A radio frequency transmitter stray radiation test system and test method

Abstract

The present invention provides a spurious radiation test system and test method for a radio frequency transmitter. The system is a near-field test system, the test field is a microwave darkroom; the servo system is a one-axis precision turntable installed in the microwave darkroom, and the antenna of the radio frequency transmitter to be tested is set on the precision turntable; the radio frequency subsystem includes a vector network analyzer, and the vector network analyzer uses a test probe to receive the radiation signal of the antenna of the radio frequency transmitter to be tested to complete the amplitude and phase parameter test of the antenna of the radio frequency transmitter to be tested. The test method adopts a field test method. The present invention uses a one-axis turntable in conjunction with a probe array to achieve spherical near-field sampling of the electromagnetic field.

Description

Technical Field

[0001] The invention relates to the field of stray radiation testing, and in particular to a stray radiation testing system and a testing method for a radio frequency transmitter. Background Art

[0002] The communication transmitter includes a power transmitter and an antenna. Currently, the transmitters and antennas of large-scale MIMO, active phased array radars, and new-generation mobile communication base stations are all designed and produced in an integrated manner. They cannot be separated and tested individually. Therefore, an air interface test method that can test the overall radiation performance must be used. Modern RF transmitters often operate in a wider frequency band, that is, they have multiple test frequencies; at the same time, each frequency has multiple wave positions, that is, multiple radiation patterns are achieved through phase control. At the same time, due to the nonlinearity of RF devices and modules, additional spectrum signals will be derived, generally called spurious signals. These signals can also be radiated through the antenna, thereby generating spurious emission patterns. The frequency components of spurious emissions mainly include RF harmonics, parasitic emissions, intermodulation products, high-order frequency conversion products, broadband noise, etc.

[0003] The main channel signal radiation performance of the communication equipment and the emission performance of the stray signal are important indicators for measuring the performance of mobile base stations, MIMO communication equipment, and active phased array equipment. With the rapid development of modern communication technology, various wireless communication equipment occupies a large amount of frequency band resources, and various communication products also generate a large amount of stray radiation. These stray signals pollute the RF communication environment, which may interfere with the communication of adjacent channels or cause other communication equipment to be interrupted. Therefore, countries around the world have formulated strict radiation standards for electronic products, requiring that the stray radiation of the products sold must meet certain indicators before they are allowed to be put on the market.

[0004] Antenna measurement technology is divided into far field and near field according to the size of the test field. Far field testing is the most basic method of antenna testing. It requires that the transmitting and receiving antennas in the test field are located in their respective far field ranges, so the test field is required to have a sufficiently large test size. The far field distance is related to the aperture size and frequency band of the antenna. It is generally believed that antennas with a far field distance of less than 20m can be tested indoors without reflection, and antennas with a far field distance of more than 20m need to be tested outdoors. Due to the influence of ground reflection waves during far field testing, it is difficult to achieve high measurement accuracy. It is also easily affected by factors such as surrounding electromagnetic interference, climatic conditions, and limited test distance, making it difficult to truly reflect the actual performance of the antenna. Antenna near field testing uses a probe with known characteristics to sample the amplitude and phase of the antenna's near field radiation at a distance of several wavelengths from the antenna to be tested, and indirectly calculate the antenna's far field characteristics. Its essence is to calculate the weighting function based on the near field test data, and expand the antenna's radiation field into the sum of spatial wave functions, where the weighting function contains the complete antenna far field pattern information. According to the Huygens-Kirchhoff equivalence principle, the test can be performed on any closed surface, but considering the feasibility of the scanning mechanism and the convenience of data processing, the near-field test mainly has three scanning methods: plane, spherical near-field and cylindrical near-field.

[0005] The test of active antennas is essentially the same as that of traditional passive antennas. Through the test, traditional indicators such as the gain and radiation pattern of the active antenna can be obtained, as well as system indicators such as equivalent radiated power and sensitivity. The antenna test system that can complete the system indicator test is called the antenna air interface test system.

