KR100606453B1 - A dual polarization antenna using inverted-f antenna - Google Patents

Abstract

The present invention relates to a dual polarized antenna using an inverted F antenna, comprising: a ground plate, a first and second inverted F antennas installed in a phase opposite to one side of the ground plate, and the first and second station It is installed so as to face each other to be perpendicular to the F antenna, it characterized in that it comprises a third and fourth inverted F antenna to be fed so that the phase difference 180 °.

According to the present invention as described above, by using two pairs of inverted F antenna is excellent in the orthogonality, and the polarization characteristics are duplicated into vertical polarization and horizontal polarization to reduce the radio shade area to extend the transmission distance between the reader and the tag and within the service interval It is effective to improve the communication quality at.

Antenna, reverse antenna, dual polarization, RFID,

Description

A dual polarization antenna using inverted antenna

1A and 1B illustrate the appearance of a dual polarized antenna using an inverse F antenna according to the present invention.

2 is a perspective view showing the internal structure of a dual polarization antenna using an inverted F antenna according to the present invention.

3A to 3C are diagrams showing the current direction and current distribution of the antenna in each inverse F antenna.

4A is a graph showing measurement values of the horizontal radiation pattern of the component E _θ in the xy plane of the vertically polarized antenna, and FIG. 4B is a graph illustrating the measurement of vertical radiation pattern of the component E _θ in the yz plane of the vertically polarized antenna. 4C is a simulation result of the horizontal radiation pattern of the E _θ component in the xy plane of the vertically polarized antenna.

5A is a graph showing the horizontal radiation pattern of the component E _φ in the xy plane of the horizontally polarized antenna, and FIG. 5B is a graph showing the vertical radiation pattern of the component E _φ in the xz plane of the vertically polarized antenna. 5c is a simulation result of the horizontal radiation pattern of the component E _φ in the xy plane of the vertically polarized antenna.

6A is a graph measuring the standing wave ratio at the input port of the vertically polarized antenna, and FIG. 6B is a graph measuring the standing wave ratio at the input port of the horizontally polarized antenna.

FIG. 7 is a graph measuring isolation between antennas. FIG.

8 is a graph illustrating simulation results of standing wave ratios of vertically polarized antennas, standing wave ratios of horizontally polarized antennas, and isolation between antennas.

9 is a plan view of a dual polarization antenna using an inverse F antenna according to another embodiment of the present invention.

10 is a plan view of a dual polarization antenna using an inverted F antenna according to another embodiment of the present invention.

<Description of the major reference numerals>

1: dual polarized antenna 10: ground plate

20-1: first station F antenna 20-2: second station F antenna

30-1: third station F antenna 30-2: fourth station F antenna

40: first input port 50: second input port

60: first transmission line 65: first power distribution unit

70: second transmission line 75: second power distribution

100: radome 200: base plate

210: first connector 220: second connector

The present invention relates to a dual polarized antenna, and more particularly, to a dual polarized antenna using an inverse F antenna, which can be implemented by an omni antenna having a dual polarization characteristic using four inverse F antennas, and particularly, a low frequency in a 400 MHz band. The present invention relates to an antenna for logistics RFID reader for port container management as a dual polarization diversity antenna that simultaneously transmits and receives horizontally and vertically polarized waves at a small size of 0.5 wavelength or less.

RFID (Radio Frequency Identification) is a non-contact recognition system that attaches a small chip (tag) to various items to transmit and process the information of the object and the surrounding environment at a radio frequency. Recently, there have been many attempts to apply them to warehouse and port container management. It's going on.

As an example, the RFID system for port container management is serviced on the ground, and since the radio wave shadowing area is generated by various radio wave reflectors such as containers, vehicles, warehouses, etc., the radio wave is shaded using polarization diversity. It is very important that the technology to eliminate the area to minimize communication disturbances.

In order to solve such radio shade areas, omni antennas having excellent dual polarization characteristics are required, and the antennas having such dual polarization characteristics should have mutually orthogonal characteristics between ports, and in general, the separation between ports of two polarized antennas is more than 25 dB. Directional radiation patterns are required.

However, since the current international standardized port container management RFID system is a low-frequency wave in the 433MHz band, it is not practical because of its excessive appearance when using a general antenna technology such as a patch or a yagi antenna to realize polarization diversity.

