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Large-distance communications beyond a few meters is challenging for Terahertz (THz) signals because of high spreading loss and absorption in the media. The smart antenna concept used for RF antennas to improve the signal-to-interference/noise level can be extended to these THz antennas. Out of the two types of implementations of this concept, viz. (i) adaptive array and (ii) switched-beam antenna, this paper presents the switched-beam nanoantenna for the THz wave region. Based on the Yagi-Uda antenna concept, switched-beam graphene nanoantennas over silicon dioxide (SiO2) substrate is proposed in this paper. In one case (Antenna-I), the antenna is able to switch the beam in ± 90o directions, whereas in the other case (Antenna-II), the switching directions are 0o, ± 90o, 180o. This pattern reconfigurability can also be observed over a frequency range leading to simultaneous pattern and frequency reconfigurable nature of the nanoantenna. The reconfigurability is obtained by changing the graphene conductivity through its chemical potential. Due to plasmonic wave propagation in graphene at THz, the proposed graphene nanoantenna resonates at a sub-wavelength scale. Design aspects and the working principle of switched-beam graphene plasmonic nanoantennas in the THz region are discussed in this paper.

Adaptive signal processing sensor arrays, known also as smart antennas .The smart antenna adaptive algorithms achieve the best weight vector for beam forming by iterative means. The Least Mean Square (LMS) algorithm, is an adaptive algorithm .LMS incorporates an iterative procedure that makes successive corrections to the weight vector in the direction of the negative of the gradient vector which eventually leads to the minimum mean square error. Beam forming is directly determined by the two factors. The performance of the traditional LMS algorithm for different parameters is analysed in this paper. This algorithm can be applied to beam forming with the software Matlab. The result obtain can achieve faster convergence and lower steady state error. The algorithms can be simulated in MATLAB 7.10 version. 1. INTRODUCTON Throughout the world, there is significant research and development on smart antennas for wireless systems. This is because smart antennas have tremendous potential to enhance the performance of future generation wireless systems as evidenced by the antennas' recent deployment in many systems. There are two basic types of smart antennas.The first type is the phased array or multibeam antenna, which consists of either a number of fixed beams with one beam turned on towards the desired signal or a single beam (formed by phase adjustment only) that is steered toward the desired signal. The other type is the adaptive antenna array is an array of multiple antenna elements, with the received signals weighted and combined to maximize the desired signal to interference plus noise power ratio. This essentially puts a main beam in the direction of the desired signal and nulls in the direction of the interference. A smart antenna is therefore a phased or adaptive array that adjusts to the environment. That is, for the adaptive array, the beam pattern changes as the desired user and the interference move; and for the phased array the beam is steered or different beams are selected as the desired user moves. Nearly every company the WTEC panel visited is doing significant work in smartantennas. Indeed, some companies placed strong emphasis on this research. In particular, researchers at NEC and NTT stated that they felt that smart antenna technology was the most important technology for fourth generation cellular systems. Researchers at Filtronics and other companies agreed that smart antenna technology was one of the key technologies for fourth generation systems. A smart antenna system at the base station of a cellular mobile system is depicted in Fig 1. It consists of a uniform linear antenna array for which the current amplitudes are adjusted by a set of complex weights using an adaptive beamforming algorithm. The adaptive beamforming algorithm optimizes the array output beam pattern such that maximum radiated power is produced in the directions of desired mobile users and deep nulls are generated in the directions of undesired signals representing co-channel interference from mobile users in adjacent cells.

Polarized smart antenna array has attracted considerable interest due to its capacity of matched reception or interference suppression for active sensing systems. Existing literature does not take full advantage of the combination of polarization isolation and smart antennas and only focuses on uniform linear array (ULA). In this paper, an innovative synthesis two-dimensional beampattern method with a null that has cross-polarization for polarized planar arrays is proposed in the first stage. This method aims to further enhance the capability of interference suppression whose optimization problem can be solved by second-order conic programming. In the second stage, a new sparse array-optimized method for the polarized antenna array is proposed to reduce the high cost caused by the planar array that is composed of polarized dipole antennas. Numerical examples are provided to demonstrate the advantages of the proposed approach over state-of-the-art methods.

In the design of smart antenna, switched-beam technology is widely used to increase the communication capacity and to reduce electromagnetic interference. This letter presents a switched-beam antenna array for the three-channel multiple-input–multiple-output (MIMO) wireless local area network operating in 2.4/5.8 GHz. In the proposed array, there are 12 directional beams, and every four partially overlapped beams form a channel. Thus, the proposed array provides three channels. For each channel, the four antenna elements used to radiate directional beams are rotationally symmetrical. Therefore, for all channels, good omnidirectional coverage is obtained by dynamically switching directional beams. To demonstrate the effectiveness and advantages of the proposed array, a prototype is fabricated and measured. In it, the peak gain of directional radiation reaches 9.5 dB, and the values of the horizontal plane fluctuation for three channels are smaller than 5 dB.