[0006] Phased array radar and MIMO in the fifth generation of mobile communications have multi-beam characteristics, and the complexity of this type of antenna testing is much higher than that of ordinary antennas. Modern phased array antenna testing requires that the probe can achieve high-density testing of multiple frequencies, multiple beams, and multiple channel patterns in a single scan. Currently, the antenna test system that can meet such test requirements is the antenna near-field scanning test system. During the near-field test, the probe samples the electromagnetic field at an appropriate distance from the antenna to be tested, and the far-field pattern of the antenna is obtained by spectrum expansion. Planar near-field testing is suitable for testing large-caliber antennas such as satellite communication antennas, reflector data transmission antennas, intersatellite link antennas, and large microwave remote sensing payload antennas. It is particularly suitable for amplitude and phase correction and near-field diagnosis of phased array antennas. The near-field scanning of the planar near-field test system can sample each antenna unit individually to obtain its amplitude and phase information, which provides the necessary data for the later amplitude and phase correction of the unit. When a phased array antenna has a fault in an individual antenna unit, the far-field pattern of the antenna as a whole does not change much. The far-field pattern with the faulty unit is different from that of a normal antenna array in details such as sidelobe height and zero depth, but it cannot indicate which unit is performing abnormally. The near-field test of the antenna can perform fault analysis and diagnosis on the radiation surface of the antenna, identify antenna units that are not working properly, and thus conduct targeted troubleshooting, repair, and replacement of the faulty antenna units. It can also determine the degree of deviation of certain antenna units that deviate from normal values, and then compensate for them in software.

[0007] A near-field test system with phased array multi-frequency, multi-wavelength test capability and unit correction test capability can also test the spurious radiation of the antenna. Spurious radiation is essentially a multi-wavelength, multi-frequency phased array radiation, and the aforementioned phased array near-field test system can be used to complete the spurious test.

[0008] China Utility Model Authorization Announcement No. CN207281181 discloses a phased array antenna test system; the phased array antenna test system, the host computer is connected to the vector network analyzer, the turntable controller, and the data acquisition processor through a network switch, the vector network analyzer is connected to the data acquisition processor, and the measured antenna measurement signal is transmitted to the data acquisition processor; the vector network analyzer is connected to the auxiliary antenna and the antenna under test through a cable, generates a test RF signal and receives the RF signal after the test; the synchronization signal port of the wave control device is connected to the synchronization signal port of the data acquisition processor, the turntable control signal port of the data acquisition processor is connected to the output end of the turntable controller, and the wave control code generated by the wave control device according to the synchronization signal is transmitted to the antenna under test through a cable. The system adds a wave control device on the basis of the existing antenna measurement system, which can extract the beam information of the measurement system during the multi-wave position and multi-frequency point measurement of the active phased array and perform synchronous control on the antenna under test.

[0009] Chinese invention patent publication CN110873824A discloses a Massive MIMO antenna test system and method, the test system includes: a signal source, a power amplifier system, a beam control system, M probes, a switch system and a spectrum analyzer arranged in a dark room, the RF ports between the signal source, the power amplifier system, the beam control system and the Massive MIMO antenna are all connected by RF cables, air interface radiation is adopted between the Massive MIMO antenna and the probe, and the RF ports of the receiving probe, the switch system and the spectrum analyzer are all connected by RF cables. The present invention can directly test the performance of the Massive MIMO antenna at different beam angles, and the test efficiency is significantly improved and the stability is good.

[0010] China Utility Model Authorization Announcement No. CN207281181U discloses a 3D-MIMO antenna test system based on multiple probes, the system includes multiple horizontally placed metal arch rings, a number of probes evenly arranged on the metal arch rings and a support platform for placing 3D-MIMO equipment, the multiple metal arch rings are located on the same spherical surface, the support platform is provided with a driving device for driving the support platform to rotate horizontally, the multiple horizontally placed metal arch rings test the receiving signals in multiple vertical dimensions at the same time, can accurately test the performance of the 3D-MIMO equipment, and adopt a multi-probe test system to make the test speed faster; the driving device can make the 3D-MIMO equipment located on the support platform rotate horizontally, and then oversample the 3D-MIMO equipment, and oversampling can increase the sampling points, thereby improving the test accuracy of the 3D-MIMO equipment to a certain extent.

[0011] Chinese invention patent application publication number CN110068738A discloses a phased array antenna test system and antenna test method, which respectively sets an antenna support platform including an antenna turntable, a speaker support platform including a linear slide rail, and respectively sets antenna fixtures that can clamp antennas of various sizes on the antenna turntable, and sets speaker fixtures that can fix various types of speakers on the slide rail, thereby realizing automatic and rapid alignment between various types of antennas under test and corresponding speakers through a controller under the calibration of an alignment module. It can also automatically complete the testing of various types of antennas through auxiliary equipment such as the signal source and spectrum analyzer provided by the system. Therefore, it has the technical effect of improving the applicability of the antenna test system and improving the efficiency of antenna testing.

