Compact Wideband Rectennas For Wireless Energy Harvesting

The work described in this thesis involves designing and fabrication of miniaturized wideband antennas and RF-DC circuitry for low powered energy applications.The implemented novel designs are useful in reducing the size and provide flexibility to operate on compatible wireless local area network(WLAN)in several different modes.The thesis can be divided into three parts.With the advent of wireless systems,there is growing need for wideband rectenna systems for wireless energy scavenging.The first section is about coplanar waveguide(CPW)wideband antennas having high gain and bidirectional radiation patterns which are suitable for radio frequency energy harvesting.The proposed and implemented designs are optimized by varying antenna shape,feed gap,embedding slots,defected ground structures(DGS)and through adjusting the spacing between radiator and grounds.It is measured that bandwidth of 1.2-2.8 GHz and 3.1-3.7 GHz for dual-band design,and 1.8 GHz to 5.1 GHz bandwidth is achieved for the wideband proposed antenna.Dualband antenna has shown excellent gain values of 8.9 d B and novel wideband antenna gain is measured to be 5.6 d B with almost omnidirectional radiation pattern.Dual-band antenna comprises compact size dimensions of 1.5 cm x 3.5 cm while wideband antenna has only 1.8 cm x 3 cm size dimensions.The detailed analysis of novel Bow-Tie slotted antenna,nature-inspired triangular split ring resonator(TSSR),an antenna with semicircular shape ground and the stacked antenna is presented for antenna quality of service parameters.All the simulated and measured designs in the thesis are suitable for wireless energy harvesting applications and well matched to the 50? standard feed line.The second part involves designing and fabrication of rectifier circuitry at 2.45 GHz frequency which is excessively deployed in our daily routine life and more suitable frequency band for energy harvesting applications.Single stage Grinchier voltage doubler circuit along with L-shaped impedance matching network is simulated in Advance design Systems(ADS)software package and fabricated on a standard inexpensive FR4 substrate with 1.6 mm thickness.RF-DC conversion efficiency is investigated by varying the input power and load resistance of rectifier.Further,Impedance matching with and without matching network is optimized/tuned through the respective lumped components values.Simulated RF-DC conversion efficiency is calculated to be 75.6% at 5 K? load.In the third section,both fabricated wideband antenna and multiplier circuit is coupled through SMA connector and the measured output voltage is found to be 3.2 V at 5 d Bm input power source near the rectenna.The measured RF-DC conversion efficiency of rectenna is 68% which is comparable to the reported conversion efficiency of rectennas in literature.Most reported rectennas in literature are huge in size which makes our proposed designs to be demanding candidates for the internet of things(Io T)and wireless sensor network(WSN)applications.Main goals of compactness of rectenna with wideband characteristics have been achieved through multiple tested and fabricated antenna designs.This research has produced novel/compact designs with efficient results for wireless energy harvesting considering wideband rectennas and is a concrete step forward to the implementation of rectennas in near future.