Closed loop calibration system and method for IQ imbalance

Abstract

The application provides an IQ imbalance closed-loop calibration system and method, and relates to the technical field of communication.The system comprises a digital transmitter, a power amplifier, a low noise amplifier and a digital receiver connected in sequence, and further comprises a digital correlator, a solving unit, a phase controller and an IQ imbalance compensator.The power amplifier and the low noise amplifier are connected through a coupling loop.The application adjusts the analog phase and the digital phase of the loop through the phase controller, combines the four-time cross-correlation operation of the digital correlator and the parameter joint estimation of the solving unit, realizes the simultaneous calibration of the IQ imbalance in the digital transmitter and the digital receiver, does not need a phase-shifting module, realizes the phase switching by using the existing tuning capacitor of the power amplifier or the low noise amplifier, is simple in design, is close to the antenna port, is not easily affected by the internal radio frequency module in terms of interference and radiation, and is not easily affected in terms of calibration accuracy;the hardware implementation is easy, the complexity is low, the estimation accuracy is high, and the stability is strong.

Description

Technical Field

[0001] This invention relates to the field of communication technology, and in particular to a closed-loop calibration system and method for IQ imbalance. Background Technology

[0002] With the rapid development of wireless communication technology, the zero-IF (ZIF) architecture has been widely used in modern communication systems due to its advantages such as simple structure, low power consumption, and high integration. In the ZIF architecture, signal modulation and demodulation rely on the orthogonality and amplitude consistency of the I (in-phase) and Q (quadrature) signals. However, due to factors such as analog path mismatch, device manufacturing tolerances, and temperature drift, it is often difficult to maintain an ideal orthogonality and amplitude matching between the I and Q signals, leading to IQ imbalance. This imbalance introduces image interference, reduces the error vector magnitude (EVM) performance of the transmitted signal, affects the demodulation quality of the received signal, and ultimately degrades the performance of the entire communication system.

[0003] To address the aforementioned issues, existing technologies typically employ a combined analog and digital calibration approach. In the analog domain, a common approach is to design two independent feedback loops, one for calibrating IQ imbalance in the transmit and the other for calibrating the other. Another approach involves introducing a phase shifter into the feedback loop to achieve simultaneous calibration of the transmit and receive paths by adjusting the phase. In the digital domain, calibration methods primarily include analytical methods based on Fast Fourier Transform (FFT) testing, Least Mean Squares (LMS) adaptive training algorithms, and blind or semi-blind estimation methods for receiver IQ imbalance. These digital methods usually rely on the feedback mechanism provided by the analog loop for parameter estimation and compensation; therefore, digital calibration techniques require a design scheme that incorporates analog loops.

[0004] However, existing technologies have some shortcomings. For example, methods that use two independent loops to calibrate the transmitter (TX) and receiver (RX) separately require designing two sets of calibration paths and control logic, resulting in wasted hardware resources, complex calibration processes, and high system implementation costs. While blind or semi-blind estimation methods on the receiver side reduce reliance on analog circuit design, they are only applicable to the calibration of the RX path and are easily affected by channel variations and noise in practical applications, leading to poor stability of calibration results. Furthermore, some schemes that attempt to achieve simultaneous calibration of the transmit and receive paths by introducing phase shifters and switches face increased hardware implementation difficulty due to the increased complexity of analog circuits. Additionally, the digital algorithm side requires an adaptive training process, resulting in long convergence times and a tendency for calibration failures or instability in dynamic environments. Summary of the Invention

[0005] The purpose of this invention is to provide a closed-loop calibration system and method for IQ imbalance, so as to at least solve one of the above-mentioned problems.

[0006] In a first aspect, the present invention provides a closed-loop calibration system for IQ imbalance, comprising a digital transmitter, a power amplifier, a low-noise amplifier, and a digital receiver connected in sequence, and further comprising a digital correlator, a calculation unit, a phase controller, and an IQ imbalance compensator; the power amplifier and the low-noise amplifier are connected through a coupling loop; the digital correlator is connected to the digital transmitter, the digital receiver, and the calculation unit respectively; the IQ imbalance compensator includes a transmitter compensator and a receiver compensator respectively disposed at one end of the digital transmitter and one end of the digital receiver; the phase controller is connected to the IQ imbalance compensator, and the phase controller is also connected to the power amplifier and / or the low-noise amplifier; The digital transmitter generates a single-tone signal when triggering a single calibration and sends the corresponding local reference signal to the digital correlator. The single-tone signal passes through a power amplifier and a low-noise amplifier before reaching the digital receiver. The digital receiver sends the received digital signal to the digital correlator. The digital correlator performs cross-correlation on the local reference signal and the received digital signal to obtain the single-correlation result, and sends the single-correlation result to the solution unit. The phase controller is used to adjust the tuning capacitor of the power amplifier and / or low noise amplifier to trigger the second calibration; the phase controller is also used to adjust the IQ imbalance compensation phase of the IQ imbalance compensator to trigger the third and fourth calibrations; wherein, the tuning capacitor during the third calibration is the same as the tuning capacitor after adjustment during the second calibration, and the tuning capacitor during the fourth calibration is the same as the tuning capacitor before adjustment during the second calibration. The calculation unit is used to obtain the first correlation result corresponding to the first calibration in the initial state, as well as the second, third, and fourth correlation results corresponding to the second, third, and fourth calibrations, respectively; based on the first, second, third, and fourth correlation results, the IQ imbalance parameter data of the set frequency point is calculated; wherein, the first calibration is triggered by the calibration command of the set frequency point, and the IQ imbalance parameter data includes the IQ imbalance parameters of the digital transmitter and the IQ imbalance parameters of the digital receiver.

[0007] In an optional implementation, the digital correlator is specifically used to perform cross-correlation operations on the in-phase reference signal in the local reference signal with the in-phase signal and the quadrature signal in the digital received signal, respectively, and to perform cross-correlation operations on the quadrature reference signal in the local reference signal with the in-phase signal and the quadrature signal in the digital received signal, respectively, to obtain four cross-correlation values.

