Antenna arrays

Intuitive Machines intends to launch and operate the first United States based Lunar Communication and Positioning, Navigation, and Timing constellation starting in 2026. This paper describes the design considerations for the constellation's orbits under the performance requirements for coverage and quality of service. The selected five satellite elliptical frozen lunar orbit constellation is presented together with a performance analysis. Additionally, the outbound Ballistic Lunar Transfer trajectory for the constellation's first satellite is presented together with a Delta-V budget assessment.

This paper presents an innovative architecture for a feasible Mobile Adaptive Digital Array Radar (MADAR) system that could be utilized for detection and tracking different sizes of short range targets from fighter aircrafts to UAV, rockets, and cannons projectiles. The author proposed the MADAR system in order to achieve a high performance level over the current radar versions in the field such as EQ-36. The proposed MADAR is an S-band phased array radar system utilizing the gallium nitride solid state cavity transceivers, microstrip radiators elements, Adaptive Beam Forming (ABF), and sophisticated digital receiver algorithms. The innovative ideas applied into the proposed MADAR will achieve improved performance parameters such as receiver dynamic range, detection range, resolution range, beam pattern, beam pointing accuracy, higher probability of small targets detection in heavy clutters, lower rate of false alarms, lower clutter to signal to noise ratio, lower side lobes level, and lighter weight aperture array. The MADAR system eventually will provide the capability to detect, classify, track and determine the location of enemy indirect fire, such as mortars, artillery and rockets in either 90-degree or 360-degree modes.

In this paper, a transmit antenna selection scheme, which is based on shadowing side information, is investigated. In this scheme, the selected single transmit antenna provides the highest shadowing coefficient between transmitter and receiver. By the proposed technique, the frequency of the usage of the feedback channel from the receiver to the transmitter and also channel estimation complexity at the receiver can be reduced. We study the performance of our proposed technique and in the analysis, we consider an independent but not identically distributed Generalized-K composite fading model. More specifically exact and closed-form expressions for the outage probability, the moment generating function, the moments of signal-to-noise ratio, and the average symbol error probability are derived. In addition, asymptotic outage probability and symbol error probability expressions are also presented in order to investigate the diversity order and the array gain. Finally, our theoretical performance results are validated by Monte Carlo simulations.

Three Methods are discussed for controlling behavior of Arrays.The first, Schelkunoff Polynomial (Null Placement) uses information on the numbers of nulls hence the number of elements and their excitations coefficient are derived.The second is statistically based and minimizes the Mean Square Error cost function between the desired output (a Known Signal) and what the array actual outputs.To do this,it is required that the direction of arrival of the desired signal and its expected power are known.The Third one,The Least Mean Square Algorithm(Adaptive Antenna Theory) employs adaptive weighting algorithm that adapts the weights based on the received signals to improve the performance of the array.The weights,minimizes the Mean-Squared Error between a desired signal and the arrays Outputs.

We have designed a Metamaterial unit-cell for 9 GHz frequency. Periodic structure was used at 4.25 × 4.25 mm with a thickness of 0.35 mm and giving us the 99.99% of absorbance at 9 GHz in simulated results. We have implemented a rectangular microstrip antenna and loaded it with Metamaterial unit-cells which provided improved results. There were results available for reflection coefficient (s11 parameter) at 9 GHz and also helping for the reduction of the Radar Cross Section of an antenna, which reduced more than 20 dB and not affected its directivity and gain.

Uniformly Spaced Antenna Array (USAA) with large radiating elements is characterized with complex feed network as well as high sidelobes level (SLL) leading to interference and power wastage. To solve these problems, research works have been carried out using different methodologies, to synthesize sparse Randomly Spaced An- tenna Array (RSAA) to reconstruct the desired radiation pattern using fewer radiating elements and suppressed SLL. In this paper, a deterministic Iteratively Reweighted Least Squares (IRLS) algorithm based on the concept of compressed sensing was used to achieve better sparsity through thinning. The SLL was also suppressed using Convex Technique (CT). The performance of the synthesized array was evaluated in terms of sparsity and SLL. Simulation results showed that it has a higher sparsity of 12 elements with SLL of -39.44dB which are 14.29% and 28.72% improvements, respectively compared to previous research work with 14 elements and SLL of -30.64dB.

