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Showing papers on "Antenna (radio) published in 2013"


Journal ArticleDOI
TL;DR: In this paper, the tradeoff between the energy efficiency and spectral efficiency of a single-antenna system is quantified for a channel model that includes small-scale fading but not large scale fading, and it is shown that the use of moderately large antenna arrays can improve the spectral and energy efficiency with orders of magnitude compared to a single antenna system.
Abstract: A multiplicity of autonomous terminals simultaneously transmits data streams to a compact array of antennas. The array uses imperfect channel-state information derived from transmitted pilots to extract the individual data streams. The power radiated by the terminals can be made inversely proportional to the square-root of the number of base station antennas with no reduction in performance. In contrast if perfect channel-state information were available the power could be made inversely proportional to the number of antennas. Lower capacity bounds for maximum-ratio combining (MRC), zero-forcing (ZF) and minimum mean-square error (MMSE) detection are derived. An MRC receiver normally performs worse than ZF and MMSE. However as power levels are reduced, the cross-talk introduced by the inferior maximum-ratio receiver eventually falls below the noise level and this simple receiver becomes a viable option. The tradeoff between the energy efficiency (as measured in bits/J) and spectral efficiency (as measured in bits/channel use/terminal) is quantified for a channel model that includes small-scale fading but not large-scale fading. It is shown that the use of moderately large antenna arrays can improve the spectral and energy efficiency with orders of magnitude compared to a single-antenna system.

2,770 citations


Journal ArticleDOI
TL;DR: JSDM achieves significant savings both in the downlink training and in the CSIT uplink feedback, thus making the use of large antenna arrays at the base station potentially suitable also for frequency division duplexing systems, for which uplink/downlink channel reciprocity cannot be exploited.
Abstract: We propose joint spatial division and multiplexing (JSDM), an approach to multiuser MIMO downlink that exploits the structure of the correlation of the channel vectors in order to allow for a large number of antennas at the base station while requiring reduced-dimensional channel state information at the transmitter (CSIT). JSDM achieves significant savings both in the downlink training and in the CSIT uplink feedback, thus making the use of large antenna arrays at the base station potentially suitable also for frequency division duplexing (FDD) systems, for which uplink/downlink channel reciprocity cannot be exploited. In the proposed scheme, the multiuser MIMO downlink precoder is obtained by concatenating a prebeamforming matrix, which depends only on the channel second-order statistics, with a classical multiuser precoder, based on the instantaneous knowledge of the resulting reduced dimensional “effective” channel matrix. We prove a simple condition under which JSDM incurs no loss of optimality with respect to the full CSIT case. For linear uniformly spaced arrays, we show that such condition is approached in the large number of antennas limit. For this case, we use Szego's asymptotic theory of Toeplitz matrices to show that a DFT-based prebeamforming matrix is near-optimal, requiring only coarse information about the users angles of arrival and angular spread. Finally, we extend these ideas to the case of a 2-D base station antenna array, with 3-D beamforming, including multiple beams in the elevation angle direction. We provide guidelines for the prebeamforming optimization and calculate the system spectral efficiency under proportional fairness and max-min fairness criteria, showing extremely attractive performance. Our numerical results are obtained via asymptotic random matrix theory, avoiding lengthy Monte Carlo simulations and providing accurate results for realistic (finite) number of antennas and users.

1,347 citations


Journal ArticleDOI
TL;DR: Measurements and models that may be used to design future fifth-generation millimeter-wave cellular networks are provided and insight into antenna beam steering algorithms for these systems are given.
Abstract: The spectrum crunch currently experienced by mobile cellular carriers makes the underutilized millimeter-wave frequency spectrum a sensible choice for next-generation cellular communications, particularly when considering the recent advances in low cost sub-terahertz/millimeter-wave complementary metal–oxide semiconductor circuitry. To date, however, little is known on how to design or deploy practical millimeter-wave cellular systems. In this paper, measurements for outdoor cellular channels at 38 GHz were made in an urban environment with a broadband (800-MHz RF passband bandwidth) sliding correlator channel sounder. Extensive angle of arrival, path loss, and multipath time delay spread measurements were conducted for steerable beam antennas of differing gains and beamwidths for a wide variety of transmitter and receiver locations. Coverage outages and the likelihood of outage with steerable antennas were also measured to determine how random receiver locations with differing antenna gains and link budgets could perform in future cellular systems. This paper provides measurements and models that may be used to design future fifth-generation millimeter-wave cellular networks and gives insight into antenna beam steering algorithms for these systems.

