This paper proposes a triple-band fractal slot antenna with enhanced gain operating at frequencies of 2.7, 3.5, and 4.8 GHz for microwave wireless power transmission. The antenna achieved more than 3 dB gain by preserving the symmetrical defected reflector structure behind it at a length of 0.54λ/4, where λ is the wavelength in free space at 2.7 GHz. A 50 Ω micro-strip line coupled at 66 mm length helps feed the triple band slot antenna. The purpose of a triple-band rectifier circuit with an impedance network is to convert the radio frequency (RF) signal into direct current. The measurements reveal that the antenna’s enhanced gain is 8.8 dB, and the rectifier’s highest RF signal to direct current conversion efficiency is 74.3%. For the combined configuration unit of measure, the antenna is assimilated into the rectifier via back-to-back 50 Ω Sub Miniature Version A (SMA) connectors. The highest recorded efficiency of 49.67% was obtained for the rectenna at optimum values of 1 kΩ resistive load and −5 dBm power input. It has been revealed that the rectifier-integrated antenna presented is effective for low-input RF energy capture and power transmission.

In this paper, three compact, high-efficiency, gain enhanced antennas, and corresponding rectifiers have been proposed for GSM1800, 3G, and 4G-LTE energy harvesting applications. The inverted L-stub is placed on the ground plane of the monopole antenna to get the desired frequency band of GSM1800 MHz. The feed length variation method has been adopted for the slot antennas to obtain the required frequency of 3G and 4G-LTE cellular bands. The performance of antennas is analyzed with the inverted L-stub, feed length variation, and the reflector distance. The maximum gain achieved with the reflector positioned at a distance of λ/4 from the antenna backside is three times greater than the gain obtained without the reflector. The prototype antennas and rectifiers have been simulated, fabricated, measured various parameters, and compared with the simulation results. The antennas provide more than 82% radiation efficiency and an enhanced gain of greater than 5.6 dB. The peak efficiency of rectifiers of more than 30% has been achieved. The aforementioned three antennas are integrated with their corresponding rectifiers for operating at 1.8, 2.1, and 2.3 GHz frequencies. The proposed rectennas are formidably suitable for the reception of RF power from the cellular bands.

A new circularly polarized microstrip array antenna using the orthogonal feed technique is proposed in this paper. The antenna has a multi-layer structure and a new 3-way power divider employing the both-sided microwave integrated circuit technology is designed to configure the feed network of the array. Circular polarization (CP) is realized by creating a quadrature phase difference between orthogonal feed circuits of the patches. The multi-layer structure gives flexibility to adjust the patch spacing that helps to reduce the sidelobe level of the antenna. It is found that the multi-layer structure exhibits a gain of about 2 dB higher than that of a single layer structure by means of sidelobe reduction. The proposed structure also exhibits good CP performances that are verified by a good agreement of measured and simulated results. Simple and compact structure makes the antenna suitable for various wireless applications.