JP6365255B2 - Ferrite composition, ferrite plate, antenna element member, and antenna element - Google Patents

Description

The present invention relates to a ferrite composition suitable for an antenna element having a long communication distance, a ferrite plate made of the composition, an antenna element member made of the ferrite plate, and an antenna element provided with any of these.

13.56 MHz band RFID (Radio Frequency IDentification) system or NFC (Near Field Communication) system is a technology that performs near-field wireless communication without contact between an IC card or IC tag and a reader / writer. . Such an IC card or IC tag includes an IC chip and an antenna coil, and the reader / writer also includes an antenna coil.

By bringing the IC card or the like closer to the reader / writer, magnetic flux is generated by electromagnetic induction generated between these antenna coils. By exchanging this magnetic flux between the IC card or the like and the reader / writer, it becomes possible to supply power and exchange information written on the IC chip.

At this time, if a metal such as a communication circuit is integrally disposed in the housing on the back surface of the antenna coil, an eddy current is generated in the metal by the generated magnetic flux, and this eddy current is opposite to the generated magnetic flux. The magnetic field is generated. As a result, the generated magnetic flux is weakened and the communication distance is shortened or communication is impossible. Moreover, thermal loss also occurs due to eddy currents.

In order to solve such a problem, it has been proposed to arrange a magnetic body made of a material having high magnetic permeability between the antenna coil and the metal. In general, the permeability μ is expressed as complex permeability μ = μ′−jμ ″ (j is an imaginary unit). The real part μ ′ of the complex permeability is a normal permeability component, and the imaginary part μ ″ is It is a material constant representing loss. These material constants are factors that govern the communication distance in short-range wireless communication. In order to improve the communication distance, it is important to focus the magnetic flux at high μ ′ while suppressing thermal loss at low μ ”.

When mounting as an antenna, not only room temperature (25 ° C.) but also high frequency characteristics in a wide temperature range (for example, 0 ° C. to 40 ° C.) are important. In Patent Document 1, the change in the amplitude permeability μa at −30 ° C. to 40 ° C. is suppressed to within 12% by adjusting the composition of NiZn ferrite. However, the frequency at this time is 130 kHz, and in the high frequency region (for example, 13.56 MHz), μ ”that is important as an index of the communication distance becomes remarkably high, and a good communication distance as an antenna cannot be obtained.

Further, Non-Patent Document 1 shows that μ ′ derived from magnetization rotation having a steep temperature characteristic becomes dominant by the pores and grain boundaries inside the crystal in the ferrite pinning the domain wall movement. However, when pores are reduced by adjusting the main composition and the firing temperature in this document, μ "in a high-frequency region (for example, 13.56 MHz) is remarkably increased, and a good communication distance as an antenna cannot be obtained.

JP 2006-160584 A

J. Hu, Physica B 400 (2007) 117

The present invention has been made in view of such a situation, and the communication distance is good even in a low temperature region (for example, 0 ° C.) in which μ ′ is assumed to be decreased or in a high temperature region (for example, 40 ° C.) in which μ ′ is expected to be increased. An object of the present invention is to provide a ferrite composition suitable for a simple antenna element, a ferrite plate made of the ferrite composition, an antenna element member made of the ferrite plate, or an antenna element having the antenna element member. .

In order to solve the above-described problems and achieve the object, the ferrite composition according to the present invention is composed mainly of 46.3 to 49.5 mol% iron oxide in terms of Fe ₂ O ₃ and copper oxide in CuO. 4.0 to 15.6 mol% in terms of conversion, zinc oxide in the range of 20.4 to 25.0 mol% in terms of ZnO, and the balance being composed of nickel oxide, unavoidable impurities with respect to the main component As an auxiliary component, titanium oxide is contained in an amount of 1.4 to 2.0% by mass in terms of TiO ₂ and cobalt oxide is contained in an amount of 0.5 to 2.0% by mass in terms of CoO. It is characterized by containing at least one of 0.005 to 0.025 mass% in terms of SiO in terms of silicon and 0.010 to 0.100 mass% of calcium oxide in terms of CaO as components. In particular, by adding at least one of SiO ₂ and CaO, it is possible to maintain a good communication distance even in a low temperature region (for example, 0 ° C.) where μ ′ is expected to decrease. Further, the communication distance can be improved by applying the ferrite plate made of the ferrite composition according to the present invention or the antenna element member to the antenna element.

