A zero-IF transmission I / Q imbalance correction method and system

Abstract

The present invention provides a zero-IF transmit I / Q imbalance correction method and system, including: S1. After the zero-IF transmitter is powered on, parameter estimation is performed through a single-tone signal set within the frequency band to obtain the I / Q imbalance parameters of the zero-IF transmitter at different frequencies; the I / Q imbalance parameters include the phase imbalance parameter, amplitude imbalance parameter, and channel imbalance parameter of the local oscillator; S2. Correction filter parameters and phase imbalance parameters independent of frequency are calculated through the I / Q imbalance parameters, and the zero-IF transmitter is preliminarily corrected through the correction filter parameters and phase imbalance parameters; S3. The signals received by the preliminarily corrected zero-IF transmitter are tracked and analyzed to obtain the correction filter parameters and phase imbalance parameters in different time periods for tracking correction of the signals; the accuracy of I / Q imbalance correction for single-tone signals is improved; the adaptability to signal sources is increased.

Description

Technical Field

[0001] The present invention relates to the technical field of radio frequency transceiver, and in particular, to a zero-IF transmit I / Q imbalance correction method and system. Background Art

[0002] Currently, in a wireless communication system, the zero-IF architecture is well-known for its simple structure, low cost, low power consumption, and wide application in RF. However, it also introduces a series of problems: due to factors such as device processing differences and environmental changes, such as the differences between the I / Q two-way LO (local oscillator) signals and the differences in LPF or RLF, it will lead to amplitude mismatches between the I / Q two-way signals, or the phase difference between the two paths is not 90°. Such deviations are collectively referred to as quadrature errors. The existence of quadrature errors will introduce image signals, resulting in a decrease in communication bandwidth and an increase in bit error rate, greatly affecting communication quality. For high-order modulation and ultra-wideband signals, the influence of the image is even more prominent. Therefore, pre-distortion correction processing needs to be performed at the Tx end to suppress the image signal and reduce the bit error rate. In quadrature correction, the image rejection ratio (IRR) is commonly used as an evaluation index for the algorithm performance. IRR is defined as the ratio of the spectral energy corresponding to the signal itself to the spectral energy of its image signal. The higher the IRR, the better the correction performance of the corresponding algorithm. According to the relationship with frequency, I / Q imbalance can be divided into two parts. One part is that the phase difference between the I-channel and Q-channel LO (local oscillator) signals is not precise and their amplitudes are different. The I / Q imbalance caused by this is called frequency-independent (FI) I / Q imbalance. The other part is the frequency-dependent (FD) I / Q imbalance caused by the mismatched analog filters in the I / Q branches. The main idea of the existing balancing methods is to analyze the I / Q imbalance parameters from the signal output by the feedback receiver, and then pre-correct the transmit signal through a correction module according to these parameters. When estimating the I / Q imbalance, it is necessary to calculate using the input and output signals to obtain their corresponding autocorrelation and cross-correlation functions, and invert the obtained matrix. When the input signal is a single-tone signal, the matrix to be inverted is non-invertible, making it impossible to accurately estimate the channel parameters. Therefore, a solution is needed to improve the accuracy of I / Q imbalance correction for single-tone signals. Summary of the Invention

[0003] The purpose of the present invention is to provide a radio frequency transmit I / Q imbalance correction method and system to achieve the technical effect of improving the accuracy of I / Q imbalance correction for single-tone signals.

[0004] In a first aspect, the present invention provides a radio frequency transmit I / Q imbalance correction method, including:

[0005] S1. After the zero-IF transmitter is powered on, parameter estimation is performed using a single-tone signal set within the frequency band to obtain the I / Q imbalance parameters of the zero-IF transmitter at different frequencies; the I / Q imbalance parameters include the phase imbalance parameter, amplitude imbalance parameter, and channel imbalance parameter of the local oscillator;

[0006] S2. Calculate the correction filter parameters and the phase imbalance parameter independent of frequency through the I / Q imbalance parameters, and perform preliminary correction on the zero-IF transmitter using the correction filter parameters and the phase imbalance parameter;

[0007] S3. Track and analyze the signal received by the preliminarily corrected zero-IF transmitter, and obtain the correction filter parameters and phase imbalance parameters at different time periods to perform tracking correction on the signal, including:

[0008] S31. Analyze whether the signal received by the zero-IF transmitter is a single-tone signal or a broadband signal;

[0009] S32. If the signal received by the zero-IF transmitter is a broadband signal, use a high-order filter and the MMSE algorithm for tracking correction;

[0010] S33. If the signal received by the zero-IF transmitter is a single-tone signal, calculate the correction filter update function and the phase imbalance update function independent of frequency according to the results of the initialization correction; perform tracking correction through the correction filter update function and the phase imbalance update function.

