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Microwave Theory and Techniques, IEEE Transactions on

Issue 4 • Date Apr 2002

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Displaying Results 1 - 25 of 25
  • Asymmetric ring-hybrid phase shifters and attenuators

    Page(s): 1146 - 1155
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (568 KB) |  | HTML iconHTML  

    A new structure of asymmetric ring-hybrid phase shifters and attenuators is presented. Each consists of an asymmetric ring hybrid and reflecting terminations, and it does not have any additional 90° phase delay line for utilizing symmetric reflecting terminations that conventional phase shifters use. To analyze these asymmetric ring-hybrid phase shifters, normalized impedance ratios NIb and NId are introduced, and the possibilities to reduce the size of the reflecting terminations are presented. Using the new structure of the asymmetric ring-hybrid phase shifters, asymmetric ring-hybrid attenuators are synthesized. To analyze the attenuators, normalized resistance ratios NRLb and NRLd are introduced, so that the resistances in the reflection terminations can arbitrarily be determined. On the basis of the derived new structures, a uniplanar asymmetric ring-hybrid -135° phase shifter and a microstrip asymmetric 4-dB attenuator with 45° phase shift have been fabricated and measured. They show good agreement between measured and simulated results and they may be used for impedance transformers besides their original functions View full abstract»

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  • Computer-aided diagnosis and tuning of cascaded coupled resonators filters

    Page(s): 1137 - 1145
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (384 KB) |  | HTML iconHTML  

    A model for the determination of the individual resonant frequencies and inter-resonator couplings of a system consisting of cascaded coupled resonators is presented. Measuring or computing the phase of the reflection coefficient of short-circuit terminated networks synthesizes all the inter-resonator couplings and resonant frequencies. The loading effect on the last resonator due to the unknown position of the short-circuit reference plane is accurately accounted for by a systematic method. A deterministic finite steps tuning method based on the model is developed. The method is proven successful experimentally and the noniterative nature of the method makes fully automatic tuning of filters possible View full abstract»

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  • A new hybrid mode-matching/numerical method for the analysis of arbitrarily shaped inductive obstacles and discontinuities in rectangular waveguides

    Page(s): 1219 - 1224
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (307 KB) |  | HTML iconHTML  

    A new and efficient hybrid mode-matching method is presented for the analysis of arbitrarily shaped inductive obstacles and/or discontinuities in a rectangular waveguide. The irregular region with obstacles and/or discontinuities is characterized using a full-wave hybrid spectral/numerical open-space technique expanding the fields in cylindrical wave functions. Next, a full-wave mode-matching procedure is used to match the cylindrical wave functions to guided modes in all ports and a generalized scattering matrix for the structure is finally obtained. The obstacles can be metallic or dielectric with complex permittivities and arbitrary geometries. The structure presents an arbitrary number of ports, each one with different orientation and dimensions. The accuracy of the method is validated comparing with results for several complex problems found in the literature. CPU times are also included to show the efficiency of the new method View full abstract»

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  • Single-MMIC four-channel transmitter module for multichannel RF/optical subcarrier multiplexed communications applications

    Page(s): 1173 - 1179
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (396 KB) |  | HTML iconHTML  

    Presents a compact single monolithic microwave integrated circuit (MMIC) transmitter module for four-channel RF/optical subcarrier multiplexed (OSCM) communication applications. The developed module consists of one fully monolithic four-channel OSCM transmitter integrated circuit (IC) and four coupled-line filters. The MMIC is designed and implemented in a commercial 0.6-μm GaAs MESFET process and five-stage coupled-line filters are fabricated for each of the four channels on the module board. The module design and bit-error-rate performance are considered. This is the first fully monolithic IC transmitter module for OSCM communications applications View full abstract»

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  • A dual-plane comb-line filter having plural attenuation poles

    Page(s): 1216 - 1219
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (288 KB) |  | HTML iconHTML  

