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1.
A dispersion formula ϵ*eff(f )=ϵ* -{ϵ*-ϵ*eff(0)}/{1+( f /f 50)m}, for the effective relative permittivity ϵ*eff(f ) of an open microstrip line is derived for computer-aided design (CAD) use. The 50% dispersion point (the frequency f 50 at which ϵ*eff(f 50)={ϵ *+ϵ*eff(0)}/2}) is used a normalizing frequency in the proposed formula, and an expression for f 50 is derived. To obtain the best fit of ϵ *eff(f ) to the theoretical numerical model, the power m of the normalized frequency in the proposed formula is expressed as a function of width-to-height ratio w / h for w /h ⩾0.7 and as a function of w /h , f 50, and f for w /h ⩽0.7. The present formula has a high degree of accuracy, better than 0.6% in the range 0.1<w /h ⩽10, 1<ϵ*⩽128, and any height-to-wavelength ratio h /λ0 相似文献
2.
A strengthening of the Assmus-Mattson theorem 总被引:1,自引:0,他引:1
Calderbank A.R. Delsarte P. Sloane N.J.A. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1991,37(5):1261-1268
Let w 1=d ,w 2,…,w s be the weights of the nonzero codewords in a binary linear [n ,k ,d ] code C, and let w ' 1, w '2, …, w '3, be the nonzero weights in the dual code C1. Let t be an integer in the range 0<t <d such that there are at most d -t weights w 'i with 0<w 'i ⩽n -t E. F. Assmus and H. F. Mattson, Jr. (1969) proved that the words of any weight w i in C form a t -design. The authors show that if w 2⩾d +4 then either the words of any nonzero weight w i form a (t +1)-design or else the codewords of minimal weight d form a {1,2,…,t ,t +2}-design. If in addition C is self-dual with all weights divisible by 4 then the codewords of any given weight w i form either a (t +1)-design or a {1,2,…,t ,t +2}-design. The proof avoids the use of modular forms 相似文献
3.
Csiszar I. Narayan P. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1991,37(1):18-26
The Gaussian arbitrarily varying channel with input constraint Γ and state constraint Λ admits input sequences x =(x 1,---,X n) of real numbers with Σx i2⩽n Γ and state sequences s =(S 1,---,s n ) of real numbers with Σs i2⩽n Λ; the output sequence x +s +V , where V =(V 1,---,V n) is a sequence of independent and identically distributed Gaussian random variables with mean 0 and variance σ2. It is proved that the capacity of this arbitrarily varying channel for deterministic codes and the average probability of error criterion equals 1/2 log (1+Γ/(Λ+σ2)) if Λ<Γ and is 0 otherwise 相似文献
4.
Complex demodulation of evolutionary spectra is formulated as a two-dimensional kernel smoother in the time-frequency domain. First, a tapered Fourier transform, y v(f , t ), is calculated. Then the log-spectral estimate, is smoothed. As the characteristic widths of the kernel smoother increase, the bias from the temporal and frequency averaging increases while the variance decreases. The demodulation parameters, such as the order, length, and bandwidth of spectral taper and the kernel smoother, are determined by minimizing the expected error. For well-resolved evolutionary, spectra, the optimal taper length is a small fraction of the optimal kernel halfwidth. The optimal frequency bandwidth, w , for the spectral window scales as w 2~λ/τ, where τ is the characteristic time and λF is the characteristic frequency scalelength. In contrast, the optimal halfwidths for the second stage kernel smoother scales as h ~1/(τλF )1(p+2)/ where p is the order of the kernel smoother. The ratio of the optimal-frequency halfwidth to the optimal-time halfwidth is determined 相似文献
5.
