A millimeter wave switchable MIMO antenna unit and antenna array

Abstract

The present invention relates to a millimeter wave switchable MIMO antenna unit, comprising a top layer, a first metal layer, a second metal layer, a third metal layer, a fourth metal layer and a bottom layer arranged in sequence from top to bottom, and also having through holes penetrating the six metal layers and four blind holes; the top layer contains 11 radio frequency switching chip patches, adopts a three-layer multiplexing structure, the first metal layer is a ground layer, the second metal layer is a control signal layer, the third metal layer is a power layer, and the fourth metal layer is a ground layer. A millimeter wave switchable MIMO antenna array comprises antenna units as above arranged in a 1×32 linear array, the polarization mode adopts vertical polarization, and the center frequency is 38.5GHZ. Compared with the prior art, the present invention has the advantages of small coupling, high reliability, clear and compact structure, high switching frequency, low cost, and can fit actual large-scale antenna base stations.

Description

Technical Field

[0001] The present invention relates to the field of wireless communication technology, and in particular to a millimeter wave switchable MIMO entity 32-element antenna unit and an antenna array suitable for a frequency band of 37.9 GHz to 39.1 GHz. Background Art

[0002] With the rapid development of personal mobile communications, the low-end frequency of the radio spectrum has become saturated, while millimeter waves have rich spectrum resources and high carrier frequencies, and their operating wavelength is short, which can reduce the size of system components and has a wide range of application scenarios. However, as a high-frequency wave, millimeter waves have obvious attenuation during transmission, and path obstruction and loss are also obvious. Therefore, suitable antennas are needed to improve the transmission efficiency of millimeter waves. In real life, the terminals used by everyone are generally equipped with single antennas or MIMO antennas, both of which have low gain, and the beam width of the single antenna radiation pattern is relatively wide. In many long-distance communication needs, highly directional antennas (such as base station antennas, etc.) are required to compensate for spatial attenuation. Antenna arrays, also known as phased arrays, are a group of antennas consisting of two or more antennas. These antennas can increase the overall total gain, achieve diversity reception, cancel interference, adjust to a specific direction, measure the source direction of the input signal, and maximize the signal-to-interference-to-noise ratio (SINR) by combining signals with each other.

[0003] Patent CN108598690A discloses a millimeter-wave Massive MIMO antenna unit and array antenna. The millimeter-wave Massive MIMO array antenna has antenna units arranged in an 8×16 array, with low mutual coupling between array elements and a compact structure. However, it still has problems such as complex structure, inability to be applied in time-varying environments, and inability to fit actual large-scale antenna base stations. Summary of the invention

[0004] The purpose of the present invention is to provide a millimeter wave switchable MIMO antenna unit and antenna array with small coupling, high reliability, clear and compact structure, high switching frequency, low cost, and suitable for actual large-scale antenna base stations.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A millimeter wave switchable MIMO antenna unit includes a top layer 101, a first metal layer 102, a second metal layer 103, a third metal layer 104, a fourth metal layer 105 and a bottom layer 106 arranged in sequence from top to bottom.

[0007] The top layer 101 adopts a three-layer multiplexing structure, including 11 radio frequency switching chips, wherein 1 switching chip is located in the first layer, 2 switching chips are located in the second layer, and 8 switching chips are located in the third layer. The input ends of the 2 chips in the second layer are connected to the 2 output ends of the chips in the first layer, wherein the 4 output ends of the 1 switching chip in the second layer are respectively connected to the input ends of the 4 switching chips in the third layer, and the 4 output ends of another switching chip are respectively connected to the input ends of the other 4 switching chips in the third layer, and the switching chip is configured to conduct only one port at a time;

[0008] The first metal layer 102 is a ground layer;

[0009] The second metal layer 103 is a control signal layer, and is provided with an RF transmission line;

[0010] The third metal layer 104 is a power layer;

[0011] The fourth metal layer 105 is a ground layer;

[0012] The outer sides of the top layer 101 and the bottom layer 106 are provided with a solder resist layer.