IETF 6TiSCH standard aims to create reliable, deterministic, and low-power networks by scheduling bandwidth resources in time and frequency domains. The main emphasis of 6TiSCH protocol is that it creates Internet of things (IoT) networks with a deterministic and controllable delay. However, many of its benefits are tied to the ability of the 6TiSCH scheduler to optimally distribute radio resources among wireless nodes which may not be possible when the number of frequency resources are limited and several other wireless technologies share the same frequency band (e.g., WiFi, Bluetooth and IEEE 802.15.4). Here the integration of a low-complexity directional antenna system with IETF 6TiSCH protocol is investigated with the aim of creating a 6TiSCH solution with higher spatial reuse. 6TiSCH nodes equipped with such smart directional antennas can schedule bandwidth resources not only in time and frequency domain but also in spatial (space) domain.

Blind beamforming algorithms are the first choice for radar applications as they won’t use any training signal. But the major downside of constant modulus algorithm (CMA) is very low convergence ra...

Wireless technology is growing rapidly in today’s era. It is very crucial to design and develop smart antenna structure which could resonate for multiple frequency bands. In this paper, the Dielectric Resonator Antenna (DRA) array has been successfully designed for multiband applications. The presented array resonates at 1.85 GHz, 5.13 GHz, 9 GHz and 14.24 GHz frequencies with the peak gain values of 1.20 dBi, 2.66 dBi, 3.91 dBi, 6.6 dBi and 2.05 dBi respectively. The microstrip line feed is utilised as feeding technique where the width of microstrip line is optimised to achieve adequate antenna resonance. The alumina ceramic has been utilised as DRA material having the relative permittivity of 9.3. The FR4 material is used as a substrate above which the dielectric resonator blocks have been formed. The overall size of the antenna is 50 x 40 mm2. There a close match between simulated results and measured results which shows proposed structure potential for GSM 1800 (1.81 GHz), WLAN (5.13 GHz), Radar (9 GHz), Direct Broadcast Satellite (12.5-15 GHz) applications

Security is the major concern in wireless sensor networks. To reduce security threats in WSNs physical layer, each node could be designed with an antenna which forms a MIMO communication system. This research work proposed a novel and effective solution to enhance the security of WSN. The sensor node at the transmitter side are used to transmit the beamforming signal to the receiver while few nodes are used to create artificial noise to jam the eavesdropper. Beamforming is used in WSNs for effective communication which enhances the received signal to noise ratio (SNR) at the receiver side. Based on beamforming, smart antennas are modified to switch the direction and adjusts the transmitted power and phase through intermediate relay nodes and constructively it is used in the destination side to combine the signal. This new beamforming technique needs the information about the channel for security concern in these relay system of destination as well as an eavesdropper. For physical layer security beamforming area along with schemes such as amplify and forward relays, decode and forward relays and also co-operative jamming relays where adopted, to confuse the eavesdropper. Two channels are used in the experimental model such as main/legitimate channel, which is used between the relay node and destination node, and the other one is the wiretap channel which is used between the intermediate relay node and the eavesdropper.

The ever-increasing numbers of new wireless technologies and services have resulted in increasing demand of smart wireless devices. The smart antennas in such devices should support all the required specifications so that these are compatible with different applications. Moreover, for realizing emerging wireless application such as cognitive radios, new requirements on the antenna are imposed. Novel antenna solutions which can easily reconfigure its operating parameter like frequency, bandwidth, pattern or polarization are required to support multiband, multimode and multi standard applications. Such antennas must support all these features in a single unit to produce small size, low cost, low profile integrated antenna which can be easily incorporated into the feature-rich applications. This paper deals with the design, simulation and fabrication of frequency reconfigurable antenna which have more than one reconfiguration features. In these we are adding extended parasitic elements to the Co-planar mono pole antenna for more than one resonant frequency. Co-planar waveguide fed polarization reconfigurable monopole antenna is used and PIN diodes are used as the switching device. The relevant design techniques, simulation results and fabrication details are presented. The integrated antenna structures need to be experimentally tested to validate the established parameters for antenna performance such as return loss, radiation pattern and gain.

Energy efficiency (EE) and spectral efficiency (SE) are two crucial performance metrics for next-generation wireless standards. In this work, the SE and EE of a full-duplex (FD) relay system based on the amplify-and-forward (AF) scheme is investigated. Specifically, it has been shown that residual self-interference (RSI) due to imperfect self-interference cancellation (SIC) impacts the SE and EE of the FD relay system. A smart antenna allocation (AA) scheme has been proposed that enhances the SE and the EE of the FD relay system through optimally allocating the antennas at the FD relay. Further, the impact of relay location has also been studied and it has been shown that the SE and EE of the FD relay systems can be maximized through optimal AA scheme and relay location. The proposed analysis is corroborated through simulations, which are in good conformity with the analytical results.

