Martin Dadić

• Professor
• Full professor at University of Zagreb Faculty of Electrical Engineering and Computing

Low-frequency working standards of inductance are generally uniformly wound toroids on a ceramic core. Planar inductors made using printed circuit board (PCB) technology are simple and cheap to manufacture in comparison to inductors wound on toroid cores, but they are significantly prone to the influence of external magnetic fields. In this paper,...

This paper proposes a novel design of shielded two-turn near-field probe with focus on high sensitivity and high electric field suppression. A comparison of different two-turn loop topologies and their influence on the probe sensitivity in the frequency range up to 3 GHz is presented. Furthermore, a comparison between a single loop probe and a two-...

This paper presents a method for Finite-Impulse-Response (FIR) modeling of voltage instrument transformers. The method is based on Wiener filtering and measurement of the transformer response in the frequency domain using a low frequency network analyzer. The proposed method allows, through digital filtering operation, an accurate simulation of the...

The purpose of this paper is to give a review of ac-dc characterization of the current shunts and application of the current shunt (nominal current 1A) within the digital sampling wattmeter. It is described the ac-dc transfer difference measurement of six cage type ac shunts from 10 mA up to 10 A using step-up measurement procedure. Furthermore, th...

A time constant standard, developed for the phase angle measurement of precision current shunts is developed and described, and its time constant has been determined. Based on a single circular loop placed in an air thermostat, its construction is very simple and it gives accurate results in the frequency band of interest, e.g. for frequencies betw...

The paper presents a method for digital compensation of the ratio and phase angle errors of a resistive voltage divider. The system consists of a separate electrical circuit of a resistive divider, and a digital compensation system based on National Instruments (NI) PCI eXtension for Instrumentation (PXI) PXI-5922 digital acquisition cards (DAQ). A...

The levitating ring experiment is presented as a method for teaching magneto-thermal interactions. The complete electromagnetic model of a problem is given, together with the insight in thermal analysis. The factors for determining the vertical displacements are explained, and an elegant method for indirect measurement of induced current in the rin...

The paper presents an accurate and simple method for the approximation of the nonlinear B-H curves using expansion into complex exponential series. The least-squares fit of the model is obtained by the application of the Moore-Penrose pseudoinverse. Due to the completeness of the orthogonal basis of the approximation, any desired accuracy can be ac...

The paper presents a resistive voltage divider (RVD), developed for power measurements at much higher frequencies than the traditional 50 Hz. The design of the RVD and the methods of its evaluation are described. The RVD is intended to be used in a digital sampling wattmeter application based on National Instruments PXI-4461 Dynamic Signal Analyzer...

This paper presents the extended results and prototype of the adiabatic copper conductor constructed with two interruption points in the external conductor layer, for use as a microcalorimeter power standard in wireless communication for a smart grid frequency range. Gaps are intended to drive down the thermal transfer from the outer environment in...

This paper compares different measuring equipment, especially sampling devices used in sampling power measuring standards. Several most frequently used digitizers are compared: HP3458A, NI 5922 and NI 4461. To calculate electric power following parameters are relevant: voltage amplitude, current amplitude and phase difference between voltage and cu...

The paper describes the DC characterization of AC current shunts recently developed at the Faculty of electrical engineering and computing, University of Zagreb (UNIZG-FER). The shunts of cage type design include nine shunts that range from 1 mA up to 10 A. The following DC properties were inspected: long time drift, temperature coefficients and po...

An efficient system for the compensation of current transformers over a wide frequency range is presented. The proposed technique is based on digital signal processing and inverse modeling using the frequency domain approach and Wiener filtering. Since the proposed technique applies finite impulse response filtering, the compensation filter is abso...

Due to the real-valued character of the measured impulse response, we propose the real discrete Fourier transform (RDFT) as a natural choice for time gating and removing reflections in antenna measurements. A computer program that applies the proposed algorithm was written. The program has a user-friendly graphical user interface (GUI) that allows...

The complete electromagnetic-mechanical-thermal modeling approach is demonstrated on the Thomson’s levitating ring experiment. This problem, but with a different set of parameters, was also described by Laithwaite and defined by Freeman and Lowther as TEAM17 problem. This paper presents its most complete solution. The factors for determining the ve...

Modern fluxmeter operation is based on electronic integration. A system consisting of an induction coil and an integrator can be used to measure incremental changes in the flux linkages associated with the induction coil. A rigorous proof is presented that the inductance and self-capacitance of the induction coil, as well as the parasitics of the l...

Measurement of the anechoic transfer function of electroacoustic systems, such as loudspeakers and ultrasound hydrophone probes, is a very important issue. The usual frequency-domain solutions for measurement of direct and early sound anechoic spectra in a normally reverberant environment are Heyser's time-delay spectrometry, and time-gating freque...

