IQ imbalance compensation method for WiFi wideband transmitting and receiving channels and its application

Abstract

The present invention discloses an IQ imbalance compensation method for WiFi wideband transmitting and receiving channels and its application, which is related to the technical field of digital signal processing. The method is applied to a transmitting channel and a receiving channel, in which an IQ signal is input to a frequency-dependent IQ imbalance compensation device (FD-IQMC), and the FD-IQMC first performs frequency-independent overall compensation for the IQ imbalance by a frequency-independent IQ imbalance compensation module (FI-iqmc), and then selects one signal from the IQ signal and inputs it into a fractional delay filter (Frac-delay filter) and a real symmetric amplitude filter (Amp-FIR filter) to perform phase compensation and amplitude compensation respectively, and another signal is input to a delay module and processed for time alignment. The present invention has the advantages of easy-to-control structure, low resource overhead, and high compensation accuracy, and is applicable to high-wideband and high-order modulation systems such as WiFi6 / WiFi6E systems.

Description

[Technical field]

[0001] The present invention relates to the technical field of digital signal processing, and in particular to an IQ imbalance compensation method for WiFi broadband transmitting and receiving channels and its application. [Background technology]

[0002] In recent years, with the continuous development of high-speed, small-sized and integrated wireless communication technology, transceivers with zero intermediate frequency (ZIF) architecture have attracted attention due to their advantages such as low cost and ease of integration, and are now widely applied in electronic systems with high bandwidth and high sampling rate. The zero intermediate frequency architecture adopts analog quadrature mixing technology to directly convert RF signals into baseband in-phase (I) and quadrature (Q) signals, so it requires fewer analog devices than the traditional superheterodyne architecture. However, since analog devices have certain non-ideal characteristics due to design constraints, the I and Q signals do not match in amplitude and phase, resulting in I / Q imbalance (or IQ imbalance), which results in problems such as distortion of the constellation diagram, increase in bit error rate and deterioration of EVM, affecting the performance of the communication system. In wideband communication systems with higher silicon integration and higher modulation orders, the above I / Q imbalance problem tends to become more serious. Considering that WiFi6 / WiFi6E needs to support wider bandwidth (160MHz) and more advanced modulation formats (1024QAM / 4096QAM), the design of systems with high bandwidth and high-order modulation puts forward more stringent standards and requirements for calibration and compensation of non-ideal characteristics of the RF front-end.

[0003] At present, various IQ imbalance estimation methods and digital compensation schemes are proposed in the industry to improve communication quality. In conventional research to solve the IQ imbalance problem, a frequency independent (FI) imbalance error value is usually used, and since the FI imbalance error value is a constant, the above method has difficulty in meeting the performance requirements of a wideband system, in which the amplitude imbalance error and phase imbalance error caused by factors such as the mismatch of the frequency response of devices between I / Q channels change with the change of signal frequency and are frequency dependent (FD) errors. As the fifth generation wireless network technology (WiFi5) and the sixth generation network technology (WiFi6) use wider bandwidths (80MHz / 160MHz), the conventional frequency independent IQ (FI-IQ) compensation method cannot meet the system performance requirements, and in order to improve the overall quality of the wideband signal, it is necessary to use digital signal processing technology to perform wideband frequency dependent IQ (FD-IQ) compensation based on the frequency selectivity of IQ imbalance.

[0004] As an example, the frequency selectivity of IQ imbalance in a wideband is explained by combining the zero intermediate frequency model of the transmit (TX) channel shown in Figure 1 and the zero intermediate frequency model of the receive (RX) channel shown in Figure 2. In Figure 1, the IQ imbalance of the TX channel is mainly caused by the DAC (Digital-to-Analog Converter, also called D / A converter), low-pass filter, IQ amplifier, and mixer, and in Figure 2, the IQ imbalance of the RX channel is mainly caused by the mixer, IQ amplifier, low-pass filter, and ADC (Analog-to-Digital Converter, also called A / D converter). Since the imbalance of the local oscillator LO (Local Oscillator) of the mixer causes a fixed deviation in IQ, the three devices that provide frequency selectivity in the model are mainly the DAC / ADC, low-pass filter, and IQ amplifier. When two signals, I channel signal and Q channel signal, pass through these three devices, their amplitude gain and phase fluctuations will not match, which will appear as different characteristics in the frequency domain; the wider the bandwidth, the more significant the change in IQ error will be, which causes the frequency selectivity of IQ imbalance in the wideband.

[0005] Currently, there are three main methods for dealing with the above-mentioned wideband IQ imbalance:

[0006] Method 1 is to add a sequence with known good characteristics to the signal through a training sequence, and then need to continuously send and receive this sequence for calibration during communication, and calculate and compensate the acquired characteristics. This calibration method is a complicated process and reduces the transmission efficiency.

[0007] Method 2 is to test the IQ characteristics with a single tone and then perform frequency domain compensation, and this calibration method is easily affected by factors such as frequency offset, which will affect the accuracy.

[0008] Method 3 is a blind estimation method that calculates and statistics the IQ characteristics by transmitting a wideband signal, and then designs and compensates a complex filter. This calibration method requires a large amount of statistical data, so the calculation process is slow and the resource overhead of the compensation structure is large.

[0009] Meanwhile, for three kinds of devices such as DAC / ADC, low-pass filter and IQ amplifier, the double sideband response after cascading at baseband frequency shows symmetrical characteristics, that is, the amplitude response is even function symmetrical, and the phase response is odd function symmetrical. At the same time, the study found that the frequency selectivity of IQ error can be approximately expressed as the distribution characteristics of amplitude symmetry and phase linear change, referring to the distribution diagram of the measured wideband IQ amplitude error shown in Figure 3 and the distribution diagram of the measured wideband IQ phase error shown in Figure 4. The above type of zero intermediate frequency structure has the characteristics of strong low-pass characteristics and not significant bandpass effect.

