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Current radar applications require the design of high-power, differential phase shift ferrite circulators with increased bandwidth and better thermal performance. To meet these requirements, a magnetostatic/microwave/thermal method is proposed to model high-power ferrite devices. Magnetic losses are included in the model, which also has a temperature-dependent saturation magnetization and thermal conductivity. An iterative approach has been implemented which uses the power dissipated by the magnetic losses as the heat source for a thermal finite-element solver. Bias field, frequency, magnetic losses, and magnetization are used to determine the temperature profile in the ferrite for a given input power. The recommended operating region for temperature stability in high-power differential phase shift devices is deduced to be below subsidiary resonance and above low field loss.

A method to enable the implementation of a broadband HF antenna only one meter above a conducting ground plane is proposed in this paper. A bowtie antenna is placed very close (0.033λ max ) to a conducting ground. In order to allow the antenna to radiate efficiently, ferrite tiles are laid over the ground plane. However, these ferrite tiles are extremely costly. Therefore, in this paper, we propose the laying of the ferrite tiles only on regions of the ground plane where high electrical current density occurs. In this way, the number of the ferrite tiles required is significantly reduced. A v-shaped bowtie antenna above conducting ground is simulated. By laying the ferrite tiles only in regions with high current density, the amount of ferrite tiles required is reduced by 78.6%. More importantly, using this technique, the VSWR can be improved at any desired frequencies. In this paper, the ferrite tiles are used to improve the performance of the HF antenna in the range of 15 to 25MHz. The measured results are used to verify the simulation results.

The saturated ferrite is a novel material that is commonly used to create a non-reciprocal device or network, such as a circulator or isolator. For example, when two crossing microstrip traces are placed on a ferrite slab it is possible to couple electromagnetic energy from trace one to trace two in a completely different fashion than from trace two to trace one. The mechanism for quasi-static coupling has been adequately explained using lumped-element circuit techniques. A TEM wave investigation of this same coupling is explored in this presentation.

Novel measurement-based models are described for ferrite bead inductor behavior at RF and microwave frequencies. Ferrite bead components are used in various applications from electromagnetic interference suppression to reduction of undesired signals in many high frequency designs. The newly developed equivalent circuit model can accurately predict the strong impedance dependence versus bias, frequency and temperature of a surface mount chip ferrite bead. This new solution gives the designer great flexibility and excellent accuracy when such a model is used in their RF simulation designs. Measurement validation of the modeling methods are illustrated for two different commercially available surface mount ferrite bead devices demonstrating accurate predictions of impedance over bias and temperature in the DC to 6 GHz frequency range.

First, a generalized theoretical approach towards beam coupling impedances and stretched-wire measurements is introduced. Applied to a circular symmetric setup, this approach allows to compare beam and wire impedances. The conversion formulas for TEM scattering parameters from measurements to impedances are thoroughly analyzed and compared to the analytical beam impedance solution. A proof of validity for the distributed impedance formula is given. The interaction of the beam or the TEM wave with dispersive material such as ferrite is discussed. The dependence of the obtained beam impedance on the relativistic velocity β is investigated and found as material property dependent. Second, numerical simulations of wakefields and scattering parameters are compared. The applicability of scattering parameter conversion formulas for finite device length is investigated. Laboratory measurement results for a circularly symmetric test setup, i.e. a ferrite ring, are shown and compared to analytic and numeric models. The optimization of the measurement process and error reduction strategies are discussed.

International audience; This paper studies the effect of ferrite beads on the audio quality of Class-D audio amplifiers. This latter is a switch-ing circuit which creates high frequency harmonics. Generally, a filter is used at the amplifier output for the sake of electro-magnetic compatibility (EMC). So often, in integrated solutions, this filter contains ferrite beads which are magnetic components and present nonlinear behavior. Time domain measurements and their equivalence in frequency domain are presented. Total Harmonic Distortion (THD) measurements according to the audio signal frequency and amplitude are exposed and discussed. It is shown that ferrite beads introduce up to 30 dB of additional THD which prove the negative effect of the ferrite bead on the amplifier audio quality.

