CN113037397B

CN113037397B - 5G antenna interface board port isolation measurement system

Info

Publication number: CN113037397B
Application number: CN202110229360.9A
Authority: CN
Inventors: 宋宏平; 郭忠海
Original assignee: Suzhou Tianxi Electronic Technology Co ltd
Current assignee: Suzhou Tianxi Electronic Technology Co ltd
Priority date: 2021-03-02
Filing date: 2021-03-02
Publication date: 2022-05-13
Anticipated expiration: 2041-03-02
Also published as: CN113037397A

Abstract

The invention discloses a 5G antenna interface board port isolation degree measuring system, which comprises a PCB and a switch matrix, wherein the switch matrix is connected with antenna ports on an interface board, a plurality of solid switches, a plurality of matched loads and a control bus are integrated on the PCB, the solid switches and the matched loads are arranged in a one-to-one correspondence mode, each solid switch is connected with the control bus, and when the isolation degree of two antenna ports is measured, the solid switches corresponding to ports to be measured can be controlled through the control bus, so that the ports to be measured are disconnected from the switch matrix and are connected to the corresponding matched loads. The 5G antenna interface board port isolation measuring system can effectively measure the port isolation, can effectively improve the measuring efficiency and the measuring precision, and has the advantages of simple structure and convenient operation.

Description

5G antenna interface board port isolation measurement system

Technical Field

The invention relates to the technical field of antennas, in particular to a 5G antenna interface board port isolation measuring system.

Background

From 4G, the antenna of the base station is not an antenna body consisting of a single antenna in the traditional sense, but is an MIMO antenna array consisting of a plurality of antenna units, the index of the antenna test is not the simple standing wave measurement of the traditional single antenna, the amplitude-phase relation between different antenna units is required to be measured, and the amplitude and phase parameters between a calibration port (Cal) and each unit are measured, and the parameters are represented by measuring S parameters through a vector network analyzer.

Because the number of the 5G base station antenna units is large, for example, 32 antenna units are commonly used at present, each 16 antenna units are connected with the antenna element unit and the base station transceiver unit through an interface board, and generally, each interface board is provided with a calibration port.

Besides the usual measurement of S-parameters of the antenna element unit (antenna standing wave, amplitude-phase relationship between antennas), the antenna interface board also needs to measure the amplitude-phase relationship between ports.

The corresponding interface board ports of the 16 oscillator units are provided with 16 pairs of antenna ports (one inlet and one outlet respectively) and a calibration port (Cal), and S parameters including standing waves and isolation of the 16 pairs of ports and the Cal port need to be measured during research and development and production. An ordinary single network analyzer only has two (at most 4) ports and cannot be competent, so two ports of the network analyzer must be allocated to 16 pairs of antenna units and 2 Cal ports in a time-sharing manner by using a radio frequency 36-port full matrix through switching of switches inside the 36-port matrix, and amplitude-phase relationship (and isolation between the antenna units and the Cal ports) between any port standing waves on any base station antenna and any two ports is measured, the connection mode is shown in fig. 1, a connecting line between an interface board port and the switch matrix is a radio frequency coaxial cable, and the nominal impedance is 50 Ω.

The 5G base station antenna interface board is connected with the base station antenna element unit and the base station signal transceiving unit and is also used for calibrating the amplitude and the phase of each antenna unit. The isolation requirements between the ports of the interface board itself (including the Cal port and the antenna interface port) are high, otherwise, additional uncertainty is brought to the test and antenna array calibration.

The port matching degree has a great influence on the measurement result of the isolation degree, so when the isolation degree between the ports of the interface board is measured, a measured port on the antenna interface board must be connected with a 50 omega matching load. In the past, the switches in the switch matrix were required to have matched loads, and when a port was open, the port was connected to a 50 Ω load. The matching of the tested port is realized by connecting the radio frequency coaxial cable to the load in the switch matrix. Theoretically, the scheme is feasible, but actual measurement shows that when the switch matrix is connected for measurement, the result of the isolation measurement cannot meet the nominal index requirement of the interface board. And in practical tests, the isolation result of the test conforms to the product index if the 50 ohm load is directly connected to the tested port of the antenna interface board. The root of the problem lies in: the radio frequency ports on the antenna interface board are not really matched, the radio frequency ports are not ideally connected with the matched load in the switch matrix, and the middle part of the antenna interface board is provided with radio frequency connecting wires, including the connecting wires from the antenna ports of the interface board to the ports of the switch matrix, the connecting wires in the switch matrix, the internal selector switch channel and the like. These connection components are equivalent to a series of resistive-capacitive (resistive, capacitive, inductive) networks on the rf microwave circuit, resulting in the ports on the antenna interface board not actually connected to a 50 ohm load.

