A technique for real-time measurement of Nth-orderderivativesdNV/dIN

A technique for the measurement of device derivatives d ^NV/dI^N of arbitrary order N described. Measurement is accomplished by injecting a test current composed of the sum of N square waves into the rest device, and then multiplying the corresponding voltage change by the product of those same square waves, followed by low-pass filtering. The algorithm is implemented in real time using a mixture of analog and digital circuitry, and its application to semiconductor laser control in high-speed optical communications is described     

Radar equation for nonsinusoidal waves

The well-known radar equation for sinusoidal waves is extended to apply to nonsinusoidal waves, in particular to binary waves with the two values ±E and ±H for the electric- and magnetic-field strength during signal transmission. Three major modifications have to be made: the concept of radar cross section is changed; the gain of the radiating antenna and the resolution angle of the receiving antenna are different from the values holding for sinusoidal waves; and the effect of noise is modified, primarily due to the absence of a rectifier     

Staircase PWM: an uncomplicated and efficient modulation techniquefor AC motor drives

An optimized staircase PWM (pulse-width modulation) technique is presented. The fundamental voltage component (U₍₁₎) is proportional to the staircase amplitude (M). Values of U ₍₁₎ higher than 90% of the corresponding value for the nonmodulated waveform are attained for M=1. The staircase is not a sampled representation of a sine wave and the number of steps and the frequency ratio are selected for a desired output voltage quality. A criterion for evaluating the quality of the output voltage (the weighted relative harmonic content) is presented. The control logic is uncomplicated and implemented by inexpensive complementary metal-oxide semiconductor logic with high noise immunity and reliability. The results have been verified by tests     

A method for calculating eigenfrequencies of arbitrarily shapedconvex targets: eigenfrequencies of conducting spheroids and theirrelation to helicoidal surface wave paths

In a previous study by the authors (1986) the phase matching of surface waves on prolate, perfectly conducting spheroids generated, for example, by the scattering of an incident plane electromagnetic wave was investigated. Now, the considerably more complex spheroidal case with an obliquely incident primary wave, whose scattering will give rise to helicoidally (i.e. quasihelically) propagating surface waves is treated. The conditions under which phase matching of such types of surface waves, which propagate along helicoidal geodesics, can occur are investigated. It is found that only a discrete set of the required closed propagation paths exists, corresponding to a discrete set of allowed angled of incidence. These angles can be associated with different azimuthal quantum numbers m of the azimuthal propagation component around the symmetry axis, where m⩽n and n is the mode number which corresponds to the number of standing wavelengths at resonance     

Modeling of nonhyperbolic sine I-Vcharacteristics in poly-Si resistors

Poly-Si resistors with an unimplanted channel region (and with n-type source/drain regions) can exhibit a nonhyperbolic sine (non-sinh) I-V characteristic at low V_DS and an activation energy which is not simply decreasing monotonically with increasing V_DS. These phenomena are not explained by conventional poly-Si resistor models. To describe these characteristics, a self-consistent model which includes the effects of a reverse-biased diode at the drain end is presented. Numerical simulation results show excellent agreement with experiment in regard to the shape of the I -V characteristic and of the effective activation energy as a function of V_DS     

A generalized recursive algorithm for wave-scattering solutions intwo dimensions

A generalized recursive algorithm valid for both the E _z and H_z wave scattering of densely packed scatterers in two dimensions is derived. This is unlike previously derived recursive algorithms which have been found to be valid only for E_z polarized waves. In this generalized recursive algorithm, a scatterer is first divided into N subscatterers. The n-subscatterer solution is then used to solve the (n+n')-subscatterer solution. The computational complexity of such an algorithm is found to be of O (N²) in two dimensions while providing a solution valid for all angles of incidence. This is better than the method of moments with Gaussian elimination, which has an O(N³) complexity     

Stability analysis and numerical simulation of multideviceamplifiers

Stability analysis of multidevice amplifiers is made on a generalized circuit comprising two n-ports with S-matrices S (active devices) and S' (passive networks) connected at n interface ports. Open-loop transfer functions defined for a signal-flow graph and its (n-1) subgraphs of incident and reflected waves at the interface ports are expressed in terms of det M_n and its minors, where M_n=S'S-I_n and I_n is the n×n identity matrix. it is shown that the Nyquist plots of the n transfer functions completely characterize the number of right-half complex-frequency-plane zeros of det M_n, and hence the amplifier stability. Insertion of an ideal circulator and isolators at the interface ports enables one to calculate the Nyquist plots and voltage distributions of possible instabilities using commercially available linear circuit simulators. Numerical simulations for two types of parallel-operated GaAs FET amplifiers are performed to verify the usefulness of the analysis in design-phase check of multidevice amplifier stability     