In this work, we consider differential modulation in two-way relay channels (TWRC). In single antenna systems, we propose non-coherent schemes for both amplify-and forward (AF) and decode-and-forward (DF) where the channel state information is not required. These new schemes are counterparts of the traditional non-coherent detection in point to point communications. The difficulty with differential modulation design in TWRC is that the received signal is a mixture of the signals from both source terminals. We derive maximum likelihood (ML) detectors for both AF and DF. The DF protocol can be considered as performing differential network coding at the physical layer. In addition, we propose several suboptimal alternatives including decision feedback and prediction based detectors. All these strategies work well as evidenced by simulation results. We also extend the schemes to the multiple-antenna case and provide design criterion of differential unitary space time modulation. This full text paper was peer reviewed at the direction of IEEE Communications Society subject matter experts for publication in the IEEE "GLOBECOM" 2008 proceedings.

In this paper, we study some relationships between the detection and estimation theories for a binary composite hypothesis test against and a related estimation problem. We start with a one-dimensional (1D) space for the unknown parameter space and one-sided hypothesis problems and then extend out results into more general cases. For one-sided tests, we show that the uniformly most powerful (UMP) test is achieved by comparing the minimum variance and unbiased estimator (MVUE) of the unknown parameter with a threshold. Thus for the case where the UMP test does not exist, the MVUE of the unknown parameter does not exist either. Therefore for such cases, a good estimator of the unknown parameter is deemed as a good decision statistic for the test. For a more general class of composite testing with multiple unknown parameters, we prove that the MVUE of a separating function (SF) can serve as the optimal decision statistic for the UMP unbiased test where the SF is continuous, differentiable, positive for all parameters under and is negative for the parameters under . We then prove that the UMP unbiased statistic is equal to the MVUE of an SF. In many problems with multiple unknown parameters, the UMP test does not exist. For such cases, we show that if one detector between two detectors has a better receiver operating characteristic (ROC) curve, 1 then using its decision statistic we can estimate the SF more -accurately, in probability. For example, the SF is the signal-to-noise ratio (SNR) in some problems. These results motivate us to introduce new suboptimal SF-estimator tests (SFETs) which are easy to derive for many problems. Finally, we provide some practical examples to study the relationship between the decision statistic of a test and the estimator of its corresponding SF.

In this paper, a transmit antenna selection scheme, which is based on shadowing side information, is investigated. In this scheme, the selected single transmit antenna provides the highest shadowing coefficient between transmitter and receiver. By the proposed technique, the frequency of the usage of the feedback channel from the receiver to the transmitter and also channel estimation complexity at the receiver can be reduced. We study the performance of our proposed technique and in the analysis, we consider an independent but not identically distributed Generalized-K composite fading model. More specifically exact and closed-form expressions for the outage probability, the moment generating function, the moments of signal-to-noise ratio, and the average symbol error probability are derived. In addition, asymptotic outage probability and symbol error probability expressions are also presented in order to investigate the diversity order and the array gain. Finally, our theoretical performance results are validated by Monte Carlo simulations.

This paper discusses the requirements on future radio access and, based on the requirements, proposes a framework for such a system. The proposed system based on orthogonal frequency-division multiplexing supports very low latencies and data rates up to 100 Mb/s with wide area coverage and 1 Gb/s with local area coverage. Spectrum flexibility is identified as one main requirement for future systems, and the proposed framework can be deployed in a wide range of spectrum allocations with bandwidths ranging from 2.5 to 100 MHz. Multihop relaying, useful to extend the range for the high data rates, and multiple-antenna configurations are integral parts of the framework. A packet-centric approach is taken for the dataflow processing, implying that the scheduling mechanism and the retransmission protocol operate on complete packets rather than segments thereof, thus allowing for cross-layer optimization. Finally, numerical evaluations are provided, illustrating the feasibility of future very wideband radio access.

The characteristics of an optically fed phased array antenna are affected by the amplitude and phase noise introduced by optical amplifiers (EDFA) used in the system. A theoretical derivation and a numerical computation of the effect of phase noise on antenna performance are given in this paper. The phase fluctuations make the main beam to jitter around a mean value directly related to the mean and the variance of the amplified spontaneous emission induced random phase change.

