CN116781470A - Broadband signal in-phase quadrature imbalance correction method and system - Google Patents
Broadband signal in-phase quadrature imbalance correction method and system Download PDFInfo
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Abstract
The invention provides a method and a system for correcting in-phase and quadrature imbalance of broadband signals, wherein the method comprises the following steps: uniformly selecting N frequency points in the passband range of the broadband signal, and acquiring corresponding I-path digital signals and Q-path digital signals based on a single-tone test signal of each frequency point; generating a frequency domain filter coefficient based on the I-path digital signal and the Q-path digital signal, and performing inverse fast Fourier transform on the frequency domain filter coefficient to obtain a time domain filter coefficient; constructing a complex filter according to the time domain filter coefficients in the time domain, and performing IQ imbalance correction on the broadband signal within the passband range by using the complex filter; n is a natural number, for example an exponent of 2. The invention provides a scheme for carrying out IQ imbalance initialization correction on a broadband signal through a single-tone test signal, which can accurately compensate IQ imbalance parameters of the broadband signal, and realize IQ imbalance initialization correction on the broadband signal, thereby improving the transmission performance of a broadband wireless communication system.
Description
Technical Field
The invention relates to the technical field of communication, in particular to a broadband signal in-phase and quadrature imbalance correction method and system.
Background
Software defined radio has been widely used in the field of wireless communications as an emerging technology. In software radio, a zero intermediate frequency receiver is often used, and the zero intermediate frequency structure has advantages in terms of cost, size, power consumption and the like, but the zero intermediate frequency structure still has some defects, including imbalance of amplitude and phase of IQ (in-phase/quadrature) modulation two-path signals caused by factors such as process angle, mismatch of analog devices and the like, so that mirror image interference signals are generated, and communication quality is reduced. The IQ modulation is that the data is divided into two paths, which are respectively modulated by carriers, and the two paths of carriers are orthogonal to each other.
At present, in an existing scheme, the problem of IQ imbalance is solved from the direction of an analog threshold, but the optimization of circuit performance in the method can lead to the increase of device cost and equipment volume, the reduction of the integration level of a chip, and the problem of IQ imbalance cannot be fundamentally solved.
In addition, in another existing scheme, an amplitude-phase imbalance parameter is obtained by a statistical averaging method, and then an imbalance correction is performed on two paths of IQ signals by adopting the calculated IQ imbalance coefficient. However, this scheme is ideal for correcting a narrowband signal, and for a wideband signal, the amplitude-phase imbalance coefficient is a function of frequency and is not a constant two correction parameters, so that the correction effect on the wideband signal is poor.
Disclosure of Invention
In view of the above-mentioned drawbacks of the prior art, an object of the present invention is to provide a method and a system for correcting in-phase and quadrature imbalance of a wideband signal, which are used for solving the problems in the prior art.
To achieve the above and other related objects, the present invention provides a method for correcting in-phase quadrature imbalance of a wideband signal, comprising the steps of:
uniformly selecting N frequency points in the passband range of the broadband signal, and acquiring corresponding in-phase digital signals and quadrature digital signals based on a single-tone test signal of each frequency point; wherein N is a natural number;
generating a frequency domain filter coefficient based on the in-phase digital signal and the quadrature digital signal, and performing inverse fast fourier transform on the frequency domain filter coefficient to obtain a time domain filter coefficient;
and constructing a complex filter in a time domain according to the time domain filter coefficient, and carrying out in-phase quadrature imbalance correction on a broadband signal in a passband range by utilizing the complex filter.
In one embodiment of the present invention, the process of generating frequency domain filter coefficients based on the in-phase digital signal and the quadrature digital signal comprises:
preprocessing the in-phase digital signal and the quadrature digital signal, and performing fast Fourier transform on the preprocessed in-phase digital signal and quadrature digital signal to obtain a frequency domain signal of the in-phase digital signal and a frequency domain signal of the quadrature digital signal respectively; wherein the preprocessing comprises: filtering direct current components and time domain average;
calculating a phase imbalance parameter and an amplitude imbalance parameter based on the frequency domain signal of the in-phase digital signal and the frequency domain signal of the quadrature digital signal;
and calculating the frequency domain filter coefficient according to the phase unbalance parameter and the amplitude unbalance parameter.
In one embodiment of the present invention, the process of calculating the phase imbalance parameter and the amplitude imbalance parameter based on the frequency domain signal of the in-phase digital signal and the frequency domain signal of the quadrature digital signal includes:
the frequency domain signal of the in-phase digital signal is denoted as X I (f) The frequency domain signal of the orthogonal digital signal is denoted as X Q (f)；
According to X in the frequency domain I (f) And X Q (f) * Product X of (2) I (f)X Q (f) * X in the frequency domain I (f) And X I (f) * Product X of (2) I (f)X I (f) * Calculating phase imbalance parametersAnd an amplitude imbalance parameter α (f) having:
let C (f) =x I (f)X Q (f) * Phase imbalance parameterAmplitude imbalance parameter
Wherein X is I (f) * Conjugation, X of frequency domain signal representing in-phase digital signal Q (f) * Representing the conjugate of the frequency domain signal of the quadrature digital signal.
In an embodiment of the present invention, the calculating the frequency domain filter coefficient according to the phase imbalance parameter and the amplitude imbalance parameter includes:
calculating phase imbalance parametersThe tangent values of (2) are: />The method comprises the steps of,
calculating phase imbalance parametersThe cosine values of (2) are: />The method comprises the steps of,
calculating an amplitude imbalance parameter alpha (f) and a phaseUnbalance parameterCosine value +.>Is a product of (1), and has:
will beAnd->As frequency domain filter coefficients.