812 citations


Journal ArticleDOI
Hubregt J. Visser1, Ruud Vullers1
09 Apr 2013
TL;DR: The feasibility of harvesting is discussed, leading to the conclusion that RF energy transport is preferred for powering small sized sensors by radio-frequency energy harvesting or transport.
Abstract: This paper presents an overview of principles and requirements for powering wireless sensors by radio-frequency (RF) energy harvesting or transport. The feasibility of harvesting is discussed, leading to the conclusion that RF energy transport is preferred for powering small sized sensors. These sensors are foreseen in future Smart Buildings. Transmitting in the ISM frequency bands, respecting the transmit power limits ensures that the International Commission on Non-Ionizing Radiation Protection (ICNIRP) exposure limits are not exceeded. With the transmit side limitations being explored, the propagation channel is next discussed, leading to the observation that a better than free-space attenuation may be achieved in indoors line-of-sight environments. Then, the components of the rectifying antenna (rectenna) are being discussed: rectifier, dc-dc boost converter, and antenna. The power efficiencies of all these rectenna subcomponents are being analyzed and finally some examples are shown. To make RF energy transport a feasible powering technology for low-power sensors, a number of precautions need to be taken. The propagation channel characteristics need to be taken into account by creating an appropriate transmit antenna radiation pattern. All subcomponents of the rectenna need to be impedance matched, and the power transfer efficiencies of the rectifier and the boost converter need to be optimized.

629 citations


Patent
09 Jan 2013
TL;DR: In this paper, the antenna element is a bracket for holding a stylus or other object within the stylus chamber that is associated with the computing device, and the dimension and composition of the antenna remain relatively constant to provide a consistent radiation pattern requiring little or no redesign when implemented across the different products.
Abstract: Technology for standardizing an antenna design for a computing device includes an antenna element in the shape of an object that is commonly useful with multiple, different computing products. For example, in one embodiment the antenna element is a bracket for holding a stylus or other object within a stylus chamber that is associated with the computing device. The dimension and composition of the antenna remain relatively constant to provide a consistent radiation pattern requiring little or no redesign when implemented across the different products, since it may be placed at an edge of a device, by a stylus holder, or similar, common location that is a distance from a ground plane and device circuitry.

453 citations


Journal ArticleDOI
TL;DR: In this paper, a planar-monopole (PM) antenna with microstrip-fed printed on one side of the substrate and placed perpendicularly to each other to achieve good isolation is proposed.
Abstract: A compact multiple-input-multiple-output (MIMO) antenna with a small size of 26×40 mm2 is proposed for portable ultrawideband (UWB) applications. The antenna consists of two planar-monopole (PM) antenna elements with microstrip-fed printed on one side of the substrate and placed perpendicularly to each other to achieve good isolation. To enhance isolation and increase impedance bandwidth, two long protruding ground stubs are added to the ground plane on the other side and a short ground strip is used to connect the ground planes of the two PMs together to form a common ground. Simulation and measurement are used to study the antenna performance in terms of reflection coefficients at the two input ports, coupling between the two input ports, radiation pattern, realized peak gain, efficiency and envelope correlation coefficient for pattern diversity. Results show that the MIMO antenna has an impedance bandwidth of larger than 3.1-10.6 GHz, low mutual coupling of less than -15 dB, and a low envelope correlation coefficient of less than 0.2 across the frequency band, making it a good candidate for portable UWB applications.

427 citations


Journal ArticleDOI
TL;DR: Analytical and numerical results show that, under certain mild conditions on the channel gains, for a fixed M, an array gain is achievable even under the stringent per-antenna CE constraint, and the proposed CE precoding scheme performs close to the sum-capacity achieving scheme for an average-only total transmit power constrained channel.
Abstract: We consider the multi-user MIMO broadcast channel with M single-antenna users and N transmit antennas under the constraint that each antenna emits signals having constant envelope (CE). The motivation for this is that CE signals facilitate the use of power-efficient RF power amplifiers. Analytical and numerical results show that, under certain mild conditions on the channel gains, for a fixed M, an array gain is achievable even under the stringent per-antenna CE constraint. Essentially, for a fixed M, at sufficiently large N the total transmitted power can be reduced with increasing N while maintaining a fixed information rate to each user. Simulations for the i.i.d. Rayleigh fading channel show that the total transmit power can be reduced linearly with increasing N (i.e., an O(N) array gain). We also propose a precoding scheme which finds near-optimal CE signals to be transmitted, and has O(MN) complexity. Also, in terms of the total transmit power required to achieve a fixed desired information sum-rate, despite the stringent per-antenna CE constraint, the proposed CE precoding scheme performs close to the sum-capacity achieving scheme for an average-only total transmit power constrained channel.