[0013] A first dielectric layer 201 is provided between the top layer 101 and the first metal layer 102;

[0014] A second dielectric layer 202 is provided between the first metal layer 102 and the second metal layer 103;

[0015] A third dielectric layer 203 is provided between the second metal layer 103 and the third metal layer 104;

[0016] A fourth dielectric layer 204 is provided between the third metal layer 104 and the fourth metal layer 105;

[0017] A fifth dielectric layer 205 is provided between the fourth metal layer 105 and the bottom layer 106;

[0018] The top layer 101 is provided with a through hole that penetrates all metal signal layers, dielectric layers and the bottom layer. At the same time, the top layer 101 and the first dielectric layer 201 are connected through a first blind hole, the first metal layer 102 and the second dielectric layer 202 are connected through a second blind hole, the second metal layer 103 and the third dielectric layer 203 are connected through a third blind hole, and the third metal layer 104 and the fourth dielectric layer 204 are connected through a fourth blind hole.

[0019] A bypass capacitor for filtering high-frequency noise is provided on the power supply line of the third metal layer 104 , and a reserved space for applying an additional bypass capacitor is provided; a resistor-capacitor filter is provided on the control line of the second metal layer 103 .

[0020] The RF transmission line uses a coplanar waveguide model with a trace width of 14 mils, a ground clearance of 7 mils, and a characteristic impedance of 50Ω. The RF input and output ports are connected to a 2.4 mm RF transmitter through a 50Ω transmission line.

[0021] The second metal layer 103 is a high-frequency signal layer, and is used to place high-frequency circuits in the circuit.

[0022] The switching chips have the same structure and size and are arranged in a tree structure.

[0023] The first metal layer 102 and the fourth metal layer 105 are respectively connected to different ground sources.

[0024] A millimeter wave switchable MIMO antenna array comprises the antenna units as claimed in claim 1 arranged in a 1×32 linear array, wherein the polarization mode adopts vertical polarization and the center frequency is 38.5 GHZ.

[0025] The horizontal distance between two adjacent antenna units of the antenna array is 0.5 wavelength.

[0026] The array antenna is rectangular and has a left-right central symmetrical structure. The antenna array is 165 mm long and 72 mm wide.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) The antenna units of the present invention use the same chip on the top layer, have the same structure and size, and are arranged together according to a certain rule. They have strong directivity and high gain, and solve a series of problems such as coupling between antennas and sidelobe level.

[0029] (2) The antenna unit of the present invention adopts a three-layer multiplexing structure, which ensures that only one antenna can be turned on at any time and can be switched arbitrarily. The switching frequency is high and time-varying measurement can be achieved.

[0030] (3) The antenna unit of the present invention places the high-speed signal layer in the inner layer so that it is effectively shielded by the ground layer and the power layer. At the same time, a decoupling capacitor is added and its frequency response is made to meet the requirements, so as to reduce the power layer noise, improve the power quality of the circuit board, and enhance the anti-interference ability.

[0031] (4) The antenna unit of the present invention utilizes multi-layer PCB technology and the design of through holes and blind holes to achieve connection of the signal layer, save space and reduce volume.

[0032] (5) The present invention adopts a 1×32 linear array, which can improve spatial resolution, reduce polarization effect, and has a simple and clear structure.

[0033] (6) The antenna array of the present invention has high reliability and low cost, can fit actual large-scale base stations, and is suitable for large-scale MIMO channel measurement scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Schematic diagram of the antenna array.

[0035] Figure 2 This is a schematic diagram of the principle of switching chip pins.

[0036] Figure 3 A cross-sectional structural diagram of the antenna unit.

[0037] Figure 4 This is a top view of the antenna unit.

