CN213546564U

CN213546564U - Improved structure for isolation among multiple antennas in MIMO system based on PIFA antenna

Info

Publication number: CN213546564U
Application number: CN202022429690.6U
Authority: CN
Inventors: 俞彬
Original assignee: Yango University
Current assignee: Yango University
Priority date: 2020-10-28
Filing date: 2020-10-28
Publication date: 2021-06-25
Anticipated expiration: 2030-10-28

Abstract

The utility model relates to an improve structure of keeping apart between multiaerial in MIMO system based on PIFA antenna, its characterized in that: the antenna comprises a plurality of PIFA antennas, a plurality of 50-ohm transmission lines with first ends respectively electrically connected with grounding arms of the PIFA antennas, an RLC series resonant circuit which is electrically connected with second ends of the 50-ohm transmission lines in common, and a plurality of groups of transmission lines with electric lengths of e1+ e2 which are electrically connected with feeding ports of the PIFA antennas, wherein each two groups of transmission lines of e1+ e2 are connected with an SIR transmission line in parallel at a node with the electric length of e 1. The utility model discloses can be applied to the isolation promotion of present indoor outer small base station qxcomm technology PIFA antenna, be the design method of a system, can solve the poor problem of isolation between the multiaerial, the design step is clear, the joining of decoupling zero network does not influence the standing wave and the radiation characteristic of the antenna that originally designed, does not need the overall arrangement of change antenna repeatedly.

Description

Improved structure for isolation among multiple antennas in MIMO system based on PIFA antenna

The technical field is as follows:

the utility model relates to an improve structure of keeping apart between multiaerial in MIMO system based on PIFA antenna.

Background art:

with the development of modern communication technology, the application of MIMO technology has been deepened into all common base stations and terminals, and a key index in MIMO technology, namely, the isolation of antennas, when the isolation between antennas is insufficient, the communication capability of the MIMO system will be reduced, and for the MIMO communication system in the industry, generally, the isolation requirement of antennas is above 20dB, and the higher the isolation is, the better the isolation is.

Because the existing base station, terminal and other devices are restricted by the factors of beauty, wind resistance and cost, the requirement on the volume of the device is more and more strict, and meanwhile, the requirement of the MIMO system on the communication rate is higher and higher, the coexistence of multiple antennas such as 4 × 4 and 8 × 8 is more common, so that the antenna spacing is difficult to avoid and the mutual coupling of the antennas is serious, which leads to the serious deterioration of the performance of the MIMO system.

In recent years, researches for reducing the mutual coupling between antennas are increasing, and the researches are mainly divided into neutral line decoupling, resonator decoupling, parasitic resonance unit decoupling, metamaterial decoupling and the like, the former two technologies are designed near an antenna input port, the latter two technologies act on an antenna radiation near field, and the main idea is to provide another coupling path, the coupling effect of which is offset with the original spatial coupling effect of the antenna.

Because the size of the indoor and outdoor small and medium base stations is between the extremely small base station or the terminal and the large outdoor base station, the space reserved for the antennas is critical, the antenna distance can still be larger than the near field radiated by the omnidirectional antenna, the indoor and outdoor small and medium base stations are not as compact as a mobile phone and are not as abundant as a macro station antenna, the antennas meet the performance, the isolation between the antennas of the MIMO system is usually between 10 dB and 20dB, many manufacturers usually achieve the requirement of the isolation through the reasonable layout of the positions of the antennas or the scheme of cross polarization, but the radiation characteristic index of the antennas is usually sacrificed under the condition, the former aims at the zero positions of the antennas to the adjacent antennas to improve the isolation between the antennas by searching the zero points radiated by the antennas, the whole directivity of the antenna radiation is deteriorated, and the latter has good improvement effect on the isolation, but because the efficiency and the coverage range of the horizontally polarized antennas are not, the horizontally polarized antennas occupy a large space in the low frequency band, which is a compromise consideration, and although the two methods improve the isolation between the antennas, the deterioration of other indexes also affects the performance of the MIMO system.

