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This paper addresses the theoretical aspects of passive intermodulation (PIM) generation in printed transmission fines. In order to elucidate the mechanisms of PIM generation, a new model of the transmission line length with distributed nonlinearity is proposed. The developed model has been validated by the near-field measurements of PIM product distributions along the microstrip fines. The contributions of nonlinear mixing, power dissipation, and load matching to PIM products have been analyzed in detail. The obtained results reveal the fundamental properties of PIM generation in finite lengths of printed fines with distributed nonlinearity and identify possible means for PIM mitigation. It was shown for the first time that the reverse PIM products in a matched transmission line with distributed nonlinearity are generated due to nonlinear scattering. Index Terms--Distributed nonlinearity, intermodulation distortion, passive intermodulation (PIM), printed circuits.

Multiple-input-multiple-output (MIMO) capacity of waveguide and cavity channels is investigated using the modal expansion technique. Rectangular and circular waveguides and cavities are studied in details. Approximate expressions for the number of modes and for the capacity are given. A MIMO system architecture is suggested for a waveguide channel, which achieves the full capacity by making use of the mode orthogonally (or near orthogonality) using an eigenmode modulator at the Tx end and a spatial correlation receiver at the Rx end. Various practical limitations (e.g., nonideal waveguides and modulators, using discrete sensors instead of continuous, one-dimensional sensors instead of two-dimensional, etc.) and their impact on the capacity are discussed. It is demonstrated that long cavities are equivalent to waveguides in terms of capacity. The concept of spatial capacity is introduced to characterize the limits on the transmission rates that are due to both electromagnetic and information-theoretic considerations, which can be evaluated in a closed form for ideal waveguides and cavities. It follows that the traditional single-mode transmission is optimum in terms of capacity in the small signal-to-noise ratio region only. Index Terms--Channel capacity, multiple-input-multiple-output (MIMO) system, modal decomposition, waveguide.

This paper reports a new circularly polarized (CP) high-gain high-efficiency rectifying antenna (rectenna). The CP rectenna can be rotated and still maintain a constant dc output voltage. The high-gain antenna has an advantage of reducing the total number of rectenna elements to cover a fixed area. The rectenna is etched on Rogers Duroid 5870 substrate with [[epsilon].sub.r]. = 2.33 and 10 mil thickness. A high-gain dual-rhombic-loop antenna and a reflecting plane are used to achieve a CP antenna gain of 10.7 dB and a 2:1 voltage standing-wave ratio bandwidth of 10%. The rectenna's pattern has an elliptical cross section with orthogonal beamwidths of 40[degrees] and 60[degrees]. The rectenna circuit has a coplanar stripline band-reject filter that suppresses the re-radiated harmonics by 20 dB. A highly efficient Schottky diode is used for RF-to-dc conversion with an efficiency of approximately 80% for an input power level of 100 mW and a load resistance of 250 [ohm]. Index Terms--Circularly polarized antennas, coplanar stripline, microwave power transmission, rectifying antenna, wireless power transmission.

The melting of frozen packed beds by a microwave with a rectangular waveguide has been investigated numerically and experimentally. It was performed for the two different layers, which consist of frozen and unfrozen layers. This paper focuses on the prediction of the temperature field, as well as the microwave energy absorbed, and the melting front within the layered packed beds. Based on the combined model of the Maxwell and heat transport equations, the results show that the direction of melting against the incident microwave strongly depends on the structural layered packed beds because of the difference in the dielectric properties between water and ice. Index Terms--FDTD method, layered packed beds, microwave melting, moving boundary, rectangular waveguide.

For coupled-line systems, 'matching' involves entire impedance matrix networks and necessarily involves multiple propagating modes. This paper presents the synthesis of several matching strategies for symmetric coupled-line microstrip structures mismatched with several types of simple passive terminations. Detailed multiconductor transmission-line analysis provides the basis for procedures to optimize the parameters of several matching networks (stubs, reactances, transformers) that yield significant line and mode reflection reduction resulting from the mismatches. Measurement of synthesized structures verifies the reflection reduction and power savings. Index Terms--Coupled microstrip, matching networks, multi-conductor transmission lines.

