JP5667501B2 - Antenna device - Google Patents

Description

  The present invention relates to an antenna device such as a keyless remote system used in, for example, a vehicle or a house.

  For example, an antenna that uses radio waves in a relatively long wavelength range (several tens of centimeters to several meters) such as UHF and VHF bands, such as a wireless device for a keyless remote system (so-called keyless receiver) used in a vehicle or a house. In the device, the size of the antenna device may be determined by the size of the antenna. Therefore, in order to reduce the size of the antenna device, it is important to reduce the size of the antenna.

  The present applicant, as two elements, one of which is a signal line and the other of which is a GND line, has a shape extending spirally along the axial direction of the external element inside the external element extending spirally with a space therebetween. A holding member made of a dielectric material that contacts the two elements and holds the two elements in a predetermined positional relationship, and the two elements are connected to the spiral portion on the side fixed to the substrate. An antenna device has been devised, each having a surface mounting portion including a portion substantially parallel to the land forming surface of the substrate, and the surface mounting portion being connected to different lands (patents). Reference 1).

JP 2008-227862 A

  In the configuration of Patent Document 1, since the two elements are held in a predetermined positional relationship by the holding member, the performance of the antenna can be held and the holding member is configured using a dielectric. As a result, the wavelength of the high-frequency current flowing through the element is shortened, and the height of the antenna from the land forming surface of the substrate (the size of the antenna device) can be reduced.

  However, there is a limit to downsizing because dielectric loss is caused by using a dielectric.

  FIG. 14 is a schematic diagram (top view and side view) of the antenna device of Patent Document 1, and FIG. 15 shows an equivalent circuit in the configuration of FIG. 14 (9b will be described later). As shown in FIG. 15, the antenna elements (120, 130) can be represented as series resonant circuits including coils (L22, L23), capacitors (C22, C23), and resistors (R22, R23), respectively. The impedance of each element is Z22 and Z23.

  The self-resonant frequency f of the antenna is uniquely determined by the capacitance C and the inductance L of the internal impedance of the antenna element, and has a relationship of f = 1 / {2π (√LC)}. In other words, in order to realize a reduction in size of the antenna, it is important to have a configuration in which C and L can be increased (of course, it is possible to resonate to a desired frequency using a matching circuit, but an antenna caused by matching loss). A decrease in gain is inevitable).

  14 and 15, a series resonance circuit is configured through a parasitic capacitance C21 between the inner and outer elements. In the prior art, the antenna element has a spiral structure, and the inductances L22 and L23 can be made relatively large. Therefore, the antenna element can resonate with an antenna length shorter than λ / 2. That is, the size can be reduced. However, for the following two reasons, there is a limit to downsizing in the configuration of the prior art.

Reason 1: For further miniaturization, it is necessary to increase the number of turns of the spiral portions (121, 131) of the inner and outer elements. However, since the capacitances C22 and C23 between the pitches of the spiral portion are increased, the combined capacitance C is decreased, and the increase in L is offset by the decrease in the combined capacitance C, and a significant reduction in size cannot be expected (that is, the self-resonant frequency). f does not lead to a decrease).
Reason 2: Increasing the spiral diameter can be expected to increase L while suppressing the decrease in C, but the increase in the size of the antenna is inevitable.

  Against the background of the above problems, an object of the present invention is to provide an antenna device that can reduce the size of the antenna and that can maintain the performance of the antenna even when the antenna is reduced in size.

Means for Solving the Problems and Effects of the Invention

An antenna device for solving the above-described problem is a substrate in which a GND pattern and a power feeding pattern are provided on a surface thereof, and an external element having a spiral portion extending spirally along a predetermined spiral axis direction, An inner element having a spiral portion disposed inside the outer element at a predetermined interval and extending spirally along the spiral axis direction of the outer element, and either one of the two elements One end of the element is connected to the power feeding pattern, and one end of the other element is connected to the GND pattern to constitute an antenna, and at least a part of the outer peripheral edge of the spiral portion of the external element is formed on the substrate. the capacitance generating member for generating an electrostatic capacitance between the elements, so as to face at a predetermined distance, placing the antenna, the capacitance Raw member, characterized in that it is formed only at a position and the vicinity thereof gap is the smallest of the outer periphery of the spiral portion of the external element.

