KR20070003382A - Multi-band loop antenna and method for adjusting resonant frequencies thereof - Google Patents

Abstract

A multi-band loop antenna and a method for adjusting a resonant frequency thereof are provided to adjust a resonant frequency of an antenna simply and efficiently by coupling a loop radiator to a planar radiator having a slit, and forming a stub. A multi-band loop antenna includes a main body(20), a planar radiator(10), a slit(18), and a loop radiator(12). The planar radiator(10) is formed on a front plane of a main body(20). The planar radiator(10) is connected to a ground terminal and a feeding terminal. An end of the loop radiator(12) is connected to the ground terminal. The other end of the loop radiator(12) is connected to the feeding terminal. The loop radiator(12) is formed to make a detour on a side plane of the main body(20). The slit(18) is formed on the planar radiator(10). The slit(18) has an L-shape.

Description

MULTI-BAND LOOP ANTENNA AND METHOD FOR ADJUSTING RESONANT FREQUENCIES THEREOF}

1 is a top perspective view showing a loop antenna according to an embodiment of the present invention.

2 is a bottom perspective view showing a loop antenna according to an embodiment of the present invention.

3 is a flowchart illustrating a resonant frequency adjusting method according to an embodiment of the present invention.

4 illustrates an embodiment of the present invention.

5 shows a ground plane used in an embodiment of the invention.

6 is a graph showing the change of S11 parameter according to the stub length of the embodiment of the present invention.

7 is a graph showing the change of the S11 parameter according to the slit length change of the embodiment of the present invention.

8 is a graph showing the change of the S11 parameter according to the slit width change of the embodiment of the present invention.

9 is a graph showing the change of the S11 parameter according to the change of the gap between the stub and the loop radiator of the embodiment of the present invention.

10 is a graph showing S11 parameters of an embodiment of the invention.

* Explanation of symbols for main parts of drawings *

10: planar radiator 12: loop radiator

14: bending portion 16: stub

18: slit 20: substrate

22: ground terminal 24: feed terminal

The present invention relates to loop antennas, and more particularly, to a small loop antenna having multiple resonance characteristics and wideband characteristics, including stubs and planar radiators.

Recently, due to the rapid development of mobile communication, terminals are becoming smaller and lighter. Accordingly, the antenna of the wireless communication terminal has been developed from the existing external antenna protruding to the outside of the terminal to an embedded type mounted inside the terminal.

Meanwhile, various types of mobile communication services, such as CDMA, GSM, DCS, etc. are used around the world, and each of these services uses different frequency bands. Therefore, in order to use one terminal for all these services, the terminal must be designed to operate in a plurality of frequency bands, and the antenna of the terminal must also be designed to have a multi-band characteristic. In addition, in recent years, the terminal has been combined to perform various functions using different frequency bands such as wireless Internet such as WiBro, digital broadcasting such as DMB, GPS service, and payment function as well as conventional voice communication. . Accordingly, the need for multiband characteristics of antennas is increasing.

Conventionally, as a built-in antenna, a PIAR (Planar Inverted F Antenna), an inverted L antenna, a loop antenna, and the like are used.

PIFA includes a planar radiator formed parallel to the ground plane, the radiator having a ground line and a feed line. The ground line and the feed line are vertically connected to the radiator to form an F shape. In general, the bandwidth of PIFA is known to increase as the height of the radiator increases, ie, the distance between the ground plane and the radiator increases. Therefore, in order to have a wide bandwidth, the thickness of the PIFA becomes thick, and there is a problem that it is difficult to miniaturize the antenna.

On the other hand, the inverted L-type antenna has a form in which the ground wire is removed from the radiator of the PIFA. That is, the inverted L-type antenna has an L shape, including a radiator parallel to the ground plane and a feed line connected perpendicularly thereto. The inverted L-type antenna has a wider bandwidth than PIFA, and thus is suitable for implementing a wideband antenna. However, the inverted L-type antenna has a lower goodness than the PIFA and has a large characteristic variation due to the external environment. Therefore, there is a problem in that the performance of the antenna is changed by the influence of the shape of the terminal, the effect of the user's tentacles, and the like.

