Reconfigurable Antennas: Switching Techniques—A Survey

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.

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.

The requirements for the next generation wireless systems seek to provide reliable high data rate at low cost. Unfortunately the current wireless communication infrastructure is not fully equipped to cover this unprecedented quality of service. Major obstacles include: limited bandwidth availability, limited transmit power, and signal strength uctuations which are intrinsic to the multivariate wireless channel. Multiple Input Multiple Output (MIMO) antenna systems have emerged as one of the most significant technical breakthrough in modern wireless communications able to satisfy these stringent requirements. However the necessity of assuring a high data rate in a large variety of environments while reducing the antenna array space occupation on portable devices requires an improvement in current MIMO technology. To overcome these limitations, we propose in this thesis, the use of reconfigurable antennas that adaptively change, through RF switches, their radiation properties and frequency of operation according to wireless channel characteristics. The key idea of this work is to show that reconfigurable antennas, through their capability to dynamically change their electrical and radiation properties, can be used to change the propagation characteristics of the wireless channel existing between the transmitting and receiving antennas. The proposed MIMO system breaks from the conventional wisdom that the wireless propagation channel cannot be changed intentionally by the transceivers in the link. Three different novel classes of electrically multi element reconfigurable antennas are proposed as suitable candidates for reconfigurable MIMO systems: i ) a reconfigurable printed dipole antenna array that exploits inter element mutual coupling to achieve pattern reconfigurability, ii ) circular patches capable of exciting higher order modes to achieve pattern and polarization diversity, and iii ) a metamaterial leaky wave array that can be reconfigured in pattern to achieve unprecedented degrees of pattern reconfigurability. To effectively use such antennas with actual communication systems, a low power consumption method for selecting the array configuration is proposed. This technique exploits the close relationship between the environment that surrounds the antenna array and the antenna radiation characteristics in order to select optimal array radiation patterns without the need for intense channel sensing or excessive training. A complete reconfigurable antenna system composed of mutli-element reconfigurable antennas and a control unit capable of efficiently driving the antennas is proposed to deliver unprecedented system performance. Analytical models of the proposed system are used to fully characterize the functionality and performance of the technology. A complete evaluation of the proposed system is conducted through electromagnetic simulations and field measurements collected with a channel sounder specifically designed to measure the performance of multi element antenna systems. It is demonstrated that the novel multi element reconfigurable antenna system is capable of providing i ) increased data rate compared to common non reconfigurable antennas in single link communications as well as in multi-link ad hoc networks, ii ) reduced space occupation by the antenna on the communication device exploiting the principles of pattern and polarization diversity, iii ) reduced number of radio-frequency chains needed at the receiver/transmitter and iv ) reduced amount of transmit power for achieving performance comparable to that of standard non reconfigurable antenna systems.

This paper presents a radiation pattern reconfigurable Yagi-Uda antenna based on graphene operating at terahertz frequencies. The antenna can be reconfigured to change the main beam pattern into two or four different radiation directions. The proposed antenna consists of a driven dipole radiation conductor, parasitic strips and embedded graphene. The hybrid graphene-metal implementation enables the antenna to have dynamic surface conductivity, which can be tuned by changing the chemical potentials. Therefore, the main beam direction, the resonance frequency, and the front-to-back ratio of the proposed antenna can be controlled by tuning the chemical potentials of the graphene embedded in different positions. The proposed two-beam reconfigurable Yagi-Uda antenna can achieve excellent unidirectional symmetrical radiation pattern with the front-to-back ratio of 11.9 dB and the10-dB impedance bandwidth of 15%. The different radiation directivity of the two-beam reconfigurable antenna can be achieved by controlling the chemical potentials of the graphene embedded in the parasitic stubs. The achievable peak gain of the proposed two-beam reconfigurable antenna is about 7.8 dB. Furthermore, we propose a four-beam reconfigurable Yagi-Uda antenna, which has stable reflection-coefficient performance although four main beams in reconfigurable cases point to four totally different directions. The corresponding peak gain, front-to-back ratio, and 10-dB impedance bandwidth of the four-beam reconfigurable antenna are about 6.4 dB, 12 dB, and 10%, respectively. Therefore, this novel design method of reconfigurable antennas is extremely promising for beam-scanning in terahertz and mid-infrared plasmonic devices and systems.

