JP4712074B2 - Antenna device - Google Patents

Description

  The present invention relates to an antenna device in which an antenna pattern made of an electrode film is formed on a dielectric substrate.

  Conventionally, in order to reduce the size of an antenna device and the size of a communication device, for example, many antenna patterns formed by electrode films on the surface of a dielectric substrate have been proposed (see, for example, Patent Documents 1 to 3). .

  Many of these antenna devices can be used by being directly mounted on a wiring board, which is one of the advantages.

Japanese Patent Laid-Open No. 10-41722 JP-A-9-162633 Japanese Patent Laid-Open No. 10-32413

  With the diversification of wireless communication systems such as mobile phones, there has been a strong demand for miniaturization of multilayer dielectric filters.

  Further, conventionally, when the antenna device is mounted on the wiring board, there is a problem that the input impedance changes greatly according to the distance from the ground line, and the input impedance is not stable.

  The present invention has been made in view of such points, and can effectively reduce the size of the antenna device, and can also stabilize the input impedance, improving the reliability of the antenna device, It is another object of the present invention to provide an antenna device capable of increasing the degree of freedom in designing electronic equipment.

An antenna device according to the present invention includes: an antenna formed on a dielectric substrate and having a rear end formed behind the input / output portion; and the dielectric substrate , the rear end of the antenna It includes and possess an inner layer ground electrode formed in the rear portion and opposing positions than the input portion, wherein Rukoto said rear end of said antenna and said innerlayer ground electrode is not connected And

The present invention can effectively reduce the size of the antenna device, can stabilize the input impedance, improve the reliability of the antenna device, and increase the degree of freedom in the design of electronic equipment. Can be planned.

And in the said structure, the filter formed integrally with the said antenna in the said dielectric substrate, It forms in the position facing the input-output part of the said antenna among the said dielectric substrates, and the said filter And an electrode electrically connected to the input / output portion of the antenna, and the input / output portion of the antenna and the input / output portion of the filter may be coupled via a capacitor. In this case, have a grounding electrode formed on the side surface of the dielectric substrate, a portion of the filter may be surrounded by the inner layer ground electrode and the ground electrode.

  As described above, according to the antenna device according to the present invention, it is possible to effectively reduce the size of the antenna device, and also to stabilize the input impedance, thereby improving the reliability of the antenna device, In addition, the degree of freedom in designing electronic devices can be increased.

  Hereinafter, embodiments of an antenna device according to the present invention will be described with reference to FIGS.

  First, as shown in FIGS. 1 and 2, the antenna device 10A according to the first embodiment has a dielectric substrate 12 formed by laminating and firing a plurality of plate-like dielectric layers on the outside. A filter 18 having one input / output electrode 14 (see FIG. 2) connected to the circuit and the other input / output electrode 16 (see FIG. 2) connected to the antenna 20 described later; An antenna 20 connected to the input / output electrode 16 via a capacitor is integrally formed.

  The filter 18 has a configuration in which two one-end open-type quarter-wave resonators (strip line conductors) 22a and 22b are formed in parallel, and the antenna 20 has an electrode film on the upper surface of the dielectric substrate 12. Thus, a meander line shape is formed.

  Further, in the antenna device 10A according to the first embodiment, as shown in FIGS. 1 and 2, an input / output terminal 26 connected to one input / output electrode 14 of the filter 18 is formed, and a dielectric First ground electrodes 28 are formed on the right and left sides of the body substrate 12 at portions corresponding to the filters 18 respectively.

  Specifically, as shown in FIG. 2, the dielectric substrate 12 is configured by laminating first to tenth dielectric layers S1 to S10 in order from the top. These first to tenth dielectric layers S1 to S10 are composed of one or a plurality of layers.

  The antenna 20 and the filter 18 are formed in a planarly separated region on the dielectric substrate 12, the antenna 20 is formed on the upper surface of the first dielectric layer S1, and the filter 18 is The third dielectric layer S3 is formed from the third dielectric layer S10 to the tenth dielectric layer S10.

  In the antenna device 10A according to the first embodiment, as shown in FIG. 2, two resonant elements (first and second resonant elements) are formed on one main surface of the seventh dielectric layer S7. 22a and 22b) are formed in parallel, and one end of each of the first and second resonance elements 22a and 22b is open and the other end is short-circuited to the ground electrode 28. .