Loop antennas are used to overcome the disadvantages of the PIFA and inverted L antennas. The loop antenna includes a radiator having one end connected to the ground part and the other end connected to the feed part to form a loop as a whole. Loop antennas generally have a wideband characteristic, and it is easy to implement a multi-band antenna by forming a plurality of loops.

However, since the loop antenna has a length of λ (wavelength corresponding to the resonance frequency), there is a problem in that the size of the loop antenna is larger than that of a PIFA or L type antenna having a length of λ / 4.

The present invention has been made in view of such a problem, and an object thereof is to provide a small loop antenna having a wide bandwidth and having multiple resonance characteristics.

It is also an object of the present invention to provide a method for simply and accurately adjusting a resonance frequency in a loop antenna.

In order to achieve the above object, according to an embodiment of the present invention, a base plate, a planar radiator formed on the front surface of the base material and connected to the ground terminal and the feed terminal, and one end is connected to the ground terminal and the other end is fed A loop antenna is provided that is connected to the terminal and includes a loop radiator configured to bypass a side of the substrate.

Preferably, slits are formed in the planar radiator.

In addition, it is preferable that the said slit is L shape.

The slit extends to one outer surface of the planar radiator to divide the planar radiator into two regions to which one end is connected, and the regions are connected to the ground terminal and the feed terminal, respectively.

Also preferably, the loop antenna further comprises a stub branching off the loop radiator and bypassing the side of the substrate.

The stub preferably extends substantially parallel to the loop radiator at a predetermined distance.

In order to achieve the above object, according to another embodiment of the present invention, a flat radiator formed on the base material, the front surface of the base material and connected to the ground terminal and the feed terminal, the slit is formed, one end is connected to the ground terminal and the other end is A loop antenna comprising a loop radiator connected to a feed terminal and bypassing a side of the substrate, and a stub branched from the loop radiator to bypass the side of the substrate and extend substantially parallel to the loop radiator at a predetermined interval. In the method of adjusting the resonant frequency of the antenna, adjusting the length of the stub to adjust the low frequency band resonance characteristics of the antenna, by adjusting the length of the slit to adjust the resonance characteristics of the high frequency band and the intermediate frequency band of the antenna Adjusting the width of the slit to obtain a high frequency band of the antenna. Adjusting the step of adjusting the resonance characteristics, and the interval between the stubs and the loop radiating element to finely adjust the resonant characteristics of the intermediate frequency band of the antenna the resonance frequency adjusting comprises the step is provided.

Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings. 1 is a top perspective view showing a loop antenna according to an embodiment of the present invention, and FIG. 2 is a bottom perspective view showing a loop antenna according to an embodiment of the present invention. The loop antenna 100 of the present embodiment includes a rectangular parallelepiped substrate 20, a planar radiator 10 formed on the front surface of the substrate 20, and a loop radiator wound along both sides, the upper surface, and the lower surface of the substrate 20 ( 12) is included.

The base 20 is a member for supporting the radiators 10, 12 and the stub 16, and easily installs the antenna in the terminal and easily connects the feed terminal 24 and the ground terminal 22 to the RF circuit of the terminal. To the radiator 10, 12 in order to be able to do so. The radiators 10 and 12 may be separately manufactured by press working or the like, and then combined with the substrate 20 or may be directly formed on the substrate 20 by double injection, plating, or printing. In addition, the substrate 20 may be formed of a dielectric to reduce the effective wavelength at the antenna 100 and to miniaturize the antenna 100.

