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This article presents a new switched beam antenna (SBA) for indoor localization applications. The SBA consists of seven circularly polarized (CP) element antennas using a novel feeding network. The...

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.

Smart antenna systems (SAS) play an important role in wireless communication systems, especially in rapidly developing fifth-generation (5G) systems. In normal device under test (DUT) applications with SAS, the antenna’s state may change in different external environments in order to obtain higher antenna gains and better connection with the base station, resulting in high uncertainties for over-the-air (OTA) tests using conventional methods. Before evaluating the transceiver performance, additional application programs are necessary to control the DUT, which increases the inconvenience for engineers and makes it impossible to reflect the real usage scenario. This article proposes a new convenient method for total isotropic sensitivity (TIS) measurement of each antenna group in SAS with multiple groups of antennas. This method monitors the status of the antenna systems, and the TIS is calculated from the received signal strength indicator (RSSI). The proposed method is suitable for Global System for Mobile Communications (GSM), wide band code division multiple access (WCDMA), long term evolution (LTE), and other wireless communication systems with RSSI report.

In the recent years, Mobile Ad-Hoc Wireless Networks (MANET) have played a key role in communication system. It is a self-configured and infrastructure-less network. It is used in different application areas like disaster recovery operations, hospitals and agricultural sectors. However, there are a lot of problems that limit the performances of this network for significantly achieving its roles in different areas. To overcome these problems, this paper enhances the performances of MANET in wireless communication system by adapting smart antenna in Ad-hoc On-Demand Distance Vector (AODV) routing protocol combining with multiple network interfaces. The improved new version AODV utilizing directional antenna and multiple network interface compared with Omni-directional antenna is evaluated based on simulations, which was done with the Network Simulator version two (NS2). Through this study, we found out that directional antennas integrating with multiple network interface throughput and end to end delays always outperform Omni-directional antennas in both random and grid scenarios for AODV routing protocol. In high communication paths and long communication distances also directional antennas have significant improvements in contrast to traditional Omni-directional antennas. Finally, we recommend that for increasing throughput and decreasing end to end delay utilizing directional antennas and multiple network interfaces in MANET technology improve the performances of the wireless communication system.

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.

Steerable directional antennas are increasingly utilised to improve the overall performance of the traditional wireless sensor networks. Steerable directional antenna based networking solutions increase the network capacity by providing a longer range of transmission and reduced interference as compared to networking solutions with omni-directional antennas. However, the use of smart antennas requires complex algorithms and such algorithms may not be easily leveraged in low power Internet of Things (IoT) networks. This study presents mechanisms for integrating low complexity smart antenna solutions into IETF 6TiSCH protocol with the aim of creating scalable and reliable industrial IoT networks. The solution defines extensions to MAC layer and scheduling mechanisms of IETF 6TiSCH protocol to enable its seamless integration with low complexity steerable smart antennas. The results of this study show that smart antenna enabled 6TiSCH protocol stack outperforms the legacy 6TiSCH stack in terms of data delivery performance especially in high density scenarios.

Multi-Beam Smart Antennas (MBSAs) achieve concurrent communications in multiple beams, thereby providing higher throughput compared to regular directional antennas. Most of the transport control schemes used today are based on TCP, which is too conservative since it indiscriminately reduces the window size upon any packet loss. The other extremity is the de-congestion control strategy, which abandons both window size control and retransmission, aggressively saturates the network, and compensates packet loss via network coding. To adapt to the features of the MBSA-based networks, this paper proposes a balanced transport control strategy between the above two categories, which is based on the idea of Adaptive Batch Coding (ABC) . The proposed ABC scheme resists random loss through redundant coding and copes with congestion via window shrink and retransmission. Using a cross-layer design (between transport and routing layer), both the coding scheme and the traffic allocation are adaptively adjusted according to network conditions. A customized simulation system has been developed to comprehensively evaluate the performance of the proposed ABC protocol. Experimental results show that the proposed scheme overcomes the drawbacks of those two extremities. It achieves both high throughput and high throughput (under packet loss) in MBSA-based networks.

