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Microwave characterization of an integrated inductor is often carried out with respect to a local ground reference. The measurement outcome, however, does not necessarily reproduce the behavior of the device in an actual circuit where a ground reference does not exist. Furthermore, inductor measurements can be affected by the unequal currents on the inner and outer conductors of the coaxial lines internal to the RF probes. Such currents tend to radiate the microwave energy into the surroundings and manifest themselves as unexpected ripple and resonance features in measurement results. In this study, a measurement model is developed including both effects and is used to analyze experimental data obtained from integrated spiral inductors. A novel deembedding technique is then proposed and applied to eliminate the local ground and unequal coaxial current effects. Index Terms--Asymmetric currents, deembedding, integrated inductor, microwave measurement, RF probe.

High-power-microwave (HPM) emission has been observed in S-band with a compact magnetically insulated line oscillator (MILO). The device is driven by a low-impedance Marx generator which was designed and built at Commissariat l'Energie Atomique, Centre d'Etudes Scientifiques et Techniques d'Aquitaine for HPM experiments. Measurements with fast and sensitive I-dot probes, installed inside the slow-wave structure (SWS), have given the evidence of the MILO oscillation. The main frequency at 2.40 GHz is confirmed by measuring the emitted radiation by using both an in-vacuum antenna and a horn placed in the far-field region. The frequency response of the MILO SWS is compared to a 3-D simulation performed with MAGIC, an electromagnetic particle-in-cell code. In the first configuration, a microwave output power of 1 GW has been obtained, which is in good agreement with the simulations. Then, an optimization of the cathode geometry has led to an increase of the pulse duration and to a better stability of the emission frequency. Finally, based on the fair agreement between the experimental results and the corresponding simulations, a novel design is presented, which should give a higher emitted power at 2.34 GHz. Index Terms--Conical antennas, magnetic insulation, microwave measurements, microwave oscillators, modeling, plasma-loaded waveguides.

The requirements for dielectric measurements on polar liquids lie largely in two areas. First there is scientific interest in revealing the structure of and interactions between the molecules--this can be studied through dielectric spectroscopy. Secondly, polar liquids are widely used as dielectric reference and tissue equivalent materials for biomedical studies and for mobile telecommunications, health and safety related measurements. This review discusses these roles for polar liquids and surveys the techniques available for the measurement of their complex permittivity at RF and Microwave frequencies. One aim of the review is to guide researchers and metrologists in the choice of measurement methods and in their optimization. Particular emphasis is placed on the importance of traceability in these measurements to international standards. Index Terms--Biomedical measurements, dielectric liquids, dielectric materials, dielectric measurements, microwave measurements, millimetre-wave measurements, moisture measurement, permittivity measurement, transmission-line measurements, UHF measurements.

Measurement of microwave and UHF signals is often done with sampling techniques. In this paper, the techniques and technology of sampling of electrical signals is reviewed from 1950 to the present. It includes both references to the open literature, as well as an extensive review of relevant patents. It also provides an overview of sampling applications and the use of computer technology to compensate and correct for errors in the sampling process. Index Terms--Microwave instrumentation and measurement, network analysis, oscilloscopes, RF sampling, samplers, sampling oscilloscopes.

The performance of a microwave frequency standard is assessed. The standard is based on a cloud of [superscript 171]Yb[superscript +] ions as a function of the size of the cloud.

Research is presented concerning the use of sputtering from cylindrical targets which were hollow in the deposition of c-axis oriented YBa2Cu3O7-delta films for use as telecommunications microstrip filters.

Material and electrical characteristics of YBa[subscript 2]Cu[subscript 3]O[subscript 7] (YBCO) thin films deposited by inverted cylindrical magnetron sputtering on (110) SrTiO[subscript 3) (STO) are examined.

The chemical 1-amino-1-ethenylcyclopropane is investigated for its behaviour when subjected to microwaves and the resulting gases recorded for conformity and structure.

This work investigates the potential use of passive and active microwave observations to monitor soil moisture and vegetation biomass over a soybean cover. The work is based on a sensitivity analysis from a large set of data generated by radiative-transfer models. Some appropriate configurations are identified. In particular, the combined use of passive data at 1.4 GHz, with multiangle active measurements at 5 GH(sub z), is found to be promising.

