Image segmentation on a 2D array by a directed split and mergeprocedure

A 2D array implementation of image segmentation by a directed split and merge procedure is proposed. Parallelism is realized on two levels: one within the split and merge operations, where more than one merge (or split) may proceed concurrently, and the second between the split and merge operations, where several splits may be performed in parallel with merges. Both the split and merge operations are based on nearest neighbor communications between the processing elements (PEs), and facilitating low communication costs. The basic arithmetic operations required to perform split and merge are comparison and addition, allowing a simple structure of the PE as well as a hardwired control. A local of 512 bytes is sufficient to hold the interim data associated with each PE. A prototype PE has been constructed using 3 μm double-metal CMOS technology. Scaling up to 0.8 μm, it is possible to incorporate 32 PEs on a 5 cm² chip. With sufficiently large PE window sizes, image segmentation can be achieved in linear time     

New 2D systolic array algorithm for DCT/DST

Presents an algorithm and the architecture of a 2D systolic array processor for the DCT (discrete cosine transform) and the DST (discrete sine transform). It is based on the IDFT (inverse discrete Fourier transform) version of the Goertzel algorithm via Horner's rule. This 2D systolic array for the DCT/DST can be met by achieving a systematic technique for transforming algorithms to specific forms for mapping onto 2D systolic arrays.<>     

2D DOA estimation for noncircular sources using L-shaped sparse array

We present an algorithm for two-dimensional (2D) direction-of-arrival (DOA) estimation of noncircular sources using an L-shaped sparse array. An L-shaped sparse array consisting of two co-prime arrays is firstly introduced. Then, the fourth-order-cumulants (FOCs) of received data are used to construct a FOC matrix (FOCM), by which we can get the estimations of elevation angles. With the estimated elevation angles, the azimuth angles can be estimated by a low-complexity signal separation algorithm. During the procedure used for estimating azimuth angles, no any eigenvalue decomposition (EVD), peak search and pair-matching procedure need to be implemented. Although the aperture is extended significantly, the computation complexity of proposed algorithm still is acceptable. Compared with some analogous algorithms, our approach shows more attractive estimation performance. A lot of simulation results prove the advantages of proposed DOA estimation technology.     

一般阵列误差情况下信号二维方向角估计

针对均匀圆阵存在一般阵列误差的情况,提出一种信号二维方向角估计方法.基于均匀圆阵的阵列流形和阵列输出的协方差矩阵,采用加权总体最小二乘法估计信号二维方向角.并给出了解整周期性模糊的方法.计算机仿真表明了此方法估计精度高,对阵列误差鲁棒性强,并且各项性能都接近于CRB.     

Subspace extension algorithm for 2D DOA estimation with L-shaped sparse array

A subspace extension algorithm for two-dimensional (2D) direction-of-arrival (DOA) estimation with an L-shaped array is proposed. This L-shaped array is comprised of two orthogonal sparse linear arrays (SLAs). Each SLA consists of two different uniform linear arrays. The cross-correlation matrix of received data is used to construct two extended signal subspaces, by which the azimuth angles and elevation angles can be estimated independently. The procedure used to extend signal subspace only needs a small amount of calculation. Then, an effective pair-matching method is addressed to pair the estimated elevation angles and azimuth angles. Although the signal subspaces are extended, the complexity of the proposed 2D DOA estimation algorithm is lower than many similar algorithms. Simulation results indicate the availability of the proposed pairing-matching method and subspace extension algorithm.     

2D phase-conjugated retrodirective array with information carrying capability

A new two-dimensional (2D) phase-conjugated retrodirective array with star-shaped antenna elements is proposed. The phase conjugators provide high isolation of -48 dB between RF and IF ports when RF/IF signals share the same ports in a balanced hybrid. By on-off keying modulation of the local oscillator (LO), the new 2D phase-conjugated retrodirective array can reflect the signal back to the interrogator with the modulation signal carried on it for information exchange. Experimental results show that this array can achieve 2D retrodirectivity within 120deg angle of wide scan range at arbitrary signal polarisation and injection direction     

A 2D adaptive beamforming method in sparse array

This study presents an Accelerated Proximal Gradient singular value thresholding based Linearly Constrained Singular Canceler (APG-LCSC) algorithm to improve the performance of two-dimensional (2D) adaptive beamforming in sparse array. Firstly, a signal model is established based on Matrix Completion (MC), which can be proved to meet Null Space Property (NSP). Subsequently, left and right singular value vector of the received signal matrix is achieved via MC, and then a linearly constrained singular canceler is obtained by employing the singular value vector. The proposed algorithm decreases the required number of antennas, lowers the computational complexity and has a robust performance. Computer simulations demonstrate that the proposed APG-LCSC algorithm can acquire high accuracy of 2D beamforming in sparse array.     

