All-pass Transfer Function Research Articles

A New Asymptotic Stability Criterion for Linear Discrete-Time Systems

In this brief, a new criterion to determine whether the roots of a polynomial <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$p(z^{-1})$ </tex-math></inline-formula> with real coefficients are strictly inside the unit circle is presented. It is based on representing the polynomial in a form corresponding to the characteristic polynomial of a closed-loop systems in which all-pass transfer functions are included in both direct chain and feedback loop. The novel and simple criterion for assessing the asymptotic stability of linear discrete-time systems is proved applying the small-gain theorem in the discrete-time domain.

Approximation and realization of power-law all-pass filters

Non-integer power-law all-pass transfer functions, are approximated by suitable integer-order transfer functions in this work. The derivation of the integer-order transfer functions is based on the analytic expansion of the (non-integer) power-law transfer functions through the utilization of the binomial theorem. The offered benefit is the derivation of stable integer-order transfer functions. This study is supported by experimental results, obtained using a Field Programmable Analog Array device, after the employment of curve fitting based approximation techniques.

Variable-Phase All-Pass Network Synthesis and Its Application to a 14–54 GHz Multiband Continuous-Tune Phase Shifter in Silicon

This article presents a novel synthesis procedure to implement variable-phase all-pass networks (VP-APNs). The synthesis procedure is based on linear-phase all-pass transfer functions, enabling implementation at millimeter waves. Using the proposed synthesis, VP-APNs with analog and digital control are implemented for the first time in silicon. Using 0.25-μm BiCMOS, the VP-APNs are manufactured and measured, validating the synthesis procedure. Finally, the validated VP-APNs are combined to realize a phase shifter. By combining the analog and digitally controlled networks, we obtain a continuous-tune phase shifter with multiband capabilities, successfully covering several bands from 14 to 54 GHz. This includes Ku-, K-, Ka-, and V-band, as well as both 5G bands around 28 and 39 GHz.

A New Low-Voltage Low-Power Dual-Mode VCII-Based SIMO Universal Filter

In this paper, a new low-voltage low-power dual-mode universal filter is presented. The proposed circuit is implemented using inverting current buffer (I-CB) and second-generation voltage conveyors (VCIIs) as active building blocks and five resistors and three capacitors as passive elements. The circuit is in single-input multiple-output (SIMO) structure and can produce second-order high-pass (HP), band-pass (BP), low-pass (LP), all-pass (AP), and band-stop (BS) transfer functions. The outputs are available as voltage signals at low impedance Z ports of the VCII. The HP, BP, AP, and BS outputs are also produced in the form of current signals at high impedance X ports of the VCIIs. In addition, the AP and BS outputs are also available in inverting type. The proposed circuit enjoys a dual-mode operation and, based on the application, the input signal can be either current or voltage. It is worth mentioning that the proposed filter does not require any component matching constraint and all sensitivities are low, moreover it can be easily cascadable. The simulation results using 0.18 μm CMOS technology parameters at a supply voltage of ±0.9 V are provided to support the presented theory.

Variable-phase filter design using linear-programming technique

Variable-phase (VP) digital filter can change its phase response during the online digital-signal processing (DSP). This paper proposes a linear-programming (LP) method for designing a VP filter in the minimax error sense, i.e., the maximum phase error is minimised. The mathematical model used to approximate a desired VP response (VP specification) is an all-pass transfer function whose numerator and denominator have exactly the same coefficients. In this paper, we first derive a frequency-response error that is a non-linear function of the VP filter coefficients, and then approximate this frequency response as a linear function of the VP filter coefficients. Consequently, the minimax design of the VP filter reduces to a linear minimisation problem, which is solved through using an LP solver. We will use an example to demonstrate that the proposed LP-based VP design technique can obtain an all-pass VP filter with high accuracy. Moreover, the stability of the designed all-pass VP filter is also guaranteed.

