• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.13 no.6
• /
• pp.552-559
• /
• 2002

The EM(Engineering Model) LO(Local Oscillator) is designed for Ka-band satellite transponder. The VCO(Voltage Controlled Oscillator) is implemented using a high impedance inverter coupled with dielectric resonator to improve the phase noise performance out of the loop bandwidth. The phase of VCO is locked to that of a stable OCXO(Oven Controlled Crystal Oscillator) by using a SPD(Sampling Phase detector) to improve phase noise performance in the loop bandwidth. This LO exhibits the harmonic rejection characteristics above 43.83 dBc and requires 15 V and 160 mA. The phase noise characteristics are performed as -102.5 dBc/Hz at 10 KHz offset frequency and -104.0 dBc/Hz at 100 KHz offset frequency, respectively, with the output power of 13.50 dBm$\pm$0.33 dB over the temperature range of -20~+7$0^{\circ}C$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.15 no.4
• /
• pp.397-405
• /
• 2004

In this paper, performance analysis of mobile phone with internal antenna for PCS band was carried out. The radiation patterns for antenna and mobile phone with internal antenna were simulated by using 3D simulation program, HFSS and SEMCAD. Radiation pattern variation was observed according to installation of LED circuit and ground pattern and by using simulation radiation pattern was improved. And radiation patterns of mobile phones with internal and external antennas were measured by using for field measurement system and chamber. Measured radiation pattern for mobile phone with internal antenna shows good agreement with simulation result. And the radio sensitivities of mobile phones with internal and external antennas were measured by using Agilent E5515C and chamber and compared. The measured radio sensitivity of mobile phone with internal antenna shows proper performances comparable to other model with external antenna. Measured result shows that the difference on averaged co-polar radio sensitivity is 0.12 ㏈.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.26 no.12
• /
• pp.1044-1049
• /
• 2015

In this paper, isolation enhanced antenna using isolating resonator was proposed. Two loop type antennas were designed to operate at Wi-Fi band(2.4~2.5 GHz), in symmetry to the center, and are closely located to each other. In order to enhance isolation characteristics at Wi-Fi bands, isolating resonator was designed between the two loop type antennas. The proposed isolating resonator is a slot type antenna that enhances isolation with the control of the size, and by adjusting the value of capacitor($C_D$) the resonant frequency of the isolating resonator can easily be adjusted to enhance isolation characteristic at the target frequency.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.39C no.9
• /
• pp.841-851
• /
• 2014

Wireless technologies sharing the same frequency band and operating in the same environment often interfere with each other, causing severe decrease in performance. In this paper, we propose a algorithm based on traffic scheduling techniques that mitigate interference between different wireless systems operating in the 2.4-GHz industrial, medical, and scientific band. In particular, we consider IEEE 802.11 wireless local area networks (WLANs) and Bluetooth data transfer, showing that the proposed algorithms can work when the two systems are able to exchange information as well as when they operate independently of one another. Results indicate that the proposed algorithm remarkably mitigate the interference between the WLAN and Bluetooth technologies at the expense of a small additional delay in the data transfer.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.12 no.1
• /
• pp.130-136
• /
• 2008

This paper describes a low-power high-performance analog front-end block for $UHF(860{\sim}960MHz)$ band RFID tag chips. It satisfies ISO/IEC 18000-6 type C(EPCgolbal class1. generation2.) and includes a memory block for test. For reducing power consumption, it operates with a internally generated power supply of 1V. An ASK demodulator using a current-mode schmitt trigger is proposed and designed. The proposed demodulator has an error rate as low as 0.014%. It is designed using a 0.18um CMOS technology. The simulation results show that the designed circuit can operate properly with an input as low as $0.2V_{peak}$ and consumes $2.63{\mu}A$. The chip size is $0.12mm^2$

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.29 no.12
• /
• pp.915-923
• /
• 2018

A concrete embedded antenna design is proposed for probing the durability of a building at an industrial scientific medical band of 902~908 MHz. The proposed antenna is designed with a stacked slot patch structure for lower impedance variation to a dielectric constant of concrete, as a dielectric constant difference is derived from the moisture content. The proposed structure has a wider bandwidth when a parasitic patch structure is used, which reduces antenna performance degradation resulting from the moisture content of concrete. The measured voltage standing wave ratio of the proposed structure is less than 2 and the beam width is approximately $80^{\circ}$, whereas the gain is greater than 7 dBi. The proposed antenna is fabricated with a rectangle-type concrete block, which is simulated and measured for return loss and antenna gain.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.30 no.2
• /
• pp.173-176
• /
• 2019

In this study, a Ka-band waveguide rotary joint that can be applied to a millimeter-wave seeker is designed and fabricated. The proposed rotary joint maintains a low standing-wave ratio and low-loss characteristics, and has two rotary axes designed to enable azimuth and elevation rotation. The rotary joint is designed as a ridge-waveguide-type mode converter and a ${\lambda}/4$ choke structure to match the electromagnetic wave propagation mode between the spherical and circular waveguides. A performance test using a network analyzer and a high-power transmitter to assess vibration and shock were conducted. Results showed that the rotary joint had a very low standing-wave ratio of less than the maximum of 1.19:1 and an insertion loss of less than 0.80 dB at $F_C{\pm}500MHz$.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.20 no.4
• /
• pp.117-134
• /
• 2010

A passive RFID tag which received attention as a future technology for automatic and quick identification faces some difficulties about security problems such as tag authentication, reader authentication, data protection, and untraceability in addition to cost and reliable identification. A representative passive RFID technology is the ISO/IEC 18000-6 Type C which is an international standard for 900 MHz UHF-band. This standard has some difficulties in applying to the security services such as originality verification, tag's internal information protection, and untraceability, because it does not provide high-level security solution. In this paper, we summarize security requirements of ISO/IEC ITC 1/SC 31 international standardization group, propose security protocols suitable for the UHF-band passive RFID system using a crypto engine, and analyze its security strength. In addition, we verify that it is possible to implement a tag conforming with the proposed security protocols by presenting concrete command/response pairs and cryptographic method.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.24 no.1
• /
• pp.103-107
• /
• 2024

This paper is a study on a triangle patch antenna using a rectangle slot and strip conductor. The length and spacing of the slot were adjusted to confirm the characteristics of the triangle patch antenna with rectangle slot, and the area and shape of the radiation patch were changed to triangle, rectangle, and hexagon for impedance matching. The HFSS simulator was used to check the antenna parameter characteristics, and the antenna size was 26 mm ×26 mm. In this proposed antenna, the simulation frequency range with VSWR of 2 or less was 5.27 to 6.24 GHz. The bandwidth was 970 MHz. The frequency range of the fabricated antenna was 5.24 to 6.38 GHz, and the bandwidth 1140 MHz. The maximum radiation gain is 5.01 dBi. It was confirmed that all radiation patterns had directional characteristics.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.38C no.1
• /
• pp.64-77
• /
• 2013

In this paper, we propose a joint bandwidth allocation and path selection scheme for IEEE 802.16j networks in uplink with cooperative relaying, and we evaluate the performance of the proposed scheme by using OPNET based simulation in hilly terrain with heavy tree density. The proposed scheme maximizes the system throughput in uplink with cooperative relaying in IEEE 802.16j networks. Then, we transform the proposed scheme into multi-dimensional multiple choice knapsack problem (MMKP) based scheme. We also propose uplink throughput maximization scheme and MMKP based scheme without cooperative relaying. We show that the system throughput of the proposed MMKP based scheme is higher than that of link quality based scheme, and cooperative relaying provides higher system throughput than the conventional case without cooperative relaying in uplink.