Disclosure of Invention
The technical problem solved by the scheme provided by the embodiment of the invention is how to realize the real-time online calibration of the circular array antenna.
The real-time calibration method for the circular array antenna provided by the embodiment of the invention comprises the following steps:
comparing each path of signals to be calibrated in the circular array antenna by using the set calibration reference signals, and determining corresponding amplitude-phase data of each path of signals;
performing multiple iterative processing on the amplitude-phase data corresponding to each path of signal to obtain radio frequency channel calibration data of the circular array antenna;
and carrying out phase calibration on the radio frequency channel calibration data of the circular array antenna to realize real-time calibration of the circular array antenna.
Preferably, the phase calibration of the channel calibration data of the circular array antenna includes radio frequency channel transmission calibration and radio frequency channel reception calibration.
Preferably, the radio frequency channel transmission calibration comprises:
the radar transmitter controls a transmitting channel thereof to transmit a single carrier frequency signal of a corresponding frequency point according to a control instruction issued by the display control terminal;
looping the single carrier frequency signal to a receiving channel through a circulator and an internal monitoring network to obtain an echo signal of the corresponding channel, and calculating an amplitude compensation quantity and a phase compensation quantity corresponding to the echo signal;
the amplitude compensation quantity of the emission calibration is compensated in the generation of radar emission waveforms, and the phase compensation quantity is completed in a wave control system.
Preferably, the calculating the amplitude compensation amount and the phase compensation amount corresponding to the echo signal includes:
obtaining a calibrated CW reference branch signal ynm(t);
With the CW reference channel as a reference, obtaining a signal y after CAL signals of all T/R component branches eliminate coupling ratios and weighting coefficientscw(t);
Are respectively paired with ynm(t),ycw(t) performing a multi-point FFT to obtain ynm(1) And ycw(1);
According to the y
nm(1) And y
cw(1) Calculating a compensation coefficient
In the formula (f)
nmThe modulus and the phase of (a) are respectively the compensation quantity of the amplitude and the compensation quantity of the phase; α, b are signal amplitudes;
nm,
is a unit level independent amplitude-phase error.
Preferably, the radio frequency channel reception calibration includes:
controlling a radar transmitter to transmit single carrier frequency signals of corresponding frequency points through an internal monitoring network through a display control terminal;
looping the single carrier frequency signal to a receiving channel through a circulator and an internal monitoring network to obtain an echo signal of the corresponding channel, and calculating an amplitude compensation quantity and a phase compensation quantity corresponding to the echo signal;
the amplitude compensation amount and the phase compensation amount of the reception calibration are completed in the DBF.
Preferably, the calculating the amplitude compensation amount and the phase compensation amount corresponding to the echo signal includes:
obtaining a calibrated CW reference branch signal ynm(t);
With the CW reference channel as a reference, obtaining a signal y after CAL signals of all T/R component branches eliminate coupling ratios and weighting coefficientscw(t);
Are respectively paired with ynm(t),ycw(t) performing a multi-point FFT to obtain ynm(1) And ycw(1);
According to the y
nm(1) And y
cw(1) Calculating a compensation coefficient
In the formula (f)
nmThe modulus and the phase of (a) are respectively the compensation quantity of the amplitude and the compensation quantity of the phase; α, b are signal amplitudes;
nm,
is a unit level independent amplitude-phase error.
Preferably, the comparing each path of signals to be calibrated in the circular array antenna by using the set calibration reference signal, and determining the corresponding amplitude-phase data of each path of signals includes:
obtaining a calibration signal x for calibrating coupling line couplingnm(t);
Using the calibrated coupled signal as a calibrated reference signal Xref(t);
Comparing the channel signal with the reference signal to give a calibration output result Pout=Xnm/Xref。
Detailed Description
The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, and it should be understood that the preferred embodiments described below are only for the purpose of illustrating and explaining the present invention, and are not to be construed as limiting the present invention.
