Transceiver Antenna Research Articles

Wireless Sensing in Complex Electromagnetic Media: Construction Materials and Structural Monitoring

In this paper, wireless sensing in the presence of complex electromagnetic media created by combinations of reinforcing bars and concrete is investigated. The wireless displacement sensing system, primarily designed for use in structural health monitoring (SHM), is composed of a comb-like nested split-ring resonator (NSRR) probe and a transceiver antenna. Although each complex medium scenario is predicted to have a detrimental effect on sensing in principle, it is demonstrated that the proposed sensor geometry is able to operate fairly well in all scenarios except one. In these scenarios that mimic real-life SHM, it is shown that this sensor exhibits a high displacement resolution of 1 $\mu \text{m}$ , a good sensitivity of 7 MHz/mm in average, and a high dynamic range extending over 20 mm. For the most disruptive scenario of placing concrete immediately behind NSRR, a solution based on employing a separator behind the probe is proposed to overcome the handicaps introduced by the medium. In order to obtain a one-to-one mapping from the measured frequency shift to the displacement, a numerical fit is proposed and used. The effects of several complex medium scenarios on this fit are discussed. These results indicate that the proposed sensing scheme works well in real-life SHM applications.

Measuring the Variance of the Vertical Orbital Velocity Component by an Acoustic Wave Gauge With a Single Transceiver Antenna

The capabilities of a new instrument for measuring the surface wave parameters are studied in detail. An acoustic wave gauge with a single antenna is designed to measure the backscatter intensity and the Doppler spectrum of the reflected acoustic signal and to retrieve the variance of the vertical orbital velocity component. The new instrument is numerically simulated, and field experiments using a prototype acoustic wave gauge are carried out. The comparison of the variances of the vertical orbital velocity component measured by acoustic and string wave gauges under field conditions, as well as the comparison of measurements and numerical simulation results, has confirmed the high accuracy of the retrieval algorithms. The advantage of the instrument is its capability of making measurements in any water basin without the use of a fixed platform.

16-channel bow tie antenna transceiver array for cardiac MR at 7.0 tesla.

To design, evaluate, and apply a bow tie antenna transceiver radiofrequency (RF) coil array tailored for cardiac MRI at 7.0 Tesla (T). The radiofrequency (RF) coil array comprises 16 building blocks each containing a bow tie shaped λ/2-dipole antenna. Numerical simulations were used for transmission field homogenization and RF safety validation. RF characteristics were examined in a phantom study. The array's suitability for high spatial resolution two-dimensional (2D) CINE imaging and for real time imaging of the heart was examined in a volunteer study. The arrays transmission fields and RF characteristics are suitable for cardiac MRI at 7.0T. The coil performance afforded a spatial resolution as good as (0.8 × 0.8 × 2.5) mm(3) for segmented 2D CINE MRI at 7.0T which is by a factor of 12 superior versus standardized protocols used in clinical practice at 1.5T. The proposed transceiver array supports 1D acceleration factors of up to R = 6 without impairing image quality significantly. The 16-channel bow tie antenna transceiver array supports accelerated and high spatial resolution cardiac MRI. The array is compatible with multichannel transmission and provides a technological basis for future clinical assessment of parallel transmission techniques at 7.0 Tesla. Magn Reson Med 75:2553-2565, 2016. © 2015 Wiley Periodicals, Inc.

Visions Towards 5G: Technical Requirements and Potential Enablers

Compared to the previous generations of mobile networks, 5G will provide a significant paradigm shift by including beyond state of the art technical solutions, like very high carrier frequencies with massive bandwidths, extreme base station and device densities, and very high number of transceiver antennas. However, unlike the previous generations, it will also be highly integrative and backward compatible: combining the novel 5G air interface and spectrum together with legacy wireless systems like LTE/LTE-A and WiFi, in order to facilitate an umbrella of high-rate coverage and a seamless user experience. In order to support this advances in the radio interface, the core network will also have to reach unprecedented levels of elasticity and intelligence. Spectrum regulation will need to be rethought and significantly improved, whereas energy and cost efficiencies will become one of the key parameters that will steer the 5G design and development. This paper elaborates on the 5G related topics, identifying the key challenges for future research and preliminary 5G standardization activities, as well as providing a comprehensive survey of the current literature.