Constructions of square, maximum rate complex orthogonal space-time block codes (CO STBCs) are well known, however codes constructed via the known methods include numerous zeros, which impede their practical implementation. By modifying the Williamson and Wallis-Whiteman arrays to apply to complex matrices, we propose two methods of construction of square, order-4n CO STBCs from square, order-n codes which satisfy certain properties. Applying the proposed methods, we construct square, maximum rate, order-8 CO STBCs with no zeros, such that the transmitted symbols are equally dispersed through transmit antennas. Those codes, referred to as the improved square CO STBCs, have the advantages that the power is equally transmitted via each transmit antenna during every symbol time slot and that a lower peak-to-average power ratio (PAPR) is required to achieve the same bit error rates as the conventional CO STBCs with zeros. C OMPLEX orthogonal space-time block codes (CO STBCs) have been intensively examined, as they provide large transmit diversity and increase the capacity of wireless channels, while requiring a very simple maximum likelihood (ML) decoding method [3]- . A CO STBC over variables is corresponding to transmit (Tx) antennas, decoding delay (or memory length) of , rate and is denoted as CO STBC. Given and , the goal is to minimize the decoding delay . Hence, square CO STBCs are particularly interesting because they require the minimum Manuscript

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This paper links the direct-sequence code-division multiple access (DS-CDMA) multiuser separation-equalization-detection problem to the parallel factor (PARAFAC) model, which is an analysis tool rooted in psychometrics and chemometrics. Exploiting this link, it derives a deterministic blind PARAFAC DS-CDMA receiver with performance close to nonblind minimum mean-squared error (MMSE). The proposed PARAFAC receiver capitalizes on code, spatial, and temporal diversity-combining, thereby supporting small sample sizes, more users than sensors, and/or less spreading than users. Interestingly, PARAFAC does not require knowledge of spreading codes, the specifics of multipath (interchip interference), DOA-calibration information, finite alphabet/constant modulus, or statistical independence/whiteness to recover the information-bearing signals. Instead, PARAFAC relies on a fundamental result regarding the uniqueness of low-rank three-way array decomposition due to Kruskal (and generalized herein to the complex-valued case) that guarantees identifiability of all relevant signals and propagation parameters. These and other issues are also demonstrated in pertinent simulation experiments.

. With user-specific, linear precoding, the data symbols to be transmitted to each user are passed through a linear transformation before being sent to the transmit antennas, and a different precoder is used for each user depending on his/her channel. For example, with 4 transmit antennas at the BS, 2 receive antennas at the mobile, and instant channel quality indicator (CQI), the cell capacity of a 4x2 2-clustered system with user-specific, linear precoding is more than 80% higher than the cell capacity of a system with one transmit antenna [10]. But such schemes are vulnerable to delayed CQI due to fast variations of interference, leading in some cases to performance that is worse than a SISO system. In this paper, we will present a method that mitigates the degradation due to fast-varying interference in MIMO systems that use linear precoding. We will show that the temporal variation of other-cell interference is almost eliminated with this method. Our results indicate that for a 4x2 2-Clustered transmit array with the proposed method, the performance loss due to delayed CQI is reduced from 35% to 5%.

Under the assumption of a frequency-flat slow Rayleigh fading channel with multiple transmit and receive antennas, we examine the effects of imperfect estimation of the channel parameters on error probability when known pilot symbols are transmitted among information data. Three different receivers are considered. The first one derives an estimate of the channel (by using either a maximum-likelihood or a minimummean-square error criterion), next uses this estimate in the same metric that would be applied if the channel were perfectly known. The second receiver derives again an estimate of the channel, but uses the maximum-likelihood metric conditioned on the channel estimate. Our last receiver processes simultaneously the pilot and data symbols received. Simulation results are exhibited, showing that only a relatively small percentage of the transmitted frame need be allocated to pilot symbols in order to experience an acceptable degradation of error probability due to imperfect channel knowledge. Algorithms for the recursive calculation of the decision metric of the last two receivers are also developed, for application to sequential decoding of trellis space-time codes.

In wireless communication, mobile technology is progressive and in this system 4 th generation is the latest at present. 4G mobile, aims to provide an effective solution for the next generation mobile usefulness. Fourth Generation mobile technology system has extremely advancement than 1G ,2G, and 3G system In this article , the major provocation provided by small-band and broadband mobile wireless channels and serviceable ways to mitigate those problems through the use of techniques that take benefit of the spatial dimension are described. In this techniques from space time processing, example as diversity bringing together, to space-time coding and spatial multiplexing and, the explanation of advancement will be the main focus of this paper.

