A 2.45 GHz rectenna screen-printed on polycotton for on-body RF power transfer and harvesting

This paper presents a 2.45 GHz rectenna on textile for RF power transfer and harvesting. Thin 350 μm polycotton is used as a baseline flexible substrate and screen printing technique is used to map different layers. A 310 μm interface layer is first printed on both sides of polycotton in order to smooth its surface. Silver layer is then printed onto the interface layers to map the antenna and the rectifier layouts. The substrate is characterized over the 0.5-4.5 GHz frequency range using the two-line method. A relative permittivity of 3.23 and a loss tangent of 0.06 have been obtained at 2.45 GHz. A standard patch antenna matched to 50 Ω and a dual-polarization rectenna have been designed. Measurement of the return loss S11 of the patch antenna shows an excellent correlation with simulation results, thus indicating that the two-line characterisation is accurate. The performance of the polycotton antenna and rectenna is evaluated and compared with FR4. The measured radiation efficiency is 11% for the polycotton antenna, and 30% for the FR4 antenna. The polycotton rectenna generates 300 mV and 100 μW, 15 cm from a 100 mW EIRP transmitter.