In an embodiment of the present invention, the process of uniformly selecting N frequency points in the passband of the wideband signal and obtaining the corresponding in-phase digital signal and quadrature digital signal based on the single-tone test signal of each frequency point includes:
recording a single-tone test signal of a frequency point selected in the passband range of the broadband signal as R (t); wherein R (t) =2 Asin (2pi t (f+f) LO ) +θ), where 2A represents the single tone test signal amplitude, f represents the signal frequency to be calibrated, f LO The local oscillation frequency is represented, and θ represents the initial phase;
introducing amplitude unbalance parameter and phase unbalance parameter after single tone test signal R (t) is transmitted through channel, and recording signal introducing amplitude unbalance parameter and phase unbalance parameter as orthogonal digital signal as X Q (t); and, taking the signal without any error as an in-phase digital signal, denoted as X I (t); wherein X is I (t)＝Asin(2πtf+θ)，In (1) the->Representing phase imbalance parameters, alpha (f) tableShowing the amplitude imbalance parameters.
In an embodiment of the present invention, after obtaining the in-phase digital signal and the quadrature digital signal, the method further includes:
quadrature down-conversion is carried out on the in-phase digital signal and the quadrature digital signal, so that an ideal equivalent baseband signal is obtained; the method comprises the following steps:
Z I (t)＝Asin(2πtf+θ)；
Z Q (t)＝-Acos(2πtf+θ)；
wherein Z is I (t) represents an ideal equivalent baseband signal of an in-phase digital signal, Z Q (t) represents an ideal equivalent baseband signal of the quadrature digital signal.
The invention also provides a broadband signal in-phase quadrature imbalance correction system, which comprises:
the observation module is used for receiving the in-phase digital signal and the quadrature digital signal, preprocessing the in-phase digital signal and the quadrature digital signal, and performing fast Fourier transform on the preprocessed in-phase digital signal and the preprocessed quadrature digital signal to respectively obtain a frequency domain signal of the in-phase digital signal and a frequency domain signal of the quadrature digital signal; the in-phase digital signal and the quadrature digital signal are uniformly selected from N frequency points in the passband range of the broadband signal, and are obtained based on a single-tone test signal of each frequency point; the pretreatment comprises the following steps: filtering direct current components and time domain average; wherein N is a natural number;
the analysis module is used for calculating phase unbalance parameters and amplitude unbalance parameters according to the frequency domain signals of the in-phase digital signals and the frequency domain signals of the quadrature digital signals;
a calculation module, configured to calculate the frequency domain filter coefficient according to the phase imbalance parameter and the amplitude imbalance parameter;
the fast Fourier inverse transformation module is used for carrying out fast Fourier inverse transformation on the frequency domain filter coefficients to obtain time domain filter coefficients; and constructing a complex filter in the time domain according to the time domain filter coefficients;
and the complex filter is used for carrying out in-phase and quadrature imbalance correction on the broadband signal in the passband range.
In an embodiment of the present invention, the process of calculating the phase imbalance parameter and the amplitude imbalance parameter by the analysis module according to the frequency domain signal of the in-phase digital signal and the frequency domain signal of the quadrature digital signal includes:
the frequency domain signal of the in-phase digital signal is denoted as X I (f) The frequency domain signal of the orthogonal digital signal is denoted as X Q (f)；
According to X in the frequency domain I (f) And X Q (f) * Product X of (2) I (f)X Q (f) * X in the frequency domain I (f) And X I (f) * Product X of (2) I (f)X I (f) * Calculating phase imbalance parametersAnd an amplitude imbalance parameter α (f) having:
let C (f) =x I (f)X Q (f) * Phase imbalance parameterAmplitude imbalance parameter
Wherein,, I (f) * conjugation, X of frequency domain signal representing in-phase digital signal Q (f) * Representing the conjugate of the frequency domain signal of the quadrature digital signal.
In an embodiment of the present invention, the calculating module calculates the frequency domain filter coefficient according to the phase imbalance parameter and the amplitude imbalance parameter, including:
calculating phase imbalance parametersThe tangent values of (2) are: />The method comprises the steps of,
calculating phase imbalance parametersThe cosine values of (2) are: />The method comprises the steps of,
calculating an amplitude imbalance parameter alpha (f) and a phase imbalance parameterCosine value +.>Is a product of (1), and has:
will beAnd->As frequency domain filter coefficients.
In an embodiment of the present invention, the process of the observation module uniformly selecting N frequency points in a passband range of a wideband signal and obtaining corresponding in-phase digital signals and quadrature digital signals based on a single-tone test signal of each frequency point includes:
recording a single-tone test signal of a frequency point selected in the passband range of the broadband signal as R (t); wherein R (t) =2 Asin (2pi t (f+f) LO ) +θ), where 2A represents the single tone test signal amplitude, f represents the signal frequency to be calibrated, f LO The local oscillation frequency is represented, and θ represents the initial phase;
introducing amplitude unbalance parameter and phase unbalance parameter after single tone test signal R (t) is transmitted through channel, and making signal simultaneously introducing amplitude unbalance parameter and phase unbalance parameterIs a quadrature digital signal, denoted as X Q (t); and, taking the signal without any error as an in-phase digital signal, denoted as X I (t); wherein X is I (t)＝Asin(2πtf+θ)，In (1) the->Represents a phase imbalance parameter, and α (f) represents an amplitude imbalance parameter.
