Reconfigurable Antennas for Wireless and Space Applications

Reconfigurable antennas are capable of dynamically altering their frequency, polarization, and radiation properties in a controlled and reversible manner. They modify their geometry and behaviour to maximize the antenna performance in response to changes in their surrounding conditions. To implement a dynamical response, they employ different mechanisms such as PIN diodes, varactors, radio-frequency microelectromechanical systems (RF-MEMS), field effect transistors (FETs), parasitic pixel layers, photoconductive elements, mechanical actuators, metamaterials, ferrites, and liquid crystals. These mechanisms enable intentional distribution of current on the antenna surface producing reversible modification of their properties. This paper presents the design process and applications of reconfigurable antennas. The activation mechanisms of reconfigurable antennas, and their design and operation optimization are discussed. The latest advances on reconfigurable metamaterial engineering, and the current trends and future directions relating to reconfigurable antennas are reviewed. Finally, the applications of reconfigurable antennas in cognitive radio, multi-input multi-output (MIMO) systems, satellite communications, and biomedical devices are highlighted.

This paper presents the design and analysis of a reconfigurable microstrip slot antenna using RF PIN diodes as switching device for S and C band. Here pattern and frequency reconfigurable microstrip antenna is designed by changing the slot length on ground plane through six MPP4203 PIN Diodes. These six PIN diodes are used to electrically connect and disconnect the slot to alter the total slot length 76 mm in x axis and 56 mm in y axis. Here three switches are positioned in slot which is cut along the x-axis and another three switches are positioned in the slot along the y-axis. The analysis of reconfigurable antenna using PIN diode is done using the simulation performed on Ansys HFSS. The pattern and frequency reconfigurability of proposed antenna is analyzed for S (2–4 GHz) and C band (4–6 GHz) in terms of return loss and radiation pattern. The microstrip antenna design shows the pattern and frequency reconfigurability at 11 resonating frequencies. The proposed reconfigurable antenna is capable to resonate at three resonating frequencies (2.2, 2.3, and 2.4 GHz) in S band and 8 resonating frequencies (5.7, 5.8, 5.9, 6, 6.1, 6.3, 6.4, and 6.5 GHz) in C band. The simulated radiation patterns at various resonating frequencies shows pattern reconfigurability with acceptable gain in xz and yz plane of microstrip patch antenna. Furthermore the re-configurable antenna reduced the front end system's size and offers pre-filtering at the receiver. The proposed microstrip patch slot antenna is quite suited to be integrated with WLAN and Bluetooth devices with less structure complexity.

A reconfigurable antenna with frequency agility and pattern-switching ability is presented in this paper. The proposed design comprises a planar and compact frequency reconfigurable monopole antenna and an active frequency selective surface (AFSS) with reconfigurable transmission and reflection properties in dual bands. The AFSS screen is divided into four sections and each section is composed of four FSS elements with only one PIN diode in each unit cell. The monopole antenna, which is situated at the center of the box-shaped AFSS to illuminate , can reconfigure its resonating frequency between 2.5 and 3.6 GHz with the help of only one PIN diode. With the help of this transformation ability of AFSS behavior electronically, the pattern can be steered across the entire X–Z plane in eight steps at two different operating frequencies independently. This antenna can be very useful in various wireless applications such as drones, small base stations, etc.

A multi-slotted Microstrip frequency reconfigurable antenna is designed-simulated and analyzed in this paper for MIMO applications. The antenna demonstrates the impact of parasitic patches, Slots, and PIN diode on the radiating surface. Designed to operate at five frequencies 3.7 GHz/ 5 GHz/ 6 GHz /9.8 GHz with S11 < -10 dB and VSWR < 2. The communicating bands and the bandwidth achieved by the reconfigurable antenna are 3.72 - 3.8 GHz / 2.1% bandwidth, 4.89 – 5 GHz / 2.2% bandwidth, 5.85 – 6.28 GHz / 7.2% bandwidth, and 9.63 – 9.97 GHz / 3.4% bandwidth. The antenna holds potential applications in areas such as Cognitive radio, C and X band (Microwave communications), MIMO, WiMAX, Satellite Communication, etc.

