Efficient calculation of near fields in the FDTD method

When calculating frequency-domain near fields by the FDTD method, almost 50 % reduction in memory and CPU operations can be achieved if only E-fields are stored during the main time-stepping loop and H-fields computed later. An improved method of obtaining the H-fields from Faraday´s Law is presented and shown to be orders of magnitude more accurate than the straightforward approach, at no additional cost. The method is validated by comparison with analytical solution of a traveling wave, and on simulations of dipole and patch antennas.