All-pass Transfer Function Research Articles

Universal multiple-output second-order digital filter

A universal, second-order, digital-filter structure is proposed, which realises simultaneously a lowpass, a highpass, a bandpass, a notch and allpass transfer function. The structure uses two unit-delays and four multipliers, and is quite attractive for VLSI implementation since a versatile universal chip can be fabricated, which can be used for the implementation of Butterworth, Chebyshev and elliptic digital filters as well as digital equalisers.

A digital all-pass transfer function with all possible coefficient combinations

Characteristics of a second-order digital all-pass network with all possible combinations of two coefficients are discussed, and the constraints that the system should be stable and the group delay characteristic on extremum are described. Approximation formulas are given for the maximum group delay and for the angular frequency at which the group delay attains its maximum value. Digital all-pass transfer functions realizable with two finite wordlength multipliers and their maximum group delay characteristics are also described.

Reply to "Comments by A. M. Soliman on 'realization of an all-pass transfer function using the second generation current conveyor'"

Reply to "Comments by A. M. Soliman on 'realization of an all-pass transfer function using the second generation current conveyor'"

Comments on "Realization of an all-pass transfer function using the second generation current conveyor"

Comments on "Realization of an all-pass transfer function using the second generation current conveyor"

Realization of current conveyor all-pass networks

Three circuits each realizing a, first-order all-pass transfer function are described in this communication, These circuits offer high input impedance and controllable voltage gain.

Comments on "Realization of an all-pass transfer function using the second generation current conveyor"

It is pointed out that an error exists in the circuit given in the above letter [1]. In correcting the circuit, it becomes identical to the general configuration previously described in the literature [1]. The realization of a first-order all-pass transfer function should not be compared with that of a second-order all-pass based on the number of circuit components.

Realization of an all-pass transfer function using the second generation current conveyor

The second generation current conveyor (CCII) is used together with only four components to realize an all-pass transfer function.

P-normalized digital two-pairs

A digital two-pair constrained by any unity magnitude all-pass transfer function and exhibiting unity L p -scaling norms of the transfer functions at all pertinent nodes is defined to be a p-normalized digital two-pair. Several such first-order two-pairs are developed, and the advantage of using these two-pairs in the realization of an arbitrary infinite-duration impulse-response (IIR) digital transfer function is pointed out.

Wave active filters based on unit-element prototypes

A general method for realising wave active filters based on unit-element (u.e.) prototype filters is described. The systhesis of a wave active filter having a general allpass transfer function is presented to illustrate the approach. Experimental results for a 2nd-order case are presented to show that the synthesis method will lead to practical realisations.

A simple design for an all-pass filter

A new simple design procedure for realizing second-order all-pass transfer functions with arbitrary pole locations is presented. It requires only one difference amplifier of maximum gain 2, two capacitors and four resistors. The coefficient and Q sensitivities, with respect to the amplifier gain, are also studied.

Two Design Techniques for Digital Phase Networks

Two computer-aided algorithms for the design of all-pass digital filters are presented. The first technique is based on a linear programming approach to solving the approximation problem posed by the minimax design of an all-pass digital filter. A new iterative algorithm with stability constraints is offered for direct form design. The second technique implements a gradient search for those quadratic factors of an all-pass transfer function that lead to a locally optimal approximation (in the least-squares sense) of a desired phase function. New initial guess procedures and the parameterization of linear-phase offset enhance the least-squares design procedure. Examples illustrating the result of both procedures are included.

Digital all-pass networks

A systematic method is outlined to realize an m th-order all-pass digital transfer function using only m multipliers as a cascade of first-order and/or second-order all-pass sections. The realization is based on the multiplier extraction approach in which the n th-order filter section is considered as a digital (n + 1) -pair of which n pairs of input and output terminal variables are constrained by n multipliers. The transfer matrix parameters of the digital (n + 1) -pair, containing only delays and adders, are first identified from which the realization is obtained by inspection. Both canonic and noncanonic realizations are derived. All realizations are then compared with regard to the effect of multiplication roundoff and hardware requirements.

Comment on "Inductorless Realization of an All-Pass Transfer Function using the Current Conveyor

Comment on "Inductorless Realization of an All-Pass Transfer Function using the Current Conveyor

A general configuration for realizing all-pass or notch niters using a grounded operational amplifier

Abstract A new structure for realizing an all-pass transfer function is given here. By adjusting one resistor the same configuration can realize a notch filter. Two special circuits using a minimum number of capacitors are derived from the general configuration, both are capable of realizing complex poles

An approach to active filter design problems using gyrators: A fresh look

Abstract The conventional approach to active filter design problems using gyrators has been to replace each individual inductor (grounded or ungrounded) of the passive filter by an active network using one or more grounded gyrators. The method fails to realize three terminal versions when the passive filter is itself a balanced one (four-terminal two-port(. Another approach is to replace the passive filter as a whole by an equivalent active network using gyrators. The transfer function as a whole is synthesized as an active network. This method makes possible the realization of three terminal versions of certain active filters which are not possible by the conventional method. The method has been illustrated for the cases of a driving-point impedance function and a constant resistance lattice filter. An all-pass transfer function has been synthesized as an example.

Active RC all-pass networks using a summation or a differential amplifier!

Abstract The paper presents a class of active RC networks using a summation amplifier or a differential amplifier for realizing all-pass transfer functions of arbitrary order, having simple poles restricted to the negative real axis. Examples are given to realize second-order all-pass transfer functions with RC null network and with the phase-shifting network of a Wien bridge.

Single-transistor all-pass networks

A network configuration consisting of a resistive twoport bridged by a lossless one-port is considered. It is shown that in certain cases this configuration is capable of realizing a voltage transfer function equal to that of a constant-resistance passive lattice. As a special case, conditions are derived on the two-port parameters for the structure to be all pass. It is determined that a single transistor suffices to realize the two-port network, thus resulting in a very simple all-pass structure; only one coil, one capacitor, and one transistor are necessary to realize a second-degree all-pass voltage transfer function. Higher order transfer functions can be realized by adding an <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</tex> branch per each additional second-order factor to the same transistor circuit. In the second-order case, losses in the coil can be compensated. In higher order realizations coil losses cannot be compensated, but a design technique which achieves an arbitrarily close approximation to the desired all-pass transfer-function is presented. Methods of cascading lower order sections are discussed and experimental results are given.

Inductorless realization of an all-pass transfer function using the current conveyor

The use of the second-generation current conveyor as the active element in realizing all-pass transfer functions is illustrated by two circuits.

Realization of all-pass transfer function using a differential amplifier

A class of active RC networks is presented with which an all-pass transfer function of arbitrary order, having simple negative real poles, has been realized by combining the output of a threeterminal RC network with a portion of its input in a differential amplifier. A synthesis procedure for such an all-pass function is also indicated. This class of networks has the advantage that the gain constant of the all-pass function may be varied by varying the gain of the differential amplifier.

Active realisation of n th-order all-pass transfer functions

Using a signal-flowgraph procedure, two active RC circuits realising the general nth-order allpass transfer functions are given. These realisations use a minimum number of capacitors and (n+1) single-ended operational amplifiers.