惯性稳定平台自适应前馈控制

An adaptive feed-forward control method combining with feedback control was proposed to improve the command tracking performance of control circuit in an inertial stabilized platform. On the basis of subspace system identification, the input-output data were used to identify a state space of the stabilized platform model and the frequency-domain loop shaping technique was used to design the feedback loop controller to reject the external disturbance. Furthermore, a Recursive Least Square (RLS) adaptive filter was taken to build the inverse model of the feedback control loop and to construct the all-pass transfer function for increasing tracking performance. Several tracking experiments were conducted on different command inputs to verify the validity of the adaptive feed-forward controller. Experimental results show that this method responses quickly to step commands and the overshoot has decreased from 30% to 4.5% as compared with that of the feedback control. For a sinusoidal signal at the frequency of 30 Hz, the adaptive feed-forward controller can obtain an amplitude response without attenuation and the phase lag is reduced to 54 from 90 as compared with that of the feedback control. This method significantly improves the transient performance and is superior to the feedback control alone. , 2015, Chinese Academy of Sciences. All right reserved.

Inverting non-minimum phase FIR transfer functions with application to reverberant speech

The problem of removing reverberation in speech is considered when the room impulse response is non-minimum phase. The method does not require multiple sensors or the use of all-pass transfer function networks as in previous techniques. Instead we use spectral factorization of large polynomials. Spectral factorization gives a method of reflecting the non-minimum phase roots without having to calculate their actual values.

Unity/Variable-gain Voltage-mode/Current-mode First-order All-pass Filters Using Single Dual-X Second-generation Current Conveyor

In this paper, two new general topologies for realizing voltage-mode (VM)/current-mode (CM) first-order all-pass Alter transfer functions (TFs) are presented. The proposed topologies use single dual-X second-generation current conveyor (DXCCII) and three impedances Z1, Z2 and Z3. Based on the selection of Z1, Z2 and Z3, new VM and CM all-pass Alters with unity or variable gains are obtained. The proposed VM/CM filters have high-input/high-output impedances which provide easy cascading at their input/output terminals, respectively. Non-ideal gain and parasitic impedance effects, associated with actual DXCCII implementation, on the performance of the developed topologies are also included. Finally, simulation program with integrated circuit emphasis (SPICE) simulation results based on level 49, 0.25 μm TSMC complementary metal-oxide-semiconductor (CMOS) technology parameters are given to confirm the theory.

Linear-Phase Delay Filters for Ultra-Low-Power Signal Processing in Neural Recording Implants

We present the design and implementation of linear-phase delay filters for ultra-low-power signal processing in neural recording implants. We use these filters as low-distortion delay elements along with an automatic biopotential detector to perform integral waveform extraction and efficient power management. The presented delay elements are realized employing continuous-time OTA-C filters featuring 9th-order equiripple transfer functions with constant group delay. Such analog delay enables processing neural waveforms with reduced overhead compared to a digital delay since it does not requires sampling and digitization. It uses an allpass transfer function for achieving wider constant-delay bandwidth than all-pole does. Two filters realizations are compared for implementing the delay element: the Cascaded structure and the Inverse follow-the-leader feedback filter. Their respective strengths and drawbacks are assessed by modeling parasitics and non-idealities of OTAs, and by transistor-level simulations. A budget of 200 nA is used in both filters. Experimental measurements with the chosen filter topology are presented and discussed.

An Ultra Low-Power CMOS Automatic Action Potential Detector

We present a low-power complementary metal-oxide semiconductor (CMOS) analog integrated biopotential detector intended for neural recording in wireless multichannel implants. The proposed detector can achieve accurate automatic discrimination of action potential (APs) from the background activity by means of an energy-based preprocessor and a linear delay element. This strategy improves detected waveforms integrity and prompts for better performance in neural prostheses. The delay element is implemented with a low-power continuous-time filter using a ninth-order equiripple allpass transfer function. All circuit building blocks use subthreshold OTAs employing dedicated circuit techniques for achieving ultra low-power and high dynamic range. The proposed circuit function in the submicrowatt range as the implemented CMOS 0.18- microm chip dissipates 780 nW, and it features a size of 0.07 mm(2). So it is suitable for massive integration in a multichannel device with modest overhead. The fabricated detector succeeds to automatically detect APs from underlying background activity. Testbench validation results obtained with synthetic neural waveforms are presented.

