Method, device, processor and readable storage medium thereof suitable for in-band amplitude and phase flatness calibration of MIMO channel simulator

Abstract

The application relates to a method suitable for MIMO channel simulator to realize in-band amplitude and phase flatness calibration, which comprises the following steps: generating a known comb spectrum signal through an internal DAC, connecting to a signal analyzer after passing through a radio frequency channel to collect and analyze the IQ signal, and completing amplitude and phase compensation data calculation of all M transmitting ports; configuring the channel simulator as a MIMO N*1 mode, taking one transmitting channel TX after the first stage calibration as a transparent channel, and calculating amplitude and phase compensation data of all N receiving ports. The method, device, processor and computer readable storage medium thereof suitable for MIMO channel simulator to realize in-band amplitude and phase flatness calibration can realize comprehensive amplitude and phase calibration, realize in-band amplitude and phase flatness calibration of the radio frequency channel of the MIMO channel simulator, effectively improve the system signal-to-noise ratio, and maximally reduce the influence of hardware on channel simulation; can reduce the system cost and the requirement for instruments, and reduce the overall cost of the calibration system.

Description

Technical Field

[0001] This invention relates to the field of communication measurement instruments, and more particularly to the field of high-performance communication systems. Specifically, it relates to a method, apparatus, processor, and computer-readable storage medium for implementing in-band amplitude and phase flatness calibration in a MIMO channel simulator. Background Technology

[0002] Current MIMO channel simulators play a crucial role in testing high-performance communication systems such as 5G / 6G. The amplitude and phase response flatness of their internal RF channels directly affect the accuracy of the simulated channel and the system signal-to-noise ratio (SNR). However, existing RF circuit flatness calibration techniques face multiple technical challenges and efficiency bottlenecks.

[0003] First, there are relatively few published documents on existing channel simulator flatness calibration techniques, and traditional calibration schemes are usually designed for narrower bandwidths, which is difficult to meet the needs of modern communication systems for large bandwidths (such as the target bandwidth of 600MHz in this paper).

[0004] Secondly, in the flatness calibration of RF instruments, the focus is usually on amplitude calibration, while phase flatness compensation is neglected. For broadband signals, phase flatness can lead to signal dispersion, generate group delay distortion, and severely reduce the fidelity of analog signals. Therefore, the lack of phase calibration is a major shortcoming of existing technologies.

[0005] Third, traditional calibration methods are extremely inefficient in multi-channel systems. MIMO channel simulators contain multiple receive and transmit channels (e.g., 8 receive and 8 transmit). Comprehensive amplitude and phase calibration of these channels requires multiple expensive instruments such as signal sources and spectrum analyzers with high bandwidth capabilities. The purchase cost of high-bandwidth instruments is very high. Furthermore, since the receive (RX) and transmit (TX) channels can be configured with different operating frequencies during system testing, the flatness of the receive and transmit channels must be calibrated separately, further increasing the complexity and time of the calibration process. For example, on a 64-receive, 64-transmit experimental platform, calibrating using traditional methods across a frequency range of 0.5–7.5 GHz, in 100 MHz steps, and with three power settings, takes 5 seconds per frequency and power setting, resulting in a total calibration time of approximately 38 hours. This lengthy calibration cycle severely restricts the production and maintenance efficiency of multi-channel instruments.

[0006] Secondly, MIMO channel simulators need to support different frequencies for the transmit and receive channels, which requires separate calibration for each channel. Current technology relies on multiple signal sources and spectrum analyzers with large signal bandwidths; the signal sources calibrate the receive channels, and the spectrum analyzers calibrate the transmit channels. However, signal sources and spectrum analyzers with large signal bandwidths are very expensive, resulting in high equipment costs.

[0007] Therefore, existing technologies face a combination of challenges, including high costs, limited calibration accuracy (amplitude only), insufficient bandwidth coverage, and extremely low efficiency of multi-channel calibration. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method, apparatus, processor and computer-readable storage medium for achieving in-band amplitude and phase flatness calibration in a MIMO channel simulator that meets the requirements of multi-channel, wide-bandwidth and large bandwidth.