In order to avoid the deviation caused by the impedance mismatch of the antenna ports, when the isolation between the ports is measured, the conventional method is to put the internal switch corresponding to the switch matrix port Myy (for example, M08) connected to the port to be measured into an open state. Because the switch matrix port is disconnected, it will be connected to signal ground through 50 Ω load, and the disconnected port is equivalent to 50 Ω matching load, theoretically, the tested antenna port is connected to the ideal 50 Ω matching load, but actually, the physical connection and equivalent circuit diagram between the antenna port on the base station interface board and the disconnected load inside the switch matrix are as shown in fig. 2.

Therefore, the purpose of performing 50 ohm matching by using the open-circuit load of the switch matrix is not achieved in the traditional method, actually 50 ohms of the terminal plate antenna port is connected with a plurality of series of RC networks in series, which are not equal to 50 ohms, and most of the superposed RC networks are arranged in the switch matrix and cannot be calibrated, so that the isolation cannot be accurately measured by the traditional method.

As can be understood from fig. 2, the reason that the conventional method cannot accurately measure the isolation is that a standard 50 Ω matching load or a matching load as close as possible to 50 Ω cannot be provided to the antenna port, and the only method is to verify that the present solution is to directly manually terminate a matching load at the antenna port of each interface board.

The method can solve the isolation test problem, but cannot be applied to production test, and has the disadvantages of slow speed, extremely low efficiency and greatly increased test cost.

Disclosure of Invention

The invention aims to provide a 5G antenna interface board port isolation measuring system with high measuring efficiency and high measuring precision.

In order to solve the above problems, the invention provides a 5G antenna interface board port isolation degree measurement system, which includes a PCB and a switch matrix, wherein the switch matrix is connected to antenna ports on an interface board, the PCB is integrated with a plurality of solid switches, a plurality of matching loads, and a control bus, the solid switches and the matching loads are arranged in a one-to-one correspondence manner, each solid switch is connected to the control bus, and when the isolation degree of two antenna ports is measured, the solid switch corresponding to a port to be measured can be controlled by the control bus, so that the port to be measured is disconnected from the switch matrix and is connected to the corresponding matching load.

As a further improvement of the present invention, the control bus may control the solid-state switches corresponding to the ports to be tested, so that the ports to be tested are disconnected from the corresponding matched loads and connected to the switch matrix.

As a further improvement of the present invention, each of the matched loads accesses a port to be tested on the interface board nearby.

As a further improvement of the invention, the matched load is a standard matched resistance of 50 ohms.

As a further improvement of the present invention, the solid state switch is a single pole double throw switch.

As a further improvement of the invention, the port standing wave ratio of the solid-state switch is less than 1.4.

As a further improvement of the invention, the solid state switch and the matching load are soldered on the PCB board.

As a further improvement of the invention, the solid-state switch is connected with the port to be tested through the SMA radio frequency connector.

As a further improvement of the invention, the SMA radio frequency connector is welded on the PCB.

As a further improvement of the invention, the number of the solid-state switches is more than 16.

The invention has the beneficial effects that:

the 5G antenna interface board port isolation measuring system can effectively measure the port isolation, effectively improve the measuring efficiency and the measuring precision, and has the advantages of simple structure and convenient operation.

The foregoing description is only an overview of the technical solutions of the present invention, and in order to make the technical means of the present invention more clearly understood, the present invention may be implemented in accordance with the content of the description, and in order to make the above and other objects, features, and advantages of the present invention more clearly understood, the following preferred embodiments are described in detail with reference to the accompanying drawings.

Drawings

FIG. 1 is a schematic diagram of the connection of a prior art network analyzer, radio frequency switch and antenna interface board;

FIG. 2 is a schematic diagram of a physical connection and an equivalent circuit between an antenna port of an antenna interface board and an internal disconnected load of a switch matrix in the prior art;

fig. 3 is a schematic diagram of a port isolation measurement system of a 5G antenna interface board in a preferred embodiment of the invention.

