JPH10173426A - Surface mount antenna and surface mount antenna device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid a problem due to the reduction of a frequency band, and to easily attain miniaturization by forming the other edge of a radiation electrode in a non- contact state with a ground electrode, and connecting the other edge with a control electrode. SOLUTION: In a dielectric substrate 11 constituted of synthetic resin with a relatively high dielectric constant, radiation electrodes 1a and 1b are formed from the upper part to the back right part, control electrodes 4a and 4b are formed from the bottom face to the front left edge face, power feeding electrodes 2a, 2b, and 2c are formed from the lower surface through the back right edge face to the upper surface, and ground electrodes 3a, 3b, and 3c are formed from the lower surface to the front left edge face and the back right edge face. Thus, an electrostatic capacity can be generated between the radiation electrode 1b and the ground electrode 3c, and the electrostatic capacitance can be generated between the power feeding electrodes 2a, 2b, and 2c and the neighborhood of the open edge of the radiation electrode (mainly, the electrode 1b). The edge parts of the electrode 1a are normally obtained as parts being the short- circuit edges of the radiation electrode, and in this case, connected with the control electrodes 4a and 4b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface mount antenna and a surface mount antenna device used for mobile communication equipment and the like.

[0002]

2. Description of the Related Art FIG. 6 shows an example of this type of conventional surface mount antenna. In the figure, reference numeral 11 denotes a dielectric substrate made of dielectric ceramics or a synthetic resin having a relatively high relative dielectric constant. Feed electrodes 2a, 2b, and 2c extend from the bottom surface to the upper surface through the end surface on the front left side. Is formed from the right rear end face to the top face in the figure.
Radiation electrodes indicated by a and 1b are formed. The ground electrode 3 is formed on almost the entire lower surface.

[0003] The above surface mount antenna has a radiation electrode 1.
The resonance frequency is determined by a resonance circuit formed by the capacitance between the vicinity of the open ends of the a and 1b and the ground electrode 3 and the inductance of the radiation electrode, and the power supply electrodes 2a, 2b and 2c and the open ends of the radiation electrode (the (The vicinity of the tip). The inductance of the radiation electrode is determined by the length of the radiation electrode.
Due to the wavelength shortening effect of the first dielectric property, a small dielectric substrate can be used as a whole, and a small surface mount antenna can be obtained.

[0004]

As described above, when a small surface-mounted antenna is obtained by the wavelength shortening effect due to the dielectric property of the dielectric substrate, the overall size is reduced as the relative dielectric constant of the dielectric substrate 11 increases. However, since the Q of the antenna increases as the dielectric material having a higher relative dielectric constant is used, there is a problem that the usable frequency bandwidth is narrowed. That is, there is a trade-off relationship between miniaturization and frequency bandwidth. Conventionally, a dielectric material capable of obtaining an appropriate frequency bandwidth is selected, and a predetermined resonance frequency is obtained when the dielectric material is used as a base. Each electrode pattern was designed so that it could be used.

It is an object of the present invention to provide a surface mount antenna which can avoid a problem caused by narrowing a frequency band by using a material having a high relative permittivity, and which can be easily miniaturized.

[0006]

According to the present invention, a power supply electrode, a ground electrode, and a radiation electrode whose one end generates a capacitance with the power supply electrode are formed on a substrate made of a dielectric or magnetic material. In order to make the resonance frequency of the resonance circuit including the inductance component of the radiation electrode variable, the other end of the radiation electrode is formed so as not to be connected to the ground electrode. The other end is connected to the control electrode. With this structure, for example, by connecting a variable capacitance element and a circuit for applying a control voltage to the variable capacitance element to the control electrode, the capacitance connected to the radiation electrode can be controlled according to the control voltage. Can change the resonance frequency. Therefore, even if the frequency bandwidth is narrowed as a whole is reduced in size, the antenna can be used as an antenna in a predetermined frequency band by adjusting or switching the center frequency of the resonance frequency to a predetermined frequency.