[0008] In an optional implementation, the solution unit is specifically used for: Based on the four cross-correlation values ​​of each single correlation result in the first, second, third, and fourth correlation results, the self-cross-correlation data corresponding to the single correlation result is calculated. The self-cross-correlation data includes the cross-correlation value of the in-phase signal itself, the cross-correlation value of the quadrature signal itself, and the cross-correlation value between the in-phase signal and the quadrature signal. Based on the self-cross-correlation data corresponding to the first, second, third, and fourth correlation results, determine the objective equation set with the IQ imbalance parameter as the unknown; Solve the objective equations to obtain the IQ imbalance parameters of the digital transmitter and the digital receiver at the set frequency.

[0009] In an optional implementation, the self-correlation data is calculated using the following formula: ; ; ; in, Indicates in-phase signal In-phase reference signal The cross-correlation value, Indicates in-phase signal Orthogonal reference signal The cross-correlation value, Indicates orthogonal signals In-phase reference signal The cross-correlation value, Indicates orthogonal signals Orthogonal reference signal The cross-correlation value, Indicates in-phase signal Its own cross-correlation value, Indicates orthogonal signals Its own cross-correlation value, Indicates in-phase signal and quadrature signals The cross-correlation value between them N Indicates the degree of relevance of the preset.

[0010] In an optional implementation, the solution unit is further configured to: obtain the first equation and the second equation based on the self-cross-correlation data corresponding to the first correlation result; obtain the third equation and the fourth equation based on the second correlation result; and obtain the fifth equation and the sixth equation based on the third correlation result and the fourth correlation result. The first equation and the second equation are respectively: ; ; The third and fourth equations are as follows: ; ; The fifth equation is: ;or ; The sixth equation is: ;or ; in, Indicates the first k The in-phase signal in the digital received signal during the second calibration. Indicates the first k Orthogonal signals in the digital received signal during secondary calibration k The values ​​are 1, 2, 3, and 4. This indicates the amplitude imbalance parameter of a digital receiver. This indicates the amplitude imbalance parameter of the digital transmitter. This represents the phase imbalance parameter of a digital receiver. This represents the phase imbalance parameter of the digital transmitter. This indicates the loop phase during the first calibration. Indicates the loop phase during the second calibration. This indicates the adjustment amount of the IQ imbalance compensation phase during the third calibration.

[0011] In an optional implementation, the transmitter compensator is disposed between the digital transmitter and the power amplifier, and a DAC module and an up-converter are also disposed between the transmitter compensator and the power amplifier; the receiver compensator is disposed between the low-noise amplifier and the digital receiver, and a down-converter and an ADC module are also disposed between the low-noise amplifier and the receiver compensator.

[0012] Secondly, the present invention provides a closed-loop calibration method for IQ imbalance, applicable to the closed-loop calibration system for IQ imbalance in any of the foregoing embodiments; the method includes: When a calibration command for a set frequency point is received, the calculation unit obtains the first correlation result output by the digital correlator based on the first calibration in the initial state triggered by the set frequency point. The digital correlator is used to perform cross-correlation calculation on the local reference signal and the digital received signal when a single calibration is triggered to obtain the single correlation result. The local reference signal corresponds to the single-tone signal generated by the digital transmitter, and the digital received signal is the signal received by the digital receiver when the single-tone signal reaches the digital receiver after passing through the power amplifier and the low-noise amplifier. The second calibration is triggered by adjusting the tuning capacitor of the power amplifier and / or low noise amplifier by the phase controller, and the calculation unit obtains the second correlation result output by the digital correlator. The phase controller adjusts the IQ imbalance compensation phase of the IQ imbalance compensator, and the third and fourth calibrations are triggered under the tuning capacitors during the second calibration and the first calibration, respectively. The calculation unit obtains the third and fourth correlation results output by the digital correlator. The calculation unit calculates the IQ imbalance parameter data for the set frequency point based on the first correlation result, the second correlation result, the third correlation result, and the fourth correlation result. The IQ imbalance parameter data includes the IQ imbalance parameters of the digital transmitter and the IQ imbalance parameters of the digital receiver.

[0013] In an optional implementation, a cross-correlation operation is performed on the local reference signal and the digital received signal to obtain a single correlation result, including: The in-phase reference signal in the local reference signal is cross-correlated with the in-phase and quadrature signals in the digital received signal, respectively. The quadrature reference signal in the local reference signal is cross-correlated with the in-phase and quadrature signals in the digital received signal, respectively, to obtain four cross-correlation values.

[0014] In an optional implementation, the calculation unit calculates the IQ imbalance parameter data at a set frequency point based on the first correlation result, the second correlation result, the third correlation result, and the fourth correlation result, including: Based on the four cross-correlation values ​​of each single correlation result in the first, second, third, and fourth correlation results, the self-cross-correlation data corresponding to the single correlation result is calculated. The self-cross-correlation data includes the cross-correlation value of the in-phase signal itself, the cross-correlation value of the quadrature signal itself, and the cross-correlation value between the in-phase signal and the quadrature signal. Based on the self-cross-correlation data corresponding to the first, second, third, and fourth correlation results, determine the objective equation set with the IQ imbalance parameter as the unknown; Solve the objective equations to obtain the IQ imbalance parameters of the digital transmitter and the digital receiver at the set frequency.

[0015] In an optional implementation, the system further includes a storage unit connected to the calculation unit, and the storage unit is also connected to the transmitter compensator and the receiver compensator; the method further includes: The calculation unit acquires IQ imbalance parameter data at multiple different set frequency points; Determine the broadband IQ imbalance compensation data based on IQ imbalance parameter data from multiple different set frequency points; Broadband IQ imbalance compensation data is stored in a storage unit so that the transmitter compensator and receiver compensator can automatically compensate based on the broadband IQ imbalance compensation data stored in the storage unit during normal operation.

