Veeraraghavan Anantha

Numerical calculation of diffraction coefficients of generic conducting and dielectric wedges using FDTD

Classical theories such as the uniform geometrical theory of diffraction (UTD) utilize analytical expressions for diffraction coefficient for canonical problems such as the infinite perfectly conducting wedge. We present a numerical approach to this problem using the finite-difference time-domain (FDTD) method. We present results for the diffraction coefficient of the two-dimensional (2-D) infinite perfect electrical conductor (PEC) wedge, the 2-D infinite lossless dielectric wedge, and the 2-D infinite lossy dielectric wedge for incident TM and TE polarization and a 90/spl deg/ wedge angle. We compare our FDTD results in the far-field region for the infinite PEC wedge to the well-known analytical solutions obtained using the UTD. There is very good agreement between the FDTD and UTD results. The power of this approach using FDTD goes well beyond the simple problems dealt with in this paper. It can, in principle, be extended to calculate the diffraction coefficients for a variety of shape and material discontinuities, even in three dimensions.

Efficient modeling of infinite scatterers using a generalized total-field/scattered-field FDTD boundary partially embedded within PML

This paper proposes a novel generalized total-field/scattered-field (G-TF/SF) formulation for finite-difference time-domain (FDTD) to efficiently model an infinite material scatterer illuminated by an arbitrarily oriented plane wave within a compact FDTD grid. This requires the sourcing of numerical plane waves traveling into, or originating from, the perfectly matched layer (PML) absorber bounding the grid. In this formulation, the G-TF/SF wave source boundary is located in part within the PML. We apply this technique to efficiently model two-dimensional (2D) transverse-magnetic diffraction of an infinite right-angle dielectric wedge and an infinite 45/spl deg/-angle perfect-electrical-conductor wedge. This approach improves the computational efficiency of FDTD calculations of diffraction coefficients by one to two orders of magnitude (16:1 demonstrated in 2D; 64:1 or more projected for three-dimensions).

Calculation of diffraction coefficients of three-dimensional infinite conducting wedges using FDTD

The finite-difference time-domain (FDTD) method is applied to obtain the three-dimensional (3-D) dyadic diffraction coefficient of infinite right-angle perfect electrical conductor (PEC) wedges illuminated by a plane wave. The FDTD results are in good agreement with the well-known asymptotic solutions obtained using the uniform theory of diffraction (UTD). In principle, this method can be extended to calculate diffraction coefficients for 3-D infinite material wedges having a variety of wedge angles and compositions.

Achieving practical MIMO network planning using the Two-Curve MIMO Performance Model

The Two-Curve MIMO Performance Model provides network planners with an intuitive model for MIMO system performance that not only incorporates the site-specific effects of multipath correlation, but also improves prediction accuracy compared to a single-curve lookup table. Most notably, the 2CMPM improved the standard deviation of the prediction by 8 Mbps in the 5.2 GHz band. Further, analysis of the data shows that in LOS environments 802.11n systems will begin to see significant decreases in MIMO performance as the LOS distance from the transmitter to the receiver increases beyond approximately 15 m at 2.4 GHz and approximately 7 m at 5.2 GHz. These results show that the performance of MIMO systems can be characterized and planned without the need for overly complicated spatio-temporal modeling techniques. The 2CMPM can provide network planners with a prediction of bit rate coverage without having to resort to time-consuming and difficult simulation techniques.

FDTD computed numerical diffraction coefficients of 3-D infinite material wedges

We apply the FDTD method of Stratis et al. (1997) and Anantha and Taflove (1998) to numerically obtain the dyadic diffraction coefficients for several infinite 3-D right-angle material wedges over a range of observation angles and frequencies. This method exploits the temporal causality inherent in FDTD modeling, as discussed in Anantha and Taflove for the infinite perfect electrical conductor (PEC) wedge case.