Debye formulas are widely used to describe the electrical dispersion characteristics of a uniform lossy material. Debye model uses some empirical coefficients to control the shape and position of spectroscopy curves. It can fit most of the data from experiments. A two-layered model is investigated through its equivalent Debye circuit model. A Finite Difference Method (FDM) is developed to extract the effective permittivity and conductivity of a two-layered model as the verification of the analytical derivation. The computation results indicate the results obtained from FDM and the layered Debye formulas agree very well, which shows the validity of the layered Debye formulas in terms of the original circuit parameters. The derived formulas are used to analyze the relationship between the effective electrical spectra and the electrical parameters of each layer. A few examples are given in the discussions. And it can be concluded that: (1) with the increase of the average value of the conductivity of the two layers, the spectra of effective permittivity transition area shifts to higher frequencies; while the spectra of effective conductivity transition kept the same with the values decrease; (2) with the increase of the average value of the relative permittivity of the two layers, the transition area of the spectra of effective permittivity kept the same with values increase; and the transition area of the spectra of effective conductivity shifts to the lower frequencies; (3) the effective permittivity enhances at the lower frequency region as the ratio between the conductivity of two layers increase.

A novel accelerating hybrid method of moments and physical optics (MOM-PO) method is presented to analyze the antenna around electrically large scatterer modeled with nonuniform rational B-spline (NURBS) surfaces. Stationary phase method (SPM) is applied to compute the PO integral of induced current. Two accelerating techniques, grouping of the MoM region and interpolation of critical points, are used to enhance the computational efficiency. The comparison of the results obtained by this method with that by existing NURBS MOM-PO and Triangle MOM-PO shows that the present method is feasible. The execution time consumed in different methods is listed to demonstrate the high efficiency of this approach. Index Terms-Accelerating techniques, MOM-PO, nonuniform rational B-spline (NURBS), stationary phase method (SPM).

No abstract

No abstract

over 100 m MMF RoF with an EVM 4% and it is possible to obtain 10 À3 BER at À12 dBm received optical power. ACKNOWLEDGMENTS V. Sittakul would like to acknowledge Royal Thai Government Scholarship for PhD funding. 2. V. Sittakul and M.J. Cryan, A 2.4 GHz wireless-over-fibre system using photonic active integrated antennas (PhAIAs) and lossless matching circuits, IEEE J Lightwave Technol, in press. 3. V. Sittakul and M.J. Cryan, A comparison of single mode and multimode fibre links for use in wireless-over-fibre systems, Microwave

No abstract

No abstract

reduction with CP radiation. A parametric study of the antenna has been carried out. It has been found that the impedance and AR can be tuned easily by adjusting the slit sizes. The antenna has a wide angle CP (3-dB AR beamwidth) of more than 100 over the 3-dB AR frequency range. The proposed antennas are compact, and it is easy to find applications as a reader antenna in handheld and portable devices. The proposed slits-loaded patch radiators are useful for compact CPMAs and array design. REFERENCES