A base station OTA intermodulation test system based on a reverberation chamber

Abstract

The utility model provides a kind of based on reverberation chamber's base station OTA intermodulation test system, comprising: shielding shell, closed cavity is formed in it;Stirrer is set in closed cavity, for stirring electromagnetic wave;Measured base station is placed in the working area of closed cavity, configured to emit main signal when intermodulation interference test is carried out;Interference signal antenna is arranged in working area parallelly with measured base station, and there is preset interval between interference signal antenna and measured base station;Signal source is connected with interference signal antenna, configured to provide interference signal to interference signal antenna when intermodulation interference test is carried out;Measuring antenna is set in closed cavity, for collecting electromagnetic wave signal;And signal analysis processing device is connected with measuring antenna, configured to analyze and process the collected electromagnetic wave signal, and obtain the measurement result of intermodulation interference test index based on total radiated power.The generality of emission intermodulation test is realized, and test cost and time are reduced.

Description

Technical Field

[0001] This utility model relates to the field of wireless device transmission intermodulation testing technology, and in particular to a base station OTA intermodulation testing system based on a reverberation chamber. Background Technology

[0002] 5G base station transmit intermodulation test refers to the measurement performed during the operation of the base station transmitter, which is conducted to examine the base station transmitter unit's ability to suppress nonlinear products because intermodulation occurs between the transmitter's main signal and the interference signal that reaches the transmitter unit through the base station antenna or antenna array.

[0003] The test requirement for 5G base station transmit intermodulation is to test the signal spectrum output by the base station transmitter under the condition that the interference signal with a certain frequency offset and power is fed into the base station transmitter port. The test must still meet the index requirements specified by the consistency standard under the condition of no interference signal, such as ACLR (Adjacent Channel Leakage Ratio), SEM (Spectrum Emission Mask), and spurious index requirements (excluding the spectrum with added interference signal).

[0004] However, on the one hand, 5G base stations are quite complex in type, including 1-C type base stations: those operating in the FR1 band with a conductive port and an external passive antenna; 1-O type base stations: those operating in the FR1 band without a conductive port, requiring air interface measurements only through an active array antenna; and 1-H type base stations: hybrid base stations operating in the FR1 band, which can be tested through both conductive ports and antenna air interface measurements. On the other hand, the frequency bands for 5G base stations are increasing, including not only allocated public network bands and refarmed bands, but also private network bands and the recently emerged U6G band. These factors bring more complexity to transmission intermodulation testing.

[0005] Currently, the commonly used conducted transmit intermodulation test system is based on 1-C or 1-H type base stations. This system requires a circulator capable of meeting the base station's transmit power to feed the interference signal into the base station's transmit port. However, because high-performance circulators typically operate in narrow frequency bands, each 5G base station requires a custom-designed circulator for its specific frequency band and power, along with isolators to protect the signal source from damage by high-power reverse signals, significantly increasing testing costs. Furthermore, for 1-H type base stations, there are numerous test ports, sometimes reaching hundreds; testing each port would be extremely labor-intensive. In addition, there is currently no standard-defined OTA intermodulation test scheme for transmitters of 1-O type base stations.

[0006] Therefore, there is an urgent need for a transmit intermodulation test system that can be used for different types of base stations and reduce testing costs and time. Utility Model Content

[0007] In view of the above, this utility model proposes a base station OTA intermodulation test system based on a reverberation chamber to overcome or at least partially solve the above problems.

[0008] One objective of this invention is to achieve universality in transmission intermodulation testing and reduce testing costs and time.

[0009] Another objective of this invention is to improve the accuracy of measurement results.

[0010] Specifically, this utility model provides a base station OTA intermodulation testing system based on a reverberation chamber, comprising: A shielding shell, within which a sealed cavity forms a reverberation chamber; A stirrer, installed inside a sealed cavity, is used to stir the electromagnetic waves propagating within the sealed cavity. The base station under test is placed in the working area of ​​a sealed cavity and configured to transmit the main signal of the first frequency and bandwidth in a preset transmission power mode when conducting intermodulation interference tests. An interference signal antenna is set parallel to the base station under test in the working area, with a preset distance between the interference signal antenna and the base station under test; A signal source, connected to an interfering signal antenna, is configured to provide an interfering signal of a second frequency and bandwidth with a predetermined power level to the interfering signal antenna during intermodulation interference testing. A measuring antenna, installed inside a sealed cavity, is used to collect electromagnetic wave signals within the sealed cavity during the testing process; and The signal analysis and processing device is connected to the measurement antenna and is configured to analyze and process the electromagnetic wave signals collected by the measurement antenna to obtain the measurement results of the intermodulation interference test index based on the total radiated power.

[0011] Optionally, the base station OTA intermodulation test system based on a reverberation chamber also includes: The turntable is set in a sealed cavity, with the base station under test and the interfering signal antenna mounted on it. The turntable is used to drive the base station under test and the interfering signal antenna to rotate horizontally during the test.

[0012] Optionally, the base station OTA intermodulation test system based on a reverberation chamber also includes: The calibration antenna is set on the turntable and rotates with the turntable during the test, and is connected to the signal source; The signal source is also configured to provide a main modulation signal with a first frequency and bandwidth having a first power level to the calibration antenna before intermodulation interference testing, so as to perform main signal calibration testing when the base station under test is not turned on and the interference signal antenna does not transmit signals. The signal analysis and processing device is also configured to analyze and process the electromagnetic wave signal collected by the measurement antenna during the main signal calibration test to obtain the main signal calibration value; And / or The signal source is also configured to provide an interference signal with a second frequency and bandwidth having a second power level to the calibration antenna before intermodulation interference testing, so as to perform interference signal calibration testing when the base station under test is not turned on and the interference signal antenna is not transmitting a signal. The signal analysis and processing device is also configured to analyze and process the electromagnetic wave signal collected by the measurement antenna during the interference signal calibration test to obtain the interference signal calibration value.

