CN114185016A - Method for measuring and compensating amplitude-phase error between channels of multi-channel satellite-borne SAR (synthetic aperture radar) antenna - Google Patents
Method for measuring and compensating amplitude-phase error between channels of multi-channel satellite-borne SAR (synthetic aperture radar) antenna Download PDFInfo
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Abstract
The invention relates to a method for measuring and compensating amplitude-phase errors among channels of a multi-channel satellite-borne SAR antenna, which comprises the following steps: step 1, measuring the amplitude-phase error between SAR antenna channels, which specifically comprises the following steps: step 1.1: acquiring ground state error data of a feed link; step 1.2, obtaining calibration network error data; step 1.3, judging the error compensation effect of the calibration network; step 1.4, error data between channels is obtained; step 2, compensating the amplitude-phase error between the channels of the SAR antenna, which specifically comprises the following steps: step 2.1, storing the error code by adopting a dummy bit technology; and 2.2, compensating the amplitude and phase errors among the channels. The method can extract high-precision channel errors and effectively distinguish the antenna feed network errors from the calibration network errors, and the finally realized channel errors are smaller than the quantization errors by adopting a virtual bit technology.
Description
Technical Field
The invention belongs to the field of multi-channel SAR active phased array antenna testing, and relates to a method for measuring and compensating amplitude and phase errors among channels of a multi-channel SAR active phased array antenna with high precision.
Background
In order to improve the imaging width and resolution of the SAR imaging radar, the main method at present adopts an antenna azimuth multi-channel technology. The radar system divides an SAR antenna into a plurality of antenna sub-arrays in the azimuth direction, each antenna sub-array is connected with a receiver to form a plurality of receiving channels, and the connection schematic block diagram of the radar system is shown in figure 1. The inter-channel amplitude and phase errors of the traditional azimuth multi-channel SAR active phased-array antenna are generally not compensated, the inter-channel amplitude and phase errors are extracted by estimating ground echo data among channels, and then the errors are compensated in an imaging algorithm. The accuracy of channel error compensation achieved by conventional methods is directly related to the error estimation algorithm and the echo data. Meanwhile, with the increasingly complex working modes of the SAR imaging radar, some modes need to complete the synthesis of the echo data between channels on the satellite in real time and then download the data to the ground. The mode cannot extract the inter-channel amplitude and phase errors through the traditional estimation algorithm, so that the inter-channel amplitude and phase error compensation cannot be realized.
The method for estimating the amplitude and phase errors through the ground echo data among the channels has the main defects that: firstly, the inter-channel amplitude and phase error estimation algorithm can increase the complexity and the operation amount of an imaging algorithm; secondly, the amplitude and phase errors estimated from the echo data of different ground targets are inconsistent, so that the estimated channel amplitude and phase error precision is not high; and thirdly, after in-orbit echo data among channels are synthesized in real time in a special mode, channel error acquisition and compensation can not be carried out through an estimation algorithm.
Disclosure of Invention
In order to solve the technical problems, the invention provides a method for measuring and compensating the amplitude-phase error between channels of a multi-channel satellite-borne SAR antenna, which mainly aims to calibrate and measure the amplitude-phase error between the channels of the SAR antenna and compensate the amplitude-phase error with high precision in an actual connection state of a multi-channel SAR radar system, and does not need to estimate echo data to compensate the channel error after compensation. The invention has the characteristics of simple measuring method, small measuring error, high compensation precision and the like.
The technical scheme of the invention is as follows: a method for measuring and compensating amplitude-phase errors among channels of a multi-channel satellite-borne SAR antenna comprises the following steps:
step 1.1: acquiring ground state error data of a feed link;
step 1.2, obtaining calibration network error data;
step 1.3, judging the error compensation effect of the calibration network;
step 1.4, error data between channels is obtained;
step 2.1, storing the error code by adopting a dummy bit technology;
and 2.2, compensating the amplitude and phase errors among the channels.
Has the advantages that:
1. the method for measuring and compensating the amplitude-phase error between the channels of the multi-channel satellite-borne SAR antenna can extract the high-precision channel error and effectively distinguish the antenna feed network error from the calibration network error.
2. The invention adopts the dummy bit technology to ensure that the finally realized channel error is smaller than the quantization error.