In modern short range wireless applications, RF, Bluetooth and UWB communication schemes are recommended with respect to power consumption, low/high data rates and location capability. Though special bandwidth is not allocated to UWB, coexistence of such signal in the available RF environment is a critical issue and hence analysis of UWB signal with respect to interference is very much required in dedicated WPAN networks. In this paper, effect of UWB interference for existing systems such as GPS, FWA, UMTS, DCS1800 is analyzed. Communication path distance is directly proportional to the UWB signal pulse width. To correctly define the UWB signal this functionality is realized by composing UWB signal and results are simulated using MATLAB.

In this paper, we proposed a newly modified cuckoo search (MCS) algorithm integrated with the Roulette wheel selection operator and the inertia weight controlling the search ability towards synthesizing symmetric linear array geometry with minimum side lobe level (SLL) and/or nulls control. The basic cuckoo search (CS) algorithm is primarily based on the natural obligate brood parasitic behavior of some cuckoo species in combination with the Lévy flight behavior of some birds and fruit flies. The CS metaheuristic approach is straightforward and capable of solving effectively general N-dimensional, linear and nonlinear optimization problems. The array geometry synthesis is first formulated as an optimization problem with the goal of SLL suppression and/or null prescribed placement in certain directions, and then solved by the newly MCS algorithm for the optimum element or isotropic radiator locations in the azimuth-plane or xy-plane. The study also focuses on the four internal parameters of MCS algorithm specifically on their implicit effects in the array synthesis. The optimal inter-element spacing solutions obtained by the MCS-optimizer are validated through comparisons with the standard CS-optimizer and the conventional array within the uniform and the Dolph-Chebyshev envelope patterns using MATLAB TM . Finally, we also compared the fine-tuned MCS algorithm with two popular evolutionary algorithm (EA) techniques include particle swarm optimization (PSO) and genetic algorithms (GA).

This paper proposes a novel iterative frequency domain multiple input multiple output (MIMO) signal detection technique for the reception of overloaded spatially multiplexed MIMO transmission for single carrier signalling in frequency-selective channels. In the presence of spatial correlation as well as the case where there are more transmit antennae than receive antennae (refered to as overloaded transmission in this paper) the performance of antenna-by-antenna (AA)-based MIMO minimum mean square error (MMSE) receivers are, in general, degraded. Therefore, we propose joint-over-antenna (JA) detection-based iterative frequency domain technique to improve the performance of receiver in the presence of overloaded antenna transmission and spatial correlation. The proposed receiver is based on the combination of maximum aposteriori probability (MAP) algorithm, and soft-cancellation (SC) and MMSE filtering for turbo-coded single carrier point-to-point MIMO systems. In the proposed receiver MIMO signal detection is comprised of two stages; At the first stage, inter-symbol interference (ISI) is suppressed with MMSE filtering. At the second stage, co-antenna interference (CAI) is suppressed by the MAP algorithm and transmitter antennae are decomposed each other. Simulation results show that performance gain of JA compared to AA technique is significant in the presence of spatial correlation as well as in overloaded cases. The performance comparison is made in terms of frame error rate (FER) with different antenna configurations and different spatial correlations in point-to-point MIMO frequency-selective fading channels.

In this paper a performance analysis of the turbo MIMO equalizer concept for broadband MIMO channel is presented. The channel modeling in the link-level simulation is based on MIMO measurement in different scenarios. The results reveal the strong relationships between the propagation conditions in terms of the available spatial and temporal multipath diversity, the antenna configurations, and the achievable bit

A version of the iterative Fourier technique (IFT) for the design of thinned antenna arrays with weighted elements is presented. The structure of the algorithm means that it is well suited to the design of weighted thinned arrays with low current taper ratios (CTRs). A number of test problems from the literature are considered, and in each case, the IFT produces results with improved sidelobe level (SLL) at lower CTR.

An iterative algorithm for the numerical optimisation of rank-1 Grassmannian codebooks is presented. This algorithm achieves the same results as the current state-of-theart algorithm, but requires a median of 9.52 times less computation time. This improvement is achieved by reformulating the optimisation problem to directly minimise coherence instead of maximising the Euclidean distance between codewords, thereby removing the need to consider large numbers of complex antipodals. The run-time improvement achieved allows the optimisation of the larger codebooks required in many applications.

