Nelu Blaž

Characterization and modelling of miniature ferrite transformer for high frequency applications

Purpose – Significant achievements in ferrite material processing enable developments of many ferrite devices with a wide range of power levels and working frequencies, which make demands for new characterization and modelling methods for ferrite materials and components. The purpose of this paper is to introduce a modelling and measurement procedure, which can be used for the characterization of two‐port ferrite components in high frequency range.Design/methodology/approach – This paper presents a commercially available ferrite component (transformer) modelling and determination of its electrical parameters using in‐house developed software. The components are measured and characterized using a vector network analyzer E5071B and adaptation test fixture on PCB board. The parameters of electrical equivalent circuit of the ferrite transformer parameters are compared with values extracted out of measured scattering parameters.Findings – A good agreement between modelled and extracted electrical parameters of...

Embedded Ferrite LTCC Inductors

This paper presents for the first time one realization of simple planar inductor realized inside the stack of ferrite LTCC (Low Temperature Co-fired Ceramic) tapes. Presented inductor is one layer square spiral fabricated in the LTCC technology. In order to point out benefits of implementation of ferrite material on inductor inductance, the same inductor geometry was fabricated between two dielectric LTCC tapes. Commercially available LTCC material (both ferrite and dielectric) were implemented for the realization of proposed inductors. Designed structures were characterized and obtained experimental results show that even implementation of a very thin layer of ferrite material around inductor lines drastically increases its inductance. For the same inductor design that occupies the same chip area the inductance enhancement over 11 times is achieved. In addition this enhancement is followed with maintenance of good performance of the inductor.

Influence of substrate thickness on performance of LTCC micro-transformer

This paper presents one aspect of research regarding various possibilities for performance improvement of integrated passive components. The paper deals with influence of substrate thickness on properties of spiral micro-transformer fabricated in LTCC technology. Designed geometry represents an interleaved spiral transformer printed on the top of one LTCC dielectric tape embedded in seven separate substrates that incorporate one to seven bottom tape layers. Obtained results of experimental characterization show trend of transformer performance improvement with increase of substrate bottom layers of transformer module. Inductance, Q-factor and coupling coefficient of transformer windings exhibit more than double enhancement of their values, while mutual inductance increases almost four times, in the lower RF frequency range. However, after certain limit increase of substrate thickness does not contributte much to transformers performance. This implies that optimal substrate thickness can be determined in order to obtain the best properties of micro-transformers.

Capacitance Dependence of Interdigital Capacitor on Amount and Type of Applied Liquid

In this paper design and fabrication of three types of interdigital capacitors are discussed, as well as influence of the liquid amount on their capacitance, and possibility of liquid type determination by using the fabricated structures. For faster and more reliable determination of capacitance in dependence of capacitor dimension and used substrate, a software tool called INDICON was developed. Capacitance of three structures fabricated in conventional PCB technology was determined by measuring S-parameters. Measurements were also performed by adding the exact amount of liquids on the capacitor surface. In addition, capacitance value in dependence of liquid amount is presented and possibility of applying this structure for detection of liquid amount is analyzed. Also, capacitance value in dependence of used liquid types was shown. For all measured and calculated values good agreement is achieved.

Characterization of LTCC Tapes in Water Presence

A large number of research have been realized related to investigation of properties of Low Temperature Co-Fired Ceramic (LTCC) materials, such as influence of geometrical parameters, mechanical, electrical, thermal properties, etc. It is well known that ceramic is considered for a material which is impenetrable for water and because of that LTCC is desired for applications in harsh operating environments, such as water. This paper is dealing with investigation regarding the behavior of the LTCC material in water presence. In order to investigate that, an interdigital capacitor (IDC) was embedded between four, six and eight LTCC tapes, positioning IDC always in the middle of the entire structure. Investigation was conducted on two types of LTCC tapes, Heraeus AHT 01-005 and Heraeus AHT 08-047. Influence of the number of substrate layers on overall capacitance of IDC has also been analyzed. Value of capacitance obtained from software was compared with measured capacitance value of fabricated IDC and good agreement was obtained. Appearance of the fabricated structures is shown and measurement results are given.

Wide Frequency Characterization of Magnetic Properties of Commercial LTCC Ferrite Material

Complex magnetic permeability and hysteresis characteristic are key parameters that determine properties of ferrite components. This paper offers effective, accurate and simple method for complex permeability determination of LTCC (Low Temperature Co-fired Ceramic) ferrite sample at wide frequency range (up to 1 GHz). Presented research can be found to be of importance in fields of ferrite components design and application, as well as RF and microwave engineering. The characterization sample is a stack of LTCC tapes forming a toroidal shape structure. Commercially available ferrite tape ESL 40012 was used and standard LTCC processing applied for the sample fabrication. Permeability is determined in the frequency range from 10 kHz to 1 GHz and characterization procedure is divided in two segments - for low and high frequencies. Low frequency measurements (from 10 kHz to 1000 kHz) are performed using LCZ meter and discrete turns of wire, while a short coaxial sample holder and Vector Network Analyzer were u...

Capacitance variation of inkjet printed interdigital capacitor by structure bending

This paper presents the capacitance change of interdigital capacitor (IDC) by bending test structure (substrate with capacitor). Interdigital capacitor is fabricated in inkjet printing technology with nanoparticle silver ink on a flexible polyimide foil. First set of tests were done by bending printed interdigital capacitor around axis that is parallel to the capacitors electrodes and around axis that is normal to the capacitors electrodes. Capacitances were measured by impedance analyzer HP 4194A and it was concluded that there is a decrease in capacitance value. Second test of capacitance measurement was done for multiple repeatedly-structure bending (up to one thousand time) and results are presented and analyzed.

Design and modelling of two-layer inductor on PCB substrate

This paper presents design and simulation of two-layer inductor on PCB substrate. Three two-layer spiral inductors were measured in the air and sandwiched between two ferrite plates, with an Impedance Analyzer HP 4191A in the frequency range up to 100 MHz. The measured results are compared with simulated, obtained with in-house developed simulation tool based on partial inductance method.

Measurement of capacitive sensor with Arduino

This paper presents a measurement system with capacitive sensor connected to an open-source electronic platform Arduino Uno. A simple code was modified in the project, which ensures that the platform works as interface for the sensor. The code can be modified and upgraded at any time to fulfill other specific applications. The simulations were carried out in the platforms own environment and the collected data are represented in graphical form. Accuracy of developed measurement platform is 0.1 pF.

Fluidic Sensor Realized in the LTCC Technology

This paper proposes a fully embedded LTCC (Low Temperature Co-fired Technology) fluidic sensor based on capacitive effect. The proposed capacitive fluidic sensor is built up by ten laser machined ceramic tape layers carrying holes and a micro-channel. The micro-channel is placed between capacitor electrodes which are screen printed and embedded inside the substrate. The operating principle of this sensor is based on the measurement of capacitance variations evoked with different permittivity values of induced fluids. By inserting various fluids in the micro-channel, capacitance of the sensor changes according to different permittivity values. Detection of various fluids has been performed. Experimentally attained results are compared with electrical characteristics determined by analytical calculations and good agreement is achieved.