• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.16 no.10 s.101
• /
• pp.1020-1027
• /
• 2005

In this paper, economic miniature RF transmitter module for intelligent transportation system(ITS) is described. This module which consists of ASK modulator, frequency synthesizer, power amplifier is operating at 5.8 GHz frequency band and implemented by using LTCC process technique. Thus, ultra small size of 0.8 CC and improved electrical performances has been obtained. From the test results, transmitting characteristics of 10 dBm ouput power and -46 dBc interchannel interference with 1.024 Mbps ASK modulated have been shown. Frequency synthesizer as a transmitting signal source reveals very short locking time of 26 usec and outstanding phase noise of -115 dBc/Hz at 1 MHz offset from 5.8 GHz center frequency.

• Journal of the Korean Society of Radiology
• /
• v.11 no.5
• /
• pp.361-370
• /
• 2017

In the Brain MRI, RF Pulse is irradiated on the human body in order to acquire an image. At this time, a considerable part of the irradiated RF Pulse energy is absorbed as it is in our body. This will raise the temperature of the human body, but depending on the extent of exposure, it will affect the human body. The change of the SAR and the temperature of the head according to the change of the magnetic field strength is examined. And to investigate the difference in results depending on the use of dental implant. In the human head model, 64 MHz RF Pulse frequency generated from 1.5 T, 128 MHz RF Pulse frequency generated from 3.0 T, and 298 MHz RF Pulse frequency generated from 7.0 T send a frequency and experiment was performed using dental implant using the XFDTD program, we measured the SAR and body temperature changes around the head. The SAR value showed up to about 5800 times the difference at the RF Pulse frequency of 256 MHz, when with dental implant than without dental implant and as the frequency increased, the use of the dental implant increased difference in the SAR value. The change of the temperature of the head showed a temperature rise nearly 2 to 4 times when with dental implant than without dental implant. As the RF Pulse frequency increase, the SAR value increase, but the change of the temperature of the head decrease. Because of as the frequency increase, wavelength is smaller and the more the amount absorbed by the surface of the human. Physiological and biochemical studies of the human body ar necessary through studies of the presence of dental implant and the cause of reaction caused by change in the RF Pulse frequency.

• Journal of the Institute of Convergence Signal Processing
• /
• v.12 no.3
• /
• pp.217-221
• /
• 2011

GaAs-based and InP-based HEMTs(High Electron Mobility Transistors) have good microwave and millimeter-wave frequency performance with lower minimum noise figure. GaAs-based MHEMTs(Metamorphic HEMTs) have some advantages, especially for cost, compared with InP-based ones. In this paper, the RF small-signal circuits of MHEMTs are simulated and analyzed for the design of millimeter-wave application systems. The simulation analysis for RF small-signal frequency can help and give some insights about the MHEMTs for the design of millimeter-wave application and communication systems.

• Proceedings of the IEEK Conference
• /
• 2003.11c
• /
• pp.323-326
• /
• 2003

본 논문은 무선 음성/영상 송수신용 RF모듈 설계 및 제작하였다. RF 주파수는 정보통신부에서 고시한 영상전송용 2410, 2430, 3450, 2470MHz 사용하였으며 IF 주파수는 479.5MHz를 사용하였다. 설계 및 제작된 RF 모듈은 FR-4 재질인 유전체 4.6, 두게 0.8mm, 양면구조의 기판을 사용하여 50mm x 40mm 크기로 제작되었다. 설계된 송신기 모듈은 ＋5V 단일전원으로 9±1dBm의 출력과 주파수허용편차 50×10/sup -6/이하, 스퓨리어스 발사강도 기본주파수의 평균전력보다 40dB이하의 성능을 만족하였다. 수신기 모듈은 +5V 단일 전원으로 -80dBm이하의 수신감도로 만족할만한 성능을 보였다.

