Sharp Correlation Peak Research Articles

Power Line Communication with Robust Timing and Carrier Recovery against Narrowband Interference for Smart Grid.

Power line communication (PLC) is an important interconnection technology for the smart grid, but the robustness of PLC transmission is faced with a great challenge due to strong non-Gaussian noise and interference. In this paper, a narrowband interference (NBI) resistant preamble is designed, and an effective timing and frequency synchronization method is proposed for OFDM-based PLC systems in the smart grid, which is capable of simultaneously conveying some bits of transmission parameter signaling (TPS) as well. In the time domain, the cyclic extension of the training OFDM symbol is scrambled, which makes it feasible to combat against NBI contamination. More accurate timing detection and sharper correlation peak can be implemented under the power line channel and the AWGN channel in the presence of NBI, compared with the conventional Schmidl’s and Minn’s methods with the same preamble length. Furthermore, the TPS transmitted using the proposed method is also immune from the NBI. The proposed method is capable of improving the synchronization performance of the PLC transmission significantly, which is verified by theoretical analysis and computer simulations.

Research on 2F Optical Correlator Based on Neural Network Filter for Recognizing Large-Angle Rotation Distortion Target

It is difficult for optical correlator to recognize the target with large rotation distortion by using existing filters. To solve this problem, a new neural network model is constructed based on the physical recognition process of planar integrated 2F optical correlator. The new optical filter is optimized by training the neural network. The planar integrated 2F optical correlator can output sharp correlation peaks by using the new filter to recognize targets with arbitrary rotation distortion. Compared with the traditional OTSDF filter, the average increase of correlation peak index is up to 1402.4%, while the recognition performance of distortion invariant is also better than the new NNCRF filter. The simulation and experimental results show that the optical filter designed in this paper can effectively solve the problem of weak recognition ability of optical correlator for rotating distortion targets, especially for large angle rotating distortion targets.

Structural Study of Four-Armed Amphiphilic Star-Block Copolymers: Pristine and End-Linked Tetronic T1307.

We present a comparative structural study of 30 wt % aqueous suspensions of two related systems based on 4-arm PEO-PPO type of macromolecules (Tetronic T1307, BASF) with the PPO block near the star center. One system concerns the pristine 4-arm PEO-PPO star block copolymer T1307. The second system is a 1:1 blend consisting of, respectively, tetra-amine (TAT) and tetra-N-hydroxysuccinimide (TNT) terminated T1307. The two systems show common characteristics which are also known from linear PEO-PPO type of copolymers (Pluronic, BASF): at low temperatures the measured structure is dominated by the characteristics of individual molecules, while at higher temperatures hydrophobic effects of the PPO domains cause self-assembly into spherical or rodlike micelles. These micelles form in both systems ordered mesophases. The pristine T1307 copolymer suspension behaves generally very similarly to linear PEO-PPO type of di- and triblock copolymers: unimers at low temperatures associating into micelles at higher temperatures, forming subsequently cubic and hexagonal phases upon further increase in temperatures. The cubic phase of the 30 wt % Tetronic T1307 has FCC symmetry. The structure of the cross-linked 30 wt % 1:1 TAT-TNT system is basically organized into two-dimensional network sheets. At low temperatures the system is rather disordered but still with a sharp correlation peak which is associated with the distance between neighboring network sheets. Upon raising temperatures, PPO self-assembly causes organization across neighboring sheets, resulting in cylinder-like assemblies perpendicular to the sheets. These cylinders form hexagonal structure.

Simulation of Determining of Circular-Harmonic Filter Expansion Center and Order

A method of determining expansion center and expansion order is proposed in optical pattern recognition. To the reference image, choose an expansion center of one order, and works out optimal order by means of the expansion center. If the optimal order is equal to the selected order, the selected expansion center and order are the optimum; or else do it again choosing another order. Computer simulation results show that the method yields a sharper correlation peak, higher signal-to-noise ration and better correlation discrimination compared with the circular-harmonic filter.

Non-linear joint transform correlator for micro-displacement measurement using speckle patterns

This work presents a procedure for measuring displacements of tens micrometer, in one and two dimensions, based on the correlation between two speckle patterns. For this purpose, two objective speckle patterns arerecorded by a digital camera -one before and one after the object has been moved- and placed in the input plane of nonlinear joint transform correlator. Nonlinear transformation of the joint power spectrum allows a sharper correlation peak and a high signal to noise ratio. The autocorrelation peak coordinates of the first pattern are set as a reference for measuring shifts of the successive cross-correlation peak. One criterion for reliable measure is proposed. Results related with different distances sample-sensor and illuminating wavelengths at 632.8 nm and 543.5 nm are presented.

