JP2001223519A - Composite antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composite antenna capable of being mounted even on a small portable terminal device and transmitting and receiving a signal of a multifrequency band being two or more optional frequencies by one very small antenna element. SOLUTION: At least one 1st folding part 11 is formed on the antenna element of an electric length L that can resonate with respect to a reference frequency f0 and a frequency 3f0 being three times as high as the reference frequency f0. The folding part 11 is formed so as to be able to resonate in both a 1st frequency f1 being higher than the reference frequency f0 and a 2ns frequency f2 being lower than the frequency 3f0 being three times as high as the reference frequency f0 by adjusting the connection of elements adjacent to each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-band complex antenna capable of transmitting and receiving signals in two or more frequency bands. More specifically, instead of cutting signals in different frequency bands via a trap or the like, a small antenna that can transmit and receive signals in multiple frequency bands different from odd-numbered and even-numbered times with only one antenna element Related to a composite antenna.

[0002]

2. Description of the Related Art In many cases, a linear antenna is used as an antenna used for receiving a signal transmitted by a radio or a television, transmitting and receiving a mobile phone, a radio, and the like. Such a linear antenna has an electrical length of λ / 4.
(Λ is the wavelength of the signal of frequency f ₀ to be transmitted / received) or λ /
It is formed to have a length of 2. In general, the shorter one is easier to handle, so that one of λ / 4 is used, and with this antenna, one of 3λ / 4, 5λ / 4,... Can also be transmitted and received in the same manner, so that 3f ₀ , 5f ₀ ,. Can be transmitted and received in a frequency band that is an odd multiple of However, it is not possible to tune a signal in an even-numbered frequency band or an intermediate frequency band as it is.

Conventionally, for example, AM (1M
Hz) and the FM (about 100 MHz) band.
It is formed to tune to the FM band, and for the AM band,
A method is adopted in which tuning is not performed by an antenna but is tuned in a receiver.

As an antenna for transmitting and receiving signals in different frequency bands, two antenna elements are connected by a trap which is open for a high frequency band, and only one of them is used for a high frequency band. Λ
/ 4 antenna, and for low frequency bands, the length of both elements connected by the trap is λ / 4.
The method used as is used.

On the other hand, as an antenna for transmitting and receiving signals in two or more frequency bands with one antenna element, JP-A-10-13135 disclosed by the present applicant discloses:
By forming the antenna element in a folded shape and adjusting the interaction between adjacent elements, the frequency f
_It operates as λ / 4 for _{0 and} 3λ for 2f ₀
It is disclosed that it can operate as / 4. With such a structure, signals in a frequency band that is an integral multiple of f ₀ or in the vicinity thereof can be transmitted and received.

[0006]

As described above, even when an antenna element has a folded shape and transmits and receives a frequency band at or near an even multiple, two or more arbitrary frequency bands are transmitted and received by one antenna element. There is a problem that you can not.

On the other hand, with the recent development of communication circumstances, for example, the 900 MHz band of cellular telephones and the PHS (Personal
1800MH of Handy Phon System (simple mobile phone)
z-band, GPS (Global Positioning System) 1500MHz band, Bluetooth 2
Information communication is performed in various frequency bands such as the 400 MHz band, and there is a demand for operating these with one antenna.

[0008] The present invention has been made in view of such a situation, and can be equipped with a small portable terminal.
It is an object of the present invention to provide a composite antenna capable of transmitting and receiving signals in two or more arbitrary frequency bands using a very small and single antenna element.

Another object of the present invention is to provide a specific configuration means of the composite antenna.

[0010]

Means for Solving the Problems The present inventors have proposed an arbitrary 2
As a result of intensive studies to transmit and receive signals in the above frequency band with one antenna element, for example, λ /
An antenna element having an electrical length of 4 (f ₀ ) is folded back so that only two adjacent elements interact with each other, and by adjusting the interaction, f ₀ and 3f _{0 are obtained.}
It has been found that the antennas can be tuned in two frequency bands between and can operate as antenna elements having apparently different lengths, and can transmit and receive signals in any two frequency bands. By forming two folded portions and connecting them in series so as to be separated from each other so as not to interact with each other, the interaction can be performed so that signals can be transmitted and received in four frequency bands as a whole. It has been found that it can be adjusted.

In the composite antenna according to the present invention, at least one first folded portion is formed in an antenna element having an electrical length capable of resonating at the fundamental frequency and three times the fundamental frequency, and the first folded portion is formed. By adjusting the coupling between adjacent elements, it is formed so as to be able to resonate in both the first frequency band higher than the fundamental frequency and the second frequency band lower than three times the fundamental frequency. I have.

Here, the folded portion means a conversion portion that returns the antenna element along a main direction of the antenna element (mainly a current flowing direction regardless of a zigzag or spiral shape in the middle).