An effective pattern reconfigurable antenna is proposed using CST-MW simulator. Essentially, the proposed antenna is a unique sort of antenna and ready to make inclusion at two headings by utilizing a couple of waveguide port without utilizing any switching technology. This antenna can reconfigure the pattern automatically. The proposed antenna can switch the beam one direction to its 180° reverse angle. Therefore, it may have called a smart antenna that has high pattern directivity. It provides about 460 MHz bandwidth at 2.4 GHz that is ideal for Wi-Fi frameworks and would be enhanced the speed. Furthermore, its compactness and provides small VSWR value to make this antenna effective for Wi-Fi systems. Consequently, this antenna could be adopted for the base station design for Wi-Fi technology.

Reconfigurable antennas are gaining greater attention in this scenario because of its diverse features in different fields. Reconfigurable antennas have an upper hand on the conventional antennas because of its versatility. They can be utilized in much wider domains than smart antennas. The reconfigurable antennas are capable to utilize available spectrum without varying physical structure of the antenna by using switches, RF-chock inductors and biasing networks. Different multi-band and ultra-wide band-notched antennas with frequency reconfigurable characteristic are analyzed, compared and summarized in this paper.

The antenna plays an important role in transmitting and receiving information. An effective pattern reconfigurable patch antenna is proposed using CST-MW simulator. This innovative patch antenna can automatically adjust pattern, where each beam is 180 degree apart. Therefore, it may have called a smart antenna that has high pattern directivity. It provides about 460MHz bandwidth at 2.4GHz that is perfect for WiFi systems and would be enhanced the speed. Furthermore, its compactness and provides small voltage standing wave ratio value to make this antenna more effective for WiFi systems. Consequently, this antenna can be adopted for the base station design in WiFi technology.

In the modern world, the smart antenna is widely used in radar, seismology, sonar, astronomy underground communication technology, and many more applications. A smart antenna with high directivity, narrow beam-width, low sidelobe levels, and false signal termination is the eminent condition for advanced communication technology. But to design, an antenna array with such characteristics is a challenge. Considering all this problem, Linearly-arranged Concentric Circular Antenna Array (LCCAA) beamformer is proposed and simulates it with robust optimal diagonal loading (ODL) technique. in this paper. It is observed from the performance analysis it is observed that the proposed beamformer under robust techniques provides better performance with respect to conventional technique analyzing beamwidth, sidelobe level, power pattern, and SINR variation with SNR performances. In this paper optimal, FDL and ODL robust technique are used where the ODL technique shows the smallest SINR variation around 2.85 dB, 2.94 dB & 3.105 dB for 1°, 2° & 3° disparity accordingly.

Obstacles are generally treated as harmful objects for millimeter wave (mmWave) networks due to the directional transmission of mmWave signals and the blockage effects of the obstacles. In this letter, smart antennas are deployed at each blockage to exploit the directivity of the mmWave signal such that the blocked signal at each obstacle can be picked up and forwarded to the destination. Assuming a random Boolean model for the spatially distributed blocking obstacles, the joint distribution of the ordered blockage distances is first characterized, which is then used to develop the exact as well as the asymptotic outage probability conditioned on a given number of blockages. Both the theoretical analysis and numerical results show that the proposed protocol achieves full diversity order and can eliminate the error floor caused by the blocking effects, achieving thus superior performance to previous solutions.

Reconfigurable frequency-selective surfaces (RFSSs) are of significant interest in applications, such as secure communication systems or tunable radomes, to improve indoor communication and smart antennas. In order to change the frequency-selective surface (FSS) characteristics, and therefore its frequency response, conventional methods include loading with active semiconductor devices such as varactors, PIN diodes, Schottky diodes and radio-frequency microelectromechanical system. Another possibility is the use of mechanical adjusts, such as spring resonators or mechanical rotation. When PIN diodes are used, commonly only the reverse and forward regions, OFF and ON states, respectively, are considered. In this study, the implementation of an RFSS is described, using PIN diodes as active components. The RFSS is based on the four-arms star geometry, and initial design equations and procedures are presented. Numerical and measured results are shown for different project stages, with a very good agreement. In addition to obtaining two distinct resonant frequencies, due to the OFF and ON states, a third situation is included, considering the PIN diode threshold region when the FSS becomes practically transparent, which is an interesting feature with potential applications.

With the demanding system requirements for the fifth-generation (5G) wireless communications and the severe spectrum shortage at conventional cellular frequencies, multibeam antenna systems operating in the millimeter-wave frequency bands have attracted a lot of research interest and have been actively investigated. They represent the key antenna technology for supporting a high data transmission rate, an improved signal-to-interference-plus-noise ratio, an increased spectral and energy efficiency, and versatile beam shaping, thereby holding a great promise in serving as the critical infrastructure for enabling beamforming and massive multiple-input multiple-output (MIMO) that boost the 5G. This paper provides an overview of the existing multibeam antenna technologies which include the passive multibeam antennas (MBAs) based on quasi-optical components and beamforming circuits, multibeam phased-array antennas enabled by various phase-shifting methods, and digital MBAs with different system architectures. Specifically, their principles of operation, design, and implementation, as well as a number of illustrative application examples are reviewed. Finally, the suitability of these MBAs for the future 5G massive MIMO wireless systems as well as the associated challenges is discussed.