[0016] The closed-loop calibration system and method for IQ imbalance provided by this invention includes a digital transmitter, a power amplifier, a low-noise amplifier, and a digital receiver connected in sequence, and further includes a digital correlator, a calculation unit, a phase controller, and an IQ imbalance compensator. The power amplifier and the low-noise amplifier are connected via a coupling loop. The digital correlator is connected to the digital transmitter, the digital receiver, and the calculation unit respectively. The IQ imbalance compensator includes a transmitter-end compensator and a receiver-end compensator respectively disposed at one end of the digital transmitter and one end of the digital receiver. The phase controller is connected to the IQ imbalance compensator and is also connected to the power amplifier and / or the low-noise amplifier. The digital transmitter generates a single-tone signal when triggering a single calibration and sends the local reference signal corresponding to the single-tone signal to the digital correlator. The single-tone signal passes through the power amplifier and the low-noise amplifier before reaching the digital receiver. The digital receiver sends the received digital received signal to the digital correlator. The digital correlator performs cross-correlation calculation on the local reference signal and the digital received signal to obtain... The system obtains the single correlation result and sends it to the calculation unit. The phase controller is used to adjust the tuning capacitor of the power amplifier and / or low noise amplifier to trigger the second calibration. The phase controller is also used to adjust the IQ imbalance compensation phase of the IQ imbalance compensator to trigger the third and fourth calibrations. The tuning capacitor during the third calibration is the same as the tuning capacitor adjusted during the second calibration, and the tuning capacitor during the fourth calibration is the same as the tuning capacitor before the adjustment during the second calibration. The calculation unit is used to obtain the first correlation result corresponding to the first calibration in the initial state, as well as the second, third, and fourth correlation results corresponding to the second, third, and fourth calibrations, respectively. Based on the first, second, third, and fourth correlation results, the IQ imbalance parameter data of the set frequency point is calculated. The first calibration is triggered by the calibration command of the set frequency point, and the IQ imbalance parameter data includes the IQ imbalance parameters of the digital transmitter and the IQ imbalance parameters of the digital receiver.

[0017] By adjusting the analog and digital phases of the loop using a phase controller, and combining this with the four cross-correlation operations of the digital correlator and the parameter estimation of the solution unit, simultaneous calibration of IQ imbalance in the digital transmitter and receiver is achieved. This eliminates the need for a phase-shifting module; phase switching can be achieved using the existing tuning capacitors of the power amplifier or low-noise amplifier. The design is simple, and the coupling loop is close to the antenna port, making it less susceptible to interference and radiation from the internal RF module, thus affecting calibration accuracy. This calibration algorithm is easy to implement in hardware, has low complexity, and offers high estimation accuracy and strong stability. Attached Figure Description

[0018] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of a closed-loop calibration system for IQ imbalance provided in an embodiment of the present invention; Figure 2 A schematic diagram of another closed-loop calibration system for IQ imbalance provided in an embodiment of the present invention; Figure 3 A schematic flowchart of a closed-loop calibration method for IQ imbalance provided in an embodiment of the present invention; Figure 4 This is a schematic flowchart of another closed-loop calibration method for IQ imbalance provided in an embodiment of the present invention.

[0020] Icons: 101-Digital transmitter; 102-Transmitter compensator; 103-DAC module; 104-Upconverter; 105-Power amplifier; 106-Low noise amplifier; 107-Downconverter; 108-ADC module; 109-Receiver compensator; 110-Digital receiver; 111-Digital correlator; 112-Solution unit; 113-Phase controller; 114-Storage unit. Detailed Implementation

[0021] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Imbalance issues in IQ modulators / demodulators during wireless communication can affect the signal quality of both the transmitter and receiver, leading to problems such as EVM degradation and image interference. To address this, this invention provides a closed-loop calibration system and method for IQ imbalance. This system employs a novel RF calibration loop and algorithm. A calibration signal is transmitted from the TX side, passes through a power amplifier (PA)-low noise amplifier (LNA) loop, and is received at the RX side. The tuning capacitor of the PA or LNA is used to change the signal phase difference, thereby decoupling the IQ imbalance between the TX and RX sides. An optimized cross-correlation algorithm and joint parameter estimation algorithm are used to calculate and extract the IQ imbalance parameters in the TX and RX sides.

[0023] To facilitate understanding of this embodiment, a closed-loop calibration system for IQ imbalance disclosed in this embodiment of the invention will first be described in detail.

[0024] This invention provides a closed-loop calibration system for IQ imbalance. The calibration link is a PA-LNA loop, coupling the PA signal to the LNA receiver. No phase-shifting module is required; phase switching can be achieved using the existing tuning capacitors of the PA or LNA. Furthermore, the loop is close to the antenna port, not an internal loop after the mixer, thus more closely resembling the actual RF signal and less susceptible to electromagnetic interference from other internal RF modules, which could affect calibration accuracy. The correlation and statistical characteristics of the single-tone signal provide strong noise and interference immunity, effectively improving calibration accuracy. A phase controller controls the phase changes in the loop, and multiple correlation results are used to establish a joint equation set for solving and extracting the TX and RX imbalance parameters.

[0025] like Figure 1 As shown, the system includes a digital transmitter 101, a power amplifier 105, a low-noise amplifier 106, and a digital receiver 110 connected in sequence. It also includes a digital correlator 111, a calculation unit 112, a phase controller 113, and an IQ imbalance compensator. The power amplifier 105 and the low-noise amplifier 106 are connected via a coupling loop. The digital correlator 111 is connected to the digital transmitter 101, the digital receiver 110, and the calculation unit 112. The IQ imbalance compensator includes components respectively disposed at one end of the digital transmitter 101 and the digital receiver 110. The receiver 110 has a transmitter compensator 102 and a receiver compensator 109 at one end. The transmitter compensator 102 is located between the digital transmitter 101 and the power amplifier 105, and the receiver compensator 109 is located between the low noise amplifier 106 and the digital receiver 110. The phase controller 113 is connected to the IQ imbalance compensator. For example, the phase controller 113 is connected to the transmitter compensator 102 and the receiver compensator 109 respectively. The phase controller 113 is also connected to the power amplifier 105 and / or the low noise amplifier 106.