  With the above configuration, the above-described combined capacitance C in the antenna can be increased by generating a capacitance between the external element and the capacitance generating member on the substrate (details will be described later). In comparison, it is possible to resonate at a desired frequency with a small size (short antenna length).

  The antenna device of the present invention is determined so that the number of turns of the spiral portion of the external element is different from the number of turns of the spiral portion of the internal element.

  With the above configuration, the facing area between the external element and the internal element is reduced, the parasitic capacitance between the inner and outer elements can be reduced, and the influence of the parasitic capacitance in the above-described combined capacitance can be reduced.

  In addition, the antenna device of the present invention includes a support portion that is attached to the substrate and supports at least one of the external element and the internal element.

  By the said structure, the space | interval of the outer periphery of the spiral part of an external element and an electrostatic capacitance generation member, or the space | interval of an internal / external element can be maintained in a desired state.

  In the antenna device of the present invention, the capacitance generating member is disposed so as to face the spiral surface of the tip of the spiral portion of the external element.

  With the above configuration, the above-described combined capacitance C in the antenna can be further increased, and the antenna can be further downsized.

  Further, the antenna device of the present invention uses a GND pattern as a capacitance generating member.

  The GND pattern is formed to be relatively thicker or wider than other wiring patterns in order for the circuit to operate reliably or to prevent noise. With the above configuration, the antenna can be arranged without greatly changing the wiring pattern of the substrate. In addition, the degree of freedom of arrangement of the antenna on the substrate is increased.

  In addition, the capacitance generating member in the antenna device of the present invention includes a dielectric layer formed on at least a part of the GND pattern.

  With the above configuration, the capacitance generated with the external element can be increased, and the antenna can be further downsized.

  In the antenna device of the present invention, the outer peripheral edge of the external element is in contact with the dielectric layer, and the dielectric layer supports the external element.

  With the above configuration, the support portion can be reduced in size. Moreover, a support part becomes unnecessary.

The front view which shows the structure of the antenna apparatus of this invention. The top view of FIG. The right view seen from the A direction of FIG. The figure which shows the electrostatic capacitance which generate | occur | produces with the antenna apparatus of this invention. The figure which shows the equivalent circuit of the antenna apparatus of this invention. The figure which shows the relationship between the resonant frequency and antenna length in the structure of this invention. The figure which shows another example of a structure of a GND pattern. The figure which shows another example of a structure of a GND pattern. The figure which shows another example of a structure of a GND pattern. The front view which shows another example of a structure of the antenna apparatus of this invention. The right view seen from the A direction of FIG. The front view which shows another example of a structure of the antenna apparatus of this invention. FIG. 13 is a top view of FIG. 12. The top view and side view of the antenna apparatus of a conventional structure. The figure which shows the equivalent circuit of the antenna apparatus of a conventional structure.

  Hereinafter, an antenna device of the present invention will be described with reference to the drawings. FIG. 1 is a front view of the antenna device 1, FIG. 2 is a top view of the antenna device 1 viewed from the top surface of the substrate 2 (excluding the support portion 7), and FIG. 3 is a view of the antenna device 1 of FIG. Each right side view is shown. The antenna device 1 is configured as a receiver of a keyless remote system used in, for example, a vehicle or a house.

  The antenna device 1 includes two elements, that is, a substrate 2, an external element 5, and an internal element 6, and includes an antenna 10 mounted on the substrate 2 and a support unit 7 that supports the antenna 10. .

