JPWO2005069439A1 - Multiband antenna and portable communication device - Google Patents

Abstract

An object of the present invention is to provide a small multiband antenna capable of multiband compatibility. Main element 10 capable of radiating high-frequency signals in a plurality of frequency bands, one or more sub-elements 20 capable of resonating at a different frequency from main element 10, and a base end portion of the sub-element and a ground conductor are electrically connected or disconnected. And a switch mechanism 40 for making a multiband antenna. When the sub-element 20 and the ground conductor are conducted by the switch mechanism 40, the sub-element 20 acts as a parasitic induction element for the main element 10, and the front end portion of the sub-element 20 and the open end portion of the main element 10 Is a high-frequency coupled short-circuited antenna. On the other hand, when the sub-element 20 and the ground conductor are non-conductive, the sub-element 20 acts as a parasitic reflection element for the main element 10.

Description

The present invention, for example, a portable communication device such as a mobile phone radio, PDA (Personal Digital Assistance) that can handle a plurality of media such as sound, images (still images, moving images), data, etc. It relates to a band antenna.
BACKGROUND OF THE INVENTION Advances in portable communication devices represented by cellular phone radios and the like are remarkable. Recently, these communication devices have a tendency toward multimedia including not only simple calls but also data communication and image communication. In response to such a trend, there is a demand for a multiband antenna that is small in size and capable of communication in a plurality of frequency bands (bands), even for antennas of mobile phone radios or mobile communication devices.
As this type of conventional multi-band antenna, for example, an antenna device described in JP-A-11-136025 (conventional example 1) and an antenna device described in JP-A-10-209733 (conventional example 2) The antenna device described in JP-A-11-68456 (conventional example 3), the antenna device described in JP-A-2002-335117 (conventional example 4), and described in JP-A-2003-124730 There is an antenna device (conventional example 5).
The antenna device described in Conventional Example 1 includes a ground electrode formed on the entire surface of one main surface of a rectangular parallelepiped base, one end on the other main surface of the base and an open end on the other main surface. A radiation electrode to be connected), a feeding electrode formed close to the open end of the radiation electrode via the first gap, and formed close to the open end of the radiation electrode via the second gap One or more control electrodes and a switch for connecting / disconnecting between the control electrode and the ground electrode are provided, and this switch is turned on and off to change the overall capacitance. Thus, the resonance frequency of the radiation electrode can be switched and used.
The antenna device described in Conventional Example 2 includes, in addition to the ground electrode, the radiating electrode, and the feeding electrode as in Conventional Example 1, one or more auxiliary radiating electrodes formed integrally with the radiating electrode, A switch for connecting / disconnecting the auxiliary radiation electrode and the ground electrode in a high-frequency manner is provided, and by turning this switch on and off to change the inductance component of the ground portion of the radiation electrode, The resonance frequency can be switched and used.
The antenna device described in the conventional example 3 includes a ground electrode, a radiation electrode, and a feeding electrode as in the conventional example 1 on the surface of a rectangular parallelepiped base, and the frequency switching means ( A semiconductor switch) is provided, and this frequency switching means is operated to change the inductance component or the capacitance component, thereby switching the resonance frequency of the radiation electrode.
In the antenna device described in Conventional Example 4, a rectangular parallelepiped base is mounted on a mounting substrate having a ground conductor portion, and a radiation electrode having one end as an open end and the other end as a ground end is mounted on the surface of the base. An antenna-side control electrode (corresponding to the control electrode of Conventional Example 1) is provided, and the substrate-side control electrode floating from the ground is mounted on the mounting substrate, and the substrate-side control electrode is used as a ground conductor portion. Resonance frequency adjusting means (solder bridge, strip, etc. having at least one of an inductance component and a capacitance component) is provided, and the impedance of the resonance frequency adjusting means is changed to change the resonance frequency of the radiation electrode. Is made variable.
Each of the antenna devices described in Conventional Example 5 has two types of antenna elements (the above-described ones), one end of which is an open end, the other end of the two branches is a ground end, and the other end is a feeding end. Equivalent to the radiation electrode) and two types of switches for making each antenna element and the ground conductor portion of the mounting board conductive / non-conductive, and one of these switches and the other are mutually mutually exclusive By switching on and off, the resonance frequency of the entire apparatus is switched.
In addition to the antenna devices of the respective conventional examples described above, a folded antenna having a plurality of resonance frequencies by bending a plurality of antenna elements as radiation electrodes and adjusting the length and interval of the folded antenna elements. Etc. exist.
Multiband antennas installed in recent mobile communication devices include AMPS (Advanced Mobile Phone System) (824 MHz to 894 MHz), GSM (Global System for Mobile Communications) 900 (880 MHz to 960 MHz), GSM 1800 (1710 MHz to 1810 MHz). DCS (Digital Cellular System) (1710 MHz to 1850 MHz), PCS (Personal Communications System 1900 (1850 MHz to 1990 MHz), UMTS (Universal Mobile Telecommunications System Bands 170 to 20 MHz) (19 MHz to 20 MHz) It can be used in a composite manner has been desired.
Since the antenna devices of Conventional Examples 1 to 4 each include a surface mount antenna as a main component, they are extremely small and convenient when incorporated in a mobile phone radio or a mobile communication device. . However, in such an antenna device, since the resonance frequency is switched by changing the inductance component and capacitance component of the radiation electrode having a fixed size, the above-described number of bands can be easily handled up to about 2 to 4. However, when the number of bands is more than that, there is a problem that adjustment of the resonance frequency becomes very difficult. In addition, a decrease in antenna gain accompanying an increase in the number of bands and a narrowing of the resonance frequency bandwidth are also problematic.
