KR20060112051A - Ultra-wideband antenna having a band notch characteristic - Google Patents

Abstract

An ultra-wideband antenna having a band notch characteristic is provided to have an omnidirectional radiation pattern. In an ultra-wideband antenna having a band notch characteristic, a radiation body(10) is formed at a surface of a substrate(12). A ground surface is formed at a lower side of the substrate(12). A feeding unit(14) is connected to the radiation body(10). And, a concave unit is formed at the ground surface.

Description

ULTRA-WIDEBAND ANTENNA HAVING A BAND NOTCH CHARACTERISTIC

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

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

3 is a diagram schematically showing a current flow in a radiator of an antenna of one embodiment of the present invention.

4 is a graph showing a simulation value of frequency vs. return loss with a change in depth of a recess of the ground plane.

5 is a graph showing a simulation value of frequency vs. return loss over slot length.

6 is a graph showing a measurement of frequency versus return loss with the formation of recesses and slots.

7 is a graph showing a measurement of frequency vs. gain with slot formation.

8 is a graph showing the radiation pattern according to the frequency of the antenna of an embodiment of the present invention.

<Description of Symbols for Major Parts of Drawings>

10: radiator 12: substrate

14: feeder 16: slot

18: notch 20: ground plane

22: recess

The present invention relates to an antenna for an ultra-wideband (UWB) communication system, and more particularly to an ultra-wideband antenna having a band-stopping characteristic in the 5 GHz band.

Ultra-wideband communication systems are defined as communication systems having a bandwidth of at least 25% of the center frequency or at least 1.5 GHz. Ultra-wideband communication uses signals in which power is spread over a wide frequency band, such as an impulse signal. In other words, by using a pulse having a width of several nanoseconds to picoseconds, the power is spread over a wide frequency band in GHz. This is a communication scheme with a much wider bandwidth than broadband CDMA communication with a bandwidth of about 5 MHz.

In UWB communication system, a signal is modulated to transmit information using a short pulse. On-Off Keying (OOK), Pulse Amplitude Modulation (PAM), or Pulse Position Modulation (PMP) is maintained while maintaining the broadband characteristics of the pulse itself. The modulation scheme of is used. Therefore, the UWB system does not require a carrier (carrier) so that the configuration of the system is simple and easy to implement. In addition, since power is spread over a very wide band, each frequency component has a very low power, very little interference with other communication systems using a narrow frequency band, and hard to intercept, which is suitable for maintaining communication security. In addition, the UWB system has advantages such as high-speed communication at very low power and excellent obstacle transmission characteristics.

Due to these advantages, the UWB system is expected to be widely applied to the next generation wireless personal area network (WPAN) field such as a wireless home network. In particular, in February 2002, the US Federal Communications Commission (FCC) approved the commercial use of UWB communications for frequencies above 3.1 GHz, accelerating the commercialization of UWB systems.

Since the UWB system uses a wider frequency band than the conventional communication system, it is necessary to develop a small antenna having a wide bandwidth characteristic. Antennas for UWB systems include horn antennas, bi-conical antennas, and the like, and are described in US Pat. No. 6,621,462 to Time Domain Corporation and Xtreme Spectrum, Inc. U. S. Pat. No. 6,590, 545, et al., Discloses another type of UWB antenna.

However, there is a problem that these antennas are not suitable for the field requiring a small and light antenna because of their large size.

Other UWB system antennas are disclosed in Korean Patent Application No. 2003-49755 of LG Electronics Co., Ltd. and Korean Patent Application No. 2002-77323 of Korea Electronics and Telecommunications Research Institute. These patent applications disclose planar antennas or inverted L-shaped antennas which are relatively small in size and have broadband characteristics.

IEEE 802.11a and HYPERLAN / 2, the standards for wireless LANs, allow the wireless LANs to use the 5.15 to 5.825 GHz band (UNII (Unlicensed National Information Infrastructure) band), which is included in the frequency band available for UWB. These standards use high power signals and can interfere with UWB systems in the UNII band. Therefore, in the UWB system, use of the UNII band overlapping with the wireless LAN is limited.