The technology to send a magnetic field in a particular direction, known as energy beamforming, has been recently introduced as a magnetic field shaping technology in nonradiative wireless power transmission. In general, one of the most efficient conditions for energy beamforming is that the magnetic fields induced by each antenna should be synthesized to head the same direction. To synthesize the magnetic fields induced at each antenna, interference by mutual inductance that can occur between transmitting (TX) antennas should be minimized. In addition, energy should not be exchanged between the TXs, otherwise it lowers the transmission efficiencies of TX and receiving antenna. In this paper, we present an optimal antenna structure that minimizes the mutual inductance between two TX antennas. First, we have analyzed the mutual inductance between TX antennas that have asymmetric sizes with different antenna lengths and arrangement angles. The directivity of the magnetic field vector is also investigated through an experimental analysis of an antenna structure. Finally, it has been verified that the optimal TX antennas for energy beamforming should be symmetric, which means that all the length of antennas are same and disposed perpendicular to each other. The experimental results show that the deviations of magnetic field directivity for symmetric and asymmetric antennas are 0.045 and 0.355, respectively, which shows that the symmetric structure shows 8.2 times larger consistency over the asymmetric structure.

Array antenna technology for wireless systems is highly integrated for demands such as multi-functionality and high-performance. This paper details recent technologies in Japan in design techniques based on computational electromagnetics, antenna hardware techniques in the millimeter-wave band, array signal processing to add adaptive functions, and measurement methods to support design techniques, for array antennas for future wireless systems. Prospects of these four technologies are also described.

This paper considers the uplink of large-scale multiple-user multiple-input multiple-output millimeter wave systems, where several mobile stations (MSs) communicate with a single base station (BS) equipped with a large-scale antenna array, for application to fifth generation wireless networks. Within this context, the use of hybrid transceivers along with antenna selection can significantly reduce the implementation cost and energy consumption of analog phase shifters and low-noise amplifiers. We aim to jointly design the MS beamforming vectors, the hybrid receiving matrices (baseband and analog), and the antenna selection matrix at the BS in order to maximize the achievable system sum-rate under a set of constraints. The corresponding optimization problem is nonconvex and difficult to solve, mainly due to the receive antenna selection and constant modulus constraints on the analog receiving matrix. By exploiting the special structure of the problem and linear relaxation, we first convert this problem into three subproblems, which are solved via an alternating optimization method. The latter iteratively updates the antenna selection matrix, the transmit beamforming vectors, and the hybrid receiving matrices by sequentially addressing each subproblem while keeping the other variables fixed. Specifically, the antenna selection matrix is optimized via the concave–convex procedure; the weighted mean-square error minimization approach is used to find the solution for the transmit beamformer; and the hybrid receiver is obtained via manifold optimization. The convergence of the proposed algorithm is analyzed and its effectiveness is verified by simulation.

A concept of scalable antenna arrays with an even number of radiating elements and nonuniform element spacing has been proposed. It has been shown that the proposed arrays can be fed with a frequency-selective network based on a well-known directional filter and with such a network the beamwidth can be kept constant across one frequency octave. The appropriate adjustment of coupled-line sections in such a directional filter allows for flexible selection of transmission coefficients between two outputs, and therefore, can be used for gradual switching of the signals between radiating elements. The proposed frequency-selective feeding network has been applied in a six-element antenna array operating in 1.75–3.5 GHz frequency range in which constant beamwidth around 16° has been achieved.

Brain-machine interface (BMI) is a multidisciplinary field that has been recently developed in an attempt to help restore functionalities for paralyzed individuals. One of the key components for the implementation of a wireless BMI necessitates unique designs for both the internal brain and external head antennas. In this paper, we initially revisited the design of an optimized 1-mm3 implantable antenna transferring power and data with a reduced size low profile external reader antenna by utilizing radio-frequency identification (RFID)-inspired backscattering. Detailed computational assessments and specific absorption rate evaluations are performed. Prototypes were characterized in terms of link efficiency through a realized RFID link with up to −25 dB link efficiency. The noise analysis for antennas in biological systems was performed using two novel absorption-noise models. And finally a channel capacity estimation was performed, proving that the BMI antenna link could support up to 100 recording channels. An end-to-end BMI antenna system characterization is detailed in this paper for multichannel implanted neural recording applications.

In this paper, a novel reconfigurable open slot antenna has been proposed for LTE smartphone applications to cover a wide bandwidth of 698–960 and 1710–2690 MHz. The antenna is located at the bottom portion of the mobile phone and is integrated with metal rim, thereby occupying a small space and providing mechanical stability to the mobile phone. Varactor diode is used to cover the lower band frequencies, so as to achieve a good frequency coverage and antenna miniaturization. The operational principles of the antenna are studied and the final design is optimized, fabricated, and tested. It has achieved the desired impedance bandwidth and the total efficiency of minimum 50% in free space throughout the required bands. The antenna performance with mobile phone components and human hand is also been studied. Furthermore, the SAR in a human head is investigated and is found to be within allowable SAR limits. Finally a multiple-input multiple-output antenna configuration with high isolation is proposed; it has an identical reconfigurable open slot antenna integrated at the top edge of the mobile phone acting as the secondary antenna for 698–960 and 1710–2690 MHz. Thus the proposed antenna is an excellent candidate for LTE smartphones and mobile devices.