Partial interference alignment for downlink multi‐cell multi‐input–multi‐output networks

Interference alignment (IA) is a novel technique to achieve the optimal degree of freedom of wireless communication systems through efficient interference management. In a large size multi-cell network, IA over a full connected model requires the impractical number of transmit/receive antennas. Moreover, extensive channel state information is delivered over the backhaul between different base-stations. For realistic scenarios with limited quantity of transceiver antennas, such a full IA scheme may even become infeasible. In this study, by exploiting the heterogeneous path losses, the authors propose a novel partial IA scheme to enhance the throughput of multi-cell networks, which requires relatively small amounts of antennas and hence can be practically implemented. They first formulate the partial IA problem in terms of a mixed integer bi-level non-linear optimal program. Then, they decompose the problem into two sub-problems to reduce the computation complexity and, furthermore, introduce two algorithms for interference links selection. It is shown that, in a 19 hexagonal wrap-around-cell layout, their proposed algorithm outperforms a standard multi-user multi-input–multi-output technique with far less transmit antennas. The present scheme is therefore of great promise to practical applications.

OSTBC transmission in MIMO AF relaying with M-FSK modulation

This paper investigates orthogonal space-time block code (OSTBC) transmission for multiple-input multiple-output (MIMO) amplify-and-forward (AF) relaying networks composed of one source, K relays, and one destination and with M-ary frequency-shift keying (FSK) modulation. A non-coherent detection scheme is proposed and analyzed in a situation where the fading channels undergo temporal correlation. Specifically, by properly exploiting the implicit pilot-symbol-assist property of FSK transmission, the destination estimates the overall channels based on the linear minimum mean square error (LMMSE) estimation algorithm. It then utilizes the maximal ratio combining (MRC) to detect the transmitted information. An upper bound on the probability of errors is derived for a network with arbitrary numbers of transceiver antennas and relays. Based on the obtained bit error rate, the full achievable diversity order is verified. Simulation results are presented to show the validity of the analytical results.

A method of wall clutter removal for through-wall radar based on entropy of expanded antenna source

Strong front wall clutter has serious impacts on the target detection and imaging in the through-wall radar (TWR) system. A method of robust wall clutter suppression based on the entropy of an expanded antenna source for ultra-wide-band through-wall radar is presented in this paper. The model of TWR scenario consists of four layers. Assume that the first and the third layers are air space, while the second and the fourth layers are composed of uniform flat concrete wall. The circular target, assumed to be a perfect electric conductor, is located in the third layer. Along the measurement line which is parallel to the front wall, the transceiver antenna scans uniformly. The echo signals that come from the target and walls are processed into discrete data at first, so that the calculation of probability space is subsequently implemented and the discrete data are expanded as well. And then the entropy of the expanded data that contain robust wall clutter and echo of target is calculated. Taking into consideration the amplitude of target signal varying in each scan, while that of clutter signal is not, it is evident that the entropy can be utilized to discriminate the signals between the target and wall. According to the difference between the entropy of the wall clutter and that of the target, a certain threshold can be set and the optimum tolerance threshold is adaptively selected on the basis of target-to-clutter ratio. With the optimum tolerance threshold, process of clutter suppression is conducted. Finally, back projection is employed for imaging of target. In this paper, data of through-wall radar for simulation are provided by GprMax2D/3D, based on the finite difference-time domain methsd. The clutter suppression and imaging are separately conducted by the method based on data entropy and the method proposed in this paper. Comparing the results of simulations, it is shown that the gain of target-to-clutter ratio for the former is 15.51 dB, and that for the latter is 19.74 dB. It is obvious that the proposed method can provide imaging with higher quality for the same measurement, and it requires fewer scans with the same quality of imaging as well. Computational complexity of the proposed method and the method based on entropy can be expressed as O(M NL) and O(M N) , respectively

基于光纤阵列的卡塞格伦收发一体天线

基于光纤阵列的卡塞格伦收发一体天线

Combined multiuser acoustic communication and localisation system for µAUVs operating in confined underwater environments

This paper describes a communication and localization system for micro-autonomous underwater vehicles (µAUVs) undertaking monitoring and mapping tasks in nuclear storage ponds. A distinctive feature of this underwater environment is the severe multipath propagation and long reverberation times. The paper describes how a common code division multiplexed signal format is used to mitigate the acoustic channel impairments and to achieve both communication and localisation. The system consists of an onshore base-station, equipped with a four-element distributed transceiver antenna, and underwater acoustic modems installed in the µAUVs. The system simultaneously provides localisation of a swarm of µAUVs, with addressed transmission of navigation commands from the base- station to µAUVs, and telemetry data transmission to the base-station from the µAUV.

