JP2011142542A - Pattern antenna, and antenna device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To miniaturize an antenna, while securing good antenna characteristics. <P>SOLUTION: A pattern antenna 1 is configured such that an F-type antenna element 3 and GND portions 4, 5 are pattern-formed in a substrate 2 and the antenna element 3 is provided with a long line portion 3a extendingly provided from one long side 2a toward another long side 2b of the substrate 2, and a short line portion 3b which connects the long line portion 3 to the GND portions 4, 5, wherein the long line portion 3a of the antenna element 3 is formed in a meandering shape by bending and the width W1 of the short hand direction of the substrate 2 is formed to be smaller than 1/4 of an operating frequency wavelength. In the longitudinal direction of the substrate 2, the size ratio of the length L4 of the occupancy area of the antenna element 3 and the length L3 of the GND portion 4 is preferable to be 3:7 to 4:6. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a small pattern antenna and an antenna device using an F-type antenna element, and more particularly to a pattern antenna suitable for use at a frequency of 950 MHz band.

  In recent years, in the radio field of electronic devices, downsizing and cost reduction have been put into practical use, and F-type antennas used in cellular phones and the like are effective for those demands. As an F-type antenna, an antenna element or the like formed on a dielectric substrate is known. For example, Patent Document 1 uses the electrical length of a ground conductor plate (hereinafter referred to as “GND section”). There has been proposed an F-type antenna which is formed to have a length of about ¼ of the wavelength λ of the frequency so as to obtain good SWR characteristics.

  FIG. 10 is a top view showing the configuration of the pattern antenna described in the above document. The pattern antenna 31 is roughly divided into a printed circuit board (hereinafter referred to as “substrate”) 32 and pattern formation on the surface of the substrate 32. The F-type antenna element 33 and the GND part 34 formed on the back surface of the substrate 32 are configured. A through hole 36 is provided at the tip of one wiring (short line part) 35 extending from the antenna element 33, and the antenna element 33 and the GND part 34 are electrically connected through the through hole 36. The other wiring 37 extending from the antenna element 33 is a power supply wiring, and other electronic devices are connected to the power supply wiring 37.

JP 2001-168629 A

  In the pattern antenna 31, the optimum length of the substrate width W of the printed circuit board 32 is ¼ of the wavelength λ of the use frequency. The pattern antenna 31 is used for communication in a 950 MHz band at a specific low power radio station. When used for an antenna, there is a problem that the substrate width W becomes relatively large, and the demand for miniaturization cannot be sufficiently met. Further, even if the printed circuit board 32 has an optimum shape for the wavelength, there is a problem that the antenna gain characteristic is deteriorated due to the shape of the GND portion 34.

  Accordingly, the present invention has been made in view of the problems in the above-described conventional technology, and an object thereof is to provide a pattern antenna or the like that can be reduced in size while ensuring good antenna characteristics. .

  In order to achieve the above object, according to the present invention, an F-type antenna element and a ground region are patterned on a substrate, and the antenna element extends from one long side of the substrate toward the other long side. A pattern antenna comprising a long wire portion and a short wire portion connecting the long wire portion to the grounding region, wherein the long wire portion of the antenna element is bent in a meandering manner, and the width in the short direction of the substrate is used. It is characterized by being smaller than a quarter wavelength of the frequency.

  According to the present invention, since the long line portion of the antenna element is bent in a meandering manner, the width of the antenna element region on the substrate can be reduced while ensuring the necessary wiring length. As a result, even if the substrate width is made smaller than a quarter wavelength of the operating frequency, good antenna characteristics can be exhibited, and the antenna can be miniaturized.

  In the longitudinal direction of the substrate, the dimensional ratio between the length of the occupied area of the antenna element and the length of the grounding area can be set to 3: 7 to 4: 6, thereby optimizing the size of the grounding area. Good antenna characteristics can be obtained.

  In the pattern antenna, the bending pitch of the long line portion of the antenna element can be set to a size of 10 times or more the wiring width of the antenna element. When the long line part of the antenna element is bent in a meandering manner, the wirings are opposed to each other in the middle of the long line part. According to the above configuration, the crosstalk between the wirings is suppressed and the antenna resonance frequency is obtained. It is possible to avoid adverse effects.

