Extension and error analysis of the microstrip transmission-line method for the broad-band measurement of the permeability tensor

In this paper, the theory associated with a noniterative and broad-band method for measuring the permeability tensor components /spl mu/=/spl mu/'-j/spl mu/' and /spl kappa/=/spl kappa/'-j/spl kappa/' is extended in order to simultaneously determine the test sample-relative permittivity /spl epsiv/=/spl epsiv/'-j/spl epsiv/'. The error sources of the method are equally presented and quantified. Detailed theoretical and experimental studies are performed to estimate the errors in the determination of /spl mu/, /spl kappa/, and /spl epsiv/ due to the quasi-static approximation for their calculation, as well as the uncertainty in the measured S-parameters of the test cell and samples length. These define the frequency-validity domain of the method.     

Asymptotic properties on codeword lengths of an optimal FV code for general sources

This correspondence is concerned with asymptotic properties on the codeword length of a fixed-to-variable length code (FV code) for a general source {X/sup n/}/sub n=1//sup /spl infin// with a finite or countably infinite alphabet. Suppose that for each n /spl ges/ 1 X/sup n/ is encoded to a binary codeword /spl phi//sub n/(X/sup n/) of length l(/spl phi//sub n/(X/sup n/)). Letting /spl epsiv//sub n/ denote the decoding error probability, we consider the following two criteria on FV codes: i) /spl epsiv//sub n/ = 0 for all n /spl ges/ 1 and ii) lim sup/sub n/spl rarr//spl infin///spl epsiv//sub n/ /spl les/ /spl epsiv/ for an arbitrarily given /spl epsiv/ /spl isin/ [0,1). Under criterion i), we show that, if X/sup n/ is encoded by an arbitrary prefix-free FV code asymptotically achieving the entropy, 1/nl(/spl phi//sub n/(X/sup n/)) - 1/nlog/sub 2/ 1/PX/sup n/(X/sup n/) /spl rarr/ 0 in probability as n /spl rarr/ /spl infin/ under a certain condition, where P/sub X//sup n/ denotes the probability distribution of X/sup n/. Under criterion ii), we first determine the minimum rate achieved by FV codes. Next, we show that 1/nl(/spl phi//sub n/(X/sup n/)) of an arbitrary FV code achieving the minimum rate in a certain sense has a property similar to the lossless case.     

Physical-layer secrecy in AWGN via a class of chaotic DS/SS systems: analysis and design

We study a class of pseudo-chaotic spread spectrum systems for secure communication over additive white Gaussian noise (AWGN) channels, whereby a symbol stream is linearly modulated on a spreading sequence generated by iterating an initial condition through a suitably chosen chaotic map. We compare the uncoded probability of error (Pr(/spl epsiv/)) attainable by intended receivers that know the initial condition to the associated Pr(/spl epsiv/) of unintended receivers that know the modulation scheme but not the initial condition. The sensitive dependence of chaotic sequences on initial conditions, together with the presence of channel noise, can be exploited to provide substantially lower Pr(/spl epsiv/) to intended than to unintended receivers. We develop computationally efficient methods for obtaining tight bounds on the best P r(/spl epsiv/) performance of intended and unintended receivers. In the process, we identify chaotic map attributes that affect the relative Pr(/spl epsiv/) advantages provided to intended receivers and develop methods for designing maps that achieve a target gap between the intended and unintended receiver Pr(/spl epsiv/).     

Efficient computation of the 2-D Green's function for 1-D periodic structures using the Ewald method

The Ewald method is applied to accelerate the evaluation of the Green's function of an infinite periodic phased array of line sources. The Ewald representation for a cylindrical wave is obtained from the known representation for the spherical wave, and a systematic general procedure is applied to extend previous results. Only a few terms are needed to evaluate Ewald sums, which are cast in terms of error functions and exponential integrals, to high accuracy. Singularities and convergence rates are analyzed, and a recipe for selecting the Ewald splitting parameter /spl epsiv/ is given to handle both low and high frequency ranges. Indeed, it is shown analytically that the choice of the standard optimal splitting parameter /spl epsiv//sub 0/ will cause overflow errors at high frequencies. Numerical examples illustrate the results and the sensitivity of the Ewald representation to the splitting parameter /spl epsiv/.     