At present, for an omnidirectional antenna, the preferable methods include two methods, namely, a first parasitic radiation array and a second parasitic radiation array which improve coupling between antennas; the method is effective for the MIMO system with a small number of antennas, but once the distance between the multiple antennas can not meet the index, the method is more complicated to design, and the situation of mutual coupling between every two antennas is more complicated; secondly, cutting off the coupling current of the ground; the method also aims at the situation that the design is difficult to carry out once the isolation indexes between multiple antennas cannot be met between every two antennas.

The invention content is as follows:

the to-be-solved technical problem of the utility model lies in providing a can promote the design of the system of the MIMO communication system inter-antenna isolation degree based on PIFA antenna for guarantee that the communication performance of MIMO system can exert the best.

The utility model discloses improve structure of keeping apart between multiaerial in the MIMO system based on PIFA antenna, its characterized in that: the antenna comprises a plurality of PIFA antennas, a plurality of 50-ohm transmission lines with first ends respectively and electrically connected with each grounding arm of the PIFA antennas, an RLC series resonant circuit which is electrically connected with the second ends of the 50-ohm transmission lines in common, and a plurality of groups of transmission lines with the electric length of e1+ e2 which are electrically connected with each feeding port of the PIFA antennas, wherein an SIR transmission line is connected in parallel at the node of each two groups of e1+ e2 transmission lines.

Further, the 50 ohm transmission line has an electrical length that is an integral multiple of 360 deg.

Further, the PIFA antenna, the 50 ohm transmission line, the RLC series resonant circuit, the e1+ e2 transmission line, and the SIR transmission line described above are provided on a metal aluminum board or an FR4 double-layer board.

Furthermore, be equipped with first PCB panel on metal aluminum plate or FR4 double-deck board, the array has 4 PIFA antennas of the same shape on the first PCB panel, each PIFA antenna is "F" shape that the level was laid, and its one end is connected with the first end of 50 ohm transmission lines, and 4 PIFA antennas connect 4 50 ohm transmission lines altogether, and 4 50 ohm transmission lines that are the shape of buckling assemble in the center of PCB panel at the second end and connect RLC series resonance circuit.

Furthermore, the other side of the above-mentioned metal aluminum plate or FR4 double-layer plate is provided with a second PCB plate, the second PCB plate is provided with the above-mentioned 4 sets of transmission lines with electrical length e1+ e2 and 2 SIR transmission lines, the other end of each PIFA antenna is respectively connected with the transmission lines with electrical length e1+ e2, and a SIR transmission line is connected in parallel at the node of the two sets of transmission lines with electrical length e1+ e 2.

Furthermore, the four 50 ohm transmission lines are identical in shape and respectively comprise a first short section, a second short section, a third short section and an oblique section connected with the third short section, wherein the first short section, the second short section and the third short section are perpendicular to each other in sequence, and the tail end of the oblique section is the second end of the 50 ohm transmission line.

Further, the SIR transmission line is linear.

Further, the transmission line shapes of the 2 groups e1+ e2 in the 4 groups of transmission lines with the electrical length of e1+ e2 are the same, and the e1+ e2 transmission line shapes different from the other 2 groups are also different.

The utility model discloses an improve method of keeping apart among the multiantenna in the MIMO system based on PIFA antenna, the multiantenna is separated including a plurality of PIFA antennas among the MIMO system based on PIFA antenna, first end and PIFA antenna connect a plurality of 50 ohm transmission lines and common RLC series resonance circuit with each 50 ohm transmission line second end electricity connection of being connected to each feeding port electricity of PIFA antenna to and the multiunit electric length that is connected with each feeding port electricity of PIFA antenna is e1+ e2, the node of every two sets of e1+ e2 transmission lines has an SIR transmission line in parallel; the second ends of the 50 ohm transmission lines are electrically connected with the RLC series resonance circuit, so that decoupling of adjacent antennas of the working center frequency is formed, due to the symmetrical relation, decoupling is achieved between the adjacent antennas, and rotational symmetry is met; and an SIR transmission line is connected in parallel at the nodes of every two groups of e1+ e2 transmission lines, so that the coupling of non-adjacent antennas is solved.