  In the pattern antenna, the distance between the lower end portion of the antenna element and the grounding region can be set to be 10 times or more the wiring width of the antenna element. According to this, it is possible to reduce the degree of coupling between the lower end portion of the antenna element and the ground region, and to prevent the capacitance generated between them from affecting the antenna resonance frequency.

  In the pattern antenna, the bent portion of the long line portion can be processed in a corner circular shape, whereby reflection at the bent portion of the long line portion can be suppressed, and line loss can be reduced.

  In the pattern antenna, the antenna can be used as a wireless antenna for use at a frequency of 950 MHz band.

  In addition, the present invention is an antenna device, wherein the pattern antenna according to any one of the above is mounted on a parent substrate having a grounding region formed on a surface or both surfaces. And according to this invention, it becomes possible to achieve size reduction of an antenna, ensuring a favorable antenna characteristic like the said invention.

  In the antenna device, the width of the ground area of the parent substrate is the same as the width of the ground area of the pattern antenna, and the length of the ground area of the parent substrate is three times or more and four times the length of the pattern antenna substrate. It can be as follows.

  In the antenna device, a metal case fixed to a ground potential and covering a circuit element on the front or back surface may be provided on the front or back surface of the pattern antenna.

  As described above, according to the present invention, it is possible to reduce the size of an antenna while ensuring good antenna characteristics.

It is a figure which shows one Embodiment of the pattern antenna which concerns on this invention, (a) is a front view, (b) is a back view. It is a figure which shows the antenna apparatus which mounted the pattern antenna of FIG. 1 on the parent board | substrate, (a) is a surface view, (b) is a side view. It is a reverse view of the pattern antenna of FIG. It is drawing which shows the other example of the antenna device of FIG. 2, (a) is a surface figure, (b) is a side view. It is drawing which shows the other example of the antenna device of FIG. 2, (a) is a surface figure, (b) is a side view. It is a figure which shows the S11 reflection characteristic of the pattern antenna of FIG. It is a figure which shows the S11 Smith chart of the pattern antenna of FIG. It is a figure which shows the antenna directivity of the pattern antenna of FIG. It is a figure which shows the radiation characteristic of the conventional pattern antenna. It is a figure which shows the conventional pattern antenna.

  Next, modes for carrying out the invention will be described in detail with reference to the drawings. Here, a case where the pattern antenna according to the present invention is a 950 MHz band antenna and has a double-sided board configuration will be described as an example.

  FIG. 1 shows an embodiment of a pattern antenna according to the present invention. This pattern antenna 1 is roughly divided into a printed circuit board 2 (hereinafter referred to as “substrate”) and an antenna patterned on the surface of the substrate 2. It is composed of the element 3 and the GND part 4 and the GND part 5 patterned on the back surface of the substrate 2.

  The substrate 2 is a dielectric substrate. As the substrate 2, for example, a glass epoxy substrate having a relative dielectric constant εr of 4.4 and a plate thickness of 1 mm can be used. The optimum length of the substrate width W when the F-type antenna element is installed on the substrate is usually ¼ of the wavelength λ of the operating frequency. However, the substrate 2 according to the present embodiment has a miniaturized design. Therefore, the width W1 is set to about ¼ of λ / 4. The length L1 of the substrate 2 is λ / 8.

  The antenna element 3 is an F-type antenna element, and is formed by patterning with a copper conductor, for example. The antenna element 3 is disposed in the vicinity of one long side 2a of the substrate 2, and is connected to a short line portion 3b that rises from the upper end of the GND portion 4 toward the upper end of the substrate 2, and an upper end portion of the short line portion 3b. 2 and a long line portion 3a extending toward the other long side 2b.

  The long wire portion 3a is connected to the GND portion 4 through the short wire portion 3b, and is connected to the feed point 6 through a power supply wiring 6a extending in an L shape from the middle of the long wire portion 3a. The long line portion 3a is bent and arranged in a meandering manner, whereby the wiring length of the antenna element 3 (the length from the feeding point 6 to the terminal end 3g of the antenna element 3) is about λ / 4, The width W2 of the element region is reduced to be smaller than λ / 4.

  However, when the long line portion 3a is bent and formed in a meandering manner, the wires come to face each other in the middle of the long line portion 3a (see, for example, 3c and 3d in the figure). There is a risk that talk will occur and affect the resonant frequency of the antenna. For this reason, the bending pitch (interline distance between the wirings 3c and 3d) W3 of the long line portion 3a needs to be a certain size, specifically, it is 10 times larger than the wiring width W4 of the long line portion 3a. It is preferable to do.

