  Over the previous few years, the millimetre wave frequency range and sub-THz
range have been received a lot of attention as they include unused frequency
spectrum resources that are appropriate for providing a lot of applications
such as automotive radars, short communication, medical imaging, security, and
5G communications to provide end-user access to Multi-Gbit/s services. On the
other hand and because of the restrictions on the communication systems in
these ranges such as power, path losses, and attenuation, the present RF
antennas can't be used for millimeter and THz applications. The needed antennas
should have low-profile, high-gain, acceptable technology, high efficiency and
low cost to compensate for these ranges restrictions. Although there are some
antenna designs for millimeter and sub THz ranges through the last decay, the
antenna designs in these ranges still under investigation and studies to
complete the vision of the proposed designs for the aforementioned
applications. Thus, they cannot be carried by the optimum response and
efficiency for these applications. This thesis aims to introduce a
comprehensive study of the main applications that occupy these ranges of
frequencies. In addition to introducing efficient antennas for each application
with acceptable technology for it.