[0038] Figure 5 Layout diagram of the RF transmission lines for the antenna unit PCB. DETAILED DESCRIPTION

[0039] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0040] The antenna unit of this embodiment adopts six-layer PCB technology, including a top layer 101, a first metal layer 102, a second metal layer 103, a third metal layer 104, a fourth metal layer 105 and a bottom layer 106 arranged in order from top to bottom, wherein layers 101, 103 and 106 are signal layers; layers 102 and 105 are ground layers; and layer 104 is a power layer, wherein the power layer and the ground layer are tightly coupled, each signal layer is adjacent to the bottom layer or metal layer, and there is no directly adjacent signal layer, thereby avoiding crosstalk of signals between layers. The RF transmission line is arranged on the second metal layer 103, so that it is effectively shielded by the ground layer (i.e., the first metal layer 102) and the power layer (i.e., the third metal layer 104), and a good return path can be provided for each signal layer when the power and ground layers are intact.

[0041] like Figure 2 As shown, the top layer 101 in this embodiment uses a radio frequency switching chip of model adrf5047 (hereinafter referred to as the "switching chip") with a total of 20 pins, including 11 ground pins, 4 antenna pins (RF1, RF2, RF3, RF4), 1 positive drive voltage VDD pin and 1 negative drive voltage VSS, 1 RC radio frequency signal transmission pin and two high and low level control pins V1 and V2.

[0042] Furthermore, each switching chip has a positive driving voltage VDD and a negative driving voltage VSS, which are 3.3V and -3.3V respectively. When the V1 pin is connected to a low level and the V2 pin is connected to a low level, RF1 is turned on; when V1 is connected to a high level and V2 is connected to a low level, RF2 is turned on; when V1 is connected to a low level and V2 is connected to a high level, RF3 is turned on; when V1 is connected to a high level and V2 is connected to a high level, RF4 is turned on, realizing a preliminary single-pole four-throw function.

[0043] The top layer 101 adopts a three-layer multiplexing structure, including 11 RF switching chip patches of model adrf5047, wherein 1 switching chip is located on the first layer, 2 switching chips are located on the second layer, and 8 switching chips are located on the third layer. The input ends of the 2 chips on the second layer are connected to the 2 output ends of the chip on the first layer, wherein the 4 output ends of the 1 switching chip on the second layer are respectively connected to the input ends of the 4 switching chips on the third layer, and the 4 output ends of another switching chip are respectively connected to the input ends of the other 4 switching chips on the third layer, and the switching chip is configured to only turn on one port at a time.

[0044] like Figure 3 As shown, they are schematic diagrams of the structure of the six-layer PCB metal layer, respectively. There is a filler above the top layer 101 as a solder resist layer, and a first dielectric layer with a core board as a filler is set between the top layer 101 and the first metal layer 102. A second dielectric layer of FR-4 material with a thin sheet insulating material as a filler is set between the first metal layer 102 and the second metal layer 103. A third dielectric layer of FR-4 material with a core board as a filler is set between the second metal layer 103 and the third metal layer 104, a fourth dielectric layer of FR-4 material with a thin sheet insulating material as a filler is set between the third metal layer 104 and the fourth metal layer 105, and a fifth dielectric layer with a core board as a filler is set between the fourth metal layer 105 and the bottom layer 106. There is a filler as a solder resist layer under the bottom layer. The top view of this physical array is shown in FIG. Figure 4 shown.

[0045] Furthermore, the top signal layer 101 as a device layer includes 11 switching chip patches and low-frequency circuits; the second metal layer 103 is used to place the high-frequency circuits in the circuit; the first metal layer 102 and the fourth metal layer 104 are connected to different ground sources respectively; the main power supply and the RC filter circuit are arranged in the third metal layer 104 and the fourth metal layer 105;

[0046] Furthermore, this embodiment includes through holes penetrating 6 metal signal layers and 5 dielectric layers, and there are 4 blind holes respectively connecting the signal layers and dielectric layers between the top layer 101 and the fourth metal layer 105. External control signals and power supply voltages are connected from 22 control pins and 2 power supply pins through the circuits of the second metal layer 103 and the third metal layer 104 to the blind holes reserved in the top layer 101 to control the antenna, and the blind holes can greatly increase the routing area.

[0047] Furthermore, in order to solve the problem of electromagnetic interference, this embodiment places the high-speed signal layer in the inner layer, and selects the decoupling capacitor and makes its frequency response meet the requirements to reduce the power layer noise. On the third metal layer 104 power line, a 100pF bypass capacitor is used to filter out high-frequency noise, and a reserved position can be used to apply additional bypass capacitors. On the second metal layer 103 control line, a resistor-capacitor (RC) filter is placed with a resistance of 1000 ohms and a capacitance of 10pF, which can improve the power quality of the circuit board and enhance the anti-interference ability.

[0048] Ideally, the thickness of the dielectric is infinite; in reality, as long as the electromagnetic field is no longer continuous before leaving the substrate, the structure can be approximately considered as a coplanar waveguide. If a ground plane is added to the other side of the dielectric, a limited coplanar waveguide can be formed. The active device can be attached to the upper layer of the circuit like a microstrip line, and since the connection to the coplanar waveguide will not introduce any parasitic discontinuities in the ground plane, a higher frequency response (100GHz or greater) can be provided. Using a coplanar waveguide can achieve higher isolation because there is an RF ground for isolation between each RF path. Usually, when designing a transmission line on a PCB, microstrip lines are considered to be used to implement a 50Ω transmission line because microstrip lines are a very suitable structure for implementation on PCBs. Strictly speaking, a coplanar waveguide is also a transmission line. It has a very similar structure to a microstrip line, and since the coplanar waveguide transmission line has more "ground" around it than the microstrip line, the coplanar waveguide transmission line has better anti-interference ability. Therefore, in order to avoid the reflection caused by the high-speed transmission line effect affecting the signal integrity and delay time, the RF transmission line is designed using a coplanar waveguide (CPWG) model, with a line width of 14 mils, a ground clearance of 7 mils, and a characteristic impedance of 50 ohms. The RF input and output ports are connected to the 2.4 mm RF transmitter through a 50 ohm transmission line to match the line characteristic impedance. The RF transmission line extends from the edge of the package to the tapered line for RF pin conversion, such as 8 mils. Figure 5 As shown, for best RF performance and thermal grounding, place as many plated through holes or blind vias as possible around the transmission line and expose the underlying packaging pads during routing.

[0049] The millimeter wave physical antenna array of this embodiment is arranged in a 1×32 linear array antenna unit, and the polarization mode adopts vertical polarization, the center frequency is 38.5GHZ, and the bandwidth is 1.2GHZ. In this embodiment, there are 32 antennas in total, which are divided into 8 groups, each with 4 antennas. Each third-layer switching chip controls a group of antennas to achieve switching; the 8 switching chips of the third layer are divided into 2 groups, each with 4 switching chips, and each second-layer switching chip controls a group of third-layer switching chips; the second-layer switching chip is controlled by a switching chip of the first group. Since a switching chip has four pins and can control four states, the two idle pins of the first-layer chip are grounded after connecting a 50Ω resistor, and correspond to the opening and closing of the entire power supply after packaging. When in an idle state, the first-layer chip is cut to two idle pins; when in a normal working state, when a certain antenna needs to be selected, the corresponding third-layer switching chip is switched to the state of connecting the antenna, and the second-layer switching chip of the third-layer switching chip is controlled to switch to the state of connecting the third-layer switching chip, and the first-layer switching chip is switched to the state of connecting the second-layer switching chip, so that only one antenna is turned on at any time.

[0050] The array antenna in this embodiment is rectangular and has a left-right centrally symmetrical structure. The antenna array is 165 mm long and 72 mm wide. The horizontal spacing between two adjacent antenna units is 0.5 wavelength.

[0051] In addition, it should be noted that the specific implementation examples described in this specification may be named differently, and the above content described in this specification is only an example of the structure of the present invention. All equivalent changes or simple changes made based on the structure, features and principles of the present invention are included in the protection scope of the present invention. Technicians in the technical field to which the present invention belongs can make various modifications or supplements to the specific examples described or adopt similar methods, as long as they do not deviate from the structure of the present invention or exceed the scope defined by the claims, they should all belong to the protection scope of the present invention.