[0010] As mentioned above, based on the characteristics of the above zero intermediate frequency structure, whether it is possible to provide a compensation scheme that can compensate for frequency selective IQ imbalance, has an easy-to-control structure, low resource overhead, and high compensation accuracy is a technical problem that needs to be solved as soon as possible. Summary of the Invention [Problem to be solved by the invention]

[0011] The present invention aims to provide an IQ imbalance compensation method for WiFi broadband transmission and reception channels and its application, in order to overcome the shortcomings of the prior art. In the IQ imbalance compensation method provided by the present invention, a frequency-dependent IQ imbalance compensation device (FD-IQMC) is used to perform IQ imbalance compensation on an IQ signal, and the FD-IQMC includes a frequency non-selective compensation structure and a frequency selective compensation structure corresponding to phase and amplitude respectively, and performs IQ imbalance compensation on the transmission channel based on a pre-compensation scheme, and performs IQ imbalance compensation on the reception channel based on a post-compensation scheme. The present invention has the advantages of easy-to-control structure, low resource overhead, and high compensation accuracy, and can effectively reduce the image rejection ratio IRR, EVM degradation, and bit error rate. [Means for solving the problem]

[0012] In order to achieve the above object, the present invention provides the following technical solution: An IQ imbalance compensation method for WiFi broadband transmitting and receiving channels includes: for a transmitting channel, an IQ signal output by a transmitting baseband (TX Baseband) is input to a frequency-dependent IQ imbalance compensation device (FD-IQMC), frequency-dependent IQ imbalance compensation is performed, and the compensated output signal I'Q' is input to a digital-to-analog converter DAC; or for a receiving channel, an IQ signal output by an analog-to-digital converter ADC is input to a frequency-dependent IQ imbalance compensation device (FD-IQMC), frequency-dependent IQ imbalance compensation is performed, and the compensated output signal I'Q' is input to a receiving baseband (RX The FD-IQMC includes a step of inputting an amplitude error and a phase error at one frequency point to a frequency-independent IQ imbalance compensation module (FI-iqmc) for the input IQ signal based on an IQ imbalance parameter estimate of the transmission channel or the reception channel, and performing single-point compensation for the input IQ imbalance by selecting an amplitude error and a phase error at one frequency point for the input I channel signal and Q channel signal by a frequency-independent IQ imbalance compensation module (FI-iqmc), thereby performing frequency-independent overall compensation for the IQ imbalance, selecting one of the I channel signal and Q channel signal output from the FI-iqmc and inputting it to a fractional delay filter (Frac-delay filter) to perform phase compensation for compensating for frequency-selective phase imbalance, inputting the signal output from the fractional delay filter (Frac-delay filter) to a real symmetric amplitude filter (Amp-FIR filter) to be used for performing amplitude compensation for compensating for frequency-selective amplitude imbalance, and a non-selected signal is processed by a delay module to be time-aligned with the selected signal.

[0013] Furthermore, the IQ imbalance parameter estimates of the transmission channel or the reception channel are obtained by a single tone test, where single tones at multiple frequency points correspond to the IQ imbalance parameter estimates at multiple frequency points.

[0014] Furthermore, the FI-iqmc is configured to perform the following steps: for a signal x=cos(θ)+j sin(θ), j is a complex number expression, and based on a phase imbalance coefficient Δφ and an amplitude imbalance coefficient Δm among the IQ imbalance parameter estimates, a compensation phase and a compensation amplitude required for an I channel signal are −Δφ / 2 and −Δm / 2, respectively, and a compensation phase and a compensation amplitude required for a Q channel signal are Δφ / 2 and Δm / 2, respectively, and are generally compensated for by the following compensation algorithm: TIFF2025501016000002.tif12144Here, x represents the IQ signal input to the FI-iqmc, and M comp represents the phase compensation matrix and the amplitude compensation matrix.

[0015] Furthermore, if Δφ is smaller than a preset value, sin(Δφ) is set equal to Δφ, cos(Δφ) is set equal to 1, and these are used as the compensation matrix M comp Substituting into the simplified M' comp And TIFF2025501016000003.tif1479The following compensation algorithm is used to globally compensate for IQ imbalance: TIFF2025501016000004.tif1498TIFF2025501016000005.tif15133At this time, the FI-iqmc performs matrix multiplication on the input IQ signals using four multipliers to compensate for frequency-independent IQ imbalance.

[0016] Furthermore, the steps of performing phase compensation on the I-channel signal or the Q-channel signal output from the FI-iqmc using a fractional delay filter are as follows: acquiring phase errors at sampling frequency points in a wide band by single-tone tests at multiple frequency points, performing linear fitting on the acquired phase errors, and calculating a phase error group delay in a wide band for the phase errors that have been linearly fitted using the following formula: TIFF2025501016000006.tif1883, where Δφ (radian) is the change in phase error in the Δω (radian) frequency band, and radian represents the radian degree. Based on the calculated group delay value, a fractional delay sample point value that needs to be compensated is calculated. Based on the fractional delay sample point value that needs to be compensated, a fractional delay value of a fractional delay filter is designed by a Lagrange interpolation method. Based on the designed fractional delay filter, phase compensation is performed on the selected I channel signal or Q channel signal, and a phase-compensated I channel signal or Q channel signal is obtained.

[0017] Furthermore, when the fractional delay filter performs phase compensation on the I-channel signal or the Q-channel signal output by the FI-iqmc, another unselected signal is input to the first delay module DI for delay processing in order to time-align the two signals.

[0018] Furthermore, the steps of performing amplitude compensation on the signal output from the fractional delay filter (Frac-FIR filter) by a real symmetric amplitude filter (Amp-FIR filter) are as follows: obtaining amplitude errors at sampling frequency points in a wide band through single-tone testing at multiple frequency points, calculating an average value of amplitude errors at frequency points where positive and negative frequencies are symmetric, designing a real filter of order N, obtaining amplitude error parameters at the frequency points of the filter through piecewise linear interpolation of test frequency points, where N is an integer multiple of 2, calculating filter coefficients of the real filter through inverse fast Fourier transform based on the amplitude error parameters at the frequency points of the filter, the filter coefficients being real and symmetric, filtering the signal by the filter coefficients to obtain an amplitude-compensated signal.

[0019] Furthermore, when the real symmetric amplitude filter (Amp-FIR filter) performs amplitude compensation on the signal output from the fractional delay filter (Frac-delay filter), the signal output from the first delay module D1 is input to a second delay module D2 for delay processing in order to align the two signals in time.

