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991.
Detailed theoretical analysis of four-wave mixing (FWM) wavelength conversion in quantum dot semiconductor optical amplifier (QD-SOA) is presented. The model takes into account the effect of the multidiscrete QD energy levels and the wetting layer. Good agreement between calculated and experimental data is obtained. Because of the discreteness of the energy levels, QD-SOAs demonstrate high FWM conversion efficiencies at high detuning frequency. Our calculations show that carrier escape from the ground state significantly affects the performance of the amplifier.  相似文献   
992.
The transition plan from the analog (NTSC) to digital terrestrial television (DTTV) in the USA was based on a simplified version of the Longley-Rice service prediction algorithm, and a link budget that mimicked the traditional planning factors for NTSC. It is now clear that the service prediction and the link budget both have serious shortfalls. This paper provides the formalism required for the development of realistic link budget and service grades for fixed and portable DTTV reception.  相似文献   
993.
This paper presents a highly power efficient 2/spl times/20-W class-D audio output power stage implemented in 0.6-/spl mu/m BCDMOS technology. The presented power stage is capable of driving 2/spl times/8-/spl Omega/ loads from a 20-V power supply at a power efficiency approaching 90%. Circuit details of thermal detection, over-current protection, and startup speaker click/pop are also presented. The performance of open-loop Class-D output stages are limited by the distortion mechanisms present within the power stage itself. A third-order PWM modulator was prototyped and used to dramatically improve the performance of the Class-D output stage by using feedback. The results of this work are also presented.  相似文献   
994.
Porous silicon interfaces have been modified with nitrided TiO2 (TiON) nanoparticles to develop highly efficient photoelectrodes. Photoelectrodes were prepared by impregnating the electrochemically prepared porous silicon microchannels with titanium oxynitride. Photocatalytic measurements were carried out on titanium oxynitride particles in water‐methanol mixture and the results showed a dependence on the nitrogen concentration. Among the photoelectrodes used for photocurrent measurements, porous silicon impregnated with TiO2 nitrided at 600 °C showed maximum photocurrent increase after exposure to sunlight‐type radiation. The enhancement in photocurrent was one order more for the porous silicon/titanium oxynitride hetero‐structure than that of polished silicon/titanium oxynitride hetero‐structure. Photoelectrodes thus prepared were found to have stable performance for a period of six months. This observation promises the possibility of using porous silicon/titanium oxynitride hetero‐structures as efficient electrodes for photovoltaic cells. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   
995.
We study the signal-to-interference (SIR) performance of linear multiuser receivers in random environments, where signals from the users arrive in “random directions.” Such a random environment may arise in a DS-CDMA system with random signature sequences, or in a system with antenna diversity where the randomness is due to channel fading. Assuming that such random directions can be tracked by the receiver, the resulting SIR performance is a function of the directions and therefore also random. We study the asymptotic distribution of this random performance in the regime where both the number of users K and the number of degrees of freedom N in the system are large, but keeping their ratio fixed. Our results show that for both the decorrelator and the minimum mean-square error (MMSE) receiver, the variance of the SIR distribution decreases like 1/N, and the SIR distribution is asymptotically Gaussian. We compute closed-form expressions for the asymptotic means and variances for both receivers. Simulation results are presented to verify the accuracy of the asymptotic results for finite-sized systems  相似文献   
996.
Data are presented on low threshold, 1.3-μm oxide-confined InGaAs-GaAs quantum dot lasers. A very low continuous-wave threshold current of 1.2 mA with a threshold current density of 28 A/cm2 is achieved with p-up mounting at room temperature. For slightly larger devices the continuous-wave threshold current density is as low as 19 A/cm2  相似文献   
997.
全球通用三频段GSM单芯片收发信机   总被引:1,自引:0,他引:1  
本文所述是一个全球通用GSM单芯片收发信机的实现方式 ,介绍了基于GSM标准的多频段无线结构方框 ,讨论了此类结构方框实现全球通用GSM收发信机的可能性。该单芯片集成电路使用了0 5 μmBiCMOS工艺 ,并封装在一块“9× 9”的CABGA中。本文还介绍了该收发信机工作参数的测量结果。  相似文献   
998.
The purpose of this study was to assess whether the artifacts presented by precordial compressions during cardiopulmonary resuscitation could be removed from the human electrocardiogram (ECG) using a filtering approach. This would allow analysis and defibrillator charging during ongoing precordial compressions yielding a very important clinical improvement to the treatment of cardiac arrest patients. In this investigation we started with noise-free human ECGs with ventricular fibrillation (VF) and ventricular tachycardia (VT) records. To simulate a realistic resuscitation situation, we added a weighted artifact signal to the human ECG, where the weight factor was chosen to provide the desired signal-to-noise ratio (SNR) level. As artifact signals we used ECGs recorded from animals in asystole during precordial compressions at rates 60, 90, and 120 compressions/min. The compression depth and the thorax impedance was also recorded. In a real-life situation such reference signals are available and, using an adaptive multichannel Wiener filter, we construct an estimate of the artifact signal, which subsequently can be subtracted from the noisy human ECG signal. The success of the proposed method is demonstrated through graphic examples, SNR, and rhythm classification evaluations.  相似文献   
999.
Gurinovich  L. I.  Trotsiuk  L. L.  Kulakovich  O. S.  Sushko  N. I.  Demir  H. V.  Gaponenko  S. V. 《Semiconductors》2018,52(16):2054-2056
Semiconductors - Anisotropic polymer films containing aligned Au nanorods and semiconductor nanoparticles of various shape were fabricated. The photoluminescence of semiconductor nanoparticles in...  相似文献   
1000.
The impact of local deep-amorphization (DA) and subsequent solid-phase epitaxial regrowth (SPER) are studied for the co-integration of devices with hybrid surface orientation. Thin-body p-channel transistors with 20 nm thick film and HfO2 gate insulator/metal gate along several directions on a (1 1 0) substrate were fabricated and characterized. No deterioration of transconductance or threshold voltage was induced by DA/SPER process. Device co-integration using DA/SPER process is therefore a realistic option. 〈1 1 0〉 channel on (1 1 0) SOI film yields a 200% gain on the current for the (1 0 0) surface orientation. However, the benefit of it decreases with the channel length.  相似文献   
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