PurposeIn wireless communication system, use of multiple antennas for different requirements of system will increase the system complexity. However, reconfigurable antenna is maximizing the connectivity to cover different wireless services that operate different frequency range. Pattern reconfigurable antenna can improve security, avoid noise and save energy. Due to their compactness and better performance at different applications, reconfigurable antennas are very popular among the researchers. The purpose of this work, is to propose a novel design of S-shaped antenna with frequency and pattern diversity. The pattern and frequency reconfiguration are controlled via ON/OFF states of the PIN diode.Design/methodology/approachThe geometrical structure of the proposed antenna dimension is 18 × 18 × 0.787 mm3 with εr = 2.2 dielectric constant. Three S-shaped patches are connected to a ring patch through PIN diodes. The approximate circumference of ring patch is 18.84 mm and length of patch is 5 mm, so approximate length of radiating patch is 14.42 mm and effective dielectric constant is 1.93. Conductor backed coplanar waveguide (CPW) is used for feeding. The proposed antenna is designed and simulated on CST microwave studio and fabricated using photolithography process. Measurements have been done in anechoic chamber.FindingsAntenna shows the dual band operation at 2.1 and 3.4 GHz frequency. The first band remains constant at 2.1 GHz resonant frequency and 200–400 MHz impedance bandwidth. Second band is switched at seven different resonant frequencies as 3.14, 3.45, 3.46, 3.68, 3.69, 3.83 and 3.86 GHz with switching of the diodes. The −10 dB bandwidth is more than 1.4 GHz.Research limitations/implicationsPattern reconfigurability can be achieved using mechanical movement of antenna easily but it is not a reliable approach for planar antennas. Electronic switching method is used in proposed antenna. Antenna size is very small so fabrication is very crucial task. Measured results are deviated from simulation results due to fabrication error and effect of leads of diodes, connecting wires and battery.Practical implicationsThe reconfiguration of the proposed antenna is controlled via ON/OFF states of the three PIN diodes. The lower band of 2.1 GHz is fixed, while second band is switched at five different resonant frequencies as 3.27, 3.41, 3.45, 3.55 and 3.88 GHz, with switching of the PIN diodes with all state of diodes and exhibit pattern reconfigurability at 2.1 GHz frequency. At second band center frequency is significantly changed with state of diodes and at 3.4 GHz pattern is also changed with state of diodes, hence antenna exhibits frequency and pattern reconfigurability.Originality/valueA novel design of pattern and frequency reconfigurable antenna is proposed. Here, work is divided into two parts: first is frequency reconfiguration and second is radiation pattern reconfiguration. PIN diodes as switch are used to select the frequency band and reconfigure the radiation pattern. This proposed antenna design is novel dual band frequency and pattern reconfigurable antenna. It resonates at two distinct frequencies, i.e. 2.1 and 3.4 GHz, and has a pattern tilt from 0° to 355°. The conductor backed CPW feed technique is used for impedance matching.

<span>Beam steering antennas is essential part of various WCN (Wireless Communication Networks) such as radar and satellite communication. The increasing demand of high data rate, high SNR (Signal to Noise Ratio) and high gain, therefore pattern reconfigurable antennas are required to improve such properties. </span><span>Beam steering is the technique of changing the main lobe direction of radiation. The constructive and distractive interference are used to steer the lobe in specific direction. Beam steering is necessary in various communications such as localization, satellite, tracking system and airborne application.</span><span> Beam steering antenna decreases interference and power consumption and also increases directivity and gain. Beam steering antenna transmit and receive signals in specific direction. </span><span>Beam steering antenna decreases interference and power consumption and also increases directivity and gain. The researchers are interested to find optimal beam steering solution for single and multi-point application. </span><span>In past various techniques are used to achieve beam reconfigurable antennas. This paper presents, beam steering principle and their theory, beam steering techniques such as; Mechanical Steering, Beamforming, Switching Pin Diodes, Reflector and array antenna (Reflectarray), Parasitic Steering, Phase Shifters, Switched Beam Antennas, Metamaterial Antennas, Traveling Wave Antennas, Retro-directive Antennas, Integrated Lens Antennas (ILAS), merits and demerits and comparison among various techniques.</span>

