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Infrastructure elements to produce microwave engineers and to promote microwave research and development in the Asia-Pacific region are described by active professors and researchers in this area as a multiauthor forum. The content of each description focuses mainly on the role of present-day universities, government, and industry. Index Terms--APMC, Asia-Pacific, Australia, China, government, India, industry, infrastructure, Japan, Korea, microwave, Singapore, Taiwan, Thailand, university.

A numerical algorithm for the analysis of transient electromagnetic fields in planar structures is proposed based on the time-domain magnetic-field integral equation (MFIE), electric-field integral equation (EFIE), and the marching-on-in-time approach. The field vectors are represented in terms of vector potential functions which are calculated either by integration or by the three-dimensional (3-D) wave equation according to the geometry of the structure. Thus, the algorithm combines the advantages of integral equation techniques and finite-difference schemes. While this approach is applicable to any geometries, it is especially suitable for multilayered planar structures and is competitive to the finite-difference time-domain (FDTD) method in the case of open and radiating problems. Theoretical results are verified by the analysis of a pulse propagation in a homogeneous open-end microstrip line. Index Terms - Integral-equation method, time-domain analysis.

The buried microstrip line (BMSL) is a promising transmission line structure for realizing low crosstalk characteristics. The measured crosstalk characteristics of model BMSL's have shown good agreement with the estimated ones based on the rectangular boundary division method and the finite-difference time-domain (FDTD) method, indicating that these calculation methods are appropriate for estimating the performance of BMSL's. These results also confirm our expectation that BMSL's have extremely low crosstalk characteristics such as -100 dB in real circuits at high microwave frequencies. The basic circuit components to construct high-density microwave circuits using BMSL's, couplers, stub matching circuits, and gap-coupled resonance filter circuits, were fabricated and experimentally evaluated.

This paper describes the characterization of a guided wave structure, buried microstrip line (BMSL), which is considered to be promising for constructing high-density microwave and millimeter-wave integrated circuits because of its high isolation characteristics. The BMSL includes a dielectric medium surrounded by ground conductor walls and a strip conductor on the top of the dielectric. The BMSL structure is characterized by the two methods, the rectangular boundary division (RBD) method and the finite-difference time-domain (FDTD) method. The RBD method is employed to obtain basic parameters of the BMSL such as characteristic impedances and coupling coefficients over a wide range of line sizes taking advantages of its high calculation efficiency. On the other hand, the FDTD method has been used for more detailed characterization such as the frequency performances of stub matching circuits. The FDTD method is also used to confirm the validity of the quasi-TEM wave approximation which the RBD is based on. The analysis results reveal that the BMSL structure possesses much lower coupling coefficients than a conventional microstrip line does, from -15 dB to -100 dB depending on their burial depths.

Two types of tight-coupling, broadband directional couplers employing open broadside-coupled coplanar waveguides (BC CPW's) are proposed which can easily be integrated with printed strip antennas. The first type uses the BC CPW's with dielectric overlays above and below the center substrate, while the second type uses the nonuniform BC CPW's. The scattering parameters of these directional couplers are derived with the even-odd mode analysis method based on the quasi-TEM wave approximation. Two 3-dB directional couplers, one for each type, are designed and measured characteristics are compared with theoretical results.

This paper describes the theoretical and experimental investigation of a scheme for microwave generation using laser heterodyne. The frequency of the generated microwave is controlled by changing the frequency difference between two temperature-controlled semiconductor laser diodes. The phase difference between the two microwaves is controlled by changing the difference between the two states of polarization of two laser beams. An attractive feature of this scheme is its easy and independent controllability in frequency and phase.

A boundary integral equation method is applied to the full-wave analysis of conductor-backed coplanar waveguides with a rectangular or trapezoidal conductor cross-section. Due to a particular choice of Green's functions for each subregion defined in a given cross-section, electromagnetic fields in each subregion are analytically expressed in terms of equivalent magnetic currents on apertures and resulting integration contours are defined only on aperture surfaces. Consequently, this approach can overcome relative convergence problems even in the case of largely different aperture widths among subregions. Numerical data show that this approach has a stable convergence property and requires a short computation time. Numerical results obtained with this approach are in excellent agreement with other available theoretical data. A series of calculated data for some rectangular and trapezoidal conductor configurations are provided to show the effects of conductor edge profile on transmission properties of conductor-backed coplanar waveguides.