Purpose Recent development of wireless communication devices dictates that miniaturization, multi-functions and high integration are the important factors for antenna structures. This has resulted in the requirement of antennas with dual or multi-frequency operations. Although the dual-band antennas can be achieved through the experience-based configuration selection with the parameter adjustment, it is still a challenging problem to design an antenna with specific dual-frequency operations effectively. The purpose of the paper is to develop an effective design method to guide the design of antennas with specific dual-frequency operations. Design/methodology/approach The topology optimization is carried out through the material distribution approach, where the patch of the antenna is taken as the design domain. The optimization formulation is established with maximizing the minimum antenna efficiency at the target frequencies. The sensitivity of the antenna efficiency with the design variables is derived, and the optimization problem is solved by a gradient-based algorithm. Findings Based on the proposed design method, an example of a patch antenna design for specific dual-frequency operations is presented. The performance of the designed antenna is cross-verified by experimentation, where the reflection coefficients (S11) obtained by simulation and experiment show a good agreement. The simulation and the experimentation of the designed antenna show that two operational bands are optimized to occur around the target frequencies, which confirms the effectiveness of the proposed design method. Originality/value This paper presents a topology optimization-based design method for patch antennas operating at dual specific frequencies.

Computational imaging at microwave frequencies has gained traction due to its potential for obtaining high-quality images with fast acquisition rates. Complex and diverse radiation patterns form the cornerstone of this approach. Electrically large antennas, such as mode-mixing cavities and metamaterial apertures, have proven to be effective platforms for generating such waveforms. Due to the complex nature of these antennas, near field scanning is often required to characterize their radiation patterns. However, accurate knowledge of the produced waveforms’ spatial distribution, with respect to the physical position of the antenna, is imperative. This relies on precise alignment between the antenna and the near field scan stage during the characterization process—a requirement that is especially cumbersome to achieve when operating at high frequencies. We present an effective method to address this problem; by introducing RF markers into the antenna the position of the antenna under test within the near field scanning setup can be obtained directly from the measurements. The proposed method is experimentally verified through comparison with measurements made using optical photogrammetry. The proposed process will find application in the alignment of computational and multistatic imaging systems, commonly used in security screening and threat detection, as well as in tiled electrically large antenna structures.

This paper presents a multiple-input-multiple-output (MIMO) antenna that has four unit elements enabled by an isolation technique for long-term-evolution (LTE) small-cell base stations. While earlier studies on MIMO base-station antennas cope with either a lower LTE band (698–960 MHz) or an upper LTE band (1710–2690 MHz), the proposed antenna meets the full LTE specification, yet it uses the maximum number of unit elements to increase channel capacity. The antenna configuration is optimized for good impedance matching and high radiation efficiency. In particular, as the spacing between unit elements is so small that severe mutual coupling occurs, we propose a simple structure with extremely low costs to enhance the isolation. By using suspended solid wires interconnecting the position having strong coupled current of two adjacent elements, an isolation enhancement of 37 dB is achieved. Although solid wires inherently aim at direct-current applications, this work successfully employs such a low-cost technique to microwave antenna development. Experimental results have validated the design guidelines and the proposed configuration, showing that antenna performances including impedance matching, isolation, radiation features, signal correlation, and channel capacity gain are highly desired for LTE small-cell base stations.

In multi-user beamforming systems, the inter-user interference are controlled by spatial filtering. Since the implementation of digital beamforming is difficult due to high hardware cost of large array system, the analog beamforming system with one phase shifter at each antenna element is considered with antenna selection scheme. However, the beamwidth is not sufficiently narrow to perfectly remove the interference due to limited size of antenna arrays. To mitigate the interference, we propose the random antenna selection system in millimeter wave channel. The random antenna selection expands the effective array size so that the beamwidth becomes narrow. We compare the beamwidth of conventional fixed antenna selection with random antenna selection and analyze the amount of interference for each selection scheme. Theoretical analysis and bit error rate simulation results indicate that the beamforming with random antenna selection can take advantage of large array.

Owing to the inherent nature, data packets in internet protocol television (IPTV) systems face two major challenges; loss and delay. On the other hand, there is a stringent constraint of minimum speed to make possible delivery of the right number of frames per second to deliver multimedia content in mobile environment. This implies that the inadequate connection speed and bandwidth available for large IPTV customer base can trim down the service quality delivered. In this paper, we have thoroughly investigated the impact of various factors which affect the key quality parameters in IPTV systems which employs worldwide interoperable microwave access WiMAX. Also, we have proposed to employ smart antenna for WiMAX network. Specifically, we have carried out a detailed study of the effect of the following parameters: (1) transmission power; (2) distance variation; (3) antenna gain; (4) channel bandwidth, and (5) mobility under six different categories of scenarios (1) variable distance between nodes; (2) various modulation techniques; (3) variable transmitted power; (4) variable coverage area; (5) different types of antennas, and (6) variable number of connection. The simulation results showed that WiMAX makes a great development in the proposed IPTV system, while ensuring that packet delay and jitter meet the requirements of video content streaming to access IPTV services anywhere and anytime under the effect of changing power ratings, modulation techniques, and distance through WiMAX coverage area. Therefore, the proposed system satisfies higher throughput rates and solves delay problems; as well as providing a stable and monotonic response for all discussed QoS parameters.

