KR100714613B1 - Broadband balanced chip antenna with integrated balun - Google Patents

Abstract

The present invention relates to a rectangular first dielectric block, first and second parallel line plates respectively disposed on a first surface of the first dielectric block and a second surface opposite to the first surface, wherein the respective parallel line plates. Slit is formed in the center of one side, part of the parallel line plate forms a parallel line acting as a λ / 4 shorting stub, is grounded, and is located between the two parallel line plates and λ / 4 open stub Balun including strip lines for signal supply with a stub operated by means of the first and second dipole radiators integrally connected to each of said first and second parallel line plates and having a symmetrical structure about said slit And a second dielectric block including the balun and the first and second dipole radiators.

Chip antenna, balun, dielectric substance block

Description

BROADBAND BALANCED CHIP ANTENNA WITH INTEGRATED BALUN}

1 is a plan view of a balun structure according to the prior art.

2 is a perspective view of a chip antenna according to an embodiment of the present invention.

3 is a front view of a chip antenna according to another embodiment of the present invention.

4A and 4B are graphs showing changes in the frequency and VSWR of the chip antenna according to the embodiment of FIGS. 2 and 3 of the present invention.

<Description of the symbols for the main parts of the drawings>

22a, 22b: parallel line plate 23: strip line

23a: stub 24a, 24b: dipole radiator

25: second dielectric blocks 26a, 26b: parallel lines

28: first dielectric block 29: balun

The present invention relates to a chip antenna, and more particularly, to an antenna in which a balun and a dipole radiator are integrated.

BACKGROUND ART In general, surface-mount chip antennas are used for antennas of small communication devices, and recently, they have been spotlighted as global positioning system (GPS) antennas embedded in mobile communication terminals. In general, the surface-mount chip antenna forms a feed pattern, a radiation electrode, and a ground electrode in a substantially rectangular parallelepiped dielectric block, and functions as an antenna that radiates a part of the high frequency signal input through the feed pattern to the space using the radiation electrode. Perform.

The chip can be miniaturized by incorporating the antenna into a ceramic or the like, and various chip antennas are commercially available. Chip antennas currently available on the market, such as MSA, PIFA, MLA, and helical antenna (HA), are mainly called unbalanced antennas. One reason for this is that unbalanced ports are generally used at the input port of the antenna in consideration of being mounted on the board. For this reason, if a balance antenna such as a dipole or loop is made, a balun-balance to unbalance trasformer is required separately.

In general, in the case of a chip antenna used in a mobile phone, among the chip antennas, MLA and HA are used. These antennas can be used as monopole antennas as antennas by using the ground plane of the substrate embedded in the cellular phone as part of the antenna. Therefore, when only the antenna portion other than the ground plane is considered, there is an advantage that the antenna element length can be reduced by half compared to a balanced antenna.

1 is a plan view of a balun according to the prior art.

The balun has a parallel line plate 12 having a slot formed at the center thereof and parallel lines 12a formed at the left and right sides of the slot, and serving as a λ / 4 short stub. A microstripline 13 having a λ / 4 open stub 13a is formed on one side of 11) and on the opposite side on which the parallel line plate 12 is formed.

The lambda / 4 short stub is composed of a parallel line 12a formed on the parallel line plate 12, denoted by θ _ab in the drawing.

The λ / 4 open stub consists of a stub connected to the microstripline 13, indicated by θ _b in the figure.

The λ / 4 open stub and short stub are used to match the impedance. When parallel lines 12a and strip lines 13 are formed on the upper and lower surfaces of the substrate 11 as described above, one surface of the balance line 12 and the strip line 13 is in contact with the substrate, but the other surface is air. Since it is exposed to the inside, it is difficult to adjust the balun's matching length to λ / 4, which makes it difficult to downsize the antenna.

In order to solve the above problems, an object of the present invention is to provide a chip antenna with an integrated balun capable of wideband characteristics and miniaturization.

The present invention relates to a rectangular first dielectric block, first and second parallel line plates respectively disposed on a first surface of the first dielectric block and a second surface opposite to the first surface, wherein the respective parallel line plates. Slit is formed in the center of one side, part of the parallel line plate forms a parallel line acting as a λ / 4 shorting stub, is grounded, and is located between the two parallel line plates and λ / 4 open stub Balun including strip lines for signal supply with a stub operated by means of the first and second dipole radiators integrally connected to each of said first and second parallel line plates and having a symmetrical structure about said slit And a second dielectric block including the balun and the first and second dipole radiators.

The first dipole radiator and the second dipole radiator may be symmetric with each other.

The first dipole radiator and the second dipole radiator may be bent at least once while maintaining parallel to each other.

The second dielectric block may use the same dielectric constant as the first dielectric block, and preferably, the dielectric constant of the first region of the dielectric positioned between the first and second dipole radiators One larger than the dielectric constant of the second region located in the upper and lower layers can be used.

