WO2012100468A1

WO2012100468A1 - Omnidirectional indoor antenna system

Info

Publication number: WO2012100468A1
Application number: PCT/CN2011/073340
Authority: WO
Inventors: Yong Ding; Rongguang WU; Jin Pan; Bing Wu; Wen Lu; Shaocong LIU; Qiaoxin LIN; Lihua Zhang; Xiaochun Gao; Yuanbo CHENG
Original assignee: Tongyu Communication Inc.; China Mobile Group Guangdong Co., Ltd.
Priority date: 2011-01-27
Filing date: 2011-04-26
Publication date: 2012-08-02
Also published as: CN102110910A; CN102110910B

Abstract

An omnidirectional indoor antenna (100) includes a metal reflector (1), a vertically polarized antenna (2) located on the metal reflector; and a horizontally polarized antenna (3) orthogonally related to the vertically polarized antenna located above the metal reflector. The vertically polarized antenna is a monopole antenna, including a hollow column (5) with a pyramid configuration (7) at the lower end. The horizontally polarized antenna comprises a plurality of coplanar dipoles (8). The antenna system of the present invention works in a broad frequency band covering all the wireless communication standards including 2G, 3G and 3G+ systems and providing good performance such as high gain and good signal propagation characteristics.

Description

SPECIFICATION

OMNIDIRECTIONAL INDOOR ANTENNA SYSTEM

BACKGROUND OF THE INVENTION

1. FIELD OF THE INVENTION

[0001] The present invention relates to a broadband indoor antenna, and especially to a dual polarized omni- directional indoor antenna.

2. Description of Related Art

[0002] It is well known thant transmission and coverage of indoor signal is very important for wireless communications. To improve the telecommunication performance in an indoor environment, indoor antennas and devices are used for transmitting or receiving wireless signals. For example, a monopole antenna is usually used as a typical indoor antenna for the second generation (2G) wireless communication system. Frequencies of 2G system are generally around 800MHz, 900MHz or lGHz which have relatively longer wavelengths. Wave propagation of these frequencies is less affected in an indoor environment due to the larger wavelength. However, by rapid progress of advanced wireless communications, 3G systems which has higher frequency are widely used. The conventional narrow band indoor antennas don't satisfy these wideband systems.

[0003] The operation frequency of 3G system are relative higher than 2G system, for instance, frequency of the TD-SCDMA system starts from 1880MHz to 2025MHz, and most advanced 3G networks such as TD-LTE is at a higher frequency range from 2570MHz to 2620MHz. The carrier frequencies of these systems are higher, the propagation characteristics are even worse because of the shorter wavelength, and it is more difficult to improve signal coverage for blind zone in the indoor environment. By the tremendous growing in the modern wireless communications, various wireless communication standards including 2G, 3G and 3G+ systems will exist simultaneously. It is desirable to develop a wideband indoor antenna system to cover all the frequency bands above. The proposed antenna should be able to provide these systems with multi services at multi bands.

[0004] Therefore, a dual-polarized wideband indoor antenna is required to overcome the disadvantages of current single-polarized narrow band indoor antenna.

SUMMARY OF THE INVENTION

[0005] A main object of the present invention is to provide an omni- directional indoor antenna which provides better signal coverage, dual-polarized operation and higher antenna gain. The proposed antenna improves transmission and coverage of indoor signals in a wideband frequency for 2G, 3G, and even 3G+ wireless systems.

[0006] To obtain the above object, an omni-directional indoor antenna in the present invention comprises a metal reflector, a first antenna and a second antenna. The first antenna is vertically mounted on the metal reflector and used to radiate or receive RF signals in a vertical polarization. The second antenna is horizontally located above the metal reflector and used to radiate or receive RF signals in a horizontal polarization. Such a dual-polarized wideband indoor antenna system is proposed for 2G, 3G and 3G+ wireless communication system.

