This letter presents a 28 GHz switched five-beam antenna system based on a rectangular waveguide and a reconfigurable semiconductor circuit (RSC) with slots. Surface p-i-n diodes are used to close or open slots in order to achieve required configuration of an aperture. The RSC with a modified WR28 waveguide composes a reconfigurable radiating structure (RRS), which provides three beams directed toward 0°, 30°, and 45°. Beam switching is achieved by reconfigurable arrangement of a set of slots. Complementary RRSs connected to the electromechanical RF switch is used to generate remaining -30° and -45° beams. The gain of each generated beam is similar because different numbers of slots are opened, i.e., three, five, and nine slots for beams directed toward 0°, 30°, and 45°, respectively. Aperture of the antenna is controlled by a unit composed of high-current operational amplifiers. Measured results validate the performance of designed millimeter-wave reconfigurable antenna.

In this letter, a novel architecture for a time-modulated antenna array (TMAA) based on single-pole double-throw (SPDT) switches is presented. The proposed TMAA has lossless switching network because there is no power loss during the off state. In addition to improved efficiency, this TMAA provides beam-scanning capabilities. Moreover, the proposed TMAA has a constant instantaneous directivity, which is favorable for some applications. The architecture has been implemented as an aperture-coupled patch antenna array and verified as a smart antenna in a digital wireless communication system.

In this paper, the radiation characteristics of a new microstrip electrically controllable scan antenna are investigated theoretically and experimentally. Both longitudinal and transverse currents are taken into account. The substrate of this antenna consists of a ceramic-polymer composite with modified ferroelectric powder Ba_0,65 Sr_0,35TiO₃ and an appropriate polymer. The permittivity of the substrate can be varied by an applied electric control dc-bias field. It allows to change electrically phase constant of the propagation wave and, in turn, changes the main beam direction. It is shown that the main beam position changes over 30deg when dc-bias field is applied up to 200 V. The comparison with experimental results has fully confirmed the usefulness of the scan-antenna concept and method of analysis. Presented results of the electrical scanned antenna investigation are promising for various fixed-frequency applications where frequency scanning is impossible

A new method for broadband characterization of dielectrics in the sub-terahertz (sub-THz) frequency range is presented. Quasi-optical free space measurement setup is used to determine the complex reflection coefficient in a wide frequency band. This method makes it possible to characterize every dielectric by using only the measured complex reflection coefficient without accurate information about the thickness of dielectric sample. This method is useful in case of lossy and/or thick dielectric samples and is based on modern measurement equipment feasibility, with the possibility to make measurements in high number of frequency points. The mathematical model of the method is formulated. Finally, results of measurements for different dielectrics are presented. The obtained permittivity values of these dielectrics are comparable to those reported in the literature.