Hereinafter, the present invention will be described in detail with reference to the drawings.

Figure 2a is a perspective view of a chip antenna with a balloon according to an embodiment of the present invention.

Referring to FIG. 2A, a balloon 29 and a radiator 24 connected to the balloon 29 are embedded in the dielectric block 25 to form a chip antenna.

As shown in the figure, dipole radiators 24a and 24b integrally connected to parallel line plates 22a and 22b formed on upper and lower layers of the balloon 29 are formed, and each radiator is centered on the balloon 29. It has a symmetrical structure and has a double layer structure.

As described above, the antennas of the present invention can be easily matched with broadband characteristics by the structure of the radiators 24a and 24b having the upper and lower duplex structures.

Here, the dipole emitter having the multilayer structure was configured to be parallel to the matching circuit (balloon).

The dipole antenna is an antenna that acts like a dipole when the length of the antenna is shorter than 1/2 of the wavelength, and the polarity of the linear potential distribution in the up, down, left and right directions is always reversed with respect to the center of the antenna. ) Operates as a main antenna for both transmission and reception, and the second dipole radiator 24b operates as a reception antenna for diversity.

Therefore, broadband can be obtained by adjusting the length and width of the dipole radiators 24a and 24b to maintain the optimum matching state.

In addition, the radiators each have a bent portion at right angles at one end. Thus, the bent portion is formed in the antenna according to the shape of the dielectric block that influences the external shape of the chip antenna, thereby increasing the line length of the antenna without increasing the physical size of the chip antenna. Can be. The chip antenna of the present invention is mainly used as an antenna formed inside the mobile communication terminal. By forming a bent portion in the radiator, the chip antenna can be reduced in length to prevent the chip antenna from deviating from the board on which the chip antenna is mounted. have.

By increasing the bending point of the radiator, the length of the antenna can be further increased. However, in this case, since the mutual coupling between adjacent elements results in narrow bands, the bending is formed only once in left and right.

A balun is used for matching the feeder with the dipole emitter.

In the balun 29 used in the present invention, parallel line plates 22a and 22b are formed on the first surface of the rectangular dielectric block 28 and the second surface opposite thereto, and the inside of the dielectric block 28 is formed. The strip line 23 is formed.

The parallel line plates 22a and 22b formed on the surface of the rectangular first dielectric block 28 are formed with one slit open in parallel to the center of one side thereof to form part of the parallel line plates 22a and 22b. Forms parallel lines 26a and 26b acting as λ / 4 shorting stubs. The formed parallel line plates 22a and 22b are electrically connected to the ground portion, so that the parallel lines 26a and 26b serve as λ / 4 shorting stubs. The grounding unit is mainly used as a ground plate formed on a substrate on which the chip antenna is mounted in a mobile communication terminal.

The strip line 23 formed inside the rectangular dielectric block 29 is connected to a feed line for supplying a signal to the antenna of the present invention, and a stub 23a is formed at one end thereof. This stub 23a serves as a lambda / 4 open stub.

Here, the λ / 4 open stub and the λ / 4 short stub form a stub so that matching occurs when the signal of the electric field is λ / 4, and in actual design, there is an error, and VSWR is most effective when the electric field is slightly longer than λ / 4. It is supposed to improve.

In the present invention, since the λ / 4 shorting stub is composed of the parallel lines 26a and 26b in the dielectric and the λ / 4 open stub is composed of the stripline 23a, the parallel line plates 22a and 22b and the strip line 23 are used. All of these are sealed inside the dielectric, so that the effective wavelength λ _g can be realized at λ / (√εr) (εr = dielectric constant of the dielectric), thereby further reducing the length of the balun. Therefore, it is possible to reduce the length of the balun by adjusting the relative dielectric constant? Of the dielectric in which both the stripline and the parallel line plate are embedded.

In FIG. 2B, the first parallel line plate 22a, the strip line 23, and the second parallel line plate 22b are separately shown.

Referring to FIG. 2B, the first parallel line plate 22a and the second parallel line plate 22b have the same shape, and the lengths of the slits are also the same.

Parallel lines 26a and 26b formed on each parallel line plate form a λ / 4 shorting stub as described above.

The strip line 23 formed between the first parallel line plate 22a and the second parallel line plate 22b is for supplying a signal to the antenna, and the stub 23a is connected at the end thereof to lambda / 4. It works as an open stub.

The simulation results of the voltage standing wave ratio (VSWR) characteristics of the antenna of the present invention having the configuration shown in FIG. 2A are shown in FIG. 4A.

4A, the horizontal axis represents frequency and the vertical axis represents voltage standing wave ratio VSWR.

From the figure, it can be seen that VSWR is 3 or less in the frequency band of UMTS (1.92-2.17 GHz, bandwidth about 12%). At this time, the relative dielectric constant epsilon r of the first dielectric material and the second dielectric material in the chip was set to 6.8, and the chip size was about 18 x 30 x 5 mm.

