CN201845871U - A Two-Element Broadband MIMO Antenna Array - Google Patents

Abstract

The utility model provides a two unit broadband MIMO antenna arrays, be 1-100 including relative dielectric constant, antenna element (15a) and antenna element (15b) of thickness 0.2-5 mm's dielectric substrate and MIMO antenna, characterized by: the antenna unit (15a) and the antenna unit (15b) are perpendicular to each other along opposite directions, a slit is embedded on the floor, and a double-strip-line structure (17a, 17b) formed by two radiation units of each antenna unit can effectively improve impedance bandwidth so as to achieve the aim of wide bandwidth. The utility model overcomes the problems of small mutual coupling, wide bandwidth, small size, unstable performance and the like which can not be realized in the prior two-unit MIMO antenna, and has compact structure, small size, low cost and good characteristics; because the utility model discloses an antenna unit adopts the plane to arrange, prints on the circuit board very easily, consequently the utility model discloses the more three-dimensional structure's MIMO antenna array is more fit for integrating to in the mobile terminal equipment system.

Description

A Two-Element Broadband MIMO Antenna Array

technical field

The utility model relates to mobile communication technology, in particular to a two-unit broadband MIMO antenna array, which overcomes the problems of small mutual coupling, wide bandwidth, small size and unstable performance that cannot be realized in the existing two-unit MIMO antenna, and has a compact structure , small size, low cost and good performance. Since the antenna units of the present invention are arranged in a plane and can be easily printed on the circuit board, the MIMO antenna array of the present invention is more suitable for integration into the mobile terminal equipment system than the three-dimensional structure.

Background technique

Wireless communication is one of the most active research fields in the world today. It breaks through the physical limitations of wired communication, allowing users to communicate freely wherever radio waves can reach, which greatly expands the space and vitality of communication. The main problem that wireless communication faces at present is how to provide higher data transmission rate. Because the traditional resources traditionally used by wireless communication to increase data transmission rates—frequency bandwidth and transmit power—are currently on the verge of saturation, it is not feasible to increase transmission rates by increasing the loss of these two resources. The third generation mobile communication (3G) has been commercially applied in many countries including our country. However, since 3G mainly adopts traditional wireless communication technology, the data transmission rate it can provide is still low (384kbit/s-2Mbit/s), and operators cannot provide "killer" services to attract users. Large-scale commercial applications are struggling. In recent years, a new wireless communication technology that can greatly increase the data transmission rate without loss of frequency band and transmission power resources - MIMO (Multiple-Input Multiple-Output) technology - has aroused widespread interest. focus on. At present, MIMO technology has been regarded as an important part of the fourth generation mobile communication technology (4G).

MIMO antenna technology is one of the main core technologies of MIMO wireless communication technology, which refers to the use of multi-element array antennas at both ends of the transceiver. A traditional wireless communication system refers to an antenna system that uses a transmitting antenna and a receiving antenna at both receiving and transmitting ends, that is, a so-called single-input single-output (SISO) antenna system. The SISO antenna system has an unbreakable bottleneck in communication in terms of channel capacity—Shannon capacity limitation. No matter what modulation technology, coding strategy or other methods are used, the wireless channel always sets a practical physical limit for wireless communication engineering. .

Under the condition of not increasing the spectrum bandwidth and transmitting power, using multi-antenna diversity technology to improve the signal-to-noise ratio of transmitting/receiving signals to increase the capacity of the system is the development trend of the current wireless communication system. In recent years, the diversity gain is mainly achieved through a multi-element transmit antenna array and a unit receive single antenna (MISO antenna system). Because the space of the mobile terminal equipment is limited, the application of the SIMO (Single Input Multiple Output) antenna system makes the processing of the mobile terminal complicated, so its feasibility is low. But whether it is MISO or SIMO system, when the number of antennas reaches a certain number, the improvement of channel capacity is very small. The MIMO system is a wireless communication system that can greatly increase channel capacity through diversity gain, and its channel capacity increases with the increase in the number of antennas.

