CN112051555A - Digital IQ calibration method based on complex signal spectrum operation - Google Patents
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Abstract
The invention discloses a digital IQ calibration method based on complex signal spectrum operation, which comprises the following steps: a frequency-dependent IQ imbalance in a receiver is compensated by receiving an echo complex signal synthesized by an IQ signal in a radar transceiving system and adding a group of calibration parameters to a frequency point of the echo complex signal. The calibration parameters are obtained through signal frequency domain change, and the process is as follows: modeling an IQ error term into a two-side error part and a one-side error part, performing frequency domain processing on an echo signal by using the characteristics of a two-side spectrum and a one-side spectrum, respectively calculating the frequency spectrums of the two error signals through the linear combination of the full frequency band and the negative frequency band of the echo signal, and forming frequency point related calibration parameters by the frequency spectrums; and finally, overlapping frequency point related calibration parameters of the initial echo signal on a frequency domain to finish calibration. According to the invention, an effective frequency-dependent IQ amplitude-phase imbalance calibration method is provided, and the overall performance of the radar system is improved.
Description
Technical Field
The invention relates to the technical field of radar signal receiving and transmitting, in particular to a digital IQ calibration method based on complex signal frequency spectrum operation.
Background
With the development of radar signal transceiving technology, the performance and structure of a signal transceiver directly affect the whole radar system.
The superheterodyne receiver is used as a common signal receiver, receives echoes reflected by a target, mixes the echoes to obtain an intermediate frequency signal, and then performs down-conversion on the intermediate frequency signal through an IQ channel to obtain an IQ signal. Due to the influence of the inconsistency of the amplitude-frequency signals of the IQ filters, the amplifiers and other devices and the influence of the time delay between the received signals, amplitude and phase errors occur between the two paths of signals, and the amplitude-phase errors are related to the frequency. The amplitude-phase error causes an error signal to appear in the image frequency of a complex signal synthesized by two paths of signals, the signal-to-noise ratio of the signal is reduced, afterimages appear in the final imaging process, the distortion of a main frequency part can also be caused, and the intensity distribution of a target image in a multi-channel radar system can be uneven.
The prior art generally calibrates for frequency-independent errors, and there are cases where the calibration is inaccurate.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a digital IQ calibration method based on complex signal frequency spectrum operation, an effective IQ amplitude-phase imbalance calibration method related to frequency, and the overall performance of a radar system is improved. To achieve the above objects and other advantages in accordance with the present invention, there is provided a digital IQ calibration radar receiver based on complex signal spectrum operation, comprising:
the system comprises a radio frequency module and a local module in signal connection with the radio frequency module;
the radio frequency module comprises a radio frequency oscillator, a first amplifier in signal connection with the radio frequency oscillator, a first frequency multiplier in signal connection with the first amplifier, a first filter in signal connection with the first frequency multiplier and a transmitting antenna in signal connection with the first filter;
the local module comprises a local oscillator, a second amplifier in signal connection with the local oscillator, a second frequency multiplier in signal connection with the second amplifier and a receiving antenna in signal connection with the second frequency multiplier, and a first mixer is connected between the receiving antenna and the second frequency multiplier;
the second frequency multiplier is connected with a second frequency mixer through a signal, the second frequency mixer is connected with a third amplifier through a signal, the third amplifier is connected with a third frequency mixer and a 90-degree phase shifter in parallel, the third frequency mixer is connected with a fourth amplifier through a signal, and the fourth amplifier is connected with a first low-pass filter through a signal;
the first frequency mixer is connected with a fifth amplifier through signals, the fifth amplifier is connected with the 90-degree phase shifter and the third frequency mixer in parallel, the 90-degree phase shifter is connected with a fourth frequency mixer through signals, the fourth frequency mixer is connected with a sixth amplifier through signals, the sixth amplifier is connected with a second low-pass filter through signals, the second low-pass filter and the first low-pass filter are both connected with an A/D converter through signals, the first low-pass filter converts a digital signal from the A/D converter into a Q signal, and the second low-pass filter converts a digital signal from the A/D converter into an I signal.