According to the present invention, non-contact short-range wireless communication between an IC card or IC tag provided with an antenna coil and a reader / writer by containing silicon oxide and calcium oxide as subcomponents in the above range. Thus, a ferrite composition suitable for an antenna element having a long communication distance can be obtained even in a low temperature region (for example, 0 ° C.) or a high temperature region (for example, 40 ° C.).

FIG. 1 is a schematic exploded perspective view of an antenna element according to an embodiment of the present invention. FIG. 2 is a partial cross-sectional view of a member for an antenna element that is held by an adhesive layer and a protective layer and divided into a number of planar small pieces.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In addition, this invention is not limited to the following embodiment. The constituent elements described below include those that can be easily assumed by those skilled in the art and those that are substantially the same. Furthermore, the constituent elements described below can be appropriately combined.

As shown in FIG. 1, the antenna element 1 according to an embodiment of the present invention includes an adhesive material layer 18, a loop-shaped antenna coil 14, a protective layer 16, and a ferrite plate 12. In FIG. 1, illustration of a connection terminal to the outside, a communication processing circuit, and the like is omitted.

The ferrite plate according to the present embodiment is composed of the ferrite composition according to the present embodiment. The ferrite composition according to this embodiment is NiCuZn-based ferrite, and contains iron oxide, copper oxide, zinc oxide, and nickel oxide as main components.

In the main component 100 mol%, the content of iron oxide, calculated as _Fe 2 _{O 3,} 46.3 to 49.5 mol%, preferably 46.8 to 49.0 mol%, more preferably 47.5～ It is 48.5 mol%. If the content of iron oxide is too small, the real part μ ′ of the complex permeability in the high frequency band decreases, and if it is too large, the complex permeability in the high frequency band at room temperature (25 ° C.) and in a high temperature region (for example, 40 ° C.). There is a tendency for the imaginary part μ ″ to increase. In any case, when used as an antenna element, it causes a decrease in the communication distance.

In 100 mol% of the main component, the content of copper oxide is 4.0 to 15.6 mol%, preferably 5.6 to 14.8 mol%, more preferably 6.8 to 12.0 in terms of CuO. Mol%. When the content of copper oxide is too small, the real part μ ′ of the complex permeability in the high frequency band is lowered in a low temperature region (for example, 0 ° C.), room temperature (25 ° C.) and a high temperature region (for example, 40 ° C.). This causes abnormal grain growth, and the real part μ ′ of the complex permeability is improved at room temperature (25 ° C.) and in a high temperature region (for example, 40 ° C.), but the imaginary part μ ″ tends to deteriorate rapidly. When used as an element, it causes a decrease in communication distance.

In 100 mol% of the main component, the content of zinc oxide is 20.4 to 25.0 mol%, preferably 21.0 to 24.5 mol%, more preferably 22.0 to 24.0 in terms of ZnO. Mol%. If the zinc oxide content is too small, the real part μ ′ of the complex permeability in the high frequency band is lowered, and if it is too large, the complex permeability in the high frequency band at room temperature (25 ° C.) and in a high temperature region (for example, 40 ° C.). There is a tendency for the imaginary part μ ″ to increase. In any case, when used as an antenna element, it causes a decrease in the communication distance.

The remainder of the main component may be composed only of nickel oxide, or may contain manganese oxide which is an inevitable impurity. When nickel oxide is contained in the remainder of the main component, the content of nickel oxide is 9.9 to 29.3 in terms of NiO in 100 mol% of the main component of the Ni—Cu—Zn-based ferrite sintered body. It is mol%, preferably 11.7 to 26.6 mol%, more preferably 15.5 to 23.7 mol%. When the content of nickel oxide is less than 9.9 mol% in terms of NiO, the resonance frequency of the complex permeability shifts to the low frequency side, and the high frequency band at room temperature (25 ° C.) and high temperature region (for example, 40 ° C.) There is a tendency that the imaginary part μ ″ of the complex permeability of Nb is increased. On the other hand, when the content of nickel oxide is more than 29.3 mol% in terms of NiO, not only in the high frequency band but also in the low frequency band ( For example, the real part μ ′ of the complex permeability tends to be low at room temperature (25 ° C.), room temperature (25 ° C.), and high temperature region (for example, 40 ° C.). It becomes.