[0009] To achieve the above objectives, the present invention provides a method, apparatus, processor, and computer-readable storage medium for implementing in-band amplitude and phase flatness calibration in a MIMO channel simulator, as follows: This method is applicable to in-band amplitude and phase flatness calibration using a MIMO channel simulator, wherein the MIMO channel simulator includes M transmit channels TX and N receive channels RX. Its main feature is that the method includes the following steps: (1) Perform TX calibration of the transmission channels, that is, generate broadband comb spectrum signals with the same amplitude and known phase through the digital-to-analog converter (DAC) inside the MIMO channel simulator, connect the M transmission channels TX to the signal analyzer in sequence to collect IQ data, and obtain the in-band amplitude error and phase error of each transmission channel TX based on the collected IQ data, and calculate the amplitude compensation data and phase compensation data of each transmission channel TX. (2) Perform receiver channel RX calibration, i.e., configure the MIMO channel simulator to N×1 working mode, substitute the obtained amplitude compensation data and phase compensation data into the transmitter channel TX, and make the active transmitter channel TX a broadband high flatness transparent transmission reference channel; use a vector network analyzer to measure the S21 transmission coefficient between the transmitter channel TX and N receiver channels RX, and analyze the in-band amplitude error and phase error of each receiver channel RX based on the measured S21 transmission coefficient, and calculate the amplitude compensation data and phase compensation data of each receiver channel RX.

[0010] Preferably, in step (1), the M transmission channels TX are sequentially connected to the signal analyzer via a single-pole M-throw switch, and the M input ports of the single-pole M-throw switch are respectively connected to the M transmission channels TX one by one, and the common output port of the single-pole M-throw switch is connected to the signal analyzer.

[0011] Preferably, in step (1), the in-band amplitude error of the transmit channel TX is the in-band amplitude unevenness obtained by parsing the acquired IQ data, and the in-band phase error of the transmit channel TX is the difference between the phase data obtained by parsing the acquired IQ data and the known phase preset when the digital-to-analog converter DAC generates the broadband comb spectrum signal.

[0012] Preferably, in step (2), the second port of the vector network analyzer is connected to the active transmit channel TX, and the first port of the vector network analyzer is connected to N receive channels RX in sequence through a single-pole N-throw switch; the N input ports of the single-pole N-throw switch are respectively connected to the N receive channels RX one by one, and the common output port is connected to the first port of the vector network analyzer.

[0013] Preferably, in step (2), the N×1 working mode is the working mode in which the signals of the N receiving channels RX of the MIMO channel simulator are all transmitted to the single active transmitting channel TX, so that the N receiving channels RX form independent transmission links with the active transmitting channel TX respectively.

[0014] Preferably, the bandwidth of the broadband comb spectrum signal generated by the digital-to-analog converter (DAC) is not less than 600MHz, and the measurement bandwidth of the vector network analyzer is not less than 600MHz.

[0015] Preferably, before performing step (1), the following steps are also included: Reset the digital equalizers of all transmit channels (TX) and receive channels in the FPGA of the MIMO channel simulator to put all channels in an initial state without compensation.

[0016] Preferably, the transmit channel TX calibration and receive channel RX calibration are both performed stepwise at preset frequency points within the operating frequency range of the MIMO channel simulator. At the same time, for each power level of the amplifier on the RF path, the calibration operation of the corresponding frequency point is completed stepwise.

[0017] Preferably, the MIMO channel simulator operates in the frequency range of 0.5GHz to 7.5GHz, the preset frequency step is 100MHz, the value of M is 8, and the value of N is 8.

[0018] This apparatus, applicable to MIMO channel simulators for in-band amplitude and phase flatness calibration, is characterized in that the apparatus comprises: A processor is configured to execute computer-executable instructions; The memory stores one or more computer-executable instructions, which, when executed by the processor, implement the steps of the method described above for implementing in-band amplitude and phase flatness calibration in a MIMO channel simulator.

[0019] The processor for implementing in-band amplitude and phase flatness calibration in a MIMO channel simulator is characterized in that the processor is configured to execute computer-executable instructions, which, when executed by the processor, implement the various steps of the method for implementing in-band amplitude and phase flatness calibration in a MIMO channel simulator.

[0020] The computer-readable storage medium is characterized in that it stores a computer program thereon, which can be executed by a processor to implement the various steps of the above-described method for implementing in-band amplitude and phase flatness calibration in a MIMO channel simulator.

[0021] This invention employs a method, apparatus, processor, and computer-readable storage medium for in-band amplitude and phase flatness calibration in MIMO channel simulators, achieving comprehensive amplitude and phase calibration. This invention simultaneously calibrates the in-band amplitude and phase flatness of the MIMO channel simulator's RF channel, solving the problem of existing technologies that only focus on amplitude calibration while neglecting phase distortion. This effectively improves the system's signal-to-noise ratio and minimizes the impact of hardware on channel simulation. This invention significantly shortens calibration time by using a single-pole multi-throw switch for staged calibration, greatly reducing the time consumed by frequency configuration and fully utilizing the characteristics of MIMO system configuration and external instruments, resulting in a significant improvement in calibration speed. This invention reduces system costs and instrument requirements. The calibration process utilizes a vector network analyzer and signal analyzer, rather than multiple expensive, ultra-high bandwidth signal sources and spectrum analyzers, significantly reducing the overall cost of the calibration system. Simultaneously, using a vector network analyzer for S21 amplitude and phase parameter measurement allows for more accurate acquisition of amplitude and phase data within the passband, reducing measurement errors. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the transmit channel TX calibration connection for the method of implementing in-band amplitude and phase flatness calibration in a MIMO channel simulator according to the present invention.

