• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.23 no.11
• /
• pp.1239-1247
• /
• 2012

In this paper, design and fabrication of solid state power amplifier(SSPA) using GaN HEMT chip for X-band frequency are presented. The SSPA consists of the power supply for stable power and the control unit for communication and controlling the internal module, the RF Part to amplify RF signal, In particular the adopted active device for the RF Parts is GaN HEMT Bare chip of TriQuint company, the RF parts consists of pre-stage, drive-stage, main power-stage and each amplifier is designed with input and out matching circuit. The developed power amplifier demonstrated more than 300 W peak output power in condition of 26 % duty, max. pulse width 100us for the X-band frequency( 500 MHz bandwidth) and can apply to marine radar systems.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.27 no.11
• /
• pp.978-986
• /
• 2016

X-band phased array antenna module for the compensation of deformed beam direction by wing deformation is designed and fabricated. The phased array antenna module consists of array antenna, phase shifter, power divider and control circuit. To select out the best component, the variation of radiation pattern by wing bending and phase error of components is simulated. The fabricated phased array antenna module shows an antenna gain of 5.84 dBi, a return loss of 13.6 dB and a bandwidth of 10.6 % at 9.375 GHz. The test bed was set up to verify the performance of beam direction compensation. This test confirmed that the main beam direction of array antenna has been well restored under wing bending of 9 %.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2001.10a
• /
• pp.675-679
• /
• 2001

In this paper, throughput is derived for slotted ALOHA wideband DS-CDMA and slotted ALOHA Multi-Carrier DS-CDMA systems in the multipath Rayleigh fading channel. The throughput of two systems are compared according to the length of a packet in the fast Rayleigh and the slow Rayleigh multipath fading. As a result, we have known that Multi-Carrier DS-CDMA system has less capacity than wideband DS-CDMA system in the same bandwidth, but throughput of Multi-Carrier DS-CDMA system is higher than that of wideband DS-CDMA system. And in Multi-Carrier DS-CDMA systems, higher throughput can be obtained through shortening the length of packet in the fast Rayleigh fading and it is efficient to control the length of a packet adequately or increase the system capacity of Multi-Carrier DS-CDMA system in the slow Rayleigh fading.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.21 no.9
• /
• pp.1635-1641
• /
• 2017

In this paper, a trellis-coded 3-dimensional (3-D) orthogonal frequency division multiplexing (OFDM) system is presented and its performance is analyzed. Here, a set-partitioning technique for trellis coding with respect to a 3-D signal constellation is also presented. We show theoretically that the proposed system, which exploits a trellis coding scheme with recursive systematic convolutional codes (RSC) of code rate R = 1/3 and 2/3, can improve symbol error rate (SER) up to 7.8 dB as compared with the uncoded OFDM system in an additive white Gaussian noise (AWGN) channel. Computer simulation confirms that the theoretical analysis of the proposed system is very accurate. It is, therefore, considered that the proposed trellis-coded 3-D OFDM system is well suited for the high quality digital transmission system without increase in the available bandwidth.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.29 no.4A
• /
• pp.458-465
• /
• 2004

To reaffirm the use of a mainstream CMOS process for designing passive-like attenuator structures, a linearly controlled variable attenuator is realized with 0.35${\mu}{\textrm}{m}$ 2-poly 4-metal CMOS process. It uses the П configuration for large attenuation range and suitable matching property. Compared to conventional passive-like CMOS attenuators, it is demonstrated that this work advances the frequency band from MHz to ㎓ (DC- l㎓), and reduces the size to 700${\mu}{\textrm}{m}$${\times}$300${\mu}{\textrm}{m}$.. Both simulation results and test results are provided. They show the improved linear relation between attenuation and control voltage. It is very useful in CDMA or GSM band, which uses under 1㎓ frequency band. An alternative topology, Bridged-T configuration, is proposed to get over the limit of applications by elevating operation bandwidth. The proposed topology covers over DC-2㎓ frequency band, which means that the proposed architecture can cover the tripleband (800MHz CDMA/GSM, 1.5㎓ GPS, 1.9㎓z PCS system) in applications as well. The simulation results are provided.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.43 no.7 s.349
• /
• pp.84-92
• /
• 2006