[0013] Optionally, the base station OTA intermodulation test system based on a reverberation chamber also includes: The controller is connected to the stirrer, turntable, signal source, and signal analysis and processing device, respectively, and is configured to control the operation of the stirrer, turntable, signal source, and signal analysis and processing device.

[0014] Optionally, the base station under test can be any one of the 1-C type 5G base station, 1-H type 5G base station, and 1-O type 5G base station equipped with an external antenna.

[0015] Optionally, the base station OTA intermodulation test system based on a reverberation chamber also includes: A shielding baffle is installed on the side of the measuring antenna facing the base station under test and the interfering signal antenna to block the direct path of signal transmission from the base station under test and the interfering signal antenna to the measuring antenna.

[0016] Optionally, the mixer includes: A horizontal stirrer, having a horizontally rotating shaft, is positioned above or below the working area of ​​a sealed cavity; and A vertical stirrer, having a vertically rotating shaft, is positioned on one side of the working area of ​​a sealed cavity.

[0017] Optionally, the antenna surface of the interfering signal antenna is coplanar with the antenna array surface of the base station under test; The preset distance between the interference signal antenna and the base station under test is 10cm.

[0018] Optionally, the signal analysis and processing device includes a spectrum analyzer; or Signal analysis and processing equipment includes a spectrum analyzer and a vector network analyzer.

[0019] Optionally, the base station OTA intermodulation test system based on a reverberation chamber also includes: A signal amplifier is connected between the signal source and the interfering signal antenna to amplify the interfering signal provided by the signal source.

[0020] This invention provides a reverberation chamber-based OTA intermodulation testing system for base stations. The system utilizes a reverberation chamber, where the base station under test and interfering signal antennas are placed parallel to each other at a preset distance within the sealed working area of ​​the reverberation chamber. A signal source provides interference signals to the interfering signal antennas, the antennas collect electromagnetic wave signals during the testing process, and a signal analysis and processing device analyzes and processes the collected signals to complete the intermodulation interference test. Because a reverberation chamber cannot perform directional EIRP testing, but can quickly measure TRP-type tests, this system can rapidly test intermodulation interference indicators based on total radiated power, significantly reducing testing time. Furthermore, due to the use of OTA testing, there is no need to customize and purchase circulators, notch filters, isolators, etc., or to measure each antenna port separately, thus effectively solving the problems of long transmission intermodulation testing time, high testing cost, and poor executability. This system does not require a conductive port for signal transmission, making it suitable for testing various types of base stations and possessing excellent versatility.

[0021] Furthermore, in the reverberation chamber-based OTA intermodulation test system provided by this utility model, a turntable is also set in the sealed cavity of the reverberation chamber to drive the base station under test and the interference signal antenna to rotate horizontally during the test. In conjunction with a stirrer, electromagnetic waves are used to stir the field to randomize it, which can ensure that the sampling signal obtained each time is an independent sample, thereby improving the accuracy of the measurement results.

[0022] Furthermore, the reverberation chamber-based OTA intermodulation testing system for base stations provided by this invention is also equipped with a calibration antenna to perform main signal calibration testing and / or interference signal calibration testing before intermodulation interference testing, thereby further improving the accuracy of measurement results.

[0023] The above description is merely an overview of the technical solution of this utility model. In order to better understand the technical means of this utility model and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this utility model more obvious and understandable, specific embodiments of this utility model are given below.

[0024] The above and other objects, advantages and features of this utility model will become more apparent to those skilled in the art from the following detailed description of specific embodiments of this utility model in conjunction with the accompanying drawings. Attached Figure Description

[0025] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of the invention. The same reference numerals in the drawings denote the same or similar parts or components. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings: Figure 1 This is a connection block diagram of a conducted intermodulation test system for 1-C or 1-H type base stations in the prior art; Figure 2 This is a schematic diagram of the structure of a base station OTA intermodulation test system based on a reverberation chamber according to an embodiment of the present invention; Figure 3a This is a schematic diagram of the base station ACLR measured without interference signals according to an embodiment of the present invention; Figure 3b This is a schematic diagram of the ACLR of a base station measured under the condition of added interference signal according to an embodiment of the present invention; Figure 4a This is a schematic diagram of the base station OBUE measured without interference signals according to an embodiment of the present invention; Figure 4b This is a schematic diagram of the base station OBUE measured under the condition of added interference signal according to an embodiment of the present invention; Figure 5a This is a schematic diagram of base station spurious emissions measured without the addition of interference signals according to an embodiment of the present invention; Figure 5b This is a schematic diagram of base station spurious emissions measured under the condition of added interference signal according to an embodiment of the present invention. Detailed Implementation

[0026] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0027] Currently, the commonly used method for conducting intermodulation testing of base stations is the conducted intermodulation testing scheme based on 1-C or 1-H type base stations.

[0028] Figure 1The diagram shows a connection block diagram of a conducted intermodulation test system for a 1-C or 1-H type base station in the prior art. When testing a port, the interference signal is fed into the transmit port of the device under test through a circulator, while the other ports of the base station are terminated with loads. In this way, all ports are tested.

