KR20080019942A - Helical antenna operating low frequency band having a open stub - Google Patents

Abstract

A helical antenna of a low frequency band having an open stub is provided to increase input resistance and reduce input reactance, thereby improving the efficiency of the antenna and increasing a frequency bandwidth. A helical antenna of a low frequency band includes a radiator(10) and an open stub(20). The radiator is constituted of a first helical body(10a) and a second helical body(10b). The first and second helical bodies are parallel to each other at a predetermined interval. The first and second helical bodies have the same rotation direction. A feed point(25) is formed on an end of the second helical body. The feed point provides a current to the first and second helical bodies. The open stub is joined to the first helical body between the helical bodies. The open stub extends in a length direction of the first helical body in a bar shape. The open stub is spaced from and parallel to a ground(5). An external surface of the open stub is coated by a dielectric material.

Description

HELICAL ANTENNA OPERATING LOW FREQUENCY BAND HAVING A OPEN STUB}

1 is a perspective view of a low frequency band helical antenna having an open stub according to an embodiment of the present invention;

2 is an equivalent circuit diagram in an antenna mode of the helical antenna of FIG. 1;

3 is an equivalent circuit diagram in a transmission mode of the helical antenna of FIG. 1;

4 is an equivalent circuit diagram of the helical antenna of FIG. 1;

5 is a graph showing S21 characteristics of the helical antenna and the conventional monopole antenna of FIG.

6 is a perspective view according to another embodiment of the helical antenna of FIG. 1;

7 is a perspective view of a helical antenna according to another embodiment of the present invention;

8 is a perspective view of a helical antenna according to another embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

 5: ground 10, 110, 210: radiator

10a: first spiral body 10b: second spiral body

20, 120, 220: Open stub 25, 125, 225: Feed point

30, 130: matching circuit 110a: first radiation unit

110b: second radiation portion 210a: whip portion

210b: spiral

The present invention relates to a low-frequency helical antenna having an open stub, and more particularly, to open-stub that can operate in the low frequency band and can be miniaturized, and can prevent the input resistance from decreasing and the input reactance from increasing according to the miniaturization. It relates to a low frequency helical antenna having a.

Recently, due to the development of mobile communication technology, various services that can be used only in limited places such as homes or companies are provided through wireless terminals.

Among these services, the most popular is the Digital Multimedia Broadcasting (DMB) or the Digital Video Broadcasting (Handhelds) (DVB-H), which receive and service broadcast signals in the VHF band.

DMB service or DVB-H service is a mobile multimedia broadcasting service of a new concept combining communication and broadcasting, and it is possible to watch low frequency broadcasting through a wireless terminal.

The DMB service is provided through a mobile terminal having mobility such as a DMB dedicated terminal having a DMB function, a laptop, a mobile terminal, a vehicle terminal, a PDA, a PMP, and classified into a satellite DMB service and a terrestrial DMB service. In Korea, the terrestrial DMB service uses the frequency band of 174 to 216 MHz, and the satellite DMB service uses the S-band 2.630 to 2.655 GHz band, which is higher than the terrestrial DMB.

On the other hand, in general, the length of the antenna is λ / 2 in the case of a dipole antenna and λ / 4 in the case of a monopole antenna, so that the higher the frequency band, the shorter the antenna length, while the lower the frequency band, The length of the antenna becomes longer. That is, since the terrestrial DMB service uses the VHF band, which is a general broadcasting band, not only the antenna length should be longer than that of the satellite DMB, but also the theoretical size is the same as that of a TV antenna. Therefore, an antenna having a length of about 30 cm or more is required, and a shorter length may be configured if the output is high.

However, in the case of terrestrial DMB, its output is very small, about 1 ~ 2KW, and the reason for this small output is because it uses tabs 8, 10, and 12 channels. In case of channel 8, there are channel 7 and 9 back and forth, so if you increase the output, it is difficult to increase the output because it brings interference to both channels. However, as the antenna is installed in the wireless terminal, which is characterized by easy portability and movement, the longer the length becomes, the more inconvenient to use.

Accordingly, antenna developers have recently faced the biggest challenge of reducing the length of terrestrial DMB-only antennas while maintaining reception sensitivity. The length of the terrestrial DMB antenna is known to be impossible to realize performance until recently 15cm or less.

