• The Journal of the Acoustical Society of Korea
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• v.32 no.4
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• pp.287-293
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• 2013

We present a parametric array signal generating system using $3{\times}16$ transducer array which is composed of multi-resonant frequency transducers of 20kHz and 32.5kHz. To drive transducer array, sixteen channel amplifier using LM1875 chips is designed and implemented, and the PXI system based on the LabView 8.6 for arbitrary signal generation and analysis is used. Using the proposed system, we measure sound pressure level and beam pattern of difference frequency and verify the nonlinear effect of difference frequency. The theoretical absorption range and the Rayleigh distance are 15.51m and 1.933m, respectively and we verify that sound pressure of difference frequency is accumulated and increased at the near-field shorter than the Rayleigh distance. We verify that the beam pattern of the measured difference frequency and the beam pattern obtained by the superposition of two primary frequencies are similar, and high directional parametric signal was generated.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.6
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• pp.1031-1036
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• 2019

This study describes the technique of the beam pattern measurement of array antenna for VHF band radar using drone and active beam pattern measuring device. There is no anechoic chamber for measuring the beam pattern of a large size antenna in the country. In this study, to test the antenna beam pattern characteristics of the developed VHF band radar, the antenna beam pattern characteristics were tested by Drone mounting an Active Beam Pattern Measuring Device. By comparing the results of the pre-simulation analysis with the measured results for the antenna, we could confirm that the beamwidth and side-lobe characteristics are satisfactory. Through the antenna beam pattern measurement technology using Drone and Active Beam Pattern Measuring Device, the beam pattern measurement technology of array antenna of low frequency band and large antenna for low band radar will be used.

• Journal of Positioning, Navigation, and Timing
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• v.6 no.2
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• pp.43-51
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• 2017

In this study, the effect of the steering vector model mismatch due to array uncertainties on the performance of array processing was analyzed through simulation, along with the alleviation of the model mismatch effect depending on array calibration. To increase the reliability of the simulation results, the actual steering vector of the array antenna obtained by electromagnetic simulation was used along with the Jahn's channel model, which is an experimental channel model. Based on the analysis of the power spectrum for each direction, beam pattern, and the signal-to-interference-plus-noise ratio of the beamformer output, the performance deterioration of array processing due to array uncertainties was examined, and the performance improvement of array processing through array calibration was also examined.

• JSTS:Journal of Semiconductor Technology and Science
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• v.15 no.6
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• pp.685-694
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• 2015

In this paper, a new dynamic reference scheme is proposed to improve the read voltage margin better than the previous static reference scheme. The proposed dynamic reference scheme can be helpful in compensating not only the background pattern dependence but also the cell position dependence. The proposed dynamic reference is verified by simulating the CMOS-memristor hybrid circuit using the practical CMOS SPICE and memristor Verilog-A models. In the simulation, the percentage read voltage margin is compared between the previous static reference scheme and the new dynamic reference scheme. Assuming that the critical percentage of read voltage margin is 5%, the memristor array size with the dynamic scheme can be larger by 60%, compared to the array size with the static one. In addition, for the array size of $64{\times}64$, the interconnect resistance in the array with the dynamic scheme can be increased by 30% than the static reference one. For the array size of $128{\times}128$, the interconnect resistance with the proposed scheme can be improved by 38% than the previous static one, allowing more margin on the variation of interconnect resistance.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.11
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• pp.1217-1224
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• 2009

This paper newly proposes a methodology towards computing antenna element weights which are satisfying asymmetric sidelobe levels(SLLs) specified arbitrarily on both sides of the main beam pattern, in the linear phased array antenna pattern synthesis problem. Opposite to the conventional methods in which the element weights are directly optimized from the array factor, this method is based on the optimum perturbations of complex roots inherent to the Schelkunoff's polynomial form which is described for the array factor. From the proposed methodology, the capability of nulling the directions of multiple jammers is also possible by independently perturbing only the complex roots corresponding to each jamming direction, hence allowing an enhancement of the simplicity of the numerical procedure by means of a proper reduction of the dimension of the solution space. The complex weights over the array are then easily computed by substituting the optimally perturbed complex roots to the Schelkunoff's polynomial. Some examples are examined and numerically verified by substituting the extracted weights into the array factor equation.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.2
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• pp.138-146
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• 2016

This paper proposes an optimum beam forming of conformal array antenna by using LSM(Least Squares Method) and GA(Genetic Algorithm). The weights which approximate conformal array antenna beam pattern to linear array antenna beam pattern have been evaluated by applying LSM. Also, the optimum locations of conformal array antenna which form wideband optimum beam pattern have been obtained by using GA. The proposed method is applied to a problem of Bezier platform array antenna for a verification purpose.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.1
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• pp.42-50
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• 2016

Recently, researches about the communication between LED array and the camera (alias 'Visual-MIMO'), have been actively conducted, and the application to the vehicle and a smart phone is expected to be maximized. Since the bit error may occur if the ISI is severe in a LED array, it is necessary to switch from the multiplexing to the diversity mode. In this paper, according to the use or not of a reference array pattern, a method for determining the transition time to the diversity mode is suggested and verified. When using the reference pattern, it determines the transition time to the diversity mode from the multiplexing using the brightness information of the received image. If the reference array pattern is not used, the size of LED array compared to the entire image according to the distance is used and the size of the LED array at the distance of a severe ISI may be used for the determination of transition time to the diversity. Finally, the proposed method is verified through the simulation and hardware experiments as well as by analyzing the performance in accordance with the ISI level and the distance.

• Journal of the Korea Institute of Military Science and Technology
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• v.19 no.4
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• pp.492-499
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• 2016

Null pattern synthesis method using the Quantum-inspired Evolutionary Algorithm(QEA) is described in this study. A $12{\times}12$ planar array antenna is considered and each element of the array antenna is controlled by 6-bit phase shifter. The maximum number of iteration of 500 is used in simulation and the rotation angle for updating Q-bit individuals is determined to make the individual converge to the best solution and is summarized in a look-up table. In this study we showed that QEA can satisfactorily synthesize the null pattern using smaller number of individuals compared with the conventional Genetic Algorithm.

• The Journal of the Acoustical Society of Korea
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• v.18 no.4
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• pp.78-83
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• 1999

This paper concerns a least square method for pattern optimization of a thinned sensor array in which the squared error between a desired pattern and a synthesized one is minimized. A weighting function is applied in the function with respect to the array visual range for a symmetric and asymmetric configuration for sensor spacing. An exponential weighting function is proposed to control the sidelobes efficiently around the mainbeam and to generate a uniform sidelobe. The resulting pattern may be employed to eliminate incoming interferences distributed uniformly around the array visual range.

• Journal of the Korea Institute of Military Science and Technology
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• v.9 no.3
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• pp.48-55
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• 2006

This paper describes the antenna based GPS anti-jamming technology called CRPA(Controlled Reception Pattern Antenna), which used $2{\times}2$ array elements. In this system, the main functions are the antenna complex weight control and the GPS digital I/Q VM(Vector Modulator). To update the VM's I/Q complex weights, the PC based DAC(Digital to Analog Converter) module was also used and the two analog output voltages were applied to the $2{\times}2$ array elements to synthesize the null pattern. In the study, we also simulated the $2{\times}2$ GPS array null patterns to compare the null depth with experimental results. The VM was also modified at the frequency of 1.575GHz for the GPS L1 and controlled by the PC based VM software.