WO2006120763A1

WO2006120763A1 - Antenna structure and radio communication device using the same

Info

Publication number: WO2006120763A1
Application number: PCT/JP2005/012946
Authority: WO
Inventors: Satoru Hirano
Original assignee: Murata Manufacturing Co., Ltd.
Priority date: 2005-05-13
Filing date: 2005-07-13
Publication date: 2006-11-16
Also published as: JPWO2006120763A1; JP4103936B2; GB2439863A; GB2439863B; GB0718977D0; GB2439863C

Abstract

An antenna structure (1) includes a circuit substrate (5) on which a base (2) having a radiation electrode (3) is mounted. The radiation electrode (3) is arranged on the base (2) so as to oppose to the circuit substrate surface via a gap. On the circuit substrate (5), there is formed an inter-ground capacity loading electrode (7) arranged to oppose to the radiation electrode (3) of the base (2) and having a capacity between itself and the radiation electrode (3). Moreover, on the circuit substrate (5), there is formed a ground electrode (6) with a gap to the inter-ground capacity loading electrode (7). Furthermore, a resonance frequency adjusting element (8) is arranged to make a connection between the inter-ground capacity loading electrode (7) and the ground electrode (6). The resonance frequency adjusting element (8) has a capacity or an inductance for adjusting the resonance frequency of the antenna structure (1) to a predetermined resonance frequency.

Description

Specification

Antenna structure and wireless communication device including the same

Technical field

The present invention relates to an antenna structure in which a base on which a radiation electrode is formed is mounted on a circuit board, and a radio communication device including the antenna structure.

Background art

[0002] As one of antennas provided in a wireless communication device, there is a surface mount antenna that is mounted on a circuit board of a wireless communication device and accommodated in a housing of the wireless communication device. This surface-mounted antenna has, for example, a configuration in which a radiation electrode for performing antenna operation is formed on a dielectric substrate.

Patent Document 1: Japanese Patent Laid-Open No. 10-209733

Patent Document 2: JP 2002-141739 A

Patent Document 3: Japanese Patent Laid-Open No. 2002-335117

Disclosure of the invention

Problems to be solved by the invention

[0004] By the way, the frequency characteristics (return loss characteristics) of radio waves from a radio communication device with a surface-mounted antenna mounted on a circuit board are not determined only by the radiation electrode of the surface-mounted antenna. This is determined by the involvement of various elements such as the ground electrode and parts of the circuit board on which the is mounted. For this reason, the resonance frequency of the radio communication radio wave of the radio communication device is shifted from the resonance frequency of the radiation electrode of the surface mount antenna. As a result, even if the same surface mount antenna is mounted, for example, if the wireless communication device model is different, the resonance frequency of the radio communication radio wave of the wireless communication device (hereinafter referred to as the antenna resonance frequency) is different. A problem occurs.

[0005] In other words, when the model of the wireless communication device is different, the size and shape of the ground electrode (Dalland) formed on the circuit board is different, or the components disposed around the surface mount antenna are different. The state of the surface mount antenna is different, such as the type and the distance between the surface mount antenna and the surrounding parts, and the housing material of the radio communication device is different. Different. Since the ambient frequency of such a surface mount antenna is involved in a complicated manner and the resonance frequency of the antenna is determined, the type of radio communication device on which the surface mount antenna is mounted differs. If the ambient conditions are different, the same surface-mount antenna is provided, and the resonance frequency of the antenna is different.

[0006] Even if the same surface mount antenna is provided in this way, the same antenna resonance frequency cannot be obtained if the models of the wireless communication devices are different. For this reason, even if the required resonance frequency of the antenna is the same, for example, if the model of the radio communication device is different, the same surface mount antenna cannot be provided, and the surface mount antenna for each radio communication device model cannot be provided. For example, it was necessary to customize the size of the radiation electrode, which was troublesome.

[0007] In addition to the surface-mounted antenna, other than the surface-mounted antenna, for example, the circuit board circuit electrically connected to the surface-mounted antenna is changed for each wireless communication device model. A method has been proposed in which the part is custom-designed and the resonance frequency of the antenna is adjusted to the set resonance frequency (see, for example, Patent Documents 1 to 3).

However, the conventional methods for adjusting the resonance frequency of the antenna with the circuit on the circuit board have a problem in that the current loss increases and the antenna gain decreases. Also, when using a component with capacitance or inductance to adjust the resonance frequency of the antenna, for example, if a general-purpose component is also used for cost, the value of V or some numerical value of capacitance or inductance Only parts with values (capacitor parts or inductor parts) can be prepared. For this reason, since it is often impossible to obtain capacitor components and inductor components having optimum values, it is difficult to accurately adjust the resonance frequency of the antenna to the set resonance frequency.