Airborne passive-microwave signatures collected in Northern Finland during EMAC-95 are analyzed with the emphasis on forested areas and dry snow conditions. The microwave signatures cover the 6.8-18.7-GH(sub z) frequency range and were acquired at both vertical and horizontal polarizations. The analysis is carried out with respect to the forest-stem volume data and comprises three different snow-depth situations. Emissivities approach saturation limit with the increasing stem volume. At 10.65 GH(sub z), the saturation level was found to be linearly related to the snow-water equivalent. On the basis of passive-microwave measurements, an empirical forest transmissivity model is developed. The model is valid at vertical polarization 50 incidence angle, and it accounts for microwave frequency and forest-stem volume effects in the range of 6.8-94 GH(sub z) and 0-150 m(super 3)/ha, respectively.

The problem of phase uncertainty arising in calibration of the est fixtures is investigated in this paper. It is shown that the problem exists no matter what kinds of calibration standards are used. It is also found that there is no need to determine the individual S-parameters of the test fixtures. In order to eliminate the problem of phase uncertainty, three different precise (known) reflection standards or one known reflection standard plus one known transmission standard should be used to calibrate symmetrical test fixtures. For the asymmetrical cases, three known standards, including at least one transmission standard, should be used. The thru-open-match (TOM) and thru-short-match (TSM) techniques are the simplest methods, and they have no bandwidth limitation. When the standards are imprecise (unknown), it is recommended to use any suitable technique, such as the thru-reflect-line, line-reflect-line, thru-short-delay, thru-open delay, line-reflect-match, line-reflect-reflect-match, or multiline methods, to accurately determine the values of the required calibration terms and, in addition, to use the TOM or TSM method with the same imprecise standards to resolve the phase uncertainty. Index Terms: Calibration, microwave network analyzer, scattering-parameter measurement, test fixtures.

A detailed investigation of the microwave linewidth of Nb-AlO(sub x)-Nb flux flow oscillators was conducted. An improved method based on harmonic mixing in the frequency range 250-600 GHz was used to calculate the dependence of the flux flow oscillators linewidth on the junctions parameters. Results illustrate the ability to decrease the intrinsic linewidth of a Josephson oscillator by an external electronic phase locked loop (PLL) system if the PLL bandwidth is larger than the initial oscillator linewidth.

The total amount of plasma, peak plasma density, and plasma density radial profile are derived from a series of measurements of ion current density (with a Faraday cup) and integrated electron line density (with a microwave interferometer) for a cathodic arc derived plasma. Comparisons are made between cathode material (erbium and titanium), arc current, background gas pressure, and the presence or absence of a series magnetic solenoid around the coaxial anode and cathode. Index Terms - Arc discharges. microwave measurements, plasma measurements, vacuum arcs.

The transfer characteristic of relative phase of the third-order intermodulation distortion ([IM.sub.3]) of a GaAs FET amplifier is measured and analyzed. The measurement system and method are also described. For drives in the weakly nonlinear region, the measured relative phase of [IM.sub.3] is equal to that of the carrier and is in agreement with the analysis results using Volterra-series representation. For drives in the saturation region, the measured relative phase of [IM.sub.3] versus the input power moves drastically compared with that of the carrier and is in agreement with numerical analysis using discrete Fourier transform. Comparison between measured and analytical results shows the drastic move of [IM.sub.3] relative phase is caused by the generation of [IM.sub.3] due to AM-PM conversion. The measured results and the measurement method are useful for the design and adjustment of predistortion-type linearizers for GaAs FET high-power amplifiers. Index Terms - Amplifier distortion, intermodulation distortion, microwave FET amplifiers, microwave measurements, Volterra series.