In inhomogeneous multiconductor transmission line (MTL) structures such as coupled microstrip, propagation is characterized by multiple quasi-TEM modes with distinct propagation constants. These 'mode delays' cause the MTL functions to exhibit longitudinal behavior that superficially appears problematic in the context of passive lossless reciprocal systems. This paper presents a thorough investigation of the longitudinal MTL functions. Using MTL formulation and computer simulation, we explain the mathematics and physics of mode delays so that their effects are not misinterpreted or attributed to error in the numerical analysis of MTLs. Index Terms--Coupled microstrip, immittance matrices, modal dispersion, multiconductor transmission lines.

Research describing the nonlinear behaviour of high temperature superconducting transmission lines is presented. In particular harmonic balance algorithms are developed and analysed.

The Berenger's perfectly matched layer (PML) absorbing boundary condition is applied to terminate a microstrip line with metal strip and multilayer dielectric media extending into the PML regions. In order to handle the inhomogeneous properties of the PML layers better, the integral form of the Maxwell's equations, approximated by central-difference expressions instead of exponential-difference expressions, are utilized to deduce the finite-difference time-domain (FDTD) equations for updating field components inside PML media. The derived formulas are proven to be flexible and convenient for generating and handling the PML layers in a nonuniform FDTD grid. Simulation result shows that the proposed multilayer PML boundary condition can effectively absorb the outgoing wave with at least -80-dB reflection coefficient under a complicated boundary situation. Index Terms - FDTD, nonuniform grid, PML.

This paper describes the design and fabrication of distributed analog phase-shifter circuits. The phase shifters consist of coplanar-waveguide (CPW) lines that are periodically loaded with varactor diodes. The circuits are fabricated on GaAs using standard monolithic processing techniques. The phase velocity on these varactor diode-loaded CPW lines is a function of applied reverse bias, thus resulting in analog phase-shifting circuits. Optimally designed circuits exhibit 0 [degrees]-360 [degrees] phase shift at 20 GHz with a maximum insertion loss (IL) of 4.2 dB. To the best of our knowledge, this is the lowest reported IL for a solid-state analog phase shifter operating at 20 GHz. Index Terms - Distributed circuit, phase shifter.

The work described in this paper addresses the problems of fault diagnosis in complex multicircuit transmission systems, in particular those arising due to mutual coupling between the two parallel circuits under different fault conditions; the problems are compounded by the fact that this mutual coupling is highly variable in nature. In this respect, artificial intelligence (AI) technique provides the ability to classify the faulted phase/phases by identifying different patterns of the associated voltages and currents. In this paper, a Fuzzy ARTmap (Adaptive Resonance Theory) neural network is employed and is found to be well-suited for solving the complex fault classification problem under various system and fault conditions. Emphasis is placed on introducing the background of AI techniques as applied to the specific problem, followed by a description of the methodology adopted for training the Fuzzy ARTmap neural network, which is proving to be a very useful and powerful tool for power system engineers. Furthermore, this classification technique is compared with a Neural Network (NN) technique based on the error backpropagation (EBP) training algorithm, and it is shown that the former technique is better suited for solving the fault diagnosis problem in complex multicircuit transmission systems. Index Terms - Artificial intelligence, fault classifier, fault diagnosis, fuzzy ARTmap, neural networks.

The properties of low-power nonlinear effects in high-temperature superconducting microwave devices were studied by measuring third harmonic generation at 76 K in coplanar waveguide transmission lines of various geometries manufactured from YBa2Cu3O7-delta thin films. The measured power in the third-harmonic signal was observed to change systematically with film thickness, center conductor linewidth and line length. Findings offer a way to set a lower limit for the expected nonlinear response of superconducting components of arbitrary geometry at microwave frequencies.

Research was conducted to examine the results of a digital transmission test of a YBa2Cu3Ox/MgO/Au microstrip line to coplanar waveguide transmission line converter. A further objective was to evaluate a digital transmission measuring system that includes the transmission line converter by an error performance analyzer. Results show that the transmission properties of the transmission line converter was almost the same as YBa2Cu3O(sub x)/MgO/Au microstrip line at frequencies from 40 MHz to 10 GHz at 30 K.

Research was conducted to examine singled-picosecond electrical pulse excitation and detection in YBa2Cu3O7-x (YBCO) transmission lines containing microbridges and grain-boundary Josephson junctions. The structures were patterned in YBCO films developed by laser ablation on MgO bicrystals. Results provide evidence of the potential of YBCO for ultrafast optical and electrical transient detection and processing.