Means for solving the problem

[0009] The present invention has the following configuration as means for solving the above problems. That is, one of the configurations of the antenna structure of the present invention is that a radiation electrode that performs antenna operation is provided on a base, and the base is mounted on a circuit board, and the radiation electrode is a substrate surface of the circuit board. In the antenna structure having a configuration provided on the base so as to face each other with a gap therebetween,

The circuit board is placed facing the radiation electrode of the base and has a capacitance between it and the radiation electrode. A grounding electrode is formed on the circuit board, and a grounding electrode is formed on the circuit board via a space between the grounding capacitor loading electrode and the grounding electrode, avoiding the formation region of the grounding capacity loading electrode. A resonance frequency adjusting element is provided to connect between the capacitance loading electrode and the ground electrode, and the resonance frequency adjusting element adjusts the resonance frequency of the antenna structure to a resonance frequency set in advance. It is characterized by having a capacitance or inductance to achieve this. In addition, the wireless communication device of the present invention is characterized in that an antenna structure having a configuration specific to the present invention is provided.

The invention's effect

[0010] According to the present invention, the base body provided with the radiation electrode is mounted on the circuit board, and the circuit board is disposed opposite to the radiation electrode of the base body and has a capacitance between the ground electrode and the ground electrode. A mass loading electrode is formed. In addition, the circuit board is provided with a ground electrode via a gap between the electrode for loading capacitance between grounds and an element for adjusting a resonance frequency for connecting between the electrode for loading capacitance between grounds and the ground electrode. ing. The resonance frequency adjusting element has a capacity or inductance. In other words, in the present invention, the radiation electrode is connected to the ground electrode via the capacitance between the capacitance loading electrode and the capacitance or inductance of the resonance frequency adjusting element. The impedance of the circuit (hereinafter referred to as the resonance frequency adjusting circuit) in which the capacitance between the radiation electrode and the electrode for capacitive loading between the ground and the capacitance or inductance of the resonance frequency adjusting element is connected in series is It is concerned with the electrical length of the radiation electrode which determines the resonance frequency of the radiation electrode. For this reason, by variably adjusting the capacitance or inductance value of the resonant frequency adjusting element, the impedance of the resonant frequency adjusting circuit is varied and the electrical length of the radiation electrode is varied. The resonance frequency of the radiation electrode (that is, the resonance frequency of the antenna structure) can be variably adjusted.

[0011] In this way, the resonant frequency of the antenna structure can be variably adjusted without changing the design of the shape of the radiation electrode of the base body, etc., simply by changing the capacitance or inductance value of the resonant frequency adjusting element. Can do. As a result, a component (antenna component) in which the radiation electrode is formed on the base can be used in common for a plurality of types of wireless communication devices, and the component can be shared. This makes it possible to reduce the cost of antenna parts and wireless communication devices. It becomes easy to plan.

[0012] In addition, as the electrode area of the electrode for loading capacitance between grounds is increased to increase the capacitance between the electrode for loading capacitance between grounds and the radiation electrode, the capacitance of the element for adjusting the resonant frequency or The amount of change in the resonance frequency of the antenna structure with respect to the amount of change in inductance value can be increased. In other words, the capacitance size or inductance of the resonance frequency adjusting element is reduced as the electrode area of the electrode for loading capacitance between grounds is reduced to reduce the capacitance between the electrode for loading capacitance between grounds and the radiation electrode. The amount of change in the resonant frequency of the antenna structure with respect to the amount of change in value can be reduced.

[0013] Therefore, for example, for low cost, a general-purpose capacitor component or inductor component is used as the resonance frequency adjustment element, and the capacitance size or inductance value of the resonance frequency adjustment element is discontinuous. Even if it can only be variably adjusted, it is possible to change the capacitance between the radiation electrode and the electrode for capacitive loading by changing the electrode area of the electrode for loading the capacitance between grounds, thereby resonating the antenna structure. The frequency change width can be reduced, and the resonance frequency of the antenna structure can be finely adjusted. This makes it easy to obtain the required resonance frequency of the radiation electrode and improve the reliability of the wireless communication device having the antenna structure of the present invention for wireless communication.