Furthermore, the transmission line can be realized by a microstrip line, a strip line or a coaxial line.

The utility model discloses can be applied to the isolation promotion of present indoor outer small base station qxcomm technology PIFA antenna, be the design method of a system, can solve the poor problem of isolation between the multiaerial, the design step is clear, the joining of decoupling zero network does not influence the standing wave and the radiation characteristic of the antenna that originally designed, does not need the overall arrangement of change antenna repeatedly.

Description of the drawings:

FIG. 1 is a schematic diagram of the present invention;

fig. 2 is a front perspective view of an embodiment of the present invention;

fig. 3 is a back perspective view of an embodiment of the present invention;

FIG. 4 is a graph of the standing wave of front and rear antennas using the present invention;

fig. 5 is a horizontal radiation pattern of front and rear antennas using the present invention;

fig. 6 is a graph showing the contrast of isolation between the antennas of the post-MIMO system.

The specific implementation mode is as follows:

in order to make the content of the present invention more understandable, the technical solution of the present invention is further described below with reference to the specific embodiments, but the present invention is not limited thereto.

The utility model discloses an improve structure of keeping apart between multiantenna in MIMO system based on PIFA antenna includes a plurality of PIFA antennas (1 in fig. 2, 3 and 4), a plurality of 50 ohm transmission lines (10 in fig. 2) that first end and each grounding arm of PIFA antenna electricity respectively are connected and the common RLC series resonance circuit 7 of being connected with each 50 ohm transmission line second end electricity to and the multiunit electric length that is connected with each feed port electricity of PIFA antenna is the transmission line (13 in fig. 3, 15, 18 and 20) of e1+ e2, and every two sets of node of e1+ e2 transmission line has a SIR transmission line (8 and 9 in fig. 2) in parallel.

The electrical length of the 50 ohm transmission line corresponding to the antenna operating center frequency may be an integer multiple of 360 deg.

The PIFA antenna, 50 ohm transmission line, RLC series resonant circuit, e1+ e2 transmission line and SIR transmission line described above are provided on a metallic aluminum plate or FR4 double-layer board 5.

Specifically, a first PCB plate 6 is arranged on a metal aluminum plate or an FR4 double-layer plate, 4 PIFA antennas (1, 2, 3 and 4 in fig. 2) with the same shape are arrayed on the first PCB plate, each PIFA antenna is in a horizontally-lying "F" shape (as shown in fig. 2), one end (the short-circuit end of the PIFA antenna) is connected with the first end of a 50-ohm transmission line, the 4 PIFA antennas are connected with 4 50-ohm transmission lines 10 in total, and the 4 50-ohm transmission lines which are bent are converged at the center of the PCB plate at the second end and connected with the RLC series resonant circuit 7.

Furthermore, the other side of the above-mentioned metal aluminum plate or FR4 double-layer plate is provided with a second PCB plate 21, the second PCB plate is provided with the above-mentioned 4 sets of transmission lines with electrical length e1+ e2 and 2 SIR transmission lines, the other end (feed end) of each PIFA antenna is respectively connected to the transmission lines with electrical length e1+ e2, and at the node of the two sets of transmission lines with electrical length e1+ e2 (at the node at the electrical length e 1), an

SIR transmission line

8 or 9 on the other side of the PCB plate is connected in parallel through a metalized via hole.

In order to achieve better effect, the four 50 ohm transmission lines are identical in shape and each of the four 50 ohm transmission lines comprises a first short section, a second short section, a third short section and a truncated section which are perpendicular to each other in sequence, and a truncated section connected with the third short section, wherein the tail end of the truncated section is the second end of the 50 ohm transmission line.

Further, the SIR transmission line is linear.