370 citations


Journal ArticleDOI
Young-Han Nam1, Boon Loong Ng1, Krishna Sayana1, Yang Li1, Jianzhong Zhang1, Younsun Kim1, Ju-Ho Lee1 
TL;DR: The simulation results show that the proposed FD-MIMO system with 32 antenna ports achieves 2-3.6 times cell average throughput gain and 1-5 times cell edge throughput gain compared to the 4G LTE system of two antenna ports at the BS.
Abstract: This article considers a practical implementation of massive MIMO systems [1]. Although the best performance can be achieved when a large number of active antennas are placed only in the horizontal domain, BS form factor limitation often makes horizontal array placement infeasible. To cope with this limitation, this article introduces full-dimension MIMO (FD-MIMO) cellular wireless communication system, where active antennas are placed in a 2D grid at BSs. For analysis of the FD-MIMO systems, a 3D spatial channel model is introduced, on which system-level simulations are conducted. The simulation results show that the proposed FD-MIMO system with 32 antenna ports achieves 2-3.6 times cell average throughput gain and 1.5-5 times cell edge throughput gain compared to the 4G LTE system of two antenna ports at the BS.

354 citations


Proceedings ArticleDOI
01 Dec 2013
TL;DR: This paper presents path loss models suitable for the development of fifth generation (5G) standards that show the distance dependency of received power, and shows that coverage is actually better than first suggested by work in [1], [7] and [8].
Abstract: Measurements for future outdoor cellular systems at 28 GHz and 38 GHz were conducted in urban microcellular environments in New York City and Austin, Texas, respectively. Measurements in both line-of-sight and non-line-of-sight scenarios used multiple combinations of steerable transmit and receive antennas (e.g. 24.5 dBi horn antennas with 10.9° half power beamwidths at 28 GHz, 25 dBi horn antennas with 7.8° half power beamwidths at 38 GHz, and 13.3 dBi horn antennas with 24.7° half power beamwidths at 38 GHz) at different transmit antenna heights. Based on the measured data, we present path loss models suitable for the development of fifth generation (5G) standards that show the distance dependency of received power. In this paper, path loss is expressed in easy-to-use formulas as the sum of a distant dependent path loss factor, a floating intercept, and a shadowing factor that minimizes the mean square error fit to the empirical data. The new models are compared with previous models that were limited to using a close-in free space reference distance. Here, we illustrate the differences of the two modeling approaches, and show that a floating intercept model reduces the shadow factors by several dB and offers smaller path loss exponents while simultaneously providing a better fit to the empirical data. The upshot of these new path loss models is that coverage is actually better than first suggested by work in [1], [7] and [8].

352 citations


Journal ArticleDOI
TL;DR: Experimental and numerical results show that the radiation characteristics, impedance matching, and SAR values of the proposed design are significantly improved compared to conventional monopole and dipole antennas, which makes it a good candidate for the wearable telemedicine application.
Abstract: We present a flexible, compact antenna system intended for telemedicine applications. The design is based on an M-shaped printed monopole antenna operating in the Industrial, Scientific, and Medical (ISM) 2.45 GHz band integrated with a miniaturized slotted Jerusalem Cross (JC) Artificial Magnetic Conductor (AMC) ground plane. The AMC ground plane is utilized to isolate the user's body from undesired electromagnetic radiation in addition to minimizing the antenna's impedance mismatch caused by the proximity to human tissues. Specific Absorption Rate (SAR) is analyzed using a numerical human body model (HUGO) to assess the feasibility of the proposed design. The antenna expresses 18% impedance bandwidth; moreover, the inclusion of the AMC ground plane increases the front to back ratio by 8 dB, provides 3.7 dB increase in gain, in addition to 64% reduction in SAR. Experimental and numerical results show that the radiation characteristics, impedance matching, and SAR values of the proposed design are significantly improved compared to conventional monopole and dipole antennas. Furthermore, it offers a compact and flexible solution which makes it a good candidate for the wearable telemedicine application.

