Notch Transfer Functions Research Articles

Fast‐converging robust PR‐P controller designed by using symmetrical pole placement method for current control of interleaved buck converter‐based PV emulator

AbstractIn this study, the interleaved buck converter‐based photovoltaic (PV) emulator current control is presented. A proportional‐resonant‐proportional (PR‐P) controller is designed to resolve the drawbacks of conventional PI controllers in terms of phase management, which means balancing currents evenly between active phases to avoid thermally stressing and provide optimal ripple cancelation in the presence of parameter uncertainties. The resonant path of the controller (PR) with a constant proportional unity gain is designed considering the changing dynamics of a notch filter by pole placement method (adding mutually complementary poles to the notch transfer function) at PWM switching frequency. The proportional gain path (P) of the controller is used to determine the compatibility of the controller with parameter uncertainty of the phases and designed by utilizing loop‐shaping method. The proposed controller shows superior performance in terms of 10 times faster‐converging transient response, zero steady‐state error with significant reduction in current ripple. Equal load sharing that constitutes the primary concern in multiphase converters is achieved with the proposed controller. Implementing of robust control theory involving comprehensive time and frequency domain analysis reveals 13% improvement in the robust stability margin and 12‐degree bigger phase toleration with the PR‐P controller. In addition to these, the proposed unconventional design process of the controller reduces the computational complexity and provides cost‐effectiveness and simple implementation. Moreover, implementing of auxiliary resistor‐capacitor (RC) circuits parallel with the inductors to sense the current in each phase removes the need for current measurement sensors that contribute to overall cost of the system.

Universal filter using a ‘pseudo’ gyrator

A filter based on a ‘pseudo’ gyrator that simultaneously makes a low-pass, band-pass and notch transfer function is presented. By adding another amplifier, this circuit can also make a high-pass and an all-pass filter. Two prototypes using usual op. amp. or current feed-back operational amplifiers (CFOAs) are proposed. SPICE simulations and measurements on prototypes confirm the validity of the theoretical analysis.

Universal two-input two-output current-mode active biquad using FTFNs

A universal active biquad using the four-terminal floating nullors (FTFNs) is presented. The proposed circuit uses two FTFNs, two capacitors and two resistors. The proposed circuit has two input currents and can provide two highimpedance output currents. Without changing the circuit topology, the output currents can realize lowpass, highpass, bandpass, and allpass transfer functions. A notch transfer function can be obtained by adding a voltage-to-current converter using an additional FTFN. The proposed circuit enjoys low passive sensitivities and orthogonal tuning of the parameters ωo and ωo/Qo.

Active-RC all-pass and notch filters using a single current conveyor

Two generalised circuit configurations for realising second-order all-pass and notch filters using a single current conveyor (CC II) are proposed. The circuits offer high input impedances, which permit the use of circuits in cascade without requiring any impedance matching device. The active sensitivities of Q and ω 0 for all-pass and notch transfer functions are low. By tuning a resistor, the networks can also realise notch filters. As an example, an all-pass filter is given with an experimental result.

Synthesis of active RC-filters using a single differential-input operational amplifier

In the paper is considered a general structure of active filter with one differential operational amplifier, which can realize any given transfer function. From this structure are obtained two networks, realizing all-pass or notch transfer function.

Further results in the noise-loading analysis of a memoryless nonlinearity characterized by a Taylor series of finite order

See also ibid., vol.IM-22, p.246-9 (1973). Provides an explicit expression for the noise power ratio (NPR) of the memoryless nonlinearity. This expression generalizes previously available results by allowing: wide-band signals; nonflat frequency-spectrum inputs; and nonrectangular notches. The NPR is expressed as a function of the `unnotched' input spectrum and the notch transfer function. Examples are presented to compare the theory with measurements.