A version of the iterative Fourier technique (IFT) for the design of thinned antenna arrays with weighted elements is presented. The structure of the algorithm means that it is well suited to the design of weighted thinned arrays with low current taper ratios (CTRs). A number of test problems from the literature are considered, and in each case, the IFT produces results with improved sidelobe level (SLL) at lower CTR.

In this paper, a polarization conversion metasurface (PCM) is designed for ultra wideband radar cross section (RCS) reduction. The proposed polarization conversion metasurface consists of doubleheads arrow unit cell with its 90°, 180° and 270° rotated ones to create the destructive interferences cancellation and radar cross section (RCS) reduction, consequently. The proposed metasurface demonstrates ultra-wide band 10-dB RCS reduction from 9 to 40 GHz (126.5%) for normally TM-and TE-polarized incident waves. The good agreement between the simulation and measurement results at 0°, 20° and 40° incident angles prove the idea, also. The ultra wideband RCS reduction of the proposed metasurface as well as its low profile, light weight and low cost prove its high capability compared with the state of the art references.

In this paper, a polarization conversion metasurface (PCM) is designed for ultra wideband radar cross section (RCS) reduction. The proposed polarization conversion metasurface consists of double-heads arrow unit cell with its 90°, 180° and 270° rotated ones to create the destructive interferences cancellation and radar cross section (RCS) reduction, consequently. The proposed metasurface demonstrates ultra-wide band 10-dB RCS reduction from 9 to 40 GHz (126.5%) for normally TM- and TE- polarized incident waves. The good agreement between the simulation and measurement results at 0°, 20° and 40° incident angles prove the idea, also. The ultra wideband RCS reduction of the proposed metasurface as well as its low profile, light weight and low cost prove its high capability compared with the state of the art references.

This paper highlights recent results obtained with the Turbulent Eddy Profiler (TEP), which was developed by the University of Massachusetts. This unique 915-MHz radar has up to 64 spatially separated receiving elements, each with an independent receiver. The calibrated raw data provided by this array could be processed using sophisticated imaging algorithms to resolve the horizontal structures within each range gate. After collecting all of the closely spaced horizontal slices, the TEP radar can produce threedimensional images of echo power, radial velocity, and spectral width. From the radial velocity measurements, it is possible to estimate the three-dimensional wind with high horizontal and vertical resolution. Given the flexibility of the TEP system, various array configurations are possible. In the present work exploitation of the flexibility of TEP is attempted to enhance the rejection of clutter from unwanted biological targets. From statistical studies, most biological clutter results from targets outside the main imaging field of view, that is, the sidelobes and grating lobes (if they exist) of the receiving beam. Because the TEP array's minimum receiver separation exceeds the spatial Nyquist sampling requirement, substantial possibilities for grating-lobe clutter exist and are observed in actual array data. When imaging over the transmit beam volume, the receiving array main lobe is scanned over a Ϯ12.5°region. This scanning also sweeps the grating lobes over a wide angular region, virtually guaranteeing that a biological scatterer outside of the main beam will appear somewhere in the imaged volume. This paper focuses on suppressing pointlike targets in the grating-lobe regions. With a subtle change to the standard TEP array hardware configuration, it is shown via simulations and actual experimental observations (collected in June 2003) that adaptive beamforming methods can subsequently be used to significantly suppress the effects of point targets on the wind field estimates. These pointlike targets can be birds or planes with strong reflectivity. By pointlike the authors mean its appearance is a distinct point (up to the imaging resolution) in the images. The pointlike strong reflectivity signature exploits the capability of adaptive beamforming to suppress the interference using the new array configuration. It should be noted that this same array configuration does not exhibit this beneficial effect when standard Fourier beamforming is employed.

