KR20150131922A - NFC chip antenna module package - Google Patents

Abstract

The present invention provides a NFC chip antenna module package. The NFC chip antenna module package includes: a substrate having a plurality of terminals; an antenna chip mounted on the substrate and embedded with a NFC antenna connected to at least one of the terminals; and an extension antenna loop formed on at least one side of the substrate and electrically connected to the antenna chip.

Description

NFC chip antenna module package < RTI ID = 0.0 >

The present invention relates to an NFC chip antenna module package, and more particularly, to an NFC chip antenna module package capable of improving the performance of an antenna.

Near Field Communication (NFC) is a non-contact short-range wireless communication standard that enables wireless communication between electronic devices at a short distance within 10 cm using a frequency of 13.56 MHz. It was developed jointly by Dutch NXP Semiconductor and Sony Japan. NFC's transmission rates per second are 106 Kbps, 212 Kbps, 424 Kbps or 848 Kbps. Its proximity characteristics and encryption technology provide excellent security and it is possible to identify devices without any complicated pairing procedure. There is an advantage that it can be recognized. In particular, NFC is a smart card type non-contact wireless communication technology that utilizes RFID technology. It is bi-directional compared to a smart card, has a relatively large storage memory space, and has a wide range of applicable services. Accordingly, this technology has been introduced to electronic devices such as smart phones and tablet PCs, which have recently been commercialized.

On the other hand, batteries are used in portable terminals such as smart phones and tablet PCs. Lithium-ion batteries are the most widely used batteries in portable handsets, but they also generate heat during overcharging and overcurrent, and when the temperature rises due to heat generation, they may deteriorate performance as well as the risk of explosion. Therefore, a conventional battery is equipped with a protection circuit device that detects and blocks overcharge, over-discharge, and over-current, or a protection circuit structure that detects overcharge, over-discharge, do.

Recently, products combining an NFC antenna structure with a battery of a portable terminal have been introduced. However, in this case, a process of separately coupling an NFC antenna structure with a battery is further required, which increases manufacturing cost and requires additional space Resulting in a large-sized battery for the purpose of charging.

It is an object of the present invention to provide an NFC chip antenna module package capable of improving the performance of an antenna for solving various problems including the above problems. However, these problems are exemplary and do not limit the scope of the present invention.

According to one aspect of the present invention, an NFC chip antenna module package is provided. The NFC chip antenna module package comprising: a substrate having a plurality of terminals; An antenna chip mounted on the substrate and having an NFC antenna connected to at least one of the plurality of terminals; And an extended antenna loop formed on at least one surface of the substrate and electrically connected to the antenna chip.

The plurality of terminals including an antenna terminal connectable to an antenna chip; At least one connection terminal capable of being electrically connected to a part of external connection terminals of the battery protection circuit package; And at least one matching element connection terminal that can be electrically connected between the antenna terminal and the connection terminal.

And an NFC matching device formed on the matching device connection terminal, the NFC matching device being connectable to the antenna chip and the extended antenna loop.

The extended antenna loop may be formed on a surface opposite to the antenna chip formed on the upper surface and / or the lower surface of the substrate.

Both ends of the extended antenna loop may be electrically connected to the antenna chip and / or the NFC matching element by at least two via patterns passing through the substrate.

The length of the extended antenna loop may be set such that the ratio of the value of the inductance generated in the extended antenna loop to the value of the inductance generated in the antenna chip is 13% or more.

The extended antenna loop may include a loop-shaped pattern formed on an upper surface and / or a lower surface of the substrate. The extended antenna loop may be formed by bending at least one time in a spiral form.

The antenna chip may include an inductor capable of resonating in an NFC frequency band.

The antenna chip may be mounted using surface mount technology on at least a portion of the substrate surface.

The substrate may comprise a printed circuit board (PCB).

And an encapsulant that exposes at least a portion of the plurality of terminals and encapsulates the antenna chip and the extension antenna loop.

According to an embodiment of the present invention as described above, an NFC chip antenna module package having an NFC antenna which is advantageous for integration and miniaturization and can improve the performance of an antenna can be realized. Of course, the scope of the present invention is not limited by these effects.