The utility model discloses the design scene of main application is indoor outer built-in omnidirectional base station antenna, and its antenna is the PIFA form and mainly places on an aluminum plate or FR4 double-layer board to guarantee the design decoupling zero of antenna and circuit, the interval between the antenna is in the condition more than half wavelength.

Fig. 1 uses 4 antenna element MIMO as an example, shows the utility model discloses a main thinking, any MIMO communication system more than 4 antennas all can promote the isolation between the system antenna through this method, at first, design the overall arrangement of all PIFA antennas according to MIMO system's demand for the standing wave and the radiation index of all PIFA antennas all reach the optimum, then, through the loading the utility model discloses a decoupling network realizes the decoupling zero between the adjacent antenna array subelement at PIFA antenna's earthing terminal, and finally, through at the input loading decoupling network, the decoupling zero of coupling between the antenna element of all the other.

The antenna set in fig. 1, wherein m1, m2, m3 and m4 represent the feeding ports of 4 PIFA antennas respectively, and n1, n2, n3 and n4 correspond to the grounding arms of the 4 PIFAs respectively, and the grounding arms are connected with a 50 ohm transmission line with 360deg electrical length corresponding to the operating center frequency of the antenna and disconnected from the ground; meanwhile, the other end of the 50 ohm transmission line with the electrical length of 360deg is connected with an RLC series resonant circuit to form the decoupling of the adjacent antenna with the working center frequency (the electrical length of the 50 ohm transmission line can be integral multiple of 360 deg). Due to the certain symmetry of the 4 PIFA antennas (first, second, third and fourth), decoupling can be achieved between the first antenna 1 and the second antenna 2 and between the third antenna 3 and the fourth antenna 4, satisfying rotational symmetry; subsequently, in order to solve the antenna coupling between non-adjacent antennas, a scheme of neutral line decoupling is adopted at the input ports of the first antenna 1, the third antenna 3 and the second antenna 2 and the fourth antenna 4, transmission lines of SIR are respectively connected in parallel, wherein the electrical length e1 needs to be determined according to different antenna designs, so that the decoupling of the non-adjacent transmission lines such as the first antenna 1, the third antenna 3 and the second antenna 2 and the fourth antenna 4 is realized.

The transmission line in fig. 1 can be implemented by various transmission lines such as microstrip line, strip line coaxial line, etc., and the effect is not different.

Fig. 2 and 3 show an embodiment implemented by the method of the present invention, wherein the first antenna 1, the third antenna 3, the second antenna 2 and the fourth antenna 4 are 4 conventional PIFA antennas, i.e. working in wifi-2.4GHz band, 5 is a metallic aluminum plate or FR4 double-layer plate, two sides are windowed and coated with copper, and two sides are connected as reference, the thickness is 1mm, 6 and 21 are PCB plates made of FR4 material, 7 is an RLC series resonant circuit, using lumped parameter components, 8 and 9 are two same SIR transmission line units, 10 is a 50 ohm transmission line with 360 deg. electrical length at center frequency, four antennas are symmetrically connected to 7, the antenna is connected to the transmission line through

position

12, 11 is an input end of the antenna, and is connected to the transmission line 13 (e 1+ e2 transmission line) at the back through a via hole, 13, 15, 18, 20 correspond to the transmission line with e1+ e2, a length of e1 (or e1+360 × n, n =0,1,2 … … integer);

reference numerals

14, 19, 17 and 16 in fig. 3 correspond to input ports connected to the first antenna 1, the third antenna 3, and the second antenna 2 and the fourth antenna 4, respectively, to serve as interfaces for interfacing the four antennas with the MIMO system.

Figure 4 is the standing wave condition picture of using the utility model discloses front and back antenna, at wifi-2.4GHz frequency channel, uses the utility model discloses afterwards, the standing wave performance of antenna does not take place to worsen.