Bistatic radar measurement of clear-air winds in the atmospheric boundary layer is considered. The context is three-dimensional wind field measurement using dense networks of short-range radars configured to operate in bistatic geometries. Such networks exploit a combination of Rayleigh scattering from insects and Bragg scattering from refractive index turbulence, the latter exhibiting enhanced scattering intensity in forward scatter geometries compared to the monostatic case. Bistatic radar fundamentals are reviewed, and beam-limited scattering volumes are considered. Measurements with sufficient precision (<1 m s À1 ) are achievable with relatively low average powers (100 W) with reasonably short dwell times (1 s) for transmitters and receivers separated by as much as 15 km. For a fixed antenna aperture size, frequency dependence of sensitivity for the Bragg component of the composite scattered signal is weak (l 2/3 ), provided that the Bragg-resonant wave number for the forward scattering geometry lies within the inertial subrange of refractive index turbulence. In contrast, the strong (l 4 ) frequency-dependent Rayleigh insect echo dominates the scattered signal for short wavelengths (i.e., X band and higher frequencies) under many conditions except for small forward scatter angles. Owing to this dominance and to the tendency for refractive index turbulence and insects to occur together in the atmospheric boundary layer, reliance on the bistatic Bragg scattering mechanism is not warranted for short-range, short-wavelength radar networks.

This paper highlights recent results obtained with the Turbulent Eddy Profiler (TEP), which was developed by the University of Massachusetts. This unique 915-MHz radar has up to 64 spatially separated receiving elements, each with an independent receiver. The calibrated raw data provided by this array could be processed using sophisticated imaging algorithms to resolve the horizontal structures within each range gate. After collecting all of the closely spaced horizontal slices, the TEP radar can produce three-dimensional images of echo power, radial velocity, and spectral width. From the radial velocity measurements, it is possible to estimate the three-dimensional wind with high horizontal and vertical resolution. Given the flexibility of the TEP system, various array configurations are possible. In the present work exploitation of the flexibility of TEP is attempted to enhance the rejection of clutter from unwanted biological targets. From statistical studies, most biological clu...

Reconfigurable intelligent surfaces (RISs) have been proposed recently as an enabling technology for tuning the wireless propagation channel between transceivers. To realize RISs advantages, however, accurate channel state information is required. In this paper, we consider a single-user RIS-aided system model and propose a two-stage high-resolution channel parameter estimation framework termed TRICE that exploits the low-rank nature of millimeter-wave MIMO channels. In both stages, we formulate the channel parameter estimation problem as a 2D direction-of-arrival estimation problem, for which several solution methods exist in the literature. Based on this formulation, we resort to a 2D DFT beamspace ESPRIT method to estimate the angular parameters of the involved communication channels. Our numerical results show that the proposed TRICE framework has a lower training overhead, as compared to benchmark methods, which makes it appealing in practical applications.

This paper describes the findings of a research into the multiple input multiple output (MIMO) channel capacity of a broadband dual-element printed inverted F-antenna (PIFA) antenna array. The dual-element antenna array is made up of two PIFAs that are meant to fit on a teeny-tiny and small wireless communication device that runs at 5 GHz. The device&#39;s frequency range is between 3.5 and 4.5 GHz. These PIFAs are also loaded into the device during the installation process. In order to investigate the channel capacity, the ray tracing method is employed in two different kinds of circumstances. For the purpose of carrying out this analysis of the channel capacity, both the simulated and measured mutual couplings of the broadband MIMO antenna are utilized.

This paper compares measurement results obtained using a 2.7 m x 3.1 m x 4.6 m reverberation chamber and a 4.9 m x 6.7 m x 8.5 m anechoic chamber to determine the EM susceptibility of equipment under te st (EUT). The frequency range was 200 M Hz -18 GHz. The "correlation factor" between the two techniques appears to be directly proportional to the gain of the EUT. Four sample EUTs included in th is study were a one centimeter dipole probe, a ridged horn antenna, a small rectangular TEM transmission cell with an aperture and a modified 7.0 cm (2.75") diameter folded fin aircraft rocket.

This presentation describes a four microstrip Yagi-Uda antenna array. The single microstrip Yagi-Uda antenna was developed by J. Huang at Jet Propulsion Laboratory, and had a maxirnurn gain of 8dBic (J. Huang; "Planar Microstrip Yagi Array Antenna", IEEE AP-S Symposium Digest June 1989, pp 894-897). A single Yagi-Uda antenna consists of a single driven patch, a larger reflector patch and two smaller director patches. This mangernent shows many advantages over a single microstrip patch antenna, which include a slightly increased forward gain and an increased directivity. The bandwidth is also increased significantly

The far field radiation pattern of closely spaced dipoles can be calculated using mutual impedance and network equations. The definition of mutual coupling for patch antennas must be reviewed to determine the radiation pattern for parasitic patch antennas

A novel Decision-Feedback (DF) aided reduced complexity Maximum Likelihood (ML) Space-Time Equalizer (STE) designed for single-carrier multiple antenna assisted receivers is introduced. The proposed receiver structure is based on a recursive tree search, which is capable of achieving ML performance at a moderate computational cost and substantially outperforms the linear benchmarker based on the Minimum Mean-Squared Error (MMSE) criterion. Additionally a further complexity reduction scheme is proposed, which exploits the specific characteristics of both the wide-band channel and the proposed DF-STE.