[0014] Further, in the present invention, the electrode for loading capacitance between grounds is provided on the circuit board and is not provided on the base on which the radiation electrode is formed. For this reason, when it is desired to change the capacitance between the radiation electrode and the electrode for loading capacitance between grounds due to a design change, etc., it is only necessary to change the electrode area of the electrode for loading capacitance between the grounds formed on the circuit board. There is no need to change the design of the component (antenna component) formed by forming the radiation electrode on the base. In other words, it is possible to use the same antenna components after the design change as before the design change. As described above, the configuration in which the electrode for ground capacitance loading is provided on the circuit board is also an important element that can promote the common use of the antenna components.

[0015] Furthermore, when the radiating electrode is provided on the base so as to face the substrate surface of the circuit board with a gap, a ground-capacitance capacity loading electrode is temporarily provided on the side of the base. In this case, the virtual plane along the electrode surface of the radiation electrode and the electrode of the electrode for loading capacitance between grounds. Since the virtual plane along the pole surface has, for example, an orthogonal relationship or a substantially orthogonal relationship, the capacitance between the radiation electrode and the electrode for loading capacitance between grounds is small. For this reason, when a large capacity is required between the radiation electrode and the electrode for loading the capacitance between the grounds, the electrode for loading the capacitance between the grounds must be enlarged, and the substrate (that is, the antenna component) is The problem of increasing the size occurs.

On the other hand, in the present invention, the grounding capacity loading electrode is formed on the circuit board surface portion facing the radiation electrode, so that the facing area between the grounding capacity loading electrode and the radiation electrode is reduced. It becomes easy to form a large capacity between the electrode for loading capacitance between ground and the radiation electrode. In addition, since the electrode for loading capacitance between grounds is not provided on the base, the size of the base (antenna component) can be reduced by not providing the electrodes for loading capacitance between grounds on the base.

[0017] Further, the capacitance loading electrode between the grounds is formed on the circuit board surface portion facing the radiation electrode, and a large capacitance can be formed between the capacitance loading electrode between the ground and the radiation electrode. Due to the configuration, it is possible to variably adjust the resonance frequency of the antenna structure while preventing the antenna gain from being deteriorated.

Brief Description of Drawings

[0018] FIG. La is a schematic plan view for explaining the antenna structure of the first embodiment.

[FIG. Lb] FIG. Lb is a schematic perspective view of the antenna structure of FIG. La.

[FIG. Lc] FIG. Lc is a schematic plan view for explaining a configuration example of a circuit board constituting the antenna structure of FIG. La.

FIG. 2 is a graph for explaining an example of a change in the return loss characteristic of the antenna structure due to a change in the capacitance of the resonant frequency adjusting element constituting the antenna structure of the first embodiment.

FIG. 3 is a graph for explaining an example of a change in the return loss characteristic of the antenna structure due to a change in the inductance value of the resonant frequency adjusting element constituting the antenna structure of the first embodiment.

[FIG. 4] FIG. 4 is a diagram illustrating a configuration example of a slit of the ground electrode constituting the antenna structure of the first embodiment. It is a figure for clarification.

FIG. 5 is a graph for explaining an example of a change in the return loss characteristic of the antenna structure with respect to a change in the length of the resonance frequency adjusting slit provided in the ground electrode.

[FIG. 6a] FIG. 6a is a model diagram for explaining the effect of obtaining the component power of the first embodiment.

[FIG. 6b] FIG. 6b is a model diagram for explaining the problems of the conventional example.

[FIG. 6c] FIG. 6c is a model diagram for explaining the problems of the conventional example together with FIG. 6b.

FIG. 7a is a sectional view for explaining one of the other embodiments together with FIG. 7b.

FIG. 7b is a cross-sectional view for explaining one of the other embodiments together with FIG. 7a.

Explanation of symbols

[0019] 1 Antenna structure

2 Dielectric substrate

3 Radiation electrode

5 Circuit board

6 Ground electrode

7 Electrode for capacitive loading between grounds

8 Resonance frequency adjustment element

13 Slit

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments according to the present invention will be described with reference to the drawings.

[0021] Fig. La shows a schematic plan view of a first embodiment of an antenna structure according to the present invention.

Fig. Lb shows a schematic perspective view of the antenna structure of Fig. La, and Fig. Lc shows a schematic plan view of a conductor pattern form of the circuit board constituting the antenna structure of Fig. La. ing.

[0022] The antenna structure 1 of the first embodiment includes a base 2 made of a dielectric, a radiation electrode 3 and a feed electrode 4 formed on the dielectric base 2, and the dielectric base 2 mounted on the surface. Circuit board 5, the ground electrode 6 formed on the circuit board 5 and the electrode 7 for loading capacitance between the ground, and the resonance frequency adjustment for connecting the electrode 6 for loading capacitance between the ground electrode 6 and the electrode 7 for loading capacitance between the ground for The device 8 includes a power supply line 9 formed on the circuit board 5 and electrically connected to the power supply electrode 4 of the dielectric substrate 2.

