Browsing by Author "Hsu, HT"

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2-V-operation delta-doped power HEMT's for personal handy-phone systems
(1997-08-01)
Lai, YL
;
Chang, EY
;
Chang, CY
;
Liu, TH
;
Wang, SP
A high-efficiency and high-power-density delta-doped AIGaAs/InGaAs HEMT with low adjacent channel leakage has been developed for the digital wireless personal handy-phone system (PHS). When qualified by 1.9-GHz pi/4-shifted quadrature phase shift keying (QPSK) modulated PHS standard signals, the 2.0-V-operation HEMT with a 1-mm gate width demonstrated a power-added efficiency of 45.3% and an output power density of 105 mW/mm. This is the highest power density ever reported by the power transistors for the PHS. The state-of-the-art results for the PHS operating at 2.0 V were achieved by the delta-doped power HEMT for the first time.
2-V-operation delta-doped power HEMT's for personal handy-phone systems
(1997-08-01)
Lai, YL
;
Chang, EY
;
Chang, CY
;
Liu, TH
;
Wang, SP
A high-efficiency and high-power-density delta-doped AIGaAs/InGaAs HEMT with low adjacent channel leakage has been developed for the digital wireless personal handy-phone system (PHS). When qualified by 1.9-GHz pi/4-shifted quadrature phase shift keying (QPSK) modulated PHS standard signals, the 2.0-V-operation HEMT with a 1-mm gate width demonstrated a power-added efficiency of 45.3% and an output power density of 105 mW/mm. This is the highest power density ever reported by the power transistors for the PHS. The state-of-the-art results for the PHS operating at 2.0 V were achieved by the delta-doped power HEMT for the first time.
ISI mitigation and channel tracking in MIMO-OFDM systems
(2005)
Wu, WR
;
Hsu, CY
;
Hsu, HT
;
電信工程研究所
;
Institute of Communications Engineering
When the channel response is longer than the guard interval in OFDM systems, inter-symbol interference (ISI) and intercarrier interference (ICI) will occur and this may seriously affect the receiver performance. In this paper, we consider the ISI and ICI mitigation in MIMO-OFDM systems. We propose to use a decision feedback technique for ISI cancelation and a cyclic reconstruction technique for ICT removal. Combining with the V-BLAST method, we obtain an iterative signal detection algorithm for MIMO-OFDM systems. Since the channel may be time-vaniant, we then further propose an adaptive time-domain channel tracking method. The algorithm can be implemented with IFFT so that its computational complexity is low. Simulations demonstrate that the proposed method can effectively enhance the overall MIMO-OFDM system performance.
Regulation and vibration control of an FEM-based single-link flexible arm using sliding-mode theory
(2001-07-01)
Chen, YP
;
Hsu, HT
;
電控工程研究所
;
Institute of Electrical and Control Engineering
Compared to the assumed-mode method (AMM), the finite-element method (FEM) is not only more applicable to the modeling of various kinds of flexible structures but also better in estimating the natural frequencies. Motivated from these features and modified from the work of Yeung and Chen for an AMM-based model, the sliding-mode controller introduced in this paper is developed to deal with the regulation problem and vibration suppression of an FEM-based single-link flexible arm. This paper will focus on the issue of how to change the FEM-bascd model into a form similar to the AMM-based model via the Schur decomposition. A technique to measure the well-estimated state variables required for the control is also presented. Finally, numerical simulation results are given to verify the robustness of the modified sliding-mode controller against payload variation.