Therefore, two loop antennas having a rectangular or circle shape are orthogonally disposed so that each loop antenna has a directional radiation pattern in both the x-axis and the ± y-axis in the xy plane, which is the service plane, respectively. As an antenna, a sector service structure for dividing an angle has been proposed.

However, such a loop antenna has a disadvantage in that dual polarized wave radiation, which can realize polarization diversity, is impossible, and it is difficult to secure isolation depending on feeding positions of two orthogonal loop antennas. In other words, in order to ensure isolation between two loops, feed points between loops are possible only at specific positions, and this point has a disadvantage of poor orthogonality in a real environment due to tolerances in manufacturing and operating processes.

The disadvantage of this separation feature is that the transmission power decreases in the communication link between the reader and the tag, which increases the possibility of causing a transmission / reception data bit error, resulting in a reduction in the communication radius.

Therefore, there is an increasing demand for an antenna capable of overcoming the problems of the conventional loop antenna and implementing a dual polarization characteristic having excellent orthogonality, thereby reducing a radio wave shade area and improving communication quality.

The present invention has been made in view of the above problems, and an object of the present invention is to improve the orthogonality by using two pairs of inverse F antennas, and to reduce the radio wave shade area by dualizing polarization characteristics into vertical polarization and horizontal polarization. It extends the transmission distance between and tags and improves the communication quality in the service interval.

According to one aspect of the present invention for achieving the above object, the ground plate, the first and second inverted F antenna is installed so as to face one side of the ground plate, and fed in phase and the first and second A dual polarized antenna using an inverted F antenna is installed so as to face each other so as to be perpendicular to the inverted F antenna, and includes third and fourth inverted F antennas that are fed so as to have a 180 ° phase difference.

The ground plate includes a first input port for feeding the first and second reverse F antennas, one end of which is connected to the first input port, and the other end is branched from a predetermined point to the first and second reverse F antennas. A first transmission line connected to the same length, a second input port for feeding the third and fourth reverse F antennas, and one end thereof connected to the second input port, and the other end is branched at a predetermined point; A second transmission line is formed in which the third and fourth inverse F antennas are connected so as to have a 180 ° phase difference.

In the above, the dual polarization antenna is operated in the band 400 ~ 450 MHz, it is preferable that the first to fourth inverted F antenna is arranged symmetrically with respect to the center of the ground plate to cancel the electromagnetic coupling between the antennas. .

The first and second reverse F antennas may be fed outwardly from the center of the ground plane, and the third and fourth reverse F antennas may be fed outwardly from the outside of the ground plane.

According to another aspect of the present invention, the ground plate, the first inverted F antenna is installed so as to be fed from the center of the ground plate and installed so as to face each other to be perpendicular to the first inverted F antenna, so that there is 180 ° phase difference A dual polarized antenna using an inverted F antenna is provided that includes a second and third inverted F antennas that are fed.

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

1A and 1B illustrate the appearance of a dual polarized antenna using an inverse F antenna according to the present invention.

As shown in FIGS. 1A and 1B, the dual polarized antenna 1 according to the present invention is provided with an antenna structure on a base plate 200 of a lower side and surrounded by a dome-shaped radome (Radome: 100) from wind pressure. It is designed to protect the internal antenna. Radome 100 is an electrical insulator is used to improve the transmission of radio waves and is formed integrally as a whole as a whole, and should be designed to be excellent in wind resistance, water resistance, weather resistance because it is installed outside.

The bottom surface of the base plate 200 is provided with a first connector 210 and a second connector 220 for supplying power to the antenna, the transmission and reception module may be mounted on this surface.

2 is a perspective view showing the internal structure of a dual polarization antenna using an inverted F antenna according to the present invention.

As shown in FIG. 2, the internal structure of the dual polarized antenna 1 is divided into four inverted F antennas 20-1, 20-2, 30-1, and 30-2 on the disk-shaped ground plate 10. And input ports 40 and 50 for supplying power thereto, and transmission lines 60 and 70.

The first and second reverse F antennas 20-1 and 20-2 are installed at positions facing each other, and the first reverse F antenna 20-1 and the second reverse F antenna 20-2 are connected to a ground plate ( 10) Let the distance between the positions installed on it be 0.33λ.

 The third and fourth inverted F antennas 30-1 and 30-2 are installed at positions opposite to each other so as to be perpendicular to the adjacent first and second inverted F antennas 20-1 and 20-2, respectively. The distance between the positions of the third reverse F antenna 30-1 and the fourth reverse F antenna 30-2 on the ground plate 10 is 0.33λ.

