An hypothesis test technique for determining a difference insampled parts defective utilizing Fisher's exact test IC production

The result of sample testing during the production of integrated circuits is often a very small number of parts defective out of a sample which is itself very small compared to its population. The ability to determine a statistically significant difference when comparing the results of two such samples is critical in correctly evaluating the outcome of experiments. Fisher's exact test can be used in this situation because it is a method for testing the difference between two proportions of parts defective when the proportions are relatively small in comparison to the sample size. The results of the test are very accurate when the populations are at least ten times the sample size. The result of the test is independent of the order of the samples. However, because the test is one-sided, care must be taken to state the alternative hypothesis based upon the order of the magnitudes of the sample fractions defective     

DESIGN OF A SHAPED BEAM BASE STATION ANTENNA USING GENETIC ALGORITHM

Genetic algorithm is used to optimize a base station antenna in order to achieve ashaped beam in a frequency band. During the optimization process5 different antenna models havebeen evaluated using the Method of Moment (MoM). As a result of this optimization, a shapedbeam antenna with suppressed sidelobe smaller than-18dB, backlobe smaller than-30dB and     

Daytime observation technology of a lidar using an atomic filter

Based on the dual-wavelength high altitude detecting lidar we developed, daytime observation capability was realized in its sodium fluorescence channel by employing a Na (sodium) atomic filter and other relevant technologies. Because of the very narrow passband and very high out-of-band suppression of the Na atomic filter, the lidar echo at an 80-110 km altitude can be obtained even at noontime when background light from the sun is very strong. The capability for a 24-h continuous observation of the lidar system has been demonstrated by the preliminary observation result. This development makes the constant detection and investigation of high altitude atmosphere over the country possible.     

Time-domain uniform geometrical theory of diffraction for a curvedwedge

A time-domain version of the uniform geometrical theory of diffraction (TD-UTD) is developed to describe, in closed form, the transient electromagnetic scattering from a perfectly conducting, arbitrarily curved wedge excited by a general time impulsive astigmatic wavefront. This TD-UTD impulse response is obtained by a Fourier inversion of the corresponding frequency domain UTD solution. An analytic signal representation of the transient fields is used because it provides a very simple procedure to avoid the difficulties that result when inverting frequency domain UTD fields associated with rays that traverse line or smooth caustics. The TD-UTD response to a more general transient wave excitation of the wedge may be found via convolution. A very useful representation for modeling a general pulsed astigmatic wave excitation is also developed which, in particular, allows its convolution with the TD-UTD impulse response to be done in closed form. Some numerical examples illustrating the utility of these developments are presented     

A practical vector control algorithm for μ-based induction motordrives using a new space vector current controller

In this paper, a very simple vector control algorithm is proposed for μ-based induction motor drives. The proposed method controls the motor torque directly and linearly to achieve instantaneous torque response without oscillation. The merits of this control method include its simple architecture and obviating the coordinate transformation. At the same time, a new space vector-based current controller is proposed to serve as a quick response torque controller of the proposed drive system. In addition to the current error, information on the current error derivative is further employed so that one can take more advantages of adding the zero voltage vector for reducing the switching frequency. As a result, the efficiency can be greatly increased. It is seen that through integration of the above two parts, the proposed drive system is very simple to implement and has very good performance     

Ray-theory interpretation of reflection of radio waves by a linearly graded plasma

When a beam of microwaves is incident at an angle ?i on a linearly graded plasma, it emerges at a distance D from the point of incidence, given by ray theory as D = 2 xe sin 2 ?i. A more accurate result can be obtained by applying the principle of stationary phase to the reflected angular spectrum of waves, making use of the reflection coefficient, which can be expressed simply in terms of Airy functions when the electric vector is perpendicular to the plane of incidence. This more accurate result can be represented, to a very close approximation, by taking into account a reflection arising from the discontinuity of gradient at the boundary of the plasma, and combining this with the geometrical-optics result which leads to the equation quoted above. The ray-theory interpretation is shown to have practical implications with the oblique-incidence diagnostic technique introduced by Kharadly.     

An Elementary Proof of a Result Used by Otoshi (Correspondence)

In a recent article, Otoshi used a matrix theoretic result at one point in his derivation. It is the purpose of this letter to present a very simple verification of that theorem, another proof of which can be found in a German textbook referenced by Abele.     

一种光纤电流传感器的设计

针对交流电的特点和传统测试仪器的缺点,以法拉第效应为理论基础,设计了一种光纤电流传感器,介绍了该传感器的工作原理、结构和测试结果.实验结果表明,该电流传感器能准确测量30kA电流,为生活中的大电流测试提供了一种切实有效和更便利的方法.     

An analysis of a staked dipole probe on a lossy Earth plane usingthe finite-difference time-domain method

Using the finite-difference time-domain (FDTD) method, an electrically short, staked, grounded horizontal probe is shown to have an open circuit voltage directly related to the horizontal electric field at the Earth's surface providing the surface coupling is subtracted from the output. This result is valid not only for an infinitely deep Earth plane but also for one which is horizontally layered. The effective length of a staked probe is found to be dependent on the conductivity of the upper layer of the Earth, its depth, the length of the stakes, and also the frequency of measurement. The effect is significant at very low frequency (VLF) for ice, permafrost and dry sand-covered regions     

化学浴法生成金属/锗间含碳层对费米能级钉扎的释放

使用化学浴的方法在金属/锗结构中插入一层含碳层,可以使得肖特基势垒高度得到调整。使用十二稀、十四稀、十六烯和十八烯在锗衬底上进行化学浴可以生成超薄含碳层,该含碳层可以阻挡金属中的自由电子波函数穿透至锗中。金属致带隙状态得到抑制,费米能级钉扎得以释放,所形成结构的肖特基势垒高度为0.17eV。这一新方法较传统方法极大低降低了工艺复杂度,并且得到了很好的结果。     