    In this paper, a dual-plane comb-line filter having plural attenuation poles is proposed. We investigate the filtering characteristics from both experiments and numerical simulations by means of the finite-difference time-domain method. It is shown that this filter has attenuation poles just above, as well as below the passband and that intersections between the curves of input susceptance of the even and odd modes agree with the attenuation-pole frequencies. Furthermore, it is demonstrated that, by changing the position of the metal pin, which connects two resonators, we can change the input susceptance of the odd mode alone and, hence, regulate the attenuation-pole frequencies View full abstract»

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  • A balanced FET FMCW radar transceiver with improved AM noise performance

    Page(s): 1224 - 1227
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (253 KB) |  | HTML iconHTML  

    A balanced FET frequency-modulated continuous-wave radar transceiver designed to suppress AM noise is presented. The transceiver utilizes the same device for output power amplification as for down-conversion of the received signal, thereby avoiding the need for separation of these signals. This makes the transceiver suitable for integration in monolithic-microwave integrated-circuit technology. A test circuit operating at 10 GHz was designed. The AM noise suppression is characterized, as well as output power and noise performance. Comparison with an unbalanced transceiver using the same principle of operation shows an improvement of 20 dB in AM noise performance. The output power is 14 dBm at 7-dBm input power View full abstract»

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  • Analysis of balanced active doubler for broad-band operation - the frequency-tuning concept

    Page(s): 1120 - 1126
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (330 KB) |  | HTML iconHTML  

    A comprehensive analysis of an active balanced frequency doubler is described and proposed as a new concept: tuning the center frequency at which the doubler exhibits its highest performance to extend the usable bandwidth of the device. The concept is validated using a fabricated V-band pseudomorphic high electron-mobility transistor frequency doubler. For this device, a substantial improvement in the usable bandwidth (more than double) is achieved, demonstrating that the proposed concept is particularly suitable for the realization of high spectral purity and widely tunable V-band frequency sources View full abstract»

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  • A fast noise and Z-parameter transformations between common emitter and common base InP DHBT

    Page(s): 1109 - 1113
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (239 KB) |  | HTML iconHTML  

    A new approach has been developed that uses only a simple set of formulas to transform noise and Z-parameters between common emitter and common base configurations. This technique is based on the typical T-model of InP double-heterojunction bipolar transistor and calculated results agree with the experimental results, demonstrating that this approach is useful for many broad-band low-noise communication circuit designs View full abstract»

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  • Electromagnetic scattering by metallic holes and its applications in microwave circuit design

    Page(s): 1198 - 1206
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (423 KB)  

    The problem of arbitrarily incident plane-wave scattering from rod structures of thick conducting plates arranged with two-dimensional (2D) periodicity has been examined. The square approximation as well as truncated-square approximation of circular cross sections is used in this study. The impedance of cascaded screens and the reflection coefficient is calculated using the multimodal variational method for both TE- and TM-polarized incident electric field. The 2D periodic structure of holes described in this paper can be used for the purpose of designing new guiding microwave structures. A transverse resonance method is applied to solve this problem. The convergence behavior of the technique has also been examined. The numerical results of the reflection coefficient, surface impedance, and dispersion curves are presented View full abstract»

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  • Large-signal modeling and characterization of high-current effects in InGaP/GaAs HBTs

    Page(s): 1084 - 1094
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (431 KB) |  | HTML iconHTML  

    High-current effects in InGaP/GaAs heterojunction bipolar transistors (HBTs) were modeled and characterized. In addition to the self-heating effect, high currents were found to degrade large-signal performance mainly through Kirk and quasi-saturation effects. New formalisms in terms of base transit time and base-collector diffusion capacitance were used to modify the conventional Gummel-Poon model. This new model was verified against large-signal characteristics measured at 2 GHz. The validity of the new model for HBTs of different emitter geometry was also explored View full abstract»

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  • A microwave gyro amplifier with a ferroelectric cathode

    Page(s): 1227 - 1230
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (222 KB) |  | HTML iconHTML  

