OFDM (Orthogonal Frequency Division Multiplexing) vector signal analysis equipment and method

Abstract

The invention relates to an OFDM (Orthogonal Frequency Division Multiplexing) vector signal analysis device and method, belongs to the technical field of communication, and solves the problems of high test cost and low flexibility of an EVM (Error Vector Magnitude Error) of an OFDM system in the prior art. The method comprises the following specific steps: a signal generation module used for generating first baseband data of an OFDM signal; the software radio transmitter is used for caching the first baseband data, modulating the first baseband data into a corresponding radio frequency signal and transmitting the radio frequency signal to a tested system; the software radio receiver is used for collecting the radio frequency signal forwarded and output by the tested system, demodulating the radio frequency signal to obtain second baseband data of the OFDM signal, and sending the second baseband data to the data processing module; and the data processing module is used for processing the second baseband data based on the first baseband data to obtain a vector amplitude error of an output signal of the tested system, so that low-cost and high-flexibility EVM test is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of communication technology, and in particular to an OFDM vector signal analysis device and method. BACKGROUND

[0002] From the fourth generation mobile communication technology standard (4G Long Term Evolution, 4G LTE) to the fifth generation mobile communication technology standard (5G New Radio, 5G NR) and Wi-Fi 6 / 7, Orthogonal Frequency Division Multiplexing (OFDM) has become the mainstream communication technology today, which has the following characteristics: (1) high spectrum efficiency: through orthogonal subcarriers to realize spectrum overlap, greatly improving the spectrum utilization rate; (2) strong anti-multipath interference: using cyclic prefix to effectively combat inter-symbol interference and channel frequency selectivity fading; (3) flexible and scalable: subcarrier number, modulation mode and other parameters can be dynamically adjusted according to channel conditions to adapt to diversified scenarios.

[0003] In order to further improve the communication transmission rate, OFDM is usually accompanied by wideband and high-order modulation, such as 4G LTE single carrier signal bandwidth up to 20MHz, and the highest support 64QAM subcarrier modulation; 5G NR single carrier signal bandwidth up to 100MHz (FR1 frequency band), and can support 256QAM subcarrier modulation.

[0004] High-order modulation has higher requirements for the phase noise, nonlinearity, clock jitter and other indicators of the communication system. The distortion of the signal caused by these non-ideal factors in the actual transmission process can be evaluated by the Error Vector Magnitude (EVM) index. EVM is the core test parameter for optimizing communication system design, verifying equipment performance and ensuring user experience. High EVM value will increase the bit error rate of the communication system and affect the reliability of data transmission.

[0005] The existing EVM test scheme needs to rely on professional instruments, such as Figure 2 , and also needs to be equipped with special modules in the professional instruments, such as SMW-K114 OFDM Signal Generation module for signal source R&S SMW200A, and FSW-K96 OFDM Vector Signal Analysis Application or The VSE-K96 OFDM Vector Signal Analysis Application module. Existing solutions have the following issues:

[0006] (1) High cost. High-end testing instruments, coupled with specialized functional modules, greatly increase testing costs and are not suitable for small-scale tests with low accuracy requirements;

[0007] (2) Low flexibility. As more and more communication systems adopt OFDM technology, OFDM will support more and more protocols, but professional instruments only support some user-defined configurations, which is not customizable enough. In particular, EVM under different subcarrier modulation styles often requires multiple independent tests to complete. Summary of the Invention

[0008] Based on the above analysis, the present invention aims to provide an OFDM vector signal analysis device and method to solve the problems of high cost and low flexibility in the existing OFDM system EVM testing.

[0009] The objective of this invention is mainly achieved through the following technical solutions:

[0010] On one hand, embodiments of the present invention provide an OFDM vector signal analysis device, comprising:

[0011] The signal generation module is used to generate the first baseband data of the OFDM signal;

[0012] A software-defined radio transmitter is used to buffer the first baseband data and modulate it into a corresponding radio frequency signal for transmission to the system under test;

[0013] A software radio receiver is used to acquire the radio frequency signal that has been forwarded and output by the system under test, demodulate it to obtain the second baseband data of the OFDM signal, and send the second baseband data to the data processing module.

