Design of IIR allpass networks for Hilbert transformers

A new method for designing an allpass network is proposed. The coefficients obtained by a Kalman filter are used for an allpass network for an IIR Hilbert transformer with a flat magnitude response.<>     

Complex notch filter design using allpass filter

Complex coefficient IIR notch filter design problems are investigated. The specification of a notch filter is first transformed into that of an allpass filter. An effective approach to the design of this desired allpass filter is developed. The realisation of the proposed notch filter is equivalent to the realisation of an allpass filter. Owing to the mirror-image symmetry relation between the numerator and denominator polynomials of allpass filters, the notch filter can be realised by a computationally efficient lattice structure with very low sensitivity     

3-D IIR filtering using decimated DFT-polyphase filter bank structures

Two three-dimensional (3-D) under-decimated uniform discrete Fourier transform polyphase filter bank structures are proposed along with two applications: first, the sub-pixel motion discrimination of two-dimensional spatial objects moving with approximately constant local velocity in a noisy 3-D spatio-temporal image sequence and, second, the selective filtering of 3-D spatio-temporal broad-band plane waves based on their directions of arrival. The desired 3-D filter passband shapes are realized utilizing combinations of highly selective first-order 3-D infinite-impulse response frequency-planar filters in each band between the analysis and synthesis sections. Measured spatio-temporal performance confirms the high-quality broad-band transmission of passband signals, high directional selectivity and low computational complexity.     

A novel first-order log-domain allpass filter

This paper proposes a first-order allpass log-domain filter, which is systematically derived using the state-space synthesis procedure. To the best knowledge of the authors, the filter is the first log-domain first-order allpass filter in the literature. The proposed filter has a simple structure and can be electronically tuned. PSPICE simulations are given to confirm the theoretical analysis.     

First-order allpass filter using multi-input OTA

A novel first-order allpass filter, operating in voltage-mode, is introduced in this article. Compared with the corresponding already proposed structures, attractive offered benefits are the capability for simultaneous offering a minimum number of active and passive components, and the absence of any realisability restriction. These have been achieved by employing a multiple-input operational transconductance amplifier as active element. The performance of the proposed circuits has been evaluated through simulation results, utilising the Analog Design Environment of Cadence software.     

Minimax design of two-channel nonuniform-division filterbanks using IIR allpass filters

The design of two-channel linear-phase nonuniform-division filter (NDF) banks constructed by infinite impulse response (IIR) digital allpass filters (DAFs) in the sense of L/sub /spl infin// error criteria is considered. First, the theory of two-channel NDF bank structures using two IIR DAFs is developed. Then, the design problem is appropriately formulated to result in a simple optimization problem. Utilizing a variant of Karmarkar's algorithm, we can efficiently solve the optimization problem through a frequency sampling and iterative approximation method to find the coefficients for the IIR DAFs. The resulting two-channel NDF banks can possess approximately linear-phase response without magnitude distortion. The effectiveness of the proposed technique is achieved by forming an appropriate Chebyshev approximation of a desired phase response and then to find its solution from a linear subspace in a few iterations. Several simulation examples are presented for illustration and comparison.     

First-order allpass filter and sinusoidal oscillators using DDCCs

A voltage-mode first-order allpass filter using one differential difference current conveyor (DDCC), one grounded capacitor and one floating resistor is presented. No passive component matching constraints are required. Because the output impedance of the proposed allpass filter is low, the output terminal can be directly connected to the next stage. Using the proposed first-order allpass filter as a basic building block, a new quadrature oscillator and even-phase sinusoidal oscillators can be obtained. The simulation results confirm the theoretical analysis.     

Tunable allpass filter for low voltage operation

A novel high-performance first-order allpass filter with electronically adjustable filter parameters is presented. The core of the circuit is an inverting unity gain amplifier with electronically adjustable output resistance, which leads to an allpass filter realisation with tunable time constant. The circuit is composed of a simple CMOS cascode circuit and a level shifter and is also very suitable for low voltage operation, since it employs two active devices between its rails. SPICE simulation and experimental results verifying theoretical analyses are also given.     

Single MIMO-OTA and single-grounded-capacitor-based first-order allpass filter design

A novel first-order voltage-mode allpass (AP) filter employing a single multiple-input-multiple-output operational-transconductance-amplifier (MIMO-OTA) and a single grounded capacitor is introduced in this article. Compared to the corresponding already published topologies, the offered benefits are as follows: it employs minimum number of active and passive components; the only capacitor is grounded, which is good for a monolithic integration of an IC; and the absence of any matching condition for its realisability. The performance of the proposed circuit has been evaluated through simulation results, utilising the analogue design environment of Cadence software.     