A full-wave characterization of the groove guide having a conductor strip is made based on the mode-matching procedure. All of the constituents of the structure, including a coupling strip, grooves and a radiating open end, are treated in a concise and rigorous way by using the generalized scattering matrix technique. Numerical results show that a set of channel guide leaky modes is also present in this structure in addition to the groove guide leaky mode. The complex propagation behaviors of both the groove guide leaky mode and the channel guide leaky mode are illustrated for various waveguide geometric parameters, and some conclusions regarding the design of leaky wave antennas using this structure are drawn.

An improved analysis method for multiport microstrip annular-ring power-dividers is presented which is essentially based on the planar circuit theory assuming a magnetic walls at conductor edges. The generalized impedance matrix of the power-dividers is evaluated using two approaches, the Green's function approach and the circular harmonic function approach. The concept of effective dimensions is adopted for taking into account fringing fields to compensate the planar circuit theory. The properties of the power-dividers can be controlled by varying the width of the conductor ring in contrast to those of disk structures. Characteristics of a four-port power-divider in the form of microstrip lines calculated with the present approach are in good agreement with experimental data.

Based on the mode-matching procedure, a unified transverse scattering matrix formulation is presented for the characterization of a class of waveguide eigenvalue problems, which include not only closed but also open structures. As examples, calculations are carried out on the dispersion characteristics of ridged waveguides and its variations, nonradiative dielectric (NRD) waveguides, groove guides, microstrip lines, finlines, and coplanar waveguides. Comparisons with published data are made, which verify the versatility and accuracy of this method. Besides its generality, this approach is also superior to some other techniques in simplicity and numerical efficiency.

The propagation and crosstalk properties of picosecond electrical pulses along coupled microstrip lines with arbitrary strip widths are investigated. The current distributions and propagation constants of the dominant c- and Pi-modes in these asymmetric coupled striplines are calculated by using the spectral domain approach; and the full-wave analysis results obtained are incorporated into an FFT algorithm to simulate pulse distortion and crosstalk in the coupled transmission lines. Several samples of asymmetric coupled microstrip lines are fabricated and their characteristics are measured. The results of experiments are found to be in good agreement with those of computer simulations. This paper provides, for the first time, rigorous results of picosecond pulse distortion and crosstalk in asymmetric coupled transmission lines.

The problem of planar transmission lines of arbitrary metallization cross sections is solved by using the generalized transverse resonance technique combined with the mode-matching procedure. Analyses are carried out on the dispersion characteristics of microstrip lines, finlines and coplanar waveguides with trapezoidal strip cross sections. Numerical results verify the versatility and accuracy of this method, and show that the profiles of the metallizations in miniaturized MMIC guiding structures give marked effects on the transmission properties.

A new boundary integral equation method is proposed for the full-wave analysis of suspended planar transmission lines with pedestals and/or finite metallization thickness. Coupled boundary integral equations are formulated on the equivalent magnetic currents only on the apertures of subregions using the Green's identity of the second kind. Because it is possible to take a large number of terms in the series expansion of Green's functions in each subregion independently from the order of resulting matrices, this approach can avoid the relative convergence problem. Numerical results of the present method on suspended coplanar waveguides are found to have a stable convergent property and to be in excellent agreement with other available theoretical results. Numerical data reveal the effects of conductor thickness and aperture width on the transmission properties of suspended planar transmission lines with pedestals.

This short paper describes an efficient method for the determination of resonant frequencies of shielded circular disks and annular ring resonators. Boundary integral equations are set up based on the Green's identity in the circular cylindrical coordinates, and are numerically solved by discretizing common boundary integral paths. The overall integration path is considerably shortened to reduce computation time by using simple eigen functions satisfying regular homogeneous boundary conditions as weighting functions instead of using Green's functions. Computational results for both circular disks and annular rings are presented and compared with other available numerical results for some cases. This method can be extended to treat thick conductors.