[0026] The digital transmitter 101 generates a single-tone signal when triggering a single calibration and sends the local reference signal corresponding to the single-tone signal to the digital correlator 111. The single-tone signal can be a sine wave signal containing one frequency component. The single-tone signal passes through the power amplifier 105 and the low-noise amplifier 106 and reaches the digital receiver 110. The digital receiver 110 sends the received digital received signal to the digital correlator 111. The digital correlator 111 performs cross-correlation calculation on the local reference signal and the digital received signal to obtain the single-correlation result and sends the single-correlation result to the calculation unit 112.

[0027] Phase controller 113 is used to adjust the tuning capacitor of power amplifier 105 and / or low noise amplifier 106 to trigger the second calibration; phase controller 113 is also used to adjust the IQ imbalance compensation phase of IQ imbalance compensator, that is, to adjust the IQ imbalance compensation phase of transmitter compensator 102 and / or receiver compensator 109 to trigger the third and fourth calibrations; wherein, the tuning capacitor during the third calibration is the same as the tuning capacitor adjusted during the second calibration, and the tuning capacitor during the fourth calibration is the same as the tuning capacitor before adjustment during the second calibration.

[0028] The calculation unit 112 is used to obtain the first correlation result corresponding to the first calibration in the initial state, as well as the second correlation result, third correlation result, and fourth correlation result corresponding to the second, third, and fourth calibrations, respectively; and calculate the IQ imbalance parameter data of the set frequency point based on the first correlation result, second correlation result, third correlation result, and fourth correlation result; wherein, the first calibration is triggered by the calibration command of the set frequency point, and the IQ imbalance parameter data includes the IQ imbalance parameters of the digital transmitter 101 and the IQ imbalance parameters of the digital receiver 110.

[0029] The calibration command for setting the frequency point can be triggered by a timer, a temperature sensor, or manually. It can also be triggered based on the IQ imbalance monitoring results of the digital transmitter 101 and the digital receiver 110. This embodiment of the invention does not limit the triggering method of the calibration command for setting the frequency point.

[0030] The closed-loop calibration system for IQ imbalance provided in this invention adjusts the analog and digital phases of the loop through a phase controller, and combines the four cross-correlation operations of the digital correlator with the parameter estimation of the solution unit to achieve simultaneous calibration of IQ imbalance in the digital transmitter and digital receiver. It eliminates the need for a phase-shifting module, utilizing the existing tuning capacitors of the power amplifier or low-noise amplifier for phase switching. The design is simple, and the coupling loop is close to the antenna port, making it less susceptible to interference and radiation from internal RF modules that could affect calibration accuracy. This calibration algorithm is easy to implement in hardware, has low complexity, and offers high estimation accuracy and strong stability.

[0031] Furthermore, such as Figure 2As shown, a DAC module 103 and an upconverter 104 are also provided between the transmitter compensator 102 (i.e., the TX IQ imbalance compensator) and the power amplifier 105; a downconverter 107 and an ADC module 108 are also provided between the low-noise amplifier 106 and the receiver compensator 109 (i.e., the RXIQ imbalance compensator). Specifically, the transmitter compensator 102 is used to pre-compensate the input digital signal to correct IQ imbalance parameters such as amplitude and phase imbalance of the digital transmitter 101; the DAC module 103 is used to convert the digital signal into an analog signal for subsequent processing; the upconverter 104 is used to convert the baseband or intermediate frequency analog signal into a radio frequency signal for transmission through the antenna; the power amplifier 105 is used to amplify the power of the radio frequency signal, simulate the actual transmission path, and provide sufficient signal strength for subsequent components; the low noise amplifier 106 is used to amplify the received weak radio frequency signal, simulate the receiving path, improve the receiving sensitivity, and ensure that the received signal is strong enough for subsequent processing; the downconverter 107 is used to convert the radio frequency signal back to the baseband or intermediate frequency signal; the ADC module 108 is used to convert the amplified analog signal into a digital signal for further digital signal processing; and the receiver compensator 109 is used to post-compensate the signal after downconversion and analog-to-digital conversion to correct IQ imbalance parameters such as amplitude and phase imbalance of the digital receiver 110.

[0032] like Figure 2 As shown, the phase controller 113 can change the signal phase difference, i.e., phase shift, by adjusting the tuning capacitor of the power amplifier 105 and / or the low noise amplifier 106, in order to decouple the IQ imbalance of TX and RX.

[0033] like Figure 2 As shown, the digital correlator 111 can acquire a local reference signal (TX IQ) from the digital transmitter 101, which includes an in-phase reference signal and a quadrature reference signal; the digital correlator 111 can also acquire a digital received signal (RX IQ) from the digital receiver 110, which includes an in-phase signal and a quadrature signal. Specifically, the digital correlator 111 performs cross-correlation operations on the in-phase reference signal in the local reference signal with the in-phase and quadrature signals in the digital received signal, and performs cross-correlation operations on the quadrature reference signal in the local reference signal with the in-phase and quadrature signals in the digital received signal, obtaining four cross-correlation values.

[0034] Optionally, the aforementioned solution unit 112 is specifically used to: calculate the self-cross-correlation data corresponding to each single correlation result based on the four cross-correlation values ​​of each single correlation result in the first, second, third, and fourth correlation results. The self-cross-correlation data includes the cross-correlation value of the in-phase signal itself, the cross-correlation value of the quadrature signal itself, and the cross-correlation value between the in-phase signal and the quadrature signal; determine the target equation system with the IQ imbalance parameter as the unknown quantity based on the self-cross-correlation data corresponding to the first, second, third, and fourth correlation results; and solve the target equation system to obtain the IQ imbalance parameter of the digital transmitter and the IQ imbalance parameter of the digital receiver at the set frequency point.

