JP2013058987A - Double resonant antenna and communication device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a double resonant antenna and a communication device using the same capable of suppressing deterioration in radiation characteristics of a high-frequency side antenna electrode caused by a high harmonic wave generated at a low-frequency side antenna electrode.SOLUTION: A low-frequency side antenna electrode 1 and a high-frequency side antenna electrode 2 are juxtaposed to a dielectric base substance 3, and provided to have one end commonly connected to a power feeding end. The other end of the low-frequency side antenna electrode 1 is a free end, and the low-frequency side antenna electrode 1 has an electric length of λ/4. The other end of the high-frequency side antenna electrode 2 configures a ground end that is electrically grounded, and the high-frequency side antenna electrode 2 has an electric length of λ/2.

Description

  The present invention relates to a multi-resonant antenna and a communication apparatus using the same.

  A double resonance antenna (sometimes referred to as a dual band antenna or a multi band antenna) includes two antenna electrodes having different resonance frequencies on one chip. Different frequency bands can be accommodated. As an example of a device using a multi-resonant antenna, a mobile communication device having a GPS (Global Positioning System) function and a Bluetooth (registered trademark hereinafter omitted) function, for example, a mobile phone can be cited. GPS uses radio waves in the 1.57 GHz band, and Bluetooth uses radio waves in the 2.45 GHz band, and a multi-resonance antenna that can handle these frequency bands is required. As such a multi-resonant antenna, for example, Patent Document 1 discloses an antenna in which a low-frequency antenna electrode and a high-frequency antenna electrode are provided on the main surface of a dielectric substrate.

  Recently, with the development of information technology, mobile phones and the like have come to include data with a large amount of information such as images in data exchanged via wireless LAN. Therefore, among the information transmitted and received by the wireless LAN, data having a large amount of information is transmitted and received in a high-frequency band (for example, 5.2 GHz band) having a high transmission rate, and normal data is transmitted in a low-frequency band (for example, 2. The 45-GHz band is used for different purposes.

  In the above-described multi-resonant antenna, the low-frequency side antenna electrode and the high-frequency side antenna electrode have a so-called bifurcated pattern in which one end is commonly connected to one feeding end and the other end is a free end. In general, the electrical length of the antenna to the end is λ / 4.

  However, in the above configuration, depending on the combination of frequencies, harmonics generated from the low frequency side antenna electrode act in a direction to attenuate the fundamental wave of the high frequency side antenna electrode for high frequencies, The radiation characteristics of the high frequency side antenna electrode may be deteriorated. The deterioration of the radiation characteristics of the high frequency side antenna electrode appears in the form of narrowing of the bandwidth.

JP 2005-167762 A

  An object of the present invention is to provide a multi-resonant antenna capable of suppressing deterioration in radiation characteristics of a high-frequency antenna electrode due to harmonics generated in a low-frequency antenna electrode, and a communication device using the same.

  In order to solve the above-described problems, a multi-resonant antenna according to the present invention includes a dielectric base, a low-frequency antenna electrode, and a high-frequency antenna electrode. The low frequency side antenna electrode and the high frequency side antenna electrode are provided side by side with the dielectric substrate, and one end thereof is commonly connected to the feeding end.

  The low frequency side antenna electrode has a free end at the other end and has an electrical length of λ / 4, and the high frequency side antenna electrode constitutes a ground end at which the other end is electrically grounded. , Λ / 2.

  As described above, the multi-resonant antenna according to the present invention includes a dielectric substrate, a low-frequency antenna electrode, and a high-frequency antenna electrode. The low-frequency antenna electrode and the high-frequency antenna electrode are dielectric materials. Since one end is connected to the base and one end is commonly connected to the power feeding end, it is possible to cope with two different frequency bands while being one chip.

  In addition, the low frequency side antenna electrode has a free end at the other end and has an electrical length of λ / 4, while the high frequency side antenna electrode constitutes a ground end at which the other end is electrically grounded. In addition, since it has an electrical length of λ / 2, harmonics generated from the low frequency side antenna electrode are prevented from attenuating the fundamental wave of the high frequency side antenna electrode, and the radiation characteristics of the high frequency side antenna electrode are deteriorated and the high frequency side Narrowing of the bandwidth at can be avoided.

