• Journal of electromagnetic engineering and science
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• v.6 no.2
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• pp.117-122
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• 2006

This paper presents the impacts of Ultra-wideband(UWB) applied in the communication applications using frequency band from 3.1 GHz to 10.6 GHz on Broadband Wireless Access(BWA) based on orthogonal frequency division multiplexing(OFDM) using frequency band of 3.5 GHz. It proposes low duty cycle(LDC) for enabling UWB to mitigate strong interference to BWA. The effects of interference mitigation are evaluated and analyzed in the environment of UWB coexistence with BWA. UWB with LDC scheme will be given to bring higher transmit power level corresponding to Federal Communications Commission(FCC) provisional limit for enabling UWB operation at 3.5 GHz bands.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.9
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• pp.1165-1171
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• 2020

In this study, we designed a single antenna taking into account the performance, such as return loss and radiation pattern, of 28 GHz and 38 GHz array antennas for 5G mobile devices. In millimeter wave band communication, high path loss occurs between transmission and reception, unlike in conventional microwave bands. In the design of array antennas for 5G millimeter wave terminals, antenna performance such as antenna gain, bandwidth, isolation between antenna elements, side-lobe level(SLL), etc. should be further considered. The performance of the designed array antennas was analyzed by spacing the antenna elements at half a wavelength. Our results proved the validity of the design and its suitability for applications in mm-Wave by showing that the 28 GHz and 39 GHz array antennas had antenna gains of 13.5 dBi and 11.3 dBi and return losses below -18.4 dB and -20 dB, correspondingly.

• Journal of information and communication convergence engineering
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• v.11 no.1
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• pp.45-49
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• 2013

A compact radio frequency (RF) bandpass filter (BPF) in low temperature co-fired ceramic (LTCC) is suggested for WiMAX applications. The center frequency ($f_0$) of the BPF is 5.5 GHz and its pass band or 3-dB bandwidth is 700 MHz to cover all the three major bands, low and middle unlicensed national information infrastructure (U-NII; 5.15-5.35 GHz), World Radiocommunication Conference (5.47-5.725 GHz), and upper U-NII/industrial, scientific, and medical (ISM) (5.725-5.85 GHz), for the WiMAX frequency band. A lumped circuit element design-the 5th order capacitively coupled Chebyshev BPF topology-is adopted. In order to design a compact RF BPF, a very thin ($43.18{\mu}m$) ceramic layer is used in LTCC substrate. An interdigital BPF is also designed in silicon substrate to compare the size and performance of the lumped circuit element BPF. Due to the high relative dielectric constant (${\varepsilon}_r$ = 11.9) of the silicon substrate, the quarter-wavelength resonator of the interdigital BPF can be reduced. In comparison to the 5th order interdigital BPF at $f_0$ = 5.5 GHz, the lumped element design is 24% smaller in volume and has 17 and 7 dB better attenuation characteristics at $f_0{\pm}0.75$ GHz.

• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.5
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• pp.759-766
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• 2022

In this paper, we propose a multi-band small antenna with CPW(Coplanar Waveguide) feeding structure WLAN(Wireless Local Area Network) and WiMAX (Worldwide Interoperability for Microwave Access) bands. The proposed antenna is designed two slit in the modified monopole type radiator and FR-4 substrate, which is thickness 1.0 mm, and the dielectric constant is 4.4. The size of proposed antenna is 15.1 mm⨯16.41 mm, and total size of proposed antenna is 17.5 mm⨯16.4 mm. From the fabrication and measurement results, From the fabrication and measurement results, bandwidths of 439 MHz (2.06 to 2.499 GHz), 840 MHz (3.31 to 4.25) and 1,315 MHz (5.23 to 6.545 GHz) were obtained on the basis of -10 dB impedance bandwidth. Also, 3D radiation pattern characteristics of the proposed antenna are displayed and measured gains 2.24 dBi, 2.83 dBi, and 2.0 dBi shown in the three frequency band, respectively.