In this contribution, a nonlinear hybrid detection scheme based on a novel soft-information assisted Genetic Algorithm (GA) is proposed for a Turbo Convolutional (TC) coded Space Division Multiplexing (SDM) aided Orthogonal Frequency Division Multiplexing (OFDM) system. Our numerical results show that the performance of the currently known GA-assisted system can be improved by about 2dB with the aid of the GA's population-based soft solution, approaching the optimum performance of the soft-information assisted Maximum Likelihood (ML) detection, while exhibiting a lower complexity, especially in high-throughput scenarios. Furthermore, the proposed technique is capable of achieving a good performance even in the so-called overloaded systems, where the number of transmit antennas is higher than the number of receiver antennas.

In this paper we propose a novel Space Division Multiplexing (SDM) detection method. The proposed technique constitutes a list search method and may be regarded as an advanced extension of the Sphere Decoder (SD). Our method may be employed in the so-called over-loaded scenario, where the number of transmit antenna elements exceeds that of the receive antenna elements. Furthermore, it is suitable for highthroughput, non-constant modulus modulation schemes, such as 16 and 64-QAM. We introduce a series of optimization rules which facilitate a substantial reduction in computational complexity. More specifically, we demonstrate that the method proposed, which we refer to as the Soft-output OPtimized HIErarchy (SOPHIE)-aided SDM detector exhibits the near-optimum performance of Log-MAP SDM detector in all considered scenarios. The associated computational complexity, which we control using two complexity-control parameters, is substantially lower than that imposed by all previously proposed methods.

In this letter, a novel iterative multiple-input multiple-output (MIM)O detector reminiscent of sphere decoding (SD) is presented. Its main benefit is that in contrast to other softinput soft-output (SISO) SD algorithms presented in the literature, the proposed iterative detector is capable of performing well in so-called overloaded systems, where the number of transmit antennas is significantly higher than the number of receive antennas, and hence, the channel's covariance matrix is rank-deficient. Furthermore, the proposed detector is guaranteed to achieve the performance of the max-log detector without the necessity of choosing a specific SD radius or an SD candidate list for generating soft-outputs. For example, when receiving signals from four transmit antennas with the aid of only two receive antennas, the proposed detector is capable of approaching the channel capacity limit within about 2 dBs.

Wireless communication systems always demand higher data rates and better quality of service (QoS). Transmission reliability in a wireless channel with high path loss, time-varying multipath fading and power and bandwidth limitations, is a testing issue. Multiple-input multiple-output (MIMO) systems can reduce the effect of these channel interferences and achieve reliable signal transmission at high data rate. Space-time block code (STBC) is a coding scheme for the use of multiple transmits antennas providing a simple transmit diversity scheme. In certain MIMO fading environments, the offered channel capacity can be very low, where despite rich local scattering and uncorrelated transmit and receive signals, the system has a single degree of freedom. This effect has been termed as keyhole or pinhole effect. This contribution analyzes the average symbol error rate (SER) performance of MIMO systems employing orthogonal STBC with M-PSK constellations over fading channels in the presence...

This study presents a robust and efficient approach for derivation of non-symmetrical closed-form Green's functions for microstrip structures. In this method, the discrete complex image technique is used to extract the closed-form expressions for stratified Green's functions. The surface-wave poles in these expressions are first extracted using a recursive contour integration method. The remainder is then approximated by a series of complex exponentials using either the Prony's method or the generalised pencil-of-function (GPOF) along the extended rooftop-shaped path in k r -plane. An analytical identity is subsequently employed to obtain the new spatial-domain Green's functions. For calculation of the integral of G zx A with respect to x, it is observed that only a single approximate Green's function can accurately represent both the near and far fields. Moreover, the method generates accurate results in the near-field region when z ′ = z and r 0. A two-part expression for the non-symmetrical potential G zx A is introduced as well. This two-part approximation is very accurate and computationally fast for the entire range of distances, especially when z ¼ z ′ = 0 or z ′ = z.