According to the present invention, in order to provide an antenna which can be made compact and has a wide bandwidth, the ground electrode is formed on substantially the entire surface of the base, as described in claim 2.
The mounting substrate according to claim 1, wherein the radiation electrode is formed on a surface facing the surface on which the ground electrode is formed, wherein a surface perpendicular to the ground electrode forming surface of the surface mounting antenna is a mounting surface. Is mounted on the electrode non-formed portion. With this structure, since the ground electrode does not exist on the mounting substrate and the surface mounting antenna in a direction perpendicular to the mounting substrate, energy confinement is reduced, and the Q of the antenna is reduced, thereby widening the frequency bandwidth.

Further, the present invention uses the above-mentioned surface-mounted antenna to make the relationship between the actual resonance frequency and the resonance frequency control signal constant, and to obtain a surface-mounted antenna having no variation in characteristics. As described, the surface-mount antenna according to claim 1 is mounted on a sub-board, and a resonance frequency adjustment circuit including a variable capacitance element connected between the control electrode and the ground electrode is provided on the sub-board. Configure. As a result, a surface-mount antenna including a resonance frequency adjusting circuit for each sub-board is formed.
With the resonance frequency adjustment circuit including the variable capacitance element mounted together with the surface mount antenna on the sub-board, the relationship between the resonance frequency control voltage and the resonance frequency is measured, so that the relationship becomes a constant relationship, for example. If the resonance frequency is adjusted by cutting a part of the radiation electrode of the surface-mount antenna, the variation in the resonance frequency of the surface-mount antenna and the variation in the capacitance value with respect to the applied voltage of the variable capacitance element can be absorbed. As a result, a surface-mounted antenna device having uniform characteristics for each sub-board can be obtained.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A configuration of a surface mount antenna and a surface mount antenna device according to a first embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a perspective view of a surface mount antenna. In the figure, reference numeral 11 denotes a dielectric substrate made of dielectric ceramics or a synthetic resin having a relatively high relative permittivity.
Are formed. Also, the dielectric substrate 11
The control electrodes 4a and 4b are formed from the bottom surface to the left front surface. 2a, 2a from the lower surface in the figure of the dielectric substrate 11 to the upper surface via the right rear end surface.
Power supply electrodes indicated by b and 2c are formed. In addition, ground electrodes 3a, 3b, and 3c are formed on the left end face and the right rear end face from the lower surface of the dielectric substrate 11 in the drawing. With such a structure, a capacitance is generated between the radiation electrode 1b and the ground electrode 3c, and the power supply electrodes 2a,
Capacitance is generated between 2b, 2c and the vicinity of the open end of the radiation electrode (mainly 1b). The end of the electrode 1a is a portion which normally becomes a short-circuit end of the radiation electrode.
a, 4b. A resonance frequency adjustment circuit including a variable capacitance diode DV, a resistor R and a capacitor C is connected to the electrodes 4a and 4b. Here, 4
Although a and 4b are distinguished from each other as control electrodes and 1a and 1b as radiation electrodes, they actually act as a part of the radiation electrodes from 1a to 4b and 4a.

FIG. 2 is an equivalent circuit diagram of the entire surface mount antenna including the resonance frequency adjusting circuit shown in FIG. FIG.
, L1 is mainly the control electrode 4b and the radiation electrode 1a,
The inductance component of the portion 1b, C21 is the feeding electrode 2
A capacitance (coupling capacitance) generated between a, 2b, 2c and the vicinity of the open end of the radiation electrode, and C13 is a capacitance generated between the vicinity of the open end of the radiation electrode and the ground electrode. The resistance R
Is the radiation resistance of the surface mount antenna. In the variable capacitance diode DV, the capacitance between the cathode and the anode changes according to the control voltage applied from the control terminal IN. As a result, the resonance frequency of the resonance circuit including L1, C13, and DV changes. The circuit including the resistor R and the capacitor C is an RF choke circuit that suppresses leakage of a high-frequency signal from the antenna toward the control terminal.

