Study and Design of Array and Beamsteering Antennas for Millimeter Wave Band Application

Millimeter wave (mmWave) communication systems have attracted significant interest regarding supporting high data rate of Gigabit/s communications for the new generation of wireless communication networks. MmWave communication systems have frequency ranges in between 30 and 300 GHz wherein an enormous amount of unused bandwidth is available. Although the available bandwidth of mmWave frequencies is promising for high data rate communications, the propagation characteristics of mmWave frequencies are significantly different from microwave frequency band in terms of path loss, diffraction and blockage, and atmospheric absorption. In general, the overall losses of mmWave signals are significantly larger than that of microwave signals in point-to-point wireless communications. To compensate the high propagation losses, due to the limited output power that the current RF active components can deliver in millimeter waves, the use of directional and beam-steerable antennas become necessary in mmWave wireless systems. The use of directional antennas can effectively alleviate the signal interference in mmWave communications. High-gain directional antennas can be used at both the transmitting and receiving ends, resulting in a significantly enhanced Signal-to-Noise ratio (SNR) and improved data security, and can be used in long-range mmWave point-to-point communications. Moreover, directional antenna beams with limited spatial coverage need to be steered either electronically or mechanically to obtain a better substitute link for non-Line of Loss (LOS) communications. Therefore, this dissertation mainly focuses on antenna design for mmWave frequency band applications. High gain and beam-steerable antennas with the merits of low profile, high gain, high efficiency and low cost are studied to address the new challenges of high frequency band antennas. First, waveguide-based technology is employed to propose a new wideband high gain antenna for 60 GHz band applications. Then, for beam-steerable antenna applications to steer the antenna beam in a specific direction, different structures of cylindrical lens antennas are studied. First, a compact two-dimensional lens antenna is designed and proposed at 28 GHz, and then a possible design of a wideband beam-steerable lens antenna is discussed and presented. Finally, a fully metallic wideband metasurface-based lens antenna is explored. The antenna is realized based on an array of periodic unit-cells to reduce the loss of the dielectric part in the conventional lens antennas. This property is exploited to design wideband cost-effective fully metallic antenna at mmWave frequencies.