Improving the rectenna recycling performance by using a wide-band band-pass prefilter

Prefiltering the rectenna input signal with a wide-band band pass filter is shown to improve considerably the rectenna performance as regarding energy recycling. The prefilter is designed to be transparent for all input frequencies in the band of interest and highly attenuating for both DC and higher harmonics. Being repeatedly reflected at the filter output and the output DC shunting capacitor the higher harmonics generated from the nonlinearity of the diode(s) convert most of their power into a DC one. The proposed filter contributes to depressing the reradiation of higher harmonics too. The performance of a rectenna structure using the proposed prefilter has been compared to that of a conventional one. An improvement of up to 38 dB has been achieved.