Linear-time encodable/decodable codes with near-optimal rate

We present an explicit construction of linear-time encodable and decodable codes of rate r which can correct a fraction (1-r-/spl epsiv/)/2 of errors over an alphabet of constant size depending only on /spl epsiv/, for every 00. The error-correction performance of these codes is optimal as seen by the Singleton bound (these are "near-MDS" codes). Such near-MDS linear-time codes were known for the decoding from erasures; our construction generalizes this to handle errors as well. Concatenating these codes with good, constant-sized binary codes gives a construction of linear-time binary codes which meet the Zyablov bound, and also the more general Blokh-Zyablov bound (by resorting to multilevel concatenation). Our work also yields linear-time encodable/decodable codes which match Forney's error exponent for concatenated codes for communication over the binary symmetric channel. The encoding/decoding complexity was quadratic in Forney's result, and Forney's bound has remained the best constructive error exponent for almost 40 years now. In summary, our results match the performance of the previously known explicit constructions of codes that had polynomial time encoding and decoding, but in addition have linear-time encoding and decoding algorithms.     

Achievable key rates for universal simulation of random data with respect to a set of statistical tests

We consider the problem of universal simulation of an unknown source from a certain parametric family of discrete memoryless sources, given a training vector X from that source and given a limited budget of purely random key bits. The goal is to generate a sequence of random vectors {Y/sub i/}, all of the same dimension and the same probability law as the given training vector X, such that a certain, prescribed set of M statistical tests will be satisfied. In particular, for each statistical test, it is required that for a certain event, /spl epsiv//sub /spl lscr//, 1 /spl les/ /spl lscr/ /spl les/ M, the relative frequency /sup 1///sub N/ /spl Sigma//sub i=1//sup N/ 1/sub /spl epsiv//spl lscr//(Y/sub i/) (1/sub /spl epsiv//(/spl middot/) being the indicator function of an event /spl epsiv/), would converge, as N /spl rarr/ /spl infin/, to a random variable (depending on X), that is typically as close as possible to the expectation of 1/sub /spl epsiv//spl lscr/,/ (X) with respect to the true unknown source, namely, to the probability of the event /spl epsiv//sub /spl lscr//. We characterize the minimum key rate needed for this purpose and demonstrate how this minimum can be approached in principle.     

Recursive decoding and its performance for low-rate Reed-Muller codes

Recursive decoding techniques are considered for Reed-Muller (RM) codes of growing length n and fixed order r. An algorithm is designed that has complexity of order nlogn and corrects most error patterns of weight up to n(1/2-/spl epsiv/) given that /spl epsiv/ exceeds n/sup -1/2r/. This improves the asymptotic bounds known for decoding RM codes with nonexponential complexity. To evaluate decoding capability, we develop a probabilistic technique that disintegrates decoding into a sequence of recursive steps. Although dependent, subsequent outputs can be tightly evaluated under the assumption that all preceding decodings are correct. In turn, this allows us to employ second-order analysis and find the error weights for which the decoding error probability vanishes on the entire sequence of decoding steps as the code length n grows.     

List decoding from erasures: bounds and code constructions

We consider the problem of list decoding from erasures. We establish lower and upper bounds on the rate of a (binary linear) code that can be list decoded with list size L when up to a fraction p of its symbols are adversarially erased. Such bounds already exist in the literature, albeit under the label of generalized Hamming weights, and we make their connection to list decoding from erasures explicit. Our bounds show that in the limit of large L, the rate of such a code approaches the "capacity" (1 - p) of the erasure channel. Such nicely list decodable codes are then used as inner codes in a suitable concatenation scheme to give a uniformly constructive family of asymptotically good binary linear codes of rate /spl Omega/(/spl epsiv//sup 2//log(1//spl epsiv/)) that can be efficiently list-decoded using lists of size O(1//spl epsiv/) when an adversarially chosen (1 - /spl epsiv/) fraction of symbols are erased, for arbitrary /spl epsiv/ > 0. This improves previous results in this vein, which achieved a rate of /spl Omega/(/spl epsiv//sup 3/log(1//spl epsiv/)).     

A Simple Technique for the Accurate Determination of the Microwave Dielectric Constant for Microwave Integrated Circuit Substrates (Correspondence)

A method of determining the microwave dielectric constant of microwave integrated circuit substrates is described. The technique is especially suitable to substrates being prepared for MICs since they are, in general, regular, rectangular, and, therefore, simple resonators. The dielectric constant using this technique has been determined in the 2- to 12-GHz range for GaAs (/spl epsiv/R = 12.46), sapphire (/spl epsiv/R =9.37), polyguide (/spl epsiv/ =2.33), and Alsimag 772 (/spl epsiv/R = 10.08).     