  The substrate 2 is, for example, a well-known printed wiring board, and a GND potential (also referred to as a ground potential) is supplied to the surface of the substrate 2, for example, a metal thin film-like GND pattern 3 and a metal thin film-like power supply pattern 4 are provided. The one end 5 b of the external element 5 is connected to the GND pattern 3, and the one end 6 b of the internal element 6 is connected to the power feeding pattern 4. The received signal from the antenna 10 is configured to be transmitted to an RF (Radio Frequency) circuit (20) (not shown) by the power feeding pattern 4 via a matching element (not shown) for impedance matching. The GND pattern 3 corresponds to the capacitance generating member of the present invention.

  The antenna 10 has an external element 5 having a spiral portion 5a that spirally extends in a direction along the land formation surface of the substrate 2 (for example, a direction substantially parallel to the surface of the substrate 2), and an interval inside the external element 5. And an internal element 6 having a spiral portion 6a extending spirally along the axial direction P of the external element 5, and one of the two elements 5 and 6 is connected to a signal line (in this embodiment, the internal element 6). ), And the other is a GND line (external element 5 in this embodiment) L (inductance) C (capacitance) resonance circuit antenna.

  In the present embodiment, as shown in FIG. 2, the external element 5 is configured by winding a conductor wire in a spiral shape so as to have a planar circular shape with an inner diameter R1 and an inter-spiral pitch P1. Further, the inner element 6 is configured by winding a conductor wire in a spiral shape so as to be a planar circular shape with an inner diameter R2 smaller than R1 and a pitch P2 between the spirals. The length L1 of the spiral portion 5a of the outer element 5 and the length L2 of the spiral portion 6a of the inner element 6 are substantially equal.

  It is desirable that the number of turns of the outer element 5 and the number of turns of the inner element 6 are different (that is, the inter-spiral pitches P1 and P2 are different). Thereby, since the opposing area of the external element 5 and the internal element 6 becomes small, the parasitic capacitance C1 (refer FIG. 4, FIG. 5) between the internal and external elements can be made smaller. Further, the spiral portion 6a is not provided in the internal element 6, and a linear shape (a spiral with zero turns) may be used.

  As shown in FIGS. 2 and 3, a GND pattern 3 is formed in a region other than the power feeding pattern 4 on the surface of the substrate 2, and a gap between the outer edge of the spiral portion 5 a of the external element 5 and the GND pattern 3 is determined in advance. The antenna 10 is arranged so that the obtained value d is obtained.

  The support portion 7 includes an external element support portion 7a and an internal element support portion 7b, and is attached to the tip portion of the antenna 10 (the end portion not connected to the GND pattern 3 and the power feeding pattern 4). Then, at least one of the distal end portion of the external element 5 and the distal end portion of the internal element 6 is supported, and the interval d between the spiral portion 5a and the GND pattern 3 and the interval between the external element 5 and the internal element 6 are substantially constant. It is said.

  Of course, assuming that the material of the antenna 10, the length of the spiral portion (L1, L2), or the connection strength with the substrate is appropriate, the distance d between the spiral portion 5a and the GND pattern 3 with only the antenna 10 and the external element 5 When the distance between the inner element 6 and the inner element 6 (for example, (R1-R2) / 2) can be maintained, either the outer element support portion 7a or the inner element support portion 7b or the entire support portion 7 becomes unnecessary.

  FIG. 4 shows the capacitance generated in the antenna device 1 of the present invention. In the antenna device 1, in addition to the parasitic capacitance C1 between the inner and outer elements, the capacitance C2 between the pitches of the spiral portions 5a of the outer element 5, and the capacitance C3 between the pitches of the spiral portions 6a of the inner element 6, the external elements An electrostatic capacity C4 between 5 and GDN pattern 3 and an electrostatic capacity C5 between internal element 6 and GDN pattern 3 are generated.

  FIG. 5 shows an equivalent circuit of the antenna device 1 of the present invention. The external element 5 (R2, C2, L2) and the internal element 6 (R3, C3, L3) are connected in series via the parasitic capacitance C1 between the above-described internal and external elements, and each element is connected to the GND pattern 3 in high frequency. A coupled parallel resonant circuit is formed. In particular, the external element 5 and the GND pattern 3 are physically close to each other and are strongly coupled. By adopting such a configuration, the combined capacitance C can be increased while maintaining the inductance (L2, L3) of each element (5, 6), so that it is smaller (shorter antenna length) than the conventional configuration. It is possible to resonate at a desired frequency. Further, since the antenna length is shortened, the number of turns of each spiral portion is reduced, and the capacitances C2 and C3 between the pitches can be reduced.