A digital IQ calibration method based on complex signal spectrum operation is characterized by comprising calibration, compensation and a complex signal Z of a signal synthesized by a Q signal and an I signal;
the calibration also comprises a calibration coefficient, the calibration is completed by adding the calibration coefficient to the frequency spectrum of the complex signal Z, the calibration process is completed at a digital end through an algorithm, the calibration coefficient is obtained by calculating the frequency spectrum of the complex signal Z and the frequency spectrum of the conjugate signal thereof, and IQ signal imbalance in the radar receiver is compensated through the calibration coefficient.
Preferably, the method for calculating the calibration coefficient between the complex signal Z spectrum and the conjugate signal spectrum thereof comprises:
s1, synthesizing the received signal after IQ demodulation to obtain a first signal which is a positive frequency complex signal containing errors, and performing FFT processing on the first signal to obtain a first signal frequency spectrum;
s2, symmetrically processing the negative frequency spectrum of the first signal to obtain a negative frequency symmetric signal of the first signal, and subtracting the frequency spectrum of the first signal from the frequency spectrum of the negative frequency symmetric signal to obtain a second signal frequency spectrum;
s3, performing conjugation processing on the first signal and the second signal to respectively obtain a third signal and a fourth signal;
s4, correspondingly adding the first signal positive frequency spectrum value and the third signal negative frequency spectrum value to obtain a first parameter, and correspondingly adding the second signal positive frequency spectrum value and the fourth signal negative frequency spectrum value to obtain a second parameter;
and S5, subtracting the second parameter from the first parameter to obtain a calibration coefficient, and subtracting the calibration coefficient from the second signal spectrum and performing IFFT to obtain the standard signal.
Preferably, the calculation between the complex signal Z spectrum and its conjugate signal spectrum comprises the steps of:
s1, demodulating the intermediate frequency signal obtained by the receiver through an IQ demodulator to obtain IQ two-path signals;
s2, synthesizing the two obtained signals into a complex signal Z1_ t containing errors in an I + jQ mode, wherein Z1_ t can be decomposed into a double-sided spectrum error, a single-sided spectrum error and a standard complex signal in a modeling mode, and the formula is as follows:
wherein N is the frequency point serial number, the total frequency point number is N, N is-N/2, …, N/2-1, and the positive and negative of N is the same as the positive and negative of the frequency point, A is the received signal amplitude, omega is the frequency, alpha is the amplitude error, theta is the signal initial phase,
the error term is phase error and can change along with the frequency point;
s3, obtaining the frequency domain signal Z1_ Fn of each frequency point of the complex signal containing the error at the digital end through FFT operation;
s4, performing FFT on the conjugate signal of Z1_ t to obtain a frequency domain signal Z1_ F [ -N ], taking frequency points when N is 1, 2 and N/2-1, and calculating to obtain a first calibration parameter SV1 ═ Z1_ F [ N ] + Z1_ F [ -N ], wherein Z1_ F [ -N ] is a negative frequency spectrum of the conjugate signal of Z1_ F [ N ];
s5, performing symmetric processing on the negative spectrum of Z1_ F [ n ], to obtain a frequency domain signal Z2_ F [ n ], where Z2_ F [ n ] ═ Z2_ F [ -n ], and Z2_ F [ n ] is a bilateral spectrum error signal, and the formula is:
and uses Z1_ Fn-Z2 _ Fn to obtain frequency domain signal Z3_ Fn, removes double-side spectrum error signal,
s6, carrying out conjugation processing on Z3_ Fn to obtain a frequency domain signal Z3_ F [ -N ], taking frequency points when N is 1, 2 and N/2-1, and calculating to obtain a second calibration parameter SV2 ═ Z3_ Fn ] + Z3_ F [ -N ];
and (7): the final calibration coefficients can be obtained from SV3 ═ SV2-SV1, and this parameter is used to remove the single-sided spectral error signal, and the formula is:
and performing IFFT processing on the frequency domain signal Z _ Fn obtained by Z3_ Fn-SV 3 to obtain a calibrated standard signal Z _ t.
