Differential Filter Research Articles

Analysis of nonidealities of N‐path circuits using impulse response

SummaryThis paper presents a new method to analyze nonidealities of N‐path circuits. This method utilizes Fourier transform of the impulse response of an N‐path circuit in the time domain to calculate the transfer functions. The time domain analysis makes the method simple and intuitive. Instead of conventional sophisticated calculations, this method limits the analysis to some integral calculations. This analysis can take into account two common nonidealities: parallel capacitance and overlapping clocks. The accuracy of the analysis is verified by simulations for both cases. Further, the analysis has been expanded to differential filters.

Recursive Polynomial Minimum Mean-Square Error Estimation with Applications to Orbit Determination

This paper presents a systematic generalization of the linear update structure associated with the extended Kalman filter for high-order polynomial estimation of nonlinear dynamical systems. The minimum mean-square error criterion is used as the cost function to determine the optimal polynomial update during the estimation process. The high-order series representation is implemented effectively using differential algebra techniques. Numerical examples show that the proposed algorithm, named the high-order differential algebra Kalman filter, provides superior robustness and/or mean-square error performance as compared to linear estimators under the condition considered.

Differential Dual-Band Filter Using Ground Bar-Loaded Dielectric Strip Resonators

In this letter, a new differential dielectric strip resonator (DSR) filter with dual passbands is proposed. By loading a pair of ground bars underneath the traditional half- wavelength ( $\lambda /2$ ) DSR with high permittivity (supported by a low-permittivity substrate with the bottom ground plane), the TM10 and TM30 modes can be controlled to be in a close spacing. Meanwhile, both of them can be differentially excited for the design of the differential dual-band bandpass filter (BPF). The external quality factors and coupling coefficients for both bands can be independently controlled through proper layout; meanwhile, the common-mode (CM) suppression in the two differential-mode (DM) passbands is more than 25 dB. Finally, a differential DSR BPF with dual-band response operating at 8.13 and 11.13 GHz is given to verify the proposed idea.

Adaptive Savitzky-Golay filtering and its applications

Noise reduction is a central issue of the theory and practice of signal processing. The Savitzky-Golay (SG) smoothing and differentiation filter is widely acknowledged as a simple and efficient method for denoising. However only few book on signal processing contain this method. As is well known, the performance of the classical SG-filter depends on the appropriate setting of the window length and the polynomial degree, which should match the scale of the signal since, in the case of signals with high rate of change, the performance of the filter may be limited. This paper presents a new adaptive strategy to smooth irregular signals based on the Savitzky-Golay algorithm. The proposed technique ensures high precision noise reduction by iterative multi-round smoothing and correction. In each round the parameters dynamically change due to the results of the previous smoothing. Our study provides additional support for data compression based on optimal resolution of the signal with linear approximation. Here, simulation results validate the applicability of the novel method.

Adaptive Savitzky-Golay filtering and its applications

Noise reduction is a central issue of the theory and practice of signal processing. The Savitzky-Golay (SG) smoothing and differentiation filter is widely acknowledged as a simple and efficient method for denoising. However only few book on signal processing contain this method. As is well known, the performance of the classical SG-filter depends on the appropriate setting of the window length and the polynomial degree, which should match the scale of the signal since, in the case of signals with high rate of change, the performance of the filter may be limited. This paper presents a new adaptive strategy to smooth irregular signals based on the Savitzky-Golay algorithm. The proposed technique ensures high precision noise reduction by iterative multi-round smoothing and correction. In each round the parameters dynamically change due to the results of the previous smoothing. Our study provides additional support for data compression based on optimal resolution of the signal with linear approximation. Here, simulation results validate the applicability of the novel method.

Dual-Band Differential Bandpass Filters Using Quadruple-Mode Stubs-Loaded Ring Resonator With Intrinsic Common-Mode Suppression for 5G

A novel quadruple-mode stubs-loaded ring resonator (SLRR) is presented in this letter, which can achieve compact dual-band differential bandpass filters (BPFs) with intrinsic common-mode suppression. The differential-mode (DM) equivalent circuit and common-mode (CM) equivalent circuit of the SLRR are given and investigated by using the even-/odd-mode theory. Two DM resonances of the SLRR can be adjusted independently and are used to construct two DM passbands. Due to the magnetic-dominated coupling between two SLRRs, the intrinsic CM suppression characteristics are achieved in the differential passbands without using any additionally loaded elements. And by loading the different short-circuited coupled lines (SCCLs) at the parallel-coupled feed-line of differential BPF separately, two transmission zeros (TZs) are introduced on both sides of the DM passbands, which improves the selectivity of dual differential passbands. Furthermore, to realize the desired external Q values for two DM passbands, hybrid feeding line structure including tapped and coupled-line feeding structures is used to produce the valid excitation for the differential BPF. At the same time, the open stubs are attached to the inside of the ring resonator to reduce the filter size. Finally, two dual-band differential BPFs with central frequencies of 3.5 GHz and 4.9 GHz are designed and fabricated for fifth generation of mobile communications (5G). The measured minimum CM suppression of the two DM passbands are 31.0 dB and 34.8 dB.