[0012] The current international conventional spurious emission test types are divided into three levels: A, B, and C. The upper limit of the spurious power amplitude of Class A is -13dBm, the upper limit of the spurious power amplitude of Class B is -36dBm, and the maximum level requirement of Class C spurious is -98dBm. When the impact of carrier aggregation is considered, the test requirements will be more stringent, requiring a further reduction of several dB (carrier aggregation factor) on the basis of the above standards. When the carrier aggregation factor is 9dB, the maximum level of Class C spurious requirements becomes -107dBm. When the RF transmitter is at 40dBm, the test system is required to be able to test both useful signals and spurious signals at the same time. For Class A and Class B spurious requirements, the dynamic range is 53dBc and 76dBc respectively, and the test can be completed using an ordinary spectrum analyzer. For Class C spurious emission requirements, the test dynamic range is required to be 138dBc. If the 9dB carrier aggregation factor is taken into account, the final dynamic range is required to be 147dBc. With the test margin, the dynamic range of the test system is required to exceed 150dBc. With the current performance level of spectrum analyzers, it is difficult to accurately measure the spurious emission of large dynamic range signals. Conventional spurious emission uses spectrum analyzers to read the level, resulting in limited dynamic range and difficulty in compatibility with high-power signal and low-power spurious emission tests; traditional antenna far-field test systems need to test each beam one by one, with low test efficiency and no unit calibration function; there is no mature test method and test equipment for phased array spurious emission testing.

[0013] Traditional antenna test systems do not have the ability to test multi-beam antennas. For phased array antennas to be tested, each beam must be tested individually, which makes the test efficiency too low. Traditional antenna test systems are only for passive antennas. For active antennas, the antenna's transmit and receive links are different, and the transmit and receive test parameters are different. Traditional test equipment does not have the ability to test active antenna parameters and system-level parameters. Summary of the invention

[0014] Aiming at the fact that current traditional testing equipment does not have the ability to test active antenna parameters and system-level parameters, the present invention provides a spurious radiation testing system and a testing method for a radio frequency transmitter.

[0015] The technical solution for realizing the technical purpose of the present invention is: a spurious radiation test system for a radio frequency transmitter is a near-field test system, comprising a test field, a servo system and a radio frequency subsystem, in which the antenna of the radio frequency transmitter to be tested moves under the drive of the servo system, and the radio frequency subsystem receives the radio frequency signal of the radio frequency transmitter to be tested and processes it to obtain the test result;

[0016] The test field is a microwave darkroom;

[0017] The servo system is a one-axis precision turntable installed in a microwave darkroom, and the antenna of the radio frequency transmitter to be tested is set on the precision turntable;

[0018] The radio frequency subsystem comprises a vector network analyzer, and the vector network analyzer uses a test probe to receive the radiation signal of the radio frequency transmitter antenna to complete the amplitude and phase parameter test of the radio frequency transmitter antenna to be tested.

[0019] A one-axis turntable is used in conjunction with a probe array to achieve spherical near-field sampling of the electromagnetic field.

[0020] Furthermore, in the above-mentioned RF transmitter spurious radiation test system: the microwave darkroom also includes a reference probe that assists a port of a vector network analyzer to send a RF excitation signal to the RF transmitter antenna to be tested.

[0021] Furthermore, in the above-mentioned RF transmitter spurious radiation test system: the RF transmitter antenna to be tested adopts a phased array antenna, and the test probe and the reference probe are a dual-polarization sampling probe array and a reference dual-polarization probe respectively.

[0022] Furthermore, in the above-mentioned RF transmitter stray radiation test system: the dual-polarization sampling probe array is evenly distributed in the microwave darkroom, on an arc-shaped probe rack with the phased array antenna of the RF transmitter to be tested as the center of the circle.

[0023] Furthermore, in the above-mentioned RF transmitter stray radiation test system: the precision turntable has a minimum step of Single axis turntable; Calculate according to the following formula:

[0024]

[0025] In the formula, R is the radius of the arc probe holder, λ min The wavelength of the highest frequency RF signal.

[0026] Furthermore, the above-mentioned RF transmitter spurious radiation test system also includes: a device for sampling the vertical polarization component and the horizontal polarization component of the dual-polarization sampling probe array respectively, and the multiple horizontal polarization signals collected by the dual-polarization sampling probe array are combined into one channel through a single-pole multi-throw switch, and the multiple vertical polarization signals are also combined into one channel through a single-pole multi-throw switch.

[0027] Furthermore, the above-mentioned RF transmitter spurious radiation test system also includes: a 90-degree bridge and a frequency hopping filter to form a coupled filtering channel, and the coupled filtering channel is divided into four groups, which respectively process a reference horizontal polarization component, a reference vertical polarization component, a sampled horizontal polarization component, and a sampled vertical polarization component.

[0028] Furthermore, in the above-mentioned RF transmitter spurious radiation test system: the high-power main beam signal will be synthesized by the filter and the rear-end 90-degree bridge and transmitted to the end, and the four main channel signals are the reference horizontal polarization component, the reference vertical polarization component, the sampled horizontal polarization component, and the sampled vertical polarization component.

