EP2999046B1

EP2999046B1 - Multi-antenna system and mobile terminal

Info

Publication number: EP2999046B1
Application number: EP14817649.8A
Authority: EP
Inventors: Huiqing ZHAI; Tong Li; Guihong LI; Changhong LIANG; Rongdao Yu; Sheng Liu
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2013-06-28
Filing date: 2014-03-06
Publication date: 2019-11-20
Anticipated expiration: 2034-03-06
Also published as: CN104253303A; WO2014206110A1; EP2999046A1; CN104253303B; EP2999046A4

Description

TECHNICAL FIELD

The present invention relates to the technical field of wireless communication and, in particular, to a multi-antenna system and a mobile terminal.

BACKGROUND

An antenna is an important constituent part of a wireless communication system. In a mobile communication terminal, generally, a single antenna is used for transmitting and receiving signals. However, with the mobile communication system continuously upgraded in function, capacity, quality and service business and the complexity of wireless signal propagation environment increased, a channel is affected by environment factors such as the geography, temperature, humidity and the like, so that the propagation of the radio waves is faded greatly in the air, which affects the quality of mobile communication. Hence, it can hardly keep a better communication performance in a complex propagation environment by just using a single antenna, and it needs to use a multi-input multi-output (Multi-Input Multi-Output, MIMO) technique to achieve requirements of a higher transmission speed, a higher channel capacity, a lower transmission power, and overcoming bad transmission environment, and etc. Where, the MIMO technique needs to be realized by a multi-antenna system.
However, mutual interference and electromagnetic interference exist among the multi antennas, which makes electromagnetic compatibility (Electro Magnetic Compatibility, briefed as EMC) goes bad, and leads to a decrease in antenna efficiency, thereby affecting communication quality of a mobile terminal. Moreover, due to miniaturization and ultra thinness of the mobile terminal, a space of the antenna provided in the mobile terminal becomes smaller and smaller. It becomes a problem desiderated to be solved for the arrangement of the antennas in the multi-antenna system of the mobile terminal, how to integrate a plurality of antennas in a limited space, and to prevent a reduced efficiency of the antennas caused by mutual interference and electromagnetic interference between the antennas in the operating state of the multiple antennas.
US 20060044186 A1 discloses a single PIFA antenna which consists of two radiating elements formed of metallic strips, one of which is rectangular and indicated by reference number 8, and the other is L-shaped and indicated by reference number 9. The two strips are arranged on a dielectric substrate 2, separated by a gap 10 and joined in the feed area 7. A continuous strip 3 is arranged on the opposite side of the dielectric substrate with ground plane functions. Two short- circuits 4 and 5, arranged at the short end of the antenna on the edges of the substrate, connect the radiating elements to the ground plane. They make it possible to operate on two bands by establishing two 24 resonant modes. The first resonant mode is generated by strip 9, and the second is generated by the smaller strip 8.
US 20120139793 discloses each antenna radiating/receiving element has a corresponding reference plane, i.e., a ground plane in its corresponding quadrant, each ground plane having a broad, rectangular central portion 60 disposed towards the middle of the board and a narrow elongate portion 50 or strip extending medially from the broad central portion 60 to the corresponding end of the board. There is a split portion 90 free of copper-clad tracing disposed between opposing elongate portions 50 and between opposing broad rectangular portions 60. The elongate portions 50 and broad rectangular portions 60 are a metal layer, while the split part 90 is non-metallic, meaning that there is a gap between the metal ground plane sections on the bottom face of the substrate, which shows the bottom face of the antenna board rotated 90° clockwise from the orientation of the antenna. The extended ground plane arm 50 and the split 90 are utilized to increase the isolation between the antenna elements. A typical value of isolation between two adjacent and similar elements is approximately 13 dB. If two different elements are used, the isolation is approximately a minimum of-15 dB.
US 20100053022 A1 discloses that numbers of antenna elements and coupling elements can be scaled for use in particular applications. System 500 includes antenna elements 501-504 and coupling elements 511-514. Coupling element 511 provides isolation between antenna elements 501 and 502; similarly, coupling element 513 provides isolation between antenna elements 503 and 504. Coupling elements 512 and 514 provide isolation between antenna elements 502 and 503, as well as 501 and 504, respectively. Embodiments can be adapted for use in any of a variety of antenna systems. For example, embodiments can be adapted for use in systems employ dipoles, monopoles, PIFAs, and any other kind of grounded or ungrounded antenna element. Furthermore, various embodiments can be adapted for use in many different arrays, such as 2D, 2.5D, and 3D arrays. FIG. 6 shows exemplary antenna arrays 610, 620, 630, 640, and 650, adapted according to embodiments.