  One input surface of the sixth dielectric layer S6 has one end connected to the input / output terminal 26 and capacitively coupled to the first resonant element 22a, and one end connected to the antenna. The other input / output electrode 16 is formed which is connected to the capacitor 20 through a capacitor and whose other end is capacitively coupled to the second resonance element 22b.

  Two inner layer ground electrodes 30a and 30b are formed on one main surface of the fifth dielectric layer S5 so as to face the open ends of the two resonance elements 22a and 22b, respectively.

  An inner layer ground electrode 32 connected to the ground electrode 28 on the outer surface is formed on a portion corresponding to the filter 18 in one main surface of the third dielectric layer S3.

  On one main surface of the eighth dielectric layer S8, a coupling adjustment electrode 34 that is in a floating state with respect to the ground electrode 28, the input / output terminal 26 of the filter 18 and the like is formed.

  The coupling adjusting electrode 34 includes a lead electrode 34c formed between a first electrode body 34a facing the first resonance element 22a and a second electrode body 34b facing the second resonance element 22b. It has an electrically connected shape.

  Two inner layer ground electrodes 36a and 36b are formed on one main surface of the ninth dielectric layer S9 so as to face the open ends of the two resonant elements 22a and 22b, respectively.

  In the antenna device 10A according to the first embodiment, as shown in FIGS. 1 and 2, the other input / output electrode 16 and the antenna 20 are formed on one main surface of the second dielectric layer S2. An electrode 38 for forming a capacitor is formed between one end of each of the two electrodes. The electrode 38 and the other input / output electrode 16 are electrically connected through a through hole 40.

  Furthermore, as shown in FIG. 1, the antenna device 10A according to the first embodiment includes an open end 20a of the antenna 20 and the first to third dielectric layers S1 on the fourth dielectric layer S4. An inner layer ground electrode 60 is formed at a position overlapping with S3. For example, as shown in FIG. 3, the inner layer ground electrode 60 is a second electrode formed at a position different from the ground electrode 28 formed on the surface of the dielectric substrate 12 on the filter 18 side (right side surface in the illustrated example). The earth electrode 62 is connected.

  Here, the electrical coupling of the electrodes in the antenna device 10A according to the first embodiment will be described with reference to the equivalent circuit diagram of FIG.

  Two resonators 50a and 50b by the first and second resonance elements 22a and 22b are connected in parallel between the input / output terminal 26 and the ground, respectively, and these adjacent resonators 50a and 50b are inductively coupled to each other. Thus, on the equivalent circuit, the inductance L is inserted between the adjacent resonators 50a and 50b.

  Further, a combined capacitance C is formed by the coupling adjustment electrode 34 between the first resonance element 22a and the second resonance element 22b, and an LC in parallel by the inductance L and the combined capacitance C is formed between the resonators 50a and 50b. Resonance circuit is connected.

  Capacitances (combined capacitors) C1 and C2 are formed between the open ends of the first and second resonance elements 22a and 22b and the corresponding inner layer ground electrodes (30a, 36a) and (30b, 36b), respectively. Is done.

  Further, a capacitance C3 is formed between the first resonant element 22a and the input / output terminal 26 via one input / output electrode 14, and the other input / output electrode 16 constituting the contact CN and the first input / output terminal 26 are connected to each other. A capacitance C4 is formed between the two resonance elements 22b, and a capacitance C5 is formed between the contact CN (the other input / output electrode 16) and the antenna 20 via the electrode 38, A capacitance C6 is formed between the contact CN (the other input / output electrode 16) and the ground (inner layer ground electrode 32).

  That is, in the antenna device 10A according to the first embodiment, the filter 18 and the antenna 20 are coupled via the capacitor C5 (and C4), and in particular, include the capacitors C5 and C6 between the filter 18 and the antenna 20. It has a circuit configuration in which an impedance matching circuit 52 is inserted and connected. The impedance matching can also be realized by changing the lengths of the resonators 50a and 50b instead of the electrostatic capacitance C6, or by making the combined capacitors C1 and C2 shown in FIG. 3 different.

