JP2001244726A - Stacked antenna using recessed rectangular patch antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stacked antenna for circularly polarized wave that relates to an antenna adopting a microstrip structure for a hand-held type mobile phone in mobile communication, adopts a structure not needing hole processing for the purpose of ease of manufacture without requiring high accuracy, even for pattern manufacture, and is a stack antenna suitable for mass- production and industrialization, especially having sufficient separation between transmission and reception. SOLUTION: The transmission reception separation type stacked antenna of this invention that is the transmission reception separation type stacked antenna used for the mobile communication hand-held mobile phone, is characterized in that the antenna has an upper layer antenna consisting of a rectangular patch antenna and a lower layer antenna, consisting of a rectangular patch antenna whose one side is recessed, and the upper layer antenna and the lower layer antenna are laminated, power is fed to the upper layer antenna by electromagnetic coupling by a strip line provided to the recessed part of the lower layer antenna and the upper layer and lower layer patch antennas are excited by a circularly polarized wave.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna for a hand-held portable telephone in mobile communication, and more particularly to an antenna having a microstrip structure.

[0002]

2. Description of the Related Art An example of a prior art relating to a microstrip antenna useful for reducing the size and weight of a portable telephone is disclosed in the document "Illustrated Antenna, Naohisa Goto" (p. 231-232).

In this document, a microstrip antenna (patch antenna) 19 as shown in FIGS. 10 and 11 is stacked as a mobile satellite communication antenna, and a transmission signal and a reception signal are separated. A self-diplexing antenna having characteristics is introduced. This is a method in which circular patch antennas of different sizes are stacked to form one antenna.

As a method of directly feeding power to two patch antennas, first, as shown in FIG. 10A, the lower patch antenna is fed by connecting the inner conductor 20 of the coaxial line at a position deviated from the center, and The power supply to the circular patch antenna is performed by a feed line 21 that extends through the inside of the thick conductor wire by making the conductor wire of the lower circular patch antenna thick (annular antenna).

[0005] The antenna thus manufactured can independently supply power to the upper and lower patch antennas, and each antenna can be independently designed. Further, since separate power supply circuits are used for transmission and reception, there is an advantage that transmission / reception signals can be separated. In order to excite circularly polarized waves, the upper and lower patch antennas are independently fed at two points (22, 23 and 24, 25) as shown in FIG. 11, and the phase between the two points is shifted by 90 degrees. I have.

In the example of the conventional stack antenna shown in FIGS. 10 and 11, a hole for supplying power to the upper-layer patch antenna, processing of a through hole or the like is required, and the upper and lower patch antennas are mechanically connected. Therefore, there is a disadvantage that adjustment is not easy.

[0007] As an improvement, a stack antenna in which rectangular patch antennas are stacked has been proposed by the same applicant (see JP-A-11-251828).

However, these conventional examples have the following disadvantages. (1) In the transmission / reception separated type stack antenna composed of the patch antenna of the prior art, the feeding structure for reducing the disturbance of the electric field distribution is complicated, and there is room for improvement such as difficulty in adjustment during manufacturing. .

(2) In the stack antenna, there is a problem of mutual coupling between the stacked patches and between the feeding parts. In particular, when the transmission and reception frequency bands are close to each other, the degree of separation is reduced, so that the self-diplexing characteristic is excellent. There is also room for improvement in the combination of patch shapes, the power supply method to each patch, and the power supply system arrangement.

(3) As a problem of industrialization and practical use, there has been a demand for further reduction in size, realization of a stack antenna having good reproducibility of required characteristics of the upper and lower antennas, and of a type which is easy to manufacture.

[0011]

The present invention employs a structure that does not require drilling, is easy to manufacture, does not require high precision in pattern manufacturing, and is suitable for mass production and industrialization. Aiming to provide a suitable stack antenna, especially by attaching it to a hand-held type mobile phone in mobile communication, an antenna unit with a simple structure and good characteristics can be realized, and the isolation between transmission and reception is sufficient. An object is to provide a circularly polarized stack antenna.

[0012]

According to the present invention, there is provided a separate transmitting / receiving stack antenna for use in a mobile communication handheld portable telephone, wherein the upper layer antenna formed by a rectangular patch antenna and one side are concave. A lower-layer antenna comprising a rectangular patch antenna (hereinafter referred to as a concave antenna), wherein the upper-layer antenna and the lower-layer antenna are stacked.

Further, power is supplied to the upper layer antenna by electromagnetic coupling using a strip line provided in a concave portion of the lower layer antenna, and the upper and lower patch antennas are excited by circularly polarized waves. .

Further, power is supplied to the lower-layer concave patch antenna by a strip line, and the lower-layer antenna power supply strip line and the upper-layer antenna power supply strip line are orthogonal to each other.

