Magneto-dielectric Substrate Research Articles

Various electromagnetic properties of magnetic Fe-based nanorods in GHz range

The introduction of magneto-dielectric substrates is required in the micro-strip antennas miniaturization due to the various dielectric and permeability constant. Most research work focus on the spherical structural Fe nanomaterials and the nanorods structures are rarely synthesized. In this paper, Fe-based nanorods have stepwise been synthesized with well maintaining their size and morphology by a moderate heat treatment of α-FeOOH nanorods. The magnetic and electromagnetic properties above GHz have been investigated. It is found that α-FeOOH, β-FeOOH and α-Fe2O3 nanorods have a constant real part of permittivity and low loss tangent tan δε. And the γ-Fe2O3, Fe3O4, and Fe nanorods are observed a resonance peak at 3 GHz which is over their nature resonance frequency and a relatively large permeability than their spherical nanoparticles. Our results indicate that Fe-based nanorods have various permittivity and permeability properties which have great potential application in high-frequency electronic or spintronic devices.

Analysis, design and fabrication of reconfigurable patch antenna on magnetodielectric composite substrate with biased ferrite particles

This study proposes a circular microstrip patch antenna on a magnetodielectric composite consisting of ferrite particles dispersed in a polymer matrix. The antenna operation is theoretically analysed using the cavity model and it is demonstrated that under the application of an external magnetic field it exhibits two resonant frequencies with opposite polarization sense. The theoretical analysis is verified numerically using a commercial electromagnetic (EM) simulator software. Moreover, it is shown that the antenna operating frequencies and polarization can be controlled through the variations of the applied magnetic field. An antenna prototype is fabricated in our laboratory and satisfactory agreement is observed between numerical and measurement results. The proposed antenna model is suitable for reconfigurable antenna applications at the 5 GHz frequency band.

Broadband Permittivity and Permeability Extraction of 3-D-Printed Magneto-Dielectric Substrates

A broadband microwave magneto-dielectric spectroscopy technique is introduced and dedicated to the characterization of 3-D-printed magneto-dielectric substrates. Complex permittivity and permeability are extracted for the material-under-test fabricated in the same manner and with the same orientation of the electro-magnetic (EM) field as in the intended applications that include, for example, miniaturized and efficient antennas. The information is derived from the measured characteristic impedance and propagation constant of a test microstrip transmission line. To exclude the influence of the coaxial-to-microstrip transitions, printed launchers are proposed with puzzle-like interlock to test substrate which is used together with a printed thru-reflect-line (TRL) de-embedding set. The presented technique was experimentally validated on an example of specialized magnetic polylactic acid (PLA) filament printed substrate in the frequency range 0.1–6 GHz and a reference PLA substrate measured with two different techniques to yield comparable results.

Large dual-equivalent permeability and permittivity using ferrite-ferroelectric particulate composite

Magneto-dielectric substrates with matched permeability and permittivity exhibit great potential in realizing physical miniaturization and efficiency improvement of radio antennas. In this work, novel magneto-dielectric particulate composites (1-x) (Bi0.5Na0.5TiO3-0.2Bi0.5K0.5TiO3)-xNi0.34Cu0.17Zn0.46Co0.03Fe1.96O3.94 [(1-x) BNKT-xNCZCF] (x=0, 0.65, 0.75, 0.85, and 1.0) were prepared via a powder-in-sol precursor hybrid process. This material system shows a tunable magnetic and dielectric response, in favor of achieving high matching values of permeability and permittivity. Specifically, the BNKT-0.75NCZCF sample delivered a matching permeability and permittivity with a value as high as ~32.5, as along with a low loss (tanδm<0.03 and tanδe<0.01) in a fairly wide frequency range. It is anticipated that this impedance-matched composite with a large miniaturization factor will be a suitable substrate for high-frequency and very-high-frequency antennas applications.