1 is a diagram illustrating a configuration of a general short range wireless communication (NFC).
FIGS. 2A and 2B are views schematically illustrating a configuration of an NFC chip antenna module package according to an embodiment of the present invention.
2C and 2D are views schematically illustrating a configuration of an NFC chip antenna module package according to another embodiment of the present invention.
3A and 3B are schematic views illustrating submodules constituting an NFC chip antenna module package according to an embodiment of the present invention.
4A is a schematic view illustrating a method of connecting an NFC chip antenna module package according to an embodiment of the present invention to a main set.
FIGS. 4B and 4C are views illustrating a method of connecting an NFC chip antenna module package according to another embodiment of the present invention to a main set.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be understood, however, that the invention is not limited to the disclosed embodiments, but may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, Is provided to fully inform the user. Also, for convenience of explanation, the components may be exaggerated or reduced in size.

It is to be understood that throughout the specification, when an element such as a film, region or substrate is referred to as being "on", "connected to", "laminated" or "coupled to" another element, It is to be understood that elements may be directly "on", "connected", "laminated" or "coupled" to another element, or there may be other elements intervening therebetween. On the other hand, when one element is referred to as being "directly on", "directly connected", or "directly coupled" to another element, it is interpreted that there are no other components intervening therebetween do. Like numbers refer to like elements. As used herein, the term "and / or" includes any and all combinations of one or more of the listed items.

Although the terms first, second, etc. are used herein to describe various elements, components, regions, layers and / or portions, these members, components, regions, layers and / It is obvious that no. These terms are only used to distinguish one member, component, region, layer or section from another region, layer or section. Thus, a first member, component, region, layer or section described below may refer to a second member, component, region, layer or section without departing from the teachings of the present invention.

Also, relative terms such as "top" or "above" and "under" or "below" can be used herein to describe the relationship of certain elements to other elements as illustrated in the Figures. Relative terms are intended to include different orientations of the device in addition to those depicted in the Figures. For example, in the figures the elements are turned over so that the elements depicted as being on the top surface of the other elements are oriented on the bottom surface of the other elements. Thus, the example "top" may include both "under" and "top" directions depending on the particular orientation of the figure. If the elements are oriented in different directions (rotated 90 degrees with respect to the other direction), the relative descriptions used herein can be interpreted accordingly.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a," "an," and "the" include singular forms unless the context clearly dictates otherwise. Also, " comprise "and / or" comprising "when used herein should be interpreted as specifying the presence of stated shapes, numbers, steps, operations, elements, elements, and / And does not preclude the presence or addition of one or more other features, integers, operations, elements, elements, and / or groups.

Hereinafter, embodiments of the present invention will be described with reference to the drawings schematically showing ideal embodiments of the present invention. In the figures, for example, variations in the shape shown may be expected, depending on manufacturing techniques and / or tolerances. Accordingly, the embodiments of the present invention should not be construed as limited to the particular shapes of the regions shown herein, but should include, for example, changes in shape resulting from manufacturing.

1 is a diagram illustrating a configuration of a general short range wireless communication (NFC).

Referring to FIG. 1, a typical short range wireless communication (NFC) configuration includes an NFC control integrated circuit portion 142, a USIM CHIP 144, and a reader 148. A first inductor 146 and a second inductor 147 are provided between the waveguide chip 144 and the reader 148 and a first capacitor portion 145 is provided between the waveguide chip 144 and the first inductor 146, May be provided. A second capacitor portion 143 may be provided between the NFC control integrated circuit portion 142 and the idler chip 144. The first inductor 146 and the first capacitor portion 145 are connected to the NFC control integrated circuit portion 142, the second capacitor portion 143 and the buffer chip 144 through the NFC external connection terminal.

FIGS. 2A and 2B are views schematically illustrating a configuration of an NFC chip antenna module package according to an embodiment of the present invention. FIGS. 2C to 2D are views showing a configuration of an NFC chip antenna module package according to another embodiment of the present invention. Fig.