For handheld devices, integrating multiple antennas in a small space will cause a large mutual coupling, and the performance of the antenna will decrease accordingly, and the channel capacity cannot be increased linearly with the increase of the number of antennas. How to reduce the size of the antenna array while reducing the coupling between antenna elements is a difficult point in MIMO antenna design. At present, the main methods to reduce coupling are: adopting EBG floor structure, embedding fine seams on the floor, adding reflection units, or adding floor branches.

However, in the existing MIMO antenna design, the main consideration is also how to reduce the mutual coupling between antenna elements, and one of the above four methods is mainly used to reduce the mutual coupling. However, reducing mutual coupling often affects impedance matching, resulting in narrow impedance bandwidth and unstable antenna array performance. However, the MIMO antenna unit of the present invention adopts a double-strip line structure, which can help reduce the mutual coupling between the two antenna units, and at the same time introduce some capacitors to improve impedance matching and achieve the purpose of wide impedance bandwidth. The utility model solves the problems of narrow bandwidth, low isolation, large size and unstable performance of the MIMO antenna.

Since the channel capacity of a MIMO wireless communication system is linearly related to the number of transmitting and receiving antennas, the channel capacity is related to the performance of the MIMO system, the performance stability of the MIMO antenna array, and the correlation between antenna units. The more stable the performance of the MIMO antenna array, the lower the correlation between antenna elements, the better the performance of the MIMO system, and the more the superiority of the MIMO antenna system can be displayed. MIMO wireless communication systems are assigned different frequencies around the world, so the design of a MIMO antenna system with wide bandwidth, high isolation, and stable performance is very important. At present, in order to reduce the mutual coupling between antenna elements, various methods for improving isolation have been developed.

US Patent US7411554B2, "MIMO antenna operable in multiband", proposes a two-unit MIMO antenna as shown in Figure 1. In Fig. 1: (101) is the MIMO antenna, (105) is the antenna unit, (110) is the radiation unit, (111) is the feeding part of the radiation unit (110), (115) is the bending of the radiation unit (110) Part, (130) is a conversion controller, (150) is a floor, and (151) is a matching part. The large distance between the two units of this invention controls the influence of mutual coupling within a certain range, and controls the MIMO antenna to work at low frequency or high frequency by switching the controller (130) on or off, but this will increase the complexity of production and manufacturing costs. Since the antennas in this invention occupy most of the area of the dielectric substrate, it is very difficult to integrate other circuit elements on the dielectric substrate.

Utility model content

The purpose of the utility model is to overcome the deficiencies in the prior art, provide a two-unit broadband MIMO antenna array, and overcome the problems of small mutual coupling, small size and wide bandwidth that cannot be realized in the existing two-unit MIMO antenna.

The purpose of the utility model is achieved by the following technical solutions: two-unit broadband MIMO antenna array, comprising a dielectric substrate (11) and an antenna unit (15a) and an antenna unit (15b) of a MIMO antenna, wherein the dielectric substrate ( 11) including a dielectric substrate back (12) and a dielectric substrate front (13), the floor (14) is printed on the dielectric substrate back (12), and the antenna unit (15a) and the antenna unit (15b) are perpendicular to each other along opposite directions, so The above-mentioned floor (14) is embedded with a slit (16). In theory, two antennas that are perpendicular to each other are mismatched, that is, they cannot receive signals from each other. Therefore, the MIMO antenna array in the utility model can reduce the space wave by adopting the antenna unit design that is perpendicular to each other. Mutual coupling caused; and the slit (16) is embedded on the floor between the two antenna units, and the slit (16) has a sinking effect on the surface current distributed on the floor (14), so it can reduce the surface wave caused by the floor surface mutual coupling. Under the premise of simultaneously reducing the mutual coupling caused by space waves and surface waves, and ensuring high isolation, the distance between the two antenna units can be greatly reduced, so as to greatly reduce the antenna array The purpose of the invention of the size. In addition, because most of the surface current of the floor (14) is distributed around the slits, the distributed current in other places on the floor (14) is very small, so the size of the floor (14) is reduced, even if conductive devices are placed on the system dielectric substrate , the performance of the MIMO antenna is less affected, and the performance of the utility model is stable.

