• Journal of Aerospace System Engineering
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• v.16 no.1
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• pp.86-96
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• 2022

The development trend of jet fighter's avionics system architecture is the digitization of subsystem component functions, increased RF sensor sharing, fiber optic channel networks, and modularized integrated structures. The avionics system architecture of the fifth generation jet fighters (F-22, F-35) has evolved into an integrated modular avionics system based on computing function integration and RF integrated sensor systems. The integrated modular avionics system of jet fighters should provide improved combat power, fault tolerance, and ease of jet fighter control. To this aim, this paper presents the direction and requirements of the next-generation jet fighter's avionics system architecture through analysis of the fifth generation jet fighter's avionics system architecture. The core challenge of the integrated modularized avionic system architecture requirements for next-generation fighters is to build a platform that integrates major components and sensors into aircraft. In other words, the architecture of the next-generation fighters is standardization of systems, sensor integration of each subsystem through open interfaces, integration of functional elements, network integration, and integration of pilots and fighters to improve their ability to respond and control.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.3A
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• pp.179-187
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• 2012

In this paper, we propose an adaptive DFE (Decision Feedback Equalizer) based on LDPC (Low Density Parity Check) code for phase noise suppression and performance improvement. The proposed equalizer in this paper is applied for wireless repeater system. So as to meet ever increasing requirements on higher wireless access data rate and better quality of service (QoS), the wireless repeater system has been studied. The echo channel and RF impairments such as phase noise produce performance degradation. In order to remove echo channel and phase noise, we suggest a novel adaptive DFE equalizer based on LDPC code. The proposed equalizer helps to compensate RF impairments and improve the performance significantly better than used independently. In addition, proposed equalizer has less iteration number of LDPC code. So, the proposed equalizer system has low complexity.

• Journal of Korea Multimedia Society
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• v.10 no.1
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• pp.49-57
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• 2007

Recently, CMOS RF integration has been widely explored in the wireless communication area to save cost, power, and chip area. The direct conversion architecture, rather than a more conventional super-het-erodyne, has been an attractive choice for single-chip integration because of its many advantages. However, the direct conversion architecture has several fundamental problems to solve in achieving performance comparable to a super-heterodyne counterpart. In this paper, we describe a programmable filter for mobile communication terminals using a direct conversion architecture. The proposed filter can be implemented with the active-RC filter and programmed to meet the requirements of different communication standards, including GSM, DECT and WCDMA. The filter can be tuned to select a detail frequency by changing the gate voltage of the MOS resistors. The gain of the proposed architecture can be programmed from 27dB to 72dB using the filter gain and VGA in 3dB steps.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.12
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• pp.2417-2424
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• 2016

Small size and light weight is very important for components used in radar mounted platform such as airborne radar. Recently, the active phased array radar is developed as an array of antennas for thousands of transmit/receive modules to be used as a multi-function radar that can detect and track targets. In this case, the size and weight of the transmit/receive modules are critical factor for developing the radar. In this paper, we developed a compact transmit/receive module using the 10W RF MEMS switch domestically localizing and reduced the circuit area to about 86.5% compared to using a circulator. The developed module satisfies not only electrical requirements but also MIL-STD's environmental specifications. So it can be used in a military device. It can be used at adaptive tunable receivers, reconfigurable smart active antennas and wide band beam electrical steering antennas.

• Investigative Magnetic Resonance Imaging
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• v.24 no.3
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• pp.95-122
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• 2020

