Although small spacecraft are small in size and light in weight compared to the conventional satellites, they can offer lots of possibilities for space exploration, scientific observation, data collection and telecommunication. Also, they cost a lot less money than the conventional satellites, and the scientific missions can be planned in a relatively short period of time by using the COTS (Commercial Off-The-Shelf) materials. However, there is a big challenge for the small spacecraft that is the limited surface area of the small spacecraft and the outnumbered components to be mounted on the surface of the small spacecraft. The most obvious one is that the competition for the limited real estate between the antenna and solar cells. UAVs, also known as drones, have become so popular that it is not only used for military and scientific applications, but also they are available for recreational use for ordinary people. Although they are getting smaller in size so that one can put them in his pocket or on his palm, they are becoming multifunctional, which requires more sensors to be mounted on the surface of the drone to achieve its multifunctionality. For example, a recreational drone can not only take pictures and videos, but also it can transmit the picture or video in real time to the operator, which needs a camera to take the picture or videos and needs an antenna to transmit the recorded data to the operator. This requires that the limited surface area needs to be efficiently used in order to accommodate the multiple needed components. This thesis presented a faster, better and cheaper way of inkjet printing conformal antennas on the cover glass of the solar cells of the small spacecraft or on the wing or other parts of the UAV body to integrate the antenna with the solar panels of the CubeSats or with or directly printing the antenna on the UAV body to efficiently use the limited real estate. Several meshed and solid patch antennas printed on a space certified AF32 glass substrate using the printing procedure outlined in this thesis and measured to verify the effectiveness of the inkjet printing procedures. A high gain reflectarray with optical transparency of 95% was inkjet printed on space certified AF32 glass and BOROFLOAT glass and measured to verify the antenna performance and solar panel efficiency. Measurement results showed that the inkjet printed reflectarray integrated on top of the solar panel has a gain of 21.5 dB. The solar panel efficiency was dropped by around 6% due to the inkjet printed reflectarray on glass. A simple conformal dual-band antenna for UAV application was designed with ANSYS HFSS and fabricated in the lab using a foam substrate. The measured antenna performances agreed well with the simulation results. This dual-band antenna also can be inkjet printed directly on the wing or other parts of the UAVs using the printing techniques discussed in this thesis.

Transparent UWB antennas have been the focus of this PhD research. The use of transparent UWB antennas for stealth and energy harvesting has been the underlying applications that have given impetus to this research. Such transparent antennas being built on materials that are discreet, flexible, conformal, conductive and having the ability to provide good antenna performance on glass to serve as the ‘last mile’ link in subsequent generation communications after 4G have been the basis for this contention. UWB in this regard is able to provide the transmission and reception of high data rates and fast video transmission that is an elementary demand of even a 4G wireless communications system. The integration of UWB antennas with photovoltaic to provide integral energy harvesting solutions that will further enhance the value of the UWB system in terms of cost effectiveness and performance are thus the basis of this work. This work hence starts with the study of a transparent conductive oxide polymer, AgHT and its properties, and culminates in the development of a transparent UWB antenna, which can be integrated with photovoltaic for window glass applications on homes and buildings. Other applications such transparent antennas can find use for like on-body wireless communications in healthcare monitoring was also analysed and presented. The radar absorbing material (RAM) property of the AgHT was investigated and highlighted using CST simulation software, as no measurement facilities were available. The transparent UWB antenna in lieu of the inherent absorbent property of the AgHT material is thus able to exhibit stealth characteristics, a feature that would be much desired in military communications. Introduction of a novel method of connecting the co-axial connector to the feed of the antenna to improve gain and efficiency of transparent polymer based antennas and the development of a UWB antenna that maintains its Omni-directional characteristic instead of becoming directional on an amorphous silicon solar cell are presented as some of the contributions for this research work. Some preliminary analysis on the impact of glass on UWB antennas for video transmission and how to improve transmission is presented. The ability of the conductive part of the antenna radiator to be used as a RF and microwave harvester and how it can further add value to a transparent UWB antenna is presented by way of experimental data. Finally yet importantly, this thesis presents some insight into how transparent antennas may be used in Green Technology Buildings to provide an integrated solution for both wireless communications and energy harvesting as part of the future work. Improvement to the aesthetics of the external appearance of residential buildings through the integration of transparent satellite dish onto solar panels on rooftops is also discussed and illustrated as part of this future work.