2A and 2B, FIG. 2A is a top view of an NFC chip antenna module package 1000 according to an embodiment of the present invention, FIG. 2B is a plan view of an NFC chip antenna module package The NFC chip antenna module package 1000 includes a substrate 200 having a plurality of terminals, an antenna chip 246 mounted on the upper surface and / or lower surface of the substrate 200, And an extended antenna loop 346. The extended antenna loop 346 is formed on at least one side of the substrate 200 and may be electrically connected to the antenna chip 246. 2A and 2B, when the antenna chip 246 is formed on the upper surface of the substrate 200, the extended antenna loop 346 is formed on the other surface opposite to the antenna chip 246 . The extended antenna loop 346 may perform the auxiliary antenna function of the antenna chip 246 according to the length of the extended antenna loop 346. [

The NFC chip antenna module package 1000 may expose at least one connection terminal 430 of the plurality of terminals of the substrate 200 to at least a part of the substrate 200. The connection terminal 430 is formed of a conductive pad and can be electrically connected to a part of the external connection terminals of the battery protection circuit package. Some of the external connection terminals may be, for example, an NFC terminal and a CF terminal.

The antenna chip 246 and the connection terminal 430 may further include an NFC matching element 245 spaced apart from each other. The matching element 245 may be composed of at least one or more capacitors. The extended antenna loop 346 may be implemented with a conductive line pattern in the form of a loop. When both ends of the extension antenna loop 346 are in contact with the NFC connection terminal 430, they can be electrically connected to the NFC matching device 245 to form a closed loop. For example, the frequency band for NFC communication of 13.56 MHz can be generated using the resonance generated in the capacitor, which is the antenna chip 246 and the NFC matching device 245, to communicate with the NFC device.

The antenna chip 246 corresponds to the first inductor 146 shown in FIG. 1, and the capacitor corresponds to the first capacitor unit 145 shown in FIG. The first inductor 146 and the first capacitor portion 145 are connected to the NFC control integrated circuit portion 142, the second capacitor portion 143 and the buffer chip 144 through the NFC external connection terminal. Here, although not shown, an NFC control integrated circuit portion 142 and a second capacitor portion 143 may be embedded in the NFC chip antenna module package 1000. In addition, the NFC chip antenna module package 1000 may be built in the waveguide chip 144 to be one-chip.

In addition, the antenna chip 246 may support Near Field Communication (NFC), for example. It includes an inductor that can resonate in the NFC frequency band, and can have a variety of winding configurations. For example, it may have a chip shape as shown in Figs. 2A and 2B. The antenna chip 246 may include an inductor capable of resonating in the NFC frequency band wherein the inductor making up the antenna chip 246 corresponds to at least a portion of the first inductor 146 shown in FIG. do.

Furthermore, the antenna chip 246 according to the embodiment of the present invention may further include at least one selected from the first capacitor unit 145, the second capacitor unit 143, and the NFC control integrated circuit unit 142 shown in FIG. 1 .

In the case of the NFC antenna according to the comparative example of the present invention, the film-shaped NFC antennas are disposed and bonded through the soldering process in the process of assembling the battery pack. However, the antenna chip 246 according to the embodiment of the present invention, The antenna soldering process can be omitted, and the antenna chip 246 can be mounted and sealed in the form of a chip to improve the shear strength from the viewpoint of the overall structure.

Referring to FIGS. 2A and 2B, the antenna chip 246 including an inductor capable of resonating in the NFC frequency band may have various winding structures.

As a first example, the winding structure shown in Figure 2a (a) includes a coil having a first winding direction. For example, the winding structure may include a core 246a of nickel ferrite; And a coil 246c having a first winding direction wound in a direction parallel to the x-axis direction and the z-axis direction so as to surround the bobbin 246b. In this case, near field communication can be realized when the direction of the induced magnetic field generated in conjunction with the NFC reader 148 is positioned in parallel with the y axis direction.

As a second example, the antenna chips 246 including the winding structure shown in (b) of FIG. 2A may be arranged in a plurality of spaced apart from each other. If the NFC antenna has a chip shape, a plurality of chips including the NFC antenna may be provided. The description of each winding structure is the same as that described in the first example. That is, each of the plurality of antenna chips 246 may include a coil 246c having the same first winding direction as shown in FIG. 2A (a). On the other hand, as a modified embodiment, when the NFC antenna has a chip form, a plurality of chips including the NFC antenna may be provided in the single chip, and a plurality of the coil structures shown in FIG. have. In the case of having such a winding structure, the effect of improving the sensitivity of the short-range magnetic field communication can be expected as compared with the case of the antenna chip 246 of the first example.

