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Microwave Theory and Techniques, IEEE Transactions on

Issue 5 • Date May 1994

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Displaying Results 1 - 25 of 29
  • Dynamic analysis of a microstrip line over a perforated ground plane

    Page(s): 820 - 825
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    A full wave analysis is presented to compute the characteristic impedance and propagation constant of a microstrip line over a perforated ground plane. The perforations in the ground plane are modeled by equivalent magnetic currents. The method of moments is applied to solve the coupled integral equations for the unknown electric current on the microstrip line and the unknown magnetic currents in the apertures. The fields are formulated using the space domain Sommerfeld type Green's functions. The matrix pencil technique is used to obtain the amplitude and the propagation constant of the fundamental modes for both current and the voltage on the microstrip line. Typical numerical results are given.<> View full abstract»

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  • Comments on "Scattering parameters measurement of a nonreciprocal coupling structure" [with reply]

    Page(s): 922 - 924
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    For the original article see ibid., vol. 41, no. 4, p. 652-7 (1993). In the aforementioned paper by P. Kwan and C. Vittoria, the commenter considers that the three scattering matrices of the novel nonreciprocal coupling structure and the numbers of independent scattering parameters presented are obtained incorrectly. He proposes a method allowing one to find relations between elements of matrices [S], [Y], and IZ] of symmetrical structures with girotropic media. The scattering matrices and the number of their independent parameters of a nonreciprocal 4-port structure are derived. In reply, Vittoria states that certain matrices in his and Kwan's paper represent a concise and compact description of the experimental data. The matrices do not represent their theory or modeling of the data. It is the "raw" data of the experiments. Additionally, the authors take the opportunity to make a number of corrections to their paper.<> View full abstract»

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  • EM-wave propagation through semi-elliptic cylindrical dielectric waveguide on a perfectly conductive planar substrate

    Page(s): 891 - 898
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    This is a theoretical study of modes in a semielliptic cylindrical dielectric waveguide on a perfectly conductive planar substrate. Interest is mainly in high eccentricity, electrically large, hence multimode, structures. The theory applies to light propagation through surface-wave transmission lines or microwave ducting by shore-bounded evaporation ducts. The rigorous formulation of fields in terms of radial and azimuthal Mathieu eigenfunctions is followed by accurate computations of the longitudinal phase constant, the fractional power trapped within the waveguide and the group velocity. The effects of size, ellipticity and refractive index step on mode features are investigated. As information, previously unavailable, about high-order modes is reported, an interesting classification of modes readily unfolds View full abstract»

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  • A comparison of two recently proposed formulas for end capacitance in open circuited, two wire transmission lines [and reply]

    Page(s): 921 - 922
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    For the original article see ibid., vol. 41, no. 4, p. 666-72 (1993). In the aforementioned paper, W.J. Getsinger has provided a solution to the problem of the excess end capacitance which results from open circuit termination of a parallel, two wire transmission line. He references some earlier work by King (1955) based on a thin wire approximation to which his solution is asymptotically equivalent in the limit of a large conductor spacing to diameter ratio. In a previous paper by H. E. Green and J.D. Cashman (see ibid., vol. 34, no. 1, p. 180-82, 1986) a solution to this problem derived by the quite different procedure of fitting an empirical relationship to a set of data derived from conductivity measurements on an analogous system of conductors in an electrolytic tank was published. In a later paper, these authors used this formula to calculate a correction term in the radiation pattern of a transmission line antenna which they also confirmed by experiment (see IEEE Trans. Antenna and Propag., vol. 38, no. 4, p. 575-8, 1990). Getsinger does not reference Green and Cashman who, at the time of carrying out their work, were equally unaware of King's earlier attack on the problem. It is interesting to compare the Getsinger and Green and Cashman solutions for the light which it throws on expectations of their likely accuracy. The two solutions use different notation and require algebraic manipulation to bring them into a form for comparison. This is done in a form which conforms essentially to the notation used by Getsinger. In reply Getsinger considers that the authors of the above letter seem to have observed that the end capacitance formulas apply to quite different physical structures, and would not be expected to yield the same values. Nevertheless, he thinks the letter serves a valuable purpose in introducing for discussion a little appreciated distinction (for end capacitance considerations) between two-conductor lines, and in leading to a new and useful result: an expression for the end capacitance of a two conductor line made of thick-walled hollow tubing View full abstract»

