Design Of Such Arrays Research Articles

Multi-Device Piezoelectric Direct Discharge for Large Area Plasma Treatment

The piezoelectric cold plasma generators (PCPG) allow for production of the piezoelectric direct discharge (PDD), which is a kind of cold atmospheric pressure plasma (APP). The subjects of this study are different arrays of PCPGs for large-area treatment of planar substrates. Two limiting factors are crucial for design of such arrays: (i) the parasitic coupling between PCPGs resulting in minimum allowed distance between devices, and (ii) the homogeneity of large area treatment, requiring an overlap of the activation zones resulting from each PCPG. The first limitation is investigated by the use of electric measurements. The minimum distance for operation of 4 cm between two PCPGs is determined by measurement of the energy coupling from an active PCPG to a passive one. The capacitive probe is used to evaluate the interference between signals generated by two neighboring PCPGs. The second limitation is examined by activation image recording (AIR). Two application examples illustrate the compromising these two limiting factors: the treatment of large area planar substrates by PCPG array, and the pretreatment of silicon wafers with an array of PCPG driven dielectric barrier discharges (DBD).

Reception Power Pattern of Distributed Absorbers in Focal Plane Arrays: A Fourier Optics Analysis

Passive imaging cameras at millimeter and sub-millimeter wavelengths are currently entering a new era with the development of large format arrays of direct detectors. Several of these arrays are being developed with bare absorbing meshes without any antenna coupling (lens or horn) structures. The design of such arrays is typically done resorting to geometrical considerations or basic broadside plane wave incidence analysis. This paper presents a spectral technique for the analysis of such focal plane arrays in reception using Fourier Optics, which is valid also for moderately skewed incident angles. The analysis constitutes a step improvement with respect to previously used methods by providing an accurate and efficient way to estimate the point-source angular response and the throughput from a distributed incoherent source of an absorbing mesh in the focal plane of a quasi-optical component (e.g., a parabolic reflector or lens). The proposed technique is validated with full-wave simulations. After presenting the analysis, this paper compares the performance of arrays of bare absorber in the focal plane of a quasi-optical component to those of corresponding antenna based arrays. It is found that absorbers lead to a comparable tradeoff, in terms of spill-over and focusing efficiency, only for very tight samplings. For larger samplings, the focusing efficiency of absorbers is significantly lower than the one for antennas.

Effect of Xenon Gas and Foils on a Multi-Foil Insulation

The miniaturization of thermal installations has been also extended to compact insulations in processes maintained at low or high temperatures, and restricted to minimal heat losses or gains. The current investigation has been conducted experimentally and numerically, aiming to predict the performance of a multi-foil array, in which xenon gas is entrapped between steel foils, separated and supported by widely spaced ceramic particles. A parametric study of the effect of an increased number of foils, as compared to the experimental array, shows the preferred directions to design of such arrays. The performance of an array operated with xenon gas at near-atmospheric pressure is compared to the performance of arrays filled with other gases. The low thermal conductivity of xenon gas leads to a lower effective thermal pseudo-conductivity of the array in all the pressure range, as compared to arrays operated with other gases. The equations of conduction and radiation are solved numerically for a wide range of pressures in temperature range of 20–500°C. Good agreement with experimental results is achieved.

An experimental comparison of the focused beamformer and the inverse method for the characterisation of acoustic sources in ideal and non-ideal acoustic environments

The current availability and affordability of multi-microphone array systems has awakened a strong interest in sound source location and characterisation in many fields of experimental acoustics and noise control. Although the theory behind the design of such arrays has been known for some time, the algorithms used to process the microphone signals are the subject of on-going research and development. The beamformer algorithm is well-known and relatively simple to implement. It is useful for ‘scanning’ an area to find the position of sound sources but has limited ability to characterise fully the spatial distribution of the strength of an acoustic source. The inverse method, on the other hand, requires prior information regarding the position of sources or an appropriate discretisation of the source strength distribution. The method is more difficult to implement but can yield more useful source characterisation data. This paper presents a comparison between the two methods based on experimental data. The results show that, in the presence of more than one source, the beamformer cannot yield reliable estimates of the source strength of individual sources since the output from the beamformer is shown to be dependent upon the degree of correlation between multiple sources as well as the source strengths themselves. The inverse method, on the other hand, is shown to yield reliable estimates of source strength when more than one source is present, regardless of the correlation between the sources, although the results presented here are restricted to the case of a relatively small number of sources. It is clearly demonstrated, both theoretically and through carefully controlled experiments, that either method can be used effectively under reverberant conditions through the use of measured Green functions in place of the simple geometrically-derived free-space values of the Green function. This greatly improves the possibility for the successful use of these methods in many important industrial applications.