This paper presents a novel square microstrip patch on the hybrid substrate that includes a square an unbiased ferrite ring in the Rogers TMM4 substrate, initially at a distance of the one-quarter of the free space wavelength from the edges of patch. Using CST Microwave studio, the results of the patch antenna above a conventional substrate (i.e., Rogers TMM4 substrate without any ferrite ring) and above the hybrid substrate (Rogers TMM4 substrate with ferrite ring) are simulated and compared. The proposed microstrip path antenna resonates at the 5.8 GHz suitable for wireless local area network applications. By this substrates design there is enhancement in gain as well as bandwidth of microstrip patch antenna.

Superconductor ferrite phase shifters are attractive for phased array radar systems. The huge reduction in size and losses mean that smaller systems are possible. This paper reports a new latching structure for a superconducting ferrite phase shifter which is compact in size and has low losses. The total size of the phase shifter is 6.0 cm/spl times/3.0 cm/spl times/2.5 cm including housing. It should be pointed out that two phase shifters can be accommodated in this size. The minimum insertion loss of the designed phase shifter was measured at 0.8 dB. The phase shifter is fabricated using a Yttrium Barium Copper Oxide (YBCO) microstrip meander-line on a one centimetre square low loss sapphire substrate. We press contacted a magnetized ferrite substrate, with a silver ground plane, onto the fabricated YBCO meander-line to obtain non-reciprocal phase shifting. To magnetize the ferrite substrate without causing magnetic field penetration into the high temperature superconductor (HTS), we propose a new latching structure comprising a single ferrite layer with magnetizing coils. This new structure will confine the magnetic field within the ferrite substrate by providing a closed magnetic path. This is achieved by making a large hole at center of the ferrite substrate.

This paper presents evaluation results of conducted noise suppression effect of a ferrite film directly plated on an interposer substrate in the long-term evolution (LTE) communication band. A test board for evaluations has an IC with digital and RF circuits which is designed for investigations of electromagnetic noise coupling at the IC chip level. Firstly, we have confirmed effectiveness of a ferrite film onto an interposer in suppression of conducted noise from a digital circuit to a board by simulations. Then, we have verified that the ferrite film reduces conducted noise coupling to the RF circuit, occurring inside the board, by measurements of In-phase/Quadrature (I/Q) signals and high frequency voltages of power supply lines.

Electromagnetic shielding properties of soft magnetic metal alloy (Fe-Al-Si) flakes and Ni-Zn ferrite composites for effective suppression of broadband and high frequency noise were investigated. In the soft magnetic composites, the maxima of reflection loss were shifted to high frequency with increase in content of Ni-Zn ferrite. The composites with content of 50 and 70% ferrite exhibited broadband absorptive characteristics. The broadband character- istics might be caused by the extended resonance due to an overlap between imaginary permeability and permittivity of the two composites over the frequency range from 2 to 10 GHz.

The design of common mode chokes (CMC) for radio frequency interference filter is considered, explained and applied to the compared magnetic core characterization and computation between ferrite and nanocrystalline materials. The latter shows some better insertion losses at low frequencies when comparison is made with the same component characteristics. The volume of the component can be reduced by 50–80% when an appropriate ferrite is replaced by a well-chosen nanocrystalline core, as a result of its superimposed advantages of high and tailored permeabilitys, high saturation and inductive behavior near CMC resonance.

Magnetic losses have been measured and analyzed upon a wide range of frequencies in Mn–Zn ferrite ring cores. Exploiting the concept of loss separation and modeling the conductivity process in the heterogeneous material as a function of frequency, the role of the different energy dissipation mechanisms has been elucidated. It is shown, in particular, that eddy current effects can be appreciated, in standard materials and cores, only on approaching and overcoming the MHz range. The basic mechanism for hysteresis and low-frequency losses is therefore identified with the domain wall relaxation engendered by spin damping processes. Resonant absorption of energy associated with magnetization rotation is in turn deemed to chiefly contribute to the loss upon the practical range of frequencies going from a few 10 4 Hz to a few MHz.