Fig. 5 is a horizontal radiation pattern of front and rear antennas using the present invention; at wifi-2.4GHz frequency channel, use the utility model discloses afterwards, the radiation performance of antenna does not take place to worsen.

Figure 6 is a graph comparing isolation between antennas of a rear MIMO system using the present invention; after the utility model is used in the wifi-2.4GHz frequency band, all isolation is superior to the requirement of 20 dB.

Above figure 4-6 illustrate using the utility model discloses a can improve the isolation between the antenna under the prerequisite of guaranteeing standing wave and radiation characteristic, satisfy the requirement of MIMO system to the spacing degree 20dB between the antenna.

The above is only the preferred embodiment of the present invention, and all the equivalent changes and modifications made according to the claims of the present invention should be covered by the present invention.

Claims

1. An improved structure for isolation among multiple antennas in a MIMO system based on PIFA antennas is characterized in that: the antenna comprises a plurality of PIFA antennas, a plurality of 50-ohm transmission lines with first ends electrically connected with the grounding arms of the PIFA antennas respectively, an RLC series resonant circuit electrically connected with the second ends of the 50-ohm transmission lines in common, and a plurality of groups of transmission lines with the electric length of e1+ e2 electrically connected with the feeding ports of the PIFA antennas, wherein an SIR transmission line is connected in parallel at the node of each two groups of the e1+ e2 transmission lines.

2. The improved structure of isolation between multiple antennas in a PIFA antenna based MIMO system as claimed in claim 1, wherein: the electrical length of the 50 ohm transmission line corresponding to the working center frequency of the antenna is an integral multiple of 360 deg.

3. The improved structure of isolation between multiple antennas in a PIFA antenna based MIMO system as claimed in claim 1, wherein: the PIFA antenna, 50 ohm transmission line, RLC resonant circuit, e1+ e2 transmission line and SIR transmission line are provided on a metallic aluminum board or FR4 dual board.

4. The improved structure of isolation between multiple antennas in a PIFA antenna based MIMO system as claimed in claim 3, wherein: the PCB comprises a metal aluminum plate or FR4 double-layer plate, wherein the metal aluminum plate or FR4 double-layer plate is provided with a first PCB plate, 4 PIFA antennas in the same shape and 2 SIR transmission lines are arrayed on the first PCB plate, the short-circuit end of each PIFA antenna is connected with the first end of each 50-ohm transmission line, the 4 PIFA antennas are connected with the 4 50-ohm transmission lines in total, and the 4 50-ohm transmission lines in the bent shape are converged at the center of the PCB plate at the second end and are connected with the RLC series resonant circuit.

5. The improved structure of isolation between multiple antennas in a PIFA antenna based MIMO system as claimed in claim 4, wherein: the other surface of the metal aluminum plate or the FR4 double-layer plate is provided with 4 groups of transmission lines with the electrical length of e1+ e2, the feed end of each PIFA antenna is respectively connected with the transmission lines with the electrical length of e1+ e2, and the two groups of transmission lines with the electrical length of e1+ e2 are connected with an SIR transmission line on the other surface of the PCB plate in parallel through metalized through holes on a node at the position with the electrical length of e 1.

6. The improved structure of isolation between multiple antennas in a PIFA antenna based MIMO system as claimed in claim 4, wherein: the four 50 ohm transmission lines are identical in shape and comprise a first short section, a second short section, a third short section and a truncated section connected with the third short section, wherein the first short section, the second short section and the third short section are perpendicular to each other in sequence, and the tail end of the truncated section is the second end of the 50 ohm transmission line.

7. The improved structure of isolation between multiple antennas in a PIFA antenna based MIMO system as claimed in claim 4, wherein: the SIR transmission line is linear.

8. The improved structure of isolation between multiple antennas in a PIFA antenna based MIMO system as claimed in claim 5, wherein: the transmission line shapes of 2 groups e1+ e2 in the 4 groups of transmission lines with the electrical length of e1+ e2 are the same, and the e1+ e2 transmission line shapes which are different from the other 2 groups are also different.