JP2013236141A - Antenna device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antenna device that is small enough to have it contained in a mobile communication device, that is able to receive a signal of FM radio broadcast, and that reduces an impact of noise without installing a metal shielding member and the like.SOLUTION: An antenna device comprises: a chip antenna provided with a first radiation electrode; a power supply terminal to the first radiation electrode; and a support member provided with a second radiation electrode. On the support member, the chip antenna is mounted such that the chip antenna overlaps with the second radiation electrode with space in between. The first radiation electrode of the chip antenna is formed in a coil shape, the second radiation electrode of the support member is formed in a linear shape, one end of the first radiation electrode is connected with the power supply terminal, the other end is connected with one end of the second radiation electrode, and the second radiation electrode is placed farther from a circuit board on which the support member is mounted than the first radiation electrode.

Description

  The present invention relates to an antenna device used in a small mobile communication device such as a mobile phone, and more particularly to an FM radio broadcast receiving antenna device that can be miniaturized.

  In recent years, mobile communication devices such as mobile phones have become more multifunctional, and many have an additional function of receiving FM radio as well as calls. In FM radio broadcasting using the VHF band, it is used as an antenna by selecting the cable length of an earphone for listening to the audio signal according to the reception frequency. On the other hand, FM radio broadcasts cannot be received unless earphones are connected, so there has been a demand for a small antenna device that can be built into a mobile communication device.

  To deal with such a problem, Patent Document 1 discloses that a conductive film is coated on the first antenna 223 mounted on the printed circuit board 220 and the empty part of the cabinet of the mobile phone as shown in FIG. It is described that the formed second antenna 213 is connected at one end side 214 and 224 to form one FM radio broadcast receiving antenna device having a necessary length.

JP 2006-217381 A

  The receiving antenna device of Patent Document 1 is configured by a monopole antenna that operates at a length of ¼ of the wavelength λ. For example, the physical length of the antenna required to receive an 80 MHz signal, which is the FM radio reception band, is approximately 86 cm. Even if the wavelength shortening effect by the insulator indicating the antenna is expected to be about 50%, a length exceeding 40 cm is required.

  In Patent Document 1, the first antenna 223 mounted on a printed circuit board is a copper plate antenna formed by bonding a plate obtained by punching a copper plate into a predetermined shape to a resin molded body 222. According to the embodiment built in the mobile phone, the length is estimated to be about 10 cm at most. In order to secure the physical length of the antenna necessary for reception, it is necessary to configure the second antenna configured as a linear vapor deposition antenna to be considerably long. Since the second antenna is formed on the same surface as the shield, if the second antenna becomes longer, the area of the shield is reduced correspondingly, and noise from inside the housing leaks to the outside, or conversely from the outside. Noise may enter and cause malfunctions.

  In addition, as a result of diligent research by the present inventor, when a receiving antenna device is built in a mobile communication device, noise is likely to be superimposed on the frequency band of FM radio broadcasting due to the influence of noise generated in the housing. found. Although the source is not clear, it becomes noise that is modulated and superimposed on the audible sound. Although it is possible to prevent noise interference by installing a metal shielding plate between the antenna device and the high-frequency circuit part that is the source of noise, it also shields radio waves from the direction of the shielding plate, thus reducing the gain as an antenna device. There was a problem of letting it go.

  Therefore, an object of the present invention is to provide an antenna device that can be incorporated in a mobile communication device, can receive FM radio broadcast signals, and has reduced noise influence.

  The present invention includes a chip antenna in which a first radiation electrode is provided on a ceramic base, a power supply terminal to the first radiation electrode on an insulating member, a mounting terminal, and a support member in which a second radiation electrode is provided. The chip antenna is mounted on the support member so as to overlap the second radiation electrode with a gap, the first radiation electrode of the chip antenna is configured in a coil shape, and the second radiation electrode of the support member is linear. The one end of the first radiation electrode is connected to the feeding terminal, the other end is connected to one end of the second radiation electrode, and the second radiation electrode is more supported than the first radiation electrode. An antenna device is characterized in that the member is located away from a substrate on which the member is mounted.

The chip antenna preferably uses a magnetic member as a ceramic substrate. Use magnetic alloys such as Ni-based, Li-based, and Mn-based soft magnetic ferrite, Fe-Si based, Fe-based and Co-based amorphous materials, and ultra-crystalline soft magnetic materials as the magnetic material constituting the magnetic member. I can do it.

