Analysis of E-H plane tee junction using avariational formulation

A three-port equivalent network for an E-H plane tee junction is determined taking into account the effect of waveguide wall thickness and considering the contribution of the dominant mode to the imaginary part of the self-reaction. The parameters of the three-port equivalent network are determined. From a knowledge of the equivalent network parameters, the net impedance loading, reflection coefficient, and coupling are evaluated for an E-H plane tee junction. A comparison between theoretical and experimental results is also presented     

S matrix of slot-coupled H-plane tee junctionusing rectangular waveguides

Complex scattering matrix parameters of a slot-coupled, waveguide tee junction are determined using a moment method of analysis with entire orthogonal basis functions and a rigorous analysis of the effect of wall thickness. The variations of the equivalent network parameter, coupling, and return loss with frequency are evaluated, and the results are compared with experimental data. The unitary property of the S matrix is verified. The dependence of coupling on slot length, slot width, and thickness is presented     

Prediction of the E and H fields produced by theSwiss mobile EMP simulator (MEMPS)

The author discusses a simple analysis for determining the electromagnetic fields produced by the MEMPS simulator. A transmission line solution for the currents flowing on the simulator structure is obtained, taking into account both the resistive loading along the simulator and the dispersive nature of the earth under the simulator. Once the current distribution is determined, the fields at an arbitrary location are found by integrating the fields produced by an electric current element located over the lossy air-earth interface. Using this model, a procedure for estimating the fields at an arbitrary location within the simulator is described. This requires a knowledge of the primary transient E and H field components at a reference point near the simulator, or equivalently, a knowledge of the incident E or H field at this point. Results of this study indicate that it is possible to predict the simulator fields at other points, based on the reference fields and the calculational model     

Robustness of mean E{X} and R charts

The effect of nonnormality on E{X} and R charts is reported. The effect of departure from normality can be examined by comparing the probabilities that E{X} and R lie outside their three-standard-deviation and two-standard-deviation control limits. Tukey's λ-family of symmetric distributions is used because it contains a wide spectrum of distributions with a variety of tail areas. The constants required to construct E{X} and R charts for the λ-family are computed. Control charts based on the assumption of normality give inaccurate results when the tails of the underlying distribution are thin or thick. The validity of the normality assumption is examined by using a numerical example     

G/T and noise figure of active array antennas

A figure of merit, G/T, for a multichannel active array antenna was derived, and the effects of the beamforming network on the overall noise figure of the system were studied. Also examined are the dependence of the noise figure on various losses, and the difference between a resistive and nonresistive taper in the combining network. When the amplifier gain is sufficiently large, the losses following the LNA can usually be ignored. For a photonic array with lossy time shift elements, however, the downstream losses become significant. Also, if resistive tapering is employed, not only the array gain but also the noise figure will be degraded by the collective effect of the feed network     

Microwave characteristics of high Tcsuperconducting coplanar waveguide resonator

A theoretical formulation has been developed to calculate the coupling coefficient, London penetration depth, and surface resistance of a coplanar waveguide resonator fabricated from films of superconducting YBCO material. Experimental data of the reflection coefficient as a function of temperature and frequency agree reasonably well with calculations. The formulation is of sufficient generality to be applicable to other guided structures     

Electrochemical C-V profiling of heterojunctiondevice structures

Electrochemical capacitance-voltage profiles of multiple (In,Al) GaAs heterostructures have been measured and compared with the results of a numerical calculation of the apparent charge density based on a one-dimensional Poisson solver. The calculation, using layer thicknesses, dopings, and heterojunction band discontinuities obtained from MBE growth calibrations, is in overall agreement with the measured data. The largest discrepancy occurs between the expected and measured heterojunction band discontinuity. This difference is consistent with an electrolyte/semiconductor interface which is not planar on a scale comparable to the layer thickness     