That is, in the first embodiment, the dielectric substrate 2 has a rectangular parallelepiped shape. A schematic cross-sectional view of this dielectric substrate 2 is shown in FIG. 6a. For example, the radiation electrode 3 is formed from the top surface of the dielectric substrate 2 so as to wrap around the edge of the bottom surface through the right end surface of FIG. Further, the edge force on the bottom surface of the dielectric substrate 2, for example, the feed electrode 4 is extended to a position passing through the left end surface in FIG. !

[0024] The corner of the circuit board 5 forms an antenna component, and a ground-loading electrode 7 and a power supply line 9 are formed on the board surface of the corner of the circuit board 5. On the substrate surface of the circuit board 5, the ground electrode 6 is formed in almost the entire area avoiding the formation area of the inter-ground capacitance loading electrode 7 and the power supply line 9. The dielectric substrate 2 on which the radiating electrode 3 and the feeding electrode 4 are formed has a posture in which the bottom surface is directed to the circuit board 5 side, and the radiating electrode 3 is formed, for example, on the right end of FIG. With the part disposed on the ground electrode 6, it is mounted (surface mounted) on the antenna component at the corner of the circuit board 5. As described above, when the dielectric substrate 2 is mounted on the circuit board 5, among the both end portions of the radiation electrode 3, the end portion far from the feeding electrode 4 (that is, the right end portion in FIG. The radiation electrode 3 that is directly joined to the ground electrode 6 and provided on the upper surface of the dielectric substrate 2 is in a state of being disposed opposite to the substrate surface of the circuit board 5.

[0025] One end of the power supply line 9 is electrically connected to the power supply electrode 4. Further, the other end side of the power supply line 9 is electrically connected to, for example, a high-frequency circuit 10 for wireless communication of a wireless communication device. That is, the power supply line 9 electrically connects the high-frequency circuit 10 for wireless communication and the power supply electrode 4. The feeding line 9 is provided with a matching element 11 constituting a matching circuit for impedance matching between the feeding electrode 4 side and the high-frequency circuit 10 side.

The power supply electrode 4 is formed with a gap from the radiation electrode 3, and the power supply electrode 4 and the radiation electrode 3 are electromagnetically coupled through a capacitor. In other words, for example, a radio transmission signal is transmitted to the power feeding electrode 4 from the radio communication high frequency circuit 10 through the power feeding line 9. Then, a signal for wireless transmission is transmitted from the feeding electrode 4 to the radiation electrode 3 by capacitive coupling between the feeding electrode 4 and the radiation electrode 3. In other words, the radiation electrode 3 is a capacitive feed type radiation electrode.

[0027] In the first embodiment, the circuit board 5 is provided with a ground-capacitance loading electrode 7 at a portion facing the radiation electrode 3 with a gap from the ground electrode 6 (see Fig. Lc). . The ground-loading capacity loading electrode 7 has a bow I protruding portion 7a formed by being drawn out from the region where the dielectric substrate 2 is mounted to the outside of the region. The resonant frequency adjusting element 8 is composed of a capacitor part or an inductor part, and is mounted on the circuit board 5 in such a manner that the lead part 7a of the electrode 7 for loading capacitance between the ground and the ground electrode 6 is connected. Has been. In this first embodiment, the dielectric substrate 2 provided with the radiation electrode 3 is of the ground mounting type. Originally, the ground electrode 6 is formed on the portion of the circuit board 5 on which the dielectric substrate 2 is mounted. However, in order to form the capacitance loading electrode 7 and the power supply line 9, the ground electrode 6 is not formed on the substrate surface in the formation region of the capacitance loading electrode 7 and the power supply line 9. It becomes the composition.

[0028] In the first embodiment, the grounding capacity loading electrode 7 is disposed opposite to the radiation electrode 3 so that a capacity is formed between the grounding electrode 3 and the grounding capacity loading electrode. 7 is connected to the ground electrode 6 through a resonant frequency adjusting element 8. In other words, the radiation electrode 3 is a circuit (resonance frequency adjustment) in which a capacitance between the radiation electrode 3 and the electrode for loading capacitance between grounds 7 and a capacitance or inductance of the resonance frequency adjustment element 8 are connected in series. It is connected to the ground electrode 6 through a circuit). The impedance of the resonance frequency adjusting circuit is related to the electrical length of the radiation electrode 3, that is, the resonance frequency. Therefore, the resonant frequency of the radiating electrode 3 (antenna structure) can be adjusted by variably adjusting the impedance or the inductance value of the resonant frequency adjusting element 8 and adjusting the impedance of the resonant frequency adjusting circuit. 1 resonance frequency) can be variably adjusted.