For the effective use of available frequency bandwidth, cognitive radio technology is evolving in the last few years. In this, spectrum is shared between primary and secondary users. Secondary users also called as unlicensed users, makes use of part of spectrum which is not used by primary or licensed users. Hence secondary user systems must be capable of sensing the spectrum and should be able to reconfigure to transmit at different frequencies. For this it must consists of spectrum sensing circuit and a reconfigurable transceiver consisting of reconfigurable antenna. This paper discuss the single module of reconfigurable transceiver which dynamically allocates two different frequencies 2.4 and 3.1 GHz for transmission. Ultra-wideband patch antenna, spectrum sensing algorithm and reconfigurable patch antenna are also discussed. The module can be modified to transmit at more frequencies in the range 2.4–9 GHz by having reconfigurable devices such as LNAs, power amplifiers, local oscillators, mixers, etc.

This paper presents a tunable decoupling and matching concept for compact multielement mobile terminal antennas. Instead of optimizing the antenna structure itself to achieve this purpose, the antenna elements are designed to be generic, small and placed closely to each other. The potential of reconfigurable decoupling and matching of such an antenna system, purely controlled by tunable decoupling and matching networks, is studied. The concept is evaluated by different classes of examples. First, fundamental aspects of decoupling and matching are discussed on the basis of several generic antenna matrices. Thereafter, a three-element antenna system of a mobile terminal is investigated by numerical simulations to calculate the achievable bandwidth of each tuning. This study is concluded by presenting efficiency measurements of a lab mock-up of a two-element mobile terminal antenna.

Exploiting multiple-input–multiple-output (MIMO) techniques by using massive antennas can significantly improve the capacity and reliability of wireless systems and has been considered as one key technique in future fifth-generation mobile communications system. Considering the limitation of antenna panel size, placing the massive antennas in 2-D grid is an effective way for its commercialization, which is termed as “3D-MIMO.” In this paper, we study the performance of 3D-MIMO with massive antennas by system-level simulation using practical assumption and 3-D channel model and test the 3D-MIMO in field trial with commercial terminal and networks. In addition, we compare the system-level simulation results and the field trial test measurements. Our system-level simulation results show that the 3D-MIMO with 64 antennas can significantly improve the performance with 56% and 147% gain on cell-average and cell-edge throughputs compared with 2D-MIMO. We perform field trial to test the 3D-MIMO, and the results verify its performance gain obtained by simulation. Furthermore, the measurement in typical high-rise scenario shows that the 3D-MIMO can significantly enhance the data rate of users located at higher floors due to the capability of flexible elevation beamforming.

For accurate beam analysis of a radiating antenna array on a complex platform, the mutual coupling and platform scattering effects are important. We proposed a beam pattern analysis method for an antenna array on a complex platform, which combines the active element pattern method of the receiving mode and hybrid geometrical theory of diffraction antenna current Green’s function technique. This proposed method clearly and mathematically divides the beam pattern of the antenna array on a complex platform into mutual coupling and platform scattering components. For a 12 linear dipole array embedded in a complex aircraft, analyses of the beam pattern and boresight error using the proposed method were verified with the method of moment results, which were simulated with FEKO. With reasonably good accuracy, the proposed method can efficiently analyze a beam pattern reflecting the mutual coupling effect and the platform scattering effect. Additionally, convex optimization with the proposed method is simply applied to synthesize the compensated beam pattern.

A wide-angle scanning planar phased array with magnetic current elements is proposed. A pattern reconfigurable technique is used to design the element that enhances scanning gain and decreases the sidelobe level throughout the entire scanning range. The array is comprised of eight elements in a $2 \times 4$ arrangement with uniform spacing. The proposed phased array operates at 5.8 GHz and can scan with 3 dB beamwidth the entire upper ground elevation plane from −90° to +90° enabled by a two-step pattern reconfigurability mechanism consisting of: 1) coarse-angle scanning and 2) fine-angle scanning. Significant outcomes also include the reduced sidelobe level (less than 7.8 dB) and the particularly small fluctuation (±0.75 dB) of the gain during scanning over a scanning range of 150° (from −75° to +75° in the elevation plane). With the absence of any structure above the ground level, the high efficiency, and the coverage of the entire upper half-space, this proposed antenna array is very attractive for a variety of phased array applications, particularly those that require a flush-mounted structure.