Preferably, in steps 4, 5 and 6, the calibration coefficient is calculated from the complex signal Z1_ F [ n ] and the positive frequency component of the signal Z3_ F [ n ] from which the double-sided error is removed, and the negative frequency component of the conjugate signal of Z1_ F [ n ] and Z3_ F [ n ], respectively.
Compared with the prior art, the invention has the beneficial effects that: the method obtains the calibration parameters by processing complex signals obtained by synthesizing IQ two-path data obtained by a receiver, thereby compensating frequency-dependent IQ imbalance caused by different initial phases of signals and devices such as a filter and the like in a down-conversion channel of an intermediate frequency signal. The calibration process is that IQ digital signals obtained after down-conversion of the receiver are synthesized by software to obtain complex signals. From this complex signal and its mirror-frequency symmetric signal another complex signal is calculated. And calculating the positive frequency point values of the two complex signals and the negative frequency point values of the conjugate signals to obtain a calibration coefficient. The calibration can be completed by calculating the calibration coefficient, the complex signal and the mirror frequency symmetrical signal thereof. The method decomposes the signal error into a bilateral symmetric error and a unilateral error, eliminates the error signal through the calibration coefficient, completes the calibration, effectively eliminates the IQ imbalance caused by the frequency response error between the receiver devices and the signal path difference, and improves the performance of the whole imaging system.
Drawings
FIG. 1 is a system block diagram of a radar transceiver and its down conversion;
fig. 2 is a flowchart of a digital IQ calibration method based on complex signal spectrum calculation.
In the figure: 10. a radio frequency oscillator; 20. a first amplifier; 30. a first frequency multiplier; 40. a first filter; 50. a transmitting antenna; 60. a local oscillator; 70. a second amplifier; 80.a second frequency multiplier; 90. a receiving antenna; 100. a first mixer; 110. a second mixer; 120. a third amplifier; 130. a third mixer; an 140.90 ° phase shifter; 150. a fourth mixer; 160. a sixth amplifier; 170. a second low-pass filter; an A/D converter; 190. a fifth amplifier; 121. a first low-pass filter; 123. and a fourth amplifier.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1-2, a digital IQ calibration radar receiver based on complex signal spectrum arithmetic, comprising: the system comprises a radio frequency module and a local module in signal connection with the radio frequency module;
the radio frequency module comprises a radio frequency oscillator 10, a first amplifier 20 in signal connection with the radio frequency oscillator 10, a first frequency multiplier 30 in signal connection with the first amplifier 20, a first filter 40 in signal connection with the first frequency multiplier 30, and a transmitting antenna 50 in signal connection with the first filter 40;
the local module comprises a local oscillator 60, a second amplifier 70 in signal connection with the local oscillator 60, a second frequency multiplier 80 in signal connection with the second amplifier 70, and a receiving antenna 90 in signal connection with the second frequency multiplier 80, wherein a first mixer 100 is connected between the receiving antenna 90 and the second frequency multiplier 80;
the second frequency multiplier 80 is connected with a second mixer 110 by signals, the second mixer 110 is connected with a third amplifier 120 by signals, the third amplifier 120 is connected with a third mixer 130 and a 90-degree phase shifter 140 in parallel, the third mixer 130 is connected with a fourth amplifier 123 by signals, and the fourth amplifier 123 is connected with a first low-pass filter 121 by signals;
a fifth amplifier 190 is connected to the first mixer 100 by a signal, the fifth amplifier 190 is connected in parallel to the 90 ° phase shifter 140 and the third mixer 130 by a signal, the 90 ° phase shifter 140 is connected by a signal to the fourth mixer 150 by a signal, the sixth amplifier 160 is connected by a signal to the second low-pass filter 170, the second low-pass filter 170 and the first low-pass filter 121 are both connected by a signal to an a/D converter 180, the first low-pass filter 121 converts a digital signal from the a/D converter 180 into a Q signal, and the second low-pass filter 170 converts a digital signal from the a/D converter 180 into an I signal.