[0013] With this structure, the capacitive and inductive coupling with elements adjacent to each other by the folding unit, operates as the fundamental frequency f ₀ side of the low frequency band f length of _1, element becomes longer while, for the high frequency band f ₂ of 3f ₀ side, the length of the element is operated to be shorter. As a result, transmission and reception can be performed by resonating in two frequency bands different from f ₀ and 3f ₀ .

In the antenna element, a second folded portion is formed separately so as not to interact with the first folded portion, and each of the first and second folded portions has a frequency higher than the fundamental frequency. Band and a frequency band lower than three times the fundamental frequency so as to resonate, and the first and second folded portions can jointly resonate in at least four frequency bands,
By forming the first and second folded portions,
Signals in four frequency bands can be transmitted and received by one antenna element.

It is possible to transmit and receive the signals of the four frequency bands.
The specific configuration of the composite antenna that can be
The substantial electrical length of the adjacent element part is
1 With respect to the electrical length L when the folded portion is not formed,
L for the lower frequency band on the fundamental frequency side₁, The basics
L for high frequency band three times the frequency_Two(L _Two
<L <L₁), The first folded portion is formed.
And the second folded portion is used to form the adjacent element portion.
The qualitative electrical length is that when the second folded portion is not formed.
In the lower frequency band on the fundamental frequency side with respect to the electrical length M
L_Three, A higher frequency on the three-times frequency side of the fundamental frequency
L for several bands_Four(L_Four<M <L_Three)
A second folded portion is formed, and the first folded portion and the second folded portion are formed.
The electrical length of the connecting part with the folded part is L₀Formed in f₁
= L₁+ L₀+ L_Three, F_Two= L₁+ L₀+ L _Four, F_Three= L_Two+ L₀
+ L_Three, F_Four= L_Two+ L₀+ L_FourSo that the first
And a second folded portion is formed.
You.

Since the dielectric constant of the substrate can be increased by forming the antenna element with a conductive pattern on the ceramic substrate, the coupling between the elements in the folded portion is increased, and adjustment is easy, which is preferable.

Since the antenna element is formed by winding a wire-shaped conductor in a coil shape, the physical length can be shortened while securing a predetermined electrical length. It is preferable because it can be downsized.

[0018]

Next, a composite antenna according to the present invention will be described with reference to the drawings. The composite antenna according to the present invention is an electric antenna capable of resonating at a fundamental frequency f ₀ and a frequency 3f ₀ that is three times the fundamental frequency f ₀ , as shown in an equivalent circuit diagram of FIG. Length L
The antenna element 1 has at least one first folded portion 11 formed therein. This first folded portion 11
By adjusting the coupling between adjacent elements,
A first frequency band f ₁ higher than the fundamental frequency f ₀ , and a second frequency band f ₂ lower than the frequency 3f ₀ three times the fundamental frequency
Are formed so as to resonate with both.

As described above, the present inventors have made intensive studies to transmit and receive two or more frequency bands different from an integer multiple of the frequency band using a single antenna element. Is provided so as to be folded back along its main direction, and by being folded back, capacitive coupling and / or inductive coupling is performed between adjacent elements, and the current pattern changes.
It has been found that a shift occurs in the resonance frequency. Moreover, the deviation is different from the frequency on the frequency f ₀ side resonating at λ / 4,
The direction of deviation is opposite to that of the frequency 3f ₀ that resonates at 3λ / 4, and the resonance frequency shifts in the direction of increasing the resonance frequency at the low frequency side of f ₀ , and the resonance frequency shifts at the high frequency side of 3f _0. It has been found that the resonance frequency shifts in the lowering direction and changes depending on the degree of coupling between adjacent elements. As the coupling increases, the deviation of the resonance frequency also increases. By adjusting the degree of coupling, it is possible to resonate at a desired frequency. Was.

That is, the current patterns at the time of operation with respect to f ₀ are shown in FIG. 1B in the case where no folded portion is formed (shown by a broken line) and in the case where the folded portion of the present invention is formed (shown by a solid line). When the folded portion is not formed as shown with the antenna element, the tip of the antenna element is 0 (node) and the ground end is maximum (antinode), and the total length (electric length) L is λ / 4. Is formed. On the other hand, when the folded portion is formed, the coupling current I ₂ flows in the opposite direction to the current I _{1 of the} antenna element due to the interaction between the adjacent elements due to the folded portion, and the electrical length changes. I ₁ is 0
Is a portion which is located inside by ΔL ₁ from the tip. That is, the frequency f at which L ₁ = L−ΔL ₁ is λ / 4
Resonates at ₁ .