This paper investigates a measurement method that characterizes lossy printed multiconductor transmission lines, its accuracy, the choice of measurement representations, and some simple approximations. We illustrate the method with measurements of a pair of lossy coupled asymmetric microstrip lines. Index Terms - Measurement, modal cross power, multiconductor transmission line.

A study was conducted to analyze rectangular coaxial line discontinuity in the form of a gap in the central conductor and steps in the outer conductor in the planes of discontinuity. A variational technique was used to carry out the analysis. The capacitances of the equivalent-Pi-network were represented as a function of gapwidth, normalized frequency and ratio of outer conductor dimensions. Results indicated that modifications in the discontinuity configuration may generate an additional design parameter in realizing a series-gap-coupled bandpass filter in the coaxial line.

A study was conducted to analyze the one-dimensional metal-insulator-semiconductor transmission line. Closed-form expressions were developed for equivalent-circuit parameters. The assumption of single-mode propagation was also examined. Results indicated that the transmission line supports a high-loss region of operation wherein its electrical behavior becomes complicated and multimodal in nature.

A study was conducted to analyze the excitation and physical validity of surface-wave and space-wave leaky modes on microstrip lines. The discrete modal spectrum excited by a realistic source on or near an infinite microstrip line was examined. The three-dimensional Green's function was then determined using a Fourier transform in the longitudinal direction. In addition, the physical significance of the leaky modes were determined using Riemann sheets.

Air-gap transmission-line structures have been fabricated and integrated on doped silicon substrates using glass microbump bonding (GMBB) techniques. The air-gap transmission lines have the advantages of low losses and low dispersion compared to conventional uniplanar transmission lines on semiconductor substrate. This bonding technique provides an alternative approach for both monolithic microwave integrated circuits (MMIC's) and optoelectronic integrated circuits (OEIC's) on silicon substrates. To demonstrate the potential of air-gap structures, several transmission-line configurations are fabricated and tested. The measured data are compared with simulation results. The results confirm the air-gap structures low-loss capabilities. To further explore the advantage of this bonding technique, several spiral inductors are fabricated in air-gap configurations. Their measured characteristics demonstrate the low dispersion potential of this technology. Finally, the integration of air-gap interconnects for OEIC's on silicon CMOS circuitry is also proposed.

The performance of finite-ground coplanar (FGC) lines on GaAs and quartz for high-frequency monolithic-microwave integrated-circuit (MMIC) applications is experimentally investigated in this paper. The FGC lines on GaAs are covered with a thin layer of polyimide for passivation purposes. Permittivity and attenuation characteristics for these lines up to 118 GHz are presented and compared with the corresponding characteristics of FGC lines on a quartz substrate, which are commonly used for millimeter-wave applications. The impact of different characteristic impedance values in attenuation properties for both GaAs and quartz is also addressed. Results indicate that the loss on the lines does not depend on the substrate material, but rather on line geometry. All the lines tested show low-loss and low-dispersion characteristics.

With the binomial transformer as a basis, a closed-form expression is derived for the Q distribution used to design maximally fiat quarter-wavelength-coupled transmission-line filters. The derived expression is shown to be valid for filters with small values of total Q. Also, an existing Q-distribution expression derived from the lumped-element prototype (LEP) circuit is discussed, and is shown to be valid for filters with large values of total Q. By combining the derived binomial transformer Q distribution and the LEP Q-distribution expressions, a piecewise closed-form Q-distribution expression is developed, which is applicable over a wide range of total Q values. Index Terms - Bandpass filters, binomial transformer, Butterworth filters, maximally flat magnitude filters, quarter-wavelength-coupled filters, Q distribution.

In this paper we find the solution of telegrapher's equations for a non-homogeneous medium applying the theory of hypergeometric functions. Also we show that such a medium is described by means of a stratified structure, so we can use the developed theory for microwave components. We find the behavior of the reflection coefficient and compare it with other known results present in literature. Moreover, we show how an Exponentially Tapered Non Uniform Transmission Line (ETNUTL) can be treated as a high-pass filter. It is found that the exponential profile improves the performance of the filter and the normalized transmission coefficient is given for different values of tapering factor. Finally, we find a lumped equivalent circuit for the filter, whose elements are dependent on the tapering factor. The high-pass characteristics of an ETNUTL are verified with techniques in the frequency domain. Index terms - Non Uniform Transmission Lines, Spectral Full-Wave Analysis, Kummer's Equations.