Meanwhile, DVB-H (Digital Video Broadcasting-Handhelds) is a service based on DVB-T (Digital Video Broadcasting- Terrestrial), a digital TV broadcasting standard developed and used mainly in Europe. It is a kind of DVB prepared in consideration of low power, mobility and portability. Since DVB-H also uses a relatively low frequency band, it may have the same problem as an antenna for terrestrial DMB.

Accordingly, it is necessary to develop a small antenna in order to receive signals in the low frequency band mainly used in terrestrial DMB service, DVB-H service and the like.

On the other hand, a small antenna has a disadvantage in that the input resistance is low and the antenna efficiency is lowered, and the input reactance is so large that the bandwidth of the antenna is narrow.

Accordingly, an object of the present invention is to provide a low frequency band helical antenna having an open stub that can operate in a low frequency band and can be miniaturized, and can prevent the input resistance from decreasing and the input reactance from increasing due to the miniaturization. .

The configuration of the present invention for achieving this object, at least a portion of the area is formed twisted in a spiral; It characterized in that it comprises a radiator having an open stub at one end formed parallel to the ground.

The radiator may be formed as a pair of spirals arranged in parallel with a predetermined distance from each other.

The off stub is formed at one end of one side of the spiral body, and a feed point is formed at one end of the other side of the spiral body; The other end of the spiral body and the other side of the spiral body may be connected to each other.

It is preferable that each said spiral body has the same rotation direction.

The radiator may include a first radiating part formed in a spiral shape and a bar-shaped second radiating part formed in parallel with the first radiating part.

A feed point is formed at one side of the first and second radiating parts, and an open stub is formed at another side of the first and second radiating parts; The feed point and the other end of the first radiating portion and the second radiating portion opposed to the open stub may be connected to each other.

It may include a pair of helixes arranged at a predetermined distance from each other, and a pair of swept portions on a rod extending from the ends of the respective threaded portions and arranged in parallel with each other.

The free ends of the respective whip portions may be connected to each other, one side of the spiral portion may be formed with the open stub, and the other side of the spiral portion may have a feed point.

The open stub may be formed in a bar shape extending a predetermined length in the horizontal direction of the radiator.

The open stub is preferably arranged at a predetermined distance from the ground.

A dielectric material may be coated on the outer surface of the open stub.

It may further include a matching circuit mounted on one side of the radiator to move the frequency band.

The helix may have a spiral plane formed of any one of a circle, an oval, a rectangle, and a polygon.

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

1 is a perspective view of a low frequency band helical antenna having an open stub according to an embodiment of the present invention.

The helical antenna of this embodiment includes a spiral radiator 10 and an open stub 20 coupled to one side of the radiator 10.

The radiator 10 is formed of the first and second spiral bodies 10a and 10b arranged in parallel with a predetermined distance from each other. The first and second helixes 10a and 10b have the same rotation direction, but as the starting points of the first and second helixes 10a and 10b are different from each other by 180 degrees, the first and second helixes 10a and 10a are different from each other. The second spiral bodies 10b are spaced apart by the diameter of the spiral. The upper ends of the first spiral body 10a and the second spiral body 10b facing outward are connected to each other.

A feed point 25 is formed at an end of the second spiral body 10b to provide current to the first and second spiral bodies 10a and 10b.

The open stub 20 is coupled to the first helix 10a of the pair of helixes, and is formed in a bar shape extending a predetermined length horizontally in the longitudinal direction of the first helix 10a. The open stub 20 is spaced apart from the ground 5 by a predetermined distance in parallel, and a dielectric material is coated on the outer surface of the open stub 20.

Meanwhile, when a monopole antenna of the same length is twisted in a spiral and manufactured as a helical antenna, the input reactance is increased by coupling between the spirals, and as the input resistance is decreased, the efficiency of the helical antenna is higher than that of the monopole antenna of the same length. Was small. Therefore, when manufacturing the helical antenna, the length of the helical antenna had to be designed longer than the monopole antenna. However, the present helical antenna can be designed to reduce the input reactance because the input reactance changes depending on the length of the open stub 20 and the distance between the open stub 20 and the ground 5. The dielectric material applied to the open stub 20 increases the input resistance. Therefore, it is not necessary to design longer than the length of the monopole antenna at the time of manufacturing the helical antenna, the height of the helical antenna is smaller than the conventional, it is possible to miniaturize the antenna.

Such a helical antenna is shortened by a pair of spiral bodies 10a and 10b and an open stub 20, and can be manufactured to a size of about 8 cm.