Large soft ferrite torroids & slabs in various Ni-Zn compositions were developed for high frequency switching magnets (kickers) & fast rise time current monitors of 450 MeV Electron Accelerator. The electric & magnetic properties of large ferrite ring cores were obtained using a special sintering process. These magnetic properties include a high saturation flux density, high initial permeability, low coercivity, large μQf products (at B:100 mT, f = 20 MHz ) & low loss rf characteristics at high magnetic amplitudes.

An integral equation relates electric charge and magnetic flux in a delay line with nonlinear and frequency-dependent elements. Iteration can approximate a transmission line that is continuously loaded with ferrite beads, revealing subnanosecond solitons, that is, pulses that resist the effects of dispersion. Electrical solitons are a new phenomenon for picosecond communications where the goal is speed, reliability, and hard-wired security.

This study demonstrates 3-D imaging of a fault using a thin (5.4 cm diameter) directional borehole radar sonde. In order to make the thin sonde, we needed to reduce interference between the centered conducting cylinder (CCC) and the antenna elements in the coaxial-fed circular dipole array in a borehole (CFCAB). Ferrite beads were loaded on the CCC for reduction of the interference. In order to determine permeability of the ferrite cores, we did experiments to measure an input impedance of a ferrite-loaded monopole antenna. Using the determined parameter of the ferrite, we design the CFCAB. We conducted singlehole measurements with the thin sonde in an air-filled borehole. In this experiment, according to the power spectrum of a direct wave, we found that the ferrite loading decreased the resonant frequency of the CCC, widening the operating frequency bandwidth. The image constructed using the directional borehole radar agrees well with the information obtained from the boring core samples and observations in the gallery.

In this investigation, a 4 channel EMI filter array for 4G-LTE application is proposed with multilayer structure and formed by low-temperature co-fired technique. In order to miniaturize the size of the component and improve its performance, a mixed powder material is employed to design and fabricated the filter. The overall dimension of EMI filter array is 1.6 mm (L) × 0.8 mm (W) × 0.5 mm (H), the smallest one reported so far. The measured results of the developed filter are in a good agreement with the simulated results by full-wave electromagnetic simulator.

In this paper we show an application of the electromagnetic modeling in order to simulate nonlinear waveforms of power converters in a precise way. These power converters include inductors with soft ferrite cores. We show the simulated voltage and current waveforms of the ferrite inductor including the nonlinear effects of saturation and power losses in its core. We validate these results by comparison with those obtained by experiment. We present relevant results provided by the electromagnetic modeling.

This paper presents three related planar EBG (electromagnetic bandgap) structures based on embedded capacitors and inductors, which have small-footprints and can be used in package power or ground planes to provide wideband isolation among different parts of the power distribution network (PDN). Measurement shows -40dB isolation from 2-2.5GHz to over 10GHz. In order to improve performance at lower frequencies we explore the synthesis of planar EBG structures and Chip Ceramic Capacitors or Ferrite Beads.

This study demonstrates 3-D imaging of a fault using a thin (5.4 cm diameter) directional borehole radar sonde. In order to make the thin sonde, we needed to reduce interference between the centered conducting cylinder (CCC) and the antenna elements in the coaxial-fed circular dipole array in a borehole (CFCAB). Ferrite beads were loaded in the CCC for reduction of the interference. We conducted singlehole measurements with the thin sonde in an air-filled borehole. In this experiment, according to the power spectrum of a direct wave, we found that the ferrite loading decreased the resonant frequency of the CCC, widening the operating frequency bandwidth. The image constructed using the directional borehole radar agrees well with the information obtained from the boring core samples and observations in the gallery.

