Order All-pass Research Articles

Novel first order all-pass sections using a single CCIII

Two novel first order voltage-mode all-pass sections using a single third generation current conveyor (CCIII) are given. In addition the first circuit uses three resistors and one capacitor and the second circuit which is derived from the first circuit uses two resistors and one capacitor. A current-mode first order all-pass section requiring one capacitor and one resistor is also proposed. SPICE simulation results are incorporated to verify the theory.

High Output Impedance Current-Mode Four-Function Filter with Reduced Number of Active and Passive Elements Using the Dual Output Current Conveyor

This paper reports a new single-input multi-output current-mode multifunction filter which can simultaneously realise LP, HP, BP and BR filter functions all at high impedance outputs. The circuit permits orthogonal adjustment of quality factor Q and \omega_0, employs only five grounded passive components and no element matching conditions are imposed. A second order all-pass function can easily be obtained. The passive sensitivities are shown to be low.

Simple first order all-pass section using a single CCII

A novel first order all-pass section using a single second generation current conveyor is given. In addition the circuit uses two resistors and only one capacitor. The circuit is also realized with a translinear conveyor. The latter circuit uses only one external resistor and a capacitor. The proposed circuits are verified using PSPICE with attractive results.

Adaptation of an all-pass equalizer for decision feedback equalization

Recording channels using decision feedback equalization require a minimum phase response and white noise at the detector to achieve maximum signal-to-noise ratio. A low order all-pass filter can equalize the feedforward path so that it approximately achieves a minimum phase response. In this paper, we describe an adaptive algorithm for iteratively determining the optimal transfer function of the all-pass filter. Adaptation is based on estimating the gradient of the mean-square error with respect to the poles of the filter. This estimate is then used to update the positions of the poles. One simplifying feature of this technique is that these gradients are determined by applying the output of the all-pass to low-order finite impulse response (FIR) filters. We do not require values from the internal states of the filter. The proposed adaptation algorithm is characterized for first- and second-order all-pass filters over a range of storage densities. The optimality of the resulting equalizer is evaluated as a function of the order of the FLR filters used in estimating the gradients.

Stabilizing Rational Controllers for a Class of a Time-Delay Systems

The problem of stabilization of a linear system characterized by its rational transfer function, with an input time delay, by a rational controller, is considered. If the delay is not known at all (its interval is infinite), it is proved that the necessary and sufficient condition for the existence of a rational controller is stability of the open loop rational plant. Moreover, the existence of a rational stabilizing controller implies the existence of a constant gain stabilizing controller. If the delay is known to lie in a given finite interval, two non-existence theorems are derived, one for the constant gain stabilizing controller and one for any rational stabilizing controller. Design method based on first order all-pass filters cascaded by a constant gain is presented.

Design and analysis of bilinear digital ladder filters

Methods for designing bilinear switched-capacitor (SC) ladder filters are well known. However, they cannot be directly extended to digital filters because of the delay-free loops allowed in SC filters. In the present paper, design methods for low-sensitive bilinearly transformed voltage-current ladder filters are developed. The matrix approach for SC filter design is extended to digital filters, and the delay-free loops are eliminated. Design equations for general order low-pass, high-pass, bandpass, bandstop, and allpass filters are obtained in a simple closed form. The design procedure gives a canonical number of delays and a number of distinct multipliers equal to the number of reactive elements in the prototype. A number of test filters are analyzed with respect to magnitude sensitivity, magnitude response with respect to coefficient quantization, occurrence of limit cycles, stability, quantization noise levels, and structural complexity. The results are compared to wave digital filters (WDF), and cascade-form filters. It is found that bilinear digital ladder filters (BDLF) in most cases perform better than WDFs, while they at the same time have a simpler structure.

On the design of a broad class of 2-D recursive digital filters with fan, diamond and elliptically-symmetric responses

This paper deals with the design of a broad class of 2-D recursive digital filters including general fan, diamond and elliptically-symmetric filters. At first, the explicit design of quadrant and /spl plusmn/45/spl deg/ fan filters is reviewed. A full-plane diamond filter (both axes are nearly of length 2 /spl pi/) can easily be obtained through an appropriate transformation of a /spl plusmn/45/spl deg/ fan filter. Using this diamond filter as a prototype, a very simple spectral transformation is then proposed to design full-plane circularly-symmetric filters (radius /spl ap//spl pi/). These filters share the same lattice wave digital structure and employ only first or second order all-pass sections which can be realized by two-port adaptors. They provide very desirable properties such as low sensitivity, high dynamic range and good stability even under finite arithmetic conditions. Using the above mentioned filters as prototypes, a multirate approach is then introduced to deal with the design of fan filters with arbitrary angle and orientation, diamond and elliptically-symmetric filters with arbitrary length of axes. Finally, some design examples are given. >

All-pass networks using current conveyors

Two circuits, each realizing a second order all-pass transfer function, are described. One circuit uses a grounded capacitor, and is thus suitable from the point of view of IC implementation. The other circuit employs a minimum of active and passive components required for a second order all-pass realization.

A high input impedance all-pass realisation using a single current conveyor

A circuit for realising a second order all-pass transfer function using a single current conveyor is proposed. The circuit offers very high input impedance.

Minimal Realizations of First Order All-Pass Functions

Minimal Realizations of First Order All-Pass Functions

Active-RC All-pass Filter

The Teramoto method of realizing an RC all-pass is modified to obtain a grounded output with convenient impedance level. Additionally, it is shown that the circuit with a unity-gain amplifier and a little increased complexity of the passive parts, provides the same facilities. An n-th order all-pass with arbitrary complex poles can also be realized in this scheme for symmetric orientation of the branch admittances of the bridge. A second-order Padé delay network is presented by way of example of the generalized realization method.

On the Design of All-Pass Signals With Peak Amplitude Constraints

In this paper, the problem is discussed of designing a signal other than the standard impulse function to be used to test a digital system of limited dynamic range. The constraints on such a signal are that it must be all-pass, of limited duration (approximately), and peak-amplitude-limited so as to utilize the limited dynamic range of the system as far as possible. Stated another way, the goal is to spread out the energy in the signal as much as possible to reduce its peak amplitude and therefore to be able to pass higher energy signals through the system without clipping them. The class of all-pass signals (obtained as the impulse response of a variable order all-pass filter) was investigated for use as the test signal. The parameters of the all-pass filter of a given order were optimized to give an all-pass signal whose peak amplitude was the smallest possible. Filter orders from first to eighth order were designed and investigated. It was found that reductions in the peak signal level of up to 11.2 dB (relative to the signal level of an equivalent energy impulse) could be obtained for an eighth-order all-pass signal. Interpolated versions of these all-pass signals showed that the peak value of the interpolated waveform was only on the order of 6 dB. Thus, the use of an all-pass signal, rather than the standard impulse, for testing a digital system can result in about 1 bit extra dynamic range.

Realizations of complex pole all-pass networks

It is shown that an all-pass function with complex poles can always be constructed by adding an appropriate all pole function to a first order all-pass function. This method has several advantages: 1) the complex pole sensitivities of the resulting all-pass network are the same as the pole sensitivities of the all pole network; 2) the output of the all pole network is available as an aid in tuning the network as well as for other purposes; 3) the method yields an abundance of networks. Three new all-pass realizations are derived to illustrate this method. One of the realizations is analyzed in detail, and analysis results are given for the other two realizations. For all three examples considered, the zero sensitivity magnitudes are approximately equal to the pole sensitivity magnitudes of the all pole function.