[0007] Preferably, the first antenna is a monopole which is configured as a vertical hollow column and an inverted pyramidal part. The hollow vertical column is substantially enclosed by four side metal walls which define the hollow interior thereof. Accordingly, the pyramidal part comprises four side metal walls extending therefrom and tapering off. For a preferable example, the side wall of the vertical column has a rectangular shape. Each of two adjacent rectangular side walls is conjoined by an arc face. The side wall of the pyramidal part has a triangular shape, which abuts against each other to form a tip on the reflector. The first antenna is fixed to the reflector by a first isolating bracket, and is conductively connected to the metal reflector by a metal plate whereby providing earth ground for lightning protection.

[0008] The second antenna comprises a plurality of coplanar dipoles. In a specific example, the dipoles are arranged as a rotational- symmetry array. Each of two adjacent dipoles is spaced with the same angle. The dipoles are perpendicularly placed on top of the first antenna and supported by a second isolating bracket on the side wall of the first antenna. The second antenna provides horizontal polarization of the dual-polarized indoor antenna.

[0009] Two feeding networks are used in the indoor antenna system for the first and second antenna, respectively. The first feeding network comprises a first RF connector positioned on back of the metal reflector and a RF cable connecting to the horizontal polarized antenna. The second feeding network comprises a second RF connector positioned on back of the metal reflector connecting to the vertical polarized antenna.

[0010] The second antenna and its feeding network (namely, the first feeding network described above) are fabricated by a same PCB. A power dividing network of the first feeding network are etched on the PCB board for electrically feeding the dipoles. A main port is used to transfer RF signal from the feeding network to the dipoles by the power dividing network. Preferably, isolation resistors are inserted between branches of the power dividing network.

[0011] Other objects, advantages and novel features of the invention will become more apparent by the following detailed description and drawings of a preferred embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG. 1 is a perspective view of an omni- directional indoor antenna system in accordance with an embodiment of the present invention;

[0013] FIG. 2 is another perspective view of the antenna system in FIG.l ;

[0014] FIG. 3 is a top view of the indoor antenna system in FIG.l ;

[0015] FIG. 4 (a) is a perspective view of the indoor antenna system in another embodiment, herein FIG. 4(b) is an enlarged view of part of FIG. 4(a) with dashed line;

[0016] FIGS 5 shows measured VSWR as a function of frequency for the vertical polarized antenna shown in FIG. 1 ;

[0017] FIG. 6 shows measured VSWR as a function of frequency for the horizontal polarized antenna shown in FIG. 1 ;

[0018] FIG. 7 shows measured isolation between vertical and horizontal polarized antennas;

[0019] FIGS 8(a)-(d) are graphs showing measured radiation pattern in the E-plane for the vertical antenna;

[0020] FIGS 9(a)-(b) are graphs showing measured radiation pattern in the E-plane for the horizontal antenna;

[0021] FIGS 10(a)-(b) are graphs showing measured radiation pattern in the H-plane for the horizontal antenna; and

[0022] FIG. l l(a)-(d) are graphs showing measured radiation pattern in the H-plane for the vertical antenna.

DETAILED DESCRIPTION OF THE INVENTION

[0023] With reference to FIGS 1 to 3, an omni- directional indoor antenna system 100 according to the embodiment of the present invention includes a metal reflector 1, a first antenna 2, and a second antenna 3. The first antenna 2 is vertically mounted on the reflector 1. The second antenna 3 is horizontally located above the reflector 1 and placed orthogonally to the first antenna 2. Thereby, the indoor antenna system 100 is constructed in such way that the vertical and the horizontal antennas provide dual-polarized application. The proposed dual-polarized antenna system satisfies the wireless signal coverage in the indoor environment which supports high gain as well as eliminate the blind zone in a very wideband frequency for the 2G, 3G and 3G+ systems. It comes true only one wideband dual-polarized indoor antenna is needed to replace various narrow band indoor antennas for different wireless communication systems.