To defeat abnormal traffic driven by DoS (Denial-of-Service) or DDoS (Distributed DoS), there has been a variety of researches or studies in a few decades. In this paper, we present the results of theoretical performance analysis between attack prevention schemes and attack mitigation schemes. The former is a scheme that prevents abnormal incoming traffic from forwarding into a specific network based on filtering rules, and the latter is a scheme that makes some perimeter or intermediate routers, which exist on the traffic forwarding path, prevent abnormal traffic based on their own abnormal traffic information, or that mitigates abnormal traffic by using quality-of-service mechanisms at the gateway of the target network. The aspects of theoretical performance analysis are defined as the transit rates of either normal traffic or false-positive traffic after an attack detection routine processes its job, and we also present the concrete network bandwidth rates to control incoming traffic.

• Journal of the Korean Institute of Telematics and Electronics D
• /
• v.35D no.12
• /
• pp.83-91
• /
• 1998

Fiber Bragg grating which has a blazed ang1e to the plane of incident wave generates a side-mode as well as main-mode. The side-mode has an identical characteristics with a long period grating that couples with a cladding mode, so rejects the special wavelength. We experimented on the side-mode characteristics with two fibers which Ge doped depressed index fiber and very high photosensitive H$_2$ loaded step index fiber according to the tilted angle. Also, using a phase mask equipped with rotation plate which has 0.02$^{\circ}$ resolution, we can control the bandwidth and the peak value of a total loss spectrum by aligned tilted grating in a fiber and using this, tried to compose the ASE band rejection filter of the Erbium doped fiber amplifier.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.38 no.8
• /
• pp.19-29
• /
• 2001

The recent explosion in the Internet applications, Internet. host number and the traffic in the IP backbone network is posing new challenges for transport network. This requires a high-speed IP backbone network that has a substantially higher bandwidth than the one offered by current networks, which prompts the development of all-optical network. To obtain optical network utilization gains, we need a software which establishs logical topology to make possible the efficient use or physical topology, and control the optical network in combination with the IP layer routing protocols. Finally, the logical topology is required higher efficient than physical topology. For this an efficient algorithm for the routing and wavelength assignment(RWA) in the WDM all-optical network is necessary. In this paper, two kinds of heuristic algorithms to establish logical topology for WDM networks and arc applied to the design of logical topology of domestic backbone network. These algorithms are found to work quite well and they arc compared with each other in terms of blocking rate, etc.

• Journal of IKEEE
• /
• v.19 no.4
• /
• pp.506-513
• /
• 2015

In this paper, an output-capacitorless, low-dropout (LDO) regulator is designed, which consumes $4.5{\mu}A$ quiescent current. Proposed LDO regulator is realized using two amplifier for good load regulation and fast response time, which provide high gain, high bandwidth, and high slew rate. In addition, a one-shot current boosting circuit is added for current control to charge and discharge the parasitic capacitance at the pass transistor gate. As a result, response time is improved during load-current transition. The designed circuit is implemented through a $0.11-{\mu}m$ CMOS process. We experimentally verify output voltage fluctuation of 260mV and recovery time of $0.8{\mu}s$ at maximum load current 200mA.

• Journal of IKEEE
• /
• v.17 no.2
• /
• pp.140-144
• /
• 2013

This paper presents the novel design of circular polarized Ka-band horn array antenna. The element antenna of the arrya is composed of two parts, microstrip patch and square horn, and the microstrip patch is fed by corner truncated microstrip patch for circular polarization. The patch antenna has the role of a feeder and polarizer of the horn, thus the whole size of the horn antennae can be considerably reduced. The $1{\times}8$ horn array was designed and fabricated by the spacing of $0.9{\lambda}_0$ among the element horn. The element horn has typical gain of 8dBi and axial-ratio bandwidth of 4.9% at 3dB, and the minimum gain and axial-ratio bandwithd of the array is 14dBi and 8.2%.