[0023] Figure 2 This is a schematic diagram of the receiving channel RX calibration connection for the method of implementing in-band amplitude and phase flatness calibration in a MIMO channel simulator according to the present invention.

[0024] Figure 3 This is a flowchart of the transmit channel TX calibration scheme for the method of implementing in-band amplitude and phase flatness calibration in a MIMO channel simulator according to the present invention.

[0025] Figure 4 This is a flowchart of the receiving channel RX calibration scheme for the method of implementing in-band amplitude and phase flatness calibration in a MIMO channel simulator according to the present invention. Detailed Implementation

[0026] To more clearly describe the technical content of the present invention, the following description is provided in conjunction with specific embodiments.

[0027] The present invention relates to a method for implementing in-band amplitude and phase flatness calibration using a MIMO channel simulator, wherein the MIMO channel simulator includes M transmit channels TX and N receive channels RX, and includes the following steps: (1) Perform TX calibration of the transmission channels, that is, generate broadband comb spectrum signals with the same amplitude and known phase through the digital-to-analog converter (DAC) inside the MIMO channel simulator, connect the M transmission channels TX to the signal analyzer in sequence to collect IQ data, and obtain the in-band amplitude error and phase error of each transmission channel TX based on the collected IQ data, and calculate the amplitude compensation data and phase compensation data of each transmission channel TX. (2) Perform receiver channel RX calibration, i.e., configure the MIMO channel simulator to N×1 working mode, substitute the obtained amplitude compensation data and phase compensation data into the transmitter channel TX, and make the active transmitter channel TX a broadband high flatness transparent transmission reference channel; use a vector network analyzer to measure the S21 transmission coefficient between the transmitter channel TX and N receiver channels RX, and analyze the in-band amplitude error and phase error of each receiver channel RX based on the measured S21 transmission coefficient, and calculate the amplitude compensation data and phase compensation data of each receiver channel RX.

[0028] In a preferred embodiment of the present invention, in step (1), the M transmission channels TX are sequentially connected to the signal analyzer through a single-pole M-throw switch. The M input ports of the single-pole M-throw switch are respectively connected to the M transmission channels TX one by one, and the common output port of the single-pole M-throw switch is connected to the signal analyzer.

[0029] In a preferred embodiment of the present invention, the in-band amplitude error of the transmitting channel TX in step (1) is the in-band amplitude unevenness obtained by parsing the acquired IQ data, and the in-band phase error of the transmitting channel TX is the difference between the phase data obtained by parsing the acquired IQ data and the known phase preset when the digital-to-analog converter DAC generates a broadband comb spectrum signal.

[0030] In a preferred embodiment of the present invention, in step (2), the second port of the vector network analyzer is connected to the active transmission channel TX, and the first port of the vector network analyzer is connected to N receiving channels RX in sequence through a single-pole N-throw switch; the N input ports of the single-pole N-throw switch are respectively connected to the N receiving channels RX one by one, and the common output port is connected to the first port of the vector network analyzer.

[0031] In a preferred embodiment of the present invention, in step (2), the N×1 working mode is the working mode in which the signals of the N receiving channels RX of the MIMO channel simulator are all transmitted to the single active transmitting channel TX, so that the N receiving channels RX form independent transmission links with the active transmitting channel TX respectively.

[0032] In a preferred embodiment of the present invention, the bandwidth of the broadband comb spectrum signal generated by the digital-to-analog converter (DAC) is not less than 600MHz, and the measurement bandwidth of the vector network analyzer is not less than 600MHz.

[0033] In a preferred embodiment of the present invention, before performing step (1), the following steps are further included: Reset the digital equalizers of all transmit channels (TX) and receive channels in the FPGA of the MIMO channel simulator to put all channels in an initial state without compensation.

[0034] In a preferred embodiment of the present invention, the transmit channel TX calibration and receive channel RX calibration are both performed stepwise at preset frequency points within the operating frequency range of the MIMO channel simulator. At the same time, for each power level of the amplifier on the RF path, the calibration operation of the corresponding frequency point is completed stepwise.

[0035] In a preferred embodiment of the present invention, the operating frequency range of the MIMO channel simulator is 0.5GHz to 7.5GHz, the preset frequency step is 100MHz, the value of M is 8, and the value of N is 8.