Progresses in on-body channel models for wireless body area networks

On-body communication channels are a physical basis for the establishment of an effective and reliable wireless link between on-body nodes in wireless body area networks (WBANs).Due to normally strict limitations in transmit power and power consumptions of on-body nodes as well as the human-centered characteristics of WBANs,on-body channels are prone to be affected by the electromagnetic properties of human tissues,human movements,application environments and transceiver antennas,which increase greatly the complexity of the research on channel models.The paper discusses the developments,mathematical expressions and application characteristics of five types of on-body channel models,such as the simple path loss model,the hybrid path loss model,the small-scale fading model,the scenario-based model and the ultra-wideband model,and reviews the current progress on the modeling on-body channels. Key words: Wireless body area network; On-body channel; Path loss; Fading

A Novel Model for Three-Dimensional Imaging Using Interferometric ISAR in Any Curved Target Flight Path

Using a second receiver antenna close to the main transceiver antenna of inverse synthetic aperture radar (ISAR), it is possible to find 3-D positions of target scattering points. Such system is called bistatic, monopulse, or interferometric ISAR (InISAR). In the conventional model of ISAR, the unknown flying object should have a linear trajectory, and only small deviations from this trajectory can be compensated. Target motions which are highly nonlinear or curvy cannot be used in the conventional model. In this paper, we propose a new model for InISAR to process all collected data from the target, regardless of the form of the flight path. More accuracy is achieved for 3-D positioning of the target scattering points by this model because all parts of the flight path contribute in it. We will show the effectiveness of the proposed model in a nonlinear flight path by simulation.

MIMO Radar for Target Detection and Localization in Sensor Networks

In this paper, we explore the use of multiple-input-multiple-output (MIMO) radar imaging systems in sensor networks for the purpose of surveillance. We show how a MIMO radar imaging system can outperform a traditional radar system by reducing the number of transceiver antennas without sacrificing the image resolution. We use a minimum mean square error (MMSE) type receiver structure for this application that minimizes both interference and hardware complexity. We show how a group of sensor nodes can work together in determining one or more targets' locations. A radar image obtained from a single node can detect the presence of targets, but not provide a precise location information. However, spatially scattered group of nodes can together interpolate the targets' positions relative to them and obtain localization information. We provide an in-depth analysis of a MIMO radar system, and demonstrate the operation and utility of such target localization methods using sensor networks through simulation.

Examination of Radio Frequency Blackout for an Inflatable Vehicle During Atmospheric Reentry

Numerical simulations of the plasma flow and electromagnetic wave around a membrane-aeroshell type reentry vehicle were performed using various physical model combinations, and the possibility of radio frequency blackout of transceiver antenna embedded at the rear of the vehicle was investigated. The flowfield was assumed to be in thermochemical nonequilibrium, and it was described by the Navier–Stokes equations with a multitemperature model and the equation of state. The simulations were performed for several altitudes, including the highest heat flux point according to reentry orbit data. Through these computations, the detailed distributions of the flowfield properties in the shock layer and wake region were successfully obtained. To evaluate the possibility of radio frequency blackout during atmospheric reentry, the distribution of the electron number density around the inflatable vehicle was clarified. A frequency-dependent finite-difference time-domain method was used for simulations of electromagnetic waves, and the physical properties were obtained from the computational results of the plasma flow calculation. Electromagnetic wave behaviors in an ionized gas region behind the inflatable vehicle were investigated. It was found that the number density of electrons was sufficiently small and that the electromagnetic waves can propagate with no reflection and less attenuation. These results suggest that radio frequency blackout may not occur during the atmospheric reentry of the inflatable vehicle.