[0014] The data processing module is used to process the second baseband data based on the first baseband data to obtain the vector amplitude error of the output signal of the system under test.

[0015] Furthermore, the first baseband data is generated based on a preset time-frequency structure. The first baseband data includes multiple OFDM symbols, namely a synchronization symbol, a pilot symbol, and multiple subcarrier modulation pattern symbols. Each subcarrier modulation pattern symbol is preceded and followed by a pilot symbol, and all pilot symbols are identical.

[0016] Furthermore, the steps for obtaining the vector amplitude error of the OFDM signal of the system under test include:

[0017] A time-domain waveform sequence is generated based on the synchronization symbols in the first baseband data to obtain the local synchronization symbols;

[0018] Based on the local synchronization symbol, the second baseband data is synchronized at a time to obtain the starting position of the time-frequency structure of the first baseband data in the second baseband data;

[0019] Based on the starting position, frequency offset compensation and channel equalization are performed on the second baseband data to obtain the constellation diagram corresponding to the subcarrier modulation pattern symbols in the second baseband data.

[0020] Based on the standard constellation points of the subcarrier modulation pattern symbols corresponding to the constellation diagram and the first baseband data, the vector amplitude error of the output signal of the system under test is obtained.

[0021] Furthermore, the constellation diagram corresponding to the subcarrier modulation pattern symbols in the second baseband data is obtained, including:

[0022] After frequency offset compensation is performed on the second baseband data, a compensated signal sequence is obtained. The signal sequence is then demodulated using OFDM to obtain the frequency domain data of each OFDM symbol in the second baseband data on the effective subcarrier.

[0023] Based on the standard constellation points of the pilot symbols in the first baseband data on the same effective subcarrier, channel estimation is performed on the frequency domain data of the pilot symbols in the second baseband data to obtain the corresponding frequency domain channel response;

[0024] By utilizing the frequency domain channel responses corresponding to the two pilot symbols before and after the subcarrier modulation pattern symbol in the second baseband data, and combining them with the frequency domain data of the subcarrier modulation pattern symbol, channel equalization is performed to obtain the constellation diagram corresponding to the subcarrier modulation pattern symbol.

[0025] Furthermore, the signal sequence is obtained based on the following steps:

[0026] Based on the starting position and combined with the preset time-frequency structure of the first baseband data, the corresponding pilot symbol in the second baseband data is determined;

[0027] Based on the frequency offset estimate obtained from any two pilot symbol sequences in the second baseband data, frequency offset compensation is performed on the second baseband data to obtain the compensated signal sequence.

[0028] Furthermore, the second baseband data includes alternating in-phase and quadrature components; the step of obtaining the starting position of the second baseband data corresponding to the first baseband data includes:

[0029] Based on the positive and negative spectral characteristics of the system under test, the in-phase and quadrature components are recombined to obtain the complex sampling sequence of the second baseband data;

[0030] Based on the local synchronization symbol, the complex sampling sequence is synchronized at a time to obtain the starting position of the first baseband data corresponding to the second baseband data.

[0031] Furthermore, the signal generation module and the data processing module are embedded in the computer. The computer is connected to the software radio transmitter and the software radio receiver via an RJ45 interface and an SFP+ interface, respectively. The software radio transmitter and the software radio receiver are connected to the input and output terminals of the system under test via an SMA RF interface, respectively.

[0032] Furthermore, the operating parameters of the software radio transmitter are set based on the operating frequency of the system under test and the first baseband data, and the first baseband data is transmitted to the system under test through the SMA RF interface based on the operating parameters; the operating parameters include master clock rate, sampling rate, transmission channel, transmission frequency, and transmission gain.