The dielectric substrate (11) adopts a dielectric substrate with a relative permittivity of 1-100 and a thickness of 0.2-5mm.

A preferred technical solution is: the antenna unit (15a) and the antenna unit (15b) are inclined at 45 degrees in opposite directions to form a mutually perpendicular attitude.

The preferred technical solution is: the antenna unit (15a) is provided with a radiation strip (21a) printed on the front side (13) of the dielectric substrate, a radiation strip (31a) printed on the back side (12) of the dielectric substrate, and a radiation strip ( 21a) feed port (22a); the antenna unit (15b) is provided with a radiation strip (21b) printed on the front side (13) of the dielectric substrate, a radiation strip (31b) printed on the back side (12) of the dielectric substrate , and the feed port (22b) of the radiation strip (21b); the radiation strip (31a) and the radiation strip (31b) are all connected to the floor (14) for short circuit;

The radiating strip (21a) and the radiating strip (31a) have overlapping portions (17a) for feeding the radiating strip (31a), and the radiating strip (21b) and the radiating strip (31b) have overlapping portions (17a) for feeding the radiating strip (31b) The overlapping portion (17b) for feeding is provided, and the overlapping portion (17a) and the overlapping portion (17b) form a double stripline structure. The role of the double-strip line structure (17a) and (17b): on the one hand, it provides effective coupling and feeding to the radiation unit (31a) and (31b), on the other hand, it also introduces some capacitance, which is beneficial to improve impedance matching and increase the impedance bandwidth. The energy is radiated effectively, and the isolation degree is also improved to a certain extent.

Compared with the prior art, the utility model has the following advantages and beneficial effects:

1. Compared with the existing MIMO antenna array, the utility model introduces two structures to improve the isolation. One is used to reduce the mutual coupling caused by space waves, and the other is used to reduce the mutual coupling caused by surface waves;

2. The existing MIMO antenna array designs are mainly dedicated to reducing the mutual coupling between antennas, so their impedance bandwidth is generally very narrow. However, in the present invention, a double-strip line structure is introduced, which can effectively improve the impedance bandwidth. Properly adjusting the double-strip line structure can get a good impedance bandwidth to meet the requirements of the multi-functional handheld device system;

3. Compared with the existing MIMO antenna array, the utility model has good robustness to the conductive elements placed around it, and has higher stability;

4. Compared with the existing MIMO antenna array, the utility model has a wider impedance bandwidth, a smaller size, and a simpler structure, so that the production cost can be reduced, and it is suitable for various multifunctional small handheld devices.

Description of drawings

Figure 1 is a schematic diagram of the structure of a two-unit MIMO antenna proposed in the existing US patent US7411554B2;

Figure 2 is a structural diagram of a two-element broadband MIMO antenna array;

Figure 3 is a front view of a two-element broadband MIMO antenna array;

Figure 4 is a back view of a two-element broadband MIMO antenna array;

Figure 5 is a comparison chart of the return loss electromagnetic simulation and experimental test _{curves of} the two-element wideband MIMO antenna array _. | curve, △△△ represents the experimental test |S ₂₂ | curve;

Figure 6 is a comparison diagram of the electromagnetic _simulation and experimental test curves of _the isolation of _the two-unit broadband MIMO antenna array. (|S ₂₁ |) curve

Fig. 7 is the schematic diagram of placing the metal box (61) on the front side of the dielectric substrate of the two-unit broadband MIMO antenna array shown in Fig. 3;

Fig. 8 is a comparison diagram of the electromagnetic simulation of the two-element MIMO antenna array shown in Fig. 3 and Fig. 8. In the figure □□□ represents the |S ₁₁ | curve without a metal box, and ○○○ represents the |S after adding a metal box ₁₁ | curve (S=1mm), △△△ represents the |S21| curve without metal box, *** represents the |S ₂₁ | curve (S=1mm) after adding metal box.

