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971.
Chein-I Chang Hsuan Ren Shao-Shan Chiang 《Geoscience and Remote Sensing, IEEE Transactions on》2001,39(4):760-768
The authors present a linearly constrained minimum variance (TCMV) beamforming approach to real time processing algorithms for target detection and classification in hyperspectral imagery. The only required knowledge for these LCMV-based algorithms is targets of interest. The idea is to design a finite impulse response (FIR) filter to pass through these targets using a set of linear constraints while also minimizing the variance resulting from unknown signal sources. Two particular LCMV-based target detectors, the constrained energy minimization (CEM) and the target-constrained interference-minimization filter (TCIMF), are presented. In order to expand the ability of the LCMV-based target detectors to classification, the LCMV approach is further generalized so that the targets can be detected and classified simultaneously. By taking advantage of the LCMV-based filter structure, the LCMV-based target detectors and classifiers can be implemented by a QR-decomposition and be processed line-by-line in real time. The experiments using HYDICE and AVIRIS data are conducted to demonstrate their real time implementation 相似文献
972.
973.
974.
Jong Duk Lee Sung Hun Jin Byung Chang Shim Byung-Gook Park 《Electron Device Letters, IEEE》2001,22(4):173-175
A novel process utilizing electrical stress is proposed for the formation of Co silicide on single crystal silicon (c-Si) FEAs to improve the field emission characteristics. Co silicide FEAs formed by electrical stress (ES) exhibited a significant improvement in turn-on voltage and emission current compared with c-Si FEAs. The improvement mainly comes from the lower effective work function of Co silicide and less blunting of tips during silicidation by electrical stress in an ultra high vacuum (UHV) environment less than 10-8 torr 相似文献
975.
采用广义梯度近似(Generalized gradient approximation,GGA)密度泛函理论与非平衡态格林函数(Non-equilibrium Green’s function,NEGF)相结合的方法对两端封闭型单壁(6,0)碳纳米管进行电子传输的理论研究。在温度为300K的条件下,对不同长度(6,0)单壁碳纳米管(SWNT)进行电子透射概率计算。结果显示,两端封闭型(6,0)碳纳米管的电子传输属于量子化传输模式,并随着碳纳米管长度的增加,某些电子透射概率峰值所对应的能量值并未有大的变化,且呈现线性分布;两端封闭型单壁(6,0)碳纳米管中电子的传输接近无散射弹道传输模式,该系统概率尖峰能量的平均间距约为n×2.2eV,n为整数且1≤n≤6。 相似文献
976.
977.
This paper presents uniplanar one-dimensional (1-D) periodical structures, so-called photonic-bandgap (PBG) structures, and defect high-Q resonators for coplanar waveguide, coplanar strip line, and slot line. Proposed uniplanar PBG structures consist of 1-D periodically etched slots along a transmission line or alternating characteristic impedance series with wide band-stop filter characteristics. A stop bandwidth obtained is 2.8 GHz with a stopband rejection of 36.5 dB. This PBG performance can be easily improved if the number of cells or the filling factor is modified in a parametric analysis. Using uniplanar 1-D PBG structures, we demonstrate new high-Q defect resonators with full-wave simulation and measured results. These structures based on defect cavity or Fabry-Perot resonators consist of a center resonant line with two sides of PBG reflectors. They achieve a loaded Q of 247.3 and unloaded Q of 299.1. The proposed circuits should have many applications in monolithic and hybrid microwave integrated circuits 相似文献
978.
Shry-Sann Liao Hsien-Ku Chen Pou-Tou Sun Chen-Yen Lai Hsien-Yuan Liao Yin-Cheng Chang 《Microwave and Wireless Components Letters, IEEE》2003,13(12):529-531
This letter presents a novel design for a small-size coplanar waveguide frequency tripler. In this study, a new BPF has been replaced the conventional stub lines in the output termination of the multiplier. Not only enhance the performance of the tripler, but also reduce the whole circuit size. to 2.125/spl times/2.275 cm/sup 2/ in the frequency 0.8/2.4 GHz, The spurious suppressions are 37.48, 33.38, and 32.08 dBc for the 1st, 2nd, and 4th harmonics, respectively. It reveals the best output power of -1.92 dBm for a 0 dBm input signal and maximum conversion gain of -1.92 dB. It is very useful for applications in the wireless communication and radar systems. 相似文献
979.
Poblenz C. Corrion A.L. Recht F. Chang Soo Suh Chu R. Shen L. Speck J.S. Mishra U.K. 《Electron Device Letters, IEEE》2007,28(11):945-947
In this letter, we report on the microwave power and efficiency performance of AlGaN/GaN high-electron mobility transistors (HEMTs) grown by ammonia molecular beam epitaxy (ammonia-MBE) on SiC substrates. At 4 GHz, an output power density of 11.1 W/mm with an associated power-added efficiency (PAE) of 63% was measured at V ds = 48 V on passivated devices. At 10 GHz, an output power density of 11.2 W/mm with a PAE of 58% was achieved for V ds = 48 V. These results are the highest reported power performance for AlGaN/GaN HEMTs grown by ammonia-MBE and the first reported for ammonia-MBE on SiC substrates. 相似文献
980.
Chen T.-h. Chang K.W. Bui S.B. Wang H. Dow G.S. Liu L.C.T. Lin T.S. Titus W.S. 《Microwave Theory and Techniques》1991,39(12):1980-1986
The design and fabrication of four broadband monolithic passive baluns including CPW Marchand, multilayer MS Marchand, planar-transformer and broadside-coupled line baluns are presented. Operational frequencies range from 1.5 GHz to 24 GHz. Maximum relative bandwidths in excess of 3:1 are achieved. Simulated performances using full wave electromagnetic analysis are shown to agree with the measured results. Two accurate equivalent circuit models constructed from either electromagnetic simulated or measured S-parameters are developed for the MS Marchand and transformer baluns making the optimization of baluns and circuit design using the baluns much more efficient. The design of monolithic double-balanced diode mixer using two planar-transformer baluns is also presented. Without DC bias, the mixer shows a minimum conversion loss of 6 dB with the RF at 5 GHz and a LO drive of 15 dBm at 4 GHz. The measured input IP3 of this mixer is better than 15 dBm over the 4 to 5.75 GHz frequency band 相似文献