[0029] This type of conducted signal testing has three main problems. First, conducted signal testing cannot be performed on 1-O type base stations. Second, apart from attenuators, which are relatively common test accessories and do not require additional purchase, other components, such as circulators, notch filters, and isolators, need to be customized according to the frequency band, bandwidth, and maximum transmit power of the device under test. Taking 5G base stations as an example, in the downlink frequency bands, in addition to the newly allocated bands such as 700M, 2.6G, 3.3G, 3.4G, 3.5G, and 4.9G, there are also a large number of refarmed frequency bands from 2G and 3G systems. Currently, a total of fifteen frequency bands have been allocated, as detailed in Table 1 below. Band 15 is a allocated but unallocated band, which may be further split into more allocated bands in the future. Each frequency band has a specified bandwidth, and the base station transmit power of each band is different, for example, ranging from 24-60dBm. Due to the large number of base station types, the required circulators, notch filters, isolators, and other components need to be customized according to their frequency, bandwidth, and power specifications for each type of base station. Customization costs, customization timelines, and customized technical specifications all affect the normal conduct of testing. Third, for 1-C type base stations, the number of ports is generally small, such as 2-8, making it feasible to test all ports. However, for 1-H base stations, the number of ports increases with the number of antenna elements. Especially for large AAS base stations, the number of ports can reach hundreds; if all ports are tested, the measurement time would be immeasurable.

[0030] Table 1 Examples of 5G NR downlink frequency bands The purpose of OTA (Over-the-Air) transmitter intermodulation testing is to measure the ability of a transmitter unit associated with a base station under test (RTB, Radio Frequency Interface Board) to control intermodulation products generated in its nonlinear components below specified levels. These intermodulation signals are generated by the desired signal and interference signals arriving at the transmitter unit from, for example, a co-location base station via an RDN (Receiver Distribution Network) and antenna array. This needs to be tested during transmitter power-on and during transmitter transients, and across all operating frequency bands supported by the base station under test.

[0031] Transmitter intermodulation level refers to the total radiated power (TRP) of the intermodulation products when an interference signal is injected into a CLTA (Co-Location Test Antenna).

[0032] The specific test requirements are shown in Table 2 below. Under the conditions of useful signals and interference signals specified in Table 2, the transmitter intermodulation level shall not exceed the following total radiated power unwanted emission limits specified for transmitters: ① OTA spurious emissions (except for co-located spurious emissions); ② OTA out-of-band unwanted emissions (OBUE); ③ OTA adjacent channel leakage ratio (ACLR) limit.

[0033] Table 2 Base Station Transmit Intermodulation Parameter Requirements For 1-O type base stations, the 3GPP standard does not currently specify a concrete OTA intermodulation test scheme for the transmitter. Since the final evaluation criteria for intermodulation testing are reflected through ACLR, OBUE, and spurious emissions testing, these tests all require the use of TRP's OTA testing to obtain the final results.

[0034] A reverberation chamber is an over-the-air (OTA) testing system with a highly reflective shielded metal enclosure that employs one or more "stirring" methods to randomize the field. This allows for the acquisition of a large number of uncorrelated samples for non-directional averaging measurements, similar to TRP (Transient Reverberation Process) tests.

[0035] Based on the above understanding, and in response to the existing technical problems, this utility model breaks with conventional testing approaches and proposes a base station OTA intermodulation testing system based on a reverberation chamber.

[0036] Figure 2 This is a schematic diagram of the structure of a base station OTA intermodulation test system 100 based on a reverberation chamber according to an embodiment of the present invention.

[0037] See Figure 2As shown, the base station OTA intermodulation test system 100 generally includes: a shielded housing 1, which forms a closed cavity with a reverberation chamber; a stirrer, disposed within the closed cavity, for stirring electromagnetic waves propagating within the closed cavity; a base station under test 7, placed in the working area 5 of the closed cavity, configured to transmit a main signal with a first frequency and bandwidth in a preset transmission power mode during intermodulation interference testing; an interference signal antenna 8, disposed parallel to the base station under test 7 within the working area 5, with a preset distance D between the interference signal antenna 8 and the base station under test 7; a signal source 12, connected to the interference signal antenna 8, configured to provide an interference signal with a second frequency and bandwidth of a predetermined power level to the interference signal antenna 8 during intermodulation interference testing; a measurement antenna 4, disposed within the closed cavity, for collecting electromagnetic wave signals within the closed cavity during testing; and a signal analysis and processing device 10, connected to the measurement antenna 4, configured to analyze and process the electromagnetic wave signals collected by the measurement antenna 4 to obtain measurement results of intermodulation interference test indicators based on total radiated power.

[0038] The shielding shell 1 can be a high-reflectivity shielding metal shell, used to isolate the air interface measurement environment from the external electromagnetic environment.

[0039] The working area 5 can also be called the testing volume. Inside the shielded outer shell 1 of the reverberation chamber, the space where the electromagnetic field is statistically uniform is called the field uniformity region, and the working area 5 is generally located within the field uniformity region. Within the field uniformity region, the statistically averaged electric field is independent of the testing location; that is, the electric field is statistically uniform in space.

[0040] The signal source 12 and the signal analysis and processing device 10 can be integrated together.

