Matching Network Elimination in Broadband Rectennas for High-Efficiency Wireless Power Transfer and Energy Harvesting

Impedance matching networks for nonlinear devices such as amplifiers and rectifiers are normally very challenging to design, particularly for broadband and multiband devices. A novel design concept for a broadband high-efficiency rectenna without using matching networks is presented in this paper for the first time. An off-center-fed dipole antenna with relatively high input impedance over a wide frequency band is proposed. The antenna impedance can be tuned to the desired value and directly provides a complex conjugate match to the impedance of a rectifier. The received RF power by the antenna can be delivered to the rectifier efficiently without using impedance matching networks; thus, the proposed rectenna is of a simple structure, low cost, and compact size. In addition, the rectenna can work well under different operating conditions and using different types of rectifying diodes. A rectenna has been designed and made based on this concept. The measured results show that the rectenna is of high power conversion efficiency (more than 60%) in two wide bands, which are 0.9-1.1 and 1.8-2.5 GHz, for mobile, Wi-Fi, and ISM bands. Moreover, by using different diodes, the rectenna can maintain its wide bandwidth and high efficiency over a wide range of input power levels (from 0 to 23 dBm) and load values (from 200 to 2000 Ω). It is, therefore, suitable for high-efficiency wireless power transfer or energy harvesting applications. The proposed rectenna is general and simple in structure without the need for a matching network hence is of great significance for many applications

Novel Compact and Broadband Frequency-Selectable Rectennas for a Wide Input-Power and Load Impedance Range

Wireless power transfer (WPT) and wireless energy harvesting (WEH) using rectennas are becoming an emerging technology. This paper presents a novel design method for a rectenna suitable for a wide range of selectable operating frequency band, input power level, and load impedance. Most importantly, it is realized without using complex impedance matching networks which shows significant advantages over existing rectennas in terms of the structure and cost. A rectenna example has been designed, made, and tested using this novel method. The proposed rectenna has a compact size of 90 × 90 × 1.58 mm 3 and operates at four different frequency bands that are selectable from 1.1 to 2.7 GHz. Over 60% (up to 85%) energy conversion efficiency is achieved for the input power from 0 to 15 dBm and load impedance between 700 and 4500 Ω. The rectenna shows excellent performance for the target applications (WPT and WEH) with a much-simplified structure and reduced cost