Measurements of the Photo-Induced Complex Permittivity of Si, Ge, and Te at 9 GHz

The photo-induced complex permittivity Delta epsilon /sub r/(=Delta epsilon'/sub r/--j Delta epsilon"/subr/)of single, crystal silicon, germanium, and tellurium samples was studied using a transmission microwave bridge method at frequencies of about 9 GHz. The measurements were made at temperatures in a range from 100 to 300 K over an optical wavelength range from about 0.6 to 1.4 µm for silicon, 0.8 to 2.0 µm for germanium, and 1.5 to 4.2 µm for tellurium. The incident monochromatic illumination was chopped at about 90 Hz. It was found that the spectral variation of Delta epsilon'/sub r/ was similar to that for Delta epsilon"/sub r/ over the wavelength ranges with the incident monochromatic light intensity in the order of 100 µw/cm²². The spectral peaks (for Si and Ge samples) of both Delta epsilon'/sub r/ and Delta epsilon"/sub r/ were found to shift towards shorter wavelengths as the temperature was decreased. From the photo-induced complex permittivity results, the collision time of the free carriers was derived.     

Some Effects of Field Perturbation Upon Cavity-Resonance and Dispersion Measurements on MIC Dielectrics

An analysis is presented of field perturbations in MIC resonators in order to examine the errors which occur in permittivity measurements made by cavity-resonance methods: Q factor, coupling effects, fringing fields, crystal misalignment (for anisotropic materials), changes in ambient temperature are all considered. Analysis of a cavity with mixed boundary conditions shows that the resonant-mode frequencies depend to the first order on that part of Q/sub 0/ associated with imperfect electric (metal) walls, but to the second order on that part associated with imperfect magnetic (open-circuit) walls. A new expression is given for the Q of an open-ended microstrip resonator when surface waves are excited in the dielectric, and it is shown that the unloaded Q (Q/sub 0/) can be dominated by this phenomenon. It is further shown that these Q-related effects, together with reactive perturbations arising from fringing, coupling structures, are the principal source of error in measurements for epsilon or epsilon/sub eff/. Such reactive effects may be treated semiquantitatively by applying Slater's perturbation theorem to the affected region. These procedures lead to the following revised values for the crystal permittivity of sapphire (monocrystalline Al/sub 2/0/sub 3/) in the microwave region: epsilon/sub ||/ (parallel to the c axis) = 11.6; epsilon/sub /spl perp// (base-plane) = 9.4.     

On the Theory and Application of the Dielectric Post Resonator (Short Papers)

This short paper deals with the modes of the dielectric post resonator when epsilon/sub r/ is large. The normalized frequency F/sub 0/ = (pi D/lambda/sub 0/) /spl radic/ as a function of D/L is discussed. The simple approximate expressions for the resonant frequencies of the lower order modes are given. The properties of the TE/sub 011/, mode are discussed in detail from the point of view of its application to the measurement of the complex permittivity of microwave dielectrics. Curves and expressions for fast and simple determination of the maximum measurement errors are given.     

Quasi-Static Characteristics of Microstrip on an Anisotropic Sapphire Substrate

The well-defined and repeatable electrical properties of single-crystal sapphire make it an attractive substrate material for microstrip, but its dielectric anisotropy constitutes an important design complication. This paper describes investigations into the quasi-static characteristics of single microstrip lines on sapphire substrates cut with a specified orientation. To account for anisotropy, a new permittivity parameter epsilon/sub req/ is introduced, which is a function of the Iinewidth to substrate-height ratio W/h. The variation of epsilon/sub req/ with W/h is derived by finite-difference methods. Universal curves for microstrip on correctly orientated sapphire are presented, showing 1) epsilon/sub req/, 2) the low-frequency limit of effective microstrip permittivity epsilon/sub e0/, and 3) the characteristic impedance of the line Z/sub 0/, all as functions of W/h.     