Real-Time Detection and Spatial Segmentation of Difference Image Motion Changes

In this article, real-time detection of moving targets is performed, and an improved moving target detection algorithm combining background modeling and three-frame difference method is studied. An improved anisotropic differential filtering algorithm is proposed. The algorithm mainly compares the gradient difference between the target and the background in eight nearby directions. Choose the average of the three directions with the smallest spread function value to filter the space, which will effectively highlight the difference between the targets. so that the target signal is well preserved in the differential space domain; then based on obtaining the difference map. The average gray level of the target and the local signal-to-noise ratio of the spatial domain obtained by the energy enhancement algorithm combining the spatial and temporal motion characteristics have reached 278 and 14.84 dB, which further improves the target signal. Strict registration of heterogeneous spatial domains is completed by affine transformation and bilinear interpolation, and in many cases, the invariance and robustness of the method are verified. Focus on the proposed color space fusion method based on spatial frequency and fuzzy transformation. The superiority of the methods is evaluated and compared from both subjective and objective aspects. Finally, it lays a good foundation for moving target detection and better dealing with complex scenes. The improved inter-frame difference method combined with background subtraction validates and compares the method in different scenarios. It shows the advanced nature of the method in both qualitative and quantitative aspects. And effectively overcome the shortcomings of the particle filter tracking algorithm based on a single feature.

A Fully Differential Synchronous Demodulator for AC Signals

We describe a new analog differential synchronous demodulator for AC signals where (i) the signal is synchronously demodulated using the floating-capacitor technique after being amplified, if necessary, by an AC amplifier with differential input and differential output, thus yielding a very high CMRR; and (ii) the differential-to-single-ended signal conversion is performed after demodulation, that is, on a low-frequency signal that can be amplified by low-cost, high-performance circuits. The possible signal-to-noise ratio degradation because of synchronous sampling is prevented by using bandpass differential filters.

0.5 V Fully Differential Universal Filter Based on Multiple Input OTAs

The design of a low-power, low-voltage, fully-differential universal biquad filter is presented in this work, which is constructed from four multiple-input gate-driven operational transconductance amplifiers (MI-OTAs) along with one passive resistor and two passive capacitors. The scheme of presented biquad filter has three high-input impedance voltage nodes and single output voltage node. Five unity gain filtering functions, all-pass (AP), low-pass (LP), band-pass (BP), high-pass (HP) and band-stop (BS) responses, are obtained. The selection of output filtering responses is obtained without the need of component matching condition, inverting or double input voltage. With this feature, it can be easily controlled with digital programming. The quality factor (Q) and angular frequency (ω <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ) are electronically and independently tuned. Moreover, the adjustment of ω <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> and Q can be done without affecting the voltage gain. A workability of the design is confirmed via Cadence software and the Spectre simulator based on the 180 nm TSMC CMOS technology parameters. The proposed fully differential filter operates with 0.5 V supply voltage. The results verify that the proposed filter dissipates the total power of 53.3 nW. Additionally, the dynamic range (DR) of band-pass filtering function is 63 dB for 2% third intermodulation distortion (IMD). Also, the simulated RMS value of the band-pass filtering noise is 45μV.

Wideband and spurious‐suppressed differential bandpass filter based on strip‐loaded slot‐line structure

In this article, a wideband and spurious-suppressed differential bandpass filter based on strip-loaded slot-line structure is presented. By means of the differential microstrip-slot-line-microstrip transition, the proposed filter has a wideband bandpass filtering response. Simultaneously, the utilization of the strip-loaded slot-line extends its upper stop-band. The proposed bandpass filter has wider upper-stopband, wideband bandpass response, and intrinsic high common-mode (CM) suppression. To verify the design concept, one filter example has been designed, fabricated, and measured. It has a differential-mode (DM) 3-dB fractional bandwidth of 157% with a low 0.82 dB minimum insertion loss. What's more, it shows a very wide 20 dB DM stop-band bandwidth of 6.5 f0d. The experienced results are in good agreement with the theoretical and simulated results.