  The meaning that the other end of the high frequency side antenna electrode is electrically grounded means that the other end of the high frequency side antenna electrode is not limited to being directly grounded. That is, the other end of the high frequency side antenna electrode may be grounded via a capacitor or an inductor. The capacitor or inductor as described above is useful for adjusting the antenna characteristics.

  As a specific form, the dielectric substrate has a main surface and four side surfaces. Most of the low-frequency side antenna electrode and the high-frequency side antenna electrode are formed on the main surface, and one end is guided to the feeding end through one of the four side surfaces. The low frequency side antenna electrode extends from the one side surface toward the opposite side surface, is folded along the other side surface, and the other end folded back ends at an intermediate position between the one side surface and the other side surface. On the other hand, the high frequency side antenna electrode is branched from the low frequency side antenna electrode at an intermediate position between the one side surface and the other side surface, extends in a direction parallel to the one side surface, and extends from the other end of the low frequency side antenna electrode to the one side surface. It is folded in the direction of one side surface at a position close to.

  According to this structure, the multi-resonant antenna according to the present invention can be realized as a miniaturized form.

  The dielectric substrate is preferably made of a composite dielectric material containing a synthetic resin and ceramic powder. The advantages of using such a composite dielectric material are that the dielectric constant of the dielectric substrate can be adjusted to adjust the antenna characteristics, the molding technique can be applied to form the required shape, and In addition, the dielectric substrate can be colored by mixing pigments or the like.

  Regarding the attachment structure of the low frequency side antenna electrode and the high frequency side antenna electrode to the dielectric substrate, the low frequency side antenna electrode and the high frequency side antenna electrode are supported by a flexible insulating film having adhesiveness, and flexible insulation is achieved. The film is preferably adhered on the dielectric substrate. This is because the low-frequency antenna electrode and the high-frequency antenna electrode can be applied quickly and efficiently to the dielectric substrate.

  In particular, when the low-frequency side antenna electrode and the high-frequency side antenna electrode are made of a conductor that is continuously formed on the same flexible insulating film, this advantage appears more remarkably. Moreover, the reinforcing action of the flexible insulating film prevents the conductors constituting the low-frequency antenna electrode and the high-frequency antenna electrode from being damaged at the corners of the dielectric substrate.

  The multi-resonant antenna according to the present invention can be widely applied to a system that needs to cope with two different frequency bands although it is a single chip. For example, there is an application to a wireless LAN used in a cellular phone. In this case, the low frequency side antenna electrode is adapted to the 2.4 GHz band, and the high frequency side antenna electrode is adapted to the 5 GHz band. In addition, a mobile communication device having a GPS (Global Positioning System) function and a Bluetooth (registered trademark hereinafter omitted) function, for example, a mobile phone can be given.

  The present invention further discloses a communication device using the above-described multi-resonant antenna. The communication device includes a multi-resonance antenna, a low-frequency communication unit, and a high-frequency communication unit, and the multi-resonance antenna is connected to the low-frequency communication unit and the high-frequency communication unit.

  As described above, according to the present invention, it is possible to provide a multi-resonant antenna capable of suppressing deterioration of radiation characteristics of a high-frequency antenna electrode due to harmonics generated in a low-circumference antenna electrode, and a communication device using the same. Can do.

  Other objects, configurations and advantages of the present invention will be described in more detail with reference to the accompanying drawings. The accompanying drawings are merely examples.

1 is a perspective view showing an embodiment of a multiple resonance antenna according to the present invention. It is the perspective view which looked at the double resonance antenna shown in FIG. 1 from the bottom face side. FIG. 3 is a circuit diagram of the multi-resonance antenna shown in FIGS. 1 and 2 in an operating state. It is sectional drawing of FPC which can be used for the multiple resonance antenna which concerns on this invention. It is a perspective view which shows the state which mounted the multiple resonance antenna which concerns on this invention on a circuit board. It is a perspective view which expands and shows the mounting state of FIG. It is the simulation data which compares the frequency-efficiency characteristic of the low frequency side about the multiple resonance antenna which concerns on this invention, and the multiple resonance antenna of the conventional structure. It is the simulation data which compares the frequency-efficiency characteristic of the high frequency side about the multiple resonance antenna which concerns on this invention, and the multiple resonance antenna of the conventional structure. It is a block diagram of the communication apparatus using the multi-resonance antenna which concerns on this invention.