However, the antennas disclosed in the above-mentioned US patent and Korean patent application have only ultra-wideband characteristics, and do not have band-stopping characteristics in a frequency band where use is limited. Therefore, in order to actually apply these antennas, it is necessary to additionally use a band rejection filter having a high quality factor for the frequency band overlapping with the wireless LAN. However, the addition of the band-stop filter not only increases the cost, but also limits the miniaturization and weight reduction of the equipment. In the UWB system using a very short pulse, there is a problem of causing a distortion of the pulse and causing performance degradation.

SUMMARY OF THE INVENTION An object of the present invention is to provide an ultra-wideband antenna having ultra-wideband characteristics and usable band-stopping characteristics in the UNII band for use in a UWB system.

In addition, an object of the present invention is to provide an ultra-wideband antenna that can be manufactured in a small size and mass production.

In order to achieve the above object, according to an embodiment of the present invention, in the antenna comprising a substrate, a radiator formed on the upper surface of the substrate, a ground plane formed on the bottom surface of the substrate, and a feeder connected to the radiator An ultra-wideband antenna is provided, wherein a recess is formed in the ground plane.

Preferably, a slot is formed in the radiator such that the antenna has band rejection characteristics.

In addition, the slot is preferably U-shaped.

인 것이 바람직하다.On the other hand, when the relative dielectric constant of the substrate is ε _r and the wavelength corresponding to the center frequency f _c of the stop band is λ _c , the length of the slot is

Is preferably.

In addition, the center frequency f _c of the stop band is preferably 5 to 6 GHz.

On the other hand, preferably, the ground plane is formed so as not to overlap with the radiator.

Also preferably, the feeder is a microstrip feeder.

On the other hand, the radiator is rectangular, it is preferable that the notch is formed in the lower edge of the radiator.

In order to achieve the above object, according to another embodiment of the present invention, in the antenna comprising a substrate, a radiator formed on the upper surface of the substrate, a ground plane formed on the bottom surface of the substrate, and a feeder connected to the radiator, There is provided an ultra-wide band antenna having a band blocking characteristic in which a U-shaped slot is formed in the radiator so that the antenna has band blocking characteristic.

Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings. Although the shape of a specific antenna and related numerical values are disclosed, this is merely an example and will be readily appreciated by those skilled in the art that various modifications or changes can be made without departing from the spirit of the present invention.

1 and 2 are top and bottom views, respectively, of an ultra-wideband antenna according to one embodiment of the invention.

The antenna of the present embodiment is basically a microstrip patch antenna, which is a substrate 12, a rectangular radiator 10 formed on the upper surface of the substrate, a feed section 14 connected to the radiator 10, and a ground formed on the lower surface of the substrate. Ground plane 20. The radiator 10 may be formed with a U-shaped slot 16, and a recess 22 may be formed at the center of the ground plane 20. In addition, the notch 18 may be formed at the lower edge of the radiator 10.

A notch 18 formed in the lower edge of the radiator 10 induces coupling between the ground plane 20 and the radiator 10. Thus, the impedance matching of the antenna can be controlled by the notch 18, thereby extending the antenna bandwidth. Bandwidth adjustment is possible by adjusting the length (N _L ) and width (N _W ) of the notch.

In addition, in the present embodiment, the concave portion 22 may be formed in the ground plane 20 to realize the ultra-wide band characteristic. The recess 22 formed in the ground plane 20 also functions as an impedance matching circuit by coupling with the radiator 10 and the power feeding section 14. Therefore, the impedance matching can be adjusted by forming the recess 22 in the ground plane of the portion where the feed section 14 is formed, and the capacitance is adjusted by adjusting the depth H _L and the width H _W of the recess 22. And since the inductance can be adjusted, it is possible to adjust the movement of the resonance frequency, that is, the degree of bandwidth expansion. In the present embodiment, the recess 22 is formed in the ground plane 20, but the present invention is not limited thereto, and variations of the ground plane 20 in various forms are also within the scope of the present invention.

