Equivalent circuit representation of open guided-wave structures

A modular equivalent circuit representation for modeling and analyzing open guided-wave structures, which takes into account both the guided and the continuous spectra, is discussed. In the development of the technique approximations that are valid for integrated optics in III-V compound semiconductors are utilized. The validity of these approximately was assessed on the basis of both physical arguments and numerical simulations. Results obtained with the present method are compared with the results of other methods of analysis for rectangular fiber and rib guides with sloped rib sides. The present method gives accurate results with limited computational effort and can analyze a wide variety of integrated optical components ranging from single waveguides of arbitrary cross-sectional profile to multiple coupled guides of arbitrary widths and spacings     

Equivalent currents for an aperture in an impedance surface

Expressions of equivalent magnetic and electric currents for an aperture in an impedance surface is derived in a self-consistent manner. Each equivalent current consists of the combination of the tangential electric and magnetic fields in the aperture, and is placed in front of the original aperture where the surface is extended to close the aperture. The result is particularly useful for problems involving apertures in an impedance ground plane     

Equivalent circuit modelling of lossy coupled lines using SPICE software

A new skin effect equivalent circuit and a propagation line equivalent circuit for time domain simulation on a single line have been presented in previous work (T. Vu Dinh et al., 1990) SPICE simulations have proved the accuracy and efficiency of the proposed method. This concept is extended for coupled line modelling. A dual line device is analysed as a typical example of the usual cases. The method has successfully been extended to N lossy coupled lines. The results show a good agreement with those obtained by other methods.<>     

Analysis of an aperture coupled microstrip antenna

A microstrip patch antenna that is coupled to a microstripline by an aperture in the intervening ground plane is analyzed. Coupled integral equations are formulated by using the Green's functions for grounded dielectric slabs so that the analysis includes all coupling effects and the radiation and surface wave effects of both substrates. A Galerkin moment method solution of the coupled integral equations agrees quite well with measured data. Design data are contained in parameter studies, many of which are verified by experimental results.     

Equivalent circuit of an evanescent-mode inductive element

By the use of a partial-fraction expansion of the propagation constant in terms of the angular frequency, a successive series of equivalent-circuit approximations is obtained for the parallel element in the II representation of a length of evanescent-mode waveguide. The first of these approximations simply adds a parallel capacitance to the low-frequency inductance, an element which can be readily absorbed into any tuning capacitor which may be required. The third-order approximation can be put in various forms, some of which similarly exhibit a parallel capacitive element.     

Equivalent circuit parameters of resonant tunneling diodesextracted from self-consistent Wigner-Poisson simulation

The equivalent circuit parameters of resonant tunneling diodes (RTD) are extracted from numerical simulation results for RTDs. The RTD models used in this paper are double barrier structures. The influence of the resonant tunneling structure (RTS) parameters, such as the height of barriers, the width of the quantum well, the width of the spacers, and the width of the barriers, on the device parameters are systematically discussed. The effects of device temperature on device parameters are also discussed. Scattering between electrons and phonons greatly affects device parameters and thereby the function of the RTDs. Physical explanations about how the structure parameters and device temperature influence the device parameters are provided. Based on the analysis results, a general way to get an RTD oscillator with a higher maximum frequency is suggested     

Equivalent network for an aperture in the center conductor ofmicrostrip line

The equivalent circuits for discontinuities in the form of a thin transverse slot and a circular aperture in the center conductor of a microstrip line are determined by a quasi-static analysis using equivalent dipole moments. The series reactance as a function of frequency is evaluated in terms of the geometrical parameters of the discontinuity. Data obtained from transmission measurements are presented to support the theory     

Analysis of an infinite phased array of aperture coupled microstrippatches

An analysis of an infinite array of aperture-coupled microstrip patch antennas is described; this type of element is well suited to integrated phased-array applications, offering several advantages over other array configurations. The solution uses the spectral-domain moment-method approach, and combines features of a previous solution of infinite arrays of probe-fed patches and a reciprocity analysis of single-aperture-coupled microstrip element. The theoretical analysis is described and data are presented for the active input impedance of several arrays. Experimental data from a waveguide simulator confirm the theory     

Equivalent circuit formulation for an array of phased waveguide apertures

An expression for the radiation admittance of an infinite planar array of rectangular waveguide apertures is formulated and a technique for finding the complete equivalent circuit of the waveguide to space junction is given. The formulation includes multiple layers of dielectric above the array ground plane and waveguide elements which are center loaded with dielectric. Experimental verification of the radiation admittance formulation and the equivalent circuit concepts is given.     