As described above, the present invention provides a method and a system for correcting in-phase and quadrature imbalance of a wideband signal, which have the following advantages: according to the invention, N frequency points are uniformly selected in the passband range of the broadband signal, and corresponding in-phase digital signals and quadrature digital signals are obtained based on the single-tone test signal of each frequency point; generating a frequency domain filter coefficient based on the in-phase digital signal and the quadrature digital signal, and performing inverse fast Fourier transform on the frequency domain filter coefficient to obtain a time domain filter coefficient; and finally, constructing a complex filter in a time domain according to the time domain filter coefficient, and carrying out in-phase quadrature imbalance correction on the broadband signal in the passband range by utilizing the complex filter. Where N is a natural number, for example, may be an exponent of 2. Therefore, the invention provides a scheme for carrying out the in-phase and quadrature unbalanced initialization correction of the broadband signal through the single-tone test signal, which can accurately compensate the in-phase and quadrature unbalanced parameters of the broadband signal, and realize the in-phase and quadrature unbalanced initialization correction of the broadband signal, thereby improving the transmission performance of the broadband wireless communication system. In addition, the digital threshold calibration technology has good flexibility, so the invention can also estimate and compensate IQ imbalance parameters of the received baseband signal, thereby inhibiting the generation of image interference signals.
Drawings
FIG. 1 is a flow chart of a method for correcting an in-phase quadrature imbalance of a wideband signal according to an embodiment of the invention;
FIG. 2 is a schematic diagram of an in-phase and quadrature imbalance initialization correction procedure for wideband signals according to an embodiment of the present invention;
FIG. 3 is a schematic circuit diagram of a complex filter according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of an in-phase and quadrature imbalance initialization correction circuit for wideband signals according to an embodiment of the present invention;
fig. 5 is a schematic hardware structure of a wideband signal in-phase quadrature imbalance correction system according to an embodiment of the invention.
Detailed Description
Other advantages and effects of the present invention will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present invention with reference to specific examples. The invention may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present invention. It should be noted that the following embodiments and features in the embodiments may be combined with each other without conflict.
It should be noted that, the illustrations provided in the present embodiment merely illustrate the basic concept of the present invention by way of illustration, and only the components related to the present invention are shown in the drawings and are not drawn according to the number, shape and size of the components in actual implementation, and the form, number and proportion of the components in actual implementation may be arbitrarily changed, and the layout of the components may be more complex.
Fig. 1 is a schematic flow chart of a wideband signal in-phase quadrature imbalance correction method according to an embodiment of the invention. Specifically, in an exemplary embodiment, as shown in fig. 1, the present embodiment provides a wideband signal in-phase quadrature imbalance correction method, which includes the steps of:
s110, uniformly selecting N frequency points in the passband range of the broadband signal, and acquiring corresponding in-phase digital signals and quadrature digital signals based on a single-tone test signal of each frequency point; wherein N is a natural number, for example, may be an exponent of 2; as an example, N may be an exponent of 32, 64, 128, etc. that is above the power of 4 of 2. In this or other embodiments, the in-phase digital signal may also be referred to as an I (in-phase) path digital signal, and the quadrature digital signal may also be referred to as a Q (quadrature) path digital signal.
S120, generating a frequency domain filter coefficient based on the in-phase digital signal and the quadrature digital signal, and performing inverse fast Fourier transform on the frequency domain filter coefficient to obtain a time domain filter coefficient;
s130, constructing a complex filter according to the time domain filter coefficient in the time domain, and carrying out in-phase quadrature imbalance correction on the broadband signal in the passband range by utilizing the complex filter.
Therefore, the present embodiment provides a scheme for carrying out wideband signal in-phase and quadrature imbalance initialization correction through a single tone test signal, which can accurately compensate in-phase and quadrature imbalance parameters of the wideband signal, and realize the in-phase and quadrature imbalance initialization correction of the wideband signal, thereby improving transmission performance of the wideband wireless communication system.
According to the above description, in an exemplary embodiment, the process of generating the frequency domain filter coefficient based on the in-phase digital signal and the quadrature digital signal in step S120 includes: preprocessing an in-phase digital signal and a quadrature digital signal, and performing fast Fourier transform on the preprocessed in-phase digital signal and the preprocessed quadrature digital signal to respectively obtain a frequency domain signal of the in-phase digital signal and a frequency domain signal of the quadrature digital signal; wherein the preprocessing comprises the following steps: the direct current component is filtered and the time domain average is carried out. A phase imbalance parameter and an amplitude imbalance parameter are calculated based on the frequency domain signal of the in-phase digital signal and the frequency domain signal of the quadrature digital signal. Frequency domain filter coefficients are calculated based on the phase imbalance parameters and the amplitude imbalance parameters.
As an example, in the present embodiment, the process of calculating the phase imbalance parameter and the amplitude imbalance parameter based on the frequency domain signal of the in-phase digital signal and the frequency domain signal of the quadrature digital signal includes: the frequency domain signal of the in-phase digital signal is denoted as X I (f) The frequency domain signal of the orthogonal digital signal is denoted as X Q (f) The method comprises the steps of carrying out a first treatment on the surface of the According to X in the frequency domain I (f) And X Q (f) * Product of (2)X I (f)X Q (f) * X in the frequency domain I (f) And X I (f) * Product X of (2) I (f)X I (f) * Calculating phase imbalance parametersAnd an amplitude imbalance parameter α (f) having: let C (f) =x I (f)X Q (f) * Phase imbalance parameter->Amplitude imbalance parameter->Wherein X is I (f) * Conjugation, X of frequency domain signal representing in-phase digital signal Q (f) * Representing the conjugate of the frequency domain signal of the quadrature digital signal.
