Wideband Harmonic Rejection Filtenna for Wireless Power Transfer

Two novel, compact, simple 2nd and 3rd harmonic rejection coplanar waveguide (CPW) feeding mechanisms for a 5.8 GHz rectenna are proposed. Both of them make use of the CPW compact microstrip resonant cell (CMRC). In the first topology, the blockage is realized by a CMRC in combination with a U-slot. In the second topology a pair of strongly coupled CMRCs is optimized. Both these new feeding mechanisms are realized in prototypes and experimentally validated, first in two back-to-back configurations, and then in combination with two CPW fed wideband monopole antennas. The measured antenna return loss at the 2nd and 3rd harmonic is in the order of 0.5 dB and 1.5 dB, respectively, which corresponds to a return loss suppression of about 4 -5 dB compared to a reference monopole antenna. Both antennas reach an 18% 10 dB return loss bandwidth, which is the highest working bandwidth reported in literature for harmonic rejection antennas. Bandwidth could become an issue when wireless power transfer systems would be implemented with a reconfigurable working frequency in order to minimize interference with local telecom equipment.