The loop radiator 12 is connected at the lower surface of the substrate 20 with one end connected to the feed terminal 24 and the other end connected to the ground terminal 22 to form a single loop. In addition, a portion of the pattern may branch from the loop radiator 12 at the bend 14 to form a stub 16. The stub 16 may extend from the bend 14 by a predetermined length along the top and side surfaces of the substrate 20.

In the planar radiator 10, slits 18 are formed. The slit 18 may be formed in an L shape. However, the shape of the slit 18 is not limited to the L shape, and any shape for achieving the function of the slit 18 described later can be adopted. Further, the slit 18 extends to the outside of the planar radiator 10 to divide the radiator 10 into two regions, one end of which is connected, each of which is one of the feed terminal 24 and the ground terminal 22. Can be connected to. Thus, the radiator 10 can also operate as a loop antenna by forming one current loop.

The loop radiator 12 of the present embodiment is adjacent to and electrically coupled with the planar radiator 10. Accordingly, the bandwidth is increased as compared with the case of using only the loop radiator 12, and a wider bandwidth can be realized with a smaller loop radiator 12 than in the related art. In addition, the slit 18 formed in the planar radiator 10 induces coupling in the planar radiator 10, thus causing resonance in the high frequency band and exhibiting the effect of bandwidth extension. By adjusting the length and width of the slit 16, the resonant frequency and bandwidth of the high frequency band can be adjusted.

The stub 16 of this embodiment increases the electrical length of the radiator of the antenna 100. Therefore, resonance of the low frequency band occurs due to the formation of the stub 16, and the effect of bandwidth expansion of the low frequency band can be obtained. In addition, the stubs 16 are arranged in parallel with the loop radiator 12 at predetermined intervals. Thus, the stub 16 and the loop radiator 12 are electrically coupled to change the resonant frequency of the antenna 100. Therefore, by adjusting the length of the stub 16 and the spacing between the stub 16 and the loop radiator 12, it is possible to adjust the bandwidth and the resonance frequency of the antenna.

Next, a resonance frequency adjusting method of an antenna according to an embodiment of the present invention will be described with reference to FIGS. 1 to 3. The method of this embodiment first adjusts the length of the stub 16 in step S100 to adjust the resonance characteristics of the low frequency band. As described above, the stub 16 increases the electrical length of the radiator and thus mainly affects the resonance characteristics of the low frequency band, so that the resonance frequency of the low frequency band can be adjusted by adjusting the length of the stub 16. At this time, the resonance characteristics of the intermediate frequency band and the high frequency band are also changed, but since the change is small compared with the change in the low frequency band, the low frequency resonance characteristic is mainly adjusted in this step.

Next, in step S110, the length of the slit 18 is adjusted to adjust the resonance characteristics of the high frequency band and the resonance characteristics of the intermediate frequency band. Since the slit 18 induces coupling in the radiator 10 to generate high frequency resonance, the slit 18 can be adjusted to adjust the high frequency resonance characteristics. In this step, the high frequency resonance characteristic is mainly adjusted, but the intermediate frequency resonance characteristic also changes. On the other hand, since the low frequency resonance characteristic is mainly determined by the stub 16, it is hardly affected by the change in the length of the slit 16. Therefore, in this step, the resonance characteristics in the intermediate band and the high frequency band can be roughly adjusted.

Next, the high frequency resonance characteristic is finely adjusted by adjusting the width of the slit 18 (step S120). The adjustment of the slit 18 width in this step also affects the resonance characteristics in the high frequency and intermediate frequency bands. However, the change in the width of the slit 18 mainly affects the resonance characteristics of the high frequency band, and does not significantly affect the resonance frequency and bandwidth of the intermediate band. Therefore, in this step, it is possible to finely adjust the resonance frequency of the high frequency band roughly determined in the previous step (S120).