SUMMARY

In view of this, embodiments of the present invention provide a multi-antenna system and a mobile terminal, in order to increase a number of antennas in a dual-band mobile terminal, and meanwhile to achieve a higher isolation degree.
In a first aspect, embodiments of the present invention provide a multi-antenna system, which includes:

two metal ground plates, which include a first metal ground plate and a second metal ground plate, where the first metal ground plate and the second metal ground plate are located in a same azimuth plane without connection to each other, and a distance between the two metal ground plates is greater than or equal to a first preset threshold;
two dielectric substrates, which comprise a first dielectric substrate and a second dielectric substrate, where the first dielectric substrate and the second dielectric substrate are located in a same azimuth plane without connection to each other, the first dielectric substrate is located above the first metal ground plate, the second dielectric substrate is located above the second metal ground plate, and a distance between the two dielectric substrates is greater than or equal to a second preset threshold;
four first planar inverted-F antenna, PIFA, antennas, where each of the first PIFA antennas comprises a radiation patch, a probe type feeder line and a metal shorting pin, and first grooves are disposed on radiation patches of the first PIFA antennas;
two of the first PIFA antennas are disposed on each dielectric substrate of the two dielectric substrates, and first isolated branch knots are disposed between the first PIFA antennas;
the radiation patches of two first PIFA antennas are disposed on the first dielectric substrate, and are connected to the first metal ground plate under the first dielectric substrate via the probe type feeder lines and the metal shorting pins of the first PIFA antennas;
the radiation patches of two first PIFA antennas are disposed on the second dielectric substrate, and are connected to the second metal ground plate under the second dielectric substrate via the probe type feeder lines and the metal shorting pins of the first PIFA antennas; and
the four first PIFA antennas are symmetrical to each other with respect to an XOZ plane and a YOZ plane, wherein an XOY plane is parallel with the azimuth plane in which the first metal ground plate and the second metal ground plate are located in, the XOY plane is perpendicular to the XOZ plane and the YOZ plane respectively, and the XOZ plane is perpendicular to the YOZ plane;
wherein the multi-antenna system further includes:
- a second PIFA antenna, which includes a radiation patch, a probe type feeder line and a metal shorting pin, wherein a second groove is disposed on the radiation patch of the second PIFA antenna;
- wherein the radiation patch of the second PIFA antenna is localized 1mm - 5mm above at least one dielectric substrate of the two dielectric substrates, and is connected to the metal ground plate under the at least one dielectric substrate, via the probe type feeder line and the metal shorting pin of the second PIFA antenna; and
- wherein second isolation branch knots are disposed between the first PIFA antennas and the second PIFA antenna.

In combination of the first aspect, in a first possible implementation of the first aspect, where the first preset threshold is 30mm.
In combination of the first aspect or its first possible implementation, in a second possible implementation of the first aspect, the second preset threshold is 40mm.
In combination of the first aspect, in a third possible implementation of the first aspect, there are two second PIFA antennas, the two second PIFA antennas are disposed 1mm-5mm above the first dielectric substrate and the second dielectric substrate respectively, and the four first PIFA antennas are symmetrical to the two second PIFA antennas with respect to the XOZ plane and the YOZ plane.
In combination of the first aspect or any one of its first to third possible implementation, in a fourth possible implementation of the first aspect, the first grooves are U-type grooves.
In combination of the first aspect or any one of its first to fourth possible implementation, in a fifth possible implementation of the first aspect, the second groove is a polygonal-shape groove.
In combination of the first aspect or any one of its first to fourth possible implementation, in a sixth possible implementation of the first aspect, the radiation patches of both the first PIFA antennas and the second PIFA antennas are rectangular.
In combination of the first aspect or any one of its first to sixth possible implementation, in an seventh possible implementation of the first aspect, a dielectric constant of the dielectric substrates is between 1 and 9.8.
In a second aspect, the embodiments of the present invention provide a mobile terminal, which includes: a mobile terminal body and any one of the above mentioned multi-antenna
systems, where the mobile terminal body is connected with the multi-antenna system, and the multi-antenna system is configured to transmit and receive signals for the mobile terminal body.
The multi-antenna system and the mobile terminal provided by the above embodiments achieves a dual band by PIFA antennas on the dielectric substrates and grooves on the radiation patches of the antennas, improves an isolation degree between the antennas by disposing isolated branch knot between the antennas, and further improves the isolation degree between the antennas on the two dielectric substrates by two independent dielectric substrates and a metal ground plate. In addition, the PIFA antennas are used, so that the multi-antenna system and the mobile terminal can increase the number of antennas in a limited space as many as possible.

BRIEF DESCRIPTION OF DRAWINGS

To describe the technical solutions in embodiments of the present invention more clearly, the following briefly introduces the accompanying drawings needed for describing the embodiments. Apparently, the accompanying drawings in the following description illustrate merely some embodiments of the present invention, and persons of ordinary skill in the art may still derive other drawings from these accompanying drawings without creative effort.