The authors consider the problem of bounding the information capacity of saturation recording. The superposition channel with additive Gaussian noise is used as a model for recording. This model says that for a saturation input signal, x (t ) (i.e., one that can assume only one of two levels), the output can be expressed as y (t )=x ˜(t )+z (t ) where x ˜(t ) is a filtered version of the input x (t ) and z (t ) is additive Gaussian noise. The channel is described by the impulse response of the channel filter, h (t ), and by the autocorrelation function of the noise. A specific example of such a channel is the differentiated Lorentz channel. Certain autocorrelation and spectrum expressions for a general Lorentz channel are derived. Upper and lower bounds on the capacity of saturation recording channels are described. The bounds are explicitly computed for the differentiated Lorentz channel model. Finally, it is indicated how the derived bounds can be applied in practice using physical measurements from a recording channel 相似文献
6.
p+-n junction diodes for sub-0.25-μm CMOS circuits were fabricated using focused ion beam (FIB) Ga implantation into n-Si (100) substrates with background doping of Nb=(5-10)×10 15 and Nb+=(1-10)×1017 cm-3. Implant energy was varied from 2 to 50 keV at doses ranging from 1×1013 to 1×1015 cm-2 with different scan speeds. Rapid thermal annealing (RTA) was performed at either 600 °C or 700°C for 30 s. Diodes fabricated on Nb+ with 10-keV Ga+ exhibited a leakage current (IR) 100× smaller than those fabricated with 50-keV Ga+. Tunneling was determined to be the major current transport mechanism for the diodes fabricated on Nb+ substrates. An optimal condition for I R on Nb+ substrates was obtained at 15 keV/1×1015 cm-2. Diodes annealed at 600°C were found to have an I R 1000× smaller than those annealed at 700°C. I -V characteristics of diodes fabricated on Nb substrates with low-energy Ga+ showed no implant energy dependence. I -V characteristics were also measured as a function of temperature from 25 to 200°C. For diodes implanted with 15-keV Ga +, the cross-over temperatures between I diff and I g-r occurred at 106°C for Nb + and at 91°C for Nb substrates 相似文献
7.
The ill-posedness of the extrapolation problem in the presence of noise is considered. A stable algorithm is constructed by solving a Fredholm equation based on a regularization method. The algorithm appears relatively robust, since the noise ηδ(t ) is taken as a function in L 2[-T ,T ](T >0) such that the error energy ∫|ηδ(t )|2 dt ⩽δ2, where integration is from - T to T , and the constructed extrapolation uniformly converges to the desired signal over (-∞, +∞) as δ→0. An estimate for the error energy of the constructed extrapolation over (-∞, +∞) and for the absolute error between the constructed extrapolation and the desired signal over (-∞, +∞) are presented 相似文献
8.
Peransin J.-M. Vignaud P. Rigaud D. Vandamme L.K.J. 《Electron Devices, IEEE Transactions on》1990,37(10):2250-2253
The 1/f noise in normally-on MODFETs biased at low drain voltages is investigated. The experimentally observed relative noise in the drain current S I/I 2 versus the effective gate voltage V G=V GS-V off shows three regions which are explained. The observed dependencies are S I/I 2∝V G m with the exponents m =-1, -3, 0 with increasing values of V G. The model explains m =-1 as the region where the resistance and the 1/f noise stem from the 2-D electron gas under the gate electrode; the region with m =0 at large V G or V GS≅0 is due to the dominant contribution of the series resistance. In the region at intermediate V G , m =-3, the 1/f noise stems from the channel under the gate electrode, and the drain-source resistance is already dominated by the series resistance 相似文献
9.
Two theorems on lattice expansions 总被引:1,自引:0,他引:1
Daubechies I. Janssen A.J.E.M. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1993,39(1):3-6
It is shown that there is a tradeoff between the smoothness and decay properties of the dual functions, occurring in the lattice expansion problem. More precisely, it is shown that if g and g ¯ are dual, then (1) at least one of H 1/2 g and H 1/2 g ¯ is n in L 2(R), and (2) at least one of Hg and g ¯ is not in L 2(R). Here, H is the operator -1/(4π2)d 2/(dt 2 )+t 2. The first result is a generalization of a theorem first stated by R.C. Balian (1987). The second result is new and relies heavily on the fact that, when G ∈W2,2(S ) with S =[-1/2, 1/2]×[-1/2, 1/2] and G (0), than 1/G ∉L 2(S ) 相似文献
10.
Double series representation of bounded signals 总被引:2,自引:0,他引:2
Jensen H.E. Hoholdt T. Justesen J. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1988,34(4):613-624
Series representations of the form f (t)~Σn=-∞∞Σ k=-∞∞an,kν(t-n)e 2πkts/ for bounded signals f (t) are studied, as are conditions on the unit function ν(t), such that coefficients an,k reveal the energy content of f (t) in the time interval n -(1/2)⩽t ⩽n +(1/2) and frequency interval 2π(k-(1/2))⩽ω⩽2π(k+(1/2)). These conditions turn out to be orthogonality and integrability. Based on these conditions a number of properties of the expansion are derived, including summability of the double series and energy and power estimations. Some examples of the expansion are presented 相似文献
11.
