Abstract
This paper introduces a wideband rectenna that can scavenge ambient wireless power to a range of frequency band from 0.91 GHz to 2.55 GHz efficiently. The proposed rectenna is based on a wideband 2 × 2 fractal monopole antenna array with omnidirectional radiation patterns and high gains of 5 to 8.3 dBi at the desired bands. An improved two-branch impedance matching technique is presented which is designed to enhance the rectifier circuit performance with a relatively low input power ranging from −25 dBm to 10 dBm. Also, a full-wave wideband rectifier that can suitably improve the RF-to-DC power conversion efficiency is designed for the rectenna. A peak efficiency of 76%, 71%, 61%, and 62% is obtained at 950, 1850, 2100, and 2450 MHz, respectively. Measurement results show that a conversion efficiency of 68% has been achieved over an optimal 4.7 kΩ resistor when the simultaneous four-band input power level is −10 dBm. Moreover, an output DC voltage of around 243 mV with voltage varying within 160–250 mV can be achieved by gathering the low ambient wireless power inside laboratory. This study proves that the proposed rectenna can be applied to a range of many low-power electronic applications.
Highlights
With the rapid development of wireless systems, the ambient radio frequency (RF) energy is increasing from several of electromagnetic power sources around the world, such as the mobile telephones, mobile base stations, television/radio broadcast stations, and Wi-Fi routers. Despite these ambient electromagnetic sources, an RF energy scavenging system is one of the most desirable technologies for steady charging of low-power electronic devices, because that could omit the requirement for a battery overall and save maintenance cost [1]. e RF energy harvesting by technologies of rectifying antenna is a practicable solution to convert the ambient wireless power to DC power
This paper focused on the wideband rectenna
A novel rectenna with wideband fractal antenna array and a wideband rectifier has been presented for ambient RF energy scavenging from 0.91 GHz to 2.55 GHz
Summary
With the rapid development of wireless systems, the ambient radio frequency (RF) energy is increasing from several of electromagnetic power sources around the world, such as the mobile telephones, mobile base stations, television/radio broadcast stations, and Wi-Fi routers. The main challenge of RF energy harvesting is how to enhance the power conversion efficiency of the rectifying circuit at low-input power levels over a wideband frequency. We designed a monopole wideband antenna array fed by a microstrip-to-slot-line transition feeding network. In the following, based on [7], a full-wave Greinacher rectifying circuit with a twobranch impedance matching network is employed in the antenna to realize the broadband rectenna with low input power levels. (1) Design a radiator patch with a hexagon-shaped, microstrip feed-line with 50 Ω impedance, and a partial rectangular ground plane, in which monopole antenna can operate in a wideband frequency with the central frequency of 1.8 GHz (Antenna I). L0 α y x Figure 2: Koch fractal monopole from zero to second iteration
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