As shown in FIG. 1 (c), when no folded portion is formed with respect to 3f ₀ , the current becomes 0 (node) at the tip of the antenna, and the ground end. Is the same as in the previous example, except that the direction of the current I ₁ is a half wavelength, and a quarter of the current I ₄ is reversed. Overall length L
Is excited as 3λ / 4 minutes. On the other hand, in the antenna element having the folded portion according to the present invention, due to the interaction of the elements of the folded portion, the coupling current I ₃ becomes the same direction as the direction of the current I ₁ of the antenna element,
The part where the current on the tip side of the antenna element becomes 0
It is a part further ahead of the tip. That is, the length of the antenna element is L ₂ = L + ΔL ₂ , and the antenna element resonates at a frequency f ₂ of 3λ / 4.

The horizontal axis indicates the frequency,
If the vertical axis indicates VSWR, it is as shown in FIG. That is, if the folded portion is not formed, the resonant frequencies are f ₀ and 3f ₀ , whereas the folded portion according to the present invention forms the antenna that resonates at f ₁ and f ₂ . This ΔL can be changed depending on the degree of coupling between adjacent elements, and by adjusting the degree of coupling, an antenna capable of transmitting and receiving in a desired frequency band to some extent is obtained.

In the adjustment of the degree of coupling, the longer the length of the element in the folded portion, the shorter the interval between the folded portions, and the permittivity of the dielectric near the element (the antenna on the ceramic substrate described later). When the element is formed, the larger the dielectric constant of the substrate is, the higher the degree of coupling becomes, and the deviation of the resonance frequency can be increased. In addition, by reversing these elements, the deviation of the resonance frequency can be reduced. As will be described further below, the folded portion is formed so as to be independent.
By changing the lengths and intervals of the elements formed as described above and coupling them together, it is possible to further adjust the resonating frequency to a desired frequency.

FIG. 2 shows an example in which two folded portions are formed. In this example, two folded portions 11 and 12 are formed in the antenna element 1 having the electric length L, and two sets A and B of adjacent elements are separated from each other so as not to interact with each other. Is provided. And
The adjacent element portions A and B formed by the respective folded portions 11 and 12 respectively cause L ₁ ,
L ₂ and L _3, L ₄ folded portions 11 and 12 so that is formed. Further, two pairs of adjacent element portion A, the length of the portion connecting the B is an L _0. Then, by adjusting the coupling degree so that L _{1 to} L ₄ satisfy the following conditions, tuning can be performed in four frequency bands.

F ₁ : L ₀ + L ₁ + L ₃ f ₂ : L ₀ + L ₁ + L ₄ f ₃ : L ₀ + L ₂ + L ₃ f ₄ : L ₀ + L ₂ + L ₄ Signals in four frequency bands can be transmitted / received by the small antenna element, and can be configured very compactly. As a result, even a portable wireless device using various media can be mounted very compactly without increasing the size of the wireless device.

Next, a 900 MHz band (f
₁ ), an antenna capable of transmitting and receiving four frequency bands of 1500 MHz band (f ₂ ) for GPS, 1800 MHz band (f ₃ ) for DCS (Digital Cellular System), and 2400 MHz band (f ₄ ) for Bluetooth. A specific structure will be described with reference to FIG.

The antenna shown in FIG. 3 has a thickness of 2 mm.
About, the size of length × width is about 16 mm × 12 mm,
A pattern of the antenna element 1 is formed on one surface of a ceramic substrate (relative permittivity ε _r = 20) 2 by applying and baking silver paste or the like. The antenna element 1 has a dimension h from the end of the substrate 1 of the first folded portion 11.
₁ is, for example, about 13.6 mm;
₁ is about 0.2 mm and the width g ₁ of the element of the folded portion 11
Is formed to about 3.2 mm. The second folded portion 12 has a dimension h ₂ from the edge of the substrate ₂ of, for example, 1
About 4 mm, distance d ₂ of the folded portion is 0.8mm approximately, width g ₂ elements of the folded portion is formed in about 3.2 mm. Further, the distance j between the first folded portion 11 and the second folded portion 12 is about 4 mm, and the width k of the connecting portion 13 between the two.
Are formed to about 3.2 mm.

One end of the antenna element 1 is connected to the rear surface of the substrate 2 via the side surface of the substrate 2, and a power supply terminal 14 is formed. Further, the folded portions 11 and 12 are led out to the rear surface side of the substrate 2 as shown in (b) in a top view of the substrate 2 (a view in the B direction of (a)) and as shown in (c) in a bottom view thereof. Tabs 15 and 16 are provided, respectively, and are used for fine adjustment of the resonance frequency. Reference numeral 17 denotes a mounting land.