FIG. 1 is a structural schematic diagram of a multi-antenna system according to an embodiment of the present invention;
FIG. 2 is a structural schematic diagram of a multi-antenna system according to another embodiment of the present invention;
FIG. 3 is a structural schematic diagram of a multi-antenna system according to another embodiment of the present invention;
FIG. 4 is a schematic diagram of the multi-antenna system shown in FIG. 3 in an XOY plane;
FIG. 5a is a front view of antenna 1 in the multi-antenna system shown in FIG. 3;
FIG. 5b is a side view of FIG. 5a;
FIG. 6a is a front view of antenna 5 in the multi-antenna system shown in FIG. 3;
FIG. 6b is a side view of FIG. 6a;
FIG. 7a and FIG. 7b are S-parameter simulation diagrams of the multi-antenna system shown in FIG. 3 in a frequency band of 2.53GHz-2.62GHz;
FIG. 8a and FIG. 8b are S-parameter simulation diagrams of the multi-antenna system shown in FIG. 3 in a frequency band of 3.45 GHz -3.6GHz;
FIG. 9a is a simulation radiation pattern of antenna 1 of the multi-antenna system shown in FIG. 3 at 2.58GHz;
FIG. 9b is a simulation radiation pattern of antenna 1 of the multi-antenna system shown in FIG. 3 at 3.5GHz;
FIG. 10a is a simulation radiation pattern of antenna 5 of the multi-antenna system shown in FIG. 3 at 2.58GHz;
FIG. 10b is a simulation radiation pattern of antenna 5 of the multi-antenna system shown in FIG. 3 at 3.5GHz; and
FIG. 11 is a structural schematic diagram of a mobile terminal according to another embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

