• Journal of the Optical Society of Korea
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• v.18 no.2
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• pp.118-123
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• 2014

For multi parameter optimization of Raman Fiber Amplifier (RFA), a simple genetic algorithm is presented in the scenario of a 320 channel Dense Wavelength Division Multiplexed (DWDM) system at channel spacing of 25 GHz. The large average gain (> 22 dB) is observed from optimized RFA with the optimized parameters, such as 39.6 km of Raman length with counter-propagating pumps tuned to 205.5 THz and 211.9 THz at pump powers of 234.3 mW, 677.1 mW respectively. The gain flattening filter (GFF) has also been optimized to further reduce the gain ripple across the frequency range from 190 to 197.975 THz for broadband amplification.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.10a
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• pp.389-391
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• 2011

This paper has been studied about design of linear 25Watt Power amplifier for VDR(VHF Data Radio). VDR's frequency band is 117.975~137MHz, and CSMA(Carrier Sense Multiple Access), D8PSK(Differential Eight Phase Shift Keyed), 25KHz's channel bandwidth use. It also stated in DO-281A MOPS output power, symbol constellation error, spurious emissions, adjacent channel power must be met. HPA is designed to meet DO-281A standard.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.53 no.3
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• pp.188-196
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• 2004

Amplifier linearity plays a major role in the quality of mordern communication systems. The Power amplifier should be operated near saturation region to achieve high efficiency But at this region amplitude and phase distortions of the amplifier remarkably increase with the input power increase and cause a significant adjacent channel interference. In this paper, an independently controllable AM/AM and AM/PM predistortion linearizers consisted of two bias feed resistance linearizers is proposed. This linearizer allows independent adjustment of the AM/AM and AM/PM curves by using two adjustable voltages to compensate tile power amplifier non-linearities. The predistortion linearizer can improve the ACPR by 5.3dB with cdma2000 multi carrier signals. And by applying this linearizer to two-tone(880MHz) power amplifier, third order IMD products are improved up to 8(dB).

• 한국ITS학회:학술대회논문집
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• v.2007 no.10
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• pp.131-135
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• 2007

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.9
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• pp.755-760
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• 2013

The electromagnetic compatibility and its effects, and the system design considerations in space environment are studied in this paper using Multipator. The system level EMC test results of digital channel amplifier(DCAMP), its affects upon the H/W improving methods regarding its over exceed value of EMC specification are discussed. These analysis values and test results can be used as the criteria for the selection of EMC requirements and of the MILSATCOM system design.

• Proceedings of the IEEK Conference
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• 2000.11a
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• pp.381-384
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• 2000

In this paper, we designed and fabricated a low noise amplifier which can be used in W-CDMA. For improving input VSWR and stability an emitter inductance series feedback was used, and for acquiring higer linearity at low current DC bais by-passing method was used. Fabricated low noise amplifier had 15.33 ㏈ power gain, 2.17 ㏈ NF, -9.53 ㏈ $S_{11}$ and -35.91 ㏈ $S_{22}$ at 2.16 GHz, and +5.34 ㏈m II $P_{ 3}$ at 10 MHz channel spacing.g.g.g.

• Journal of Radiation Industry
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• v.6 no.3
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• pp.231-237
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• 2012

This paper introduces a gamma-ray measurement system for a transportable tomography which is applicable for an industrial process diagnosis. The gamma-ray measurement system consists of pulse mode operating 72 channel CsI detectors, main AMP-pulse shaper, single channel analyzer, counter and control PC. The CsI crystal is coupled with a PIN diode which is connected to an amplifier and pulse shaper. For a compact design, the amplifier and pulse shaping circuit are included in a single package. 36 sets of CsI detectors are connected to a multi-channel counter through single channel analyzers. A computer controls and collects data from two multi-channel counters. This configuration results in 72 channel counting system in total. The CT rotator and radiation measurement system are controlled by a PC with LabVIEW program. Tomographic data were measured for a phantom by the measurement system and transportable gamma-ray CT. From the experimental data image reconstructions were performed by ML-EM algorithm. The result showed that the CsI detector system can be a suitable component for transportable gamma-ray CT system.

• Journal of IKEEE
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• v.4 no.2 s.7
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• pp.241-248
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• 2000

A linear power amplifier is particular emphasized on the CDMA system using a linear modulation scheme, because intermodulation distortion which cause adjacent channel interference and co channel interference is mostly generated in a nonlinear power amplifier. In this paper, a new type of linearization technique proposed. It is presented that balanced MESFET predistortion linearizer added. Experimental result are present for Korea PCS(Personal Communication Service) frequency band. The implemented linearizer is applied to a 30dBm class A power amplifier for simulation Performance. The predistortion linearizer improves the 1dB compression point of the HPA about 2dBm, and intermoudulation distortion about 12.5dBc.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.1
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• pp.24-36
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• 2003

The digital mobile communication will be developed till getting multimedia service in anyone, any where, any time. Theses requiring items are going to be come true via IMT-2000 system. Transmitting signal bandwidth of IMT-2000 system is 3 times as large as IS-95 system. That is mean peak to average of signal is higher than IS-95A system. So we have to design it carefully not to effect in adjacent channel. HPA(High Power Amplifier) located in the end point of system is operated in 1-㏈ compression point(Pl㏈), then it generates 3rd and 5th inter modulation signals. Theses signals affect at adjacent channel and RF signal is distorted by compressed signal which is operated near by Pl㏈ point. Then the most important design factor is how we make HPA having high linearity. Feedback, Pre-distorter and Feed-forward methods are presented to solve theses problems. Feed-forward of these methods is having excellent improving capacity, but composed with complex structure. Generally, Linearity and Efficiency in power amplifier operate in the contrary, then it is difficult for us to find optimal operating point. In this paper we applied algorithm which searches optimal point of linear characteristics, which is key in Power Amplifier, using minimum current point of error amplifier in 1st loop. And we made 2nd loop compose with new structure. We confirmed fabricated LPA is operated by having high linearity and minimum current condition with ACPR of -26 ㏈m max. @ 30㎑ BW in 3.515㎒ and ACLR of 48 ㏈c max@${\pm}$㎒ from 1W to 40W.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.10 no.5
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• pp.99-104
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• 2011

This paper presents a high power and high efficiency unbalanced Doherty power amplifier used to extend the output power back-off (OPBO). The proposed unbalanced amplifier uses the same type of transistors in both the main amplifier and the peaking amplifier, similar to a conventional symmetric Doherty amplifier. The unbalanced amplifier can have the impedance of a ${\lambda}/4$ transformer located at the output of the main amplifier modified. This enables the OPBO to exceed 6 dB, the maximum OPBO for a conventional symmetric Doherty amplifier. The efficiency and linearity performance of the unbalanced Doherty amplifier are almost same as those found for the asymmetric Doherty amplifier, even though the unbalanced Doherty amplifier structure is simpler than the asymmetric Doherty structure. In order to verify the proposed amplifier performance, a 46 W Doherty amplifier has been both simulated and measured using a CDMA2000 1FA signal. From the measured results, the proposed unbalanced Doherty amplifier achieved an added power efficiency of 38 % and an adjacent channel power ratio of -34 dBc at a 885 kHz offset frequency and -35.6 dBc at a 1.98 MHz offset frequency.