As a third example, the antenna chip 246 includes a plurality of antenna chips 246 spaced from each other, and some antenna chips 246 of the plurality of antenna chips 246 are connected to the first And the other of the plurality of antenna chips 246 includes a coil 246c having a winding direction that is perpendicular to the first winding direction as shown in FIG. And a coil 246c having a second winding direction. For example, the winding structure having the first winding direction may include a core 246a made of nickel ferrite; And a coil (246c) wound in parallel with the x-axis direction and the z-axis direction so as to surround the bobbin (246b), and the winding structure having the second winding direction includes a core (246a) made of nickel ferrite; And a coil 246c wound in a direction parallel to the y-axis direction and the z-axis direction so as to surround the bobbin 246b.

If the NFC antenna has a chip form, the first antenna structure having a chip-shaped winding structure having the first winding direction and the second antenna structure having a chip-shaped winding structure having the second winding direction . As another example, a winding structure including a winding structure including the coil 246c having the first winding direction and a coil 246c having the second winding direction in a single chip including the antenna chip 246 . In the case of having such a winding structure, near field communication can be realized even if an arbitrary angle is formed without being positioned side by side, and the sensitivity of the near field communication can be expected to be improved.

On the other hand, a winding wire structure constituting the antenna chip 246 has been described as a winding structure in which a coil is wound around a core as an example. However, the antenna chip 246 according to the technical idea of the present invention is not limited to such a winding structure, and may be realized by patterning a conductive material, for example.

2C is a top view of an NFC chip antenna module package 1000 according to another embodiment of the present invention. FIG. 2D is a cross-sectional view of the NFC chip antenna module package shown in FIG. 1000, respectively. At least a part of the NFC chip antenna module package 1000 may be sealed by the sealing material 900 to protect the NFC chip antenna module package 1000. [ For example, it is possible to seal the NFC chip antenna module package 1000 shown in FIGS. 2A and 2B using an encapsulant 900, so that at least a part of the connection terminal 430 is exposed. That is, the surface of the connection terminal 430 may be exposed so that the surface of the connection terminal 430 can be electrically connected to a part of the external connection terminals of the battery protection circuit package or other electronic component material.

3A and 3B are schematic views illustrating submodules constituting an NFC chip antenna module package according to an embodiment of the present invention.

Referring to FIGS. 3A and 3B, the sub-module 100 constituting the NFC chip antenna module package according to an embodiment of the present invention may include a printed circuit board (PCB) as the substrate 200. The connection terminals 430 may be formed on the upper surface and / or the lower surface of the substrate 200 as shown in FIGS. 2A and 2B. Here, since the connection terminal 430 is the same as that described above with reference to FIGS. 2A and 2B, a detailed description of the connection terminal 430 is omitted.

The submodule 100 may include at least one antenna terminal 410 that is different from the connection terminal 430 among the plurality of terminals of the substrate 200. The antenna terminals 410 may be spaced apart from each other according to the size of the antenna chip 246 so that the antenna chip 246 shown in FIG. 2A can be mounted. The antenna chip 246 may be mounted using at least a portion of the surface of the substrate 200 and on the antenna terminal 410 using surface mount technology. The submodule 100 may further include a matching element connection terminal 420 between the antenna terminal 410 and the connection terminal 430 among the plurality of terminals of the substrate 200 to be electrically connected. The NFC matching element 245 may be mounted using the surface mounting technique on the matching element connection terminal 420. The NFC matching element 245 may be composed of at least one or more capacitors.

An extended antenna loop 346 may be formed on the other surface of the substrate 200 on which the antenna chip 246 shown in FIG. 2A is mounted. Both ends of the extended antenna loop 346 are connected to the antenna chip 246 and / or the NFC matching device 500 shown in FIG. 2A by at least two via patterns 500a, 500b, 500c, (Not shown). As shown in FIGS. 2A and 2B, the circuit can be configured such that the conductive line pattern, that is, the wiring pattern can be electrically connected by the via patterns 500a, 500b, 500c, and 500d provided on the substrate 200 . Thereby, the antenna chip 246, the extension antenna loop 346, the matching element 245, or the connection terminal 430 formed on the upper surface and / or the lower surface of the substrate 200 can be electrically connected. Concrete structures and techniques for the via patterns 500a, 500b, 500c, and 500d are already well known, and a detailed description thereof will be omitted.