Improved target detection and recognition in complicated background with joint transform correlator

We present an effective method to enhance target detection and recognition by Canny algorithm, which can obtain the continuous and distinct image edges, also suppress back-ground noise effectively, for this reason, correlation output processed by our proposed method provides higher discrimination than the classical JTC. Computer simulations demonstrate the improved method can obviously suppress noise and sidelobes, also enhance the performance of detection and recognition for JTC. An optoelectronic hybrid JTC is constructed to verify the efficiency. Experimental results present the sharp correlation peak and also confirm the method effectiveness.

Optical authentication technique based on interference image hiding system and phase-only correlation

An optical authentication technique based on interference image hiding system and phase-only correlation is proposed. In this method, some predefined complex images with different amplitudes and the same phase are respectively encoded into two phase-only masks according to the interference principle. This technique can easily generate different verification keys for different users, so it brings convenience for multi-user application. In the verification stage, both a sharp correlation peak and a significant image represented the identity of a user are generated simultaneously. Therefore, in addition to simple verification, this method can also recognize the identity of the user. Moreover, this technique can effectively avoid the verification key being forged by other person. All the performances and the feasibility of our proposed method are tested by numerical simulations.

Improved approach for target detection and recognition on optoelectronic hybrid joint transform correlator

A conventional joint transform correlator (JTC) often generates large correlation sidelobes as well as a large correlation peak width, strong zero-order peak, and low diffraction efficiency in target detection and recognition, which make the detection ability of JTC lower. To conquer these difficulties, firstly, a joint power spectrum (JPS) subtraction technique was proposed in Fourier plane, where power spectrum of reference image and power spectrum of object image are subtracted from the JPS before inverse Fourier-transform operation, it is evident that the improved JPS removes the zero-order term. Secondly, a fringe-adjusted filter (FAF) was presented to restrain sidelobes and noises. The revised JPS is multiplied by a FAF before the inverse Fourier-transform operation to obtain the cross-correlation peak. Computer simulations showed the improved method can markedly eliminate zero-order diffraction and effectively control the sidelobes and noises compared to traditional JTC, and then enhance the detection ability for JTC. Experimental results presented the sharp correlation peak and also demonstrated this approach effectiveness.

Real-Time Opto-Electronic Hybrid Joint-Transform-Correlator for Scene Matching Guidance

In this paper, an optoelectronic hybrid processing system for cruise missile scene matching guidance based on convolute structure Joint-Transform-Correlator(JTC) was proposed. By edge detection of input image and binaryzation processing of joint power spectrum, the system can achieve sharper correlation peak and location accuracy. Simulation calculation and optical experiments show that even in noisy background, the system can obtain excellent recognition and location performances with 16frames/s, recognition probability greater than 94%, and location accuracy better than a pixel. It is very advantageous to meet the demands of further improving performance, speed, and shoot accuracy of the cruise missiles.

Improved Method of Target Detection on Optoelectronic Hybrid Joint Transform Correlator in Cluttered Scences

A classical joint transform correlator (JTC) usually yields large correlation sidelobes as well as a large correlation peak width, strong zero-order peak, and low diffraction efficiency, which make the detection ability of JTC lower. To overcome these difficulties, firstly, a joint power spectrum (JPS) subtraction technique in Fourier plane was proposed, where reference image power spectrum and object image power spectrum are subtracted from the JPS before inverse Fourier-transform operation, it is obvious that the modified JPS removes the zero-order term. Secondly, a fringe-adjusted filter (FAF) was presented to suppress sidelobes and noises. The modified JPS is multiplied by a FAF before the inverse Fourier-transform operation to obtain the cross-correlation peak. Computer simulations demonstrated the improved method can obviously remove zero-order diffraction and effectively suppress the sidelobes and noises compared with classic JTC, and then improve the detection ability for JTC. Experimental results presented the sharp correlation peak and also confirmed the method effectiveness.

