Study And Design Of Reconfigurable Antenna

Reconfigurable antennas can adjust the operating frequency,radiation pattern and polarization of the antennas by loading the RF switching elements,and then have the function of multiple antennas.The reconfigurable antennas can effectively reduce the number of antennas on wireless communication platforms and improve their electromagnetic environment.In this thesis,we study the frequency reconfigurable antennas and pattern reconfigurable antennas,the main work and achievements are proposed as follows:1.A frequency reconfigurable monopole antenna for WLAN applications is proposed.A stepped microstrip feedline is used to improve the impedance match of the antenna.By controlling the states of two switches between the feedline and L-shaped stubs,the corresponding radiating element is excited.The proposed antenna can operate at three modes: a dual-band mode(2.4/5.2 GHz)and two single-band modes(2.4 GHz and 5.2 GHz).2.A band-notch reconfigurable monopole antenna for UWB applications is presented.The notched rectangular patch and defect ground structure are employed to achieve ultra-wideband operation.By cutting an open slot and a split-ring resonator on the radiating patch,and loading a C-shaped parasitic strip above the ground plane,the antenna can realize band-notched characteristics of 3.3-3.6 GHz,5.15-5.35 GHz and 7.25-7.75 GHz,respectively.The PIN diodes are loaded in the proper locations of the open slot,split-ring resonator and C-shaped parasitic strip.By controlling the states of diodes,the antenna can operate at eight modes: ultra-wideband mode,three single-band notch modes,three dual-band notch modes and tri-band notch mode.3.A pattern reconfigurable antenna is proposed.The antenna is composed of a simple dipole and an active frequency selective surface loaded with PIN diodes.The active frequency selective surface unit consists of a rectangularring and two discontinuous strips.The PIN diodes loaded in the gaps of the discontinuous strips can change the transparent or opaque characteristics of the frequency selective surface,and then an omnidirectional radiation pattern of the dipole is converted into a directional one.By switching the diodes of each sector,the beam-switching of the proposed antenna in the azimuth plane can be achieved.