[0036] The apparatus of the present invention for implementing in-band amplitude and phase flatness calibration in a MIMO channel simulator is characterized in that the apparatus comprises: A processor is configured to execute computer-executable instructions; The memory stores one or more computer-executable instructions, which, when executed by the processor, implement the steps of the method described above for implementing in-band amplitude and phase flatness calibration in a MIMO channel simulator.

[0037] The processor of the present invention, applicable to MIMO channel simulators for implementing in-band amplitude and phase flatness calibration, is characterized in that the processor is configured to execute computer-executable instructions, which, when executed by the processor, implement the various steps of the above-described method for implementing in-band amplitude and phase flatness calibration in MIMO channel simulators.

[0038] The main feature of the computer-readable storage medium of the present invention is that it stores a computer program thereon, which can be executed by a processor to implement the various steps of the above-described method for implementing in-band amplitude and phase flatness calibration in a MIMO channel simulator.

[0039] This invention aims to overcome the shortcomings of existing MIMO channel simulator RF calibration technologies in terms of cost, calibration range, and efficiency, and to provide a high-speed, high-precision, and more cost-effective in-band amplitude and phase flatness calibration scheme. Specifically, this invention aims to solve the following technical problems: To address the issue of in-band amplitude and phase synchronization calibration in MIMO channel simulators: This solves the problem that existing technologies mainly rely on amplitude calibration and lack phase calibration, thus ensuring the transmission fidelity of large bandwidth signals.

[0040] Reduce calibration system costs and performance requirements for external instruments: Use a relatively inexpensive vector network analyzer in combination with a signal analyzer to replace the expensive, high-bandwidth signal source and spectrum analyzer required in traditional methods for calibration.

[0041] Addressing the issue of slow calibration speed for multi-channel MIMO systems: Through innovative system configuration and a phased calibration strategy, the total calibration time of multi-channel MIMO systems is significantly shortened, achieving fast and efficient calibration.

[0042] This invention aims to protect a fast in-band amplitude and phase flatness calibration method for multiple channels of a MIMO channel simulator, wherein the MIMO channel simulator has M transmit channels TX and N receive channels RX. The method includes the following steps: a. Transmit channel TX calibration: Generate broadband comb spectrum signals with the same amplitude and known phase through the internal digital-to-analog converter (DAC); connect M transmit channels TX sequentially to the signal analyzer for IQ data acquisition; analyze the IQ data, perform inverse smoothing and inversion operation to obtain the amplitude and phase compensation data of the transmit channel TX.

[0043] b. Receive Channel RX Calibration: Configure the MIMO channel simulator to N×1 mode and substitute the transmit channel TX compensation data obtained in step a into the unique active transmit channel TX, making this transmit channel TX a wideband, high-flatness transparent transmission reference channel. Measure the S21 transmission coefficients between the transmit channel TX and the N receive channels RX using a vector network analyzer. The second port of the vector network analyzer is connected to the transmit channel TX, and the first port of the vector network analyzer is sequentially connected to the N receive channels RX via a switch matrix.

[0044] This invention proposes a staged in-band amplitude and phase flatness calibration method for MIMO channel simulators. The core technology of this scheme lies in calibrating the transmit channel (TX) and receive channel (RX) separately, and utilizing the configuration flexibility of the MIMO channel simulator itself (N×1 mode) and the measurement accuracy of commercial instruments to achieve fast and accurate calibration.

[0045] The calibration process consists of two main stages: Phase 1: Transmit Channel TX Calibration: A known comb spectrum signal is generated through the internal DAC, and after passing through the RF path, it is connected to the signal analyzer for IQ signal acquisition and analysis, completing the amplitude and phase compensation data calculation for all M transmit ports.

[0046] Phase 2: Receive Channel RX Calibration: Configure the channel simulator to MIMO N×1 mode, and use one of the transmit channels TX after Phase 1 calibration as a transparent path. Use a vector network analyzer to measure the S21 transmission coefficient (including amplitude and phase) and complete the amplitude and phase compensation data calculation for all N receive ports.

[0047] The details are as follows: During the launch calibration phase, instrument connections are as follows: Figure 1 As shown, the calibration process is as follows: Figure 3 As shown, the channel simulator is configured with M transmit states. The internal digital-to-analog converter (DAC) generates a broadband comb spectrum signal with a bandwidth of at least 600MHz. The main characteristics of this comb spectrum are uniform amplitude and a known phase sequence. The M transmit ports of the channel simulator are sequentially connected to the M input ports of a single-pole M-throw switch. The common port of the switch is connected to a signal analyzer with a signal bandwidth of at least 600MHz. The signal analyzer is configured in IQ Analyzer mode to acquire IQ data transmitted through the RF circuitry and the switch box. This IQ data is transmitted to the back-end software for data analysis via a high-speed interface.