[0029] For example, when the resonant frequency adjusting element 8 is constituted by a capacitor component, the resonant frequency of the antenna structure 1 can be made lower than when the resonant frequency adjusting element 8 is not provided. it can. The amount of decrease in the resonance frequency increases as the capacitance of the resonance frequency adjusting element (capacitor component) 8 increases. FIG. 2 shows examples of return loss characteristics of five types of antenna structures 1 having the same configuration except for the configuration related to the resonance frequency adjusting element 8. That is, the dotted line A in the drawing of FIG. 2 is an example of the return loss characteristic of the antenna structure 1 when the resonance frequency adjusting element 8 is not provided. In addition, the solid lines B to E in the graph of FIG. 2 are examples of the return loss characteristics of the antenna structure 1 when a capacitor component is provided as the resonance frequency adjusting element 8, and the solid line B is the resonance frequency. This is an example when the capacitance of the adjustment element 8 is 0.5 pF, the solid line C is an example when the capacitance of the resonance frequency adjustment element 8 is lpF, and the solid line D is a capacitance of the resonance frequency adjustment element 8 of 3 pF. The solid line E is an example when the capacitance of the resonant frequency adjusting element 8 is 6 pF. As can be seen from the graph in FIG. 2, the resonant frequency of the antenna structure 1 is lower by providing the resonant frequency adjusting element (capacitor component) 8 than when the resonant frequency adjusting element 8 is not provided. Become. Further, the amount of decrease in the resonance frequency of the antenna structure 1 Δ ί, Δ ί,

B C

Δ ί and Δ ί increase as the capacitance of the resonance frequency adjusting element 8 increases.

D Ε

[0031] Also, when the resonant frequency adjusting element 8 is formed of an inductor component, the resonant frequency of the antenna structure 1 can be increased compared to the case where the resonant frequency adjusting element 8 is not provided. it can. The amount of increase in the resonance frequency is such that as the inductance value of the resonance frequency adjustment element (inductor component) 8 decreases, the influence of the resonance frequency adjustment element 8 increases, and the resonance frequency of the antenna structure 1 increases. Become.

FIG. 3 shows examples of return loss characteristics of five types of antenna structures 1 having the same configuration except for the configuration related to the resonant frequency adjusting element 8. That is, the dotted line a in the drawing of FIG. 3 is an example of the return loss characteristic of the antenna structure 1 when the resonance frequency adjusting element 8 is not provided. Also, the solid lines b to e in the graph of FIG. 3 are examples of the return loss characteristics of the antenna structure 1 when an inductor component is provided as the resonance frequency adjusting element 8, and the solid line b is the resonance frequency. The adjustment element 8 is an example when the inductance value is 6.8 nH, and the solid line c is an example when the resonance frequency adjustment element 8 has an inductance value of 4.7 nH, and the solid line d is for resonance frequency adjustment. The element 8 is an example when the inductance value is 3.9 nH, and the solid line e is an example when the inductance value of the resonance frequency adjusting element 8 is 2.7 nH. Resonance circumference so that the graph force in Fig. 3 is also divided. By providing the wave number adjusting element (inductor component) 8, the resonance frequency of the antenna structure 1 becomes higher than when the resonant frequency adjusting element 8 is not provided. Further, the amount of increase Afb, Afc, Afd, Afe of the resonance frequency of the antenna structure 1 increases as the inductance value of the resonance frequency adjusting element 8 decreases.

[0033] Note that the resonance frequency adjusting circuit in which the capacitance between the radiation electrode 3 and the ground-capacitance loading electrode 7 and the capacitance or inductance of the resonance frequency adjusting element 8 are connected in series is the radiation electrode 3 The amount of change in the impedance of the resonance frequency adjustment circuit with respect to the amount of change in the capacitance or the inductance value of the resonance frequency adjustment element 8 differs depending on the capacitance between the capacitor and the electrode 7 for loading capacitance between grounds. As a result, the capacitance of the resonant frequency adjusting element 8 can be adjusted by variably adjusting the capacitance between the radiation electrode 3 and the grounded capacitance loading electrode 7, that is, by adjusting the electrode area of the grounded capacitance loading electrode 7. The resonant frequency of the antenna structure 1 can be variably adjusted by adjusting the amount of change in the impedance of the resonance frequency adjusting circuit with respect to the amount of change or the amount of change in inductance value.

