• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.6
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• pp.912-918
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• 2001

This paper presents a performance analysis of experimental observations of a uplink smart antenna system operating in a wide-band CDMA environment designed for a WLL (Wireless Local Loop) system. The numerical results shown in this paper have been obtained from practical experiments using commercially developed mobile terminals. The beam pattern provided by the weight vector and the resultant BER (Bit Error Rate) are observed in both indoor and outdoor signal environments. From the experimental observations, it is concluded that the proposed smart antenna system provides significant improvements in receiving both indoor and outdoor signal environments.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.9B
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• pp.1511-1517
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• 2000

A new slot-coupled back-to-back microstrip array antenna is proposed for using in the IMT-2000 base station or repeater antenna. This antenna is composed of symmetrical SSAIP(Strip Slot, Air Inverted Patch) It has bidirectional radiation pattern in horizontal plane and 22.5$^{\circ}$main beam squint in vertical plane. The analysis is based on the cavity model and the design is achieved using Ensemble. Experimental results for the radiation pattern and the return loss have shown that the direction of the main beam is about 21$^{\circ}$and the impedance bandwidth is approximately 22.9% Thus the proposed antenna is able to operate over both uplink and downlink frequencies in IMT-2000.

• Journal of Biomedical Engineering Research
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• v.27 no.1
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• pp.22-29
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• 2006

This paper proposes an efficient array beamforming method using spatial matched filtering for ultrasound imaging. In the proposed method, ultrasound waves are transmitted from an array subaperture with fixed transmit focus as in conventional array imaging. At receive, radio frequency (RF) echo signals from each receive channel are passed through a spatial matched filter that is constructed based on the system transmit-receive spatial impulse response. The filtered echo signals are then summed. The filter remaps and spatially registers the acoustic energy from each element so that the pulse-echo impulse response of the summed output is focused with acceptably low side lobes. Analytical beam pattern analysis and simulation results using a linear array show that the proposed spatial filtering method can provide more improved spatial resolution and contrast-to-noise ratio (CNR) compared with conventional dynamic receive focusing (DRF) method by implementing two-way dynamically focused beam pattern throughout the field.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.4
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• pp.181-190
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• 2014

The underwater acoustic lens system is one of the systems getting high-resolution images on the seafloor by the beam forming method using acoustic lens. The beam forming using acoustic lenses reduces complexity and driving power. When receiving an incoming beam with the acoustic lens array, beam pattern analysis and arrangement problem of the array sensor must be addressed. Introducing SIR (Signal to Interference Ratio), the relationship among sensor interval, beam pattern and image quality would be analyzed. Generally if the sensor interval getting wider, the less effect of the side lobes makes SIR high. If the amplitude of a side lobe is high, SIR is generally getting low. The type of the apodization function changes the width, shape and amplitude of both main lobe and side lobes. Thus an appropriate apodization function can improve SIR. In this paper, SIR is stable at the sensor interval of 13mm with 0-10dB, which is not high relatively. By applying the Chebyshev function, the SIR becomes 80dB over the sensor interval of 37 mm or higher. The Hann and triangular functions demonstrate better SIR when the sensor interval becomes narrower.

• Vacuum Magazine
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• v.2 no.2
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• pp.17-23
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• 2015

Medium Energy Ion Scattering (MEIS) has been successfully used for ultrathin film analysis such as gate oxides and multilayers due to its single atomic depth resolution in compostional and structural depth profiling. Recently, we developed a time-of-flight (TOF) MEIS for the first time, which can analyze a $10{\mu}m$ small spot. Small spot analysis would be useful for test pattern analysis in semiconductor industry and various thin film technology. The ion beam damage problem is minimized due to its improved collection efficiency by orders of magnitude and the ion beam neutralization problem is removed completely for quantitative analysis. Newly developed TOF-MEIS has been applied for gate oxides, ultra shallow junctions, nanoparticles, FINFET structures to provide compositional and structural profiles. Further development for submicron spot analysis and applications for functional nano thin films and nanostructured materials are expected for various nanotechnology and biotehnology.

• Proceedings of the IEEK Conference
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• 2002.07a
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• pp.545-548
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• 2002

This paper proposes a unidirectional beam antenna using a probe excited circular ring near the reflector. The antenna structure is simple. The radiation characteristics of the antenna fur various spacing between a probe excited circular ring and the reflector are analyzed. These characteristics are also compared with the conventional single aperture near the reflector. It is found that the proposed structure yields better characteristics than the conventional structure. The numerical results of the radiation pattern, elevational beam peak, beamwidth, and maximum directivity are investigated. The result of the analysis is very useful to design the antenna of the high directivity with unidirectional beam.

• 제어로봇시스템학회:학술대회논문집
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• 1992.10a
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• pp.474-478
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• 1992

The non-rational transfer function of a Bernoulli-Euler beam, as an important component of a flexible structure, is analyzed. The true pattern of zeros of that transfer function is investigated as a function of sensor and actuator seperation. Translational displacement sensors are used for two cases in which a force input and a moment input are seperately applied. When the displacement sensor is located at a certain point, the first pair of zeros on the real axis of the s-plane arrive at the origin and cancel the rigid-body mode. The location of the translational displacement sensors on the beamat which the rigid-body mode of the beam is unobservable is analyzed as the center of percussion and is uniquely located for each case. If sensor is moved beyond such a point, a pair of zeros appear on the imaginary axis and move away from the origin along the imaginary axis of the s-plane.

• Proceedings of the KIEE Conference
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• 2003.07d
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• pp.2073-2075
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• 2003

This paper presents the active vibration control of flexible cantilever beam using piezoceramic actuators. The transfer function from the force input to the bending displacement was obtained via modal analysis results and piezoelectric constitutive equations. For the active vibration control piezoceramic actuators and sensors were used to construct a flexible smart cantilever beam. To further enhance the sensing and actuation properties of the piezoceramics, a typical interdigitated electrode pattern was fabricated. The PID controller was designed via various simulation and experiment trials. It was shown that the PID controller could suppress vibration of the beam effectively. Simulations and experiments verified good performances of the designed controller.

• Journal of Satellite, Information and Communications
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• v.10 no.4
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• pp.46-51
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• 2015

In this paper, I design a linear array antenna simulator for anti-jamming GPS systems and perform various performance analysis by simulation. First, I generate simulated transmission signals through the analysis of GPS satellite signal structure, and analyze SNR(Signal to Noise power Ratio) performance of linear array antenna according to number of arrays under noise environments. In addition, I analyze the performance of the anti-jamming beam pattern using MMSE(Minimum Mean Square Error) signal processing method, and also analyze the anti-jamming performance considering antenna calibration problem when there are different delays between arrays.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.5
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• pp.37-44
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• 2018

In laser material processing for high thermal conductivity, the thermal effect of laser beam shape was examined through computer simulations. In this paper, a circular beam with a focal radius of $500{\mu}m$, an elliptical beam with a major axis of 4 mm and a minor axis of 1 mm, and a rotating beam with a focal radius of $500{\mu}m$ and an angular velocity of 5 rad/sec were compared. Simulation results showed that there was no clear difference in the maximum temperature between the circular focus and the elliptical shape, but the heating and cooling rates were different. The simulation result for a laser beam rotating in a circular pattern with a radius of 5 mm showed an asymmetric temperature rise due to the combination of linear and rotational motion. At points where the rotational and linear speeds combined, the temperature gradually rose and reached the maximum temperature; whereas at points where the rotational and linear speeds were attenuated, the temperature tended to gradually decrease after reaching the maximum temperature. Based on the results of this study, the authors expect to be able to optimize laser material processing by designing patterns of laser beams.