Goggin E.M. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1992,38(3):1091-1100
For each N , and each fixed time T , a signal X N and a `noisy' observation Y N are defined by a pair of stochastic difference equations. Under certain conditions (X N, Y N) converges in distribution to (X , Y , where dX (t )= f (t , X (t ))dt +dV ( t ), dY (t )=g (t , X ( t ))dt +dW (t ). Conditions are found under which convergence in distribution of the conditional expectations E{F(XN)|YN} to E{F(X)|Y} follows, for every bounded continuous function F . The case in which the conditional expectations still converge but the limit is not E { F (X )|Y } is also studied. In the situation where f and g are linear functions of X , an examination of this limit leads to a Kalman-Bucy-type estimate of X N which is asymptotically optimal and is an improvement on the usual Kalman-Bucy estimate 相似文献
12.
Chough K.B. Chang T.Y. Feuer M.D. Sauer N.J. Lalevic B. 《Electron Device Letters, IEEE》1992,13(9):451-453
Record high f TL g products of 57 and 46 GHz-μm have been achieved in Ga1-x Inx As/AlInAs MODFETs with a strain compensated channel of x =0.77 and a lattice-matched channel of x =0.53, respectively. Although gm as high as 950 mS/mm has been obtained by conventional deep recess for the gate, these latter devices show a prominent kink effect which lowers f T and the voltage gain. By limiting the depth of final nonselective recess etch to 3 nm with the help of selective step etches, f T as high as 47 GHz and gm as high as 843 mS/mm have been achieved for MODFETs with x =0.77 and L g=1.1 μm 相似文献
13.
The small-signal characteristics have been clarified by S -parameter measurements and equivalent circuit modeling. A large intrinsic transconductance of 630 mS/mm and a maximum cutoff frequence f T of 70 GHz have been achieved for a MISFET with a gate length of 0.4 μm. The average electron drift velocity in the channel, evaluated from the f T, was as high as 1.7×107 cm/s. In obtaining an equivalent-circuit model, a gate conductance parallel to the gate-source capacitance is introduced to take into account the gate forward current of normally-off FETs The gate conductance does not cause the f T of the MISFET to deteriorate due to a small gate forward current at a large gate bias, in contrast to GaAs MESFETs 相似文献
14.
Consider a zero-mean, stationary Gaussian process g (t ), to which a large positive constant A has been added. Define a distortion process h A(t ) as equal to g (t )+A when the latter is negative and equal to zero otherwise. The author calculates the power spectrum of the process h A(t ) asymptotically as A becomes large. The results have application for estimating the nonlinear-distortion power in the recovered signal when many frequency-multiplexed subcarriers collectively modulate a laser's output power, as would be the case for CATV transmission over an optical fiber. The process h A(t ) then models the nonlinear distortion caused by occasional clipping of the DC-biased laser input 相似文献
15.
Electrical characteristics of Al/yttrium oxide (~260 Å)/silicon dioxide (~40 Å)/Si and Al/yttrium oxide (~260 Å)/Si structures are described. The Al/Y2O3/SiO2/Si (MYOS) and Al/Y2 O3/Si (MYS) capacitors show very well-behaved I -V characteristics with leakage current density <10-10 A/cm2 at 5 V. High-frequency C - V and quasistatic C -V characteristics show very little hysteresis for bias ramp rate ranging from 10 to 100 mV/s. The average interface charge density (Q f+Q it) is ~6×1011/cm2 and interface state density D it is ~1011 cm-2-eV-1 near the middle of the bandgap of silicon. The accumulation capacitance of this dielectric does not show an appreciable frequency dependence for frequencies varying from 10 kHz to 10 MHz. These electrical characteristics and dielectric constant of ~17-20 for yttrium oxide on SiO2/Si make it a variable dielectric for DRAM storage capacitors and for decoupling capacitors for on-chip and off-chip applications 相似文献
16.