As an example, in the present embodiment, the process of calculating the frequency domain filter coefficients from the phase imbalance parameter and the amplitude imbalance parameter includes: calculating phase imbalance parametersThe tangent values of (2) are: />And, calculating a phase imbalance parameter +.>The cosine values of (2) are: />And calculating an amplitude imbalance parameter alpha (f) and a phase imbalance parameterCosine value +.>Is a product of (1), and has: />Will->And->As frequency domain filter coefficients.
According to the above description, in an exemplary embodiment, step S110 uniformly selects N frequency points within the passband of the wideband signal, and the process of obtaining the corresponding in-phase digital signal and quadrature digital signal based on the single tone test signal of each frequency point includes: recording a single-tone test signal of a frequency point selected in the passband range of the broadband signal as R (t); wherein R (t) =2 Asin (2pi t (f+f) LO ) +θ), where 2A represents the single tone test signal amplitude, f represents the signal frequency to be calibrated, f LO The local oscillation frequency is represented, and θ represents the initial phase; introducing amplitude unbalance parameter and phase unbalance parameter after single tone test signal R (t) is transmitted through channel, and recording signal introducing amplitude unbalance parameter and phase unbalance parameter as orthogonal digital signal as X Q (t); and, taking the signal without any error as an in-phase digital signal, denoted as X I (t); wherein X is I (t)＝Asin(2πtf+θ)，In (1) the->Represents a phase imbalance parameter, and α (f) represents an amplitude imbalance parameter.
According to the above description, in an exemplary embodiment, after the in-phase digital signal and the quadrature digital signal are acquired, the present embodiment may further include: quadrature down-conversion is carried out on the in-phase digital signal and the quadrature digital signal, so that an ideal equivalent baseband signal is obtained; the method comprises the following steps: z is Z I (t)＝Asin(2πtf+θ)；Z Q (t) = -Acos (2pi tf+θ); wherein Z is I (t) represents an ideal equivalent baseband signal of an in-phase digital signal, Z Q (t) represents an ideal equivalent baseband signal of the quadrature digital signal.
As shown in fig. 2, in another exemplary embodiment of the present invention, this embodiment further provides a wideband in-phase quadrature signal imbalance correction method, including the steps of:
step one, according to the sampling frequency f of the receiving system s Uniformly selecting N frequency points in the passband range, and sequentially transmitting a single-tone test signal corresponding to each frequency point; IQ two paths of digital signals received by the correction circuit are X I (t) and X Q (t). Wherein N is a natural number, for example, may be an exponent of 2; as an example, N may be an exponent of 32, 64, 128, etc. that is above the power of 4 of 2. As an example, the receiving system in the present embodiment may be a zero intermediate frequency receiver system. Wherein the correction circuit is shown in fig. 4.
Step two, direct current components of the IQ two paths of signals are filtered respectively, and time domain averaging is carried out on the I path of digital signals and the Q path of digital signals;
step three, respectively performing fast Fourier transform on the I path signal and the Q path signal to obtain X I (f) And X Q (f) In rectangular form;
step four, performing correlation calculation in a frequency domain to obtain X I (f)X Q (f) * 、X I (f)X I (f) * And C (f) in rectangular form, and performing frequency domain averaging;
step five, converting C (f) into a form of amplitude phase angle, and then calculating a phase imbalance parameterAnd amplitude imbalance parameter->
Step six, obtaining N (i.e. N frequency points) frequency domain filter coefficients according to the construction mode of the complex filter.
And seventhly, obtaining N time domain filter coefficients through inverse fast Fourier transform, and completing construction of a complex filter in a time domain.
And step eight, after the received digital signal is filtered by a complex filter, IQ imbalance initialization correction is completed.
Specifically, theoretical analysis work of the IQ imbalance problem of the reception path will be described below.
As shown in fig. 3, the transmitted Radio Frequency (RF) signal R (t) is split into two paths IQ at the receiving end after being transmitted through a channel. The I path is used as a reference, no error is introduced, all errors are introduced in the Q path, and the amplitude imbalance coefficient and the phase imbalance coefficient of the Q path signal are deviations relative to the I path signal and are relative values rather than absolute values.
Assume that the input tone test signal is: r (t) =2asin (2pi t (f+f) LO ) +θ), wherein 2A is the single tone test signal amplitude, f is the signal frequency to be calibrated, f LO For the local oscillation frequency, θ is the initial phase, the ideal equivalent baseband signal obtained after the quadrature down-conversion of the two paths of IQ is: z is Z I (t)＝Asin(2πtf+θ)，Z Q (t) = -Acos (2pi tf+θ); wherein Z is I (t) ideal equivalent baseband signal representing I-path digital signal, Z Q And (t) represents an ideal equivalent baseband signal of the Q-way digital signal.
Next, in this embodiment, the I-path is used as a reference signal, and the amplitude imbalance coefficient and the phase imbalance coefficient are introduced into the Q-path. For wideband correction, both the phase imbalance coefficient and the amplitude imbalance coefficient will have the characteristics of frequency f.