Performance analysis of MIMO cognitive amplify‐and‐forward relay networks with orthogonal space–time block codes

AbstractIn this paper, we study the performance of multiple‐input multiple‐output cognitive amplify‐and‐forward relay networks using orthogonal space–time block coding over independent Nakagami‐m fading. It is assumed that both the direct transmission and the relaying transmission from the secondary transmitter to the secondary receiver are applicable. In order to process the received signals from these links, selection combining is adopted at the secondary receiver. To evaluate the system performance, an expression for the outage probability valid for an arbitrary number of transceiver antennas is presented. We also derive a tight approximation for the symbol error rate to quantify the error probability. In addition, the asymptotic performance in the high signal‐to‐noise ratio regime is investigated to render insights into the diversity behavior of the considered networks. To reveal the effect of network parameters on the system performance in terms of outage probability and symbol error rate, selected numerical results are presented. In particular, these results show that the performance of the system is enhanced when increasing the number of antennas at the transceivers of the secondary network. However, increasing the number of antennas at the primary receiver leads to a degradation in the secondary system performance. Copyright © 2014 John Wiley & Sons, Ltd.

Wireless cellular network for high speed (up to 500 km/h) vehicles

In the last 25-30 years, wireless communications have become an essential part of people’s lives all over the globe. Currently, commercial high data rate mobile services are pro-vided with a peak data rate of 28Mbps using a bandwidth of 5MHz. However, this peak data rate is insufficient and even higher transmission rates are already desired, especially when multiple users and multimedia traffic are considered. The development of high-speed railway makes people’s lives more and more convenient; meanwhile, it puts forward much higher requirements on high-speed railway communication services. In this paper, the wireless cellular network for high speed train is designed that can be deployed in the environment where the passengers have speed up to 500 km/h. For this purpose, two different network architectures are designed for inside and outside the train respectively. Inside the train, the MSs are connected to the wireless access point to communicate. The APs are connected to one transceiver antenna on the top of the train by wired connections. In the outside of the train the BSs for railway is designed in a different manner. The Omni-directional antennas are used for the railway BSs for less energy consumption. The coverage area of one BS is overlapped with the nearest BS as a function of the average expected speed of the train. The railways Base Stations are connected to the BSC, MSC and PSTN as like the conventional cellular system as well as there is a point to point connection line between two adjacent BSs to transfer the control information firstly. When the train passes through the overlapping area of the cells, the handoff is occur and all the controls are transferred from the previous BS to the next BS to the moving direction of the train. For a train with maximum speed of 500 km/h we use the BS antenna that can cover an area of radius 10 km. The maximum distance between the overlapped boundary, (5*138) m= 690m (500000/3600= 138). So it will take 5 sec for a train to pass through the overlapping area. During this period of time, the handoff can occur smoothly.

Distributed Wireless Sensor Network Localization Algorithm using Space Standard Normal Vector (SSNV)

—In this paper a low cost but effective localization algorithm for wireless sensor networks (WSNs) is introduced. From the proposed scheme unknown nodes only have to listen to three anchor nodes and establish a space standard normal vector (SSNV) to estimate the coordinates of them. Many localization algorithms for WSNs require the exits of extra components, such as a GPS, ultrasonic transceiver, and unidirectional antenna on sensor nodes. Conversely the proposed localization scheme is range-free which means there is no demanding of any extra devices for the sensors. In this scheme, by collecting information from the three nearest anchors a geometric plane surface is built whose standard normal vector is also obtained correspondingly. The estimated location of each unknown sensor is adjusted according to its relative normal vector in the space which belongs to the built plane surface. This paper compares the proposed scheme with the well-known DV-Hop mechanism, Centroid method and the OSSDL algorithm that we proposed before. Simulation results show that the proposed scheme outperforms the other three in localization accuracy, communication cost, and computational complexity. Analysis about the effects of different length of normal vector is also made.

Prediction of MIMO Channel Distribution with Transceiver AntennaLimitations

The ability of ideal MIMO channels has a high-SNR slope that equals the minimum of the number of transceiver antennas. This work evaluates if this result holds when there are distortions from physical transceiver limitations. We prove analytically that such physical MIMO/SISO channels have a finite upper capacity limit, for any channel distribution and SNR. The high-SNR slope thus collapses to zero. This appears discouraging, but we prove the encouraging result that the relative capacity gain of employing MIMO/SISO is at least as large as with ideal transceivers. The entire results will be shown in MATLAB platform effectively.

