A calibration method and a calibration device

Abstract

The present application discloses a calibration method and a calibration device. The calibration device is used to calibrate the non-linear distortion components of the IQ signals in a non-linear system. The non-linear system includes a front-end device and a digital down-converter. The calibration device includes a training signal source, a switch, a processor, and a calibration module. The training signal source and the receiving link of the external signal are selectively connected to the front-end device of the non-linear system through the switch. The digital down-converter is connected to the calibration module, and the processor is respectively connected to the training signal source, the switch, the digital down-converter, and the calibration module. The processor controls the switch to make the non-linear system in a training mode or a calibration mode. When the non-linear system is in the training mode, the processor calculates the calibration parameters and loads them into the calibration module. When the non-linear system is in the calibration mode, the calibration module performs non-linear calibration on the output signal of the digital down-converter to obtain distortion-free IQ signals. The present application can effectively remove the signal distortion generated by the non-linear system.

Description

Technical Field

[0001] This application relates to the technical field of signal processing, and in particular, to a calibration method and a calibration device. Background Art

[0002] In order to process high-rate communication signals, some signal processing systems often use Digital Down Converter (DDC) technology to perform operations such as frequency conversion and decimation on high-speed signals, so as to convert them into low-speed IQ (In-phase Quadrature) signals. Front-end devices of these systems, such as power amplifiers and analog-to-digital converters, will inevitably introduce non-linear spurs into the received signal, resulting in non-linear distortion of the received signal. The existence of non-linear distortion components will significantly affect the performance of communication devices.

[0003] As Figure 1 shown, assuming that the input signal of the non-linear system is a two-tone signal, after passing through the radio frequency front-end and the analog-to-digital converter, second-order, third-order and other non-linear distortion components will be introduced. After being processed by the digital down converter, some non-linear distortion components will remain in the intercepted in-band signal, seriously affecting indicators such as the overall dynamic range of the non-linear system.

[0004] Currently, the methods for analyzing and processing non-linear signals mainly target real signals, that is, signals that have not been processed by a digital down converter. However, compared with IQ signals, real signals have a high rate and consume a large amount of computing resources required for the same operations, which is not conducive to applications in resource-limited embedded computing systems such as FPGA (Field Programmable Gate Array). In addition, most high-speed analog-to-digital conversion devices have built-in digital down converters. In order to make full use of the computing resources of the chip itself, there is an urgent need for a calibration method for non-linear distortion of IQ signals. Summary of the Invention

[0005] Based on the above problems existing in the prior art, embodiments of the present application provide a calibration method and a calibration device to effectively remove signal distortion generated by a non-linear system with a digital down converter.

[0006] Embodiments of the present application adopt the following technical solutions:

[0007] In a first aspect, an embodiment of the present application provides a calibration device for calibrating non-linear distortion components of IQ signals in a non-linear system. The non-linear system includes a front-end device and a digital down converter. The calibration device includes: a training signal source, a switch, a processor, and a calibration module;

[0008] The training signal source and the receiving link of the external signal are selectively connected to the front-end device of the non-linear system through the switch. The digital down-converter is connected to the calibration module, and the processor is respectively connected to the training signal source, the switch, the digital down-converter, and the calibration module;

[0009] The processor controls the switch to put the non-linear system in the training mode or the calibration mode. When the non-linear system is in the training mode, the processor calculates the calibration parameters of the calibration module and loads the calibration parameters into the calibration module; when the non-linear system is in the calibration mode, the calibration module performs non-linear calibration on the output signal of the digital down-converter to obtain the calibrated IQ signal.

[0010] In a second aspect, an embodiment of the present application further provides a calibration method for calibrating the non-linear distortion component of the IQ signal in a non-linear system. The non-linear system includes a front-end device and a digital down-converter. The calibration method is executed by a processor of a calibration device, and the calibration method includes:

[0011] Control the non-linear system to enter the training mode and control the training signal source to output a training signal to the non-linear system;

[0012] Obtain the training signal and the IQ training signal with non-linear distortion output by the non-linear system;

[0013] Obtain the calibration parameters of the calibration module according to the training signal and the IQ training signal, and load the calibration parameters into the calibration module;

[0014] Control the non-linear system to enter the calibration mode, and use the calibration module to perform non-linear calibration on the output signal of the non-linear system to obtain the calibrated IQ signal.

[0015] In a third aspect, an embodiment of the present application further provides an electronic device, including:

[0016] A processor; and

[0017] A memory arranged to store computer-executable instructions, and the executable instructions, when executed, cause the processor to execute the calibration method.

[0018] In a fourth aspect, an embodiment of the present application further provides a computer-readable storage medium. The computer-readable storage medium stores one or more programs, and when the one or more programs are executed by an electronic device including a plurality of application programs, the electronic device is caused to execute the calibration method.