  In addition, when the long line portion 3 a is bent in a meandering manner, the lower end portion 3 e of each bent portion is positioned in the vicinity of the GND portion 4. In this case, since the lower end portion 3e has a capacity and may affect the antenna resonance frequency, the interval L2 between the lower end portion 3e and the GND portion 4 is set to be 10 times or more the wiring width W4 of the long line portion 3a. It is preferable to reduce the degree of bonding.

  In FIG. 1, the antenna element 3 is formed in a rectangular wave shape, but in order to reduce reflection points and suppress line loss, corner round processing is performed on the lower end 3 e and the upper end 3 f of each bent portion, The bent portion may be U-shaped.

  A through hole (not shown) is provided at the feed point 6 of the antenna element 3, and the feed point 6 and the feed line 7 formed on the back surface of the substrate 2 are connected through the through hole. The power supply wiring 7 can be an impedance-matched microstrip line, strip line, coplanar line, or the like. It is also possible to attach a coaxial wiring on the substrate 2 and perform power feeding.

  The GND portions 4 and 5 are disposed on the front surface and the back surface of the substrate 2, respectively, and are patterned by a copper conductor, like the antenna element 3. These GND parts 4 and 5 are connected to each other by through holes 8 distributed over the entire region. The GND part 5 on the back side is for stabilizing the antenna characteristics and can be omitted. In this case, the through hole 8 is not necessary.

  The length L3 of the GND portion 4 is such that the ratio of the length L4 of the antenna element region to the length L3 of the GND portion 4 is 3: 7 to 4: 6, preferably regardless of the presence or absence of the GND portion 5 on the back side. The length is set to 34:66 to 36:64. On the other hand, the length L3 ′ of the GND portion 5 on the back surface side is the same as or shorter than the length L3 of the GND portion 4 on the front surface side.

  In the pattern antenna 1, antenna characteristics such as resonance frequency and radiation characteristics can be adjusted by changing the position of the feeding point 6 and the wiring length of the antenna element 3.

  Next, a method for manufacturing the pattern antenna 1 shown in FIG. 1 will be described. In manufacturing the pattern antenna 1, an organic substrate or a ceramic substrate is prepared, and the antenna element 3, the GND portion 4, and the like are formed on the organic substrate or the ceramic substrate.

  The substrate 2 is composed of a single layer substrate, a double-sided substrate, a multilayer substrate, or the like. As the material of the substrate 2, various materials such as a low dielectric loss tangent substrate material having a low high frequency loss and a high dielectric substrate material can be used. In this case, considering the wavelength shortening rate corresponding to each dielectric constant. The antenna design needs to be adjusted.

  On the other hand, as a pattern forming method, a mask printing process used for a ceramic substrate, a pattern forming process using etching used for a printed board, a pattern forming process using vapor deposition used for a semiconductor process, or the like can be used. When the substrate 2 is formed of a multilayer substrate, the antenna element 3 and the GND portion 4 can be formed on the inner layer of the substrate 2 (between the upper layer substrate and the lower layer substrate). In that case, since the effective dielectric constant changes, the antenna design value is taken into consideration as described above.

  In designing the pattern antenna 1, depending on the frequency band to be used, the wiring width W4 and wiring length of the antenna element 3, the position of the feeding point 6, the size of the substrate 2, the thickness of the substrate 2, the conductor thickness, the resist thickness, etc. The antenna gain characteristics are optimized by combining the dimensions of these elements at a specific ratio, or by appropriately selecting the material of the substrate 2. Although the dielectric constant of the substrate material varies depending on the material, the effective dielectric constant is calculated according to the dielectric constant and the position of the layer constituting the pattern antenna 1 (whether it is the front layer or the back layer), and Determine the optimum dimensions and position. When the pattern antenna 1 is provided on the surface layer, the application state of the coating material such as a resist on the surface layer and silk is reflected in the design value of the antenna element 3.