Reflection and transmission operators for strips or disks embeddedin homogenous and layered media

A notation is proposed to simplify the solution of scattering by strips and disks. Vector Fourier transforms are used and a double dot product for inner products in an uncountably infinite dimensional linear vector space is introduced. Scattering by a strip or a disk is characterized using a reflection operator and a transmission operator that relate the continuum of scattered waves to a continuum of incident waves. After the reflection operator for a single strip or disk is derived, it is shown how the reflection operator for a strip or disk in the presence of another reflecting medium, e.g. a layered medium, can be derived. The scattering by N strips or disks in a homogeneous medium is also discussed. The reflection operator for an embedded strip or disk in a layered medium is then derived. The method can be generalized to N strips or disks embedded in a layered medium and to a slot or aperture     

Optimum number of errors corrected before releasing a softwaresystem

Software release problems based on Jelinski-Moranda and decreasing-failure-rate models are considered. The following software release policy is considered: after a preassigned number, n, of errors are removed, the test is terminated and the software system is released to the operational phase. The average gain is used as a criterion; there exists a unique optimal value of n. Numerical examples indicate that the software release policy based on the number of errors detected can be a good alternative to the existing policy     

Interpretation and control of C-V measurementsusing pattern recognition and expert system techniques

The authors demonstrate how a pattern-recognition system can be applied to the interpretation of capacitance-voltage (C-V ) curves on an MOS test structure. By intelligently sequencing additional measurements it is possible to accurately extract the maximum amount of information available from C-V and conductance-voltage (G-V) measurements. The expert system described, (CV-EXPERT), is completely integrated with the measurement, instrumentation, and control software and is thus able to call up a sequence of individually tailored tests for the MOS test structure under investigation. The prototype system is able to correctly identify a number of process faults, including a leaky oxide, as shown. Improvements that could be gained from developing rules to coordinate G-V, capacitance-time, and doping profile measurements simply by recognizing the important factors in the initial C- V measurement are illustrated     

A hybrid (finite difference-surface Green's function) method forcomputing transmission losses in an inhomogeneous atmosphere overirregular terrain

A standard parabolic equation (SPE) is used to approximate the Helmholtz equation for electromagnetic propagation in an inhomogeneous atmosphere. An implicit finite difference (IFD) scheme to solve the SPE is applied between the irregularly shaped ground and an altitude z =z_h, below which all inhomogeneities of the medium are assumed localized. The boundary condition at z=z _h is obtained by matching the IFD solution to a surface Green's function (SGF) solution within the uniform region above z =z_h. For ground slopes above about 1°, the IFD implementation of the impedance boundary condition at the ground is shown to maintain the validity of the approximation only for vertically polarized waves. Predictions using this hybrid finite difference (FD)-SGF method agree well with results obtained using other computational methods     

A universal model for lossy and dispersive transmission lines fortime domain CAD of circuits

Branin's method of characteristics has been extended to obtain a universal equivalent model for lossy and dispersive transmission lines. Existing CAD software packages, such as SPICE, can be used for this implementation. The starting point for obtaining the model is the analog filters that approximate the characteristic impedance Z₀ (s) and the propagation function F(s)=exp(-γl) of the transmission line. The circuits are synthesized using conventional network synthesis techniques. An examination of the validity of the model is carried out by analyzing an example of RLCG lines driven by bipolar logic gates and the distortion of a DC Gaussian pulse as it propagates along a microstrip line     

Analysis of a centered-inclined waveguide slot coupler

Integral equations are developed for a centered-inclined coupling slot (including the effect of finite wall-thickness of the common broad-wall) and the slot-aperture electric intensity field is found using the method of moments. Numerical results for resonant length, backscattered wave amplitude, and phase variation off-resonance are presented over a range of values of the waveguide b dimension, wall thickness, slot width, and frequency. It is shown that the resonant length is relatively insensitive to slot tilt, &thetas;, for a standard-height X-band waveguide, whereas its dependence on &thetas; is significant for reduced-height waveguides. The phase variation of scattered TE₁₀ waves in both waveguides off-resonance is less for wider slots and smaller b dimensions. Shunt-series coupling slots exhibit greater phase variation off resonance when compared to a centred-inclined coupling slot. Also, the former has a longer resonant length for a smaller b dimension and for a wider slot. Thus the centred-inclined slot coupler possesses superior characteristics. The higher-order mode coupling between a centred-inclined slot coupler and a pair of straddling radiating slots in the branch waveguide is significant     

An algorithm for determining if a rate (n-1)/npunctured convolutional encoder is catastrophic