[0024] The first antenna 2 is a kind of monopole antenna made of metal and in a shape of hollow case vertically extends upward. In a specific embodiment, the vertical antenna 2 comprises a rectangular column 4 and an inverted pyramid bottom 7. The rectangular column 4 is open at the upper end, and the other end thereof extends downward to form the inverted pyramidal configuration 7. The rectangular column 4 is substantially enclosed by four rectangular side walls 5 and thus defines a hollow space therein. Each of two adjacent side walls 5 are conjoined by an arc face 6. The pyramid configuration 7 correspondingly comprises four side walls 70 which abut against each other and are converged to a tip 71. The tip 71 is near from the reflector 1. Each side wall 70 has an exemplary shape of triangle, but it is not limited to. The antenna 2 may have a variety of shapes, such as circular, elliptical, rectangular, square, polygonal or some other configurations.

[0025] The monopole antenna 2 works in vertical polarization. It is used to transmit or receive wireless signals within all the frequency bands of 2G, 3G and 3G+ systems. The working frequency of the antenna 2 starts from 880MHz to 2690MHz.

[0026] The horizontal antenna 3 comprises a plurality of dipoles 8. Preferably, the dipoles 8 are horizontally arranged in coplanar. More specifically, the dipoles 8 are configured as an integral and rotational- symmetry structure in which the angles between each of two adjacent dipoles are the same.

[0027] In a preferable embodiment, the dipoles 8 are etched on a PCB board 17. The plurality of dipoles 8 and the PCB 17 are configured as an integral and coplanar structure, too. The dipoles 8 are extended outward from the PCB 17 and kept symmetric around the center of the PCB 17. For example, one or two pair(s) of dipoles 8 in a shape of "T" are fabricated in a rotational- symmetry way, and the peripheral of dipoles are located in the same circumference. It should be understood that the dipoles 8 can be designed in various shapes and any number according to the antenna frequency and the specific indoor environment.

[0028] The horizontal antenna 3 is located above the first antenna 2 and provides the horizontal polarization. Its working frequency starts from 1880MHz to 2690MHz, thus covers the frequency band of TD-SCDMA and TD-LTE systems.

[0029] Each dipole 8 is supported on the vertical antenna 2 or on the reflector 1 using a dielectric bracket 9. In a preferable embodiment, the dielectric brackets 9 orthogonally support dipoles 8 on top of the vertical antenna 2 by gripping the sidewall of the vertical column 4. Thereby, the horizontal antenna covers the upper open end of the vertical antenna.

[0030] The vertical antenna 2 is steadily mounted on the reflector 1 using a insulating bracket 10. A metal plate 16 is used to connect the vertical antenna 2 with the reflector 1, thus the vertical antenna 2 is kept ground connection for lightning protection.

[0031] A power dividing network 11 is etched on the PCB board 17 to electrically feed the dipoles 8. In a specific example, three two-way power dividers 19 are used to distribute RF signal from the main port 18 to each dipole 8 in same phase and equal amplitude. An isolating resistor 12 is inserted in the branch circuitries in order to eliminate the coupling between each other.

[0032] The omni-directional indoor antenna system 100 further comprises a first feeding network 13 and a second feeding network 15. The first feeding network 13 comprises an RF connector 130 mounted on the back of the reflector 1, and a RF cable 14 with one end connecting to the horizontal antenna 3 and the other end connecting to the first RF connector 130. Specifically, first end of the cable 14 is engaged with the horizontal antenna 3, extends from the main port 18 of the power dividing network 11 into the hollow interior of the vertical antenna 2, and passes through the sidewall of the vertical antenna 2, then passes through the reflector, and finally, the other end thereof connects with the RF connector 130 on the back of the reflector 1.

[0033] The second feeding network 15 comprises a second RF connector 150 mounted on the back of the reflector 1. One end of the RF connector 150 passes through the reflector 1 to electrically connect with the vertical antenna 2. The end of the RF connector 150 substantially connects to the tip 71 of the pyramidal part 7 of the vertical antenna 2.

