Power Radiation Pattern Research Articles

A Self-Replicating Single-Shape Tiling Technique for the Design of Highly Modular Planar Phased Arrays—The Case of L-Shaped Rep-Tiles

The design of irregular planar phased arrays (PAs) characterized by a highly-modular architecture is addressed. By exploiting the property of self-replicating tile shapes, also known as rep-tiles, the arising array layouts consist of tiles having different sizes, but equal shape, all being generated by assembling a finite number of smaller and congruent copies of a single elementary building-block. Towards this end, a deterministic optimization strategy is used so that the arising rep-tile arrangement of the planar PA is an optimal trade-off between complexity, costs, and fitting of user-defined requirements on the radiated power pattern, while guaranteeing the complete overlay of the array aperture. As a representative instance, such a synthesis method is applied to tile rectangular apertures with L-shaped tromino tiles. A set of representative results, concerned with ideal and real antenna models, as well, is reported for validation purposes, but also to point out the possibility/effectiveness of the proposed approach, unlike state-of-the-art tiling techniques, to reliably handle large-size array apertures.

Path Loss Modeling and Measurements for Reconfigurable Intelligent Surfaces in the Millimeter-Wave Frequency Band

Reconfigurable intelligent surfaces (RISs) provide an interface between the electromagnetic world of wireless propagation environments and the digital world of information science. Simple yet sufficiently accurate path loss models for RISs are an important basis for theoretical analysis and optimization of RIS-assisted wireless communication systems. In this paper, we refine our previously proposed free-space path loss model for RISs to make it simpler, more applicable, and easier to use. The impact of the antenna's directivity of the transmitter, receiver, and the unit cells of the RIS on the path loss is explicitly formulated as an angle-dependent loss factor. The refined model gives more accurate estimates of the path loss of RISs comprised of unit cells with a deep sub-wavelength size. Based on the proposed model, the properties of a single unit cell are evaluated in terms of scattering performance, power consumption, and area, which allows us to unveil fundamental considerations for deploying RISs in high frequency bands. Two fabricated RISs operating in the millimeter-wave (mmWave) band are utilized to carry out a measurement campaign. The measurement results are shown to be in good agreement with the proposed path loss model. In addition, the experimental results suggest an effective form to characterize the power radiation pattern of the unit cell for path loss modeling.

Neural Network-Based Phase Estimation for Antenna Array Using Radiation Power Pattern

In this letter, a neural network-based interelement phase estimation method using radiation power pattern of the linear phased array is proposed. To validate the proposed method, a radiation pattern measured in an anechoic chamber is input to the neural network to estimate the initial phase errors, and to confirm practical estimation accuracy. The proposed method requires only single radiation pattern measurement and no additional measurements only for estimation. This indicates the proposed method is significantly more time-saving, compared to other conventional techniques. Furthermore, we propose a method to suppress the failure rate of estimation by recursively reinputting patterns into the neural network, and discuss its effectiveness. These results show that the proposed methods useful for phase estimation of the linear array in experiments.

Wideband Receive Beamforming Based on 4-D Antenna Arrays With Postmodulation

A wideband receive beamforming configuration and method based on four-dimensional (4-D) antenna arrays with postmodulation is proposed. Two pairs of single-pole-triple-throw switches are utilized for beamforming at the center frequency. Postmodulation is introduced to increase the degree of freedom of 4-D antenna arrays and achieve a deep null point at the steering direction of sidebands power pattern. The reception of 16 quadrature amplitude modulation signal, whose bandwidth is larger than the time modulation frequency, is implemented by a 16-element 4-D dipole array. The results of wideband beamforming show that the sidebands power at the steering direction can be eliminated ideally, whereas the sidelobes level of averaged radiated power pattern is suppressed to a low value. The 4-D array with postmodulation shows obviously improved bit error rates performance as compared to the 4-D array with conventional beamforming method and phased arrays, which confirms that the 4-D array with postmodulation has potential advantages in the application of wideband communication systems.