In the antenna device of Conventional Example 5, it is possible to cope with an increase in the number of bands, but there are restrictions such as the need to arrange two types of antenna elements on substantially the same plane, and each antenna element has Since it has a special and complicated shape, a sufficient area for the antenna element has to be secured, and there is a problem that miniaturization is difficult.
In order to solve such a problem, an object of the present invention is to provide a small-sized wideband multiband antenna and communication device that can support multiband.

The multiband antenna provided by the present invention has a main element having an open end and a feed end, and capable of radiating high-frequency signals in a plurality of frequency bands fed to the feed end; One or more sub-elements disposed at a predetermined distance from the open end of the main element and capable of resonating at a frequency different from that of the main element; a grounding conductor disposed at a base end of the sub-element and a predetermined part A switch mechanism for conducting or non-conducting between the base element and the grounding conductor when the switch mechanism is in a first state in which the sub-element is in the main state. It acts as a parasitic induction element for the element and becomes a tip short-circuited antenna in which the tip of the sub-element and the open end of the main element are coupled at high frequency, Write, in which the sub-elements when the second state by the switching mechanism and the proximal end and the ground conductor becomes non-conductive to act as a passive reflection element for the main element.
In this way, the sub-element that can resonate at a frequency different from that of the main element can be switched between the parasitic induction element and the parasitic reflection element, so that the resonance frequency can be increased without increasing the number of elements. Therefore, it is possible to realize a multiband antenna that is small and can handle a wide band.
Specifically, the switch mechanism is inserted and connected between the base end portion of the sub-element and the ground conductor, and the semiconductor switching element that performs a switching operation according to the signal level of a control signal input from the outside is connected to the conduction or It is comprised including as a component for switching non-conduction. By configuring the switch mechanism with the semiconductor switching element in this way, it is possible to easily switch between the first state and the second state.
Preferably, the electrical area of the main element is set to a value of about 3 to about 18 times the sum of the electrical areas of all the sub-elements. Thereby, the electrical area of the multi-band antenna becomes substantially the same as the electrical area of the main element, and the influence on the radiation characteristics due to the provision of the sub-element can be mitigated.
The main element is formed of a conductive thin plate having, for example, an inverted L shape, an inverted F shape, a meander shape, or a plate shape, and the sub element has a predetermined positional relationship with respect to the main element, for example. It is formed with a strip-shaped conductive member formed in the above.
From the viewpoint of enabling a plurality of frequencies to be radiated without contradiction, an impedance adjusting element is further provided with one end connected to the ground conductor and the other end being a free end substantially parallel to the main element. Is preferable.
From the viewpoint of facilitating mounting on a communication device, it is preferable to configure the multiband antenna by including a base body that can be mounted on the communication device. A part of the base body receives the ground conductor, a power supply terminal for connection with a high-frequency transmission / reception circuit for transmitting / receiving a predetermined high-frequency signal, and a control signal for controlling a switch mechanism input from the outside. The main element and the sub-element are attached to the base body while maintaining a predetermined positional relationship with respect to the ground conductor, and the feeding end of the main element is The semiconductor switching element is connected to a power supply terminal, and is configured to be supplied with the control signal input through the control terminal.
In consideration of convenience when using a plurality of frequencies, an impedance matching circuit composed of a combination of an inductive element and a capacitive element is interposed between the feeding end and the feeding terminal. May be. Similarly, when the switch mechanism is a semiconductor switching element, an impedance adjustment circuit is provided between the semiconductor switching element and the control terminal to cut off the control terminal at a high frequency and to conduct the current in a direct current manner. You may comprise so that.
As described above, in the case where a base is provided, an element mounting base made of a dielectric having a pair of main surface portions, a pair of side end portions and a pair of short end portions respectively facing the other is fixed to the base body. To be. The main element and the sub-element are attached to the element attachment base along the shape thereof.
In this case, the main element and the sub-element are each formed on one main surface portion of the element mounting base, and the main surface portion is on the same plane as the surface portion of the ground conductor. . Alternatively, each of the main element and the sub-element extends in a direction substantially perpendicular to the ground conductor along one side end of the element mounting base, and further passes through one main surface of the element mounting base. The other side end portion is formed, and the open end portion of the main element and the tip end portion of the sub element are opposed to each other at a predetermined interval at the side end portion. Alternatively, the main element and the sub-element each extend in a direction substantially perpendicular to the ground conductor along one side end portion of the element mounting base, and further on the one main surface portion of the element mounting base. The main conductor is bent in a substantially horizontal direction with respect to the ground conductor so that the open end of the main element and the tip of the sub-element face each other at a predetermined interval on the main surface.
In the multiband antenna of the present invention, each of the main element and the sub-element is one, the wavelength of the first setting frequency is λ _f1 , the wavelength of the second setting frequency is λ _f2 , and the wavelength of the third setting frequency is When λ _f3 , the wavelength of the fourth set frequency is λ _f4 , and the wavelength of the fifth set frequency is λ _f5 , the element length of the main element is approximately λ _f2 / 4 and approximately 3λ _f5 / 4, The element length of the sub-element is approximately nλ _f3 / 2, and the element length of the short-circuited tip antenna in the first state is approximately λ _f1 / 2 and approximately λ _f4 .
The first use frequency band and the second use frequency band are substantially 824 MHz to 894 MHz or 880 MHz to 960 MHz, and the third use frequency band, the fourth use frequency band, and the fifth use frequency band. Are substantially 1710 MHz to 1880 MHz, 1850 MHz to 1990 MHz, and 1920 MHz to 2170 MHz.