New View on an Anisotropic Medium and Its Application to Transformation from Anisotropic to Isotropic Problems

The metric factor is defined as m(epsilon*/sub x/, epsilon*/sub y/, theta/sub x/) = /spl radic/ cos/sup 2/theta/sub x/ / epsilon*/sub x/ + sin/sup 2/theta/sub x/ / epsilon*/sub y/ in the radial direction, with the angle theta/sub x/ from the x axis being one of the principal axes in an anisotropic dielectric medium filling the two-dimensional space. The normalized metric factor is defined as n(epsilon*/sub x/, epsilon*/sub y/, theta/sub x/, beta) /spl equiv/ m(epsilon*/sub x/, epsilon*/sub y/, theta/sub x/) / m(epsilon*/sub x/, epsilon*/sub y/, beta) in the form normalized by the metric factor in the direction with the angle beta from the x axis. The effective path length d'/sub P1P2/ between the points P1 and P2 is defined as d'/sup P1P2/ = n(epsilon*/sub x/, epsilon*/sub y/, theta/sub x/, beta)d/sub P1P2/ where d/sub P1P2/ is the actual path length of the straight line P1P2 with the angle theta/sub x/ from the x axis. We propose the minimun principle of the effective path length for electric flux in the region with multilayered anisotropic media. It is applied to solving the electrostatic problem with two anisotropic media whose principal axes are different. We show by using the normalized metric factor that the anisotropic problem can be transformed into the isotropic problem.     

Correction Due to a Finite Permittivity for a Ring Resonator in Free Space

To better determine the resonant fields of a dielectric resonator with high permittivity epsilon/sub r/, the asymptotic theory with1//spl radic/epsilon/sub 3/ as a small parameter is extended by adding higher order terms in 1//spl radic/epsilon /sub r/ in the fields, the resonant wavenumber, and radiation Q. Extensive data are shown for the Phi independent "nonconfined" mode of a ring resonator, which radiates as a magnetic dipole. Some results are added for the "magnetic quadruple" mode.     

Computer-Aided Design of Three-Port Waveguide Junction Circulators

The complete performance of a lossless three-port H-plane waveguide junction loaded coaxially with various inhomogeneous ferrite cylanders has been evaluated over the waveguide bandwidth and compared with experiment. Qualitative agreement between the predicted and measured performance was generally good using only the first three modes, n=0/spl plusmn/1. It has been shown theoretically and verified experimentally that if the 4/spl pi/M/sub s/ of a homogeneous rod or the internal field is increased, the circulation frequency f/sub 0/ increases; conversely, if the pemittivity is increased, f/sub 0/ decreases. These conflicting effects are modified when the magnetization 4/spl pi/M/sub s/ and permittivity /spl epsiv/ are inhomogeneous. For example, if the 4/spl pi/M/sub s/(/spl gamma/) is small at the outer surface of the rod (with permittivity held constant), the effect on f/sub 0/ is very small; but if 4/spl pi/M/sub s/(spl gamma) approaches zero for /spl gamma/ small, then f/sub 0/ may decrease significantly. On the other hand, if /spl epsiv//sub/spl gamma//(/spl gamma/) approaches unity near the outer surface of the rod, f/sub 0/ may increase significantly; but if /spl epsiv//sub/spl gamma//(/spl gamma/) approaches unity near the center of the rod, f/sub 0/ is affected relatively little. The inhomogeneous structure has also shown that decreasing the ferrite volume may improve the performance, and high-power applications are suggested. With a conducting pin down the center of the ferrite, relative bandwidths of 40-50 percent are predicted.     

Gate-induced drain leakage current degradation and its time dependence during channel hot-electron stress in n-MOSFETs

The effects of channel hot-electron stress on the gate-induced drain leakage current (GIDL) in n-MOSFETs with thin gate oxides have been studied. It is found that under worst case stress, i.e. a high density of generated interface states Delta D/sub it/, the enhanced GIDL exhibits a significant drain voltage dependence. Whereas Delta D/sub it/ increases significantly the leakage current at low V/sub d/, it has minor effects at high V/sub d/. On the other hand, the electron trapping was found to increase the leakage current rather uniformly over both low and high V/sub d/ regions. In addition, GIDL degradation can be expressed as a power law time dependence (i.e. Delta I/sub leak/=A.t/sup n/), and the time dependence value n varies according to the dominant damage mechanism (i.e. electron trapping against Delta D/sub it/), similar to that reported for on-state device degradation.<>     

Characteristic Impedance of a Wide Slotline on Low-Permittivity Substrates (Short Paper)

Computed results on the characteristic impedance of wide slots etched on an electrically thin substrate of low dielectric constant epsilon/sub r/ are presented. These results combined with those in [1] provide design data for these slotlines. Curves are presented for epsilon/sub r/= 2.22, 3.0, 3.8, and 9.8. Comparison is shown for the characteristic impedance between the present calculations and those available in the literature for high-epsilon/sub r/ substrates. Empirical formulas, based on least-square curve fitting, are presented for the normalized slot wavelength lambda'/lambda/sub 0/ and the characteristic impedance Z/sub 0/ over the range 0.0015<=W/lambda/sub 0/<=1.0, 0.006<=d/lambda/sub 0/<=0.06, 2.22<=epsilon/sub r/<=9.8.     