A new algorithm using array beamforming for estimating waves and currents from marine X-band radar image sequences is proposed. Array beamforming is used to extract the wave directional spectrum from the image sequences; the image intensity time series is considered as the signal received by the “antennas” in conventional array beamforming. To retrieve the current velocity, the following feature is utilized: the total power reaches a maximum when a suitable current is used in the beamforming calculation. Because the new algorithm is based on individual pixel points, as opposed to the full image in the conventional method, the coordinate transformation procedure can be avoided. Because of the filter capacity in beamforming, moving vessels and shadowing have little effect on the estimate results, and the empirical modulation transfer function is not required to amend the wave spectrum. The wave and current retrieval scheme is validated using a simulation and by comparing results with data from an in situ buoy.

Presently certain applications demand two or more radiation patterns by using a single antenna array due to miniature and cost effective measures of the device. Hence, reconfigurable array is suitable for this purpose. This paper presents differential evolution (DE) algorithm based design of a reconfigurable antenna array. This method effectively obtains the optimum phase weights for efficient antenna performance in dual mode. The problem attempted is to find an optimal common amplitude weight distribution with minimum amplitude range ratio. 4-bit discrete amplitudes and 5-bit discrete phases have been considered to simplify the design of the array feed network. Based on simulation results, it is established that DE-based reconfigurable antenna array design provides better performance in terms of side lobe levels and null steering.

The principle and experimental validation of a frequency- and polarization-reconfigurable antenna using switching PIN diodes is presented in this letter. The antenna is based on a center-fed circular cavity with switchable shorting vias along its outer edge. Turning a set of shorting vias on on one side and off on the other side creates a radiating slot with controllable length and location along the side wall of the cavity that results in different antenna resonance frequencies and polarizations. As a proof of concept, a particular realization of the antenna is designed that can change the linear polarization in six different angles and at five discrete frequencies (spanning more than one octave). Based on the proposed concept, quasi-continuous frequency- and polarization-reconfiguration is feasible using individual control of a large number of switching devices.

An accurate and reliable massive MIMO channel model is crucial for supporting design and performance evaluation of such systems in the future. However, massive MIMO channel sounding systems are cost prohibitive and complicated, where a large number of antenna elements and associated radio frequency transceiver chains are needed. Virtual large-scale arrays have been extensively utilized as an alternative for massive MIMO channel characterization. In this paper, we investigate virtual large-scale array systems formed by repositioning a real subarray system for channel characterization. With this scheme, we have the flexibility to scale between system cost and system channel sounding capability. Based on this scheme, general beampatterns of subarrays and subarray-based virtual large-scale arrays are derived, based on measured complex antenna patterns of antenna elements on the subarray. Three real subarray antenna systems, i.e., a 16-element uniform rectangular array (URA) at 3.5 GHz, an 8-element uniform circular array at 3.5 GHz, and an 8-element uniform linear array (ULA) at 10 GHz, were utilized to form the respective large-scale virtual arrays, i.e., a 128-element URA, a 48-element uniform cylinder array, and a 64 element ULA, respectively. Beamforming analysis based on the measured complex radiation patterns of the real arrays is provided to demonstrate that virtual large-scale arrays can significantly improve the capability of multipath parameter detection compared with the subarrays. Therefore, such cost-effective systems are promising for characterization massive MIMO propagation channels.

This letter deals with the problem of determining the number of RF sources faced by wireless communication systems. In presence of several sources, it is unavoidable to have signal superposition, loss of tracking, and degrading (ambiguous) estimation. Moreover, the well-known subspace-based methods for tracking and estimating sources require prior knowledge of the number of sources. It is shown here that the independent component analysis (ICA) method can be used not only to determine the number of sources, but also to increase the number of sensors (measures) by combining the array elements. The results also show that narrowband sources having a very small frequency difference $(\mathbf{\Delta F} = \mathbf{0.41}\%)$ are detected. The ICA ability of blind sources separation makes it suitable to determine the number of unknown sources, which is crucial in subspace-based techniques. For instance, the ICA can be used as preprocessing model order estimation in direction of arrival algorithms for smart antenna systems.

International audience; A new methodology of statistical modeling of the far field (FF) radiated by antennas undergoing random disturbances is presented. Firstly, the radiated FF is transformed into a parsimonious form using the Spherical Modes Expansion Method (SMEM); then a surrogate model relating the parsimonious field with the input random parameters is constructed using the Polynomial Chaos Expansion Method (PCEM). The combination of the SMEM and the PCEM allows to develop a compact and precise model with a minimized experimental design cost. The obtained model is computationally costless for generating statistical samples of disturbed antennas easily usable as surrogate models in various types of analyses. In order to demonstrate its performance , the proposed methodology is validated with a deformable canonical antenna – a dipole undergoing three independent random deformations (stretching, bending and torsion), deriving a compact and precise surrogate model.