Claims

1. A millimeter wave switchable MIMO antenna unit, characterized in that: The invention comprises a top layer (101), a first metal layer (102), a second metal layer (103), a third metal layer (104), a fourth metal layer (105) and a bottom layer (106) which are arranged in sequence from top to bottom. The top layer (101) adopts a three-layer multiplexing structure, including 11 radio frequency switching chips, wherein 1 switching chip is located in the first layer, 2 switching chips are located in the second layer, and 8 switching chips are located in the third layer, the input ends of the 2 chips in the second layer are connected to the 2 output ends of the chips in the first layer, wherein the 4 output ends of the 1 switching chip in the second layer are respectively connected to the input ends of the 4 switching chips in the third layer, and the 4 output ends of another switching chip are respectively connected to the input ends of the other 4 switching chips in the third layer, and the switching chip is configured to conduct only one port at a time; The first metal layer (102) is a ground layer; The second metal layer (103) is a control signal layer and is provided with an RF transmission line; The third metal layer (104) is a power layer; The fourth metal layer (105) is a ground layer.

2. A millimeter wave switchable MIMO antenna unit according to claim 1, characterized in that: A solder resist layer is provided on the outer sides of the top layer (101) and the bottom layer (106); A first dielectric layer (201) is provided between the top layer (101) and the first metal layer (102); A second dielectric layer (202) is provided between the first metal layer (102) and the second metal layer (103); A third dielectric layer (203) is provided between the second metal layer (103) and the third metal layer (104); A fourth dielectric layer (204) is provided between the third metal layer (104) and the fourth metal layer (105); A fifth dielectric layer (205) is provided between the fourth metal layer (105) and the bottom layer (106); The top layer (101) is provided with a through hole that penetrates all metal layers, dielectric layers and the bottom layer; the top layer (101) and the first dielectric layer (201) are connected via a first blind hole, the first metal layer (102) and the second dielectric layer (202) are connected via a second blind hole, the second metal layer (103) and the third dielectric layer (203) are connected via a third blind hole, and the third metal layer (104) and the fourth dielectric layer (204) are connected via a fourth blind hole.

3. A millimeter wave switchable MIMO antenna unit according to claim 1, characterized in that: A bypass capacitor for filtering high-frequency noise is provided on the power supply line of the third metal layer (104), and a reserved space position for applying an additional bypass capacitor is provided; a resistor and capacitor filter is provided on the control line of the second metal layer (103).

4. The millimeter wave switchable MIMO antenna unit according to claim 1, characterized in that: The RF transmission line uses a coplanar waveguide model with a trace width of 14 mils, a ground clearance of 7 mils, and a characteristic impedance of 50Ω. The RF input and output ports are connected to a 2.4 mm RF transmitter through a 50Ω transmission line.

5. The millimeter wave switchable MIMO antenna unit according to claim 1, characterized in that: The second metal layer (103) is a high-frequency signal layer, and is used to place a high-frequency circuit in the circuit.

6. The millimeter wave switchable MIMO antenna unit according to claim 1, characterized in that: The switching chips have the same structure and size and are arranged in a tree structure.

7. The millimeter wave switchable MIMO antenna unit according to claim 1, characterized in that: The first metal layer (102) and the fourth metal layer (105) are respectively connected to different ground sources.

8. A millimeter wave switchable MIMO antenna array, characterized in that: The antenna unit according to claim 1 is arranged in a 1×32 linear array, the polarization mode is vertical polarization, and the center frequency is 38.5 GHZ.

9. The millimeter wave switchable MIMO antenna array according to claim 8, characterized in that: The horizontal distance between two adjacent antenna units of the antenna array is 0.5 wavelength.

10. The millimeter wave switchable MIMO antenna array according to claim 8, characterized in that: The antenna array is rectangular and has a left-right central symmetrical structure. The antenna array is 165 mm long and 72 mm wide.

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