Among them: (11) is a dielectric substrate with a relative dielectric constant of 1-100 and a thickness of 0.2-5mm, (12) is the back of the dielectric substrate, (13) is the front of the dielectric substrate, and (14) is printed on the back of the dielectric substrate ( 12) on the floor, (15a, 15b) are the antenna unit 1 and the antenna unit 2 of the MIMO antenna respectively, (16) is the slit on the floor (14), (17a, 17b) are respectively the antenna unit (15a) and the antenna unit ( The overlapping part of the two radiating strips of 15b is the above-mentioned double-stripline structure, (21a, 21b) and the antenna unit (15a) and the antenna unit (15b) are respectively printed on the radiating strip of the front surface of the dielectric substrate (13), (22a, 22b) are the feed port 1 and the feed port 2 of the two antenna elements respectively, the radiation strips (21a) and (21b) are respectively fed by the port (22a) and the port (22b), and (31a, 31b) are respectively The radiation strips printed on the back of the dielectric substrate for the antenna unit (15a) and the antenna unit (15b), which are respectively fed by the double-strip line structure (17a) and (17b), and their terminals are short-circuited with the floor (14) , (41) is the resonance point 1650MHz, (42) is the resonance point 2300MHz, (43) is the resonance point 3400MHz, (44) is the resonance point 4500MHz, (45) is the resonance point 5200MHz, (61) is the metal box, (62) ) is the distance S between the metal box and the feed ports of the two antenna elements.

Detailed ways

The utility model will be further described in detail below in conjunction with the embodiments and accompanying drawings, but the implementation of the utility model is not limited thereto.

Example 1

Fig. 2 shows the structure of the small broadband two-element MIMO antenna proposed by the present invention, which includes two antenna elements (15a and 15b) perpendicular to each other. Because in theory, the antenna units that are perpendicular to each other are mismatched, and they cannot receive signals from each other, so the utility model tilts the two antenna units to different directions by 45 degrees to form a mutually perpendicular attitude, which is beneficial Reduce the mutual coupling caused by space waves. The floor (14) is printed on the back side (12) of the dielectric substrate (11), and the surface wave of the floor (14) will cause mutual coupling. In order to reduce the mutual coupling between the antenna elements of the surface wave band of the floor (14), the Slits (16) are embedded in the floor. To the floor (14) surface current/wave, the slit (16) has a trapping effect, which limits most of the floor (14) surface current to its surroundings, hindering most of the floor (14) surface current from a feeder port flows to another feed port, thereby reducing mutual coupling between antenna elements.

Figure 3 shows the front view of the MIMO antenna, and Figure 4 shows the rear view of the MIMO antenna. The antenna unit (15a) is composed of radiation units (21a) and (31a), and the radiation unit (15b) is composed of radiation units (21b) and (31b). Wherein the radiation units (21a) and (21b) are printed on the front surface (13) of the dielectric substrate (11), and they are directly fed by the feed ports (22a) and (22b) respectively. The radiating elements (31a) and (31b) are printed on the back side (12) of the dielectric substrate (11), and their ends are short-circuited with the floor (14).

Radiation units (21a) and (31a), overlapping parts of radiation units (21b) and (31b) constitute the double stripline structure (17a) and (17b), through the double stripline structure (17a) and (17b) respectively The radiating elements (31a) and (31b) are coupled and fed. The function of the double-strip line structure (17a) and (17b): on the one hand, it provides effective coupling and feeding to the radiating units (31a) and (31b), on the other hand, it introduces some capacitance, which is beneficial to improve impedance matching. The radiating elements (31a) and (31b) resonate at frequencies 2300MHz (42) and 4500MHz (44), increasing the impedance bandwidth. The energy is radiated effectively, and the isolation degree is also improved to a certain extent. The radiation unit (21a, 21b) produces 3 resonance points at frequencies of 1650MHz (41), 3400MHz (43) and 5200MHz (45), and the resonance unit (31a, 31b) occurs at frequencies of 2300MHz (42) and 4500MHz (44) resonance. These five resonance points interact to form a wide impedance bandwidth as shown in Figure 6.