[0011] Further, the S1 includes: performing parameter estimation using single-tone signals with equal frequency intervals within the transmission frequency band to obtain the I / Q imbalance parameters at different frequencies.

[0012] Further, the S2 includes: fitting each of the I / Q imbalance parameters by polynomial fitting to obtain the response function of the imbalance parameters within the frequency band to frequency; calculating the correction filter parameters and the phase imbalance parameter independent of frequency according to the response function.

[0013] Further, the calculation method of the S33 is:

[0014]

[0015]

[0016]

[0017]

[0018] In the above formula, tan( ) represents the currently updated phase imbalance function, represents the currently updated phase imbalance parameter; tan( ) represents the previously updated phase imbalance function; represents the previously updated phase imbalance parameter; g represents the currently updated amplitude imbalance parameter; represents the previously updated amplitude imbalance parameter; h d (n) represents the currently updated calibration filter function; represents the previously updated calibration filter function; and represents the transitional parameter during the calculation process.

[0019] Further, the high-order filter is a fourth-order filter.

[0020] In a second aspect, the present invention provides a radio frequency transmit I / Q imbalance calibration system, including:

[0021] An I / Q imbalance parameter analysis module, configured to perform parameter estimation through a single-tone signal set within a frequency band after the zero-IF transmitter is powered on, so as to obtain the I / Q imbalance parameters of the zero-IF transmitter at different frequencies;

[0022] A preliminary calibration module, configured to calculate calibration filter parameters and frequency-independent phase imbalance parameters through the I / Q imbalance parameters, and perform preliminary calibration on the zero-IF transmitter through the calibration filter parameters and the phase imbalance parameters;

[0023] A tracking and calibration module, configured to perform tracking and analysis on the signal received by the zero-IF transmitter after preliminary calibration, and obtain calibration filter parameters and phase imbalance parameters at different time periods, so as to perform tracking and calibration on the signal.

[0024] Further, the tracking and calibration module includes a single-tone signal tracking and calibration unit and a broadband signal tracking and calibration unit; the broadband signal tracking and calibration unit is configured to perform tracking and calibration using a high-order filter and the MMSE algorithm when the signal received by the zero-IF transmitter is a broadband signal; the single-tone signal tracking and calibration unit is configured to calculate a calibration filter update function and a frequency-independent phase imbalance update function according to the result of the initialization calibration when the signal received by the zero-IF transmitter is a single-tone signal; and perform tracking and calibration through the calibration filter update function and the phase imbalance update function.

[0025] The beneficial effects that can be achieved by the present invention are as follows: The zero-IF transmit I / Q imbalance correction method provided by the present invention can, on the basis of the existing correction of broadband signals, continuously update the filter coefficients according to the received signals when the channel parameters change, achieving continuous tracking of the transmit channel, improving the accuracy of I / Q imbalance correction for single-tone signals; at the same time, it also increases the adaptability to signal sources. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required to be used in the embodiments of the present invention. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0027] Figure 1 It is the overall flowchart of a zero-IF transmit I / Q imbalance correction method provided by an embodiment of the present invention;

[0028] Figure 2 It is the simulation result diagram of the IRR of single-tone signal tracking correction provided by an embodiment of the present invention;

[0029] Figure 3 It is the amplitude imbalance parameter of a single-tone signal provided by an embodiment of the present invention g when changing, the simulation result diagram of single-tone signal tracking;

[0030] Figure 4 It is the phase imbalance parameter of a single-tone signal provided by an embodiment of the present invention when changing, the simulation result diagram of single-tone signal tracking;

[0031] Figure 5 It is the schematic diagram of the topological structure of a zero-IF transmit I / Q imbalance correction system provided by an embodiment of the present invention.

[0032] Reference numerals: 10 - zero-IF transmit I / Q imbalance correction system; 100 - I / Q imbalance parameter analysis module; 200 - preliminary correction module; 300 - tracking correction module; 310 - single-tone signal tracking correction unit; 320 - broadband signal tracking correction unit. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] The following will describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention.

[0034] It should be noted that similar reference numerals and letters denote similar items in the following figures. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. At the same time, in the description of the present invention, terms such as "first" and "second" are only used for distinguishing descriptions and cannot be construed as indicating or implying relative importance.