码分多址通信的计算机仿真

随着通信技术的发展，通信系统的研究成为一项越来越复杂的工程，所以，对通信系统的仿真就日益成为一种重要的研究手段。本文介绍一种对CDMA码分多址通信系统进行计算机仿真的方法。该方法基于通信过程的基本特征，充分利用软件系统的技术特点，具有非常好的可扩展性和执行速度。通过把仿真结果同理论结论进行对比，证明该仿真方法非常有效。     

一款低相位噪声分谐波采样锁相振荡源的设计

现介绍了一种低相位噪声锁相振荡源，以分谐波采样式鉴相取代传统的分频式鉴相。这种方案除了压控振荡器是高频微波部件外，其余都可以用集总参数的电路构成，系统的结构较简单，便于实现小型化，突出优点在于它的灵活性，一个宽带取样鉴相器可对各个频段的压拉振荡器直接进行取样鉴相和锁相。在同等条件下，分谐波采样式锁相源比分频式锁相源的相位噪声更低。     

Collision analysis for a multi-Bluetooth picocells environment

Operating in the unlicensed 2.4-GHz ISM band, a Bluetooth piconet will inevitably encounter the interference problem from other piconets. With a special channel model and packet formats, one research issue is how to predict the packet collision effect in a multi-piconet environment. In an earlier work (El-Hoiydi (2001)), this problem is studied, but the result is still very limited, due to the assumptions that packets must be single-slot ones and that time slots of each piconet must be fully occupied by packets. A more general analysis is presented in this work by eliminating these constraints.     

Design of a nanopower current reference with reduced process variability

In this paper we present the design of a 0.18 μm CMOS current reference based on a variability-aware approach, in such a way to obtain a very low process sensitivity of the reference current. Its relative standard deviation is 1.4 % based on measurements performed over 23 samples from a single batch. The requirement of low process sensitivity is met together with the very low power consumption of 290 nW, at the cost of a large area occupation of 0.245 mm². Key to obtain this result are the use of the “classical” bipolar bandgap topology, which can be optimized for low-power/low-spread operation so as to outperform MOS-based bandgap circuits, and the use of devices that are intrinsically more stable towards process, such as diffusion resistors.     

Light coupling from a semiconductor laser into a polarisation-maintaining single-mode fibre

For laser to polarisation-maintaining fibre coupling we propose the insertion of a short piece of normal single-mode fibre. As a result a power coupling loss of 2.8 dB is obtained, whereas additional crosspolarisation is very small compared with the unwanted polarisation excitation of the laser itself.     

On the optimal characteristics of a memoryless power amplifier system

The performance of the piecewise linear limiter with multi-carrier input signal with arbitrary carrier amplitudes is analysed by using a simple, accurate and general approach. The limiter characteristic is expanded as an infinite Fourier series and convergent series expressions are obtained for the output carriers and intermodu-lation products. The special case of an input consisting of two equal-amplitude carriers is considered in detail and the results are found to be very accurate. This result will help in deciding whether the piecewise linear limiter will produce optimal or suboptimal results under specific traffic and criterion of optimality.     

Design of a Fiber Bragg Grating External Cavity Diode Laser to Realize Mode-Hop Isolation

Recently, a unique approach has been reported in which optical signal degradation is suppressed by realizing mode-hop isolation. This paper analyzes the mode-hop isolation condition in fiber Bragg grating type external-cavity diode lasers (FBG-ECDL). As a result, it has become possible to determine whether mode-hop isolation could be achieved. Moreover, it was verified experimentally that the mode-hop isolation of FBG-ECDLs was actually achieved with this method. The analytical method described in this paper is very useful for designing the uncooled ECDLs whose mode-hop must be isolated.     

Exact solution of a π-pulse problem

The exact solution describing steady-state resonant pulse propagation in a two-level inverted medium is given. This steady-state pulse is often referred to as a 180° or π-pulse. No approximation of a slowly varying envelope is made, and hence the solution satisfies the second-order wave equation as well as the equations of motion of the density matrix of the system. As a result the theory is able to describe very short pulses, whose width can be of the order of the period of the optical carrier. The model for the system includes a nonresonant loss and a finite value of the transverse relaxation time T2, but neglects dispersion in the host medium. The steady-state pulse is found to be frequency modulated and asymmetric in shape.     

Timed arrays in a nutshell

Timed arrays are the time-domain counterpart of phased arrays, where each array element is excited by wideband instead of narrowband signals. By referring to idealized, but meaningful canonical configurations, the array parameters in the transmit and receive mode are defined in a simple way, by following a purely time-domain intuitive analysis. Obtained results extend steady-state concepts of beamwidth, directivity, gain, effective receiving area, Fresnel and Fraunhofer regions to the case of transient excitation. Application is made to both real and synthetic arrays. The final main conclusion is that the role of the carrier wavelength associated with narrowband excitation is taken by the spatial width of the (carrierless) pulse. This result appears to be rather robust, because it turns out to be independent from the different norms used in the definition of the antenna parameters: it sheds light on the physics of the transient radiation and may be very useful for initiating a more technical analysis of the array performance.     

On a multivibrator that employs a fractional capacitor

The simple free running multivibrator built around a single fractional capacitor is examined in this letter. Equations for the oscillation frequency of the multivibrator are derived taking into account the positive feedback factor around the multivibrator. We show that the use of the fractional capacitance allows the multivibrator to have very high frequencies of oscillation for reasonable time constants used. PSPICE simulation and experimental results demonstrate the analysis with an approximation to a fractional capacitor that yields a result, which is at least 1000 times in frequency compared to if a normal capacitor of the same value was employed.