[0035] In one possible implementation, considering the periodicity and correlation of the single-tone signal, the aforementioned self-cross-correlation data is calculated using the following formula: ; ; ; in, Indicates in-phase signal In-phase reference signal The cross-correlation value, Indicates in-phase signal Orthogonal reference signal The cross-correlation value, Indicates orthogonal signals In-phase reference signal The cross-correlation value, Indicates orthogonal signals Orthogonal reference signal The cross-correlation value, Indicates in-phase signal Its own cross-correlation value, Indicates orthogonal signals Its own cross-correlation value, Indicates in-phase signal and quadrature signals The cross-correlation value between them N Indicates the degree of relevance of the preset.

[0036] In one possible implementation, considering the periodicity and correlation of the single-tone signal, the solution unit 112 is further configured to: obtain the first equation and the second equation based on the self-cross-correlation data corresponding to the first correlation result; obtain the third equation and the fourth equation based on the second correlation result; and obtain the fifth equation and the sixth equation based on the third and fourth correlation results. The first equation and the second equation are respectively: ; ; The third and fourth equations are as follows: ; ; The fifth equation is: ;or ; The sixth equation is: ;or ; in, Indicates the first k The in-phase signal in the digital received signal during the second calibration. Indicates the first k Orthogonal signals in the digital received signal during secondary calibration k The values ​​are 1, 2, 3, and 4. This indicates the amplitude imbalance parameter of the digital receiver 110. This indicates the amplitude imbalance parameter of the digital transmitter 101. This indicates the phase imbalance parameter of the digital receiver 110. This represents the phase imbalance parameter of the digital transmitter 101. This indicates the loop phase during the first calibration. Indicates the loop phase during the second calibration. This indicates the adjustment amount of the IQ imbalance compensation phase during the third calibration.

[0037] The above six equations involve six unknowns, which can be calculated based on the fifth equation and the third or fourth equation. And based on the sixth equation and the first or second equation, the following is calculated: Then, in the known , In this case, the above objective equations can be degenerated into a 4×4 linear system, which can then be directly eliminated or used in matrix calculations to obtain the amplitude imbalance parameters of the digital transmitter 101. and phase imbalance parameters and the amplitude imbalance parameters of the digital receiver 110 and phase imbalance parameters .

[0038] Furthermore, such as Figure 2As shown, the system also includes a storage unit 114 connected to the calculation unit 112. The storage unit 114 is also connected to the transmitter compensator 102 and the receiver compensator 109. The calculation unit 112 is also used to acquire IQ imbalance parameter data at multiple different set frequency points; determine broadband IQ imbalance compensation data based on the IQ imbalance parameter data at multiple different set frequency points; and store the broadband IQ imbalance compensation data in the storage unit 114 so that the transmitter compensator 102 and the receiver compensator 109 can automatically compensate based on the broadband IQ imbalance compensation data stored in the storage unit 114 during normal operation. The storage unit 114 is used to store the broadband TX and RX IQ imbalance compensation data. During normal transmission and reception services, the transmitter compensator 102 and the receiver compensator 109 can call the data stored in the storage unit 114 to automatically compensate for amplitude imbalance parameters and phase imbalance parameters.

[0039] The present invention proposes a PA-LNA loop calibration system for calibrating IQ imbalance (i.e., closed-loop calibration of IQ imbalance), which adjusts the analog phase and digital phase of the loop through the phase controller 113, and uses the multiple correlation results of the loop phase adjustment to solve the equation system simultaneously based on the cross-correlation algorithm and the joint estimation algorithm of TX and RX parameters, and extracts the IQ imbalance parameters of TX and RX.

[0040] The PA-LNA loop calibration system in this embodiment of the invention can simultaneously calibrate the IQ imbalance of TX and RX. It has a simple design, and because it is closer to the antenna port, the loop is less susceptible to interference and radiation from the internal radio frequency module, which affects the calibration accuracy. The cross-correlation algorithm and the joint estimation algorithm of TX and RX parameters in this embodiment of the invention are easy to implement in hardware, have low complexity, and have high estimation accuracy and strong stability.

[0041] This invention also provides a closed-loop calibration method for IQ imbalance, which is applied to the aforementioned closed-loop calibration system for IQ imbalance. See also... Figure 3 The diagram shows a closed-loop calibration method for IQ imbalance, which mainly includes the following steps S310 to S340: Step S310: When a calibration command for a set frequency point is received, the first calibration in the initial state is triggered according to the set frequency point, and the calculation unit obtains the first correlation result output by the digital correlator.

[0042] The digital correlator is used to perform cross-correlation operations on the local reference signal and the digital received signal when triggering a single calibration to obtain the single correlation result. The local reference signal corresponds to the single-tone signal generated by the digital transmitter, and the digital received signal is the signal received by the digital receiver when the single-tone signal reaches the digital receiver after passing through the power amplifier and the low-noise amplifier.

[0043] In some possible embodiments, the above-described cross-correlation operation on the local reference signal and the digital received signal to obtain a single correlation result includes: performing cross-correlation operations on the in-phase reference signal in the local reference signal with the in-phase signal and the quadrature signal in the digital received signal, respectively, and performing cross-correlation operations on the quadrature reference signal in the local reference signal with the in-phase signal and the quadrature signal in the digital received signal, respectively, to obtain four cross-correlation values.

[0044] In step S320, the tuning capacitors of the power amplifier and / or low-noise amplifier are adjusted by the phase controller to trigger the second calibration, and the calculation unit obtains the second correlation result output by the digital correlator.

[0045] In step S330, the IQ imbalance compensation phase of the IQ imbalance compensator is adjusted by the phase controller, and the third and fourth calibrations are triggered under the tuning capacitors during the second calibration and the first calibration, respectively. The calculation unit obtains the third and fourth correlation results output by the digital correlator.

[0046] In step S340, the calculation unit calculates the IQ imbalance parameter data at the set frequency point based on the first correlation result, the second correlation result, the third correlation result, and the fourth correlation result.

[0047] IQ imbalance parameter data includes IQ imbalance parameters for digital transmitters and IQ imbalance parameters for digital receivers.