The increased interest in vacuum tube audio amplifiers led to an increased interest in mathematical modelling of such kind of amplifiers. The main purpose of this paper is to develop a novel global numerical approach in calculation of the harmonic distortion (HD) and intermodulation distortion (IM) of vacuum-triode audio amplifiers, suitable for ap...

This paper presents a quasi-Monte Carlo method for calculating the mutual inductance of misaligned circular coils which can be useful in the areas of designing and producing the devices based on the mutual inductance (biomedical applications, sensor modelling, wireless battery chargers, etc.). Validation of the method is presented through the examp...

The increase of the load in modern turbogenerators causes higher local heating, higher magnetic leakage, increased forces of the electromagnetic origin and the increased acoustic noise level. Stator damper winding is an active cage-shaped constructive element positioned at the outer stator core diameter. Presented numerical calculations show that t...

Modern electronics found in various measuring equipment is sensitive to the effect of transient over-voltages. This paper treats the measurement procedure for the estimation of Finite Impulse Response (FIR) models of voltage instrument transformers, dedicated for the study of fast electromagnetic transients, with the special concern to its influenc...

The increase of the load in specific active parts of modern turbogenerators causes higher local heating, higher magnetic leakage, increased forces of the electromagnetic origin and the increased acoustic noise level. Stator damper winding is an active cage-shaped constructive element positioned at the outer stator core diameter. Its influence has b...

The purpose of this paper is to present a novel approach in time-domain simulations based on the time-stepping finite element method (FEM). The method uses a single time-stepping FEM simulation to determine the unit step response of the system. On the basis of this response, a digital filter with transfer function equal to that of the target system...

The paper describes a technique for analyzing antenna measurements and removing reflected components present in measurements performed in echoic environments. The method is based on digital signal processing methods, and frequency-domain measurements are used to design a discrete-time, finite impulse response digital filter using least-squares meth...

The purpose of this paper is to review demands and possible application of digital linear filtering and equalization techniques in audio engineering, especially in digital audio mixing consoles. In high-pass and low-pass filtering Butterworth filters are preferred. As shelving filters and mid-range equalizers Regalia-Mitra filters of first and seco...

Linear phase response and flat magnitude response are highly desirable characteristics of any filter in audio signal processing. This paper proposes a simple and efficient novel procedure for the design of finite impulse response (FIR) maximally flat filters with linear phase. The procedure is based on Butterworth polynomials, bilinear transformati...

The purpose of this article is to present a novel approach in the modelling of pulsed eddy-current systems. Frequency-domain finite element analysis is used to build up a z-domain, finite impulse response (FIR) model. The FIR model allows excitation to be varied without need for the field analysis to be performed again. Furthermore, the proposed ap...

The main goal of this paper was the equalization of an inexpensive PC audio card and the application of a PC computer as a storage device for the sound pressure and vibration measurements. Since magnitude response of the audio card is not flat in the desired frequency band, a finite impulse response (FIR) digital filter was designed and implemented...

This paper deals with the application of the Hilbert transform in acoustical measurements. Determination of a reflecting surface and computation of the energy-time curve is explained.

Lumbar puncture was performed in 195 children and the depth of needle was recorded. Our results show that the depth of lumbar puncture necessary to obtain uncontaminated cerebrospinal fluid correlates best with the child's weight. The simple formula: mean depth of insertion (cm) = 1.3 + 0.07 x body weight (kg), can be used to estimate the depth of...

The measurement of mutual coupling between stacked patch antennas was performed in presence of distant reflections. Time domain analysis and processing were used for canceling out reflection influence on the measurements. Thus, actual values of measured mutual coupling parameter are obtained. These measurements were used for verification of theoret...

Discrete-time analysis and modeling of resonant and reverberant systems has many applications in acoustics. Although autoregressive moving average modeling, which yields a pole-zero filter has a lot of modeling power, Prony's and Steiglitz-McBride estimation methods can result in an unstable model, even for stable target systems. On the other hand,...

Nonuniform deflection of a pressure condenser microphone membrane causes nonlinearities of a relationship between peak deflection of the membrane and the induced voltage. This paper describes how the numerical analysis carried out with the finite element method can help in more accurate determination of this nonlinearity. The dependence of the inve...

Nonuniform deflection of pressure condenser microphone membrane causes nonlinearities between peak deflection of membrane and induced voltage. The microphone's capacitance was determined for the first time with finite element method. The dependence of capacitance and inverse capacitance dependence on deflection is fitted by a polynomial. These data...

Ghosts are time delayed, attenuated and distorted versions of the intended television signal. This paper treats the influence of the channel transfer function on performance of an adaptive inverse modeling method, namely the least mean squares (LMS) algorithm. The zeros in the channel transfer function correspond to poles in the inverse model. With...

After reviewing the development of active noise control principles, we analyzed the elements of the active noise control system in ducts. On the basis of this analysis, we created a model of these elements. Especially, we brought a model of the loudspeaker in the z-domain, suitable for description of systems containing analog and digital parts. Suc...