A Microwave Power Transmission System Using Sequential Phase Ring Antenna and Inverted Class F Rectenna

A high-efficiency microwave power transmission (MPT) system based on an inverted class F (
$\text{F}^{-1 }$
) rectifier for microwave wireless charging applications is presented in this paper. A left-hand circular polarization (LHCP) transmitting antenna (Tx) is designed based on a modified sequential phase rotation (SPR) divider integrated with a
$2\times 2$
array. The proposed Tx exhibits compact size with LHCP maximum gain of 11.85 dBi at 5.8 GHz. Furthermore, the receiver is composed of an LHCP receiving antenna (Rx) and a microwave
$\text{F}^{-1}$
rectifier. To realize the power radiated region of the Tx, an Rx with a wide beamwidth for minimizing distance loss is proposed, which has a 3-dB axial ratio (AR) beamwidth of 165.55° and 175.17° in the
$x - z$
and
$y - z$
planes, respectively. In addition, to improve the RF to DC conversion efficiency (
$\eta $
), the class
$\text{F}^{-1}$
harmonic processing network is utilized at the load of the rectifier that can process the voltage and current waveforms without using a DC pass filter. The proposed
$\text{F}^{-1}$
rectifier circuit occupies a compact area of
$15.3\times12.7$
mm
²
, and it exhibits an average
$\eta $
of 50% for the input power range from 4 to 20 dBm with a peak efficiency of 77.9% at 18 dBm. Overall, the experimental results show that our proposed system achieves a maximum power transmission efficiency (PTE) of 8.8% for wirelessly charging low-power multiple devices at a distance of 60–200 mm.