[0033] On the other hand, embodiments of the present invention provide an OFDM vector signal analysis method, comprising the following steps:

[0034] The first baseband data that generates and transmits OFDM signals to the software radio transmitter;

[0035] The first baseband data is buffered using a software radio transmitter and modulated into a corresponding radio frequency signal for transmission to the system under test;

[0036] The radio frequency signal output by the system under test is acquired using a software radio receiver, and the second baseband data of the OFDM signal is obtained by demodulation.

[0037] Based on the first baseband data, the second baseband data is processed to obtain the vector amplitude error of the OFDM signal of the system under test.

[0038] Furthermore, the steps for obtaining the vector amplitude error of the OFDM signal of the system under test include:

[0039] Based on the first baseband data, a time-domain waveform sequence is generated to obtain the local synchronization symbol;

[0040] Based on the local synchronization symbol, the second baseband data is synchronized at regular intervals to obtain the starting position of the first baseband data in the second baseband data;

[0041] After performing frequency offset compensation and channel equalization on the second baseband data based on the starting position, and combining it with the first baseband data, the vector amplitude error of the output signal of the system under test is obtained.

[0042] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0043] 1. This invention uses commercial software-defined radio equipment (software-defined radio receiver and transmitter) combined with signal generation module and data processing module to perform EVM testing on OFDM systems. On the one hand, since it does not require professional instruments and dedicated modules, it greatly reduces the cost for electronic engineers to evaluate the EVM performance of the system under test. On the other hand, through the flexible configuration of software-defined radio equipment and test signals, multiple debugging styles can be covered in a single test, which greatly improves the flexibility and efficiency of EVM testing under different subcarrier modulation styles.

[0044] 2. This invention can flexibly configure the test baseband data according to the requirements. By customizing the time-frequency structure of the baseband data, pilot symbols are set before and after each test subcarrier modulation style symbol. While ensuring the flexibility and efficiency of EVM testing under different subcarrier modulation styles, the accuracy of frequency offset estimation compensation and channel estimation equalization during the processing is improved.

[0045] 3. This invention integrates the signal source and analyzer in traditional EVM testing. By utilizing the flexibility and versatility of software-defined radio equipment, more transmit and receive parameters can be set, and the process of importing the signal source settings into the analyzer, which is required in traditional EVM testing, is avoided, thus simplifying the testing process.

[0046] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0047] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0048] Figure 1 This is a structural block diagram of the OFDM vector signal analysis device according to an embodiment of the present invention;

[0049] Figure 2 This is a schematic diagram of EVM testing in the prior art of this invention;

[0050] Figure 3 This is a schematic diagram of the time-frequency structure of the first baseband data of the OFDM signal according to an embodiment of the present invention;

[0051] Figure 4 This is a flowchart illustrating the processing of the second baseband data of the OFDM signal at the receiving end in an embodiment of the present invention.

[0052] Figure 5This is a flowchart of the OFDM vector signal analysis method according to an embodiment of the present invention. Detailed Implementation

[0053] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0054] Example 1

[0055] One specific embodiment of the present invention discloses an OFDM vector signal analysis device, such as... Figure 1 As shown, it includes:

[0056] The signal generation module is used to generate the first baseband data of the OFDM signal;

[0057] A software-defined radio transmitter is used to buffer the first baseband data and modulate it into a corresponding radio frequency signal for transmission to the system under test; wherein the system under test includes frequency converters, filters, amplifiers and attenuators, etc.

[0058] A software radio receiver is used to acquire the radio frequency signal that has been forwarded and output by the system under test, demodulate it to obtain the second baseband data of the OFDM signal, and send the second baseband data to the data processing module.

[0059] The data processing module is used to process the second baseband data based on the first baseband data to obtain the vector amplitude error (EVM) value of the output signal of the system under test.