[0020] The present invention further provides an IQ imbalance three-stage compensation system for WiFi broadband transmission and reception channels, the system comprising: a frequency-dependent IQ imbalance compensation device (FD-IQMC), the FD-IQMC being provided in a transmission channel and used to perform pre-compensation processing on an IQ signal input to a digital-to-analog converter DAC, or the FD-IQMC being provided in a reception channel and used to perform post-compensation processing on an IQ signal output from an analog-to-digital converter ADC, the frequency-dependent IQ imbalance compensation device (FD-IQMC) performs single-point compensation by selecting amplitude error and phase error at one frequency point for the input I channel signal and Q channel signal based on an IQ imbalance parameter estimate of the transmission channel or the reception channel, thereby performing frequency-independent overall compensation for IQ imbalance, and selecting one of the I channel signal and Q channel signal output from the FI-iqmc to perform fractional delay filter (Frac-delay filter) the signal output from the fractional delay filter (Frac-delay filter) is input to a real symmetric amplitude filter (Amp-FIR filter) for amplitude compensation to compensate for frequency selective amplitude imbalance; and the unselected signals are processed by a delay module to time align with the selected signal.

[0021] The present invention further provides an IQ imbalance compensation method for WiFi broadband transmission and reception channels, which includes, for a transmission channel, inputting an IQ signal output by a transmission baseband (TX Baseband) to a frequency-dependent IQ imbalance compensation device (FD-IQMC), performing frequency-dependent IQ imbalance compensation, and inputting the compensated output signal I'Q' to a digital-to-analog converter (DAC); or, for a reception channel, inputting an IQ signal output by an analog-to-digital converter (ADC) to a frequency-dependent IQ imbalance compensation device (FD-IQMC), performing frequency-dependent IQ imbalance compensation, and inputting the compensated output signal I'Q' to a reception baseband (RX The FD-IQMC inputs the IQ signal to a frequency independent IQ imbalance compensation module (FI-iqmc) based on an IQ imbalance parameter estimate of the transmission channel or the reception channel, and performs single-point compensation by selecting an amplitude error and a phase error at one frequency point for the input I channel signal and Q channel signal, thereby performing frequency-independent overall compensation for the IQ imbalance. For the I channel signal and the Q channel signal output from the FI-iqmc, one of the signals is selected and input to a single channel filter, which is used for processing to compensate for frequency selective phase and frequency selective amplitude, and the single channel filter has a filter coefficient generated by convolving a fractional delay filter coefficient and an amplitude filter coefficient, and can compensate for fractional delay by its phase-frequency response and can compensate for amplitude error by its amplitude-frequency response, and the filter coefficient of the single channel filter is real and asymmetric, and another signal that is not selected is processed by a delay module to time-align with the selected signal.

[0022] The present invention further provides an IQ imbalance compensation system for WiFi broadband transmitting and receiving channels, the system comprising: a frequency-dependent IQ imbalance compensation device (FD-IQMC), the FD-IQMC being provided in a transmitting channel and used for pre-compensating an IQ signal input to a digital-to-analog converter DAC, or the FD-IQMC being provided in a receiving channel and used for post-compensating an IQ signal output from an analog-to-digital converter ADC, the frequency-dependent IQ imbalance compensation device (FD-IQMC) calculating an amplitude error at one frequency point for the input I and Q channel signals by a frequency-independent IQ imbalance compensation module (FI-iqmc) based on an IQ imbalance parameter estimate of the transmitting channel or the receiving channel. and phase error to perform single-point compensation, thereby performing frequency-independent global compensation for IQ imbalance; and for the I channel signal and Q channel signal output from the FI-iqmc, one of the signals is selected and input to a single channel filter for processing to compensate for frequency-selective phase and frequency-selective amplitude, the single channel filter having filter coefficients generated by convolving fractional delay filter coefficients and amplitude filter coefficients, the phase-frequency response of which can compensate for fractional delay and the amplitude-frequency response of which can compensate for amplitude error, the filter coefficients of the single channel filter being real and asymmetric in form, and another unselected signal being processed by a delay module to align it in time with the selected signal. Effect of the Invention

[0023] Because the present invention adopts the above technical solution, it has the following advantages and positive effects, for example, compared with the prior art. In the IQ imbalance compensation method, a frequency-dependent IQ imbalance compensation device (FD-IQMC) is used to perform IQ imbalance compensation on an IQ signal, and the FD-IQMC includes a frequency non-selective compensation structure and a frequency selective compensation structure corresponding to phase and amplitude, respectively, and performs IQ imbalance compensation based on a pre-compensation method in a transmission channel, and performs IQ imbalance compensation based on a post-compensation method in a reception channel. The frequency selective IQ imbalance can be compensated by wideband IQ calibration according to the above compensation method, and the present invention has the advantages of easy structure control, low resource overhead, and high compensation accuracy, and can effectively reduce indexes such as image rejection ratio IRR, EVM degradation, and bit error rate, and improve communication quality. [Brief description of the drawings]

[0024] [Figure 1] FIG. 1 is a schematic diagram of a TX zero intermediate frequency model in the prior art. [Diagram 2] FIG. 1 is a schematic diagram of an RX zero intermediate frequency model in the prior art. [Diagram 3] FIG. 13 is a distribution diagram of measured wideband IQ amplitude errors. [Figure 4] FIG. 1 is a distribution diagram of actually measured wideband IQ phase errors. [Diagram 5] FIG. 2 is a logical structure diagram of an IQ imbalance compensation structure of a transmission channel according to an embodiment of the present invention; [Figure 6] FIG. 2 is a logical structure diagram of an IQ imbalance compensation structure of a receiving channel according to an embodiment of the present invention; [Figure 7] FIG. 11 is a graph showing changes in IQ amplitude error before and after compensation according to an embodiment of the present invention. [Figure 8] FIG. 11 is a graph showing changes in IQ phase error before and after compensation according to an embodiment of the present invention. [Figure 9] FIG. 4 is a graph showing changes in the image rejection ratio IRR before and after compensation according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] The IQ imbalance compensation method for WiFi broadband transmission and reception channels and its application disclosed in the present invention will be described in more detail below in combination with the drawings and specific embodiments. It should be noted that the technical features or combinations of technical features described in the following embodiments should not be considered in isolation, but may be combined with each other to achieve better technical effects. In the drawings of the following embodiments, the same reference numerals appearing in each drawing represent the same features or components and may be applied to different embodiments. Therefore, once an item is defined in one attached drawing, there is no need to further discuss it in the subsequent drawings.