[0035] Please refer to Figure 1 , Figure 1 which is the overall flowchart of a zero-IF transmit I / Q imbalance correction method provided by an embodiment of the present invention.

[0036] In one embodiment, the embodiment of the present invention provides a zero-IF transmit I / Q imbalance correction method, and the specific content is as follows.

[0037] S1. After the zero-IF transmitter is powered on, parameter estimation is performed using a single-tone signal set within the frequency band to obtain the I / Q imbalance parameters of the zero-IF transmitter at different frequencies; the I / Q imbalance parameters include the phase imbalance parameter, amplitude imbalance parameter, and channel imbalance parameter of the local oscillator.

[0038] When performing the above process, parameter estimation can be performed using a single-tone signal that sweeps the frequency band at equal frequency intervals to obtain the I / Q imbalance parameters at different frequencies. Among them, the frequency interval can be artificially set according to actual requirements.

[0039] S2. Calculate the correction filter parameters and the phase imbalance parameter independent of frequency through the I / Q imbalance parameters, and perform preliminary correction on the zero-IF transmitter using the correction filter parameters and the phase imbalance parameter.

[0040] In one embodiment, after obtaining the I / Q imbalance parameters at different frequencies, the I / Q imbalance parameters can be fitted by polynomial fitting to obtain the response function of the imbalance parameters within the frequency band with respect to frequency; then, the correction filter parameters and the phase imbalance parameter independent of frequency are calculated according to the obtained response function.

[0041] Specifically, the I / Q imbalance channel can be expressed as:

[0042]

[0043] where is the baseband input signal, y (n) is the baseband output signal, represents the equivalent channel model of the I path, represents the equivalent channel model of the Q path. d is a DC parameter, w (n) is noise.

[0044] For the estimation of I / Q imbalance parameters, without considering the influence of noise for the moment, the I / Q imbalance parameters are estimated based on the principle of Minimal Mean Square Error (MMSE), and the model can be further written as:

[0045]

[0046]

[0047]

[0048]

[0049] is an all - one vector of length N - K + 1. Regarding the influence of I / Q imbalance, in order to obtain the least - squares estimate of the channel parameters, a cost function is defined:

[0050]

[0051] By solving the gradient of the cost function to obtain the parameter values at its extreme points, and the necessary condition at the extreme points is that the gradient is 0. Therefore, we have:

[0052]

[0053] From this, we can obtain:

[0054]

[0055] So, the I / Q imbalance parameters are obtained:

[0056]

[0057] From and the frequency - independent phase imbalance can be obtained:

[0058]

[0059] The calibration filter h d :

[0060]

[0061] In the above formula, angle (.) represents the phase extraction function; ifft (.) represents the inverse fast Fourier transform function.

[0062] By the obtained phase imbalance and calibration filter h d Initialization and calibration can then be performed.

[0063] S3. Track and analyze the signals received by the zero-IF transmitter after preliminary calibration, and obtain the calibration filter parameters and phase imbalance parameters for different time periods to perform tracking calibration on the signals.

[0064] Specifically, when S3 is executed, it specifically includes the following steps:

[0065] S31. Analyze whether the signal received by the zero-IF transmitter is a single-tone signal or a broadband signal;

[0066] S32. If the signal received by the zero-IF transmitter is a broadband signal, use a high-order filter and the MMSE algorithm for tracking calibration;

[0067] S33. If the signal received by the zero-IF transmitter is a single-tone signal, calculate the calibration filter update function and the phase imbalance update function independent of frequency based on the results of the initialization calibration; perform tracking calibration through the calibration filter update function and the phase imbalance update function.

[0068] In one implementation, if the signal received by the zero-IF transmitter is a broadband signal, a fourth-order filter and the MMSE algorithm can be used for tracking calibration. Since the frequency-dependent I / Q imbalance is less affected by temperature and can be approximately considered non-time-varying, while the parameters of the LO are more affected by the environment and temperature and are considered time-varying, the imbalance parameters of the local oscillator can be updated during the single-tone tracking process using the initialized parameters to achieve calibration in the case of single-tone signals.

[0069] Specifically, when the signal received by the zero-IF transmitter is a single-tone signal, the calculation method can be expressed as:

[0070]

[0071]

[0072]

[0073]

[0074] In the above formula, tan( ) represents the currently updated phase imbalance function, represents the currently updated phase imbalance parameter; tan( ) represents the previously updated phase imbalance function; represents the phase imbalance parameter of the previous update; g represents the amplitude imbalance parameter of the current update; represents the amplitude imbalance parameter of the previous update; h d (n) represents the correction filter function of the current update; represents the correction filter function of the previous update; and represents the transitional parameter during the calculation process.