Comparative characterization of microstrip patch antenna array with defected ground structure for biomedical application

In this paper, microstrip dual band antenna array with defected ground structure has been proposed for low frequency wearable on-body applications. The array has been simulated with Cotton, Polyimide, Polyester and Teflon (PTFE) flexible materials which are mostly used for biomedical applications. The performance of 2x2 trapezoidal patch array with partial ground, thin slot defection at center has been studied in terms of return loss, VSWR, power handling capability, radiation pattern and surface current distribution. All substrates exhibits acceptable fractional bandwidth below -10 dB and Cotton proves its superiority than other substrates with -20 dB and -48 dB return loss with 16.12% and 7.73% bandwidth at 1.24 GHz and 1.94 GHz respectively. The proper matching of array has been proved with VSWR value below 1.3 for all substrates. The observation of input port impedance shows that, Cotton array has good impedance matching nearly to 50 Ω and PTFE array has 100 Ω poor impedance matching. The proposed four flexible array exhibit omnidirectional pattern in H plane with 1.43 dBi gain and bidirectional pattern in E plane with 1.4 dBi gain which are support for ideal fitness of proposed flexible material array for medical applications.

Multi-robot formation based on RSSI power level and radiation pattern

This paper studies a formation control scheme to achieve a ‘dispersion’ of a group of robots using the Received Signal Strength Indication (RSSI) measurements of their on-board wireless nodes as feedback signals and their antenna radiation patterns (which is not omnidirectional in most of the cases) as a distance sensor between pairs of robots. In this sense, the multi-robot coordination evolves from a distance formation control to a power-based dispersion strategy. Thus, with the use of feedback through RSSI levels, the heading angle between the agents and the differences of its orientation angles, the control law becomes decentralised, avoiding the need of distance sensors. The result applies to a group of robots with a directed spanning tree topology, with root in the leader and the rest of followers are formed with respect to a unique local leader. The approach considers distinct radiation patterns found in Bluetooth or WiFi communication devices. As the approach ensures the convergence to desired values of RSSI, then a connectivity between the wireless nodes can be adjusted to maintain a desired communication data rate and wireless coverage by the robots posture. Simulations and real-time experiments illustrate the performance of the system.

Broad Coverage Precoder Design for Synchronization in Satellite Massive MIMO Systems

In this paper, we investigate the massive multi-input multi-output (MIMO) transmission for the satellite communication systems equipped with a uniform rectangular array (URA) and aim to design the precoder with broad coverage radiation power pattern to improve the performance of time and frequency synchronizations. The modified Cramér-Rao vector bounds (MCRVB) are chosen as the benchmark of symbol timing offset and frequency offset estimation problem, which can be viewed as the time and frequency synchronization performance metric for the broad coverage precoder design. By considering the minimax MCRVB criterion and the per-antenna equal power constraint, the precoder design approach is formulated as the non-convex constrained minimax problem over the discrete radiation power pattern. This optimization problem is solved by the smoothing techniques combined with the manifold optimization method. To reduce the calculation complexity, the nonmonotone conjugate gradient method is applied. Simulation results show that the average and the minimum received powers in the coverage area of the proposed scheme are higher than those of the scheme based on fairness criterion. Compared with the existing omnidirectional and broad coverage schemes, the proposed scheme has the best synchronization performance among all the contrast solutions.

장거리 전송을 위한 서브 테라헤르츠 고이득 안테나

In this study, a sub-terahertz high-gain antenna for long-distance transmission in the 200-GHz frequency band is designed, fabricated, and measured. Three types of antennas are fabricated, namely, a horn reflector antenna, cassegrain antenna, and an elliptical cassegrain antenna for beam-width expansion, and a measurement environment is configured to measure antenna performance. Additionally, the reception power level and radiation pattern are measured. As a result of the measurement, antenna gains of 36, 52, and 33.3 dBi and beam widths of 3.5, 0.4, and 30° are measured at the center frequency of 245 GHz.