[0048] The closed-loop calibration method for IQ imbalance provided in this invention adjusts the analog and digital phases of the loop through a phase controller, and combines the four cross-correlation operations of the digital correlator with the joint estimation of parameters from the solution unit to achieve simultaneous calibration of IQ imbalance in the digital transmitter and digital receiver. It eliminates the need for a phase-shifting module, utilizing the existing tuning capacitors of the power amplifier or low-noise amplifier for phase switching. The design is simple, and the coupling loop is close to the antenna port, making it less susceptible to interference and radiation from internal RF modules that could affect calibration accuracy. This calibration algorithm is easy to implement in hardware, has low complexity, and offers high estimation accuracy and strong stability.

[0049] In some possible embodiments, step S340 may include: calculating the self-cross-correlation data corresponding to each single correlation result based on the four cross-correlation values ​​of each single correlation result in the first, second, third, and fourth correlation results, wherein the self-cross-correlation data includes the cross-correlation value of the in-phase signal itself, the cross-correlation value of the quadrature signal itself, and the cross-correlation value between the in-phase signal and the quadrature signal; determining the target equation set with the IQ imbalance parameter as the unknown quantity based on the self-cross-correlation data corresponding to the first, second, third, and fourth correlation results; and solving the target equation set to obtain the IQ imbalance parameter of the digital transmitter and the IQ imbalance parameter of the digital receiver at the set frequency point.

[0050] In one possible implementation, the aforementioned self-correlation data is calculated using the following formula: ; ; ; in, Indicates in-phase signal In-phase reference signal The cross-correlation value, Indicates in-phase signal Orthogonal reference signal The cross-correlation value, Indicates orthogonal signals In-phase reference signal The cross-correlation value, Indicates orthogonal signals Orthogonal reference signal The cross-correlation value, Indicates in-phase signal Its own cross-correlation value, Indicates orthogonal signals Its own cross-correlation value, Indicates in-phase signal and quadrature signals The cross-correlation value between them N Indicates the degree of relevance of the preset.

[0051] In one possible implementation, determining the objective equation set with the IQ imbalance parameter as the unknown based on the self-cross-correlation data corresponding to the first, second, third, and fourth correlation results may include: obtaining the first and second equations based on the self-cross-correlation data corresponding to the first correlation results; obtaining the third and fourth equations based on the second correlation results; and obtaining the fifth and sixth equations based on the third and fourth correlation results. The first equation and the second equation are respectively: ; ; The third and fourth equations are as follows: ; ; The fifth equation is: ;or ; The sixth equation is: ;or ; in, Indicates the first k The in-phase signal in the digital received signal during the second calibration. Indicates the first k Orthogonal signals in the digital received signal during secondary calibration k The values ​​are 1, 2, 3, and 4. This indicates the amplitude imbalance parameter of a digital receiver. This indicates the amplitude imbalance parameter of the digital transmitter. This represents the phase imbalance parameter of a digital receiver. This represents the phase imbalance parameter of the digital transmitter. This indicates the loop phase during the first calibration. Indicates the loop phase during the second calibration. This indicates the adjustment amount of the IQ imbalance compensation phase during the third calibration.

[0052] The aforementioned system may further include a storage unit connected to the calculation unit, and the storage unit is also connected to the transmitter compensator and the receiver compensator; based on this, embodiments of the present invention also provide another closed-loop calibration method for IQ imbalance, which is Figure 3 The following are the subsequent processing steps based on the illustrated workflow. See also: Figure 4 The flowchart of another closed-loop calibration method for IQ imbalance is shown, which includes the following steps S410 to S430: Step S410: The calculation unit acquires IQ imbalance parameter data at multiple different set frequency points. This can be done according to... Figure 3 The process shown obtains IQ imbalance parameter data for multiple frequency points.

[0053] Step S420: Determine broadband IQ imbalance compensation data based on IQ imbalance parameter data at multiple different set frequency points.

[0054] It can convert IQ imbalance parameter data from multiple different set frequency points into broadband IQ imbalance compensation data.

[0055] Step S430: The broadband IQ imbalance compensation data is stored in the storage unit so that the transmitter compensator and receiver compensator can automatically compensate based on the broadband IQ imbalance compensation data stored in the storage unit during normal operation.

[0056] The method provided in this embodiment has the same implementation principle and technical effect as the aforementioned system embodiment. For the sake of brevity, any parts not mentioned in the method embodiment can be referred to the corresponding content in the aforementioned system embodiment.

[0057] To facilitate understanding, the closed-loop calibration system and method for IQ imbalance described above will be introduced in detail below.

[0058] This invention provides a novel PA-LNA loop and digital calibration algorithm, which uses the tuning capacitor of the PA or LNA to achieve phase switching, establishes a joint equation system, and solves for the imbalance parameters. Specific steps include: 1. After triggering a single calibration, the digital baseband (i.e., digital transmitter) of TX generates a single-tone signal, which is converted from digital to analog by the DAC module, up-converted by the upconverter, passed through the PA-LNA loop, down-converted by the downconverter, and converted from analog to digital by the ADC module, and finally reaches the digital receiver of RX. 2. The local reference single-tone sequence (i.e., local reference signal) generated by TX and the single-tone sequence (i.e., digital received signal) received by RX are fed into a digital correlator, and after cross-correlation calculation, the correlation result is obtained; 3. The single correlation results generated by the digital correlator are stored in the solution unit; 4. After the phase controller adjusts the tuning capacitor (PA and / or LNA terminals), it triggers calibration again to obtain the second relevant result and stores it in the calculation unit; 5. The phase controller adjusts the IQ imbalance compensation phase (TX or RX terminal), triggers calibration again, obtains the third correlation result, and stores it in the solution unit; 6. After the phase controller reverses the adjustment of the tuning capacitor (PA and / or LNA terminals), the calibration is triggered again to obtain the fourth correlation result and store it in the calculation unit. 7. Based on the relevant results of the four calibrations, the solution unit establishes a joint equation system for solution and extracts the IQ imbalance parameters in TX and RX; The above process can be used to obtain the imbalance characteristics of TX and RX at a single frequency point. By calibrating multiple sets of single tones at different frequency points, the broadband IQ imbalance characteristics can be obtained.