The preparation and high-frequency electromagnetic properties of Co80Ni20 alloy particles for potential antenna applications

A magneto-dielectric substrate material with high permeability and low loss at high frequency is necessary for a miniaturized antenna. Keeping the loss low is essential, in order to restrain the eddy current effect and to possess a high magnetic resonance frequency. In this work, the effects of the NaOH concentration and soaking time on crystal structures and morphologies of Co80Ni20 alloy particles are studied based on a polyol process. The results reveal that the size of particles increase with the promotion of the concentration of NaOH and soaking time. The electromagnetic (EM) properties of Co80Ni20 alloy particles/ polyurethane composites with various soaking times are studied at the NaOH concentration of 1.5 mol/L. The results reveal that the real part of permeability (μ'), the real part of permittivity (ε'), the magnetic loss tangent (tanδμ), the dielectric loss tangent (tanδε) of the composite with the soaking time of 3 h are 2.0, 11.0, 0.09, and 0.057 at 1 GHz, respectively, and the eddy current effect is suppressed effectively. The calculation of the permeability shows that the composite possesses a high domain wall resonance frequency. This work is significant for developing a magneto-dielectric substrate material using at 1 GHz.

Electrically tunable miniaturized band-stop frequency selective surface on engineered substrate with embedded permalloy patterns

This paper presents a miniaturized and electrically tunable band-stop frequency selective surface (FSS) with magneto-dielectric engineered substrate which has high and electrically tunable effective permeability. The perspective magneto-dielectric substrate is implemented with multiple layers of 100 nm thick patterned Permalloy (Py) thin film embedded in Roger RT/Duriod 5880 substrate, and each Py thin film layer consists of an array of 15μm×20μm Py patterns with 10 μm gaps among them to suppress the magnetic loss. The tunability of effective permeability for the proposed substrate is achieved by the static magnetic field produced from the applied DC current through the patterned gold bias lines beneath Py patterns. The engineered substrate has been implemented and studied, results show that the substrate embedded with a single layer of patterned Py has an equivalent permeability of 1.14 with tunability of 3.3%, and the substrate embedded with ten layers of patterned Py has an increased equivalent permeability of 2.398 and tunability of 15.8%. A magnetic FSS is designed on the implemented engineered substrate to demonstrate the efficacy of miniaturization and tunability. Compared to non-magnetic FSS on normal dielectric substrate, the size of the designed FSS has been reduced by 16.02%, and the operating frequency of the proposed FSS is continuously tunable from 2.450GHz to 2.672GHz with DC current.

Preparation and characterization of Ba4Co2Fe36O60 filled PP composites

Phase pure U type hexaferrites having molecular formula Ba4Co2Fe36O60 is synthesized through solid state route as filler for the fabrication of magneto-dielectric (MD) composite. Being a MD material the U type hexaferrite has a promising future in information and communication sector as a base substrate for electronic circuits. Since they exhibit both electric and magnetic properties, they can contribute effectively to circuit miniaturization and bandwidth enhancement compared to an antenna printed on a dielectric substrate. The filler material is then blended with PP (Poly Propylene) matrix and Magneto dielectric substrates are produced via hot pressing technique. Filler concentration has been varied from 70 to 90 wt. % in PP matrix and ascertained amount of optimum filler fraction for dimensionally stable substrate having acceptable properties. Dielectric and magnetic characterizations have been done using Impedance analyzer. It is found that the density of the composite and the dielectric constant is increasing with the increase in filler loading up to an optimum level and further filler loading reduces the density as well as the dielectric constant due to increased porosity. For optimum filler loading a maximum density of 2.96 g/cm3 is achieved. Relative permeability values are found increasing with filler loading even beyond the optimum filler loading. The optimum loaded poly Propylene/Ba4Co2Fe36O60 composite has an effective dielectric constant of 9.21, loss tangent of 0.083, relative permeability of 3.6 and a magnetic loss of 0.060 at 1MHz. Coefficient of thermal expansion (CTE) of the composite has been investigated using thermo mechanical analyzer. Moisture absorption rate of the optimum filler loaded composite is studied and found to be less than 0.1%. Relatively good dielectric constant, low loss tangent together with better relative permeability make the Ba4Co2Fe36O60 filled PP composites an excellent choice as Microwave substrate.