349 citations


Book
11 Jan 2013
TL;DR: In this article, the authors present a comprehensive insight into the design techniques for different types of circularly polarized antenna elements and arrays, including the basic principles, design techniques and characteristics of various types of CP antennas, such as CP patch antennas, CP helix antennas, quadrifilar helix antenna, printed slots, spiral antennas, monopoles, dielectric resonator antennas, etc.
Abstract: This book presents a comprehensive insight into the design techniques for different types of CP antenna elements and arraysIn this book, the authors address a broad range of topics on circularly polarized (CP) antennas. Firstly, it introduces to the reader basic principles, design techniques and characteristics of various types of CP antennas, such as CP patch antennas, CP helix antennas, quadrifilar helix antennas (QHA), printed quadrifilar helix antennas (PQHA), spiral antenna, CP slot antennas, CP dielectric resonator antennas, loop antennas, crossed dipoles, monopoles and CP horns. Advanced designs such as small-size CP antennas, broadband, wideband and ultra-wideband CP antennas are also discussed, as well as multi-band CP antennas and dual CP antennas. The design and analysis of different types of CP array antennas such as broadband CP patch arrays, dual-band CP arrays, CP printed slot arrays, single-band and multi-band CP reflectarrays, high-gain CP waveguide slot antennas, CP dielectric resonator antenna arrays, CP active arrays, millimetre-waveband CP arrays in LTCC, and CP arrays with electronically beam-switching or beam-steering capabilities are described in detail. Case studies are provided to illustrate the design and implementation of CP antennas in practical scenarios such as dual-band Global Navigation Satellite Systems (GNSS) receivers, satellite communication mobile terminals at the S-band, Radio Frequency Identification (RFID) readers at 2.4 GHz, and Ka-band high-speed satellite communication applications. It also includes the detailed designs for a wideband Logarithmic spiral antenna that can operate from 3.4-7.7 GHz. In addition, the book offers a detailed review of the recent developments of different types of CP antennas and arrays.Presents comprehensive discussions of design techniques for different types of CP antennas: small-size CP antennas, broadband CP antennas, multi-band CP antennas and CP arrays.Covers a wide range of antenna technologies such as microstrip antennas, helix, quadrifilar helix antenna, printed quadrifilar helix antenna, dielectric resonator antennas, printed slots, spiral antennas, monopoles, waveguide slot arrays, reflectarrays, active arrays, millimetre-wave arrays in LTCC, electronically beam-switching arrays and electronically beam-steerable arrays.Reviews recent developments in different types of CP antennas and arrays, reported by industries, researchers and academics worldwide.Includes numerous case studies to demonstrate how to design and implement different CP antennas in practical scenarios.Provides both an introduction for students in the field and an in-depth reference for antenna/RF engineers who work on the development of CP antennas.Circularly Polarized Antennas will be an invaluable guide for researchers in RD system engineers (antenna, telecom, space and satellite); postgraduates studying the subjects of antenna and propagation, electromagnetics, RF/microwave/millimetre-wave systems, satellite communications and so on; technical managers and professionals in the areas of antennas and propagation.

Journal ArticleDOI
02 Apr 2013
TL;DR: This paper discusses far-field wireless powering for low-power wireless sensors, with applications to sensing in environments where it is difficult or impossible to change batteries and where the exact position of the sensors might not be known.
Abstract: This paper discusses far-field wireless powering for low-power wireless sensors, with applications to sensing in environments where it is difficult or impossible to change batteries and where the exact position of the sensors might not be known. With expected radio-frequency (RF) power densities in the 20-200- μW/cm2 range, and desired small sensor overall size, low-power nondirective wireless powering is appropriate for sensors that transmit data at low duty cycles. The sensor platform is powered through an antenna which receives incident electromagnetic waves in the gigahertz frequency range, couples the energy to a rectifier circuit which charges a storage device (e.g., thin-film battery) through an efficient power management circuit, and the entire platform, including sensors and a low-power wireless transmitter, and is controlled through a low-power microcontroller. For low incident power density levels, codesign of the RF powering and the power management circuits is required for optimal performance. Results for hybrid and monolithic implementations of the power management circuitry are presented with integrated antenna rectifiers operating in the 1.96-GHz cellular and in 2.4-GHz industrial-scientific-medical (ISM) bands.