A frequency reconfigurable patch antenna has been designed and analyzed controlled by two PIN diodes to shift among multiple frequencies. Different mode of operation has been made using computer simulation program (CST) software. A circular patch antenna has complex design calculations; thus, the proposed antenna offered a reduction in complexity using an uncomplicated structure. Tow active switching elements have been used to reconfigure the proposed antenna design to operate in multiple bands by shifting between ON and OFF states. Extensive investigation has been made by varying the resistance, inductance, and capacitance components of the selected PIN diodes. A compact size structure of 31.16 mm x 27.04 mm x 1.6 mm functions in the C-band at 4.7 GHz, X-band at 9.2 GHz, Ku-band at 13.3 GHz, and 17 GHz, and K-band at 18.7 GHz when both PIN diodes are OFF state. When the first PIN diode is ON and the second is OFF, it functions in the X- band at 8.7 GHz, Ku-band at 13.1 GHz and 15.9 GHz, and K-band at 18.7 GHz. Then, when the first PIN diode is OFF and the second PIN diode is ON, it functions in the C- band at 5.4GHz, X- band at 9.4 GHz, Ku- band at 13.6 GHz and 17.1 GHz, and K- band at 18.7 GHz. Finally, when both PIN diodes are ON state, it functions in the Ku- band at 12 GHz and 15.8 GHz, and K- band at 18.7 GHz. The proposed reconfigurable circular patch antenna presented a compact unfussy size, cheap, and meek to implement to operate in current communication systems such as satellite communications (space operation, earth exploration, earth-to-space, space-to-earth, satellite TV Broadcasting, and fixed satellite services (FSS)), Mobile communication long-term evolution (LTE band 46), Mobile communication 5G sub-6GHz, Wireless-Fidelity 7 and Radio implant medical devices (IMD).

Nowadays, a novel compact frequency and polarization reconfigurable microstrip antenna is an engaging alternative to fit CR (cognitive radio) system engrossment. In this chapter, the proposed design has a straightforward and effortless construction. A simple rectangular microstrip patch cut by slot and the patch interconnect with four L-shaped strip lines. By enabling/disabling (ON/OFF) the (HPND4005) PIN diodes, the antenna operates at different frequency bands like 7.4, 9.1, 10.5, 10.9, and 11.4 GHz. The antenna performance parameters, such as VSWR, gain, radiation pattern, return loss, and surface current, are also presented. The proposed antenna design used FR4 substrate with dielectric constant εr = 4.4. Antenna dimensions are (35.9×58.94×1.6) mm. The designed antenna structure can be used for applications such as satellite communications and cognitive radio.KeywordsAxial ratioCognitive radioFrequency reconfigurationMicrostrip patchPolarization reconfiguration