[0041] During intermodulation interference testing, the base station under test (BUT) 7 is activated, transmitting a main signal with a first frequency and bandwidth at a preset transmission power mode. The signal source 12 provides an interference signal with a second frequency and bandwidth at a predetermined power level to the interference signal antenna 8, generating intermodulation interference on the BUT 7, thereby conducting the intermodulation interference test. With the stirrer activated for electromagnetic wave agitation, the measuring antenna 4 collects electromagnetic wave signals within the sealed cavity (i.e., performs signal sampling) and transmits them to the signal analysis and processing device 10. The signal analysis and processing device 10 analyzes and processes the collected electromagnetic wave signals to obtain measurement results of the intermodulation interference test indicators based on the total radiated power.

[0042] The OTA intermodulation testing system 100 for base stations based on a reverberation chamber provided in this embodiment employs a reverberation chamber. The base station under test 7 and the interfering signal antenna 8 are placed parallel to each other at a preset distance within the working area 5 of the sealed cavity of the reverberation chamber. A signal source 12 provides an interference signal to the interfering signal antenna 8, a measuring antenna 4 collects electromagnetic wave signals during the test, and a signal analysis and processing device 10 analyzes and processes the collected signals to complete the intermodulation interference test. Since the reverberation chamber cannot perform directional EIRP testing but can quickly measure TRP-type tests, the system 100 of this invention can quickly test intermodulation interference indicators based on total radiated power, greatly reducing test time. Furthermore, because it uses the OTA testing method, there is no need to customize and purchase circulators, notch filters, isolators, etc. of different specifications, nor is it necessary to measure each antenna port separately. Therefore, it can effectively solve the problems of long transmission intermodulation test time, high test cost, and poor executability. The system 100 of this invention does not require a conductive port for signal transmission, thus it is suitable for testing various types of base stations and has excellent versatility.

[0043] The measurement antenna 4 must meet the required test frequency band requirements. If one antenna cannot cover all test frequency bands, the measurement antenna 4 must be replaced for each frequency band.

[0044] In some specific embodiments, the signal analysis and processing device 10 may employ a spectrum analyzer.

[0045] In some embodiments, the base station 7 under test can be any one of a 1-C type 5G base station, a 1-H type 5G base station, and a 1-O type 5G base station equipped with an external antenna. In other words, the reverberation chamber-based base station OTA intermodulation test system 100 of this invention is applicable not only to 1-C type base stations and 1-H type base stations, but also to 1-O type base stations, and has good versatility.

[0046] In some embodiments, the base station under test 7 transmits the main signal in the maximum transmit power mode.

[0047] The first frequency and bandwidth, as well as the second frequency and bandwidth, can be determined according to the actual application requirements, so that the frequency offset and bandwidth of the interference signal relative to the main signal meet the test requirements.

[0048] In some embodiments, the antenna surface of the interfering signal antenna 8 is coplanar with the antenna array surface of the base station under test 7. The preset distance D between the interfering signal antenna 8 and the base station under test 7 is 10 cm. Thus, the interfering signal antenna 8 is configured as a co-located antenna to emit an interfering signal.

[0049] In practical applications, the interference signal antenna 8, which transmits interference signals, needs to support the interference signal frequency band and meet certain antenna pattern requirements. The pattern should be defined based on the interference signal systems that the actual base station may encounter during use. For example, if a 5G base station is interfered with by adjacent co-located 2G, 3G, and 4G base stations, the horizontal beamwidth of the interference signal antenna 8 can be approximately 65°.

[0050] In some embodiments, the base station OTA intermodulation test system 100 based on a reverberation chamber may further include a turntable 9. The turntable 9 is disposed within the sealed cavity of the reverberation chamber. The base station under test 7 and the interfering signal antenna 8 are disposed on the turntable 9. The turntable 9 is used to drive the base station under test 7 and the interfering signal antenna 8 to rotate horizontally during the test.

[0051] Specifically, the base station under test 7 and the interfering signal antenna 8 are supported on a turntable 9 by a support structure. The support structure can be made of a material that does not transmit electromagnetic waves, such as a non-metallic material. The turntable 9 is a one-dimensional turntable that can rotate uniformly in the horizontal direction.

[0052] In some embodiments, during intermodulation interference testing, while the stirrer is turned on to stir the electromagnetic waves, the turntable 9 is also activated to drive the base station under test 7 and the interference signal antenna 8 to rotate horizontally, and the measuring antenna 4 periodically collects electromagnetic wave signals in the sealed cavity at set time intervals.

[0053] In the reverberation chamber-based OTA intermodulation test system 100 of this embodiment, a turntable 9 is also set in the sealed cavity of the reverberation chamber to drive the base station under test 7 and the interference signal antenna 8 to rotate horizontally during the test. In conjunction with a stirrer, electromagnetic waves are used to stir the field to randomize it, which can ensure that the sampling signal obtained each time is an independent sample, thereby improving the accuracy of the measurement results.

[0054] In some embodiments, the agitator may include: a horizontal agitator 2 having a horizontally rotating shaft and disposed above or below the working area 5 of the sealed cavity; and a vertical agitator 3 having a vertically rotating shaft and disposed on the lateral side of the working area 5 of the sealed cavity.

[0055] Horizontal stirrer 2 and vertical stirrer 3 are electromagnetic stirrers that agitate electromagnetic waves. The rotation of horizontal stirrer 2 and vertical stirrer 3, combined with the rotation of turntable 9, allows for the acquisition of a large number of unrelated test samples during the testing process.