In the present embodiment, the ground plane 20 may be formed only on a part of the bottom surface of the substrate 12 so as not to overlap the radiator 10. Therefore, electromagnetic waves radiated by the radiator 10 can be emitted without being shielded by the ground plane 20, and can obtain omnidirectional radiation characteristics similar to those of a general monopole antenna.

In the antenna of this embodiment, the band blocking characteristic is represented by the U-shaped slot 16 formed in the radiator 10. Band rejection characteristics by the slot 16 will be described with reference to FIG.

3 is a diagram showing the flow of current in the radiator. The current supplied through the feed section 14 flows into the slot 16 due to the coupling. The current started inside the slot 16 by the coupling bypasses the outside of the slot 16 and flows out again through the feed section 14. When the current flows as described above, since the current flowing in the slot and the current flowing outside the adjacent slot have opposite directions as shown in FIG. 3, the electromagnetic field generated by these currents can be canceled out. That is, the slot 16 constitutes a half wave resonant structure so that radiation at the corresponding wavelength can be suppressed.

(ε_r 은 유전체의 비유전률)의 파장으로 전달되므로, 중심 주파수 f_c (파장 λ_c) 에서 대역 저지 특성을 갖도록 하기 위한 슬롯의 길이 (L_slot) 는 다음 식으로 주어진다.At this time, it is possible to determine the wavelength at which the electromagnetic field is canceled by adjusting the length of the slot 16. In general, electromagnetic waves of free-space wavelength λ

Since ε _r is transmitted at the wavelength of the dielectric constant, the length of the _slot L _slot for giving the band blocking characteristic at the center frequency f _c (wavelength λ _c ) is given by the following equation.

As described above, in the present embodiment, the band 16 can be added to the antenna by forming the slot 16 in the radiator 10, and the center frequency of the stop band is adjusted in the UNII band by appropriately determining the slot length. It is possible to derive the band blocking characteristic of. It is also possible to adjust the bandwidth of the stop band by adjusting the width of the slot 16. In general, as the width of the slot 16 becomes wider, the bandwidth of the stop band tends to increase.

Although the present embodiment has been described with reference to the U-shaped slots, the present invention is not limited thereto, and those skilled in the art can easily recognize that various types of slots can be applied without departing from the principles disclosed herein. There will be.

On the other hand, the antenna of the present embodiment has a patch antenna adopting microstrip feeding as the power feeding portion 14 as a basic structure, achieving light weight and miniaturization of the antenna, and having a structure suitable for mass production. In addition, as the substrate 10, FR4, high resistance silicon, glass, alumina, Teflon, epoxy, LTCC, etc. may be used, and in particular, the manufacturing cost may be reduced by using the FR4 substrate.

Performance was tested by actually implementing an antenna according to one embodiment of the invention. The implemented antenna has the same configuration as shown in FIGS. 1 and 2, and the dimensions of each part are shown in the following table. Each dimension is given in mm. On the other hand, the width | variety of the feed part 14 was set to 2 mm, and length was 5.5 mm, and the board | substrate 12 used the FR4 board | substrate of thickness 1.6mm and the dielectric constant 4.4.

W L P _W P _L N _W 16 18 7 11.5 One N _L G _W G _L H _W H _L 2.5 4.5 4 7 1 to 2

4 is a graph showing a simulation value of frequency vs. return loss according to the change of the depth H _L of the recess 22 of the ground plane 20. Looking at the curve for a simple monopole antenna, resonance occurs at a frequency of about 5.5 GHz, with return losses below -10 dB in the 3-8 GHz band. However, when looking at the graph of the antenna formed with the recess 22, resonance occurs around 4.5 GHz and around 9 GHz, which improves impedance matching in the high frequency band of 8 GHz or more compared to a simple monopole antenna, and overall about 3 ~. In the 11 GHz range, return loss values remain below -10 dB. Therefore, it was confirmed that the ultra wide band characteristic can be obtained by the formation of the concave portion 22.