The ferrite composition according to the present embodiment contains titanium oxide, cobalt oxide, silicon oxide, and calcium oxide as subcomponents in addition to the above main components.

The content of titanium oxide is 1.4 to 2.0% by mass, preferably 1.5 to 1.9% by mass, more preferably 1.6 to 1.8% in terms of TiO _{2 with} respect to the main component. % By mass. If the content of titanium oxide is too small, the real part μ ′ of the complex permeability in the high frequency band is lowered, and if it is too much, the resonance frequency of the complex permeability is significantly shifted to the low frequency side. As a result, room temperature (25 ° C. ) And an imaginary part μ ″ of the complex permeability in the high frequency band tend to increase in a high temperature region (for example, 40 ° C.). When both are used as antenna elements, they cause a decrease in communication distance.

The content of cobalt oxide is 0.5 to 2.0% by mass, preferably 0.6 to 1.5% by mass, more preferably 0.7 to 1.0% by mass in terms of CoO with respect to the main component. %. If the content of cobalt oxide is too small, the imaginary part μ ″ of the high frequency band will deteriorate rapidly at room temperature (25 ° C.) and in a high temperature region (for example, 40 ° C.). 25) and a high temperature region (for example, 40.degree. C.), the real part .mu. 'Of the high-frequency band is lowered, and when both are used as antenna elements, it causes a reduction in communication distance.

The content of silicon oxide, with respect to the main component, in terms of SiO _2, 0.005 to 0.030 wt%, preferably from 0.008 to 0.020 wt%, more preferably from 0.010 to 0.015 % By mass. If the content of silicon oxide is too small, the effect of addition cannot be obtained. If too large, crystal grains grow abnormally, and the imaginary part μ ″ in the high frequency band rapidly deteriorates at room temperature (25 ° C.) and in a high temperature region (for example, 40 ° C.). In addition, silicon oxide may be added in combination with calcium oxide or may be added alone.

The content of calcium oxide is 0.020 to 0.100 mass%, preferably 0.030 to 0.080 mass%, more preferably 0.040 to 0.060 mass%, in terms of CaO, with respect to the main component. %. If the content of cobalt oxide is too small, the effect of addition cannot be obtained. If too large, crystal grains grow abnormally, and the imaginary part μ ″ in the high frequency band rapidly deteriorates at room temperature (25 ° C.) and in a high temperature region (for example, 40 ° C.). Calcium oxide may be added in combination with silicon oxide or may be added alone.

In the ferrite composition according to the present embodiment, in addition to the composition range of the main component being controlled within the above range, titanium oxide, cobalt oxide, silicon oxide and calcium oxide are contained in specific amounts as subcomponents. Yes. By adding titanium oxide, the frequency dependence of the imaginary part μ ″ of the complex permeability shows a steep behavior, and in the vicinity of the RFID or NFC communication frequency of 13.56 MHz, a low μ ”is maintained while maintaining a high μ ′. Can be realized. This steepness realizes a good communication distance even in a high temperature region (eg, 40 ° C.). Further, by adding silicon oxide and calcium oxide alone or in combination, the temperature dependence of μ ′ is reduced. As a result, the decrease of μ ′ in the low temperature region (for example, 0 ° C.) is reduced. From the above, when such a ferrite composition is used as an antenna element, the communication distance can be improved in a wide temperature range (for example, 0 ° C. to 40 ° C.).

Next, an example of the manufacturing method of the ferrite plate comprised from the ferrite composition concerning this embodiment is demonstrated.

First, starting materials (raw materials of main components and raw materials of subcomponents) are weighed and mixed so as to have a predetermined composition ratio to obtain a raw material mixture. Examples of the mixing method include wet mixing using a ball mill and dry mixing using a dry mixer. It is preferable to use a starting material having an average particle size of 0.1 to 3.0 μm.

As a raw material of the main component, iron oxide (α-Fe ₂ O ₃ ), copper oxide (CuO), zinc oxide (ZnO), nickel oxide (NiO), or a composite oxide containing these can be used. In addition, various compounds that become oxides or composite oxides by firing can be used. Examples of the oxide that becomes the above-mentioned oxide upon firing include simple metals, carbonates, oxalates, nitrates, hydroxides, halides, organometallic compounds, and the like.

