Josef Bajer

Realization of electronically tunable voltage-mode/current-mode quadrature sinusoidal oscillator using ZC-CG-CDBA

This paper presents a first of its kind canonic realization of active RC (ARC) sinusoidal oscillator with non-interactive/independent tuning laws, which simultaneously provides buffered quadrature voltage outputs and explicit quadrature current outputs. The proposed circuit is created using a new active building block, namely the Z-copy controlled-gain current differencing buffered amplifier (ZC-CG-CDBA). The circuit uses three resistors and two grounded capacitors, and provides independent/non-interactive control of the condition of oscillation (CO) and the frequency of oscillation (FO) by means of different resistors. Other advantageous features of the circuit are the inherent electronic tunability of the FO via controlling current gains of the active elements and the suitability to be employed as a low-frequency oscillator. A non-ideal analysis of the circuit is carried out and experimental results verifying the workability of the proposed circuit are included.

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 for transforming nonlinear resistor into memristor

A method of analogue emulation of the memristor with its prescribed charge (q<inf>M</inf>) - flux (ϕ<inf>M</inf>) constitutive relation is presented. The memristor is emulated via a resistor with nonlinear current (i<inf>R</inf>) - voltage (v<inf>R</inf>) relationship, and a mutator. The purpose of the mutator is to provide a similarity transformation of the current-voltage characteristic of the resistor into the constitutive relation of the memristor according to the equations q<inf>M</inf>=k<inf>y</inf>i<inf>R</inf>, ϕ<inf>M</inf> =k<inf>x</inf>v<inf>R</inf>, or ϕ<inf>M</inf>=k<inf>y</inf>i<inf>R</inf>, q<inf>M</inf>=k<inf>x</inf>v<inf>R</inf>, where k<inf>x</inf>, k<inf>y</inf> are real numbers fulfilling the condition k<inf>x</inf>k<inf>y</inf>>0. It is shown that there are eight versions of these mutators. One of them is selected for experimental verification.

Single-input multi-output resistorless current-mode biquad

A universal current-mode 2nd-order filter employing two ZC-CITA (Z-Copy Current Inverter Transconductance Amplifier) active elements and two grounded capacitors is proposed. The filter has one low-impedance current input and several high-impedance current outputs which are easy to combine to yield all basic types of transfer functions. The active element is implemented on the basis of commercial integrated circuits. The filter is manufactured and the results measured are compared with theoretical responses.

Voltage-mode electronically tunable all-pass filter employing CCCII+, One capacitor and differential-input voltage buffer

The paper introduces a novel voltage-mode firstorder electronically tunable resistorless all-pass filter employing current-controlled-second-generation current conveyor, differential-input voltage buffer, and one grounded capacitor. The workability of the proposed configuration is verified via the filter implementation from commercial components.

A new building block for analog signal processing: current follower/inverter buffered transconductance amplifier

A new active element for analog signal processing is proposed, namely the Current Follower/Inverter Buffered Transconductance Amplifier (CFBTA, CIBTA). This multiterminal device is a synthesis of the well-known Current Differencing Buffered Amplifier (CDBA) and Current Differencing Transconductance Amplifier (CDTA). The common input stage of these amplifiers, the Current Differencing Unit (CDU), is replaced by a simpler current follower or inverter. Computer simulations and experiments based on commercially available integrated circuits demonstrate the usefulness of these elements for analog signalprocessing filters.

Low-distortion current-mode quadrature oscillator for low-voltage low-power applications with non-linear non-inertial automatic gain control

The paper introduces a novel sinusoidal quadrature oscillator (QO) with low harmonic distortion. The oscillator utilizes the non-linear non-inertial principle for amplitude stabilization and thus a fast transition to 0 steady state oscillations should be accomplished. This feature makes the QO suitable for operation at very low frequencies. The oscillator operates in the current-mode and is is intended for low-voltage low-power applications. It employs only three active elements, Z-Copy Current Inverter/Follower Transconductance Amplifiers (ZC-CITA/ CFTA), one of which provides automatic gain control (AGC). The proposed principle was experimentally verified.

Differential-input buffered and transconductance amplifier-based all-pass filter and its application in quadrature oscillator

The paper deals with a novel all-pass filter circuit employing Differential-input Buffered and Transconductance Amplifier (DBTA), two grounded resistors and two grounded capacitors. The proposed all-pass filter functionality is demonstrated on its application in quadrature oscillator, which provides a couple of both voltage and current output signals shifted in phase by 90° and equal in amplitude. The frequency of oscillation can be set independently on the oscillation condition. Theoretical behavior of the all-pass filter as well as the whole quadrature oscillator have been verified using PSpice simulation.

Software defined radio based receiver for TDOA positioning system

The paper is aimed at the determination and verification of system parameters, that can be achieved with the utilization of commonly available RTL-SDR software defined receiver in TDOA based system intended for position determination of the small-UAS. The paper describes a way of performing practical experiments, measurement setup and properties of the signal used. Experimental results lead to the specification of potentially achievable accuracy and resolution of time difference of arrival measurement.

Immunity testing in an airborne radio-communication system

The paper discusses immunity of an airborne radio communication system against low and high power interfering signals of power electronics. Modern avionics power switching power power electronics can provide undesireable responses which requires immunity testing of the radio receiver. The paper focuses on interferences which occur in the chain of intermediate frequency processing and the effects which compromise the radio immunity. Interferences are measured as triggered by both strong and weak signals. All analyses and methodologies are in accordance with recommendations and standards valid for communication systems in VHF band (118 MHz - 137 MHz). Results are presented for a fully certified airborne radio communication system.