By Topic

Circuits and Systems I: Fundamental Theory and Applications, IEEE Transactions on

Issue 10 • Date Oct 1996

Filter Results

Displaying Results 1 - 12 of 12
  • Small-signal modeling for microwave FET linear circuits based on a genetic algorithm

    Page(s): 839 - 847
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (932 KB)  

    In this paper we present a new method to efficiently optimize small-signal equivalent circuits for microwave and millimeter-wave FET linear circuit design. The method couples the stochastic search of a Partially Elitistic Genetic Algorithm with a local search procedure. Up to 19 equivalent circuit elements have been included in the small-signal model for completeness and flexibility. Optimization examples are given for an ion-implanted MESFET up to 12 GHz, a pseudomorphic HEMT up to 50 GHz, and for synthetic data. The results show that the proposed algorithm is able to consistently provide an excellent fit between measured and calculated S-parameters without any need of a careful initial guess for the circuit element values. Also, once the device parasitics have been de-embedded, the algorithm is able to extract unique, physically meaningful values for the intrinsic device parameters, and it is numerically shown not to be affected by measurement uncertainties View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Stability analysis of discrete-time singularly perturbed systems

    Page(s): 848 - 850
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (272 KB)  

    Stability results for discrete-time singularly perturbed systems are obtained under less severe assumptions than in previous work. Exact upper bounds on the singular perturbation parameter ensuring system stability are obtained in the course of the analysis View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Model conversion of continuous-time uncertain systems via the interval geometric-series method

    Page(s): 851 - 854
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (360 KB)  

    This brief presents an interval geometric-series approximation method to convert a continuous-time uncertain system to an equivalent discrete-time uncertain model. The system matrices characterizing the state-space representation of the original uncertain systems are assumed to be interval matrices. The exponential matrix-valued function with an interval system matrix is approximated by a rational interval matrix-valued function using the geometric-series approximation method. Then, the desired enclosing interval approximant is obtained by adding an error interval matrix, which accounts for the approximation error, to the rational interval approximant. The model thus constructed is guaranteed to enclose the precise original interval model. The proposed enclosing digital interval model provides less conservative results than the existing Pade enclosing digital interval model. The newly developed digital interval model can be utilized for analysis and design of continuous-time uncertain systems View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Predicting chaos through an harmonic balance technique: an application to the time-delayed Chua's circuit

    Page(s): 872 - 874
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (272 KB)  

    The time-delayed Chua's circuit (TDCC) can be considered as a paradigm for studying chaos in circuits described by difference-differential equations. The dynamics of such circuits cannot be investigated by means of the standard time-domain techniques developed for finite dimensional systems. We show that through a spectral approach the occurrence of periodic limit cycles and of chaotic attractors can be easily predicted, without performing any simulations View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Output control of the line type pulse modulator by a duration of “on” state of an additional switch tube

    Page(s): 858 - 862
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (384 KB)  

    A technique is presented that enables rapid control of the output peak voltage of the line-type pulse modulator by changing the pulsewidth of the gate voltage applied to an additional switch tube in parallel with the thyratron. The current and voltage characteristics of the pulse modulator with an additional switch tube are analyzed to establish design rules. It is shown by a numerical example that output pulse voltages of a modulator with 5 kV DC source can be changed from 5 kV to 15 kV during 1 ms by changing the gate pulsewidth from 0 to 0.693 ms. This technique can be applied to the amplitude modulation or the rapid regulation of output pulses of radars and similar equipment View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Experimental Poincare maps from the twist-and-flip circuit

    Page(s): 874 - 879
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1332 KB)  

    We present a physical implementation of the twist-and-flip circuit containing a nonlinear gyrator. Many phase portraits and their associated Poincare maps are observed experimentally from this circuit and presented in this paper View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Full text access may be available. Click article title to sign in or learn about subscription options.
  • Synchronization of Chua's circuits with time-varying channels and parameters

    Page(s): 862 - 868
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (760 KB)  

    We study the use of adaptive controllers to maintain the synchronization of two Chua's circuits with time-varying channel and time-varying parameters. Both simulation results and experimental results are provided to verify the operation of the designs View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Synchronization of chaotic optical dynamical systems through 700 m of single mode fiber

    Page(s): 869 - 872
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (328 KB)  

    We introduce a limiting case of a nonlinear dynamical optical system one of which we have shown in previous publications the possibility of self-synchronization. A static synchronization scheme permits us to prove the synchronization and to realize a very simple setup. A chaos switching modulation scheme is proposed. Experimental results on synchronization are presented and discussed View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The global stability of fuzzy cellular neural network

    Page(s): 880 - 883
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (200 KB)  

    In this letter, the global stability of fuzzy cellular neural network (FCNN) is proposed. First, we prove a FCNN has at least one equilibrium point. Then, we gives conditions under which a FCNN has only one globally stable equilibrium point View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Application of simplified line searches in the design of adaptive envelope-constrained filters

    Page(s): 854 - 857
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (408 KB)  

    Envelope-constrained (EC) filtering is to design a finite impulse response filter such that the output of the filter is guaranteed to lie within a prescribed output pulse mask with respect to a given input pulse. The standard unconstrained least mean squares (LMS) or recursive least squares (RLS) algorithms are not applicable to this kind of adaptive filtering problem coupled with inequality constraints. New types of recursive algorithms were proposed recently for designing an adaptive EC filter, and the corresponding convergence properties were established. In this paper, it is shown that faster convergence can be achieved by incorporating a simplified line search into the developed recursive algorithms. The modified recursive algorithms are very efficient, and very simple to implement View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Multiparameter homotopy methods for finding DC operating points of nonlinear circuits

    Page(s): 824 - 838
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1596 KB)  

    This paper introduces multiparameter homotopy methods for finding dc operating points. The question of whether adding extra real or complex parameters to a single-parameter homotopy function can lead to improved solution paths is investigated. It is shown that no number of added real parameters can lead to local fold avoidance, but that generic folds may be efficiently avoided by complexifying the homotopy parameter and tracing a closed curve in complex parameter space around the critical fold value. A combination of real 2-parameter homotopy and complex parameter homotopy is shown to be sufficient for avoiding real fork bifurcations and enumerating all real, locally connected branches. Additionally, the potential of complex parameter homotopy methods for finding all circuit solutions is explored. Results from algebraic geometry indicate that if an analytic homotopy function with a single complex parameter is irreducible, then there exist regular paths through the complex parameter plane connecting any solution of H(x,λ')=0 to any other solution of H(x,λ')=0. Thus, in principle at least, complex parameter homotopy can be used to find all circuit solutions View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.