Fig. 1 is a flowchart of a real-time calibration method for a circular array antenna according to an embodiment of the present invention, as shown in fig. 1, including:
step 1: comparing each path of signals to be calibrated in the circular array antenna by using the set calibration reference signals, and determining corresponding amplitude-phase data of each path of signals;
step 2: performing multiple iterative processing on the amplitude-phase data corresponding to each path of signal to obtain radio frequency channel calibration data of the circular array antenna;
and step 3: and carrying out phase calibration on the radio frequency channel calibration data of the circular array antenna to realize real-time calibration of the circular array antenna.
Specifically, the phase calibration of the channel calibration data of the circular array antenna includes a radio frequency channel transmission calibration and a radio frequency channel reception calibration.
Further, the radio frequency channel transmission calibration includes: the radar transmitter controls a transmitting channel thereof to transmit a single carrier frequency signal of a corresponding frequency point according to a control instruction issued by the display control terminal; looping the single carrier frequency signal to a receiving channel through a circulator and an internal monitoring network to obtain an echo signal of the corresponding channel, and calculating an amplitude compensation quantity and a phase compensation quantity corresponding to the echo signal; the amplitude compensation quantity of the emission calibration is compensated in the generation of radar emission waveforms, and the phase compensation quantity is completed in a wave control system.
Wherein the calculating the amplitude compensation amount and the phase compensation amount corresponding to the echo signal comprises: obtaining a calibrated CW reference branch signal y
nm(t); with the CW reference channel as a reference, obtaining a signal y after CAL signals of all T/R component branches eliminate coupling ratios and weighting coefficients
cw(t); are respectively paired with y
nm(t),y
cw(t) performing a multi-point FFT to obtain y
nm(1) And y
cw(1) (ii) a According to the y
nm(1) And y
cw(1) Calculating a compensation coefficient
In the formula (f)
nmThe modulus and the phase of (a) are respectively the compensation quantity of the amplitude and the compensation quantity of the phase; α, b are signal amplitudes;
nm,
is a unit level independent amplitude-phase error.
Further, the radio frequency channel reception calibration includes: controlling a radar transmitter to transmit single carrier frequency signals of corresponding frequency points through an internal monitoring network through a display control terminal; looping the single carrier frequency signal to a receiving channel through a circulator and an internal monitoring network to obtain an echo signal of the corresponding channel, and calculating an amplitude compensation quantity and a phase compensation quantity corresponding to the echo signal; the amplitude compensation amount and the phase compensation amount of the reception calibration are completed in the DBF.
Wherein the calculating the amplitude compensation amount and the phase compensation amount corresponding to the echo signal comprises: obtaining a calibrated CW reference branch signal y
nm(t); with the CW reference channel as a reference, obtaining a signal y after CAL signals of all T/R component branches eliminate coupling ratios and weighting coefficients
cw(t); are respectively paired with y
nm(t),y
cw(t) performing a multi-point FFT to obtain y
nm(1) And y
cw(1) (ii) a According to the y
nm(1) And y
cw(1) Calculating a compensation coefficient
In the formula (f)
nmThe modulus and the phase of (a) are respectively the compensation quantity of the amplitude and the compensation quantity of the phase; α, b are signal amplitudes;
nm,
is a unit level independent amplitude-phase error.
The step of comparing each path of signals to be calibrated in the circular array antenna by using the set calibration reference signal, and determining the corresponding amplitude-phase data of each path of signals comprises: obtaining a calibration signal x for calibrating coupling line couplingnm(t); using the calibrated coupled signal as a calibrated reference signal Xref(t); comparing the channel signal with the reference signal to give a calibration output result Pout=Xnm/Xref。
The technical solution of the present application will be described below with specific examples
1. Echo signal model
And comparing each path of signals to be calibrated by using a given calibration reference signal, giving corresponding amplitude and phase data, and realizing the calibration of the channel through multiple iterations. Corresponding to the T/R component with the (m, n) th number, the calibration signals coupled by the calibration coupling lines are as follows:
wherein, in the formula: α is the signal amplitude;
nm,
is a unit level independent amplitude-phase error; w is a
nmAnd phi
nmIs a magnitude-phase weighting coefficient; c
nmTo calibrate the coupling ratio; u. of
s,v
sThe amount of phase stepping between elements, achieved by the phase shifters, when scanning for antenna azimuth and elevation beams, is 0 when the beams point to the normal.