[0048] The software performs amplitude and phase analysis on the IQ data acquired by the signal analyzer. The measured amplitude unevenness is the in-band amplitude unevenness error of the transmit channel TX. Subtracting the preset known phase from the comb spectrum transmitted by the digital-to-analog converter (DAC) from the measured phase data yields the in-band phase error of the transmit channel TX. The software calculates the required amplitude and phase compensation data for the transmit channel TX based on these error data by performing an inverse smoothing operation. This invention primarily emphasizes the calibration scheme of the entire system, rather than the specific calculation compensation algorithm; therefore, the compensation algorithm for the transmit channel TX is not described in detail.

[0049] The core innovation of this invention is the rapid amplitude and phase calibration of the receiving channels RX. It utilizes the configurability of the channel simulator to MIMO N×1 mode and uses a calibrated transmit channel TX as a transparent transmission channel. The N receiving ports of the channel simulator are traversed and switched using a single-pole N-throw switch, with the common port of the switch connected to the first port of the vector network analyzer. The N×1 configuration of the channel simulator represents that all N receiving channels RX transmit to a single transmit channel TX. This transmit channel TX incorporates the amplitude and phase compensation values ​​from stage one, and can be considered a transparent transmission channel. This transmit channel TX is connected to the second port of the vector network analyzer. The vector network analyzer can accurately measure the S21 amplitude and phase transmission coefficients, and since the transmit channel TX is pre-compensated, its own amplitude and phase unevenness is theoretically extremely low. Therefore, the S21 data measured by the VNA mainly reflects the amplitude and phase unevenness errors of the N receiving ports. The software performs an inverse operation on the precise amplitude and phase error data provided by the vector network analyzer to obtain the amplitude and phase compensation data for the N receiving channels RX. Similarly, this invention mainly emphasizes the calibration scheme of the entire system, rather than the specific calculation compensation algorithm, so the compensation algorithm of the receiving channel RX is not described in detail.

[0050] In a specific embodiment of the present invention, this embodiment takes an 8-receive, 8-transmit MIMO channel simulator platform as an example, with an operating frequency range of 0.5 to 7.5 GHz and a calibration bandwidth of 600 MHz.

[0051] In-band amplitude and phase flatness calibration involves first calibrating the amplitude and phase flatness of the transmit channel (TX), and then calibrating the amplitude and phase flatness of the receive channel (RX). For transmit channel TX calibration, a comb spectrum generated by a digital-to-analog converter (DAC) is transmitted through the RF channel and connected to a signal analyzer to acquire IQ data for amplitude and phase calibration. For receive channel RX calibration, based on the transmit channel TX calibration, an 8×1 MIMO configuration (8 transmit, 1 receive) is used. The calibration data from the transmit channel TX is then substituted, and a vector network analyzer is used to measure S21 to perform amplitude and phase calibration of the receive channel RX. Before starting calibration, the digital equalizers for both the transmit and receive channels RX in the FPGA must be reset to ensure that calculations begin from an uncompensated initial state.

[0052] The first step is to calibrate the amplitude and phase flatness of the transmit channel TX. The transmit channel TX in-band amplitude and phase calibration is performed within the frequency range [500, 7500MHz], with testing and compensation in 100MHz frequency steps, i.e., testing and compensation at 500, 600, ..., 7500MHz. Power is calibrated according to the three amplifier direct-through or bypass settings on the RF path.

[0053] Eight transmit channels (TX) are configured with the same initial frequency. Using eight channels of the digital-to-analog converter (DAC) in the channel simulator, each channel generates a broadband comb spectrum signal (with identical amplitude and known phase), which is then transmitted through the RF transmit channels (TX) in the channel simulator. The eight transmit channels (TX) are sequentially switched via an RF single-pole eight-throw SP8T switch and connected to a signal analyzer. After the signal analyzer is configured to the current frequency, it directly acquires amplitude and phase data within a 600MHz bandwidth. The calibration software decomposes the amplitude and phase of the received intermediate frequency signal. Uneven amplitude indicates in-band amplitude unevenness of the transmit channel (TX). Subtracting the phase of the comb spectrum transmitted by the DAC from the phase of the transmit channel (TX) yields the in-band phase error of the transmit channel (TX). A second frequency is then configured, and this process continues until the amplitude and phase of all eight transmit channels (TX) are calibrated for the final frequency.

[0054] Next, the amplitude and phase flatness of the receive channels RX are calibrated, with the frequency configuration the same as the transmit channels TX. Using an SP8T switch, the eight receive channels RX of the channel simulator are connected to the first port of the vector network analyzer, and the second port of the vector network analyzer is connected to the transmit port of the channel simulator. The channel simulator is configured in 8×1 mode, and the eight receive channels RX are calibrated sequentially.