As shown in fig. 1, the rf oscillator 10 generates a chirp signal with a center frequency f0 and a bandwidth B, i.e. an rf signal, which passes through the first amplifier 29, the first frequency multiplier 30 and the first low-pass filter 121 and then is transmitted through the transmitting antenna 50.
While the local oscillator 60 generates a central frequency f0+fIFThe linear frequency modulation signal with the bandwidth of B, i.e. the local oscillator signal, passes through the second amplifier 70 and the second frequency multiplier 80 and then is mixed with the radio frequency signal to obtain a reference intermediate frequency signal with the frequency fIF。
The local oscillator signal is mixed with the radio frequency reflected signal received by the receiving antenna 90 to obtain a test intermediate frequency signal with a frequency fIF+fτ。
The reference IF signal and the signal after the 90 DEG phase shifter 140 are mixed with the test IF signal respectively to obtain two echo signals with the frequency fτ。
The two paths of signals are respectively in signal connection with an a/D converter 180 through the second low-pass filter 170 and the first low-pass filter 121, the first low-pass filter 121 converts a digital signal from the a/D converter 180 into a Q signal, the second low-pass filter 170 converts the digital signal from the a/D converter 180 into an I signal, and the IQ signals are unbalanced in amplitude and phase due to path loss and device loss between the two paths of signals
A digital IQ calibration method based on complex signal spectrum operation is characterized by comprising calibration, compensation and a complex signal Z of a signal synthesized by a Q signal and an I signal;
the calibration also comprises a calibration coefficient, the calibration is completed by adding the calibration coefficient to the frequency spectrum of the complex signal Z, the calibration process is completed at a digital end through an algorithm, the calibration coefficient is obtained by calculating the frequency spectrum of the complex signal Z and the frequency spectrum of the conjugate signal thereof, and IQ signal imbalance in the radar receiver is compensated through the calibration coefficient.
Further, the method for calculating the calibration coefficient between the complex signal Z spectrum and the conjugate signal spectrum thereof comprises the following steps:
s1, synthesizing the received signal after IQ demodulation to obtain a first signal which is a positive frequency complex signal containing errors, and performing FFT processing on the first signal to obtain a first signal frequency spectrum;
s2, symmetrically processing the negative frequency spectrum of the first signal to obtain a negative frequency symmetric signal of the first signal, and subtracting the frequency spectrum of the first signal from the frequency spectrum of the negative frequency symmetric signal to obtain a second signal frequency spectrum;
s3, performing conjugation processing on the first signal and the second signal to respectively obtain a third signal and a fourth signal;
s4, correspondingly adding the first signal positive frequency spectrum value and the third signal negative frequency spectrum value to obtain a first parameter, and correspondingly adding the second signal positive frequency spectrum value and the fourth signal negative frequency spectrum value to obtain a second parameter;
and S5, subtracting the second parameter from the first parameter to obtain a calibration coefficient, and subtracting the calibration coefficient from the second signal spectrum and performing IFFT to obtain the standard signal.
