Browsing by Author "Ho, JS"

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A low-power ASIC design for cell search in the W-CDMA system
(2004-05-01)
Li, CF
;
Chu, YS
;
Sheen, WH
;
Tian, FC
;
Ho, JS
This paper presents a low-power ASIC design for cell search in the wideband code-division multiple-access (W-CDMA) system. A low-complexity algorithm that is able to work satisfactorily under the effect of large frequency and clock errors is designed first. Then, a set of low-power measures are employed in the design of hardware architecture and circuits. Finally, through power analysis, critical blocks are identified and redesigned so as to further reduce the power consumption. The final design shows that the power is reduced by 51 % from the original design of 133.6 mW to 65.49 mW, and its core area is also reduced by 31.9% from 3.4 x 3.4 mm(2) to 2.8 x 2.8 mm(2). The design is implemented and verified in a 3.3-V 0.35-mum CMOS technology with clock rate 1 36 MHz.
A three-parameters-only MOSFET subthreshold current CAD model considering back-gate bias and process variation
(1997-04-01)
Chen, MJ
;
Ho, JS
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
In this paper we introduce a new subthreshold conduction CAD model for simulation of VLSI subthreshold CMOS analog circuits and systems, This model explicitly formulates the back-gate bias effect and preserves the original advantages of the existing four-parameter model while reducing the fitting parameter number down to three, A transparent relationship between the fitting parameters and the process parameters has been derived, and its correlation with a recently widely used CAD model as well as with a well-known two-parameter model has been established, Our extensive measurement work on n-channel MOSFET's has highlighted the potential of the model in handling the variations in the subthreshold I-V characteristics at different back-gate biases arising from process variations, The mismatch analysis has further been successfully performed with emphasis on the reverse back-gate bias effect. In summary, the proposed model can serve as a promising alternative in the area of VLSI subthreshold CMOS analog circuit simulation.
A three-parameters-only MOSFET subthreshold current CAD model considering back-gate bias and process variation
(1997-04-01)
Chen, MJ
;
Ho, JS
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
In this paper we introduce a new subthreshold conduction CAD model for simulation of VLSI subthreshold CMOS analog circuits and systems, This model explicitly formulates the back-gate bias effect and preserves the original advantages of the existing four-parameter model while reducing the fitting parameter number down to three, A transparent relationship between the fitting parameters and the process parameters has been derived, and its correlation with a recently widely used CAD model as well as with a well-known two-parameter model has been established, Our extensive measurement work on n-channel MOSFET's has highlighted the potential of the model in handling the variations in the subthreshold I-V characteristics at different back-gate biases arising from process variations, The mismatch analysis has further been successfully performed with emphasis on the reverse back-gate bias effect. In summary, the proposed model can serve as a promising alternative in the area of VLSI subthreshold CMOS analog circuit simulation.
Back-gate forward bias method for low-voltage CMOS digital circuits
(1996-06-01)
Chen, MJ
;
Ho, JS
;
Huang, TH
;
Yang, CH
;
Jou, YN
The back-gate forward bias method suitable for present standard hulk CMOS processes has been promoted for low-voltage digital circuit application, A CMOS inverter employing the method has experimentally exhibited the ability of electrically adjusting the transition region of the de voltage transfer characteristics. Transient measurement has further shown that the inverter with a back-gate forward bias of 0.4 V can operate at low supply voltages down to 0.6 V without significant loss in switching speed, Guidelines for ensuring proper implementation of tile method in a bulk CMOS process has been set up against latch-up, parasitic bipolar, impact ionization, and stand-by current, Following these guidelines, a cost-effective low-power, low-voltage, high-density mixed-mode CMOS analog/digital integrated circuits chip with both reasonable speed and improved precision has been projected for the first time.
Burst synchronization of slotted random access with preamble power ramping in the reverse link of CDMA systems
(2003-09-01)
Sheen, WH
;
Tseng, CC
;
Ho, JS
;
電信工程研究所
;
Institute of Communications Engineering
Efficient random access is one of the key designs in code-division multiple-access (CDMA) cellular systems. Random access is used by user equipment for initial access, requesting dedicated channels and transmitting short packet data to a base station. In random access, a preamble part is usually devised for fast and reliable burst synchronization, which is essential in order to avoid excessive access delay and/or repeated transmissions that may reduce the overall system capacity. This paper investigates the issue of burst synchronization for the slotted random access with preamble power ramping in the reverse link of CDMA systems. A flexible burst synchronizer based on a parallel-serial code-phase detector is proposed, which can be easily configured to achieve different complexity/performance tradeoffs. A general analysis is also presented with important design parameters being taken into account, including the number of correlators, power control error, power ramping step, diversity order, frequency offset, multipath combining, and others. The analysis is verified by computer simulations.
