Summary of Reconfigurable Antennas for Wireless and Space Applications

Satellite and Mobile Communication Course Course Number 361-2-5931 subscriber Professor Ar no. Shlomi Article Summary appointment Reconfigurable Antennas for Wireless and Space Applications By Christos G. Christodoulou, Fellow IEEE, Youssef Tawk, Steven A. Lane, and Scott R. Erwin, Senior Member IEEE Proceedings of the IEEE 100, no. 7 (2012) 2250-2261 Assignment by 1. Introduction A reconfigurable transmitting aerial (RCA) is an aerial that is able to be formed, or bent. From this definition one faeces deduce the signifi drive outce of such forward pass to demarcationr communication. RCA will allow adaptation, additional functionality and more versatility.Therefore, RCAs, with the dexterity to radiate more than one pattern at contrasting frequencies and polarizations, argon necessary in modern telecommunication systems. The article discusses the different reconfigurable components that throw out be used in an barbel to modify its structure and function. These reconfigurat ion techniques be either based on the integration of radio-frequency micro-electromechanical systems (RF-MEMS), PIN semiconductor diodes, var secondors, photoconductive elements, or on the physical alteration of the aerial radiating structure, or on the use of smart bodilys such as ferrites and gas crystals.All of the above techniques distribute the forward pass currents and thus alter the electromagnetic fields of the antennas effective aperture. Therefore, enabling the antenna to enhance its bandwidth, change it operating frequency, polarization, and ray of turn on pattern. 2. Reconfiguring Techniques Six major subjects of reconfiguration techniques argon used to implement reconfigurable antennas, as indicated in Fig. 1. Here I shell focus on two, electrical and optical RCAs. RCAs tolerate be classified into four different categories. a) frequency RCA (b) beam pattern RCA, for this category, the antenna radiation pattern changes in terms of shape, complaint, or sop up (c) polarization RCA and (d) combination of the previous categories. There be several(prenominal) advantages in using reconfigurable antennas. (a) Ability to support more than one wireless standard. Hence, it minimizes cost and volume requirements, simplifies integration and offers good isolation between different wireless standards (b) lower front-end processing.Therefore, there is no fate for front-end filtering and there is a good out-of-band rejection (c) best gougedidate for softwargon-defined radio. Thus, has the capability to adapt and learn and can be automated via a microcontroller or a field programmable ingress straddle (FPGA) and (d) multifunctional capabilities. Consequently, can change functionality as the mission changes, can act as a single element or as an array and can provide narrow- or wide-band operation. However, there are disadvantages for adding tunability to the antenna look. a) the objective of the biasing network for activation/deactivation of th e switching elements which add complexity to the antenna structure (b) incr liberalisation in the required power consumption cod to the incorporation of active components which augments the system cost (c) generation of harmonics and inter conversion products and (d) need for fast tuning in the antenna radiation characteristics to say a correct functioning of the system. Figure 1 Techniques to achieve RCAs 2. 1.Electrically RCAs The ease of integration of such switching elements into the antenna structure has attracted antenna researchers to this type of RCAs despite the numerous issues surrounding such reconfiguration techniques. These issues include the nonlinearity effects of switches, and the interference, losses, and disconfirming effect of the biasing lines used to control the state of the switching components on the antenna radiation pattern. RF-MEMS The antenna shown in Fig. 2 is a reconfigurable orthogonal helical antenna with a set of RF-MEMs switches, which are monol ithically integrated and packaged onto the like substrate.The antenna is printed on a PCB substrate and fed through a coaxial cable at its center point. The structure consists of five sections that are connected with four RF-MEMS switches. The spiral arm is increased by trenchant steps as integer multiplications of the length of the first segment of the rectangular spiral. It is increased following the right-hand direction to provide right-hand visor polarization for the radiated field. The location of switches is determined such that the axial ratio and gain of the antenna are optimum at the frequency of interest.Based on the billet of the integrated RF-MEMS, the antenna can change its radiation beam direction 2. Figure 2 (Left) a radiation pattern RCA. (Right) fabricated figure with the biasing line 2. 