To make the objectives, technical solutions, and advantages of the present invention clearer, the following comprehensively describes the present invention with reference to the accompanying drawings. Apparently, the described embodiments are merely a part rather than all embodiments of the present invention. All other embodiments obtained by persons of ordinary skill in the art based on embodiments of the present invention without creative effort shall fall within the protection scope of the present invention.
FIG. 1 is a structural schematic diagram of a multi-antenna system according to an embodiment of the present invention. In the present embodiment, the multi-antenna system includes: two metal ground plates, two dielectric substrates, four first kind of PIFA antennas and four isolated branch knots.
The two metal ground plates include metal ground plate 8a and metal ground plate 8b, and the metal ground plate 8a and metal ground plate 8b are located in a same azimuth plane, where a distance between the two metal ground plates is greater than or equal to a first preset threshold, e.g. 30mm, which can reduce coupling between antennas 1, 3 on the dielectric substrate 7a and antennas 4, 6 on the dielectric substrate 7b, and can improve an isolation degree between antennas 1, 3 and antennas 4, 6.
The two dielectric substrates include dielectric substrate 7a and dielectric substrate 7b, where the dielectric substrate 7a and the dielectric substrate 7b are located in a same azimuth plane, the dielectric substrate 7a is located above the metal ground plate 8a, and the dielectric substrate 7b is located above the metal ground plate 8b. A distance between the two dielectric substrates is greater than or equal to a second preset threshold, e.g. 40mm, which can reduce the coupling between the antennas 1, 3 on the dielectric substrate 7a and the antennas 4, 6 on the dielectric substrate 7b, and can improve the isolation degree between the antennas 1, 3 and the antennas 4, 6.
The four first kind of PIFA antennas includes: the antenna 1, the antenna 3, the antenna 4, and the antenna 6, and each of the first kind of PIFA antennas includes: a radiation patch, a probe type feeder line and a metal shorting pin, for example, the antenna 1 includes radiation patch 1d, probe type feeder line 1a and metal shorting pin 1b (see below and description about FIG. 3 - FIG. 5b).
First grooves are disposed on the radiation patches of the first kind of PIFA antennas. A shape of the first grooves is not limited herein, as long as it can enable an antenna to which it belongs work in a new frequency band. For example, a U-type groove 1c is etched on the radiation patch 1d of the antenna 1.
Two first kind of PIFA antennas are disposed on each of the two dielectric substrates, and an isolated branch knot is disposed between the first kind of PIFA antennas.
As shown in FIG. 1, the antenna 1 and the antenna 3 are disposed on the dielectric substrate 7a, and the antenna 4 and the antenna 6 are disposed on the dielectric substrate 7b. The isolated branch knot 11 and the isolated branch knot 12 are disposed between the antenna 1 and the antenna 3 and between the antenna 4 and the antenna 6, respectively.
Specifically, the isolated branch knot 11 and the isolated branch knot 12 are printed on the dielectric substrate 7a, and the dielectric substrate 7b. Taking the isolated branch knot on the dielectric substrate 7a as an example, the isolated branch knot 11 is an E-type isolated branch knot, including a horizontal branch knot 111, a first longitudinal branch knot 112, a second longitudinal branch knot 113, and a third longitudinal branch knot 114. Where, the horizontal branch knot 111 is located at a side of the antenna 1 and the antenna 3 which is close to the dielectric substrate 7b, and is configured to isolate the antennas 1, 3 from the antennas 4, 6. The first longitudinal branch knot 112 is located between the antenna 1 and the antenna 3, to isolate the antenna 1 from the antenna 3; the second longitudinal branch knot 113 and the third longitudinal branch knot 114 are located at the lateral side of the antenna 3 and the lateral side of the antenna 1 respectively, to isolate the antenna 1, the antenna 3 from the external.
The isolated branch knot 12 is a T-type isolated branch knot, including a horizontal branch knot 121 and a longitudinal branch knot 122, which interlocks with the isolated branch knot 11, so that the antenna 1 and the antenna 3 are enveloped in a space formed by the horizontal branch knot 121, the horizontal branch knot 111 and the longitudinal branch knot 122, the first longitudinal branch knot 112, the second longitudinal branch knot 113 and the third longitudinal branch knot 114.
The radiation patches of the antenna 1 and the antenna 3 on the dielectric substrate 7a are disposed on the dielectric substrate 7a, and are connected to the metal ground plate 8a under the dielectric substrate 7a via the probe type feeder lines and the metal shorting pins thereof. For example, the radiation patch 1d of the antenna 1 is connected to the metal ground plate 8a via the probe type feeder line 1a and the metal shorting pin 1b.
Similarly, the radiation patches of the two first kind of PIFA antennas on the dielectric substrate 7b are disposed on the dielectric substrate 7b, and are connected to the metal ground plate 8b under the dielectric substrate 7b via the probe type feeder lines and the metal shorting pins of the first kind of PIFA antennas.
The four first kind of PIFA antennas: the antenna 1, the antenna 3, the antenna 4 and the antenna 6 are symmetrical to each other with respect to XOZ plane and YOZ plane.