The distance between adjacent inverse F antennas is 0.23λ, making it much smaller than conventional RFID antennas.

The first input port 40 is installed at a position corresponding to the first connector 210, and the first input port 40 is disposed between the first input port 40 and the first and second inverted F antennas 20-1 and 20-2. The transmission line 60 is connected to supply the power supplied from the first input port 40 to the first and second inverse F antennas 20-1 and 20-2. The first transmission line 60 is connected through one line and is branched into two lines in the T-type first power distribution unit 65 forming a diverging point, so that the first and second inverse F antennas 20-1, 20-2) respectively. The transmission line between the first input port 40 and the first power divider 65 has a length of λ / 4 for impedance matching, and the first power divider 65 and the first and second reverse F antennas ( The lengths of the transmission lines connecting 20-1 and 20-2 are the same so that the first and second inverted F antennas 20-1 and 20-2 are fed in phase.

The second input port 50 is installed at a position corresponding to the second connector 220, and the second input port 50 is disposed between the second input port 50 and the third and fourth inverted F antennas 30-1 and 30-2. The transmission line 70 is connected to supply the power supplied from the second input port 50 to the third and fourth inverse F antennas 30-1 and 30-2. The second transmission line 70 is connected through one line and is branched into two lines in the T-type second power distribution unit 75 forming a branching point, so that the third and fourth inverse F antennas 30-1, 30-2) respectively. The transmission line between the second input port 50 and the second power distribution unit 75 has a length of λ / 4 for impedance matching, and the second power distribution unit 75 and the third and fourth reverse F antennas ( The transmission line connecting 30-1 and 30-2 has a length difference of λ / 2 so that the first and second inverted F antennas 20-1 and 20-2 are in phase with a phase difference of 180 °. Make sure to feed.

3A to 3C are diagrams showing the current direction and current distribution of the antenna in each inverse F antenna.

Hereinafter, with reference to FIGS. 3A to 3C, a principle of operating as a vertically polarized antenna, a horizontally polarized antenna and a perfect separation between the vertically polarized antenna and the horizontally polarized antenna in the dual polarized antenna according to the present invention will be described.

1. Vertically polarized antenna

When the in-phase input signals are applied to two radiating elements arranged in the x-axis direction on the xz plane of FIG. 1, the first and second inverse F antennas 20-1 and 20-2 are current in the direction of the solid black arrow of FIG. 3a. Is applied. As shown in Fig. 3A, since the x-axis components are opposite vector components at adjacent distances of about 0.2 wavelengths and cancel each other out, horizontal polarization radiation hardly occurs, thus vertical monopole omniantenna of the same vector component on the z-axis. Becomes 0.33 wavelengths of adjacent array antennas to create omnidirectional vertical polarization in the service plane xy plane. That is, it operates as a vertically polarized antenna.

2. Horizontally Polarized Antenna

When an input signal having a phase difference of 180 degrees is applied to two radiation elements arranged in the y-axis direction on the yz plane, the third and fourth inverted F antennas 30-1 and 30-2 move in the direction of the black solid line in FIG. 3A. Current is applied. Since the z-axis is offset from each other by about 0.33 wavelengths and is canceled with each other, vertical polarization radiation hardly occurs. Therefore, due to the current flowing through the radiation element, about 0.2 of the same vector component on the y-axis. It creates horizontal polarization in the xy plane, which is a service plane arranged adjacent to the wavelength, and works like a horizontal dipole antenna. That is, it operates as a horizontal polarized antenna.

3. Separation between antennas

Electromagnetic waves input to the first connector 210 for vertical polarization are surface currents flowing in the first and second inverse F antennas 20-1 and 20-2, which are two radiating elements on the x-axis (black solid line direction). Coupling occurs in the third and fourth inverse F antennas 30-1 and 30-2 arranged on the y-axis by the third and fourth inverse F antennas 30-1 and 30-. In 2), an induced current (red solid line direction) of the same intensity is generated in the same direction. These in-phase induction currents in the same direction are summed over the transmission lines 70 having different lengths having a 180 degree phase difference while reaching the second power distribution unit 75 of the second transmission line 70. Therefore, the second connector 220 of the second input port 50 does not flow out at all. Therefore, electromagnetic waves from the first and second inverted F antennas 20-1 and 20-2 constituting the vertically polarized antenna to the third and fourth inverted F antennas 30-1 and 30-2 constituting the horizontally polarized antennas. Isolation is complete.