[0060] Using the aforementioned equipment, the signal generation module can flexibly generate various baseband data required for testing. A software-defined radio transmitter transmits the modulated RF signal of the first baseband data to the system under test (DUT). A software-defined radio receiver acquires and modulates the video signal output from the DUT, and the data processing module analyzes the modulated second baseband data to obtain the vector amplitude error. This equipment significantly reduces the cost of EVM performance evaluation of the DUT while improving the flexibility and efficiency of EVM testing.

[0061] It should be noted that the signal generation module and data processing module are embedded in the computer. The computer is equipped with a gigabit network card with an RJ45 interface and a 10-gigabit network card with an SFP+ interface. The software radio transmitter and software radio receiver are connected to the RJ45 interface and SFP+ interface respectively. The software radio transmitter and software radio receiver are connected to the input and output terminals of the system under test respectively through SMA RF interfaces. The RJ45 interface is used to send control commands to the software radio transmitter to set the operating parameters of the software radio transmitter, and is also used to send the first baseband data of the OFDM signal to the software radio transmitter. The SFP+ interface is used to send control commands to the software radio receiver to set the operating parameters of the software radio receiver, and is also used to receive the second baseband data of the OFDM signal from the software radio receiver.

[0062] Specifically, the steps for connecting the OFDM vector signal analysis device to the system under test using the above connection method, and performing EVM analysis using the OFDM vector signal analysis device, include:

[0063] First, the computer's signal generation module generates the first baseband data according to a preset time-frequency structure and sends it to the software radio transmitter. The first baseband data includes multiple OFDM symbols, namely a synchronization symbol, a pilot symbol, and multiple subcarrier modulation pattern symbols. Each subcarrier modulation pattern symbol is preceded and followed by a pilot symbol, and all pilot symbols are identical.

[0064] For example, software-defined radio devices can use USRP X310, USRP N310, etc. OFDM signal baseband data is a discrete-time complex sampled sequence after all OFDM modulation steps (subcarrier mapping → IFFT → cyclic prefix addition) have been completed. For example... Figure 3 Taking the time-frequency structure shown as an example, the horizontal axis in the figure represents the OFDM symbol index (time domain). One OFDM symbol is the time-domain signal generated by a complete IFFT (Inverse Fourier Transform) operation, with a duration of one symbol period. The vertical axis represents the OFDM subcarrier index (frequency domain). The subcarrier number refers to the number of each subcarrier in the frequency domain, which is the index in the FFT / IFFT point count. Among them, the synchronization symbol is used for timing synchronization at the receiver (software radio receiver), the pilot symbol (all pilot symbols have the same content) is used for frequency offset estimation and compensation, channel estimation and equalization at the receiver, and the BPSK, QPSK, 16QAM, and 64QAM symbols are multiple subcarrier modulation style symbols, used by the receiver to estimate the constellation diagram and EVM under different modulation styles.

[0065] It should be noted that the time-frequency structure of the first baseband data is expandable. Other subcarrier modulation styles such as 32QAM and 256QAM can be added arbitrarily, or the number of subcarrier modulation styles can be reduced according to test requirements, as long as pilot symbols are present before and after the subcarrier modulation style symbols to be tested.

[0066] By flexibly configuring the test baseband data, the flexibility and efficiency of EVM testing under different subcarrier modulation styles can be guaranteed; and the customized time-frequency structure adopts the method of interleaving pilot symbols with subcarrier modulation style symbols, which can improve the accuracy of frequency offset estimation compensation and channel estimation equalization processes in subsequent signal analysis.

[0067] Secondly, the software radio transmitter is equipped with an onboard DDR memory chip, which buffers the first baseband data of the OFDM signal sent by the computer into the DDR memory chip. According to the set operating parameters, the first baseband data of the OFDM signal stored in the DDR memory chip is modulated into a corresponding radio frequency signal and then repeatedly transmitted, and input to the system under test through the connection cable.