Summary form only given. Electromagnetic Band Gap (EBG) surfaces have been of intense interest in recent years given their ability to suppress the propagation of electromagnetic waves in a frequency band. This suppression of electromagnetic waves leads to an enhancement of the maximum gain when a microstrip patch antenna is placed above one of these surfaces. However, this comes at the expense of complexity of construction of the antennas, because many of these designs include a large number of vias. As an alternative, we are proposing a new design that uses a ferrite ring to enhance the antenna gain without compromising the antenna bandwidth. The proposed design forces constructive interference between the incident and reflected fields inside the substrate. The interference is created by introducing a ferrite ring at a distance d1 (d1 = ρ1 - a, a is the radius of the circular patch) from the circumference of the patch with a ring width d2 (d2 = ρ2 - ρ1). Initial values of d1 and d2 of one-quarter of the free-space wavelength (d1 = d2 = λ0/4) were selected. The ferrite is maintained unbiased with a relative permeability of μr2 = 14 and a relative permittivity of er2 = 10. Using HFSS, the results of the patch antenna above a conventional dielectric substrate (i.e., no ferrite ring) and above the proposed substrate (which includes the ferrite ring) were compared. The former is referred to as the conventional substrate and the latter (dielectric-ferrite) as the hybrid substrate. The design that uses the hybrid substrate achieves a maximum gain of 10.9 dB within the frequency range of 5.5 GHz to 6 GHz, with an average of 9.28 dB. On the other hand, the conventional substrate achieves a maximum of 6.37 dB in the same frequency range, and the average is only 4.4 dB. Clearly, the response of the propose hybrid substrate structure exhibits gain enhancement. Another important characteristic of microstrip patch antennas is the impedance bandwidth, which in most cases is reduced as the gain is increased. However, in the proposed configuration, it is not reduced but increased. A bandwidth of 8.62% is attained using the hybrid substrate, while only 6.7% is achieved for the conventional substrate (using S11 = -10 dB as a criterion to compute the bandwidth). Therefore, by using the new design, an enhancement of about 2% in the impedance bandwidth is achieved.

In this paper measured results are presented to show the effect of shielding slots, seems and cables interconnecting different subsystems on the radiated emissions. It is shown that by using proper shielding Radiated Emission (RE) levels can be reduced by as much as 40dB. Similarly the attenuation of at least 20 dB in measured voltage levels in the conducted emission tests can be achieved by the use of π-filters and chassis ground. In case of power unit, it has also been diagnosed that major cause of conducted emissions (CE) is the switching of DC-DC convertor. Measurements with ferrite beads showed that these are useful only at frequencies below few megahertz.

Experimental investigation of electromagnetic interference created by transport fleet management module is presented. Novel conducted interference evaluation technique has been rectified from CISPR 25 standard which was adapted to limited abilities for electromagnetic compatibility pre-compliance estimation. Several input filter topologies have been investigated aiming to evaluate the best performer. Common mode current measurement transformer has been designed and calibrated. Ferrite bead impedances have been measured in order to evaluate the suitability for DC input filtering. Common mode and differential mode conducted interference measurement results are given. Optimal filter selected. DOI: http://dx.doi.org/10.5755/j01.eee.19.4.2019

This paper presents the design comparisons of BLDC motor for the water pump for washer. Before the study, the Nd-Fe-B magnet was applied in the conventional water pump motor. This water pump BLDC motor should have waterproofing property, so the IPM rotor using Nd-Fe-B magnet is encapsulated by synthetic resin plastic. This motor's manufacturing cost was expensive by the using of Nd-Fe-B magnet and the process of plastic capsulation. We studied about the rotor design change using ferrite ring magnet to reduce material cost in the condition of the same stator core design. In the proposed water pump SPM BLDC motor using ferrite PM, the outer and inner diameter of stator is fixed to the value of the conventional IPM BLDC motor using Nd-Fe-B magnet.

