Andres C. Salazar

Considerations of the Padé approximant technique in the synthesis of recursive digital filters

The Pade approximant technique provides a quick design of recursive digital filters. An added advantage of the technique lies in that spectrum shaping requirements as well as linear phase constraints can be handled easily, even for higher order filters. This is important in supplying initial guesses of the filter parameters to iterative routines that would then seek a locally optimal design solution. These advantages are among those discussed in a partly tutorial presentation of the technique that relates to filter needs found in data transmission systems. In addition, the question of stability is treated and a new criterion is presented. The criterion provides sufficient conditions in establishing stability for a filter designed by using the Pade approximant technique.

Recursive digital filter synthesis in the time domain

The nonlinear minimization problem that results from recursive digital filter design with phase constraints is simplified somewhat by working in the time domain. This paper describes techniques that utilize the time samples of the desired response as target values for an iterative minimization. Initial values for the α and β (feedforward and feedback) coefficients can be obtained by one of several reliable methods and fed into iterative routines that lead to a locally optimal solution for the coefficients. The initial guess procedures, stemming from regressionlike equations, only require the solution of a set of linear equations. In addition, the iteration procedures described in this paper lead to recursive filter designs requiring little computer time. Examples are presented to illustrate a range of applications.

Effects of finite coefficient precision on FIR filter spectra

Finite Impulse Response filters (FIR) and other digital signal processing algorithms are implemented either with special purpose hardware or as programs on special purpose computers or signal processors. In either case the state variables and the coefficients are stored in binary format in registers or memory elements with finite lengths. Register length is an economic factor in hardware implementations and in software implementations it is generally forced upon the designer by the architecture of the available processor or computer.

Statistical Methods for Testing Quality of Communication Channels

The reliable transmission of information over communication channels depends greatly on the adequacy of the maintenance program provided for the transmission medium. An integral part of such a program is the procedure used for determining the quality of a communication link. In this concise paper, we discuss several statistical methods for ascertaining those impairments-and their respective levels-which reveal the most information about the fidelity of the channel in signal transmission. For the purpose of illustration, an example is presented which demonstrates how a testing program could implement each particular statistical method.

Markov Process Analysis of PCM Line Monitors

In PCM transmission systems, ensuring repeater timing and regenerative capabilities requires monitored enforcement of the ones density of the line waveform. One possible corrective monitor action is to pre-empt information bits and insert ones when necessary, and thus introduce errors into the pulse stream. The analysis of the resultant error rates for classes of digital and analog implementations of a PCM monitor is accomplished via theoretical consideration of certain stationary Markov processes.