Further, the calculation between the complex signal Z spectrum and its conjugate signal spectrum comprises the following steps:
s1, demodulating the intermediate frequency signal obtained by the receiver through an IQ demodulator to obtain IQ two-path signals;
s2, synthesizing the two obtained signals into a complex signal Z1_ t containing errors in an I + jQ mode, wherein Z1_ t can be decomposed into a double-sided spectrum error, a single-sided spectrum error and a standard complex signal in a modeling mode, and the formula is as follows:
wherein N is the frequency point serial number, the total frequency point number is N, N is-N/2, …, N/2-1, and the positive and negative of N is the same as the positive and negative of the frequency point, A is the received signal amplitude, omega is the frequency, alpha is the amplitude error, theta is the signal initial phase,
the error term is phase error and can change along with the frequency point;
s3, obtaining the frequency domain signal Z1_ Fn of each frequency point of the complex signal containing the error at the digital end through FFT operation;
s4, performing FFT on the conjugate signal of Z1_ t to obtain a frequency domain signal Z1_ F [ -N ], taking frequency points when N is 1, 2 and N/2-1, and calculating to obtain a first calibration parameter SV1 ═ Z1_ F [ N ] + Z1_ F [ -N ], wherein Z1_ F [ -N ] is a negative frequency spectrum of the conjugate signal of Z1_ F [ N ];
s5, performing symmetric processing on the negative spectrum of Z1_ F [ n ], to obtain a frequency domain signal Z2_ F [ n ], where Z2_ F [ n ] ═ Z2_ F [ -n ], and Z2_ F [ n ] is a bilateral spectrum error signal, and the formula is:
and uses Z1_ Fn-Z2 _ Fn to obtain frequency domain signal Z3_ Fn, removes double-side spectrum error signal,
s6, carrying out conjugation processing on Z3_ Fn to obtain a frequency domain signal Z3_ F [ -N ], taking frequency points when N is 1, 2 and N/2-1, and calculating to obtain a second calibration parameter SV2 ═ Z3_ Fn ] + Z3_ F [ -N ];
and (7): the final calibration coefficients can be obtained from SV3 ═ SV2-SV1, and this parameter is used to remove the single-sided spectral error signal, and the formula is:
and performing IFFT processing on the frequency domain signal Z _ Fn obtained by Z3_ Fn-SV 3 to obtain a calibrated standard signal Z _ t.
Furthermore, in the steps 4, 5 and 6, the calibration coefficient is obtained by calculating the positive frequency component of the complex signal Z1_ F [ n ] and the signal Z3_ F [ n ] after the double-edge error is removed, and the negative frequency component of the conjugate signal of Z1_ F [ n ] and Z3_ F [ n ].
In the embodiment, the radio frequency signal is set to be a chirp signal with a center frequency of 32.5GHz and a bandwidth of 5GHz, the local oscillator signal is set to be a chirp signal with a center frequency of 32.6GHz and a bandwidth of 5GHz, the frequency of the intermediate frequency signal is 100MHz, the sampling rate of the IQ signal is 100MHz, and the sampling point is 600. The calibration method comprises the following steps:
step (1): and reading the sampled digital IQ signals into MATLAB software, and performing digital signal processing in the software in the whole calibration process.
Step (2): the radar echo signals are negative frequency signals, and in order to use a calibration mode conveniently, the echo signals are subjected to conjugation processing to obtain positive frequency signals Z1_ t, wherein Z1_ t can be modeled and decomposed into a two-sided spectrum error, a one-sided spectrum error and a standard complex signal.
Wherein N is the frequency point serial number, the total frequency point number is N, according to the parameter N of the actual system being 600, N being-300, -299, …, 299, 300,
and the positive and negative of n is the same as the positive and negative of frequency point, A is the received signal amplitude, omega is frequency, alpha is amplitude error, theta is signal initial phase,
for phase errors, the error term will vary with frequency.
And (3): and performing 600-point FFT operation on the complex signal Z1_ t containing the error at a digital end to obtain a discrete frequency domain signal Z1_ Fn of each frequency point.
And (4): performing 600-point FFT on the conjugate signal of Z1_ t to obtain a frequency domain signal Z1_ F [ -n ], taking frequency points when n is 1, 2, … and 300, and obtaining a first calibration parameter SV1 ═ Z1_ F [ n ] + Z1_ F [ -n ] through the addition calculation of matlab corresponding matrixes, wherein Z1_ F [ -n ] is a negative frequency spectrum of the conjugate signal of Z1_ F [ n ], and SV1 is a complex value corresponding to 300 positive frequency points;
and (5): and symmetrically processing the negative frequency spectrum of Z1_ F [ n ] through matrix inversion operation of matlab to obtain a frequency domain signal Z2_ F [ n ], wherein Z2_ F [ n ] ═ Z2_ F [ -n ], Z2_ F [ n ] is a bilateral spectrum error signal, and the formula is as follows:
obtaining a frequency domain signal Z3_ Fn by using Z1_ Fn-Z2 _ Fn, removing a double-side spectrum error signal, and eliminating the image frequency error of the signal;
and (6): performing conjugation processing on Z3_ F [ N ] to obtain a frequency domain signal Z3_ F [ -N ], taking a frequency point when N is 1, 2, N/2-1, and calculating to obtain a second calibration parameter SV2 which is Z3_ F [ N ] + Z3_ F [ -N ];
and (7): the final calibration coefficients for removing the single-sided spectral error signal can be obtained from SV3 ═ SV2-SV1, and are expressed as:
and performing IFFT processing on the frequency domain signal Z _ Fn obtained by Z3_ Fn-SV 3 to obtain a calibrated standard signal Z _ t.