Radio Frequency (RF) plays a vital role nowadays in harvesting RF Energy from the ambient source. An antenna is required to harvest RF energy and solve the spectrum underutilization problem for the Cognitive Radio (CR) system. This paper presents an optimization of a reconfigurable Coplanar Waveguide Antenna (CPW), which harvests RF energy and is also used for sensing and communication purposes. The performance metrics of the proposed antenna are gain, radiation efficiency, front-back ratio (FBR) and group delay. First, the optimized CPW antenna (sensing antenna) is designed and fabricated in the FR4 substrate for the wideband frequency range of (0.25–3 GHz) with the fractional bandwidth percentage of 175%. The gain of the proposed optimized CPW antenna for different frequency band is: DTV band (UHF-0.47 GHz)-3.327 dBi, GSM 900-2.39 dBi, GSM 1800-3.42 dBi, 3G-3.227 dBi, and Wi-Fi-3.21 dBi. The average gain of the optimized CPW antenna for the frequency range of (0.25–3 GHz) is 3.11 dBi, and the maximum radiation efficiency of the antenna is 91.05%. Next, the optimized CPW antenna is reconfigurable, and it can be reconfigured for a specific frequency band using a PIN diode switch. When the PIN diode switch is in ON state, the antenna acts as a reconfigurable antenna (communicating antenna), and it is operated for the specific frequency band of (0.47 GHz-DTV [UHF] band), (0.9, 1.8, and 2.1 GHz-mobile bands), and (2.4 GHz-Wi-Fi bands). The maximum gain of the optimized frequency reconfigurable CPW antenna is 3.61 dBi, and the radiation efficiency is 92.5%. In the OFF state, the antenna acts as a sensing antenna, and it operates at a wideband frequency range of (0.25–3 GHz). Finally, the prototype of a four-stage Villard voltage multiplier RF-dc conversion circuit using an adjustable impedance matching network is proposed for powering the cognitive radio applications.

Due to the fast development of wireless communication technology, reconfigurable antennas with multimode and cognitive radio operation in modern wireless applications with a high-data rate have drawn very close attention from researchers. Reconfigurable antennas can provide various functions in operating frequency, beam pattern, polarization, etc. The dynamic tuning can be achieved by manipulating a certain switching mechanism through controlling electronic, mechanical, physical or optical switches. Among them, electronic switches are the most popular in constituting reconfigurable antennas due to their efficiency, reliability and ease of integrating with microwave circuitry. In this paper, we review different implementation techniques for reconfigurable antennas. Different types of effective implementation techniques have been investigated to be used in various wireless communication systems such as satellite, multiple-input multiple-output (MIMO), mobile terminals and cognitive radio communications. Characteristics and fundamental properties of the reconfigurable antennas are investigated.

Reconfigurable antennas offer attractive potential solutions to solve the challenging antenna problems related to cognitive radio systems using the ability to switch patterns, frequency, and polarization. In this paper, a novel frequency reconfigurable E-shaped patch design is proposed for possible applications in cognitive radio systems. This paper provides a methodology to design reconfigurable antennas with radio frequency microelectromechanical system (RF-MEMS) switches using particle swarm optimization, a nature-inspired optimization technique. By adding RF-MEMS switches to dynamically change the slot dimensions, one can achieve wide bandwidth which is nearly double the original E-shaped patch bandwidth. Utilizing an appropriate fitness function, an optimized design which works in the frequency range from 2 GHz to 3.2 GHz (50% impedance bandwidth at 2.4 GHz ) is obtained. RF-MEMS switch circuit models are incorporated into the optimization as they more effectively represent the actual switch effects. A prototype of the final optimized design is developed and measurements demonstrate good agreement with simulations.