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.

In this paper, we propose a novel pattern reconfigurable planar antenna for employment in a 2×2 multiple input, multiple output (MIMO) system. By switching between the microstrip elements, the antenna can generate a single omnidirectional mode or four directional modes. The design has been tuned for a frequency of 3.8 GHz and has a bandwidth of at least 400 MHz, depending on the configuration. The flexibility in directional and omnidirectional operation, in concert with the wide operating bandwidth, makes this antenna an ideal candidate for future MIMO systems. This paper presents the antenna array architecture as well as simulated return loss and mutual coupling.

Reconfigurable antennas (RAs) and movable antennas (MAs) have been recognized as promising technologies to enhance the performance of wireless communication and sensing systems by introducing additional degrees of freedom (DoFs) in tuning antenna radiation and/or placement. This paradigm shift from conventional non-reconfigurable/movable antennas offers tremendous new opportunities for realizing multifunctional, more adaptive, and efficient next-generation wireless networks. In this paper, we provide a comprehensive survey on the fundamentals, architectures, and applications of these two emerging antenna technologies. First, we provide a chronological overview of the parallel historical development of both RA and MA technologies. Next, we review and classify the state-of-the-art hardware architectures for implementing RAs and MAs, followed by a detailed comparison of their distinct mechanisms, performance metrics, and functionalities. Subsequently, we focus on various applications of RAs and MAs in wireless communication systems, analyzing their respective performance advantages and key design considerations such as mode selection, movement optimization, and channel acquisition. We also explore the significant roles of RAs and MAs in advancing wireless sensing and integrated sensing and communication (ISAC). Furthermore, we present numerical performance comparisons to illustrate the distinct characteristics and complementary advantages of RA and MA systems. Finally, we outline key challenges and identify promising future research directions to inspire further innovations in this burgeoning field.

With the rapid development of science and technology, it is an inevitable trend for wireless communication systems to work on the same platform in different frequency bands. Reconfigurable antenna realizes the reconfiguration of parameters such as resonant frequency, polarization mode and radiation direction. The function of traditional multi-antennas can be realized by a single antenna. This paper presents a frequency reconfigurable antenna, which is especially suitable for multi-band and single-band hopping network communication systems. The simulation results show that the bias network has little effect on the antenna performance. In this paper, a polarization reconfigurable clover antenna fed by coplanar waveguide is proposed, which can realize switching function between left-handed circular polarization and right-handed circular polarization.

Recently, a new wireless communication scheme called Spatial Modulation MIMO (SM-MIMO) has been introduced for Green wireless communications. Here, an application of a compact reconfigurable antenna working at 2.45 GHz to SM-MIMO is presented. The designed antenna can generate up to eight different radiation patterns. It is composed of two meanderlines radiating elements surrounded by parasitic electronically switchable resonators. The impedance matching has been optimized for six states of the reconfigurable antenna. The spatial diversity, which is a key parameter for SM-MIMO is estimated from the analysis of the complex inter-correlation matrix of the radiation patterns at the operating frequency. Finally, the performance of the designed reconfigurable antenna is assessed by computing the bit error rate (BER) in a Non-Line-of-Sight (NLOS) configuration. The proposed reconfigurable antennas are particularly suitable for indoor SM-MIMO applications that require low power and compact devices.