Patent
14 Jun 2013
TL;DR: In this paper, a transmit antenna generates an electromagnetic field having a region for wirelessly transferring power from the transmit antenna to a plurality of receiver devices, and a controller determines a power allocation for a particular one of the plurality of receivers disposed within the region, and adjusts the power allocation based at least in part on a power requirement received from the particular receiver devices.
Abstract: Exemplary embodiments are directed to wireless power transfer. A transmit antenna generates an electromagnetic field having a region for wirelessly transferring power from the transmit antenna to a plurality of receiver devices. A controller is operably coupled to the transmit antenna. The controller determines a power allocation for a particular one of the plurality of receiver devices disposed within the region, and adjusts the power allocation based at least in part on a power requirement received from the particular one of the plurality of receiver devices.

Journal ArticleDOI
TL;DR: In this article, a fully electronically reconfigurable 400-element transmitarray is studied numerically and experimentally in the X-band, where two p-i-n diodes are integrated on the active side of each cell to control its transmission phase.
Abstract: A fully electronically reconfigurable 400-element transmitarray is studied numerically and experimentally in X-band. The array operates in linear polarization and consists of 20 × 20 unit-cells. A 1-bit phase resolution has been selected for the unit-cell in order to reduce the complexity of the biasing network and steering logic, the insertion loss and the overall cost of the antenna system. The unit-cell stack-up is simple and is made of four metal layers: active side, biasing lines, ground plane and passive side. Two p-i-n diodes are integrated on the active side of each cell in order to control its transmission phase. The active array contains 800 diodes in total. It demonstrates experimentally pencil beam scanning over a 140 × 80-degree window over a 15.8% fractional bandwidth, with a maximum gain of 22.7 dBi at broadside. We also show that the same antenna array can be used for beam shaping applications (flat-top beam). The experimental results presented between 8 and 12 GHz are in good agreement with the theoretical performance calculated using full-wave electromagnetic simulations and an in-house CAD tool based on analytical modeling.

Journal ArticleDOI
TL;DR: This paper exploits the potential of large antenna arrays at millimeter-wave (mm-Wave) frequencies to develop a low-complexity directional modulation technique, Antenna Subset Modulation (ASM), for point-to-point secure wireless communication.
Abstract: The small carrier wavelength at millimeter-wave (mm-Wave) frequencies enables featuring a large number of co-located antennas. This paper exploits the potential of large antenna arrays to develop a low-complexity directional modulation technique, Antenna Subset Modulation (ASM), for point-to-point secure wireless communication. The main idea in ASM is to modulate the radiation pattern at the symbol rate by driving only a subset of antennas in the array. This results in a directional radiation pattern that projects a sharply defined constellation in the desired direction and expanded further randomized constellation in other directions. Two techniques for implementing ASM are proposed. The first technique selects an antenna subset randomly for every symbol. While randomly switching antenna subsets does not affect the symbol modulation for a desired receiver along the main direction, it effectively randomizes the amplitude and phase of the received symbol for an eavesdropper along a sidelobe. Using a simplified statistical model, an expression for the average uncoded symbol error rate (SER) is derived as a function of the observation angle. To overcome the problem of large sidelobes in random antenna subset switching, the second technique uses an optimized antenna subset selection procedure based on simulated annealing to achieve superior performance compared with random selection. Numerical comparisons of the SER performance and secrecy capacity of the proposed techniques against those of conventional array transmission are presented to highlight the potential of ASM.

Patent
25 Nov 2013
TL;DR: In this paper, an embodiment of a system for wirelessly charging a wrist-worn device may include a radio frequency charging energy generating element, and an antenna configured to radiate the RF charging energy, the antenna comprising a first coil and a second coil, each comprising a plurality of windings, the windings of the first coil being wound in a direction opposite the direction of the second coil.
Abstract: An embodiment of a system for wirelessly charging a wrist-worn device may include a radio frequency (RF) charging energy generating element, and an antenna configured to radiate the RF charging energy, the antenna comprising a first coil and a second coil, the first coil and the second coil each comprising a plurality of windings, the windings of the first coil being wound in a direction opposite the direction of the windings of the second coil. An embodiment of a wrist-worn charge-receiving device may include an antenna coil adapted to receive radio frequency (RF) charging energy, the antenna coil comprising non-uniform windings; and a rechargeable power source coupled to the antenna coil, the antenna coil adapted to provide the RF charging energy to the rechargeable power source.