[0029] Furthermore, in the above-mentioned RF transmitter spurious radiation test system: the spurious signal frequency is reflected by the filter, reversely synthesized by a 90-degree bridge, and output at the isolation end, and the four spurious signals are respectively a reference horizontal polarization spurious component, a reference vertical polarization spurious component, a sampled horizontal polarization spurious component, and a sampled vertical polarization spurious component.

[0030] The present invention also provides a method for testing stray radiation of a radio frequency transmitter, which adopts a field test method. During the test, the azimuth angle word: l=1~L, the pitch angle word: n=1~N, the frequency word: m=1~M, the wave position word: q=1~Q, and the stray frequency word: p=1~P are taken; the following steps are included:

[0031] 1) At azimuth angle l, frequency m, wave position q, and pitch angle n, the corresponding probe samples the horizontal polarization component and the vertical component, and sets the coupling filter channel frequency word to m, thereby obtaining the main channel vector data of the horizontal component and the vertical component in this state; the coupling filter channel reflects the stray frequency to the amplification filter channel, and the frequency hopping filter of the channel traverses the stray frequency word: p=1~P, and obtains p groups of stray channel vector data;

[0032] 2) Traverse each pitch angle word: n=1~N, obtain the near-field scanning data of all pitch angles, at this time, the main channel data is n groups, and the stray channel data is N×P groups in total;

[0033] 3) Then traverse each wave position word: q=1~Q, and obtain the near-field scanning data of all wave positions. At this time, the main channel data has Q×N groups, and the stray channel data has Q×N×P groups;

[0034] 4) Then traverse all frequency words: m=1~M, and obtain near-field scanning data of all frequencies. At this time, the main channel data has a total of M×Q×N groups, and the stray channel data has a total of M×Q×N×P groups;

[0035] 5) Then traverse all the azimuth words: l=1~L, and obtain the near-field scanning data of all azimuths. At this time, the main channel data has a total of L×M×Q×N groups, that is, M×Q groups of main channel spherical scanning matrix data; the stray channel data has a total of L×M×Q×N×P groups, that is, M×Q×P groups of stray matrix data;

[0036] 6) Perform data post-processing and calculate the far-field radiation pattern corresponding to each set of matrix data.

[0037] The present invention adopts a group of arc-shaped dual-polarization probes and a single-axis turntable to realize antenna near-field scanning.

[0038] In addition, the present invention can obtain the radiation pattern of the main beam radiation and stray radiation of the radio frequency transmitter in one scan.

[0039] The split coupler is realized by the frequency hopping filter and the bridge to separate the high-power main channel signal from the low-power stray signal, thereby realizing signal processing with a large dynamic range.

[0040] A one-axis turntable is used in conjunction with an arc-shaped probe array to achieve spherical near-field sampling of the electromagnetic field. A dual-polarization probe is used to simultaneously read the vertical polarization component and the horizontal polarization component. A dual-polarization reference probe is used to provide amplitude and phase reference for near-field sampling data. Near-field data obtained by multiple sets of sampling probes are combined through a single-pole, multi-throw RF switch and sent to the post-processing circuit. The post-processing circuit includes a frequency hopping filter shunt coupler, which can extract the high-power main channel radiation signal and separate the spurious signals of different frequencies; the low-power spurious signals of different frequencies are passed through a low-noise amplifier and a frequency hopping filter to improve the signal amplitude and spectrum purity, which is convenient for subsequent amplitude and phase discrimination; the test system can obtain the radiation parameters of the whole machine (especially the test of multi-frequency and multi-wavelength radiation patterns of phased array antennas) and the automatic test of spurious radiation parameters (also with multi-frequency and multi-wavelength characteristics) in a complete near-field scan under software control.

[0041] The present invention will be described in more detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Attached Figure 1 This is a structural diagram of a phased array spurious emission test system according to Embodiment 1 of the present invention.

[0043] Attached Figure 2 This is a sampling signal processing circuit of a phased array spurious emission test system according to embodiment 1 of the present invention.

[0044] Attached Figure 3 It is a schematic diagram of the main beam and stray beam of the phased array spurious emission test system in Example 1 of the present invention.

[0045] Attached Figure 4 It is a schematic diagram of phased array multi-wavelength positions of a phased array spurious emission test system in Example 1 of the present invention. DETAILED DESCRIPTION

[0046] This embodiment is a phased array spurious emission test system, the system components are as follows Figure 1 shown.