The Air Force Research Laboratory/Phillips Laboratory magnetically insulated transmission line oscillator (MILO) is a gigawatt-class, L-band, high-power microwave tube driven by a 500-kV, 60-kA electron beam. A previous version of this tube [1] generated 1.5 GW pulses, but with significant RF pulse shortening. This paper reports on improvements to the tube that have allowed us to increase the output power by 25% and to increase the RF pulse duration by a factor of two and a half. Index Terms - Crossed-field device, high-power microwave tube, magnetically insulated transmission line oscillator, MILO.

This paper describes a series of experiments performed to isolate the RF breakdown mechanisms in the hard tube magnetically insulated transmission line oscillator (MILO) Experiment at the Air Force Phillips Laboratory, Albuquerque, NM. Specifically, several causes of RF breakdown in the region of the vacuum-air interface and the antenna region have been investigated. These causes are X-ray induced electron emission, VUV and visible photoemission of electrons, and breakdown due to large field stresses in the antenna. Each of these mechanisms has the effect of liberating electrons from a surface in a high field region which then are a seed for a breakdown. This paper discusses measurements in the X-ray, VUV, and visible regimes with support from computer simulation. Also, imagery results are shown, which in conjunction with the computer work, point to the presence of high electric field stresses in the antenna, which cause a subsequent breakdown. In particular, X-rays, VUV, visible light, and plasmas do not seem to be the major source of RF breakdown in this tube. Index Terms - Crossed field devices, high power microwave sources, magnetically insulated transmission line, magnetically insulated transmission line oscillator (MILO), RF breakdown.

Silicon circuits, now penetrating well into the microwave frequency range, use lossy silicon substrates. Consequently, the microwave performance of transmission lines on this substrate becomes increasingly important and has been investigated here up to 20 GHz. It is shown that transmission lines on 20-[Omega] [center dot] cm substrates have no need for backside metallization and backside via holes. Two models for different line types are derived from measurements and verified against them. A coplanar waveguide (CPW) with an overall width of less than 30 [[micro]meter] was fabricated with an attenuation of 0.5 dB/mm at 20 GHz, which is acceptable for monolithic microwave integrated circuit (MMIC) design. Index Terms - Coplanar waveguides, microstrip, MMIC's, silicon, transmission lines.

In this paper, propagation properties of both standard and multilayer coplanar lines on different types of silicon substrates, as well as a number of quasi-lumped and stub-type circuit elements, are investigated. For the transmission lines, emphasis is placed on losses. As examples for circuit elements, a lumped parallel resonator and a high-low impedance low-pass filter are demonstrated. Index Terms - Coplanar, multilayer, passive components, silicon, transmission lines.

This paper extends the transmission-line simulation method of [1] to nonuniform lines. The method is applicable to multiconductor lossy frequency-dependent transmission lines characterized by sampled frequency-domain responses. The resulting model can be directly incorporated into a circuit simulator. The implementation includes ac, dc, and transient analyses. The method is reliable, accurate, and as efficient as the simple replacement of interconnects by lumped resistors. The method is based on approximation, and its accuracy and efficiency result from the simplicity of characteristic responses. To apply the method to nonuniform lines, two novel nonuniform line models are introduced. An open-loop model completely separates forward and backward waves and results in the simplest aperiodic responses, but does not guarantee their stability. An open-loop distributed-reflection model explicitly includes the internal distributed reflections, and provides the simplest stable characterization. It is shown that for nonuniform lines, the generalized method of characteristics no longer separates forward and backward waves. Numerical example of a parabolically tapered frequency-dependent four-conductor line is given. Index Terms - Circuit simulation, interconnect simulation, nonuniform transmission lines, signal-integrity analysis, transient analysis, transmission lines.

A multimode analysis is used to describe how leakage effects are manifested in general printed interconnects situated on substrates of finite size. In the vicinity of discrete frequencies, it is shown that the analysis reduces to classical coupled-mode theory. The general results are then specialized to the particular case of shielded microstrip on an anisotropic substrate, for which numerical and experimental mode-coupling results are presented. The numerical results are demonstrated in the form of dispersion curves and field plots, and are computed using the finite-element method and the spectral-domain technique. The experimental results are performed using a network analyzer, and are given in terms of scattering parameters. Index Terms - Interconnect, leakage, mode coupling, transmission line.