  Next, an antenna device in which the pattern antenna 1 shown in FIG. 1 is mounted on a parent substrate will be described with reference to FIGS. In these drawings, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

  The antenna device 10 has a configuration in which a pattern antenna 1 and a parent substrate 11 having a GND portion 12 patterned on the entire surface or both surfaces are connected via a connection connector 13. The pattern antenna 1 and the parent substrate 11 are connected so that the positions of the upper end 4a of the GND portion 4 of the pattern antenna 1 and the upper end 11a of the parent substrate 11 are aligned.

  Since the size of the GND portion 12 of the parent substrate 11 affects the antenna gain characteristics, the width W6 is made substantially the same as the width W5 (see FIG. 1) of the GND portions 4 and 5 of the pattern antenna 1, and the length L6 is The length L1 of the substrate 2 is 3 to 4 times. Thereby, a favorable antenna gain can be obtained, and performance improvement of about 4 dB can be achieved as compared with the case where the pattern antenna 1 is used alone.

  It is possible to make the width W6 of the GND portion 12 larger than the width W5 of the GND portions 4 and 5, but if the width W6 of the GND portion 12 is increased, the resonance becomes steep, so that the pattern and the substrate There arises a problem that the manufacturing deviation affects the antenna gain performance. Therefore, the width W6 of the GND portion 12 is made substantially the same as the width W5 of the GND portions 4 and 5, and the length L6 of the GND portion 12 is expanded to adjust the antenna gain.

  At this time, if the length L6 is 3 to 4 times the length L1 of the substrate 2 of the pattern antenna 1, an optimum antenna gain within −0.5 dB can be realized. If the length L6 is shortened beyond this range, the antenna gain is greatly reduced. For example, when the length L6 is shortened to 2.5 times the length L1 of the substrate 2, the optimum antenna gain is reduced by about 1 dB.

  As shown in FIG. 3, in the antenna device 10, a wireless circuit unit (not shown) is mounted on the back surface 2 a of the substrate 2 of the pattern antenna 1, and is shared with the GND potential of the pattern antenna 1. The structure is covered with a metal case 14. By providing the metal case 14, an unnecessary resonance state between the pattern antenna 1 and the parent substrate 11 can be prevented, and more stable antenna characteristics can be obtained.

  The height M of the metal case 14 is preferably set to a height that fills the gap between the pattern antenna 1 and the parent substrate 11 in order to assist the mechanical strength. Here, it is possible to share the potential of the metal case 14 by connecting the metal case 14 directly to the GND portion 12 of the parent substrate 11 or to the GND portion 4 of the pattern antenna 1.

  The wireless circuit unit and the metal case 14 can be arranged on the surface side of the substrate 2 of the pattern antenna 1, but the height M of the metal case 14 in this case is a height that can cover the circuit element. It is enough to secure it. In addition, it is not necessary to cover all the wireless circuit portions with the metal case 14, and components that do not need to be protected by the metal case 14 in accordance with the Radio Law can be mounted on the parent substrate 11.

  In the above embodiment, the case where the pattern antenna 1 and the mother board 11 are separately formed and connected by the connection connector 13 is exemplified. However, the pattern antenna 1 and the mother board 11 can be integrally formed. . Even in that case, equivalent performance can be realized by making the dimensions of the respective elements the same as those described above.

  Further, as shown in FIG. 4, even when the center portion of the GND portion 12 of the parent substrate 11 is the circuit region 15, equivalent performance can be realized. At this time, the board surface opposite to the side on which the circuit area 15 is installed can be used as either the GND area or the component mounting surface. By housing components related to wireless performance defined by the Radio Law in the metal case 14 and arranging other components in the circuit region 15 of the parent substrate 11, high-density mounting becomes possible.

  Furthermore, in the said embodiment, although the case where the GND part 12 was pattern-formed on the whole surface or both surfaces of the main substrate 11 was illustrated, as shown in FIG. The GND part 12 can also be formed on part of both sides.

  Next, the effects of the pattern antenna according to the present invention will be described with reference to test examples. As an example, a single pattern antenna 1 shown in FIG. 1 (not mounted on the parent substrate 11) was used, and the materials and dimensions of each element were as follows.