This letter investigates reliable size reduction of antennas through electromagnetic-driven optimization. It is demonstrated that conventional formulation of the design task by direct footprint miniaturization with imposing constraints on electrical performance parameters may not lead to optimum results. The reason is that—in a typical antenna structure—only a few geometry parameters explicitly determine the antenna footprint, and therefore sensitivity of antenna size to other parameters is zero. At the same time, finding the genuine optimum requires adjustment of all parameters as the optimum is determined by the tradeoff between the size and other figures of merit such as reflection characteristic. Here, an alternative design methodology is proposed that involves relaxation between size reduction and matching improvement. Our methodology is demonstrated using two examples of ultrawideband antenna structures. It is superior over the conventional approach in terms of the optimized antenna size achieved. Experimental validation of the results is also provided.

A reconfigurable loop antenna with two parasitic grounded strips for modern smartphone devices is presented in this paper. The most essential merit of this proposed reconfigurable antenna is that it can keep the intactness of the outer metal rim. In addition, it can generate multiantenna modes. The outer metal rim generates three loop modes and the inner parasite grounded strips can provide two monopole modes. By merging these two types of antenna modes, it can offer two wide bandwidths to cover GSM850/900, DCS/PCS/UMTS2100, and LTE2300/2500 operations with a compact antenna size of 945 mm2. The detailed operating principles and design considerations of this proposed reconfigurable antenna are described. In order to validate this proposed antenna, it was fabricated and tested. The measured antenna efficiencies and gains are satisfied with the requirements for the modern communication devices.

An integrated antenna interference cancellation chip (AIC^2) reducing the inevitable interference between two closely located dual-band multiple-input–multiple-output (MIMO) antennas is introduced. The chip is realized by semilumped components in a volume of 1.6 × 0.8 × 0.6 mm3 using multilayer low temperature co-fired ceramic technology. The proposed topology is applied to two MIMO antennas for IEEE 802.11 n/ac dual-band application. One demonstration board containing only antennas that are strongly coupled and its counter-part containing an integrated AIC^2 chip are designed, fabricated, and measured. It is shown that 10-dB isolation improvement can be achieved within the 2.4-GHz band while the performance at the 5.8-GHz band is well maintained simultaneously. The presented AIC^2 device is suitable for use in mobile Wi-Fi hotspots, smartphones, and wearable devices.

Directional antennas shape transmission patterns to provide greater coverage distance and reduced coverage angle. Use of adaptive directional antenna arrays can minimize interference while also being more energy efficient. When used in an ad-hoc network, this reduces interference among transmitting nodes and thereby increases throughput. Such “smart antennas” use digital beamforming based on signal processing algorithms to compute the appropriate weights to form effective antenna patterns. Smart antennas require the knowledge of the signal received at each antenna in the antenna array, thereby increasing the complexity of hardware and cost. Also, conventional smart antennas optimize results for each individual node, while it is preferable to have a global optimal solution. A problem that has not been addressed is how to compute individual beam patterns that maximize some measure of global network performance. Historically, the focus has been on finding node antenna patterns that give locally optimal performance. In this paper, we investigate a low hardware complexity beamforming approach aimed at improving global performance that uses average Noise-to-Signal ratio as the performance measure. Given a multi-hop route from source to destination, beam patterns are shaped to maximize average signal-to-noise ratio across all nodes on the route, which reduces bit-error rates and extends battery and network lifetime. The antenna weights are sequentially adjusted across all nodes in the route to achieve optimization across the network. By using phase-only weights, hardware costs are minimized. The performance of the algorithm using different path loss models is explored.

This paper presents system modelling and characterization of multiple-band notched ultra-wideband (UWB) antennas using the singularity expansion method (SEM). Multiple-band notches in a classical UWB coplanar disc monopole antenna are achieved by introducing systematic defection slots in the coplanar ground structure solely. The antenna uses two dual-band meander ground-defects to create quadruple band notches to avoid possible interference with pre-existing standard services. The SEM with an improved pole-residue extraction scheme is developed to precisely characterize the band-notched antenna in the time and frequency domains. The improved matrix pencil method is applied to the bore sight impulse response of the proposed notched-band UWB antenna to precisely recognize the band-notches and extract the complex poles and residues at the operating bands between the reject-bands. This procedure is validated by reconstructing the impulse response of the antenna from the extracted poles and residues. The obtained simulation and measurement results are in a very good agreement and demonstrate the reliability of the proposed antenna model and characterization method.

International audience; The problem of choosing a set of N antennas from M possible radiators to optimize the performances of antenna arrays is addressed. Solving this combinatorial problem by evaluating all possible choices is untractable unless both N and M are small. Convex relaxations are proposed to solve approximately this antenna selection problem and quickly get bounds on the performance that can be achieved over all possible antenna combinations. Two approaches are also presented to rapidly construct, from these approximated results, good suboptimal solutions, i.e., good antenna selections. For (N, K)= (30, 10), i.e., 10(30) possible antenna arrays, the methods can be carried out in a few seconds on a laptop. The proposed approaches are applied to solve various representative numerical instances, and they provide quickly valuable information for antenna array designers.

In this paper, system requirements to implement efficient underground IoT systems are overviewed, and novel manhole-cover shaped antenna is proposed. To verify its performance, the antenna prototype is designed for 900MHz-band operation, and it provides an omni-directional radiation pattern for reaching wide coverage.