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  • TEM coupling between orthogonal crossing wires: a closed-form approximation

    Page(s): 884 - 890
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    The equations describing the coupling mechanism between two crossing, orthogonal thin wires over a perfectly conducting ground plane are derived from first principles. Cast in the form of two cross-coupled Fredholm integral equations of the second kind, the equations are manipulated in such a way as to show the nature of the coupling between the TEM modes, the evanescent modes and the radiation terms. The assumption is made that the coupling between the evanescent and radiation terms to the TEM mode is weak after the first wave bounce. By neglecting such effects, we derive a closed-form approximation for the equivalent lumped junction capacitances. The resulting expressions are surprisingly simple and are amenable to desktop calculation. The final formulas are numerically compared with previously published data View full abstract»

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  • General noise analysis of nonlinear microwave circuits by the piecewise harmonic-balance technique

    Page(s): 807 - 819
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    This paper presents a self-consistent set of algorithms for the numerical computation of noise effects in forced and autonomous nonlinear microwave circuits. The analysis relies upon the piecewise harmonic-balance method, and thus retains all the peculiar advantages of this technique, including general-purposeness in the widest sense. The noise simulation capabilities include any kind of forced or autonomous nonlinear circuit operated in a time-periodic large-signal steady state, as well as microwave mixers of arbitrary topology. The limitations of the traditional frequency-conversion approach to noise analysis are overcome. The analysis takes into account the thermal noise generated in the passive subnetwork, the noise contributions of linear and nonlinear active devices, and the noise injected by sinusoidal driving sources of known statistical properties. The nonlinear noise models of two representative families of microwave devices (FET's/HEMT's and Schottky-barrier diodes) are discussed in detail, and several applications are illustrated View full abstract»

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  • Complex image method for sources in bounded regions of multilayer structures

    Page(s): 860 - 865
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    Other researchers have employed complex image theory to rapidly evaluate spatial-domain Green's functions in layered media. While workable in instances where the source lies within or at the interface of an unbounded region, the more general methodology given for a source embedded in a dielectric layer is incorrect. This paper explains the nature of the error and how it can be corrected View full abstract»

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  • A 75 GHz to 115 GHz quasi-optical amplifier

    Page(s): 899 - 901
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    A wideband quasi-optical amplifier employing two pyramidal back-to-back horns has been developed. Using a four-stage W-band low noise amplifier (LNA) designed and fabricated by Martin Marietta Laboratories, the quasi-optical amplifier gives a system gain greater than 11 dB from 86 GHz to 113 GHz without any low frequency oscillations. A peak system gain of 15.5 dB is measured at 102 GHz, and the measured noise figure of the system is 7.4 dB at 94 GHz. The quasi-optical amplifier design maintains the same polarization of the received and transmitted signal, provides better than -40 dB isolation, and can be fabricated monolithically at millimeter-wave frequencies View full abstract»

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  • Maximum and minimum return losses from a passive two-port network terminated with a mismatched load

    Page(s): 787 - 792
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    An analytical expression is derived for determining load-reflection coefficient phase-angle values that will lead to maximum and minimum return losses from a terminated two-port network. The expression is derived in terms of two-port network S-parameters and a load whose reflection-coefficient magnitude is a constant but can be any value greater than zero and less than or equal to unity. The equation is useful for cases where it is desirable to know how to position a load (1) to obtain maximum return loss for network-matching purposes or (2) to obtain minimum return loss for some types of reflector antenna applications. Two examples are given: One shows that for some types of reflector antennas with a mesh-type surface that is backed by another reflecting surface, a resonance phenomenon can occur and cause unexpectedly large dissipative losses (>30 dB) to occur. The other example shows that when a particular type of reflector antenna with a dielectric layer becomes wet from rain or condensation, large (>10 dB) signal losses can occur. For both examples, equations presented in this article were used to calculate the exact load-reflection coefficient phase values that led to worst-case return loss values. In practical situations, once the phenomenon is understood and predictable, steps can be taken to avoid these resonance regions View full abstract»