[0026] In addition, the structure, proportion, size, etc. shown in the accompanying drawings in this specification are used only in combination with the contents disclosed in this specification so that those familiar with this technology can easily understand and read, and are not intended to limit the limited conditions implemented in the present invention, and any structural changes, changes in proportional relationships, or size adjustments should be included in the scope of the technical contents disclosed in the present invention without affecting the effectiveness and purpose of the present invention. The scope of the preferred embodiments of the present invention includes additional embodiments that may not perform functions in the order described or discussed, including essentially simultaneous aspects or reverse order depending on the functions involved, as understood by a person skilled in the art to which the embodiments of the present invention belong.

[0027] Techniques, methods and equipment known to those skilled in the relevant art may not be described in detail, but where appropriate, said techniques, methods and equipment should be considered as part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as illustrative and not limiting. Thus, other examples of the exemplary embodiments may have different values.

[0028] The present invention provides an IQ imbalance compensation method for WiFi broadband transmission and reception channels, which realizes frequency-dependent IQ imbalance compensation by providing a frequency-dependent IQ imbalance compensation device (FD-IQMC) in a signal digital processing channel. The IQ imbalance compensation method is applied to frequency-selective IQ imbalance compensation of a transmission (TX) channel and a reception (RX) channel.

[0029] For the transmission channel, as shown in FIG. 5, the IQ signal output by the transmission baseband (TX Baseband) is input to a frequency-dependent IQ imbalance compensation device (FD-IQMC), which performs frequency-dependent IQ imbalance compensation, and the compensated output signal I'Q' is input to a digital-to-analog converter DAC.

[0030] For the receiving channel, as shown in FIG. 6, the IQ signal received by the analog-to-digital converter ADC is input to a frequency-dependent IQ imbalance compensation device (FD-IQMC) to perform frequency-dependent IQ imbalance compensation, and the compensated output signal I'Q' is input to the receiving baseband (RX Baseband).

[0031] In this embodiment, the estimated values ​​of the IQ imbalance parameters of the transmitting channel and the receiving channel may be obtained by a single-tone test. Specifically, a single-tone signal (e.g., a single-tone signal with a frequency ω) is transmitted, a loop signal is collected, and the IQ imbalance parameters are estimated by a correlation calculation method, and the IQ imbalance parameters may specifically include an amplitude imbalance coefficient (or called an amplitude mismatch parameter) and a phase imbalance coefficient (or called a phase mismatch parameter). Since a single tone at a different frequency point corresponds to a different IQ imbalance parameter estimate, the single-tone test at multiple frequency points can obtain the IQ imbalance parameter estimate at multiple frequency points. The parameter estimates of the transmitting channel and the receiving channel are measured respectively by switching on / off the internal circuit.

[0032] In one preferred embodiment, the frequency-dependent IQ imbalance compensation device (FD-IQMC) adopts a three-stage compensation structure including a first-stage frequency non-selective compensation structure, a second-stage phase filter structure, and a third-stage amplitude filter structure, which are cascaded together. The IQ signal input to the FD-IQMC device is sequentially processed by the first-stage frequency non-selective compensation structure, the second-stage phase filter structure, and the third-stage amplitude filter structure based on the IQ imbalance parameter estimates of the transmission channel or the reception channel.

[0033] Specifically, the first stage frequency non-selective compensation structure is a frequency independent IQ imbalance compensation module (FI-iqmc). Still referring to Figures 5 and 6, the I channel signal and the Q channel signal of the IQ signal are input to the FI-iqmc, and the amplitude error and the phase error at one frequency point are selected to perform single point compensation, thereby performing frequency independent overall compensation for the IQ imbalance.

[0034] A single-tone signal may be expressed as x=cos(θ)+j sin(θ), where j is a complex number representation, and the overall compensation principle of FI-iqmc is as follows:

[0035] In the case of a single-tone signal x = cos(θ) + j sin(θ), the phase imbalance coefficient of the IQ imbalance parameter estimates obtained by the single-tone test is Δφ, the amplitude imbalance coefficient is Δm, and IQ imbalance occurs. If the phases that need to be compensated for in the I channel and Q channel are -Δφ / 2 and Δφ / 2, respectively, the signal equation after phase compensation is as follows: TIFF2025501016000007.tif16167If the amplitudes that need to be compensated for in the I channel and Q channel are -Δm / 2 and Δm / 2, respectively, the signal equation after amplitude compensation is as follows: TIFF2025501016000008.tif11132TIFF2025501016000009.tif1466The signal formula after phase compensation and amplitude compensation is as follows: TIFF2025501016000010.tif14127 compensation matrix M comp The formula for this can be obtained. TIFF2025501016000011.tif15165TIFF2025501016000012.tif19149The compensation algorithm for FI-iqmc can be obtained. TIFF2025501016000013.tif15165Here, x represents the IQ signal input to the FI-iqmc, and M comp represents the phase compensation matrix and the amplitude compensation matrix.

[0036] In this embodiment, taking into consideration that the phase imbalance coefficient Δφ is generally small (the imbalance deviation is generally small), when Δφ is small, sin(Δφ)≈Δφ, cos(Δφ)≈1, so in order to reduce the overhead of the compensation structure resource, M comp Simplify.