[0055] Eight receive channels (RX) and one transmit channel (TX) are configured with the same initial frequency, and the vector network analyzer is configured to the same frequency with a bandwidth of 600MHz. Using an SP8T switch, the eight ports of the channel simulator are switched sequentially to calibrate the amplitude and phase of each of the eight receive channels (RX). Then, a second frequency is configured, and this process continues until the amplitude and phase of the last frequency point are calibrated for all eight receive channels (RX).

[0056] This scheme was verified and tested on an 8-receive, 8-transmit experimental platform with a frequency range of 0.5–7.5 GHz and a bandwidth of 600 MHz. The amplitude and phase flatness of the entire system before and after calibration at a center frequency of 3 GHz and a bandwidth of 600 MHz were tested. The specific test results are summarized in the table below. Experimental results show that after calibration, the amplitude flatness was significantly improved from approximately 8.3 dB to less than 2 dB, while the phase flatness improved from over 250° to approximately 25°. Phase flatness is limited by the order of the FPGA's internal equalizer (the current order is insufficient to fully compensate for sideband distortion). Nevertheless, the method of this invention has eliminated most of the phase non-flatness, providing crucial technical support for MIMO channel simulator systems.

[0057] The calibration time is explained below. The channel simulator operates on a single frequency point. The configuration process for a single frequency point is relatively long, approximately 60 seconds, while the amplitude and phase flatness calibration under a single power configuration for a single frequency point takes approximately 5 seconds. This experimental method calibrated a total of 16 channels, 7 at one frequency point, and 3 at 3 power levels. The total time consumption is calculated as follows: Eight transmit channels TX: The frequency configuration time is 71×60=4260s, and the calibration time for all frequencies and all power configurations of the eight transmit channels TX is 8×71×3×5=8520s. Subtotal 4260+8520=12780s≈3.6h; Eight receive channels RX: transmit channel TX, approximately 3.6 hours.

[0058] Therefore, using the method of this invention, the total calibration time is approximately 7.2 hours.

[0059] Using the traditional method, traversing each frequency point and power point one by one, and calibrating the receiver and transmitter separately, the required calibration time is (8+8)×71×3×(5+60)=221520s≈61.5h.

[0060] It can be seen that by using the method of the present invention, the in-band amplitude and phase calibration time is reduced by about 90% compared with the traditional method, and this calibration time becomes more and more significant as the scale of MIMO increases.

[0061] In summary, using the method of this invention, in-band amplitude can be greatly improved, in-band phase can be improved by an order of magnitude, and calibration time can be significantly shortened. This ensures both calibration effectiveness and a significantly reduced engineering cycle, making it highly suitable for in-band amplitude and phase calibration of MIMO channel simulators.

[0062] Figure 1 This diagram illustrates the TX calibration connection for the transmit channel. A digital-to-analog converter (DAC) generates a comb spectrum signal, and M transmit ports are connected to a signal analyzer via single-pole M-throw switches. A common reference signal is required between the signal analyzer and the channel simulator.

[0063] Figure 2 The diagram shows the connection for RX calibration of the receiving channel. The MIMO channel simulator is configured with N×1. The compensated transmit port is connected to Port2 of the vector network analyzer, and the N receive ports are connected to Port1 of the vector network analyzer via a single-pole N-throw switch for S21 measurement.

[0064] Figure 3 This is a flowchart of the TX calibration scheme for the transmit channel.

[0065] Figure 4 This is a flowchart of the RX calibration scheme for the receiver channel.

[0066] Before the channel simulator is fully calibrated, the in-band amplitude / phase flatness test curve (vector network test) is obtained.

[0067] After the channel simulator is fully calibrated, the in-band amplitude / phase flatness test curve (vector network test) is obtained.

[0068] This invention does not emphasize the algorithm level, but rather addresses the flatness calibration of the receive channel (RX) and transmit channel (TX) in a MIMO system under high bandwidth conditions at the system level. The multi-channel MIMO system of this invention requires calibration for both reception and transmission, rather than only transmitting or receiving in one direction. High bandwidth conditions present limitations due to expensive and restrictive instruments. In particular, this invention emphasizes utilizing the unique performance of the MIMO system in conjunction with a vector network analyzer to calibrate the receive channel (RX).

[0069] The present invention aims to address the following issues: flatness calibration of several receive channels (RX) and several transmit channels (TX) in a MIMO system under high bandwidth conditions; then, at the system level, the calibration process faces limitations due to the extremely high requirements for instrument configuration and the high cost of instruments under high bandwidth conditions; and finally, it aims to reduce the impact of limitations on the flatness performance of the instruments themselves.