A generalization of the previously proposed transmission-line matrix (TLM)-based finite-difference time-domain (FDTD) method is presented for modeling frequency-dependent and anisotropic media. The generalized scheme incorporates electric- and magnetic-flux densities in addition to variable mesh sizes. Since it is in an FD form, modeling techniques developed for the conventional FDTD can be easily adapted into the proposed TLM-based technique. In this paper, a modified z-transform technique for frequency-dependent media is implemented, and a two-dimensional (2-D) full-wave technique for guided-wave structures is developed. In all the FDTD computations, no conversions between the field quantities and TLM circuit parameters such as open- and short-circuited stubs are required. Index Terms - Anisotropic, FDTD, frequency dependent, TLM.

An original multimode thru-reflection line (TRL) algorithm is used to derive the generalized scattering parameters of multimode two-port networks. Theoretical developments are detailed for calibration procedures based on two ports as well as multiple-port vector network analyzer (VNA) measurements. First-run experimental results demonstrate the validity of this technique. This method allows the experimental characterization of multiconductor transmission-line devices. It could also be used to characterize power coupling to undesired modes in monolithic microwave integrated circuit (MMIC) structures using conductor-backed coplanar waveguides. Index Terms - Calibration, multiconductor transmission lines, multimode waveguides, scattering parameters, scattering parameters measurement.

The multifunctionality of microwave links based on remote heterodyne detection (RHD) of signals from a dual-frequency laser transmitter is discussed and experimentally demonstrated in this paper. Typically, direct detection (DD) in conjunction with optical intensity modulation is used to implement fiber-optic microwave links. The resulting links are inherently transparent. As opposed to DD links, RHD links can perform radio-system functionalities such as modulation and frequency conversion in addition to transparency. All of these three functionalities are presented and experimentally demonstrated with an RHD link based on a dual-frequency laser transmitter with two offset phase-locked semiconductor lasers. In the modulating link, a 1-Gb/s baseband signal is QPSK modulated onto a 9-GHz RF carrier. The frequency converting link demonstrates up-conversion of a 100-Mb/s PSK signal from a 2-GHz carrier to a 9-GHz carrier with penalty-free transmission over 25 km of optical fiber. Finally, the transparent link transmits a standard FM video 7.6-GHz radio-link signal over 25 km of optical fiber without measurable distortion. Index Terms - Microwave communication, millimeterwave communication, optical-fiber communication, optical phase-locked loops, semiconductor lasers, signal processing.

Laboratory measurements of a backscattered signal for large spherical scatterers are performed to investigate the range of applicability of approximate theory, which we used in interpreting the measured depolarization signatures of rain. The measured linear depolarization ratios (LDR's) are in remarkably good agreement with theoretical calculations.

Experimentally observed subpicosecond electrical pulses generated by edge illumination of silicon photoconductive switches are examined using a two-dimensional (2-D) numerical simulation model. Simulation results are in qualitative agreement with experimental analysis while the dielectric-relaxation interpretation is consistent with other theories based on the full-wave analysis and the Monte Carlo model.

If a ring hybrid is terminated by arbitrary impedances, design equations cannot be derived with conventional methods because symmetry planes for even- and/or odd-mode excitation are not available. Therefore, under these conditions, new design equations for ring hybrids were derived. They can be applied to ring hybrids with both arbitrary termination impedances and arbitrary power-division ratios. Also, new design equations for small-sized ring hybrids have been developed. They allow the design of arbitrary power division, arbitrary termination impedances, and especially small-sized ring hybrids. On the basis of these derived equations, a theoretical evaluation was made using microstrip ring hybrids, and experiments are demonstrated using a coplanar ring hybrid. Index Terms - Arbitrary power division, arbitrary termination impedances, power divider, ring coupler.

The concept of nonradiating (NR) sources is introduced to transmission lines in the time-domain analysis. A method is presented to construct localized voltage and current sources which do not produce any fields outside the source domain. These sources cannot, therefore, be detected by measurements made outside the source region. The importance of such sources for the uniqueness of the inverse-source problem is pointed out, and energy conditions for the uniqueness are discussed. The analysis can be advantageously used in the design and optimization of the electromagnetic compatibility (EMC) properties of transmission lines. Index Terms - Nonradiating sources, partial differential equations, transmission-line theory.

