• Journal of IKEEE
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• v.3 no.1 s.4
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• pp.69-78
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• 1999

In this paper, direct conversion receiver was designed to even harmonic anti-paralled diode pair ring mixer. Using a second harmonic component of LO instead of LO signal and RF signal are mixed by SHP(Sub Harmonic Pumped) mixer with anti-parallel diode pair. Canceling the harmonics of LO signal in ring mixer, SHP mixer using anti-parallel diode pair could mostly reduce the radiation of LO signal through a input port the most, good isolation characteristic, and low spurious characteristic by LO signal was shown over broad band. The produced SHP mixer showed LO/IF, RF/IF and LO/RF isolation was 24.6dB,36.2dB and 22.5dB respectively. And conversion loss was measured 15.6dB, IF output -35.6dBm with -20dBm RF input and 5.5dBm LO signal. 1dB compression point of If signal, in respect to RF signal, was found at the 0dbm RF signal.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.10
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• pp.979-986
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• 2013

In this paper, a TVS diode which is commonly used as a ESD protector in wireless communication devices could cause antenna wireless sensitivity to decrease has been analyzed. When a smartphone doesn't have enough space to place many components, there would be its speaker near antenna area. In order to protect ESD coming through the speaker there also could be a TVS within antenna GND area. Digital audio signal which was sent to speaker and CDMA RF communication signal coupled from antenna was mixed by TVS. And this leakage current running through TVS resulted in decrease of antenna wireless sensitivity. The results of various experiments can be explained using circuit simulation. Following works will give us some insights that can reduce unwanted summation of digital and RF signal due to nonlinearity of ESD protectors.

• Current Optics and Photonics
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• v.3 no.4
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• pp.311-319
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• 2019

A hybrid free-space-optical/radio-frequency (FSO/RF) communication system is considered, with the help of amplify-and-forward (AF) relaying. We consider various weather conditions to investigate their effects on the system's performance. We begin by obtaining the cumulative distribution function and probability density function of the end-to-end signal-to-noise ratio for the AF dual-hop FSO communication system with RF backup link. Then, these results are used to derive closed-form expressions for the outage probability, average bit-error rate, and average ergodic capacity. The results show that the considered system efficiently employs the complementary nature of FSO and RF links, resulting in impressive performance improvements compared to non-hybrid systems.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.11A
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• pp.909-917
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• 2009

In this paper, we proposed and implemented the method to efficiently generate TDD synchronization signal and the digital circuit for the RF repeater which can eliminate the shadow region in the wireless communication field using the time division duplex (TDD) method. After detecting the TDD signal from the transmitted or received RF signal, the detected TDD signal is fed to the RF repeater for the normal operation. The proposed technique detects the envelop of the downlink signal and amplifies the detected envelop, and then restores the degraded envelop with the proposed digital filtering method. Finally the restored envelop is manipulated to the TDD synchronization signal. Our focus on the proposed algorithm is to develop it with simple feature and low cost but robust performance. The proposed scheme was implemented to the integrated system which has both RF and digital circuit and tested under the same condition with the commercial WiBro service.

• Journal of Communications and Networks
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• v.16 no.1
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• pp.92-97
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• 2014

A novel method for extracting frequency slippage signal from radar full pulse sequence is presented. For the radar full pulse sequence received by radar interception receiver, radio frequency (RF) and time of arrival (TOA) of all pulses constitute a two-dimensional information sequence. In a complex and intensive electromagnetic environment, the TOA of pulses is distributed unevenly, randomly, and in a nonstationary manner, preventing existing methods from directly analyzing such time series and effectively extracting certain signal features. This work applies Gaussian noise insertion and structure function to the TOA-RF information sequence respectively such that the equalization of time intervals and correlation processing are accomplished. The components with different frequencies in structure function series are separated using empirical mode decomposition. Additionally, a chaos detection model based on the Duffing equation is introduced to determine the useful component and extract the changing features of RF. Experimental results indicate that the proposed methodology can successfully extract the slippage signal effectively in the case that multiple radar pulse sequences overlap.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.3
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• pp.305-310
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• 2015

In this paper, a wireless spectrum sensing receiver system is proposed. While a conventional Cognitive Radio(CR) system utilizes frequency down-conversion and demodulation to recognize wireless spectral signal, the proposed one is able to recover and sense valid signal at an RF front-end. It has been designed with a super-regeneration type circuit with a channel selectivity and variability for FDM applications with which a conventional single-channel super-regeneration circuit could not provide. From experimental evaluation, the implemented system has been optimized for channel allocation with quenching signal, and verified for 5 MHz-channel spacing.

• Journal of Satellite, Information and Communications
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• v.12 no.4
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• pp.26-33
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• 2017

A drone performs a mission through remote control or automatic control, which uses wireless communications technology. Recently the increasing use of drones, the drone signal RF detection is necessary. In this paper, we propose an efficient dron RF detection method through simulations considering Wi-Fi, Bluetooth and dedicated protocol dron communication method in ISM(Industry Science Medical) band.. After configuring an environment where a common terminal and a drone signal are mixed, a general terminal and a drone signal are distinguished from each other by using a RF characteristic according to a dron movement. The proposed drone RF detection method is the WRMD(Windowed RSSI Moving Detection) operation and the Doppler frequency identification method. The simulation environments consist to mixed for two signals and four signals. We analysis the performance to proposed drone RF detection technique thorough detection rate.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.7
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• pp.500-507
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• 2018

A three-channel radio frequency (RF) monopulse receiver using a data signal with a maximum transmission rate of 274 Mbps was designed. A monopulse receiver using a broadband communication signal was designed to operate in the Ku band, and it consists of a down-conversion module and a signal-processing module. To satisfy the performance of the proposed RF monopulse receiver, a signal-processing function less than the reception sensitivity for each transmission rate according to the adaptive transmission rate is required. To minimize signal reception and mutual frequency interference of various bandwidths, two RF filters were applied. To verify the satisfaction of system requirements, an AWR Corp. simulation tool was used.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.1
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• pp.179-184
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• 2012

A conventional wireless rf communication has relatively high ratio of power dissipation to transmit power for short-range links, susceptibility to interference, interception and jamming of electromagnetic wave. The study on alternative using ultraviolet signal to remedy the shortcomings of conventional rf communication has recently received attention. In this paper, the simulation results about the data rate performance of ultraviolet non-line-of-sight communication are provided. It is found that the direction of transmitting beam, receiving field of view width and the transmitting signal power have a seriously effect on the data rate of on-off-keying non-line-of-sight ultraviolet communication.

• Journal of the Korea Institute of Military Science and Technology
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• v.24 no.3
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• pp.317-327
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• 2021

Low Frequency Active Sonobuoy(hereinafter referred to as LFAS) are being developed in Korea in consideration of compatibility with existing overseas sonobuoys, and a communication device for acoustic signals receiving and operating control of LFAS has been developed. The communication device needs to verify compatibility with the existing Sonobuoy, and for this purpose, the standardized Sonobuoy communication protocol was applied. The communication device is designed/manufactured to transmit the acoustic signal received in real time from the Sonobuoy through VHF band RF communication to the data processing device, and transmit CFS/CSG commands for operation control to the Sonobuoy through UHF band RF communication. In order to verify the manufactured communication device, the communication status and performance were verified by interlocking test through Ultra Electronics' PASS-II equipment and domestically developed electronic device of Sonobuoy. In addition, operability was verified through environmental tests, water tanks, and marine operations. In the future, the communication device of sonobuoy can be used for verification of the Sonobuoy developed in Korea.