FIG. 3 is a perspective view showing a state in which the surface mount antenna shown in FIG. 1 is mounted on a circuit board. In the figure, reference numeral 12 denotes a dielectric plate, and the ground electrode 1
3, 14 and the like are formed to constitute the circuit board 16 as a whole. On the upper surface of the circuit board 16, in addition to the ground electrode 13, a control electrode connection electrode 18 to which the control electrodes 4 a and 4 b shown in FIG. 1 are connected, a control signal input electrode 17 to which a control signal is input, and FIG. A power supply electrode (hidden in the figure) to which the electrode 2a shown is connected is formed. A variable capacitance diode DV is connected between the control electrode connection electrode 18 and the ground electrode 13, a chip resistor R is connected between the control electrode connection electrode 18 and the control signal input electrode 17,
Further, a chip capacitor C is mounted between the control signal input electrode 17 and the ground electrode 13. Control signal input electrode 1
7 is provided with a through hole, and a control signal is supplied from the back side of the circuit board 16.

Next, the configurations of a surface mount antenna and a surface mount antenna device according to a second embodiment will be described with reference to FIGS.

FIG. 4 is a perspective view of a surface mount antenna. Control electrodes 4a and 4b are formed from the lower surface of the dielectric substrate 11 to the left end surface in the drawing. Further, radiation electrodes 1a, 1b, 1c, and 1d are formed from the upper surface to the upper surface and the lower surface via the right rear end surface. Feed electrodes 2a and 2b are formed from the lower surface of the dielectric substrate 11 to the left end surface in the figure. Further, ground electrodes 3a, 3b and 3c are formed from the lower surface in the figure of the dielectric substrate 11 to the upper surface via the end surface on the front left side. With this structure, the vicinity of the open end of the radiation electrode (mainly 1c, 1d) and the ground electrode 3a,
3b and 3c, and a capacitance is generated between the vicinity of the open end of the radiation electrode and the feeding electrodes 2a and 2b. The electrode 1a is a portion which is normally grounded as a short-circuit end of the radiation electrode, but is connected to the control electrodes 4a and 4b here. A resonance frequency adjusting circuit including a variable capacitance diode DV, a resistor R and a capacitor C is connected to the control electrodes 4a and 4b.

FIG. 5 is a perspective view showing a configuration of a surface-mounted antenna device in which the surface-mounted antenna and the resonance frequency adjusting circuit shown in FIG. 4 are mounted on a sub-board. In the figure, reference numeral 19 denotes a sub-substrate made of an insulator or a dielectric material, and the control electrodes 4a and 4 shown in FIG.
b, the control electrode connection electrode 18 to which the power supply electrodes 2a and 2b and the ground electrodes 3a and 3b are connected, respectively, and the power supply electrode 1
5 and a ground electrode 13 are formed. Sub-substrate 1
The control signal input electrode 17 and the ground electrode 20 are further provided on the upper surface of 9. Further, an electrode extending from the power supply electrode 15, the ground electrode 13, the control signal input electrode 17, and the ground electrode 20 is formed from the end surface of the sub-substrate 19 to a part of the bottom surface. In addition, a dummy electrode to which the electrode 1d shown in FIG. 4 is connected is formed on the sub-substrate 19, and the mounting strength of the surface-mounted antenna 10 on the sub-substrate 19 is increased.

As described above, the surface-mounted antenna 10 in which the ground electrode 3b is formed on substantially the entire surface of one surface of the dielectric substrate, and the radiation electrode is formed on the surface opposite to the surface on which the ground electrode 3b is formed, is connected to the ground electrode. The sub-substrate 19 is mounted on the non-electrode-formed portion, with the surface perpendicular to the surface on which 3b is formed as the mounting surface. With this structure, since the ground electrode does not exist on the mounting substrate and the surface mounting antenna in a direction perpendicular to the mounting substrate, energy confinement is reduced, and the Q of the antenna is reduced, thereby widening the frequency bandwidth.

The equivalent circuit of the surface mount antenna device shown in FIG. 5 is the same as that shown in FIG. Therefore, the resonance frequency of the surface mount antenna is controlled in accordance with the control voltage applied to the control signal input electrode 17, and the antenna can be used as a surface mount antenna device having a built-in resonance frequency adjustment circuit.