The algorithm determines whether or not the punctured state diagram contains a zero-weight cycle. The punctured encoder is assumed to be obtained from a rate 1/b, b⩽n, antipodal encoder of a given constraint length. The algorithm is much simpler to implement in software than the previously known method of calculating the GCD of the determinants of the n distinct (n-1)×(n-1) submatrices of the generator matrix. The computational complexity of the algorithm is no worse than the computational complexity of the GCD method for relatively short constraint lengths, that is, the constraint lengths for which the Viterbi algorithm is implemented     

Antenna patterns of nonsinusoidal waves with the time variation ofa Gaussian pulse. IV

For pt.III see ibid., vol.31, no.1, p.34-47 (1989). An experimental setup of a large-current radiator and a closed-loop sensor has recently been developed for the radiation and reception of nonsinusoidal electromagnetic waves. The time variation of the radiated waves approximately equals that of a Gaussian pulse. Here, oscillograms of antenna current and radiated nonsinusoidal pulses are presented. Magnetic flux lines representing the radiation of Gaussian pulses from a large-current sheet radiator of physical dimensions w×d×s are plotted in analogy to the plots first derived by Hertz in the late 1800s for the radiation of sinusoidal waves by a Hertzian dipole. The flux lines form closed contours as they radiate from the surface of the radiator to the far zone. The density of the flux lines at any distance from the radiator is proportion to the magnitude of the produced field strength     

Traveling wave lobe locations

A simple and reasonably accurate formula for the angular locations of traveling wave lobes has been available for many years, but the formula holds only for surface waves that travel at the speed of light. It is shown how the formula may be modified to account for propagation velocities less than the speed of light. It is shown that when the equation derived by the author is used to estimate a starting value for cosQ in the Newton-Raphson method, the solution usually requires no more than three iterations for an accuracy of 10^-6 in the solution for Q     

Pseudocyclic maximum-distance-separable codes

The (n, k) pseudocyclic maximum-distance-separable (MDS) codes modulo (xⁿ- a) over GF(q) are considered. Suppose that n is a divisor of q+1. If n is odd, pseudocyclic MDS codes exist for all k. However, if n is even, nontrivial pseudocyclic MDS codes exist for odd k (but not for even k) if a is a quadratic residue in GF(q), and they exist for even k (but not for odd k) if a is not a quadratic residue in GF(q). Also considered is the case when n is a divisor of q-1, and it is shown that pseudocyclic MDS codes exist if and only if the multiplicative order of a divides (q-1)/n, and that when this condition is satisfied, such codes exist for all k. If the condition is not satisfied, every pseudocyclic code of length n is the result of interleaving a shorter pseudocyclic code     

A simple prediction method for L-band multipath fading inrough sea conditions

Quantitative analysis of the coherent and incoherent power of sea-reflected waves at 1.5 GHz was performed using multipath-fading data obtained by field experiments. The experiments were carried out for shore-to-shore, satellite-to-shore, and satellite-to-ship paths, and antennas with gains from 13 dBi to 21 dBi were used for signal reception. Results indicate that in rough sea conditions where the incoherent component is dominant, the power of the incoherent component can reach the maximum power of the coherent component (generated in calm sea) in most cases, except for a few cases such as when measurements using narrow-beam antennas or elevation angles below 7° are made. On the results obtained, a simple prediction method for multipath fading caused by sea reflection is presented     

Design of lightweight, broad-band microwave absorbers using geneticalgorithms

A procedure for synthesizing multilayered radar absorbing coatings is presented. Given a predefined set of N_m available materials with frequency-dependent permittivities ∈_i(f) and permeabilities μ_i(f ) (i=1,. . ., N_m), the technique determines simultaneously the optimal material choice for each layer and its thickness. This optimal choice results in a screen which maximally absorbs TM and TE incident plane waves for a prescribed range of frequencies {f₁,f₂,. . ., f _Nf} and incident angles {&thetas;₁, &thetas;₂,. . .,&thetas;_N&thetas;}. The synthesis technique is based on a genetic algorithm. The technique automatically places an upper bound on the total thickness of the coating, as well as the number of layers contained in it, which greatly simplifies manufacturing. In addition, the thickness or surface mass of the coating can be minimized simultaneously with the reflection coefficient. The algorithm was successfully applied to the synthesis of wideband absorbing coatings in the frequency ranges of 0.2-2 GHz and 2-8 GHz     

High Tc superconducting active antenna withreflector

A high-T_c superconducting (SC) active antenna with a corner reflector is found to be useful for detecting electromagnetic waves (f=9.55 GHz). The SC active antenna is a new type of antenna which consists of material properties and antenna properties. The microwaves with fixed polarizations are radiated to the SC active antennas, and the detectivities and the directivities were confirmed experimentally. With the use of the corner reflector, the sensitivity and the directivity can be improved