When soft magnetic ferrite is used as the magnetic material, the main component is ferric oxide (Fe ₂ O ₃ ), zinc oxide (ZnO), nickel oxide (NiO), and copper oxide (CuO). And a magnetic member is obtained by sintering. The sintered body may be used as a magnetic member as it is, but may be processed into a predetermined shape by a processing means such as grinding.

  In some cases, a green sheet obtained by a known sheet forming technique such as a doctor blade method is processed into a predetermined shape, and a single layer or a laminate is formed, and the obtained laminate is sintered to form a magnetic member. Also in this case, the green sheet or the sintered body may be processed into a predetermined shape by means such as grinding.

  Magnetic alloys such as amorphous and ultra-microcrystalline soft magnetic materials are usually provided in the form of ribbons, so they are made into powder or flakes, dispersed in resin or rubber, and then formed into sheets or blocks of a predetermined shape It can also be used as a magnetic member.

The first radiation electrode is formed of a coiled conductor on a ceramic base, and a conducting wire is wound in the winding axis direction. The conducting wire used for the first radiation electrode is preferably a single enameled wire, more preferably an enameled wire (self-bonded wire) on which an overcoat (fused layer) having a fusion force is formed. The fusion layer is activated by heat or a solvent, and handling in the assembly process is facilitated by making the coil 20 a self-fusion coil. Moreover, it is preferable that the wire diameter is 30 micrometers-80 micrometers.
When a ceramic substrate is formed as a multilayer body, a conductive paste of a low resistance metal such as Ag or Cu is used and printed on a green sheet in a predetermined pattern. A well-known coil configuration may be used.

  The support member is made of an insulating material, but it is preferable to use a resin member in view of formability and ease of integration of the power supply terminal and the like. The resin member is preferably configured using a high heat-resistant thermoplastic engineering plastic such as a liquid crystal polymer or polyphenylene sulfide that can withstand high temperatures such as solder reflow as the resin composition.

The support member is provided with a power supply terminal, a mounting terminal, and a second radiation electrode on the surface of an insulating member formed in a substantially rectangular shape. It is preferable that the power supply terminal and the mounting terminal are configured to appear at least on the bottom surface and the side surface of the support member. Further, it is preferable that the second radiating electrode is configured so as to appear at the top surface opposite to the bottom surface at a position at least overlapping with the chip antenna.
Cu, Cu, brass, phosphor bronze, and other Cu alloys and Fe-Ni-Co alloys are used for the power supply terminal, mounting terminal, and second radiation electrode, respectively. In some cases, it may be fixed to the insulating member by means of, for example, or may be integrated by insert molding.

  The support member is formed as a cap shape by forming a groove from one side of the pair of opposite side surfaces of the resin member toward the other and forming a U-shaped cross section or forming a recess. It is preferable to dispose the chip antenna in the groove or recess.

  In the present invention, the winding axis of the first radiation electrode of the chip antenna is preferably configured to be substantially parallel to the substrate on which the receiving antenna device is mounted. By preventing the conductor included in the second radiation electrode from spreading vertically with respect to the magnetic flux passing through the base, it is possible to prevent a decrease in gain of the antenna device.

  The other end of the second radiation electrode is a free end, and the second radiation electrode is bent in a plane where the free end of the second radiation electrode of the support member is located, and the physical length of the second radiation electrode is increased. It is also preferable to secure the configuration.

  According to the present invention, an antenna that is small enough to be incorporated in a mobile communication device, can receive FM radio broadcast signals, and has reduced influence of noise without providing a metal shielding member or the like. A device can be provided.

  Since the receiving antenna device can be built in the mobile communication device without increasing the number of parts and the work process, the manufacturing time can be shortened and the manufacturing cost can be reduced, and the mobile communication device can be provided at low cost. Become. In addition, since a shielding member or the like is not necessary, it is possible to increase the number of functions or to reduce the size by using the corresponding empty area.