In the formula: Ψ
s,
Pitch angle and azimuth angle when the beam points to the plane relative to the normal line respectively; dx, dy is the spacing between adjacent cells in the vertical and horizontal directions; w is a
dIs the Doppler frequency offset; Ψ
0Is the random initial phase of the signal.
The calibrated reference signal is selected from the calibrated coupled signals and is represented as
Comparing the channel signal with the reference signal to give a calibration output result
Pout=Xnm/Xref
And comparing the result with target amplitude-phase data, and enabling the test data to trend to the target result through a plurality of iterations, wherein the variance meets the index requirement.
2. Calibration algorithm
2.1 calibration procedure
The digital array antenna is a circular array comprising 24 antenna elements which are distributed at equal intervals. The radio frequency channel comprises a digital T/R component receiving and transmitting related passage, a radio frequency joint, a radio frequency cable, an antenna array and the like, the digital array is based on independent receiving and transmitting of each array, space synthesis is carried out on transmitting signals, and digital synthesis is carried out on receiving signals through a digital beam forming functional block. Based on the above, the phase consistency of the rf channel has a great influence on the system performance, and therefore, the phase calibration of the rf channel is required. The rf channel transmit/receive calibration diagrams are shown in fig. 0 and 0 below.
The 24 antenna arrays of the digital array antenna array are uniformly distributed on the circle, and the receiving amplitude of the radio frequency channel is in a reasonable interval by controlling the amplitude of a transmitting signal during the transmitting calibration of the radio frequency channel.
The method comprises the following steps of receiving and transmitting amplitude and phase calibration of a radio frequency channel:
1) the T/R channel 1 and the antenna array 1 are used for transmitting, the T/R channel 2 and the antenna array 2 as well as the T/R channel 24 and the antenna array 24 are used for receiving simultaneously to obtain receiving phase values phi R2 and phi R24 and amplitude values Fr2 and Fr24, and the difference value between the receiving phase values phi R2 and phi R24 is the receiving phase difference between the radio frequency channels 2 and 24 due to the sharing of transmission;
2) the T/R channel 3 and the antenna array 3 transmit, the T/R channel 2 and the antenna array 2 receive and the T/R channel 4 and the antenna array 4 simultaneously receive, so that received phase values phi R2 and phi R4 and amplitude values Fr2 and Fr4 are obtained, and a receiving phase difference and an amplitude ratio between the radio frequency channels 2 and 4 are also obtained;
3) through the process, when the radio frequency channels 1 and 3 transmit, the radio frequency channel 2 receives the common signal, and the transmitting phase difference and the amplitude ratio between the radio frequency channels 1 and 3 can be obtained;
4) by analogy, receiving phase differences and amplitude ratios between every two radio frequency channels with even serial numbers and transmitting phase differences and amplitude ratios between every two radio frequency channels with odd serial numbers are obtained, and the receiving phase differences and the amplitude ratios of all the radio frequency channels with even serial numbers and the transmitting phase differences and the amplitude ratios of all the radio frequency channels with odd serial numbers are obtained by using a certain radio frequency channel as a reference normalization treatment;
5) the process is changed into the process of transmitting by radio frequency channels with even serial numbers, receiving by adjacent radio frequency channels with odd serial numbers, and obtaining the receiving phase difference and amplitude ratio of all radio frequency channels with odd serial numbers and the transmitting phase difference and amplitude ratio of all radio frequency channels with even serial numbers;
6) and finally, through the transmission of the radio frequency channel 1 and the simultaneous reception of the radio frequency channel 3, the transmission, reception phase and amplitude of the radio frequency channels with even and odd serial numbers can be normalized to obtain the transmission and reception phase difference and amplitude ratio of all the radio frequency channels (the coupling phase rule of adjacent antenna arrays such as the transmission of 1 and the reception of 2 and alternate antenna arrays such as the transmission of 1 and the reception of 3 can be obtained through darkroom measurement), the process is the radio frequency channel calibration process of 1 frequency point, and the process is repeated after the frequency is set.
