Miloljub D. Lukovic

Comparative characteristics of thick-film integrated LC filters

The paper describes the design, fabrication and test of integrated LC filters in thick film technology. The range of filters was electrically characterized using a HP 8566B network analyzer. We present a scalable analytical model for thick film integrated LC filters that is suitable for design and circuit simulations. We also provide simple expressions for evaluating the optimum conductor thicknesses.

Micro‐flow sensor for water using NTC thick film segmented thermistors

Purpose – The purpose of this paper is to apply negative thermal coefficient (NTC) thick film segmented thermistors (TFSTs) in a micro‐flow sensor for water.Design/methodology/approach – A TFST is printed using NTC paste based on nickel manganite. The resistance of this thermistor is measured in a climatic chamber and the resulting curves are calibrated. A micro‐flow sensor is designed using a self‐heated segmented thermistor. The sensing principle is based on heat loss depending on the water flow intensity through the capillary. Water flow calibration is performed. The sensor sensitivity, inertia, and stability are analyzed.Findings – The micro‐flow sensor exhibits good stability, suitable sensitivity, and inertia for integral measurements of water flow.Practical implications – Advantages of a micro‐flow sensor using a TFST include low energy consumption, simple measuring procedure, and passive electronics.Originality/value – This paper describes initial work on a micro‐flow sensor for water using TFSTs.

Analysis of Effects of Dielectric and Material Characteristics on the Performance of Thick Film Thermistors Using Commercial Software Tools

In this paper an alternative approach to analysis of NTC thermistors based on the use of commercial electromagnetic simulator tool is presented. Structure analyzed was a thick film segmented NTC thermistor. Influence of the material characteristics of thermistor paste used on the overall thermistor performance was analyzed and simulated. Obtained simulation results were compared with experimental results and validity of the adopted approach was verified

Thick film symmetrical EMI LC cells

Thick film symmetrical LC cells with two pairs of terminations were printed on alumina using PdAg paste and crossover dielectric. Planar inductors such as meander, spiral, bispiral, and solenoid in plane were distributed over planar capacitors such as sandwich, interdigitated and segmented. Attenu‐ation and Smith charts of symmetrical EMI LC cells were measured on network analyzer in the range of 1 MHz to 3 GHz. Two or three main LC cells were joined in series to sum attenuation. The obtained results were compared mutually, at first, and than with the cubic (chip) EMI LC filters. The obtained EMI noise suppression was similar, but the filter band of thick film LC cells was much wider.

A Thermal Sensor for Water Using Self-Heated NTC Thick-Film Segmented Thermistors

A simple thermal (heat loss) sensor system was designed in a small plastic tube housing using a negative thermal coefficient (NTC) thick-film thermistor as a self-heating sensor. The voltage power supply [range constant voltage (RCV)-range constant voltage] uses the measured input water temperature to select the applied voltage in steps (up and down) in order to enable operation of the sensor at optimal sensitivity for different water temperatures. The input water temperature was measured using a “cold” NTC thick-film segmented thermistor. The measured calibration curves were modeled. Additional calculated curves were interpolated between the experimental curves in fine steps to cover each temperature of input water and can be used for determining the water volume flow rate or water velocity. The realized prototype flow meter inertia, stability, repeatability, and tolerance were measured and analyzed. The proposed intelligent RCV thermal flow meter system will include a smart power supply with range-constant-voltages (auto-range), a simple acquisition card and custom designed flow meter software.

EM Simulator Analysis of Optimal Performance Thick-Film Segmented Thermistors versus Material Characteristics Selection

In this paper, an alternative approach to the analysis of thick-film segmented negative temperature coefficient thermistors based on the use of a commercial electromagnetic simulator tool is presented. The influence of the geometrical parameters and material characteristics of the used thermistor paste on the overall thermistor performance was analyzed and simulated. A physical model for the segmented thermistors is given in brief, together with experimental data. The diffusion of electrode metal into the thermistor layer was analyzed, simulated, and estimated. Obtained simulation results were compared with experimental results, and the validity of the adopted approach was verified.