Further, the inductance component of the radiation electrode of the surface mount antenna 10 and the capacitance component between the open end thereof and the ground electrode vary, and the capacitance characteristics with respect to the applied voltage of the variable capacitance diode DV also vary. However, in order to make the relationship between the control voltage and the resonance frequency a predetermined characteristic, the resonance frequency when the control voltage is changed at several points is measured, and the relationship between the control voltage and the resonance frequency becomes the predetermined relationship. The resonance frequency characteristics of the surface mount antenna 10 may be adjusted as described above. For example, when the resonance frequency with respect to the control voltage is too low, the resonance frequency is increased by deleting a part (part indicated by A) of the electrode 1c, which is the open end of the radiation electrode, and adjusting the amount of the deletion. Direction can be adjusted.
If the resonance frequency for the control voltage is too high,
The resonance frequency is adjusted in the decreasing direction by deleting the portion near the short-circuited end of the radiation electrode, for example, the portion indicated by B of the electrode 1a.

Although the dielectric substrate is used in each of the embodiments described above, a magnetic material having dielectric properties may be used. In this case, if a material having a high magnetic permeability is used, the impedance of the electrode is increased, so that Q is appropriately reduced, and a wideband characteristic can be easily obtained.

[0020]

According to the first aspect of the present invention, by connecting a variable capacitance element and a circuit for applying a control voltage to the variable capacitance element to the control electrode, the capacitance connected to the radiation electrode can be controlled by the control voltage. And the resonance frequency can be changed. Therefore, even if the frequency bandwidth is narrowed as a whole is reduced in size, the antenna can be used as an antenna in a predetermined frequency band by adjusting or switching the center frequency of the resonance frequency to a predetermined frequency.

According to the second aspect of the present invention, since there is no ground electrode on the mounting substrate and the surface mounting type antenna in a direction perpendicular to the mounting substrate, energy confinement is reduced and the Q of the antenna is reduced. This increases the frequency bandwidth.

According to the third aspect of the present invention, a surface mount antenna including a resonance frequency adjusting circuit is configured. Also, measure the relationship between the resonance frequency control voltage and the resonance frequency,
If the resonance frequency is adjusted by, for example, cutting a part of the radiation electrode of the surface-mounted antenna so that the relationship becomes a constant relationship, the variation in the resonance frequency of the surface-mounted antenna and the Variations in the capacitance value with respect to the applied voltage can be absorbed, and a surface-mounted antenna device having uniform characteristics for each sub-substrate can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view of a surface mount antenna according to a first embodiment.

FIG. 2 is an overall equivalent circuit diagram including a resonance frequency adjustment circuit of the surface mount antenna shown in FIG.

FIG. 3 is a perspective view illustrating a configuration of the surface-mounted antenna device according to the first embodiment.

FIG. 4 is a perspective view illustrating a configuration of a surface mount antenna according to a second embodiment.

FIG. 5 is a perspective view illustrating a configuration of a surface-mounted antenna device according to a second embodiment.

FIG. 6 is a perspective view showing a configuration of a conventional surface mount antenna.

[Explanation of symbols]

 Reference Signs List 1-radiation electrode 2-feed electrode 3-ground electrode 4-control electrode 10-surface mount antenna 11-dielectric substrate 12-dielectric plate 13,14-ground electrode 15-feed electrode 16-circuit board 17-control Signal input electrode 18-Control electrode connection electrode 19-Sub board 20-Ground electrode

Claims (3)

[Claims] 1. A surface-mounted antenna in which a feed electrode, a ground electrode, and a radiation electrode whose one end generates a capacitance between the feed electrode and a feed electrode are formed on a base made of a dielectric material or a magnetic material, respectively. The radiation electrode is formed in a non-connected state with the ground electrode,
A surface-mounted antenna, wherein the other end of the radiation electrode is connected to a control electrode. 2. The surface-mounted antenna according to claim 1, wherein the ground electrode is formed on substantially the entire surface of the base, and the radiation electrode is formed on a surface facing the surface on which the ground electrode is formed. A surface-mounted antenna device characterized by being mounted on a non-electrode-formed portion of a mounting board, with a surface perpendicular to a ground electrode forming surface of the surface-mounted antenna being a mounting surface. 3. A resonance frequency adjusting circuit including a variable capacitance element connected between the control electrode and a ground electrode, wherein the surface-mount antenna according to claim 1 is mounted on a sub-board. A surface-mounted antenna device characterized in that: