CN202434698U - MIMO Antenna Using Closed Current Loop in Antenna Unit to Improve Isolation - Google Patents

Abstract

The utility model provides a MIMO antenna which utilizes a closed current loop in an antenna unit to improve isolation, which comprises a substrate, a first antenna unit, a second antenna unit, a system floor, a first floor branch and a second floor branch; the antenna unit I and the antenna unit II form a first overlapping part and a second overlapping part with the floor branch I and the floor branch II respectively; the antenna unit I and the antenna unit II form an overlapping part III and an overlapping part IV with the system floor respectively; the system floor, the floor branch sections I and the antenna unit I form a first closed current loop through the first overlapping part, the system floor, the floor branch sections II and the antenna unit II form a second closed current loop through the second overlapping part, the system floor and the antenna unit I form a third closed current loop through the three overlapping parts, and the system floor and the antenna unit II form a fourth closed current loop through the fourth overlapping part. The utility model discloses can improve the isolation between the antenna unit effectively to reduce the cross coupling that the surface wave of floor arouses.

Description

MIMO Antenna Using Closed Current Loop in Antenna Unit to Improve Isolation

technical field

The utility model relates to the technical field of a two-unit MIMO (Multiple-Input Multiple-Output, multiple-input multiple-output) antenna array, and more specifically relates to a MIMO antenna that utilizes a closed current loop in an antenna unit to improve isolation.

Background technique

The third generation mobile communication system (3G) has some deficiencies, including the low communication rate, the dynamic range of the service rate is not large, the seamless roaming between different service environments in different frequency bands cannot be truly realized, and the requirements of various service types cannot be met. , and the frequency resources assigned to the 3G system have become saturated, etc., so 3G is difficult to meet the growing needs of users, and cannot provide dynamic range multi-rate services. So people began to study the long-term evolution LET (Long Term Evolution, long-term evolution) project of 3G and the fourth generation mobile communication (4G).

MIMO technology is considered to be one of the key technologies of the LET project and 4G. The MIMO technology was first proposed by Marconi in 1908, which uses multiple antennas to suppress channel fading. MIMO technology uses multiple antennas for transmit/receive diversity to obtain a certain diversity gain; MIMO technology uses multiple antennas for spatial multiplexing to improve spectrum utilization and greatly increase the transmission rate without increasing the system's transmit power.

MIMO antenna design is the key technology of MIMO communication system. For the base station, the application of multi-antenna technology is easy to realize because of the large available space. Due to the different frequencies allocated to LTE and 4G communication systems around the world, it is very important to design a small MIMO antenna with wide bandwidth, high isolation, stable performance, and suitable for mobile terminal equipment such as mobile phones. However, for handheld devices (such as mobile phones), integrating multiple antennas in a small space will cause large mutual coupling, and the performance of the antennas, such as operating bandwidth, transmission efficiency, radiation pattern, etc., will cause transmission distortion. Small, broadband/multi-frequency, high-isolation mobile phone antenna design is an important research direction in the field of MIMO technology.

At present, in order to reduce the mutual coupling between the antenna units and improve the isolation between the antenna units, various methods have been developed and formed.

In 2004, Gaoming Chi, Binhong Li, and Dongsheng Qi et al published an article titled "Dual-Band Printed Diversity Antenna for 2.4/5.2-GHz WLAN Application" in MICROWAVEAND OPTICAL TECHNOLOGY LETTERS, in which they proposed the use of T-shaped floor branches To improve the isolation between the two antenna elements.

In 2005, Kyeong-Sik Min and others published an article entitled "Improved MIMO Antenna by Mutual Coupling Suppression between Elements" at the European Microwave Conference, reporting that parasitic elements can reduce mutual coupling between antenna elements. This article uses six parasitic unit, in the 5.15-5.35GHz (|S ₁₁ |<-10dB) frequency band, the isolation is increased to 25dB.

In 2007, Yuan Ding, Zhengwei Du, Ke Gong and others published an article entitled "A Novel Dual-Band Printed Diversity Antenna for Mobile Terminals" on IEEE TRANSACTIONSON ANTENNAS AND PROPAGATION, which proposed to use two pairs of L-shaped floor branches to reduce The mutual coupling caused by the small floor surface wave improves the isolation between the two elements of the MIMO antenna.

In 2008, Angus C.K.Mak, Corbett R.Rowell, and Ross D.Murch published an article entitled "Isolation Enhancement Between Two Closely Packed Antennas" on IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, which confirmed that the floor gap can improve Isolation between MIMO antenna elements.

It can be seen that the main methods to reduce coupling are: EBG floor structure, decoupling network, floor gap, reflection unit, floor branch and neutralization line. However, the above decoupling methods are only suitable for narrow-band working bandwidth, and most of the structural designs are complex, making it difficult to achieve the design requirements of small size, broadband/multi-frequency, and high isolation.

Utility model content

The purpose of the utility model is to overcome the shortcomings and deficiencies in the prior art, and provide a MIMO antenna that utilizes a closed current loop in the antenna unit to improve isolation. The MIMO antenna has a simple structure, easy fabrication, wide bandwidth and high isolation, and is suitable for As a mobile terminal device such as a mobile phone, it can provide good diversity gain in a multipath communication environment, resist multipath fading, or provide multiplexing gain to improve the channel capacity of the system.

In order to achieve the above object, the utility model is achieved through the following technical solutions: a MIMO antenna that utilizes a closed current loop in the antenna unit to improve isolation, including a substrate, antenna unit one, antenna unit two, micro Stripline 1 and microstrip line 2, the system floor printed on the back of the substrate and the excitation port 1 and excitation port 2 connecting antenna unit 1 and antenna unit 2 through microstrip line 1 and microstrip line 2 respectively; the antenna unit 1 and antenna unit 2 are fed through microstrip line 1 and microstrip line 2 respectively; it is characterized in that: it also includes floor stub 1 and floor stub 2 printed on the back of the substrate; the antenna unit printed on the front of the substrate The first and the antenna unit two and the floor branch one and the floor branch two printed on the back of the substrate respectively form an overlapping part one and an overlapping part two; The system floor respectively forms overlapping part three and overlapping part four; the system floor, floor branch one and antenna unit one form a closed current loop one through overlapping part one, and the system floor, floor branch two and antenna unit two form overlapping part two Closed current loop two, system floor and antenna unit one form closed current loop three through overlapping part three, system floor and antenna unit two form closed current loop four through overlapping part four; said closed current loop one and closed current loop two belong to One type of current loop, closed current loop three and closed current loop four belong to another type of current loop.

Through the above scheme, a broadband MIMO antenna with simple structure, easy fabrication and high isolation can be obtained. A closed current loop is formed in the antenna unit of the MIMO antenna, and most of the surface current distributed on the system floor is limited to the closed current loop. In order to improve the isolation between MIMO antenna elements and reduce the mutual coupling caused by the floor surface current.

More specifically, the first microstrip line and the second microstrip line are 50 ohm microstrip lines.

The first antenna unit and the second antenna unit are triangular antenna units, and are printed on the front surface of the substrate perpendicular to each other. The antenna elements that are perpendicular to each other are theoretically mismatched, and this design is conducive to reducing the mutual coupling caused by space waves.

The substrate is a dielectric substrate with a relative permittivity of 1-1000.

The working principle of the MIMO antenna of the utility model is as follows: when the antenna unit 1 and the antenna unit 2 are excited, a relatively large coupling current will be induced on the system floor, and the surface current of the system floor is a strong coupling current between the two antenna units. The main reason for mutual coupling. At the low frequency of the working bandwidth of the MIMO antenna proposed by the utility model, the closed current loop inside the antenna unit of the utility model can effectively suppress the floor surface current generated when most of the antenna units are excited in the closed current loop. , thereby greatly reducing the floor surface current from excitation port 1 to excitation port 2; the same principle, at the low frequency of the working bandwidth of the MIMO antenna proposed by the utility model, the closed current loop 2 inside the antenna unit 2 can effectively The ground suppresses most of the floor surface current generated when the antenna unit 2 is excited in the closed current loop 2, thereby greatly reducing the floor surface current flowing from the excitation port 2 to the excitation port 1. At the high frequency of the working bandwidth of the MIMO antenna proposed by the utility model, the closed current loop 3 inside the antenna unit 1 of the utility model can effectively suppress the floor surface current generated when most of the antenna unit 1 is excited in the closed current loop Three, thus greatly reducing the floor surface current from the excitation port one to the excitation port two; the same principle, at the high frequency of the working bandwidth of the MIMO antenna proposed by the utility model, the closed current loop four inside the antenna unit two It can effectively restrain most of the floor surface current generated when the antenna unit 2 is excited in the closed current loop 4, thereby greatly reducing the floor surface current flowing from the excitation port 2 to the excitation port 1. Through the above working principle, within the wide working bandwidth of the MIMO antenna proposed by the utility model, the isolation between antenna unit 1 and antenna unit 2 is effectively improved, and the internal closed current loop does not occupy additional space, which is beneficial The miniaturized design of the MIMO antenna reduces the difficulty of processing and manufacturing.

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

1. Compared with the MIMO antenna design of the existing mobile terminal equipment, the utility model proposes that the internal closed current loop of the antenna unit can effectively improve the isolation between the antenna units within the broadband working bandwidth, thereby reducing the current caused by the floor surface mutual coupling.

2. Compared with the existing MIMO antenna design for mobile terminal equipment, the utility model proposes two types of internal current loops with improved isolation to cancel each other out on the impedance matching of the antenna unit, which helps to obtain a wide impedance bandwidth.

3. Compared with the MIMO antenna design of the existing mobile terminal equipment, the utility model has a smaller size, which is conducive to the miniaturization of the MIMO antenna. The utility model has a simpler structure, thereby reducing production costs, and is suitable for various A multifunctional small handheld device.

Description of drawings

Fig. 1 (a) is the substrate schematic diagram that the utility model MIMO antenna utilizes;

Fig. 1 (b) is the structure schematic diagram of the two-unit MIMO antenna that the utility model utilizes the closed current loop in the antenna unit to improve the isolation;

Fig. 2 is the schematic diagram of the electromagnetic simulation curve of the MIMO antenna frequency response of the present invention;

FIG. 3 is a schematic diagram of a traditional MIMO antenna structure;

FIG. 4 is a schematic diagram of an electromagnetic simulation curve of a frequency response of a conventional MIMO antenna.

Detailed ways

The utility model is described in further detail below in conjunction with the accompanying drawings and specific embodiments.

Example

The utility model is described by taking the substrate whose model is FR4 as an example.

The utility model uses the closed current loop in the antenna unit to improve the structural diagram of the two-unit MIMO antenna structure shown in Figure 1 (a) and Figure 1 (b). The MIMO antenna includes a substrate 11 with a model of FR4, and also includes Two triangular antenna units (antenna unit one 16a and antenna unit two 16b), two excitation ports (excitation port one 17a and excitation port two 17b), system floor 14 and two floor stubs (floor stub one 15a and floor stub two 15b). Antenna unit 1 16a and antenna unit 2 16b are printed on the front 12 of the FR4 substrate 11 perpendicular to each other, and the system floor 14 , floor stub 1 15a and floor stub 2 15b are printed on the back 13 of the FR4 substrate 11 . Antenna unit one 16a is fed by a 50-ohm microstrip line one 18a also printed on the front side 12 of the FR4 substrate 11; antenna unit two 16b is fed by a 50-ohm microstrip line two 18b also printed on the front side 12 of the FR4 substrate 11 Feed. Antenna unit one 16a and antenna unit two 16b printed on the front side 12 of the FR4 substrate 11 and floor branch one 15a and floor branch two 15b printed on the back side 13 of the FR4 substrate 11 have an overlapping part one 19a and an overlapping part two 19b respectively; Antenna unit 1 16a and antenna unit 2 16b printed on the front 12 of the FR4 substrate 11 and the system floor 14 printed on the back 13 of the FR4 substrate 11 have overlapping portions 3 110a and 4 110b respectively. Among them, the system floor 14, floor branch one 15a and antenna unit one 16a form a closed current loop one through overlapping part one 19a and overlapping part three 110a; system floor 14, floor branch two 15b and antenna unit two 16b form an overlapping part two 19b Closed current loop two; system floor 14 and antenna unit one 16a form closed current loop three through overlapping part three 110a; system floor 14 and antenna unit two 16b form closed current loop four through overlapping part four 110b.

The traditional MIMO antenna structure schematic diagram is shown in Figure 3. Compared with Figure 1 of the present invention, the traditional MIMO antenna does not have printed floor stub 1 15a and floor stub 2 15b on the back 13 of the FR4 substrate 11, nor does the utility model The first overlapping part 19a, the second overlapping part 19b, the third overlapping part 110a and the fourth overlapping part 110b, so the first closed current loop, the second closed current loop, the third closed current loop and the fourth closed current loop cannot be formed.

