A unified polyphase representation of analysis and synthesis filter banks is introduced in this paper, and then the efficient implementation on digital signal processors (DSP) is investigated. Especially, the number of memory accesses, power consumption, processing accuracy and the required instruction cycles are discussed. Firstly, a unified representation is given, and then two types of procedures, SIMO system-based and MISO system-based procedures, are shown, where SIMO and MISO are abbreviations for single-input/multiple-output and multiple-input/single-output, respectively. These procedures are compared to each other. It is shown that the number of data load in SIMO system-based procedure is a half of that in MISO system-based procedure for two-channel filter banks. The implementation of M-channel filter banks is also discussed.

This paper proposes distributed evolutionary digital filters (EDFs) as an improved version of the original EDF. The EDF is an adaptive digital filter which is controlled by adaptive algorithm based on evolutionary computation. In the proposed method, a large population of the original EDF is divided into smaller subpopulations. Each sub-EDF has one subpopulation and executes the small-sized main loop of the original EDF. In addition, the distributed algorithm periodically selects promising individuals from each subpopulation. Then, they migrate to different subpopulations. Numerical examples show that the distributed EDF has a higher convergence rate and smaller steady-state value of the square error than the LMS adaptive digital filter, the adaptive digital filter based on the simple genetic algorithm and the original EDF.

Linear adaptive digital filters are applied to various fields for their simplicity in the design and implementation. Considering many kinds of nonlinearities inherent in practical systems, however, nonlinear adaptive filtering will be more desirable. This paper presents a design method for multi-input single-output nonlinear adaptive digital filters using recurrent neural networks. Furthermore, in comparison with this method and the method based on the conventional linear theory, if the proposed method is used, better results can be obtained, and, it is possible that the learning efficiency is improved, because the parallel learning is carried out in this method. Finally, the results of computer simulation are presented to illustrate the effectiveness of the proposed method.

An unwrapping of signal coefficients in transform domain is proposed for applications in which a lossy operation is performed on the coefficients between analysis and synthesis. It is shown that the unwrapping-based modification of signal-to-additive-signal ratio can employ the fact that an implementation of a biorthogonal decomposition is characterized by a mutually orthogonal eigenvectors. An example to illustrate the benefits of the presented approach in lossy image compression applications is shown.

A new approach for extracting significant characteristic within speech signal for distinct speaker is presented. Based on the multiresolution property of wavelet transform, quadrature mirror filters (QMFs) derived by Daubechies is used to decompose the input signal into varied frequency channels. Owning to the uncorrelation property of each resolution derived from QMFs, Linear Predict Coding Cepstrum (LPCC) of lower frequency region and entropy information of higher frequency region for each decomposition process are calculated as the speech feature vectors. In addition, a hard thresholding technique for lower resolution in each decomposition process is also used to remove the effect of noise interference. The experimental result shows that by using this mechanism, not only effectively reduce the effect of noise inference but improve the recognition rate. The proposed feature extraction algorithm is evaluated on MAT telephone speech database for Text-Independent speaker identification using vector quantization (VQ). Some popular existing methods are also evaluated for comparison in this paper. Experimental results show that the performance of the proposed method is more effective and robust than that of the other existing methods. For 80 speakers and 2 seconds utterance, the identification rate is 98.52%. In addition, the performance of our method is very satisfactory even at low SNR.

A complex coefficient filter obtained by directly exchanging several reactance elements included in a real coefficient BPF for imaginary valued resistors is described. By using the proposed method, we obtain four varieties of complex coefficient filters. The stability problem is examined.

Efficient query processing in multi-dimensional indexing structures is an important issue for multimedia data applications. In this paper, we propose incremental k-nearest neighbor query (k-NNQ) and range query algorithms for R-tree based structures. The novel aspect of these algorithms is that they make use of the notion of VP filtering, a concept borrowed from the MVP-tree. The filtering notion allows for delaying of computational overhead until absolutely necessary. By so doing, we attain considerable performance benefits while paying insignificant overhead during the construction of the index structure. We implemented our algorithms and carried out experiments to demonstrate the capability and usefulness of our method. Results show that improvements range from 8% to 23% in response time for the experimental environment that we considered.