[0037] In a specific implementation, the Δφ can be compared with a preset value. If Δφ is smaller than the preset value, sin(Δφ) is set equal to Δφ and cos(Δφ) is set equal to 1, i.e., sin(Δφ / 2)=Δφ / 2, cos(Δφ / 2)=1, and these are used as the compensation matrix M comp Substituting this, we get the following formula: TIFF2025501016000014.tif17111Because Δφ is small, the value of the product of the equation (Δm / 2 Δφ / 2) is also very small, (Δm / 2Δ φ / 2) =0, simplified compensation matrix M' comp can be obtained. TIFF2025501016000015.tif1879That is, the IQ imbalance is globally compensated for using the following compensation algorithm. TIFF2025501016000016.tif1498TIFF2025501016000017.tif15133In this case, the frequency-independent IQ imbalance compensation module (FI-iqmc) can compensate for the frequency-independent IQ imbalance by using four multipliers and performing matrix multiplication on the input signal.

[0038] Of the I-channel and Q-channel signals output from the FI-iqmc module, one of them is selected and sequentially input into the second-stage phase filter structure and the third-stage amplitude filter structure for processing, while the other unselected signal is delayed by the delay module to align it in time with the selected signal.

[0039] In this embodiment, the second-stage phase filter structure is a fractional delay filter, and can perform phase compensation to compensate for frequency-selective phase imbalance on a signal.

[0040] In the case of zero intermediate frequency structures such as DAC / ADC, low-pass filter and IQ amplifier, the frequency selective phase error of IQ imbalance is generally expressed linearly, that is, the IQ phase error in a wide band shows a phase change or an approximate phase change, and due to the linear characteristic, when the phase filter structure is provided in this embodiment, the phase imbalance is compensated by a fractional delay filter. The fractional delay filter adopts a single channel filter that performs compensation processing on only one of the I channel signal or the Q channel signal.

[0041] Specifically, the steps of performing phase compensation on the I-channel or Q-channel signal output from the FI-iqmc by the fractional delay filter module are as follows.

[0042] S211, obtaining phase errors at sampling frequency points in a wide band through single-tone testing at multiple frequency points.

[0043] S212, performing linear fitting on the obtained phase error.

[0044] S213, for the phase error that has been linearly fitted, calculate the phase error group delay in the wideband using the following formula, which is as follows: TIFF2025501016000018.tif1883Here, Δφ (radian) is the change in phase error in the Δω (radian) frequency band, and radian represents the radian angle.

[0045] S214, calculate fractional delay sample point values ​​that need to be compensated based on the calculated group delay values, and design fractional delay values ​​of a fractional delay filter by Lagrange interpolation based on the fractional delay sample point values ​​that need to be compensated.

[0046] S215, performing phase compensation on the selected I-channel signal or Q-channel signal based on the designed fractional delay filter to obtain a phase-compensated I-channel signal or Q-channel signal.

[0047] When the fractional delay filter module performs phase compensation on the I-channel signal or the Q-channel signal output by the FI-iqmc, another unselected signal is input to the first delay module DI for delay processing in order to align the two signals in time.

[0048] Referring to Figures 5 and 6, it is shown that the Q channel signal is processed by a fractional delay filter module, that is, when the Q channel signal is selected, the I channel signal is input to a first delay module D1 for delay processing in order to time align the two signals (I channel signal and Q channel signal).

[0049] Next, the signal output from the fractional delay filter module is input to the third stage amplitude filter structure for processing.

[0050] In this embodiment, the third stage amplitude filter structure is a real symmetric amplitude filter (Amp-FIR filter), and can perform amplitude compensation for compensating for frequency selective amplitude imbalance on a signal.

[0051] In the case of zero intermediate frequency structures such as DAC / ADC, low-pass filters and IQ amplifiers, the frequency selective amplitude error of IQ imbalance is generally expressed as an even function distribution, that is, as a bilateral symmetric characteristic of positive and negative frequencies. Due to the symmetric characteristic, when providing an amplitude filter structure in this embodiment, a real symmetric amplitude filter (Amp-FIR filter) is used to compensate for the amplitude imbalance. Compared with the conventional method of directly using a complex filter for compensation, this embodiment can greatly reduce resource overhead and chip area while ensuring that performance accuracy meets requirements.

[0052] Specifically, the steps of performing amplitude compensation on the signal output from the fractional delay filter (Frac-FIR filter) by the real symmetric amplitude filter (Amp-FIR filter) are as follows.

[0053] S311, by single-tone testing at multiple frequency points, amplitude errors at sampling frequency points within a wide band are obtained.

[0054] S312, the average value of the amplitude error at the frequency points where the positive frequency and the negative frequency are symmetrical is calculated.

[0055] S313, design a real filter of order N, and the amplitude error parameters at the frequency points of the filter are obtained by piecewise linear interpolation of the test frequency points, where N is generally an integer multiple of 2.

[0056] S314, calculating filter coefficients (IFFT) of the real filter according to the amplitude error parameters at the frequency points of the filter through an inverse fast Fourier transform (IFFT), where the filter coefficients are real and symmetric.

[0057] S315, filtering the signal with the filter coefficients to obtain an amplitude compensated signal.

[0058] Continuing to refer to Figures 5 and 6, when the amplitude filter (Amp-FIR filter) performs amplitude compensation on the phase-compensated Q channel signal output from the fractional delay filter (Frac-delay filter), the I channel signal output from the first delay module D1 is input to the second delay module D2 for delay processing in order to align the two signals in time.

[0059] The above technical solution provided by the present invention estimates IQ imbalance parameters based on a single-tone signal test method in a wideband, and uses a time domain compensation method, which does not require a specific training sequence, does not require large-scale calculation statistics using a wideband signal, and the time domain compensation is more stable than the frequency domain compensation; at the same time, according to the characteristic discipline of the zero intermediate frequency structure such as DAC / ADC, low-pass filter, IQ amplifier, etc., a cascaded real filter compensation method is designed, which reduces the resource overhead and chip area compared with the traditional method of adopting complex filters, and at the same time ensures the performance accuracy.

[0060] Another embodiment of the present invention further provides an IQ imbalance three-stage compensation system for wideband transmit and receive channels based on said method.

[0061] The system comprises a frequency-dependent IQ imbalance compensation device (FD-IQMC), the FD-IQMC being provided in a transmit channel and used to perform pre-compensation processing on an IQ signal input to a digital-to-analog converter DAC, or the FD-IQMC being provided in a receive channel and used to perform post-compensation processing on an IQ signal output from an analog-to-digital converter ADC.

