Browsing by Author "Hsu, SK"

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A 0.18-mu m CMOS CMFB downconversion micromixer with deep N-well technology for LO-RF and LO-IF isolation improvements
(2005-04-20)
Meng, CC
;
Hsu, SK
;
Wu, TH
;
Huang, GW
;
電信工程研究所
CMOS deep N-well technology can eliminate the physical effects of NMOS transistors and reduce substrate noise and coupling in order to reach the NMOS channel. These properties result in better LO-IF and LO-RF isolations in a Gilbert micromixer. Two identical 0.18-mu m CMOS downconversion micromixers (except at the RF input stage) with deep N-well or without deep N-well are fabricated in adjacent areas of the same wafer for the purpose of isolation comparison. A -37-dB LO-IF and -38-dB LO-RF isolation downconversion micromixer with 19-dB conversion gain and IP1dB = -20 dBm and IIP3 = -13 dBm when RF = 2.4 GHz and LO = 2.25 GHz is demonstrated here using 0.18-mu m-deep N-well CMOS technology. On the other hand, a downconversion micromixer without deep N-well has almost identical power performance but achieves only -20-dB LO-IF isolation and -21-dB LO-RF isolation. (c) 2005 Wiley Periodicals, Inc.
A fully integrated 5.2 GHz GaInP/GaAs HBT upconversion micromixer with output LC current combiner and oscillator
(2003-01-01)
Meng, CC
;
Hsu, SK
;
Peng, AS
;
Wen, SY
;
Huang, GW
A 5.2 GHz; upconversion micromixer with output LC current combiner and integrated oscillator is demonstrated in 2 mum GaInP/GaAs HBT technology in this paper. Micromixer has a single-ended input and a passive LC current combiner is used to convert mixer differential output into a single-ended output. A cross-coupled LC oscillator with oscillation frequency of 4.3 GHz; and a cascode buffer amplifier are also integrated in the same chip. The die size is 1 mm(2). The fully integrated upconversion micromixer has conversion gain of -2.5 dB, OP1dB of -12.5 dBm and 40 dB RF-IF isolation when input IF=0.9 GHz and thus output RF=5.2 GHz. The IF input return loss is better than 25 dB for frequencies up to 6 GHz: while RF output return loss is better than 12 dB for frequencies from 5.15 GHz; to 5.35 GHz.
A fully integrated 5.2 GHz GaInP/GaAs HBT upconversion micromixer with output LC current combiner and oscillator
(2003)
Meng, CC
;
Hsu, SK
;
Peng, AS
;
Wen, SY
;
Huang, GW
A 5.2 GHz upconversion micromixer with output LC current combiner and integrated oscillator is demonstrated in 2 mum GaInP/GaAs HBT technology in this paper. Micromixer has a single-ended input and a passive LC current combiner is used to convert mixer differential output into a single-ended output. A cross-coupled LC oscillator with oscillation frequency of 4.3 GHz and a cascode buffer amplifier are also integrated in the same chip. The die size is 1 mm(2). The fully integrated upconversion micromixer has conversion gain of -2.5 dB, OP1dB of -12.5 dBm and 40 dB RF-IF isolation when input IF=0.9 GHz and thus output RF=5.2 GHz. The IF input return loss is better than 25 dB for frequencies up to 6 GHz while RF output return loss is better than 12 dB for frequencies from 5.15 GHz to 5.35 GHz.
A monolithic 5.2-GHz single-ended input and single-ended output GaInP/GaAs HBT upconversion Gilbert mixer with integrated oscillator
(2005-05-20)
Meng, CC
;
Hsu, SK
;
Huang, GW
;
電信工程研究所
;
Institute of Communications Engineering
A truly balanced operation of a 5.2-GHz Gilbert micromixer with a single-ended input and a single-ended output is demonstrated using 2-mu m GaInP/GaAs HBT technology. Because the micromixer has a single-ended input, a passive LC current combiner is used to convert the mixer-differential output into a single-ended output. A cross-coupled LC oscillator with oscillation frequency of 4.3 GHz and a cascode buffer amplifier are also integrated in the same chip. The fully integrated upconversion micromixer has conversion gain of -2.5 dB and OPIdb of - 12.5 dBm when input IF = 0.9 GHz and thus output RF = 5.2 GHz. The IF input return loss is better than 25 dB for frequencies up to 6 GHz, while the RF output return loss is better than 12 dB for frequencies from 5.15 to 5.35 GHz. (c) 2005 Wiley Periodicals, Inc.
Structure-stability-activity relationship in covalently cross-linked N-carbamoyl D-amino acid amidohydrolase and N-acylamino acid racemase
(2006-06-09)
Chiu, WC
;
You, JY
;
Liu, JS
;
Hsu, SK
;
Hsu, WH
N-Acylamino acid racemase (NAAAR) and N-carbamoyl-D-amino-acid amidohydrolase (D-NCAase) are important biocatalysts for producing enantiopure a-amino acids. NAAAR forms an octameric assembly and displays induced fit movements upon substrate binding, while D-NCAase is a tetramer that does not change conformation in the presence of a ligand. To investigate the effects of introducing potentially stabilizing S-S bridges in these different multimeric enzymes, cysteine residues predicted to form inter or intra-subunit disulfide bonds were introduced by site-directed mutagenesis. Inter-subunit S-S bonds were formed in two NAAAR variants (A68C-D72C and P60C-Y100C) and two D-NCAase variants (A302C and P295C-F304C). Intra-subunit S-S bonds were formed in two additional NAAAR variants (E149C-A182C and V265C). Crystal structures of NAAARs variants show limited deviations from the wild-type overall tertiary structure. An apo A68C-D72C subunit differs from the wild-type enzyme, in which it has an ordered lid loop, resembling ligand-bound NAAAR. The structures of A222C and A302C D-NCAases are nearly identical to the wild-type enzyme. All mutants with inter-subunit bridges had increases in thermostability. Compared with the wild-type enzyme, A68C-D72C NAAAR showed similar k(cat)/K-m ratios, whereas mutant D-NCAases demonstrated increased k(cat)/K-m ratios at high temperatures (A302C: 4.2-fold at 65 degrees C). Furthermore, molecular dynamic simulations reveal that A302C substantially sustains the fine-tuned catalytic site as temperature increases, achieving enhanced activity. (c) 2006 Elsevier Ltd. All rights reserved.