The multi-antenna system provided by the present embodiment reduces coupling of the antennas on the two dielectric substrates in the multi-antenna system in two frequency bands, by disposing two independent dielectric substrates and two correspondingly parallel and independent metal ground plates, and it can achieve a dual band by disposing the four symmetric first kind of PIFA antennas on the dielectric substrates and disposing grooves on the radiation patches of the antennas. In addition, it can further improve the isolation degree of the multi-antenna system by disposing the isolated branch knot between the antennas. Moreover, the PIFA antennas are small, and the antenna system can increase the number of antennas in a limited space and can achieve a higher isolation degree. Additionally, the PIFA antenna has a low cost, is easy to be manufactured, and is easy to be integrated with the microwave circuits at the radio frequency front-end.
FIG. 2 is a structural schematic diagram of a multi-antenna system according to another embodiment of the present invention. The present embodiment is similar to that according to FIG. 1, a second kind of PIFA antenna is disposed on the dielectric substrate 7b, i.e., an antenna 5, and that the dielectric substrate 7b has 4 isolated branch knots, including two T-type isolated branch knots 9 and two π-type isolated branch knots 10 (referring to the embodiment according to FIG. 3 in the below).
The T-type isolated branch knots 9 are printed between antenna 4 and antenna 5, as well as between antenna 5 and antenna 6, which can effectively reduce coupling between adjacent antennas in high frequency band.
The π-type isolated branch knots 10 are printed between antenna 4 and antenna 5, as well as between antenna 5 and antenna 6, which can effectively reduce coupling between adjacent antennas in low frequency band.
Where, the antenna 5 includes a radiation patch 5d, a probe type feeder line 5a and a metal shorting pin 5b, and the radiation patch 5d is above the dielectric substrate 7b. Due to that there is a certain distance between the antenna 5 and the dielectric substrate 7b, and the antenna 5 and its adjacent antenna 4 and antenna 6 are not in a same plane, it can effectively reduce the coupling of the adjacent antenna 4 and antenna 6 in both high frequency band and low frequency band. For example, the distance between the antenna 5 and the dielectric substrate 7b is 1mm~5mm, which improves the isolation degree between the antenna 5 and the antennas 4, 6.
In addition, a second groove is etched on the radiation patch 5d, such as a polygonal-shape groove 5c, and the antenna 5 is located between the antenna 4 and the antenna 6, which further reduce the coupling between the antenna 4 and the antenna 6 effectively.
In the aforementioned embodiments, a dielectric constant of the dielectric substrate 7a and the dielectric substrate 7b may be between 1 and 9.8.
FIG. 3 is a structural schematic diagram of a multi-antenna system according to another embodiment of the present invention. In the present embodiment, the multi-antenna system includes six PIFA antennas, eight isolated branch knots, two metal ground plates and two dielectric substrates.
Where, there are four first kind of PIFA antennas: an antenna 1, an antenna 3, an antenna 4 and an antenna 6, and two second kind of PIFA antennas: an antenna 2 and an antenna 5.
The isolated branch knots includes four T-type isolated branch knots 9 and four π-type isolated branch knots 10.
Two metal ground plates include metal ground plate 8a and metal ground plate 8b.
Two dielectric substrates include dielectric substrate 7a and dielectric substrate 7b.
The dielectric substrate 7a is located above the metal ground plate 8a, and the dielectric substrate 7b is located above the metal ground plate 8b. A foam support layer may be used to support between the dielectric substrate 7a and the metal ground plate 8a, as well as between the dielectric substrate 7b and the metal ground plate 8b.
A distance between the dielectric substrate 7a and the dielectric substrate 7b is 40mm, and a distance between the metal ground plate 8a and the metal ground plate 8b is 30mm. The isolation degree between the antennas on the surface of substrate 7a and the antennas on the surface of substrate 7b can be adjusted by changing the distance between the dielectric substrate 7a and the dielectric substrate 7b, and the distance between the metal ground plate 8a and the metal ground plate 8b.
The antenna 1, the antenna 2 and the antenna 3 are disposed on the dielectric substrate 7a, and the antenna 4, the antenna 5 and the antenna 6 are disposed on the dielectric substrate 7b. As shown in FIG. 4, the multi-antenna system provided by the present embodiment is symmetrical to each other with respect to the XOZ plane and the YOZ plane.
The structure and principle of the antenna 1 is the same as those of the antenna 3, the antenna 4 and the antenna 6, and the following takes the antenna 1 as an example to describe the first kind of PIFA antennas.
Referring to FIG. 3, the antenna 1 includes a radiation patch 1d, a probe type feeder line 1a and a metal shorting pin 1b. Referring to FIG. 5b, the radiation patch 1d is connected to the metal ground plate 8a via the probe type feeder line 1a and the metal shorting pin 1b. The radiation patch 1d has a length of 15.1mm, and a width of 9mm, forming a working frequency band of the antenna 1 in 2.53GHz-2.62GHz, and a low frequency working frequency band needed by antenna 1 can be obtained by adjusting the size of the radiation patch 1d.
A U-type groove 1c is etched on the radiation patch 1d, and as shown in FIG. 5a, for the U-type groove 1, a width c1 =8mm, a length c2=13mm, the groove width c3=0.5mm, and a distance c4 between the bottom of the U-type groove 1c and the bottom of the radiation patch 1d =0.6mm, and a distance between its left side and the left side of the radiation patch and a distance between its right side and the right side of the radiation patch are c5=c6=0.5mm. The U-type groove 1c forms the working frequency band of the antenna 1 in 3.44GHz-3.6GHz, and a high frequency working frequency band needed by the antenna 1 can be obtained by adjusting the sizes of c1 and c2. In such a way, the antenna 1 covers two working frequency bands in both 2.53GHz-2.62GHz and 3.44 GHz - 3.6GHz.