The introduced amplitude imbalance coefficient is alpha (f), and the introduced phase imbalance coefficient isThe IQ two paths of signals to be calibrated are obtained as follows: x is X I (t) =asin (2pi tf+θ) and +.>
After fourier transformation, expressed in exponential form, there are: x is X I (f)＝Me jφ(f) M is X I (f) Phi (f) is X I (f) Is used for the reference phase of the reference phase(s).
Let C (f) =x I (f)X Q (f) * ThenThus, the phase imbalance parameter can be obtainedAnd the amplitude imbalance parameters α (f) are respectively: />
In addition, the manner of construction of the complex filter will be analyzed below.
Assume that after the above processing, IQ two paths of signals of the remaining amplitude imbalance coefficient and the phase imbalance coefficient are respectively: i=asin (θ),
constructing complex filtersThe filtering process is as follows:
after filtering, the embodiment only takes the Q path as follows:
it can be seen that after filtering by the complex filter, the IQ two paths are completely orthogonal.
Based on the above description, the complex filter circuit principle in this embodiment is shown in fig. 3, and the frequency response of the complex filter CFIR is constructed as follows:
and obtaining a time domain filter coefficient by carrying out inverse fast Fourier transform on the frequency domain filter coefficient, and after the IQ two paths of signals are filtered by a complex filter in the time domain, completely orthogonalizing the IQ two paths of signals.
According to the above description, in one test example, in order to implement wideband IQ imbalance wideband calibration, the present embodiment may select 64 sampling points within a frequency band range, and 32 positive and negative frequency points respectively; 64 frequency points are evenly distributed in the whole passband range, auxiliary single-tone test signals corresponding to each frequency point are independently transmitted each time, each single-tone signal generates a frequency domain filter coefficient, 64 frequency domain filter coefficients in total are obtained after IFFT (Inverse Fast Fourier Transform ) is carried out, then a complex filter is constructed in the time domain to correct IQ data, and IQ imbalance initialization correction of the whole channel is completed.
In summary, the invention provides a method for correcting in-phase and quadrature imbalance of a wideband signal, which comprises the steps of uniformly selecting N frequency points in a passband range of the wideband signal, and acquiring corresponding in-phase digital signals and quadrature digital signals based on a single-tone test signal of each frequency point; generating a frequency domain filter coefficient based on the in-phase digital signal and the quadrature digital signal, and performing inverse fast Fourier transform on the frequency domain filter coefficient to obtain a time domain filter coefficient; and finally, constructing a complex filter in a time domain according to the time domain filter coefficient, and carrying out in-phase quadrature imbalance correction on the broadband signal in the passband range by utilizing the complex filter. Where N is a natural number, for example, may be an exponent of 2. Therefore, the method provides a scheme for carrying out the in-phase and quadrature unbalanced initialization correction of the broadband signal through the single-tone test signal, can accurately compensate in-phase and quadrature unbalanced parameters of the broadband signal, and realizes the in-phase and quadrature unbalanced initialization correction of the broadband signal, thereby improving the transmission performance of the broadband wireless communication system. In addition, the digital threshold calibration technology has good flexibility, so the method can also estimate and compensate IQ imbalance parameters of the received baseband signal, thereby inhibiting the generation of image interference signals.
In another exemplary embodiment of the present invention, as shown in fig. 5, the embodiment further provides a wideband signal in-phase quadrature imbalance correction system, the system comprising:
the observation module 510 is configured to receive the in-phase digital signal and the quadrature digital signal, perform preprocessing on the in-phase digital signal and the quadrature digital signal, and perform fast fourier transform on the in-phase digital signal and the quadrature digital signal after the preprocessing, so as to obtain a frequency domain signal of the in-phase digital signal and a frequency domain signal of the quadrature digital signal, respectively; the method comprises the steps that in-phase digital signals and quadrature digital signals are uniformly selected from N frequency points in the passband range of a broadband signal, and the in-phase digital signals and the quadrature digital signals are obtained based on a single-tone test signal of each frequency point; the pretreatment comprises the following steps: filtering direct current components and time domain average; wherein N is a natural number, for example, may be an exponent of 2; as an example, N may be an exponent of 32, 64, 128, etc. that is above the power of 4 of 2.
An analysis module 520 for calculating a phase imbalance parameter and an amplitude imbalance parameter from the frequency domain signal of the in-phase digital signal and the frequency domain signal of the quadrature digital signal;
a calculation module 530, configured to calculate frequency domain filter coefficients according to the phase imbalance parameter and the amplitude imbalance parameter;
an inverse fast fourier transform module 540, configured to perform inverse fast fourier transform on the frequency domain filter coefficients to obtain time domain filter coefficients; and constructing a complex filter in the time domain according to the time domain filter coefficients;
a complex filter 550 for in-phase quadrature imbalance correction of the wideband signal in the passband range.
Therefore, the present embodiment provides a scheme for carrying out wideband signal in-phase and quadrature imbalance initialization correction through a single tone test signal, which can accurately compensate in-phase and quadrature imbalance parameters of the wideband signal, and realize the in-phase and quadrature imbalance initialization correction of the wideband signal, thereby improving transmission performance of the wideband wireless communication system.