In general, it is practically important to design the element length so that the resonance frequency of the multiband antenna falls within the frequency band used, so the element length of the main element is used, for example, When the wavelength of the set frequency set in the frequency band is λ, it is approximately (2n + 1) λ / 4 (where n is 0, 1, 2,...) Or approximately nλ / 2 (where n is 1, 2). ,..., The element length of the sub-element is approximately nλ / 2 (where n is 1, 2,...), The total element length when the main element and the sub-element operate as a short-circuited antenna. Is designed to be approximately nλ / 2 (where n is 1, 2,...). This relationship is the same when there are a plurality of sub-elements for one main element.
A communication device according to the present invention is a portable communication device that is configured to house the above-described multiband antenna in a housing and is configured to perform switching of a used frequency band by switching of the signal level of the control signal. is there.
According to the present invention, since it is possible to provide portable communication devices such as mobile phone radios equipped with antennas that are highly sensitive, small, and capable of multiband, the applications of these devices can be greatly expanded. .

FIG. 1 is a configuration diagram of a multiband antenna according to the present invention.
FIG. 2A is a diagram for explaining the principle when operating as a short-circuited tip antenna in the first state by cooperation of the main element and the sub-element, and FIG. 2B is a diagram showing no sub-antenna in the second state. It is principle explanatory drawing when it operate | moves as a feeding reflective element.
FIG. 3 is a VSWR-frequency characteristic diagram of the multiband antenna shown in FIG.
4A to 4C are diagrams showing variations in the shape of each element.
FIG. 5A shows a radiation pattern of the coplanar structure, and FIG. 5B shows a radiation pattern of the overlay structure.
FIG. 6 is an explanatory diagram of a mounting state of a multiband antenna having a planar coplanar structure.
FIG. 7 is an explanatory diagram of a mounting state of a multiband antenna having a three-dimensional coplanar structure.
FIG. 8 is an explanatory diagram of a mounting state of a multiband antenna having a planar overlay structure.
FIG. 9 is an explanatory diagram of a mounting state of a multiband antenna having a three-dimensional overlay structure.
FIGS. 10A to 10C are explanatory diagrams for illustrating a state in which the multiband antenna is mounted on the mobile radio telephone.
FIG. 11 is a configuration diagram of a multiband antenna provided with a plurality of sub-elements.
FIG. 12 is a VSWR-frequency characteristic diagram of the multiband antenna of FIG.
FIG. 13A is a diagram showing a state where a capacitive element is inserted between the switch mechanism and the ground conductor, and FIG. 13B is a diagram showing a state where an inductive element is inserted. .
FIG. 14 is a VSWR-frequency characteristic diagram in the case of FIG.
FIG. 15A is a front view of a base for a mobile phone radio, and FIG. 15B is a side view thereof.
FIG. 16 is a configuration diagram of a multiband antenna according to an embodiment of the present invention.
FIG. 17A is a chart showing the relationship between the set band, the set frequency, and the element length, and FIG. 17B is a chart showing the relationship between the voltage value of the control signal and the set band.
18A shows VSWR characteristics in AMPS and GSM900, and FIG. 18B shows VSWR characteristics in GSM1800, DC, PCS1900, and UMTS.
19A shows gain characteristics in AMPS and GSM900, and FIG. 19B shows gain characteristics in GSM1800, DCS, PCS1900, and UMTS.
FIG. 20 is a relationship diagram between the ground conductor spacing and the antenna gain in the case of AMPS and GSM1800.

A basic configuration example of the multiband antenna of the present invention will be described with reference to FIG.
As shown in FIG. 1, the multiband antenna of the present invention includes a set of a main element 10 and a sub-element 20. The main element 10 is made of, for example, a conductive thin plate formed in an inverted L shape, and the electric area thereof is formed so as to substantially cover the entire electric area of the multiband antenna. .
Of the both ends of the main element 10, one end is an open end 11 and the other end is a power supply end 12. The power supply end 12 is provided with a power supply terminal 30 to which a high-frequency transmission / reception circuit (not shown) is connected. At the time of transmission, a high-frequency signal having a predetermined power value is supplied from the high-frequency transmission / reception circuit to the power supply terminal 30 so that the multiband antenna can operate as a transmission antenna.
The sub-element 20 is made of, for example, a bar-shaped or strip-shaped conductive member so that the electrical area is sufficiently smaller than the electrical area of the main element 10. The substantially central portion of the conductive member is formed in a meander shape, for example. The distal end portion 21 of the sub-element 20 is disposed away from the open end portion 11 of the main element 10 by a distance d1.
The substantially center portion of the sub-element 20 is substantially opposed to the portion of the main element 10 near the power feeding end portion with a distance d2.
In the following description, the tip portion 21 of the sub-element 20 includes not only the most advanced cross-sectional portion as shown in FIG. To do). The interval d1 may be designed in a fixed manner, but may be arbitrarily adjusted after the antenna is manufactured. In the latter case, for example, one or both of the open end 11 of the main element 10 and the tip 21 of the sub-element 20 are displaced, or the length near the tip 21 of the sub-element 20 is cut. Realize it. The same applies to the interval d2.
A switch mechanism 40 is provided at the base end portion 22 of the sub-element 20.
The switch mechanism 40 switches conduction / non-conduction between the ground conductor 50 arranged at a predetermined portion and the base end portion 22 of the sub-element 20 according to a control signal input to the control terminal 41. In addition to a switch that mechanically conducts (on) / non-conduct (off) between the input and output, the switch mechanism 40 substantially conducts (on) / non-conducts between the input and output according to the signal level of the control signal. A semiconductor switching element that is rendered conductive (off) can be used.