Utilization of soft magnetic nanoparticles for ultra-high frequency range

In the communication sector especially at ultra-high frequency range, a major challenge is to maintain the real permeability (μ′) and real permittivity (ε′) with controlled electromagnetic losses. To fulfill this demand, the present work reported electromagnetic studies over the frequency range of 2–3.4 GHz for magnetic nanoparticles of Sr2+-doped Z-type hexaferrites of compositions Ba3-xSrxCo2Fe24O41(x = 0, 0.5, 1.0, 1.5 and 2.0) synthesized by sol-gel auto combustion soft chemical route. The most desirable results obtained at 2 GHz for composition Ba1·5Sr1·5Co2Fe24O41 hexaferrite were μ′ = 5.002 with magnetic loss tangent of 0.003, and ε′ = 4.734 with electric loss tangent of 0.005. The multiple manifestations of electromagnetic studies are reported which are explained on the basis of a suitable Globus model, a theoretical model of Herzer, Snoek's law, a Maxwell–Wagner model together with Koop's model, and pertinent existing theories. Such magneto-dielectric substrate material could be favorable for fabrication of antennas with reduced physical dimensions and, also, almost equal values of μ′ and ε′ led to good impedance-match to free space in the gigahertz range for communication applications.

Solar panel integrated compact magneto-dielectric loaded sequentially rotated navigation antenna

In this paper we present a novel solar panel integrated navigation antenna for solar powered vehicles and devices. The radiator is a compact sequentially rotated patch array loaded with a magneto-dielectric (MD) layer to achieve miniaturization for ease of integration with solar panels. The magneto-dielectric substrate of the proposed antenna consists of MD unit cells created by vertical split ring resonators (SRR). The unit cells are arranged in 11 × 1 fashion beneath each radiator to reduce the dimension of the same to 70% with equivalent performance compared with the respective original patch radiators. An array of such radiators is formed and fed with a sequential feed network comprising T-junction power dividers and delay lines. The proposed antenna is then integrated and tuned with a solar panel and measured. The measured results show that the antenna operates in the L1 GPS band with an impedance bandwidth of 20 MHz centered at 1.575 GHz. The antenna is Right Handed Circularly Polarized (RHCP) with axial ratio bandwidth (ARBW) of 100% due to the sequential rotation. The peak Axial Ratio (AR) values are <3 dB with a peak gain of 7.89 dBic. The proposed solar panel integrated navigation antenna is developed with the view of using it as a multipurpose candidate in a compact shared dimension in solar powered vehicles and devices to provide power to the systems as well as global positioning and navigation of the same.

Miniaturized Multi-Port Microstrip Patch Antenna Using Metamaterial for Passive UHF RFID-Tag Sensor Applications.

In this paper, a miniaturized Ultra High Frequency Radio Frequency Identification (UHF-RFID) tag-based sensor antenna using a magneto- dielectric substrate (MDS) for wireless identification and sensor applications is presented. Two models of RFID tag-based sensors are designed, fabricated and measured. The first model uses two RFID tags; both of the tags are incorporated with two RFID chips. A passive sensor is also integrated in one of the proposed tags to serve as a sensor node, while the other tag is used as a reference node. Based on the difference in the minimum power required to activate the reference and sensor nodes, the sensed data (temperature or humidity) can be determined. The magneto-dielectric substrate layer is placed underneath the patch antenna to reduce the size of the proposed sensor by about 75% compared to a conventional RFID tag-based sensor. The magneto-dielectric layer is thin enough to embed in the planer circuit. To reduce the size of the proposed sensor, a multi-port tag for including the reference and sensor node in one antenna is also presented. The proposed RFID tag-based sensors have several features such as small size, they are completely capable for two objectives at the same time and easy to integrate with a planer circuit.

Fabrication and Characterization of Flexible Polymer Iron Oxide Composite Substrate for the Imaging Antennas of Wearable Head Imaging Systems