Meanwhile, in FIG. 1, the cross-sections of the first and second spiral bodies 10a and 10b are circular, but the cross-sections of the spiral bodies may be formed in various shapes such as squares, ellipses, and polygons.

Such a helical antenna may be interpreted as a sum of an unbalanced mode in which radiation occurs and a transmission mode in which radiation does not occur.

In the antenna mode, as indicated by I _U and VI _U in FIG. 1, current flows in the same direction along each spiral to emit electromagnetic waves. At this time, I _U is a current flowing along the second spiral body 10b connected to the feed point 25 in the antenna mode, and I _U is supplied and flows from the feed point 25. In contrast, VI _U is a current flowing along the first spiral body 10a connected to the open stub 20 and is a current induced by I _U. Where V represents the current amplitude ratio.

In this antenna mode, the current flowing in the open stub 20 is not radiated by the image current of the ground 5 flowing in the opposite direction to the current flowing in the open stub 20. That is, the role of the open stub 20 can be ignored in the antenna mode. Accordingly, in the antenna mode, an equivalent circuit as shown in FIG. 2 is formed, wherein the load impedance Z _{in_u} in the antenna mode is Z _{in_u} = n ² Z _u . Here, n represents the number of spirals, and the load impedance Z _{in_u} of the antenna is increased by the square of the number of twists of the spirals.

In the transmission mode, as shown in FIG. 1, the same current I _b flows in both spirals in the reverse direction, and I _b is supplied from the feed point 25 and flows along both helices to reach the open stub 20. . At this time, in the open stub 20, capacitance is generated between the ground 5 and the ground 5. That is, the open stub 20 operates as a capacitor.

이 된다. Accordingly, the capacitor C and the resistor R are connected in series to the equivalent circuit in the transmission mode shown in FIG. 3. Here, the resistance R represents the loss caused by the dielectric material applied to the surface of the open stub 20. The impedance Z _{in_b} in this transmission mode is

Becomes

4 is an overall equivalent circuit of an antenna in which an antenna mode and a transmission mode are added together.

As illustrated, the parallel mode, the sum of the antenna input impedance (Z _{in_u),} an input impedance of the transmission mode _{(in_b} Z) is the input impedance (Z _in) of the helical antenna. Therefore, the input impedance Z _in of the helical antenna can be adjusted by using the capacitance generated by the open stub 20.

5 is a graph showing S21 characteristics of the helical antenna and the conventional monopole antenna of FIG. Here, the helical antenna and the conventional monopole antenna are both formed of 8 cm.

This S21 characteristic graph is a result of measuring the transmission coefficient between the helical antenna and the conventional monopole antenna with the monopole antenna having a length of 40 cm at a distance of 180 cm from the radiator 10.

As shown, the helical antenna shows an S21 characteristic that is 10 dB or more higher than that of the conventional monopole antenna in the 170-240 MHz band that is the DMB band. Therefore, it can be seen that the helical antenna works better as an antenna than the conventional monopole antenna.

6 is a perspective view according to another embodiment of the helical antenna of FIG.

The helical antenna of this embodiment is formed in almost the same structure as the helical antenna of FIG. However, a matching circuit 30 for moving the operating frequency band of the helical antenna is further provided. In general, each channel of DMB broadcasting is formed at 6MHz, and a total of seven channels are used. Accordingly, the matching circuit 30 may be used to match the operating frequency of the helical antenna to the frequency width of each channel and to move the operating frequency according to the movement of the channel. In FIG. 6, the matching circuit 30 is mounted at the end of the open stub 20, but may be connected to any of the radiators 10.

7 is a perspective view of a helical antenna according to another embodiment of the present invention.

In the helical antenna of the present embodiment, the radiator 110 is formed of a spiral first radiating part 110a and a bar-shaped second radiating part 110b.

Like the helical antenna of FIG. 1, the first radiation unit 110a is formed in a spiral shape twisted in one direction, and a feed point 125 is formed at an end thereof. The second radiation portion 110b is disposed in parallel with the first radiation portion 110a, and an open stub 120 is formed at an end thereof. In addition, the feed point 125 of the first radiation unit 110a and the second radiation unit 110b and the other end opposite to the open stub 120 are connected to each other.

Of course, in the present embodiment, the open stub 120 may be formed at the end of the first radiation unit 110a, and the feed point 125 may be formed at the end of the second radiation unit 110b.