[0019] The above at least one technical solution adopted in the embodiments of the present application can achieve the following beneficial effects: The embodiments of the present application design a dedicated calibration device for a non-linear system with a digital down-converter. The front-end device of the non-linear system is controlled by the switch of the calibration device to receive the training signal of the training signal source or receive an external signal, so as to control the non-linear system to enter the training mode or the calibration mode. When the non-linear system enters the training mode, the processor of the calibration device calculates the calibration parameters of the calibration module. Since the non-linear distortion components generated in the non-linear system are related to the hardware performance of the non-linear system, therefore, when the hardware of the non-linear system is determined, the calibration parameters calculated based on the training signal can correct the non-linear distortion generated when the non-linear system receives an external signal, and can effectively remove the non-linear distortion signal generated by the non-linear system. The entire signal calibration process has the advantage of low computational complexity and can be applied to an embedded environment with limited computing resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings described herein are used to provide a further understanding of the present application, and constitute a part of the present application. The illustrative embodiments and descriptions thereof of the present application are used to explain the present application and do not constitute an improper limitation of the present application. In the drawings:

[0021] Figure 1 It is a schematic diagram of the processing effect of a dual-tone signal by a non-linear system in the prior art;

[0022] Figure 2 It is a schematic structural diagram of the calibration device shown in the embodiments of the present application;

[0023] Figure 3-1 It is a schematic diagram of a connection manner between the calibration module and a digital down-converter shown in the embodiments of the present application;

[0024] Figure 3-2 It is a schematic diagram of another connection manner between the calibration module and a digital down-converter shown in the embodiments of the present application;

[0025] Figure 3-3 It is a schematic diagram of a connection manner between the calibration module and multiple digital down-converters shown in the embodiments of the present application;

[0026] Figure 3-4 It is a schematic diagram of another connection manner between the calibration module and multiple digital down-converters shown in the embodiments of the present application;

[0027] Figure 3-5 It is a schematic diagram of yet another connection manner between the calibration module and multiple digital down-converters shown in the embodiments of the present application;

[0028] Figure 4-1 It is a schematic structural diagram of a calibration module shown in the embodiments of the present application;

[0029] Figure 4-2 It is a schematic structural diagram of the Nth-order nonlinear correction module shown in the embodiments of the present application;

[0030] Figure 4-3 It is a schematic diagram of the Nth-order delay combination shown in the embodiments of the present application;

[0031] Figure 5 It is a flowchart of the correction method shown in the embodiments of the present application;

[0032] Figure 6 It is a schematic diagram of the visual relationship of the target equation shown in the embodiments of the present application;

[0033] Figure 7 It is a schematic diagram of the signal spectrum change during the correction process shown in the embodiments of the present application;

[0034] Figure 8 It is a schematic structural diagram of an electronic device in the embodiments of the present application. Detailed implementation manners

[0035] To make the objectives, technical solutions, and advantages of the present application clearer, the technical solutions of the present application will be clearly and completely described below in conjunction with the specific embodiments of the present application and the corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0036] The following will describe in detail the technical solutions provided by each embodiment of the present application with reference to the drawings.

[0037] The embodiments of the present application provide a correction device for correcting the nonlinear distortion components of the IQ signal in a nonlinear system. Among them, the nonlinear system can be referred to Figure 1 as shown, for example, including a front-end device and a digital down-converter. The nonlinear system in the present application includes two working modes. One is the training mode, and the other is the correction mode. The training mode is used to train the correction parameters of the correction module, and the correction mode is used to correct the nonlinear distortion components in the corrected IQ signal.

[0038] Figure 2 It is a schematic structural diagram of the correction device shown in the embodiments of the present application. As Figure 2 shown, the correction device in the present application includes: a training signal source, a switch, a processor, and a correction module;

[0039] The receiving link of the training signal source and the external signal is selectively connected to the front-end device of the nonlinear system through a switch. The digital downconverter is connected to the calibration module, and the processor is connected to the training signal source, the switch, the digital downconverter, and the calibration module respectively. To ensure that Figure 2 the connection relationship between the relevant devices in Figure 2 is clearly understood,

[0040] The processor controls the switch to put the nonlinear system in the training mode or the calibration mode. When the switch is switched to the training signal source, the training signal source is connected to the front-end device of the nonlinear system, and at this time the nonlinear system is in the training mode; when the switch is switched to the external signal terminal, the front-end device of the nonlinear system receives the external signal, and at this time the nonlinear system is in the calibration mode.

[0041] When the nonlinear system is in the training mode, the processor calculates the calibration parameters of the calibration module and loads the calibration parameters into the calibration module; when the nonlinear system is in the calibration mode, the calibration module performs nonlinear calibration on the output signal of the digital downconverter to obtain the calibrated IQ signal.

[0042] According to Figure 2 the shown calibration device, this embodiment is a dedicated calibration device for a nonlinear system with a digital downconverter. The switch of the calibration device is used to control the front-end device of the nonlinear system to receive the training signal of the training signal source or the external signal, so as to control the nonlinear system to enter the training mode or the calibration mode. When the nonlinear system enters the training mode, the processor of the calibration device calculates the calibration parameters of the calibration module. Since the nonlinear distortion components generated in the nonlinear system are related to the hardware performance of the nonlinear system, therefore, when the hardware of the nonlinear system is determined, the calibration parameters calculated based on the training signal can correct the nonlinear distortion generated when the nonlinear system receives the external signal, effectively removing the signal distortion generated by the nonlinear system. The entire signal calibration process has the advantage of low computational complexity and can be applied to embedded environments with limited computing resources.