[0070] In low-bandwidth applications, the cost of instruments is not high. The flatness of the receiving channel (RX) can be directly calibrated using a signal source, and the flatness of the transmitting channel (TX) can be calibrated using a spectrum analyzer, which reduces limitations. It can be used in situations with only a transmitter or only a receiver. Furthermore, the technology for low-bandwidth applications is relatively mature, and the influence of the instruments themselves is also small.

[0071] This invention utilizes a spectrum analyzer and a vector network analyzer for transmission and reception calibration. The vector network analyzer is a gold standard tool for flatness (amplitude and phase) measurement, which is inexpensive and reliable. It also ensures the flatness calibration performance of the MIMO system and reduces the cost of instruments during calibration.

[0072] The main approach of this invention is to first perform TX calibration of the transmit channel, and then use vector calibrator to perform RX flatness calibration of the receive channel.

[0073] When calibrating the receive channel RX using vector network analysis (VNA), the VNA's expertise in measuring flatness (amplitude and phase) is fully utilized, along with the unique characteristics of MIMO systems. The calibration configuration consists of N receive channels RX and one transmit channel TX, i.e., a MIMO N×1 configuration. In MIMO systems, any one of the N receive channels RX can be independently connected to its corresponding transmit channel TX. After substituting the flatness calibration data from the transmit channel TX, this transmit channel TX can be considered almost transparent. This means that any flatness error in any receive channel RX will be transmitted to the VNA, which reliably and accurately measures this error and then compensates for the flatness.

[0074] This invention emphasizes a flatness calibration scheme for both reception and transmission in a high-bandwidth MIMO system, and its reliability and practicality, rather than a specific algorithm. The flatness calibration algorithm for the transmit channel (TX) in this invention is not limited to a specific algorithm; it can be any other algorithm capable of calibration.

[0075] For the specific implementation scheme of this embodiment, please refer to the relevant descriptions in the above embodiments, which will not be repeated here.

[0076] It is understood that the same or similar parts in the above embodiments can be referred to each other, and the contents not described in detail in some embodiments can be referred to the same or similar contents in other embodiments.

[0077] It should be noted that in the description of this invention, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means at least two.

[0078] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process, and the scope of the preferred embodiments of the invention includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as will be understood by those skilled in the art to which embodiments of the invention pertain.

[0079] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution device. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0080] Those skilled in the art will understand that all or part of the steps of the methods in the above embodiments can be implemented by a program instructing related hardware. The corresponding program can be stored in a computer-readable storage medium. When the program is executed, it includes one or a combination of the steps of the method embodiments.

[0081] Furthermore, the functional units in the various embodiments of the present invention can be integrated into a processing module, or each unit can exist physically separately, or two or more units can be integrated into a module. The integrated module can be implemented in hardware or as a software functional module. If the integrated module is implemented as a software functional module and sold or used as an independent product, it can also be stored in a computer-readable storage medium.

[0082] The storage media mentioned above can be read-only memory, disk, or optical disk, etc.

[0083] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0084] This invention employs a method, apparatus, processor, and computer-readable storage medium for in-band amplitude and phase flatness calibration in MIMO channel simulators, achieving comprehensive amplitude and phase calibration. This invention simultaneously calibrates the in-band amplitude and phase flatness of the MIMO channel simulator's RF channel, solving the problem of existing technologies that only focus on amplitude calibration while neglecting phase distortion. This effectively improves the system's signal-to-noise ratio and minimizes the impact of hardware on channel simulation. This invention significantly shortens calibration time by using a single-pole multi-throw switch for staged calibration, greatly reducing the time consumed by frequency configuration and fully utilizing the characteristics of MIMO system configuration and external instruments, resulting in a significant improvement in calibration speed. This invention reduces system costs and instrument requirements. The calibration process utilizes a vector network analyzer and signal analyzer, rather than multiple expensive, ultra-high bandwidth signal sources and spectrum analyzers, significantly reducing the overall cost of the calibration system. Simultaneously, using a vector network analyzer for S21 amplitude and phase parameter measurement allows for more accurate acquisition of amplitude and phase data within the passband, reducing measurement errors.

[0085] In this specification, the invention has been described with reference to specific embodiments thereof. However, it will be apparent that various modifications and variations can be made without departing from the spirit and scope of the invention. Therefore, the specification and drawings should be considered illustrative rather than restrictive.