As a semiconductor switching element, for example, a general-purpose Schottky diode can be used, but a PIN diode is used when isolation is important, an FET switch or an IC switch when low current operation is important, and a strong electric field / low distortion is used. When importance is attached, a MEMS switch (Micro Electro Mechanical Systems: a combination of a fine electric circuit and a mechanical structure) can be used. The control signal is a voltage signal for band selection of the communication device of the present invention input from an interface device (not shown) through the control terminal 41. For example, a voltage signal of 0 to 3V can be used.
A state where the base end portion 22 and the ground conductor 50 are electrically connected by the switch mechanism 40 is referred to as a “first state”, and a state where both are not conductive is referred to as a “second state”.
In the first state, since the base end portion 22 of the sub-element 20 is grounded, the sub-element 20 acts as a parasitic induction element for the main element 10, and the sub-element 20 and the main element 10 are coupled at high frequency. It operates as a short-circuited (loop) antenna. That is, in this example, as shown in FIG. 2A, the resonance of the sub-element 20 is induced by the main element 10, and the entire main element 10 and the entire sub-element 20 are inductively coupled (magnetic field coupling). At the same time, it operates as one loop antenna in which the open end 11 of the main element 10 and the tip 21 of the sub-element 20 are capacitively coupled (electric field coupling). Thus, in the first state, the main element 10 and the sub-element 20 operate so as to take two types of coupled states, and thus can have a plurality of resonance frequencies.
On the other hand, in the second state, since the base end portion 22 of the sub-element 20 is opened, the sub-element 20 does not have an electrical influence on the main element 10 as shown in FIG. Acts as a very small parasitic reflection element.
<Size and arrangement of each element>
Here, the size of the main element 10 and the sub-element 20 (element length, electrical area, etc.) and arrangement (intervals d1, d2, the interval between the horizontal portion of the main element 10 and the ground conductor (inter-ground conductor interval), etc.) A preferred example will be described.
Regarding the element length, it is practically important to design so that the resonance frequencies of the multiband antenna are all substantially within the use frequency band.
Therefore, the element length of the main element 10 having the configuration illustrated in FIG. 1 is set such that, for example, the wavelength of the second set frequency f2 arbitrarily set in the use frequency band is λ _f2 and the wavelength of the fifth set frequency is λ _f5. , Approximately (2n + 1) λ _{f2, f5} / 4 (where n is 0, 1, 2,...) Is preferably designed. The value of “n” varies depending on the number of sub-elements 20 and the number of set frequencies. For example, when the number of sub-elements 20 is one as shown in FIG. 1 and the set frequency is the first to fifth set frequencies, λ _f2 / 4 at the second set frequency f2 and approximately 3λ at the fifth set frequency. _f5 / 4.
The element length of the sub-element 20 is, for example, approximately nλ _f3 / 2 (where n is 0, 1, 2,...), Where λ _f3 is the wavelength of the third set frequency f3 set within the use frequency band. It is preferable to design so that
Further, in the first state, that is, when the main element 10 and the sub-element 20 operate as the short-circuited tip antenna, the total element length (including the interval d1) is, for example, a first frequency set within the use frequency band. When the wavelength of the set frequency f1 is λ _f1 , and the wavelength of the fourth set frequency f4 is λ _f4 , it is designed to be approximately nλ _{f1, f4} / 2 (where n is 1, 2,...). preferable. That is, it is approximately λ / 2 at the first set frequency and approximately λ _{f4 at} the fourth set frequency.
In this case, f ₁ and f ₄ are resonance frequencies due to capacitive coupling between the main element 10 and the sub-element 20, f ₃ is a resonance frequency due to inductive coupling between the two elements described above, and f ₂ and f ₅ are sub-frequency resonances. This is the resonance frequency of the main element 10 when the element 20 acts as a parasitic reflection element.
“Abbreviated” means that some fine adjustment is made in order to improve the VSWR of the antenna. For example, the resonance frequency of the multiband antenna in the first state changes so as to increase as the interval d1 increases and decrease as the interval d1 decreases. Further, the bandwidth of the resonance frequency due to the inductive coupling between the main element 10 and the sub-element 20 in the first state is wider as the distance d2 is narrower and narrower as it is wider. Furthermore, the antenna impedance also changes depending on whether the base end portion 22 of the sub-element 20 is open or short-circuited. Therefore, while measuring the value of VSWR at the time of power feeding (at the time of antenna resonance), adjusting the length of each element or the arrangement (intervals d1, d2) so that the value is optimum, the above-described element lengths are also reduced. In fact, it will change somewhat.
The ratio of the electrical area of the main element 10 and the sub-element 20 is also designed so that the value of VSWR at the time of antenna resonance is optimal. For this purpose, it is necessary to form the sub-element 20 so that the frequency band usable in the entire multiband antenna is not narrowed and the radiation characteristics are not greatly affected. According to the experiments by the inventors, the area ratio of the sub-element 20 with respect to the main element 10 is substantially within the range of about 3: 1 to about 18: 1, so that radiation characteristics and the like that do not hinder practical use can be obtained. It has been confirmed that Within this range, the electrical area of the multiband antenna is approximately the electrical area of the main element 10, so even if the number of sub-elements 20 is increased to a plurality, the narrow band of the resonance frequency is minimized. It can be done. In addition, since the electrical area of the sub-element 20 is small, the overall size of the multiband antenna can be reduced.
The interval d1 determines the strength of inductive coupling, and the interval d2 determines the strength of capacitive coupling. Therefore, it is necessary to make a decision while looking at the VSWR in the band including the frequency to be used. As the distance between the ground conductors is reduced, the radiation characteristics are lowered, and the antenna gain is lowered. Therefore, it is necessary to determine an interval at which there is no problem in terms of performance.