Planar ferrite resonators are widely used in microwave and millimeter-wave junction circulators. Recent trends toward broadbanding and miniaturization of devices have led to interest in novel inhomogeneous structures. To simplify design procedures, a finite element package for the calculation of modal resonant frequencies in terms of a specified applied bias field and material magnetization has been developed. The frequency dependence of the ferrite tensor components is included in the analysis, and so the resulting eigenvalue problem is nonlinear. An iterative finite element scheme is used to solve this problem for resonators with arbitrary geometries, making full use of the symmetry of the modes. For the special case of homogeneous resonators of arbitrary shape the calculations may be simplified through the use of normalized parameters. To illustrate the technique and the limitations of the use of normalized parameters, a homogeneous ferrite ring resonator and an inhomogeneous dielectric-ferrite ring resonator have been analyzed. In both cases, good agreement with the exact solution is obtained. Calculations are also presented for a practical circulator geometry with threefold symmetry: a dielectric triangle inserted within a ferrite disk.

In mixed-signal systems, effective noise isolation between analog and digital circuits is required for power integrity (PI). In this paper, Ferrite absorb material layer is deposited under the power plane to absorb high frequency noise from 500 MHz to 10 GHz. High dielectric constant nano BaTiO3 is used between the power plane and the ground for large buried capacitance to filter high frequency noise. First, noise isolation for High Dielectric Constant BaTiO3 Substrate is researched. Then, noise isolation for Ferrite Absorb Material researched. Third, the above two noise isolation are combined to form the designed technique. The designed power / ground structure from top to bottom is Power plane / Ferrite / nano BaTiO3 / Ground. The noise isolation is greatly improved for the designed power / ground structure than that for FR4 substrate without ferrite absorb material layer. In the mean time, the signal integrity effect is simulated, and the designed power / ground structure causes no signal integrity problem.

The operation of a ferrite drop-in circulator is theoretically predicted and experimentally confirmed. The cavity model is applied both to the ferrite disc and the dielectric region directly below the ferrite disc. The standing-wave condition required by the dielectric cavity plus the two ferrite circulation conditions determine uniquely three design parameters for the circulator: the magnitude biasing field, the radius of the ferrite disc, and the dielectric constant of the dielectric sleeve surrounding the ferrite disc. In addition, the characteristic impedance of the microstrip feeder lines was purposely designed for 50 /spl Omega/ in order to eliminate the need for impedance transformers. We found that for a thin dielectric substrate with dielectric constant smaller than that of the ferrite, the circulation frequency can be slightly above FMR resonance. Three circulators were fabricated using design parameters calculated by our theory. The measurements are in reasonable agreement with predicted performance of the device. >

By combining a ferrite-type electromagnetic wave absorber and a lossy dielectric layer, an electromagnetic wave absorber with a super wideband characteristic can be realized. In this paper, a grid-type ferrite absorber and a rubber ferrite loaded ferrite multilayered absorber are treated as a ferrite-type absorber. When a lossy dielectric material is mounted in front of these ferrite-type wave absorbers, the thickness of a lossy dielectric layer necessary for realization of a return loss of more than 20 dB at any frequency above 30 MHz was computed. It was found that the thickness is much less than that for the lossy dielectric attached to a single layer ferrite. Further, by means of a model experiment in the coaxial tube, the thickness of the lossy dielectric layer was proven to be smaller if a lossy dielectric is combined with the grid-type ferrite absorber loaded with rubber ferrite.

Spiral-type transmission-line devices using an Mn-Zn ferrite core were developed, which consisted of a spiral winding with a polyimide dielectric and a ground plane, an Mn-Zn ferrite pot core (TDK; PC-50). The devices exhibited 20-dB attenuation in a wideband frequency range, which was not only due to the high frequency loss of the ferrite but also due to the distributed constant circuit operation. To analyze the characteristics, a distributed constant circuit model was introduced considering magnetic coupling between different turns in the spiral winding.