  Furthermore, in the first embodiment, as shown in FIG. 4, a capacitance C <b> 10 is formed between the open end 20 a of the antenna 20 and the inner layer ground electrode 60.

  Thus, in the antenna device 10A according to the first embodiment, the antenna 20 is configured by a strip line formed on the dielectric substrate 12. This strip line can be regarded as equivalent to the resonators 50a and 50b formed in the filter 18, and can be equivalently converted as a parallel resonant circuit.

  In the first embodiment, as described above, the inner-layer ground electrode 60 that forms the capacitance C10 is provided between the open end 20a of the antenna 20 and the antenna 20 is provided. In this case, the capacitance C10 formed between the open end 20a of the antenna 20 and the inner layer ground electrode 60 is added to the capacitance of the parallel resonant circuit when the antenna 20 is equivalently converted. The center frequency (resonance frequency) can be reduced. That is, if the center frequency is the same, the inductance of the parallel resonant circuit can be reduced, and as a result, the antenna length can be further shortened, and the overall size of the antenna device 10A can be reduced.

  Further, when the antenna device 10A is mounted on the wiring board, the input impedance of the antenna device 10A hardly depends on the distance between the antenna 20 and the ground line, and the input impedance can be stabilized. This can improve the reliability of the antenna device 10A and increase the degree of freedom in designing the electronic device provided with the antenna device 10A.

  If it is desired to increase the capacitance C10, as shown in FIG. 1, the electrode area at the open end 20a of the antenna should be wide.

  Here, two experimental examples (referred to as first and second experimental examples for convenience) are shown. The first experimental example is a comparative example in which the capacitor C10 is not added to the open end 20a of the antenna 20, the embodiment 1 in which a capacitor C10 of 1.2 pF is added to the open end 20a of the antenna 20, and the open end 20a of the antenna 20. Example 2 in which a capacitor C10 of 3.5 pF was added to the above was prepared, and the respective center frequencies were measured. The measurement results are shown in FIG.

  From this measurement result, it can be seen that the center frequency decreases from about 2 GHz to about 1 GHz as the capacitance C10 added to the open end 20a of the antenna 20 increases to 0 pF, 1.2 pF, and 3.5 pF.

  Next, in the second experimental example, as shown in FIG. 6, the antenna device 10 </ b> A in which the antenna 20 having a width of 3.2 mm is formed at one corner portion of the wiring board 70 is mounted. A ground plate 74 having a ground electrode 72 formed on almost the entire surface is attached to the ground plate 74, and a large number of samples having a rectangular notch 76 provided in a portion corresponding to the antenna device 10A are prepared.

  The positional relationship between the mounting position of the antenna device 10A and the notch 76 is such that the center of the antenna 20 is positioned at a position of 2.5 mm from the left end to the right end of the wiring board 70 as shown in FIG. The distance from the left end of the ground plate 74 (the left end of the wiring board 70) to the end of the notch 76 is defined as a notch amount D. Therefore, the distance m from the right end of the antenna 20 to the end of the notch 76 is the notch amount D-4.1 mm.

  Among these samples, a large number of samples having no capacity C10 added to the open end 20a of the antenna 20 and having a notch amount D of 5 mm, 10 mm, 20 mm, and 30 mm are prepared as comparative examples. For example, a large number of open ends 20a with a capacitance C10 of 3.5 pF, for example, with notches D of 5 mm, 10 mm, 20 mm, and 30 mm were prepared.

  And the reflection coefficient of these comparative examples and an Example was measured. The measurement results are shown in FIG. In FIG. 7, the characteristics of the comparative example are shown by a plot of ●, and the characteristics of the example are shown by a plot of ■.

  From this measurement result, it can be seen that the change in the reflection coefficient with respect to the change in the notch amount D is smaller in the example. This indicates that the input impedance is more stable in the example than in the comparative example. Particularly, regarding the change in the notch amount D, which is preferable in terms of characteristics, from 5 mm to 10 mm. In the comparative example, the change is steep, but in the example, the change is gradual. This shows that the antenna device 10A according to the first embodiment is advantageous in terms of mounting.

  Next, an antenna device 10B according to a second embodiment will be described with reference to FIGS. In addition, about the thing corresponding to FIG.1 and FIG.2, the same code | symbol is attached | subjected and the duplication description is abbreviate | omitted.