In accordance with the above description, in an exemplary embodiment, the process of calculating the phase imbalance parameter and the amplitude imbalance parameter by the analysis module 520 according to the frequency domain signal of the in-phase digital signal and the frequency domain signal of the quadrature digital signal includes: the frequency domain signal of the in-phase digital signal is denoted as X I (f) The frequency domain signal of the orthogonal digital signal is denoted as X Q (f) The method comprises the steps of carrying out a first treatment on the surface of the According to X in the frequency domain I (f) And X Q (f) * Product X of (2) I (f)X Q (f) * X in the frequency domain I (f) And X I (f) * Product X of (2) I (f)X I (f) * Calculating phase imbalance parametersAnd an amplitude imbalance parameter α (f) having: let C (f) =x I (f)X Q (f) * Phase imbalance parameterAmplitude imbalance parameter->Wherein X is I (f) * Conjugation, X of frequency domain signal representing in-phase digital signal Q (f) * Representing the conjugate of the frequency domain signal of the quadrature digital signal.
In accordance with the foregoing, in an exemplary embodiment, the calculating module 530 calculates the frequency domain filter coefficients according to the phase imbalance parameter and the amplitude imbalance parameter, including: calculating phase imbalance parametersThe tangent values of (2) are:and, calculating a phase imbalance parameter +.>The cosine values of (2) are: />And, calculating an amplitude imbalance parameter α (f) and a phase imbalance parameter +.>Cosine value +.>Is a product of (1), and has: />Will beAnd->As frequency domain filter coefficients.
According to the above description, in an exemplary embodiment, the process of the observation module 510 uniformly selecting N frequency points within the passband of the wideband signal and obtaining the corresponding in-phase digital signal and quadrature digital signal based on the single tone test signal of each frequency point includes: recording a single-tone test signal of a frequency point selected in the passband range of the broadband signal as R (t); wherein R (t) =2 Asin (2pi t (f+f) LO ) +θ), where 2A represents the single tone test signal amplitude, f represents the signal frequency to be calibrated, f LO The local oscillation frequency is represented, and θ represents the initial phase; introducing amplitude unbalance parameter and phase unbalance parameter after single tone test signal R (t) is transmitted through channel, and recording signal introducing amplitude unbalance parameter and phase unbalance parameter as orthogonal digital signal as X Q (t); and, taking the signal without any error as an in-phase digital signal, denoted as X I (t); wherein the method comprises the steps of，X I (t)＝Asin(2πtf+θ)，In (1) the->Represents a phase imbalance parameter, and α (f) represents an amplitude imbalance parameter.
In another example embodiment of the present invention, the embodiment further provides a wideband in-phase quadrature signal imbalance correction system comprising an IQ imbalance correction circuit. The IQ imbalance correction circuit in this embodiment is shown in fig. 4. Specifically, the correction circuit may be divided into 3 parts, which are observation paths single: observe→analysis→calculation, IFFT block and correction filter: CFIR.
The observation path single mainly completes observation of the frequency point f single-tone signal, unbalanced parameter extraction and frequency domain recorder coefficient calculation of the frequency point.
The observation module observer is used for completing the observation function of the IQ signal and calculating to obtain the X of the single-tone signal at the f frequency point I (f)X Q (f) * And |X I (f) 2 ＝X I (f)×X I (f) * Values. The observation module observ can be further divided into a DCC/TDA module, an FFT module and an SEP/FDA module. The DDC/TDA function is to filter the direct current component of the IQ two-wheel signal and to time-domain average the I, Q two paths of data. And the FFT module performs FFT operation on the time-domain averaged signal to obtain frequency-domain signal data, and then the SEP/FDA module calculates a required result and performs frequency-domain averaging.
The analysis module analysis converts C (f) of the frequency point f into a mode value phase angle form, and then calculates an amplitude imbalance parameter and a phase imbalance parameter of the frequency point.
The calculation module calculates frequency domain filter coefficients of the correction filter CFIR by receiving information such as phase imbalance parameters and amplitude imbalance parameters from the analysis module analysis.
And the Inverse Fast Fourier Transform (IFFT) module converts the frequency domain filter coefficients into time domain filter coefficients and sends the time domain filter coefficients to the correction filter for use, and finally the correction filter finishes correction of the IQ received data.
According to the above description, specifically, the processing procedure for one pair of frequency points is as follows: after the observation module calculates the frequency domain parameters of the positive frequency point, the corresponding negative frequency point single tone test signal is input, the observation module calculates the frequency domain parameters of the negative frequency point, then the observation channel receives the frequency domain parameters of the positive and negative frequency points, the calculation of the amplitude imbalance coefficient and the phase imbalance coefficient is completed, the frequency domain filter coefficient of the frequency point is obtained, the time domain filter coefficient of the frequency point after passing through the IFFT module is obtained, and then the filter coefficient of the next frequency point is calculated.
According to the above description, in one test example, in order to implement wideband IQ imbalance wideband calibration, the present embodiment may select 64 sampling points within a frequency band range, and 32 positive and negative frequency points respectively; 64 frequency points are evenly distributed in the whole passband range, auxiliary single-tone test signals corresponding to each frequency point are independently transmitted each time, each single-tone signal generates a frequency domain filter coefficient, 64 frequency domain filter coefficients are obtained after IFFT, then a complex filter is constructed in the time domain to correct IQ data, and IQ imbalance initialization correction of the whole channel is completed.