[0056] By controlling the rotation angle and speed of the horizontal stirrer 2, the vertical stirrer 3, and the turntable 9, the signal acquisition time interval of the measuring antenna 4 is synchronized (specifically, the time interval for each scan by instruments such as the spectrum analyzer). Specifically, the time interval for instrument scanning can be made greater than or equal to the time interval for one change in the position of the stirrer / turntable 9, ensuring the independence of each sampling sample.

[0057] For example, in a specific test instance, the turntable 9, along with the horizontal stirrer 2 and the vertical stirrer 3, rotate uniformly. The turntable 9 is set to a step size of 5°, controlling its reciprocating rotation. Each rotation angle is timed at 500ms. The spectrum analyzer's scan time is also set accordingly to 500ms. The horizontal stirrer 2 and the vertical stirrer 3 can be set to rotate at different speeds, for example, 10° / s and 14° / s respectively, ensuring that each sampled data is an independent sample.

[0058] In some embodiments, the reverberation chamber-based base station OTA intermodulation testing system 100 may further include a controller 11. The controller 11 is connected to the stirrer, turntable 9, signal source 12, and signal analysis and processing device 10, respectively, and is configured to control the operation of the stirrer, turntable 9, signal source 12, and signal analysis and processing device 10. The controller 11 may be, for example, a control computer.

[0059] Furthermore, the controller 11 may be equipped with a software control interface to receive adjustment commands through the software control interface, thereby modifying and adjusting the rotation angle and speed of the agitator and the turntable 9.

[0060] In some embodiments, the base station OTA intermodulation test system 100 based on a reverberation chamber may further include a calibration antenna 6, which is disposed within the working area 5 of the sealed cavity of the reverberation chamber and connected to the signal source 12.

[0061] In some embodiments, the signal source 12 is further configured to provide a main modulation signal with a first frequency and bandwidth having a first power level to the calibration antenna 6 before performing an intermodulation interference test, so as to perform a main signal calibration test when the base station under test 7 is not turned on and the interfering signal antenna 8 does not transmit a signal. When the stirrer is turned on for electromagnetic wave stirring, the measuring antenna 4 collects the electromagnetic wave signal within the sealed cavity and transmits it to the signal analysis and processing device 10. The signal analysis and processing device 10 is further configured to analyze and process the electromagnetic wave signal collected by the measuring antenna 4 during the main signal calibration test to obtain the main signal calibration value. The main signal calibration value is the power transfer function of the reverberation chamber at the first frequency and bandwidth.

[0062] In other words, the reverberation chamber-based base station OTA intermodulation test system 100 can also perform main signal calibration tests before performing intermodulation interference tests.

[0063] The operating conditions for the stirrer and electromagnetic wave acquisition during the main signal calibration test are the same as those for the stirrer and electromagnetic wave acquisition during the intermodulation interference test.

[0064] In some embodiments, the signal source 12 is further configured to provide an interference signal with a second frequency and bandwidth having a second power level to the calibration antenna 6 before performing an intermodulation interference test, so as to perform an interference signal calibration test when the base station under test 7 is not turned on and the interference signal antenna 8 is not transmitting a signal. With the stirrer turned on for electromagnetic wave stirring, the measuring antenna 4 collects the electromagnetic wave signal within the sealed cavity and transmits it to the signal analysis and processing device 10. The signal analysis and processing device 10 is further configured to analyze and process the electromagnetic wave signal collected by the measuring antenna 4 during the interference signal calibration test to obtain an interference signal calibration value. The interference signal calibration value is the power transfer function of the reverberation chamber at the second frequency and bandwidth.

[0065] In other words, the reverberation chamber-based base station OTA intermodulation test system 100 can also perform interference signal calibration tests before performing intermodulation interference tests.

[0066] The operating conditions for the stirrer and electromagnetic wave acquisition during the interference signal calibration test are the same as those for the stirrer and electromagnetic wave acquisition during the intermodulation interference test.

[0067] The first power level and the second power level can be set according to actual test requirements.

[0068] In some embodiments, the calibration antenna 6 is mounted on a turntable 9 together with the base station under test 7 and the interference signal antenna 8. Specifically, the calibration antenna 6 is supported on the turntable 9 by a support. The support may be made of a material that does not transmit electromagnetic waves, such as a non-metallic material.

[0069] Accordingly, during the main signal calibration test and interference signal calibration test, while the measuring antenna 4 is collecting electromagnetic wave signals in the sealed cavity, in addition to the stirrer being turned on to stir the electromagnetic waves, the turntable 9 is also turned on to drive the base station under test 7, the interference signal antenna 8 and the calibration antenna 6 set on it to rotate horizontally.

[0070] At this time, the operating conditions of the stirrer, turntable 9, and electromagnetic wave acquisition during the main signal calibration test are the same as those during the intermodulation interference test. The operating conditions of the stirrer, turntable 9, and electromagnetic wave acquisition during the interference signal calibration test are the same as those during the intermodulation interference test.

[0071] It should be noted that in actual test examples, the execution order of the main signal calibration test and the interference signal calibration test is interchangeable. In other words, the interference signal calibration test can be performed first, followed by the main signal calibration test, or vice versa.

[0072] In some embodiments, the signal analysis and processing apparatus 10 may include a spectrum analyzer and a vector network analyzer.

[0073] Single-carrier calibration can be performed using a vector network analyzer, while broadband modulated signal calibration can be accomplished using a broadband vector signal source 12 in conjunction with a spectrum analyzer. Signal sampling and measurement averaging are performed using a spectrum analyzer.