    A ferroelectric cathode is employed for the first time as the electron-beam source in a microwave amplifier tube. A PLZT 12/65/35 ferroelectric ceramic with a high dielectric constant (εr ~4000) is used in a form of a hollow cathode. The tube is operated in poor vacuum conditions (2×10-5 Torr) at room temperature, in a mechanism of a cyclotron-resonance maser amplifier. The device operates near the waveguide cutoff frequency at 6927 MHz. A 22-dB electronic gain and a 25-W output power are measured in this experiment View full abstract»

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  • A high-power and high-gain X-band Si/SiGe/Si heterojunction bipolar transistor

    Page(s): 1101 - 1108
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (329 KB) |  | HTML iconHTML  

    A double mesa-type Si/SiGe/Si (n-p-n) heterojunction bipolar transistor (HBT) with record output power and power gain at X-band (8.4 GHz) is demonstrated. The device exhibits collector breakdown voltage BV CBO of more than 24 V and a maximum oscillation frequency f max of 37 GHz. Under continuous-wave operation and class-AB biasing conditions, 24.2-dBm (263-mW) RF output power with concurrent gain of 6.9 dB is measured at the peak power-added efficiency (28.1%) from a single ten-emitter fingers (780-μm2 emitter area) common-base HBT. The maximum RF output power achieved is as high as 26.3 dBm (430 mW in saturation) and the maximum collector efficiency is 36.9%. The low collector doping concentration together with the device layout result in negligible thermal effects across the transistor and greatly simplifies the large-signal modeling. The conventional Gummel-Poon model yields good agreement between the modeled and the measured de characteristics and small-signal S-parameters. The accuracy of the model is further validated with the measured power performance of the SiGe power HBT at X-band. These results set a benchmark for power performance for SiGe-based HBTs and indicate promise for their implementation in efficient X-band power-amplifier circuits View full abstract»

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  • Full-wave design and optimization of circular waveguide polarizers with elliptical irises

    Page(s): 1077 - 1083
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (295 KB) |  | HTML iconHTML  

    We describe the design and optimization of a new polarizer structure realized in circular waveguide with insertion of elliptical irises. The device is compact, showing a considerable reduction in size and weight when compared to previously known realizations. It requires manufacturing by milling techniques only and, since it is composed entirely by waveguides with separable cross sections, it is also well suited for electromagnetic modeling. Measured and theoretical results for a polarizer with a 90°±1° differential phase shift and a return loss better than 35 dB for both polarizations over the operating frequency band confirm the validity of the proposed design View full abstract»

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  • Device-level simulation of wave propagation along metal-insulator-semiconductor interconnects

    Page(s): 1127 - 1136
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (343 KB) |  | HTML iconHTML  

    A device-level simulation is presented for studying wave propagation along metal-insulator-semiconductor interconnects. A set of nonlinear equations is first formulated by combining the motion equations of charged carriers and Maxwell's equations. The set of nonlinear equations is then transformed into the frequency domain, which leads to sets of nonlinear equations for the fundamental mode and its harmonics. Finally, the sets of nonlinear equations in the frequency domain are discretized using the finite-element method and solved using Newton's iterations. Special numerical enhancements are implemented to speed up the computational convergence and handle the boundary layer nature of the problem under study. This device-level simulation provides knowledge on field-carrier interactions, semiconductor substrate loss, and nonlinearity, as well as slow-wave and screening effects of charged carriers. This device-level simulation scheme enables a rigorous full-wave study of nonlinearity effects that arise from semiconductor substrates. Numerical examples for some practical material and geometrical parameters are included to illustrate capabilities and efficiency of the proposed device-level simulation scheme View full abstract»

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  • Application of the SSOR preconditioned CG algorithm to the vector FEM for 3D full-wave analysis of electromagnetic-field boundary-value problems

    Page(s): 1165 - 1172
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (349 KB) |  | HTML iconHTML  