  As the substrate 2, a dielectric substrate made of glass epoxy resin (relative permittivity εr = 4.4) was used, and its thickness was 1 mm. Further, the width W1 of the substrate 2 is set to about ¼ of λ / 4, and the length L1 of the substrate 2 is set to λ / 8. The antenna element 3 and the GND parts 4 and 5 were patterned by copper conductors, and the film thickness after through-hole plating and the thickness of the resist material were 20 μm and 35 μm, respectively. The dimensional ratio between the length L4 of the antenna element region and the length L3 of the GND portion 4 is 35:65, and the wiring length of the antenna element 3, the wiring width W4, and the position of the feeding point 6 are 950 MHz resonance points. Adjusted to match.

  The S11 reflection characteristic, S11 Smith chart, and radiation characteristic from the feeding point 6 in the pattern antenna 1 are shown in FIGS. The waveform in FIG. 8 is an antenna directivity pattern rotated about the vertical axis with respect to the substrate plane of the antenna substrate, and shows gain characteristics with respect to vertical polarization and horizontal polarization.

  Moreover, the radiation characteristic of the conventional pattern antenna 31 as a comparative example is shown in FIG. In preparing the comparative example, the substrate width W of the printed circuit board 32 is set to be substantially the same as λ / 4 (about four times the substrate width W1 of the embodiment), and then the wiring length of the antenna element 33 is set. The wiring width and the position of the feeding point were adjusted to match the resonance point of 950 MHz.

  As shown in FIGS. 6 and 7, the S11 reflection characteristic in the example has a resonance point at 950 MHz, and the antenna radiation characteristic is most obtained at 950 MHz. Since the 950 MHz band in the specific low power is 950 to 956 MHz, the radiation performance is satisfied within the use band.

  Further, as shown in FIG. 8, in the embodiment, it is recognized that it is non-directional and has a good radiation characteristic particularly with respect to the polarization in the horizontal direction. On the other hand, in the comparative example, as shown in FIG. 9, even when the S11 reflection characteristic is optimized, it is about −4 dB lower than that in the example.

DESCRIPTION OF SYMBOLS 1 Pattern antenna 2 Printed circuit board 2a One long side 2b The other long side 2c Back surface 3 Antenna element 3a Long line part 3b Short line part 3c, 3d Opposite wiring 3e Lower end part 3f Upper end part 3g End of antenna element 4 GND part 4a GND part Upper end 5 GND part 6 Feeding point 6a Feeding line 7 Feeding line 8 Through hole 10 Antenna device 11 Parent board 11a Parent board upper end 12 GND part 13 Connector 14 Metal case 15 Circuit region L1 Printed board length L2 Lower end of antenna element The distance L3 between the portion and the GND portion The length L3 ′ of the GND portion on the front side The length L4 of the GND portion on the back side The length L4 of the antenna element region L6 The length W1 of the GND portion W1 The width W2 of the printed circuit board The width of the antenna element region W3 Bending pitch W4 Wiring width W5 GND width

Claims (9)

An F-type antenna element and a ground region are patterned on a substrate, the antenna element extends from one long side to the other long side of the substrate, and the long line portion is connected to the ground region. A pattern antenna having a short line portion connected to
A pattern antenna, wherein a long line portion of the antenna element is bent in a meandering manner, and a width in a short side direction of the substrate is smaller than a quarter wavelength of a use frequency.   2. The pattern antenna according to claim 1, wherein in the longitudinal direction of the substrate, a dimensional ratio between the length of the occupied area of the antenna element and the length of the grounding area is 3: 7 to 4: 6.   3. The pattern antenna according to claim 1, wherein a bending pitch of the long line portion of the antenna element has a size of 10 times or more of a wiring width of the antenna element.   4. The pattern antenna according to claim 1, wherein an interval between a lower end portion of the antenna element and the grounding region is 10 times or more a wiring width of the antenna element.   5. The pattern antenna according to claim 1, wherein a bent portion of the long line portion is subjected to a corner circular process.   6. The pattern antenna according to claim 1, wherein the pattern antenna is used at a radio frequency of 950 MHz.   7. An antenna device, wherein the pattern antenna according to any one of claims 1 to 6 is mounted on a parent substrate having a grounding region formed on a surface or both surfaces thereof.   The width of the ground area of the mother board is the same as the width of the ground area of the pattern antenna, and the length of the ground area of the mother board is not less than 3 times and not more than 4 times the board length of the pattern antenna. The antenna device according to claim 7.   The antenna device according to claim 7 or 8, further comprising a metal case fixed to a ground potential on a front surface or a back surface of the pattern antenna and covering circuit elements on the front surface or the back surface.

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