[0074] Based on the principle of vector network analyzer, the power transfer function of the reverberation chamber is obtained for site calibration. G ref,t As shown in the following formula: Where N represents the number of samples, and n represents the nth sample. F represents the number of frequencies during sampling. f Representing the f One frequency point. S 21 The S-parameters are collected by a vector network analyzer. e mismatch，meas S11 represents measuring antenna 4. e mismatch，ref S11 represents the calibration antenna 6. η meas This represents the antenna efficiency of measurement antenna 4. η ref This represents the antenna efficiency of calibrated antenna 6.

[0075] Regarding measuring antenna 4 e mismatch，meas and η meas This will be canceled out during the measurement process, and the formula for the average TRP power ultimately measured in the reverberation chamber is as follows: in, P t The relevant TRP power transmitted by the base station to be measured; P SA This is the power result read by the spectrum analyzer. Generally, the spectrum analyzer can directly obtain the power by performing linear power averaging. This requires that the number of points N and the frequency F selected during the calibration test be consistent with those selected during the intermodulation interference test.

[0076] In some embodiments, the signal analysis and processing device 10 is further configured to send an interference signal calibration value to the controller 11. The controller 11 determines a predetermined power level of the interference signal based on the interference signal calibration value and the interference signal power level required for the intermodulation interference test, and generates a corresponding control command to send to the signal source 12, so as to control the signal source 12 to provide an interference signal of the predetermined power level to the interference signal antenna 8.

[0077] In some specific embodiments, the minimum value of the interference signal power level required in Table 2 is added to the interference signal calibration value to obtain the predetermined power level of the interference signal.

[0078] In some embodiments, the base station OTA intermodulation test system 100 based on a reverberation chamber may further include a signal amplifier (not shown in the figure). The signal amplifier is connected between the signal source 12 and the interfering signal antenna 8 to amplify the interfering signal provided by the signal source 12. When the link loss is too high and the maximum output power of the signal source 12 cannot meet the power level requirements of the interfering signal, amplifying the interfering signal output by the signal source 12 using the signal amplifier before feeding the signal into the interfering signal antenna 8 can ensure that the interfering signal meets the test requirements.

[0079] In some embodiments, the base station OTA intermodulation test system 100 based on a reverberation chamber may further include a shielding baffle (not shown in the figure). The shielding baffle is disposed on the side of the measuring antenna 4 facing the base station under test 7 and the interfering signal antenna 8, and is used to block the direct path of signal transmission from the base station under test 7 and the interfering signal antenna 8 to the measuring antenna 4, thereby ensuring the effectiveness of signal sampling and improving the accuracy of measurement results.

[0080] When a calibration antenna 6 is provided in the base station OTA intermodulation test system 100, the shielding baffle is also used to block the direct path of the signal transmitted from the calibration antenna 6 to the measurement antenna 4.

[0081] In some embodiments, intermodulation interference test metrics may include adjacent channel leakage ratio, out-of-band unwanted emissions, and stray emissions.

[0082] The analysis and processing of electromagnetic wave signals collected in the reverberation chamber, especially the processing using a spectrum analyzer, to obtain adjacent channel leakage ratio, out-of-band unwanted emissions, and stray emissions results should be known to those skilled in the art, and will not be specifically described in this utility model.

[0083] In some embodiments, when the intermodulation interference test index includes out-of-band unwanted emissions, the signal analysis and processing apparatus 10 is further configured to use the main signal calibration value as compensation when analyzing and processing the acquired electromagnetic wave signal to obtain the measurement result of out-of-band unwanted emissions based on the total radiated power.

[0084] The reverberation chamber-based OTA intermodulation testing system 100 of this invention can also perform main signal calibration test and / or interference signal calibration test before conducting intermodulation interference test, thereby further improving the accuracy of measurement results.

[0085] In some embodiments, the signal analysis and processing device 10 may also be configured to: after analyzing and processing the acquired electromagnetic wave signal to obtain the measurement results of the intermodulation interference test index based on the total radiated power, determine whether the measurement results of the intermodulation interference test index meet the specified test requirements.

[0086] The following specific embodiment further illustrates the testing process of the reverberation chamber-based base station OTA intermodulation testing system 100 of this utility model.

[0087] Example 1 The base station OTA intermodulation test system 100 based on a reverberation chamber in this embodiment adopts... Figure 2 The structure shown.

[0088] The test procedure of the base station OTA intermodulation test system 100 based on the reverberation chamber in this embodiment is as follows: (1) Use signal source 12 to send a 5G NR main modulation signal to calibration antenna 6, start turntable 9 and horizontal stirrer 2 and vertical stirrer 3 to rotate uniformly, where turntable 9 is set to a step of 5°, control turntable 9 to rotate back and forth, the time interval for each rotation angle is 500ms; the scan time of spectrum analyzer is also set to 500ms accordingly; horizontal stirrer 2 and vertical stirrer 3 are set to rotate in steps of 10° and 14° respectively to ensure that the sampled data obtained each time is an independent sample. Connect measurement antenna 4 to spectrum analyzer, perform power (channel power) measurement within the main signal frequency bandwidth, and set the spectrum analyzer detection mode to RMS (Root Mean Square), the frequency span is set to 1.2 times the signal bandwidth, turn on the linear power averaging mode of spectrum analyzer, the averaging number generally needs to be greater than 100 times, the averaging number setting needs to ensure that the value of the obtained measurement average value remains basically unchanged after one decimal place. The average result at this time is the power transfer function of the reverberation chamber in this frequency bandwidth after electromagnetic stirring, that is, the main signal calibration value. If there are multiple bandwidths in the main signal frequency band, multiple calibrations are required.