[0068] It should be noted that before transmitting the first baseband data, the computer sets the operating parameters of the software-defined radio transmitter and receiver based on the operating frequency of the system under test (SUT) and the first baseband data. The operating parameters of the software-defined radio transmitter include the master clock rate, sampling rate, transmit channel, transmit frequency, and transmit gain. The operating parameters of the software-defined radio receiver include the master clock rate, sampling rate, receive channel, receive frequency, and receive gain. The operating frequency of the SUT determines the settings of the transmit and receive frequencies. If the SUT is a frequency conversion system (such as an up-converter or down-converter), the difference between the transmit and receive frequencies should correspond to the frequency conversion. If the SUT is a non-frequency conversion system (such as an amplifier or filter), the transmit and receive frequencies should be set to be the same. The master clock rate and sampling rate settings should match the sampling rate of the first baseband data, and the software-defined radio transmitter and receiver should be set to be the same. The transmit and receive channels can be arbitrarily set according to the available channels of the software-defined radio transmitter and receiver. The transmit and receive gain settings should match the input / output power range of the software-defined radio transmitter, the SUT, and the software-defined radio receiver.

[0069] Then, the software radio receiver, equipped with an SFP+ interface, collects the radio frequency signal output by the system under test according to the set operating parameters, and demodulates it to obtain the second baseband data of the OFDM signal.

[0070] Finally, the data processing module is used to process the second baseband data to obtain the vector amplitude error of the output signal of the system under test. The specific steps include:

[0071] S41. Generate a time-domain waveform sequence based on the synchronization symbols in the first baseband data to obtain local synchronization symbols;

[0072] S42. Based on the local synchronization symbol, perform timed synchronization on the second baseband data to obtain the starting position of the time-frequency structure of the first baseband data in the second baseband data;

[0073] The second baseband data includes alternating in-phase and quadrature components; the step of obtaining the starting position of the second baseband data corresponding to the first baseband data includes:

[0074] Based on the positive and negative spectral characteristics of the system under test, the in-phase and quadrature components are recombined to obtain the complex sampling sequence of the second baseband data;

[0075] Based on the local synchronization symbol, the complex sampling sequence is synchronized at a time to obtain the starting position of the first baseband data corresponding to the second baseband data.

[0076] S43. Based on the starting position, perform frequency offset compensation and channel equalization on the second baseband data to obtain a constellation diagram corresponding to the subcarrier modulation pattern symbols in the second baseband data, specifically including:

[0077] S431. After frequency offset compensation of the second baseband data, a compensated signal sequence is obtained. The signal sequence is demodulated by OFDM to obtain the frequency domain data of each OFDM symbol in the second baseband data on the effective subcarrier.

[0078] Specifically, based on the starting position and combined with the preset time-frequency structure of the first baseband data, the corresponding pilot symbol in the second baseband data is determined; based on the frequency offset estimate obtained from any two pilot symbol sequences in the second baseband data, frequency offset compensation is performed on the second baseband data to obtain the compensated signal sequence.

[0079] S432. Based on the standard constellation points of the pilot symbols in the first baseband data on the same effective subcarrier, perform channel estimation on the frequency domain data of the pilot symbols in the second baseband data to obtain the corresponding frequency domain channel response;

[0080] S433. Using the frequency domain channel response corresponding to the two pilot symbols before and after the subcarrier modulation pattern symbol in the second baseband data, and combining it with the frequency domain data of the subcarrier modulation pattern symbol, channel equalization is performed to obtain the constellation diagram corresponding to the subcarrier modulation pattern symbol.

[0081] S44. Based on the standard constellation points of the subcarrier modulation pattern symbols corresponding to the constellation diagram and the first baseband data, the vector amplitude error of the output signal of the system under test is obtained.