H/sub /spl infin// filtering for fuzzy singularly perturbed systems with pole placement constraints: an LMI approach

This paper addresses the problem of designing an H/sub /spl infin// filter for a class of nonlinear singularly perturbed systems described by a Takagi-Sugeno (TS) fuzzy model. Based on a linear matrix inequality (LMI) approach, we develop a fuzzy H/sub /spl infin// controller that guarantees that i) the L/sub 2/-gain from an exogenous input to a filter error is less than or equal to a prescribed value and ii) the poles of each local filter are within a prespecified region. In order to alleviate the ill-conditioning resulting from the interaction of slow and fast dynamic modes, solutions to the problem are given in terms of linear matrix inequalities, which are independent of the singular perturbation /spl epsiv/, when /spl epsiv/ is sufficiently small. The proposed approach does not involve the separation of states into slow and fast ones, and it can be applied not only to standard but also to nonstandard singularly perturbed nonlinear systems. A numerical example is provided to illustrate the design developed in this paper.     

Guided Waves in Inhomogeneous Focusing Media Part III: Wall Effects, Losses, and the Transition from Fast to Slow Waves

This paper is concerned with the determination of field patterns, propagation constants, and losses for axially propagating modes guided by an enclosed circular cylindrical, radially inhomogeneous dielectric of the type discussed in Parts I and II. The homogeneous outer medium (/spl gamma/ /spl ges/ /a) is assumed to have a large relative permittivity /spl epsiv//sub 2/, and the analysis includes the perfect conductor case /spl epsiv//sub 2/ /spl rarr/ /spl infin/. The transition to trapped waves as the binding effect increases is demonstrated. Propagation constants in the case with loss are determined using a perturbation technique.     

Measurements of effective dielectric permittivity of microstrip-line-type liquid crystal devices using inductive coupled ring resonator

The effective dielectric permittivity of microstrip-line-type liquid crystal devices was determined in the 3-33 GHz frequency range by using a newly developed inductive coupled ring resonator. The frequency performance of /spl epsiv/'/sub /spl par// and /spl epsiv/'/sub /spl perp// can be obtained from the measured and simulated resonant frequencies of an inductive coupled ring resonator with or without a DC electric field E/sub 0/.     

A fiber Bragg grating sensor system for simultaneously static and dynamic measurements with a wavelength-swept fiber laser

A novel fiber Bragg grating (FBG) sensor system for static and dynamic measurements with a wavelength-swept fiber laser is proposed and demonstrated. In this system, both static and dynamic perturbation of each FBG in the sensor arrays can be interrogated simultaneously. The experiments demonstrated the strain resolutions of /spl sim/1 /spl mu//spl epsiv/ and 3.4 n/spl epsiv///spl radic/Hz at 500 Hz for static and dynamic measurements, respectively.     

On coverings of ellipsoids in Euclidean spaces

The thinnest coverings of ellipsoids are studied in the Euclidean spaces of an arbitrary dimension n. Given any ellipsoid, the main goal is to find its /spl epsiv/-entropy, which is the logarithm of the minimum number of the balls of radius /spl epsiv/ needed to cover this ellipsoid. A tight asymptotic bound on the /spl epsiv/-entropy is obtained for all but the most oblong ellipsoids, which have very high eccentricity. This bound depends only on the volume of the sub-ellipsoid spanned over all the axes of the original ellipsoid, whose length (diameter) exceeds 2/spl epsiv/. The results can be applied to vector quantization performed when data streams from different sources are bundled together in one block.     

Almost security of cryptographic Boolean functions

The propagation criterion, PC(/spl lscr/) of order k, is one of the most general cryptographic criteria of secure Boolean functions f. In this paper, we formalize its /spl epsiv/-almost version. The new definition requires that f(X)+f(X+/spl Delta/) is almost uniformly distributed while in the original definition, it must be strictly uniformly distributed. Better parameters are then obtained than the strict PC(/spl lscr/) of order k functions. To construct /spl epsiv/-almost PC(/spl lscr/) of order k functions, we introduce a notion of domain distance.     