A NiZn ferrite film (3 μm thick) was deposited at 90 °C by the spin-spray ferrite plating from an aqueous solution onto a 50 Ω microstrip line formed on an epoxy printed circuit board (PCB). A strong magnetic loss was caused by the ferrite film in a GHz range, ΔPloss reaching 67% attenuation at 3 GHz, the upper limit of our measurement. Furthermore, the reflection loss was very weak, S11 being smaller than 7%. Thus plated NiZn ferrite films hold strong promise to be actually applied to a type of thin film electromagnetic noise suppressors; the films can be directly deposited onto noise sources (semiconductor elements or electronic circuits) to attenuate conducted-electromagnetic noises in the GHz range. Because the plated NiZn ferrite film was magnetically isotropic in film plane, the noise suppressors will be isotropic, attenuating noise electromagnetic waves radiated from any directions. The NiZn ferrite film was also plated on a flat glass substrate as a standard, which exhibited natural resonance freq...

This paper discusses a level set-based topology optimization method for the design of metallic waveguides loaded with ferrite inclusions. Ferrite materials can have frequency dependent permeability value due to the magnetic resonance phenomenon in a specific frequency range that can be altered by the magnitude of an external DC magnetic field. Thus, a rectangular waveguide loaded with periodic ferrite inserts can offer advantages in the tunability of operating frequencies and compactness. Here, the level set-based topology optimization incorporating a fictitious interface energy is used to find the configuration of ferrite materials in the waveguide that maximizes the transmission power of electromagnetic waves at prescribed frequencies. The objective function is formulated to maximize the transmission coefficient S21 at prescribed desirable frequencies. A numerical example is provided to examine the validity and utility of the presented method.

This paper compares and suppresses the conducted Electromagnetic Interference (EMI) in Silicon Carbide (SiC) JFET and IGBT based motor drive systems. Two inverter prototypes - with SiC JFETs and Si IGBTs as the transistors are built using the same circuit layout and investigated accordingly. The comparisons start from the transient level of the inverter tested under clamped inductive switching conditions by using of a single inverter leg to the system level conditions of all three phases of each of the inverter drives are functioning. The conducted EMI comparisons include with no filter and with conventional CM filters. To identify the exhibited different filtering performance with the identical filters, two inverters are tested in the CM mode. This allows for the identification and analysis of their maximized CM and DM wave shape differences. The comparisons show that the high frequency noise level of SiC JFET drive under filtered condition is much higher than that of the IGBT's. Therefore, two methods of inserting ferrite beads at different current paths are proposed to mitigate the increased EMI. Respectively, the middle and high frequency noise of SiC JFET drive system are effectively suppressed to comply with the standard of IEC61800-3: C2.

Bulk ferrite chokes are widely used to reduce common-mode (CM) currents on system harnesses. The impact of the ferrite on the CM currents depends on a variety of factors and is difficult to predict. A simple closed-form analytical model of the CM impedance of the ferrite that allows efficient evaluation of the impact of the ferrite is considered. In order to apply this model to a real active power system with cable harnesses, information about the system's CM loop impedance is measured using the minimally-invasive dual current clamp method. The predicted impact of the ferrite on the CM loop impedance of the system and the CM currents on the harness showed reasonable agreement with measurements in both a simple passive test setup and in a real active system.

An LED circuit of a cell phone is analyzed using the System-Efficient-ESD-Design (SEED) methodology [1]. The method allows simulation of the ESD current path, and the interaction mechanisms between the clamp and the on-chip ESD protection circuit. The I-V curve and the non-linear behavior under high current pulses of every component including R, L, C, and ferrite beads are measured and modeled. By combining all of the component models, a complete circuit model is built for predicting the circuit behavior and damaging threshold at a given setting-voltage of a Transmission Line Pulser (TLP).