In this article, we evaluated the performance of radiofrequency (RF) coils in terms of the signal-to-noise ratio (S/N) and homogeneity of magnetic resonance images when used for ultrahigh-frequency (UHF) 7T magnetic resonance imaging (MRI). High-quality MRI can be obtained when these two basic requirements are met. However, because of the dielectric effect, 7T magnetic resonance imaging still produces essentially a non-uniform magnetic flux (|B₁|) density distribution. In general, heterogeneous and homogeneous RF coils may be designed using electromagnetic (EM) modeling. Heterogeneous coils, which are surface coils, are used in consideration of scalability in the |B₁| region with a high S/N as multichannel loop coils rather than selecting a single loop. Loop coils are considered state of the art for their simplicity yet effective |B₁|-field distribution and intensity. In addition, combining multiple loop coils allows phase arrays (PA). PA coils have gained great interest for use in receiving signals because of parallel imaging (PI) techniques, such as sensitivity encoding (SENSE) and generalized autocalibrating partial parallel acquisition (GRAPPA), which drastically reduce the acquisition time. With the introduction of a parallel transmit coil (pTx) system, a form of transceiver loop arrays has also been proposed. In this article, we discussed the applications and proposed designs of loop coils. RF homogeneous coils for volume imaging include Alderman-Grant resonators, birdcage coils, saddle coils, traveling wave coils, transmission line arrays, composite right-/left-handed arrays, and fusion coils. In this article, we also discussed the basic operation, design, and applications of these coils.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.10 no.6
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• pp.535-544
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• 2017

In this paper, to overcome the limitation of information transmission and reception according to the RF system of UAV, it is necessary to check the position of many UAVs in flight on the basis of mobile communication and to make the LTE modem lightweight and low power And UAVs that are in operation are received and controlled. Through this study, we proposed a method to control real-time location tracking by connecting high-resolution images to the network anytime and anywhere. For this purpose, we propose the requirements and requirements of LTE modem using real-time high-speed data communication technology (3G, 4G LTE, Bluetooth) by presenting the communication module system of LTE-based UAV. N:N control system concept and implementation technology(Control system structure, control data flow chart, flight planning and transmission, real-time location tracking).

• Aerospace Engineering and Technology
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• v.6 no.2
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• pp.79-86
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• 2007

In order to operate Low Earth Orbit(LEO) satellite on space, technical requirements and administrative procedure which are defined by the International Telecommunication Union(ITU) should be followed on satellite development. Main technical requirements to follow are purpose of use, bandwidth, Radio Frequency(RF) intensity, and constraints on new satellite network about existing satellite networks according to frequency spectrum. Such ITU's requirements are reflected and designed on system specification and space to ground interface control document. In order to have a right and protection about using the satellite network on space, the satellite network has to be registered on Master International Frequency Register(MIFR) and procedure for this has to be followed. Coordination with countries raising objection is needed in order to register. And reference and method for coordination are also needed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.4B
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• pp.624-628
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• 2000

In this paper, the phenomenon to show in CDMA handset in case of which CDMA handset do not meet Traffic Rho value of IS-98B specifications, which have minimum requirements of CDMA handset about electrical performance is analyzed. This paper proposed method to improve Traffic Rho through improving the matching circuit of TX IF SAW FILTER and deleting noise of LDO(Low Dropout Regulator) to generate 3.OV_TX in TX block. HP8924C(CDMA Mobile Station Tester Set) and HP8595E(Spectrum Analyzer) measures the improved CDMA waveform.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1370_1372
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• 2009

A conventional linear accelerator system requires a flat-topped pulse with less than $\pm$ 0.5% ripple to meet the beam energy spread requirements and to improve pulse efficiency of RF systems. A a line-type pulsed modulator is widely used in pulsed power circuits for applications such as accelerators, radar, medical radiation, or ionization systems. The high-voltage pulse generator system with an output voltage of 284 kV, a pulse width of $10{\mu}s$, and a rise time of $0.84{\mu}s$ has been designed and fabricated to drive a klystron which has 30-MW peak and 60-kW average RF output power. The high-voltage test was performed using the klystron load. This thesis describes the design and test results of high-power pulse generator system for industrial accelerator application. The experimental results were analyzed and compared with the design.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.6
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• pp.134-141
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• 2004

The three-dimensional precision measurement technology for industrial product of middle and/or large scale has been developed. Theodolite measurement system which is one of the technology is widely used in aerospace industry. This paper describes a range alignment method of parabolic antenna to RF probe in the near field range by using the theodolite system, The range alignments of the Ku-band and Ka-band antennas have been accomplished within the requirements, ${\pm}1mm\;and\;{\pm}0.05^{\circ}$.