• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.5
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• pp.87-92
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• 2022

In this paper, a study was conducted on the design of an array element that can be applied to the AESA radar for seeker. An antenna for application to AESA radar should choose an optimal radiation element to be applied to an array antenna in order to secure electronical beam steering characteristics, and consider beam steering characteristics when designing. In particular, in order to satisfy the wide-angle beam steering characteristics, the wide-angle impedance matching technique should be used to minimize the scan blindness region that may occur during wide-angle steering. As such, securing the stability of system operation is becoming an important design consideration for AESA radar. In this paper, WAIM is applied to the end of the radiation element to improve the characteristics of the radiation element applied to the AESA radar antenna device, and the change in the performance of the active reflection coefficient, which is a stable operation index of the system, is reviewed. The final performance result verified the validity of the proposed method by mathematically synthesizing the simulation data.

• Journal of the Korea Knowledge Information Technology Society
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• v.12 no.4
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• pp.539-550
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• 2017

In this paper, we designed, fabricated and tested an UHF band cylindrical dipole array antenna. In the proposed antenna, cylindrical dipoles were vertically arranged in four stages. A parallel structure feeding circuit was installed inside the cylindrical dipole and mounted so as to be broadband matching. The feeding circuit was installed at the center of the cylindrical dipole to optimize the gain flatness characteristic of the azimuth direction omnidirectional radiation pattern. Minimizing the difference between the signals branched from the feeding circuit and realizing the symmetry of the radiation pattern. The required specifications are more than 11.2% bandwidth in UHF band, above 6dBi antenna gain, standing wave ratio of 2:1 or less, less than ${\pm}1dB$ gain flatness in azimuth radiation pattern, more than 13 degrees in elevation radiation pattern of 3dB beamwidth. We confirmed the possibility of implementation through M&S and verified the result of M&S through production and testing. The test results are 11.2% bandwidth in the UHF band, 6.30 to 8.31 dBi gain, 1.53:1 standing wave ratio or less, within ${\pm}0.2dB$ gain flatness in the azimuth radiation pattern, elevation radiation pattern of 3dB beam width was 15.62 to 15.84 degrees. The test result meets all requirements specifications.

• ETRI Journal
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• v.41 no.4
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• pp.536-548
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• 2019

In this study, an electronically steerable parasitic array radiator (ESPAR) antenna via analog radio frequency (RF) switches for a single RF chain MIMO system is presented. The proposed antenna elements are spaced at ${\lambda}/64$, and the antenna size is miniaturized via a dielectric radome. The optimum reactance load value is calculated via the beamforming load search algorithm. A switch simplifies the design and implementation of the reactance loads and does not require additional complex antenna matching circuits. The measured impedance bandwidth of the proposed ESPAR antenna is 1,500 MHz (1.75 GHz-3.25 GHz). The proposed antenna exhibits a beam pattern that is reconfigurable at 2.48 GHz due to changes in the reactance value, and the measured peak antenna gain is 4.8 dBi. The reception performance is measured by using a $4{\times}4$ BPSK signal. The measured average SNR is 17 dB when using the proposed ESPAR antenna as a transmitter, and the average SNR is 16.7 dB when using a four-conventional monopole antenna.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.5A
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• pp.503-509
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• 2007

Low-power motion estimation is required for video coding in portable information devices. In this paper, we propose a low-power motion estimation algorithm and 1-D systolic may VLSI architecture using full search block matching algorithm (FSBMA). Main power dissipation sources of FSBMA are complex computations and frequent memory accesses for data in the search area. In the proposed algorithm, memory accesses and computations are reduced by using 1D PE (processing array) array architecture performing motion estimation of two neighboring blocks in parallel and by skipping unnecessary computations during motion estimation. The VLSI implementation results of the algorithm show that the proposed VLSI architecture can save 9.3% power dissipation and can operate two times faster than an existing low-power motion estimator.

• Journal of Navigation and Port Research
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• v.31 no.6
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• pp.503-507
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• 2007

In this paper, the ultra-widebend, microstrip patch antenna with the bandwidth of 3 GHz was implemented for ultra-wideband(UWB) wireless communication applications. In order to cover the very wide bandwidth of 3 GHz, a multi-resonance antenna was designed, each resonance frequency was separated into five frequency bend, 7.5, 8.1, 8.7, 9.3, and 9.9GHz with the interval of 600MHz BW. And for wideband characteristics of each antenna, U-slot antennas were designed at each center frequency. Designed five U-slot antennas were connected in series for multi-resonance of 3GHz BW and wideband matching was also designed for impedance matching transmission line calculated. The relative dielectric constant, the height, the loss tangent of the PCB substrate were ${\epsilon}_r=4.8,\;h=0.6$ and loss tangent=0.0009 respectively. The implemented antenna's radiation patterns and gain were directivity characteristics and $1.46{\sim}4.08dBi$ at the five separated center frequency.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.05a
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• pp.61-62
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• 2018