The probe type feeder line 1a has a radius of 0.7mm and a height of 8.4mm, and a distance between its circle center and the bottom of the radiation patch is 10.1mm.
The metal shorting pin 1b has a radius of 0.9mm and a height of 8.4mm, and a distance between its circle center and the circle center of the probe type feeder line 1a is 3.8mm.
The working bandwidth and impedance matching characteristic of the antenna 1 can be adjusted by adjusting the radiuses, positions and heights of the probe type feeder line 1a and the metal shorting pin 1b.
The structure and principle of the antenna 2 is the same as those of the antenna 5, and the following takes the antenna 5 as an example to describe the second kind of PIFA antennas.
As shown in FIG. 3, FIG. 4, FIG. 6a and FIG. 6b, the antenna 5 includes a radiation patch 5d, a probe type feeder line 5a and a metal shorting pin 5b. The radiation patch 5d is connected to the metal ground plate 8b via the probe type feeder line 5a and the metal shorting pin 5b. The radiation patch 5d is located above the dielectric substrate 7b, and has a distance to the dielectric substrate 7b of 1mm~5mm.
The radiation patch 5d has a length of 15.2mm, and a width of 10mm, which forms a working frequency band of an antenna in 2.52GHz-2.63GHz, and it can get a low frequency working frequency band needed by the antenna 5 can be obtained by adjusting the size of the radiation patch 5d.
As shown in FIG. 4 and FIG. 6a, a polygonal-shape groove 5c is etched on the radiation patch 5d, the polygonal-shape groove 5c has d1=8mm, d2=14mm, d3=1mm, d4=1.7mm, and a groove width d5=0.5mm, a distance between the bottom of the polygonal-shape groove 5c and the bottom of the radiation patch 5d d6=0.7mm, and a distance between its left side and the left side of the radiation patch and a distance between its right side and the right side of the radiation patch are d7=d8=0.5mm. The polygonal-shape groove 5c forms the working frequency band of the antenna 5 in 3.45GHz-3.61GHz, and a high frequency working frequency band needed by the antenna 5 can be obtained by adjusting the sizes of dl, d2, d3 and d4. In such a way, the antenna 5 covers two frequency bands in both 2.52GHz-2.63GHz and 3.45 GHz -3.61GHz.
The probe type feeder line 5a has a radius of 0.7mm, and a height of 10.4mm, and a distance between its circle center and the bottom of the radiation patch is 10.2mm.
The metal shorting pin 5b has a radius of 0.9mm, and a height of 10.4mm, and a distance between its circle center and the circle center of the probe type feeder line 5a is 3.8mm.
The working bandwidth and impedance matching characteristic of the antenna 5 can be adjusted by adjusting the radiuses, positions and heights of the probe type feeder line 5a and the metal shorting pin 5b.
The dielectric substrate 7a has a length of 70mm, and a width of 40mm, and a height of 0.9mm, and a relative dielectric constant ε_r =4.4, and the metal ground plate 8a has a length of 70mm, a width of 45mm, and a distance of 7.5mm to the dielectric substrate 7a.
As shown in FIG. 4, the radiation patches of the antenna 1 and the antenna 3 are printed at both sides of the dielectric substrate 7a, the distance between the antenna 1 and the antenna 3 is W1=56mm, and the antenna 2 is placed between the antenna 1 and the antenna 3. Due to that the antenna 2 has a same working frequency with those of the antenna 1 and the antenna 3, the coupling between the antenna 1 and the antenna 3 can be reduced, and the isolation degree between the antenna 1 and the antenna 3 can be increased.
Both a distance between the antenna 1 and the antenna 2, and a distance between the antenna 2 and the antenna 3 are W2=28mm.
T-type isolated branch knots 9 and inverted π-type isolated branch knots 10 are printed on the dielectric substrate 7a. Longitudinal branch knots of the T-type isolated branch knots 9 and the inverted π-type isolated branch knots 10 are located between the antenna 1 and the antenna 2 and between the antenna 2and the antenna 3, and horizontal branch knots of the T-type isolated branch knots 9 and the inverted π-type isolated branch knots 10 are located at both sides of the antenna 1, the antenna 2 and the antenna 3.
The T-type isolated branch knot 9 includes a horizontal branch knot 91 and a longitudinal branch knot 92, where the horizontal branch knot 91 is closely next to an upper edge of the substrate 7a, with a distance of 1mm to the side edge of the substrate, and the horizontal branch knot 91 has a length of 28mm and a width of 1mm. The longitudinal branch knot 92 has a length of 15mm and a width of 2mm. By adjusting the size and position of the T-type isolated branch knot 9, the isolation degree between the antenna 1 and the antenna 2 in high frequency, as well as the isolation degree between the antenna 2 and the antenna 3 in high frequency can be adjusted.
The π-type isolated branch knot 10 includes a horizontal branch knot 101, a first longitudinal branch knot 102 and a second longitudinal branch knot 103. The π-type isolated branch knot 10 is placed invertedly, and its horizontal branch knot 101 has a distance of 2.9mm to the bottom edge of the dielectric substrate 7a, and both sides of the horizontal branch knot 101 are closely next to the side edges of the dielectric substrate 7a. The horizontal branch knot 101 has a length of 33mm and a width of 0.5mm. The longitudinal branch knot 102 has a length of 11.5mm and a width of 1mm, and the longitudinal branch knot 103 has a length of 7mm and a width of 2.375mm. By adjusting the size and position of the π-type isolated branch knot 10, the isolation degree between the antenna 1 and the antenna 2 in low frequency, as well as the isolation degree between the antenna 2 and the antenna 3 in low frequency can be adjusted.