  FIG. 6 shows a numerical calculation simulation result of the relationship between the resonance frequency and the antenna length, comparing the configuration of the antenna device 1 of the present invention with the configuration of the prior art. When the resonance frequency is, for example, 265 to 285 MHz, the antenna length necessary for resonance can be shortened by about 100 mm as compared with the configuration of the prior art by applying the configuration of the present invention. That is, the configuration of the present invention can be further downsized as compared with the configuration of the prior art.

  In the configuration of FIG. 1, when the top plate of the housing in which the antenna device 1 is housed is a metal, this top plate is grounded and used instead of the GND pattern 3, and the antenna 10 (that is, the outer periphery of the external element 5). May be arranged at a position facing the top plate at a distance d.

  7 to 9 show other examples of the configuration of the GND pattern 3. The GND pattern 3 does not need to be formed on the entire surface of the opposing surface of the antenna 10 (that is, the outer peripheral edge of the external element 5) on the surface of the substrate 2 as shown in FIG. For example, as shown in FIG. 7, the length X1 of the GND pattern 3 in the direction of the spiral axis P may be shorter than L1. In the example of FIG. 7, the length Y1 of the spiral portion in the inner diameter direction is the same as Y (the length of the substrate 2 in the vertical direction, see FIG. 1). Moreover, as shown in FIG. 8, the length Y2 of the spiral portion in the inner diameter direction of the GND pattern 3 may be smaller than Y or the inner diameter R1 of the spiral portion 5a. In the example of FIG. 8, Y2 = R2 and X1 = L1. In addition, as shown in FIG. 9, the GND pattern 3 may be formed so that the GND pattern 3 and the spiral axis P intersect at a predetermined angle. Reference numeral 3a denotes a GND pattern to which the one end 5b of the external element 5 is connected. Although not shown, it is electrically connected to the GND pattern 3.

  FIG. 10 shows another example (front view) of the configuration of the antenna device 1. Since this configuration is a modification of FIG. 1, the same reference numerals are given to the same configurations as those in FIG. 1, and detailed descriptions thereof are omitted. In the configuration of FIG. 10, an insulating dielectric layer 8 is formed on the upper surface of the GND pattern 3. In addition, the gap d between the outer edge of the spiral portion 5a of the external element 5 and the dielectric layer 8 is 0 (that is, the outer edge of the spiral portion 5a and the dielectric layer 8 are in contact). The dielectric layer 8 corresponds to the capacitance generating member of the present invention.

  In the configuration of FIG. 10, the dielectric layer 8 also serves as a support portion for the external element 5. Therefore, the support part 7 may be only the internal element support part 7b. Of course, the gap d may be a value other than zero.

  Similarly to the other examples of the configuration of the GND pattern 3 in FIGS. 7 to 9, for example, the dielectric is formed only at a position where the gap d between the outer edge of the spiral portion 5 a of the external element 5 and the GND pattern 3 is the smallest and in the vicinity thereof. The dielectric layer 8 may not be formed on the entire upper surface of the GND pattern 3 as in the case where the layer 8 is formed.

  FIG. 11 shows another example of the configuration of FIG. 10 (right side view from the direction A). In the example of FIG. 11, a concave support portion 8 a for supporting the outer element 5 is formed on the surface of the dielectric layer 8 in contact with the outer edge of the spiral portion 5 a of the outer element 5 along the direction of the spiral axis P. Is. At this time, if the dielectric layer 8 is not formed between adjacent conductor lines (between the pitches) of the spiral portion 5a, an increase in the capacitance C2 between the pitches of the spiral portion 5a can be suppressed.