    The symmetric successive overrelaxation (SSOR) preconditioning scheme is applied to the conjugate-gradient (CG) method for solving a large system of linear equations resulting from the use of edge-based finite-element method (FEM). For this scheme, there is no additional computing time required to construct the preconditioning matrix and it contains more global information of the coefficient matrix when compared with those of the banded-matrix preconditioning scheme. The efficient implementation of this preconditioned CG (PCG) algorithm is described in details for complex coefficient matrix. With SSOR as the preconditioner and its efficient implementation in the CG algorithm, this PCG approach can reach convergence in five times CPU time shorter than CG for several typical structures. By comparison with other preconditioned techniques, these results demonstrate that SSOR preconditioning strategy is especially effective for CG iterative method when an edge FEM is applied to solve large-scale time-harmonic electromagnetic-field problems View full abstract»

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  • Field-extracted lumped-element models of coplanar stripline circuits and discontinuities for accurate radiofrequency design and optimization

    Page(s): 1207 - 1215
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (377 KB) |  | HTML iconHTML  

    Presents original lumped-element models of a large variety of coplanar stripline (CPS) circuits and discontinuities for accurate design and optimization of radiofrequency integrated circuits. These circuit models are extracted by applying a recently proposed deembedding technique called short-open calibration to calibrate the calculated field parameters obtained from the full-wave method of moments (MoM). It is realized by defining the two calibration standards, i.e., short and open elements, to evaluate and remove the error terms existing in the deterministic MoM algorithm, such as the approximation of port discontinuity and inconsistency of two-dimensional and three-dimensional characterizations of CPS external lines. In contrast to the static models, these field-extracted models can account for all the physical effects subject to the core area of CPS discontinuity, including frequency dispersion, high-order modes, and radiation loss. With this scheme, several CPS circuits and discontinuities are investigated over a wide frequency range to formulate their lumped-element models View full abstract»

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  • Wide-band equal-ripple filters in nonuniform transmission lines

    Page(s): 1114 - 1119
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (258 KB) |  | HTML iconHTML  

    In this paper, a novel method to realize equal-ripple filters over microwave frequencies is presented. All networks are implemented by using cascade serial and shunt transmission-line sections having the same electrical length. The transfer functions of such networks are formulated in the Z domain. In particular, it can be shown that some shunt components are able to contribute zeros locating on the unit circle if the components are open circuited. Due to the feature of transfer-function zeros locating on the unit circle, we may use an optimization procedure to implement equal-ripple filters. Both low-pass and bandpass filters are realized in the form of microstrip lines and their frequency responses are measured to validate this novel method View full abstract»

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  • A novel drain current I-V model for MESFET

    Page(s): 1188 - 1192
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (248 KB) |  | HTML iconHTML  

    The conventional approach for modeling the dc I-V characteristics of a MESFET transistor usually adopts the hyperbolic tangent dependence on Vds. On the contrary, our new empirical model describes the device drain current as a polynomial of effective gate-source voltage Veff. The derived model is capable of accurately modelling the subthreshold effect and the device current-voltage behavior at different operating regions, in particular, the device operation around the pinchoff region. Measured and modeled results of a 0.5-μm gatelength MESFET device are compared and good agreement has been obtained. Comparisons between the proposed model, Curtice model, Chalmers model, and Parker model are also made in this paper. In addition, a single-stage class-AB amplifier was built with a commercial high-power MESFET transistor to verify the new model View full abstract»

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  • Analysis of the numerical dispersion of the 2D alternating-direction implicit FDTD method

    Page(s): 1156 - 1164
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (381 KB) |  | HTML iconHTML  

    The numerical dispersion property of the two-dimensional alternating-direction implicit finite-difference time-domain (2D ADI FDTD) method is studied. First, we notice that the original 2D ADI FDTD method can be divided into two sub-ADI FDTD methods: either the x-directional 2D ADI FDTD method or the y-directional 2D ADI FDTD method; and secondly, the numerical dispersion relations are derived for both the ADI FDTD methods. Finally, the numerical dispersion errors caused by the two ADI FDTD methods are investigated. Numerical results indicate that the numerical dispersion error of the ADI FDTD methods depends highly on the selected time step and the shape and mesh resolution of the unit cell. It is also found that, to ensure the numerical dispersion error within certain accuracy, the maximum time steps allowed to be used in the two ADI FDTD methods are different and they can be numerically determined View full abstract»