Chaotic synchronization in small assemblies of driven Chua's circuits

Chaotic synchronization is studied in experiments performed on dynamic arrays of Chua's circuits that are connected by using a recently introduced driving method especially suited for the design of such arrays. Namely, the driven circuit has the same number of energy storage elements as the driving circuit. The experimental results, which are supported by theoretical analysis, are different depending on the geometric arrangement of the array. In the case of linear arrays, the first circuit always imposes its behavior on the rest of the chain at a finite velocity. Instead, in the case of ring geometries, the chaotic synchronized state is only stable up to a certain size of the ring. Beyond this critical size a desynchronizing bifurcation occurs, leading to a chaotic rotating wave that travels through the array. This instability is explained by performing an analysis in terms of modes.

Stochastic optimization of linear sparse arrays

In conventional beamforming systems, the use of aperiodic arrays is a powerful way to obtain high resolution employing few elements and avoiding the presence of grating lobes. The optimized design of such arrays is a required task in order to control the side-lobe level and distribution. In this paper, an optimization method aimed at designing aperiodic linear sparse arrays with great flexibility is proposed. Simulated annealing, which is a stochastic optimization methodology, has been utilized to synthesize the positions and the weight coefficients of the elements of a linear array in order to minimize the peak of the sidelobes and to obtain a beam pattern that meets given requirements. An important novelty is the fact that the latter goal can be achieved in parallel to the minimization of both the number of elements and the spatial aperture, resulting in a global optimization of the array characteristics. The great freedom that simulated annealing allows in defining the energy function to be minimized is the main reason for the notable versatility and the good results of the proposed method. Such results show an improvement in the array characteristics and performances over those reported in the literature.

VLSI arrays for digital signal processing:Part I-A model identification approach to digital filter realizations

A study of VLSI arrays that implement single-input singleoutput linear time-invariant digital filters is initiated in this paper. The arrays are restricted to be comprised of several similar processing elements in a linear configuration with only nearest neighbor links. The requirement of pipelineability in the resulting circuits is also imposed. A general framework is developed for the design of such arrays when each processing element is assumed to have a certain model with a single state variable. Several existing canonical form realizations are shown to be obtainable as special cases of the array configurations developed in this paper.

Position-modulated phased array-space factor considerations

The space factor of an element position-modulated array is expressed as an Anger function series for a general amplitude distribution. The behavior of the main lobe and the diffraction sidelobes for uniform excitation are presented in the form of universal curves. It is found that the nulls near the main lobe disappear for the modulation index above a critical value. The peak level of the grating plateaus and their shapes are given in terms of approximate expressions and are exactly determined computationally. The nature of the curves suitable for design of such arrays for a given scan range and permissible peak sidelobe level is given. An example shows that a high resolution beam may be obtained with a comparatively smaller number of elements than required by a uniformly illuminated periodic array. An exact-series summation formula for the directivity of nonuniformly spaced antenna arrays of isotropic elements is given. The directivity of the modulated array computed by this formula shows a smooth variation at the ends of the scan range in contrast to the sudden fall in the case of the periodic array.

The radiation resistance of off-set series slots in microstrip line

The radiation resistance of off-set series slots has been calculated for microstrip lines using the method proposed by Breithaupt for strip lines. A suitable transformation is made to allow for the difference in structure. Curves relating the slot resistance to the microstrip length, width and off-set distance have been obtained.Microstrip slot antenna arrays are becoming important in applications where size and weight are of significance. The radiation resistance is a very significant parameter is the design of such arrays. Oliner first calculated the radiation conductance of centered series slots in strip transmission lines and that analysis was extended by Breithaupt to the off-set series slots in stripline. The radiation resistance of off-set series slots in microstrip lines is calculated in this paper and data are obtained for different slot lengths, slot widths and off-set values. An example of the use of these data in array antenna design in shown.

Condenser-microphone arrays in acoustical holography—a review

The primary difficulties in producing acoustical holograms have been associated with the recording technique. This paper presents some of the important recording techniques and highlights the desirability and advantages of using two-dimensional arrays of linear, electroacoustic transducers for detecting holographic data in real time. Recent developments of a class of such arrays, namely the condenser-microphone arrays, are reviewed. This is followed by an outline of the major considerations involved in the design of such arrays, the discussion of their characteristics, and their immediate and future prospects in acoustical holography.

A Pseudodynamic Programming Technique for the Design of Correlator Supersynthesis Arrays

A correlator supersynthesis array is defined as an array of antennas connected together in pairs as interferometers and capable of tracking a radio source during its apparent motion in the sky. Some problems in the design of such arrays are discussed. A computerized optimization technique, termed pseudodynamic programming, is described for the design of such arrays and some results are presented. The limitations and capabilities of the technique are discussed.