Electromagnetic waves input to the second connector 220 for horizontal polarization are surface currents flowing in the third and fourth inverted F antennas 30-1 and 30-2, which are two radiating elements on the y-axis (black solid line direction). By doing so, electromagnetic coupling is generated to the first and second inverted F antennas 20-1 and 20-2 which are the vertically polarized radiating elements arranged on the x-axis. Due to the surface current of the third reverse F antenna 30-1, induced currents in the green solid line direction are generated in the first and second reverse F antennas 20-1 and 20-2, and the fourth reverse F antenna 30. The surface current of -2) causes the first and second inverse F antennas 20-1 and 20-2 to generate induction currents in the solid blue direction to cancel each induced current component so that electromagnetic isolation is inherently made. .

4A is a graph showing measurement values of the horizontal radiation pattern of the component E _θ in the xy plane of the vertically polarized antenna, and FIG. 4B is a graph illustrating the measurement of vertical radiation pattern of the component E _θ in the yz plane of the vertically polarized antenna. 4C is a simulation result of the horizontal radiation pattern of the E _θ component in the xy plane of the vertically polarized antenna.

4A is a graph measuring the radiation pattern of the E _θ component in the xy plane, which is the service plane while rotating the reflector 10 by 360 degrees with the z-axis as the rotation axis, and distortion of the radiation pattern occurs due to measurement error due to low frequency measurement. Overall, the horizontal radiation pattern of the omnidirectional vertical monopole omni antenna can be seen.

Figure 4b is a graph measuring the vertical radiation pattern of the component E _θ in the yz plane perpendicular to the service plane while rotating the reflector 10 by 360 degrees with the y axis as the axis of rotation, and also the vertical radiation pattern of the omnidirectional vertical monopole omni antenna You can see the characteristics.

FIG. 4C is a graph comparing the measured values of the vertically polarized radiation patterns and the results of the finite disc time domain (FDTD) simulation in the environment of FIG. 4A. It can be seen that vertical polarization is mainly generated with little horizontal polarization.

FIG. 5A is a graph showing the horizontal radiation pattern of the component E _φ in the xy plane of the horizontally polarized antenna, FIG. 5B is a graph showing the vertical radiation pattern of the component E _φ in the yz plane of the horizontally polarized antenna, and FIG. 5C. Is a simulation result for the horizontal radiation pattern of the component E _φ in the xy plane of the horizontally polarized antenna.

FIG. 5A shows the xy plane which is the service plane while rotating the reflector 10 by 360 degrees with the z-axis as the rotation axis. It is a graph measuring the radiation pattern of the E _φ component. The distortion of the radiation pattern occurs due to the measurement error due to the low frequency measurement, but the characteristics of the horizontal radiation pattern of the horizontal dipole antenna can be seen.

FIG. 5B is a graph measuring the vertical radiation pattern of the component E _φ in the xz plane perpendicular to the service plane while rotating the reflector 10 by 360 degrees with the x-axis as the rotation axis, and also shows the vertical radiation pattern characteristics of the horizontal dipole antenna. have.

FIG. 5C is a graph comparing a measured value of a horizontal polarized wave radiation pattern and a result of a finite disc time domain (FDTD) simulation in the environment of FIG. 4A. FIG. 5C shows that vertical polarization hardly occurs and horizontal polarization mainly occurs.

In the horizontal polarization radiation pattern of FIG. 5A, the y-axis radiation is about 15 dB lower than the x-axis radiation, so the diversity effect is inferior to the y-axis. Radiation is generated, which is a characteristic of breakthrough diversity performance with a small antenna structure.

6A is a graph measuring the standing wave ratio at the input port of the vertically polarized antenna, and FIG. 6B is a graph measuring the standing wave ratio at the input port of the horizontally polarized antenna.

In the graph of FIG. 6A, standing wave ratios were measured at two frequencies 433.4 MHz and 434.37 MHz near the 433 MHz frequency band of the dual polarization antenna of the present invention. As a result, it was found that the input impedance matching was good.

In the graph of FIG. 6B, standing wave ratios were measured at two frequencies 433.4 MHz and 434.37 MHz near the 433 MHz frequency band of the dual polarization antenna of the present invention, and the impedance matching was found to be 1.63: 1 or less.

FIG. 7 is a graph measuring isolation between antennas. FIG.