  First, referring to FIG. 1, the multi-resonant antenna according to the present invention includes a low-frequency antenna electrode 1, a high-frequency antenna electrode 2, and a dielectric substrate 3. The dielectric substrate 3 is preferably made of a composite dielectric material obtained by mixing a synthetic resin and a dielectric ceramic powder. Examples of the synthetic resin include ABS (Acrylonitrile butadiene styrene) resin and PC (Polycarbonate) resin. As the dielectric ceramic powder, a barium titanate ceramic powder or a titanium oxide ceramic powder can be used. The advantage of using such a composite dielectric material is that the relative permittivity of the dielectric substrate 3 can be adjusted, it can be formed into a required shape by applying a forming technique, and the dielectric can be mixed by mixing pigments. For example, the body substrate 3 can be colored.

  The dielectric substrate 3 may be a solid block shape or a shape having an outer wall surface with most of the contents removed. In this embodiment, the latter shape is selected, and has an outer shape hexahedron having a main surface 31 and four side surfaces 32 to 35 and a bottom surface facing the main surface 31 having an opening 38. However, the outer shape is not limited to a hexahedral shape. Other shapes can be employed.

  The low frequency side antenna electrode 1 and the high frequency side antenna electrode 2 are provided side by side with the dielectric substrate 3, and one end thereof is commonly connected to the feeding end 100. The low frequency side antenna electrode 1 has a free end at the other end and has an electrical length of λ / 4, and the high frequency side antenna electrode 2 constitutes a ground end at which the other end is electrically grounded, It has an electrical length of λ / 2.

  Referring to FIG. 3, the low-frequency antenna electrode 1 and the high-frequency antenna electrode 2 have one end P <b> 1 serving as a power feeding end 100 connected to the signal source SG in common. The other end of the low frequency side antenna electrode 1 is a free end, and the other end P2 which is a ground end of the high frequency side antenna electrode 2 is electrically grounded.

  As a specific form, most of the low frequency side antenna electrode 1 and the high frequency side antenna electrode 2 are formed on the main surface 31 of the dielectric substrate 3, and one end of the side surface 35 of the four side surfaces 32 to 35 is formed. Then, it is guided to the power feeding end 100. One end of the low frequency side antenna electrode 1 and the high frequency side antenna electrode 2 is guided to the step surface 37 of the step portion 36 formed through the one side surface 35 and extending under the one side surface 35. The end 100 is configured.

  The low-frequency antenna electrode 1 extends from the side surface 35 toward the opposite side surface 33 and is folded along the other side surface 33, and the other end folded back is the side surface 35 and the other side surface 33. Ends at an intermediate position between. The low frequency side antenna electrode 1 has a length L1 from the feeding end 100 to the other end longer than the length L2 of the high frequency side antenna electrode 2, and the forward path portion 101 from one end to the return and the return path portion 102 after the return. And have. The forward path portion 101 and the return path portion 102 are continuous by the turn-back portion 103. The length L1 of the low-frequency antenna electrode 1 is a dimension measured along a center line passing through the width center. However, the strict start point of the length L1 varies depending on the electrode width, the assembly structure, and the like, and is not necessarily the end of the power feeding end 100 in FIG.

  On the other hand, the high-frequency antenna electrode 2 is branched from the low-frequency antenna electrode 1 at an intermediate position P0 between the one side surface 35 and the other side surface 33 and extends in a direction parallel to the one side surface 35. It is folded in the direction of the one side surface 35 at a position closer to the one side surface 35 than the other end. The high-frequency antenna electrode 2 passes through one side surface 35 and is guided to a step surface 37 of a step portion 36 formed over the lower side of the one side surface 35, and constitutes a ground end on the step surface 37. The length L2 of the high frequency side antenna electrode 2 is also a length from the feeding end 100 to the grounding end through the branch point with the low frequency side antenna electrode 1 and measured along the center line passing through the width center. Dimensions.

  The length L1 of the low-frequency antenna electrode 1 is determined so as to have an electrical length of λ / 4 in consideration of the target frequency and the relative dielectric constant of the dielectric substrate 3. Similarly, the length L2 of the high-frequency antenna electrode 2 is determined so as to have an electrical length of λ / 2 in consideration of the relative dielectric constant of the dielectric substrate 3. For example, when the multi-resonant antenna according to the present invention is applied to a mobile phone using a wireless LAN, the low-frequency antenna electrode 1 has an electrical wavelength of (λL) / 4 as a wavelength λL in the 2.4 GHz band. The high-frequency antenna electrode 2 has a length and is designed to have an electrical length of (λH) / 2 as a wavelength λH in the 5 GHz band.