In this paper, we studied a wideband double-sided dipole antenna operating at 3.5 GHz (WiMAX) band. The each printed dipoles are placed on the both sides of the substrate. It can be easily implemented and is suitable for connection with an active circuit. In order to obtain wideband printed dipole characteristics, thick rectangular shaped dipole is adopted. Feeding Circuit for dipole array and balun were designed for impedance matching with a $50{\Omega}$ microstrip feed line. The antenna is designed by simulation for an operation in the frequency range of 3.4~3.7 GHz Simulation results show that the maximum gain in the 3.5 GHz band is 5.5 dBi and the bandwidth with VSWR less than 2 is about 1 GHz.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.5
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• pp.100-105
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• 2010

A multi-band low noise amplifier (LNA) is designed in 90 nm RF CMOS process for 3GPP LTE (3rd Generation Partner Project Long Term Evolution) applications. The designed multi-band LNA covers the eight frequency bands between 1.85 and 2.8 GHz. A tunable input matching circuit is realized by adopting a switched capacitor array at the LNA input stage for providing optimum performances across the wide operating band. Current steering technique is adopted for the gain control in three steps. The performances of the LNA are verified through post-layout simulations (PLS). The LNA consumes 17 mA at 1.2 V supply voltage. It shows a power gain of 26 at the normal gain mode, and provides much lower gains of 0 and -6.7 in the bypass-I and -II modes, respectively. It achieves a noise figure of 1.78 dB and a IIP3 of -12.8 dBm over the entire band.

• Journal of IKEEE
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• v.22 no.2
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• pp.408-412
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• 2018

In this paper, a 26GHz variable gain amplifier fabricated using a 40nm CMOS process is studied. In the case of an automobile radar using 79 GHz, it is advantageous in designing and driving to drive down to a low frequency band or to use a low frequency band before up conversion rather than designing and matching the entire circuit to 79 GHz in terms of frequency characteristics. In the case of a Phased Array System that uses time delay through TTD (True Time Delay) in practice, down conversion to a lower frequency is advantageous in realizing a real time delay and reducing errors. For a VGA (Variable Gain Amplifier) operating in the 26GHz frequency band that is 1/3 of the frequency of 79GHz, VDD : 1V, Bias 0.95V, S11 is designed to be <-9.8dB (Mea. High gain mode) and S22 < (Mea. high gain mode), Gain: 2.69dB (Mea. high gain mode), and P1dB: -15 dBm (Mea. high gain mode). In low gain mode, S11 is <-3.3dB (Mea. Low gain mode), S22 <-8.6dB (Mea. low gain mode), Gain: 0dB (Mea. low gain mode), P1dB: -21dBm (Mea. Low gain mode).

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.4
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• pp.515-525
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• 1998

In this paper, for both transmission and reception with single antenna system of satellite communication, dual-frequency antennas which operate simultaneously at 12.5 GHz and at 14.25 GHz are designed, constructed and measured. Also by using dual feeding structure, the problems of single-fed dual-frequency antenna such as the separation of transmitting and receiving signals and single polarization, are solved. Microstrip patch as a radiation element of dual-fed dual-frequency antenna has width and length which are the resonance lengths of the corresponding frequencies for transmission and reception, respectively. The effects of the feed line on the other frequency feeding are minimized with the optimal matching scheme for the feed lines. For solving the space problems of dual-fed two-dimensional array antennas, microstrip-line and coaxial probe feedings are used for each frequency and a two-dimensional $2\times2$ array antenna was designed and measured their characteristics. The experimental results show that errors of resonance frequencies are less than 1.44%, the return losses are less than -21 dB and the isolations between two feeding ports are less than -21 dB. The characteristics of radiation patterns of dual frequency microstrip antenna are measured and evaluated. The directivities, sidelobe levels and cross polarizations are also measured and compared with the simulations. The results show some errors due to the misalignment of coaxial probe feeding.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.2
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• pp.151-158
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• 2012

This paper proposes a H-plane 8-way rectangular waveguide power divider using Y-junction. A general N-way power divider can be composed of multi-stage T-junctions. However, if the distances of output ports are close, the matching characteristic is not improved by using only T-junctions because of space limitation. In this case, since other types of 3-port junctions should be used to final output stage, Y-junctions are used with T-junctions in this paper. The proposed Y-junction uses the tapered-line impedance transformer and inductive irises to improve impedance matching characteristic. The 8-way power divider using Y-junction is fabricated and measured. The measured return loss and insertion loss from input port to output port are -30.8 dB and -9.3 dB at operating frequency, respectively. The measured maximum phase difference is about $1^{\circ}$. Therefore, the proposed power divider will be useful to apply to various microwave systems, which need to divide the input power equally, such as feed networks for array antennas.