The present-day ocean remote sensing instruments that operate at low microwave frequencies are limited in spatial resolution and do not allow for monitoring of the coastal waters. This is due to the difficulties of employing a large reflector antenna on a satellite platform, and generating high-quality pencil beams at multiple frequencies. Recent advances in digital beamforming focal-plane arrays (FPAs) have been exploited in this paper to overcome the above problems. A holistic design procedure for such novel multibeam radiometers has been developed, where: 1) the antenna system specifications are derived directly from the requirements to oceanographic surveys for future satellite missions and 2) the numbers of FPA elements/receivers are determined through a dedicated optimum beamforming procedure minimizing the distance to coast. This approach has been applied to synthesize FPAs for two alternative radiometer systems: a conical scanner with an offset parabolic reflector and a stationary wide-scan torus reflector system, each operating at $C$ -, $X$ -, and Ku-bands. Numerical results predict excellent beam performance for both systems with as low as 0.14% total received power over the land.

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.

The data model for direction of arrival (DOA) estimation is revisited and studied with more attention to the practical implementation of the antenna arrays and verified through measurement results. A complete data model for a single-channel direction finding system that includes, for the first time, the effects of the switching mechanism among antennas is presented. In order to combat coupling among antenna elements and the radio frequency switch nonidealities, a comprehensive model is developed, which includes more accurate noise modeling. The effect of the phase center (PC) in DOA estimation is then discussed and an improved data model is presented, which includes the antenna’s PC movement. The Cramer–Rao bound for circular arrays including the newly introduced parameter for the PC is derived. The new model shows significant improvement in the estimation accuracy.

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.

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.

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.

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.

In the past six years or so, the number of scientific articles and conference papers providing possible multiple-input, multiple-output (MIMO) antenna system solutions has noticeably increased. Flagship conferences on antennas and propagation have recently had multiple sessions addressing MIMO antenna systems and their applications. The importance of such antenna systems lies in the magnitude of their application in current wireless devices and gadgets, and this thrust will continue because fourth-generation (4G) and the upcoming fifth-generation (5G) wireless standards rely heavily on MIMO technology. But throughout the years, and up until now, a wide range of publications still suffer from some major misconceptions and unclear understanding of the fundamental aspects while designing, characterizing, and evaluating such multiantenna systems.

We address the synthesis of isophoric sparse ring arrays for full-Earth coverage from Geostationary Earth Orbit (GEO) satellites by means of steerable beams, switchable between two different widths. In particular, we pursue the desired beam zooming/shrinking through two interleaved sparse arrays deployed over the available circular aperture. To this aim, we propose two different antenna architectures. In one case, the two beams are radiated by two separate interleaved arrays; in the other case, the two beams are instead radiated by two interleaved arrays that share a common part of their layouts. Both the proposed architectures allow us to exploit a synthesis procedure that calculates the two interleaved arrays separately, through the cascade of two steps, both implemented with a (computationally) very efficient deterministic density-tapering approach. The proposed strategy allows to obtain isophoric sparse layouts, satisfying the required design constraints with a significant reduction of the control points with respect to the solution achievable exploiting noninterleaved isophoric sparse arrays.

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.

An improved antenna system with long range and good coverage is essential for Wi-Fi based marine communication system. For a sea to shore communication, the performance of a Smart Antenna (SA) at Base Station (BS) and Customer Premises Equipment (CPE) antenna in boat is used for Wi-Fi based marine communication system is presented in this paper. The results shows that, smart antenna at base station can provide more directionality and connectivity to focus the antenna beam towards the receiver CPE antenna fixed in boat. Compared to the directional antenna and phased array antenna, the proposed smart antenna at base station with multiple access technique can achieve a good coverage along with long range marine communication.

In this paper, we used combination of smart antenna and ant colony optimization for designing an effective Wireless Sensor Network. Novelty of this work exists in the designed algorithm for localization which uses smart antenna as a base station and directional antenna with eight sectors instead of Omni-directional for nodes. Also, we applied ant colony optimization's characteristic for working simultaneous with smart antenna to minimize search time and blind spots when we lose our connection with base station. In addition, another algorithm lets a simple nodes processor decide how and in which direction data transfer quickly.

The use of smart directional antennas in ad-hoc networks has recently received much attention since this technology offers a way to optimize power consumption, increase spatial reuse and reduce co-channel interference. Neighbor discovery is an important first step for these self-configured networks because it makes it possible to identify the active nodes surrounding a given node and this information is essential for other higher layer protocols like medium access control, routing and topology control protocols. In this article, we present two algorithms that aim to take full advantage of the capabilities of smart antennas. The first one aims to increase the number of discovered nodes by considering the nodes that are located in the second-hop neighborhood of a node. The second algorithm seeks to reduce the number of hops in a route between source and destination nodes by using the extended range that can be achieved when the nodes are equipped with directional antennas. The results of the simulations have shown a reduction in the end-to-end delay and an increase in the network throughput when the scheme is compared with other reactive routing protocols.