Dynamic reconfiguration of antenna devices is becoming a prime need in emerging telecommunication and remote sensing systems operating in the portion of the electromagnetic (EM) spectrum spanning from millimeter-wave (MMW) to terahertz. Different techniques and materials are currently available for the implementation of a given EM reconfiguration in antenna systems at microwaves andMMW, such as semiconductors, RF-MEMS, Liquid Crystal, and ferroelectrics. However, a common feature to all these technologies is the significant increased loss and complexity with regard to the devices fixed counterpart. Both loss and complexity further increase when high-performance reconfiguration capabilities are addressed atMMWand above, constituting a major limitation to the future deployment of dynamically controllable systems. Advanced performance, low-complexity and low-cost are, therefore, the cornerstones in the development of new technologies for antenna reconfiguration. In this framework, the main objective of this thesis is to contribute to the advancement of low-cost and efficient technologies enabling antenna reconfiguration capabilities fromMMWto THz frequencies. Within this scope, it is proposed the analysis, design and implementation of mechanically reconfigurable devices using dielectric elastomer actuators (DEAs). DEAs are an emerging technology that possesses unique properties, and represents a potential alternative to conventionalmechanical reconfiguration schemes. DEAs are especially attractive for their large strain combined with low-costmaterials and fabrication, analog control and near-zero DC power consumption. These characteristics make them particularly suited to the realization of low-cost and low-loss reconfigurable antennas. The high potential of DEAs for the realization of adaptive devices is experimentally validated by the development of different prototypes operating atMMWand THz frequencies: i) a very low-loss true-time-delay phase shifter operating at Ka-band; ii) a Ka-band reconfigurable reflectarray with 1-D beam-scanning capability; iii) a stretchable and beam-scanning THz reflectarray exhibiting the uncommon potential for the implementation of conformal or reconfigurable devices based on mechanical stretching. The designs and concepts demonstrated in this thesis pave the way for the evolution of new DEA-based reconfigurable devices resulting in low-cost, low loss and compact structures.

Nowadays, the communication industry is looking for a cognitive radio platform that can be used to handle multiple frequency bands, utilize various transmission protocols and be reconfigurable. For spectrum allocation, two methodologies have been adopted for CR between users who are licensed (PU) and those who are not (SU). They are spectrum overlay and spectrum underlay. Secondary users need to operate below the principal users' noise level therefore, significant restrictions resisted on the strength of their transmission in spectrum underlay methodology. Spectrum underlay is a type of underlay that is used in the construction of the unoccupied section of the spectrum searched by CR in the spectrum overlay process. A reconfigurable antenna is needed on RF front-end side of CR, which will a range of completely to span a vast array of frequencies specified sub-bands of frequency, and this is often a major design challenge. An antenna with a flexible monopole for Ultra-wideband equipment competent to function between the frequency range of 3.1 GHz to 10.6 GHz. Designs of reconfigurable antennas reported in the literature are mostly observed to be capable of manual tuning or switching between two or a few frequency bands. Hence, the requirement of new designs of integrated UWB and reconfigurable narrowband antennas that operate from 2 GHz and up to 12 GHz frequency range with a high degree of automated tunability or switching facility into different narrow bands would have a strong application potential for CRs.

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> A new kind of double- and single-arm cantilever type DC-contact RF MEMS actuators has been monolithically integrated with an antenna architecture to develop a frequency reconfigurable antenna. The design, microfabrication, and characterization of this “reconfigurable antenna (RA) annular slot” which was built on a microwave laminate TMM10i (<formula formulatype="inline"> <tex Notation="TeX">$\varepsilon _{r} $</tex></formula> = 9.8, <formula formulatype="inline"> <tex Notation="TeX">$\tan \delta $</tex></formula> = 0.002), are presented in this paper. By activating/deactivating the RF MEMS actuators, which are strategically located within the antenna geometry and microstrip feed line, the operating frequency band is changed. The RA annular slot has two reconfigurable frequencies of operation with center frequencies <formula formulatype="inline"> <tex Notation="TeX">$f _{\rm low} $</tex></formula> =2.4 GHz and <formula formulatype="inline"><tex Notation="TeX">$f _{\rm high} $</tex></formula> = 5.2 GHz, compatible with IEEE 802.11 WLAN standards. The radiation and impedance characteristics of the antenna along with the RF performance of individual actuators are presented and discussed. </para>