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  • A new structure of microwave ultrawide-band differential phase shifter

    Page(s): 762 - 765
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    A new structure for TEM transmission line ultrawide-band differential phase shifters is proposed. This consists of a cascade of two-ports, each of which is a single coupled section with parallel transmission lines connected to each other at one end. The section lengths and coupling coefficients are different. The results of numerical synthesis have been tabulated for phase shifters of 90 degrees differential phase shift. The proposed structure has the advantage of a lower coupling coefficient and improved phase-frequency characteristic in comparison with the other stepped phase shifters View full abstract»

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  • FDTD method coupled with FFT: a generalization to open cylindrical devices

    Page(s): 870 - 874
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    The extension of a numerical method, based on an FDTD algorithm coupled with FFT, is presented. It can be widely applied to the analysis of axially symmetric passive microwave devices. By incorporating the proper radiation conditions in the algorithm, its capacity to deal with the study of open systems is shown; this allows the determination of its quality factor, as well as the resonant frequency and the spatial distribution of the modes. On the other hand, the proper performance of the technique has been verified (stability of the algorithm, accuracy of results) for modes of high angular dependence View full abstract»

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  • Infrared fiberoptic temperature control of the heating process in a microwave oven

    Page(s): 901 - 903
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    An infrared (IR) fiberoptic temperature sensor was used to monitor non-uniform heating of biological samples. The developed system allows the monitoring of temperature with an accuracy of ±0.5°C and can be very useful for medical, industrial and domestic applications View full abstract»

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  • Nonsquarelaw behavior of diode detectors analyzed by the Ritz-Galerkin method

    Page(s): 840 - 846
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    It is widely believed that diode detectors exhibit true square-law behavior at low power levels, and that at higher power levels there is a gradual change to a linear (peak-detecting) law. This paper demonstrates that this idea is correct only under restrictive conditions, and that slopes corresponding to eighth and higher-order laws can easily be encountered in practical situations. It is shown that these high-order slopes are inherent in conventional diode detector circuits and that the behavior can be predicted by a closed-form solution involving both exponential and modified Bessel functions. The nonlinear theory, which does not depend on a truncated power-series approximation to the diode I-V characteristic, is confirmed by measured data View full abstract»

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  • The method of lines analysis of striplines with double-layered or suspended bianisortropic biaxial substrates

    Page(s): 917 - 920
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    The method of lines (MoL) is extended to study propagation properties of microstrip transmission lines printed on double-layered and suspended bianisotropic biaxial substrates. Unlike previous formulations, the MoL presented here is based on coupled governing equations that are expressed in terms of two components of the electric field which are tangential to interfaces between planar isotropic and anisotropic regions. Numerical results presented in this paper show which elements of permittivity and permeability tensors most significantly affect dispersion characteristics of widely used microwave and millimeter-wave integrated circuit (MIC) transmission lines View full abstract»

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  • FDTD simulation of microwave sintering of ceramics in multimode cavities

    Page(s): 793 - 800
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    Microwave sintering of ceramics in multimode cavities, particularly the use of picket-fence arrangements, has recently received considerable attention. Various types of ceramics have been successfully sintered and, in some cases, a desirable and unique “microwave effect” has been observed. At present, various aspects of the sintering profess such as preparation of sample sizes and shapes, types of insulations, and the desirability of including a process stimulus such as SiC rods are considered forms of art and highly dependent on human expertise. The simulation of realistic sintering experiments in a multimode cavity may provide an improved understanding of critical parameters involved and allow for the development of guidelines towards the optimization of the sintering process. In this paper, we utilize the FDTD technique to model various geometrical arrangements and material compatibility aspects in multimode microwave cavities and to simulate realistic sintering experiments. The FDTD procedure starts with the simulation of a field distribution in multimode microwave cavities that resembles a set of measured data using liquid crystal sheets. Also included in the simulation is the waveguide feed as well as a ceramic loading plate placed at the base of the cavity View full abstract»

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  • A block iterative technique to expand MMP's applicability to EM problems of higher complexity

