Field trials have been performed in Covilhã to identify
the spectrum opportunities for radio frequency (RF) energy
harvesting through power density measurements from 350 MHz
to 3 GHz. Based on the identification of the most promising
opportunities, a dual-band band printed antenna was conceived,
operating at GSM bands (900/1800), with gains of 1.8 and 2.06
dBi, and efficiency varying from 77.6 to 82%, for the highest and
lowest operating frequency bands, respectively. In this paper,
guidelines for the design of RF energy harvesting circuits and
choice of textile materials for a wearable antenna are briefly
discussed. Besides, we address the development and experimental
characterization of three different prototypes of a five-stage
Dickson voltage multiplier (with and with no impedance
matching circuit) responsible for RF energy harvesting. All the
three prototypes (1, 2 and 3) can power supply the sensor node
for RF received powers of 2 dBm, -3 dBm and -4 dBm, and
conversion efficiencies of 6, 18 and 20%, respectively.