In this paper, we will utilize ferrite beads so that the coaxial-fed circular dipole array in a borehole (CFCAB) can work below 100 MHz. The CFCAB suffers from scattered wave from the centered conducting cylinder (CCC), and this disturbs estimation of direction of arrival. The commercial ferrite beads works as resistance typically above 100 MHz, and it does not consume the electromagnetic power below the frequency. However the MoM analysis showed that the ferrites on the CCC below 100 MHz works as an inductor rather than resistance, and this makes resonance frequency of the CCC lower. This leads to extension of the operating frequencies of the CFCAB. We conducted two field experiments to verify the effect of the ferrite. In these experiments, although the CFCAB without the ferrite beads failed in DOA estimation, the CFCAB with ferrites succeeded in estimation because of the effect of the ferrites.

A nonlinear transmission line (NLTL) provides a solidstate means of generating high power, microwave pulses. The NLTLs in this study are coaxial transmission lines whose center conductor is encapsulated by ferrite beads. Operational frequency can be controlled by varying the dimensions of the ferromagnetic material, which affects azimuthal magnetic fields and material losses, or by varying the biasing field strength. This research demonstrates frequency agility of an NLTL by documenting the design, construction, and testing of three NLTLs. The NLTL will be one meter long, and to test for frequency agility, three different sizes of ferrites will be loaded onto NLTL with various biasing fields applied. Azimuthal field strengths due to an incident high voltage pulse range from 10-36 kA/m with magnetic biasing fields between 0 kA/m and 50 kA/m.

This paper proposes to use separate heat sinks to reduce the conducted electromagnetic interference (EMI) for a Silicon Carbide (SiC) JFET inverter for motor drives. The inverter circuit layout is implemented with discrete SiC JFETs attached on top of the heat sink, which creates extensive capacitive couplings and moreover increases the parasitic oscillations. To minimize the influence, the solution of using separate heat sinks is proposed. For better CM performance, the high side heat sink is grounded to avoid the fast dv/dts that occur between the drain of the lower switch and the low side heat sink. For better DM performance, the RC snubber circuit and ferrite beads are used to dampen the parasitic oscillations. Two 2.2 kW inverters prototypes - with six discrete SiC JFETs on one common heat sink and separate heat sinks respectively are built using the same circuit layout. Their EMC performance is compared under unfiltered and filtered conditions. The experiments show that the separate heat sinks inverter system exhibits a significantly reduced EMI, however still can not satisfy the imposed standard. Finally, three improved methods are proposed, which effectively suppresses the emitted EMI to comply with the standard of IEC61800-3-C2: Qp.

The passive magnetic ferrite components used in EMI filters have a complex magnetic permeability (CMP) which varies with frequency. The CMP in frequency range from 150 kHz to 30MHz is not given by manufactures. Moreover, measurement techniques require some specific size and shape of sample to measure CMP of ferrites. Common application of these passives components are EMI filters, where toroid ferrite cores need to be characterized to determine the insertion loss function. In this paper a CMP measure procedure is proposed. The leakage inductance and parasitic capacitance of an inductor are determined. Then, a rational function approximation (RTA) is applied to represent the HF equivalent impedance of CMP.

The goal of this work is to investigate the efficiency of a ferrite electromagnetic interference (EMI) suppressor when it is placed in a real surrounding. Because of that, commercially available ferrite component is tested in a simple digital circuit realized on PCB. Two configurations of digital circuits are analyzed: with and without EMI suppressor placed on a conductive line at the output of the first circuit, which is a potential “source” of the interference. The measurement is obtained by digital oscilloscope TDS 2024B in the frequency range up to 200 MHz. Measured data with and without implemented EMI suppressor are presented.

A novel ferrite grid electromagnetic wave absorber composed of sintered ferrite is proposed. Based on the condition that the return loss should be above 20 dB at 30 MHz, its wideband characteristics for suppressing reflections compared to a single-layer absorber are demonstrated by computer simulation. Calculating the return loss by varying the geometrical parameters of the ferrite grid, an optimum structure is determined which gives the maximum frequency band. In addition, it is found that the return loss of the grid absorber is impaired by an air gap between the ferrite and conductor. Moreover, the operating characteristics of the grid absorber are demonstrated by experimental models.