  12 and 13 show another example of the configuration of the antenna device 1. Since this configuration is a modification of FIG. 1, the same reference numerals are given to the same configurations as those in FIG. 1, and detailed descriptions thereof are omitted. FIG. 12 is a front view of this configuration, and FIG. 13 is a top view of the antenna device 1 of FIG. In this configuration, the surface-shaped GND pattern 9 is formed so as to face the spiral surface of the tip portion (end portion not connected to the GND pattern 3) of the external element 5 with a predetermined interval d2. Yes.

  The shape of the GND pattern 9 may be a rod shape in addition to the surface shape. Further, the shape of the surface may be any of a rectangular shape, a polygonal shape, and a circular shape. Furthermore, the GND pattern 9 only needs to face at least a part of the spiral surface. When the side wall of the housing in which the antenna device 1 is housed is a metal, the side wall may be grounded and used in place of the GND pattern 9, and the antenna 10 may be disposed near the side wall.

  Further, the dielectric layer 9a may be formed on at least a part of the surface facing the spiral surface of the GND pattern 9 (see FIG. 12).

  The configuration of the prior art of FIG. 14 is arranged with an outer element 120 having a spiral portion 121 extending spirally in a direction away from the land forming surface of the substrate 110 and an inner side of the outer element 120 with a space therebetween. An internal element 130 having a spiral portion 131 that spirally extends along the axial direction of the surface, and a planar GND pattern that faces the spiral portion 121 with a predetermined interval d3 therebetween. 9b may be formed.

  Moreover, you may form the GND pattern 9c in the opposing surface with the external element 5 of the support | pillar 7c of the support part 7 of FIG.

  The present invention can also be applied to an antenna device other than a keyless remote system used in a vehicle or a house. Moreover, it is applicable not only to a receiver but also to a transmitter.

  Although the embodiments of the present invention have been described above, these are merely examples, and the present invention is not limited to these embodiments, and the knowledge of those skilled in the art can be used without departing from the spirit of the claims. Various modifications based on this are possible.

DESCRIPTION OF SYMBOLS 1 Antenna apparatus 2 Board | substrate 3 GND pattern (electrostatic capacity generation member)
DESCRIPTION OF SYMBOLS 4 Power supply pattern 5 External element 5a Spiral part 6 Internal element 6a Spiral part 7 Support part 8,9a Dielectric layer (electrostatic capacity generating member)
9, 9b, 9c GND pattern (capacitance generating member)
10 Antenna

Claims (7)

A substrate on which a GND pattern and a power feeding pattern are provided;
An external element having a spiral portion extending spirally along a predetermined spiral axis direction;
An inner element having a spiral portion disposed inside the outer element at a predetermined interval and extending in a spiral shape along the spiral axis direction of the outer element;
Have
One end of one of the two elements is connected to the feeding pattern, and one end of the other element is connected to the GND pattern to constitute an antenna.
At least a part of the outer peripheral edge of the spiral portion of the external element is formed on the substrate, and is separated from a capacitance generating member that generates a capacitance with the external element by a predetermined distance. Arrange the antennas to face each other ,
The antenna device is characterized in that the capacitance generating member is formed only at a position where the gap with the outer peripheral edge of the spiral portion of the external element is the smallest and in the vicinity thereof .   The antenna device according to claim 1, wherein the number of turns of the spiral portion of the outer element is determined to be different from the number of turns of the spiral portion of the inner element.   The antenna device according to claim 1, further comprising a support portion attached to the substrate and supporting at least one of the outer element and the inner element.   The antenna device according to any one of claims 1 to 3, wherein the capacitance generating member is disposed so as to face a spiral surface of a distal end portion of the spiral portion of the external element.   The antenna device according to claim 1, wherein the GND pattern is used as the capacitance generating member.   The antenna device according to claim 1, wherein the capacitance generating member includes a dielectric layer formed on at least a part of the GND pattern.   The antenna device according to claim 6, wherein an outer peripheral edge of the external element is in contact with the dielectric layer, and the dielectric layer supports the external element.

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