Journal ArticleDOI
TL;DR: It is shown that the proposed antenna selection based SM systems are capable of attaining a significant gain in signal-to-noise ratio (SNR) compared to conventional SM systems, and also outperform the conventional MIMO systems employing antenna selection at both low and medium SNRs.
Abstract: Novel transmit antenna selection techniques are conceived for Spatial Modulation (SM) systems and their symbol error rate (SER) performance is investigated. Specifically, low-complexity Euclidean Distance optimized Antenna Selection (EDAS) and Capacity Optimized Antenna Selection (COAS) are studied. It is observed that the COAS scheme gives a better SER performance than the EDAS scheme. We show that the proposed antenna selection based SM systems are capable of attaining a significant gain in signal-to-noise ratio (SNR) compared to conventional SM systems, and also outperform the conventional MIMO systems employing antenna selection at both low and medium SNRs.

Journal ArticleDOI
TL;DR: A novel stochastic 300 GHz indoor channel model is introduced that combines both the modeling in time as well as in frequency domain in order to account for the significant frequency dispersion of ultra broadband THz channels.
Abstract: Providing the basis for fast system simulations and the adequate design of upcoming THz communication systems, a novel stochastic 300 GHz indoor channel model is introduced. It combines both the modeling in time as well as in frequency domain in order to account for the significant frequency dispersion of ultra broadband THz channels. Not only amplitude, phase and temporal, but also spatial channel information is considered. That way, MIMO systems as well as novel antenna concepts can be simulated. Verified and calibrated frequency domain ray tracing simulations in an office scenario provide the data basis for the derivation of model parameters. Model channel realizations are tested against ray tracing predictions and channel measurements. A complete scenario-specific parameter set is given for the considered environment, so that the model can be implemented for further use and future THz communication links can be designed under consideration of realistic propagation conditions.

Patent
29 May 2013
TL;DR: In this paper, a substantially hollow housing containing an antenna arrangement and configured to define an inner cavity for propagation of electromagnetic radiation from the antenna arrangement is presented, where the inner cavity of the housing operates as a waveguide for directionally guiding the electromagnetic radiation to the charging zone.
Abstract: The present invention provides wireless charging techniques and devices for charging electronic device(s) within a closed space defined by a substantially hollow housing containing an antenna arrangement and configured to define an inner cavity for propagation of electromagnetic radiation from the antenna arrangement. The housing has an inner surface, encompassing the inner cavity, which geometry and material composition selected to define a general propagation path for the predetermined electromagnetic radiation from the antenna arrangement towards a charging zone. The inner cavity of the housing operates as a waveguide for directionally guiding the electromagnetic radiation to the charging zone and providing substantially maximal intensity of the electromagnetic radiation within the charging zone.

Journal ArticleDOI
TL;DR: This paper addresses the EE optimization problem for MIMO-BC with a practical power model, taking into account a transmit independent power which is related to the number of active transmit antennas, and proposes a new optimization approach, in which the transmit covariance is optimized under fixed active transmit antenna sets, and thenactive transmit antenna selection (ATAS) is utilized.
Abstract: Characterizing the fundamental energy efficiency (EE) limits of MIMO broadcast channels (BC) is significant for the development of green wireless communications. We address the EE optimization problem for MIMO-BC in this paper and consider a practical power model, i.e., taking into account a transmit independent power which is related to the number of active transmit antennas. Under this setup, we propose a new optimization approach, in which the transmit covariance is optimized under fixed active transmit antenna sets, and then active transmit antenna selection (ATAS) is utilized. During the transmit covariance optimization, we propose a globally optimal energy efficient iterative water-filling scheme through solving a series of concave-convex fractional programs based on the block-coordinate ascent algorithm. After that, ATAS is employed to determine the active transmit antenna set. Since activating more transmit antennas can achieve higher sum-rate but at the cost of larger transmit independent power consumption, there exists a tradeoff between the sum-rate gain and the power consumption. Here ATAS can explore the optimal tradeoff curve and thus further improve the EE. Optimal exhaustive search and low-complexity norm based ATAS schemes are developed. Through simulations, we discuss the effect of different parameters on the EE of the MIMO-BC.

Journal ArticleDOI
TL;DR: A key observation is that distributed antenna systems are tightly integrated into the cellular architecture, and incorporate physical layer technologies like MIMO communication and multiuser MIMo to provide higher data rates.
Abstract: Providing uniformly high capacity in cellular systems is challenging due to fading, path loss, and interference. A partial solution to this problem is the deployment of distributed antenna systems, where transmission points are distributed throughout the cell using coax cable or fiber, instead of being centrally located on a single tower. This article reviews how distributed antenna systems are evolving to provide higher performance on the downlink in cellular systems. Research trends in distributed antennas for the downlink of cellular systems are described along with current progress on their integration into commercial wireless cellular standards. A key observation is that distributed antenna systems are tightly integrated into the cellular architecture, and incorporate physical layer technologies like MIMO communication and multiuser MIMO to provide higher data rates.

