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A 60 GHz Medium Power Amplifier for Radio-over-Fiber System
Woojin Chang,Haecheon Kim,Seung-Hyueb Oh 한국전자통신연구원 2007 ETRI Journal Vol.29 No.5
We present the design and fabrication of a 60 GHz medium power amplifier monolithic microwave integrated circuit with excellent gain-flatness for a 60 GHz radio-over-fiber system. The circuit has a 4-stage structure using microstrip coupled lines instead of metal-insulator-metal capacitors for unconditional stability of the amplifier and yield enhancement. The gains of each stage of the amplifier are modified to provide broadband characteristics of input/output matching for the first and fourth stages and to achieve higher gains for the second and third stages to improve the gainflatness of the amplifier for wideband.
A Ku-Band 5-Bit Phase Shifter Using Compensation Resistors for Reducing the Insertion Loss Variation
Woo-JinChang,Kyung-HoLee 한국전자통신연구원 2003 ETRI Journal Vol.25 No.1
This paper describes the performance of a Ku-band 5-bit monolithic phase shifter with metal semiconductor field effect transistor (MESFET) switches and the implementation of a ceramic packaged phase shifter for phase array antennas. Using compensation resistors reduced the insertion loss variation of the phase shifter. Measurement of the 5-bit phase shifter with a monolithic microwave integrated circuit demonstrated a phase error of less than 7.5° root-mean-square (RMS) and an insertion loss variation of less than 0.9 dB RMS for 13 to 15 GHz. For all 32 states of the developed 5-bit phase shifter, the insertion losses were 8.2± 1.4 dB, the input return losses were higher than 7.7 dB, and the output return losses were higher than 6.8 dB for 13 to 15 GHz. The chip size of the 5- bit monolithic phase shifter with a digital circuit for controlling all five bits was 2.35 mm×1.65 mm. The packaged phase shifter demonstrated a phase error of less than 11.3° RMS, measured insertion losses of 12.2± 2.2 dB, and an insertion loss variation of 1.0 dB RMS for 13 to 15 GHz. For all 32 states, the input return losses were higher than 5.0 dB and the output return losses were higher than 6.2 dB for 13 to 15 GHz. The size of the packaged phase shifter was 7.20 mm× 6.20 mm.
60 ㎓ Amplifier Module Using Low Temperature Co-fired Ceramic Technology
Woojin Chang,Dong-Young Kim,Jong-Won Lim,Ho-Kyun Ahn,Hong-Gu Ji,Haecheon Kim 대한전자공학회 2009 ITC-CSCC :International Technical Conference on Ci Vol.2009 No.7
This paper presents a module with a 60 ㎓ drive amplifier (DA) and a power amplifier (PA) microwave monolithic integrated circuits (MMICs) using a low temperature co-fired ceramic (LTCC) technology. The 60 ㎓-band DA and PA MMICs have been designed the 4-staged structures and fabricated using 0.12 ㎛ GaAs pseudomorphic high electron mobility transistor (PHEMT) process. The performance of the fabricated DA MMIC has the small signal gain (S₂₁) of 20.0 ~ 20.6 ㏈, the input reflection coefficient (S₁₁) of -13 ~ -9 ㏈ and the output reflection coefficient (S₂₂) of -7 ~ -6 ㏈ for 59.5 ~ 60.5 ㎓. And the performance of the fabricated PA MMIC has the S₂₁ of 16.5 ~ 17.2 ㏈ and the gain-flatness of 0.7 ㏈ for 56 ~ 62.5 ㎓. It was also measured the S₂₁ of 16.5 ~ 16.8 ㏈, the S11 of -16 ~ -13 ㏈ and the S₂₂ of -13 ~ -11 ㏈ for 59.5 ~ 60.5 ㎓. The 60 ㎓ amplifier module using the LTCC technology was measured the S₂₁ of 34.8 ~ 35.0 ㏈, the gain-flatness of 0.2 ㏈, the S11 of -12 ~ -7 ㏈ and the S₂₂ of -6 ~ -5 ㏈ for 59.5 ~ 60.5 ㎓. The S₂₁ of the module is decreased about 2 ㏈ compared with the bare chips.
Articles : Mathematical Modeling for the Estimation of Lipase Activity by Agar Diffusion Method
( Woo Jin Chang ),( Yoon Hee Moon ),( Yoon Mo Koo ) 한국화학공학회 1997 Korean Journal of Chemical Engineering Vol.14 No.3
A mathematical model was developed to estimate the lipase activities from the experimentally obtained physical dimension of halo, formed by a diffusing lipase through agar media. A diffusion equation based upon the mass balance was derived in cylindrical coordinates, the integration of which was carried out by using finite difference method. A regressional analysis of the experimental data using the proposed model has brought the values for the hindered diffusivity of lipase through agar media and the minimum effective lipase concentration of 0.817 x 10^(-6) ㎠/s and 2.86 unit/㎤, respectively. The procedures, delineated in this work are considered to be useful for the quantitative analysis of haloforming enzymes at predetermined standard conditions.