A Study on Frequency Reconfigurable Antennas for Applications in Frequency Agile Radio and mm-Wave.

As the current technologies in mobile communications are constantly growing it is becoming a necessity for researchers to investigate and deliver novel, versatile and agile devices providing adaptive performance in order to fulfil the ever changing requirements for communication engineering standards in the next and currently developing generation of mobile communications known as 5G. The current technologies in adaptive antennas have provided optimal numbers using comprehensive technologies that are compatible with the past generations of mobile communications. However, the increasing amounts of data exchanged by mobile devices nowadays require multiple services to be covered by reduced number of devices. In order to overcome this inconvenience, the use of reconfigurable antennas, specifically frequency reconfigurable antennas introduce an adaptive and innovative concept for versatile devices with applications in radio agility that overcomes the limitations of the current devices that are unable to cover multiple services by a single antenna. Two different kinds of frequency reconfigurable antennas are discussed in this work. The design, simulations, manufacture, and measurements for the discussed antennas are developed in this thesis. The first discussed designs are three prototypes of 1×2 triple-slotted antennas with different positions in the board. These boards offered independent frequency tuning using varactor-loaded slots that are electrically tunable by voltages from 0 – 25 V offering a fully tunable frequency range from 0.57 GHz and up to 2.73 GHz. The commented antennas offered independent metrics for frequency response and radiation patterns as well as good agreement between simulations and measurements. Moreover, the three slot antenna prototypes were object of a study in diversity metrics as they present spatial diversity schemes. The simulated and measured diversity parameters observed agreed on optimal numbers for frequencies above 750 MHz for the three prototypes with correlations well below 0.3 and diversity gains near the ideal value of 10 dB which allows reduction of required power in multi-antenna systems and determines its capacity to operate in MIMO systems for 5G. The second kind of antennas discussed in this is a dielectric resonant antenna (DRA) designed to operate at 28 GHz using bioplastics with relatively low dielectric constants and filled by different materials in order to achieve frequency reconfiguration including electrically tunable substances such as graphene oxide covering a frequency range from 26.3 GHZ to 28.3 GHz presenting good agreement between measured and simulated reflection coefficients and radiation patterns.