  The antenna device 10B according to the second embodiment has substantially the same configuration as the antenna device 10A according to the first embodiment described above, as shown in FIGS. The end 20b extends rearward from the input / output portion (portion connected to the electrode 38), and the rear end 20b of the antenna 20 and the inner layer ground electrode 32 are electrically connected through the through hole 90. It is different.

  In the antenna device 10B according to the second embodiment, similarly to the antenna device 10A according to the first embodiment described above, it is possible to effectively reduce the size of the antenna device 10B and stabilize the input impedance. Can be achieved.

  In particular, in the antenna device 10B according to the second embodiment, since the antenna length La is defined by the length from the open end 20a to the rear end 20b, as shown in FIG. By positioning the end 20 b rearward near the filter 18, the open end 20 a of the antenna 20 can be positioned closer to the filter 18.

  That is, as shown in FIG. 11, when the rear end 20b of the antenna 20 is used as an input / output portion, only the antenna length La is required as a region for forming the antenna 20 in the dielectric substrate 12. In the antenna device 10B according to the second embodiment, since the open end 20a of the antenna 20 can be positioned closer to the filter 18, a region shorter than the antenna length La is sufficient as a region where the antenna 20 is formed.

  That is, as shown in FIG. 10, in the antenna device 10B according to the second embodiment, the length of the dielectric substrate 12 can be reduced by the amount indicated by the arrow A as compared with the antenna device shown in FIG. Thus, the antenna device 10B can be significantly reduced in size.

  In the above-described example, the electrode 38 is disposed between the rear end 20b of the antenna 20 and the other input / output electrode 16 in the filter 18, so that the rear end of the antenna 20 and the other input / output electrode 16 in the filter 18 Are connected via the capacitor C5, but they may be directly connected.

  Of course, the antenna device according to the present invention is not limited to the above-described embodiments, and various configurations can be adopted without departing from the gist of the present invention.

It is a perspective view which shows the antenna apparatus which concerns on 1st Embodiment seeing from one direction. 1 is an exploded perspective view showing an antenna device according to a first embodiment. It is a perspective view which shows the antenna apparatus which concerns on 1st Embodiment from another direction. 1 is an equivalent circuit diagram illustrating an antenna device according to a first embodiment. It is a characteristic view which shows the measurement result (change of the center frequency with respect to additional capacity) of the 1st experiment example. It is explanatory drawing which shows the measuring method of a 2nd experiment example. It is a characteristic view which shows the measurement result (the notch amount dependence of a reflection coefficient) of the 2nd experiment example. It is a perspective view which shows the antenna device which concerns on 2nd Embodiment. It is a disassembled perspective view which shows the antenna device which concerns on 2nd Embodiment. It is explanatory drawing which shows the effect of the antenna device which concerns on 2nd Embodiment. It is explanatory drawing which shows the structural example of the antenna apparatus at the time of setting the rear end of an antenna as an input-output part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10A, 10B ... Antenna apparatus 12 ... Dielectric board | substrate 18 ... Filter 20 ... Antenna 20a ... Open end 20b ... Rear end 22a, 22b ... Resonance element 28 ... First earth electrode 38 ... Electrode 40 ... Through-hole 50a, 50b ... Resonance 60 ... Inner layer ground electrode 62 ... Second ground electrode 70 ... Wiring board 90 ... Through hole

Claims (3)

An antenna formed on a dielectric substrate and having a rear end formed behind the input / output portion;
An inner layer ground electrode formed in a position in the dielectric substrate, including the rear end of the antenna, and facing a portion behind the input / output portion;
The antenna device, wherein the rear end of the antenna and the inner layer ground electrode are connected. The antenna device according to claim 1, wherein
A filter integrally formed with the antenna in the dielectric substrate ;
In the dielectric substrate, the electrode is formed at a position facing the input / output portion of the antenna, and has an electrode electrically connected to the input / output portion of the filter ,
An antenna device, wherein an input / output portion of the antenna and an input / output portion of the filter are coupled via a capacitor. The antenna device according to claim 2, wherein
Have a grounding electrode formed on the side surface of the dielectric substrate,
A part of the filter is surrounded by the inner layer ground electrode and the ground electrode .

Images