    Page(s): 875 - 883
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    The present multiple multipole (MMP) approach exhibits limitations with problems of higher complexity. Its dense and strongly overdetermined system of equations is badly conditioned even for smaller problems such that only expensive, more stable QR decomposition methods can generally be applied. With growing complexity and size of the problem, the matrix often becomes near-rank deficient. Additionally, the performed row and column weighting is unsatisfactory if the averaged power density values vary strongly throughout the boundaries. Some of these limitations can be avoided by using the iterative technique introduced here. It is shown that these systems of equations can easily be built and partitioned according to physical considerations in such a way that diagonally dominant block matrices are obtained. For many problems, a few block Gauss-Seidel or successive block overrelaxation (SBOR) steps produce a sufficiently converged solution. Even more significant than the numerical advantage is the fact that this technique opens new possibilities for the modeling and the validation of solutions and therefore considerably facilitates and extends the applicability of the MMP code to a larger spectrum of problems. Furthermore, the alternating procedure presents new possibilities for directly coupling MMP with other codes, such as finite difference (FD) and method of moments (MoM) View full abstract»

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  • Analytical analyses of v, elliptic, and circular-shaped microshield transmission lines

    Page(s): 855 - 859
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    Several new types of monolithic coplanar transmission lines, v, elliptic, and circular-shaped microshield coplanar waveguide, have been proposed. The characteristic impedance expressions for those transmission lines have been derived using the conformal mapping method (CMM) under the assumption of the pure-TEM propagation and zero dispersion. In the analyses of the elliptic and the circular-shaped microshield coplanar lines, the methods using the graphical approximation and taking the geometric mean value of the upper and the lower bounds to the size of the line are put forward to calculate the characteristic impedance of this two kinds of microshield coplanar lines. The numerical results show the effects of the different shaped microshield walls on characteristic impedances View full abstract»

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  • Optimum design of nonlinear microwave circuits

    Page(s): 779 - 786
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    This paper reports a direct optimization method of nonlinear circuits. The procedure consists in determining in the power space, a surface including all the extremum allowed powers at terminal ports of each nonlinear component of the circuit. According to the required nonlinear function, an appropriate choice of the tangent planes to this surface allows to calculate the optimum loads for the nonlinear components. This method optimizes the parameters of nonlinear devices without any constraint on the circuit. A small signal analysis is then taken in order to deduce the optimum performance of the nonlinear designed circuit. The realization of a single balanced diode mixer has shown good agreement between the calculated values and the experimental results View full abstract»

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  • Analysis of wide inclined slot coupled narrow wall coupler between dissimilar rectangular waveguides

    Page(s): 914 - 917
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    Analysis of a waveguide coupler coupled through a wide inclined slot in the common narrow wall of a rectangular waveguide for high power applications is presented. A simplified technique to find the internal scattered magnetic field due to this wide inclined slot has been used. Both variational method and method of moments using entire domain basis functions and Galerkin's technique have been used in finding out the S parameters of the four port coupler. The experimental results have shown good agreement with the corresponding theoretical results View full abstract»

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  • Slit coupled E-plane rectangular T-junctions using single port mode matching technique

    Page(s): 903 - 907
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    A new simple mode matching method, called single port mode matching technique (SPMMT) for modeling rectangular waveguide T-junctions is presented. The reflection coefficient at port 2 (side arm of the T-junction) is computed with both ports 1 and 3 shorted. The three-port scattering matrix of the T-junction is obtained from nine reflection coefficient computations using different short circuit lengths in ports 1 and 3. This method is rigorous, simple, reduces the computational effort significantly and can be applied to other structures. Comparison of S-parameters with classical equivalent circuit in Marcuvitz(1951) and new equivalent circuit given by Lampariello and Oliner(1993) is presented. Dependence of S-parameters on the slit thickness is also given. Open T-junctions are analyzed as a special case of the slit T-junction, and the results are in good agreement with experimental measurements View full abstract»

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  • Characterization of a shielded transition to a dielectric waveguide