In summary, the invention provides a wideband signal in-phase quadrature imbalance correction system, which is characterized in that N frequency points are uniformly selected in the passband range of a wideband signal, and corresponding in-phase digital signals and quadrature digital signals are obtained based on a single-tone test signal of each frequency point; generating a frequency domain filter coefficient based on the in-phase digital signal and the quadrature digital signal, and performing inverse fast Fourier transform on the frequency domain filter coefficient to obtain a time domain filter coefficient; and finally, constructing a complex filter in a time domain according to the time domain filter coefficient, and carrying out in-phase quadrature imbalance correction on the broadband signal in the passband range by utilizing the complex filter. Wherein N is a natural number, for example, may be an exponent of 2. Therefore, the system provides a scheme for carrying out the in-phase and quadrature unbalanced initialization correction of the broadband signal through the single-tone test signal, can accurately compensate in-phase and quadrature unbalanced parameters of the broadband signal, and realizes the in-phase and quadrature unbalanced initialization correction of the broadband signal, thereby improving the transmission performance of the broadband wireless communication system. In addition, the digital threshold calibration technology has good flexibility, so the system can also estimate and compensate IQ imbalance parameters of a received baseband signal, thereby inhibiting the generation of image interference signals.
It should be noted that, the wideband signal in-phase quadrature imbalance correction system provided in the above embodiment and the wideband signal in-phase quadrature imbalance correction method provided in the above embodiment belong to the same concept, and the specific manner in which each module performs the operation has been described in detail in the method embodiment, which is not repeated here. In practical application, the wideband signal in-phase quadrature imbalance correction system provided in the above embodiment may be implemented by different functional modules according to needs, that is, the internal structure of the system is divided into different functional modules to implement all or part of the functions described above, which is not limited herein. Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.
It should be understood that although the terms first, second, third, etc. may be used to describe the preset ranges, etc. in the embodiments of the present invention, these preset ranges should not be limited to these terms. These terms are only used to distinguish one preset range from another. For example, a first preset range may also be referred to as a second preset range, and similarly, a second preset range may also be referred to as a first preset range without departing from the scope of embodiments of the present invention.
The above embodiments are merely illustrative of the principles of the present invention and its effectiveness, and are not intended to limit the invention. Modifications and variations may be made to the above-described embodiments by those skilled in the art without departing from the spirit and scope of the invention. Accordingly, it is intended that all equivalent modifications and variations of the invention be covered by the claims, which are within the ordinary skill of the art, be within the spirit and scope of the present disclosure.
Claims (10)
1. A method for correcting wideband signal in-phase quadrature imbalance, the method comprising the steps of:
uniformly selecting N frequency points in the passband range of the broadband signal, and acquiring corresponding in-phase digital signals and quadrature digital signals based on a single-tone test signal of each frequency point; wherein N is a natural number;
generating a frequency domain filter coefficient based on the in-phase digital signal and the quadrature digital signal, and performing inverse fast fourier transform on the frequency domain filter coefficient to obtain a time domain filter coefficient;
and constructing a complex filter in a time domain according to the time domain filter coefficient, and carrying out in-phase quadrature imbalance correction on a broadband signal in a passband range by utilizing the complex filter.
2. The method of claim 1, wherein generating frequency domain filter coefficients based on the in-phase digital signal and the quadrature digital signal comprises:
preprocessing the in-phase digital signal and the quadrature digital signal, and performing fast Fourier transform on the preprocessed in-phase digital signal and quadrature digital signal to obtain a frequency domain signal of the in-phase digital signal and a frequency domain signal of the quadrature digital signal respectively; wherein the preprocessing comprises: filtering direct current components and time domain average;
calculating a phase imbalance parameter and an amplitude imbalance parameter based on the frequency domain signal of the in-phase digital signal and the frequency domain signal of the quadrature digital signal;
and calculating the frequency domain filter coefficient according to the phase unbalance parameter and the amplitude unbalance parameter.
3. The method of correcting wideband signal in-phase-quadrature imbalance as claimed in claim 2, wherein the process of calculating the phase imbalance parameter and the amplitude imbalance parameter based on the frequency domain signal of the in-phase digital signal and the frequency domain signal of the quadrature digital signal comprises:
the frequency domain signal of the in-phase digital signal is denoted as X I (f) The frequency domain signal of the orthogonal digital signal is denoted as X Q (f)；
According to X in the frequency domain I (f) And X Q (f) * Product X of (2) I (f)X Q (f) * X in the frequency domain I (f) And X I (f) * Product X of (2) I (f)X I (f) * Calculating phase imbalance parametersAnd an amplitude imbalance parameter α (f) having:
let C (f) =x I (f)X Q (f) * Phase imbalance parameterAmplitude imbalance parameter
Wherein X is I (f) * Conjugation, X of frequency domain signal representing in-phase digital signal Q (f) * Representing the conjugate of the frequency domain signal of the quadrature digital signal.
4. A wideband signal in-phase quadrature imbalance correction method as claimed in claim 3, wherein the process of calculating the frequency domain filter coefficients from the phase imbalance parameter and the amplitude imbalance parameter comprises:
calculating phase imbalance parametersThe tangent values of (2) are: />The method comprises the steps of,
calculating phase imbalance parametersThe cosine values of (2) are: />The method comprises the steps of,
calculating an amplitude imbalance parameter alpha (f) and a phase imbalance parameterCosine value +.>Is a product of (1), and has:
will beAnd->As frequency domain filter coefficients.