[0034] In another embodiment, referring to FIG. 4, the cable 14 is a kind of coaxial feed cable. The cable 14 connects the horizontal antenna 3 with the first RF connector 130, while outer conductor 140 of the coaxial feed cable 14 is conductively connected to the metal reflector 1, which provides the horizontal antenna 3 grounding connection and thus lightning protection.

[0035] The indoor antenna system 100 of the present invention comprises the vertical polarized monopole antenna 2 and the horizontal polarized antenna 3 as mentioned above, thus providing the antenna dual polarization. It works for a very wide frequency band which covers wireless communication standards including 2G, 3G and 3G+ systems with good performance, such as high gain and dual-polarized signal propagation. Furthermore, the horizontal antenna 3 of the antenna system 100 has a plurality of dipoles 8 etched on the PCB board

17, and is supported above the vertical antenna 2, therefore, good polarization isolation is remained and independent control of both polarizations is possible.

[0036] Table 1 demonstrates measured antenna gain as a function of frequency for the vertical antenna 2 and horizontal antenna 3 of the antenna system 100 in

FIGS 1-3. As shown in Table 1, for the vertical antenna 2, the antenna gain is about 2.5dBi and 6.5dBi for frequency bands of 880-960MHz and 1750-2620MHz, respectively. For the horizontal antenna 3, the gain is about

3.5dBi in operating bands of 1900-2350MHz. The gain values indicate desirable indoor antenna system 100 in terms of performance. As a consequence, the indoor antenna system 100 of the present invention has achieved good performance in the frequency bands of the 2G, 3G and 3G+ system. Both senses of polarization radiate efficiently over a broad band.

TABLE 1

The gain values in various frequencies for the indoor antenna system

Frequency (MHz) G_ant (dBi)

Vertical Polarized Antenna

880 2.29

960 2.73

1750 6.17

1800 6.25

1900 7.2

2018 7.22

2350 5.65

2480 6.78

2570 6.84

2620 6.12

Horizontal Polarized Antenna

1900 2.86

2018 3.65

2350 4.36

[0037] FIG. 5 shows measured VSWR (Voltage Standing Wave Ratio) as a function of frequency for the vertical polarized antenna 2. As shown in FIGS. 5(a) and 5(b), the values of VSWR are less than 1.46 within the operating frequencies from 880 to 960MHz, and less than 1.47 within the operating frequencies from 1710 to 2690MHz, respectively. FIG. 6 shows measured VSWR as a function of frequency for the horizontal polarized antenna 3. As shown in FIG. 6, the value of VSWR is less than 1.33 within the operation frequencies from 1880 to 2400MHz. Hence, it can be understood from FIGS 5-6 that the antenna system 100 of the present invention is adapted to broad frequency bands of the 2G, 3G and 3G+ system.

[0038] FIG. 7 shows the isolation between vertical polarized antenna 2 and horizontal polarized antenna 3. As a result, the isolation between two polarizations is less than -25.8dB which indicates that the isolation is sufficiently high to make two polarizations decoupled and operated independently. It is recognized from measurement results above that configuration of antenna system 100 of the present embodiment is appropriate.

[0039] FIGS 8(a)-(d) show the measured radiation patterns in the E-plane at frequencies of 880MHz, 1800MHz, 1900MHz and 2620MHz for the vertical polarized antenna 2, respectively. FIGS 9(a)-(b) show the measured radiation patterns in the E-plane at frequencies of 1900MHz and 2350MHz for the horizontal polarized antenna 3, respectively. As a result, the measured symmetrical E-plane radiation patterns provide the antenna system 100 of the present invention good performance.

[0040] FIGS 10(a)-(b) show the measured radiation patterns in the H-plane at frequencies of 1900MHz and 2350MHz for the horizontal polarized antenna 3, respectively. FIGS l l(a)-(d) show the measured radiation patterns in the H-plane at frequencies of 880MHz, 1800MHz, 1900MHz and 2620MHz for the vertical polarized antenna 2, respectively. As a result, circularity is related to the degree in which the uniform distribution is approximated.