Edge finite elements are widely used in the analysis of waveguides and transmission lines. They have tangential continuity and they do not produce spurious modes. However, they cannot model the singular behavior of the transverse fields in the neighborhood of sharp edges. This fact limits the accuracy of the representation of the fields and the order of convergence of the method. In this paper, we present a new edge element in which the singular approximation of the three fields components and the correct modeling of the curl is incorporated. The development of the basis functions is described. Some numerical results for waveguides with sharp metal edges are shown in order to validate this theory.

This paper presents a technique for accurately designing maximally flat quarter-wavelength-coupled transmission-line filters using arbitrary resonant elements. The design procedure currently used, which is based on the lumped-element low-pass prototype, yields a response that is only approximately maximally fiat. In addition, the current procedure results in an inaccurate prediction of the total Q for the filter. The technique presented in this paper, herein called the Q-distribution (QD) method, corrects these problems. With the QD method, the designer chooses the number and type of resonant elements and the total Q desired. In turn, the designer is provided with the individual resonator QD, which gives the designer flexibility in selecting the resonator that is most appropriate. Index Terms - Bandpass filters, Butterworth filters, maximally fiat magnitude filters, Q, Q distribution, quarter-wavelength-coupled network, transmission-line resonators.

In this paper, the hybrid finite-element method (FEM) is proposed to analyze the coplanar-waveguide (CPW) discontinuities with finite-metallization thickness. A variational formula for the electric field in the slot region between upper and lower half-space is derived by applying the variational-reaction theory and solved by the FEM. In the limiting case of zero metallization thickness, this finite-element analysis is reduced to a moment-method analysis using Galerkin's approach with rooftop basis functions. The edge profile effects of a trapezoidal slot cross resulting from the etching or sputtering process can also be easily considered by this approach. Some numerical results are presented for short- and open-ended CPW discontinuities for different conductor thicknesses. It has been shown that not only the metallization thickness, but also the conductor-edge profile, can produce noticeable effects on circuit performance and should be taken into account for accurately modeling the CPW discontinuities. Index Terms - Coplanar waveguides (CPW's), finite-element method (FEM), transmission-line discontinuities.

Magnetoresistive elements (MRE's) containing exchange-biased spin valve multilayers as the magnetoresistive material have been fabricated. Their electrical response has been measured using an integrated test coil. Both parallel and crossed arrangements of the easy axes of the free and biased layers have been studied. Output voltage levels of these elements in response to an ac magnetic field are typically a factor of 7-10 higher than those obtained in similar elements based on a conventional, 30 nm thick anisotropic magnetoresistive (AMR) [Ni.sub.80][Fe.sub.20] film linearized by the 'barber-pole' method. The parallel arrangement is found to result in a switching behavior which is characteristic of domain wall movement and contains hysteresis, Barkhausen noise, and strong harmonic distortion. The arrangement with crossed anisotropies is found to display a behavior characteristic of switching by magnetization rotation as evidenced by a strong reduction of hysteresis, Barkhausen noise, and harmonic distortion. Demagnetization effects are calculated in order to quantitatively explain the shape of the response curve and the difference in output voltage when compared to AMR-based MRE's. Index Terms - Barkhausen effect, magnetoresistive devices, spin valve, technology, transmission line model.

This paper presents an efficient and accurate procedure for computing the quasi-static matrix parameters ([C], [L], [G], and [R]) of rectangular-shaped conductors embedded in a multilayered dielectric medium over an infinite ground plane. An additional top ground plane can also be considered. The problem is formulated in terms of the space-domain integral equation for the free-charge distribution on the slab conductor surfaces. The spatial Green's function is computed from its spectral counterpart using system identification techniques [Prony's method or matrix pencil method (MPM)]. The integral equation is solved by means of a Galerkin scheme employing entire domain basis functions. This results in a small matrix size. In addition, the quasi-analytical evaluation of the entries of the Galerkin matrix leads to a very efficient and accurate computer code. A detailed study on the convergence and accuracy of the method has been included. Index Terms - Losses, microstrip, multiconductor transmission lines, quasi-TEM analysis, thick conductors.

A novel design for simulating a lumped element transmission line is described. Op-amp subcircuits replace discrete inductances - an approach which overcomes a number of disadvantages associated with conventional components. The apparatus models a lossy line which is free of amplitude and phase distortion. Experiments are described which demonstrate the design's precise measurement capabilities with respect to determining frequency-dependent input impedance and phase shift, as well as the real and imaginary parts of the complex propagation function. Several pulse experiments are also discussed.

