Image postprocessing by Non-local Kuan’s filter

Blocking artifacts exist in images and video sequences compressed to low bit rates using block-based discrete cosine transform (DCT) compression standards. In order to reduce blocking artifacts, two image postprocessing techniques, DNLK filter and OCDNLK filter, are presented in this paper. A more accurate DCT domain Kuan’s filter based on Non-local parameter estimation was proposed from the linear minimum mean-square-error (MMSE) criterion. We analyze the required two assumptions for the filter theoretically. Then the DCT domain Kuan’s filter for low frequency coefficients and Non-local mean filter for high frequency AC coefficients constitute the proposed Non-local Kuan’s (NLK) filter. After that, we propose the Dual Non-local Kuan’s (DNLK) filter by applying the proposed filter in dual layer. The DNLK filter is extended to form the Overcomplete Dual Non-local Kuan’s (OCDNLK) filter by applying to the overcomplete DCT coefficients. Experimental results on coded images using test quantization tables and JPEG coded images show the effectiveness of the two methods.     

Novel Voltage-Mode All-Pass Filter Based on Using DVCCs

In this paper, a novel design for realizing a voltage-mode (VM) all-pass filter utilizing two differential voltage current conveyors (DVCCs) is proposed. Also, the suggested filter uses a canonical number of passive elements (one grounded capacitor and one resistor) without requiring any element matching condition. The proposed filter has high input and low output impedances, which make it suitable for cascading. The effects of the nonidealities of the DVCCs on the proposed design are investigated. As an application, a quadrature oscillator is designed using the proposed VM all-pass filter and an integrator. The proposed filter and oscillator circuits are simulated using the SPICE simulation program to confirm the theory.     

一种槽线扰动的基片集成波导双模滤波器

该文提出一种新型小型化基片集成波导(SIW)双模滤波器。通过使用正交的输入输出馈线,和一段倾斜的槽线来扰动腔体的两个简并模,滤波器能产生两个传输零点(TZ)。采用该方法设计了一个中心频率为15 GHz,带宽为350 MHz的基片集成波导双模滤波器。该滤波器结构简单,成本低廉,易于加工。测试结果和仿真结果吻合,较好地验证了设计的可行性和有效性。     

A Wideband and High Rejection Multimode Bandpass Filter Using Stub Perturbation

A novel multimode bandpass filter with high and wide rejection band is proposed by using an open stub. The open-stub has two functions in the filter: (1) perturbation for the multimode operation and (2) zero point generation at the stopband for the stopband control. With proper input/output coupling, additional two poles, i.e., four poles, can be generated for the proposed filter structure. The design is then verified by experiment. The single structure four-mode filter has low insertion loss, good stopband performance, and compact size and linear phase.     

Second Order Band-Pass Filter Design Using Single CC-CDBA

Six new second order band-pass filter configurations using only a single current-controlled current differencing buffered amplifier (CC-CDBA) are proposed. Further, the proposed filters also have a minimum number of external electronic components. They realize current-mode, voltage-mode and transadmittance-mode filter characteristics. The quality factor and natural frequency can be adjusted electronically without changing the values of the passive components. The proposed filters use a minimum number of passive elements (two or three). There is no second order active filter structure which uses two passive components and one active component in the literature. The validity of the proposed filters is verified through PSpice simulations.     

Universal Current-Mode Active-C Filter Employing Minimum Number of Passive Elements

A universal current-mode active-C filter simultaneously realizing low-pass, band-pass and high-pass responses is proposed. The filter can also realize notch and all-pass responses with interconnection of relevant output currents. The presented filter employs four second-generation current controlled conveyors (CCCIIs) as active elements and only two capacitors as passive elements. The proposed active-C filter can be tuned electronically, and has low element sensitivities.     

一种新型广义交叉耦合滤波器的设计

含广义交叉耦合的N个谐振器滤波器,即含源-负载交叉耦合的滤波器能产生N个传输零点,通过给出这种滤波器的等效网络模型和传输函数,设计了两种新颖六边形结构的含源-负载交叉耦合的微带滤波器,一种为对称结构,一种为非对称结构.对其进行了仿真分析,仿真结果与理论值吻合较好.与传统两腔发夹形滤波器相比,这种两腔六边形结构的滤波器尺寸要缩小27.5%,频率选择性更高.     

