Wearable Textile-Based Dual-Band 8-Element Rectenna Array for Polarization Independent Far-Field RF Energy Harvesting

This study introduces a dual-band wearable 8-element rectenna for self-powered wearable sensors based on far-field RF energy harvesting at 2.45 and 5.8 GHz. The array was patterned on a textile substrate by laser-cutting a conductive textile and tested in body-worn configuration for both radiation pattern and RF-to-DC conversion properties. It comprises eight monopole-type dual-band element antennas, arranged in a circular configuration that ensures 50<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\%$</tex-math></inline-formula> combined mutual polarization efficiency with an incident electromagnetic wave impinging on it regardless of the wave's polarization. Single element exhibits the gain of 2.5 dBi at 2.45 GHz and 5.7 dBi at 5.8 GHz with the corresponding input reflection coefficients below <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-$</tex-math></inline-formula>15 dB in the body-worn configuration. The mutual coupling between the elements remains well below <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-$</tex-math></inline-formula>20 dB at both operating frequencies. With the serial-type DC-combining approach, this yielded a stable 1.8 V output DC voltage from the rectenna array over a 4 k<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\Omega$</tex-math></inline-formula> load.