Efficient method for trimming allpass sections

It is shown how excitation by triangular waves can be used to construct a very efficient method for trimming 2nd-order allpass sections. An oscilloscope is used as the measuring instrument.     

Novel allpass filter configuration employing single OTRA

A new circuit configuration uses a single operational transresistance amplifier (OTRA) and four passive elements to realize both first- and second-order allpass filters. Owing to internal grounding of the OTRA input terminals, effects of input parasitics are significantly reduced. Applications of the circuit include the realization of the phase equalizer, the quadrature oscillator, and the high-Q bandpass filter for analog signal processing. The performance of the allpass filter is illustrated by circuit-level simulation of a quadrature oscillator with CMOS realization of the OTRA.     

Interpolated LIR Mth-band filter design with allpass subfilters

We propose a new allpass-based structure for the IIR Mth-and 2Mth-band filters. These filters consist of M allpass filters and an interpolation filter (sum of two allpasses). Consequently, the proposed structure is very efficient in implementation. By choosing the allpass phase appropriately, the resulting phase response of the IIR Mth-band filter becomes approximately linear. An example is designed and compared with FIR Mth-band filters     

New orthogonalised IIR adaptive filter

A new IIR-ADF algorithm is proposed in which the discrete cosine transform, a fairly good approach of KLT for a large number of signal classes, is used to split the input signal into a set of nearly orthogonal transform coefficients. Subsequently these coefficients are filtered by a bank of IIR-ADFs whose coefficients are independently updated to minimise a common error. Computer simulations show that the proposed algorithm provides a faster convergence rate than the Gauss-Newton algorithm with a much reduced computational load     

An IIR median hybrid filter

A new class of nonlinear filters, the multidirectional infinite impulse response median hybrid (MIMH) filters, is presented and analyzed. The input signal is processed twice using a linear shift-invariant (LSI) infinite impulse response (IIR) filtering module: once with normal causality and a second time with inverted causality. The final output of the MIMH filter is the median of the two-directional outputs and the original input signal. Thus, the MIMH filter is a concatenation of linear filtering (a LSI IIR filtering module) and nonlinear filtering (a median filtering module). Because of this unique scheme, the MIMH filter possesses many desirable properties which are both proven and analyzed (including impulse removal, step preservation, and noise suppression). A comparison to other medium-type filters is also provided     

Electro-optic tunable filter

Theoretical analysis of electro-optic tunable filters (EOTFs) using colinear and noncolinear interactions is presented. An effective electro-optic coefficient is derived for various classes of birefringent crystal. We propose to implement the EOTF using the nonlinear photorefractive effect. The photorefractive EOTF can be used for optical storage.     

Efficient miniature fiber-optic tunable filter based on intracoreBragg grating and electrically resistive coating

An electrically tunable reflection filter based on a platinum-coated single-mode optical fiber that contains an intracore Bragg grating has been demonstrated. The device shows a dc tuning range of 2.15 nm with a corresponding electrical power of 0.54 W. Wavelength modulation (WM) has been observed at frequencies lower than 100 Hz. The wavelength shift depends linearly on the electrical input power. A maximum efficiency of 4.1 nm/W is obtained for dc tuning     

IIR数字滤波器的研究与设计

文中探讨了利用模拟滤波器设计IIR数字滤波器过程中的转换方法,脉冲响应不变法和双线性变换法,在MATLAB中以两种方法设计了数字巴特沃思低通滤波器。探讨了MATLAB中非低通数字滤波器的完全工具函数设计法和分步函数设计法,以上述方法分别设计了切比雪夫I型数字低通、高通、带通、带阻滤波器。     

Alternative and effective adaptive IIR filter structure

An adaptive IIR filter with a full-feedback structure is presented and a suitable LMS algorithm is derived. Using this algorithm, some examples are demonstrated where this structure has a distinct performance advantage over the conventional adaptive IIR filter structure     

Design of IIR digital filters using complex allpass network based on eigenvalue problem

A new design method is presented for complementary IIR digital filters with given magnitude specifications based on the eigenvalue problem, which are composed of a single complex allpass section.<>     

Cascadable allpass filter with a single DO-CCII and a grounded capacitor

In the literature sufficient emphasis has not been given to dual-output current conveyors in all-pass filter designs. In this study, a cascadable voltage-mode all-pass filter with a grounded capacitor using a single dual-output current conveyor has been reported.