem for a Schrodinger equation on the positive semiaxis. The pulse envelope is closely related to the central potential and asymptotically the wave function takes the form of a regular solution of the radial Schrodinger equation for s-wave scattering. An integral equation, which allows the calculation of the pulse amplitude (the potential) from the phase shift of the asymptotic solution, is derived. An exact analytical inversion of the integral equation shows that the detuning-independent π/2 pulse amplitude is given by a delta function. The equation also provides a means to calculate numerically approximate π/2 pulses for broadband excitation.

Bandwidth Enhancement of a Broadband Ultrasonic Mosaic Transducer using 48 Tonpilz Transducer Elements with 12 Resonance Frequencies (12 주파수의 48 tonpilz 진동소자를 이용한 광대역 초음파 모자이크 변환기의 대역폭 확장)

  • Lee, Dae-Jae
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.47 no.3
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    • pp.302-312
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    • 2014
  • This article describes the design and performance characteristics of a broadband ultrasonic mosaic transducer. We focus on the improved bandwidth in the high frequency band of a previously designed broadband ultrasonic transducer (Lee et al., 2014). The improvement in the pulse-echo bandwidth was achieved by employing twelve $2{\times}2$ element subarrays, operating at different resonance frequencies, and utilizing the mosaic array concept. We found that the -6 dB and -12 dB bandwidths of the newly developed broadband ultrasonic mosaic transducer, were up to 155% and 170% of the previously designed model, with a quality factor of 1.71 and 1.25, respectively. The averaged TVR (transmitting voltage response), SRT (receiving sensitivity), and FOM (figure of merit) values in a nearly flat transmitting response band, from 45 to 105 kHz providing a -12 dB bandwith of 60 kHz, were 163.3 dB (re $1{\mu}Pa/V$ at 1 m), -192.8 dB (re $1V/{\mu}Pa$), and -30.9 dB, respectively.

Analysis of the Wave Propagation Characteristic for Pulse Signal on Tapered Microstrip Line in Time Domain (테이퍼형 마이크로스트립 전송선로에서 펄스 신호의 시간 영역 전송특성 해석)

  • Kim Girae;Choi Young-Kvu
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.55 no.1
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    • pp.40-44
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    • 2006
  • In this paper, the distortion characteristics of an electrical pulse which has a rise/fall time due to the dispersion and the reflection, on nonuniform tapered microstrip lines has investigated in time domain. The transmission characteristics on uniform microstrip lines in time domain had represented already, but the results for the nonuniform tapered microstrip lines not represented yet. We investigated the transmission characteristics for pulse signal on the nonuniform tapered microstrip lines, and the result applied to design of wide band impedance matching circuit in design of MMIC. The voltage and current transfer functions are shown for the tapered line. The dispersion and distortion obtained by using these transfer functions are represented for the nonideal square pulse.

The Study on Signal Distortion of Meander-shaped Microstrip Line (마이크로스트립 미앤더 선로의 신호 왜곡 현상 연구)

  • Du, Jin-Kyoung;Hong, Young-Pyo;Kim, Jung-Min;Yook, Jong-Gwan
    • Proceedings of the Korea Electromagnetic Engineering Society Conference
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    • 2005.11a
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    • pp.197-202
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    • 2005
  • In this paper, we analyzed the signal distortion incorporating meander-shaped transmission line on PCB in broadband frequency range, up to 50GHz. This broadband characteristic provides reasonable analysis of digital pulse having very short rising time. Simulation results reveal suppression characteristic at multiband which is dependent on only the width of meander arm. This width of arm also can be adjusted using different permittivity because it provides different effective wave-length. It is found that the suppression characteristic shows sharpness with as a function of the number of arms. However, these characteristics shown limitation for microstrip line structure rather than for stripline structure, so we can avoid these unwanted phenomena using stripline structure.

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Design of the Broadband Microstrip Bow-tie Patch Antenna for a Subsurface Radar (표면하 레이더용 광대역 마이크로스트립 보우타이 패치 안테나 설계)

  • 김민준;곽영복
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.6 no.8
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    • pp.1305-1309
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    • 2002
  • Subsurface radar characterize a broadband frequency to collect a information, such as a crack of building, because of using narrow pulse. In this paper, we design a broadband bowtie antenna, using a microstrip, with a FR-4 substrate of ${\varepsilon}_r=4.0$, t=1.6mm. It has a 9.31% bandwidth at s11<-10 dB and s11=-27.45 dB, VSWR=1.089 at 5.78GHz.