2. Optically RCAs An optical switch is formed when laser light is incident on a semiconductor material. This results in exciting electrons from the valence to the conduction b and and thus creating a conductive connection. The linear behavior of optical switches, in addition to the absence of biasing lines, compensates for their lossy aspect and the need for laser light to activate them.Integrated Laser Diode Optically RCAs can be implemented by integrating laser diodes directly into the antenna substrate. A copper piece is attached to the back of the antenna ground, as shown in Fig. 3. This piece has a minimal effect on the antenna radiation pattern since it has a small depth and a little width and height as the antenna ground plane. The laser diodes are activated via a current driver to generate the required take optical power. An example of this type of reconfigurable antenna is shown in Fig. 3a. The antenna brighten layer is the radiating patch while the bottom layer represents the antenna ground plane.Two silicon switches (S1 and S2) are included to allow the antenna to tune its resonant frequency. To activate the silicon switches, laser diodes a re integrated inwardly the antenna substrate by attaching a small copper piece to the ground of the antenna, as shown in Fig. 3b. Two holes are drilled end-to-end the substrate in order to allow the light from the laser diode to be delivered to the silicon switches. These copper pieces are excessively used as a heat sink for the laser diodes 3. Figure 3 (a) optically RCA. (b) Laser diode integration with copper fixture, back layer. (c) Prototype, to layer . 3. wise(p) Materials RCAs Antennas are also made reconfigurable through a change in the substrate characteristics by using materials such as liquid crystals or ferrites. The change in the material is achieved by a change in the relative electric permittivity or magnetic permeability. In fact, a liquid crystal is a nonlinear material whose dielectric constant can be changed under different voltage levels, by altering the orientation course of the liquid crystal molecules. As for a ferrite material, a static use electric/magne tic field can change the relative material permittivity/permeability. . Satellite Applications The need for dynamic space applications has led to the realization of RCAs for planet communication. In such systems, it is necessary to reconfigure the antenna radiation pattern to exercise a new coverage zone, limit fading in wet areas, and maintain high data rate at all assertable frequency bands of operation. E. g. an antenna structure for broadcast applications generates an elliptical beam ranging from 10. 95 to 14. 5 GHz using an 85-cm aperture. Using a rotational and zooming mechanism, the antenna can tune its radiated beam from a small ellipse of 2. 3X3. to a large ellipse of 6X9 4. Reconfiguration in space has also been achieved through the use of deployable antennas. These antennas change their shape from compact, small structures to large prime antennas in space. The objectives are to realize high gain and high directivity, which are primarily determined by the size of an a ntenna aperture. The antenna itself can be reconfigurable to cover several frequency bands as the mission of the satellite changes. 4. Summary Reconfigurable antennas were divided into electrically, optically, physically, and smart-material-based tunable structures.Christodoulou et-al expect future smart reconfigurable antennas to be wholly multifunctional and software controlled with machine learning capabilities that can detect changes in their RF environment and react accordingly. Moreover, the merging of deployable and reconfigurable antennas will open new frontiers in the design of antennas for space communications. 5. References 1. Christodoulou, Christos G. , Youssef Tawk, Steven A. Lane, and Scott R. Erwin. Reconfigurable Antennas for Wireless and Space Applications. Proceedings of the IEEE 100, no. 7 (2012) 2250-2261. 2. won Jung, Chang, Ming-jer Lee, G. P.Li, and Franco De Flaviis. Reconfigurable scan-beam single-arm spiral antenna integrated with RF-MEMS switches. Ante nnas and Propagation, IEEE Transactions on 54, no. 2 (2006) 455-463. 3. Tawk, Y. , J. Costantine, S. E. Barbin, and C. G. Christodoulou. Integrating laser diodes in a reconfigurable antenna system. In Microwave & Optoelectronics Conference (IMOC), 2011 SBMO/IEEE MTT-S International, pp. 794-796. IEEE, 2011. 4. Roederer, Antoine G. Antennas for Space Some Recent European Developments and Trends. In Applied Electromagnetics and Communications, 2005. ICECom 2005. 18th International Conference on, pp. 1-8. IEEE, 2005.