Drawings
FIG. 1 is a schematic diagram of the SAR radar system of the present invention;
FIG. 2 is a schematic diagram of a near field single T/R calibration test in accordance with the present invention;
FIG. 3 is a flow chart of a method of the present invention;
FIG. 4 shows the effect of phase compensation, (a) before compensation, (b) after compensation;
FIG. 5 receives the amplitude compensation effect, (a) before compensation, (b) after compensation;
FIG. 6 receives the phase compensation effect, (a) before compensation, (b) after compensation;
FIG. 7 scales the effect of network error compensation, (a) before compensation, and (b) after compensation.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying 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, rather than all embodiments, and all other embodiments obtained by a person skilled in the art based on the embodiments of the present invention belong to the protection scope of the present invention without creative efforts.
The invention provides a method for measuring and compensating amplitude-phase errors among channels of a multi-channel satellite-borne SAR antenna, wherein a radio frequency network of the SAR antenna is shown as figure 1, the radio frequency network of the SAR antenna is mainly divided into a transmitting network, a receiving network and a calibration network,
the transmitting network path is pre-power amplifier → microwave combination → power division network → time delay amplification → power division network → T/R component → radiation unit.
The path of the receiving network is a front surface unit → a T/R component → a power division network → time delay amplification → a power division network → microwave combination → a receiver.
The scaling network path is the antenna scaling network → the inner scaler → the receiver.
Wherein, the transmitting and receiving network is called a feed link of the SAR imaging radar antenna, and the calibration network is called a calibration link.
The invention relates to a method for measuring and compensating high-precision amplitude-phase errors of a multi-channel antenna in a multi-channel SAR imaging radar system by aiming at an active phased array radar.
The method for measuring and compensating the amplitude-phase error between the channels of the multi-channel space-borne SAR antenna according to the present invention will be further described in detail with reference to the accompanying drawings and embodiments, wherein the flow of the method is shown in fig. 3, and the specific steps are as follows:
firstly, calibrating and measuring an amplitude-phase error between SAR antenna channels:
the first step is as follows: obtaining feeder link ground state error data
And (3) using a near field test system to complete the measurement of the amplitude and phase errors of the receiving and transmitting feed link from the SAR antenna radiation unit to the microwave combined section, wherein the feed link of the radar system is shown in figure 1. The receiving and transmitting amplitude-phase measurement and correction of each feed link of the SAR antenna are realized by carrying out calibration test on the radiation unit corresponding to each T/R component of the SAR antenna receiving and transmitting link, and a test configuration diagram of the near-field single T/R calibration test is shown in figure 2. During testing, the SAR antenna uses all-zero-state wave control codes (namely, the delay codes of the delay amplification component, the receiving and transmitting phase shift codes of the T/R component and the receiving attenuation codes are all zero), and during testing, the ground wave control is used for controlling the SAR antenna to have only one T/R component in a working state, and other components are in a load state. And simultaneously, the near-field test probe measures the amplitude-phase data of the position of the T/R assembly, completes the amplitude-phase test of the receiving and transmitting of all assemblies and obtains the ground state error data.
The second step is that: obtaining scaled network error data
And completing SAR antenna calibration link error test by using an internal calibration function of the SAR radar. And calibrating the feed link on the basis of acquiring SAR antenna ground state error data in the first step. Then, the internal calibration function of the SAR radar is used for carrying out emission single T/R calibration test on the SAR antenna, in the test process, radio frequency signals are fed into a microwave combination by a pre-power amplifier and are transmitted to an SAR antenna array surface, then energy is coupled to an SAR antenna calibration network through a coupling port of a T/R assembly, and finally the energy is received by a receiver after the combination of an internal calibrator and the microwave. In the test process, only one T/R component channel is in a working state, and the rest T/R components are in a load state. Since the T/R assembly is at saturated output in the transmit state, the output amplitude of the feeder link can be considered consistent, while the test calibrates the transmit feeder link with the ground state error code. Therefore, the data acquired at this time can be equivalent to the amplitude-phase error data of the SAR antenna array in-plane scaling network. Since the internal calibration network is a passive network (only including a power divider and a radio frequency cable), the internal calibration network error data of the transceiving link is the same value.