That is, as technical means of the present invention,
This is a combination of the following means for downsizing and simple structure of the antenna including the power supply method. (1) In order to dispose the strip line at the excitation position of the upper patch, a concave patch antenna having a shape in which one side of the lower patch antenna is recessed is used as the lower patch antenna, and the upper patch is a stack antenna type in which a rectangular patch is used. . (2) To simplify the production and adjustment by a power supply system on the same plane by a strip line, and to excite the upper layer patch as a method for realizing a structure capable of exciting the upper layer patch without a hole drilling structure. Consider a method using electromagnetic coupling. (3) In order to improve the self-diplexing characteristics (degree of separation), the excitation directions are orthogonalized. Further, the arrangement of the upper-layer patch excitation stripline and the lower-layer patch antenna excitation stripline is made orthogonal to reduce the coupling.

As a result, there are the following advantages. (1-1) As a combination of the shape of the patch antenna of the stack antenna, a strip line can be provided in the concave portion by using a concave shape in which one side is concave in the lower layer patch.

(1-2) The upper patch is excited by a strip line on the same plane as the lower patch by using the electromagnetic coupling at the face of the strip patch with the open end provided in the recess and the upper patch. be able to.

(1-3) In the concave patch shape, the resonance frequency is equivalently reduced because a part of the current distribution is bent along the concave portion. Therefore, the size of the resonance patch for the same frequency is reduced.

(2-1) Since there is no thin pattern portion in the shape of the lower layer patch, the accuracy in manufacturing by etching or the like is eased. (2-2) Since electromagnetic coupling is used as an excitation method for the upper layer patch, drilling and through-holes required when power is supplied from the rear side are not required, and the production can be simplified.

(3-1) Since the upper patch antenna is not mechanically connected to the feeder line, it is easy to adjust the degree of electromagnetic coupling and the mutual coupling with the lower antenna. (3-2) Since the feeding direction to the lower-layer patch antenna is orthogonal to the strip line with the open end provided in the concave portion, the coupling between the patch and the strip line is small,
Therefore, the degree of separation between the upper and lower patch antennas is good, and the self-diplexing operation is good.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in more detail with reference to the accompanying drawings. FIG. 1 shows an overall perspective view of a stack antenna 1 of the present invention. A concave patch antenna 2 is provided in a lower layer, and a rectangular patch antenna 3 is provided in an upper layer, and these are stacked. The feeding of each patch antenna is performed by strip lines 4 and 5 formed on the same plane as the lower patch antenna. In addition,
6 and 7 are dielectric substrates.

The excitation power supply for the lower-layer patch antenna is a strip line power supply type structure in which the patch antenna and the strip line are directly connected as shown in FIG. 2, and the upper-layer patch antenna is as shown in FIG. The lower patch antenna is a patch antenna that is one size smaller,
It is placed at a position where the vertical and horizontal central axes are common, and is electromagnetically coupled to the upper layer antenna by a strip line formed on the same plane as the lower layer patch surface.

In general, since the transmitting and receiving frequencies are different in the stack antenna, the single antennas are stacked to reduce the occupied area of the entire antenna. At this time, the upper and lower patch antennas are excited by the respective feed systems, but by stacking, the feed structure is restricted,
In order to operate as an independent antenna, measures have been taken to reduce the disturbance of the electric field distribution of each other.

FIG. 4A shows an example of a rectangular patch antenna with holes as a lower layer patch antenna of the above stack antenna as a lower layer antenna for comparing characteristics.
FIG. 4B shows the shape of the concave patch antenna used in the present invention. The above-described rectangular patch antenna with holes is a patch antenna having a square hole centered on a feeding point when power is supplied to the upper patch antenna from the back surface.
A concave patch antenna is a rectangular patch antenna with a rectangular depression, with the pattern part between one side of the hole of the patch antenna with holes and the side of the patch removed. Shape.

FIG. 5 shows the FDTD (Finite-Difference Time-Domain) of the resonance characteristics for the two patch shapes of FIG.
It is an analysis result by the method. FDTD (Finite-Differe
The nceTime-Domain method is an analysis method called the finite-difference time-domain method. The algorithm that differentiates the Maxwell equation of the electromagnetic field equation in time and space, and alternately calculates the electromagnetic field in the analysis space between the electric field and the magnetic field. This method is used to obtain a time response of the output point by updating the time point using the time. In the figure, the solid line 8 is
The characteristics of a patch antenna (with hole) in which a 16 mm square hole is opened for a 50 mm square patch.
This is a characteristic of a concave patch antenna (concave) having a concave portion of × 18 mm.