FIG. 5 is a graph showing a simulation value of frequency versus return loss according to the _slot length (L _slot ). Looking at the curve when the slot is not formed, since the return loss value is maintained below -10 dB from about 3 GHz to 11 GHz, it does not exhibit the band blocking characteristic in the UNII band. On the other hand, looking at the curve when the slot is formed, it can be seen that in the 4 GHz, 5 GHz, and 6 GHz band, the return loss value is increased to about -3 dB, indicating the band blocking characteristic. In particular, as the slot length (L _slot ) gets shorter, the center frequency of the stop band increases from 4.3 GHz to 6.5 GHz, and the slot length is given as 14 mm (L _slot / 2 = 7 mm). Shows band-stopping characteristics in the UNII band.

6 is a graph showing measurements of frequency versus return loss with slot and recess formation. Compared with a simple monopole antenna, as shown in the simulation, when only the recess is formed, an impedance matching effect occurs in the high frequency band (approximately 7.9 GHz to 10.5 GHz), thereby extending the bandwidth, and both the recess and the slot If formed, additional band-stopping characteristics appear in the 5 GHz band (UNII band), specifically 4.92 GHz to 5.86 GHz. Therefore, by forming a recess and a slot, it was possible to implement an ultra-wideband antenna having a band blocking characteristic at 4.92 GHz to 5.86 GHz and a bandwidth of 3.1 GHz to 11.25 GHz.

7 is a graph showing a measurement of frequency versus gain according to slot formation. In the case where the slot is not formed, the band blocking characteristic is not shown. However, when the slot is formed, the gain is greatly reduced in the 5 GHz band, indicating that the band blocking characteristic is shown. In addition, gain variation of less than 2.8 dBi was observed in all bands (3 GHz to 11 GHz).

8 is a graph showing a radiation pattern according to the frequency of the implemented antenna. (A), (b) and (c) of FIG. 8 show radiation patterns for 3 GHz, 6 GHz and 9 GHz, respectively, in which the dotted line represents the radiation pattern for the main polarization (co-pol), The radiation pattern for cross-pol perpendicular to the main polarization is shown. Since the antenna implemented as described above uses a ground plane having a small area without overlapping with the radiator, it can be confirmed that the antenna has omnidirectionality similar to a general monopole antenna.

According to the present invention, it is possible to implement an ultra-wideband antenna having a wide bandwidth of 3 GHz to 11 GHz by forming a recess in the ground plane.

In addition, according to the present invention, by forming a slot in the radiator, it is possible to implement an ultra-wideband antenna having a band blocking characteristic.

In addition, according to the present invention, it is possible to implement an ultra-wideband antenna having a omni-directional radiation pattern while being lightweight and compact and suitable for mass production.

Claims (9)

An antenna comprising a substrate, a radiator formed on an upper surface of the substrate, a ground plane formed on a bottom surface of the substrate, and a feeder connected to the radiator. An ultra wide band antenna, wherein a recess is formed in the ground plane. The method of claim 1, And a slot formed in the radiator such that the antenna has band rejection characteristics. The method of claim 2, The slot is U-shaped. The method of claim 2 or 3, When the relative dielectric constant of the substrate is ε _r and the wavelength corresponding to the center frequency f _c of the stop band is λ _c , The slot length is

Phosphorus, ultra-wideband antenna. The method of claim 4, wherein And a center frequency f _c of the stop band is 5 to 6 GHz. The method according to any one of claims 1 to 3, And the ground plane is formed so as not to overlap with the radiator. The method according to any one of claims 1 to 3, And the feed section is a microstrip feed line. The method according to any one of claims 1 to 3, The radiator is rectangular, And a notch formed in a lower edge of the radiator. An antenna comprising a substrate, a radiator formed on an upper surface of the substrate, a ground plane formed on a bottom surface of the substrate, and a feeder connected to the radiator. And an U-shaped slot is formed in the radiator so that the antenna has a band blocking property.

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