Statistics of the antenna arrays field with heterogeneous errors (Average antenna characteristics)

A methodology for studying the directional properties of antenna arrays with heterogeneous (in dispersion) errors in the excitation and placement of radiators is described. Mechanisms of origin and the mathematical model of heterogeneous errors are determined. Features and differences in statistical effects inherent in the average antenna characteristics of heterogeneous and uniform errors are revealed. General properties of the average power radiation pattern (RP), represented as an expansion into coherent and scattered components, for arbitrary antenna arrays, error values, and their distribution law are investigated. The coherent component does not depend on the correlation properties of errors and is formed by a statistical amplitude-phase distribution (APD), the differences of which from a regular APD depend on the degree of error heterogeneity. The degree of error correlation affects the directional properties of the dissipated power. For completely correlated errors, the average RP does not coincide with the RP in the absence of errors. Numerical results are given for linear antenna arrays and three types of heterogeneous phase errors with increasing/decreasing dispersion towards the edges of the antenna and its two-level value. A criterion for the equivalence of heterogeneous phase errors by the intensity of their impact on the radiated fields is selected. The analysis of the average RP, the limiting average level of lateral radiation was carried out using a generalized angular variable, which allowed us to extend the results to antenna arrays with transverse, inclined, and axial radiation with different electric sizes and steps, as well as compare them with continuous radiated systems and determine the areas where the results coincide. The question of the average directive gain (DG) is studied. For antenna arrays with axial radiation, the optimal relations are determined to achieve its maximum value, taking into account the type of heterogeneous phase errors, their correlation properties, and the antenna arrays spacing. It is shown that it is advisable to take into account the properties of error heterogeneity in the statistical analysis of the antenna field, since the nature of their influence on the directional and energy parameters of the array and its sensitivity depends significantly on their type and amplitude distribution. The types of phase errors causing increased distortion of the average characteristics are determined. The obtained theoretical data generalize the results of the theory of antenna arrays with uniform errors and supplement them with new ideas about the characteristics of random fields and ways of practical use of research results.

Omnidirectional Precoding for Massive MIMO With Uniform Rectangular Array—Part II: Numerical Optimization Based Schemes

In Part II of this two-part paper, we develop novel numerical optimization approaches to design omnidirectional precoding schemes for a massive multiple-input multiple-output system equipped with a uniform rectangular array (URA). To this end, we first formulate the omnidirectional precoding design as a semidefinite program (SDP) with rank constraint. An iterative rank-reduction algorithm is then proposed to produce omnidirectional transmission solution with a minimum number of precoding vectors. It is shown that the proposed algorithm can always obtain three precoding vectors (i.e., a rank-3 precoding matrix) to generate a perfectly omnidirectional power radiation pattern for any <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$P \times Q$</tex-math></inline-formula> URA with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\min \lbrace P, Q\rbrace &gt;2$</tex-math></inline-formula> , or yield an omnidirectional transmission solution with (theoretically minimum) two precoding vectors for any <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$P \times Q$</tex-math></inline-formula> URA with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\min \lbrace P, Q\rbrace \leq 2$</tex-math></inline-formula> . In addition, to facilitate analog precoding design, we further impose constant-modulus constraints for every entries of the precoding matrix. Through judicious (re-)formulation, we develop an efficient Newton's method, which can compute four constant-modulus precoding vectors to generate an omnidirectional power radiation pattern for any URA configuration. The numerical results demonstrate the merits of the proposed schemes.

Omnidirectional Precoding for Massive MIMO With Uniform Rectangular Array—Part I: Complementary Codes-Based Schemes

In the public channels, it is desirable to transmit the common signals omnidirectionally to ensure cell-wide coverage. In Part I of this two-part paper, we develop low-cost closed-form omnidirectional precoding designs for a massive multiple-input multiple-output (MIMO) system equipped with a uniform rectangular array (URA). By formulating the omnidirectional transmission design for a general URA as a feasibility optimization problem, we derive an optimal solution based on the complementary set (CS) or the complete complementary codes (CCC). We prove that the precoding vectors based on the CS or CCC sequences can generate a perfectly omnidirectional power radiation pattern. Since both CS and CCC sequences are binary and constant-modulus, the proposed schemes are well suited to be implemented in the radio frequency analog domain with low hardware cost and suppressed peak-to-average power ratio. The numerical results validate the superior performance of the proposed schemes over the existing alternatives.

