Recently, reconfigurable antennas have attracted significant interest due to their high adaptation with changing system requirements and environmental conditions. Reconfigurable antennas have the ability to change their radiation pattern, frequency or polarization independently according to the application requirements. In this thesis, three different reconfigurable antenna structures have been designed / beam-steerable meanderline antenna, dual circularly polarized meanderline antenna and dual-frequency slot-dipole array. Traveling wave meanderline antenna arrays are investigated in detail and a beam-steerable traveling wave meanderline antenna array has been introduced for X-band applications. Beam-steering capability of the antenna array has been achieved by loading the antenna elements with varactor diodes. Theoretical analysis and computer simulations of the proposed antenna have been verified with experimental results. Radiation direction of the 8-element meanderline array can be rotated 10&deg / by changing the varactor diode&rsquo / s bias voltage from 0V up to 20V. Also, a polarization-agile meanderline antenna array has been designed and simulated. Polarization of the circularly polarized meanderline array can be altered between right hand circularly polarized and left hand circularly polarized by using RF MEMS switches. The third type of reconfigurable antenna investigated in this thesis is a dual frequency slot-dipole array operating at X- and Ka-band. Electrical length of the slot dipoles has been tuned by using RF MEMS switches. Antenna prototypes have been manufactured for &lsquo / on&rsquo / and &lsquo / off&rsquo / states of RF MEMS switches and it has been shown that the operating frequency can be changed between 10 GHz and 15.4 GHz.