A framework is proposed for segmenting image textures by using Gabor filters to detect boundaries between adjacent textured regions. By performing a multi-channel filtering of the input image with a small set of adaptively selected Gabor filters, tuned to underlying textures, feature images are obtained. To reduce the variance of the filter output for better texture boundary detection, a Gaussian post-filter is applied to the Gabor filter response over each channel. Significant local variations in each channel response are detected using a gradient operator, and combined through channel grouping to produce the texture gradient. A subsequent post-processing produces expected texture boundaries. The effectiveness of the proposed technique is demonstrated through experiments on synthetic and natural textures.

Access control plays an important role in the area of information security, which guarantees that any access to data is authorized. Hierarchical access control is a special access control model in distributed environment, in which each user protects his local data using a secret key; moreover, for any two related users ui and uj, ui can access uj's data if, and only if, ui's priority is higher than uj. Therefore, there should be a way for ui to obtain the secret key of uj if ui's priority is higher than uj. This paper presents an efficient solution to the problem. A special kind of function called secure filter is used as the building block of the proposed solution. In the solution, an authorized user can acquire correct keys efficiently and securely via secure filters. The proposed solution is also well-performed while inserting/deleting users, injecting/removing relations, and changing secret keys. Especially, only deleting users and removing relations will change some keys in the system, other operations can be performed freely without affecting other keys in the system; only secure filters need to be modified in these cases.

Explicit formulas for the tap-coefficients of Taylor series based type III FIR digital differentiators have already been presented. However, those formulas were not derived mathematically from the Taylor series and were based on observation of different sets of the results. In this paper, we provide a mathematical proof of the formulas by deriving them mathematically from the Taylor series.

A wavelength demultiplexer made of 2-D photonic crystal capable of simultaneously separating many channels from WDM light is analyzed in order to study the properties and clarify the design parameters. Numerical analyses are carried out for the optical filter structure and the demultiplexer structure which consists of several filters and waveguides carved in the crystal. The results of this paper show the considerations regarding the frequency tuning, the device size, the bandwidth and integration of filters. Further more, for a photonic crystal filter, a method for realizing a flat-top pass-band generally required from the dense-WDM systems is presented and its property is shown. The calculation method is the scattering matrix method which is proper to the analysis of the frequency domain in a 2-D photonic crystal with finite size and with some defects.

A novel temperature insensitive wavelength filter consisting of GaAlAs/GaAs distributed Bragg reflectors (DBRs) has been demonstrated. This micromachined DBR is mechanically tuned by differential thermal expansion. The strain-induced displacement of one mirror can generate wavelength tuning and trimming functions with an adjustable temperature dependence. We succeeded in the control of temperature dependence in this micromachined semiconductor filter by properly designing a vertical cavity structure. The achieved temperature dependence was as small as +0.01 nm/K, which is one-tenth of that of conventional semiconductor based optical filters. Also, a wavelength trimming of over 20 nm was demonstrated after completing the device fabrication. In addition, we demonstrated a 4 4 multiple wavelength micromachined vertical cavity filter array. The multi-wavelength filter array with a wavelength span of 45 nm was fabricated by partially etching off a GaAs wavelength control layer loaded on the top surface of device.

In this report, we propose an integrated lossy and lossless image coding, which is possible to be implemented on one architecture, based on combination of lossless wavelet transform (LWT) and lossy-lossless multi-channel prediction (LLMP). The LWT is applied to divide input signals into frequency subbands as octave-band decomposition, whereas the LLMP is designed as a non-separable two-dimensional filter bank including quantization step size and local decoding to enhance coding performance in both lossless coding and lossy coding. Its filter coefficients are determined to minimize total bit rate for lossless coding, and the optimum quantization step size is applied to maximize lossy coding gain. The local decoding is applied to avoid quantization error effect. The experimental results confirm effectiveness of our proposed method.

We present a new family of algorithms that solve the bias problem in the equation-error based adaptive infinite impulse response (IIR) filtering. A novel constraint, called the constant-norm constraint, unifies the quadratic constraint and the monic one. By imposing the monic constraint on the mean square error (MSE) optimization, the merits of both constraints are inherited and the shortcomings are overcome. A new cost function based on the constant-norm constraint and Lagrange multiplier is defined. Minimizing the cost function gives birth to a new family of bias-free adaptive IIR filtering algorithms. For example, two efficient algorithms belonging to the family are proposed. The analysis of the stationary points is presented to show that the proposed methods can indeed produce bias-free parameter estimates in the presence of white noise. The simulation results demonstrate that the proposed methods indeed produce unbiased parameter estimation, while being simple both in computation and implementation.