High gain p-n-p gated lateral bipolar action in a fully depleted counter-type: Channel p-MOSFET structure
(1996-02-01)
Ho, JS
;
Huang, TH
;
Chen, MJ
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A three-terminal p-n-p gated lateral bipolar transistor in a counter-type channel p-MOSFET structure has exhibited experimentally ideal I-V characteristics in low-level injection, with a peak current gain exceeding 1000. Two-dimensional device simulation and additional experiments have revealed that high current gains with ideal bipolar I-V characteristics can be obtained only if the counter-type channel is fully depleted. Under this condition, not only the surface emitter-base junction barrier beneath the gate is lowered, but also the holes injected from the emitter almost go through the potential valley in the channel. An analytical model and its validity range have both been established to provide understanding of such behavior, and have been supported experimentally by two-dimensional device simulation. The measured I-V characteristics, including high-level injection, have also been appropriately reproduced.
High-pressure synthesis and characterization of rare-earth substituted (Y,R)(2)Ba4Cu7O15-delta (R = La, Tb, Yb, Lu) cuprates
(1998-04-01)
Chen, TM
;
Lee, SY
;
Ho, JS
;
應用化學系
;
Department of Applied Chemistry
In an attempt to investigate the formation of unknown R2Ba4Cu7O15-delta (R247; R = La, Tb, Yb, Lu) phases, we have prepared and characterized four series of (Y1-xRx)(2)Ba4Cu7O15-delta (R-doped Y247; R = La, Tb, Yb, Lu) cuprates. The substitution limit of R for Y was determined to be <: 10%, 50%, < 20% and 30% for phases with R = La, Yb, Tb and Lu, respectively, as indicated by x-ray diffraction (XRD) patterns. The lattice parameters for R-doped Y247 (R = Yb, Lu) phases were found to decrease with increasing R content due to the smaller size of R3+ compared to that of Y3+. With increasing content of R's the superconducting transition temperature (T-c) were found to first increase and then decrease from 77.1 K of pristine Y247, whereas the width of superconducting transition (Delta T-c) was found to increase with increasing dopant R content. The oxygen contents of R-doped Y247 phases have been experimentally determined by iodometric titration and were found to vary in a small range. Furthermore, a series of (Y0.9R0.1)(2)Ba4Cu7O15-delta (R = Y, Nd, Gd, Yb, Lu) phases were also synthesized and the effect of R3+ substitution on T-c was also investigated. With 10% of R3+ substitution T-c of R-doped Y247 phases was discovered to decrease with increasing ionic radii of R3+ and the corresponding oxygen composition was found to be essentially unchanged.
Optimizing the match in weakly inverted MOSFET's by gated lateral bipolar action
(1996-05-01)
Chen, MJ
;
Ho, JS
;
Chang, DY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The on-chip n-type MOSFET current mirror circuit with different drawn gate widths and lengths has been fabricated, and has been characterized across the wafer with back gate slightly forward biased. The weakly inverted MOSFET device with a small back-gate forward bias represents equivalently the high-gain gated lateral bipolar transistor in low-level injection, Experimental results have exhibited a substantial improvement in the match of the drain current in weak inversion due to action of the gated lateral bipolar transistor, especially for the small size devices. The extensively measured mismatch of the weak inversion drain current has been successfully reproduced by an analytic statistical model with back-gate forward bias and device size both as input parameters. The experimentally extracted variations in process parameters such as the Rat band voltage and the body effect coefficient each have been found to follow the inverse square root of the device area, The mismatch model thus can serve as a quantitative design tool, and has been used to optimize the trade-off between the device area and the match with the forward back-gate bias as a parameter.
Synthesis and characterization of (Tl1-xMx)(Ba,Sr)(2)Ca2Cu3Oz (M = Pb, K, Bi) cuprates: The chemical control of high-temperature superconductivity
(1997-08-01)
Chen, TM
;
Ho, JS
;
交大名義發表
;
應用化學系
;
National Chiao Tung University
The correlation of dopant stoichiometry and superconducting transition temperature (T-c) of three series of metal-doped (Tl1-xMx)(Ba-0.5,Sr-1.5)Ca2Cu3Oz (M = Pb, K, Bi; M-doped Tl-1223) cuprates was investigated. X-ray pure samples were obtained for all phases with x less than or equal to 0.25, less than or equal to 0.25 and 0.60 for M = K, Bi and Pb, respectively. The T-c's of M-doped Tl-1223 phases were found to increase significantly with increasing M content for M = Pb and Bi, whereas that for M = K tends to decrease slightly, as indicated by Meissner effect measurements. The enhancement or suppression of superconductivity (i.e., T-c of Tl-223 upon M-doping can not be satisfactorily rationalized without including both empirical oxygen and TI stoichiometry as well as M content.