Eigenmodes of a 2D array of coupled slot lines in the impedance approximation

A 2D periodic array of coupled slot transmission lines is considered in the approximation of equivalent boundary conditions. The eigenmode problem for an array operating in the quasi-periodic mode is formulated and solved. The dispersion equation for eigenmode propagation constants and expressions for eigenmode fields are obtained. The behavior of eigenmodes in a frequency band and in a range of values of geometric parameters is analyzed. The orthogonality of eigenmodes is shown. Theoretical results are compared to the results of numerical calculation performed with the use of electromagnetic simulation systems.     

High power, high-efficiency 770 nm 2D laser diode array

A two-dimensional (2D) AlGaAs laser diode array is described which operates at a power density of 2 kW/cm², with an overall efficiency of 35% and a slope efficiency of 56%. The wavelength of operation is 770 nm     

Matrix and vector multiplications using a 2/sup 1///sub 2/-dimensional systolic array

A pseudo-three-dimensional network, called a 2/sup 1///sub 2/-dimensional systolic array, to compute matrix-vector and matrix-matrix multiplications is introduced. The new architecture achieves twice the throughput rate as that of the conventional systolic arrays with the same number of processing elements. This new approach provides a practical means for the implementation using current integration technology.<>     

A monolithic voltage-comparator array for A/D converters

Describes a monolithic circuit consisting of an array of 8 voltage comparators, a resistive voltage divider, and associated logic circuits. Intended as an encoding component for high-speed parallel A/D converters, this `3-bit quantizer' uses regeneration for voltage gain and signal storage. A Gray-code output minimizes the problem of comparator indecision. The principal error sources are an asymmetry-induced comparator offset with 2-mV standard deviation and a thermally induced offset of a much as /spl plusmn/2.5 mV, dependent on signal history. The quantizer has been incorporated in an experimental 6-bit 200 megasample/s (MS/s) A/D converter.     

Binomial array as a multistate phase diversity antenna

If two in-phase plane waves arrive at an antenna from different directions, the resulting signal is not necessarily the coherent sum of the two incoming signals. This is due to the fact that the antenna radiation pattern is actually a complex quantity containing amplitude and phase properties. Thus, it can be stated that antenna phase characteristics may vary as a function of direction. In free space, the antenna phase pattern does not have any role in radio communications in contrast to mobile communications in an urban microcell where the radio channel is very complicated due to multipath propagation. Array antennas offer possibilities to control its phase properties in transmission and reception, which offer a simple technique to improve the combination of received multipath signal components. Binomial arrays are one possibility to implement similar directive beams which, however, have different phase patterns compared to each other. A set of these beams could be used in a discretely optimizing receiver system much in the same way as other diversity techniques are used. A four-element array and results from a microcell radio channel environment simulation are presented as a demonstration of this technique     

Analysis of the structure of a terahertz-band 2D array with sensors on the edge of a superconductor transition

Film detectors on the edge of a Ti or Mo/Cu (T _c ≈ 0.4 K) superconductor transition are included in an N × M 2D array of planar polarization-separated antennas. The detectors are simultaneously sensors and absorbers of the total electric power from an antenna and bias circuits. The detectors are heat-insulated because of weak electron-phonon interaction with the substrate and because of the effect of the Andreev reflection of electrons in Nb electrodes. Readout based on the projection method necessitates only N + M channels in the case when the signal is continuously accumulated for all N × M detectors. Simulation of a 3 × 3 2D array at a frequency of 600 GHz shows that the matching band is ～30%.     