High-pass filtering and frequency spectrum correlation for larger size image recognition

A new method for larger size images recognition is proposed based on high-pass filtering and frequency spectrum correlation. The input images are first filtered by a high-pass filter. Then the filtered input images, which are overlapped rather than displaced from each other in the input plane, serve as the input images for frequency spectrum correlator. As a result, only one sharp correlation peak yields in the center of output plane when the target image matches with the reference image. More importantly, the method is especially suitable for larger size image recognition because of the input and correlation ways, which ensures better utilization of the space-bandwidth product and efficient utilization of the spatial light modulator and detector. Computer simulation results are presented to demonstrate the feasibility and effectiveness of this method.

Real-Time Interrogation of a Linearly Chirped Fiber Bragg Grating Sensor Based on Chirped Pulse Compression With Improved Resolution and Signal-to-Noise Ratio

A novel approach to interrogating in real time a linearly chirped fiber Bragg grating (LCFBG) sensor based on spectral-shaping and wavelength-to-time (SS-WTT) mapping with improved interrogation resolution and signal-to-noise (SNR) ratio is proposed and experimentally demonstrated. The proposed system consists of a mode-locked laser source, an optical interferometer incorporating an LCFBG, and a dispersive element. The optical interferometer has a spectral response with an increasing free spectral range (FSR). The incorporation of the LCFBG in the interferometer would encode the sensing information in the spectral response as a change in the FSR. After SS-WTT mapping, a linearly chirped microwave waveform is obtained. The correlation of the linearly chirped microwave waveform with a chirped reference waveform would provide a sharp correlation peak with its position indicating the wavelength shift of the LCFBG. A theoretical analysis is carried out, which is validated by a numerical simulation and an experiment. The experimental results show that the proposed system can provide an interrogation resolution as high as 0.25 με at a speed of 48.6 MHz.

Spectral fringe-adjusted joint transform correlation

A novel spectral fringe-adjusted joint transform (SFJTC) correlation based technique is proposed for detecting very small targets involving only a few pixels in hyperspectral imagery. In this technique, spectral signatures from the unknown hyperspectral imagery are correlated with the reference signature using the SFJTC technique. This technique can detect both single and/or multiple desired targets in constant time while accommodating the in-plane and out-of-plane distortions. Furthermore, in this paper, a new metric, called the peak-to-clutter mean, is introduced that provides sharp and high correlation peaks corresponding to targets and makes the proposed technique intensity invariant. Test results using real life hyperspectral image datacubes are presented to verify the effectiveness of the proposed technique.

Accurate definition of correlation peak position by optical speckle-displacement correlation technique

An optical speckle-displacement correlator based on hybrid optical–digital joint transform correlator architecture with a digital first stage and an optical second stage has been used to determine the correlation peak position with subpixel accuracy, without the use of intricate interpolation algorithms. A thorough analysis and a calculation of the parameters of the second optical stage are performed in order to achieve the necessary magnification of the correlation peak, so as to obtain an accurate definition of the peak position. The experiment setup for the realization of the optical speckle-displacement technique was constructed with a digital Fourier processor as its basic component, making possible a joint power spectrum median and ring median binarization, and an optical Fourier processor. The results which were obtained demonstrate that a setup of this kind can produce sharp and narrow correlation peaks, and can provide the necessary magnification for finding the peak position with subpixel accuracy.

Dynamic holographic joint fourier transform correlator based on a CdF2:Ga crystal

A joint Fourier transform correlator based on a bulk holographic medium—a CdF2:Ga crystal serving a dynamic matched spatial-frequency filter—is implemented. Specific features of the correlator design are discussed. Correlatorf’s possibilities for selective recognition of objects of different type are demonstrated. Experimental data, results of mathematical modeling, and their analysis are reported. Suggestions for modifying the correlator scheme in order to improve its characteristics (operating speed, stability with respect to orientational and scale changes in objects, signal-to-noise ratio, correlation peak sharpness) are formulated.

Spectral band independent recognition in a differential binary joint transform correlator

Images of a target in a specific spectral band in general show no correlation with images of the same target in a different spectral band. Hence in a joint transform correlator (JTC) architecture, if the reference and input target are the images captured through a visible (e.g., charge-coupled device or CCD camera) and infrared (IR) detector, autocorrelation peaks are not obtained. This drawback has been overcome in this paper by the use of a CCD–IR fused image as the reference image. Daubechies wavelet transform, which produces the least root-mean-square (RMS) error in the fusion process in comparison to other wavelets, has been used for the purpose. A comparative analysis of the proposed idea has been carried out for the classical JTC (CJTC), binary JTC (BJTC) and differential binary JTC (DBJTC) algorithms. Since the DBJTC removes the dc completely and produces sharp correlation peaks compared to the other techniques, computer simulation and experimental results are shown for the proposed idea using DBJTC. The same fused reference image has also been used to identify multiple targets in a scene using DBJTC. Performance measures like correlation peak intensity (CPI), dc/ac and peak correlation energy (PCE) have been calculated as metrics of goodness for the proposed scheme.