5. The method for correcting in-phase and quadrature imbalance of wideband signals according to any one of claims 1 to 4, wherein the process of uniformly selecting N frequency points in the passband of the wideband signals and obtaining corresponding in-phase digital signals and quadrature digital signals based on the single tone test signal of each frequency point comprises:
recording a single-tone test signal of a frequency point selected in the passband range of the broadband signal as R (t); wherein R (t) =2 Asin (2pi t (f+f) LO ) +θ), where 2A represents the single tone test signal amplitude, f represents the signal frequency to be calibrated, f LO The local oscillation frequency is represented, and θ represents the initial phase;
at a single toneThe test signal R (t) is transmitted through the channel and then is introduced with the amplitude unbalance parameter and the phase unbalance parameter, and the signal which is simultaneously introduced with the amplitude unbalance parameter and the phase unbalance parameter is taken as the quadrature digital signal and is marked as X Q (t); and, taking the signal without any error as an in-phase digital signal, denoted as X I (t); wherein X is I (t)＝Asin(2πtf+θ)，In (1) the->Represents a phase imbalance parameter, and α (f) represents an amplitude imbalance parameter.
6. The method of claim 5, further comprising, after the in-phase digital signal and the quadrature digital signal are obtained:
quadrature down-conversion is carried out on the in-phase digital signal and the quadrature digital signal, so that an ideal equivalent baseband signal is obtained; the method comprises the following steps:
Z I (t)＝Asin(2πtf+θ)；
Z Q (t)＝-Acos(2πtf+θ)；
wherein Z is I (t) represents an ideal equivalent baseband signal of an in-phase digital signal, Z Q (t) represents an ideal equivalent baseband signal of the quadrature digital signal.
7. A wideband signal in-phase quadrature imbalance correction system, the system comprising:
the observation module is used for receiving the in-phase digital signal and the quadrature digital signal, preprocessing the in-phase digital signal and the quadrature digital signal, and performing fast Fourier transform on the preprocessed in-phase digital signal and the preprocessed quadrature digital signal to respectively obtain a frequency domain signal of the in-phase digital signal and a frequency domain signal of the quadrature digital signal; the in-phase digital signal and the quadrature digital signal are uniformly selected from N frequency points in the passband range of the broadband signal, and are obtained based on a single-tone test signal of each frequency point; the pretreatment comprises the following steps: filtering direct current components and time domain average; wherein N is a natural number;
the analysis module is used for calculating phase unbalance parameters and amplitude unbalance parameters according to the frequency domain signals of the in-phase digital signals and the frequency domain signals of the quadrature digital signals;
a calculation module, configured to calculate the frequency domain filter coefficient according to the phase imbalance parameter and the amplitude imbalance parameter;
the fast Fourier inverse transformation module is used for carrying out fast Fourier inverse transformation on the frequency domain filter coefficients to obtain time domain filter coefficients; and constructing a complex filter in the time domain according to the time domain filter coefficients;
and the complex filter is used for carrying out in-phase and quadrature imbalance correction on the broadband signal in the passband range.
8. The wideband signal in-phase-quadrature imbalance correction system of claim 7, wherein the process of calculating the phase imbalance parameter and the amplitude imbalance parameter from the frequency domain signal of the in-phase digital signal and the frequency domain signal of the quadrature digital signal by the analysis module comprises:
the frequency domain signal of the in-phase digital signal is denoted as X I (f) The frequency domain signal of the orthogonal digital signal is denoted as X Q (f)；
According to X in the frequency domain I (f) And X Q (f) * Product X of (2) I (f)X Q (f) * X in the frequency domain I (f) And X I (f) * Product X of (2) I (f)X I (f) * Calculating phase imbalance parametersAnd an amplitude imbalance parameter α (f) having:
let C (f) =x I (f)X Q (f) * Phase imbalance parameterAmplitude imbalance parameter
Wherein X is I (f) * Conjugation, X of frequency domain signal representing in-phase digital signal Q (f) * Representing the conjugate of the frequency domain signal of the quadrature digital signal.
9. The wideband signal in-phase quadrature imbalance correction system of claim 8, wherein the computing module computes the frequency domain filter coefficients based on the phase imbalance parameter and the amplitude imbalance parameter comprises:
calculating phase imbalance parametersThe tangent values of (2) are: />The method comprises the steps of,
calculating phase imbalance parametersThe cosine values of (2) are: />The method comprises the steps of,
calculating an amplitude imbalance parameter alpha (f) and a phase imbalance parameterCosine value +.>Is a product of (1), and has:
will beAnd->As frequency domain filter coefficients.
10. The wideband signal in-phase quadrature imbalance correction system of any one of claims 7 to 9, wherein the process of the observation module uniformly selecting N frequency points within the passband of the wideband signal and acquiring corresponding in-phase digital signals and quadrature digital signals based on the single tone test signal of each frequency point comprises:
recording a single-tone test signal of a frequency point selected in the passband range of the broadband signal as R (t); wherein R (t) =2 Asin (2pi t (f+f) LO ) +θ), where 2A represents the single tone test signal amplitude, f represents the signal frequency to be calibrated, f LO The local oscillation frequency is represented, and θ represents the initial phase;
introducing amplitude unbalance parameter and phase unbalance parameter after single tone test signal R (t) is transmitted through channel, and recording signal introducing amplitude unbalance parameter and phase unbalance parameter as orthogonal digital signal as X Q (t); and, taking the signal without any error as an in-phase digital signal, denoted as X I (t); wherein X is I (t)＝Asin(2πtf+θ)，In (1) the->Represents a phase imbalance parameter, and α (f) represents an amplitude imbalance parameter.
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