Dynamic Range Ratio Research Articles

3D Power Synthesis with Reduction of Near-Field and Dynamic Range Ratio for Conformal Antenna Arrays

A simple method of power synthesis for 3D radiation patterns of conformal antenna arrays is presented. The method enables to synthesize a desired far-field pattern simultaneously controlling the dynamic range ratio (DRR) of the array excitations and the electric field amplitude in a given region of interest close to the antenna. The power synthesis problem is reduced to a field synthesis one by introducing an auxiliary phase pattern, which is incorporated in a cost function together with the desired far-field pattern, the array pattern, the near electric field amplitude, and the array excitations. Such cost function is minimized by iteratively modifying the auxiliary phase pattern and the array excitations. Applications of the proposed method to conformal arrays of different geometries show that accurate results are obtained also in presence of stringent requirements and within acceptable CPU times, even when hundreds of elements are involved.

Amplitude-only pattern synthesis of nonuniform linear arrays using a generalized pattern search optimization

In this work, synthesis of linear array geometry and excitation amplitudes is first formulated as a linearly constrained multiobjective optimization problem with the goals of minimum sidelobe level, null control and high directivity and then solved by a generalized pattern search (GPS) algorithm for the optimum element locations and excitation amplitudes. The constraints are imposed on the interelement spacing and dynamic range ratio of the amplitude tapering to reduce mutual coupling effects between the elements. GPS methods are newly discovered, derivative-free methods where the current iterate is updated by sampling the fitness function at a finite number of points along a suitable set of search directions to find a decrease in the function value. Thus, GPS methods can be exploited efficiently in solving optimization problems without requiring any information about the gradient of the fitness function which may be even discontinuous, nondifferentiable, stochastic or highly nonlinear. Finally, four worked examples are presented that illustrate the use of the whole GPS synthesis method, and the optimization goal in each example is easily achieved. Furthermore the full-wave simulations of the synthesized arrays are also completed to examine the mutual coupling effects. Finally the results of the GPS algorithm are validated by comparing with results obtained using the genetic algorithm, and the results of the uniform and Dolph - Chebyshev arrays, having the same number of element and the same aperture length. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.

Hybrid Differential Evolution with Biogeography-Based Optimization for Design of a Reconfigurable Antenna Array with Discrete Phase Shifters

Multibeam antenna arrays have important applications in communications and radar. This paper presents a new method of designing a reconfigurable antenna with quantized phase excitations using a new hybrid algorithm, called DE/BBO. The reconfigurable design problem is to find the element excitation that will result in a sector pattern main beam with low sidelobes with additional requirement that the same excitation amplitudes applied to the array with zero-phase should be in a high directivity, low sidelobe pencil-shaped main beam. In order to reduce the effect of mutual coupling between the antenna-array elements, the dynamic range ratio is minimized. Additionally, compared with the continuous realization and subsequent quantization, experimental results indicate that the performance of the discrete realization of the phase excitation value can be improved. In order to test the performances of hybrid differential evolution with biogeography-based optimization, the results of some state-of-art algorithms are considered, for the purposed of comparison. Experiment results indicate the better performance of the DE/BBO.

DESIGN OF A RECONFIGURABLE ANTENNA ARRAY WITH DISCRETE PHASE SHIFTERS USING DIFFERENTIAL EVOLUTION ALGORITHM

The reconfigurable design problem is to find the element that will result in a sector pattern main beam with side lobes. The same excitation amplitudes apply to the array with zero-phase that should be in a high directivity, low side lobe pencil shaped main beam. Multi-beam antenna arrays have important applications in communications and radar. This paper presents a new method of designing a reconfigurable antenna array with quantized phase excitations using a new evolutionary algorithm called differential evolution (DE). In order to reduce the effect of mutual coupling among the antenna-array elements, the dynamic range ratio is minimized. Additionally, compared with the continuous realization and subsequent quantization, experimental results indicate better performance of the discrete realization of the phase-excitation value of the proposed algorithm.