FIG. 4 shows the result of measuring the VSWR of the antenna having this structure. As is clear from FIG.
Four resonance is obtained at a frequency band, f ₁ is 0.925GHz
In, VSWR is 1.24, f ₂ is at 1.575GHz, V
SWR is 1.70, f ₃ is at 1.795GHz, VSWR
2.0 1.29, f ₄ is at 2.450GHz, VSWR is
4 were obtained.

The antenna 3 is mounted on a circuit board 5 in a housing 4 as shown in FIG. 5, for example, as shown in FIG. Functions as an antenna.

In the above-described example, the antenna element is formed on the ceramic substrate in a pattern of a conductive film. However, the antenna element may be formed on a normal printed board or the like in a similar pattern without using a ceramic substrate. In this case, since the dielectric constant of the substrate is reduced, the degree of coupling can be increased by using a means such as narrowing between adjacent elements by the folded portion, and the deviation of the resonance frequency can be increased. Further, when providing two folded portions, by significantly changing the length of both elements, the aforementioned difference of L ₁ and L ₃ or L ₂ and L ₄ is increased, due to a combination of both frequency (described above The change in f ₂ and f ₃ ) can be increased.

Further, in the above-described example, the pattern is made of a conductor. However, such a pattern may be formed by a plate-like body, and the pattern may be attached or wound on a dielectric plate. Alternatively, it may be formed into a similar shape by a thin rod-shaped body, or may be formed in a coil shape as shown in FIG. By making such a coil, the electrical length can be shortened physically while maintaining the required length,
This is preferable because further miniaturization can be achieved.
In the case of FIG. 6B, as shown in the figure, if a covered wire such as an enamel wire is used, a short circuit between the wires can be more easily prevented.

[0033]

According to the present invention, signals in any two or more frequency bands different from odd-numbered and even-numbered times can be transmitted and received by a very small antenna. As a result, even in the diversified communication broadcasting field in recent years, multimedia can be supported by one antenna,
It greatly contributes to simplification of communication equipment.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an embodiment of a composite antenna according to the present invention and the principle thereof.

FIG. 2 is a diagram illustrating another embodiment of the composite antenna according to the present invention.

FIG. 3 is an explanatory diagram showing a specific example of a composite antenna according to the present invention.

FIG. 4 is a diagram showing VSWR characteristics of the antenna shown in FIG.

FIG. 5 is an explanatory diagram showing a state where the antenna shown in FIG. 3 is mounted on a wireless device.

FIG. 6 is a diagram illustrating an example in which an antenna element is formed in a coil shape.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Antenna element 2 Ceramic substrate 11 1st folded part

Claims (5)

[Claims] At least one first folded portion is formed in an antenna element having an electrical length capable of resonating at a fundamental frequency and three times the fundamental frequency, and the first folded portion is formed between adjacent elements. A composite antenna formed so as to be able to resonate in both a first frequency band higher than the fundamental frequency and a second frequency band lower than three times the fundamental frequency by adjusting the coupling. 2. The antenna element according to claim 1, wherein a second folded portion is formed separately from the first folded portion so as not to interact with the first folded portion, and the first and second folded portions are each higher than the fundamental frequency. It is formed so as to be able to resonate in a high frequency band and a frequency band lower than three times the fundamental frequency, and the first and second folded portions are jointly resonable in at least four frequency bands. The composite antenna according to claim 1, wherein the composite antenna is formed. 3. The substantial electrical length of the element portion adjacent to the first folded portion is larger than the electrical length L in the case where the first folded portion is not formed, and is smaller than the electrical length L of the element portion adjacent to the lower frequency band on the fundamental frequency side. L ₁ , the first folded portion is formed such that L ₂ (L ₂ <L <L ₁ ) with respect to a higher frequency band on the triple frequency side of the fundamental frequency, and the first folded portion is adjacent to the second folded portion. The substantial electrical length of the element portion
With respect to the electrical length M when the folded portion is not formed, L ₃ for the lower frequency band on the fundamental frequency side and L ₄ (L ₄ <L for the higher frequency band on the triple frequency side of the fundamental frequency side.
M <L ₃ ), the second folded portion is formed,
In addition, the electrical length of the connecting portion between the first folded portion and the second folded portion is formed to be L ₀ , and f ₁ = L ₁ + L ₀ + L ₃ , f ₂ =
_{L 1 + L 0 + L 4} , f 3 = L 2 + L 0 + L 3, f 4 = L 2 + L 0 +
It said first and second folded portions, which are formed according to claim 2 composite antenna according to resonate at L _4. 4. The antenna element according to claim 1, wherein said antenna element is formed by a conductive pattern on a ceramic substrate.
Or the composite antenna according to 3. 5. The composite antenna according to claim 1, wherein the antenna element is formed by winding a wire-like conductor into a coil shape.