[0059] The calibration algorithm is described below.

[0060] Assume the in-phase and quadrature signals of the TX digital signal are X i and X q The digital received signal Y, after passing through DAC, up-conversion, PA-LNA loop, down-conversion, and ADC to RX, is... i and Y q Wherein, the amplitude imbalance parameter of TX is The phase imbalance parameter of TX is The amplitude imbalance parameter of RX is The phase imbalance parameter of RX is ; G For loop gain, θ Let be the loop phase. Then the digital received signal has the following expression: (1); Expanding and combining equation (1) above, we can obtain the transmission equation for the IQ signal as follows: (2); (3); Utilizing the periodicity and correlation of single-tone signals, assume the TX transmitted signal is... , Meanwhile, the local reference monotone signal in the digital correlator is , , δ This represents the phase difference between the reference signal and the transmitted signal.

[0061] , , , Substituting the above monotone signal forms (i.e., the TX transmission signal and the local reference monotone signal) into equations (2) and (3) and then performing cross-correlation operations on the four cross-correlation values ​​generated by the digital correlator, we can obtain the following equations: (4); (5); (6); By substituting the above monotone signal forms and equations (2) and (3) into the definitions of E1 and E2 for merging and simplification, we can obtain the following equations: (7); Based on equations (4)(5)(6)(7) above, a set of equations for the imbalance parameters can be established based on the correlation results output by the digital correlator.

[0062] The first calibration yields a system of equations consisting of two equations as shown in equation (7). Equation (7) has five unknowns, and more equations need to be solved simultaneously.

[0063] The second calibration involves adjusting the tuning capacitor of the PA or LNA using a phase controller, thereby changing the loop phase. Assume the loop phase before adjustment is... After adjustment, it is: Then we can obtain the following system of four equations, with six unknowns: (8); For the third and fourth calibrations, the known IQ imbalance phase parameter ∆ is added to the digital terminal via the phase controller. α This yields a system of six equations with six unknowns: (9); or: (10); The parameters can then be solved based on equation (9) or (10) above. First, calculate the two phase shifts of the simulated loop. Taking equation (9) as an example, we have: (11); Thus, equation (9) degenerates into a system of 4×4 linear equations: (12); Equation (12) can be calculated directly by elimination, or it can be calculated using the following matrix method: (13); (14); Equation (12) can be rewritten as Equation (13), and then Equation (14) can be used to calculate the matrix consisting of the four imbalance parameters. .

[0064] Therefore, after four calibrations, the imbalance parameters of TX and RX can be directly solved by solving a system of equations based on the relevant results. The PA-LNA loop calibration system and algorithm implementation in this embodiment of the invention can achieve a phase error estimation accuracy of 0.01 degrees, an amplitude error estimation accuracy of 0.01 dB, and an overall image rejection ratio below -60 dBc in low signal-to-noise ratio (SNR) scenarios (<10 dB).

[0065] In this document, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A alone, A and B simultaneously, and B alone. Furthermore, the term "at least one" in this document means any combination of at least two of any one or more elements. For example, including at least one of A, B, and C can mean including any one or more elements selected from the set consisting of A, B, and C.

[0066] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0067] Furthermore, in the description of the embodiments of the present invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention based on the specific circumstances.

[0068] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A closed-loop calibration system for IQ imbalance, characterized in that, The system comprises a digital transmitter, a power amplifier, a low-noise amplifier, and a digital receiver connected in sequence, and further includes a digital correlator, a calculation unit, a phase controller, and an IQ imbalance compensator. The power amplifier and the low-noise amplifier are connected via a coupling loop. The digital correlator is connected to the digital transmitter, the digital receiver, and the calculation unit, respectively. The IQ imbalance compensator includes a transmitter compensator and a receiver compensator respectively disposed at one end of the digital transmitter and one end of the digital receiver. The phase controller is connected to the IQ imbalance compensator and is also connected to the power amplifier and / or the low-noise amplifier. The digital transmitter generates a single-tone signal upon triggering a single calibration and sends the corresponding local reference signal to the digital correlator. The single-tone signal passes through the power amplifier and the low-noise amplifier before reaching the digital receiver. The digital receiver sends the received digital signal to the digital correlator. The digital correlator performs cross-correlation calculations on the local reference signal and the received digital signal to obtain a single-correlation result, and sends the single-correlation result to the solution unit. The phase controller is used to adjust the tuning capacitor of the power amplifier and / or the low-noise amplifier to trigger a second calibration; the phase controller is also used to adjust the IQ imbalance compensation phase of the IQ imbalance compensator to trigger a third and a fourth calibration; wherein the tuning capacitor during the third calibration is the same as the tuning capacitor after adjustment during the second calibration, and the tuning capacitor during the fourth calibration is the same as the tuning capacitor before adjustment during the second calibration; The calculation unit is used to obtain the first correlation result corresponding to the first calibration in the initial state, and the second correlation result, third correlation result, and fourth correlation result corresponding to the second calibration, the third calibration, and the fourth calibration, respectively; based on the first correlation result, the second correlation result, the third correlation result, and the fourth correlation result, the IQ imbalance parameter data of the set frequency point is calculated; wherein, the first calibration is triggered by the calibration command of the set frequency point, and the IQ imbalance parameter data includes the IQ imbalance parameters of the digital transmitter and the IQ imbalance parameters of the digital receiver.

2. The system according to claim 1, characterized in that, The digital correlator is specifically used to perform cross-correlation operations on the in-phase reference signal in the local reference signal with the in-phase signal and the quadrature signal in the digital received signal, respectively, and to perform cross-correlation operations on the quadrature reference signal in the local reference signal with the in-phase signal and the quadrature signal in the digital received signal, respectively, to obtain four cross-correlation values.