[0043] In some embodiments of the present application, the training signal source is composed of two or more independent signal sources and a combiner, or the training signal source can also be an independent instrument or an integrated DAC (Digital to Analog Converter) chip.

[0044] The non-linear system in the embodiments of the present application may include one digital down-converter or multiple digital down-converters. When the non-linear system includes multiple digital down-converters, the non-linear distortion components in each channel where the digital down-converter is located may be affected not only by the hardware performance of the non-linear system but also by the fundamental frequency components in the channels where other digital down-converters are located. Therefore, the connection method between the calibration module and the digital down-converter in the non-linear system is related to the number of digital down-converters.

[0045] When the non-linear system includes one digital down-converter, as Figure 3-1 shown, the calibration module forms the cancellation branch of the digital converter, and the non-linear distortion components in the output signal of the digital down-converter are cancelled by the cancellation signal output by the calibration module.

[0046] In Figure 3-1 the scenario shown, the IQ signal output by the digital down-converter is divided into two paths. The first path of the IQ signal is corrected by the calibration module and then the cancellation signal is output. The second path of the IQ signal is processed by delay / filtering and then combined with the cancellation signal through a combiner, so that the cancellation signal can cancel the non-linear distortion components in the IQ signal and obtain the corrected IQ signal.

[0047] Alternatively, as Figure 3-2 shown, the output end of the digital down-converter is connected to the calibration module, and the corrected IQ signal is output through the calibration module.

[0048] Comparing Figure 3-1 with Figure 3-2 the two connection methods of the calibration module shown, in Figure 3-1 the scenario shown, it is necessary to divide the IQ signal output by the digital down-converter into two paths, while in Figure 3-2 the scenario shown, it is not necessary to divide the IQ signal output by the digital down-converter, and the non-linear correction can be directly performed on the IQ signal output by the digital down-converter. Therefore, those skilled in the art can, according to the application scenario of the non-linear system, for example, in the analog-to-digital conversion scenario, use Figure 3-1 the connection method shown, while in the power amplifier scenario, use Figure 3-2 the connection method shown.

[0049] When the non-linear system includes multiple digital down-converters, it is very likely that the fundamental frequency signal and the related non-linear distortion components are not within the output frequency band of the same digital down-converter. At this time, it is necessary to combine and utilize the IQ signals output by multiple digital down-converters to achieve the correction of non-linear distortion. The embodiments of the present application show the following two connection methods between the digital down-converter and the calibration module here.

[0050] The first connection method:

[0051] The multiple digital down-converters include a first type of digital down-converter and a second type of digital down-converter. For the first type of digital down-converter, the output signal is affected by the fundamental frequency components of other digital down-converters. For the second type of digital down-converter, the fundamental frequency components of the output signal affect the output signals of other digital down-converters.

[0052] Then, each second type of digital down-converter is connected to one of the correction modules, and the non-linear distortion components in the output signals of the corresponding first type of digital converters are cancelled by the cancellation signals output by the correction modules.

[0053] A possible implementation solution of this embodiment is as follows:

[0054] When the output signals of the first type of digital down-converters contain non-linear distortion components generated by the fundamental frequency components of multiple second type of digital down-converters, the output end of each second type of digital down-converter is connected to one of the correction modules, and the output IQ signals of the first type of digital down-converters are non-linearly cancelled by the cancellation signals output by the correction modules.

[0055] For example, as Figure 3-3 shown, assume that digital down-converter 1 is the first type of digital down-converter, and digital down-converters 2 and 3 are the second type of digital down-converters. That is, the output signal of digital down-converter 1 contains non-linear distortion components generated by the fundamental frequency components of digital down-converters 2 and 3. At this time, connect digital down-converter 2 to a correction module 1, and connect digital down-converter 3 to a correction module 2. Then, the cancellation signals output by correction modules 1 and 2 are combined with the signals in the channel where digital down-converter 1 is located through a combiner. Since the IQ signals in the channels where digital down-converters 2 and 3 are located need a certain amount of time for correction processing, the signals in the channel where digital down-converter 1 is located need to be delayed / filtered so that the three signals reach the combiner simultaneously for combining processing, and finally the corrected IQ signals are output through the combiner.

[0056] Another possible implementation solution of this embodiment is as follows:

[0057] When the output signals of multiple first type of digital down-converters all contain non-linear distortion components generated by the fundamental frequency components of a certain second type of digital down-converter, the output end of this second type of digital down-converter is connected to one of the correction modules, and the output IQ signals of multiple first type of digital down-converters are non-linearly cancelled by the cancellation signals output by the correction module.