The procedure for receiving calibration is similar to that described above.
2.2 calibration Algorithm
According to the calibration procedure, the calibration algorithm is performed as follows:
the calibrated CW reference branch signal is
In the formula, b is the signal amplitude, and other parameters are the same as above.
With the CW reference channel as a reference, obtaining the CAL signals of all T/R component branches after eliminating the coupling ratio and the weighting coefficient
For ynm(t),ycw(t) performing a multi-point FFT to obtain
ycw(1)=bexpj(Ψ0)
The compensation factor is calculated as follows:
in the formula: f. ofnmThe modulus and phase of (a) are the compensation of the amplitude and the compensation of the phase, respectively, wherein the exact values of a, b will affect the absolute correction, but not the side lobe level of the front antenna. Because of the strong coupling between the attenuator and the phase shifter, the amplitude is calibrated first and then the phase is calibrated. The calibration may be performed 3-4 times until the latest amplitude-phase mean square error meets the requirement.
2.3 calibrating fault tolerant design
Because the calibration process is implemented by using a radio frequency channel iterative processing method, the calibration is greatly affected when the radio frequency channel fails, measures need to be taken for abnormal conditions, and the measures that can be taken are as follows:
1) for the condition that a certain path of the radio frequency channel has a fault, the serial number of the radio frequency channel with the problem can be basically judged through the self-checking and calibration processes (the receiving amplitude of the radio frequency channel is in a reasonable range during calibration), and the radio frequency channel with the problem can be isolated during calibration without participating in the calibration process because the digital array antenna array is a circular array;
2) on a calibration interface of a monitoring maintenance unit, whether a component of the system has an option of replacement or disordered installation is set, and if the component of the system does not have the option, the difference between the current calibration value and the calibration value in the system stored last time is judged reasonably (the phase change should not exceed a certain range);
3) the calibration process adopts multiple calibrations of different phases and different amplitude references to judge consistency (for example, the phase change of the same radio frequency channel is within 10 degrees), and reduces errors by averaging.
2.4, carrying out the step
The steps executed during the emission calibration are as follows:
1) controlling a radar transmitter to transmit single carrier frequency signals of corresponding frequency points through a transmitting channel by a display control terminal;
2) the signal is looped back to the receiving channel through the circulator and the internal monitoring network to obtain an echo signal of the corresponding channel;
3) calculating the compensation quantity of corresponding amplitude and the compensation quantity of corresponding phase according to the calibration process provided by the method;
4) the amplitude compensation quantity of the emission calibration is compensated in the generation of radar emission waveforms, and the phase compensation quantity is completed in a wave control system.
The receiving calibration is executed by the following steps:
1) controlling a radar transmitter to transmit single carrier frequency signals of corresponding frequency points through an internal monitoring network through a display control terminal;
2) the signal is looped back to the receiving channel through the circulator and the internal monitoring network to obtain an echo signal of the corresponding channel;
3) calculating the compensation quantity of corresponding amplitude and the compensation quantity of corresponding phase according to the calibration process provided by the method;
4) the amplitude compensation amount and the phase compensation amount of the reception calibration are completed in the DBF.
According to the scheme provided by the embodiment of the invention, an amplitude and phase error calibration algorithm is provided, and the problem of sample point alignment in a time domain is solved.
Although the present invention has been described in detail hereinabove, the present invention is not limited thereto, and various modifications can be made by those skilled in the art in light of the principle of the present invention. Thus, modifications made in accordance with the principles of the present invention should be understood to fall within the scope of the present invention.