Titanium oxide (TiO ₂ ), cobalt oxide (Co ₃ O ₄ ), silicon oxide (SiO ₂ ), calcium oxide (CaCO ₃ ) can be used as a raw material for the accessory component. Cobalt oxide may be CoO or cobalt ferrite (CoFe ₂ O ₄ ), but Co ₃ O ₄ is easy to store and handle, has a stable valence even in air, and has excellent mass productivity. Therefore, it is preferable as a raw material for cobalt oxide.

Next, the raw material mixture is calcined to obtain a calcined material. Calcining promotes thermal decomposition of raw materials, homogenization of ingredients, formation of ferrite, disappearance of ultrafine powder due to sintering and grain growth to an appropriate particle size, and converts the raw material mixture into a form suitable for subsequent processes. To be done. Such calcination is preferably performed at a temperature of 800 to 1100 ° C. for about 1 to 3 hours. The calcination may be performed in the air (air), or may be performed in an atmosphere having a higher oxygen partial pressure or in a pure oxygen atmosphere than in the air. The mixing of the main component raw material and the subcomponent raw material may be performed before calcining or after calcining.

Next, the calcined material is pulverized to obtain a pulverized material. The pulverization is performed in order to break down the coagulation of the calcined material to obtain a powder having appropriate sinterability. When the calcined material forms a large lump, wet pulverization is performed using a ball mill or an attritor after coarse pulverization. The wet pulverization is performed until the average particle size of the pulverized material is preferably about 0.5 to 2.0 μm.

Using the obtained pulverized material, the ferrite plate according to the present embodiment is manufactured. The method for producing the ferrite plate is not limited, but in the following, the sheet method is used.

First, the obtained pulverized material is slurried together with additives such as a solvent, a binder, a dispersant, and a plasticizer to prepare a paste. And the green sheet which has a thickness of 50-600 micrometers is formed using this paste. A plurality of obtained green sheets may be laminated. Next, the formed green sheet is processed into a predetermined shape, and a ferrite plate having a thickness of 30 to 500 μm according to the present embodiment is obtained through a binder removal step and a firing step. Firing is preferably performed at a temperature of 900 to 1300 ° C., usually for about 2 to 5 hours. The firing may be performed in the atmosphere (air) or in an atmosphere having a higher oxygen partial pressure than in the atmosphere. In this way, the ferrite plate according to the present embodiment is obtained.

In the embodiment described above, the ferrite plate is manufactured by the sheet method. For example, after the ferrite powder and the binder resin are mixed, the ferrite plate is manufactured by a known method such as a powder compression molding method, an injection molding method, a calendar method, an extrusion method, or the like. May be.

Next, an adhesive layer 18, for example, a double-sided adhesive tape is provided on one side (one surface) of the obtained ferrite plate. A protective layer 16 for preventing the ferrite plate from dropping off is provided on the surface opposite to the surface on which the adhesive layer is formed (the other surface). The protective layer is formed by adhering a resin film or sheet constituting the protective layer to the surface of the sintered ferrite plate through an adhesive, if necessary, or by applying a paint containing the resin constituting the protective layer. This is done by applying to the surface of the sintered ferrite plate. The ferrite plate is formed by holding both sides of the ferrite plate with the two layers (adhesive layer 18 and protective layer 16) and passing them once in the 0 degree direction and 90 degree direction with respect to the roller of the rolling device. Are divided into a large number of planar small pieces in a lattice shape to form voids 19 (see FIG. 2). In this way, the antenna element member having flexibility and flexibility according to the present embodiment is obtained.

Next, the antenna coil 14 for non-contact communication is attached to the surface of the adhesive material layer 18 of the obtained antenna element member 20. The antenna coil 14 has a loop-shaped loop antenna structure with an opening at the center, and the loop shape may be circular, substantially rectangular, or polygonal. Furthermore, the material of the antenna coil 14 can be appropriately selected from conductive metal wire, metal plate, metal foil, metal cylinder, etc., for example, metal wire, metal foil, conductor paste The antenna coil 14 can be formed by plating transfer, sputtering, vapor deposition, or screen printing. Thus, the antenna element 1 according to the present embodiment is obtained.

As mentioned above, although embodiment of this invention was described, this invention is not limited to such embodiment at all, Of course, in the range which does not deviate from the summary of this invention, it can implement in various aspects.