[0034] Specifically, as the electrode area of the capacitance loading electrode 7 between the grounds is reduced and the capacitance between the capacitance loading electrode 7 and the radiation electrode 3 is reduced, the resonance frequency adjusting element 8 The amount of change in the resonance frequency of the antenna structure 1 with respect to the amount of change in capacitance or inductance value is small. In other words, the capacitance of the resonant frequency adjusting element 8 increases as the electrode area of the electrode 7 for loading capacitance between grounds increases and the capacitance between the electrode 7 for loading capacitance between grounds and the radiation electrode 3 increases. The change in the resonance frequency of the antenna structure 1 with respect to the change in the inductance value or the inductance value becomes large. From this, for example, even if the capacitance size or inductance value of the resonance frequency adjusting element 8 is changed in the same manner, the variation width of the resonance frequency of the antenna structure 1 depends on the electrode area of the electrode 7 for capacitive load between grounds. Change. As a result, when fine adjustment of the resonance frequency of the antenna structure 1 is desired, the electrode area of the electrode 7 for loading the capacitance between the grounds is reduced, and conversely, the resonance frequency of the antenna structure 1 is greatly changed. For this purpose, the electrode area of the electrode 7 for capacity loading between grounds is increased.

In the first embodiment, a slit 13 is formed in the ground electrode 6 so as to extend from a portion joined to the radiation electrode 3. The slit 13 is for causing a part of the ground electrode 6 connected to the radiation electrode 3 to function as a part of the radiation electrode 3. The slit 13 The portion of the ground electrode 6 that functions as a part of the electrode 3 is formed to be separated from the other portions of the ground electrode 6.

By forming the slit 13, for example, a part of the ground electrode 6 surrounded by a chain line Z in FIG. 4 functions as a part of the radiation electrode 3. For this reason, changing the shape and length of the slit 13 to change the electrical length of the portion Z of the ground electrode 6 that functions as a part of the radiation electrode 3 makes it Therefore, the resonance frequency of the antenna structure 1 can be changed. That is, for example, as the length of the slit 13 is extended as indicated by the dotted line from the length of the slit 13 as indicated by the solid line in FIG. The solid line in the graph of 5 changes from L a → solid line Lb → solid line Lc → solid line Ld → solid line Le → solid line Lf. That is, the resonance frequency of the antenna structure 1 can be lowered as the length of the slit 13 increases and the equivalent electrical length of the radiation electrode 3 increases.

[0037] It should be noted that the resonance frequency of the antenna structure 1 can be set to, for example, a unit of about 10 MHz by variable adjustment of the capacitance or inductance value of the resonance frequency adjusting element 8 and variable adjustment of the electrode area of the capacitance loading electrode 7 between grounds. Alternatively, depending on the electrode area of the electrode 7 for loading capacitance between grounds, it can be variably adjusted in units of 1 MHz or several MHz. On the other hand, the resonance frequency of the antenna structure 1 can be variably adjusted, for example, in units of about 100 MHz by variably adjusting the slit 13. As described above, in this first embodiment, the resonance frequency of the antenna structure 1 is roughly adjusted by the slit 13, and the resonance frequency adjusting element 8 and the electrode area of the capacitance loading electrode 7 are adjusted depending on the electrode area. By finely adjusting the resonance frequency of the antenna structure 1, the resonance frequency of the antenna structure 1 can be adjusted with high accuracy.

In the first embodiment, as described above, the capacity size or inductance value of the resonant frequency adjusting element 8 and the electrode area of the grounding capacity loading electrode 7 (the grounding capacity loading electrode 7 and The resonance frequency of the antenna structure 1 can be variably adjusted by variably adjusting the capacitance between the radiation electrode 3 and the length and shape of the slit 13. From this, the magnitude or inductance value of the resonance frequency adjusting element 8 and the electrode of the ground-to-ground capacity loading electrode 7 are set so that the resonance frequency of the antenna structure 1 becomes a resonance frequency set in advance. Area and The length and shape of the slit 13 are appropriately adjusted and set.

[0039] By providing the configuration of the first embodiment, the capacitance or inductance value of the resonance frequency adjusting element 8 provided on the circuit board 5 without changing the size or shape of the radiation electrode 3, or the ground It is possible to obtain the effect that the resonance frequency of the antenna structure 1 can be adjusted to the set resonance frequency only by adjusting the electrode area of the capacitor loading electrode 7 and the length and shape of the slit 13 in a variable manner.