[0041] While the invention has been described in conjunction with specific embodiments, it is evident that numerous alternatives, modifications, and variations will be apparent to those skilled in the art in light of the forgoing descriptions.

Claims

What is claimed is:

1. An omni-directional indoor antenna system comprising:

a metal reflector;

a first antenna vertically mounted on the metal reflector as a vertical polarized antenna; and

a second antenna horizontally located above the metal reflector as a horizontal polarized antenna;

whereby the omni-directional indoor antenna system is dual polarized to radiate or receive RF signals in vertical and horizontal polarization, and able to provide wideband working frequency for 2G, 3G and 3G+ system.

2. The antenna system according to claim 1, wherein the first antenna is a monopole and configured as a vertical hollow case; the second antenna comprises a plurality of dipoles.

3. The antenna system according to claim 2, wherein the first antenna substantially comprises a hollow vertical column and an inverted pyramidal lower part; and the pyramidal lower part extends from a lower end of the vertical column.

4. The antenna system according to claim 3, wherein the hollow vertical column defines a hollow interior substantially enclosed by side walls, each of two adjacent side walls are conjoined by an arc face; accordingly the pyramidal lower part comprises side walls extending therefrom and tapering off; and side walls of the column and the lower part substantially have a shape of polygon, circle, ellipse or irregular configuration.

5. The antenna system according to claim 4, wherein the vertical column substantially has four rectangular side walls conjoined by arc faces therebetween; and the pyramidal lower part has four triangular side walls which abut against to each other and converges to a metal tip.

6. The antenna system according to claim 1, wherein the vertical polarized antenna is fixed to the reflector by a first isolating bracket, and is conductively connected to the metal reflector by a metal plate whereby providing earth ground for lightning protection.

7. The antenna system according to claim 2, wherein the dipoles are placed above the metal reflector and supported on the vertical polarized antenna using a second isolating bracket.

8. The antenna system according to claim 2, wherein the dipoles of the horizontal polarized antenna are configured as a coplanar and integral structure.

9. The antenna system according to claim 7, wherein the dipoles are arranged as a rotational- symmetry array, each of two adjacent dipoles are spaced with the same angle; the dipole is perpendicularly supported on top of the first antenna by means of the second isolating bracket gripping side wall of the first antenna.

10. The antenna system according to claim 8, wherein the horizontal polarized antenna further comprises a PCB board; a power dividing network is etched on the PCB board for electrically feeding the dipoles from a main port; and an isolation resistor is inserted between branches of the power dividing network.

11. The antenna system according to claim 10, wherein the dipoles are etched on the PCB board and substantially extended outward from the PCB board as a coplanar configuration; and the power dividing network comprises at least one power divider distributing same phase and equal amplitude RF signal from the main port.

12. The antenna system according to claim 10, further comprising a first and a second feeding networks respectively feeding the second and first antenna, wherein, the first feeding network comprises a first RF connector and a RF cable, the first RF connector is positioned on back of the metal reflector, the RF cable electrically connects the first RF connector to the horizontal antenna; and the second feeding network comprises a second RF connector, the second RF connector is arranged on back of the metal reflector and electrically connected to the vertical polarized antenna.

13. The antenna system according to claim 12, wherein the feed cable extends from the main port of the power dividing network, enters into the hollow interior and passes through side wall of the vertical polarized antenna, and finally goes through the reflector connecting to the first RF connector.

14. The antenna system according to claim 12, wherein the feed cable is a kind of coaxial cable, of which an outer metal conductor is conductively connected to the metal reflector, thereby providing the horizontal polarized antenna with ground- connection for lightning-protection.

15. An omni- directional indoor antenna comprising:

a metal reflector; and

a vertical polarized antenna and a horizontal polarized antenna orthogonally placed to each other, and both located above the metal reflector;

two feeding networks feeding the vertical and horizontal polarized antennas, respectively;

wherein the vertical polarized antenna is a monopole antenna substantially comprising a hollow case with a pyramid configuration at one end thereof; and the horizontal polarized antenna comprises a plurality of coplanar dipoles.