A nonresonant perturbation (NRP) theory is developed from first principles for the measurement of dispersion and interaction impedance characteristics of a helical slow-wave structure (SWS). The phase of the reflected signal from a test helical structure varies when a perturber, also in the form of a helix, is moved along the axis of the test structure. The variation of phase with perturber position is interpreted to find the phase velocity of the structure under test. The interaction impedance of the structure is found by measuring the change in the axial phase-propagation constant of the structure as a dielectric rod is placed along the axis of the structure. For this purpose, first a 'resonant' perturbation formula is derived for interaction impedance which, with proper interpretation, is then extended to get a 'nonresonant' perturbation formula in terms of the above change in the axial phase-propagation constant. The formula shows an improvement over the first-order formula derived under 'thin-rod approximations' in the form of a correction factor that takes into account the finite perturbation of the axial electric field inside the dielectric-rod perturber, the presence of a radial electric field, the nonuniformity of fields over the rod cross section, and the space-harmonic effects. However, the TE-field contributions are considered to be insignificant, thereby allowing one to ignore the presence of the azimuthal electric field. Measurements are carried out with the help of an automated setup using an HP 8510 vector network analyzer (VNA) and a PC to collect the phase informations for the various precisely controlled positions of the perturber using a stepper motor, which is also interfaced with the PC. The experimental and theoretical values of the phase velocity and the interaction impedance of a typical 'cold' experimental helical structure for a wide-band TWT are found to be close within 0.5% and 5%, respectively, in an octave band of 8-16 GHz. Index Terms - Microwave measurement, nonresonant perturbation, slow-wave structure, traveling-wave tube.

The frequency of the 171YB+ 12.6 GHz MF = 0 - 0 ground state hyperfine clock transition in buffer gas-cooled ion clouds has ben measured. The ion clouds are confined in two similar linear Paul traps. The frequency of the transition at zero temperature, velocity, electric field and magnetic field was determined to be 12 642 812 118.466 plus or minus 0.002 Hz. The model used is believed to be valid under present operating parameter ranges to within plus or minus 1.5 mHz.

This paper refers to quantitative reconstruction of the dielectric and conductive property distributions of biological objects by means of active microwave imaging. An iterative reconstruction algorithm based on the Levenberg-Marquardt method is tested with synthetic data. The influence of the receiver geometry is investigated and two methods for choosing the regularization parameter, an empirical method and generalized cross validation (GCV) method, are examined. Index Terms - Microwave imaging.

In the collinear interaction between magnetostatic waves and optical guided modes, the use of high microwave power is experimentally observed to broaden the range of microwave frequencies over which a significant optical mode conversion occurs. A mechanism contributing to this broadening is described that is based on a nonlinear shift in the wavelength of the magnetostatic waves at high power along with magnetic damping. Comparisons between previous experiments and our theoretical predictions show that this mechanism can explain some, but not all, of the changes observed in the optical spectrum at high microwave power levels.

A wide variety of microwave ferrite phase-shifting materials have been measured in the demagnetized state. The relative magnetic permeability and loss factor were determined near and above natural gyromagnetic resonance using [H.sub.011] cylindrical dielectric ring resonators. These low-loss dielectric sleeves were dimensioned for accurate magnetic property measurements of single ferrite rod samples at logarithmically sampled resonant frequencies from 2 GHz to 25 GHz. Permeability and magnetic loss factor are computed from the measured resonant frequencies and Q factors of these resonators, with and without the ferrite sample, using exact eigenvalue equations. Generally, the real part of the complex magnetic permeability increases with decreasing saturation magnetization, while the magnetic loss factor increases nonlinearly with increasing saturation. Schloemann's theoretical model for the real part of initial permeability of a cylindrically symmetric domain configuration in the completely demagnetized state shows excellent agreement with measured data when 2[[Pi].sub.[Gamma]][M.sub.s]/[Omega] < 0.75. The data allow design optimization of circulators and dual-mode and polarization-insensitive phasers, which are widely used in antenna array systems.

A two-port flanged coaxial probe for measuring the dielectric and magnetic properties of thin material sheets is analyzed. Closed form solutions for the two-port scattering parameters are presented. The solution assumes an incident TEM wave together with evanescent [TM.sub.0n] modes. Numerical results are obtained for both the forward and inverse problem. Computations indicate that at low frequencies the incident waves are almost totally reflected. As the frequency is increased, transmission through the sample increases. Experimental results compare closely with theory. The inverse solution yielded good permittivity determination for the cases tested. The technique should prove useful for nondestructive testing of circuit boards or substrates. Index Terms - Coaxial line, dielectric constant, flanged coaxial holder, loss factor, microwave measurements, nondestructive, open-ended probe, permeability measurement, permittivity measurement, shielding effectiveness, two port.