Maximum Achievable Capacity in Airborne MIMO Communications with Arbitrary Alignments of Linear Transceiver Antenna Arrays

In this paper, the capacity of airborne multiple-input-multiple-output (MIMO) wireless communication systems with arbitrary alignments of linear transmit and receive antenna arrays is systematically analyzed and the maximum achievable capacity is determined. Based on a general three-dimensional (3D) airborne MIMO communication model, we are able to approximate the airborne MIMO capacity as a function of the transmit and receive antenna array geometry in the 3D space. The capacity approximation is asymptotically tight as the distance between the transmit and receive antenna arrays large compared to their size. Based on the asymptotically tight capacity approximation, we derive an upper bound as well as a lower bound of the airborne MIMO capacity. Interestingly, both the upper and lower bounds are achievable. We also derive a necessary and sufficient condition for airborne MIMO communication systems to achieve the capacity upper bound for any given 3D transceiver antenna array geometry. The necessary and sufficient condition allows us to properly select the system parameters and design airborne MIMO communication systems that reach the best possible performance in terms of system capacity. We prove that when the distance between the transmit and receive antenna arrays is within a certain range, there exists a set of system parameter values (e.g. antenna element separation) for which the capacity of the MIMO communication system achieves the theoretical upper bound and this capacity value is larger than the average capacity of the corresponding conventional MIMO communication system under Rayleigh fading. Finally, we prove that the airborne MIMO capacity converges to the capacity lower bound when the distance between the transmit and receive antenna arrays goes to infinity. Extensive numerical studies included in this paper illustrate and validate our theoretical developments.

The short-term effects of antenna insulation thickness on path losses in wireless telemetry implants at microwave frequencies

Various physiological parameters can be monitored non-invasively using wireless biotelemetry links. The development of sophisticated ultra low power consuming transceivers allows the transmission of large amounts of data from the inside of the body to an external receiver in real time at microwave frequencies.Antenna impedance matching is crucial for obtaining an acceptable propagation link budget in a wireless telemetry link. The dielectric properties of biological tissue induce detuning to transceiver antennas when implanted into the body. To counteract detuning problems, implant antennas are coated with biocompatible insulating material. The study investigates the propagation losses of a wireless communication link at different insulation thicknesses of medical grade silicone in the Industrial-Scientific-Medical (ISM) radio band at 2.45 GHz. The wireless link consisted of an implantable unit which was placed between two pads of tissue substitute material and an external receiver which was connected to a laptop. Predefined data packets were transmitted from the implant, the received packets were analyzed, packet errors and packet losses were logged and the received signal strength indicator values (RSSI) were recorded. Our results showed that the mean RSSI values of insulated transmitter antennas - embedded in tissue equivalent material - provide more safety distance to critical receiver sensitivity level than uncoated antennas.The conducted measurements let us conclude that with increasing thickness of the insulation layer, the antenna becomes less sensitive to detuning by adjacent tissue substitute material. Therefore tuned antennas are less influenced by the surrounding tissue after implantation.

The short-term effects of antenna insulation thickness on path losses in wireless telemetry implants at microwave frequencies

Various physiological parameters can be monitored non-invasively using wireless biotelemetry links. The development of sophisticated ultra low power consuming transceivers allows the transmission of large amounts of data from the inside of the body to an external receiver in real time at microwave frequencies.Antenna impedance matching is crucial for obtaining an acceptable propagation link budget in a wireless telemetry link. The dielectric properties of biological tissue induce detuning to transceiver antennas when implanted into the body. To counteract detuning problems, implant antennas are coated with biocompatible insulating material. The study investigates the propagation losses of a wireless communication link at different insulation thicknesses of medical grade silicone in the Industrial-Scientific-Medical (ISM) radio band at 2.45 GHz. The wireless link consisted of an implantable unit which was placed between two pads of tissue substitute material and an external receiver which was connected to a laptop. Predefined data packets were transmitted from the implant, the received packets were analyzed, packet errors and packet losses were logged and the received signal strength indicator values (RSSI) were recorded. Our results showed that the mean RSSI values of insulated transmitter antennas - embedded in tissue equivalent material - provide more safety distance to critical receiver sensitivity level than uncoated antennas.The conducted measurements let us conclude that with increasing thickness of the insulation layer, the antenna becomes less sensitive to detuning by adjacent tissue substitute material. Therefore tuned antennas are less influenced by the surrounding tissue after implantation.