Improvement of Power Spectrum in Ultrashort Pulse Reflectometry Signals Using Three Chirp Configuration

  • Roh, Young-Su
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.28 no.3
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    • pp.51-56
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    • 2014
  • The flat power spectrum of the transmitter output signal for the desired frequency range is ideal to achieve the best performance of ultrashort pulse reflectometry. However, the power spectrum of a typical pulse generator decreases significantly as frequency increases. A configuration of three chirped waveforms was employed to improve the power spectrum of the transmitter signal at higher frequencies. To determine the amplification gain required for higher frequency components, three chirped waveforms were theoretically generated and their power spectra were measured using numerical band-pass filters. Based on the results of numerical computations, the three chirp configuration was successfully applied to the design of the transmitter for a broadband system.

Characteristics of Echolocation Calls of the Parti-coloured Bat, Vespertilio sinensis, in Relation to Environment Type (환경특성에 따른 안주애기박쥐(Vespertilio sinensis)의 반향정위 특징)

  • Chung, Chul-Un;Han, Sang-Hoon
    • Journal of Environmental Science International
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    • v.24 no.3
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    • pp.353-358
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    • 2015
  • In this study, we analyzed two types of echolocation calls used by the parti-coloured bat, Vespertilio sinensis. Bats were captured in the Naejangsan National Park in October 2013. Call sounds of hand-released bats were recorded at the location of capture within the National Park. We analyzed pulse duration (PD), pulse interval (PI), peak frequency (PF), maximum frequency ($F_{MAX}$), minimum frequency ($F_{MIN}$), and bandwidth (BW). V. sinensis emitted the different types of the echolocation calls depending on the surrounding environment. Frequency modulated-constant frequency (FM-CF) signal of audible range was emitted when they flew in the uncluttered space over the canopy. However, when flying in the cluttered space below the canopy, they only emitted FM signal. FM-CF signal is in the audible range (e.g., low frequency), and FM signal has a harmonic broadband frequency range of two. There were significant differences in PD, PI, PF, FMAX, FMIN, and BW between the calls emitted over and below the canopy. Considering the functional characteristics of FM and CF signals, we conclude that the foraging activity of V. sinensis was observed below the canopy, and recommend the use of FM signal and broadband as echolocation signals.

Near-elliptic Core Triangular-lattice and Square-lattice PCFs: A Comparison of Birefringence, Cut-off and GVD Characteristics Towards Fiber Device Application

  • Maji, Partha Sona;Chaudhuri, Partha Roy
    • Journal of the Optical Society of Korea
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    • v.18 no.3
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    • pp.207-216
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    • 2014
  • In this work, we report detailed numerical analysis of the near-elliptic core index-guiding triangular-lattice and square-lattice photonic crystal fiber (PCFs); where we numerically characterize the birefringence, single mode, cut-off behavior and group velocity dispersion and effective area properties. By varying geometry and examining the modal field profile we find that for the same relative values of $d/{\Lambda}$, triangular-lattice PCFs show higher birefringence whereas the square-lattice PCFs show a wider range of single-mode operation. Square-lattice PCF was found to be endlessly single-mode for higher air-filling fraction ($d/{\Lambda}$). Dispersion comparison between the two structures reveal that we need smaller lengths of triangular-lattice PCF for dispersion compensation whereas PCFs with square-lattice with nearer relative dispersion slope (RDS) can better compensate the broadband dispersion. Square-lattice PCFs show zero dispersion wavelength (ZDW) red-shifted, making it preferable for mid-IR supercontinuum generation (SCG) with highly non-linear chalcogenide material. Square-lattice PCFs show higher dispersion slope that leads to compression of the broadband, thus accumulating more power in the pulse. On the other hand, triangular-lattice PCF with flat dispersion profile can generate broader SCG. Square-lattice PCF with low Group Velocity Dispersion (GVD) at the anomalous dispersion corresponds to higher dispersion length ($L_D$) and higher degree of solitonic interaction. The effective area of square-lattice PCF is always greater than its triangular-lattice counterpart making it better suited for high power applications. We have also performed a comparison of the dispersion properties of between the symmetric-core and asymmetric-core triangular-lattice PCF. While we need smaller length of symmetric-core PCF for dispersion compensation, broadband dispersion compensation can be performed with asymmetric-core PCF. Mid-Infrared (IR) SCG can be better performed with asymmetric core PCF with compressed and high power pulse, while wider range of SCG can be performed with symmetric core PCF. Thus, this study will be extremely useful for designing/realizing fiber towards a custom application around these characteristics.