3. The system according to claim 2, characterized in that, The solution unit is specifically used for: Based on the four cross-correlation values ​​of each single correlation result in the first correlation result, the second correlation result, the third correlation result, and the fourth correlation result, the self-cross-correlation data corresponding to the single correlation result is calculated. The self-cross-correlation data includes the cross-correlation value of the in-phase signal itself, the cross-correlation value of the quadrature signal itself, and the cross-correlation value between the in-phase signal and the quadrature signal. Based on the self-cross-correlation data corresponding to the first correlation result, the second correlation result, the third correlation result, and the fourth correlation result, the objective equation set with the IQ imbalance parameter as the unknown is determined; Solving the objective equations yields the IQ imbalance parameters of the digital transmitter and the digital receiver at the set frequency.

4. The system according to claim 3, characterized in that, The self-cross-correlation data is calculated using the following formula: ； ； ； in, Indicates in-phase signal In-phase reference signal The cross-correlation value, Indicates in-phase signal Orthogonal reference signal The cross-correlation value, Indicates orthogonal signals In-phase reference signal The cross-correlation value, Indicates orthogonal signals Orthogonal reference signal The cross-correlation value, Indicates in-phase signal Its own cross-correlation value, Indicates orthogonal signals Its own cross-correlation value, Indicates in-phase signal and quadrature signals The cross-correlation value between them N Indicates the degree of relevance of the preset.

5. The system according to claim 3, characterized in that, The solution unit is further configured to: obtain the first equation and the second equation based on the self-cross-correlation data corresponding to the first correlation result; obtain the third equation and the fourth equation based on the second correlation result; and obtain the fifth equation and the sixth equation based on the third correlation result and the fourth correlation result. The first equation and the second equation are as follows: ； ； The third equation and the fourth equation are respectively: ； ； The fifth equation is: ;or ； The sixth equation is: ;or ； in, Indicates the first k The in-phase signal in the digital received signal during the second calibration. Indicates the first k The orthogonal signals in the digital received signal during the second calibration. k The values ​​are 1, 2, 3, and 4. This indicates the amplitude imbalance parameter of the digital receiver. This indicates the amplitude imbalance parameter of the digital transmitter. This represents the phase imbalance parameter of the digital receiver. This represents the phase imbalance parameter of the digital transmitter. This indicates the loop phase during the first calibration. This indicates the loop phase during the second calibration. This indicates the adjustment amount of the IQ imbalance compensation phase during the third calibration.

6. The system according to claim 1, characterized in that, The transmitting end compensator is disposed between the digital transmitter and the power amplifier, and a DAC module and an up-converter are also disposed between the transmitting end compensator and the power amplifier; the receiving end compensator is disposed between the low-noise amplifier and the digital receiver, and a down-converter and an ADC module are also disposed between the low-noise amplifier and the receiving end compensator.

7. A closed-loop calibration method for IQ imbalance, characterized in that, The method is applied to the closed-loop calibration system for IQ imbalance according to any one of claims 1-6; the method includes: When a calibration command for a set frequency point is received, the calculation unit obtains the first correlation result output by the digital correlator in the initial state triggered by the set frequency point. The digital correlator is used to perform cross-correlation operation on the local reference signal and the digital received signal when triggering a single calibration to obtain a single correlation result. The local reference signal corresponds to the single-tone signal generated by the digital transmitter, and the digital received signal is the signal received by the digital receiver when the single-tone signal passes through the power amplifier and the low-noise amplifier. The second calibration is triggered by adjusting the tuning capacitor of the power amplifier and / or the low-noise amplifier through the phase controller, and the calculation unit obtains the second correlation result output by the digital correlator. The phase controller adjusts the IQ imbalance compensation phase of the IQ imbalance compensator, and triggers the third and fourth calibrations under the tuning capacitors during the second calibration and the first calibration, respectively. The calculation unit obtains the third and fourth correlation results output by the digital correlator. The calculation unit calculates the IQ imbalance parameter data of the set frequency point based on the first correlation result, the second correlation result, the third correlation result, and the fourth correlation result. The IQ imbalance parameter data includes the IQ imbalance parameters of the digital transmitter and the IQ imbalance parameters of the digital receiver.

8. The method according to claim 7, characterized in that, Perform cross-correlation on the local reference signal and the digital received signal to obtain the single correlation result, including: The in-phase reference signal in the local reference signal is cross-correlated with the in-phase signal and the quadrature signal in the digital received signal, respectively, and the quadrature reference signal in the local reference signal is cross-correlated with the in-phase signal and the quadrature signal in the digital received signal, respectively, to obtain four cross-correlation values.

9. The method according to claim 8, characterized in that, The calculation unit calculates the IQ imbalance parameter data at the set frequency point based on the first correlation result, the second correlation result, the third correlation result, and the fourth correlation result, including: Based on the four cross-correlation values ​​of each single correlation result in the first correlation result, the second correlation result, the third correlation result, and the fourth correlation result, the self-cross-correlation data corresponding to the single correlation result is calculated. The self-cross-correlation data includes the cross-correlation value of the in-phase signal itself, the cross-correlation value of the quadrature signal itself, and the cross-correlation value between the in-phase signal and the quadrature signal. Based on the self-cross-correlation data corresponding to the first correlation result, the second correlation result, the third correlation result, and the fourth correlation result, the objective equation set with the IQ imbalance parameter as the unknown is determined; Solving the objective equations yields the IQ imbalance parameters of the digital transmitter and the digital receiver at the set frequency.

10. The method according to claim 7, characterized in that, The system further includes a storage unit connected to the calculation unit, and the storage unit is also connected to the transmitter compensator and the receiver compensator; the method further includes: The calculation unit acquires IQ imbalance parameter data at multiple different set frequency points; Based on IQ imbalance parameter data from multiple different set frequency points, determine broadband IQ imbalance compensation data; The broadband IQ imbalance compensation data is stored in the storage unit so that the transmitter compensator and the receiver compensator can automatically compensate based on the broadband IQ imbalance compensation data stored in the storage unit during normal operation.

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