In an ideal fiber grating having a uniform refractive index modulation, the reflection or the transmission spectrum is symmetric with equal amount of side lobes on both sides of the resonant wavelength of the fiber grating. It is observed that a long-period fiber grating made by a non-uniform UV laser beam through a uniform amplitude mask has an asymmetric transmission spectrum. The asymmetric characteristic is explained with Mach-Zehnder effect in the long-period fiber grating. The non-uniform UV laser beam makes also a non-uniform index modulation along the fiber core. Therefore, a beam coupled to a cladding mode at a section of the grating can be re-coupled to the core mode after passing a certain distance. The re-coupled beam makes Mach-Zehnder-like interference with the un-coupled core mode. However, it is presented that the asymmetric phenomenon can be overcome by scanning the UV laser beam along the fiber over the mask. The beam scanning method is able to suffer the same fluence of the UV laser beam on the fiber. Finally, a linearly chirped long-period fiber grating was made using the non-uniform UV laser beam. Due to the asymmetricity the chirping effect was not clearly observed. It is also presented that the beam scanning method could remove the asymmetric problem and recover the typical spectrum of the linearly chirped fiber grating.

A wavelength demultiplexer made of 2-D photonic crystal capable of simultaneously separating many channels from WDM light is analyzed in order to study the properties and clarify the design parameters. Numerical analyses are carried out for the optical filter structure and the demultiplexer structure which consists of several filters and waveguides carved in the crystal. The results of this paper show the considerations regarding the frequency tuning, the device size, the bandwidth and integration of filters. Further more, for a photonic crystal filter, a method for realizing a flat-top pass-band generally required from the dense-WDM systems is presented and its property is shown. The calculation method is the scattering matrix method which is proper to the analysis of the frequency domain in a 2-D photonic crystal with finite size and with some defects.

In an ideal fiber grating having a uniform refractive index modulation, the reflection or the transmission spectrum is symmetric with equal amount of side lobes on both sides of the resonant wavelength of the fiber grating. It is observed that a long-period fiber grating made by a non-uniform UV laser beam through a uniform amplitude mask has an asymmetric transmission spectrum. The asymmetric characteristic is explained with Mach-Zehnder effect in the long-period fiber grating. The non-uniform UV laser beam makes also a non-uniform index modulation along the fiber core. Therefore, a beam coupled to a cladding mode at a section of the grating can be re-coupled to the core mode after passing a certain distance. The re-coupled beam makes Mach-Zehnder-like interference with the un-coupled core mode. However, it is presented that the asymmetric phenomenon can be overcome by scanning the UV laser beam along the fiber over the mask. The beam scanning method is able to suffer the same fluence of the UV laser beam on the fiber. Finally, a linearly chirped long-period fiber grating was made using the non-uniform UV laser beam. Due to the asymmetricity the chirping effect was not clearly observed. It is also presented that the beam scanning method could remove the asymmetric problem and recover the typical spectrum of the linearly chirped fiber grating.

A novel temperature insensitive wavelength filter consisting of GaAlAs/GaAs distributed Bragg reflectors (DBRs) has been demonstrated. This micromachined DBR is mechanically tuned by differential thermal expansion. The strain-induced displacement of one mirror can generate wavelength tuning and trimming functions with an adjustable temperature dependence. We succeeded in the control of temperature dependence in this micromachined semiconductor filter by properly designing a vertical cavity structure. The achieved temperature dependence was as small as +0.01 nm/K, which is one-tenth of that of conventional semiconductor based optical filters. Also, a wavelength trimming of over 20 nm was demonstrated after completing the device fabrication. In addition, we demonstrated a 4 4 multiple wavelength micromachined vertical cavity filter array. The multi-wavelength filter array with a wavelength span of 45 nm was fabricated by partially etching off a GaAs wavelength control layer loaded on the top surface of device.

We will present the theoretical analysis of and experimental measurements on the transmission characteristics of multi-channel long period fiber gratings in terms of the physical parameters like the separation distance, grating length and number of gratings. These parameters can be used to control the spectral channel spacing, number of channels, loss peak depth, and channel bandwidth of multi-channel long period fiber gratings.

In this paper, we present improved alternative sequential filter-edge detector using generalized directional morphological filters. Based on the properties of effective noise removal and detail preservation of the generalized directional morphological filters, we apply these filters to edge detection of noisy images. The performance of the edge detection in the presence of mixed noise is evaluated. Simulations show that edge detection method using generalized directional morphological filters can also improve the performance.