Zdeněk Kolka

Z Copy-Controlled Gain-Current Differencing Buffered Amplifier and its applications

The Z Copy-Controlled Gain-Current Differencing Buffered Amplifier (ZC-CG-CDBA) is introduced in the paper. In addition to the well-known CDBA, the input Current Differencing Unit (CDU) is modified and completed by special circuits. Analogously to the conventional CDBA, the z terminal is internally connected to the input of voltage buffer. The current gain from the difference input p, n to the output z can be controlled electronically or by an external device. In addition, an independent high-impedance output zc is available, providing difference current Ip−In. In the paper, the extension of application range of the ZC-CG-CDBA compared with the conventional CDBA is referred to. The novel circuit element is assembled from commercial integrated circuits and its principle is verified experimentally on a universal second-order filter. Copyright

Mutators simulating memcapacitors and meminductors

Whereas the memristor can be emulated via digital potentiometer controlled by a microcontroller, a similar implementation of memcapacitor and meminductor is problematic. The paper describes a synthesis of mutators which transform the emulated memristor into memcapacitor and meminductor. The transformations preserve the unambiguous constitutive relations of these elements, which are derived from the constitutive relation of the memristor. An example of the circuit configuration and the simulation results are demonstrated.

Some fingerprints of ideal memristors

Since there are many possible types of nonlinear charge-flux constitutive relations of ideal memristors, such elements can manifest various behavior, and the identification of typical memristor fingerprints from the measured data or simulator outputs can be difficult in some cases. The aim of this paper is to reveal several fingerprints of ideal memristors, which extend the repertoire of hitherto published and currently well-known memristor fingerprints. These results can be useful for a clear and fast identification of a system behavior that violates the principles of the operation of ideal memristors.

Approximate parametric fault diagnosis

The paper shows a procedure for testing large analog circuits or circuits with parasitic parameters via multi-frequency parametric fault diagnosis. To simplify and accelerate calculations the approximate symbolic analysis is used and unknown tested parameters are analyzed in separate frequency bands. Classification of unknown parameters into frequency bands is based on sensitivities. The proposed procedure is shown on parametric diagnosis of an EMI filter.

Test frequency selection for band-pass filters

The paper discusses the selection of an appropriate set of test frequencies in the multifrequency parametric fault diagnosis of band-pass filters. Selected frequencies depend on the filter quality factor Q and they are the same for all groups of testable components. The selection of single frequency and double frequencies is shown for the second-order band-pass filter in the current-mode. The method can be used either to locate faulty components or to estimate a priori unknown parasitic parameters of active circuit elements.

Variation of a classical fingerprint of ideal memristor

Gradual disappearance of hysteresis with increasing frequency of the exciting signal is considered a classical fingerprint of general memristive systems. The paper analyzes a special version of this fingerprint, when the value of the charge delivered within the half-period remains constant while the frequency of the sinusoidal current is increasing. Under these conditions, the area of the pinched hysteresis loop of the ideal memristor increases with the square of the frequency. Breaking the rules of this fingerprint indicates reliably that the element analyzed is not an ideal memristor. Copyright

Hybrid FSO/RF test link

The paper deals with the design of a test link for the characterization of a hybrid Free Space Optical/Radio-Frequency (FSO/RF) atmospheric channel. The ever-increasing demand on broadband connectivity, specifically in the Last-Mile networks, leads to the use of Free-Space optical systems in combination with RF systems above 100 GHz, which are able to reach data rates in the order of 10 Gb/s. However, both systems are strongly influenced by weather conditions. A significant increase in the link availability can be achieved by combining both technologies. An optimum design of such systems requires reliable models of atmospheric channels. The test link presented in this paper is intended for long-term monitoring of atmospheric attenuation and turbulence in the optical band at 850 nm and 1550 nm, and in the millimeter band at 122 GHz. The bandwidth of both measuring systems has been chosen narrow but sufficient for capturing all important phenomena. This results in the dynamical range of nearly 50 dB, which is not available from the RSSI signal of commercial broadband systems.

Analysis of memristors with nonlinear memristance versus state maps

Summary According to the axiomatic definition of the memristor from 1971, its properties are unambiguously determined by the memristance versus charge (or flux) map. The original model of the ‘HP memristor’ introduces this map via a linear function that represents this memristor as a variable resistor whose resistance is linearly dependent on the amount of charge flowing through. However, some analog applications require nonlinear, frequently exponential or logarithmic dependence of the resistance on an external controlling variable. The memristor with nonlinear memristance versus charge map is analyzed in the paper. The results are specified for the exponential type of this nonlinearity, which may be useful for future applications. Analytic formulae of the area of the pinched hysteresis loop of such a memristor are derived for harmonic excitation. It is also shown that the current flowing through such a memristor, which is driven by a voltage of arbitrary waveform, conforms to the Abel differential equation, and its closed-form solution is found. Copyright

Decomposed parametric form of the state model of a piecewise-linear system

The basic form of the state model of a piecewise-linear (PWL) system is modified to the so called decomposed parametric form. Such a modification has all advantages of the basic form. However, it is more suitable namely for finding the model parameters. This property provides a new possibility to verify all the attainable types of PWL functions that can be modelled by the state model and to transform the corresponding decomposed form back into the basic form. In the contribution the relations between these two forms and also some typical examples of one- and two-dimensional decomposed PWL models are introduced.<<ETX>>

Analog Emulator of Genuinely Floating Memcapacitor with Piecewise-Linear Constitutive Relation

This paper presents a method for emulating floating memcapacitors with piecewise-linear constitutive relations between time-domain integrals of voltage and charge. The emulation is based on multiple-state floating capacitor, implemented via the switched-capacitor technique. The states of internal switches are derived from the memcapacitor memory, which stores the history of the terminal voltage. The procedure is demonstrated on a two-state memcapacitor. Computer simulations are compared with measurements on the manufactured specimen.