Antenna filter co-design for TV white space energy harvesting applications
Date of Issue2014
School of Electrical and Electronic Engineering
The dissertation aims at proposing an "Antenna Filter Co-Design for TV White Space Energy Harvesting Applications". The project demands to create a Filtenna (Integrated Antenna and Filter unit) with high gain and omnidirectional radiation patterns to be able to harness the ambient RF energy efficiently and then convert it to electrical energy with the help of a rectifier circuit. This project discusses only on the design of antenna and filter co-design and not on the design of rectifier circuit. The co-design consists of two parts: 1. An Omnidirectional high-gain antenna 2. A filter with good rejection and narrow passband characteristics to suppress the other non-desirable frequency components The frequency of operation is 600MHz. For future prospects of integration with other devices, the antenna is chosen to be designed as a microstrip planar monopole antenna. As the desired frequency demands a large antenna size, different fractal geometries have been used to reduce the size of the antenna. Three antenna different antenna structures have been proposed in this project in which one is a normal square patch, second one is structure with Peano fractal applied on the patch edges and the last one with modified Peano fractal and notches at the bottom edge. 260MHz of frequency reduction and 52% of size reduction is achieved. The feeding technique has been implemented using microstrip line feed for ease of fabrication. In addition, circular ground which flushes only the feed line has been used. This along with an impedance inverter has been designed in the feedline, which helps in impedance matching, increasing the bandwidth and maintaining omnidirectionality. The filter designed is a meander square loop resonator which is etched on the same side as the radiating patch and in between the feedline. Perturbations have been incorporated in the loop to increase the gap between the modes of resonance so that one mode lies at the desired resonant frequency of 600MHz and other one goes beyond the antenna's working frequency. The designed is able to achieve a fractional bandwidth of 29.7% and 3-dB bandwidth of 178MHz. The designed antenna and filter are then combined on the same substrate to produce a co-design. The integrated filter is able to cancel the unwanted antenna resonances. The simulated bandwidth is measured to be around 1 08MHz at 600MHz center frequency. Also, the gain of the antenna has been increased from 1.88dBi to 2.09dBi. In addition to the required filtering characteristics, the filter is also improving the system efficiency.
DRNTU::Engineering::Electrical and electronic engineering::Antennas, wave guides, microwaves, radar, radio