Postcorrection of Pipelined Analog–Digital Converters Based on Input-Dependent Integral Nonlinearity Modeling

The integral nonlinearity (INL) is used for the postcorrection of analog-digital converters (ADCs). An input-frequency-dependent INL model is developed for the postcorrection. The model consists of a static term that is dependent on the ADC output code and a dynamic term that has an additional dependence on the input frequency. The concept of ADC digital output postcorrection by INL is first introduced. The INL model is subtracted from the digital output for postcorrection. The static compensation part is made by adjacent sets of gains and offsets, where each set corrects a range of output codes. The dynamic information, i.e., the frequency dependence of the INL dynamic component is used to construct a set of filter blocks that performs ADC compensation in the time domain. The compensation scheme is applied to the measured data of two ADCs of the same type (Analog Devices AD9430). Performance improvements in terms of spurious-free dynamic range, signal-to-noise and distortion ratio, intermodulation distortion, and noise are obtained. The dynamic compensation part, due to its frequency dependence, can be generalized; hence, a postcorrection block model can be used for compensating multiple ADCs of the same type.

Arbitrary Footprints from Arrays with Concentric Ring Geometry and Low Dynamic Range Ratio

A common method of antenna array synthesis uses least-squares approximation to fit the radiation pattern of the array to a set of samples of an ideal desired pattern Fid . However, it has long been known that discontinuities in Fid prevent close approximation, and that sampling a target pattern Ftar that approximates Fid can afford better results. Here we show, for the case of circular planar arrays, that an appropriate target pattern can be obtained by modification of a Taylor pattern for a circular aperture.

Fast Iterative Method of Power Synthesis for Antenna Arrays

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> A fast and simple method of power synthesis for antenna arrays of arbitrary geometry is presented. The method adopts an auxiliary function having the desired amplitude pattern and a generic phase pattern, and determines in closed form the array pattern approximating the auxiliary function in both amplitude and phase. A cost function involving the auxiliary function and the approximating pattern is minimized by modifying the phase pattern of the auxiliary function, using a simple and fast iterative technique. Once the optimal phase pattern has been found, the array pattern approximating the corresponding auxiliary function is the synthesized pattern. The proposed method allows to satisfy stringent requirements on the amplitude pattern, including multibeam synthesis and radiation suppression within large angular regions. Numerical results show the effectiveness of the algorithm and are compared to those obtained using other existing methods. In order to achieve a more significant comparison such methods have been properly modified to improve their performances. Such comparison shows that the presented algorithm allows a significant reduction of CPU time with respect to the other considered methods, as well as a weaker dependence on the starting point. Finally, the presented method is extended in such a way as to reduce the dynamic range ratio (DRR) of the array excitations. </para>

Synthesis of satellite footprint patterns from time‐modulated planar arrays with very low dynamic range ratios

AbstractAn efficient pattern synthesis approach has been developed for the synthesis of satellite footprint patterns using time‐modulated planar arrays. The approach can be used to effectively control both the ripples in the coverage zone and the sidelobe levels, due to the adoption of time‐modulated antenna arrays. The optimized time sequences and element excitations are obtained by the method based on a combination of a differential evolution strategy (DES) and a modified 2D Woodward–Lawson method. Normally, planar array synthesis is rather time consuming, partly due to the inherently large number of optimization variables and partly due to the fact that the calculation of fitness function is also time consuming. A fast computation approach based on the 2D fast Fourier transform (FFT) is thus applied in the DES for the planar array pattern computation. Several representative examples are presented to show the flexibility and effectiveness of the proposed approach. Copyright © 2008 John Wiley &amp; Sons, Ltd.

Reconfigurability and Beam Scanning With Phase-Only Control for Antenna Arrays

A new method is presented on constrained power synthesis for reconfigurable arrays of arbitrary geometry. Given a number of suitable masks, the algorithm yields excitation vectors whose array patterns belong to such masks, and for each array element the excitation amplitude holds constant during the pattern reconfiguration, so as to ensure phase-only control. Each excitation amplitude is optimized, and the method allows to control the dynamic range ratio (DRR) of the excitations. The solution to the synthesis problem is found as a point of the intersection between two suitable sets, by using the method of successive projections. The proposed method can also be used to solve problems of constrained beam scanning. To this aim it is sufficient to select a high number of masks, close to each other in the angular sector of interest and shaped in such a way as to reproduce the desired scanning beam. The algorithm yields array patterns belonging to these masks, thus performing a discrete scanning by phase-only control, and allows to control the DRR. Several numerical examples show the effectiveness and the capabilities of the method.