A T1 ones-density controller based on finite-statemachines

T1 clock recovery equipment requires that transmitted data not contain long sequences of 0 bits. For this reason, equipment that interfaces to T1 networks must meet a ones-density specification that ensures that 1 bit occurs frequently enough. Most schemes for meeting this specification require a substantial amount of overhead that consumes a significant portion of the available bandwidth. In this paper, and approach that meets the ones-density requirement with very little wasted bandwidth is described. Two practical coding schemes based on the approach are presented. The first, a block coding scheme, requires an overhead rate on the order of one bit per T1 frame, along with a delay of several frames. In an error-free channel, it introduces some errors, the rate of which is made acceptably low by using sufficient delay and overhead. In an errored channel, extension of errors is negligible. The second scheme, a sliding code scheme, requires an overhead rate on the order of a fraction of a bit per T1 frame, along with a delay of only several bit times. In an error-free channel, the rate of errors introduced is negligible. In an errored channel, approximately one out of every 2000 channel errors is extended into a burst, the length of which can be made acceptably low by using sufficient overhead     

DC I-V characteristics of field emitter triodes

A simple model that is applicable to Spindt-type emitter triodes is presented. Experimentally, it has been observed that the gate current at zero collector voltage follows the same Fowler-Nordheim law as the collector current at high collector voltage, and that for low emission current densities, the sum of gate and collector currents is constant for any collector voltage and is given by the Fowler-Nordheim current I_FN. Based on these observations, a simple model has been developed to calculate the I-V characteristics of a triode. By measuring the Fowler-Nordheim emission, emission area and field enhancement can be obtained assuming a value for the barrier height. Incorporating the gate current, the collector current can be calculated from I_c=I_FN-I_g as a function of collector voltage. The model's accuracy is best at low current density. At higher emission currents, deviations occur at low collector voltages because the constancy of gate and collector currents is violated     

Parameter extraction from I-V characteristics ofsingle MOSFETs

A method is presented to extract the bias-dependent series resistances and intrinsic conductance factor of individual MOS transistors from measured I-V characteristics. If applied to groups of scaled channel length devices, it also allows determination of the effective channel length together with the transversal field dependence of the carrier mobility. The method is exactly derived from conventional MOS theory based on the gradual channel approximation, and the deviations from such an ideal case are studied by means of two-dimensional device simulations. Experimental results obtained with n- and p-channel transistors of conventional as well as LDD type are presented to show the correctness of the proposed extraction procedure     

Analysis of N×N passive optical starcoupler based on the normal modes of N input waveguides

An integrated passive N×N optical star coupler on silicon wafer is described. Antiresonant reflecting optical waveguides (ARROWs) are analyzed and utilized as the input and output waveguides of the N×N coupler. Combining the exact solutions of the slab ARROW waveguide with the effective index method, a 5×5 coupler is analyzed. In the slab waveguide analysis, the input waveguides are coupled to their neighbors. The interaction of the waveguides is described in terms of the normal modes of propagation. The resultant field distribution is then diffracted into the free space region which separates the input and output sections. The radiation illuminates the receiving aperture from which the receiving N waveguides branch out, each output element obtaining equal power levels. Different types of loss such as spillover loss and mismatch loss were analyzed and estimated for N=5. A 5×5 star coupler with a transmission efficiency of 56% at a wavelength of 1.3 μm is achievable     

A new I-V model for short gate-length MESFET's

An I-V model for short gate-length MESFETs operated in the turn-on region is proposed, in which the two-dimensional potential distributions contributed by the depletion-layer charges under the gate and in the ungated region are separately obtained by conventional 1-D approximation and the Green's function solution technique. Moreover, the bias-dependent parasitic resistances due to the modulation of the depletion layer in the ungated region for non-self-alignment MESFETs are also taken into account in the developed I-V model. It is shown that good agreement is obtained between the I-V model and the results of 2-D numerical analysis. Moreover, comparisons between the proposed analytical model and the experimental data are made, and excellent agreement is obtained     

Near-ideal I-V characteristics of GaInP/GaAsheterojunction bipolar transistors

GaInP/GaAs heterojunction bipolar transistors (HBTs) have been fabricated and these devices exhibit near-ideal I-V characteristics with very small magnitudes of the base-emitter junction space-charge recombination current. Measured current gains in both 6-μm×6-μm and 100-μm×100-μm devices remain constant for five decades of collector current and are greater than unity at ultrasmall current densities on the order of 1×10^-6 A/cm². For the 6-μm×6-μm device, the current gain reaches a high value of 190 at higher current levels. These device characteristics are also compared to published data of an abrupt AlGaAs/GaAs HBT having a base layer with similar doping level and thickness     