A device for determining the microwave electric field intensity of single high-power radiowave pulses is shown. A surface acoustic wave (SAW) dielectric acoustic line which has nonlinear electroacoustic characteristics and composed of two transducers is utilized. One transducer is affected by a microwave electric field and generates the SAW excitation because of its nonlinearity. A linear interdigital transducer receives data about the electric field strength.

A programmable active load-pull measurement system using two six-port reflectometers and three passive two-port standards has been developed to obtain load-pull contours of the transistor's input-output phase shift variations over a wide dynamic range of the input power. The output power, gain, power-added efficiency, and phase shift are measured simultaneously at the transistor's input and output reference planes. The phase distortion versus input power, [Phi] [similar to] [P.sub.in], and the AM-PM conversion coefficient at various power levels, k [similar to] [P.sub.in], are obtained for different load impedances by post-measurement calculations. A NE8001 MESFET is tested at f = 1.7 GHz for the class A operation. The experimental results are also given.

Interferometers with many loops and comprising two and four strongly damped Josephson junctions with finite capacitance are proposed as microwave absorption models. The average microwave losses of these interferometers are simulated as a function of an external magnetic field. Results indicate that microwave absorption depend in a complicated way on the static threshold characteristic and the microwave current amplitude and frequency.

We have fabricated active probes for on-wafer wave-form and network measurements. The probes incorporate GaAs nonlinear transmission line (NLTL) based network analyzer (NWA) integrated circuits and low-loss quartz coplanar-waveguide probe tips. The active probes show step response falltimes of 2.7 ps when excited by a 0.7-ps falltime input. Using these active probes, we demonstrate both waveform measurements with 2.7-ps risetime and network measurements to 200 GHz. We discuss the probe tip and NWA IC design, the hybrid assembly and mechanical design, and system design considerations. On-wafer waveform and S-parameter measurements of monolithic millimeter-wave integrated circuits are demonstrated.

In this paper we present a novel approach to deriving local boundary conditions, that can be employed in conjunction with the Finite Difference/Finite Element Methods (FD/FEM) to solve electromagnetic scattering and radiation problems involving periodic structures. The key step in this approach is to derive linear relationships that link the value of the field at a boundary grid point to those at the neighboring points. These linear relationships are identically satisfied not only by all of the propagating Floquet modes but by a few of the leading evanescent ones as well. They can thus be used in lieu of absorbing boundary conditions (ABCs) in place of the usual FD/FEM equations for the boundary points. Guidelines for selecting the orders of the evanescent Floquet modes to be absorbed are given in the paper. The present approach not only provides a simple way to derive an accurate boundary condition for mesh truncation, but also preserves the banded structure of the FD/FEM matrices. The accuracy of the proposed method is verified by using an internal check and by comparing the numerical results with the analytic solution for perfectly conducting strip gratings.

An application of multilevel (ML) methods to compute the modes and eigenvalues of resonant cavities is presented. The involved methods include an ML eigenvalue solver, an ML mode separation technique, a boundary treatment method, and a subspace continuation technique (SCT) for sequences of problems. In the presented numerical experiments, an asymptotic convergence factor of order 0.1 is obtained for ML cycles on all fine levels, while performing only a few relaxations per cycle. This factor is obtained for a rectangular cavity as well as for cavities having reentrant corners, holes and narrow regions, and presenting clusters of close and equal eigenvalues. A second order scheme is obtained for the computed eigenvalues and modes with an amount of work of order O(qN) for q modes of size N on the finest level. The SCT is illustrated on a moving boundary problem, where solutions change fast at a small boundary change. Such computations are applied to the design of new microwave selective devices. Index Terms - Maxwell equations, microwave device, resonant cavity, multilevel numerical techniques, multigrid, eigenvalue algorithms, continuation techniques.