3 is a front view of a chip antenna according to the present invention.

Referring to FIG. 3, the second dielectric block 35 including the dipole emitter 34 having a multilayer structure and the balloon 39 for matching is formed of three layers 35a bordering the dipole emitters 34a and 34b. , 35b, 35c).

The dielectric block having such a multilayer structure may be formed by stacking dielectrics similarly to the process of manufacturing low temperature co-fired ceramic (LTCC).

When using one line of the parallel line as an outer conductor or grounding plate of the λ / 4 shorting stub in a compensated balun, the effective permittivity of the portion constituting the parallel line and the portion constituting the parallel line are the same. In this case, since the front part of the line of the λ / 4 shorting stub is close to the ground, there is a problem in adjusting to the optimum length. In order to solve this problem, it is necessary to make the dielectric constant of the portion constituting the lambda / 4 short stub different from the dielectric constant of the portion constituting the balanced line.

In the embodiment of FIG. 2, a dielectric having the same dielectric constant of the second dielectric block 25 and the first dielectric block 28 is used. In the embodiment of FIG. 3, the dielectric constant of the dielectric layer is different. That is, the dielectric constant of the first region layer 35b of the dielectric formed between the dipole radiators 34a and 34b is set to the second region layer 35a of the dielectric formed above and below the first region layer 35b. Higher than the dielectric constant of 35c). By forming the antenna in such a configuration, it is possible to optimize the line length of the λ / 4 shorting stub, thereby miniaturizing the overall chip antenna size.

The dielectric constant of the first region layer 35b may be different from that of the adjacent first dielectric 38, but preferably a dielectric having the same dielectric constant may be used.

FIG. 4B shows a dielectric constant inside the chip in the balanced chip antenna with the balun of the present invention, and shows the relative dielectric constant of the upper and lower layers of the dipole emitter (ie, the second region layer of the second dielectric) as shown in FIG. Is a graph showing the VSWR characteristic when the dielectric constant of the intermediate layer (that is, the first region layer of the second dielectric and the first dielectric) is set to 30. FIG. At this time, the frequency of VSWR of 3 or less became 1.92-2.14 kHz, and the VSWR band became slightly narrower than the case where the relative dielectric constant was the same by increasing the dielectric constant of the intermediate layer. However, simulations have shown that it is possible to reduce the size of the chip antenna to 12 x 30 x 5 mm.

Although the first dielectric block and the second dielectric block are shown as different materials in the drawing, the description of the first dielectric block and the second dielectric block in this manner is to distinguish the area of the balun from the entire area of the antenna. The shape is a case where the first region of the first dielectric block and the second dielectric block are made of the same material, and the second region of the second dielectric block is made of a material having a lower dielectric constant than the first dielectric block, as described in the above embodiment. .

Therefore, it should be understood that the concept of 'block' described in the claims is intended to represent a region of a dielectric, and in embodiments, such a chip antenna is generally manufactured by an LTCC process, so the 'block' should not be construed as too limited. I will not.

As such, the present invention is not limited by the above-described embodiment and the accompanying drawings. That is, the length of the antenna and the shape of the radiation pattern may be variously implemented. It is intended that the scope of the invention be defined by the appended claims, and that various forms of substitution, modification, and alteration are possible without departing from the spirit of the invention as set forth in the claims. Will be self-explanatory.

It is possible to implement a wideband antenna by using a multi-layered radiator, and to provide a chip antenna that can be miniaturized by integrating a balloon into the antenna and adjusting the dielectric constant of the dielectric.

Claims (6)

First and second parallel line boards each having a rectangular first dielectric block, a first surface of the first dielectric block, and a second surface opposite to the first surface, each parallel line plate having one side portion; A slit is formed at the center of the parallel line plate to form a parallel line which acts as a λ / 4 shorting stub and is grounded, and is located between the two parallel line plates and operated as a λ / 4 open stub A balun including a strip line for signal supply with a stub; First and second dipole radiators integrally connected to each of the first and second parallel line plates and having a symmetrical structure around the slit; And And a second dielectric block containing the balun and the first and second dipole radiators. The method of claim 1, The first dipole radiator and the second dipole radiator, Broadband balanced chip antennas, characterized in that they are symmetrical to each other. The method of claim 1, The first dipole radiator and the second dipole radiator, Broadband balanced chip antenna, which is bent at least once while being in parallel with each other. The method of claim 1, The second dielectric block, And a dielectric constant equal to the first dielectric block. The method of claim 1, The second dielectric block, And a dielectric constant of a first region of a dielectric positioned between the first and second dipole radiators is greater than a dielectric constant of a second region located above and below the first region. The method of claim 5, And a dielectric constant of the first dielectric block and a dielectric constant of the first region of the second dielectric block are the same.

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