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  • An accurate photonic capacitance model for GaAs MESFETs

    Page(s): 1193 - 1197
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (255 KB) |  | HTML iconHTML  

    A new set of pseudoempirical equations is presented in order to simulate the optical and bias dependencies of GaAs MESFET junction capacitances, which is valid for the whole I-V plane. The variations induced in the small-signal equivalent circuit by the optical illumination are extracted from on-wafer scattering parameter measurements. New linear and quasi-logarithmic variations versus the incident optical power are shown for gate-drain and gate-source (Cgd and Cgs) capacitances. Furthermore, experimental results are in very good agreement with the simulated values for a wide range of optical power and bias conditions. Large signal MESFET models show a better fit with measured S-parameters than those previously published, leading to a greater degree of confidence in the design of photonic monolithic microwave integrated circuits View full abstract»

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  • Six-port self-calibration based on active loads synthesis

    Page(s): 1237 - 1239
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (195 KB) |  | HTML iconHTML  

    An automatic method for self-calibrating six-port reflectometers is reported in this paper. It is based on the use of an active impedance synthesis system. This self-calibration method allows a completely autonomous operation, reduces measurement errors caused by the frequent connecting and disconnecting of calibration standards, and is suitable for low and high frequencies, where sliding shorts are difficult to manufacture. In addition, it simplifies operation of six-port reflectometers to nonspecialized users. The experimented impedance synthesis presented relies on an in-phase and quadrature vector modulator, and the entire system is computer controlled View full abstract»

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  • Attenuation characteristics in confocal annular elliptic waveguides and resonators

    Page(s): 1095 - 1100
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (308 KB) |  | HTML iconHTML  

    The perturbation method is used to obtain the attenuation constant and Q-factor of several TEM, TE, and TM modes in confocal annular elliptic waveguides (CAE-Ws) and confocal annular elliptic resonators (CAE-Rs). Normalized attenuation and Q-factor charts are given for a variety of possible combinations of the focal distance and the eccentricities. Comparisons between the first higher mode in a CAE-W and a coaxial waveguide with the same cutoff frequency and cross-sectional propagating area reveals a lower attenuation in elliptic geometry. Consequently, the Q-factor in a CAE-R is 20%-40% greater than a Q factor for a coaxial resonator with the same volume and resonant frequency View full abstract»

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  • A novel tap input coupling structure for a narrow bandpass filter using TM010 mode of a microstrip circular-disk resonator

    Page(s): 1230 - 1232
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (314 KB) |  | HTML iconHTML  

    This paper discusses a new method to couple into the TM010 mode of a microstrip circular-disk resonator. This method can achieve reasonably strong input coupling, which is useful for narrow-band filters with fractional bandwidths of approximately 0.5% and above. A comparison between this newly proposed input coupling structure and the conventional gap input coupling structure will be addressed. A decision threshold for using either the tap input or the conventional gap-coupled input is also explained. Experimental results of a filter fabricated using this novel input coupling structure is also presented View full abstract»

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  • A genetic algorithm for the evaluation of material parameters of compound multilayered structures

    Page(s): 1180 - 1187
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (327 KB) |  | HTML iconHTML  

    Presents a new method to obtain the material parameters of each single layer in a multilayered structure. The compound structure has to be measured over frequency or for different incidence angles in the microwave frequency range. The genetic algorithm for parameter extraction from the reflection or transmission measurement data is based on a simplified evolution strategy. In this paper, the evolution optimization is described briefly and is verified by measurements performed in the frequency range from 115 to 145 GHz. The parameters obtained by the algorithm show good agreement with reference values gained by other researchers View full abstract»

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  • The ψo=constant mode in free-space and conical waveguides

    Page(s): 1233 - 1237
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (329 KB)  

    ψo=constant is one of the Neumann eigenfunctions used to expand the axial H component in a cylindrical waveguide. It cannot be omitted, lest erroneous results are obtained in, for example, aperture coupling with the exterior region. This paper investigates whether the same situation holds for a conical waveguide, and extends the analysis to free space, which may be considered as a radial waveguide 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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