X.T. Dong

Perfectly matched layer-absorbing boundary condition for left-handed materials

The perfectly matched layer (PML) absorbing boundary condition (ABC) is extended to truncate the boundary of left-handed materials in the Finite-Difference Time-Domain (FDTD) simulation. The uniaxial material parameters are given in the frequency domain, and discretized in the FDTD update procedure by means of the Z-Transform technique. The effectiveness of the PML is demonstrated by numerical results.

General formulation of unconditionally stable ADI-FDTD method in linear dispersive media

The unconditionally stable alternating-direction-implicit-finite-difference time-domain (ADI-FDTD) method is used to model wave propagation in dispersive media. A formulation is presented by introducing the Z-transform method into the ADI-FDTD scheme to handle the frequency-dependent features of the media. This formulation is applicable to arbitrary dispersive media, and can be easily coded. Numerical results are compared to those based on the conventional FDTD method to show the efficiency of the proposed method.

Perfectly matched layer implementation using bilinear transform for microwave device applications

This paper presents an extensive study on the perfectly matched layer (PML) implementation using bilinear transform in the finite-difference time-domain (FDTD) simulation. The bilinear transform is used to implement both the stretched coordinate PML (SC-PML) and the uniaxial PML (UPML) with the complex frequency-shifted (CFS) equations. It is shown that with the CFS factor, the implemented SC-PML and UPML attain significantly lower relative reflection error over wide frequency range with both superior in performance to the split-field PML. The FDTD algorithm incorporating these PMLs is applied to analyze wide-band responses of some complex microwave devices, including RF microelectromechanical systems switch and coplanar waveguide crossover junction.

Average power handling capability of finite-ground thin-film microstrip lines over ultra-wide frequency ranges

Based on the distributed parameters extracted and the thermal model proposed to calculate the rise in temperature, the average power handling capabilities (APHCs) of finite-ground thin-film microstrip lines (TFMLs) on benzocyclobutene (BCB) and polyimide films over ultra-wide frequency ranges are investigated. Numerical results are given to show the enhancement in APHCs achieved by choosing appropriate metallization conductivity and thickness, BCB thermal conductivity, and polyimide thickness etc. It is believed that the proposed approach is useful in the design of practical TFML circuits.

Comparative study on the interaction of electromagnetic waves with multi-layer omega(chiro)ferrite slabs

A comparative study was performed to examine the co(cross)-polarized reflection and transmission characteristics of multilayer omega(chiro)ferrite slabs, with or without a backing soft and hard surface (SHS), respectively. The omegaferrite models examined here can be described by the Dmitrievs continuous groups of the symmetry: C ∞v (C ∞), C 2v (C 2), C 2v (Cs )1, and C 2v (C s )2. Based on various numerical experiments, some generalized relations governing the co(cross)-polarized reflection and transmission coefficients are found, which are related to the biasing dc magnetic field as well as the orientation of all omega(chiro)ferrite particles, but independent of the incident wavelength, slab thickness or its loss.

DISTORTION OF PULSE WAVES PROPAGATING IN SOME FERRITE MICROSTRIP TRANSMISSION LINES

The distortion of pulse waves propagating in some shielded composite ferrite microstrip transmission lines (FMTLs) is studied in this paper. The mathematical treatment is based on the Galerkins method in the spectral domain and the fast Fourier transformation (FFT). The hybrid effects of the biasing magnetic dc field intensity and its orientation on the pulse wave distortion are examined and compared. It is shown that the pulse distortion can be effectively reduced by changing the biasing field intensity or orientation.

Breakdown predictions of microstrip interconnects and coplanar waveguide-built devices in the presence of HP-EMPs

Electrical breakdown of microstrip interconnects and coplanar waveguide-built devices in the presence of high-power electromagnetic pulses (HP-EMP) is addressed in this paper, and some effective methodologies are outlined and proposed for fast predicting maximum current carrying density of bonding wire, electric field breakdown strength of thin film capacitors, average and peak power handling capabilities of conventional and thin film microstrip and coplanar waveguides. An efficient FDTD procedure is also presented for characterizing electric breakdown strength of the substrate dielectrics based on their high-field conduction models

FDTD and PSTD simulations for double negative (DNG) materials applications

As a full wave simulation method, the finite-difference time-domain (FDTD) method is capable of capturing the transient characteristics of wave propagation. This method has been successfully used in modeling the interactions of electromagnetic waves with double negative (DNG) materials. Another method, the pesudospectral time-domain (PSTD) method, is superior to FDTD in its linear dispersion relation. Another advantage of PSTD is that all field components are now located at a same position in the unit cell. Therefore, it is more natural to handle the boundary condition on interfaces between different materials. In this paper, FDTD and PSTD are used to simulate the transient evolution of wave propagation in structures with DNG materials. Numerical results are given to provide clear descriptions of the novel wave behaviors.

Finite-ground thin-film microstrip interconnects (TFMIs) and their power handling capabilities over ultra-wide frequency ranges

Various finite-ground thin-film microstrip interconnects (TFMIs) used in the design of high-speed circuit, monolithic microwave and millimeter-wave integrated circuits are studied and compared. Based on the distributed parameters extracted and the thermal model proposed to calculate the rise in temperature, the average power handling capabilities (APHCs) of finite-ground TFMIs on benzocyclobutene (BCB), polyimide and LTCC films over ultra-wide frequency ranges are investigated. Numerical results are given to show the enhancement in APHCs achieved by choosing appropriate metallization conductivity and thickness, BCB thermal conductivity, and polyimide thickness etc.

Average power-handling capability of the signal line in coplanar waveguides on polyimide and GaAs substrates including the irregular line edge shape effects: Research Articles

Low-frequency parameters have important effects on the nonlinear performances of power amplifiers. Injection at the output of a low-frequency-voltage device, following the signal envelope, is proposed. Two-tone simulations, measurements using the principle of a low-frequency active load-pull system, and implementation of the technique are presented.