[0062] The frequency-dependent IQ imbalance compensation device (FD-IQMC) is configured to, for an input IQ signal, select an amplitude error and a phase error at one frequency point for the input I channel signal and Q channel signal by a frequency-independent IQ imbalance compensation module (FI-iqmc) based on an IQ imbalance parameter of the transmission channel or the reception channel to perform single-point compensation, thereby performing frequency-independent overall compensation for the IQ imbalance, the IQ imbalance parameter includes phase error and amplitude error information, select one of the I channel signal and Q channel signal output from the FI-iqmc and input it to a fractional delay filter (Frac-delay filter) to perform phase compensation for compensating for frequency-selective phase imbalance, input the signal output from the fractional delay filter (Frac-delay filter) to a real symmetric amplitude filter (Amp-FIR filter) to perform amplitude compensation for compensating for frequency-selective amplitude imbalance, and another signal that is not selected is processed by a delay module to be time-aligned with the selected signal.

[0063] The three-stage compensation system provided by the above embodiment can compensate for wideband IQ imbalance, and adopts a pre-compensation method in the receiving channel and a post-compensation method in the receiving channel. In terms of resource overhead, the first stage frequency non-selective compensation in this embodiment is equivalent to a first-order structure, and can be completed with only four multipliers; the second stage phase filter can meet the precision requirements of fractional delay with only a few stages; the third stage amplitude filter is related to the order and precision requirements of single-tone test and the sampling rate of the system, and can generally meet the requirements from 16th to 32nd order according to actual measurement. This embodiment has a clear structure and is easy to control, has low resource usage, and has high compensation accuracy. With reference to the changes in phase error, amplitude error and IRR before and after compensation in the actual measurement of the example shown in Figures 7 to 9, IRR (image rejection ratio), EVM and bit error rate are significantly improved.

[0064] For other technical features, please refer to the above embodiments and the repeated explanation will be omitted here.

[0065] In another embodiment of the present invention, the second-stage phase filter and the third-stage amplitude filter can be combined to design a single-channel filter FIR module with fractional time delay and amplitude compensation effect. The difference from the above embodiment is that the second-stage phase filter and the third-stage amplitude filter in the frequency-dependent IQ imbalance compensation device (FD-IQMC) are combined into one module, and the delay module in Figure 5 and Figure 6 is correspondingly adjusted into one delay module, but other technical features remain the same.

[0066] Specifically, an IQ imbalance compensation method for WiFi wideband transmit and receive channels is provided.

[0067] For the transmission channel, the IQ signal output by the transmit baseband (TX Baseband) is input to a frequency-dependent IQ imbalance compensation device (FD-IQMC) to perform frequency-dependent IQ imbalance compensation, and the compensated output signal I'Q' is input to a digital-to-analog converter DAC.

[0068] For the receive channel, the IQ signal received by the analog-to-digital converter ADC is input to a frequency-dependent IQ imbalance compensation device (FD-IQMC) to perform frequency-dependent IQ imbalance compensation, and the compensated output signal I'Q' is input to the receive baseband (RX Baseband).

[0069] The FD-IQMC performs single-point compensation by selecting amplitude error and phase error at one frequency point for the input I channel signal and Q channel signal through a frequency-independent IQ imbalance compensation module (FI-iqmc) based on an IQ imbalance parameter of the transmission channel or the reception channel for the input IQ signal, thereby performing frequency-independent overall compensation for the IQ imbalance, the IQ imbalance parameter includes phase error information and amplitude error information, and for the I channel signal and Q channel signal output from the FI-iqmc, one of the signals is selected and input to a single channel filter for processing to compensate for frequency-selective phase and frequency-selective amplitude, the single channel filter has a filter coefficient generated by convolving a fractional delay filter coefficient and an amplitude filter coefficient, and its phase-frequency response can compensate for fractional delay and its amplitude-frequency response can compensate for amplitude error, the filter coefficient of the single channel filter is real and asymmetric, and another unselected signal is processed by a delay module to align it in time with the selected signal.

[0070] At this time, the frequency-dependent IQ imbalance compensator (FD-IQMC) is configured as a two-stage compensation structure, and after the IQ signal is totally compensated by the FI-iqmc module in the first stage, one signal is selected from the I channel signal and the Q channel signal and input to the single channel filter FIR module in the second stage for compensation, and the single channel filter can compensate for frequency selectivity phase and frequency selective amplitude. For example, the Q channel signal is selected and input to the single channel filter to compensate for frequency selective phase and frequency selective amplitude, and another signal that is not selected, i.e., the I channel signal, is processed by one delay module to align with the selected Q channel signal.

[0071] Specifically, the single-channel filter, whose filter coefficients are generated by convolving the fractional delay filter coefficients and the magnitude filter coefficients, has a phase-frequency response that can compensate for fractional delay and a magnitude-frequency response that can compensate for amplitude errors. This single-channel filter contains the properties of combining the previous two filters (i.e., the fractional delay filter and the magnitude filter).

[0072] As an example, for example, if the fractional time delay filter coefficient is H1 and the amplitude filter coefficient is H2 (the filter coefficient of a general filter is a real number), the filter coefficient of the single channel filter is H=conv(H1,H2), where the function conv(H1,H2) represents the convolution of the return coefficients H1 and H2, and H is the filter coefficient after convolution. The convolution operation for the coefficients H1 and H2 can be calculated based on software, and the calculation result can be set in the memory RAM.

[0073] Compared with the three-stage compensation structure of the above embodiment, after the fractional delay and amplitude compensation are combined into a single-channel filter for compensation processing, the filter coefficient H is in a real symmetrical form, and compared with the real symmetrical filter, the resource overhead is increased, and those skilled in the art can make an adaptive selection according to their needs. Note that, compared with the traditional method of adopting a complex filter, the resource overhead of the above combination scheme is still small.

[0074] Corresponding to the combination scheme of the second-stage phase filter and the third-stage amplitude filter, the present invention further provides an IQ imbalance compensation system for WiFi wideband transmitting and receiving channels, which is a two-stage compensation structure combining an FI-iqmc module and a single-channel filter.