[0089] (2) Signal source 12 shuts down the main signal and adjusts the frequency and bandwidth to send the interference signal to calibration antenna 6. According to Table 2, select the minimum bandwidth 5G NR signal with an SCS (Sub-carrier Spacing) of 15kHz as the interference signal. Perform channel power averaging within the interference signal frequency bandwidth. The turntable 9, stirrer settings, and spectrum analyzer settings are the same as in (1). Measure the power transfer function of the reverberation chamber at this frequency bandwidth, i.e., the interference signal calibration value. If there are multiple interference signal frequency bandwidths, multiple calibrations are required.

[0090] (3) Turn on the base station under test 7 and turn on the interference signal source 12. According to Table 2 and the interference signal calibration value in step (2), the transmission power that the interference signal source 12 should be set to is obtained. If the link loss is too large and the maximum output power of the signal source 12 cannot meet the requirements, a signal amplifier is needed to amplify the signal output by the signal source 12 before feeding the signal into the interference signal antenna 8.

[0091] (4) Start the control software to rotate the stirrer and turntable 9. The settings of turntable 9 and stirrer are the same as in (1). The base station under test 7 and the interference signal antenna 8, together with the calibration antenna 6, are placed on the turntable 9 as shown in Figure 3, and rotated stably and uniformly on the support in the working area 5. The rotation speed, interval, and spectrum analyzer settings in this step are completely consistent with those in the calibration stage.

[0092] (5) During the rotation process in (4), the interference signal generates intermodulation interference to the base station under test 7 through the co-located antenna. Then, the ACLR, OBUE and spurious emissions at this time are measured by the measuring antenna 4. When performing spurious emission measurements, it is necessary to replace the necessary measuring antenna 4 to meet the requirements of the spurious frequency band.

[0093] Figure 3a This is a schematic diagram of the base station ACLR measured without the addition of interference signals according to an embodiment of the present invention. Figure 3b This is a schematic diagram of the base station ACLR measured under the condition of added interference signal according to an embodiment of the present invention. According to Table 2, the added interference signal is a 20MHz bandwidth NR signal with n=1 on the left side of the lower edge of the main signal. Figure 3a and Figure 3b The results show that the added interference signal is in the red area on the left. In this case, it is only necessary to consider whether the adjacent channel result of the ACLR on the right meets the specified test requirements. Similarly, when an interference signal is added on the right, it is necessary to consider whether the adjacent channel limit of the ACLR on the left meets the requirements.

[0094] Figure 4aThis is a schematic diagram of the base station OBUE measured without interference signals according to an embodiment of the present invention. Figure 4b This is a schematic diagram of the base station OBUE measured under the condition of added interference signal according to an embodiment of the present invention. Figure 4a and Figure 4b The comparison of the results shows that because the interference signal is applied to the right side of the upper edge frequency of the main signal, the OBUE measurement results show interference signals at the right edge of the frequency range. In this case, it is necessary to consider whether the OBUE test area outside the frequency range of the right-side interference signal meets the specified test requirements.

[0095] Figure 5a This is a schematic diagram of base station spurious emissions measured without the addition of interference signals according to an embodiment of the present invention. Figure 5b This is a schematic diagram of spurious emissions from a base station measured under interference signals according to an embodiment of the present invention, wherein the spurious frequency band is in the 1-31 GHz band. Figure 5a and Figure 5b The results show that, since the frequency offset of the interference signal in this example is still within the operating frequency band relative to the main signal, and the spurious emission measurement excludes the measurement results of the main signal 2.5 times the bandwidth, the impact on the spurious emission measurement results is not significant.

[0096] The base station OTA intermodulation testing system 100 based on a reverberation chamber of this invention has the following advantages: 1) Measuring intermodulation via OTA (Over-The-Air) allows for flexible definition of the frequency offset position of the interfering signal. Currently, the standard specifies the frequency offset of the interfering signal from the main signal as shown in Table 2. (n=1, 2, 3), but with the widespread development of wireless communication, the inter-system interference situations that need to be considered are diverse, not limited to the frequency band near the main signal carrier. For circulators, when the insertion loss is <0.5 dB and the isolation is >20 dB, the bandwidth that a common circulator can achieve is only about 10%-20% of the center frequency. For example, the bandwidth of the 3.5 GHz center frequency is about 350M-700M, which cannot be used to test intermodulation signals at 2.1 GHz or 5.9 GHz. If it is desired to test the intermodulation between two systems with far apart frequencies, the use of circulators will be limited. The S-parameter test diagram of circulators shows that, in terms of insertion loss and suppression, the effective operating frequency band is only within the 2300-2700MHz bandwidth. The suppression at frequencies outside this bandwidth becomes very poor and cannot be used. However, OTA testing is not subject to this limitation. As long as an antenna of appropriate frequency band is used, interference signals with larger frequency offsets can be generated, without being limited by RF devices. In addition, OTA testing is closer to the actual state of a device under real-world usage, and the test results are closer to the actual performance.