FIG. 7 is a measurement of the degree of separation of the influence between the horizontally polarized antennas 30-1 and 30-2 and the vertically polarized antennas 20-1 and 20-2. The frequency band of the dual polarized antenna of the present invention is 433MHz. The separation measurements at the two adjacent frequencies 433.4MHz and 434.37MHz show that -28dB or less is achieved, resulting in almost perfect isolation, below -25dB, which is a requirement for diversity antennas.

FIG. 8 is a graph showing the results of FDTD simulation of standing wave ratios of vertically polarized antennas, standing wave ratios of horizontally polarized antennas, and separation between antennas.

In FIG. 8, when the simulation graphs of standing wave ratios of the vertical polarization antennas 20-1 and 20-2 and the horizontal polarization antennas 30-1 and 30-2 are compared with the graphs measured in FIGS. 6A and 6B, the overall shape is consistent. It can be seen that the separation is also almost similar to the graph measured in FIG.

9 is a plan view of a dual polarization antenna using an inverse F antenna according to another embodiment of the present invention.

The embodiment of Figure 9 is one of the first station F of the vertical polarization xy due to the antenna 20-1 at the center of the grounding plate 10 is disposed at the center as the case of using a vertical polarization antenna plane radiation pattern E _θ The omni pattern is further improved. In this case, since the x-component of the inverted F antenna 20-1 disposed at the center is asymmetric, there exists an xy plane E _φ radiation pattern. Even if such a radiation pattern exists, there is no problem in use.

10 is a plan view of a dual polarization antenna using an inverted F antenna according to another embodiment of the present invention.

The embodiment of FIG. 10 is a method for removing the xy plane E _φ radiation pattern generated according to the embodiment of FIG. 9 and operating it as a purely vertically polarized antenna. 2) are arranged in opposite directions with respect to the center.

9 and 10, the radio wave isolation diagrams of the horizontally polarized antenna and the vertically polarized antenna operate in the same principle as the case where four inverted F antennas are arranged at the edges.

In this embodiment, a transmission line is used as a feed line by way of example. However, the present invention is not limited thereto, and the same characteristics can be obtained using a microstrip line or a dielectric coaxial cable using a PCB substrate, and also a dielectric It is possible to make the size of the antenna much smaller than 0.33 wavelength by filling with and to make various modifications such as to improve the electrical performance by making it larger, and such modification is naturally included in the technical idea of the present invention.

According to the present invention as described above, by using two pairs of inverted F antenna is excellent in the orthogonality, and the polarization characteristics are duplicated into vertical polarization and horizontal polarization to reduce the radio shade area to extend the transmission distance between the reader and the tag and within the service interval It is effective to improve the communication quality at.

Although the present invention has been described in connection with the above-mentioned preferred embodiments, it is possible to make various modifications or variations without departing from the spirit and scope of the invention. Accordingly, the appended claims will cover such modifications and variations as fall within the spirit of the invention.

Claims (6)

Ground plate; First and second inverted F antennas installed to face one side of the ground plate and fed in phase; And A dual polarized antenna using an inverted F antenna, which is installed to face each other to be perpendicular to the first and second inverted F antennas, and includes third and fourth inverted F antennas that are fed with a 180 ° phase difference . The method of claim 1, The ground plate A first input port for feeding the first and second reverse F antennas; A first transmission line having one end connected to the first input port and the other end connected to the first and second inverse F antennas having the same length after being branched at a predetermined point; A second input port for feeding the third and fourth reverse F antennas; And An inverted F antenna having one end connected to the second input port and a second transmission line connected to the third and fourth inverted F antennas 180 degrees out of phase after the other end is branched at a predetermined point. Dual polarized antenna using The method of claim 2, The dual polarized antenna is a dual polarized antenna using an inverted F antenna, characterized in that operating in the 400 ~ 450 MHz band. The method of claim 1, And the first to fourth inverted F antennas are symmetrically disposed with respect to the center of the ground plate to cancel electromagnetic coupling between the antennas. The method of claim 1, The first and second reverse F antennas are fed outward from the center of the ground plane, and the third and fourth reverse F antennas are fed outward from the ground plane toward the center direction. Dual polarized antenna using Ground plate; A first inverse F antenna installed to be fed at the center of the ground plate; And And a second and a third inverted F antennas installed to face each other to be perpendicular to the first inverted F antennas, and to be fed with a 180 ° phase difference.

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