Microwave Measurement of Dielectric Properties of Low-Loss Materials by the Dielectric Rod Resonator Method

Improvements both in accuracy and speed are described for the technique of measuring the microwave dielectric properties of low-loss materials by using a dielectric rod resonator short-circuited at both ends by two parallel conducting plates. A technique for measuring the effective surface resistance R/sub s/ of the conducting plates is proposed to allow the accurate measurement of the loss tangent tan delta. By means of the first-order approximation, the expressions are analytically derived for estimating the errors of the measured values of relative permittivity epsilon/sub r/, tan delta, and R/sub r/, for measuring the temperature coefficient of epsilon/sub r/, and for determining the required size of the conducting plates. Computer-aided measurements are realized by using these expressions. It is shown that the temperature dependence of R/sub s/, should be considered in the tan delta measurement. The copper plates used in this experiment have the relative conductivity of 91.0+-2.7 percent at 20°C, estimated from the measured R/sub s/ value. For a 99.9-percent alumina ceramic rod sample, the results measured at 7.69 GHz and 25°C show that epsilon/sub r/,= 9.687+-0.003 and tan delta = (1.6+-0.2)x 10/sup -5/. The temperature coefficients measured between 25 and 100°C are 112x10/sup -6//°C for epsilon/sub r/, and 23x10/sup -4//°C for tan delta.     

The Dependence of Reflection on Incidence Angle

A Iossy dielectric sheet has complex dielectric constant epsilon = epsilon (x) and complex permeability µ = µ(x), where x is the distance to one interface. This sheet is backed by a conducting surface and used as an absorber. If | epsilon (x)µ(x) | >>epsilon/sub 0/µ/sub 0/, so that (epsilon/epsilon/sub0/)(µ/µ/sub0/) - sin² theta is nearly independent of the incidence angle theta, then the amplitude reflection R(theta) is wholly determined by R(0). Typical results: When R(theta/sub0/) = 0 at one polarization, then at theta=theta/sub 0/ the reflection for the other polarization corresponds to a voltage standing-wave ratio SWR =sec² theta/sub 0/. At perpendicular polarization max | R(theta) | on (theta/sub 1/, theta/sub 2/) is least, for given | R(0) I, if R(0) is real and positive; and then R(theta) = 0 at tan²theta/2 = R(0). But for parallel polarization R(0) must be real and negative to get optimum performance. When the absorber functions at both polarizations the best obtainable result is | R(theta) | = tan²theta/2, no matter what interval (theta/sub 1/, theta/sub 2/) is specified. The error in the approximation is investigated theoretically and experimentally. A complete set of graphs is included, suitable for design of those absorbers to which the theory applies. The analysis also yields an exact expression for the limiting behavior of the reflection at grazing incidence. This can be used in problems such as computation of the field due to a dipole over a plane earth. Finally, the theory of the Salisbury screen is re-examined as an aid in checking the other developments.     

A Broad-Band, Automated, Stripline Technique for the Simultaneous Measurement of Complex Permittivity and Permeability

A broad-band automated technique for making frequency-swept measurements of complex permittivity and permeability simultaneously is described. Epsilon/sub r/ and µ/sub r/ are computed from S-parameter measurements made on a strip transmission-line device loaded with the material under test. The derivation of epsilon/sub r/ and µ/sub r/ as functions of S/sub 11/ and S/sub 21/ is included, as well as a practical design for a stripline sample holder. Measured epsilon/sub r/ and µ/sub r/ data for several dielectrics and ceramic ferrites is also presented. The technique has been found to have an overall accuracy of better than +-5 percent.     

Propagation in Rectangular Waveguide Containing Inhomogeneous, Anisotropic Dielectric

The Wentzel, Kramers and Brillouin (WKB) approximation is used to solve the wave equations for propagation of guided waves in rectangular waveguide containing an inhomogeneous dielectric. The simplest form of anisotropy is used to characterize the relative dielectric constant, i.e., it is assumed that the relative permittivity tensor is diagonalized with respect to the waveguide coordinants. Each of the elements of the relative permittivity tensor is allowed to vary continuously across the broad dimension of the waveguide. The TE/sub nm/ and TM/sub nm/ cases are analyzed for the instance of completely filled guide, while the TE/sub no/ modes are considered for slab-loaded guide.     