It is the perspective view which looked at the antenna apparatus which concerns on one Example of this invention from the upper surface side. It is the top view which looked at the antenna apparatus which concerns on one Example of this invention from the lower surface side. It is the side view which looked at the antenna apparatus which concerns on one Example of this invention from the A direction side. It is the side view which looked at the antenna apparatus which concerns on one Example of this invention from the B direction side. It is a-a 'sectional drawing of the antenna device which concerns on one Example of this invention. It is an external appearance perspective view of the chip antenna used for the antenna apparatus which concerns on one Example of this invention. It is an external appearance perspective view of the chip antenna used for the antenna apparatus which concerns on the other Example of this invention. It is a figure for demonstrating the mounting state to the board | substrate of the antenna apparatus which concerns on one Example of this invention. It is a figure for demonstrating the built-in state to the mobile communication apparatus of the antenna apparatus which concerns on one Example of this invention. It is a perspective view which shows the structure of the conventional antenna device.

The antenna device of the present invention will be described with reference to the drawings.
1 is a perspective view of the antenna device as viewed from the upper surface side, FIG. 2 is a plan view as viewed from the lower surface side, FIG. 3 is a side view as viewed from the A direction side, and FIG. The seen side view is shown, and aa 'sectional drawing is shown in FIG. 6 is an external perspective view of a chip antenna used in the antenna device, and FIG. 7 is an external perspective view of a chip antenna having another configuration used in the antenna device. FIG. 8 is a perspective view showing a state where the antenna device is mounted on a substrate.

  The antenna device 1 shown here includes a chip antenna 5 in which a coil serving as a first radiation electrode 7 is provided on a ceramic base 6, a power supply terminal 10 to the first radiation electrode on an insulating member, a mounting terminal 15, The support member 20 provided with the second radiation electrode 30 is provided. A linear second radiation electrode 3 is provided so as to overlap the first radiation electrode 7, and the antenna device is configured to be downsized in plan.

  The support member 20 is formed with a groove portion 22 in the longitudinal direction from one side to the other of a pair of opposing side surfaces, and has a U-shaped cross section. On the two leg portions facing each other with the groove portion 22 in between, the feeding terminal 10 and the mounting terminal 15 are formed on both ends in the longitudinal direction. Each of the power supply terminal 10 connected to the power supply line 70 formed on the substrate 61 and the mounting terminal 15 connected to the mounting pad (not shown) formed on the substrate 61 is a leg portion of the resin member. Is U-shaped so that it is gripped in the thickness direction. Furthermore, the power supply terminal 10 reaches the bottom of the groove 22 and constitutes a connection portion 11 a for connection with the coil end portion 8 b of the chip antenna 5.

  A linear second radiation electrode 30 is formed on the top surface side of the support member 20. One end side of the second radiation electrode 30 passes through the side surface of the support member 20 and reaches the bottom of the groove portion 22, and the end portion constitutes a connection portion 11 b for connection with the coil end portion 8 a of the chip antenna 5. It is formed wide. Solder or conductive adhesive is used for electrical connection.

  The groove portion 22 formed in the support member 20 can accommodate the chip antenna 5, and has such a depth that the entire chip antenna 5 falls below the bottom surface of the support member 2 that is the mounting surface on the substrate 61. Yes.

  FIG. 8 shows a state where the antenna device is mounted on a substrate. Usually, the substrate 61 on which the antenna device 1 is mounted is provided with a ground electrode GND. If a parasitic capacitance is formed between the ground electrode GND and the first radiating electrode 7 or the second radiating electrode 30, the gain of the receiving antenna device 1 deteriorates due to the capacitance, or an operating frequency (referred to as a resonance frequency). May move). In addition, an electromagnetic field that should be incident on the coil-shaped first radiation electrode 7 may be absorbed by the ground electrode, leading to a decrease in gain.

  According to the study by the present inventors, there are two methods for improving the gain characteristic which is reception performance among antenna characteristics of an antenna device using a chip antenna. One is to increase the volume of the chip antenna 5, and the other is to set the length of the conductor (also referred to as an element) that contributes to reception to the required length according to the monopole operation. .

  When the volume of the chip antenna is increased, the resonance frequency fo tends to decrease. Therefore, the element must be adjusted to an appropriate resonance frequency fo by extremely shortening the element, and as a result, the reception performance decreases. On the other hand, minimizing the chip antenna and extending the element makes it easier to pick up noise while improving the reception performance, so it becomes as if it was received by the human ear, resulting in a voice that contains noise. It feels like the performance has dropped.