Low temperature co-fired ceramic (LTCC) ferrite materials are promising candidates for magnetic substrate of high frequency converters. The inductors can be fabricated into the magnetic substrate so the power density of the converter can be dramatically increased. There are three types of LTCC ferrite tape materials from ESL Electro Science®: 40010, 40011 and 40012. To utilize these materials for suitable applications, their permeability and core loss characteristics under different pre-magnetization conditions should be measured in order to estimate the inductance and core loss of the inductor in high frequency integrated converters. The measurement uses a new high frequency measurement setup, which can provide permeability and core loss density information under DC pre-magnetization condition. Finally, three LTCC ferrite materials' characteristics are compared and discussed.

A practical approach for lumped-parameter circuit modeling of SMT ferrite beads is introduced. Vector Network Analyzer (VNA) measurements are utilized to provide the frequency-dependent characteristics for SPICE analysis. The measured data is imported into the simulation environment via Analog Behavioral Models (ABM) accounting for the frequency-dependent behavior of the ferrite sheets. It demonstrates a significant departure from a simple R-L-C circuit network. Model accuracy is validated by realization of an ad hoc test-board and by experimental characterization of the component in terms of Insertion Loss.

High performance ASICs (Application-Specific Integrated Circuits) are getting dominant in modern high-end networking systems. Provisions on the power supplies for these extremely high integrated ASICs are somewhat demanding and strict especially for sensitive analog power rails. To meet the power requirements from ASIC vendors, ferrite bead is used to fulfil the analog filtering. In order to complete the filter design and analysis, a genetic algorithm is developed to extract circuit model from a ferrite bead impedance curve. The extracted circuit model is used for filter performance analysis. As a case study, the designed filter is implemented on a PCB (printed circuit board) in a real product. Measured power noise on the analog power rail confirms that the ferrite bead filter design is successful and the analog power meets the specifications from ASIC vendors.

Ferrite materials are widely used as chokes to minimize common-mode currents in antenna feeds, in the design of artificial magnetic conductors, and in the filtering of noise at radio frequencies (RF). Miniature inductors, consisting of a thinwire coil around a high-permeability soft ferrite core, find wide application in RF and microwave circuits. An understanding of the high-frequency parasitic and packaging effects, such as stray capacitance, magnetic losses, resonant characteristics, etc., useful in the design of these components, can be gained from an equivalent circuit characterization of the inductor. In this paper, we present a rigorous experimental method to fully characterize the frequency dependent RF behavior of ferrite inductors. The equivalent circuit parameters of the inductor, as well as the complex effective permeability of the core, are extracted in closed form from an accurate measurement of the RF impedance, without recourse to cumbersome optimization procedures.

The frequency range below 135kHz is preferred for inductively coupled radio frequency identification (RFID) systems. At low frequency, the magnetic field coupling between reader and transponder can be increased by using a ferrite core transponder antenna. In this paper, the magnetic field pattern of such a device is investigated. A semi-numerical procedure is presented, how to calculate the magnetic fields resulting from coil and core with avoidance of virtual boundaries. Consequently, calculations at short as well as at large distances can be conducted with high accuracy and minimum computational expense. The model is finally verified by measurements and further simulation based on finite element method (FEM).

A new methodology is presented for designing baluns exhibiting multi-decade bandwidths at microwave frequencies. Simulations show that resistors terminating the outer transmission line suppress the half-wavelength resonance and greatly extend the bandwidth. Using linear measurements at microwave frequencies, ferrite beads have been shown to behave as resistors with a small reactance, suitable for terminating the outer transmission line. This paper shows that ferrite beads can perform the dual role of improving magnetic coupling at low frequency and suppressing resonance at higher frequencies. The design methodology was applied to produce a balun that operates between 30MHz and 6GHz, displays less than 1dB of power loss up to 4.4GHz, and delivers an impedance transformation of 2∶1.