A Simple Numerical Method for Studying the Propagation Characteristics of Single-Mode Graded-Index Planar Optical Waveguides

A simple numerical method based on the Runge-Kutta method is presented to compute the propagation constant, the modal field, and the cutoff wavelength corresponding to the fundamental TE/sub 0/ and TM/sub 0/ modes of a planar optical waveguide with an arbitrary refractive index profile. The method is much simpler and requires less computational effort than the earlier reported numerical methods. We have also used the technique for an estimation of the effect of the /spl nabla/epsilon term in TM modes.     

Metallized Dielectric Horn and Waveguide Structures for Millimeter-Wave Oscillator/Mixer Systems

A new method of producing millimeter-wave oscillator/mixers and associated antenna horns has been developed. This uses the technique of metal coating of dielectric body, and hence avoids the expensive and difficult machining of conventional metal cavities. A sensitive self-oscillating mixer has been tested in this structure and shown to be free from the unstable operation associated with surface radiation of unshielded dielectric waveguide. Low epsilon/sub r/ dielectric was used, thus facilitating ease of matching in contrast with the high epsilon/sub r/ necessary with the unshielded guide.     

Excitation and Scattering of Guided Modes on a Helically Corrugated Dielectric Cylinder

The excitation and scattering of guided modes on a dielectric cylinder with a helical corrugation are investigated. A finite number of radiatiorr modes and an infinite number of surface modes are considered, with the consequence that both the amplitude and phase of the interacting modes can be evaluated. The effect of the pitch angle on the coupling and conversion between the guided modes and the radiation modes of various polarizations is investigated. It is found that TE/sub 0/ guided modes undergo a Brewster phenomenon in the low permittivity dielectrics. The power conservation relation is developed and the reciprocity relations are treated. The aperture fields are used to study the radiation characteristics of a novel dielectric-helix antenna capable of yielding a circularly, elliptically, or linearly polarized radiation.     

Wideband simple cylindrical dielectric resonator antennas

Bandwidths of the coaxial fed and aperture coupled cylindrical dielectric resonator antennas (DRAs) with broadside radiation patterns are enhanced by exciting the HEM/sub 11/spl Delta// (1相似文献   

Dispersion Characteristics for Wide Slotlines on Low-Permittivity Substrates (Short Paper)

This paper provides additional dispersion data on slotlines not available in the literature to date. In particular, data are presented on wide slots etched on an electrically thin substrate of low-dielectric constant. The range of parameters covered in this paper are 0.006<= d/lambda/sub 0/ <=0.06, 0.005 <= W/lambda/sub 0/ <=2.0, and epsilon /sub r/ =2.22, 3.0, 3.8, 9.8. The problem is formulated using the spectral-domain technique, and the spectral Galerkin's method is employed to compute the slot wavelength. Numerical results are compared to the experimental data over 2-6 GHz for slotlines on a 1.57-mm substrate (epsilon/sub r/ = 2.55). Agreement to within 2.0 percent is obtained.     

Accurately Approximate Formula of Effective Filling Fraction for Microstrip Line with Isotropic Substrate and its Application to the Case with Anisotropic Substrate

The accurately approximate formula of effective filling fraction q/sub w/ is obtained for the microstrip line with zero-thickness strip and isotropic substrate. The line capacitance per unit length C/epsilon/sub 0/ for the case with anisotropic substrate can easily be obtained by using the approximate formula of q/sub w/ and C/sub 0//epsilon/sub 0/ tabulated for the wide range of shape ratio w/h. The parameters Z, v, and lambda for such a line can be calculated by using C/ epsilon/sub 0/ and C/sub 0//espsilon/sub 0/.     

Correction to "Theory of an Efficient Electronic Phase Shifter Employing a Multilayer Dielectric-Waveguide Structure" (Letters)

A factor of n/sub g/ should appear in the numerator of the right side of (11). This error affects the design of the structure in Fig. 3, as follows: To obtain values of Delta phi/Delta iota of the order 50-80/spl deg//cm, it is necessary that d/sub g//lambda/sub 0/ be raised to 0.4375, and an additional layer of refractive index 3.4 and thickness 0.4375 lambda/sub 0/ be placed between the active layer and the superstrata. Other indices and thicknesses remain unchanged.