Electronically tunable versatile voltage-mode universal filter

A novel electronically tunable versatile voltage-mode universal biquad filter by using two single-output-operational transconductance amplifiers (OTAs), one differential difference current conveyor (DDCC) and two capacitors is proposed. The proposed circuit, which can be used as either a four-input single-output universal filter or a single-input three-output multifunction filter with the same topology. Besides, the new circuit offers the following advantageous features: realization of all the non-inverting and inverting biquadratic filter signals from the same configuration, no need to employ inverting-type input signals, no need to component-matching conditions and low passive sensitivity performance.     

双极点滤波器组:一种新的非相参积累器

 本文提出了一种新的非相参积累器——双极点滤波器组.它比传统双极点滤波器具有更高的稳定性,更低的滤波器系数灵敏度.因而双极点滤波器组是一种稳健的积累器.此外,它与双极点滤波器具有相同的运算量和几乎相同的性能.所以,双极点滤波器组具有较好的实用性.     

Adaptive filtering approaches for colour image and video restoration

An adaptive simplified model Kalman filter (ASMKF) is developed for image and video impulsive noise suppression. The ASMKF is more effective than the median filter (MF) and the robust reduced update Kalman filter (RRUKF) in suppressing the impulsive noise, especially when the signal-to-noise ratio is low. Further, a hybrid filter is presented for colour image and video restoration in a mixed noise environment, where both the impulsive and correlated noise may be present. The proposed hybrid filter is composed of two stages, where the first stage removes the impulsive noise while the second removes the correlated noise. The ASMKF is suggested for the first stage of the hybrid filter. In the second stage of the proposed hybrid filter, a discrete wavelet transform (DWT) filter formulated using a biorthogonal wavelet with adaptive shrinkage is applied on the impulsive-noise-free image obtained from the first stage. The efficacy of the developed ASMKF and the proposed hybrid filter are illustrated through implementation results on colour image and video restoration.     

A switched-capacitor preprocessor for speech recognition

A switched-capacitor (SC) preprocessing system (preprocessor) which extracts and emphasizes the local peaks of the spectrum in real time is proposed for speech recognition systems. Main components of the system are a specially designed bandpass filter bank, a low-pass decimation filter bank, two-dimensional local peak extraction (LPE) filters, and a LPE filter selection circuit. Furthermore, a SC cascaded integrator-comb filter design technique is proposed to realize the decimation low-pass filter and the LPE filter. Finally, the system is tested by using two speech recognition systems.     

Reconfigurable filter bank structures for low complexity digital channelizer using fractional interpolation and MFIR filters with cosine modulation

A low complexity digital reconfigurable filter bank structure which is suitable for digital channelizers in software defined radio is proposed in this paper. In order to get a sharp transition width with low hardware complexity, multiplicative finite impulse response (MFIR) filter is used as the prototype filter in the proposed structure. A masking stage and a channel generation stage constitute the two stages of the proposed structure. In the masking stage, 5 sub-bands are generated by performing cosine modulation technique on the prototype filter. In the channel generation stage, different channels are generated by doing spectral addition/subtraction operations on the interpolated versions of the MFIR filter. Hence, the basic techniques used in the proposed structure are, cosine modulation and fractional interpolation technique. By adjusting a 3-bit control signal, different regions and channels, generated by the two stages, can be obtained. The proposed structure has a hardware complexity, which is much lesser than that of the state-of-the art techniques used for SDR channelizers. The number of channels generated using the proposed structure is also more. The main advantage of the proposed structure is that the hardware complexity of the proposed structure remains the same even if the number of channels is increased.     

Impulsive Noise Suppression from Highly Distorted Images with Triangular Interpolants

In this paper a new filter, Triangular Interpolant Based Impulsive Noise Suppression Filter (SF), is proposed to restore images corrupted by fixed valued impulsive noise (IN). The proposed filter comprises two main stages: detection of noise and restoration of corrupted pixels. The SF achieves the restoration of the detected noisy pixels by using one of the Triangular Interpolant techniques and leaves the other pixels unaltered. Simulation results reveal that the proposed filter shows better performance than the highly approved IN suppression filters across a wide noise density ranging from 10% to 90%. The proposed filter also perfectly achieves the robustness anddetail preservation with reduced computational complexity.     

Dual-band filter using composite microstrip/CPW structure

A novel and compact dual-band filter using a microstrip/coplanar waveguide (CPW) composite structure is proposed. At the bottom of the substrate material, two CPW open-circuited resonators are broadside-coupled to the top microstrip open-circuited stubs. The proposed filter was designed, fabricated and measured. The obtained frequency responses demonstrated that the filter has good dual-band property.     