On the scaling limit of ultrathin SOI MOSFETs

In this paper, a detailed study on the scaling limit of ultrathin silicon-on-insulator (SOI) MOSFETs is presented. Due to the penetration of lateral source/drain fields into standard thick buried oxide, the scale-length theory does not apply to thin SOI MOSFETs. An extensive two-dimensional device simulation shows that for a thin gate insulator, the minimum channel length can be expressed as L/sub min//spl ap/4.5(t/sub Si/+(/spl epsiv//sub Si///spl epsiv//sub I/)t/sub I/), where t/sub Si/ is the silicon thickness, and /spl epsiv//sub I/ and t/sub I/ are the permittivity and thickness of the gate insulator. With t/sub Si/ limited to /spl ges/ 2 nm from quantum mechanical and threshold considerations, a scaling limit of L/sub min/=20 nm is projected for oxides, and L/sub min/=10 nm for high-/spl kappa/ dielectrics. The effect of body doping has also been investigated. It has no significant effect on the scaling limit.     

Design and performance of an ultrawide-band ceramic-loaded slot spiral

The miniaturization of a broadband square slot spiral antenna is proposed using high-contrast (/spl epsiv//sub r/>30) dielectric materials. A previously developed circular slot spiral antenna is the starting point of the design. This spiral is first modified in terms of its feed and termination to facilitate the dielectric loading of the antenna by means of a superstrate. The subsequently placed superstrate is also modified by tapering its thickness to improve impedance matching. Several measurements were carried out using square spiral apertures having diameters of 2' and 6', respectively. It is demonstrated that the ceramic loading of a 2' spiral with an /spl epsiv//sub r/=90 shifts the initial operating frequency by nearly 320 MHz down to 564 MHz representing a size reduction of 36%. Additionally, a 6' aperture loaded with a superstrate having /spl epsiv//sub r/=30 is shown to operate down to 270 MHz corresponding to a size reduction of 18%.     

Characterization of copper germanide as contact metal for advanced MOSFETs

The material and electrical characteristics of /spl epsiv/-Cu/sub 3/Ge as a contact metal were investigated. The samples were prepared by direct copper deposition on germanium wafers, followed by rapid thermal annealing. The /spl epsiv/-Cu/sub 3/Ge formed at 400 /spl deg/C has a resistivity of 6.8 /spl mu//spl Omega//spl middot/cm, which is lower than typical silicides for silicon CMOS. Cross-sectional transmission electron microscopy showed smooth germanide/germanium interface, with a series of nanovoids aligning close to the top surface. These voids are believed to be the results of Kirkendall effect arising from the different diffusion fluxes of copper and germanium. The specific contact resistivity of Cu/sub 3/Ge, obtained from four-terminal Kelvin structures, was found to be as low as 8/spl times/10/sup -8/ /spl Omega//spl middot/cm/sup 2/ for p-type germanium substrate. This low resistivity makes Cu/sub 3/Ge a promising candidate for future contact materials.     

The duals of MMD codes are proper for error detection

A linear code, when used for error detection on a symmetric channel, is said to be proper if the corresponding undetected error probability increases monotonically in /spl epsiv/, the symbol error probability of the channel. Such codes are generally considered to perform well in error detection. A number of well-known classes of linear codes are proper, e.g., the perfect codes, MDS codes, MacDonald's codes, MMD codes, and some Near-MDS codes. The aim of this work is to show that also the duals of MMD codes are proper.     

Computer-Aided Design of Three-Port Waveguide Junction Circulators

The complete performance of a lossless three-port H-plane waveguide junction loaded coaxially with various inhomogeneous ferrite cylanders has been evaluated over the waveguide bandwidth and compared with experiment. Qualitative agreement between the predicted and measured performance was generally good using only the first three modes, n=0/spl plusmn/1. It has been shown theoretically and verified experimentally that if the 4/spl pi/M/sub s/ of a homogeneous rod or the internal field is increased, the circulation frequency f/sub 0/ increases; conversely, if the pemittivity is increased, f/sub 0/ decreases. These conflicting effects are modified when the magnetization 4/spl pi/M/sub s/ and permittivity /spl epsiv/ are inhomogeneous. For example, if the 4/spl pi/M/sub s/(/spl gamma/) is small at the outer surface of the rod (with permittivity held constant), the effect on f/sub 0/ is very small; but if 4/spl pi/M/sub s/(spl gamma) approaches zero for /spl gamma/ small, then f/sub 0/ may decrease significantly. On the other hand, if /spl epsiv//sub/spl gamma//(/spl gamma/) approaches unity near the outer surface of the rod, f/sub 0/ may increase significantly; but if /spl epsiv//sub/spl gamma//(/spl gamma/) approaches unity near the center of the rod, f/sub 0/ is affected relatively little. The inhomogeneous structure has also shown that decreasing the ferrite volume may improve the performance, and high-power applications are suggested. With a conducting pin down the center of the ferrite, relative bandwidths of 40-50 percent are predicted.