Given the increased interest in wearable electromagnetic imaging systems, developing a low-cost, lightweight, flexible, and conformal customized substrate to accommodate the imaging antenna array is essential. The characterization and assessment of a custom-made composite substrate using a flexible polymer poly-di-methyl-siloxane (PDMS) and magnetite iron oxide ( ${\text{FeO.Fe}}_{2}{\text{O}}_{3}$ ) for wearable head imaging systems is presented. Micro-scale ${\text{FeO.Fe}}_{2}{\text{O}}_{3}$ particles are homogeneously combined with PDMS in different ratios to build the flexible engineered magneto-dielectric (MD) composite substrate. Besides the low cost, fabrication simplicity, and durability, the magnetite ${\text{FeO.Fe}}_{2}{\text{O}}_{3}$ particles can be used to control the relative permittivity and permeability over a wide range of values to suit the proposed application. The permittivity, permeability, and losses of the developed substrate are extracted using a custom-made two-port multilayer microstrip transmission line test fixture with the help of conformal mapping algorithms. The characterization is performed across the microwave frequency range 1.2–4 GHz, which is widely adopted for head imaging. The extracted permittivity is successfully verified by using a Keysight 85070E dielectric slim probe kit.

Magneto‐dielectric substrate‐based microstrip antenna for RFID applications

A new planar magneto-dielectric substrate (MDS) is used for miniaturising a rectangular microstrip patch antenna for radio frequency identification (RFID) applications. The proposed magneto-dielectric unit cells are embedded underneath the microstrip patch. Increasing the constitutive parameters of the host substrate decreases the size of the antenna. This use of a MDS as the host substrate allows the antenna size to be reduced by up to 80% compared with a conventional microstrip patch antenna, and the proposed smaller antenna exhibits almost the same performance. The simulated and measured results show a good agreement. The magneto-dielectric layer is thin enough to be embedded underneath the antenna. The proposed antenna offers a reasonable impedance bandwidth from 847 to 853 MHz. The antenna is therefore suitable for RFID applications.

Design of SRR-Based Microwave Sensor for Characterization of Magnetodielectric Substrates

A novel split-ring resonator (SRR)-based microwave sensor for accurately determining the real parts of the complex permittivity and the complex permeability of magnetodielectric composites is proposed. The proposed sensor is realized using the microstrip technology, where two SRRs coupled magnetically with the microstrip line are printed on two sides of the line. The sensor is designed using the full-wave electromagnetic solver and its equivalent circuit model is obtained. A numerical model of the proposed sensor is developed for extracting the magnetic and the dielectric properties of the sample under test in terms of change in resonance frequency after loading the device with the test specimen. The proposed methodology is validated by fabricating the sensor on RT/duroid 6006 substrate and testing various standard dielectric and magnetodielectric samples viz. Teflon, Poly vinyl chloride, Plexiglas, Polyethylene, Carbonyl iron, Ni0.6Co0.4Fe2O4, and Cobalt (30%)/Polystyrene composite in S-band. The measured relative permeability and the relative permittivity of the test specimens are found to be in close agreement with their values available in literature with maximum error of less than 8%.

Machine-Learning Approach for Design of Nanomagnetic-Based Antennas

We propose a machine-learning approach for design of planar inverted-F antennas with a magneto-dielectric nanocomposite substrate. It is shown that machine-learning techniques can be efficiently used to characterize nanomagnetic-based antennas by accurately mapping the particle radius and volume fraction of the nanomagnetic material to antenna parameters such as gain, bandwidth, radiation efficiency, and resonant frequency. A modified mixing rule model is also presented. In addition, the inverse problem is addressed through machine learning as well, where given the antenna parameters, the corresponding design space of possible material parameters is identified.

Low-loss NiZnCo ferrite processed at low sintering temperature with matching permeability and permittivity for miniaturization of VHF-UHF antennas

Spinel ferrites of a nominal composition of Ni0.5Zn0.3Co0.2Fe2O4 (NiZnCo) with various B2O3–Bi2O3–SiO2–ZnO (BBSZ) glass additions were successfully synthesized at a relatively low temperature of 930 °C for their potential applications as magneto-dielectric antenna substrate materials. Measurements of magnetic and dielectric properties show that, with an increasing content of BBSZ from 0 to 2 wt. %, the permeability μ′ at low frequencies was increased from ∼4.7 to ∼8.9, whereas the permittivity ε′ was improved from ∼5.9 to ∼12.5. These tunable permeability and permittivity were proved to be closely related to the grain size and density, based on the magnetic circuit model and effective medium theory. Importantly, the sample with 0.5 wt. % addition demonstrated the optimal magneto-dielectric performance with nearly equivalent values of μ′ and ε′, which yields a large miniaturization factor of ∼6.5 and the normalized impedance of ∼1 over the frequency range of 10 MHz–1 GHz. Moreover, this sample exhibits low loss characteristics over a wide frequency range, where the dielectric loss tan δε is in the order of 10−3 and the magnetic loss tan δμ is less than 0.15. These properties make the ferrite material a promising candidate for miniaturized antennas with good impedance matched to free space and open a great potential for low-temperature co-fired ceramic applications toward the practical fabrication and high integration of the antennas.

