Cable shielding measurements at microwave frequencies

A matched triaxial device is developed and constructed to measure the transfer impedance of braided coaxial cables at microwave frequencies. Full-design principles of the device have been developed and given in detail in the paper. The device is particularly suited for shielding measurements at frequencies up to 3.5 GHz, for which no comparable technique exists. The performance of the device is fully evaluated both theoretically and by measurements. The accuracy of the device is studied by comparing the results against those obtained from the low-frequency International Electrotechnique Committee triple-coaxial apparatus, and using well-known theoretical models.     

Electronic tuning of a dielectric resonator at microwave frequencies

This aper deals with electronic tuning of a 950MHz shielded dielectric resonator by using a varactor-loop circuit. A theoretical investigation based on an accurate model circuit is resented. henomena such as jumps in frequency and amplitude, and degradation of the DR qualities are described     

Automatic measurement of complex dielectric constant and permeability at microwave frequencies

With the advent of the computer and automatic test equipment, new techniques for measuring complex dielectric constant (ε) and permeability (µ) can be considered. Such a technique is described where a system is employed that automatically measures the complex reflection and transmission coefficients that result when a sample of material is inserted in waveguide or a TEM transmission line. Measurement results of ε and µ for two common materials are presented.     

Frequency dependence of rain attenuation measurements at microwave frequencies

The values of attenuation versus frequency for 10 mm/h, 25 mm/h, and 40 mm/h rain rates for frequencies of 11, 18, and 22.2 GHz are presented. On the basis of these observations the attenuation at frequencies below 10 GHz and above 22.2 GHz have been obtained. The values obtained at various frequencies show an agreement with those calculated on the basis of Oguchi's work. Comparison of the above values in dB/km (assuming a path length of 2.5 km) have been made and they show an agreement with International Radio Consultative Committee (CCIR) values. Also cumulative distributions of attenuation at various frequencies have been given taking 11 GHz results as the reference point.     

Test structures for dielectric spectroscopy of thin films at microwave frequencies

This work describes the application of two different test structures to execute broadband microwave measurements of the dielectric constant of ceramic thin films. Coplanar waveguide probes and vector network analyzer were used to measure the dielectric constant versus frequency of thin films of lead zirconate titanate and zirconium titanate, fabricated by sol gel methods. One-step lithography was used to produce planar metal-insulator-metal and interdigitated capacitor test patterns. The two test structures are compared for zirconium titanate films. The metal-insulator-metal method has been applied also to a lead zirconate titanate film and to show the capability of computing the dielectric tunability.     

The dielectric properties of brine in sea ice at microwave frequencies

The dc conductivity and complex dielectric constant at frequencies of 7.50, 9, 11, 30, and 40 GHz of 16 samples of sea water brine in equilibrium with sea ice with freezing temperatures ranging from -2.8degC to-25.0degC have been measured. The data is analyzed to yield parameters occurring in a Debye relaxation equation so that the dielectric constant of brine may be calculated throughout the microwave region of the electromagnetic spectrum.     

An improved model for the dielectric constant of sea water at microwave frequencies

The advent of precision microwave radiometry has placed a stringent requirement on the accuracy with which the dielectric constant of sea water must be known. To this end, measurements of the dielectric constant have been conducted atS-band andL-band with a quoted uncertainty of tenths of a percent. These and earlier results are critically examined, and expressions are developed which will yield computations of brightness temperature having an error of no more than 0.3 K for an undisturbed sea at frequencies lower thanX-band. At the higher microwave and millimeter wave frequencies, the accuracy is in question because of uncertainties in the relaxation time and the dielectric constant at infinite frequency.     

Design of MMICs employing whispering-gallery mode dielectric resonators at microwave and millimeter wave frequencies

A simple theoretical model for predicting the resonant frequencies of the modes of the whispering — gallery (WG) mode dielectric resonators MICs (Microwave Integrated Circuits) at microwave and millimetre wave frequencies is presented. The unsymmetric field distribution for WGE mode in the axial direction is taken into account. The theoretical results are found to be in good agreement with the practical results taken at microwaves C-X bands. In addition, the variation of resonant modes against dielectric resonator's dimensions and dielectric constant is modelled. The effect of the width of dielectric substrate on resonant modes is also illustrated.     

Effects of PAI on interface properties between HfSiO gate dielectric and silicon substrate

The effects of preamorphization implantation (PAI) on the interface properties between hafnium-silicate (HfSiO) gate dielectrics and silicon substrates were examined. In the case of an NH/sub 3/ nitrided interface, it was found that the PAI can improve the interface trap density (D/sub IT/) compared with the no PAI case. However, for the PAI samples, it was also found that samples with sacrificial screening oxide (Sac Ox) had worse interface properties compared with the samples without Sac Ox. It is attributed to the recoiled oxygen from Sac Ox during PAI.     

Comments on "Automatic measurement of complex dielectric constant and permeability at microwave frequencies"

In the above paper, erroneous data were obtained for some frequencies and were attributed to equipment instability. However, it is shown in this letter that the "errors" were due to singularities in the parameters being measured, as can be seen by examining the equations involved. Additionally, comments are made with regard to resolving the phase ambiguity in the measurement.     