The radiation patch of the antenna 2 is located above the dielectric substrate 7a, and has a distance of 1mm-5mm to the dielectric substrate 7a. By adjusting this distance, the isolation degree between the antenna 1 and the antenna 2 in high frequency and low frequency, as well as the isolation degree between the antenna 2 and the antenna 3 in high frequency and low frequency can be adjusted.
Since the multi-antenna system is totally symmetric with respect to the XOZ plane, the dielectric substrate 7b, the metal ground plate 8b, the antenna 3∼ the antenna 6 and the isolated branch knots in the lower half part of the multi-antenna system have the same structures as those aforementioned, which will not be repeated herein.
The multi-antenna system provided by the present embodiment can work in the frequency bands of both 2.53-2.62GHz and 3.45-3.6GHz, and the isolation degree can reach under -20dB in the working frequency band, requirements of a new generation mobile communication system can be met. By changing sizes and positions of a radiation patch, a U-type groove, a polygonal-shape groove, a coaxial feeding unit, a shorting unit and an isolated branch knot, a resonance working point of an antenna can be adjusted, and different application requirements can be met.
Parameter s simulation results of the multi-antenna system as shown in FIG. 3 are as shown in FIG. 7a ∼ FIG. 7b and FIG. 8a ∼ FIG. 8b.
In the FIG. 7a, S11 is impedance matching characteristic of the antenna 1, S22 is impedance matching characteristic of the antenna 2, S33 is impedance matching characteristic of the antenna 3, and S12 is the isolation degree between the antenna 1 and the antenna 2. It can be seen that, the working frequency range of the antenna 1 and the antenna 3 is 2.535GHz -2.615GHz, and the working frequency range of the antenna 2 is 2.528GHz -2.625GHz, and S12 is lower than -20dB.
In FIG. 7b, S13 is the isolation degree between the antenna 1 and the antenna 3, S14 is the isolation degree between the antenna 1 and the antenna 4, S15 is the isolation degree between the antenna 1 and the antenna 6, S16 is the isolation degree between the antenna 1 and the antenna 6, and S26 is the isolation degree between the antenna 2 and the antenna 6. It can be seen that, in the working frequency band of 2.53GHz-2.62GHz, S13, S14, S15, S16 and S26 are all lower than -20dB.
In the FIG. 8a, S11 is impedance matching characteristic of the antenna 1, S22 is impedance matching characteristic of the antenna 2, S33 is impedance matching characteristic of the antenna 3, and S12 is the isolation degree between the antenna 1 and the antenna 2. It can be seen that, the working frequency range of the antenna 1 and the antenna 3 is 3.44GHz -3.6GHz, and the working frequency range of the antenna 2 is 3.45GHz -3.66GHz, and S12 is lower than -20dB.
In FIG. 8b, S13 is the isolation degree between the antenna 1 and the antenna 3, S14 is the isolation degree between the antenna 1 and the antenna 4, S15 is the isolation degree between the antenna 1 and the antenna 6, S16 is the isolation degree between the antenna 1 and the antenna 6, and S26 is the isolation degree between the antenna 2 and the antenna 6. It can be seen that, in the working frequency band of 3.45GHz-3.6GHz, S13, S14, S15, S16 and S26 are all lower than -20dB.
According to the above FIG. 7a ∼ FIG. 8b, it can be seen that, the multi-antenna system as shown in FIG. 3 has a better impedance matching effect in the working frequency bands of both 2.53GHz-2.62GHz and 3.45GHz-3.6GHz, where the bandwidth at 2.58GHz is 90MHz, and the impedance bandwidth at 3.5GHz is 150MHz. Further, it has higher isolation degrees in the frequency bands of both 2.53GHz-2.62GHz and 3.45GHz -3.6GHz, which are both lower than -20dB.
Radiation pattern simulation results of the multi-antenna system as shown in FIG. 3 are as shown in FIG. 9a ∼ FIG. 9b and FIG. 10a ∼ FIG. 10b.
FIG. 9a is a radiation pattern of the antenna 1 at 2.58GHz;
FIG. 9b is a radiation pattern of the antenna 1 at 3.5GHz;
FIG. 10a is a radiation pattern of the antenna 5 at 2.58GHz; and
FIG. 10b is a radiation pattern of the antenna 5 at 3.5GHz.
Due to that the multi-antenna system as shown in FIG. 3 is symmetrical about XOZ plane and YOZ plane respectively, the S-parameters and radiation patterns of other antennas have same simulation results with the aforementioned, which will not be repeated herein.
FIG. 11 is a structural schematic diagram of a mobile terminal according to another embodiment of the present invention. The mobile terminal in the present embodiment includes a mobile terminal body 111 and an antenna system 112. Where, the mobile terminal body 111 is connected to the antenna system 112, and includes essential functional parts of a mobile terminal such as a processor, a memory, and the like. The antenna system 112 may be any one of the multi-antenna systems provided by the aforementioned embodiments, and is configured to transmit and receive signals for the mobile terminal body 111. The mobile terminal body 111 processes the signals received by the antenna system 112, generates signals and transmits the generated signals through the antenna system 112.
The mobile terminal provided by the present embodiment, by using the aforementioned multi-antenna system, can have a smaller volume, and can further improve the communication performance of the mobile terminal since it can dispose antennas as many as possible in a smaller space.
Finally, it should be noted that the foregoing embodiments are merely intended for describing the technical solutions of the present invention other than limiting the present invention. Although the present invention is described in detail with reference to the foregoing embodiments, persons of ordinary skill in the art should understand that they may still make modifications to the technical solutions described in the foregoing embodiments or make equivalent substitutions to part of or all technical features thereof; but these modifications or substitutions cannot make the essence of the corresponding technical solutions depart from the scope of the technical solutions of embodiments of the present invention.