Direct Detection Frequency Discrimination Optical Receiver for Minimum-Shift Keying Format Transmission

An incoherent detection scheme based on frequency discrimination for minimum-shift keying (MSK) optical transmission systems is proposed to significantly extend the reach of uncompensated transmission distance. The receiver consists of dual narrowband optical filters in association with an optical delay line. This photonic front end operates based on frequency discrimination principles of matched filters, rather than relying on the phase of the optical carrier. Hence, its performance is less sensitive to the all-pass quadratic phase transfer function of the fiber transmission medium and is thus less susceptible to fiber chromatic dispersion. The photonic front-end optical receiver for 40-Gb/s optical MSK offers a dispersion tolerance of up to plusmn340 ps/nm for 1-dB power penalty at a bit-error rate of 10-9. This achievement is approximately five to seven times better than that of the existing value based on the Mach-Zehnder delay interferometer (MZDI) optical balanced receiver. Furthermore, the receiver is shown to be robust to polarization-mode dispersion.

A Study on Adaptive Notch Filter Using Exponential All-Pass Transfer Function

In this paper, we propose an adaptive notch filter that realizes the phase shift of the all-pass filter by the expression of Fourier sine series. The method to control the weights of the all-pass filter composed by IIR filter is known well. However, these adaptive notch filters have not been put to practical use since the peculiar stability problem of IIR filter and the problem concerning the determination method of the degree of IIR filter exist. The proposed adaptive notch filter is always stable since the all-pass filter is composed by an exponential filter. Moreover, the adaptive algorithm is a simple gradient based algorithm and the convergence of weights is guaranteed. The degree of the all-pass filter only depends on the required steepness of the elimination characteristic and does not depend on the number of narrowband signals that should be eliminated. Moreover, it can be said that the proposed method is a suitable method for practical use since the elimination characteristic hardly influenced by the broadband signal added to the narrowband signal. Finally, the analytical results and the above mentioned feature are strictly verified by computer simulation.

Versatile current-mode biquadratic circuit using only plus type CCCIIs and grounded capacitors

This paper introduces a versatile current-mode biquadratic circuit using second generation current-controlled current conveyors (CCCIIs). The circuit is constructed with two plus type multiple current output CCCIIs (MO-CCCIIs) and two grounded capacitors. The circuit can realize low-pass, band-pass, high-pass, band-stop and all-pass transfer functions by choosing appropriate input and output terminals without any component matching conditions. Additionally, the circuit parameters Q and ω0 can be set orthogonally by adjusting the bias currents of the MO-CCCIIs and grounded capacitors. The biquadratic circuit enjoys very low sensitivities to the circuit components. Some examples are given together with simulated results by PSPICE.

Factorized All-Pass Based IIR Adaptive Notch Filters

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This paper introduces a new family of infinite impulse response adaptive notch filters that forms multiple notches using a second-order factorization of an all-pass transfer function. The new orthogonal realization is amenable for adaptive filtering to obtain the unknown frequencies of interest. Two new adaptive filtering algorithms are presented that can achieve fast convergence at low computational cost. Local convergence analysis for the new algorithms is performed, and a detailed discussion of their properties is provided. The new all-pass based notch realization intro duces a different compromise between bias and signal-to-noise ratio (SNR) when compared with realizations previously reported in the literature. Specifically, it achieves lower bias than other approaches at low SNR. This property is particularly attractive for the estimation and tracking of multiple sinusoids. Furthermore, the bias can be made arbitrarily small or can be accurately estimated and compensated for. Extensive computer simulations are provided to illustrate the performance of the proposed adaptive notch filters in terms of bias, speed of convergence, and tracking capability. </para>

A study on an estimation system of inverse transfer function using adaptive filter estimating minimum‐phase and allpass transfer function

AbstractA structure is proposed for an adaptive system with an adaptive filter located before the unknown system (pre‐inverse adaptive system) for estimation of the inverse of the transfer function (inverse transfer function) of the unknown system. In general, when an adaptive transversal filter is used as an adaptive filter, the delay signal of the output of the unknown system is needed in the adaptive algorithm for the weights. Since an adaptive filter is inserted in the front stage, this signal cannot be observed, so that a replica of the unknown system is needed. In this paper, an adaptive system that does not require this replica is discussed. Estimation of the inverse transfer function of the minimum phase of the unknown system is performed by an adaptive exponential filter and an inverse copy of the weights of the exponential filter placed in front of the unknown system. The signal within the adaptive algorithm consists of the observable input signal to the adaptive exponential filter and the estimation error. Estimation of the inverse transfer function for the allpass transfer function of the unknown system is performed by the adaptive transversal filter and the reversing copy of the weight to the transversal filter located before the unknown system. The signal in the adaptive system consists of the observable input signal to the exponential filter and the estimation error. Convergence of the weight is studied from the point of view of monotonic increase of the gradient. The unique feature of the approach is that the algorithm of the two adaptive filters consists of a gradient algorithm with guaranteed convergence for the weights and of copies of the weights after updating. Finally, a performance evaluation of the adaptive system and a comparison with conventional systems are performed by numerical simulation. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 3, 90(9): 10– 17, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjc.20305