[0075] Please refer to Figure 2 、 Figure 3 and Figure 4 ; Figure 2 is a single-tone signal tracking and correction IRR simulation result diagram provided by an embodiment of the present invention; Figure 3 is the amplitude imbalance parameter of a single-tone signal provided by an embodiment of the present invention g when the single-tone signal tracking simulation result diagram changes; Figure 4 is the phase imbalance parameter of a single-tone signal provided by an embodiment of the present invention when the single-tone signal tracking simulation result diagram changes.

[0076] In order to measure the correction effect of this correction algorithm at different frequency points, the embodiments of the present invention use multiple single-tone signals within the frequency band for testing, calculate the IRR at different frequencies, and its simulation results are as Figure 2 shown. This figure shows the simulation results obtained when the channel parameters in the initialization and tracking stages are the same, that is, when the I / Q two-channel parameters do not change during the working process. The simulation results show that the frequency of the single-tone input signal in the tracking stage is 10 MHz, and it is tracked once to estimate the new FI phase deviation (that is, the phase imbalance parameter ) and the correction filter parameter h d , and then the above correction parameters are used to correct multiple single-tone signals within the frequency band to test its correction performance. It can be seen from the simulation results that the IRR after tracking and correction is greatly improved compared with the IRR before correction, and the IRR after correction can reach more than 70 dB.

[0077] Due to the change of the working environment, the I / Q two-channel parameters will also change, introducing a new I / Q mismatch, so it is necessary to perform tracking and correction on the signal. This scheme mainly aims at the problem in the case of single-tone signal input, so only the simulation results in the case of single-tone signal are shown. The simulation results are as Figure 3 and 4 shown, Figure 3 and Figure 4 correspond to the FI amplitude imbalance parameter g and the FI phase imbalance parameter Different simulation results show that when the channel parameters change, the IRR before calibration also changes accordingly. When the channel parameters change, the IRR after calibration remains above 70 dB. Therefore, it can be seen from the results that this scheme can achieve continuous tracking and calibration of the single-tone input signal.

[0078] Please refer to Figure 5 , Figure 5 which is a schematic diagram of the topology of a zero-IF transmit I / Q imbalance correction system provided by an embodiment of the present invention.

[0079] In one embodiment, the embodiment of the present invention also provides a zero-IF transmit I / Q imbalance correction system 10, which includes:

[0080] An I / Q imbalance parameter analysis module 100, which is used to estimate parameters through a single-tone signal set within the frequency band after the zero-IF transmitter is powered on, so as to obtain the I / Q imbalance parameters of the zero-IF transmitter at different frequencies;

[0081] A preliminary correction module 200, which is used to calculate the correction filter parameters and the phase imbalance parameters independent of frequency through the I / Q imbalance parameters, and perform preliminary correction on the zero-IF transmitter through the correction filter parameters and the phase imbalance parameters;

[0082] A tracking correction module 300, which is used to track and analyze the signal received by the zero-IF transmitter after preliminary correction, and obtain the correction filter parameters and the phase imbalance parameters at different time periods to perform tracking correction on the signal.

[0083] Through the above embodiments, the single-tone signal can be tracked and corrected, improving the accuracy of I / Q imbalance correction for the single-tone signal; at the same time, the adaptability to the signal source is also increased.

[0084] In one embodiment, the tracking correction module 300 includes a single-tone signal tracking correction unit 310 and a wideband signal tracking correction unit 320; the wideband signal tracking correction unit 320 is used to perform tracking correction using a high-order filter and the MMSE algorithm when the signal received by the zero-IF transmitter is a wideband signal; the single-tone signal tracking correction unit 310 is used to calculate the correction filter update function and the phase imbalance update function independent of frequency according to the result of the initial calibration when the signal received by the zero-IF transmitter is a single-tone signal; and perform tracking correction through the correction filter update function and the phase imbalance update function.

[0085] Through the above embodiments, both the tracking correction of the single-tone signal can be realized, and the corresponding signal processing method can be selected according to the characteristics of different input signals, improving the adaptability.

[0086] In summary, the embodiment of the present invention provides a zero-IF transmission I / Q imbalance correction method and system, including: S1. After the zero-IF transmitter is powered on, parameter estimation is performed through a single-tone signal set within the frequency band to obtain the I / Q imbalance parameters of the zero-IF transmitter at different frequencies; the I / Q imbalance parameters include the phase imbalance parameter, amplitude imbalance parameter, and channel imbalance parameter of the local oscillator; S2. The correction filter parameters and the phase imbalance parameter independent of frequency are calculated through the I / Q imbalance parameters, and the zero-IF transmitter is preliminarily corrected through the correction filter parameters and the phase imbalance parameter; S3. The signals received by the preliminarily corrected zero-IF transmitter are tracked and analyzed to obtain the correction filter parameters and the phase imbalance parameters at different time periods for tracking correction of the signals.

