Research And Design Of Reconfigurable Antenna

Modern wireless communication systems usually have multiple standards so that they require modern antenna systems with multiple capabilities and functions without enlarging occupied volume. The reconfigurable antenna becomes a popular solution because it provides variety in antenna performance to satisfy diverse communication requirements and decrease the interference from other irrelevant signals. Usually reconfigurable antenna has frequency, polarization, or radiation pattern tunableness. The multitude of different standards in cell phones and other personal mobile devices require multi-band antennas and smart antennas with reconfigurable features. The use of the same antenna for different purposes, preferably in different frequencies is highly desirable. Moreover, as the number of the same spectrum increase, there is an increasing probability of interference between users. Thus, antennas with reconfigurable null positioning are critical. Pattern reconfigurable antennas can switch radiation beams in several predefined directions, which results in the improvement of signal-to noise ratio. Polarization diversity is used to avoid the detrimental fading loss, caused by multipath effects. Three kinds of reconfigurable antennas are proposed in the paper.Firstly, a frequency-reconfigurable antenna designed using artificial structure surface unit with periodic structure to operate at around 3.4GHz and 5GHz is proposed and studied. The frequency-reconfigurable antenna is composed of a simple circular patch antenna with u-shaped slot, and a circular artificial structure surface. Artificial structure surface is placed directly at top of the circular patch antenna using planar technology, making entire structure very compact and low profile with a thickness of only 2.6mm. Frequency reconfigurability of the antenna can be obtained by rotating artificial structure surface around the center relative to the circular patch antenna. Results show that the antenna has a large tuning range at higher frequencies, while a small tuning range at lower frequencies.Secondly, a novel pattern-reconfigurable antenna is proposed. The antenna consists of a rectangular driven patch, two symmetric semicircular parasitic elements with a pair of arc-shaped slots and two symmetric rectangular ring slots in the ground plane. Two sets of p-i-n diodes are placed on two symmetric rectangular ring slots, respectively. Three parts on the ground plane are connected through these switches? By switching the different states of the p-i-n diodes, the antenna can be achieve radiation pattern tunability. Detailed design considerations of the proposed antenna are described. Simulated results are also shown and discussed.Finally, a planar polarization-reconfigurable antenna designed using artificial structure surface unit with periodic structure to operate at around 3.6GHz is presented and studied. The antenna consists of a planar periodic structure and indirect contact with a H-shaped slot antenna, both having a circular shape with a diameter of 60 mm and a height of 1mm, making it compact and low profile. By rotating artificial structure surface around the center with respect to the H-shaped slot, the antenna can realize linear polarization, left-hand and right-hand circular polarizations. Results show that the antenna in circular polarization achieves an operating bandwidth of 3.55-3.67 GHz, high-polarization isolation of larger than 15 dB, a gain of above 6dBi.