  As shown in FIG. 4, the low-frequency antenna electrode 1 and the high-frequency antenna electrode 2 are preferably supported by a flexible insulating film CF having an adhesive layer A. The adhesive strength of the adhesive layer A is used to adhere to the dielectric substrate 3. An electrode film C to be an antenna electrode is provided on the main surface of the flexible insulating film CF. Specifically, FPC (Flexible Printed Circuits) having a low frequency side antenna electrode 1 and a high frequency side antenna electrode 2 formed to have a predetermined pattern on one surface is used. That is, the low-frequency antenna electrode 1 and the high-frequency antenna electrode 2 are composed of conductors continuously formed on the same flexible insulating film. And it adheres to the dielectric substrate 3 using the adhesive force of the adhesive layer A applied to the other surface of the FPC. According to this configuration, the low-frequency antenna electrode 1 and the high-frequency antenna electrode 2 can be applied to the dielectric substrate 3 quickly and efficiently.

  In addition, since the low-frequency antenna electrode 1 and the high-frequency antenna electrode 2 can be patterned on the flexible insulating film CF, high pattern accuracy can be ensured for the low-frequency antenna electrode 1 and the high-frequency antenna electrode 2. Can do.

  Further, since the low-frequency antenna electrode 1 and the high-frequency antenna electrode 2 are supported by the flexible insulating resin film CF, the low-frequency antenna electrode can be used even when attached to the corner of the dielectric substrate 3 or the like. 1 and the high frequency side antenna electrode 2 do not cause problems such as thinning of the electrode film.

  The multi-resonant antenna shown in FIGS. 1 to 3 is mounted on one surface of the circuit board 5 with the bottom of the dielectric substrate 3 facing each other, as shown in FIGS. 5 and 6. Then, the feeding end 100 and the ground end 202 (see FIG. 2) formed on the step surface 37 are connected to the conductor patterns 51 and 52 on the circuit board 5 by the bonding materials 53 and 54. In the high frequency side antenna electrode 2, a capacitor or an inductor can be inserted between the ground end 202 and the ground conductor. According to this configuration, the antenna electrical length and the radiation characteristics can be adjusted by selecting a constant of the capacitor or the inductor. The side surface 32 is located at an end (corner) of the circuit board 5. Usually, since an electronic component or the like is mounted on the side surface 34 side, the side surface 32 faces the non-mounting surface of the electronic component and becomes a surface on the substrate open side.

  As described above, in the multi-resonant antenna according to the present invention, the low frequency side antenna electrode 1 and the high frequency side antenna electrode 2 are provided side by side with the dielectric substrate 3 and one end thereof is commonly connected. A multi-resonant antenna having the antenna electrode 1 and the high-frequency side antenna electrode 2 formed into one chip is realized.

  In addition, since the low-frequency antenna electrode 1 is folded, the required physical length L1 of the low-frequency antenna electrode 1 is reduced while reducing the external dimensions of the dielectric substrate 3 and reducing the overall shape. Can be secured.

  Further, as a characteristic configuration, the low-frequency antenna electrode 1 has a free end at the other end and has an electrical length of λ / 4, while the high-frequency antenna electrode 2 has an electrical end at the other end. Since the ground end is grounded and has an electrical length of λ / 2, the harmonics generated from the low frequency side antenna electrode 1 are prevented from attenuating the fundamental wave of the high frequency side antenna electrode 2, and the high frequency Degradation of the radiation characteristics of the side antenna electrode 2 and narrowing of the bandwidth on the high frequency side can be avoided. This point will be described with reference to the frequency-efficiency characteristic diagrams obtained by the simulations of FIGS. 7 and 8, the horizontal axis represents frequency (GHz) and the vertical axis represents efficiency (dB). The efficiency shown is the radiation efficiency, but is also reflected in the reception efficiency. The conventional product as a comparative example has a so-called bifurcated pattern in which one end of the low-frequency side antenna electrode and the high-frequency side antenna electrode is commonly connected to one feeding end and the other end is a free end. The antenna electrical length to the free end is λ / 4.