[0075] The system comprises a frequency-dependent IQ imbalance compensation device (FD-IQMC), the FD-IQMC being provided in a transmit channel and used to perform pre-compensation processing on an IQ signal input to a digital-to-analog converter DAC, or the FD-IQMC being provided in a receive channel and used to perform post-compensation processing on an IQ signal output from an analog-to-digital converter ADC.

[0076] The frequency-dependent IQ imbalance compensation device (FD-IQMC) is configured to, for an input IQ signal, select an amplitude error and a phase error at one frequency point for the input I channel signal and Q channel signal by a frequency-independent IQ imbalance compensation module (FI-iqmc) based on an IQ imbalance parameter estimate of the transmission channel or the reception channel to perform single-point compensation, thereby performing frequency-independent overall compensation for the IQ imbalance, and for the I channel signal and Q channel signal output from the FI-iqmc, select one of the signals and input it to a single channel filter to process it to compensate for frequency-selective phase and frequency-selective amplitude, the single channel filter has a filter coefficient generated by convolving a fractional delay filter coefficient and an amplitude filter coefficient, the phase-frequency response of which can compensate for fractional delay, and the amplitude-frequency response of which can compensate for amplitude error, the filter coefficient of the single channel filter is real and asymmetric, and another unselected signal is processed by a delay module to align it in time with the selected signal.

[0077] For other technical features, please refer to the above embodiments and the repeated explanation will be omitted here.

[0078] In the above description, the disclosure of the present invention is not intended to be limited to these aspects. Within the scope of protection covered by the contents of this disclosure, each component can be selectively and operably combined in any number. The steps of the method or algorithm described in combination with the embodiments disclosed herein may be directly implemented in hardware, a software module executed by a processor, or a combination of both. The software module may be provided in a random access memory (RAM), a memory, a read-only memory (ROM), an electrically programmable ROM, an electrically erasable programmable ROM, a register, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. In addition, terms such as "comprises", "comprehensive", and "having" should be interpreted as inclusive or open, rather than exclusive or closed, unless expressly limited to the contrary. All technical, scientific, or other terms have the same meaning as understood by a person skilled in the art, unless expressly limited to the contrary. General terms found in dictionaries should not be interpreted as too ideal or unrealistic in the context of the relevant technical document, unless the contents of this disclosure expressly limit them. Any variations or modifications made by those skilled in the art of the present invention on the basis of the above disclosure shall fall within the scope of protection of the claims.

Claims

1. 1. A method for IQ imbalance compensation for a WiFi broadband transmit / receive channel, comprising: For a transmission channel, an IQ signal output by a transmission baseband (TX Baseband) is input to a frequency-dependent IQ imbalance compensation device (FD-IQMC), frequency-dependent IQ imbalance compensation is performed, and the compensated output signal I'Q' is input to a digital-to-analog converter DAC; or for a reception channel, an IQ signal output by an analog-to-digital converter ADC is input to a frequency-dependent IQ imbalance compensation device (FD-IQMC), frequency-dependent IQ imbalance compensation is performed, and the compensated output signal I'Q' is input to a reception baseband (RX Baseband); Here, the FD-IQMC performs single-point compensation by selecting an amplitude error and a phase error at one frequency point of the input I-channel signal and Q-channel signal by a frequency-independent IQ imbalance compensation module (FI-iqmc) based on an IQ imbalance parameter estimate of the transmission channel or the reception channel, thereby performing frequency-independent overall compensation for the IQ imbalance; One of the I-channel and Q-channel signals output from the FI-iqmc is selected and input to a fractional delay filter (Frac-delay filter) for phase compensation to compensate for frequency-selective phase imbalance, and the signal output from the fractional delay filter (Frac-delay filter) is input to a real symmetric amplitude filter (Amp-FIR filter) for amplitude compensation to compensate for frequency-selective amplitude imbalance, and the other unselected signal is processed by a delay module to be time-aligned with the selected signal. IQ imbalance compensation method for WiFi wideband transmit and receive channels.

2. The IQ imbalance parameter estimates of the transmission channel or the reception channel are obtained by a single tone test, and a single tone at a plurality of frequency points corresponds to the IQ imbalance parameter estimates at the plurality of frequency points. The IQ imbalance compensation method according to claim 1 .

3. The frequency independent IQ imbalance compensation module (FI-iqmc) is configured to perform the following steps: In the case of a signal x=cos(θ)+j sin(θ), j is a complex number expression, and based on the phase imbalance coefficient Δφ and the amplitude imbalance coefficient Δm of the IQ imbalance parameter estimates, the compensation phase and compensation amplitude required for the I channel signal are set to −Δφ / 2 and −Δm / 2, respectively, and the compensation phase and compensation amplitude required for the Q channel signal are set to Δφ / 2 and Δm / 2, respectively, and generally compensated for by the following compensation algorithm: Here, x represents the IQ signal input to the FI-iqmc, and M comp represents a phase compensation matrix and an amplitude compensation matrix, The IQ imbalance compensation method according to claim 1 .

4. If Δφ is smaller than a preset value, sin(Δφ) is set equal to Δφ, cos(Δφ) is set equal to 1, and these are used as the compensation matrix M comp Substituting into the simplified M' comp And 、 The IQ imbalance is globally compensated for by the following compensation algorithm: At this time, the frequency independent IQ imbalance compensation module (FI-iqmc) performs matrix multiplication on the input signal by four multipliers to compensate for frequency independent IQ imbalance. The IQ imbalance compensation method according to claim 3 .

5. The steps of performing phase compensation on the I-channel signal or the Q-channel signal output from the FI-iqmc using a fractional delay filter are as follows: obtain phase errors at sampling frequency points in a wide band through single-tone tests at multiple frequency points, perform linear fitting on the obtained phase errors, and calculate the phase error group delay in the wide band for the phase errors that have been linearly fitted using the following formula: where Δφ (radian) is a change in phase error in a Δω (radian) frequency band, and radian represents a degree of radian; calculating a fractional delay sample point value that needs compensation based on the calculated group delay value; designing a fractional delay value of a fractional delay filter by a Lagrange interpolation method based on the fractional delay sample point value that needs compensation; and performing phase compensation on a selected I-channel signal or Q-channel signal based on the designed fractional delay filter to obtain a phase-compensated I-channel signal or Q-channel signal. The IQ imbalance compensation method according to claim 1 .