Detailed Description

The present invention is further described below in conjunction with the following figures and specific examples so that those skilled in the art may better understand the present invention and practice it, but the examples are not intended to limit the present invention.

As shown in fig. 3, the system for measuring the port isolation of a 5G antenna interface board in the preferred embodiment of the present invention includes a PCB and a switch matrix, where the switch matrix is connected to antenna ports on the interface board, the PCB is integrated with a plurality of solid state switches, a plurality of matching loads, and a control bus, the solid state switches and the matching loads are arranged in a one-to-one correspondence manner, each solid state switch is connected to the control bus, and when the isolation of two antenna ports is measured, the solid state switch corresponding to a port to be measured can be controlled by the control bus, so that the port to be measured is disconnected from the switch matrix and is connected to the corresponding matching load.

When the antenna parameters are measured, the control bus can control the solid-state switch corresponding to the port to be measured, so that the port to be measured is disconnected with the corresponding matched load and is connected with the switch matrix.

In this embodiment, each matching load is accessed to the port to be tested on the interface board nearby, so as to ensure that the matching load is closest to the port to be tested on the antenna interface board to the greatest extent. The port matching is close to the resistance of the matched load to the maximum extent, and the optimal matching is achieved, so that the measurement result is more accurate.

In addition, the space of the interface board is limited, and the matched load is ensured to be close to the port on the antenna interface board to the maximum extent, so that a mechanical switch cannot be selected, and only a solid-state switch can be selected.

Optionally, the matched load is a standard matched resistance of 50 ohms.

In some embodiments, the solid state switch is a single pole double throw switch.

Optionally, the insertion loss of the solid-state switch is small enough, and the port standing wave ratio is as small as possible, and further, the port standing wave ratio of the solid-state switch is less than 1.4.

In some embodiments, the solid state switch and matching load are soldered on the PCB board.

Optionally, the solid-state switch is connected to the port to be tested through the SMA radio frequency connector. Further, the SMA radio frequency connector is welded on the PCB.

Optionally, the number of the solid-state switches is greater than 16.

Through practical tests, before the measuring system is used, the isolation measured by the Cal port and the antenna port is 65dB, and after the measuring system is used, the measured value of the isolation is superior to 68 dB. The isolation index can be improved by more than 3dB, and the phase measurement precision is improved.

It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications of the invention may be made without departing from the spirit or scope of the invention.

Claims

1. A5G antenna interface board port isolation degree measuring system is characterized by comprising a PCB and a switch matrix, wherein the switch matrix is connected with antenna ports on an interface board, a plurality of solid-state switches, a plurality of matched loads and a control bus are integrated on the PCB, the solid-state switches and the matched loads are arranged in a one-to-one correspondence mode, each solid-state switch is connected with the control bus, and when the isolation degree of two antenna ports is measured, the solid-state switches corresponding to ports to be measured can be controlled through the control bus, so that the ports to be measured are disconnected with the switch matrix and are connected to the corresponding matched loads.

2. The 5G antenna interface board port isolation measurement system of claim 1, wherein the control bus controls a solid state switch corresponding to the port under test such that the port under test is disconnected from the corresponding matched load and connected to the switch matrix.

3. The 5G antenna interface board port isolation measurement system of claim 1, wherein each of the matched loads accesses a port to be tested on an interface board nearby.

4. The 5G antenna interface board port isolation measurement system of claim 1, wherein the matched load is a 50 ohm standard matched resistor.

5. The 5G antenna interface board port isolation measurement system of claim 1, wherein the solid state switch is a single pole double throw switch.

6. The 5G antenna interface board port isolation measurement system of claim 1, wherein the port standing wave ratio of the solid state switch is less than 1.4.

7. The 5G antenna interface board port isolation measurement system of claim 1, wherein the solid state switch and matching load are soldered to the PCB board.

8. The 5G antenna interface board port isolation measurement system of claim 1, wherein the solid state switch is connected to the port under test via an SMA radio frequency connector.

9. The 5G antenna interface board port isolation measurement system of claim 8, wherein the SMA radio frequency connector is soldered to the PCB board.

10. The 5G antenna interface board port isolation measurement system of claim 1, wherein the number of solid state switches is greater than 16.