[0097] 2) While OTA intermodulation testing can be conducted using various OTA environments such as compact field, far field, plane wave synthesis systems, and near field, these OTA anechoic chambers are all directional anechoic chambers. When performing OTA measurements such as ACLR, OBUE, and spurious emissions, TRP measurements are required. This means that the base station under test and the interfering signal antenna must be scanned point-by-point across the entire sphere, and the power value at each frequency point is calculated using the TRP calculation formula. Therefore, compared to a reverberation chamber, the measurement time of a test system using a directional anechoic chamber can be dozens of times longer, resulting in significantly higher testing costs and impacting the feasibility of the test. For example, based on a main signal frequency band, the testing time of a directional OTA anechoic chamber test system would require at least half a month or even a month, while the reverberation chamber-based test system proposed in this invention only requires one hour.

[0098] 3) Based on the testing principle of the reverberation chamber, the reverberation chamber presents a wireless scattering environment with statistical characteristics, which is a rich isotropic multipath environment. This characteristic can better simulate the actual use scenarios of communication systems such as 4G and 5G, and is more advantageous for interference testing.

[0099] Numerous specific details are set forth in the specification provided herein. However, it will be understood that embodiments of the present invention may be practiced without these specific details. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.

[0100] Therefore, those skilled in the art should recognize that although many exemplary embodiments of the present invention have been shown and described in detail herein, many other variations or modifications conforming to the principles of the present invention can be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the present invention. Therefore, the scope of the present invention should be understood and recognized as covering all such other variations or modifications.

Claims

1. A base station OTA intermodulation testing system based on a reverberation chamber, characterized in that, include: A shielding shell, within which a sealed cavity forms a reverberation chamber; A stirrer is disposed within the sealed cavity and is used to stir the electromagnetic waves propagating within the sealed cavity. The base station under test is placed in the working area of ​​the sealed cavity and configured to transmit a main signal with a first frequency and bandwidth in a preset transmission power mode when performing intermodulation interference testing. An interference signal antenna is arranged parallel to the base station under test in the working area, and there is a preset distance between the interference signal antenna and the base station under test; A signal source, connected to the interfering signal antenna, is configured to provide the interfering signal antenna with a second frequency and bandwidth of a predetermined power level during intermodulation interference testing. A measuring antenna is installed inside the sealed cavity to collect electromagnetic wave signals inside the sealed cavity during the test. as well as A signal analysis and processing device, connected to the measuring antenna, is configured to analyze and process the electromagnetic wave signals collected by the measuring antenna to obtain measurement results of intermodulation interference test indicators based on total radiated power.

2. The base station OTA intermodulation test system based on a reverberation chamber according to claim 1, characterized in that, Also includes: A turntable is disposed within the sealed cavity, wherein the base station under test and the interference signal antenna are disposed on the turntable, and the turntable is used to drive the base station under test and the interference signal antenna to rotate horizontally during the test.

3. The base station OTA intermodulation test system based on a reverberation chamber according to claim 2, characterized in that, Also includes: A calibration antenna is mounted on the turntable and rotates with the turntable during the test, and is connected to the signal source; The signal source is further configured to provide the calibration antenna with a first frequency and bandwidth having a first power level before conducting intermodulation interference testing, so as to perform main signal calibration testing when the base station under test is not turned on and the interference signal antenna does not transmit signals. The signal analysis and processing device is further configured to analyze and process the electromagnetic wave signal collected by the measurement antenna during the main signal calibration test to obtain the main signal calibration value; And / or The signal source is also configured to provide an interference signal with a second frequency and bandwidth having a second power level to the calibration antenna before performing an intermodulation interference test, so as to perform an interference signal calibration test when the base station under test is not turned on and the interference signal antenna does not transmit a signal. The signal analysis and processing device is further configured to analyze and process the electromagnetic wave signal collected by the measuring antenna during the interference signal calibration test to obtain the interference signal calibration value.

4. The base station OTA intermodulation test system based on a reverberation chamber according to claim 2 or 3, characterized in that, Also includes: The controller is connected to the stirrer, the turntable, the signal source, and the signal analysis and processing device, respectively, and is configured to control the operation of the stirrer, the turntable, the signal source, and the signal analysis and processing device.

5. The base station OTA intermodulation test system based on a reverberation chamber according to claim 1, characterized in that, The base station under test is any one of the 1-C type 5G base station, 1-H type 5G base station, and 1-O type 5G base station equipped with an external antenna.

6. The base station OTA intermodulation test system based on a reverberation chamber according to claim 1, characterized in that, Also includes: A shielding baffle is disposed on the side of the measuring antenna facing the base station under test and the interference signal antenna, for blocking the direct path of signal transmission from the base station under test and the interference signal antenna to the measuring antenna.

7. The base station OTA intermodulation test system based on a reverberation chamber according to claim 1, characterized in that, The stirrer includes: A horizontal stirrer, having a horizontally rotating shaft, is positioned above or below the working area of ​​the sealed cavity; and A vertical stirrer, having a vertically rotating shaft, is located on one side of the working area of ​​the sealed cavity.

8. The base station OTA intermodulation test system based on a reverberation chamber according to claim 1, characterized in that, The antenna surface of the interference signal antenna is coplanar with the antenna array surface of the base station under test; The preset distance between the interference signal antenna and the base station under test is 10cm.

9. The base station OTA intermodulation test system based on a reverberation chamber according to claim 1, characterized in that, The signal analysis and processing device includes a spectrum analyzer; or The signal analysis and processing device includes a spectrum analyzer and a vector network analyzer.

10. The base station OTA intermodulation test system based on a reverberation chamber according to claim 1, characterized in that, Also includes: A signal amplifier is connected between the signal source and the interference signal antenna to amplify the interference signal provided by the signal source.

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