High‐Efficiency Millimeter‐Wave Scalable Rectenna Array With Individual Impedance Control

ABSTRACT This study proposes a millimeter‐wave scalable rectenna array with individual fundamental and second harmonic impedance control to realize high‐efficiency wireless power transfer. The proposed rectenna array features a series arrangement of highly efficient series diode rectifiers, four 2 × 6 patch antenna arrays, and a DC combining network utilizing low turn‐on voltage diodes to perform optimal output voltage summation from each rectifier. Furthermore, to maximize the power conversion efficiency (PCE) of the rectenna array, an individual impedance control network is introduced, allowing independent control of the input impedance observed by each rectifier at both fundamental and second harmonic frequencies. This ensures that the input impedance remains unaffected by the output impedance observed by the connection line during DC combining. A radial stub‐based DC pass filter is used to render the input impedance observed by the load as short and open circuits at fundamental frequencies for input matching and at second harmonic frequencies for recycling harmonic signals. A single rectifier achieved a peak PCE of 64% at 33 GHz and maintained over 40% PCE within the input power range of 11.4–21.7 dBm. The four rectifiers were integrated with the DC combining network and the four patch antenna arrays. Consequently, the rectenna array was validated in a free‐space environment, providing an output DC voltage of 16.2 V when a transmitter delivered an incident wave power density of 19.8 dBm/cm 2 at a distance of 50 cm from the rectenna array.