Near-field reconstruction for portable wireless devices by deconvolution from input impedance changes

The near-field validation of computational electromagnetic models of personal wireless communication devices is becoming indispensable, especially, when assessing specific absorption rate (SAR) compliance to regulatory limits by computer simulation. A possible practice for such validation is to compare measured and simulated electromagnetic field distributions in a standard flat phantom designed for SAR compliance measurements. The authors recently presented an input impedance measurement-based validation method. They extend their scheme with a deconvolution procedure. This enables near field validation based on the reconstructed ${\bi E}^2$E2 field obtained by the deconvolved measurement of the impedance change compared to the calculated ${\bi E}^2$E2. However, the reconstruction problem is inherently ill conditioned and requires numerical treatment. They demonstrate that the regularisation of the convolution matrix makes the reconstruction of the ${\bi E}^2$E2 field feasible with promising error. Through examples of a 1 GHz printed inverted F and a 1.8 GHz printed monopole antenna, they show that the mean-square error as low as 1% between the original and the reconstructed ${\bi E}^2$E2 is achievable with the proposed method.