The functions of the closed current loop 1, closed current loop 2, closed current loop 3 and closed current loop 4 of the utility model can be well understood from the electromagnetic simulation curve diagrams of the two frequency responses in Fig. 2 and Fig. 4 . It can be observed from Figure 2 that, compared with Figure 3, the operating bandwidth of the antenna in Figure 1(b) has a relatively small change, but the isolation between antenna elements has been greatly improved (12dB within the bandwidth). It can be seen that the closed current loop 1, the closed current loop 2, the closed current loop 3 and the closed current loop 4 proposed by the present invention can effectively improve the isolation between MIMO antenna units. Among them, current loops 1 and 2 belong to one type of current loops, and current loops 3 and 4 belong to another type of current loops, and the reactions of these two current loops to the impedance matching of the MIMO antenna unit can cancel each other out, so the two The application of this current loop has little influence on the working bandwidth of the MIMO antenna, and realizes the design requirements of wide band, high isolation, simple structure and small size.

The utility model can realize wide impedance bandwidth by adjusting the size of antenna unit one 16a and antenna unit two 16b; by adjusting the overlapping part one 19a, overlapping part two 19b, overlapping part three 110a and overlapping part four included in the closed current loop 110b, can realize the design requirement of high isolation.

The working principle of the utility model MIMO antenna is as follows: when the antenna unit one 16a and the antenna unit two 16b are excited, a relatively large coupling current will be induced on the system floor 14, and the surface current of the system floor 14 is to generate two antenna units The main reason for the strong mutual coupling between. The closed current loop one and the closed current loop three inside the antenna unit one 16a of the present utility model effectively suppress the floor surface current generated when most of the antenna unit one 16a is excited at the low frequency and high frequency of the working bandwidth respectively in the closed current loop one and the closed current loop three, thereby greatly reducing the floor surface current flowing from the excitation port one 17a to the excitation port two 17b; the same principle, the closed current loop two and the closed current loop four inside the antenna unit two 16b are respectively within the working bandwidth The low frequency and high frequency effectively restrain most of the floor surface current generated when the antenna unit two 16b is excited in the closed current loop two and closed current loop four, thereby greatly reducing the flow from the excitation port two 17b to the excitation port one 17a floor surface currents. Through the above-mentioned working principle, the isolation between antenna unit one 16a and antenna unit two 16b is effectively improved, and the internal closed current loop does not take up additional space, which is conducive to the miniaturization design of MIMO antennas, and the internal closed current loop The structure is simple, and the work difficulty of processing and manufacturing is reduced.

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. MIMO antenna that utilizes closed path loop in the antenna element to improve isolation; Comprise substrate; Be printed on antenna element one, antenna element two, microstrip line one and the microstrip line two of substrate front side, the excitation port one and excitation port two that are printed on the system floor of substrate back and are connected antenna element one and antenna element two respectively through microstrip line one with microstrip line two; Said antenna element one carries out feed through microstrip line one and microstrip line two respectively with antenna element two; It is characterized in that: also comprise the floor minor matters one and floor minor matters two that are printed on substrate back; The said antenna element one that is printed on substrate front side forms lap one and lap two respectively with antenna element two and floor minor matters that are printed on substrate back one and floor minor matters two; The said antenna element one that is printed on substrate front side forms lap three and lap four respectively with antenna element two and the system floor that is printed on substrate back; Said system floor, floor minor matters one and antenna element one form closed path loop one through lap one; System floor, floor minor matters two and antenna element two are formed closed path loop two through lap two; System floor and antenna element one are formed closed path loop three through lap three, and system floor and antenna element two form closed path loop four through lap four; Said closed path loop one belongs to one type of current circuit with closed path loop two, and closed path loop three belongs to another kind of current circuit with closed path loop four.

2. the MIMO antenna that utilizes raising isolation in closed path loop in the antenna element according to claim 1 is characterized in that: said microstrip line one and microstrip line two are 50 ohm microstrip line.

3. the MIMO antenna that utilizes raising isolation in closed path loop in the antenna element according to claim 1, it is characterized in that: said antenna element one is leg-of-mutton antenna element with antenna element two, and is printed on the front of substrate mutual vertically.

4. according to each described MIMO antenna that utilizes raising isolation in closed path loop in the antenna element in the claim 1 to 3, it is characterized in that: said substrate is that relative dielectric constant is the medium substrate of 1-1000.

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