Design of a rectangular spiral planar inverted-F antenna (PIFA) at 915 MHz for wireless power transmission applications is proposed. The antenna and the rectifying circuitry form a rectenna which can produce DC power from a distant radio frequency energy transmitter. The generated DC power is used to operate a low power deep brain stimulation pulse generator. The proposed antenna has the dimensions of 10 mm × 12.5 mm × 1.5 mm, resonance frequency of 915 MHz with a measured bandwidth of 15 MHz at return loss of −10 dB. A dielectric substrate of FR-4 of εr = 4.8 and δ = 0.015 with thickness of 1.5 mm is used for both antenna and rectifier circuit simulation and fabrication because of its availability and low cost. An Lsection impedance matching circuit is used between the PIFA and the voltage doubler rectifier. The impedance matching circuit also works as a low pass filter for elimination of higher order harmonics. Maximum DC voltage at the rectenna output is 7.5 V in free space and this rectenna can drive a deep brain stimulation pulse generator at a distance of 30 cm from a radio frequency energy transmitter which transmits power of 26.77 dBm.
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