Data processing method for measuring ionosphere by satellite-ground non-time-synchronous dual-frequency ground station

Abstract

The invention relates to a data processing method for measuring an ionized layer by a satellite-ground non-time-synchronous dual-frequency ground station, and the method comprises the steps: carrying out the data subpackage based on a certain criterion, so as to carry out the data processing based on the processing capability of an existing computer; carrying out pulse compression on the received signal, extracting a correct peak value position, and estimating the absolute quantity of the TEC value of the ionized layer; and performing phase ambiguity resolution on the dual-frequency SAR signal, and estimating the variable quantity of the TEC value of the ionized layer. The invention provides a set of complete data processing method aiming at practical problems encountered in data processing for measuring the ionosphere by a satellite-ground non-time-synchronous dual-frequency ground station, the set of data processing method can be applied to ground station data processing, and the data processing efficiency is improved based on the processing capacity of an existing computer. And the absolute quantity and the variable quantity of the TEC value of the ionized layer are successfully inverted.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of ionosphere measurement, in particular to a data processing method for measuring ionosphere by a non-time-synchronized dual-frequency ground station. BACKGROUND

[0002] The ionosphere is located about 70km~1000km above the earth. The ionosphere has various effects on the signal propagation of the satellite-earth link radio system. In order to describe the influence of the ionosphere on the electromagnetic wave propagation, the existing technology introduces the ionosphere total electron content TEC (Total Electronic Content): the integral of the electron density along the propagation path, which is a very important parameter.

[0003] The influence of the ionosphere on the electromagnetic wave signal is related to the frequency. The lower the frequency, the more serious the influence of the ionosphere on the electromagnetic wave signal. The ionosphere will deteriorate the low-frequency SAR imaging, such as P, L band SAR imaging. In order to correct the influence of the ionosphere on the SAR imaging, the ionosphere TEC value of the same path at the same time must be known. When obtaining the ionosphere TEC value, the existing technology has a contradiction between the massive data and the existing computer configuration. SUMMARY

[0004] In order to overcome at least one of the deficiencies in the prior art, the present application provides a data processing method for measuring ionosphere by a non-time-synchronized dual-frequency ground station.

[0005] In a first aspect, a data processing method for measuring ionosphere by a non-time-synchronized dual-frequency ground station is provided, comprising: The ground station receives a dual-frequency SAR signal, the dual-frequency SAR signal includes two SAR signals with different carrier frequencies, denoted as a first SAR signal and a second SAR signal; the data packets of each SAR signal in the dual-frequency SAR signal are packetized to obtain a plurality of data packets; The data packets of each SAR signal are pulse compressed to determine the positions of all pulse compression peaks; According to the positions of all pulse compression peaks of the first SAR signal and the positions of all pulse compression peaks of the second SAR signal, a time delay difference is determined; based on the time delay difference, an absolute amount of ionosphere TEC value is determined; For each SAR signal, the phase ambiguity integer number is determined according to the phase change amount of the signal at the adjacent pulse compression peak positions; the phase change amount of the ionosphere TEC value change introduced into the signal is determined according to the phase ambiguity integer number; According to the phase change amount of the ionosphere TEC value change introduced into the signal corresponding to each SAR signal, the ionosphere TEC value change amount is calculated.

[0006] In one embodiment, data packets are packaged for each of the dual-frequency SAR signals, and the following criterion is adopted: It is necessary to ensure that the data packets before and after overlap with each other; the overlapping data is stored as an overlapping data packet.

[0007] In one embodiment, the positions of all pulse compression peak values are determined, including: The position of the last pulse compression peak value of each data packet is determined by the following method: The two adjacent data packets before and after are denoted as a first data packet and a second data packet respectively; the overlapping data of the first data packet and the second data packet is stored as an overlapping data packet; The serial number of the last pulse compression peak value in the overlapping data packet is determined, and the pulse compression peak value corresponding to the serial number in the second data packet is found; the position of the pulse compression peak value is the position of the last pulse compression peak value of the first data packet.

[0008] In one embodiment, the time delay difference is determined according to the positions of all pulse compression peak values of the first SAR signal and the positions of all pulse compression peak values of the second SAR signal, including: The position difference is obtained by subtracting the positions corresponding to the same pulse for the positions of all pulse compression peak values of the first SAR signal and the positions of all pulse compression peak values of the second SAR signal; The time delay difference is obtained according to the position difference and the sampling frequency.

[0009] In one embodiment, the absolute amount of ionospheric TEC value is determined based on the time delay difference, and the following formula is adopted:

[0010] wherein, is the time delay difference, is the absolute amount of ionospheric TEC value, is the speed of light, is the carrier frequency of the first SAR signal, is the carrier frequency of the second SAR signal.

