Dual-band CPW rectenna for low input power energy harvesting applications

A dual-frequency band low input power rectenna is proposed in this study. The rectenna is comprised of a co-planar waveguide (CPW) rectifier integrated with a rectangular split ring antenna loaded by a spiral strip line. A single diode series connection topology is used to miniaturise the losses at low input power. A spiral coil in addition to two short circuit stubs are used as a matching network for maximum power transfer between the antenna and the rectifying circuit. The proposed rectenna operates at low input power with relatively high measured RF-DC conversion efficiency up to 74% at input power of −6.5 dBm at the first resonant frequency f₁ = 700 MHz and 70% at −4.5 dBm at the second operating frequency f₂ = 1.4 GHz with a resistive load of 1.9 kΩ. The measured rectenna sensitivity (the rectenna ability to receive low power with acceptable conversion efficiency) reaches up to −20 dBm with a conversion efficiency of 47 and 36% at f₁ and f₂, respectively, and a DC output voltage of 0.18 V. The measured efficiency is over 50% from −18 to −3.5 dBm and from −15 to −1.5 dBm at f₁ and f₂, respectively.