Highly Sensitive and Compact Quad-Band Ambient RF Energy Harvester

A highly efficient and compact quad-band energy harvester (QBEH) circuit based on the extended composite right- and left-handed transmission lines (E-CRLH TLs) technique is presented. The design procedure based on E-CRLH TLs at four desired frequency bands is introduced to realize a quad-band matching network. The proposed QBEH operates at four frequency bands: <tex-math notation="LaTeX">f₁ = 0.75\, GHz;\, f₂ = 1.8\, GHz;\, f₃ = 2.4\, GHz</tex-math> ; and <tex-math notation="LaTeX">f₄ = 5.8\, GHz</tex-math> . The simulations and experimental results of the proposed QBEH exhibit overall (end to end) efficiency of 55% and 70% while excited at four frequency bands simultaneously with <tex-math notation="LaTeX">- 20\, dBm</tex-math> (10 μW) and <tex-math notation="LaTeX">- 10\, dBm</tex-math> (100 μW) input power, respectively. Due to applying multitone excitation technique and radio frequency (RF) combining method in the QBEH circuit, the sensitivity is improved, and sufficient power is generated to realize a self-sustainable sensor ( S 3 ) using ambient low-level RF signals. A favorable impedance matching over a broad low input power range of <tex-math notation="LaTeX">$ - $</tex-math> 50 to <tex-math notation="LaTeX">$ - $</tex-math> 10 dBm (0.01 to 100 μ W) is achieved, enabling the proposed QBEH to harvest ambient RF energy in urban environments. Moreover, an accurate theoretical analyses based on the Volterra series and Laplace transformation are presented to maximize the output dc current of the rectifier over a wide input power range. Theoretical, simulation and measurement results are in excellent agreement, which validate the design accuracy for the proposed quad-band structure. The proposed new energy harvesting technique has the potential to practically realize a green energy harvesting solution to generate a viable energy source for low-powered sensors and IoT devices, anytime, anywhere.