Abstruct-A new method is proposed for dominant polezero (or pole-residue) analysis of large linear microwave circuits containing both lumped and distributed elements. The method is based on a multipoint Pad6 approximation. It finds a reducedorder rational s-domain transfer function using a data set obtained by solving the circuit at only a few frequency points. We propose two techniques in order to obtain the coefficients of the transfer function from the data set. The proposed method provides a more efficient computation of both transient and frequency domain responses than conventional simulators and more accurate results than the techniques based on single-point PadC approximation such as asymptotic waveform evaluation.

Abstract-A new method is proposed for dominant polezero analysis of large linear circuits containing both lumped and distributed elements. This method is based on a multipoint Pad6 approximation. It finds a reduced order s-domain transfer function using a data set obtained by solving the circuit at only a few frequency points. The proposed method yields more accurate computation of transient and frequency responses with respect to the AWE-type techniques.

of time varying linear systems," IEEE Trans. Automat. Contr., vol. 33, pp. 150-155, 1988. B. E. Ydstie, "Stability of discrete model reference control revisited," Syst. Contr. Lett., vol. 13, pp. 429438, 1989. -, "Stability of the direct self-tuning regulator," in Foundations of Adaptive Control, P. V. Kokotovic, Ed., 1991, pp. 201-238 [61-[81).The main objective of this paper is to link the stability robustness problem of discrete-time systems to that of continuous-time systems. We show, using two different approaches, that stability robustness of a discrete-time system can be reformulated as that of an auxiliary continuous-time system. One of these approaches makes use of Lyapunov theory and yields a sufficient condition. The second approach, which is based on the properties of Kronecker products, provides a necessary and sufficient condition at the expense of an increase in the dimensionality. This is a pleasing development, since it allows for a direct application of the known results on stability robustness bounds for continuous-time systems to discrete-time systems. The results are applied to stability analysis of interconnected systems, where the interconnections are treated as perturbations on a collection of stable subsystems. This demonstrates how a knowledge of the structure of perturbations can be exploited to obtain simple robustness bounds. PROBLEM STATEMENT Robust Stability of Discrete-Time Systems Under Parametric PerturbationsConsider a discrete-time system under additive multiparameter perturbations, which is described as Mehmet Karan, M. Erol Sezer, and Ogan Ocali Absfract-Stability robustness analysis of a system under parametric perturbations is concerned with characterizing a region in the parameter space in which the system remains stable. In this paper, two methods are presented to estimate the stability robustness region of a linear, time-invariant, discrete-time system under multiparameter additive perturbations. An inherent difficulty, which originates from the nonlinear appearance of the perturbation parameters in the inequalities defining the robustness region, is resolved by transforming the problem to stability of a higher order continuous-time system. This allows for application of the available results on stability robustness of continuous-time systems to discrete-time systems. The results are also applied to stability analysis of discrete-time interconnected systems, where the interconnections are treated as perturbations on decoupled stable subsystems.

The frequency planning of the VHF and UHF broadcasts in Turkey is described. This planning is done with the aid of computer databases and digital terrain map. The frequency offset is applied whenever applicable t o increase the channel capacity. The offset assignment is done through Simulated Annealing algorithm. The international rules and regulations concerning Turkey are also considered.

Robust adaptive sampled-data control of a class of linear systems under structured perturbations is considered. The controller is a time-varying state-feedback law having a fixed structure, containing an adjustable parameter, and operating on sampled values. The sampling period and the controller parameter are adjusted with simple adaption rules. The resulting closed-loop system is shown to be stable for a class of unknown perturbations. The same result is also shown to be applicable to decentralized control of interconnected systems