• Journal of Advanced Navigation Technology
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• v.27 no.2
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• pp.209-213
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• 2023

Currently, 2.4 GHz and 5 GHz bands are used as frequencies for drone operation. In December 2019, the Ministry of Science and ICT newly allocated the 433 MHz band for the invisible long-distance operation of drones. However, since the 433 MHz band is the same as the previously allocated frequency band for amateur radio communication, interference cannot be avoided. Therefore, as a prerequisite for the development of a drone operation system based on the 433 MHz band, interference avoidance technology for this frequency band must be developed and applied. In this paper, we report the results of measurement and analysis of 433 MHz band signals necessary for the development of interference avoidance and reduction technologies for 433 MHz signals. The measurement and analysis of the 433 MHz band signal are performed through the spectrum measured at 5-minute intervals at three locations. Since the measurements and analyzes performed in this study considered spatial characteristics, temporal characteristics, and traffic characteristics, it is considered to be the basic data necessary for the development of interference avoidance technology in the 433 MHz band.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.7
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• pp.3431-3436
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• 2013

Band-notched ultra-wideband (UWB) antennas using frequency selective surfaces (FSSs) are presented. The proposed antennas utilized the band rejection characteristic of typical FSS unit cells. We loaded the FSS unit cells on the same plane of planar UWB antenna. These antennas are designed to reject the interference from the wireless local area network band, 5.15-5.825 GHz in the UWB band, 3.1-10.6 GHz. The measured peak gains of the proposed antennas are more than 2 dBi at both operation edge and center frequencies, and sufficient to apply for commercial purpose. The antennas are small size and planar shape for the purpose of the small mobile application, and enhanced design freedom by using various existing FSS unit cells.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.9
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• pp.749-755
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• 2017

In this paper, a wideband microwave absorber for X-band(8~12 GHz) applications is proposed. The structure of the proposed absorber unit cell consists of a resonator with a slot and slit, a backing ground plate, and a Taconic RF-30(${\varepsilon}_r=3$, $tan{\delta}=0.0014$) substrate with a dimension of $8.5{\times}8.5{\times}0.5mm^3$. The proposed absorber has a dual resonance at 9.83 and 10.37 GHz. To demonstrate the operating principle of the proposed absorber structure at each resonance frequency, the simulated current distributions on the unit cell are analyzed. To verify the performance of the proposed absorber, a prototype absorber was fabricated with a planar array of $20{\times}20$ unit cells. The measured results exhibit two absorptivity peaks stronger than 99 % and full-width at half-maximum(FWHM) bandwidth of 1.1 GHz(9.51~10.61 GHz).

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2000.11a
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• pp.225-228
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• 2000

In this paper, the design for a low noise amplifier with the EM simulation is presented. The ATF36077 pHEMT device is applied to design LNA for U-NII frequency band (5 GHz ～ 6 GHz). The matching networks have been designed by the only open ended stub in order to reduce parasitic effects generated from a via structure. Through EM simulator, the simulation result shows that the linear gain (@5.5 GHz) is over 10 dB, input return loss and output return loss (@ 5.5 GHz) are a below 10 dB respectively, and the 3rd order intercept point is about 17 dBm.

• Journal of the Korean Institute of Navigation
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• v.23 no.3
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• pp.29-34
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• 1999

In this paper, an X-band power amplifier using GaAs FET was designed and fabricated, which is to be used as SART transmitter sweeping at the frequency range of 9.2 GHz~9.5 GHz. The amplifier is consist of two stages using ATF-46101 FET of Hewllett-Packard. Finally, the amplifier using microstrip line matching solution shows that MAG is 23 dB at the center frequency of 9.35 GHz.

• Journal of the Institute of Electronics Engineers of Korea TE
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• v.39 no.3
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• pp.59-64
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• 2002

In the RFID system using ISM-band, The tag mounted at the object has used the DC power by rectifying the RF signals of the small antenna for operating the micro-controller and memory. The performance of the tag would be reduced because of the second harmonics generated by the nonlinearity of the semiconductor and the spurious signal excited the high order mode of the antenna. This paper has realized the novel type low-pass filter with "the Stub-I type DGS slot structure" to improve the efficiency of the tag by suppressing the harmonics. The optimized frequency character at the pass-band/stop-band has obtained by tuning the stub width and slit width of I type slot. The measured result of the LPF has the cutoff frequency 3.25 GHz, the insertion loss about -0.29~-0.3 dB at pass-band 2.4 GHz~2.5 GHz, the return loss about -27.688~-33.665 dB at pass-band with a good performance, and the suppression character is about -19.367 dB at second harmonics frequency 4.9 GHz. This DGS LPF may be applied the various application as the RFID, WLAN to improve the efficiency of the system by suppressing the harmonics and spurious signals.