• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.249-250
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• 2006

Nowadays adaptive technique allows arrays of any geometry to be used with fast direction-of-arrival (DOA) estimators designed for linear arrays. So the interpolation of data from a given antenna array onto the output of a virtual array is needed before the direction finding technique is applied to the outputs of a uniform linear virtual array (ULVA). In this paper some superresoluntion methods are used to estimate DOA by best-fit transformation matrix T under different nonuniformly spaced array.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.6
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• pp.1036-1044
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• 2021

A linear array acoustic transducer with 12 tonpilz elements mounted independently on a gradual wedge-shaped tail mass was fabricated, tested and analyzed. The compensated transducer, which is modified by including a series inductance of 137 µH in the developed linear array transducer, attained improved figure of merit (FOM) performance characteristics compared with the uncompensated transducer. The four resonant frequency bands were identified from the measured FOM curve. The FOM response patterns over the frequency ranges of 31 to 40 kHz and 50 to 60 kHz were relatively uniform, whereas sharp resonance peaks were observed at around 73 kHz and 84 kHz. These results indicate that the developed linear array transducer can be used as an enhanced broadband transducer of echo sounder, and the operating frequency can be selected for more effective echo surveys in the fishing ground.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.1
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• pp.16-22
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• 2015

This paper proposes a power allocation method for multiple node beamforming with uniform circular array antennas to increase SIR of nodes in wireless mesh network. The proposed method calculates beamforming power allocation vectors that maximizes SIR satisfied with power constraint of HPA. The simulation results demonstrate the proposed method achieves the enhanced SIR of nodes than that of beamforming method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.4
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• pp.481-489
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• 1993

The charge distribution is calculated to analyze the quasi-static impedance of periodic interdigital transducer taking into account the effect of infinite neighboring electrodes. The charge distribution can be represented by the element factor and array factor. The radiation conductance, susceptance and static capacitance of the input and output IDT's with arbitrary voltages are obtained by the charge distribution. The impedance of apodized IDT, is analyzed by multi-track model in which IDT is represented by the parallel connection of the uniform tracks. The calculated input and output impedances are in good agreement with the experimental results.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.489-496
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• 2001

Two perforated plates are used to investigate local heat/mass transfer characteristics in an impingement/effusion cooling system. A naphthalene sublimation method is conducted to determine the local heat/mass transfer coefficients on the upward facing surface of the effusion plate. The two plates are placed in parallel position with gap distances of 1, 2, 4 and 6 times of effusion hole diameter. The effects of hole arrangements of the plates are studied for staggered, square, and hexagonal arrays. The experiments are conducted at Reynolds number of 10,000 based on the effusion hole diameter. The results show that the smaller hole size in the staggered array has the higher transfer coefficients on the stagnation region due to the formation of higher momentum flows through the impingement holes. In the square array, heat/mass transfer on the target plate is more uniform as the number of impingement holes increases. High and uniform heat/mass transfer coefficients are obtained in the hexagonal array.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.5
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• pp.85-93
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• 1994

We have studied the effect of channel and/or spacing chirpings on the near field and near field intensity patterns, modal gains and radiation angles of 6 supermodes in the index-guided laser arrays with 6 channels, on the basis of the coupled mode theory. The spacings between channels can be indenpendent parameters for control of the radiation angle. It is found that an asymmetrically v channel-chirped array has both a smaller radiation angle and better supermode discrimination characteristics than a uniform array. Comparing two approaches for enhancing modal stability in point of supermode discrimination characteristics, approach I which increases the coupling cofficient between the outer-most waveguides at each end of an otherwise uniform array, has superior discrimination characteristics to the approach II which increases the propagation constant for the end elements with the same coupling between neighbor elements. Approach III which has a narrower spacing between the outer-most waveguides at one end and a wider channel width of the outer-most waveguide at another end, gets a narrower radiation angle than the approach I and good supermode discrimination characteristics by applying optimized gain profiles.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.1
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• pp.101-109
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• 2002

Two perforated plates are used to investigate local heat/mass transfer characteristics in an impingement/effusion cooling system. A naphthalene sublimation method is conducted to determine the local heat/mass transfer coefficients on the upward facing surface of the effusion plate. Two plates are placed in parallel position with gap distances of 1, 2, 4 and 6 times of effusion hole diameter. The effects of hole arrangements of the plates are studied fur staggered, square, and hexagonal arrays. The experiments are conducted at Reynolds number of 10,000 based on the effusion hole diameter. The results show that the smaller hole size in the staggered array has the higher transfer coefficients on the stagnation region due to the formation of higher momentum flows through the impingement holes. In the square array, heat/mass transfer on the target plate is more uniform as the number of impingement holes increases. High and uniform heat/mass transfer coefficients are obtained for the hexagonal array.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.14 no.1
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• pp.68-76
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• 2015

This paper proposes the antenna selection scheme and power control algorithms of multiple nodes beamforming when the vehicles equipped with circular array antennas is moving and construct mobile mesh networks. The proposed antenna selection scheme chooses beamforming antenna elements considering antenna radiation gain and allows duplicated antenna selection for multiple adjacent nodes. The proposed power control algorithms maximize SIR for the duplicated antenna selection. The simulation demonstrates that the proposed antenna selection and power control achieve 2.5dB higher SIR gain than that of conventional methods when two nodes are apart from $15^{\circ}$.

• Journal of Information Processing Systems
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• v.19 no.4
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• pp.527-539
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• 2023

In the positioning algorithm of two-dimensional planar sensor array, the estimation error of time difference-ofarrival (TDOA) algorithm is difficult to avoid. Thus, how to achieve accurate positioning is a key problem of the positioning technology based on planar array. In this paper, a method of sensor reliability discrimination is proposed, which is the foundation for selecting positioning sensors with small error and excellent performance, simplifying algorithm, and improving positioning accuracy. Then, a positioning model is established. The estimation characteristics of the least square method are fully utilized to calculate and fuse the positioning results, and the non-uniform weighting method is used to correct the weighting factors. It effectively handles the decreased positioning accuracy due to measurement errors, and ensures that the algorithm performance is improved significantly. Finally, the characteristics of the improved algorithm are compared with those of other algorithms. The experiment data demonstrate that the algorithm is better than the standard least square method and can improve the positioning accuracy effectively, which is suitable for vibration detection with large noise interference.

• Journal of the Korea Convergence Society
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• v.8 no.1
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• pp.1-6
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• 2017

In this paper, we propose a new method for a correlative phase comparison direction finding(DF) which detects the arrival direction of radio waves by data fusing the calculated phase difference and the measured phase difference between the antennas when the radio waves are incident on the circular array antenna composed of 7 antennas respectively. The correlation type phase comparison method uses a uniform circular array(UCA) and a linear array method. The phase difference data calculated formally and the phase difference data measured in the test environment are fused with a correlation function, therefore, it is superior to the currently used phase comparison direction detection method. When the signal-to-noise ratio (SNR) of the received signal is 20dB and the inter-antenna distance to the wavelength of the received signal($L/{\lambda}$) is 0.5, the accuracy of the correlative DF is $1.7^{\circ}$ while measurement phase comparison's is larger than $2.5^{\circ}$, It can be used for electromagnetic signal monitoring and military direction detection.