Enhanced Single-Sideband Time-Modulated Phased Array With Lower Sideband Level and Loss

This article presents an enhanced single-sideband time-modulated phased array (ESTMPA) using modulating pulses with stepped waveforms. Based on the in-phase/quadrature (I/Q) complex modulation technique, this phase-only weighting array generates a scanning beam at the 1st sideband. The proposed modulating pulses realized through a reconfigurable power divider in I/Q time modulator can avoid the power loss from the switches during switch-OFF state and eliminate the maximum undesired sideband—the 5th harmonic in STMPA. As a result, it brings a power spectrum with less undesired sidebands, lower sideband level (−16.9 dB), higher harmonic efficiency (94.96%), and wider allowable signal bandwidth (eight times as wide as that of the conventional time modulated array). To experimentally verify the feasibility of the proposed design, a wideband enhanced I/Q time modulator and its corresponding eight-element ESTMPA are designed and manufactured. A detailed study on the effect of the magnitude and phase deviations in the circuit and the transition period of modulating pulse are presented. The measured results of power spectrum and radiation pattern have a good agreement with the simulated ones.

A simple design substrate-integrated waveguide horn antenna with reduced back lobe

ABSTRACTA simple technique to design stable gain and low back lobe substrate-integrated waveguide (SIW) horn antenna is proposed. Matching is achieved by placing a metallised via in a specific distance from the aperture of the horn. The proposed design method is based on the analytical equivalent circuit that derived for the impedance of the antenna aperture and the matching metallic via in SIW. The aperture impedance and metallic via in SIW are studied and design curves are extracted for a specified substrate. Also, to reach a directive pattern and reduce the back lobe of the antenna, some chokes are used on the aperture of the horn. The effect of chokes on some parameters such as power flow and radiation pattern, the front to back ratio (FBR), side lobe level (SLL) and increasing directivity of the antenna is reported. The measurement results confirm simulation, appropriately. The proposed structure has high compactness due to the matching technique and design. The proposed SIW horn has compact dimensions as 18.7 * 23.34*7.62 mm (0.93 * 1.16 * 0.37 λ0) and the measured gain of the horn is about 5.5 dB at 15 GHz and bandwidth of six percent.

Integrated core-SOL modelling of fuelling, density control and divertor heat loads for the flat-top phase of the ITER H-mode D-T plasma scenarios

The operation of a tokamak designed to test the sustainability of a thermonuclear grade plasma like the international tokamak experimental reactor (ITER) presents several challenges. Among them is the necessity of fuelling the plasma to reach the density required to generate enough fusion power to achieve and, at the same time, to avoid excessive power loads at the divertor targets (beyond 10 MW m). Whether this goal is achievable or not depends on the details of the fuelling scheme, of the atomic species that are injected into the plasma, of the power radiation pattern in the scrape-off layer and in the divertor, of the additional heating schemes and of the transport mechanisms at work in the core and near the edge of the plasma.In this study we present, for different operational scenarios, the results of an integrated modelling approach to the problem taking into account all the different aspects of it, albeit with some limitations and simplifications discussed in the paper. The tool adopted for our simulations is the JINTRAC suite of codes, which can simulate in an integrated fashion the transport of particles and heat in different regions of the plasma.Within the limitation of our modelling our assessment is that, by carefully tuning the gas fuelling and impurity seeding, it is indeed possible for ITER to achieve and at the same time maintain acceptable divertor power loads. We also investigate the sensitivity of this result to some of the uncertainties in the modelling assumptions underlying the simulations presented in the paper.

Correction of array failure using grey wolf optimizer hybridized with an interior point algorithm

We design a grey wolf optimizer hybridized with an interior point algorithm to correct a faulty antenna array. If a single sensor fails, the radiation power pattern of the entire array is disturbed in terms of sidelobe level (SLL) and null depth level (NDL), and nulls are damaged and shifted from their original locations. All these issues can be solved by designing a new fitness function to reduce the error between the preferred and expected radiation power patterns and the null limitations. The hybrid algorithm has been designed to control the array’s faulty radiation power pattern. Antenna arrays composed of 21 sensors are used in an example simulation scenario. The MATLAB simulation results confirm the good performance of the proposed method, compared with the existing methods in terms of SLL and NDL.