Hereinafter, the present invention will be described based on further detailed examples, but the present invention is not limited to these examples.

First, Fe ₂ O ₃ , NiO, CuO, and ZnO are prepared as main component materials, and TiO ₂ , Co ₃ O ₄ , SiO ₂ , and CaCO ₃ are prepared as subcomponent materials. It weighed so that it might become a composition, 500 mL ion-exchange water was added to this as a solvent, and it mixed for 16 hours with the steel ball mill, and obtained the raw material mixture.

The obtained raw material mixture was calcined at a maximum temperature of 800 ° C. for 2 hours using a heating furnace, and then cooled in a furnace to obtain a calcined material. After the calcined material was crushed with a 30 mesh sieve, 500 mL of ion-exchanged water was added again as a solvent, and wet pulverization was performed for 16 hours in a steel ball mill to obtain a pulverized material.

100% by mass of ferrite powder of the obtained pulverized material, 3.5% by mass of dioctyl adipate, 8% by mass of butyral resin, and a mixed solution of xylene and isobutyl alcohol as a solvent (xylene: isobutyl alcohol = 6: 4 (mass ratio) )) 72% by mass was mixed, dissolved and dispersed by a ball mill to obtain a mixture (paste). After degassing the mixture with an oil rotary vacuum pump, the resulting mixture was applied to a polyethylene terephthalate (PET) film to a certain thickness with a doctor blade, dried with hot air at 100 ° C. for 30 minutes, and a thickness of 120 μm. The green sheet was obtained.

Next, the obtained green sheet was heated from room temperature (25 ° C.) to 500 ° C. at a heating rate of 1 ° C./min, degreased by holding at 500 ° C. for 3 hours, then heated to 1000 ° C. and baked for 2 hours. As a result, a ferrite plate having a thickness of about 100 μm was obtained.

A commercially available acrylic double-sided tape (30 μm) as an adhesive layer is applied to one surface of the obtained ferrite plate, and a single-sided adhesive sheet (30 μm) coated with a commercially available acrylic adhesive is applied as a protective layer to the other surface. Then, the ferrite plate held by the adhesive layer and the protective layer is passed through the roller of the rolling machine whose GAP amount is adjusted to 150 μm once each in the 0 degree direction and the 90 degree direction, so that the ferrite plate is latticed. An antenna element member divided into a large number of planar small pieces was obtained.

When the single-sided adhesive sheet of the antenna element member was peeled and the shape and size of the divided ferrite plate were confirmed, it was divided into a 2 to 3 mm lattice.

<Evaluation of magnetic properties>
The complex magnetic permeability is obtained by punching a toroidal shape from a member for antenna element having a thickness of 160 μm (the ferrite plate is 100 μm thick) divided into a large number of planar small pieces using a pinnacle mold having an outer diameter of 18 mm and an inner diameter of 10 mm. An antenna analyzer (made by Agilent Technologies, product name: RF impedance / material analyzer, model: E4291A) and magnetic material measuring electrode (manufactured by Agilent Technologies, product) Name: Magnetic material test fixture, type: 16454A), magnetic characteristics were evaluated at a measurement temperature of 0 to 40 ° C.

<Antenna communication distance>
From a member for antenna element having a thickness of 160 μm divided into a large number of planar pieces (the thickness of the ferrite plate is 100 μm), a pinnacle mold is used to punch out a rectangle having a size of 50 mm × 40 mm and a sample for measuring a communication distance did. An antenna coil for an NFC system having a size of 50 mm × 40 mm on a surface having an adhesive material layer, on which a copper plate imitating a metal such as a housing cell or a battery pack is disposed on the surface having a protective layer of the antenna element member. A loop antenna structure, pattern: substantially rectangular) was affixed to obtain a measurement tag. An antenna module is configured between the tag and a reader / writer for NFC (product name: contactless reader, model: ViVOpay5000, manufactured by ID Tech Co.). The communication distance at a resonance frequency of 56 MHz was measured.

The obtained measurement evaluation results are shown in Tables 1 and 2. In addition, the composition value in a table | surface is an analysis value by a fluorescent X ray analysis.