Analysis of electronic properties of pseudobrookite thick films with possible application for NO gas sensing

Two pseudobrookite (PSB) containing pastes were composed of a mixture of starting nanopowders of hematite (a-Fe2O3) and anatase (TiO2) in the molar ratios 1:1 (referred to as PSB-1) and 1:1.5 (referred to as PSB-1.5), respectively, organic vehicle and glass frit. The pastes were screen printed on alumina (Al2O3) substrates and sintered in a hybrid conveyor furnace at 850 °C/10 min in air. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis showed that the resulting thick film samples were composed of pseudobrookite (Fe2TiO5) and also excess rutile (TiO2) in the case of PSB-1.5 samples with a small grained and relatively homogenous microstructure. An electric resistivity with negative temperature coefficient (NTC) was observed. An interdigitated electrode geometry was designed and different electrode spacing (0.2 and 0.25 mm) was analyzed. The electrode structure was printed of PdAg paste. The resistivity of pseudobrookite was measured and analyzed in view of possible applications as a sensor of environmental gases with sufficiently high sensitivity at operating temperatures lower than conventional gas sensor systems.

Optimization and Application of NTC Thick Film Segmented Thermistors

NTC thermistor paste for printing thermal sensors on alumina was formed of very fine Ni0.5Cu0.2Zn1.0Mn1.3O4 thermistor powder obtained by a combined mechanical activation/thermal treatment process, organic vehicle and glass frit. Sheet resistivity was measured using an R-test matrix and it was much lower than the value determined for pure nickel manganite thermistors. The thermistor exponential coefficient was calculated from the R[ diagram measured in the temperature range-30 to +120°C in a climatic chamber. Thick film segmented thermistors with reduced dimensions (optimized construction) were printed sequentially layer by layer, dried and fired at 850°C/10 min in air. Electrodes were printed of PdAg conductive and solderable paste. The samples obtained were characterized by electrical and thermal measurements. The obtained NTC segmented thermistors with reduced dimensions were applied in a thermal sensor for water flow in the water mains. It contained a cold thermistor for measuring input water temperature and a self-heating thermistor for measuring the dependence of water current on water flow rate at a set input voltage power. Initial measurements show that the thermal sensor system requires a low input voltage power making it much easier and safer for operation.

Heterotube Mn-Zn Ferrite Bundle EMI Suppressor With Different Magnetic Coupling Configurations

Two types of heterotube ferrite bundle electromagnetic interference (EMI) suppressors were formed using Mn-Zn ferrite tubes with different inner and outer tube diameters. The suppressing principle based on magnetic coupling between the central tube and outer tubes in the bundle, e.g., primary half-turn to different short circuited secondary turns, was applied. Several different configurations, such as meander, frame, chain, cage, and short-circuited turns, were realized for both types of ferrite hetorotube bundle suppressors. They were characterized in the EMI frequency region (1-1000 MHz). The results obtained were compared mutually and with the standard half-turn wire configuration and other round core ferrite tube suppressors. Certain correlations were noticed between changes of characteristic parameter values, such as maximum of impedance Zm, frequency of maximum impedance Fm, and suppressing range Δf around Fm for all measured configurations. Possible applications as devices suitable for EMI suppressing were considered.

Analysis of a Mn–Zn Ferrite Bundle EMI Suppressor Using Different Suppressing Principles and Configurations

A novel round cable electromagnetic interference (EMI) suppressor comprising a bundle of Mn-Zn ferrite tubes was realized using different principles of suppressing, such as direct suppressing, inverting/suppressing, transform/inverting suppressing, and transform/short circuited secondary suppressing. Different primary to secondary configurations were realized for each suppressing principle and characterized in the EMI frequency region. The results obtained for different bundle configurations were compared with known commercial round cable ferrite suppressors and the initial bundle configuration made of a half turn wire through the central ferrite tube of the bundle. The results obtained for different principles and configurations were correlated in order to optimize the electromagnetic coupling between primary and secondary circuits. The values such as maximums of impedance Zm, frequency of maximum impedance Fm and suppressing range Δf around Fm calculated on 0.707 Zm were defined as the main parameters for each configuration. Certain correlations were noticed between impedance Zm and frequency Fm changes. Finally, the realized configurations were considered as devices suitable for EMI suppressing applications.