The size of the utility model is very small, because the performance of the MIMO antenna is stable, and the size of the floor is reduced, which has little influence on the characteristics of the antenna. In order to prove that the performance of the two-element MIMO antenna is stable, as shown in Figure 7, a metal box (61) is placed on the front of the dielectric substrate of the MIMO antenna array shown in Figure 2, and the metal box (61) is connected to two feed ports The distance between (22a, 22b) is S(62). As shown in Figure 8, when S is reduced to 1mm, compared with the MIMO antenna array (as shown in Figure 2) without placing the metal box (61) in the MIMO antenna array shown in Figure 7, the return loss and isolation are affected effects are very small. It can be known that the MIMO antenna array has good robustness to the conductive elements placed around the array, and the antenna performance is stable, which is very important for practical applications. This application defines: |S ₁₁ |, |S ₂₂ | represent the return loss modulus of antenna unit (15a) and antenna unit (15b) respectively, |S ₁₂ |(|S ₂₁ |) represents antenna unit 2 (1) Mode of coupling to antenna element 1(2). |S ₁₁ |, |S ₂₂ |, |S ₁₂ |, |S ₂₁ | are collectively referred to as scattering parameters.

Embodiment: The small broadband two-element MIMO antenna array has the advantages of small size, wide bandwidth, and stable performance. By adjusting the size of the slits, high isolation can be achieved. In order to improve impedance matching, a double-strip line structure is adopted, and a wide impedance bandwidth can be achieved by adjusting the size of the double-strip line; the simulation and measured response curves of the utility model are shown in Figures 5 and 6.

The above-mentioned embodiment is a preferred implementation mode of the present utility model, but the implementation mode of the present utility model is not limited by the above-mentioned embodiment, and any other changes, modifications and substitutions made without departing from the spirit and principle of the present utility model , combination, and simplification, all should be equivalent replacement methods, and are all included in the protection scope of the present utility model.

Claims (4)

1. Two-element broadband MIMO antenna array, it is characterized in that: comprise the antenna element (15a) and the antenna element (15b) of dielectric substrate (11) and MIMO antenna, wherein, described dielectric substrate (11) comprises the dielectric substrate back side (12 ) and the front of the dielectric substrate (13), the floor is printed on the back of the dielectric substrate (12), the antenna unit 115a) and the antenna unit (15b) are perpendicular to each other along the opposite direction, and the floor (14) is embedded with a slit (16) . 2. The two-unit broadband MIMO antenna array according to claim 1, characterized in that: the dielectric substrate (11) is a dielectric substrate with a relative permittivity of 1-100 and a thickness of 0.2-5mm. 3. The two-unit broadband MIMO antenna array according to claim 1, characterized in that: the antenna unit (15a) and the antenna unit (15b) are inclined at 45 degrees in opposite directions. 4. The two-unit broadband MIMO antenna array according to claim 1, characterized in that: the antenna unit (15a) is provided with a radiation strip (21a) printed on the front side (13) of the dielectric substrate, printed on the dielectric substrate The radiation strip (31a) on the back side (12) and the feed port (22a) of the radiation strip (21a); the antenna unit (15b) is provided with the radiation strip (21b) printed on the front side (13) of the The radiation strip (31b) made on the back side (12) of the dielectric substrate, and the feed port (22b) of the radiation strip (21b); the radiation strip (31a) and the radiation strip (31b) are both connected to the floor (14); The radiation strip (21a) and the radiation strip (31a) form an overlapping portion (17a) for providing coupled feeding to the radiation strip (31a), and the radiation strip (21b) and the radiation strip (31b) form an overlapping portion (17a) for feeding the radiation strip (31b) ) to provide the overlapping portion (17b) of the coupling feed, the overlapping portion (17a) and the overlapping portion (17b) are the above-mentioned double stripline structure.

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