With the tremendous growth of wireless communications, the electromagnetic frequency spectrum has become very congested. This attracts increasing attention to band-reconfigurable or frequency-reconfigurable communication systems for their ability to use the spectrum efficiently. Cognitive radio (CR) [1], [2] is one candidate for future wireless communication systems because it utilizes bandreconfigurable antennas to sense the spectrum and communicate at some unoccupied frequencies. In recent years, a great deal of research has been published on the design of band-reconfigurable antennas [3]?[14]. In general, a wideband antenna for sensing and a reconfigurable narrowband antenna for communication are needed [3]?[5]. In these designs, a relatively small antenna (reconfigurable narrowband antenna) was placed on the ground [3], [4] or free position [5] of a relatively large antenna (wideband antenna). The frequency reconfiguration was realized by using a varactor diode [3], tuning circuit [4], or even rotational motion [5]. Although these designs [3]?[5] can combine wideband and narrowband antennas, it is difficult to provide sufficient isolation between sensing and communication antennas within a limited space. Therefore, the approach that uses one wide-narrowband reconfigurable antenna for both sensing and communication [6]?[8] is a good choice for CR applications. An L-shaped slot antenna was demonstrated in [6] by using microelectromechanical switches. Two designs with band-switchable functionality [7], [8] were designed based on Vivaldi antennas. A wideband mode or several narrowband modes can be achieved with the help of the inserted reconfigurable filters [7], [8]. Furthermore, many designs have been proposed recently with frequency-reconfigurable narrowband characteristics [9]?[13], which may be used as communication antennas for CR applications.

This paper proposes frequency reconfigurable antenna for outdoor wireless communication systems, the 4 x 4 array antenna has designed at two resonant frequencies 7.5 GHz and 8.85 GHz. The periodic dumbbell geometry etched on the ground layer newly proposed with dual functionality, to control desired frequency and to couple radiating patches at the top substrate with feeding line at the bottom substrate. The reconfigurability of the patch antenna is controlled by utilizing the copper pad of the feeding network with OPEN and SHORT states. The reconfigurable antenna has been simulated and optimized using Computer Simulation Technology (CST) to get the desired responds. The good agreement between simulation and measured results indicates that the frequency reconfigurable patch array antenna using Periodic Dumbbell Slotted Aperture Structure (FRPDSA) is feasible to support outdoor wireless communication systems.

The rapid development of wireless mobile communication systems is highly affected by the availability of innovative antenna technologies such as reconfigurable antennas. In this paper, the reconfiguration feature is implemented based on a novel concept, namely, reconfigurable printed ridge gap waveguide technology (RPRGW). This technology will enable the implementation of reconfigurable microwave components that needed for the construction of robust and adaptable communication systems. A reconfigurable patch antenna is designed based on this technology. The simulation results show that a frequency-reconfigurable patch antenna can be achieved using the proposed revolutionary configuration

Emerging advances in reconfigurable radio-frequency (RF) front-ends and antenna arrays are enabling new physical modes for accessing the radio spectrum that extend and complement the notion of waveform diversity in wireless communication systems. However, theory and methods for exploiting the potential of reconfigurable RF front-ends are not fully developed. In this paper, we study the impact of reconfigurable antenna arrays on maximizing the capacity of multiple input multiple output (MIMO) wireless communication links in sparse multipath environments. There is growing experimental evidence that physical wireless channels exhibit a sparse multipath structure, even at relatively low antenna dimensions. We propose a model for sparse multipath channels and show that sparse channels afford a new dimension over which capacity can be optimized: the distribution or configuration of the sparse statistically independent degrees of freedom (DoF) in the available spatial signal space dimensions. Our results show that the configuration of the sparse DoF has a profound impact on capacity and also characterize the optimal capacity-maximizing channel configuration at any operating SNR. We then develop a framework for realizing the optimal channel configuration at any SNR by systematically adapting the antenna spacings at the transmitter and the receiver to the level of sparsity in the physical multipath environment. Surprisingly, three canonical array configurations are sufficient for near-optimum performance over the entire SNR range. In a sparse scattering environment with randomly distributed paths, the capacity gain due to the optimal configuration is directly proportional to the number of antennas. Numerical results based on a realistic physical model are presented to illustrate the implications of our framework

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.

An optically controlled compact reconfigurable antenna with integration of wide and narrow bands is investigated for cognitive radio (CR) systems. The proposed antenna consists of two parts, one for spectrum sensing and the other for communication. With an inherent property, four photoconductive silicon switches are used to achieve reconfigurable frequency characteristics. An antenna prototype has been designed, fabricated and measured. The simulated and measured results show that the proposed antenna is a potential candidate for future cognitive radio communications.