Wide-band amplitude control of the second-order oscillator circuit

In this paper, a new analysis technique of an ordinary second-order oscillator which is based on multi-time concept is proposed. This mathematical analysis results in a new closed-form solution of a system complete response. It is found that amplitude of the natural response is not constant but varied with the forced response of the system. For a constant forcing function proposed, the new analysis is identical to the conventional analysis. In the case of time-varying forcing function, however, it is different from the conventional approach. Based on such analysis, it implies that the amplitude of a second-order oscillator can easily be controlled by forced response of the system. Hence, the obtained result based on the proposed analysis technique provides a proper mathematical solution for the system, especially in a time-varying forcing function. Moreover, the mathematical analysis for the wide-band characteristic of a second-order oscillator is also described. The experimental results demonstrate the responses of the oscillator which agree well between the theoretical and simulation results.     

Linear prediction based adaptive algorithm for a complex sinusoidal frequency estimation

The complex direct frequency estimation (CDFE) adaptive algorithm is developed and proposed in this paper. The motivation of this work is obtained from the previous real DFE (RDFE) adaptive algorithm. The methodology of the CDFE is based on the linear prediction property of complex sinusoidal signals. The proposed algorithm is unbiased and computationally efficient. Moreover, it is easy to implement and appropriate for real-time applications. In addition, the convergence behavior is analyzed and the steady-state mean square error (MSE) of the frequency estimate is derived in closed form. Computer simulations are treated to corroborate the theoretical analysis.     

Simple frequency/voltage convertor with low output ripple

A frequency/voltage convertor with theoretically zero output ripple is presented. It has a simpler structure and four times faster response than an earlier system. Moreover, it may easily be modified to a switched-capacitor version, if so desired.<>     

Reliability optimization of topology communication network design using an improved ant colony optimization

Network design problem is a well-known NP-hard problem which involves the selection of a subset of possible links or a network topology in order to minimize the network cost subjected to the reliability constraint. To overcome the problem, this paper proposes a new efficiency algorithm based on the conventional ant colony optimization (ACO) to solve the communication network design when considering both economics and reliability. The proposed method is called improved ant colony optimizations (IACO) which introduces two addition techniques in order to improve the search process, i.e. neighborhood search and re-initialization process. To show its efficiency, IACO is applied to test with three different topology network systems and its results are compared with those obtained results from the conventional approaches, i.e. genetic algorithm (GA), tabu search algorithm (TSA) and ACO. Simulation results, obtained these test problems with various constraints, shown that the proposed approach is superior to the conventional algorithms both solution quality and computational time.     

Current controlled oscillator based on translinear conveyors

A current controlled oscillator based on translinear current conveyors is presented. The oscillation frequency can be varied proportionally to the bias current. The oscillator uses two CCCII's, and two grounded capacitors. SPICE simulation results agree with the theory     

A novel versatile modulator circuit

A novel versatile modulator that can operate either as a delta modulator, a sigma-delta modulator, an amplitude modulator or a frequency modulator is presented. The proposed circuit mainly composes of a few components: which are three OTAs, one capacitor and two resistors. Among these components, two OTAs and two resistor construct a Schmitt trigger network whereas the other OTA and a capacitor compose an integrator. The advantage of this circuit is that the clock (carrier) signal employed for modulation is inherent in the circuit. No external clock is needed, only the modulating signal is required for an input. With the compactness of the circuit, it is thus suitable for IC realization. The computer simulation based on CMOS technology demonstrates that the results agree well with the theoretical analysis.