[0058] For example, as Figure 3-4As shown, assume that digital down-converters 4 and 5 are the first type of digital down-converters, and digital down-converter 6 is the second type of digital down-converter. That is, the output signals of digital down-converters 4 and 5 both contain non-linear distortion components generated by the fundamental frequency component of digital down-converter 6. This situation is common in scenarios where the output frequency bands of digital down-converters overlap. At this time, connect a correction module 3 to digital down-converter 6, and then combine the cancellation signal 3 output by the correction module 3 with the signals in the channels where digital down-converters 4 and 5 are located through a combiner. Since the IQ signals in the channel where digital down-converter 6 is located require a certain amount of time for correction processing, it is necessary to perform delay / filter processing on the signals in the channels where digital down-converters 4 and 5 are located, so that the two signals reach the combiner at the same time for combination processing, and finally output the corrected IQ signal through the combiner.

[0059] The second connection method:

[0060] Group multiple digital down-converters according to the center frequency and effective bandwidth of each digital down-converter, and connect a correction module to the output end of each digital down-converter in each group. The corrected IQ signal corresponding to each group is output through the correction module.

[0061] It is found that whether the channel where each digital down-converter is located contains non-linear distortion components generated by the fundamental frequency components of other channels is related to the center frequency and effective bandwidth of the digital down-converter. Therefore, in some scenarios where the correction module needs to directly output the corrected IQ signal, the digital down-converters that can contain non-linear distortion components generated by relevant fundamental frequency components can be divided into a group based on the center frequency and effective bandwidth of the digital down-converter. For example Figure 3-5 As shown, digital down-converters 7, 8, and 9 are divided into one group, and digital down-converter 9 is separately divided into one group. Each of these two groups is connected to a correction module, and the corrected IQ signal is output through the correction module.

[0062] The above embodiments of the present application show several connection methods between the correction module and the digital down-converter. In practical applications, the connection method with the correction module can be designed according to the application scenario of the non-linear system, the number of digital down-converters in the non-linear system, the working bandwidth and center frequency of each digital down-converter.

[0063] As Figure 4-1 shown, the correction module of the present application includes a first digital oscillator (Numerically Controlled Oscillator, NCO), a non-linear combination correction module, and a second digital oscillator connected in sequence. The input end of the first digital oscillator is connected to the output end of the digital down-converter corresponding to the correction module, and the output end of the second digital oscillator is the output end of the correction module.

[0064] In this application, the connection between the input end of the first digital oscillator and the output end of the digital down-converter corresponding to the calibration module can be understood as follows: when the calibration module is connected to a digital down-converter, the calibration module includes a first digital oscillator, and this first digital oscillator is connected to the digital down-converter, such as the connection cases shown in Figure 3-1 , 3-2, 3-3, and 3-4; when the calibration module is connected to m digital down-converters, the calibration module includes m first digital oscillators, and the m first digital oscillators are connected to the corresponding digital down-converters, such as the connection case shown in Figure 3-5 . The calibration module 4 includes 3 first digital oscillators. The first of the first digital oscillators is connected to the digital down-converter 7, the second of the first digital oscillators is connected to the digital down-converter 8, and the third of the first digital oscillators is connected to the digital down-converter 9. The first digital oscillator is used to perform spectral shift on the IQ signal output by the corresponding digital down-converter.

[0065] Among them, the non-linear combination calibration module in this application includes a combining module, a first-order non-linear calibration module to an n-order non-linear calibration module, where n is a positive integer greater than 1;

[0066] The input ends of the first-order non-linear calibration module to the n-order non-linear calibration module are all connected to the output end of the first digital oscillator, the output ends of the first-order non-linear calibration module to the n-order non-linear calibration module are all connected to the input end of the combining module, and the output end of the combining module is connected to the input end of the second digital oscillator.

[0067] Such as Figure 4-2 shown, the N-order non-linear calibration module includes multiple N-order delay combinations. Specifically, the number of N-order delay combinations is related to the maximum delay value of the delay device. Among them, as Figure 4-3 shown, each order of non-linear calibration module includes multiple delay combinations. Each delay combination is used to perform an optional conjugate operation on the input signal, then perform a delay operation, and multiply the signal after the delay operation by a coefficient value through a multiplier and output it.

[0068] The calibration parameters required for the calibration module described in this application can be understood as Figure 4-3 the parameters indicating whether the conjugate operation shown is performed, the delay value parameters, and the coefficient values corresponding to the delay combinations.

[0069] Based on the calibration device provided in the above embodiments, its working method is as follows: After the non-linear system is powered on, the processor of the calibration device controls the switch to switch to the training signal source. The processor sends a control signal to the training signal source. Each signal source of the training signal source outputs a single-tone signal, and after being combined by the combiner, the training signal is output to the non-linear system. The processor constructs a calibration parameter calculation model (this calibration parameter calculation model is the target equation described in the following text) by controlling the signal source parameters and receiving the IQ signal with non-linear distortion components output by the non-linear system, calculates the calibration parameters through the calibration parameter calculation model, and loads the calibration parameters into the calibration module. Thereafter, the processor controls the switch to switch to the receiving link of the external signal, the non-linear system enters the normal working state, and the calibration module performs non-linear calibration on the IQ signal with non-linear distortion components output by the non-linear system to obtain the calibrated IQ signal.