Planar Wideband High-Selectivity Impedance-Transforming Differential Bandpass Filter With Deep Common-Mode Suppression

In this brief, a novel balanced filter named impedance-transforming differential bandpass filter (ITDBPF) is proposed, which is the first differential device to realize both wideband impedance transformation and bandpass filtering simultaneously. A core block consisting of cascaded transmission lines and parallel stubs forms this presented circuit with two additional open stubs. Under differential-mode excitation, the transfer function of the equivalent circuit is the same as the one of Chebyshev, and the filtering characteristics are obtained corresponding to the specified filtering parameters. The open stubs increase multiple transmission zeros under common-mode excitation to greatly broaden the bandwidth of common-mode rejection. To verify the proposed theory, a wideband balanced filter centered at 2 GHz with a theoretical 3-dB bandwidth of 72% is designed and measured to prove the correctness of the design theory.

Optimal Design of a DC–DC Boost Converter in Load Transient Conditions, Including Control Strategy and Stability Constraint

An optimization method is proposed to design a dc–dc boost converter, including the differential input filter and the associated control strategy, for embedded applications [aerospace, electric vehicle/hybrid electric vehicle (EV/HEV)], where high power density and high efficiency are strongly required. The problem is treated as a multiobjective optimization, whose purpose is to maximize compactness and efficiency of the converter. In order to find a tradeoff between the two objective functions (volume and power losses), a genetic algorithm was employed (NSGA-II) to generate the most convenient design solutions. The operating conditions includes both steady-state and load power transients of a constant power load (CPL). In order to comply with the specification on the output voltage admitted range in both conditions, the control strategy is discussed and included in the design procedure. The interaction of a differential input filter with a CPL may lead to serious instability issues. A constraint function in the algorithm excludes all the unstable and unfeasible design solutions. A high-efficiency converter ( $\eta =98.5\%$ ) was realized, and experimental tests prove that stability and design specifications are respected.

Commutation error in reduced order modeling of fluid flows

For reduced order models (ROMs) of fluid flows, we investigate theoretically and computationally whether differentiation and ROM spatial filtering commute, i.e., whether the commutation error (CE) is nonzero. We study the CE for the Laplacian and two ROM filters: the ROM projection and the ROM differential filter. Furthermore, when the CE is nonzero, we investigate whether it has any significant effect on ROMs that are constructed by using spatial filtering. As numerical tests, we use the Burgers equation with viscosities ν = 10− 1 and ν = 10− 3 and a 2D flow past a circular cylinder at Reynolds numbers Re = 100 and Re = 500. Our investigation (i) measures the size of the CE in these test problems and (ii) shows that the CE has a significant effect on ROM development for high viscosities, but not so much for low viscosities.

A Self-Adaptive Contractive Algorithm for Enhanced Dynamic Phasor Estimation

In this paper, a self-adaptive contractive (SAC) algorithm is proposed for enhanced dynamic phasor estimation in the diverse operating conditions of modern power systems. At a high-level, the method is composed of three stages: parameter shifting, filtering and parameter unshifting. The goal of the first stage is to transform the input signal phasor so that it is approximately mapped to nominal conditions. The second stage provides estimates of the phasor, frequency, rate of change of frequency (ROCOF), damping and rate of change of damping (ROCOD) of the parameter shifted phasor by using a differentiator filter bank (DFB). The final stage recovers the original signal phasor parameters while rejecting misleading estimates. The most important features of the algorithm are that it offers convergence guarantees in a set of desired conditions, and also great harmonic rejection. Numerical examples, including the IEEE C37.118.1 standard tests with realistic noise levels, as well as fault conditions, validate the proposed algorithm.

Differential Narrow Bandpass Microstrip Filter Design for Material and Liquid Purity Interrogation

In this paper, a new narrow bandpass microstrip filter is proposed with a differential structure based on an analytical approach. A new model of the differential structure, employing an LC equivalent circuit is discussed. Differential/common mode using an odd/even mode analysis is used to calculate the operating frequency of the circuit theoretically. The narrow bandwidth structure is a suitable choice in sensory applications to detect the purity of various liquid materials. The permittivity of materials was measured by using various liquid materials as upper substrates; this changed the resonance frequency depending on the material used and the results could be interpreted as a measured material permittivity. The resonance frequency of the proposed filter fabricated with Rogers RO4003 substrate was 1.75 GHz. Compact size (0.3018λ × 0.141λ), higher sensitivity, roll-off sharpness, noise reduction, and a new theoretical method are advantages of this proposed design.