  First, referring to FIG. 7, in the 2.4 GHz band, the multi-resonant antenna according to the present invention has an improved antenna radiation efficiency on both the low-frequency side and the high-frequency side in comparison with the conventional product, and the bandwidth BW It can be seen that is enlarged.

  Next, referring to FIG. 8, even in the 5 GHz band, the multi-resonant antenna according to the present invention has not only improved antenna radiation efficiency on the low frequency side in comparison with the conventional product, but also on the high frequency side. Even when the frequency is increased, the reduction in efficiency is small, and a remarkable antenna efficiency improvement effect is obtained.

  The present invention further discloses a communication device using the above-described multi-resonant antenna. An example is shown in FIG. The illustrated communication device includes a multi-resonance antenna 7 according to the present invention, a low-frequency communication unit 8, and a high-frequency communication unit 9.

  The double resonance antenna 7 includes a low frequency side antenna electrode 1 and a high frequency side antenna electrode 2. The details are as described above. The feeding path of the multi-resonant antenna 7 is connected to the input / output sides of the low-frequency communication unit 8 and the high-frequency communication unit 9. The low frequency communication unit 8 and the high frequency communication unit 9 include transmission circuit units 81 and 91 and reception circuit units 82 and 92, respectively. In the case of a mobile phone constituting a wireless LAN, the high frequency communication unit 9 is responsible for data transmission with a large amount of information, and the low frequency communication unit 8 is responsible for normal data transmission. Throughout this specification, the expressions low frequency and high frequency are relative expressions. Although not shown, a circuit portion necessary for this type of communication device is naturally added.

  Although the contents of the present invention have been specifically described above with reference to the preferred embodiments, it is obvious that those skilled in the art can take various modifications based on the basic technical idea and teachings of the present invention. It is.

1 Low Frequency Side Antenna Electrode 2 High Frequency Side Antenna Electrode 3 Dielectric Substrate

Claims (9)

A multi-resonant antenna including a dielectric substrate, a low-frequency antenna electrode, and a high-frequency antenna electrode,
The low-frequency side antenna electrode and the high-frequency side antenna electrode are provided side by side with the dielectric base, and one end is commonly connected to a power feeding end,
The low frequency antenna electrode has a free end at the other end and an electrical length of λ / 4.
The high frequency side antenna electrode constitutes a ground end where the other end is electrically grounded, and has an electrical length of λ / 2.
Double resonance antenna.   2. The multi-resonant antenna according to claim 1, wherein the high-frequency side antenna electrode constitutes a ground end whose other end is grounded via a capacitor or an inductor. The multi-resonant antenna according to claim 1 or 2,
The dielectric substrate has a main surface and four side surfaces,
Most of the low-frequency antenna electrode and the high-frequency antenna electrode are formed on the main surface, and one end is led to the feeding end through one of the four side surfaces,
The low-frequency side antenna electrode extends from the one side surface toward the opposite side surface, is folded along the other side surface, and the other end folded is between the one side surface and the other side surface. Ends in an intermediate position,
The high frequency side antenna electrode is branched from the low frequency side antenna electrode at an intermediate position between the one side surface and the other side surface, extends in a direction parallel to the one side surface, and extends from the other end of the low frequency side antenna electrode. Is folded in the direction of the one side surface at a position close to the one side surface,
Double resonance antenna.   4. The multi-resonant antenna according to claim 1, wherein the dielectric substrate is made of a composite dielectric material containing a synthetic resin and ceramic powder. The multi-resonant antenna according to any one of claims 1 to 4,
The low frequency side antenna electrode and the high frequency side antenna electrode are supported by a flexible insulating film having adhesiveness,
The flexible insulating film is bonded onto the dielectric substrate;
Double resonance antenna.   6. The multi-resonant antenna according to claim 5, wherein the low-frequency side antenna electrode and the high-frequency side antenna electrode are made of a conductor continuously formed on the same flexible insulating film. .   7. The multi-resonant antenna according to claim 1, wherein the low-frequency antenna electrode is adapted to a 2.4 GHz band, and the high-frequency antenna electrode is adapted to a 5 GHz band. A communication device including a multi-resonant antenna, a low-frequency communication unit, and a high-frequency communication unit,
The multi-resonant antenna is described in any one of claims 1 to 7, and is connected to the low-frequency communication unit and the high-frequency communication unit.
Communication device.   The communication device according to claim 8, wherein the communication device is a mobile phone.

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