The digital IQ calibration method based on complex signal spectrum operation provided by the embodiment effectively eliminates the problem of IQ amplitude phase imbalance caused by the path difference between echoes and the frequency response error difference between devices, and effectively improves the imaging performance of a radar system.
The number of devices and the scale of the processes described herein are intended to simplify the description of the invention, and applications, modifications and variations of the invention will be apparent to those skilled in the art.
While embodiments of the invention have been described above, it is not limited to the applications set forth in the description and the embodiments, which are fully applicable in various fields of endeavor to which the invention pertains, and further modifications may readily be made by those skilled in the art, it being understood that the invention is not limited to the details shown and described herein without departing from the general concept defined by the appended claims and their equivalents.
Claims (5)
1. A digital IQ calibration radar transceiver based on complex signal spectral arithmetic, comprising: the system comprises a radio frequency module and a local module in signal connection with the radio frequency module;
the radio frequency module comprises a radio frequency oscillator, a first amplifier in signal connection with the radio frequency oscillator, a first frequency multiplier in signal connection with the first amplifier, a first filter in signal connection with the first frequency multiplier and a transmitting antenna in signal connection with the first filter;
the local module comprises a local oscillator, a second amplifier in signal connection with the local oscillator, a second frequency multiplier in signal connection with the second amplifier and a receiving antenna in signal connection with the second frequency multiplier, and a first mixer is connected between the receiving antenna and the second frequency multiplier;
the second frequency multiplier is connected with a second frequency mixer through a signal, the second frequency mixer is connected with a third amplifier through a signal, the third amplifier is connected with a third frequency mixer and a 90-degree phase shifter in parallel, the third frequency mixer is connected with a fourth amplifier through a signal, and the fourth amplifier is connected with a first low-pass filter through a signal;
the first frequency mixer is connected with a fifth amplifier through signals, the fifth amplifier is connected with the 90-degree phase shifter and the third frequency mixer in parallel, the 90-degree phase shifter is connected with a fourth frequency mixer through signals, the fourth frequency mixer is connected with a sixth amplifier through signals, the sixth amplifier is connected with a second low-pass filter through signals, the second low-pass filter and the first low-pass filter are both connected with an A/D converter through signals, the first low-pass filter converts a digital signal from the A/D converter into a Q signal, and the second low-pass filter converts a digital signal from the A/D converter into an I signal.
2. The digital IQ calibration method according to claim 1, comprising calibrating, compensating and synthesizing the complex signal Z of the Q signal and the I signal;
the calibration also comprises a calibration coefficient, the calibration is completed by adding the calibration coefficient to the frequency spectrum of the complex signal Z, the calibration process is completed at a digital end through an algorithm, the calibration coefficient is obtained by calculating the frequency spectrum of the complex signal Z and the frequency spectrum of the conjugate signal thereof, and IQ signal imbalance in the radar receiver is compensated through the calibration coefficient.