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.

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.

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.

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.

This paper introduces a multiple-input and multiple-output (MIMO) antenna system for deployment in the closed hinge slot region of notebook computers for long-term evolution (LTE)/wireless wide area network (WWAN)/wireless local area network (WLAN) applications. This antenna system was placed in the closed hinge slot region formed by the full metal cover, metal ground plate, and metal hinges. The MIMO antenna system, includes a main antenna (Ant 1), an auxiliary antenna (Ant 2), and an isolation element. The main and auxiliary antennas were integrated with the metal surrounding them and were used to excite several resonance modes of the closed hinge slot. Excellent antenna efficiency was achieved using the small antennas. Although Ant1 and Ant2 are only 25 mm $\times5$ mm in size, they could cover LTE/WWAN or WLAN operating bands by switching feed points in the same antenna pattern. The isolation element—a 10 mm $\times6$ mm metal sheet—was placed at the center of the closed hinge slot region, and enhanced isolation by more than 7 dB. The isolation levels exceeded 18 dB for LTE700/2300/2500 bands and 15 dB for 2.4/5.2/5.8 GHz WLAN bands.

This letter presents a parameter estimation method using an imperfectly calibrated array of vector antennas. Based on a series of separation of different types of model errors and a subsequent iterative and alternate self-calibration procedure, the proposed method works well in the case of coexistence of channel mismatch, antenna misorientation, and element position error. The mutual coupling effect among antennas is reduced by spreading sparsely the array elements. Simulation results show that the proposed method has a superior performance over the conventional uncalibrated counterpart in terms of incident angle and polarization estimation accuracy.

A new directional modulation system that uses radiation pattern data for modulation encoding is proposed. The approach allows compact multiport antennas (e.g., MIMO-capable antennas) to be used for directional modulation, replacing extensive arrays. The modulation weighting coefficients are calculated with a fixed, antenna specific equation, thus reducing computational complexity. The solution is intended to enhance privacy in small, battery-operated wireless devices, required for ""Internet of Things"" applications.

This paper studies the electronically steerable parasitic array radiator (ESPAR) antenna as a solution for beam pattern switching to implement blind interference alignment (BIA). The ESPAR antenna uses a single radio-frequency (RF) chain, and its beamforming is achieved by simply tuning the reactance loads of parasitic elements. Furthermore, ESPAR's beam pattern can be designed to enhance the received signal-to-noise ratio (SNR), thereby improving the performance of BIA. The focus of this work is the design of the ESPAR beam pattern to realize and improve BIA. In the first approach, each receiver ESPAR antenna dynamically selects the proper beam patterns from among the sector beam patterns, which are pre-designed to access different angular sectors with constant optimal antenna efficiency. We also propose a singular value decomposition (SVD) beamforming method, by means of the available channel state information at the receiver and a dynamic matching network for a high antenna efficiency. The simulation results illustrate the improvement of BIA with proposed methods, especially in the low and moderate SNR region, due to ESPAR's beamforming capability.

This paper presents compact pattern reconfigurable antennas for mobile handsets in MIMO configuration. Each antenna of the MIMO configuration being coupled fed monopole in meandered form is capable of covering several cellular frequency bands in the range of 1.75–2.67 GHz including 4G-LTE, 2G-GSM, 3G-UMTS, and WLAN. The MIMO antennas are printed diagonally at the left and right no-ground portions on the top layer of the substrate to enhance the isolation performance. The substrate used is FR-4 with relative permittivity of 4.35 and loss tangent of 0.02. The volume of the substrate is 120 × 65 × 1.6 mm3 with each antenna occupying an area of 26.5 × 14.5 mm2. The pattern reconfigurability is achieved by connecting and disconnecting a 4.5 × 2 mm2 metallic strip using the p-i-n diode switch. The antennas are pattern reconfigurable in the frequency range of 1.9–2.1 GHz. The isolation achieved is better than 16 dB over all the frequency bands covered by each antenna. A prototype has been fabricated and tested. The simulated and measured results show a good performance of the MIMO antennas. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:148–156, 2017

A novel approach to full-polarimetric short-range imaging with rotating arrays is proposed. Instead of taking advantage of all four possible combinations of the polarizations of transmit and receive antennas as in the typical full-polarimetric imaging systems, the suggested antenna array acquires three different co-polarized measurements at each spatial sampling point with its rotation. A simple algebraic operation is derived to accurately retrieve the full-polarimetric signals in the H/V polarization basis from the co-polarized measurements. After the retrieval of the full-polarimetric signals, the traditional imaging algorithms can be applied to reconstruct the polarimetric images. The effectiveness and accuracy of the suggested approach to fullpolarimetric imaging are validated on the signal and image levels through both numerical simulations and experiments. The results show that the proposed approach can accurately retrieve the fullpolarimetric signals and provides an alternative method to signal acquisition for full-polarimetric imaging.

