• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.6
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• pp.591-596
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• 2016

This paper presents a study on the subject for the design and implementation of high-speed frequency hopping RF transceiver used for tactical communications systems. Jump the transmission / reception frequency of the L-band to hop tens per second is possible by maximizing the immunity to interference, and is applicable to communication systems having a charging rotation function. To high-speed frequency hopping it is necessary to apply the necessary fast frequency hopping scheme DDS Driven PLL added. In this paper, the RF transceiver design and simulation analysis capabilities with fast frequency tactical communication systems, were implemented after the main test for functionality and performance. Was demonstrated hop high-speed jump tens per second through a test, the main transmission output, were measured RF key performance, such as received noise figure, by using the VSG and VSA generates a ${\pi}/4$ DQPSK modulated signal constellation and by EVM measurement that there is no problem in applying the communications system described above was pre-validated.

• Journal of Korea Society of Industrial Information Systems
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• v.20 no.1
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• pp.49-55
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• 2015

This paper proposes a 2.4 GHz RF oscillator with a very low close-in phase noise performance. This is composed of a low frequency crystal oscillator and three frequency multipliers such as two doubler (X2) and one tripler (X3). The proposed oscillator is implemented as a hybrid type circuit design using a discrete silicon bipolar transistor. The measurement results of the proposed oscillator structure show -115 dBc/Hz close-in phase noise at 10 kHz offset frequency, while only dissipating 5 mW from a 1-V supply. Its close-in phase noise level is very close to that of a low frequency crystal oscillator with little degradation of noise performance. The proposed structure which is consisted of a low frequency crystal oscillator and a frequency multiplier provides new method to implement a low power low close-in phase noise RF local oscillator.

• Journal of Communications and Networks
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• v.10 no.1
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• pp.55-62
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• 2008

Bandpass sampling (BPS) techniques for the direct down-conversion of RF bandpass signals have become an essential technique for software defined radio (SDR), due to their advantage of minimizing the radio frequency (RF) front-end hardware dependency. This paper proposes an algorithm for finding the minimum BPS frequency for simultaneously down-converting multiple RF signals through full permutation over all the valid sampling ranges found for the multiple RF signals. We also present a scheme for reducing the computational complexity resulting from the large scale of the purmutation calculation involved in searching for the minimum BPS frequency. In addition, we investigate the BPS frequency allowing for the guard-band between adajacent down-converted signals, which help lessen the severe requirements in practical implementations. The performance of the proposed method is compared with those of other pre-reported methods to prove its effectiveness.

• International journal of advanced smart convergence
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• v.11 no.3
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• pp.28-35
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• 2022

Interference always exists between wireless communication systems used in the same frequency band or adjacent frequency bands. In order to deploy a new wireless communication system such as a 5G system, a new frequency band must be allocated to the system. For this purpose, after analyzing interference between the existing system and the new system, a method of setting a frequency guard band or a minimum separation distance has been used as a passive method to limit the interference effect. This paper presents a wideband RF IRM(Interference Reduction Module) that can actively reduce the influence of interference between wireless communication systems. The wideband RF IRM can reduce the interference effects of 5G signals on satellite signals. The principle and structure of the wideband RF IRM are presented. The wideband RF IRM can suppress approximately 20dB of interference signal in 100MHz bandwidth when only interference signal exists. It also shows that when a 5G interference signal of -45dBm/100MHz and a satellite signal of -55dBm/40MHz exist simultaneously at a center frequency of 3.83GHz, about 15dB of 5G interference signal can be reduced in the frequency range covered by the satellite signal. The experimental results demonstrate that the wideband RF IRM can actively reduce the 5G interference signal on the satellite signal and can be used for the purpose of reducing the interference effect in a similar environment.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.9
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• pp.46-53
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• 2014

In this paper, ku-band RF transceiver system is designed for the unmanned aerial vehicle(UAV) line-of-sight(LOS) datalink. The RF transceiver system is consisted of the transmitting and receiving unit, RF front-end unit, and high power amplification unit. The transmitting and receiving unit has the functions of frequency up/down converting and channel changing. The RF front-end unit has the functions of transmitting and receiving signal duplexing, antenna selection, small signal amplification, and frequency filtering excluding the receiving signal. The high power amplification unit has the functions of ku-band power amplification and transmitting power variation(High/Middle/Low/Mute). The frequency up/down converting of transmitting and receiving unit is designed by using the superheterodyne method. The RF transceiver system is designed to obtain the broadband and high linearity properties for the reliable transmission and reception of high data-rate and high speed data. Also, the channel changing function is designed to use selectively the frequency as the operation environment of UAV.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.26 no.1
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• pp.51-55
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• 1981

Seed proteins of 51 varieties of soybean were separated by disc electrophoresis. Nine varieties had Rf 0.79 electrophoretic band, and 42 varieties had Rf 0.83 band. The frequency for Rf 0.79 was 0.176 and the frequency for Rf 0.83 was 0.824. The F_1 seeds of crossed between Kumgangdaepp (Rf 0.79) and Uidu (Rf 0.83) possessed both bands. Analysis of 96 F_2 seeds showed a ratio of 22 : 53 : 21 (Rf 0.79 : Rf 0.79/Rf 0.83 : Rf 0.83), suggesting single gene control with two co dominant alleles.

• Carbon letters
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• v.13 no.1
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• pp.17-22
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• 2012

Currently, graphene is a topic of very active research in fields from science to potential applications. For various radio-frequency (RF) circuit applications including low-noise amplifiers, the unique ambipolar nature of graphene field-effect transistors can be utilized for high-performance frequency multipliers, mixers and high-speed radiometers. Potential integration of graphene on Silicon substrates with complementary metal-oxide-semiconductor compatibility would also benefit future RF systems. The future success of the RF circuit applications depends on vertical and lateral scaling of graphene metal-oxide-semiconductor field-effect transistors to minimize parasitics and improve gate modulation efficiency in the channel. In this paper, we highlight recent progress in graphene materials, devices, and circuits for RF applications. For passive RF applications, we show its transparent electromagnetic shielding in Ku-band and transparent antenna, where its success depends on quality of materials. We also attempt to discuss future applications and challenges of graphene.

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

• JSTS:Journal of Semiconductor Technology and Science
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• v.4 no.2
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• pp.83-87
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• 2004

Phase noise performance and current consumption of Radio Frequency (RF) Voltage-Controlled Oscillator (VCO) are largely dependent on the Quality (Q) factor of inductor-capacitor (LC) tank. Because the Q-factor of LC tank is determined by on-chip spiral inductor, we designed, analyzed, and modeled on-chip differential inductor to enhance differential Q-factor, reduce current consumption and save silicon area. The simulated inductance is 3.3 nH and Q-factor is 15 at 2 GHz. Self-resonance frequency is as high as 13 GHz. To verify its use to RF applications, we designed 2 GHz differential LC VCO. The measurement result of phase noise is -112 dBc/Hz at an offset frequency of 100 kHz from a 2GHz carrier frequency. Tuning range is about 500 MHz (25%), and current consumption varies from 5mA to 8.4 mA using bias control technique. Implemented in $0.35-{\mu}m$ SiGe BiCMOS technology, the VCO occupies $400\;um{\times}800\;um$ of silicon area.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.5
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• pp.663-666
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• 2013

This paper demonstrates four different radio frequency (RF) resonators at 3 T magnetic resonance imaging (MRI) system. An approach based on microstrip transmission line to identical RF resonators except upper stripline structure is investigated. Electromagnetic simulation results are compared for RF resonators and discussed in detail at 3 T.