[0047] The test field of this test system is a microwave darkroom 10. The phased array antenna 12 used by the RF transmitter to be tested is placed on a single-axis precision turntable 11. The single-axis precision turntable 11 can rotate with high resolution. The near-field test requires that the arc length corresponding to the probe when the turntable rotates in a single step should be less than the half wavelength corresponding to the highest frequency, that is:

[0048]

[0049] Where R is the radius of the arc probe array, and the antenna to be tested is placed at the center of the arc. It is the minimum stepping of single-axis rotary table.

[0050] The radio frequency subsystem includes a vector network analyzer, which uses a test probe 14 to receive the radiation signal of the radio frequency transmitter antenna to be tested to complete the amplitude and phase parameter test of the radio frequency transmitter antenna to be tested.

[0051] like Figure 1 As shown, 120 represents the main beam antenna pattern on the antenna, and 121 and 122 represent the spurious beam patterns.

[0052] In this embodiment, the antenna multi-beam test system involved adopts planar near-field test technology. Near-field measurement can overcome the limited distance effect and does not require a large indoor or outdoor test field. When measuring the antenna near field, a probe with known characteristics is used to sample the amplitude and phase distribution of the electromagnetic field on a certain surface in the near area of ​​the antenna, and the field established in the space by the antenna to be tested is expanded into the sum of plane wave functions, and the far-field characteristics of the antenna are determined through strict mathematical transformation formulas. The characteristics of near-field measurement technology are as follows: a) The measurement is performed in the near area of ​​the antenna to be tested; b) The influence of the probe on the primary field radiated by the antenna to be tested is taken into account; c) The complete spatial radiation pattern of the antenna (including the phase radiation pattern and the polarization radiation pattern) can be calculated based on the measurement, unlike ordinary far-field direct measurement which can only determine the radiation pattern in one or several planes.

[0053] Phased array antennas contain T / R components, power division networks, antennas and other components. Due to process inconsistency, there will be certain deviations in the power, spectrum, amplitude and phase of each channel after the antenna is assembled, and the antenna units need to be corrected for amplitude and phase. That is, first obtain the amplitude and phase characteristics of each unit of the phased array antenna, and then compensate each unit. A phased array radar usually contains hundreds or thousands of T / R components. If the phased array radar antenna is measured manually, it will take a long time and cost a lot. Therefore, it is necessary to develop automatic testing technology for phased array antennas. The finished product test of the phased array requires near-field radiation pattern testing of the entire array at each frequency point and each wave position. The test modes of the phased array antenna include the transmit array test (pulse) and the receive array test mode. Among them, the array test is divided into sub-array test and full array test according to the array scale, and is divided into amplitude and phase calibration and other wave position measurement according to the steps.

[0054] Since the communication RF transmitter works at high power, the nonlinearity of the internal components will cause the generation of spurious frequency signals. When the transmitter transmits the carrier signal, these spurious signals will also be transmitted to the free space through the antenna. With the rapid development of mobile communication technology, the density of wireless base stations has increased significantly, the electromagnetic environment has become more complex, and the problem of wireless interference is particularly prominent. It has become an important factor affecting the communication performance and customer satisfaction of mobile base stations. Effective and accurate spurious emission assessment is of great significance for purifying the communication environment and improving communication quality.

[0055] Phased array automated test equipment combines the DUT, servo, and RF instrument into an organic system, which can realize automatic testing, data acquisition, and post-processing of phased array antennas. The test instrument is usually a vector network analyzer, which is mainly used for the generation, reception, acquisition, and processing of RF signals required for antenna testing. The main function of the microwave interface adapter is to perform necessary modulation, amplification, switching, and filtering of RF signals according to test requirements. The wave control module is used to simulate the radar wave control unit to output the wave control and timing signals that control the antenna beam pointing and the switching of transmission and reception. The test probe uses a wide-band, low-gain dual-polarization open waveguide antenna.

[0056] When testing the antenna transmission pattern, the vector network analyzer sends an RF excitation signal through one port to the antenna under test to radiate the test probe. The test probe receives the RF signal and transmits it to another port of the vector network analyzer to complete the antenna amplitude and phase parameter test. During the test, the instrument's signal frequency, power and other parameters are set by the main control computer according to the test requirements, and the test data is also transmitted to the main control computer in real time.