Equivalent current excitation for an aperture antenna embedded in an arbitrarily shaped impedance surface

It is demonstrated, via the equivalence principle, that if the aperture fields are known, one can explicitly obtain the equivalent current excitation required for modeling an aperture in an arbitrarily shaped impedance surface, when the aperture surface is closed, by replacing it with an impedance surface. It is also demonstrated that the impedance condition over the antenna body and the closed aperture can be nonuniform and anisotropic and that different choices are possible for the value of the surface impedance of the surface that closes the aperture. It is expected that the procedures described will be most useful in approximately modeling aperture antennas embedded in nonplanar impedance surfaces where the aperture electric field is known.     

Equivalent circuit of transistor mixer

A modified hybrid ? equivalent circuit is developed for the transistor mixer. It is based on input-port measurements and simple theory. This equivalent circuit is valid for a wide range of emitter current and local-oscillator voltage, provided that the local oscillator and signal frequencies are small compared with the ft of the transistor.     

Full-wave aperture coupled patch antenna

An aperture coupled patch antenna with a dual-lobed (cavity mode TM/sub 200/) radiation pattern is described. The antenna employs a full-wavelength long patch fed via a butterfly-shaped aperture and a stripline feed network. This configuration provides high patch to feed network coupling and reduced back radiation. Measured return loss and pattern data are presented with proposals for several potential applications of this element.<>     

Equivalent circuit model of quantum-well lasers

A study of equivalent circuit model of quantum well lasers derived from quantum well rate equation has been carried out. Pulse response simulation results obtained from a SPICE simulator indicates that various modulation properties, e.g., turn-on delay, relaxation oscillation frequency, and on/off aspect ratio, have a substantially different behavior than those of DH lasers. This model offers a fundamental building block for the simulation of the over all signal transmission when using quantum-well lasers as a light source     

Equivalent circuit of microstrip spiral inductor circuit generation by computer

A method of equivalent circuit generation by computer is illustrated using a microstrip spiral inductor as an example. The computer program modifies the circuit topology, adding nodes and components as necessary. Results are compared with a model derived from physical considerations and show a great improvement in performance for a small increase in complexity.     

Multifunctional aperture coupled stack patch antenna

A multifunctional aperture coupled stacked patch antenna is presented that operates at dual frequency bands. At the lower frequency band, the antenna exhibits a 2:1 VSWR bandwidth of 20%, and at the higher frequency band, it behaves like a conventional narrowband patch antenna with a 2:1 VSWR bandwidth of 3%. Measured VSWR and far-field radiation patterns as well as numerical predictions are presented. A proper choice of the patch dimensions has been found critical to achieve this multifunctional performance.<>     

Circularly polarised aperture coupled microstrip antenna

The orthogonal mode of an aperture coupled rectangular microstrip antenna can be coupled to the aperture-excited mode with coplanar microstrip lines to provide a compact circularly polarised element with a single aperture feed. An equivalent circuit model was developed for the analysis and design of this element, and a working version was used to demonstrate the concept. The features of this antenna are compared with several other circularly polarised microstrip antennas     

Equivalent circuit for the acoustoelectric oscillator

An equivalent circuit is proposed for the acoustoelectric oscillator, and results are presented which show that the circuit can provide a good analogue of a practical device. Suppression of oscillations and changes of the resonant frequency were observed when an oscillator was connected to a reactive load. Both of these effects may be explained in terms of the equivalent circuit.     

FDTD analysis of wideband aperture coupled interconnect

Recent developments in high speed chip modules, multilayer printed circuit boards and aperture coupled phased microstrip patch antenna arrays require wideband and cost effective interconnections in frequency bands that are steadily moving upwards in the gigahertz range. The concept of a microstrip aperture coupled interconnect is proposed by the authors and investigated using Gabor excitation in the finite difference time domain (FDTD) and verified through measurements. The surprisingly ultra-wideband and efficient performance of the interconnect and the simplicity of its implementation, mean that it can replace many of the interconnects presently in use     

Equivalent circuit for injection-locked negative-resistance oscillators

Calculations are carried out for a van der Pol type oscillator with external force. It is illustrated how the condition of synchronisation is changed when (i) the admittance of the microwave diode is assumed to consist of an additional voltage-dependent susceptance and (ii) the frequency-determining resonator has a series reactance.     

Equivalent circuit representation of lossy coplanar waveguides

The study of the dispersion properties of planar transmission lines including metallic losses with the generalized transverse resonance method is formalized in building an equivalent network of the cross-section which specifies the relationships between the tangential components of the fields on each side of the interfaces. Virtual sources represent the trial quantities chosen to describe the problem. With twoport type boundary conditions, the trial quantities are not easily defined from physical considerations, but the virtual sources obey to specific rules. This purpose is illustrated in studying the attenuation in lossy suspended coplanar transmission lines.