From this analysis result, it can be seen that the resonance frequency shifts due to the structural difference, but that the return loss at each resonance frequency is -25 dB or more and sufficient characteristics are obtained if matching is achieved.

FIG. 6 shows an analysis result of the E-plane radiation characteristics of each antenna in the above-mentioned state, and it can be seen that the radiation pattern of the main polarized wave substantially matches at the resonance frequency of each antenna. However, the cross polarization level is increased in the concave type, but the level is about -15 dB, and there is no practical problem even if the patch antenna with holes is a concave patch antenna.

FIG. 1 is a configuration diagram (perspective view) of a stack antenna according to the present invention. The thickness t, the dielectric substrate 6 on the dielectric constant .epsilon.r ₁ (back surface entirely ground) to have concave patch antenna 2 in the lower, the length of one side is a structure in which there is a concave portion of a × b in L ₁ I have. An upper layer antenna having the same size as the dielectric substrate is formed on the dielectric substrate with a thickness h, a dielectric constant εr ₂ , and a side L ₂ interposed therebetween. Both upper layer antenna 3 and lower layer antenna 2 are fed from a strip line,
In the case of the upper layer antenna 3, the concave portion 10 of the lower layer antenna 2
Through a strip line, and electromagnetically coupled with an upper layer antenna to excite. The feed strip line 5 of the upper antenna 3 has a length f ₁ and a width w, and the feed strip line 4 of the lower antenna 3 has a length f ₂ , a width w and an offset length fo ₂ .

According to the present invention, since the feeding method by the strip line that can be formed on the same plane, the excitation directions of the upper and lower patch antennas can be made orthogonal, which is advantageous in terms of electrical orthogonality. We investigated the effect of stacking when the antenna uses electromagnetic coupling excitation.

FIGS. 7A and 7B show an antenna structure for investigating the influence of electromagnetic coupling excitation. FIG. 7A shows a concave patch antenna alone, FIG. 7B shows an electromagnetic coupling excitation patch antenna alone, and FIG. It is a structure of a stack antenna. Since the concave patch antenna can provide a strip line in the concave portion, the upper layer antenna can be excited by electromagnetic coupling. In this case, the excitation directions of the upper and lower patch antennas can be made orthogonal, which is advantageous in terms of electrical orthogonality.

[0031] FIG. 8 is a diagram showing an analysis result of a single time of resonance characteristics and the stack when resonance characteristics of one side of the patch length L _1,
L ₂ are each 49.6 mm, the resonance characteristic when the 32 mm, S
11 (only EMC patch) The solid line 15 is the electromagnetically coupled excitation patch antenna alone, the S22 (onlyconcave patch) dashed dotted line 16 is the concave patch antenna alone, S11 (stackedpattern)
ch) Dotted line 17, S22 (stacked patch) 2 dotted broken line 18
Indicates the impedance characteristic at the time of stacking. From this figure, it can be seen that the effect of stacking is small in the concave patch antenna in the lower layer to the extent that the resonance frequency is slightly lowered.

On the other hand, when the patch in the upper layer is changed from FIG. 7B to FIG. 7C, the dielectric layer is divided into two parts by the concave patch antenna entering between the rectangular patch antenna and the ground, so that the effective patch is effective. Even if the increase in frequency due to the change in thickness from (h + t) to h is excluded, the resonance frequency tends to shift higher, indicating that the stacking effect of the lower concave patch is slight. However, this is not a problem as a stack antenna.

FIG. 9 shows the results of analysis of the resonance characteristics of the stack configuration of the present invention shown in FIG. 1 (each dimension below the figure corresponds to the symbol shown in FIG. 1). S11, the impedance characteristic of the lower patch antenna is indicated by S22, and the isolation characteristic between the upper and lower patch antennas is indicated by S12. The upper layer patch antenna (solid line 11) resonates at 2.28 GHz, and the lower layer concave patch antenna (dotted line 12) resonates at 2.12 GHz, and the mutual coupling 13 is -15 dB or less, almost sufficient characteristics. Therefore, it can be seen that sufficient characteristics can be realized as a self-diplexing antenna.

In the above description, a linearly polarized antenna has been described. However, in order to use a circularly polarized antenna, the upper and lower patches may be replaced with a single-point feeding type circularly polarized patch antenna. The principle of operation also applies to circularly polarized waves. FIG. 12 shows a specific example of a single-point feeding type circularly polarized patch antenna.
(A) is a rectangle in which the sides of the rectangular patch antenna have different lengths in the vertical and horizontal directions, (b) is a shape in which the diagonal of the rectangular patch antenna is chamfered, and (c) is a concave patch for the rectangle as in (a). The antenna, (d), has a shape in which the diagonal of the concave patch is chamfered.