In addition, since the electrode 7 for loading capacitance between the grounds is formed on the substrate surface portion of the circuit board 5 facing the radiation electrode 3, the increase in size of the dielectric substrate 2 can be suppressed. And you can get the effect. That is, for example, as shown in the schematic cross-sectional view of FIG. 6b, an electrode 14 for forming a capacitance between the radiation electrode 3 and the ground electrode 6 is formed on the end surface of the dielectric substrate 2. In this case, for example, the left side force of FIG. 6b is a view of the end face configuration of the dielectric substrate 2, and the electrode 14 is formed on the end surface of the dielectric substrate 2 in addition to the feeding electrode 4, as shown in FIG. 6c. It will be. For this reason, the dielectric substrate 2 must be enlarged, and the antenna structure 1 is enlarged. In addition, since the electrode 14 and the radiation electrode 3 are not arranged to face each other, the capacitance between the electrode 14 and the radiation electrode 3 is small. For this reason, when the capacitance between the electrode 14 and the radiation electrode 3 is increased, for example, the electrode 14 is formed to extend toward the radiation electrode 3 and the gap (gap) between the electrode 14 and the radiation electrode 3 is reduced. It is conceivable to increase the capacitance between 14 and the radiation electrode 3. However, as the distance between the electrode 14 and the radiation electrode 3 becomes narrower, the variation in the capacity variation between the electrode 14 and the radiation electrode 3 due to the variation in the distance increases, which is not preferable. Therefore, if the electrode area of the electrode 14 is increased in order to increase the capacitance between the electrode 14 and the radiation electrode 3, the dielectric substrate 2 must be enlarged, and the antenna structure 1 has a large size. The problem of inviting it occurs.

On the other hand, in the first embodiment, as shown in the schematic cross-sectional view of FIG. 6a, the ground-capacitance capacity loading electrode 7 is the substrate of the circuit board 5 facing the radiation electrode 3. The composition was formed on the surface. For this reason, since the capacitance loading electrode 7 is disposed opposite to the radiation electrode 3, it is easy to obtain a large capacity between the radiation electrode 3. In addition, the electrode 7 for loading capacitance between grounds is formed on the substrate surface of the circuit board 5 and is not provided on the dielectric substrate 2, but the surface of the circuit board on which the electrodes 7 for loading capacitance between the grounds are formed. Part is dielectric This is a powerful dead space that has been used up to now with the substrate 2 mounted. From these facts, in order to increase the capacitance between the grounding capacitance loading electrode 7 and the radiation electrode 3, the dielectric substrate 2 is increased in size (i.e., the antenna Increase in size of structure 1) can be suppressed.

Furthermore, even if the resonance frequency adjusting element 8 is provided as shown in the first embodiment, fluctuations in the antenna gain can be suppressed to a small value. This has been confirmed by experiments of the present inventors. In the experiment, three types of antenna structures 1 (samples α, β, γ) were prepared under the same conditions except for the configuration related to the resonance frequency adjusting element 8. That is, the sample a is not provided with the resonance frequency adjusting element 8. The sample is provided with a capacitor component having a capacity of 6 pF, for example, as the resonant frequency adjusting element 8. In the sample γ, for example, an inductor component having an inductance value of 3.9 nH is provided as the resonance frequency adjusting element 8. For each of these samples α, β, and γ, the linearly polarized antenna gain was determined. The experimental results are shown in Tables 1 to 3. Table 1 relates to Sampnore, Table 2 relates to Sampnore] 3, and Table 3 relates to sample γ.

[0043] [Table 1]

[0044] [Table 2]

[0045] [Table 3]

[0046] Table 1 showing the antenna gain of sample a (which is provided with the resonant frequency adjusting element 8) and samples i8 and y (provided with the resonant frequency adjusting element 8). As shown in the comparison with Table 2 and Table 3 showing the antenna gain, even if the resonant frequency adjustment element 8 is provided, the same antenna gain as when the resonant frequency adjustment element 8 is not provided is obtained. It can be confirmed that

[0047] The second embodiment will be described below. The second embodiment relates to a radio communication device. The wireless communication device of the second embodiment is provided with the antenna structure 1 shown in the first embodiment. There are various configurations of the wireless communication device, and any configuration of the wireless communication device other than the antenna structure 1 may be adopted, and the description thereof is omitted here. In addition, since the configuration of the antenna structure 1 has been described in the first embodiment, redundant description thereof is omitted.

[0048] It should be noted that the present invention is not limited to the forms of the first and second embodiments, but can take various forms. For example, in the antenna structure 1 of each of the first and second embodiments, the slit 13 for causing one part of the ground electrode 6 to function as a part of the radiation electrode 3 is provided. However, for example, if the resonance frequency of the antenna structure 1 can be adjusted to the set resonance frequency without providing the slit 13, the slit 13 may be omitted.

