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A parasitic layer-based multifunctional reconfigurable antenna (MRA) design based on multi-objective genetic algorithm optimization used in conjunction with full-wave EM analysis is presented. The MRA is capable of steering its beam into three different directions simultaneously with polarization reconfigurability having six different modes of operation. The MRA consists of a driven microstrip-fed patch element and a reconfigurable parasitic layer, and is designed to be compatible with IEEE-802.11 WLAN standards (5-6 GHz range). The parasitic layer is placed on top of the driven patch. The upper surface of the parasitic layer has a grid of 5 5 electrically small rectangular-shaped metallic pixels, i.e., reconfigurable parasitic pixel surface. The EM energy from the driven patch element couples to the reconfigurable parasitic pixel surface by mutual coupling. The adjacent pixels are connected/disconnected by means of switching, thereby changing the geometry of pixel surface, which in turn changes the current distribution over the parasitic layer, results in the desired mode of operation in beam direction and polarization. A prototype of the designed MRA has been fabricated on quartz substrate. The results from simulations and measurements agree well indicating 8 dB gain in all modes of operation.Index Terms-Beam steering, full-wave analysis, multi-objective genetic algorithm, reconfigurable antenna.

The design, fabrication, and characterization of a frequency reconfigurable antenna for the United States Public Safety (PS) wireless communication applications are presented. This antenna is quad band operating in the PS bands -220, 470, 800, and 4960 MHz. It is an electrically small antenna with calculated ka ~ 0.55 at 220 MHz. The antenna has two reconfigurable modes of operations. In mode 1, 220, 470 and 4960 MHz bands are excited. Mode 2 provides operation over 800 and 4960 MHz bands. This dynamic frequency reconfiguration is accomplished by two radio frequency microelectromechanical systems switches strategically located within the antenna architecture. The measured and simulated results for impedance and radiation characteristics agree well, where, ~3%, 4%, 21%, and 17% fractional bandwidths have been measured in the four bands respectively, while maintaining integrity of radiation pattern.Index Terms-Frequency-reconfigurable antennas (FRAs), multi-layered antennas, broad-band antennas, multi-band antennas, UHF antennas, electrically small antennas, antenna measurements, antenna radiation patterns

A beam-steering antenna based on a parasitic layer operating at around 5.6 GHz is presented. It is capable of steering its beam into three directions (u m ¼ 2308, 08, 308). The structure consists of a driven microstrip-fed patch element and a parasitic layer located on top of the driven patch. The upper surface of the parasitic layer has a grid of 5 × 5 electrically-small rectangular-shaped metallic pixels, which can be connected/disconnected by means of switching, thus the parasitic pixel surface geometry is changed. The electromagnetic mutual coupling between the driven patch and the parasitic pixel surface is responsible for achieving the desired beam-steering. Prototypes of the designed antennas have been fabricated showing 8 dB realisedgain in all steered beam directions.Introduction: Multifunctional reconfigurable antennas (MRAs) with dynamically changeable antenna properties in frequency, radiation pattern and polarisation have recently gained significant interest [1, 2]. A typical MRA structure consists of a number of metallic segments of various geometries along with a switching circuitry. The switching circuitry is used to connect/disconnect the metallic segments, thereby changing the current distribution on the antenna, which in turn changes the antenna properties. The majority of MRAs presented so far [1, 3] integrate the switching network along with the associated control circuitry within the driven antenna region. However, for an MRA with a large number of reconfigurable modes of operation, the switching network becomes very complex, which may severely degrade the antenna performance owing to deleterious coupling effects. In this Letter, we present a new reconfiguration technique, where the switching network is separated from the driven patch element [4]. As shown in Fig. 1, the switching network lies on the upper surface of the parasitic layer (which contains 5 × 5 rectangularshaped metallic pixels); thereby it is separated from the driven element. This reconfiguration approach provides significant advantages. 1. Since switches are separated from the driven antenna, they get exposed to only a minor portion of the RF power available on the driven antenna, which prevents switch failures (due to limited power handling capability of the switches). 2. As the switching control circuitry is separated from the driven antenna element, it can be designed separately to meet the overall system performance requirements. Also, deleterious coupling effects that may otherwise disturb the antenna performance are minimised owing to the separation. 3. The fabrication of the antenna becomes easier as the switching network can be fabricated separately. It can then simply be assembled together with the driven antenna. It is also worth noting that, with the presented technique, there is no constraint on the distance from the driven antenna to the parasitic pixel surface, which is simply chosen to be the thickness of integrated circuit (IC) compatible quartz substrate (0.525 mm). In contrast to the typical distance of l/4...

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