[0082] For example, the processing flow for the second baseband data of an OFDM signal is as follows: Figure 4 As shown. The local synchronization symbol is a sequence generated by the computer that is identical to the synchronization symbol in the first baseband data of the OFDM signal, denoted as sync(m), m = 0, 1, 2, ..., M-1, where M is the length of the local synchronization symbol sequence; the second baseband data of the OFDM signal is represented by alternating in-phase and quadrature components, with the nth in-phase component I... n and orthogonal components Q n The number of signal data samples r(n) is determined by the positive and negative spectral characteristics of the system under test. If the system under test has a positive spectral characteristic, then the complex sampling sequence is expressed as: r(n) = I n +j×Q n n = 0, 1, 2, ..., N-1, where N is the total number of data samples in the complex sampling sequence, i.e., the length of the signal data samples; if it is an inverse spectrum, it is expressed as r(n) = I n -j×Q n n = 0, 1, 2, ..., N-1, where j is the imaginary unit. The timing synchronization operation is based on the following formula:

[0083]

[0084] Where, sync(m) * The conjugate of the local synchronization symbol sequence. This indicates the value of n when the function within the parentheses reaches its maximum value. Through timing synchronization, the starting position idx of the first baseband data corresponding to the second baseband data of the OFDM signal can be obtained, and the data corresponding to other symbols can also be extracted sequentially.

[0085] Let the pilot symbol sequence be p l (k), where l is the OFDM symbol number index, and l = 1, 3, 5, 7, 9, and K is the length of the pilot symbol sequence, k = 0, 1, 2, ..., K-1, then we have:

[0086] p l (k)=r(idx+M+K·(l-1)+k),

[0087] Select any two pilot symbol sequences for frequency offset estimation, as follows:

[0088]

[0089] Where Δf is the frequency offset estimate; l1∈l, l2∈l, and arctan(·) is the arctangent function, with the output unit being radians. Based on this, the frequency offset compensation operation is as follows:

[0090] y(n)=r(n)·exp(-j·Δf·n), n=0,1,2,...N-1.

[0091] The frequency domain data Y of each OFDM symbol can be obtained by OFDM demodulating the frequency offset compensated signal sequence y(n). l (c), where l = 1, 2, 3, ..., 9, c ∈ C, and C is the set of effective subcarriers. Channel estimation is performed based on the following equation:

[0092]

[0093] Among them, H l (c) is the channel estimate, which is the estimated frequency domain channel response; l = 1, 3, 5, 7, 9, c ∈ C, P(c) is the ideal value of the pilot symbol on the effective subcarrier c, that is, the standard constellation point of the pilot symbol of the first baseband data on the same effective subcarrier.

[0094] Channel equalization operations are as follows:

[0095]

[0096] Among them, X l (c) is the output after channel equalization, which approximates the original constellation points of the transmitter; l = 2, 4, 6, 8, c ∈ C. That is, when l = 2 (corresponding to the BPSK symbol sequence), channel equalization is performed using the pilot symbol sequences H1(c) and H3(c) before and after it.

[0097] By drawing a constellation diagram for X2(c) (c∈C), we can obtain the BPSK constellation diagram. Let the ideal value of the originating BPSK be S. BPSK (c) represents the standard constellation point for transmitting the BPSK symbol corresponding to the first baseband data, c∈C. The EVM under BPSK subcarrier modulation is calculated as follows:

[0098]

[0099] Where, N C This represents the total number of effective subcarriers.

[0100] Similarly, by drawing a constellation diagram for X4(c), we can obtain the QPSK constellation diagram. Let the ideal value of the originating QPSK be S. QPSK (c) The EVM under QPSK subcarrier modulation is calculated as follows:

[0101]

[0102] By drawing a constellation diagram for X6(c), we can obtain a 16QAM constellation diagram. Let the ideal value of the originating 16QAM be S. 16QAM (c), c∈C, the EVM under 16QAM subcarrier modulation is calculated as follows:

[0103]

[0104] By drawing a constellation diagram for X8(c), a 64QAM constellation diagram can be obtained. Let the ideal value of the originating 64QAM be S. 64QAM (c), c∈C, the EVM under 64QAM subcarrier modulation is calculated as follows:

[0105]

[0106] The above method allows for the acquisition of EVM values ​​for multiple debugging styles in a single test, improving the flexibility and efficiency of EVM testing under different subcarrier modulation styles.