Journal ArticleDOI
TL;DR: In this article, a dual-band rectenna operating at 915 MHz and 2.45 GHz was proposed, which is optimized for low input power densities using harmonic balance (HB) simulation.
Abstract: A compact dual-band rectenna operating at 915 MHz and 2.45 GHz is presented. The rectenna consists of a slot-loaded dual-band folded dipole antenna and a dual-band rectifier. The length of the proposed antenna is only 36.6% of the half-wavelength $(\lambda_{0}/2)$ dipole antenna at 915 MHz while keeping dual-band property at 915 MHz and 2.45 GHz. The rectifier circuit is optimized for low input power densities using harmonic balance (HB) simulation. The efficiencies of the rectifier are evaluated with both single- and dual-frequency input signals. The measured results show an efficiency of 37% and 30% at 915 MHz and at 2.45 GHz when illuminated by a microwave signal of available power of $-$ 9 dBm for a load resistor of 2.2 k $\Omega$ .

Patent
Gabriel Isaac Mayo1
02 Dec 2013
TL;DR: In this article, a first antenna array of antenna coils is configured to generate a first wireless field and a second antenna array generates a second wireless field, at least partially overlaps the first and second antenna arrays.
Abstract: Systems and methods for wireless power transmission are described herein In one aspect, an apparatus for wireless power transmission comprises a first antenna array of antenna coils configured to generate a first wireless field A second antenna array of antenna coils generates a second wireless field The first antenna array at least partially overlaps the second antenna array A driver circuit generates first and second drive signals for generation of the first and second wireless fields via the first and second antenna arrays, respectively The first wireless field is orthogonal with respect to the second wireless field The first antenna array and the driver circuit power the antenna coils of the first antenna array with alternating polarities The second antenna array and the driver circuit power the antenna coils of the second antenna array with alternating polarities

Patent
21 Oct 2013
TL;DR: In this article, a surface scattering antenna with an electromagnetic waveguide structure and a plurality of electromagnetic wave scattering elements is described, and a gain definition circuit defines a radiation pattern configured to acquire a possible interfering signal.
Abstract: Described embodiments include an antenna system and method. The antenna system includes a surface scattering antenna that has an electromagnetic waveguide structure and a plurality of electromagnetic wave scattering elements. The plurality of electromagnetic wave scattering elements are distributed along the waveguide structure, have a respective activatable electromagnetic response to a guided propagating electromagnetic wave, and produce a controllable radiation pattern. A gain definition circuit defines a radiation pattern configured to acquire a possible interfering signal. The defined antenna radiation pattern has a field of view covering at least a portion of an undesired field of view of an associated antenna. An antenna controller establishes the defined radiation pattern in the surface scattering antenna by activating the respective electromagnetic response of selected electromagnetic wave scattering elements. A correction circuit reduces an influence of the received possible interfering signal in a contemporaneously received signal by the associated antenna.

Patent
04 Feb 2013
TL;DR: In this paper, a charging device (200) is provided for communicating with one or more consumer devices (300) for remotely charging at least one of them upon demand of the consumer.
Abstract: A charging device (200) is provided for communicating with one or more consumer devices (300) for remotely charging at least one of them upon demand of the consumer. The charging device (200) comprises a transmitter unit associated with an antenna unit comprising a power antenna configured to define at least one charging zone for transmitting charging power to the at least one charging zone; a receiver for receiving signals from consumers (300) located within the charging zone; and a controller unit. The controller is configured and operable to be responsive to a request signal from a consumer(300) indicative of demand for charging, to initiate a charging process of the consumer by radiation from the power antenna toward said consumer (300) to supply power required for operating a functional unit of said consumer(300). The power antenna may comprise an array of directional antenna elements, each defining the charging zone within a different angular segment of entire charging space defined by a radiation pattern of the antenna array.