Laminated waveguide as radiating element for array applications

This paper reports on the study of a new antenna as well as a five-element array prototype developed for communications in K-band and suitable for low temperature co-fired ceramic technology. The radiating element is an open waveguide realized in laminated technology. A special coaxial-to-waveguide transition has also been designed as feed port for measuring the prototypes. The element exhibits a 1 GHz bandwidth centered at 20.7 GHz and a 2.7 dBi gain. In an array configuration, mutual coupling between the elements is lower than -18 dB across the bandwidth. The simulated boresight radiation pattern of a five-element array is stable over the bandwidth and the gain reaches 9.2 dBi at 20.7 GHz. The measurements of the radiation pattern for a 20-degree scan angle, as well as the simulation, demonstrate the scanning capability of this array.     

Summary of HgCdTe 2D array technology in the U.K.

HgCdTe 2D arrays are needed in both medium (MW) and long (LW) wavebands for imaging, search, and track and guidance applications. Often the detector is the performance-limiting component in the system, and it is necessary to use detectors with very low excess noise and few defective pixels. Normally the detector is cooled sufficiently to freeze-out thermally generated leakage currents, so the main interest is to understand the mechanisms that determine the general detector performance and the cause of defective pixels. This paper describes the detector technology and the ion beam junction-forming process. The fundamental performance limits of homojunction HgCdTe technology and the doping levels needed to produce a detector with impact-ionization limited performance are discussed. Extensive studies have been made on defective pixels in long wavelength arrays and some technologies for reducing them are described here. Defective pixels have been found to be associated with material dislocations crossing the p-n junction and a model has been proposed for the noise-generating mechanism.     

Frequency sampling method for designing 2-D FIR real-coefficientdigital filters using Hermite interpolation

A novel frequency-sampling method for designing 2-D real-coefficient FIR filters, given the values and slope estimates of the desired frequency response at each of the node points of a rectangular grid, is presented. Based on a new class of bivariate Hermite-type polynomials suitable for interpolating at complex conjugate points, and using Kronecker products, the original 2-D filter design problem is reduced to the solution of two 1-D systems of linear equations. Additional advantages of the method are the securing of the existence and uniqueness of the solution of the design problem, computational efficiency, the use of simple and recursive 1-D algorithms; the guarantee of real accurate results; and the inherent parallelism. The method is also applied to design 2-D symmetric FIR filters and can be extended to m-D design problems     

A high-speed NMOS A/D converter with a current source array

A high-speed MOS analog-to-digital (A/D) converter has been designed and fabricated in a standard single channel metal-gate enhancement/depletion MOS process. The use of current switching performs a conversion time of 13.2 /spl mu/s at a resolution of 8 bits. To replace the resistance ladder a binary weighted current source array has been implemented which consists of MOS transistors. The test circuit requires 4 mm/SUP 2/ including all analog circuit functions without the successive approximation register.     

Direction-of-arrival estimation for a lens-based array

In this paper, we describe a high-resolution direction-of-arrival (DOA) estimation algorithm for the enhancement of a lens-based array system. In such a system, the antenna array is followed by an electromagnetic lens and a bank of power detectors (crystal video receivers). This system can handle sources over a large bandwidth and is capable of detecting pulsed sources that exist for short periods of time. The proposed algorithm operates directly on the power estimates provided by a bank of crystal video receivers (CVRs), yielding accurate DOA estimates for multiple narrowband sources. This approach is most effective when the sources are uncorrelated, and it potentially is capable of operating in environments where the signals are highly correlated. We present computer simulations to demonstrate the improved performance achieved by the algorithm for different source scenarios     

1 kW peak power 808 nm 2-D laser diode array

A 2-D laser array delivering a peak power of 1 kW, with an overall efficiency of 33.4% is described. The operating parameters of this array are a 100- mu s pulse width, a 15-Hz reception rate, a temperature of 16 degrees C, and at the nominal wavelengths of 808 nm. The spectrometer used in the system is an ISA model HR-320 monochromator. In conjunction with the PAR mode 1453 1024-element array, a resolution of 0.6 nm/element is achieved which allows a 61 nm range to be displayed at any one time.<>     

A phased array optical scanning (PHAROS) device used as a 1-to-9way switch

An optical switch is demonstrated which uses a phased array of 30 closely spaced, individually addressed electrooptic AlGaAs-GaAs waveguides to focus and steer a light beam under electronic control in a planar output waveguide. A small and potentially very high speed 1-to-9 way optical switch, (with -15 dB of crosstalk) was made by placing an array of nine output waveguides at different positions in a focal plane 1 mm from the end of the electrooptic array