Secondary-emission amplification at microwave frequencies

Two types of photomultipliers exhibiting flat base-band response to ∼4 Gc/s are described. One photomultiplier employs crossed electric and magnetic fields, the other is purely electrostatic. At present both devices consist of eight Cu-Be secondary emission stages and an internally situated, opaque-backed S-1 photocathode. Current gain exceeds 10⁵, and the transit time dispersion is less than7 times 10^{-11}s. Frequency response measurements have used heterodyning between the modes of the Zeeman-split Doppler profiles of a 6328 Å He-Ne laser, and also shot noise in the current from a steadily illuminated photocathode as sources of microwave modulated currents. Transient response measurements have been made using sub-nanosecond light pulses from phase-locked He-Ne and argon ion lasers, the results being consistent with the measured frequency response. A calculation of the frequency response to be expected fromnidentical stages of secondary emission when only the secondary electron emission velocities contribute to electron transit time differences, as is true of the geometries used in the experiments, gives results in agreement with experiment, assuming a value of 3 eV for the most probable secondary electron emission energy from BeO. This value is consistent with direct observations by others.     

Measurement of the dielectric constants of metallic nanoparticles embedded in a paraffin rod at microwave frequencies

A cylindrical rod composed of a uniform mixture of metallic nanoparticles and alumina powder dissolved in paraffin was inserted in the center of a cylindrical microwave cavity. The real and imaginary parts of the complex dielectric constant of metallic nanoparticles at various microwave frequencies of the TM/sub 010/ mode can be determined from the resonant frequency and quality factor, respectively, of the transmission resonance spectrum. This method involves the protection of the sample from adsorbed moisture and prevents the rod from filling with air, thus making the experimental values more accurately and stably determined than they are by the dielectric double-cavity method. The real parts of the dielectric constants of metallic nanoparticles are negative and their magnitudes decrease as the particle size decreases. This finding is consistent with theory, which states that conduction becomes weaker as the particle size is reduced.     

Single-horn reflectometry for in situ dielectric measurements atmicrowave frequencies

The ability of single-horn reflectometry to determine reflectivity and, hence, calculate dielectric properties using plane-wave interpretation theory, has been investigated experimentally. The horn is part of a portable field unit operating at X-band and was placed above various natural materials. Good results were obtained for water and saline ice, which were flat and lossy, but not for an electrically thick sheet of fresh lake ice, for which reflectivity at the bottom interface was strong     

The epHEMT gate at microwave frequencies

This paper examines the high-frequency behavior of the enhancement-mode pseudomorphic high electron-mobility transistor (epHEMT) gate. During this study, no bias was applied between the drain and source. Rather, the gate was forward biased with either the drain, source, or channel (drain and source connected together) grounded. While applying positive voltage V/sub g/ to the gate, one-port S-parameters were measured from 0.1 to 10 GHz and then converted to Z-parameters. Plotting the real part R of the impedance reveals two sharp peaks. The first peak occurs near the device threshold voltage for conduction in the InGaAs well. A second peak occurs at higher voltages where conduction begins to occur in the surface AlGaAs layer. An equivalent-circuit model is proposed to account for the epHEMT gate's high-frequency behavior and the proposed model is shown to be in good agreement with the experimental data.     

The silicon cryosar at microwave frequencies

Microwave and low-frequency measurements are reported onn^{+}-v-n^{+}silicon cryosars fabricated with narrow intrinsic region widths. The low-frequency measurements includeV-Idata with and without incident microwave power. The electric field required to cause impact ionization of the donors was found to be greater than 10⁵V/m. The microwave measurements include a demonstration of mixing, harmonic mixing, and harmonic generation. Small-signal impedance measurements as a function of bias are reported at 1.33 and 3.05 GHz, and the diode noise temperature was measured to be 16 000 or 3000 K depending on bias polarity. Mobile electron lifetime is 10^-10s.     

`Source-pull? technique at microwave frequencies

A technique to produce a variable and controlled source impedance is described in order to evaluate the performance of microwave devices under source impedance variable conditions. The procedure for a systematic error correction is also presented.     

Circular polarization of the magnetic field in the WG modes ofresonance of a dielectric disc at microwave frequencies

The circular polarization of the magnetic field of the whispering-gallery (WG) modes of resonance of a dielectric disk resonator was tested in the evanescent-field region outside the dielectric material. Microwaves in the frequency range from 18 to 26.5 GHz (K-band) and the techniques of electron spin response (ESR) were used. The distribution of the electromagnetic fields was obtained with a finite element method, and it was found to be in agreement with the experimental results     

Conductivity measurements of the earth at ELF

This paper describes a simple method for determining the effective conductivity of a relatively flat conducting earth at ELF. The method is based on the quasi-static approximations to the Hertz vector potential for both the vertical and horizontal magnetic dipole. From these approximations, expressions for the magnetic field are obtained. By taking the ratio of the vertical component to the horizontal component, a simple relation is obtained for conductivity which is independent of the magnetic dipole moment. The relation is also independent of the source and receiver height provided they are located near the boundary.     

Magnetoresistance of the Corbino disk at microwave frequencies

The behavior of a Corbino disk of InSb in a static, transverse magnetic field and a high frequency electric field is investigated. Measurements and analysis show that, owing to an internal magnetic field effect, the impedance of the Corbino disk shows a frequency dependence even at microwave frequencies. Measurements performed on rectangular samples show the same effect even more pronounced. It is concluded that, in the case of medium to high Hall angles, this effect may determine an upper frequency limit of Hall-effect devices which is considerably lower than the dielectric relaxation frequency.