[0057] The transmit and receive channels of ordinary passive antennas are shared, so the transmit pattern in the pulse state can be directly obtained by testing the receive pattern in the continuous wave state. Phased array antennas are generally active antennas. The transmit and receive channels of the T / R components are completely different. The transmit and receive patterns must be tested separately. The receive pattern is tested in the continuous wave state, while the transmit pattern must be tested in the pulse state. Therefore, the antenna test system must have a pulse test function. Two common detection technologies are used in vector network analyzers: broadband detection and narrowband detection. When the main spectrum of the RF pulse signal falls within the bandwidth of the network analyzer receiver (i.e., IF BW), broadband detection can be used to test the pulse S parameters. The RF pulse signal is demodulated by the instrument and converted into a baseband pulse signal. Broadband detection can be achieved through analog circuits or digital signal processing technology. In the broadband detection working mode, the vector network analyzer must be synchronized with the pulse stream so that data is collected only when the pulse signal appears. This means that the vector network analyzer must provide a pulse trigger signal with the same frequency as the PRF, and the delay relationship of this pulse trigger signal relative to the pulse stream needs to be correctly set. Therefore, the broadband detection working mode is also called the synchronous data acquisition mode. The advantages of broadband detection are fast test speed, simple test steps, and no loss of dynamic range when the duty cycle of the pulse signal is low (that is, the time interval between pulses is long). The smaller the duty cycle of the pulse signal, the longer the test time required. However, since the network analyzer always samples the pulse signal when it appears, the signal-to-noise ratio relative to the duty cycle variation signal is basically constant.

[0058] When the receiver bandwidth is too small to include enough RF pulse spectrum energy within the intermediate frequency bandwidth, an analog filter can be used to retain only the center spectrum component of the signal. After filtering, the RF pulse signal becomes a sinusoidal (continuous wave) signal, so there is no need to synchronize the data sampling of the vector network analyzer with the input pulse signal, and the corresponding pulse data acquisition trigger signal is not required. Since narrowband detection does not require a data acquisition trigger signal, this technology is also called asynchronous data acquisition mode. The main advantage of narrowband detection is that the minimum value of the testable pulse width is very small, because no matter how wide the pulse spectrum is distributed, most of the spectrum components will be filtered out, leaving only the center frequency component. In narrowband mode, pulse S parameters with a pulse width of 100ns can be measured.

[0059] Phased array antennas and the MIMO antennas that have emerged in recent years have multi-beam scanning characteristics. For complex multi-functional phased array antennas, the antenna has thousands of beam positions at different angles, such as Figure 4As shown, the directivity coefficient, beam width, sidelobe level, dispersion, polarization mode, beamforming and broadening parameters of each wave position are different. In order to fully grasp the performance of the antenna, comprehensive testing and optimization must be carried out. If traditional far-field testing is used, each beam needs to be individually controlled and tested, which consumes a huge amount of time and cost. Antenna near-field testing can greatly improve the test efficiency of multi-beam antennas. Near-field testing can perform multi-wave position parallel testing. During testing, the test system must be synchronized with the phased array antenna wave controller to achieve parallel testing of multi-wave position antennas. In the near-field test of the antenna, a scanning plane sampling can obtain the multi-wave position and multi-frequency near-field data of the antenna. In post-processing, the far-field radiation pattern and aperture field inversion distribution diagram of each beam and each frequency of the antenna can be obtained.

[0060] Near-field testing requires that the probe be several wavelengths away from the antenna to be tested, the probe unit spacing be less than half the minimum wavelength, and when the single-axis turntable rotates, the single step arc length at the probe is less than half a wavelength. The probe uses a dual-polarization probe, which can sample the vertical polarization component and the horizontal polarization component at the same time, and transmit the sampled data to the processing circuit. A dual-polarization reference probe is placed at a fixed position of the single-axis turntable relative to the antenna to be tested to collect horizontal and vertical reference signals. The multi-channel horizontal polarization signals collected in the near field are combined into one channel through a single-pole multi-throw switch, and similarly, the multi-channel vertical polarization signals are also combined into one channel through a single-pole multi-throw switch. Figure 2 In the figure, 16 represents a single-pole multi-throw switch; 17 represents a 90-degree bridge; 18 represents a main beam frequency hopping filter; 19 represents a low noise amplifier; 20 represents an amplitude detector and a phase detector (amplitude detection and phase detection); and 21 represents a spurious frequency hopping filter.

[0061] The main beam signal power of the phased array antenna is relatively large, while the spurious signal power is relatively small. Therefore, a coupled filter circuit is required to separate the large-amplitude and small-amplitude signals to achieve signal processing with a large dynamic range.

[0062] Since the main beam signal and the stray signal have different frequencies, the present invention uses a 90-degree bridge 17 and a frequency hopping filter 18 to form a coupled filtering channel. The filtering channel is divided into four groups, which process the reference horizontal polarization component, the reference vertical polarization component, the sampling horizontal polarization component, and the sampling vertical polarization component respectively. The high-power main beam signal will be synthesized by the filter 18 and the rear-end 90-degree bridge and transmitted to the end. The four main channel signals are the reference horizontal polarization component (REF_H), the reference vertical polarization component (REF_V), the sampling horizontal polarization component (R_H), and the sampling vertical polarization component (R_V). The four groups of filter channels and a total of eight frequency hopping filters work in the same frequency state.