<VSWR characteristics>
FIG. 3 shows the relationship between the VSWR and the set frequency by the multiband antenna having the configuration illustrated in FIG. As shown in FIG. 3, the multiband antenna of this example can have at least five resonance frequencies according to the element length, and the resonance frequency can be adjusted only by inputting a control signal to the switch mechanism 40. Can be done. As described above, according to the present invention, it is possible to obtain a multiband antenna that can easily adjust the resonance frequency with a small size and a wide band corresponding to the multiband.
<Other examples of element shape>
The shape of each of the main element 10 and the sub-element 20 is not necessarily limited to the example shown in FIG. 1, and various shapes can be used depending on the application.
For example, in the example of FIG. 4A, the sub-element 20 is the same as that shown in FIG. 1, but a main element 10a made of an inverted F-shaped conductive thin plate is adopted, and among the main elements 10a, One of the two ends other than the open end is a feeding end, and the other is a grounding end. When the main element 10a has such a shape, the size of the multiband antenna can be made smaller than that shown in FIG. 1 while ensuring the electrical area and characteristics.
In the example of FIG. 4B, the sub-element 20 is the same as that shown in FIG. 1, but the main element 10b made of meandering conductive thin plate is adopted. When the meander shape is used, the element length can be shortened, which contributes to a reduction in the size of the multiband antenna.
In the example of FIG. 4C, a sub-element 20a that has not been subjected to meander molding and a main element 10c made of a rectangular conductive thin plate are employed. By adopting such a shape, the cost can be reduced because the molding cost is not required, and a multiband antenna with high radiation efficiency can be easily realized.
<Antenna mounting structure and radiation pattern>
The multiband antenna of the present invention can adopt either a coplanar structure or an overlay structure depending on the application.
FIG. 5A shows a basic antenna mounting structure when a coplanar structure is employed, and a radiation pattern of a high-frequency signal at that time. In the coplanar structure, since the multiband antenna 1 is provided substantially parallel to the ground conductor E, the radiation pattern is the first coverage pattern (FRONT) P11 in the front direction of the multiband antenna 1 and the second coverage in the back direction. The area pattern (BACK) P12 is substantially symmetric.
On the other hand, in the overlay structure, as shown in FIG. 5B, the multiband antenna 1 is laminated on the ground conductor E. Therefore, the radiation pattern is blocked by the ground conductor E. The second coverage pattern P12 is reduced relative to the first coverage pattern P11.
<Multiband antenna mounting example>
Next, a mounting example of the multiband antenna of the present invention will be specifically described.
The multiband antenna of the present invention includes a planar configuration and a three-dimensional configuration for both the coplanar structure / overlay structure. Specific examples of these will be described below.
[Planar coplanar structure]
For example, as shown in FIG. 6, the multi-band antenna having a planar coplanar structure includes a ground conductor E1 formed by covering the entire surface of the dielectric substrate K1 or one main surface of the front and back surfaces with a conductor, for example, FR-4. The element mounting base D1 made of a dielectric is joined on the same plane. It is also possible to cover only a part of one dielectric base with a conductor to be the ground conductor E1, and the rest to be the element mounting base D1.
An inverted L-shaped main element 101 and a meander-molded sub-element 201 are fixed to the main surface of the element mounting base D1 by vapor deposition or adhesion, respectively. The open end portion of the main element 101 and the tip end portion of the sub-element 201 are opposed to each other with a predetermined distance (d1). Of the main surface of the element mounting base D1, a power supply terminal 301 connected to the power supply end is provided in the vicinity of the power supply end of the main element 101. Further, in the vicinity of the base end of the sub-element 202, A switch mechanism 401 and a control terminal 411 are provided. The switch mechanism 401 is interposed between conductive members that connect the base end portion of the sub-element 202 and the ground conductor E1, and when the switch mechanism 401 is on, the sub-element 201 and the ground conductor E1 are electrically connected. It has become. A connector on the high frequency transmission / reception circuit side (not shown) is coupled to the power supply terminal 301, and a connector on the control device side of the communication device (not shown) is coupled to the control terminal 411, thereby enabling operation as a multiband antenna. .
[Three-dimensional coplanar structure]
For example, as shown in FIG. 7, the multi-band antenna having a three-dimensional coplanar structure has a ground conductor E2 formed by covering a part of a dielectric base K2 with a conductor and a conductor formed of the dielectric base K2. An element mounting base D2 made of, for example, FR-4 dielectric is laminated on the part that is not. The element mounting base D2 is, for example, formed into a rectangular parallelepiped shape having a pair of front and back main surface portions, a pair of side end portions, and a pair of end portions having a large area. In addition, the shape of this element attachment base | substrate D2 can be arbitrarily changed according to the housing | casing shape of the communication apparatus in which a multiband antenna is mounted.
Each of the inverted L-shaped main element 102 and the meander-shaped sub-element 202 extends from the side end adjacent to the ground conductor E2 of the element mounting base D2 to the other side end via the front main surface portion. Exist. The open end portion of the main element 102 and the tip end portion of the sub-element 202 are opposed to each other with a predetermined distance (d1). The base end portion of the sub element 202 is electrically connected to the ground conductor E <b> 2 via the switch mechanism 402 and the mounting bracket 422. A power supply terminal 302 that is electrically connected to a power supply end of the main element 102 and a control terminal 412 for supplying a control signal to the switch mechanism 402 are provided at predetermined portions of the dielectric substrate K2. A connector on the high frequency transmission / reception circuit side (not shown) is coupled to the power supply terminal 302, and a connector on the control device side of the communication device (not shown) is coupled to the control terminal 412, thereby enabling operation as a multiband antenna. .