Superconducting millimeter-wave E-plane filters

The authors report on the measured performance of a three-pole E-plane filter constructed from high-T_c superconducting bulk materials at 34.5 GHz. Experimental results are presented for the insertion loss and return loss of the filter at 77 K. The problems associated with the use of bulk materials at the millimeter-wave range are addressed. Other possible superconducting waveguide filter configurations are proposed. While the experimental results are taken at low input power level, the current distribution inside the filter structure is calculated, and the power handling capability of the superconducting filter is discussed     

A complete model of the I-V characteristics fornarrow-gate MOSFETs

A unified and process-independent MOSFET model for accurate prediction of the I-V characteristics and the threshold voltages of narrow-gate MOSFETs is discussed. It is based on several enhancements of the SPICE2 LEVEL3 MOS model and the author's previous subthreshold I-V model. The expressions achieved for the drain current hold in the subthreshold, transition, and strong inversion regions. A continuous model is proposed for the transition region, using a scheme that ensures that both the current and conductance are continuous and will not cause convergence problems for circuit simulation applications. All of the modeled parameters are taken from experimentally measured I-V characteristics and preserve physical meaning. Comparisons between the measured and modeled I-V characteristics show excellent agreement for a wide range of channel widths and biases. The model is well suited for circuit simulation in SPICE     

A rigorous variational formulation of an H planeslot-coupled tee junction

A rigorous analysis for the determination of an exact equivalent network for the slot-coupled H-plane tee junction that takes the effect of wall thickness into account is presented. A variational formulation is used for the determination of the parameters of the network. The parameters of the S-matrix as well as coupling are evaluated from the exact equivalent network. Comparisons between theoretical and experimental results are presented     

Input I-V and sampling time characteristics ofthe ACT device

The input I-V and sampling-time characteristics of the acoustic charge transport (ACT) device are presented for ohmic-contact charge injection and Schottky-gate-modulated charge injection. A computationally efficient analysis technique is developed to calculate the I-V and sampling-time data from two-dimensional potential and carrier-density distributions. Device physics and architecture are incorporated into the analysis through a numerical charge-injection model which is used to compute the potential and carrier-density distributions. Theoretical results are presented to demonstrate the charge injection characteristic of some typical device structures. The effects that the injection method, the epitaxial layer structure and the acoustic wave amplitude have on device performances are discussed. The physical basis of the analysis enables it to be used to study several other design parameters. Experimental measurements of a device I-V and input transconductance show good agreement with calculated data. This analysis technique provides a means of assessing the performance potential of new device designs     

Nonlinear analysis of Y-junction laser arrays

An analysis of Y-junction arrays above threshold is presented. The analysis incorporates nonlinear gain saturation and shows that the gain becomes nonuniform above threshold even if the array is otherwise ideal. The nonuniform, nonlinear gain saturation causes the near field and the radiation patterns to deteriorate with increasing output power. Although the far-field lobe width does not necessarily increase greatly above threshold, the Strehl ratio may decrease significantly depending on the device design. Empirically, it is found that, when the Strehl ratio decreases to approximately 0.7, the second-order array mode attains threshold and both the first and second array modes lase simultaneously. An improved design, whose far-field Strehl ratio remains 0.85 even well in excess of 1 W output power and in which the second-order array mode never attains threshold, is discussed     

A low-noise K-Ka band oscillator AlGaAs/GaAsheterojunction bipolar transistors

The design considerations, fabrication process, and performance of the first K-Ka-band oscillator implemented using a self-aligned AlGaAs/GaAs heterojunction bipolar transistor (HBT) are described. A large-signal time-domain-based design approach has been used which applies a SPICE-F simulator for optimization of the oscillator circuit parameters for maximum output power. The oscillator employs a 2×10-μm² emitter AlGaAs/GaAs HBT that was fabricated using a pattern inversion technology. The HBT has a base current 1/f noise power density lower than 1×10^-20 A²/Hz at 1 kHz and lower than 1×10^-22 A/²/Hz at 100 kHz for a collector current of 1 mA. The oscillator, which is composed of only low-Q microstrip transmission lines, has a phase noise of -80 dBc/Hz at 100 kHz off carrier when operated at 26.6 GHz. These results indicate the applicability of the HBTs to low-phase-noise monolithic oscillators at microwave and millimeter-wave frequencies, where both Si bipolar transistors and GaAs FETs are absent