[0107] Compared with existing technologies, the OFDM vector signal analysis device provided in this embodiment uses commercial software-defined radio equipment combined with signal generation and data processing modules to perform OFDM system EVM testing. It eliminates the need for professional instruments and dedicated modules, greatly reducing the cost of EVM performance evaluation of the system under test. By utilizing the flexibility and versatility of software-defined radio equipment and the flexible setting of test baseband data, multiple debugging styles can be covered in a single test, improving the flexibility and efficiency of EVM testing under different subcarrier modulation styles.

[0108] Example 2

[0109] Another specific embodiment of the present invention discloses an OFDM vector signal analysis method, such as... Figure 5 As shown, it includes the following steps:

[0110] Step S1: Connect the OFDM vector signal analysis device to the system under test; the device includes a computer, a software radio transmitter, and a software radio receiver.

[0111] Step S2: According to the test requirements, the computer uses the signal generation module to generate OFDM signal first baseband data and sends the first baseband data to the software radio transmitter; wherein, before sending the first baseband data, the operating parameters of the software radio transmitter and receiver need to be set;

[0112] Step S3: Buffer the first baseband data using a software radio transmitter, modulate it into a corresponding radio frequency signal, periodically transmit the radio frequency signal, and transmit it to the system under test through a connection line;

[0113] Step S4: Use a software radio receiver to acquire the radio frequency signal output by the system under test, and demodulate it to obtain the second baseband data of the OFDM signal;

[0114] Step S5: The computer uses the data processing module to process the second baseband data to obtain the constellation diagram and EVM value.

[0115] The method described herein can be used to perform OFDM vector signal analysis based on the device described in any of the schemes in Embodiment 1. Related aspects can be referenced from each other, but are not repeated in this embodiment.

[0116] Compared with existing technologies, the OFDM vector signal analysis method provided in this embodiment generates various baseband data required for testing through a signal generation module. Utilizing the flexibility and versatility of software-defined radio transmitters and receivers, the first baseband data is modulated into a radio frequency signal and sent to the system under test (SUT). The software-defined radio receiver then collects and modulates the radio frequency signal output by the SUT. Finally, a data processing module performs frequency offset estimation compensation and channel estimation equalization on the modulated second baseband data, ultimately obtaining the constellation diagram and vector amplitude error of the SUT's output signal. This method significantly reduces the cost of EVM performance evaluation of the SUT while improving the flexibility and efficiency of EVM testing.

[0117] Those skilled in the art will understand that all or part of the processes of the methods described in the above embodiments can be implemented by a computer program instructing related hardware, and the program can be stored in a computer-readable storage medium. The computer-readable storage medium may be a disk, optical disk, read-only memory, or random access memory, etc.

[0118] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. An OFDM vector signal analysis device, characterized in that, include: The signal generation module is used to generate the first baseband data of the OFDM signal; A software-defined radio transmitter is used to buffer the first baseband data and modulate it into a corresponding radio frequency signal for transmission to the system under test; A software radio receiver is used to acquire the radio frequency signal that has been forwarded and output by the system under test, demodulate it to obtain the second baseband data of the OFDM signal, and send the second baseband data to the data processing module. The data processing module is used to process the second baseband data based on the first baseband data to obtain the vector amplitude error of the output signal of the system under test.

2. The device according to claim 1, characterized in that, The first baseband data is generated based on a preset time-frequency structure. The first baseband data includes multiple OFDM symbols, namely a synchronization symbol, a pilot symbol, and multiple subcarrier modulation pattern symbols. Each subcarrier modulation pattern symbol is preceded and followed by a pilot symbol, and all pilot symbols are identical.