[0063] The spurious signal frequency is reflected by the filter 18, reversely synthesized by a 90-degree bridge, and output at the isolation end. The four spurious signals are the reference horizontal polarization spurious component (REF_S_H), the reference vertical polarization spurious component (REF_S_V), the sampled horizontal polarization spurious component (R_S_H), and the sampled vertical polarization spurious component (R_S_V). The spurious channel signal power is low, so a low-noise amplifier is required to increase the power level, and a frequency hopping filter is used to filter out the corresponding noise frequency components. The four frequency hopping filters of the spurious signal processing channel work in the same frequency state.

[0064] The reference horizontal polarization component of the main channel and the sampled horizontal polarization component are subjected to amplitude and phase discrimination to obtain a horizontal polarization vector signal (Main_H), and the reference vertical polarization component and the sampled vertical polarization component are subjected to amplitude and phase discrimination to obtain a reference polarization vector signal (Main_V). Similarly, the reference horizontal polarization spurious component and the sampled horizontal polarization spurious component are subjected to amplitude and phase discrimination to obtain a horizontal polarization spurious vector signal (Spur_H), and the reference vertical polarization spurious component and the sampled vertical polarization spurious component are subjected to amplitude and phase discrimination to obtain a vertical polarization spurious vector signal (Spur_V).

[0065] The system includes N sampling probes, and the single-pole multi-throw switch traverses each probe to complete the near-field sampling of one azimuth angle. For phased array antennas, it is generally necessary to test an azimuth range of 120 degrees. Assuming that L azimuth angles need to be tested, all azimuth angles are traversed to obtain the near-field vector data of all spherical arc surfaces. The near-field sampling data obtained from each near-field test is an L×N matrix. Then, according to the near-field to far-field algorithm, the real far-field radiation pattern of the antenna, the antenna gain (EIRP), half-power beam width, and the parameters of the beam radiation direction can be calculated.

[0066] Near-field test method for the entire transmitter: For a phased array antenna, assuming that the main channel has M operating frequencies, the active phased array antenna has Q wave positions at each frequency, and at the same time, P spurious frequencies are radiated at each main channel frequency and each wave position. Figure 3 As shown in the figure, there are two spurious frequency radiation patterns under a certain main channel frequency and a certain wave position. Therefore, for the antenna to be tested, a complete near-field test will obtain M×Q groups of main channel spherical scanning matrix data, and also include M×Q×P groups of spurious channel spherical scanning matrix data. Each group of matrix data contains two L×M matrices (L represents the number of steps in the azimuth angle, and N represents the number of probes, that is, the number of steps in the pitch angle), which are the vector matrix of the horizontal polarization component and the vector matrix of the vertical polarization component. The corresponding far-field radiation pattern can be calculated for each group of matrix data, so a complete test can obtain M×Q main channel radiation patterns, and M×Q×P spurious channel radiation patterns.

[0067] During the test, take the azimuth word: l = 1 ~ L, the pitch angle word: n = 1 ~ N, the frequency word: m = 1 ~ M, the wave position word: q = 1 ~ Q, and the stray frequency word: p = 1 ~ P. The detailed test steps are as follows:

[0068] 1) At azimuth angle l, frequency m, wave position q, and pitch angle n, the corresponding probe samples the horizontal polarization component and the vertical component, and sets the coupling filter channel frequency word to m, thereby obtaining the main channel vector data of the horizontal component and the vertical component in this state; the coupling filter channel reflects the stray frequency to the amplification filter channel, and the frequency hopping filter of the channel traverses the stray frequency word: p = 1 ~ P, and obtains p groups of stray channel vector data.

[0069] 2) Traverse each pitch angle word: n = 1 ~ N, obtain the near-field scanning data of all pitch angles, at this time, the main channel data is n groups, and the stray channel data is N × P groups.

[0070] 3) Then traverse each wave position word: q = 1 ~ Q, and obtain the near-field scanning data of all wave positions. At this time, the main channel data has a total of Q × N groups, and the stray channel data has a total of Q × N × P groups.

[0071] 4) Then traverse all frequency words: m = 1 ~ M, and obtain the near-field scanning data of all frequencies. At this time, the main channel data has a total of M×Q×N groups, and the stray channel data has a total of M×Q×N×P groups.

[0072] 5) Then traverse all the azimuth words: l = 1 ~ L, and obtain the near-field scanning data of all azimuths. At this time, the main channel data has a total of L×M×Q×N groups, that is, M×Q groups of main channel spherical scanning matrix data; the stray channel data has a total of L×M×Q×N×P groups, that is, M×Q×P groups of stray matrix data.

