Table of Content

20 June 2003 Volume 30 Issue 3

  

Original Articles

A compact closed form of standard normal distribution

LIANG Chang-hong;LI Long;SHI Xiao-wei

J4. 2003, 30(3):  289-292. 

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It is well known that the probability integral and quantile of a standard normal distribution are usually calculated by table look-up. A lot of literature gave also some approximate formulas, which are very complex and inconvenient to use. In this paper, the compact closed forms of the standard normal distribution and quantile are presented by using the two-dimensional circular approximation and inverse function, which make calculation of the probability much casier. Furthermore, we make use of the compensation of primary and remainder integrals to derive more accurately compact closed forms, with the error distributions of the compact closed forms given.

Analysis of the frequency property in SiGe HBT

ZHANG He-ming;DAI Xian-ying;Lü Yi;LIN Da-song;HU Hui-yong;WANG Wei

J4. 2003, 30(3):  293-297. 

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The main factor influencing the frequency property in SiGe HBT is the delay times during carrier transportation. Based on the analysis of the carrier transportation and distribution, the time constant models with clearly physical meanings are proposed. Themodels reveal the relationship between the time constants and the parameters of device structure and the current density in SiGe HBT. The base extending effect is also taken into account in these models. Also, the relationship between f_T and the parameters of device structure and the current density is analyzed and discussed.

Evolutionary design of analon circuits using a novel adaptive genetic algorithm

ZHAO Shu-guang1;LIU Gui-xi2;YANG Wan-hai1

J4. 2003, 30(3):  298-301. 

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First we introduce the current research status of evolutionary design for analog circuits briefly, and then we propose a multi-objective adaptive Genetic Algorithm and discuss it in detail. It features an encoding-decoding scheme based on typical structures of circuits and standard values of components(i.e. discrete values in common use), a multi-objective fitness evaluation method using Pspice simulation and dynamic adjusting of weight vectors, and a genetic parameter adaptiation technique for considering the different effect of each locus on fitness and tracking the course of evolution. Some experiments on active filters show that with our approach a suitable type and an optimal value of each component in the circuit can be found automatically, so an effective circuit with a response very close to the design target can be developed, and only modest computational resource is required that a PC can afford.

Analysis of X-ray photoelectron spectroscopy on Si₃N₄/SiO₂ double-gate medium under irradiation

FAN Long1;2;HAO Yue1;YAN Rong-liang2;LU Wu2

J4. 2003, 30(3):  302-305. 

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A depth profiles analysis of the irradiation effect of Si₃N₄/SiO₂ double-gate medium under ⁶⁰Co-γ ray irradiation has been carried out by using the X-ray photoemission spectroscopy(XPS) method, with Ar⁺ ion etching. The experimental results show that there is distinct interface region between Si₃N₄ and SiO₂ as well as between SiO₂ and Si, respectively, and after irradiation, a shift to Si₃N₄/SiO₂ interface of the center SiO₂/Si interface region occurs. In addition, the SiO₂/Si interface region is broadened. A great decrease in concentration of Si middle state located in a region from SiO₂/Si interface to Si substrate is induced by irradiation. With the same bias, the amount of break-bond of Si middle states located in SiO₂/Si inteface region increases with increasing radiation doses, and it is found that the bias on the sample radiated plays an obvious role in breaking the bonds of Si middle states. Finally a discussion on experimental results is presented.

Growth of the SiGe HBT material by UVCVD/UHVCVD

DAI Xian-ying;HU Hui-yong;ZHANG He-ming;SUN Jian-cheng

J4. 2003, 30(3):  306-308. 

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A new CVD technique, called UVCVD/UHVCVD, is developed for SiGe HBT materials. The technique is characterized by its low temperature and ultrahigh vacuum. The device-quality SiGe materials are grown by UVCVD/UHVCVD under an ultrahigh vacumm of 10^-7Pa at a low temperature of 450℃. The result of SIMS shows that the interfaces are distinct and the rising and falling edges are steep. Furthermore, the SiGe HBT device based on the materials is developed.

A novel MAC protocol for the mobile Ad Hoc network with smart antennas

YANG Jun;LI Jian-dong;LI Wei-ying

J4. 2003, 30(3):  309-314. 

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The MAC protocol for supporting the application of smart antennas in the mobile Ad Hoc network(MANET) is studied. An adaptive beamforming CSMA/CA protocol(ABF-CSMA/CA) is proposed. In ABF-CSMA/CA, the RTS/CTS dialogue is used and training sequences are transmitted just before RTS and CTS packets, so the temporal reference beamforming(TRB) can be performed. An improved virtual carrier-sense mechanism is also proposed to enhance collisioin avoidance(CA) and obtain efficient space division multiple access(SDMA). In this scheme, every node has two kinds of network allocation vector(NAV)- o NAV and b NAV. A theoretical analysis of channel utilization is presented. Results show that the ABF-CSMA/CA protocol can support the application of smart antennas effectively and rpovide higher channel utilization.

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J4. 2003, 30(3):  315-319. 

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J4. 2003, 30(3):  320-325. 

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J4. 2003, 30(3):  326-330. 

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J4. 2003, 30(3):  331-334. 

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J4. 2003, 30(3):  335-339. 

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J4. 2003, 30(3):  340-344. 

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J4. 2003, 30(3):  345-348. 

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J4. 2003, 30(3):  349-352. 

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J4. 2003, 30(3):  353-356. 

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J4. 2003, 30(3):  357-361. 

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J4. 2003, 30(3):  362-366. 

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J4. 2003, 30(3):  367-369. 

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J4. 2003, 30(3):  370-373. 

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J4. 2003, 30(3):  374-377. 

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J4. 2003, 30(3):  378-380. 

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J4. 2003, 30(3):  381-385. 

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J4. 2003, 30(3):  386-390. 

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J4. 2003, 30(3):  391-393. 

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J4. 2003, 30(3):  394-398. 

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J4. 2003, 30(3):  399-402. 

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J4. 2003, 30(3):  403-406. 

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J4. 2003, 30(3):  407-409. 

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J4. 2003, 30(3):  410-414. 

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J4. 2003, 30(3):  415-420. 

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J4. 2003, 30(3):  421-425. 

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J4. 2003, 30(3):  426-428. 

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