An analysis is presented for the behavior of the superconducting quasi-particle nonlinear transmission line driven by a high-frequency local oscillator (LO). The theory developed includes a large-signal nonlinear analysis, a small-signal analysis, and a noise analysis. This model is used to simulate the conversion loss and noise temperature of distributed quasi-particle mixers based on the nonlinear transmission line. The numerical results are compared to an experimental mixer at 460 GHz. The theory also predicts that the nonlinear transmission line will provide parametric amplification when the idler frequency is inductively tuned. This new phenomenon may present new opportunities to low-noise receiver systems at submillimeter wavelengths. Index Terms - Distributed mixers, nonlinear transmission lines, parametric amplifier, SIS mixers, submillimeter waves.

Injection-locked semiconductor lasers were investigated using single-mode-laser rate equations. It was shown that injection-locked lasers are not fully correlated, including the stability of the master laser is not fully transferred to the two secondary lasers. The frequency stability of the master laser was shown preserved on the side bands.

A novel photoconductive GaAs switch is proposed. The circuit, which may be directly integrated onto an existing high temperature circuit, is made up of coupled gold/YBa2Cu3Ox coplanar transmission lines. The photoconductive switch exhibits subpicosecond electric pulses when it is irradiated with femtosecond laser pulses that are capable of propagating over 1 mm along the transmission line.

A superconductor-insulator-superconductor transmission line's non-linear quasiparticle tunnel current was used to develop a novel distributed mixer. The mixer employs Nb/Al/AlOx/Nb junctions with lengths between 1 and 2 guided wavelengths and a width of 200 nm. The mixer uses simpler tuning circuity, lower critical currents densities and lower magnetic field as compared to traditional submillimeter lumped element quasiparticle mixers.

Si and Ai ion-implantation patterning was used to develop low-loss microwave transmission lines in high-temperature superconductor thin films. The approach led to the fabrication of coplanar waveguide transmission lines in YBaCu3O7-delta thin films on LaAlO3 substrates. The performance of the structures was characterized using broadband and resonant measurements. The approach was demonstrated to be effective in high-temperature superconducting microwave device development.

A low-temperature vector network measuring system was used to measure the characteristic impedance of micro strip lines with a Tl2Ba2CaCu2Ox/MgO/Au structure. A correction technique was also employed to obtain characteristic impedance from the data at low temperature (80 K). Results show that the impedance for micro strip lines 360 micrometers wide with 380 micrometer high MgO substrate was 49.3+2.2 - 1.8 ohm at 80 K, 5-15 GHz.

In this paper we use the method of characteristics to derive a new simulation model of lossy transmission lines, and we present the sensitivity analysis in the time domain. The simulation model is as fast as the recursive convolution model based on moment matching and Pade' approximation, but does not have the stability problem. The sensitivity analysis model is particularly useful for transmission line circuits containing nonlinear elements, and is believed to be the first time domain model. Both the simulation and sensitivity analysis models are applicable to uniform and nonuniform transmission lines with arbitrary nonzero initial states. Also we show that any nonlinear circuit element has a very simple linear model in sensitivity analysis. Furthermore, we demonstrate that for any circuits, the modified nodal admittance (MNA) matrices in simulation and in sensitivity analysis equations are the same, therefore no LU decomposition is needed in sensitivity analysis. The contributions in this paper have been implemented into a general-purpose program CSSC (Circuit Simulation and Sensitivity Analysis with Characteristics) which shows excellent accuracy and efficiency in both simulation and sensitivity analysis of transmission line circuits. Index Terms - Sensitivity analysis, simulation, transmission lines.

The characteristic impedance of a TEM transmission line, shaped as a double-ridged rectangular coaxial line, is analyzed in this paper as the customary transversal static problem. This type of transmission line is useful, for example, as a part of a cascaded transition between a double-ridged waveguide and a coaxial line. The solution of the transversal problem is achieved by dividing the cross-sectional region into distinct, separable regions, each one being characterized by a closed-form Green's functions relating the flux function to the electric field. Surface-type integral equations are then formulated over the boundaries between the regions. Solution of these equations via the method of moments (MoM's) using the Galerkin choice yields the results for the characteristic impedance as a function of cross-sectional dimensions. Convergence of the solution is also studied. Index Terms - Characteristic impedance, Galerkin method, ridged TEM line.