SHAPED BEAM PATTERN SYNTHESIS WITH NON-UNIFORM SAMPLE PHASES

For a long time power pattern synthesis has been considered to produce shaped beam patterns due to the number of degrees of freedom when compared with field pattern synthesis. However, severaladvantages exist if synthesis techniques are based on field patterns, since the relationship between the array factor and the source distribution is a Fourier transform. In this case, quicker and efficient algorithms are obtained with the Fast Fourier Transform (FFT) to perform the calculations. Therefore, this work presents a new technique that synthesizes shaped beam patterns through the control of non-uniformly samples of the array factor, both in amplitude and phase. The sample phases increase the number of degrees of freedom. To produce complex patterns, the sample phases of the shaped beam region are used to create more oscillations in the ripple structure than the ones produced with the realpatterns. Not onl y this procedure yields a narrower transition region between the beam zone and the sidelobe zone but also smaller dynamic range ratios are obtained. Furthermore, it is described how to impose nulls in prescribed directions of the complex patterns. Some examples are presented to demonstrate the application of the synthesis technique.

A Unifying Perspective on the Quasi-steady Analysis of Magnetorheological Dampers

A magnetorheological (MR) fluid, modeled as a Bingham plastic (BP) material, is characterized by a field dependent yield stress, and a (nearly constant) postyield plastic viscosity. Based on viscometric measurements, such a BP model is an idealization to physical MR behavior, albeit a useful one. A better approximation involves modifying both the preyield and postyield constitutive behavior as follows: (1) assume a high viscosity preyield behavior when the shear stress is less than the transition stress, and (2) assume a power law fluid (i.e., strain rate dependent viscosity) when the shear stress is greater than the transition stress. Assuming a power law fluid in postyield allows the model to account for shear thinning behavior exhibited by MR fluids at higher strain rates. Such an idealization for MR fluid constitutive behavior is called an viscous-power law model, or a Herschel—Bulkley (HB) model with preyield viscosity. This study develops a quasi-steady analysis for such a constitutive MR fluid behavior applied to an MR flow mode damper. Closed form solutions are developed for the fluid velocity, as well as key performance metrics, such as damping capacity and dynamic range (ratio of field-on to field-off force). For the given fluid properties and flow mode damper geometry, the fluid velocity profile and gradient, and the relationship of the damper force and piston velocity are analyzed. In addition, specializations to existing models, such as the HB, biviscous, and BP models, are shown to be easily captured by this model when physical constraints (idealizations) are placed on the rheological behavior of the MR fluid.

Consistency of Constraints on Nulls and on Dynamic Range Ratio in Pattern Synthesis for Antenna Arrays

Given an antenna array of N elements, we deal with the problem of finding an array pattern that approximates a desired pattern, while: a) null constraints are imposed in M(les N - 2) assigned directions; b) an upper bound D is imposed on the dynamic range ratio (DRR) of the excitations. At first we show that the system of constraint equations has solutions if and only if D ges D <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> , where D <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is a parameter depending on the null directions, and describe a method to evaluate D <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> . Then we propose two simple and fast algorithms to solve the synthesis problem and show their effectiveness by numerical examples. Statistical results show that usually D <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> = 1 when M is small compared to N, thus exact nulls can be formed for any D ges 1. This result provides an insight into the numerical results.

Genetic Algorithms for Design of Discrete Phase-only Reconfigurable Array Antennas with Fixed Dynamic Range Ratio

In this paper, we present a new method based on real-coded Genetic Algorithm (GA) with elitist model for optimal design of a reconfigurable symmetrical dual-beam uniformly spaced linear isotropic antenna array with phase-only control of quantized phase shifters. The problem is to find a common amplitude distribution that will generate a pencil beam with zero phases and a flat-top beam with discrete phases of a six-bit discrete phase shifter, without or with pre-fixing the value of dynamic range ratio (|I max/I min|) of excitation current amplitude distribution equal to or less than five.