[Plane overlay structure]
As a multiband antenna having a planar overlay structure, for example, a known plate-like inverted F antenna (PIFA) as shown in FIG. 8 can be used as the main element 103.
That is, for example, the main element 103 formed in an inverted F shape is disposed at a predetermined portion of the ground conductor E3 formed by covering the entire dielectric substrate K3, and the power supply end portion thereof is perpendicular to the power supply terminal 303. Provide to extend. Further, the front end of the meander-like sub-element 203 is arranged with a predetermined distance from the open end of the inverted F-type main element 103, and its proximal end is connected to the ground conductor E3 via the switch mechanism 403. It is provided so as to extend in the vertical direction. The other ground end 103a of the inverted F-type main element 103 is joined to the ground conductor E3. The control terminal 413 is provided at a predetermined portion of the ground conductor E3.
A connector on the high frequency transmission / reception circuit side of a communication device (not shown) is coupled to the power supply terminal 303, and a connector on the control device side (not shown) is coupled to the control terminal 413, thereby enabling operation as a multiband antenna. .
[Three-dimensional overlay structure]
For example, as shown in FIG. 9, a multi-band antenna having a three-dimensional overlay structure is formed of, for example, an FR-4 dielectric on a ground conductor E4 configured by covering the entire main surface of the dielectric substrate K4 with a conductor. The element mounting base D4 is formed by stacking. The element mounting base D4 is formed, for example, in a rectangular parallelepiped shape having a pair of front and back main surface portions, a pair of side end portions, and a pair of end portions having a large area.
Each of the inverted L-shaped main element 104 and the meander-shaped sub-element 204 extends from the side end portion adjacent to the ground conductor E4 of the element mounting base D4 to the main surface portion on the front side. The open end portion of the main element 104 and the tip end portion of the sub-element 204 are opposed to each other with a predetermined distance (d1). The base end portion of the sub-element 204 is electrically connected to the ground conductor E4 via the switch mechanism 404 and the mounting bracket 424. A power supply terminal 304 that is electrically connected to a power supply end of the main element 104 and a control terminal 414 for supplying a control signal to the switch mechanism 404 are provided at predetermined portions of the dielectric substrate K4.
A connector on the high frequency transmission / reception circuit side (not shown) is coupled to the power supply terminal 304, and a connector on the control device side of the communication device (not shown) is coupled to the control terminal 414, thereby enabling operation as a multiband antenna. .
As the size of the ground conductors E1 to E4 and the distances and distances between the ground conductors E1 to E4 and the main elements 101 to 104 are increased, the antenna impedance is lowered and the radiation efficiency is lowered, and the bandwidth is also narrowed. Tend to be. Therefore, in this example, the area of the ground conductors E1 to E4 and the distances and intervals of the ground conductors E1 to E4 with respect to the main elements 101 to 104 are set so that sufficient performance is ensured in the frequency band to be used.
<Communication equipment with multiband antenna>
The multiband antenna of the present invention is used by being mounted on a mobile communication device such as a mobile phone radio or a PDA that can handle a plurality of media such as sound, images (still images, moving images), and data. Suitable for For example, when it is mounted on a mobile phone radio, it can be used with a multiband antenna attached, as shown by hatching in FIG. FIG. 10A shows an example in which a ground conductor is attached to the back side of the operation unit of the mobile phone radio and a multiband antenna 1a is attached to the end of the operation unit. FIG. 10B shows an example in which a ground conductor is attached to the back side of the display unit of the mobile phone radio and a multiband antenna 1b is attached to the tip of the display unit. FIG. 10C shows an example in which a ground conductor is attached to the back side of the operation unit and a multiband antenna 1c is attached to the back end. It may be configured to be housed (built in) inside the housing.
The communication device is provided with a control device that generates a control signal having a required signal level as described above in order to switch the used frequency band.
Note that the multiband antenna can be used by appropriately replacing depending on the required performance. In this case, a mechanism for detachably mounting the multiband antenna is provided at each of the above-described portions of the communication device, and a mounting mechanism that fits the above mechanism is provided on one or both sides of the main element and the sub-element. To form.
<Another embodiment of multiband antenna>
Next, another embodiment of the multiband antenna of the present invention will be described.
FIG. 11 is a configuration diagram when a plurality of sub-elements are used as a modification of the multiband antenna shown in FIG. The multiband antenna having such a configuration includes one main element (for example, an inverted L-shaped element) 10 and two sub-elements 20a and 20b each having a front end facing the open end of the main element 10 at a distance d1. It is configured with. As described above, the sum of the electrical areas of the sub-elements 20a and 20b is an area that can be substantially ignored with respect to the electrical area of the main element 10.
A power supply terminal 30 is provided at the power supply end of the main element 10. Between the base end portion of the sub-element 20a and the ground conductor 50, there is provided a switch mechanism 40a that is switched on / off by a control signal supplied to the control terminal 41a. Similarly, the sub-element 20b is provided between the base end portion and the ground conductor 50 with a switch mechanism 40b that is switched on / off by a control signal supplied to the control terminal 41b.
In the multiband antenna having the configuration shown in FIG. 11, the relationship between the element lengths is almost the same as that shown in FIG.
That is, only (2n + 1) λ _{f3, f8} / 4 (where n = 0, 1, 2,...) With the main element 10 alone, and when the main element 10 and the sub-element 20a operate as a short-circuited tip antenna. About nλ _{f1, f5} / 2 (where n = 1, 2,...), When operating as a short-circuited antenna with the main element 10 and the sub-element 20b, about nλ _{f2, f7} / 2 (where n = 1, 2,..., Approximately nλ _f4 / 2 (provided that n = 1, 2,...) Only by the sub-element 20a, and approximately nλ _f6 / 2 (provided that n = 1, n). 2, ...).
f ₁ , f ₂ , f ₅ , f ₇ are resonant frequencies due to capacitive coupling, f ₄ , f ₆ are resonant frequencies due to inductive coupling, and f ₃ , f ₈ are sub-elements 20 a, 20 b acting as parasitic reflection elements. Is the set frequency.