Finally, in step S130, by adjusting the interval between the loop radiator 12 and the stub 16, the resonance characteristics of the intermediate frequency band is finely adjusted. Since the influence on the resonance frequency due to the coupling of the loop radiator 12 and the stub 16 is not large, the resonance characteristics can be finely adjusted by adjusting the interval therebetween. In particular, since the resonance characteristics of the low frequency band are mainly determined by the stub 16 and the resonance characteristics of the high frequency band are mainly determined by the slit 18, the spacing adjustment in this step mainly changes the resonance characteristics in the intermediate frequency band. . Accordingly, in this step, the resonance frequency of the intermediate frequency band is finely adjusted to complete the adjustment of the resonance frequency of the antenna.

According to the present embodiment, the resonance characteristics of the low frequency band are adjusted by adjusting the length of the stub 16, and the resonance characteristics of the high frequency band are adjusted by adjusting the length and width of the slit 18, so that the low frequency band and the high frequency band The resonance frequencies can be adjusted independently of each other. In addition, since the intermediate band frequency can be finely adjusted by adjusting the interval between the stub 16 and the loop radiator 12, the intermediate band frequency can be accurately adjusted. Therefore, the resonance characteristics of the high frequency band, the intermediate frequency band and the high frequency band can be adjusted simply and accurately.

The loop antenna of the above embodiment was implemented, and simulations were performed using Microwave Studio 5.1 of CST. 4 (a) and 4 (b) show a front view and a left side view of the implemented antenna, respectively. The antenna is 880 to 960 MHz, which is a frequency band of GSM (Group Special Mobile), 1710 to 1880 MHz, which is a frequency band of Digital Cellular Network (DCS), 1574 to 1577 MHz, a frequency band of GPS (Global Positioning System). And 2630 to 2655 MHz, which is a frequency band used for DMB (Digital Multimedia Broadcasting). Specifically, the width Wr of the antenna is 36 mm, the height Hr is 16 mm, and the thickness Tr is 8 mm. As the substrate 20, a dielectric having a dielectric constant of 3.5 was used, and the hollow substrate had a thickness of 0.8 mm. As the ground plane on which the antenna is installed, as shown in FIG. 5, the FR4 substrate having the same shape as the ground plane of the actual terminal was used. The width Wg of the ground plane is 40 mm, the height Hg is 86 mm, and the thickness is 1 mm. Therefore, the height of the actual ground plane excluding the mounting portion of the antenna is 70 mm.

For the embodied antenna, the length of the stub (L1), the length of the slit (L2), the width of the slit (W) and the spacing (G) between the stub 16 and the radiator 12 are varied, respectively. Observed.

6 is a graph showing the change of the S11 parameter according to the stub length L1 of the embodiment of the present invention. The graph shows the S11 parameter when the stub length L1 was changed within the range of 4-16 mm for G = 1.5 mm, L2 = 25 mm, and W = 2 mm. As shown, as the stub length L1 increases, the resonance characteristic in the low frequency band changes greatly, and when the stub length L1 is 16 mm, a resonance frequency is introduced at about 1 GHz. Therefore, it was confirmed that the resonance characteristics of the low frequency band can be adjusted by adjusting the stub length L1.

7 is a graph showing the change of the S11 parameter according to the change of the slit length (L2) of the embodiment of the present invention. The graph shows the S11 parameter when the slit length L2 is changed within the range of 10-25 mm, when L1 = 16 mm, G = 1.5 mm, and W = 2 mm. As shown, the change in the slit length L2 hardly affects the resonance characteristics of the low frequency band, and brings about a shift in the intermediate band resonance frequency and a change in the resonance characteristics of the high frequency band. In particular, since the bandwidth of the high frequency band tends to increase as the slit length L2 increases, it was confirmed that the resonance characteristics of the high frequency band can be adjusted by the slit length L2. In addition, as the slit length L2 increases, the resonant frequency of the intermediate band frequency also tends to shift to the high frequency band, and it was confirmed that the resonance frequency of the intermediate frequency band can be adjusted.