Novel current-mode biquad filter using OTAs and DO-CCII

This paper presents a realization of a current-mode biquad filter using operational transconductance amplifiers (OTAs) and a dual current output second generation current conveyor (DO-CCII). The proposed filter is constructed with two multiple current output OTAs (MO-OTAs), one OTA, one DO-CCII and two grounded capacitors. The circuit can realize low-pass, band-pass, high-pass, band-stop and all-pass transfer functions by choosing appropriate current outputs without any matching conditions of the circuit elements. And the characteristic parameters ω0 and Q can be tuned orthogonally through adjusting the bias currents of the OTAs. The biquad filter enjoys very low sensitivities with respect to the circuit elements. An example is given together with simulated results by PSPICE. The filter circuit configuration is well suited for implementation in both bipolar and CMOS technologies.

VOLTAGE-MODE DDCC-BASED MULTIFUNCTION FILTERS

Two new voltage-mode multifunction biquadratic filter configurations were proposed. The first proposed high-input impedance multifunction filter with single input and four outputs, which can simultaneously realize voltage-mode low-pass, band-pass, and high-pass filter responses employing all grounded passive components. The second proposed configuration is a slight modification of the first proposed circuit. It leads two more notch and all-pass transfer functions than the first proposed circuit. Moreover, both the proposed circuits still offer the following advantages: (i) orthogonal control of ωo and Q, (ii) low active and passive sensitivity performances, (iii) simpler configuration due to the use of noninverting type differential difference current conveyors (DDCCs) only.

A Study on Pre-Inverse Adaptive System Based on Estimation of Minimum-Phase and Allpass Transfer Function

In this paper, we discuss a pre-inverse adaptive system in which the adaptive filter is located before the unknown system. We then propose an adaptive system that does not require a replica of the unknown system, as in the case of the filtered-x adaptive system. With the proposed method, we can therefore avoid the instability that arises from error in the replica of the unknown system. In the proposed method, the inverse transfer function of the minimum-phase part of the unknown system is estimated by an adaptive exponential filter. The inverse transfer function of the allpass part of the unknown system is estimated by an adaptive transversal filter, whose inverse can be easily realized by reversing the order of the weights. Finally, a numerical verification of the analytical results, the convergence performance of the adaptive systems, and a performance comparison with the filtered-x adaptive system are obtained by computer simulation

Novel current-mode active-only biquad with loss-less and lossy integrators

This paper presents a realization of a current-mode active-only biquad with a two-integrator loop structure. The proposed circuit is constructed solely with operational amplifiers (OAs) and operational transconductance amplifiers (OTAs). The circuit can realize low-pass, band-pass, high-pass, band-stop and all-pass transfer functions, and the circuit characteristics can be electronically tuned by adjusting the transconductance gains of the OTAs. An example is given together with simulated results by PSPICE. The circuit configuration is very suitable for implementation in both bipolar and CMOS technologies.

Conversão DSB/SSB a capacitores chaveados usando transformadores de Hilbert recursivos

Neste trabalho é apresentada a implementação completa de um conversor de modulação DSB (double-sideband) para SSB (single-sideband) a capacitores chaveados, usando componentes discretos. Para se conseguir uma modulação SSB eficiente, um Transformador de Hilbert é utilizado. Uma boa faixa dinâmica e sensibilidade baixa ao erros nas razões de capacitâncias são conseguidas pela implementação do Transformador de Hilbert através de circuitos com funções de transferência recursivas do tipo passa-tudo. A taxa de amostragem do sinal SSB pode ser reduzida por um fator igual a 2 (dois) sem perda de informação, reduzindo a complexidade do circuito e o seu consumo de energia. A conversão de DSB para SSB completa é ilustrada pela apresentação de resultados experimentais. Alguns aspectos práticos relacionados à possível implementação monolítica CMOS deste circuito são considerados.