Claims

1. A method for implementing in-band amplitude and phase flatness calibration using a MIMO channel simulator, wherein the MIMO channel simulator comprises M transmit channels TX and N receive channels RX, characterized in that, The method includes the following steps: (1) Perform TX calibration of the transmission channels, that is, generate broadband comb spectrum signals with the same amplitude and known phase through the digital-to-analog converter (DAC) inside the MIMO channel simulator, connect the M transmission channels TX to the signal analyzer in sequence to collect IQ data, and obtain the in-band amplitude error and phase error of each transmission channel TX based on the collected IQ data, and calculate the amplitude compensation data and phase compensation data of each transmission channel TX. (2) Perform receiver channel RX calibration, i.e., configure the MIMO channel simulator to N×1 working mode, substitute the obtained amplitude compensation data and phase compensation data into the transmitter channel TX, and make the active transmitter channel TX a broadband high flatness transparent transmission reference channel; use a vector network analyzer to measure the S21 transmission coefficient between the transmitter channel TX and N receiver channels RX, and analyze the in-band amplitude error and phase error of each receiver channel RX based on the measured S21 transmission coefficient, and calculate the amplitude compensation data and phase compensation data of each receiver channel RX.

2. The method for implementing in-band amplitude and phase flatness calibration in a MIMO channel simulator according to claim 1, characterized in that, In step (1), the M transmission channels TX are connected to the signal analyzer in sequence through a single-pole M-throw switch. The M input ports of the single-pole M-throw switch are connected to the M transmission channels TX one by one, and the common output port of the single-pole M-throw switch is connected to the signal analyzer.

3. The method for implementing in-band amplitude and phase flatness calibration in a MIMO channel simulator according to claim 1, characterized in that, In step (1), the in-band amplitude error of the transmission channel TX is the in-band amplitude flatness obtained by parsing the acquired IQ data, and the in-band phase error of the transmission channel TX is the difference between the phase data obtained by parsing the acquired IQ data and the preset known phase when the digital-to-analog converter DAC generates a broadband comb spectrum signal.

4. The method for implementing in-band amplitude and phase flatness calibration in a MIMO channel simulator according to claim 1, characterized in that, In step (2), the second port of the vector network analyzer is connected to the active transmit channel TX, and the first port of the vector network analyzer is connected to N receive channels RX in sequence through a single-pole N-throw switch; the N input ports of the single-pole N-throw switch are respectively connected to the N receive channels RX one by one, and the common output port is connected to the first port of the vector network analyzer.

5. The method for implementing in-band amplitude and phase flatness calibration in a MIMO channel simulator according to claim 1, characterized in that, In step (2), the N×1 working mode is the working mode in which the signals of the N receiving channels RX of the MIMO channel simulator are all transmitted to the single active transmitting channel TX, so that the N receiving channels RX form independent transmission links with the active transmitting channel TX respectively.

6. The method for implementing in-band amplitude and phase flatness calibration in a MIMO channel simulator according to claim 1, characterized in that, The bandwidth of the broadband comb spectrum signal generated by the digital-to-analog converter (DAC) is not less than 600MHz, and the measurement bandwidth of the vector network analyzer is not less than 600MHz.

7. The method for implementing in-band amplitude and phase flatness calibration in a MIMO channel simulator according to claim 1, characterized in that, Before performing step (1), the following steps are also included: Reset the digital equalizers of all transmit channels (TX) and receive channels in the FPGA of the MIMO channel simulator to put all channels in an initial state without compensation.

8. The method for implementing in-band amplitude and phase flatness calibration in a MIMO channel simulator according to claim 1, characterized in that, The aforementioned transmit channel TX calibration and receive channel RX calibration are both performed stepwise at preset frequency points within the operating frequency range of the MIMO channel simulator. At the same time, for each power level of the amplifier on the RF path, the calibration operation of the corresponding frequency point is completed stepwise.

9. The method for implementing in-band amplitude and phase flatness calibration in a MIMO channel simulator according to claim 1, characterized in that, The MIMO channel simulator operates in the frequency range of 0.5GHz to 7.5GHz, the preset frequency step is 100MHz, the value of M is 8, and the value of N is 8.

10. An apparatus for implementing in-band amplitude and phase flatness calibration in a MIMO channel simulator, characterized in that, The device includes: A processor is configured to execute computer-executable instructions; The memory stores one or more computer-executable instructions, which, when executed by the processor, implement the steps of the method for implementing in-band amplitude and phase flatness calibration in a MIMO channel simulator as described in any one of claims 1 to 9.

11. A processor suitable for implementing in-band amplitude and phase flatness calibration in a MIMO channel simulator, characterized in that, The processor is configured to execute computer-executable instructions, which, when executed by the processor, implement the steps of the method for implementing in-band amplitude and phase flatness calibration in a MIMO channel simulator as described in any one of claims 1 to 9.

12. A computer-readable storage medium, characterized in that, It stores a computer program that can be executed by a processor to implement the steps of the method for implementing in-band amplitude and phase flatness calibration in a MIMO channel simulator as described in any one of claims 1 to 9.

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