8 is a graph showing the change of the S11 parameter according to the change of the slit width (W) of the embodiment of the present invention. The graph shows the S11 parameter when the slit width W is varied within the range of 2-6 mm for L1 = 16 mm, G = 1.5 mm, and L2 = 25 mm. As shown, the bandwidth of the high frequency band tends to increase as the slit width W increases. On the other hand, in the intermediate frequency band, only the magnitude of the S11 parameter changes, the resonance frequency and the bandwidth hardly change, and the characteristics of the low frequency band also remain unchanged. Therefore, it was confirmed that the resonance frequency of the high frequency band can be adjusted independently by adjusting the slit width W. FIG.

9 is a graph showing the change of the S11 parameter according to the change of the gap G between the stub and the loop radiator of the embodiment of the present invention. The graph shows the S11 parameter when the gap G between the stub and the loop radiator is changed within the range of 1 to 2.5 mm when L1 = 16 mm, L2 = 25 mm, and W = 2 mm. As shown, the change in the gap G slightly changes the resonant frequency of the intermediate band, and hardly affects the resonance characteristics of the high frequency band and the low frequency band. Therefore, it was confirmed that fine adjustment of the intermediate band resonant frequency is possible by adjusting the gap G.

10 is a graph illustrating S11 parameters of an implemented antenna. The antenna has dimensions of stub length L1 16 mm, slit length L2 25 mm, gap G 1.5 mm, and slit width W 2 mm. As shown, the designed antenna has a bandwidth of about 2.3% in the low frequency band, about 47% in the middle frequency band, and about 27% in the high frequency band based on return loss-6 dB (VSWR = 3). Have As such, it was confirmed that the multiband and wideband characteristics are realized by a small loop antenna of 36 mm × 16 mm.

Although the present invention has been described above in connection with specific embodiments, this is only an example and the scope of the present invention is not limited thereto. In addition, those skilled in the art can make various modifications and changes to the present embodiment without departing from the scope of the present invention, which is also within the scope of the present invention.

According to the present invention, a multiband loop antenna having a small and wide bandwidth can be obtained by coupling a planar radiator having a slit with a loop radiator and forming a stub.

In addition, according to the present invention, the resonant characteristics in each of the high frequency band, the intermediate frequency band, and the low frequency band can be adjusted through separate components to adjust the resonant frequency of the antenna simply and efficiently.

Claims (7)

materials; A planar radiator formed on a front surface of the substrate and connected to a ground terminal and a feed terminal; And And a loop radiator having one end connected to the ground terminal and the other end connected to the feed terminal, the loop radiator being configured to bypass the side surface of the substrate. The method of claim 1, And a slit formed in the planar radiator. The method of claim 2, The slit is L-shaped. The method of claim 2, And the slit extends to one outer surface of the planar radiator to divide the planar radiator into two regions, one end of which is connected, the regions connected to the ground terminal and the feed terminal, respectively. The method according to any one of claims 1 to 4, And a stub branched from the loop radiator to bypass the side of the substrate. The method of claim 5, The stub extends substantially parallel to the loop radiator at a predetermined distance. A substrate, a planar radiator formed on a front surface of the substrate and connected to a ground terminal and a feed terminal, and having a slit, a loop radiator formed so that one end is connected to the ground terminal and the other end is connected to the feed terminal and bypasses a side of the substrate, And a stub branched from the loop radiator to bypass a side of the substrate and extending substantially parallel to the loop radiator at a predetermined distance, the method of adjusting the resonance frequency of the loop antenna. Adjusting the length of the stub to adjust the low frequency resonance characteristics of the antenna; Adjusting the length of the slit to adjust resonance characteristics of a high frequency band and an intermediate frequency band of the antenna; Adjusting the width of the slit to adjust the resonance characteristic of the high frequency band of the antenna; And And adjusting the distance between the stub and the loop radiator to fine tune the resonance characteristics of the intermediate frequency band of the antenna.

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