On one side of such a helical antenna, a matching circuit 130 is mounted, as in the above-described embodiment.

8 is a perspective view of a helical antenna according to another embodiment of the present invention.

The radiator 210 of the helical antenna of this embodiment has a spiral portion 210b and a whip portion 210a.

Similar to the helical antenna of FIG. 1, the spiral portions 210b are formed in a pair arranged in parallel with each other at predetermined intervals, and are twisted in the same direction. Here, an open stub 220 is formed at one side of the pair of spiral parts 210b, and a feed point 225 is formed at the other side.

The whip portions 210a are formed in a pair, and each whip portion 210a is formed in a bar shape extending vertically from the end of each threaded portion 210b. Each whip 210a is arranged in parallel with each other, and the free ends thereof are connected to each other.

Meanwhile, although the matching circuit is not mounted in FIG. 8, the matching circuit may be mounted as necessary.

The helical antenna of the present embodiment has a shape in which a helical antenna and a monopole antenna are combined, and the length of the helical antenna is longer than that of the embodiment of FIG. 1, but can exhibit more stable antenna characteristics.

As described above, the helical antenna may include the open stubs 20, 120 and 220 to reduce the input impedance and the input reactance, and further increase the input resistance by applying a dielectric material to the open stubs 20, 120 and 220.

In addition, the antenna can be miniaturized by being formed to a length 1/4 of the conventional monopole antenna. In addition, since the input impedance can be adjusted by adjusting the length of the open stubs 20, 120 and 220 and the distance between the open stubs 20, 120 and 220 and the ground 5, the input impedance can be easily adjusted.

As described above, according to the present invention, the antenna can be miniaturized by being formed to a length 1/4 of the conventional monopole antenna. In addition, since the input resistance can be increased and the input reactance can be reduced, the efficiency of the antenna can be improved and the frequency bandwidth can be increased.

Further, in the detailed description of the present invention, specific embodiments have been described, which should be taken as exemplary, and various modifications may be made without departing from the technical spirit of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the claims below, but also by the equivalents of the claims.

Claims (13)

At least some of the regions are twisted in a spiral; A low frequency band helical antenna having an open stub, the radiator having an open stub formed at one end in parallel to ground. The method of claim 1, The radiator is a low-frequency band helical antenna having an open stub, characterized in that formed in a pair of spirals arranged in parallel with a predetermined distance from each other. The method of claim 2, The off stub is formed at one end of one side of the spiral body, and a feed point is formed at one end of the other side of the spiral body; A low frequency band helical antenna having an open stub, wherein the one end of the spiral body and the other end of the other spiral body are connected to each other. The method of claim 2, The helical antenna of the low frequency band having an open stub, characterized in that each spiral is the same direction of rotation. The method of claim 1, The radiator includes a first radiation portion formed in a spiral shape, and a bar-shaped second radiation portion formed in parallel with the first radiation portion. The low frequency band helical antenna having an open stub. The method of claim 5, wherein A feed point is formed at one side of the first and second radiating parts, and an open stub is formed at another side of the first and second radiating parts; A low frequency band helical antenna having an open stub, wherein the first end of the first radiator and the second radiator and the other end of the feed point and the open stub are connected to each other. The method of claim 1, A low frequency band helical antenna having an open stub, characterized by comprising a pair of spirals arranged at predetermined intervals from each other, and a pair of whips extending from the ends of the respective threaded portions and arranged in parallel with each other. The method of claim 7, wherein The free end of each of the whip portion is connected to each other, the open stub is formed on one side of the spiral portion, the low frequency band helical antenna having an open stub, characterized in that the feed point is formed on the other side of the spiral portion. The method of claim 1, The open stub is a low-frequency band helical antenna having an open stub, characterized in that formed in the form of a bar extending in the longitudinal direction of the radiator longitudinally. The method of claim 1, The open stub is a low frequency band helical antenna having an open stub, characterized in that arranged at a predetermined distance from the ground. The method of claim 1, A low frequency band helical antenna having an open stub, wherein a dielectric material is coated on an outer surface of the open stub. The method of claim 1, A low frequency band helical antenna having an open stub, further comprising a matching circuit mounted on one side of the radiator to move a frequency band. The method of claim 1, The spiral is a low frequency band helical antenna having an open stub, characterized in that the spiral plane is formed of any one of a circle, an ellipse, a square, a polygon.

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