The third step: determining scaled network error compensation effects
And adding the calibration network error data obtained in the second step and the transmission link error data to obtain total error data, and calibrating the SAR antenna. The internal calibration function of the SAR radar is adopted to carry out the calibration test of the emission single T/R, and the phase-shifting code inside the T/R component is 6bit, so the minimum quantization error is 5.625 degrees. Checking whether the obtained phase data is in the range of +/-5.625 degrees or not, if the obtained phase error data is not in the range of +/-5.625 degrees, adding the obtained phase data and the calibration network error data to update the calibration network error data, and repeating the step three. If the error value is within the range of +/-5.625 degrees, the next step is carried out.
The fourth step: obtaining inter-channel error data
And adding the calibration network error data obtained in the second step or the third step and the receiving link error data obtained in the first step to obtain total error data, and calibrating the SAR antenna. And performing a receiving single T/R calibration test by adopting an internal calibration function of the SAR. In the testing process, radio frequency signals are fed into the microwave combination through the pre-power amplifier and are sent to the antenna internal calibration network through the internal calibrator, then energy is coupled to the SAR antenna receiving feed link through the coupling port of the T/R component, and finally the radio frequency signals of each receiving channel are received through the microwave combination and the corresponding receiver. In the test process, only one T/R component channel is in a working state, and the rest T/R components are in a load state. And respectively carrying out complex number average on the obtained amplitude and phase data for each receiving channel to obtain amplitude and phase error data among the channels.
Secondly, high-precision compensation of amplitude-phase errors among SAR antenna channels:
the first step is as follows: error code storage using dummy bit technique
Since the phase shift and attenuation inside the T/R component is 6bit, the minimum quantization error is 5.625 deg./0.5 dB. And storing the acquired ground state error data, the calibration network error data and the inter-channel error data by adopting 8 bits, wherein the lower two bits are dummy bits, and the upper 6 bits are actual control bits (dummy bit technology) of the component, and the storage precision of the data is 4 times higher than the quantization precision of the T/R component.
The second step is that: high precision compensation for channel error
And respectively storing the obtained 8-bit ground state error data code, the calibration network error code and the channel error code in a storage space of the wave control machine. And when channel compensation is carried out, adding the base state error code and the channel error code, and then taking the high 6 bits of the result to control the T/R assembly. The satellite-borne SAR antenna is provided with a plurality of T/R component channels in each receiving channel, and the final compensation effect of each receiving channel is equivalent to the mean value of the T/R component compensation values of the whole channel due to the adoption of 8-bit storage and calculation, so that the compensation accuracy with the equivalent accuracy reaching 1.4063 degrees/0.125 dB can be obtained. Therefore, high-precision compensation can be performed by using the method.
Examples
A certain space-borne SAR radar system is a 6-channel active phased-array antenna, and a system connection schematic diagram of the system is shown in fig. 4.
Step 1.1, a single T/R calibration test is carried out on the SAR antenna through a near field test system, the measurement and compensation of the error of a feed link from an SAR antenna array surface to a microwave combined link are completed, and the test result is shown in figures 4-6: FIG. 4 illustrates the effect of transmit phase compensation, (a) before compensation, and (b) after compensation; FIG. 5 illustrates the effect of receiving amplitude compensation, (a) before compensation, and (b) after compensation; FIG. 6 is a diagram showing the effect of the received phase compensation, (a) before compensation, and (b) after compensation;
step 1.2, obtaining an internal calibration network error code by transmitting an internal calibration list T/R test, and obtaining a test result after compensation as shown in FIG. 7, wherein 7 is the calibration network error compensation effect, (a) is before compensation, and (b) is after compensation;
and (3) extracting inter-channel amplitude-phase error data of the SAR antenna receiver link through the step 1.4, and storing the ground state error data, the calibration network error data and the channel error data by adopting an imaginary bit technology.
High accuracy compensation is performed by step 2.2. The result after test compensation is shown in the following table 1, the amplitude-phase error between the SAR antenna channels after the compensation according to the test result is 1.13 degrees/0.13 dB and is far higher than the quantization error 5.635 degrees/0.5 dB of the T/R component, and the high-precision compensation of the amplitude-phase error between the channels is realized.