[0087] As described above, the above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A zero-IF transmit I / Q imbalance correction method, characterized in that, Including: S1. After the zero-IF transmitter is powered on, parameter estimation is performed using single-tone signals set within the frequency band to obtain the I / Q imbalance parameters of the zero-IF transmitter at different frequencies. S2. Calculate the correction filter parameters and the phase imbalance parameters independent of frequency based on the I / Q imbalance parameters, and perform preliminary correction on the zero-IF transmitter using the correction filter parameters and the phase imbalance parameters. Specifically: after obtaining the I / Q imbalance parameters at different frequencies, fit each I / Q imbalance parameter by polynomial fitting to obtain the response function of the imbalance parameters within the frequency band to frequency; then calculate the correction filter parameters and the phase imbalance parameters independent of frequency based on the obtained response function. S3. Track and analyze the signals received by the zero-IF transmitter after preliminary correction, and obtain the correction filter parameters and phase imbalance parameters at different time intervals to perform tracking correction on the signals, including: S31. Analyze whether the signal received by the zero-IF transmitter is a single-tone signal or a broadband signal. S32. If the signal received by the zero-IF transmitter is a broadband signal, use a high-order filter and the MMSE algorithm for tracking correction. S33. If the signal received by the zero-IF transmitter is a single-tone signal, calculate the correction filter update function and the phase imbalance update function independent of frequency based on the results of preliminary correction; perform tracking correction using the correction filter update function and the phase imbalance update function.

2. The method according to claim 1, characterized in that, The S1 includes: Perform parameter estimation using single-tone signals with equal frequency intervals within the transmission frequency band to obtain the I / Q imbalance parameters at different frequencies.

3. The method according to claim 1, wherein The S2 includes: Fit each of the I / Q imbalance parameters by polynomial fitting to obtain the response function of the imbalance parameters within the frequency band to frequency. Calculate the correction filter parameters and the phase imbalance parameters independent of frequency based on the response function.

4. The method according to claim 1, wherein The calculation method of S33 is: In the above formula, tan( ) represents the currently updated phase imbalance function, represents the currently updated phase imbalance parameter; tan( ) represents the phase imbalance function of the previous update; represents the phase imbalance parameter of the previous update; g represents the currently updated amplitude imbalance parameter; represents the amplitude imbalance parameter of the previous update; h d (n) represents the currently updated calibration filter function; represents the calibration filter function of the previous update; and represent the intermediate parameters in the calculation process.

5. The method according to claim 1, characterized in that, The high-order filter is a fourth-order filter.

6. A zero-IF transmit I / Q imbalance correction system, characterized in that, Including: I / Q imbalance parameter analysis module, which is used to perform parameter estimation using single-tone signals set within the frequency band after the zero-IF transmitter is powered on to obtain the I / Q imbalance parameters of the zero-IF transmitter at different frequencies. Preliminary correction module, which is used to calculate the correction filter parameters and the phase imbalance parameters independent of frequency based on the I / Q imbalance parameters, and perform preliminary correction on the zero-IF transmitter using the correction filter parameters and the phase imbalance parameters. Specifically: after obtaining the I / Q imbalance parameters at different frequencies, fit each I / Q imbalance parameter by polynomial fitting to obtain the response function of the imbalance parameters within the frequency band to frequency; then calculate the correction filter parameters and the phase imbalance parameters independent of frequency based on the obtained response function. Tracking correction module, which is used to track and analyze the signals received by the zero-IF transmitter after preliminary correction, and obtain the correction filter parameters and phase imbalance parameters at different time intervals to perform tracking correction on the signals. The tracking and correction module includes a single-tone signal tracking and correction unit and a broadband signal tracking and correction unit; the broadband signal tracking and correction unit is used to perform tracking and correction using a high-order filter and the MMSE algorithm when the signal received by the zero-IF transmitter is a broadband signal; the single-tone signal tracking and correction unit is used to calculate a correction filter update function and a frequency-independent phase imbalance update function based on the result of preliminary correction when the signal received by the zero-IF transmitter is a single-tone signal; tracking and correction are performed through the correction filter update function and the phase imbalance update function.

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