6. When the fractional delay filter (Frac-delay filter) performs phase compensation on the I-channel signal or the Q-channel signal output by the FI-iqmc, another signal that is not selected to time-align the two signals is input to the first delay module DI for delay processing. The IQ imbalance compensation method according to claim 5 .

7. The steps of performing amplitude compensation on the signal output from the fractional delay filter (Frac-FIR filter) by a real symmetric amplitude filter (Amp-FIR filter) are as follows: obtain amplitude errors at sampling frequency points in a wide band through single-tone testing at multiple frequency points; calculate an average value of amplitude errors at frequency points where positive and negative frequencies are symmetric; design a real filter of order N, whose amplitude error parameters at the frequency points are obtained by piecewise linear interpolation of the test frequency points, where N is an integer multiple of 2; calculate filter coefficients of the real filter by inverse fast Fourier transform according to the amplitude error parameters at the frequency points of the filter; the filter coefficients are real and symmetric; and filter the signal by the filter coefficients to obtain an amplitude-compensated signal. The IQ imbalance compensation method according to claim 6 .

8. When the real symmetric amplitude filter (Amp-FIR filter) performs amplitude compensation on the signal output from the fractional delay filter (Frac-delay filter), the signal output from the first delay module D1 is input to the second delay module D2 for delay processing in order to time-align the two signals. The IQ imbalance compensation method according to claim 7.

9. 1. A three-stage IQ imbalance compensation system for a WiFi broadband transmit and receive channel, comprising: The frequency-dependent IQ imbalance compensation device (FD-IQMC) includes a frequency-dependent IQ imbalance compensation module (FI-iqmc), the FD-IQMC being provided in a transmission channel and used to perform pre-compensation processing on an IQ signal input to a digital-to-analog converter (DAC), or the FD-IQMC being provided in a reception channel and used to perform post-compensation processing on an IQ signal output from an analog-to-digital converter (ADC). The frequency-dependent IQ imbalance compensation device (FD-IQMC) performs single-point compensation by selecting amplitude error and phase error at one frequency point for the input I channel signal and Q channel signal based on an IQ imbalance parameter estimate of the transmission channel or the reception channel, thereby performing frequency-independent overall compensation for the IQ imbalance, and selects one of the I channel signal and Q channel signal output from the FI-iqmc to perform a fractional delay filter (Frac-delay filter) a signal output from the fractional delay filter (Frac-delay filter) to a real symmetric amplitude filter (Amp-FIR filter) to perform amplitude compensation to compensate for frequency selective amplitude imbalance; and a signal output from the fractional delay filter (Frac-delay filter) to a real symmetric amplitude filter (Amp-FIR filter) to perform amplitude compensation to compensate for frequency selective amplitude imbalance; and a non-selected signal is processed by a delay module to time-align with the selected signal. A three-stage IQ imbalance compensation system for WiFi wideband transmit and receive channels.

10. 1. A method for IQ imbalance compensation for a WiFi broadband transmit / receive channel, comprising: For a transmission channel, an IQ signal output by a transmission baseband (TX Baseband) is input to a frequency-dependent IQ imbalance compensation device (FD-IQMC), frequency-dependent IQ imbalance compensation is performed, and the compensated output signal I'Q' is input to a digital-to-analog converter DAC; or for a reception channel, an IQ signal output by an analog-to-digital converter ADC is input to a frequency-dependent IQ imbalance compensation device (FD-IQMC), frequency-dependent IQ imbalance compensation is performed, and the compensated output signal I'Q' is input to a reception baseband (RX The FD-IQMC inputs a frequency independent IQ imbalance compensation module (FI-iqmc) for the input IQ signal, based on an IQ imbalance parameter estimate of the transmission channel or the reception channel, to select an amplitude error and a phase error at one frequency point for the input I channel signal and Q channel signal to perform single-point compensation, thereby performing frequency-independent overall compensation for the IQ imbalance; and for the I channel signal and Q channel signal output from the FI-iqmc, select one of the signals to input to a single channel filter and process it to compensate for frequency selective phase and frequency selective amplitude, the single channel filter has a filter coefficient generated by convolving a fractional delay filter coefficient and an amplitude filter coefficient, the phase-frequency response of which can compensate for fractional delay, and the amplitude-frequency response of which can compensate for amplitude error; the filter coefficient of the single channel filter is real and asymmetric, and another signal that is not selected is processed by a delay module to time-align with the selected signal. IQ imbalance compensation method for WiFi wideband transmit and receive channels.

11. 1. An IQ imbalance compensation system for a WiFi broadband transmit and receive channel, comprising: The frequency-dependent IQ imbalance compensation device (FD-IQMC) includes a frequency-dependent IQ imbalance compensation module (FI-iqmc), the FD-IQMC being provided in a transmission channel and used to perform pre-compensation processing on an IQ signal input to a digital-to-analog converter (DAC), or the FD-IQMC being provided in a reception channel and used to perform post-compensation processing on an IQ signal output from an analog-to-digital converter (ADC), and the frequency-dependent IQ imbalance compensation device (FD-IQMC) selects amplitude errors and phase errors at one frequency point for the input I channel signal and Q channel signal by a frequency-independent IQ imbalance compensation module (FI-iqmc) based on an IQ imbalance parameter estimate value of the transmission channel or the reception channel. a single-channel filter that selects one of the I-channel and Q-channel signals output from the FI-iqmc to input the one of the I-channel and Q-channel signals into a single-channel filter and processes the one of the I-channel and Q-channel signals to compensate for frequency-selective phase and frequency-selective amplitude, the filter coefficient of the single-channel filter being generated by convolving a fractional delay filter coefficient with an amplitude filter coefficient, the phase-frequency response of the single-channel filter being capable of compensating for fractional delay and the amplitude-frequency response of the single-channel filter being capable of compensating for amplitude errors, the filter coefficient of the single-channel filter being real and asymmetric, and the other unselected signal being processed by a delay module to time-align with the selected signal. IQ imbalance compensation method for WiFi wideband transmit and receive channels.

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