In this paper we investigate the propagation and dispersion characteristics of picosecond electrical pulses in a suspended coplanar waveguide (SCPW) and show that the SCPW is a very promising transmission structure for ultra-short pulses with picosecond and subpicosecond durations, compared with conventional coplanar waveguides (CPWs). Numerical results of modal dispersion of the SCPW are presented and compared to those of the conventional CPW, and a field coupling theory is employed to explain the evolution in the dispersion behavior. An evaluation based on the numerical analysis shows that the SCPW with properly controlled dispersion can result in an improvement of about 5 times in pulse transmission capability than the conventional CPW. The propagation of picosecond pulses along the SCPW has been studied by both computer simulations and experimental measurements, both showing a substantial suppression in pulse distortion compared to the case of conventional coplanar waveguides.

A capacitance characterization method for thick-conductor multiple planar ring structures on multiple substrates layers has been made for the first time by extending the rectangular boundary division method. The region to be considered in the analysis is divided into subregions of thick-wall cylindrical tubes in each of which Laplace's equation is solved by the method of the separation of variables. A special application scheme of the boundary conditions is devised to decrease the number of necessary equations. Numerical results are shown for circular disk and planar ring structures in comparison with other available data.

A time-domain vector-potential (TDVP) approach for the analysis of transient electromagnetic fields is proposed in this paper. The field is analyzed by the magnetic VP for which the wave equation is solved by a finite-difference (FD) scheme. The feasibility of the method has been shown by simulations of several transmission-line problems. The results have been compared with reported data obtained by the conventional finite-difference time-domain (FDTD) method, empirical formulas, and measurements. The proposed approach is not inferior to the FDTD method in terms of generality and memory requirements. At the same time, a reduction of central processing unit (CPU) time is achieved because only three scalar wave equations are solved instead of the six Maxwell equations for all field components. It has also been shown that there are certain structures where the components of the magnetic VP are decoupled, which implies the possibility for a consecutive algorithm with reduced memory requirements. Index Terms--Electromagnetic transient propagation, FDTD method, time-domain analysis.

Compared to microstrip lines, suspended strip lines have characteristics of low loss and weak dispersion and are being applied to millimeters-wave circuits. Suspended strip line structures analyzed in the past have been limited to those which have the same substrate width as that of the outer conductor. However, in many practical cases, the side-walls of the outer conductor have grooves to support a dielectric substrate. The authors have already proposed a quasi-TEM wave analysis method based on a variational approach using the spline function for trial functions to estimate the effects of these grooves on the characteristics of single-conductor suspended strip lines. This paper applies this method to characterize broad-' side coupled strip lines which are necessary to design millimeter-wave directional coupplers and filters, and considers the effects of the grooves on characteristic impedance, propagation velocity, and coupling coefficient. The proper selection of spline knots is discussed to attain various characteristic constants with high accuracy. [ABSTRACT FROM AUTHOR]

The hologram of a single-point object is called a Fresnel zone plate (FZP), and the hologram of a general object is represented as a superposition of FZP's. Since a point image can be reconstructed from the FZP at a reasonable location, there can be considered an image reconstruction method based on FZP. This paper proposes the FZP sampled hologram and the corresponding two-dimensional image reconstruction method. The FZP sampled hologram is sampled with small interval at the central part and large interval at the periphery. By multiplying the phase function with the one-dimensional hologram and performing the Fourier transform, the two-dimensional image distribution can be determined for the azimuth and range. By analyzing the point-image distribution, it is seen that the azimuth resolution of 6 mrad is obtained I or the millimeter wave frequency of 35 GKz and the hologram length of 25 cm. It is seen also from the distribution that there exist side peaks of -4.8 dB at an azimuth angle of ±11 mrad apart from the peak. An experiment was made for the millimeter-wave holography with a simple object, and a satisfactory agreement with the theory was observed. [ABSTRACT FROM AUTHOR]

The generalized circular structures imply combinations of concentric strip rings with various potentials. The rectangular boundary division method is extended to estimate the total electric field energy from which the capacitance is effectively calculated. Numerical results based on this method are compared with other available numerical results and experimental data. [ABSTRACT FROM AUTHOR]

This paper applies an improved version of the point-matching method for estimating the cutoff frequencies of the dominant mode of a class of polarization-maintaining composite optical fibers and shows an existence condition for nonzero cutoff frequencies of the dominant mode. [ABSTRACT FROM AUTHOR]

An analytical method for estimating the transmission characteristics of a composite circular planar circuit is presented. The impedance matrix of the circuit is calculated from the circular harmonic expansion of fields. The calculated values of the transmission parameters are compared with experimental results. [ABSTRACT FROM AUTHOR]