[0070] An embodiment of the present application also provides a calibration method, and the execution subject of this calibration method is the processor in the above calibration device embodiment. Please refer to Figure 5 , Figure 5 Taking the execution subject as the processor as an example, a calibration method provided by an embodiment of the present application will be introduced. As Figure 5 shown, a calibration method provided by an embodiment of the present application may include the following steps S510 to S540:

[0071] Step S510, control the non-linear system to enter the training mode, and control the training signal source to output a training signal to the non-linear system.

[0072] Among them, the non-linear system can enter the training mode by controlling the switch to switch to the training signal source.

[0073] Step S520, obtain the training signal and the IQ training signal with non-linear distortion output by the non-linear system.

[0074] Step S530, obtain the calibration parameters of the calibration module according to the training signal and the IQ training signal, and load the calibration parameters into the calibration module.

[0075] Step S540, control the non-linear system to enter the calibration mode, and use the calibration module to perform non-linear calibration on the output signal of the non-linear system to obtain the calibrated IQ signal.

[0076] Among them, the non-linear system can enter the calibration mode by controlling the switch to switch to the receiving link of the external signal, and the calibration mode is also the normal working mode of the non-linear system.

[0077] As Figure 5According to the calibration method shown above, in this embodiment, the nonlinear system is first controlled to enter the training mode. The training signal is processed by the nonlinear system, and the calibration parameters are calculated using the IQ training signal with nonlinear distortion components output by the nonlinear system and the training signal, and then loaded into the calibration module. In this way, when the nonlinear system enters the calibration mode, the calibration module can be used to perform nonlinear calibration on the IQ signal output by the nonlinear system to obtain the calibrated fundamental frequency IQ signal. The calculation method is simple and is convenient to be applied to the embedded environment with limited computing resources.

[0078] In some embodiments of the present application, after controlling the nonlinear system to enter the calibration mode, the method further includes:

[0079] Obtaining the output signal of the nonlinear system and the IQ signal after being calibrated by the calibration module for the output signal; determining the signal difference between the output signal and the calibrated IQ signal; if the signal difference is greater than a preset value, controlling the nonlinear system to enter the training mode.

[0080] In some embodiments of the present application, controlling the training signal source to output a training signal to the nonlinear system includes:

[0081] Setting the signal frequency points according to the operating frequency band and operating frequency of the nonlinear system; controlling the training signal source to output the training signal at each signal frequency point.

[0082] In some embodiments of the present application, obtaining the calibration parameters of the calibration module according to the training signal and the IQ training signal includes:

[0083] Obtaining the spectral values of the training signal and the spectral values of the IQ training signal corresponding to each signal frequency point; constructing a training matrix A in the order of the signal frequency points and according to the spectral values of the IQ training signal and the delay combination at each signal frequency point, and setting the vector x to be solved according to the coefficient values corresponding to the delay combination; constructing a target vector b in the order of the signal frequency points and according to the spectral values of the training signal at the corresponding signal frequency points; constructing a target equation A×x = b based on the training matrix A, the vector x to be solved, and the target vector b, and obtaining the vector x to be solved by solving the target equation A×x = b; obtaining the calibration parameters according to the delay combinations corresponding to the non-zero elements in the solved vector x.

[0084] Taking the dual-tone training signal as an example, the processor controls the dual-tone training signal source to switch the dual-tone frequencies within the combination [F1, F2], so that it covers the operating frequency band of the non-linear system. Summarize the respective signal frequency points [F1, F2], [F3, F4]…, [Fi, Fj] of each dual-tone combination, and obtain the spectral values [FNL1, FNL2, … FNLi, FNLj] of the dual-tone training signal at each signal frequency point, as well as the spectral values [NLV1, NLV2, … NLVi, NLVj] of the dual-tone IQ training signal at each signal frequency point, where i and j are the number of signal frequency points of the dual-tone signal.

[0085] Then, construct the training matrix A, the vector x to be solved, and the target vector b as shown in Figure 6 Each vector element in the vector x to be solved corresponds to a delay combination scheme as shown in Figure 4-3 One matrix element of the training matrix A corresponds to one vector element in the vector x to be solved, and also corresponds to a delay combination scheme as shown in Figure 4-3 Therefore, after solving the vector b, the corresponding delay combination scheme can be determined according to the correspondence between the non-zero elements in the vector b and the corresponding matrix elements in the training matrix A. This delay combination scheme includes whether the conjugate operation is performed, the delay value corresponding to each conjugate operation, and the specific delay value, so as to obtain the required calibration parameters.

[0086] Among them Figure 6 Only the matrix form corresponding to the second-order delay combination is shown, and the matrix forms corresponding to other orders of delay combinations are as shown in the second-order delay combination.