[0073] 6) Perform data post-processing and calculate the far-field radiation pattern corresponding to each set of matrix data.

Claims

1. A spurious radiation test system for a radio frequency transmitter is a near-field test system, comprising a test field, a servo system and a radio frequency subsystem, wherein the antenna of the radio frequency transmitter to be tested moves under the drive of the servo system in the test field, and the radio frequency subsystem receives the radio frequency signal of the radio frequency transmitter to be tested and processes it to obtain the test result; characterized in that: The test field is a microwave darkroom (10); The servo system is a single-axis precision turntable (11) installed in a microwave darkroom (10), and the antenna (12) of the radio frequency transmitter to be tested is arranged on the precision turntable (11); The radio frequency subsystem comprises a vector network analyzer, and the vector network analyzer uses a test probe (14) to receive the radiation signal of the radio frequency transmitter antenna to be tested to complete the amplitude and phase parameter test of the radio frequency transmitter antenna to be tested; The microwave darkroom (10) also includes a reference probe (13) which assists a port of a vector network analyzer to send a radio frequency excitation signal to the radio frequency transmitter antenna to be tested; The radio frequency transmitter antenna to be tested adopts a phased array antenna, and the test probe (14) and the reference probe (13) are respectively a dual-polarization sampling probe array and a reference dual-polarization probe; The dual-polarization sampling probe array is evenly distributed in the microwave darkroom, on an arc-shaped probe frame (15) with the phased array antenna of the radio frequency transmitter to be tested as the center of the circle; The precision turntable (11) has a minimum step of Single axis turntable; Calculate according to the following formula: ； In the formula, R is the radius of the arc probe holder, λ min The wavelength of the highest frequency RF signal; It also includes a device for sampling the vertical polarization component and the horizontal polarization component of the dual-polarization sampling probe array respectively, wherein the multiple horizontal polarization signals collected by the dual-polarization sampling probe array are combined into one channel through a single-pole multi-throw switch, and the multiple vertical polarization signals are also combined into one channel through a single-pole multi-throw switch; It also includes a 90-degree bridge (17) and a frequency hopping filter (18) to form a coupled filter channel, wherein the coupled filter channel is divided into four groups, which respectively process a reference horizontal polarization component, a reference vertical polarization component, a sampled horizontal polarization component, and a sampled vertical polarization component; The high-power main beam signal will be synthesized by the filter (18) and the rear 90-degree bridge (17) and transmitted to the end. The four main channel signals are the reference horizontal polarization component (REF_H), the reference vertical polarization component (REF_V), the sampled horizontal polarization component (R_H), and the sampled vertical polarization component (R_V). The spurious signal frequency is reflected by the filter (18), reversely synthesized by the 90-degree bridge (17), and output at the isolation end. The four spurious signals are respectively a reference horizontal polarization spurious component (REF_S_H), a reference vertical polarization spurious component (REF_S_V), a sampled horizontal polarization spurious component (R_S_H), and a sampled vertical polarization spurious component (R_S_V).

2. The test method of a radio frequency transmitter stray radiation test system according to claim 1, adopting a field test method, characterized in that: When testing, take the azimuth word: l=1~L , pitch angle: n=1~N , frequency word: m=1~M , wave bit word: q=1~ Q , spurious frequency word: p=1~P; The following steps are involved: 1) At azimuth angle l, frequency m, wave position q, and pitch angle n, the corresponding probe samples the horizontal polarization component and the vertical component, and sets the coupling filter channel frequency word to m, thereby obtaining the main channel vector data of the horizontal component and the vertical component in this state; the coupling filter channel reflects the spurious frequency to the amplification filter channel, and the frequency hopping filter of the channel traverses the spurious frequency word: p=1~P, and obtains p groups of spurious channel vector data; 2) Traverse each pitch angle word: n=1~N, and obtain the near-field scanning data of all pitch angles. At this time, there are n groups of main channel data and N×P groups of stray channel data; 3) Then traverse each wave position word: q=1~Q, and obtain the near-field scanning data of all wave positions. At this time, the main channel data has Q×N groups, and the stray channel data has Q×N×P groups; 4) Then traverse all frequency words: m=1~M, and obtain the near-field scanning data of all frequencies. At this time, the main channel data has a total of M×Q×N groups, and the spurious channel data has a total of M×Q×N×P groups; 5) Then traverse all the azimuth words: l=1~L, and obtain the near-field scanning data of all azimuths. At this time, the main channel data has a total of L×M×Q×N groups, that is, M×Q groups of main channel spherical scanning matrix data; the stray channel data has a total of L×M×Q×N×P groups, that is, M×Q×P groups of stray matrix data; 6) Perform data post-processing and calculate the far-field radiation pattern corresponding to each set of matrix data.

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