Browsing by Author "Liu, HY"

Now showing 1 - 9 of 9

A 528MS/s frequency synchronizer for OFDM-based UWB system
(2005)
Chen, LH
;
Chang, WC
;
Liu, HY
;
Lee, CY
;
電子工程學系及電子研究所
A novel frequency synchronizer is proposed for 528MHz OFDM-based UWB system. It can reduce 75% memory and 59% power consumption through a low-power scheme based on data. partition. Measured result shows the proposed design can achieve 528MSamples/s throughput in 0.18 mu m CMOS process.
A COMM baseband processor with robust synchronization for high-speed WLAN applications
(2004)
Liu, HY
;
Yu, YH
;
Lin, CC
;
Chung, CC
;
Hsu, TY
in this paper, a high-performance and low-cost COFDM baseband processor is presented. With algorithm exploration in channel estimation and phase error tracking, synchronization becomes more robust to enhance system performance. And better design SNR (1.35similar to7.16 dB) can be achieved compared to current solutions. Moreover through architectural exploration, the proposed baseband processor designed in 0.18 um CMOS process contains only 370 K logic gates and 3.3 K byte memory. Measurement results show that better hardware efficiency and performance enhancement is achieved for high-speed WLAN applications.
A dynamic scaling FFT processor for DVB-T applications
(2004-11-01)
Lin, YW
;
Liu, HY
;
Lee, CY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This paper presents an 8192-point FFT processor for DVB-T systems, in which a three-step radix-8 FFT algorithm, a new dynamic scaling approach, and a novel matrix prefetch buffer 1 are exploited. About 64 K bit memory space can be saved in the 8 K point FFT by the proposed dynamic scaling approach. Moreover, with data scheduling and pre-fetched buffering, single-port memory can be adopted without degrading throughput rate. A test chip for 8 K mode DVB-T system has been designed and fabricated using 0.18-mum single-poly six-metal CMOS process with core area of 4.84 mm(2). Power dissipation is about 25.2 mW at 20 MHz.
An area and power efficient frame synchronizer for 480Mb/s OFDM-based UWB system
(2005)
Chang, WC
;
Chen, LH
;
Liao, WC
;
Liu, HY
;
Lee, CY
A novel frame synchronizer is proposed for OFDM-based UWB system. Integrating the improved matched filters and dynamic threshold design, the proposed design can reduce 65% area and 58% power with an acceptable performance loss. It can achieve 528MS/s throughput for 480Mb/s UWB system in 0.18 mu m CMOS process.
Combining adaptive smoothing and decision-directed channel estimation schemes for OFDM WLAN systems
(2003)
Liu, HY
;
Yu, YH
;
Hung, CJ
;
Hsu, TY
;
Lee, CY
In this paper, a new channel estimation method for OFDM WLAN systems is proposed. This proposal mainly consists of smoothing filtering and decision-directed tracking loop schemes, where the former is used to enhance performance at low SNR and the latter is exploited to enhance performance at high SNR respectively. Together with an adaptive channel management, better performance in terms of MSE and PER can be achieved. Simulation shows the proposed method (1) achieves better 9.0dB similar to 13.0dB gain in MSE than zero forcing criterion and better 2.0dB gain in MSE than conventional approaches in BPSK transmission, and (2) contributes 0.8dB similar to 2.0dB gain in SNR for 10% PER in different transmission modes.
Continuous-wave high-power (320 mW) single mode operation of electronic vertically coupled InAs/GaAs quantum dot narrow-ridge-waveguide lasers
(2005-12-01)
Wang, JS
;
Lin, G
;
Hsiao, RS
;
Yang, CS
;
Lai, CM
High-power 3 mu m-wide narrow-ridge-waveguide lasers with ten stacks of electronic vertically coupled InAs/GaAs quantum dots in the active region were demonstrated. Unlike that from conventional uncoupled InAs quantum dot lasers, a narrow lasing spectrum was observed because the carriers tunneled in the vertical direction. Continuous-wave operation in single lateral mode yielded a kink-free output power of 320 mW with an efficiency of 0.46 W/A , and a sensitivity of lasing wavelength to temperature of 0.28 nm/K.
Molecular-beam-epitaxy growth of high-quality InGaAsN/GaAs quantum well lasers emitting at 1.3 mu m
(2004-11-01)
Wang, JS
;
Hsiao, RS
;
Lin, G
;
Lin, KF
;
Liu, HY
Molecular-beam-epitaxy growth of high structural and optical-quality InGaAsN/GaAs quantum wells (QW) has been investigated. The material quality can be improved significantly by using low-temperature growth to suppress the phase separation. High-performance ridge-waveguide InGaAsN/GaAs single QW lasers emitting at 1.3 mum have been demonstrated. Infinite-cavity-length threshold-current density of 400 A /cm(2), internal quantum efficiency of 96%. and a slope efficiency of 0.67 W/A for a cavity length L=1 mm were obtained. A TO46 packaging laser shows sin-le lateral-mode kink-free output power of more than 200 mW with a maximum total wallplug efficiency of 29% at room temperature under continuous wave (cw) operation. Moreover. 1.3 Am InGaAsN/GaAs QW vertical-cavity surface-emitting lasers with a threshold current density lower than 2 KA/cm(2) at room temperature have been achieved. We obtained multimode cw output power and slope efficiency in excess of 1 mW and 0.15 W/A. respectively. (C) 2004 American Vacuum Society.
Single mode 1.3 mu m InGaAsN/GaAs quantum well vertical cavity surface emitting lasers grown by molecular beam epitaxy
(2004-12-01)
Hsiao, RS
;
Wang, JS
;
Lin, KF
;
Wei, L
;
Liu, HY
The growth by molecular-beam-epitaxy of high-quality 1.3 mum InGaAsN/GaAs quantum wells (QW) intra-cavity contacted vertical cavity surface emitting lasers (VCSELs) was demonstrated. Low-temperature growth, which suppresses the phase separation significantly improves material quality in the active region. Room-temperature continuous wave (RT-CW) single mode output power of 0.75 mW with an initial slope efficiency of 0.17 W/A and a side mode suppression ratio of 40 dB at a lasing wavelength of as long as 1304 nm were obtained.
Voltage collapse detection of a power system based on the FIDF technique
(2005)
Liang, YW
;
Liu, HY
;
Xu, SD
;
Lin, SJ
;
電控工程研究所
In this paper, an effective linear-based fault identification filter (FIDF) design technique is applied to voltage collapse detection in a power system so that a corrective action can be made at the onset of unstable phenomena. This is achieved by treating the difference between the load voltage of the power system and that of its linearized model at a stable operating point as a fault vector and then investigating the effect of the fault on the designed FIDE. In practical applications, since FIDF has a low pass filter property and is easily calculated, it can effectively attenuate the influences of high frequency measurement noises and be employed as an on-line detection scheme. Simulation results for Dobson and Chiang's power system model (1990) are finally given to demonstrate the effectiveness of the FIDE design.