In addition, the extended antenna loop 346 may include a pattern in the form of a loop formed on the upper surface and / or the lower surface of the substrate 200, that is, a conductive line pattern. The extended antenna loop 346 may be a pattern formed by bending at least one time in a helical form. 3B, when the substrate 200 is divided into two halves, the center of the upper side of the substrate 200 is rotated in a counterclockwise direction by an axis (axis perpendicular to the substrate 200 surface) The line pattern can be formed by being wound about four times. That is, a plurality of lines are formed by rotating the via pattern 500a disposed on the upper side of the substrate 200 in a counterclockwise direction about a central axis perpendicular to the substrate 200, and the via patterns 500a, An extended antenna loop 346 finished in another via pattern 500b may be formed. Here, the loop has an arbitrary shape capable of generating an inductance. Also, the loop is not necessarily limited to a closed loop.

Meanwhile, the length of the extended antenna loop 346 is set so that the ratio of the value of the inductance generated in the extended antenna loop 346 and the value of the inductance generated in the antenna chip 246 shown in FIG. 2A is 13% or more .

The conductive line pattern shown in Figs. 2A, 2B and 3B, that is, the extended antenna loop 346, has a shape capable of generating an inductance and can have at least some shape of a loop capable of generating, for example, have. The inductance is a quantity representing the ratio of the counter electromotive force generated by the electromagnetic induction by the change of the current flowing through the circuit, and the unit is H (Henry).

The present inventor has found that the inductance value generated in the extended antenna loop 346 is smaller than the predetermined value of the inductance value generated in the antenna chip 246 so that the extended antenna loop 346 does not remain in a simple conductive pattern, Of the total population.

Table 1 shows the results of testing whether the NFC auxiliary antenna functions according to the magnitude of the inductance value generated in the extended antenna loop 346 when the inductance value generated from the antenna chip 246 is 0.56 μH.

Experimental Example Extended antenna inductance value (μH) Extension antenna length (mm) Inductance ratio NFC auxiliary antenna
Functionality Experimental Example 1 0.04 34 6% x Experimental Example 2 0.05 37 8% x Experimental Example 3 0.07 43 11% x Experimental Example 4 0.08 47 13% o Experimental Example 5 0.09 50 14% o

Referring to Experimental Example 1, when the length of the extended antenna loop 346 forming the loop is 34 mm, the inductance value generated in the extended antenna loop 346 is 0.04 μH, but the extended antenna loop 346 has the NFC auxiliary antenna function . That is, when the inductance value generated in the extended antenna loop 346 is only 6% of the inductance value generated in the antenna chip 246, an extension antenna composed of the extended antenna loop 346 is introduced. However, It did not appear.

On the other hand, referring to Experimental Example 4, when the length of the extended antenna loop 346 forming the loop was 47 mm, the inductance value generated in the extended antenna loop 346 was 0.08 μH, and the extended antenna loop 346 was NFC Auxiliary antenna function was performed. That is, when the inductance value generated in the extended antenna loop 346 reaches 13% of the inductance value generated by the antenna chip 246, the improvement of the NFC recognition distance is performed by the extended antenna composed of the extended antenna loop 346 appear.

The results of the experiments 1 to 5 are as follows. By ensuring that the length of the extended antenna loop 346 constituting the extended antenna is equal to or longer than the predetermined length, the value of the inductance generated in the extended antenna loop 346, It is confirmed that the NFC recognition distance is improved by the extension antenna formed by the extended antenna loop 346 when the ratio of the inductance value generated in the extended antenna loop 346 is equal to or larger than a predetermined ratio (for example, 13%).

As described above with reference to Table 1, by ensuring that the length of the extended antenna is longer than the predetermined length, the value of the inductance generated in the extended antenna loop 346 and the value of the inductance generated in the antenna chip 246 It is confirmed that the NFC recognition distance is improved by the extension antenna when the ratio of the values is more than a predetermined ratio (for example, 13%).