The circularly polarized wave excitation of the lower layer antenna is described in "Illustrated Antenna" (Naohisa Goto, IEICE Polarization.)
223, a feed point may be provided on the diagonal line of the rectangular patch antenna as shown in FIG. 3.62. (In this case, as will be described later, for example, a feed structure from the back side is assumed.) In the case of the upper layer antenna, it is preferable that the tip of the feed strip line be below the diagonal line of the upper layer patch antenna. Then, as shown in FIG. 12, it is possible to generate circularly polarized waves by devising the corners of a rectangular patch.

Further, in the present invention, the feeding by the strip line has been described for the purpose of simplifying the structure and the manufacturing.
In the case of circularly polarized waves), a method of feeding power from the back with a coaxial structure may be used.

[0037]

As described above, a hand-held portable telephone for mobile communication (Japanese Patent Application No. 9-36899) has been proposed.
This is a structure in which a microstrip antenna is attached to an antenna plate (deployment part) housed on the back of a handheld type mobile phone. Next, a mechanism that rotates and fixes the deployed part (can be used with either the left or right ear) so that the antenna surface can be used in a state where it is almost in the zenith direction (horizontal to the ground) It is a handheld type mobile phone having the same.

By using the circularly polarized stack antenna of the present invention for a hand-held portable telephone in the above-mentioned mobile communication, an antenna unit having a simple structure and good characteristics can be realized, and the degree of separation between transmission and reception is sufficient. Therefore, it is possible to omit the diplexer, which is effective in simplifying and reducing the size of the telephone.

The stack antenna of the present invention employs a structure that does not require drilling, so that it is extremely easy to manufacture, and since pattern manufacturing does not require high precision, it is suitable for mass production and industrialization. Suitable for.

[Brief description of the drawings]

FIG. 1 is an overall perspective view of a stack antenna of the present invention.

FIG. 2 is an explanatory diagram of a power feeding method using a microstrip line of a lower-layer rectangular patch antenna of the stack antenna of the present invention.

FIG. 3 is an explanatory diagram of a stack antenna based on a rectangular patch antenna which is a premise of the present invention.

FIG. 4 is a diagram showing the shapes of a rectangular patch antenna with holes and a concave patch antenna.

FIG. 5 is a diagram showing an analysis result of resonance characteristics of a rectangular patch with holes and a concave patch.

FIG. 6 is a diagram showing an analysis result of a radiation pattern (E surface) of a rectangular patch with holes and a concave patch.

FIG. 7 is a diagram showing an antenna structure diagram for investigating the effect of stacking.

FIG. 8 is a diagram illustrating analysis results of resonance characteristics at the time of a single body and resonance characteristics at the time of a stack.

FIG. 9 is a diagram showing an analysis result of a resonance characteristic of the stack antenna of the present invention.

FIG. 10 is a diagram illustrating an example of a conventional stack antenna.

FIG. 11 is an explanatory diagram of circularly polarized wave excitation of a conventional stack antenna.

FIG. 12 is a specific example of a single-point feeding circularly polarized patch antenna.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 Stack antenna 2 Lower patch antenna 3 Upper patch antenna 4 Microstrip line 5 Microstrip line 6 Dielectric substrate 7 Dielectric substrate 8 Resonance characteristics of rectangular patch antenna with holes 9 Resonance characteristics of concave patch antenna

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshikazu Takano 2-12-5 Iwamotocho, Chiyoda-ku, Tokyo Research Institute for Next-Generation Satellite Communications and Broadcasting Systems (72) Inventor Shigehisa Yoshimoto Chiyoda, Tokyo 2-12-5 Iwamotocho, Ward F-term (reference) 5J045 AA02 AB06 DA10 EA08 HA03 LA01 MA07 NA03 5J047 AA19 AB13 FC06 FD01

Claims (4)

[Claims] 1. A transmission / reception separate stack antenna used for a mobile communication handheld mobile phone, comprising: an upper layer antenna formed by a rectangular patch antenna; and a lower layer antenna formed by a rectangular patch antenna having a concave side. A separated transmitting / receiving stack antenna, wherein an antenna and a lower antenna are stacked. 2. The separated transmitting / receiving stack antenna according to claim 1, wherein power is supplied to the upper layer antenna by electromagnetic coupling using a strip line provided in a concave portion of the lower layer antenna. 3. The separated transmitting / receiving stack antenna according to claim 1, wherein the upper and lower patch antennas are excited by circularly polarized waves. 4. The power supply to the lower-layer concave patch antenna is also performed by a stripline, and the lower-layer antenna power supply stripline and the upper-layer antenna power supply stripline are orthogonal to each other. Item 5. A transmission / reception separated type stack antenna according to any one of Items 1 to 3.