[0087] Next, solve the target equation A × x = b to obtain the coefficient values corresponding to each delay combination term. Optionally, sparse optimization methods such as matching pursuit, heuristic algorithms, gradient descent, etc. can be used to solve the sparse form of the vector x within an acceptable error, and then the final calibration parameters can be determined according to the delay combinations corresponding to the non-zero elements in the vector x.

[0088] It should be understood that if the center frequencies of the input signals of each digital down-converter are Fin01, Fin02…, and the center frequencies of the output signals of each digital down-converter are Fout01, Fout02…, then the frequencies of the first digital oscillators in each branch of the calibration module are Fin01, Fin02…, and the frequencies of the second digital oscillators are -Fout01, -Fout02….

[0089] For the convenience of understanding the calibration method of the present application, it will be described in detail in combination with Figure 7

[0090] Suppose the non-linear system is an analog-to-digital converter (ADC) with an operating frequency band from 200 MHz to 1200 MHz and a sampling frequency of 3072 MHz. When a radio frequency (RF) signal passes through this ADC, non-linear distortion components will be generated. To clearly show the non-linear distortion characteristics of the non-linear system in the prior art, in this embodiment, a two-tone signal is used as the training signal. After passing through the ADC, second-order, third-order, etc. non-linear distortions are generated, and each order of non-linear distortion contains components such as harmonics and intermodulation. When the two-tone signal is input into the uncalibrated ADC, after the digital down converter (DDC) performs operations such as mixing, decimation, and filtering on the signal, IQ baseband signals with different frequency ranges are output. That is, the output signal of the uncalibrated ADC appears as a combination of the input signal and various types of non-linear distortion components in the frequency spectrum.

[0091] As Figure 7 shown, assume that the center frequency of DDC1 is F01 = 450 MHz, the covered frequency range is 66 - 834 MHz, and the decimation ratio is 4; the center frequency of DDC2 is F02 = 950 MHz, the covered frequency range is 566 - 1334 MHz, and the decimation ratio is 4. The input two-tone signal frequency is [280, 330] MHz. When it passes through the ADC, second-order sum-frequency components with frequencies of [560, 610, 660] MHz, third-order difference-frequency components with frequencies of [230, 380] MHz, and third-order sum-frequency components with frequencies of [840, 890, 940, 990] MHz are generated within the operating frequency band.

[0092] The existence of these non-linear distortion components will mask the input signal that appears at the same frequency point, reducing the available dynamic range of the ADC by about 20 dB. After being processed by DDC1 and DDC2, the fundamental frequency component, second-order sum-frequency, and third-order difference-frequency distortion components are located in the IQ signal output by DDC1, while the third-order sum-frequency component is located in the IQ signal output by DDC2.

[0093] To remove the non-linear distortion components in the IQ signals output by DDC1 and DDC2, the calibration module in this embodiment first shifts the frequency spectrum of the IQ signal output by DDC1 to the right by F01. This operation can be achieved by NCO mixing or by performing a Fourier transform on the time-domain signal and then shifting the frequency spectrum. The purpose of this operation is to make the fundamental frequency phase in the IQ signal correspond to the fundamental frequency phase when the non-linear distortion occurs. Then, according to the type of non-linear distortion component to be cancelled, delay combinations are constructed, and these delay combinations perform operations such as conjugation, delay, and multiplication on the shifted IQ signal.

[0094] For the third-order difference frequency distortion component, the IQ signal output by the shifted DDC1 is divided into three paths, each path is delayed by N1, N2, and N3 respectively. One of the signals is conjugated, and then the three signals are multiplied by coefficient values. The delay values and coefficient values of N1, N2, and N3 are obtained through the training mode.

[0095] For the second-order sum frequency distortion component, the IQ signal output by the shifted DDC1 is divided into two paths, each path is delayed by N1 and N2 respectively, and then the two signals are multiplied by coefficient values. The delay values and coefficient values of N1 and N2 are obtained through the training mode.

[0096] For the third-order sum frequency distortion component, the IQ signal output by the shifted DDC1 is divided into three paths, each path is delayed by N1, N2, and N3 respectively, and then the three signals are multiplied by coefficient values. The delay values and coefficient values of N1, N2, and N3 are obtained through the training mode.

[0097] Then, the non-linear combination of the third-order difference frequency distortion component and the second-order sum frequency distortion component is shifted left by F01, and after an inverting operation, it is added to the IQ signal output by the DDC1 before correction, and the corrected IQ signal corresponding to the DDC1 can be obtained. The non-linear combination of the third-order sum frequency distortion component is shifted left by F02, and after an inverting operation, it is added to the IQ signal output by the DDC2 before correction, and the corrected IQ signal corresponding to the DDC2 can be obtained.

[0098] After the above non-linear distortion correction operation, the non-linear distortion components in the IQ signals output by the DDC1 and DDC2 are reduced to the noise floor, increasing the spurious-free dynamic range index of the analog-to-digital converter by approximately 20 dB.

[0099] It should be noted that the dual-tone swept excitation signal training method used in the above embodiments can use signals with three tones or more as training signals, or broadband noise or broadband modulation signals such as QPSK (Quadrature Phase Shift Keying) can be transmitted at one time for training.

