Reconfigurable antennas and radio wave propagation at millimeter-wave frequencies

Aalto University, P.O. Box 11000, FI-00076 Aalto www.aalto.fi Author Vasilii Semkin Name of the doctoral dissertation Reconfigurable antennas and radio wave propagation at millimeter-wave frequencies Publisher School of Electrical Engineering Unit Department of Radio Science and Engineering Series Aalto University publication series DOCTORAL DISSERTATIONS 151/2016 Field of research Radio Engineering Manuscript submitted 21 April 2016 Date of the defence 2 September 2016 Permission to publish granted (date) 13 June 2016 Language English Monograph Article dissertation Essay dissertation Abstract For the last decades we have been witnessing the evolution of wireless radio networks. Since new devices appear and the mobile traffic, as well as the number of users, grows rapidly, there is a great demand in high capacity communications with better coverage, high transmission quality, and more efficient use of the radio spectrum. In this thesis, reconfigurable antennas at microand millimeter-wave frequencies and peculiar properties of radio wave propagation at mm-wave frequencies are studied. Reconfigurable antennas can improve radio link performance. Recently, many different concepts have been developed in the reconfigurable antenna design to control the antenna bandwidth, resonant frequency, polarization, and radiation properties. In the first part of the thesis, we investigate mechanically tunable antennas operating at microwave frequencies with the ability to change the shape of the conductor element and, consequently, to control the radiation properties of the antenna. Also in the first part, we study conformal antenna arrays for 60 GHz applications based on cylindrical structures. Beam switching technology is implemented by realizing several antenna arrays around the cylinder with a switching network. Scanning angles of +34 ̊/-32 ̊ are achieved. Moreover, it is vital to study radio wave propagation peculiarities at mm-wave frequencies in indoor and outdoor environments to be able to deploy wireless networks effectively. The propagation part of the thesis focuses on several aspects. First, we investigate how the estimation of optimum antenna configurations in indoor environment can be done using realistic propagation models at 60 GHz. Ray tracing simulations are performed and realistic human blockage models are considered. Second, we present the results from a measurement campaign where reflection and scattering properties of two different built surfaces are studied in the millimeter-wave E-band (71-76 and 81-86 GHz). Next, we present a geometry based channel model for a street canyon scenario, using angular-domain measurement results to calculate realistic power angular spectra in the azimuth and elevation planes. Then, we evaluate propagation effects on the radio channel on the rooftop of the buildings by measurements and simulations. We have used unmanned aerial vehicles and photogrammetry technique to create a highly accurate 3D model of the environment. Based on a comparison of the measured and simulated power delay profiles, we show that the highly accurate 3D models are beneficial in radio wave propagation planning at mm-wave frequencies instead of using simple geometrical models.For the last decades we have been witnessing the evolution of wireless radio networks. Since new devices appear and the mobile traffic, as well as the number of users, grows rapidly, there is a great demand in high capacity communications with better coverage, high transmission quality, and more efficient use of the radio spectrum. In this thesis, reconfigurable antennas at microand millimeter-wave frequencies and peculiar properties of radio wave propagation at mm-wave frequencies are studied. Reconfigurable antennas can improve radio link performance. Recently, many different concepts have been developed in the reconfigurable antenna design to control the antenna bandwidth, resonant frequency, polarization, and radiation properties. In the first part of the thesis, we investigate mechanically tunable antennas operating at microwave frequencies with the ability to change the shape of the conductor element and, consequently, to control the radiation properties of the antenna. Also in the first part, we study conformal antenna arrays for 60 GHz applications based on cylindrical structures. Beam switching technology is implemented by realizing several antenna arrays around the cylinder with a switching network. Scanning angles of +34 ̊/-32 ̊ are achieved. Moreover, it is vital to study radio wave propagation peculiarities at mm-wave frequencies in indoor and outdoor environments to be able to deploy wireless networks effectively. The propagation part of the thesis focuses on several aspects. First, we investigate how the estimation of optimum antenna configurations in indoor environment can be done using realistic propagation models at 60 GHz. Ray tracing simulations are performed and realistic human blockage models are considered. Second, we present the results from a measurement campaign where reflection and scattering properties of two different built surfaces are studied in the millimeter-wave E-band (71-76 and 81-86 GHz). Next, we present a geometry based channel model for a street canyon scenario, using angular-domain measurement results to calculate realistic power angular spectra in the azimuth and elevation planes. Then, we evaluate propagation effects on the radio channel on the rooftop of the buildings by measurements and simulations. We have used unmanned aerial vehicles and photogrammetry technique to create a highly accurate 3D model of the environment. Based on a comparison of the measured and simulated power delay profiles, we show that the highly accurate 3D models are beneficial in radio wave propagation planning at mm-wave frequencies instead of using simple geometrical models.