TABLE 1 calibration results of magnitude-phase errors between channels
Although illustrative embodiments of the present invention have been described above to facilitate the understanding of the present invention by those skilled in the art, it should be understood that the present invention is not limited to the scope of the embodiments, but various changes may be apparent to those skilled in the art, and it is intended that all inventive concepts utilizing the inventive concepts set forth herein be protected without departing from the spirit and scope of the present invention as defined and limited by the appended claims.
Claims (7)
1. A method for measuring and compensating amplitude and phase errors among channels of a multi-channel satellite-borne SAR antenna is characterized by comprising the following steps:
step 1, measuring the amplitude-phase error between SAR antenna channels, which specifically comprises the following steps:
step 1.1: acquiring ground state error data of a feed link;
step 1.2, obtaining calibration network error data;
step 1.3, judging the error compensation effect of the calibration network;
step 1.4, error data between channels is obtained;
step 2, compensating the amplitude-phase error between the channels of the SAR antenna, which specifically comprises the following steps:
step 2.1, storing the error code by adopting a dummy bit technology;
and 2.2, compensating the amplitude and phase errors among the channels.
2. The method for measuring and compensating the amplitude-phase error among the channels of the multi-channel space-borne SAR antenna according to claim 1, wherein the step 1.1 of obtaining the ground state error data of the feed link specifically comprises:
and under the condition that the wave control codes are all zero, a plane near-field test system is adopted to measure the amplitude-phase data, namely the ground state error data, of the radiation unit corresponding to each T/R component of the SAR receiving and transmitting feed link, the T/R component of the radiation unit corresponding to the near-field probe is in a working state, and other T/R components are in a load state during each test.
3. The method for measuring and compensating the amplitude-phase error between the channels of the multi-channel space-borne SAR antenna according to claim 1, wherein the step 1.2 obtains the calibration network error data, specifically as follows:
on the basis of obtaining the ground state error data of the feed link in the step 1.1, the feed link is calibrated, then the internal calibration function of the SAR radar is used for carrying out emission single T/R calibration test on the SAR antenna, and the amplitude-phase error data of the in-plane calibration network of the SAR antenna array is obtained.
4. The method for measuring and compensating the amplitude-phase error among the channels of the multi-channel space-borne SAR antenna according to claim 1, wherein the step 1.3 judges the effect of calibrating the network error compensation, and specifically comprises the following steps:
adding the calibration network error data obtained in the step 1.2 and the transmission feeder link ground state error data to obtain total transmission error data, calibrating the SAR antenna, performing transmission single T/R calibration test by adopting an internal calibration function of the SAR radar, checking whether the obtained phase data is in a range of +/-5.625 degrees, if the obtained phase data is not in the range of +/-5.625 degrees, iteratively updating the calibration network error data, and repeating the step 1.3; if the error value is within the range of +/-5.625 degrees, the next step is carried out.
5. The method for measuring and compensating the inter-channel amplitude-phase error of the multi-channel space-borne SAR antenna according to claim 1, wherein the step 1.4 of obtaining inter-channel error data specifically comprises:
adding the calibration network error data obtained in the step 1.2 or 1.3 and the receiving feeder link ground state error data obtained in the step 1.1 to obtain total receiving error data, and calibrating the SAR antenna; and performing a receiving single T/R calibration test by adopting an internal calibration function of the SAR, and respectively performing complex average on each receiving channel according to the obtained amplitude-phase data to obtain inter-channel amplitude-phase error data.
6. The method for measuring and compensating the amplitude-phase error between the channels of the multi-channel space-borne SAR antenna according to claim 1, wherein in the step 2.1, the error code is stored by using a dummy bit technique, which specifically comprises:
and storing the acquired ground state error data, the calibration network error data and the inter-channel error data by adopting 8 bits, wherein the lower two bits are dummy bits, and the upper 6 bits are actual control bits of the T/R component.
7. The method for measuring and compensating the inter-channel amplitude and phase errors of the multi-channel space-borne SAR antenna according to claim 1, wherein the step 2.2 of compensating the inter-channel amplitude and phase errors specifically comprises:
and respectively storing the obtained 8-bit ground state error data code, the calibration network error code and the inter-channel error code in a storage space of a wave control machine, adding the ground state error code and the channel error code when performing channel compensation, and then taking the high 6 bits of the result to control the T/R assembly.
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