3. The digital IQ calibration method according to claim 2, wherein the method of calculating calibration coefficients between the complex signal Z spectrum and its conjugate signal spectrum comprises:
s1, synthesizing the received signal after IQ demodulation to obtain a first signal which is a positive frequency complex signal containing errors, and performing FFT processing on the first signal to obtain a first signal frequency spectrum;
s2, symmetrically processing the negative frequency spectrum of the first signal to obtain a negative frequency symmetric signal of the first signal, and subtracting the frequency spectrum of the first signal from the frequency spectrum of the negative frequency symmetric signal to obtain a second signal frequency spectrum;
s3, performing conjugation processing on the first signal and the second signal to respectively obtain a third signal and a fourth signal;
s4, correspondingly adding the first signal positive frequency spectrum value and the third signal negative frequency spectrum value to obtain a first parameter, and correspondingly adding the second signal positive frequency spectrum value and the fourth signal negative frequency spectrum value to obtain a second parameter;
and S5, subtracting the second parameter from the first parameter to obtain a calibration coefficient, and subtracting the calibration coefficient from the second signal spectrum and performing IFFT to obtain the standard signal.
4. The digital IQ calibration method according to claim 3, wherein the calculation between the complex signal Z spectrum and its conjugate signal spectrum comprises the steps of:
s1, demodulating the intermediate frequency signal obtained by the receiver through an IQ demodulator to obtain IQ two-path signals;
s2, synthesizing the two obtained signals into a complex signal Z1_ t containing errors in an I + jQ mode, wherein Z1_ t can be decomposed into a double-sided spectrum error, a single-sided spectrum error and a standard complex signal in a modeling mode, and the formula is as follows:
wherein N is the frequency point serial number, the total frequency point number is N, N is-N/2, …, N/2-1, and the positive and negative of N is the same as the positive and negative of the frequency point, A is the received signal amplitude, omega is the frequency, alpha is the amplitude error, theta is the signal initial phase,
the error term is phase error and can change along with the frequency point;
s3, obtaining the frequency domain signal Z1_ Fn of each frequency point of the complex signal containing the error at the digital end through FFT operation;
s4, performing FFT on the conjugate signal of Z1_ t to obtain a frequency domain signal Z1_ F [ -N ], taking frequency points when N is 1, 2 and N/2-1, and calculating to obtain a first calibration parameter SV1 ═ Z1_ F [ N ] + Z1_ F [ -N ], wherein Z1_ F [ -N ] is a negative frequency spectrum of the conjugate signal of Z1_ F [ N ];
s5, performing symmetric processing on the negative spectrum of Z1_ F [ n ], to obtain a frequency domain signal Z2_ F [ n ], where Z2_ F [ n ] ═ Z2_ F [ -n ], and Z2_ F [ n ] is a bilateral spectrum error signal, and the formula is:
and uses Z1_ Fn-Z2 _ Fn to obtain frequency domain signal Z3_ Fn, removes double-side spectrum error signal,
s6, carrying out conjugation processing on Z3_ Fn to obtain a frequency domain signal Z3_ F [ -N ], taking frequency points when N is 1, 2 and N/2-1, and calculating to obtain a second calibration parameter SV2 ═ Z3_ Fn ] + Z3_ F [ -N ];
and (7): the final calibration coefficients can be obtained from SV3 ═ SV2-SV1, and this parameter is used to remove the single-sided spectral error signal, and the formula is:
and performing IFFT processing on the frequency domain signal Z _ Fn obtained by Z3_ Fn-SV 3 to obtain a calibrated standard signal Z _ t.
5. The digital IQ calibration method according to claim 4, wherein in steps 4, 5 and 6, the calibration coefficients are calculated from the complex signal Z1_ Fn and its positive frequency component of the signal Z3_ Fn after removing the double-sided error, and the negative frequency components of the conjugated signals Z1_ Fn, Z3_ Fn.
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| US11796663B2 (en) | 2021-02-20 | 2023-10-24 | International Business Machines Corporation | Automatic image rejection calibration for radar systems using quadrature transceivers |
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| CN114844579B (en) * | 2022-04-28 | 2024-02-06 | 杭州城芯科技有限公司 | Time domain statistics QEC (quality of control) calibration method and device based on narrow-band filter |
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| CN112051555B (en) | 2023-07-25 |
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