3. The device according to claim 2, characterized in that, The steps to obtain the vector amplitude error of the OFDM signal of the system under test include: A time-domain waveform sequence is generated based on the synchronization symbols in the first baseband data to obtain the local synchronization symbols; Based on the local synchronization symbol, the second baseband data is synchronized at a time to obtain the starting position of the time-frequency structure of the first baseband data in the second baseband data; Based on the starting position, frequency offset compensation and channel equalization are performed on the second baseband data to obtain the constellation diagram corresponding to the subcarrier modulation pattern symbols in the second baseband data. Based on the standard constellation points of the subcarrier modulation pattern symbols corresponding to the constellation diagram and the first baseband data, the vector amplitude error of the output signal of the system under test is obtained.

4. The device according to claim 3, characterized in that, Obtain the constellation diagram corresponding to the subcarrier modulation pattern symbols in the second baseband data, including: After frequency offset compensation is performed on the second baseband data, a compensated signal sequence is obtained. The signal sequence is then demodulated using OFDM to obtain the frequency domain data of each OFDM symbol in the second baseband data on the effective subcarrier. Based on the standard constellation points of the pilot symbols in the first baseband data on the same effective subcarrier, channel estimation is performed on the frequency domain data of the pilot symbols in the second baseband data to obtain the corresponding frequency domain channel response; By utilizing the frequency domain channel responses corresponding to the two pilot symbols before and after the subcarrier modulation pattern symbol in the second baseband data, and combining them with the frequency domain data of the subcarrier modulation pattern symbol, channel equalization is performed to obtain the constellation diagram corresponding to the subcarrier modulation pattern symbol.

5. The device according to claim 4, characterized in that, The signal sequence is obtained based on the following steps: Based on the starting position and combined with the preset time-frequency structure of the first baseband data, the corresponding pilot symbol in the second baseband data is determined; Based on the frequency offset estimate obtained from any two pilot symbol sequences in the second baseband data, frequency offset compensation is performed on the second baseband data to obtain the compensated signal sequence.

6. The device according to claim 3, characterized in that, The second baseband data includes alternating in-phase and quadrature components; The steps for obtaining the starting position of the first baseband data corresponding to the second baseband data include: Based on the positive and negative spectral characteristics of the system under test, the in-phase and quadrature components are recombined to obtain the complex sampling sequence of the second baseband data; Based on the local synchronization symbol, the complex sampling sequence is synchronized at a time to obtain the starting position of the first baseband data corresponding to the second baseband data.

7. The device according to any one of claims 1-6, characterized in that, The signal generation module and data processing module are embedded in the computer. The computer is connected to the software radio transmitter and software radio receiver via RJ45 and SFP+ interfaces, respectively. The software radio transmitter and software radio receiver are connected to the input and output terminals of the system under test via SMA RF interfaces, respectively.

8. The device according to claim 7, characterized in that, The operating parameters of the software radio transmitter are set based on the operating frequency of the system under test and the first baseband data. Based on the operating parameters, the first baseband data is transmitted to the system under test through the SMA RF interface. The operating parameters include master clock rate, sampling rate, transmission channel, transmission frequency, and transmission gain.

9. An OFDM vector signal analysis method, characterized in that, Includes the following steps: The first baseband data that generates and transmits OFDM signals to the software radio transmitter; The first baseband data is buffered using a software radio transmitter and modulated into a corresponding radio frequency signal for transmission to the system under test; The radio frequency signal output by the system under test is acquired using a software radio receiver, and the second baseband data of the OFDM signal is obtained by demodulation. Based on the first baseband data, the second baseband data is processed to obtain the vector amplitude error of the OFDM signal of the system under test.

10. The method according to claim 9, characterized in that, The steps to obtain the vector amplitude error of the OFDM signal of the system under test include: Based on the first baseband data, a time-domain waveform sequence is generated to obtain the local synchronization symbol; Based on the local synchronization symbol, the second baseband data is synchronized at regular intervals to obtain the starting position of the first baseband data in the second baseband data; After performing frequency offset compensation and channel equalization on the second baseband data based on the starting position, and combining it with the first baseband data, the vector amplitude error of the output signal of the system under test is obtained.

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