Nematic liquid crystal (LC)-based beam steering has been reported for wide applications. However, for conventional nematic LC beam steering the thickness is of several microns in order to have a wider deflection angle. The response time is relatively slow and the diffraction efficiency is low. In this work, novel beam steering based on polymer stabilized blue phase liquid crystal (PS-BPLC) has been designed and theoretically analyzed. This special mesophase of the chiral doped nematic LC has several advantageous characteristics, for example no need for alignment layers, microsecond response time and an isotropic voltage-off state. The results reveal control over phase retardation. The direction of the steered beam can be tuned by voltage. Depending on voltage configuration, either diffractive beam steering (0.5deg deviation for 1st order) or a tunable continuous phase (tunable deviation of 0.002deg) can be obtained. In the first case, the deflection angle could be tuned by stacks of samples. The second option has the same phase shift for the TE and TM modes so unpolarized light could be used. Full Text: PDF ReferencesF. Feng, I. White, T. Wilkinson, "Free Space Communications With Beam Steering a Two-Electrode Tapered Laser Diode Using Liquid-Crystal SLM", J. Lightwave Technol. 31, 2001 (2013). CrossRef E. Oton, J. Perez-Fernandez, D. Lopez-Molina, X. Quintana, J.M. Oton, M.A. Geday, "Reliability of Liquid Crystals in Space Photonics", IEEE Photonics Journal 7, 1 (2015). CrossRef J. Stockley, S. Serati, "Multi-access laser terminal using liquid crystal beam steering", IEEE in Aerospace Conference, 1972 (2005). CrossRef D. Zografopoulos and E. Kriezis, "Switchable beam steering with zenithal bistable liquid-crystal blazed gratings", Opt. Lett. 39, 5842 (2014). CrossRef Benedikt Scherger, et al., "Discrete Terahertz Beam Steering with an Electrically Controlled Liquid Crystal Device", J. Infrared. Millim. Terahertz Waves 33, 1117 (2012). CrossRef M.A. Geday, X. Quintana, E. Otón, B. Cerrolaza, D. Lopez, F. Garcia de Quiro, I. Manolis, A. Short, Proc. ICSO, Rhodes, Greece, pp. 1-4 (2010). CrossRef Y. Chen, S.-T. Wu, "The outlook for blue-phase LCDs", Proc. SPIE 9005, Advances in Display Technologies IV, 900508 (2014). CrossRef G.D. Love, A.F. Naumov, "Modal liquid crystal lenses", Liq. Cryst. Today 10, 1 (2000). CrossRef V. Urruchi, J.F. Algorri, J.M. Sánchez-Pena, M.A. Geday, X. Quintana, N. Bennis, "Lenticular Arrays Based on Liquid Crystals", Opto-Electron. Rev. 20, 38 (2012). CrossRef J.F. Algorri, G. Love, and V. Urruchi, "Modal liquid crystal array of optical elements", Opt. Express 21, 24809 (2013). CrossRef J.F. Algorri, V. Urruchi, N. Bennis, J. Sánchez-Pena, "Modal liquid crystal microaxicon array", Opt. Lett. 39, 3476 (2014). CrossRef J.F. Algorri, V. Urruchi, B. Garcia-Camara, J.M. Sánchez-Pena, "Generation of Optical Vortices by an Ideal Liquid Crystal Spiral Phase Plate", IEEE Elect. Dev. Lett. 35, 856 (2014). CrossRef D. Xu, Y. Chen, Y. Liu, S. Wu, "Refraction effect in an in-plane-switching blue phase liquid crystal cell", Opt. Express 21, 24721 (2013). CrossRef Z. Ge, S. Gauza, M. Jiao, H. Xianyu, S.T. Wu, "Electro-optics of polymer-stabilized blue phase liquid crystal displays", Appl. Phys. Lett. 94 101104 (2009). CrossRef J. Yan et al., "Extended Kerr effect of polymer-stabilized blue-phase liquid crystals", Appl. Phys. Lett. 96, 071105 (2010). CrossRef X. Wang, D. Wilson, R. Muller, P. Maker, D. Psaltis, "Liquid-crystal blazed-grating beam deflector, Appl. Opt. 39, 6545 (2000). CrossRef