Brain tumor classification based on DWT fusion of MRI sequences using convolutional neural network

Tumor in brain is an anthology of anomalous cells. It leads to increase in death rate among humans. Therefore, in this manuscript, a fusion process is proposed to combine structural and texture information of four MRI sequences (T1C, T1, Flair and T2) for the detection of brain tumor. A discrete wavelet transform (DWT) along with Daubechies wavelet kernel is utilized for fusion process which provides a more informative tumor region as compared to an individual single sequence of MRI. After the fusion process, a partial differential diffusion filter (PDDF) is applied to remove noise. A global thresholding method is used for segmenting tumor region which is then fed to proposed convolutional neural network (CNN) model for finally differentiating tumor and non-tumor regions. Five publicly available datasets i.e., BRATS 2012, BRATS 2013, BRATS 2015, BRATS 2013 Leader board and BRATS 2018 are used for proposed method evaluation. The results show that fused images provide better results as compared to individual sequences on benchmark datasets.

SPATIAL-SPECTRAL MORPHOLOGICAL FEATURE EXTRACTION FOR HYPERSPECTRAL IMAGES CLASSIFICATION

Abstract. Remote sensing image classification is a method for labeling pixels to show the Land cover types. The ambiguity in the classification process can be reduced if the spatial dependencies, which exist among the adjacent pixels, are intelligently incorporated into the feature extraction process. One of the methods for spatial feature extraction is applying morphological filters. The basic idea of the morphological filters is comparison of structures within the image with a reference form called structural element. Four types of important morphological filters are included (dilation, erosion, opening, and closing) in this work. Opening morphological filter is used to extract spatial features where this filter is implemented by applying two successive sequences dilation and erosion operators. This filter removes the light areas smaller than the structural element in binary images; and in the gray level images, the areas smaller than the structural element and brighter than the neighboring regions are removed. Differential morphology filters are other important morphological filters, which are also used in this work. In the proposed method, the principal component analysis is used to reduce the data dimensions and an SVM classifier is applied to classify the hyperspectral data. The proposed method provides better classification results than the conventional morphological profile about 2%-5% for the University of Pavia and Pavia Center datasets. The results represent the good performance of the proposed method by using a small number of training samples.

Odometer Velocity and Acceleration Estimation Based on Tracking Differentiator Filter for 3D-Reduced Inertial Sensor System.

Velocity information from the odometer is the key information in a reduced inertial sensor system (RISS), and is prone to noise corruption. In order to improve the navigation accuracy and reliability of a 3D RISS, a method based on a tracking differentiator (TD) filter was proposed to track odometer velocity and acceleration. With the TD filter, an input signal and its differential signal are estimated fast and accurately to avoid the noise amplification that is brought by the conventional differential method. The TD filter does not depend on an object model, and has less computational complexity. Moreover, the filter phase lag is decreased by the prediction process with the differential signal of the TD filter. In this study, the numerical simulation experiments indicate that the TD filter can achieve a better performance on random noises and outliers than traditional numerical differentiation. The effectiveness of the TD filter on a 3D RISS is demonstrated using a group of offline data that were obtained from an actual vehicle experiment. We conclude that the TD filter can not only quickly and correctly filter velocity and estimate acceleration from the odometer velocity for a 3D RISS, but can also improve the reliability of the 3D RISS.

A Low Power Frequency Tunable FSK Receiver Based on the N-Path Filter

This brief presents a low power frequency tunable frequency shift keying (FSK) receiver based on N-path filter. The N-path filter serves as the first stage of the receiver and converts the frequency difference between two tones to amplitude difference. To evaluate the maximum achievable data rate of the proposed receiver, we studied the behavior of N-path filter under two-tone input condition. With linear periodically time-variant theory, the equations for transient response between two tones are derived for differential two-port N-path filters and verified by the simulation. Based on the analysis, an optimum data rate is obtained for the proposed N-path filter-based FSK receiver. Implemented in 0.13- $\mu \text{m}$ CMOS process, the chip occupies 300 $\times700\,\,\mu \text{m}^{2}$ , achieves data rate of 2.5 Mb/s, and 74 pJ/bit energy per bit at −65 dBm sensitivity. Frequency tuning is also demonstrated.

Circular-shaped differential wideband band pass filter

AbstractThe design of a circular-shaped differential wideband band pass filter (BPF) is described. The proposed filter is compact and provides good common mode (CM) suppression. It consists of four ports with a circular-shaped differential mode (DM). The analysis of the filter has been carried out by bisecting it into identical two-port networks along the symmetry plane, resulting in a band stop or band pass response under CM or DM excitations, respectively. The length and width of the stubs can be tuned to obtain the desired pass band and stop band of the differential BPF. The proposed design is fabricated and measured. The results obtained using measurements are in close agreement with those obtained using simulations.