Active Filter Topology Research Articles

Noise wave techniques analysis applied to various planar microwave active filter topologies

This article deals with the improvement of noise figure for various topologies of microwave active filters. We show how, using a noise wave formalism, the noise factor of different filters can be analytically derived and effectively minimized. We validate our approach with simulated examples for each topology. © 1998 John Wiley & Sons, Inc. Int J RF and Microwave CAE 8: 116–130, 1998.

Noise wave techniques analysis applied to various planar microwave active filter topologies

Noise wave techniques analysis applied to various planar microwave active filter topologies

Eigen analysis of series compensation schemes reducing the potential of subsynchronous resonance

A.A. Edris (see ibid., vol.5, no.1, p.219-36, 1990) described a new concept for mitigation of the phenomenon of subsynchronous resonance (SSR) based on asymmetrical series capacitor compensation at SSR frequencies. The studies reported by A.A. Edris are based on a digital time-domain simulation technique. This paper provides a quantitative evaluation of the concept using a novel eigen analysis approach. The eigen analysis approach represents the mathematical models of power system components in the three-phase basis, and can evaluate the impacts of asymmetry and imbalance on the system dynamics in the subsynchronous frequency range. The study results restate the technical feasibility of the proposed SSR countermeasure. This paper opens the avenue for examination of active power filter topologies to introduce artificial asymmetry at SSR frequencies to counteract torsional oscillations.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Biquads and allpass functions in current mode waveactive filters

The authors present two features new to the current mode wave active filter topology. Bandpass biquadratic filter blocks with quality factors lower than those of the overall transfer function may be used for bandpass filters. Allpass filters may be implemented using the building blocks used for conventional filter simulation.

Active microwave filters with noise performance considerations

Active microwave filters offer a unique solution for certain filtering problems in modern microwave integrated circuit applications. A number of authors have reported novel active filter topologies in this connection; however, noise considerations for these exotic designs have seldom been addressed, and only Bonetti and Williams (1990, 1992) have provided actual reliable repeatable measured noise data across a band of frequencies. The main objective of this paper is to present a precision computer-oriented technique to accurately predict and quantify the noise performance of various active microwave filter realizations. Experimental examples are presented which validate the computer-oriented simulation methodology. Noise performance results are presented for a representative realization of each class of active microwave filter considered.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Novel CCI-OTA-Based Grounded Capacitor Current-Mode Biquadratic Bandpass and Lowpass Filters

A novel current-mode active filter topology using a first generation current conveyor (CCI) and an operational transconductance amplifier (OTA) is presented. Using this topology, grounded-capacitor biquadratic bandpass and lowpass filter sections, with at most five one-port passive elements, are realized. In these realizations, the parameterω0can be adjusted without disturbing the parameterω0/ Q0

A simple method for cable compensation with fast pulse transmission applications

Abstract A simple method for compensating signal cable effects on fast pulse transmission is described. The effects which are compensated here are mainly the long tail, that appears when fast signals are transmitted through cables, and the deterioration of the rise time. The method described is rather general and suitable for many applications, including circuit design and off-line analysis. It characterizes cables by a summation of exponentials, which has proved to be an accurate and relatively easy to implement representation. The compensation network is then implemented in the frequency domain by means of pole-zero cancellation. The computer simulation results are presented and a modular active filter topology and design procedure are discussed. Experimental results using commercial cables are also included. The method has been used for acquiring and processing signals from the Spaghetti calorimeter which is currently being developed at CERN.

Comparison of dynamic range properties of high-order active bandpass filters

The design procedures necessary for maximising dynamic range of cascade, f.l.f., i.f.l.f. and m.l.f. active-filter topologies, are presented and equations are derived for computing the total output-noise voltage contributed by internal-noise sources. Further, it is shown that the equivalent input noise of a second-order biquad section is dependent not only on circuit configuration and pole-Q, but in some cases also on the section gain. As a result, the total output noise of high-order filters may or may not be a function of the overall filter gain, depending on whether the equivalent input noise of the second-order section used as building block is not or is, respectively, a function of section gain. A comparison of the different topologies indicates that in addition to the advantage of being easy to design, the f.l.f. filter is the only topology whose output noise can remain constant regardless of the overall filter gain and the type of second-order used.

Sensitivity minimization in a single amplifier biquad circuit

The single amplifier biquad (SAB) circuit of J. J. Friend is critically examined with a view to minimize its sensitivity properties. This is shown to involve the proper choice of the free design parameters to achieve a trade off between the contributions due to passive and active element variations. First the bandpass configuration is analyzed. A statistical measure of the overall pole variation due to both passive and active components is formulated. The analysis includes a novel but very simple approach for estimating the effects due to op amp variations which is applicable to many of the active filter topologies known. Using the figure of merit obtained in this fashion, it is shown that a near optimal design exists which permits ready physical realization, and which has the property that the transmission error terms are dominated by the irreducible fixed contribution due to the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RC</tex> product which defines the resonant frequency. From the aspect of sensitivity, therefore, it is concluded that no other circuit topology can have superior performance. The frequency range over which these conclusions remain valid are determined by using reasonable estimates of circuit component tolerances. For a simple operational amplifier of the 741-type this range is shown to extend to approximately 2 kHz, while if a more sophisticated two-pole single zero compensation is used for the operational amplifier the range of validity is extended to about 20 kHz. The above results are then shown to hold for all the other important