The synthesis of pencil beam and arbitrarily shaped beam patterns of linear antenna arrays (LAA) using reduced number of antenna elements attracts the attention of researchers in recent years. In this paper, a hybrid beamforming technique based on the combination of the genetic algorithm (GA) optimization technique and the l 1 minimization method denoted as (GA/l 1 ) is introduced for LAAs synthesis. The proposed GA/l 1 beamforming technique optimizes both the elements excitations and interelement spacing to synthesize the desired LAA pattern with a minimum number of antenna elements. The GA/l 1 technique provides an excellent approximation to the desired radiation pattern with high accuracy and low complexity (less number of iterations and computational time) compared to the other synthesis approaches introduced in the literature. In addition, as an application of this work, the proposed GA/l 1 technique is used to build up a proposed hybrid precoding and beamforming (HP-BF) structure for Massive Multi-input Multi-output (M-MIMO) systems. In this structure, the transmit antenna array is synthesized for maximum gain realization using the existing number of antenna elements. In the HP-BF structure, the proposed GA/l 1 technique is used to make full use of the existing transmit array elements to synthesize the radiation pattern of much larger size and higher gain arrays without the need for additional elements. Thereby, significant savings in the number of antenna elements and their corresponding radio frequency (RF) chains are achieved, which reduces the system complexity. In addition, the array gain maximization will maximize the received signal to noise ratio (SNR) giving rise to higher system performance in terms of spectral efficiency (SE) and power utilization. INDEX TERMS Array synthesis, analog phase shifters, hybrid precoding and beamforming structure, massive multi-input multi-output, millimeter waves, spectral efficiency, uniform linear array.

In this paper, the impact of amplitude and phase imbalance on a proposed dual differential fed patch antenna is analyzed in the context of system effective reflection coefficient and axial ratio (AR). A single square patch with four ports is used as a solo radiating element and provides absolute symmetry at radiating. An in-depth analysis will be presented to understand the impact of external RF chain components on the performance of the proposed antenna. When fully differential excitations and perfect symmetry can be achieved, all six polarization states exhibit identical system effective reflection coefficients with close to ideal AR for CP. When phase imbalance and amplitude imbalance only exist in between the two differential pairs, the antenna system matching performance is found to be unchanged. In the presence of the feed network, circular polarization (CP) achieves a measured maximum AR of 0.49dB along the antenna pointing angle, while linear polarization (LP) has a measured maximum cross polarization of -30dB. This work monitors the beamwidth over which the AR can be kept below 1dB (BW-AR -1dB ). Based on the optimization of phase imbalance, a novel BW-AR -1dB enhancement technique is introduced. Compared to the case with better AR at the main beam location, an improvement of 14 • beamwidth is measured without significant degradation of AR. Isolation better than 40dB across an operating frequency of 9.27 -9.4 GHz has been experimentally demonstrated for the proposed dual differential fed technique. The resulting antenna is compact and low profile which is an appealing candidate for phased array applications. INDEX TERMS Dual differential fed, 1dB AR beamwidth, patch antenna, polarization diversity, system effective reflection coefficient, high isolation.

Before establishing a communication link with the serving base station (eNodeB), a user equipment (UE) operating in a long-term evolution (LTE) multi-cellular network must acquire some specific information, including the sector identity and cell group identity. For this purpose, two training sequences called primary synchronization signal (PSS) and secondary synchronization signal (SSS) are periodically transmitted in the downlink to convey such information. In this work, we present a novel maximum likelihood (ML) approach for SSS detection assuming that the PSS has been successfully identified at an earlier stage. As we shall see, the resulting scheme turns out to be too complex for practical implementation as it requires perfect knowledge of the channel covariance matrix. Therefore, we look for simpler solutions and propose two reduced-search methods that operate in a mismatched mode. The first scheme exploits channel state information emerging from both the primary and secondary synchronization signals, while the second scheme operates using only the secondary synchronization signal. Numerical analysis indicates that the proposed methods outperform existing alternatives and can be successfully applied even in a severe propagation scenario. The price for such an advantage is a certain increase of the processing requirement.