[0100] In addition, before and after passing through the correction module, filtering operations can be added to filter out some non-linear distortions in the signal to simplify the complexity of the subsequent correction module.

[0101] The correction method and correction device provided in this application can simultaneously correct the multi-path non-linear distortions of the complex signal system, can significantly improve the spurious-free dynamic range of common complex signal devices and transceiver systems, and greatly improve the performance of these systems. At the same time, the operation methods used in the correction module of this application are also more suitable for embedded environments such as FPGAs.

[0102] Figure 8It is a schematic structural diagram of an electronic device according to an embodiment of the present application. Please refer to Figure 8 , at the hardware level, the electronic device includes a processor, and optionally also includes an internal bus, a network interface, and a memory. Among them, the memory may include a memory, such as a high-speed random access memory (Random-Access Memory, RAM), and may also include a non-volatile memory, such as at least one disk memory, etc. Of course, the electronic device may also include other hardware required for other services.

[0103] The processor, network interface, and memory can be interconnected through an internal bus, and the internal bus can be an ISA (Industry Standard Architecture) bus, a PCI (Peripheral Component Interconnect) bus, or an EISA (Extended Industry Standard Architecture) bus, etc. The bus can be divided into an address bus, a data bus, a control bus, etc. For the sake of representation, Figure 8 only a bidirectional arrow is used in

[0104] The memory is used to store programs. Specifically, the program may include program code, and the program code includes computer operation instructions. The memory can include a memory and a non-volatile memory, and provide instructions and data to the processor.

[0105] The processor reads the corresponding computer program from the non-volatile memory into the memory and then runs it. The processor executes the program stored in the memory and is specifically used to perform the following operations:

[0106] Control the non-linear system to enter the training mode, and control the training signal source to output a training signal to the non-linear system;

[0107] Obtain the training signal and the IQ training signal with non-linear distortion output by the non-linear system;

[0108] Obtain the calibration parameters of the calibration module according to the training signal and the IQ training signal, and load the calibration parameters into the calibration module;

[0109] Control the non-linear system to enter the calibration mode, use the calibration module to perform non-linear calibration on the output signal of the non-linear system, and obtain the calibrated IQ signal.

[0110] The above is as in the present application Figure 5The calibration method disclosed in the illustrated embodiments can be applied to or implemented by a processor. The processor may be an integrated circuit chip with signal processing capabilities. In the implementation process, each step of the above method can be completed by the integrated logic circuit in the hardware of the processor or instructions in the form of software. The above-mentioned processor may be a general-purpose processor, including a Central Processing Unit (CPU), a Network Processor (NP), etc.; it may also be a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field-Programmable Gate Array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components. It can implement or execute the various methods, steps, and logic block diagrams disclosed in the embodiments of the present application. The general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc. The steps of the method disclosed in combination with the embodiments of the present application can be directly embodied as being executed and completed by a hardware decoding processor, or executed and completed by a combination of the hardware and software modules in the decoding processor. The software module may be located in a mature storage medium in the art such as a random access memory, a flash memory, a read-only memory, a programmable read-only memory, or an electrically erasable programmable memory, a register, etc. This storage medium is located in the memory, and the processor reads the information in the memory and combines its hardware to complete the steps of the calibration method.

[0111] The electronic device can also execute Figure 5 the illustrated calibration method, which will not be elaborated in the embodiments of the present application.

[0112] The embodiments of the present application also propose a computer-readable storage medium that stores one or more programs. The one or more programs include instructions that, when executed by an electronic device including multiple application programs, can enable the electronic device to execute Figure 5 the calibration method in the illustrated embodiments, which will not be elaborated in the embodiments of the present application.

[0113] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk memories, CD-ROMs, optical memories, etc.) containing computer-usable program code.

[0114] The present invention is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to embodiments of the present invention. It should be understood that each flow and / or block in the flowchart and / or block diagram, and the combination of flows and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing devices generate means for implementing the functions specified in one Figure 1 flow or multiple flows and / or blocks Figure 1 block or multiple blocks.

[0115] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory generate a manufactured article including instruction means that implement the functions specified in one Figure 1 flow or multiple flows and / or blocks Figure 1 block or multiple blocks.

[0116] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operational steps are executed on the computer or other programmable device to generate a computer-implemented process, and thus the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one Figure 1 flow or multiple flows and / or blocks Figure 1 block or multiple blocks.

[0117] In a typical configuration, a computing device includes one or more processors (CPUs), an input / output interface, a network interface, and a memory.

[0118] The memory may include non-permanent memory in the form of computer-readable media, random access memory (RAM), and / or non-volatile memory such as read-only memory (ROM) or flash RAM. The memory is an example of computer-readable media.

[0119] A computer-readable medium includes both permanent and non-permanent, removable and non-removable media and can implement information storage by any method or technology. The information can be computer-readable instructions, data structures, program modules, or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, compact disc read-only memory (CD-ROM), digital versatile disc (DVD) or other optical storage, magnetic cassette tapes, magnetic tape magnetic disk storage or other magnetic storage devices, or any other non-transitory medium that can be used to store information that can be accessed by a computing device. As defined herein, a computer-readable medium does not include transitory computer-readable media, such as modulated data signals and carrier waves.