Performance assessment of the modified-hybrid optical neural network filter

We present in detail the recorded results of the modified-hybrid optical neural network (M-HONN) filter during a full series of tests to examine its robustness and overall performance for object recognition tasks. We test the M-HONN filter for its detectability and peak sharpness with within-class distortion of the input object, its discrimination ability between an in-class and out-of-class object, and its performance with cluttered images of the true-class object. The M-HONN filter is found to exhibit good detectability, an ability to maintain its correlation-peak sharpness throughout the recorded tests, good discrimination ability, and an ability to detect the true-class object within cluttered input images. Additionally we observe the M-HONN filter's performance within the tests in comparison with the constrained-hybrid optical neural network filter for the first three series of tests and the synthetic discriminant function-maximum average correlation height filter for the fourth set of tests.

Synthesis and Characterization of Well-Defined 12,12-Ammonium Ionenes: Evaluating Mechanical Properties as a Function of Molecular Weight

Water-soluble 12,12-ammonium ionenes were prepared via the Menschutkin reaction from 1,12-dibromododecane and 1,12-bis(N,N-dimethylamino)dodecane. A stoichiometric imbalance of monomers controlled the final molecular weights of the polymers. The absolute molecular weights were determined for the first time using an online multiangle laser light scattering (MALLS) detector in aqueous size exclusion chromatography (SEC). Weight-average molecular weights ranged from 4300 to 20 900 g/mol. Relationships between weight-average molecular weight and mechanical properties were established for a series of 12,12-ammonium ionenes using both tensile testing and dynamic mechanical analysis (DMA). Tensile analysis of the higher molecular weight ionenes revealed an average tensile strength of 20 MPa and elongations ranging from 230 to 440%. Dissociation of ionic aggregates was observed at 85−88 °C in DMA experiments, and the glass transition temperatures increased with increasing molecular weight (61−88 °C). X-ray scattering revealed an amorphous polyethylene peak at ≈14 nm−1 and a sharp ionic group correlation peak at 4.38 nm−1. These correlations agreed well with the proposed macromolecular structure.

Small-angle scattering model for multilamellar vesicles

A small-angle neutron-x-ray-light-scattering model for multilamellar vesicles is developed on the basis of a simple geometry. N spherical shells with radii of an arithmetic series are allowed for displacements DeltaR which are limited by DeltaR<R/N due to sterical reasons, with R being the radius of the vesicle. The model shows many properties over a large Q range which include a Guinier region, a first power law, a correlation peak, and a second power law connected to the surface properties of the bilayer. The first power law is related to the compactness of the vesicle and lies between Q(-2) for surfaces and Q(-4) for compact volumes (Porod law). The exact exponent is related to the number of shells N. The correlation peak has a maximum sharpness for rather small displacements DeltaR, but no second order peak is predicted. Only for rather large displacements the correlation peak widens up and shifts to smaller scattering angles. Then the important bilayer spacing is larger. The predictive power of the model lies in the connection of the compactness with N and in the maximum correlation peak sharpness. This model considers many length scales at a time while existing theories focus on length scales of the bilayer spacing and the bilayer itself.

Correlation filters with controlled scale response

Correlation filtering methods are becoming increasingly popular for image recognition and location. The recent introduction of optimal tradeoff circular harmonic function filters allowed the user to specify the response of a correlation filter to in-plane rotation distortion. In this paper we introduce a new correlation filter design that can provide a user-specified response to in-plane scale distortion. The design is based on the Mellin radial harmonic (MRH) transform and incorporates multiple harmonics into the correlation filter for improved discrimination capability. Additionally, the filter design minimizes the average correlation energy in order to achieve sharp correlation peaks, and thus we refer to these filters as minimum average correlation energy Mellin radial harmonic (MACE-MRH) filters. We present underlying theory, a MACE-MRH filter design method, and numerical simulation results.