    Page(s): 847 - 854
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    A shielded sub-mm/THz monolithic transition between a layered dielectric waveguide and a strip-ridge line is characterized using two different approaches: the integral equation-mode matching (IEMM) method and the finite difference time domain (FDTD) technique. While higher order modes are considered, a simple method for determining the transition's circuit model (i.e., two-port scattering matrix) from the IEMM results is implemented and the electrical performance is studied as frequency and conductor width are varied. The FDTD analysis gives further insight into the behavior of the transition in a very wide frequency range (0-540 GHz). The transition is found to be very efficient over a wide frequency band and a broad range of conductor widths View full abstract»

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  • Analysis of pulse dispersion distortion along exponential and Chebyshev microstrip tapers

    Page(s): 834 - 839
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    The voltage and current transfer functions are shown for the tapered line. The dispersion distortion obtained by using these transfer functions are shown for the nonideal square pulse along the exponential taper and the Chebyshev taper. The great and sharp peak in the front of the distorted wave is caused due to the frequency dispersive characteristics of effective relative permittivity. The sustained tail and the ascent of gentle slope in the plateau in the distorted wave are caused due to the multi-reflection in the tapered line and are inherent characteristics in the configuration of taper. The sustained tail starts to vanish after the time of about one and half times of the echo time View full abstract»

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  • InGaAs microwave switch transistors for phase shifter circuits

    Page(s): 772 - 778
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    A new InGaAs insulated-gate FET (IGFET) with 1 μm gate length and three different gate widths has been designed, fabricated and characterized as switch devices for microwave control applications in phase shifter circuits. The devices employed a plasma deposited silicon dioxide gate insulator and had multiple air bridged source regions. The details of the DC current-voltage (I-V) characteristics and small signal S-parameter measurements up to 20 GHz are presented. The switch IGFET's had a drain saturation current density of 300 mA/mm gate width with breakdown voltages of higher than 35 V. An insertion loss of 1.0, 0.6, and 0.4 dB at 10 GHz and 1.4, 0.8, and 0.4 dB at 20 GHz have been measured for the 300, 600, and 1200 μm gate width IGFET's, respectively. Equivalent circuit models fitted to the measured S-parameters for IGFET's yielded on-state resistances from 10.7 to 3.3 Ω, off-state resistances from 734.4 to 186.8 R and off-state capacitances from 0.084 to 0.3 pF as the gate width is increased from 300 to 1200 μm The simulation results using IGFET models for the phase shifter circuits indicated a maximum phase error of 0.11°, 0.26°, and 0.479 with 0.74, 0.96, and 1.49 dB maximum insertion loss and greater than 33, 26, and 19 dB return loss for the 11.25°, 22.5°, and 45° phase bits, respectively, over the 9.5-10.5 GHz frequency band View full abstract»

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  • Computation of external circuit impedance of active devices in a millimeter wave harmonic power combiner

    Page(s): 910 - 914
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    In this note, the external circuit impedance looking outside from two active devices, which are abreast mounted in the rectangular waveguide cavity of a millimeter wave harmonic power combiner, are analyzed and computed by strict field analysis method and the technique uniting Galerkin method with Collocation method. The numerical results are very useful to design the millimeter wave harmonic power combiner and develop its CAD View full abstract»

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  • Performance prediction and optimization of a coherent phase modulated low noise analog optical link operating at microwave frequencies

    Page(s): 801 - 806
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    Analog optical communication links operating at microwave frequencies are useful for applications like antenna remoting, transceivers, optical signal distribution (CATV), etc. In recent years great progress has been achieved on AM optical links, however, very little has been published on the use of coherent optical links for analog applications. In this paper, we present the analysis, calculated performance, and design guidelines for a coherent phase modulated analog optical link. The performance of this link is compared to that of AM links, and a substantially improved performance is predicted View full abstract»

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The IEEE Transactions on Microwave Theory and Techniques focuses on that part of engineering and theory associated with microwave/millimeter-wave components, devices, circuits, and systems involving the generation, modulation, demodulation, control, transmission, and detection of microwave signals. This includes scientific, technical, and industrial, activities. Microwave theory and techniques relates to electromagnetic waves usually in the frequency region between a few MHz and a THz; other spectral regions and wave types are included within the scope of the Society whenever basic microwave theory and techniques can yield useful results. Generally, this occurs in the theory of wave propagation in structures with dimensions comparable to a wavelength, and in the related techniques for analysis and design..

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