Synthesis of Shaped-Beam Radiation Patterns at Millimeter-Waves Using Transmit Arrays

Transmit arrays have been mostly used for beam collimation applications, either with fixed or scanning beam capability. But transmit arrays can also be used to synthesize power radiation patterns complying with power pattern templates. A new analytical formulation is presented here to obtain a phase-only correction function corresponding to a given power template. The transmit-array transforms the known power radiation pattern of the primary source into a desired output power pattern. The proposed formulation, specialized for axial-symmetric structures, is based on geometrical optics and provides the solution directly from the evaluation of two closed-form first-order differential equations. As a proof of concept, a sec2 with a roll-off at 45° is defined as the target power pattern, at the 30 GHz Ka-band. A 10.8 dBi radiation pattern with the circular polarization is used to illuminate a 180 mm $\times \,\, 180$ mm transmit array with 60 mm focal distance. Previously designed 3.35 mm thick phase-delay unit cells are used as an example to implement the calculated phase distribution over the transmit-array aperture. The measured antenna radiation pattern matches quite well the template, with a steep fall of the radiation at the roll-off angle and low cross-polarization. This validates the concept, the formulation, and the fabricated prototype.

Far‐Field Pattern Tolerance Analysis of Reflector Antenna with Random or System Error Based on Interval Arithmetic

A novel analytic approach for the research of effect on electromagnetic performance of reflector antennas with deformation, including random processing error and system error caused by external loads(such as wind,gravity, and solar radiation), in panels of the reflector surface is proposed. The deformations are modeled as error intervals, and their impact on the electromagnetic performance, including radiation power pattern and some main electromagnetic characteristics(such as side lobe level,peak power, and half-power beamwidth), are efficiently estimated by Interval analysis(IA). The closed-form equations indicate the relationship between the error interval and the bounds(upper and lower bounds) of the radiated power pattern interval by exploiting the rules of interval arithmetic. Two kinds of surface errors(random and system error) and two shapes of deformation area(bump-like and sector) are taken into account in the numerical examples to assess the validation and effectiveness of the proposed approach. The results of the examples show that the proposed IA-based approach has great capability and effectiveness regarding the traditional statistical method(such as Monte-Carlo method).

All-Optical Switching and Unidirectional Plasmon Launching with Nonlinear Dielectric Nanoantennas

High-index dielectric nanoparticles have become a powerful platform for modern light science, enabling various fascinating applications, especially in nonlinear nanophotonics for which they enable special types of optical nonlinearity, such as electron-hole plasma photoexcitation, which are not inherent to plasmonic nanostructures. Here, we propose a novel geometry for highly tunable all-dielectric nanoantennas, consisting of a chain of silicon nanoparticles excited by an electric dipole source, which allows tuning their radiation properties via electron-hole plasma photoexcitation. We show that the slowly guided modes determining the Van Hove singularity of the nanoantenna are very sensitive to the nanoparticle permittivity, opening up the ability to utilize this effect for efficient all-optical modulation. We show that by pumping several boundary nanoparticles with relatively low intensities may cause dramatic variations in the nanoantenna radiation power patterns and Purcell factor. We also demonstrate that ultrafast pumping of the designed nanoantenna allows unidirectional launching of surface plasmon-polaritons, with interesting implications for modern nonlinear nanophotonics.

The Radiation System Synthesis by the Power Criterion as a Problem of Optimization with Restrictions

A nonlinear synthesis problem of antennas according to the prescribed power (squared amplitude) radiation pattern (RP) is considered in the variational statement that yields in the possibility to take into account an additional restriction to the synthesized power RP. The problem of synthesis consists of finding such currents in antenna, which generates the RP with the best approximation to the given one. The respective Euler’s equation is reduced on the basis of used functional. This is nonlinear integral equation of Hammerstein’s type. The effective numerical methods are elaborated and applied for its solving. The computational results verify the effectiveness of approach proposed.

Correction of failure in linear antenna arrays with greedy sparseness constrained optimization technique.

This paper proposes the correction of faulty sensors using a synthesis of the greedy sparse constrained optimization GSCO) technique. The failure of sensors can damage the radiation power pattern in terms of sidelobes and nulls. The synthesis problem can recover the wanted power pattern with reduced number of sensors into the background of greedy algorithm and solved with orthogonal matching pursuit (OMP) technique. Numerical simulation examples of linear arrays are offered to demonstrate the effectiveness of getting the wanted power pattern with a reduced number of antenna sensors which is compared with the available techniques in terms of sidelobes level and number of nulls.