A Spectral Rotation Approach for the Efficient Calculation of the Mutual Coupling Between Rectangular Apertures
In this letter, a procedure based on the spectral rotation is introduced that allows us to calculate the mutual coupling between apertures in the spectral domain without evaluating any convolution products (reaction integral) directly. A numerical evaluation of the computational cost is presented to show the efficiency of the method for electrically large problems. Numerical examples are given to highlight the agreement between the spatial and spectral rotation methods. Finally, the procedure is applied for the de sign of a horn antenna array with rotated apertures.
We study in this paper the properties of a two-body random matrix ensemble for distinguishable spins. We require the ensemble to be invariant under the group of local transformations and analyze a parametrization in terms of the group parameters and the remaining parameters associated with the 'entangling' part of the interaction. We then specialize to a spin chain with nearest-neighbour interactions and numerically find a new type of quantum-phase transition related to the strength of a random external field, i.e. the time-reversal-breaking one-body interaction term.