[0049] In addition to the configurations of the first and second embodiments, a schematic cross-sectional view of Fig. 7a is also shown on the bottom surface portion of the dielectric substrate facing the inter-ground capacitance loading electrode 7 of the circuit board 5. Further, as shown in FIG. 7b which is an exploded view thereof, an electrode 7 ′ for loading capacitance between grounds may be provided. The grounding-capacitance loading electrode 7 ′ on the dielectric substrate 2 side is joined to the grounding-capacitance loading electrode 7 on the circuit board 5 side by a conductive joining material such as solder. With this configuration, the following effects can be obtained. That is, the dielectric substrate 2 is mounted on the circuit board 5 with a conductive bonding material such as solder. A part of the conductive bonding material is interposed between the dielectric substrate 2 and the circuit board 5. The amount of the intervening material varies depending on various conditions such as the heating state and the molten state of the conductive bonding material when the dielectric substrate 2 is mounted on the circuit board 5 with the conductive bonding material. For this reason, the distance between the dielectric substrate 2 and the circuit board 5 varies. As a result, the distance between the radiation electrode 3 of the dielectric substrate 2 and the grounded capacitance loading electrode 7 of the circuit board 5 varies. For example, in the case of the configuration shown in FIG. The capacitance between the radiation electrode 3 of the substrate 2 and the ground-capacitance loading electrode 7 of the circuit board 5 also varies. On the other hand, by providing the electrode for loading capacitance between grounds 7 ′ on the bottom surface of the dielectric substrate 2, the distance between the radiation electrode 3 and the electrode for loading capacitance between the grounds 7 ′ is approximately as designed with high accuracy. can do. For this reason, the gap between the dielectric substrate 2 and the circuit board 5 is bonded to the capacitance loading electrode 7 ′ of the circuit board 5 via the conductive bonding material. Even if there is variation, it is possible to suppress the variation in capacitance between the radiation electrode 3 and the electrodes 7 and 7 'for grounding capacitance loading. Thereby, the antenna performance can be further improved.

Furthermore, in each of the first and second embodiments, the dielectric substrate 2 has a rectangular parallelepiped shape, but may have another shape such as a columnar shape or a polygonal column shape. Furthermore, the radiation electrode 3 may have a shape other than the shape shown in FIG. 1, for example, as long as it is a radiation electrode of a capacitive power supply type. Further, in each of the first and second embodiments, the force of the circuit board in which the ground electrode 6 is not formed in the circuit board region in which the inter-ground capacitor loading electrode 7 is formed. For example, the circuit board 5 The electrode 7 for capacitive loading between the grounds is formed on the surface of the electrode, and the electrode 7 for capacitive loading between the grounds is formed. The ground electrode 6 may be formed on the inner layer of the back surface of the part of the circuit board 5 that is V. The dielectric substrate 2 having the radiation electrode 3 is mounted on the ground region. However, the present invention is also applied to a configuration in which the dielectric substrate having the radiation electrode is mounted on the non-ground region. It can be applied.

Industrial applicability

The present invention can easily adjust the resonance frequency of the antenna structure to the set resonance frequency with high accuracy while suppressing an increase in the size of the antenna structure and the badness of the antenna gain. It is effective to apply to structures and wireless communication devices.

Claims

The scope of the claims

[1] A radiation electrode for performing an antenna operation is provided on a base, and the base is mounted on a circuit board. The radiation electrode is provided on the base so as to face the substrate surface of the circuit board with a gap. The antenna structure with the structure

The circuit board is provided with a ground-capacity loading electrode having a capacity between the radiation electrode and the radiation electrode of the base, and the circuit board has a capacitance loading electrode between the ground. A ground electrode is formed through a gap between the electrode for grounding the capacitance and avoiding the formation region, and an element for adjusting the resonance frequency for connecting between the electrode for loading the capacitance between the ground and the ground electrode is provided. The resonance frequency adjusting element has a capacitance or an inductance for adjusting the resonance frequency of the antenna structure to a resonance frequency set in advance.

[2] The base is mounted on the circuit board with a part of the base disposed on the ground electrode, and the radiation electrode extends to the ground electrode through the base part that is placed on the ground electrode. It is configured to be formed and directly bonded to the ground electrode, and the ground electrode has a partial force to which the radiation electrode is bonded. In this case, the slit for causing the ground electrode part to function as a part of the radiation electrode is formed so as to separate the ground electrode part functioning as one part of the radiation electrode from the other ground electrode parts. The antenna structure according to claim 1, wherein:

[3] A wireless communication device provided with the antenna structure according to claim 1 or claim 2.