PHASE-ONLY AND AMPLITUDE-PHASE ONLY SYNTHESIS OF DUAL-BEAM PATTERN LINEAR ANTENNA ARRAYS USING FLOATING-POINT GENETIC ALGORITHMS

In this paper, we present a comparison study between phase-only and amplitude-phase synthesis of symmetrical dual-pattern linear antenna arrays using floating-point or real-valued genetic algorithms (GA). Examples include a sum pattern and a sector beam pattern. In the former, phase is only optimized with predetermined Gaussian amplitude distribution of fixed dynamic range ratio (|amax/amin|) and in the latter, both are optimized with less dynamic range ratio than the former and yet share a common amplitude distribution.

Design of Fully Digital Controlled Reconfigurable Array Antennas with Fixed Dynamic Range Ratio

In this paper, we propose an optimization method based on Genetic Algorithm (GA) for design of reconfigurable dual-beam linear isotropic antenna arrays with phase only control of digital phase shifters. The problem is to find a fixed amplitude distribution using four-bit digital attenuator that will generate two broadsided symmetrical beams in vertical plane: a pencil beam with zero phases and a flat-top beam with discrete phases of a five-bit digital phase shifter, with or without pre-fixing the dynamic range ratio (I max /I min) of excitation amplitude distribution to a value equal to or less than seven.

A Clonal Selection Algorithm for null Synthesizing of Linear Antenna Arrays by Amplitude Control

This paper presents a clonal selection algorithm based on human immune system for null steering of linear antenna arrays by controlling only the element amplitudes. Design requirements such as the null depth level, maximum sidelobe level, and dynamic range ratio are considered in the optimization process. Several examples of Chebyshev pattern with the imposed single, multiple and broad nulls are given to show the accuracy and flexibility of the proposed clonal selection algorithm.

Design of Phase-Differentiated Reconfigurable Array Antennas With Minimum Dynamic Range Ratio

In this letter, we propose a real-coded genetic algorithm (GA) for optimal design of reconfigurable dual-beam linear array antennas with phase only control. The problem is to find a common amplitude distribution with minimum dynamic range ratio (DRR) that will generate a pencil beam with zero phases and a flat-top beam with continuously controllable phases of an analog phase shifter. Results are also shown for the same design without minimizing dynamic range ratio (a <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max </sub> /a <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">min</sub> ) of excitation amplitude

Novel automatic control for the optimum optical gain and phase differences in SOA–MZI wavelength converter: Theory and experiment

We have proposed, simulated, and experimentally verified the novel automatic control method and apparatus to automatically adjust and constantly maintain the optimum optical gain and phase differences in order to achieve the automatically optimized semiconductor optical amplifier (SOA)–Mach-Zehnder interferometer (MZI) wavelength converter (WC) with wide input power dynamic range (IPDR) and maximum extinction ratio (ER). Our automatic control algorithm is proposed through the results of simulation and its validity is confirmed through the experiment.

Time modulated planar arrays with square lattices and circular boundaries: Research Articles

The time modulation approach is extended to planar antenna arrays with square lattices and circular boundaries to synthesize ultra-low sidelobe patterns. Time modulation is achieved by switching on–off each of the array elements in pre-determined sequences, thus introducing an additional degree of design freedom to reduce the dynamic-range ratio and error tolerance requirements. The generalized Tseng–Cheng distributions, which generate axis-symmetric patterns in all p-cuts for planar arrays with square lattices and boundaries, are utilized in the synthesis of time modulated planar arrays. The sideband levels of the time modulated planar arrays are effectively suppressed by utilizing the differential evolution (DE) algorithm. Numerical results show that ultra-low sidelobes can be synthesized for time modulated planar arrays, with very low dynamic-range ratio, low sideband levels and minimal reduction in directivity. Copyright © 2005 John Wiley & Sons, Ltd.

Improvement of Input Power Dynamic Range and Extinction Ratio for Wavelength Converters Based on Cross-Gain Modulation

A technique for improving the input power dynamic range and extinction ratio of wavelength converters based on cross-gain modulation in a semiconductor optical amplifier is presented.