Nguyen L.D. Schaff W.J. Tasker P.J. Lepore A.N. Palmateer L.F. Foisy M.C. Eastman L.F. 《Electron Devices, IEEE Transactions on》1988,35(2):139-144
The authors describe a study of charge control in conjunction with DC and RF performance of 0.35-μm-gate-length pseudomorphic AlGaAs/InGaAs MODFETs. Using C -V measurements, they estimate that a two-dimensional electron gas (2DEG) with density as high as 1.0×1012 cm-2 can be accumulated in the InGaAs channel at 77 K before the gate begins to modulate parasitic charges in the AlGaAs. This improvement in charge control of about 10-30% over a typical AlGaAs/GaAs MODFET may partially be responsible for the superior DC and RF performance of the AlGaAs/InGaAs MODFET. At room temperature, the devices give a maximum DC voltage gain g m/g d of 32 and a current gain cutoff frequency f T of 46 GHz. These results are state of the art for MODFETs of similar gate length 相似文献
17.
The ramp recovery method for the measurement of carrier lifetime in p-i-n diodes is analyzed to show that B. Tien and C. Hu's (1988) formula τ=(t A(t A+t B))1/2, where t A and t B are the two intervals for the recovery, gives a good estimate of the lifetime. The recovery can be assumed to be complete at a time t 2 at which the reverse current has reduced to 10% of its peak value. This eliminates the necessity of assuming the ramp recovery waveform to be a triangle 相似文献
18.
Yiqi Zhuang Qing Sun 《Electron Devices, IEEE Transactions on》1991,38(11):2540-2547
Accelerated life tests with high-temperature storage and electric aging for n+-p-n silicon planar transistors were carried out. Current gain h FE increases monotonously with time during the tests, and the h FE drift is correlated with initial measured 1/f noise in the transistors, i.e. the drift amount significantly increases with the increase of noise level. The correlation coefficient of relative drift Δh FE /h FE and 1/f noise spectral density S iB(f ) is far larger than that of Δ h FE/h FE and initial DC parameters of the transistors. A quantitative theory model for the h FE drift has been developed and explains the h FE drift behavior in the tests, which suggests that the h FE drift and 1/f noise can be attributed to the same physical origin, and both are caused by the modulation of the oxide traps near the Si-SiO2 interface to Si surface recombination. 1/f noise measurement, therefore, may be used as a fast and nondestructive means to predict the long-term instability in bipolar transistors 相似文献
19.
Janssen A.J.E.M. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1992,38(1):168-171
It is shown how the Zak transform can be used to find nontrivial examples of functions f , g ∈L 2(R ) with f ×g ≡0≡F ×G , where F , G are the Fourier transforms of f , g , respectively. This is then used to exhibit a nontrivial pair of functions h , k ∈L2(R ), h ≠k , such that |h |=|k |, |H |=|K |. A similar construction is used to find an abundance of nontrivial pairs of functions h , k ∈L2 (R ), h ≠k , with |A h |=|A k| or with |W h|=|W k| where A h, A k and W h, W k are the ambiguity functions and Wigner distributions of h , k , respectively. One of the examples of a pair of h , k ∈L 2(R ), h ≠k , with |A h|=|A k| is F.A. Grunbaum's (1981) example. In addition, nontrivial examples of functions g and signals f 1≠f 2 such that f 1 and f 2 have the same spectrogram when using g as window have been found 相似文献
20.
Ng G.-I. Pavlidis D. Jaffe M. Singh J. Chau H.-F. 《Electron Devices, IEEE Transactions on》1989,36(10):2249-2259
Strained In0.52Al0.48 As/InxGa 1-xAs (x >0.53) HEMTs (high electron mobility transistors) are studied theoretically and experimentally. A device design procedure is reported that is based on band structure and charge control self-consistent calculations. It predicts the sheet carrier density and electron confinement as a function of doping and thickness of layers. The DC performance at 300 K is presented. Wafer statistics demonstrate improvement of device characteristics with excess indium in the channel (g¯m, intr=500 and 700 mS/mm for x=0.60 and 0.65). Microwave characterization shows the f T improvement (f T=40 and 45 GHz for x =0.60 and 0.65, respectively) and the R ds limitations of the 1-μm-long-gate HEMTs 相似文献