Low-Profile Spiral Antenna Placed on an Extremely Thin Magnetodielectric Substrate

This letter presents a low-profile spiral antenna with an extremely thin magnetodielectric substrate (MagDS), which is backed by a conducting plane. A MagDS thickness of 0.1 mm (0.0001 λ at 300 MHz) provides a purely input resistance with an axial ratio of less than 3 dB across a wide frequency range. Using this thickness value, the radiation characteristics are analyzed. It is revealed that a VSWR of less than 2 and an axial ratio of less than 3 dB are obtained across a frequency range of 300–1000 MHz (fractional bandwidth: 108%). It should be emphasized that the total antenna height from the bottom conducting plane to the antenna top surface is very small: 0.061 λ at 300 MHz. Simulated results are confirmed by experimental work.

Greatly enhanced magneto-dielectric performance of the Ni0.5Zn0.5Fe2O4/polyvinylidene fluoride composites with annealed ferrite powders for antenna applications

Abstract

Performance analysis of cobalt metal with fluoropolymer matrix as a substrate for patch antenna

ABSTRACTSince many decades material plays major role in all fields. In recent years, materials are more useful in specific field of science and engineering. This paper deals with micro-strip patch antenna designed using FR-4 and magneto dielectric substrate. To compare these results, CSTMWS Suite (Computer Simulation Technology Micro-Wave Studio) software is used. The results show that different substrate produce different gain and directivity based on their properties. Here, two different materials namely FR-4, Cobalt metal with fluoropolymer matrix are used as a substrate for same structure.

Magnetodielectric hexaferrite flake/polymer substrate for implantable antenna with an enhanced insensitivity to implant position

A magnetodielectric substrate is firstly proposed for implantable antennas in medical implant communication service (MICS) band. Ba3Co2Fe24O41 (Co2Z), Z-type hexaferrite flakes synthesized by molten-salt method were incorporated with a polymer matrix, having a real permeability of 2.88 and a magnetic loss of 0.029 at 402MHz. A spiral antenna with the magnetodielectric substrate has a bandwidth 70% and 50% broader than that with a commercial dielectric substrate, Rogers 3210, in a 2/3-phantom model and a multi-layered body model, respectively. The band broadening retains the bandwidth to be overlapped after implant positions change, leading to an enhancement in insensitivity to the implant position.

Analysis of Miniature Metamaterial and Magnetodielectric Arbitrary-Shaped Patch Antennas Using Characteristic Modes: Evaluation of the &lt;inline-formula&gt; &lt;tex-math notation="LaTeX"&gt;$Q$ &lt;/tex-math&gt; &lt;/inline-formula&gt; Factor

Evaluating the $Q$ factor of antennas using metamaterial substrates is a challenge and requires new analysis techniques. This challenge is even more important for arbitrary-shaped antennas. In this paper, we address the problem of analysis and evaluation of metamaterial-based antennas through the use of characteristic modes. We propose a new expression for the total $Q$ factor, which is independent of the excitation and based on the eigenvalues of the structure. The proposed expression is used to compute the $Q$ factor of an arbitrary-shaped resonant antenna and shows excellent agreement with other expressions in the literature such as the ones proposed by Yaghjian, Best, and Gustafsson. The approach is then used to analyze small patch antennas over metamaterial and magnetodielectric substrates. It is shown using the defined $Q$ factor expression that a magnetic substrate offers a significant bandwidth enlargement for the first active modes, and a dielectric substrate presents the opposite effect. This agrees with other works based on analytical approaches. Furthermore, we demonstrate that a reactive impedance metamaterial substrate presents identical modal significances that are identical to a conventional magnetodielectric substrate when associated with a patch antenna. This analysis is suitable for structures presenting noncanonical geometries and arbitrary shapes such as metamaterial inclusions.