This paper presents very close and high isolation composite right left handed transmission line MIMO antennas. The MIMO antennas consist of two elements each operates at 5.8 GHz for wireless applications. The two antenna elements are designed using one composite right left handed unit cell separated by only 0.034 λ0. The reduction of mutual coupling between the two antenna elements depends on current reversal between two antenna elements. The proposed MIMO antennas have the advantage of compactness (its size is only 3 × 2.6 cm2). In order to evaluate the performance of MIMO antennas, analysis of mutual coupling, correlation coefficient, diversity gain and total active reflection coefficient are presented. The proposed antennas can achieve isolation = 45 dB and envelope correlation = 0.0002 at 5.8 GHz. The simulated results are confirmed by the measurement results.

In this paper, we propose a new block coding scheme to increase the diversity gain of multiple-input–multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) systems over slow-fading wireless channels. We assume that the antenna elements at the transmitter are reconfigurable and capable of independently changing the physical characteristics of their radiation patterns. The composite right-left handed leaky-wave antenna is an example of reconfigurable antennas with such characteristics. We use this feature of the antennas and develop a block coding scheme that exploits, in addition to the spatial and frequency diversity, a new additional degree of diversity, which is called state diversity. We determine the maximum achievable diversity order of the proposed coding scheme in spatially correlated frequency-selective channels. To demonstrate the performance of the proposed block coding technique, we provide numerical results and compare them with those of the previously developed coding schemes for MIMO-OFDM systems. The results indicate that the proposed code achieves significantly higher diversity and coding gain, even in spatially correlated channels, compared with the existing counterparts.

Tunable antennas are very promising for future generations of mobile communications, where broad frequency coverage will be increasingly required. This article describes the design of small highquality factor (high-Q) tunable antennas based on microelectromechanical systems (MEMS) that are capable of operation in the frequency ranges of 600-960 MHz and 1,710-2,690 MHz. Some aspects of high-Q tunable antennas are investigated here through experimental measurements, and the results are presented.

Bolometer antennas are required to have not only a large gain–bandwidth product but also a fast heating rate suitable for video rate operation. However, while the gain–bandwidth product of an antenna increases with the fraction of the antenna bulk volume occupied by its enclosing sphere, its heating rate decreases. In this paper, we show that for a typical heating rate requirement, wire antennas such as dipole and bow-tie antennas are preferable over planar antennas such as triangular and pentagonal antennas. More complex bent-wire antenna geometries achieved by a genetic algorithm are shown to yield better performance.

A new low-profile, full-space, electronic beam-steering antenna architecture which combines the full-space beam-steering properties of reconfigurable transmitarrays with the low-profile feeding characteristics of leaky-wave antennas is proposed. The design uses an integrated leaky-wave feed to spatially distribute power across a reconfigurable transmitarray aperture in a low-profile manner while individual element phase control using varactor diodes enables full-space pencil-beam-steering. A $6\times 6$ element array was fabricated and experimentally verified, and full-space (both azimuth and elevation) beam-steering was demonstrated at angles up to 45° off broadside with a total efficiency for all scan angles on the order of 25%–35%. The design demonstrates a tenfold reduction in the overall thickness over the original transmitarray, improved aperture amplitude distribution control, as well as improved spillover control. The design also acts as a lower cost, scalable alternative to phased arrays as it does not require a complicated beamforming network and the feed and aperture are easily scaled.

The problem of resolution in antenna ground-penetrating radar (GPR) is very important for the investigation and detection of buried targets. We should solve this problem with software or a numeric method. The purposes of this paper are the modelling and simulation resolution of antenna radar GPR using three antennas, arrays (as in the software REFLEXW), the antenna dipole (as in GprMax2D), and a bow-tie antenna (as in the experimental results). The numeric code has been developed for study resolution antennas by scattered electric fields in mode B-scan. Three frequency antennas (500, 800, and 1,000 MHz) have been used in this work. The simulation results were compared with experimental results obtained by Rial and colleagues under the same conditions.