The VSWR-set frequency characteristics of the multiband antenna configured as described above are obtained by adjusting the signal level of the control signal input to the control terminals 41a and 41b, thereby adjusting the eight resonance frequencies f1 to f8 as shown in FIG. It can have more multi-bunts.
[Various adjustment circuits]
For example, in the multiband antenna having the configuration shown in FIG. 1, a resonant element can be changed by inserting a capacitive element or an inductive element between the switch mechanism 40 and the ground conductor 50. For example, FIG. 13A shows an example in which a capacitive element 61 is inserted, and FIG. 13B shows an example in which an inductive element is inserted. Since the element length of the sub-element 20 is apparently shortened in the case of FIG. 13A and apparently extended in the case of FIG. 13B, the resonance frequency of the antenna changes as shown in FIG. In this way, the resonance frequency can be finely adjusted.
In addition to this, an impedance matching circuit composed of a parallel circuit or a series-parallel circuit of an inductive element and a capacitive element is inserted between the power feeding end of the main element 10 and the power feeding terminal 30, or a control terminal. Instead of directly supplying a control signal from 41 to the switch mechanism 40, a control signal is supplied to the switch mechanism 40 via an inductive element that intervenes a resistor for current adjustment or has a high impedance with respect to the operating frequency band. May be supplied.
Further, for impedance adjustment, an adjustment element may be provided which is substantially parallel to the main element 10 at a certain interval and one end of which is joined substantially perpendicularly to the ground conductor 50.

Next, an embodiment of the multiband antenna of the present invention will be described.
Here, an example of a multiband antenna having a planar coplanar structure suitable for mounting on a mobile phone radio is shown. FIGS. 15A and 15B are views for explaining the structure and size of a base for mounting the multiband antenna. FIG. 15A is a plan view and FIG. 15B is a side view.
In this base, among the FR-4 dielectric bases having a diameter of 96 mm, a width of 40 mm, and a thickness of 1.0 mm, the length of 80 mm is used as the ground conductor E0, and the remaining length of 16 mm is used as the element mounting base D0.
As shown in FIG. 16, the element mounting base D0 has an inverted L-type main element 10 with an element length of length A + length B, an (electrical) element length of length C, and a meander size of length D. In addition to the meander-type sub-element 20, a PIN diode PD 1 is interposed between the base end of the sub-element 20 and the ground conductor 50.
Further, an adjustment element 80 having a length E and an impedance matching circuit are provided. The adjustment element 80 and the impedance matching circuit are provided because impedance matching of the antenna is required depending on the set frequency and the number of used frequency bands. As the impedance matching circuit, for example, as shown in FIG. 16, a series-parallel circuit including coils L2 and L3 and a capacitor C1 can be employed. The coil L3 is interposed between the power supply terminal 30 and the power supply end. The adjustment element 80 is substantially parallel to the main element 10 with a distance d3, and one end is provided substantially perpendicular to the ground conductor E0.
As described above, the distance between the open end of the main element 10 and the tip of the sub-element 20 is d1, and the distance between the sub-element 20 and the main element 10 is d2.
A control signal having a signal level corresponding to the purpose of use is input to the PIN diode PD1 from the control terminal 43 via the coil L1 and the resistor R1. The resistor R1 is for current adjustment, and the coil L1 is ignored so that the control terminal 43 has a high impedance with respect to the used frequency band, that is, with respect to the used frequency band, as described above. It is for making it possible. In this way, the influence of the presence of the control terminal 43 on the characteristics is suppressed. The voltage of the control signal supplied to the PIN diode PD1 is 0 to 3V, the current consumption is 3.0mA, and the frequency band (band) is switched by changing the voltage from 0V (off) to 3V (on). be able to.
Bands that can be set in this embodiment are AMPS (824 MHz to 894 MHz), GSM900 (880 MHz to 960 MHz), GSM1800 (1710 MHz to 1880 MHz), DCS (1710 MHz to 1850 MHz), PCS1900 (1850 MHz to 1990 MHz), and UMTS (1920 MHz to 2170 MHz), and the switching operation is performed with the set band, the set frequency, the element length shown in FIG. 17A, and the control signal having the value shown in FIG.
According to these charts, for example, the element length of the main element 10 is set to approximately λ / 4 of the set frequency in the GSM900 band and approximately 3λ / 4 of the set frequency in the UMTS band. Are set to approximately λ / 2 of the set frequency in the GSM1800 and DCS band.
In the multiband antenna configured as described above, the VSWR characteristics when the control signal is switched between 0 [V] and 3 [V] are as shown in FIG. 18A shows VSWR characteristics in AMPS and GSM900, and FIG. 18B shows VSWR characteristics in GSM1800, DCS, PCS1900, and UMTS.
The gain characteristics when the control signal is switched between 0 [V] and 3 [V] are as shown in FIG. 19A shows gain characteristics in AMPS and GSM900, and FIG. 19B shows gain characteristics in GSM1800, DCS, PCS1900, and UMTS.
Each of these values is sufficiently usable even when each band is selected. Considering these characteristics, the constants shown in FIG. 16 are set as follows, for example.
d1: 0.8 mm, d2: 28 mm, d3: 1.0 mm, P1: 1.0 mm, A: 38.0 mm, B: 16.0 mm, C: 14.0 mm, D: 6.0 mm, E: 6. 0 mm, L1: 100 nH, L2: 10 nH, L3: 6.8 nH, C1: 0.75 pF, R1: 1.0 kΩ.