[0120] It should also be noted that the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, such that a process, method, commodity or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, commodity or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the process, method, commodity or device comprising the element.

[0121] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system or a computer program product. Therefore, the present application can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0122] The above description is only for the embodiments of the present application and is not intended to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application should be included within the scope of the claims of the present application.

Claims

1. A calibration device for calibrating the non - linear distortion components of IQ signals in a non - linear system, the non - linear system including a front - end device and a digital down - converter, characterized in that, The correction device includes: a training signal source, a switch, a processor, and a correction module; The training signal source and the receiving link of the external signal are selectively connected to the front-end device of the non-linear system through the switch. The digital down-converter is connected to the correction module, and the processor is respectively connected to the training signal source, the switch, the digital down-converter, and the correction module; The processor controls the switch to make the non-linear system in the training mode or the correction mode. When the non-linear system is in the training mode, the processor calculates the correction parameters of the correction module and loads the correction parameters into the correction module; when the non-linear system is in the correction mode, the correction module performs non-linear correction on the output signal of the digital down-converter to obtain the corrected IQ signal; The correction module includes a first digital oscillator, a non-linear combination correction module, and a second digital oscillator connected in sequence. The input end of the first digital oscillator is connected to the output end of the digital down-converter corresponding to the correction module, and the output end of the second digital oscillator is the output end of the correction module; The non-linear system includes a plurality of digital down-converters. According to the center frequency and effective bandwidth of each digital down-converter, the plurality of digital down-converters are grouped. The output ends of the digital down-converters in each group are connected to a correction module, and the corrected IQ signal corresponding to each group is output through the correction module; The plurality of digital down-converters include a first type of digital down-converter and a second type of digital down-converter. The output signal of the first type of digital down-converter is affected by the fundamental frequency component of other digital down-converters, and the output signal of the second type of digital down-converter affects the output signals of other digital down-converters; each second type of digital down-converter is connected to a correction module, and the non-linear distortion component in the output signal of the corresponding first type of digital converter is cancelled by the cancellation signal output through the correction module.

2. The calibration device according to claim 1, characterized in that, The non-linear combination correction module includes a combining module, a first-order non-linear correction module to an nth-order non-linear correction module, where n is a positive integer greater than 1; The input ends of the first-order non-linear correction module to the nth-order non-linear correction module are all connected to the output end of the first digital oscillator, the output ends of the first-order non-linear correction module to the nth-order non-linear correction module are all connected to the input end of the combining module, and the output end of the combining module is connected to the input end of the second digital oscillator; Each order of non-linear correction module includes a plurality of delay combinations. Each delay combination is used to perform an optional conjugate operation on the input signal, then perform a delay operation, and multiply the signal after the delay operation by a coefficient value through a multiplier and output.

3. A calibration method for calibrating the non - linear distortion components of IQ signals in a non - linear system, the non - linear system including a front - end device and a digital down - converter, the calibration method being executed by a processor of the calibration device according to claim 1 or 2, the calibration method comprising: Control the non-linear system to enter the training mode and control the training signal source to output a training signal to the non-linear system; Obtain the training signal and the IQ training signal with non-linear distortion output by the non-linear system; Obtain the correction parameters of the correction module according to the training signal and the IQ training signal, and load the correction parameters into the correction module; Control the non-linear system to enter the calibration mode, and use the calibration module to perform non-linear calibration on the output signal of the non-linear system to obtain the calibrated IQ signal; The control of the training signal source to output a training signal to the non-linear system includes: Setting the signal frequency points according to the operating frequency band and operating frequency of the non-linear system; Controlling the training signal source to output a training signal at each signal frequency point.

4. The calibration method according to claim 3, characterized in that, The obtaining of the calibration parameters of the calibration module according to the training signal and the IQ training signal includes: Obtaining the spectral values of the training signals corresponding to each signal frequency point and the spectral value of the IQ training signal; Constructing a training matrix A in the order of the signal frequency points and according to the spectral value and delay combination of the IQ training signal at each signal frequency point, and setting the vector x to be solved according to the coefficient value corresponding to the delay combination; Constructing a target vector b in the order of the signal frequency points and according to the spectral value of the training signal at the corresponding signal frequency point; Constructing a target equation A×x = b according to the training matrix A, the vector x to be solved, and the target vector b, and obtaining the vector x to be solved by solving the target equation A×x = b; Obtaining the calibration parameters according to the delay combinations corresponding to the non-zero elements in the solved vector x.

5. The calibration method according to claim 3, characterized in that, After controlling the non-linear system to enter the calibration mode, the method further includes: Obtaining the output signal of the non-linear system and the IQ signal after the output signal is calibrated by the calibration module; Determining the signal difference between the output signal and the calibrated IQ signal; If the signal difference is greater than a preset value, controlling the non-linear system to enter the training mode.

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