A joint estimation approach for two-tone image deblurring by blind deconvolution

A new statistical method is proposed for deblurring two-tone images, i.e., images with two unknown grey levels, that are blurred by an unknown linear filter. The key idea of the proposed method is to adjust a deblurring filter until its output becomes two tone. Two optimization criteria are proposed for the adjustment of the deblurring filter. A three-step iterative algorithm (TSIA) is also proposed to minimize the criteria. It is proven mathematically that by minimizing either of the criteria, the original (nonblurred) image, along with the blur filter, will be recovered uniquely (only with possible scale/shift ambiguities) at high SNR. The recovery is guaranteed not only for i.i.d. images but also for correlated and nonstationary images. It does not require a priori knowledge of the statistical parameters or the tone values of the original image; neither does it require a priori knowledge of the phase or other special information (e.g., FIR, symmetry, nonnegativity, etc.) about the blur filter. Numerical experiments are carried out to test the method on synthetic and real images.     

Narrow-band spectral filter made of W-index and step-index fibers

An all-fiber spectral filter constructed with a W-index fiber, supporting a dominant mode with nonzero cutoff frequency, and a step-index single-clad fiber is proposed and analyzed. The proposed filter offers a spectral width on the order of one nanometer, considerably narrower than that provided by a filter made of two single-clad fibers having the same transmission wavelength. The narrow spectral width is achieved by exploiting a relatively large slope difference between the dispersion characteristics of the W-index and step-index fibers constituting the filter. As an example case, the transmission characteristic of the proposed filter with peak transmission at 1300 nm is calculated and compared with that of a corresponding filter made of two single-clad fibers     

High input impedance voltage-mode universal biquadratic filter using two OTAs and one CCII

A three-input and single-output voltage-mode universal biquadratic filter with high input impedance, using only two operational transconductance amplifiers (OTAs), one plus-type second-generation current conveyor (CCII) and two capacitors, is presented. The proposed circuit can realize all the standard filter responses, that is, highpass, bandpass, lowpass, notch and allpass filters, from the same configuration. The proposed circuit has no requirements for component matching conditions.     

Design of a new low power MISO multi-mode universal biquad OTA-C filter

ABSTRACT

In this article, a new low-power multiple-input, single-output (MISO) multi-mode universal biquad operational transconductance amplifier-capacitor (OTA-C) filter with a minimum number of active and passive components is proposed. The proposed filter employs three OTAs, one inverter and two grounded capacitors. The proposed filter can realise all filter frequency responses including low-pass (LP), band-pass (BP), high-pass (HP), band-stop (BS) and all-pass (AP) in all operation modes including voltage, current, tranasresistance and transconductance modes using the same topology. Furthermore, sensitivity analysis is done which shows that the proposed filter has a low sensitivity to the values of the active and passive elements. The proposed filter is simulated in HSPICE using 0.18 µm CMOS technology. The HSPICE simulation results demonstrate that the proposed filter consumes only 35 μW at 2.5 MHz from a ±0.5 V supply voltage, while all of the transistors are biased in strong inversion region. Also, the simulation results are in a close agreement with the theoretical analysis which is done in MATLAB. Furthermore, the process, voltage and temperature variation simulations are done to study the effect of non-idealities on the performance of the proposed filter. It is shown that the simulation results justify a 4.8%, 0.8% and 20% variations of the centre frequency for process, voltage and temperature, respectively. Finally, Monte-Carlo, noise and transient simulations are done to justify the good performance of the proposed filter performance.     

A General Method to Design GCF Compensation Filter

This brief addresses the design of the compensation filter of a generalized comb filter (GCF). The proposed method is general and can be applied to different design constraints, i.e., maximally flat, least square, and minimax. The coefficients of the proposed filter for all three cases can be obtained by solving two simple linear equations. The filter operates at a low rate and considerably reduces the passband droop of the GCF.      

Recursive cubic spline interpolation filter approach for the removal of high density salt-and-pepper noise

Spline-based approach is proposed to remove very high density salt-and-pepper noise in grayscale and color images. The algorithm consists of two stages, the first stage detects whether the pixel is noisy or noise-free. The second stage removes the noisy pixel by recursive spline interpolation filter. The proposed recursive spline interpolation filter is based on the neighborhood noise-free pixels and previous noise-free output pixel; hence, it is termed as recursive spline interpolation filter. The performance of the proposed algorithm is compared with the existing algorithms like standard median filter, decision-based filter, progressive switched median filter, and modified decision-based unsymmetric trimmed median filter at very high noise density. The proposed algorithm gives better peak signal-to-noise ratio, image enhancement factor, and correlation factor results than the existing algorithms.