From Tables 1 and 2, 100% by mass of Ni—Cu—Zn-based ferrite containing Co, Ti oxide and containing Fe, Ni, Cu and Zn as main components, calcium oxide or silicon oxide as an accessory component When the content is within the range of the present invention (Examples 1 to 17), a good communication distance can be obtained even in a wide temperature range (for example, 0 ° C. to 40 ° C.). confirmed. Here, a good communication distance in the high temperature region is a combined effect of titanium oxide and cobalt oxide, and a good communication distance in the low temperature region is an effect of adding at least one of calcium oxide and silicon oxide. On the other hand, when the main component and subcomponents, particularly calcium oxide and silicon oxide are not contained in the above range (Comparative Examples 2 to 5), in a low temperature region (for example, 0 ° C.) or a high temperature region (for example, 40 ° C.). A decrease in communication distance was confirmed, and it was confirmed that it was not suitable for application to an antenna element for non-contact communication.

From these results, the ferrite composition of the example according to the present invention has a high μ ′ even in the low temperature region as compared with the comparative example and the reference example, and the communication distance is remarkably improved by applying it for the antenna element. Confirmed to do.

As described above, it was confirmed that a long communication distance was maintained even in a low temperature and high temperature environment by applying the ferrite composition according to the present invention to the antenna element member. As a result, it is expected that it can be used without feeling a change in the communication distance even in an outdoor area where the temperature difference is severe.

DESCRIPTION OF SYMBOLS 1 ... Antenna element 12 ... Ferrite plate 14 ... Antenna coil 16 ... Protective layer 18 ... Adhesive material layer 19 ... Air gap 20 ... Antenna element member

Claims (7)

Main component, 46.3 to 49.5 mol% of iron oxide calculated as _Fe 2 _{O 3,} 4.0 to 15.6 mol% of copper oxide in terms of CuO, zinc oxide in terms of ZnO 20.4 to 25 containing 2.0 mole%, the balance is constituted by nickel oxide, with respect to said main component, except for unavoidable impurities, as a subcomponent, 1.4 to 2.0 wt% of titanium oxide in terms of TiO ₂ Cobalt oxide is contained in an amount of 0.5 to 2.0% by mass in terms of CoO. Further, silicon oxide is contained in an amount of 0.005 to 0.030% by mass in terms of SiO ₂ and calcium oxide is CaO as an auxiliary component with respect to the main component. A ferrite composition comprising at least one of 0.020 to 0.100 mass% in terms of conversion. Main component, 46.8 to 49.0 mol% of iron oxide calculated as _Fe 2 _{O 3,} 5.6 to 14.8 mol% of copper oxide in terms of CuO, zinc oxide in terms of ZnO 21.0 to 24 0.5 mol%, the balance being composed of nickel oxide, and with respect to the main component, except for inevitable impurities, titanium oxide as a subcomponent is 1.5 to 1.9% by mass in terms of TiO _2. Cobalt oxide is contained in an amount of 0.6 to 1.5% by mass in terms of CoO. Further, silicon oxide is contained in an amount of 0.008 to 0.020% in terms of SiO ₂ as an auxiliary component with respect to the main component, and calcium oxide is CaO. A ferrite composition comprising 0.030 to 0.080 mass% in terms of conversion. Main component, 47.5 to 48.5 mol% of iron oxide calculated as _Fe 2 _{O 3,} 6.8 to 12.0 mol% of copper oxide in terms of CuO, zinc oxide in terms of ZnO 22.0 to 22 .4 mol%, and the balance is composed of nickel oxide, and with respect to the main component, except for inevitable impurities, titanium oxide as a subcomponent is 1.6 to 1.8% by mass in terms of TiO _2. Cobalt oxide is contained in an amount of 0.7 to 1.0% by mass in terms of CoO. Further, silicon oxide is contained in an amount of 0.010 to 0.015% in terms of SiO ₂ as an auxiliary component with respect to the main component, and calcium oxide is CaO. A ferrite composition characterized by containing at least one of 0.040 to 0.060 mass% in terms of conversion. The ferrite plate which consists of a composition as described in any one of Claims 1-3.   5. An adhesive material layer is provided on one surface of the ferrite plate, and a protective layer is provided on the other surface, and the ferrite plate is divided into a number of planar small pieces while being held by the two layers. The member for antenna elements using the ferrite plate of description. An antenna element having the ferrite plate according to claim 4 . An antenna element having the antenna element member according to claim 5 .

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