Claims

A multi-antenna system, comprising:
two metal ground plates (8a, 8b), which comprise a first metal ground plate (8a) and a second metal ground plate (8b), wherein the first metal ground plate (8a) and the second metal ground plate (8b) are located in a same azimuth plane without connection to each other, and a distance between the two metal ground plates (8a, 8b) is greater than or equal to a first preset threshold;

two dielectric substrates (7a, 7b), which comprise a first dielectric substrate (7a) and a second dielectric substrate (7b), wherein the first dielectric substrate (7a) and the second dielectric substrate (7b) are located in a same azimuth plane without connection to each other, the first dielectric substrate (7a) is located above the first metal ground plate (8a), the second dielectric substrate (7b) is located above the second metal ground plate (8b), and a distance between the two dielectric substrates (7a, 7b) is greater than or equal to a second preset threshold;

four first planar inverted-F antenna, PIFA, antennas (1, 3, 4, 6), wherein each of the first PIFA antennas (1, 3, 4, 6) comprises a radiation patch (1d), a probe type feeder line (1a) and a metal shorting pin (1b), and first grooves (1c) are disposed on radiation patches (1d) of the first PIFA antennas (1, 3, 4, 6);

two of the first PIFA antennas are disposed on each dielectric substrate of the two dielectric substrates (7a, 7b), and first isolated branch knots (11,12) are disposed between the first PIFA antennas;

the radiation patches (1d) of two first PIFA antennas (1, 3) are disposed on the first dielectric substrate (7a), and are connected to the first metal ground plate (8a) under the first dielectric substrate (7a) via the probe type feeder lines (1a) and the metal shorting pins (1b) of the first PIFA antennas (1, 3);

the radiation patches of two first PIFA antennas (4, 6) are disposed on the second dielectric substrate (7b), and are connected to the second metal ground plate (8b) under the second dielectric substrate (7b) via the probe type feeder lines and the metal shorting pins of the first PIFA antennas (4, 6); and

the four first PIFA antennas (1, 3, 4, 6) are symmetrical to each other with respect to an XOZ plane and a YOZ plane, wherein an XOY plane is parallel with the azimuth plane in which the first metal ground plate (8a) and the second metal ground plate (8b) are located in, the XOY plane is perpendicular to the XOZ plane and the YOZ plane respectively, and the XOZ plane is perpendicular to the YOZ plane;

the multi-antenna system further comprising:
a second PIFA antenna (5), which comprises a radiation patch (5d), a probe type feeder line (5a) and a metal shorting pin (5b), wherein a second groove (5c) is disposed on the radiation patch (5d) of the second PIFA antenna (5);

wherein the radiation patch (5d) of the second PIFA antenna (5) is localized 1mm - 5mm above at least one dielectric substrate of the two dielectric substrates (7a, 7b), and is connected to the metal ground plate under the at least one dielectric substrate, via the probe type feeder line (5a) and the metal shorting pin (5b) of the second PIFA antenna (5); and

wherein second isolation branch knots (9,10) are disposed between the first PIFA antennas (1, 3, 4, 6) and the second PIFA antenna (5).
The system according to claim 1, wherein the first preset threshold is 30mm.
The system according to claim 1 or 2, wherein the second preset threshold is 40mm.
The system according to claim 1, wherein there are two second PIFA antennas (2, 5), the two second PIFA antennas (2, 5) are disposed 1mm-5mm above the first dielectric substrate (7a) and the second dielectric substrate (7b) respectively, and the four first PIFA antennas (1, 3, 4, 6) are symmetrical to the two second PIFA antennas (2, 5) with respect to the XOZ plane and the YOZ plane.
The system according to any one of claims 1-4, wherein the first grooves (1c) are U-type grooves.
The system according to any one of claims 1-5, wherein the second groove (5c) is a polygonal-shape groove.
The system according to any one of claims 1-5, wherein the radiation patches (1d, 5d) of both the first PIFA antennas (1, 3, 4, 6) and the second PIFA antennas (2, 5) are rectangular.
The system according to any one of claims 1-7, wherein a dielectric constant of the dielectric substrates (7a, 7b) is between 1 and 9.8
A mobile terminal, characterized by comprising: a mobile terminal body and a multi-antenna system according to any one of the above claims 1-8, wherein the mobile terminal body is connected with the multi-antenna system, and the multi-antenna system is configured to transmit and receive signals for the mobile terminal body.