Patent
18 Dec 2013
TL;DR: In this paper, a three-dimensional transmitting antenna for wireless power charging, which wirelessly transmits power to charge a device, includes a first antenna coil section for producing a magnetic field in a first direction, and a second antenna coils section for generating a magnetic fields in a second direction.
Abstract: The present invention has been made in an effort to overcome the disadvantage that a user has to consciously adjust the positions of a wireless power transmitter and a wireless power receiver. The transmitting antenna for wireless power charging, which wirelessly transmits power to charge a device, includes a first antenna coil section for producing a magnetic field in a first direction, and a second antenna coil section for producing a magnetic field in a second direction. Accordingly, the three-dimensional transmitting antenna can minimize decreases in efficiency caused by the position and direction of the receiver and maximize reception efficiency at a particular point or within a particular range.

Journal ArticleDOI
TL;DR: The theoretical analysis and simulations show the somewhat surprising result that for a given number of receivers the improved transmit diversity dominates the performance of practical linear precoders.
Abstract: We explore the performance of multiple input multiple output (MIMO) transmitters in correlated channels where increasing numbers of antenna elements are fitted in a fixed physical space. As well investigated in the literature, two main effects emerge in such a design: transmit spatial correlation and mutual antenna coupling. In contrast to the literature however, here we investigate the combined effect of reducing the distance between the antenna elements with increasing the number of elements in a fixed transmitter space. In other words, towards the implementation of large-scale MIMO transmitters in limited physical spaces, we investigate the joint effect of two contradicting phenomena: the reduction of spatial diversity due to reducing the separation between antennas and the increase in transmit diversity by increasing the number of elements. Within this context, we analytically approximate the performance of two distinct linear precoding designs. The theoretical analysis and simulations show the somewhat surprising result that for a given number of receivers the improved transmit diversity dominates the performance of practical linear precoders. Consequently, important benefits in the system sum rate can be gleaned by fitting more antenna elements in a fixed space by employing separations smaller than the wavelength of the transmit frequency.

Journal ArticleDOI
TL;DR: The impact of antenna correlation on secrecy performance of multiple-input multiple-output wiretap channels where transmitter employs transmit antenna selection while receiver and eavesdropper perform maximal-ratio combining with arbitrary correlation is analyzed.
Abstract: We analyze the impact of antenna correlation on secrecy performance of multiple-input multiple-output wiretap channels where transmitter employs transmit antenna selection while receiver and eavesdropper perform maximal-ratio combining with arbitrary correlation. New closed-form expressions are derived for the exact and asymptotic (high signal-to-noise ratio in transmitter-receiver channel) secrecy outage probability.

Journal ArticleDOI
TL;DR: In this paper, a planar gold film with a thickness of 100 nm is used to construct a V-shaped antenna array for light propagation manipulation and filtering in planar planar optical elements.
Abstract: Various ultrathin planar optical elements, including cylindrical lens, spherical lens, and phase holograms, are designed based on the interface phase modulation of antenna resonances in the terahertz (THz) range. The focusing and imaging performance of the lenses and image-reconstruction ability of the pure phase holograms are demonstrated experimentally. In contrast to conventional bulky optical elements where curve surfaces are used to control the light propagation, the manipulations of light propagation for these thin planar optical elements are achieved through designed arrays of complementary V-shaped antennas in the planar gold films with a thickness of 100 nm (1/4000th of the wavelength of the illuminating light). The adoption of the complementary V-shaped antennas makes the optical elements have double functions: light propagation manipulation and filtering, which improves the performance of the optical elements by blocking the disturbance from the direct transmission. This research is a significant step towards the reduction of the THz elements size and, therefore, to the development of micro-integrated THz systems and to other applications where the compaction is necessary. The approach used here can be expanded to multifarious optical elements in different wave bands.

Journal ArticleDOI
TL;DR: In this article, the spontaneous emission rate and the radiation pattern of colloidal quantum dots deterministically positioned in a plasmonic patch antenna were demonstrated. But the authors did not consider the double dipole structure of the emitters, which corresponds to a Purcell factor up to 80.
Abstract: We experimentally demonstrate the control of the spontaneous emission rate and the radiation pattern of colloidal quantum dots deterministically positioned in a plasmonic patch antenna. The antenna consists of a thin gold microdisk separated from a planar gold layer by a few tens of nanometers thick dielectric layer. The emitters are shown to radiate through the entire patch antenna in a highly directional and vertical radiation pattern. Strong acceleration of spontaneous emission is observed, depending on the antenna geometry. Considering the double dipole structure of the emitters, this corresponds to a Purcell factor up to 80 for dipoles perpendicular to the disk.