FIG. 4A is a schematic view illustrating a manner in which an NFC chip antenna module package according to an embodiment of the present invention is connected to a main set. FIGS. 4B and 4C are views showing an NFC chip antenna module package according to another embodiment of the present invention. Lt; / RTI > is connected to the main set.

4A, the NFC chip antenna module package 1000 according to an embodiment of the present invention is not inserted and fixed in the form of a semiconductor package, but the NFC chip antenna module package 1000 is separated from the battery protection circuit package Can be mounted and fixed using surface mount technology on at least a portion of the main set 10.

Referring to FIGS. 4B and 4C, the NFC chip antenna module package 1000 according to another embodiment of the present invention may be connected to the main set 10 using a coaxial cable. Here, the connection terminal 1100 may be formed on one side of the NFC chip antenna module package so that one end 50a of the coaxial cable 50 can be connected. At this time, the other end 50b of the coaxial cable 50 may be connected to at least a part of the main set 10. Accordingly, the NFC chip antenna module package 1000 can be electrically connected to the main set 10 separately from the battery protection circuit package.

As described above, when the conventional NFC antenna is used, the mounting position is very limited due to the size of the antenna itself by using the RF antenna. Further, if a battery pack is manufactured by employing a metal body, the performance of the antenna is reduced. In addition, when the NFC chip antenna is used, the antenna size is small, so that the recognition range distance is limited according to the size of the NFC chip antenna, thereby reducing the performance of the antenna.

In order to solve this problem, the NFC chip antenna module package according to the embodiment of the present invention can be integrated and miniaturized, and it is possible to give a degree of freedom to the positioning of the antenna. Further, it is possible to extend the recognition range and the distance of the antenna using the extended antenna loop, and to provide the NFC chip antenna module package with improved antenna performance. In addition, it can be formed directly on the main set separately from the battery protection circuit package to perform the NFC antenna function.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

10: Main set 50: Coaxial cable
100: Sub-module 200: Substrate
245: Matching element 246: Antenna chip
346: Extension antenna loop 410: Antenna terminal
420: matching device connection terminal 430: connection terminal
500: via pattern 900: sealing material
1000: NFC Chip Antenna Module Package

Claims (12)

A substrate having a plurality of terminals;
An antenna chip mounted on the substrate and having an NFC antenna connected to at least one of the plurality of terminals; And
An elongated antenna loop formed on at least one side of the substrate and electrically connected to the antenna chip;
/ RTI >
NFC chip antenna module package. The method according to claim 1,
The plurality of terminals including an antenna terminal connectable to an antenna chip;
At least one connection terminal capable of being electrically connected to a part of external connection terminals of the battery protection circuit package; And
And at least one matching element connection terminal capable of being electrically connected between the antenna terminal and the connection terminal. 3. The method of claim 2,
And an NFC matching device formed on the matching device connection terminal, the NFC matching device being connectable to the antenna chip and the extended antenna loop. The method according to claim 1,
Wherein the extended antenna loop is formed on the other surface opposite to one surface of the substrate on which the antenna chip is mounted. 5. The method of claim 4,
Wherein both ends of the extended antenna loop are electrically connectable to the antenna chip and / or the NFC matching element by at least two via patterns passing through the substrate. The method according to claim 1,
Wherein the length of the extended antenna loop is set such that the ratio of the value of the inductance generated in the extended antenna loop to the value of the inductance generated in the antenna chip is 13% or more. The method according to claim 1,
Wherein the extended antenna loop includes a loop-shaped pattern formed on an upper surface and / or a lower surface of the substrate. 8. The method of claim 7,
Wherein the extended antenna loop is formed by bending at least once in a spiral form. The method according to claim 1,
Wherein the antenna chip comprises an inductor capable of resonating in an NFC frequency band. The method according to claim 1,
Wherein the antenna chip is mounted using surface mount technology on at least a portion of the surface of the substrate. The method according to claim 1,
Wherein the substrate comprises a printed circuit board (PCB). The method according to claim 1,
And an encapsulant that exposes at least a portion of the plurality of terminals and encapsulates the antenna chip and the extended antenna loop.

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