Further, the relationship between the distance between the horizontal portion of the main element 10 and the ground conductor (distance to ground conductor) and the antenna gain is as shown in FIG. FIG. 20 is an example for AMPS and GSM1800. From this characteristic diagram, in this example, the interval was set to 12 mm, which is a value that is not problematic in terms of performance.
As described above, according to the embodiment of the present invention and the example that embodies it, the sub-element capable of resonating at a frequency different from that of the main element can be switched between the parasitic induction element and the parasitic reflection element. Without increasing the number of elements, it is possible to have a larger number of resonance frequencies, and it is possible to easily realize a multiband antenna that is small and can support a wide band.
It should be noted that the numerical values and arrangements representing the shapes and sizes of the elements shown in the above-described embodiments and examples are merely examples, and it is needless to say that the scope of the present invention is not limited thereto.

Claims (15)

A main element having an open end and a feed end and capable of radiating high-frequency signals in a plurality of frequency bands fed to the feed end;
One or more sub-elements, each of which has a tip portion spaced apart from the open end of the main element by a predetermined distance and capable of resonating at a different frequency from the main element;
A switch mechanism for electrically connecting or disconnecting the base end portion of the sub-element and the ground conductor disposed at a predetermined position;
When the switch mechanism is in the first state in which the base end and the ground conductor are in conduction, the sub-element acts as a parasitic induction element for the main element, and the sub-element tip and the main On the other hand, the sub-element is connected to the main element in a second state where the open end of the element is a high-frequency coupled short-circuited antenna and the base end and the ground conductor are non-conductive by the switch mechanism. Acts as a feeding reflective element;
Multiband antenna. The switch mechanism is inserted and connected between a base end portion of the sub-element and the ground conductor, and switches a semiconductor switching element that performs a switching operation according to a signal level of a control signal input from the outside to the conduction or non-conduction. Including as a component for switching,
The multiband antenna according to claim 1. The electrical area of the main element is about 3 to about 18 times the sum of the electrical areas of all the sub-elements,
The multiband antenna according to claim 1. The main element is formed of a conductive thin plate having an inverted L shape, an inverted F shape, a meander shape, or a plate shape, and the sub element is formed so as to have a predetermined positional relationship with the main element. Molded with a strip-shaped conductive member,
The multiband antenna according to claim 3. An impedance adjusting element having one end connected to the ground conductor and the other end being a free end substantially parallel to the main element;
The multiband antenna according to claim 1. It has a base that can be attached to communication equipment,
Part of this base is formed with the ground conductor, a power supply terminal for connection with a high frequency transmission / reception circuit that transmits and receives a predetermined high frequency signal, and a control terminal to which the control signal is input,
The main element and the sub element are attached to the base body while maintaining a predetermined positional relationship with the ground conductor,
The power feeding end of the main element is connected to the power feeding terminal,
The semiconductor switching element is configured to be supplied with the control signal input through the control terminal.
The multiband antenna according to claim 2. An impedance matching circuit composed of a combination of an inductive element and a capacitive element is interposed between the feeding end and the feeding terminal.
The multiband antenna according to claim 6. Between the semiconductor switching element and the control terminal, an impedance adjustment circuit for interrupting the control terminal at a high frequency and conducting in a direct current is interposed.
The multiband antenna according to claim 6. An element mounting base made of a dielectric having a pair of main surface portions, a pair of side end portions, and a pair of short end portions facing each other is fixed to the base body,
The main element and the sub-element are attached to the element attachment base along the shape thereof,
The multiband antenna according to claim 6. The main element and the sub-element are each formed on one main surface portion of the element mounting base, and the main surface portion exists on the same plane as the surface portion of the ground conductor.
The multiband antenna according to claim 9. The main element and the sub-element extend in a direction substantially perpendicular to the ground conductor along the negative side end of the element mounting base, and further pass through one main surface of the element mounting base. To the other side end, the open end of the main element and the tip of the sub-element are opposed at a predetermined interval at the side end,
The multiband antenna according to claim 9. The main element and the sub-element each extend in a direction substantially perpendicular to the ground conductor along one side end of the element mounting base, and further, the ground conductor on one main surface of the element mounting base And bent in a substantially horizontal direction, and on the main surface portion, the open end portion of the main element and the tip end portion of the sub-element face each other at a predetermined interval.
The multiband antenna according to claim 9. The main element and the sub-element are each one, the wavelength of the first setting frequency is λ _f1 , the wavelength of the second setting frequency is λ _f2 , the wavelength of the third setting frequency is λ _f3 , and the fourth setting frequency is When the wavelength is λ _f4 and the wavelength of the fifth set frequency is λ _f5 ,
The element length of the main element is approximately λ _f2 / 4 and approximately 3λ _f5 / 4,
The element length of the sub-element is approximately λ _f3 / 2,
The element length of the short-circuited tip antenna in the first state is approximately λ _f1 / 2 and approximately λ _f4 .
The multiband antenna according to claim 1. The first used frequency band and the second used frequency band are substantially 824 MHz to 894 MHz or 880 MHz to 960 MHz, and the third used frequency band, the fourth used frequency band, and the fifth used frequency band are: Substantially 1710 MHz to 1880 MHz, 1850 MHz to 1990 MHz and 1920 MHz to 2170 MHz,
The multiband antenna according to claim 13. The multiband antenna according to any one of claims 1 to 14 is accommodated in a housing,
It is configured to switch the use frequency band by switching the signal level of the control signal.
Portable communication device.

Images