• Electronics and Telecommunications Trends
• /
• v.23 no.5
• /
• pp.131-142
• /
• 2008

최근 ITU-R에서는 전파혼신과 밀접한 관계가 있는 무선기기의 RF 항목(주파수허용편차, 점유주파수대역폭, 불요발사 등)에 대한 권고안 SM.1045, SM.328, SM.853, SM.329, SM.1539 등을 제정하거나 개정하였다. 이와 관련하여 본 논문에서는 국내 무선설비규칙의 전파 질 허용치 및 측정방법과 연계하여 ITU-R RF 성능 권고(안)의 핵심내용에 대한 분석결과를 제시하였다. 본 논문의 내용은 무선기기의 인증 및 무선국 검사에 적용되는 국내 무선설비 기술기준치를 이해하는 데 참고자료로 활용될 것으로 기대된다.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.22 no.1
• /
• pp.91-99
• /
• 2018

This paper has proposed a low-noise and high-linear RF receiver supporting TV white space from 470 MHz to 698 MHz), which is implemented in $0.13-{\mu}m$ CMOS technology. It consists of a low-noise amplifier, a RF band-pass filter, a RF amplifier, a passive down-conversion mixer, and a channel-selection low-pass filter. A low-noise amplifier and RF amplifier provide a high voltage gain to improve the sensitivity level. To suppress strong and nearby interferers, two RF filtering schemes have been performed by using a RF BPF and a down-conversion mixer. The proposed LPF has been based on the common-gate topology and adopted a bi-quad cell to achieve -24dB/oct characteristics. In addition, the RF receiver can support the overall TV band by controlling a LO frequency. The simulated results show a voltage gain of 56 dB, a noise figure of less than 2 dB, and an out-of-channel IIP3 of -2.3 dBm. It consumes 37 mA from a 1.5 V supply voltage.

• Journal of Satellite, Information and Communications
• /
• v.10 no.2
• /
• pp.24-29
• /
• 2015

Recently, with developments of various networks, devices and various services, energy efficiency has become one of the most crucial issues with respect to sustainability of mobile devices. For connecting to networks seamlessly to offer services, a scenario of RF energy harvesting which supplies energy to wireless devices with RF signals is assumed. To increase the efficiency of RF energy harvesting, this paper proposes a RF energy harvesting algorithm which is based upon a frequency selective fading map. Through the algorithm, a receiver of mobile device can get fading information at each frequency and select a frequency which has the best quality. At the end, the simulation result demonstrates its superiority by showing a 4.45dB improvement in comparison to a deep fading frequency point.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.8 no.3
• /
• pp.454-459
• /
• 2007

In this work, micro-scale, high-performance solenoid-type RF chip inductors utilizing amorphous $Al_2O_3$ core material were investigated. The size of the chip inductors was $0.86{\times}0.46{\times}0.45mm^3$ and copper(Cu) wire with $27{\mu}m$ diameter was used as the coil. High frequency characteristics of the inductance(L), quality factor(Q), impedance(Z), and equivalent circuit parameters of the RE chip inductors were measured and analyzed using an RF impedance/material analyzer(HP4291B with HP16193A test fixture). It was observed that the RF chip inductors with the number of turns of 9 to 12 have the inductance of 21 to 34nH and exhibit the self-resonant frequency(SRF) of 5.7 to 3.7GHz. The SRF of inductors decreases with increasing the inductance and inductors have the quality factor of 38 to 49 in the frequency range of 900MHz to 1,7GHz.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.45 no.5
• /
• pp.409-416
• /
• 2017

In order that multiple wideband RF transmitters which have mission to deliver essential information to aircraft operate at the same time, RF transmitter has a variable sub-carrier frequency to modulate the signal. In case of exposure to weak environment, Wide-band RF transmitter is designed to check component of transmitter that includes antenna BIT to increase system reliability. Normally, Antenna BIT measure the reflection RF power of antenna to check system condition. However, Antenna BIT has a difference that depends on testing frequency to use the long RF cable which is located between the power amp and the antenna. The periodic phenomenon of the reflected antenna power are theoretically explained about dependence on the RF cable length. Based on presented result, suggested measurement methods is effectively able to be applied to diagnosis system condition.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.8 no.2
• /
• pp.239-244
• /
• 2004

In this paper, we have developed a frequency mixer which can be used as a microwave phase conjugator in the LS band retrodirective antenna system. The mixer as a phase conjugator must have an If signal of which frequency is nearly as high as that of an RF signal, so this fact brings difficulty in the combination of input signals and the design of impedance matching circuit. The circuit configuration is chosen to be of the gate mixer using a pseudomorphic HEMT device. The operating frequencies are 4.00 ㎓, 2.01 ㎓, and 1.99 ㎓ for LO, RF, and IF, respectively. Conversion gain is measured to be 12.5 ㏈ and 1 ㏈ compression point -34 ㏈m at the LO power of -7 ㏈m. The mixer fabricated in this research is the single-ended type, where RF leakage signal appears inevitably at the If port because RF and If frequencies are almost the same. The circuit topology suggested here can be applied directly to the design of balanced-type mixers and phase conjugators.