  Since mobile communication devices differ in size and structure of the case and component arrangement around the chip antenna, the optimum element length or the optimum chip antenna volume cannot be specified in general, but noise is individually applied to each device. It is possible to find a combination that is difficult to pick up and that satisfies the reception performance. However, after mounting the chip antenna on the printed circuit board, there is a phenomenon that the resonance frequency drifts, and the cause is capacitive coupling with the ground pattern of the printed circuit board, and it has been found that this greatly affects the reception performance.

  In the antenna device 1 of the present invention, there is a space between the mounting surface on the substrate 61 and the chip antenna 5, and the second radiation electrode 30 is located farther from the substrate 61 than the first radiation electrode 7, Each radiation electrode is kept as far as possible from the ground electrode, and an air layer is positively provided between the first and second radiation electrodes and the ground electrode. According to such a configuration, the generated parasitic capacitance can be reduced. With such a configuration, a configuration insensitive to a signal from a noise source generated in the housing can be obtained, and noise superimposed on the audible sound can be reduced.

  The resin member constituting the support member 20 is made of a resin such as a liquid crystal polymer, polyphenylene sulfide, or other heat-resistant thermoplastic engineering plastic in consideration of heat exposed during solder reflow during mounting on the substrate 61. Is preferred. A polyimide resin, a fluororesin having a relative dielectric constant of 5 or less, preferably 4 or less, or a glass epoxy resin having a limited shape can also be used.

  The ceramic base 6 constituting the chip antenna 5 provided with the first radiation electrode 7 is preferably made of a magnetic member. Use magnetic alloys such as Ni-based, Li-based, and Mn-based soft magnetic ferrite, Fe-Si based, Fe-based and Co-based amorphous materials, and ultra-crystalline soft magnetic materials as the magnetic material constituting the magnetic member. I can do it. Magnetic alloys such as amorphous and microcrystalline soft magnetic materials are usually provided in the form of ribbons, so they are processed into sheets of a predetermined shape and laminated into a single layer or multiple layers to form a magnetic member It can be. Also, the magnetic material can be made into a powder or flake form, dispersed in resin or rubber, and then molded into a magnetic member. The shape is not limited as long as it does not depart from the idea of the present invention, such as a sheet shape or a block shape.

  As shown in FIG. 6, the chip antenna 5 has a structure in which a conducting wire 7 is wound around a magnetic member constituting the base 6 or inside the magnetic member constituting the base 6 as shown in FIG. There is a laminated structure constituting the conductor 7.

  Further, the first radiating electrode 7 and the second radiating electrode 30 are stacked to form a parasitic capacitance between them. The operating frequency of the receiving antenna device can be lowered by the capacity. The capacitance value can be adjusted by an interval and an area where the first radiation electrode 7 and the second radiation electrode 30 are opposed to each other, or a relative dielectric constant of an interposed resin member. In addition, as shown in FIG. 2, a recess 45 may be formed at the bottom of the groove 22 provided in the support member 20, and an air layer may be provided to adjust the parasitic capacitance.

  FIG. 9 shows a state where the antenna device is built in the mobile communication device. An excellent reception performance can be obtained by arranging the second radiation electrode 30 close to the housing 90 of the mobile communication device.

DESCRIPTION OF SYMBOLS 1 Antenna apparatus 5 Chip antenna 7 1st radiation | emission electrode 8a, 8b Coil end part 10 Feed terminal 11a, 11b Connection part 15 Mounting terminal 20 Support member 22 Groove part 30 2nd radiation electrode

Claims (3)

A chip antenna provided with a first radiation electrode on a ceramic substrate; a power supply terminal for the first radiation electrode on an insulating member; a mounting terminal; and a support member provided with a second radiation electrode. And the chip antenna is mounted so as to overlap the second radiation electrode with a gap,
The first radiating electrode of the chip antenna is configured in a coil shape, the second radiating electrode of the support member is configured in a linear shape, one end of the first radiating electrode is connected to the feeding terminal, and the other end is Connected to one end of the second radiation electrode;
The antenna device, wherein the second radiation electrode is located farther from a substrate on which the support member is mounted than the first radiation electrode. The antenna device according to claim 1,
The antenna device according to claim 1, wherein a winding axis of the first radiation electrode of the chip antenna is substantially parallel to the substrate. The antenna device according to claim 1 or 2,
The antenna device, wherein the other end of the second radiation electrode is a free end, and the second radiation electrode is bent in a plane where the free end of the second radiation electrode of the support member is located.

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