Jean-René Poirier

A multilevel implementation of the QR compression for method of moments

We present a multilevel version of a previously reported compression technique for the method of moments (Poirier, J.-R. et al., ibid., vol.46, p.1175-6, 1998). This method is based on QR compression of the impedance matrix off-diagonal blocks. The block structure of the matrix is built up to optimize the compression rate. It results from the study that the compression threshold is the unique adjustment parameter, which makes this method very easy to handle. Some results are presented, which stress the improvement in memory storage and computation time obtained through this approach with respect to the mono-level algorithm.

Finite Volume Time Domain modelling of microwave breakdown and plasma formation in a metallic aperture

Abstract The modelling of plasma formation during microwave breakdown is a difficult task because of the strong non-linear coupling between Maxwellʼs equations and plasma equations, and of the large plasma density gradients that form during breakdown. An original Finite Volume Time Domain (FVTD) method has been developed to solve Maxwellʼs equations coupled with a simplified fluid plasma model and is described in this paper. This method is illustrated with the study of the shielding of a metallic aperture by the plasma generated by an incident high power electromagnetic wave. Typical results obtained with the FVTD method for this shielding problem are shown.

Physically-based preconditioner for the WCIP

A physically-based preconditioner for the 1d and 2d Wave Concept Iterative Procedure is introduced in this paper. Numerical results are provided to assess the efficiency of this technique.

Modelling the effects of realistic environments in the nearfield and farfield of Low Frequency Antennas with 3D FDTD method

Ground wave radiation of Low Frequency Antennas is well known for the canonical case of a flat, azimuthally homogeneous, soil. In this paper, more complex kinds of environment are considered in the surroundings of the antenna or in the far field. Both of them are treated by FDTD. Some realistic environments are studied in the near field zone including forest and slopes. An original methodology is proposed for the far field zone. It rests on the use of the direct numerical integration of Sommerfelds integrals which is presented also.

Long range ground wave scattering of Low Frequency Antennas due to ground discontinuities

Ground wave radiation of Low Frequency Antennas is well known for the canonical case of a flat, azimuthally homogeneous, soil. In this paper, more complex kinds of environment like forests, hills, valleys, lakes... are considered with an original hybridization of a direct numerical integration of Sommerfelds integrals with 3D FDTD. The results show that the effects of discontinuities are less important when they are located in the vicinity of the antenna and that major effects are close to the perturbed zone.

Adaptive Cross Approximation for Scattering by Periodic Surfaces

The adaptive cross approximation is applied to boundary element matrices coming from 2D scattering problems by an inflnite periodic surface. This compression technique has the advantage to be applied before the assembly of the matrix. As a result, the computational times for both assembly and solution phases are reduced. Numerical results assess the e-cacy of the method on scattering problems with several periodic surfaces.