[0011] In one embodiment, for each SAR signal, the phase ambiguity integer number is determined according to the signal phase change amount at the positions of adjacent pulse compression peak values, including: All satisfying the following formula are determined: :

[0012] wherein, is the phase ambiguity integer number corresponding to the first SAR signal, is the phase ambiguity integer number corresponding to the second SAR signal, a signal phase change amount at a position of an adjacent pulse compression peak value of the first SAR signal, a signal phase change amount at a position of an adjacent pulse compression peak value of the second SAR signal, a carrier frequency of the first SAR signal, a carrier frequency of the second SAR signal, a threshold value; if , the value of is not unique, the final phase ambiguity integer number corresponding to the first SAR signal is determined according to the following formula , and the final phase ambiguity integer number corresponding to the second SAR signal is determined according to the following formula : .

[0013] In an embodiment, the phase change amount introduced into the signal by the ionospheric TEC value change amount is determined according to the phase ambiguity integer number, and the following formula is used:

[0014]

[0015] wherein, is the phase change amount introduced into the signal by the ionospheric TEC value change amount corresponding to the first SAR signal, is the final phase ambiguity integer number corresponding to the first SAR signal, is a signal phase change amount at a position of an adjacent pulse compression peak value of the first SAR signal, is the phase change amount introduced into the signal by the ionospheric TEC value change amount corresponding to the second SAR signal, is the final phase ambiguity integer number corresponding to the second SAR signal, is a signal phase change amount at a position of an adjacent pulse compression peak value of the second SAR signal.

[0016] In an embodiment, the ionospheric TEC value change amount is calculated according to the phase change amount introduced into the signal by the ionospheric TEC value change amount corresponding to each SAR signal, and the following formula is used:

[0017]

[0018]

[0019] wherein, is the ionospheric TEC value change amount obtained according to the first SAR signal, is the speed of light, is a carrier frequency of the first SAR signal, a phase variation amount of the ionospheric TEC value variation amount introduced into the signal corresponding to the first SAR signal, an ionospheric TEC value variation amount obtained according to the second SAR signal, a carrier frequency of the second SAR signal, a phase variation amount of the ionospheric TEC value variation amount introduced into the signal corresponding to the second SAR signal, an estimated value of the ionospheric TEC value variation amount.

[0020] In a second aspect, a data processing device for measuring an ionosphere by a non-time-synchronized dual-frequency ground station is provided, and the device comprises: a data packet module configured to receive a dual-frequency SAR signal by the ground station, wherein the dual-frequency SAR signal comprises two SAR signals with different carrier frequencies, denoted as a first SAR signal and a second SAR signal; and perform data packeting on each SAR signal in the dual-frequency SAR signal to obtain a plurality of data packets; a pulse compression peak position determination module configured to perform pulse compression on the data packets of each SAR signal to determine positions of all pulse compression peaks; a TEC value absolute amount determination module configured to determine a time delay difference according to the positions of all pulse compression peaks of the first SAR signal and the positions of all pulse compression peaks of the second SAR signal; and determine an absolute amount of the ionospheric TEC value based on the time delay difference; a phase variation amount determination module configured to, for each SAR signal, determine a phase ambiguity integer number according to a phase variation amount of the signal at adjacent pulse compression peak positions; and determine a phase variation amount of the ionospheric TEC value variation amount introduced into the signal according to the phase ambiguity integer number; a TEC value variation amount calculation module configured to calculate the ionospheric TEC value variation amount according to the phase variation amount of the ionospheric TEC value variation amount introduced into the signal corresponding to each SAR signal.

[0021] Compared with the prior art, the present application has the following beneficial effects: 1. The present application proposes a data packeting criterion based on the characteristics of continuous reception data and signal processing, solves the contradiction between massive data and existing computer configurations, and ensures the continuity of signal processing while meeting the existing computer capabilities.

[0022] 2. The present application provides an accurate method for determining the peak value of the pulse compression signal, which improves the estimation accuracy of the absolute amount of the ionospheric TEC value.

[0023] 3. The present application adopts a phase demodulation method of the dual-frequency SAR signal, so that the measurement of the ionospheric TEC value variation amount can not be limited. BRIEF DESCRIPTION OF DRAWINGS

[0024] This application can be better understood by referring to the description given below in conjunction with the accompanying drawings, which, together with the detailed description below, are incorporated in and form part of this specification. In the drawings: Figure 1 A schematic diagram illustrates the data processing method for measuring the ionosphere using a dual-frequency ground station with non-synchronous satellite-to-ground communication. Figure 2 The estimated results of the absolute value of TEC are shown; Figure 3 This shows the estimation error of the absolute value of TEC; Figure 4 The estimated results of the change in TEC value are shown; Figure 5 The estimation error of the change in TEC value is shown. Detailed Implementation

[0025] Exemplary embodiments of the present application will be described below with reference to the accompanying drawings. For clarity and brevity, not all features of the actual embodiments are described in the specification. However, it should be understood that many embodiment-specific decisions can be made in the development of any such actual embodiment to achieve the developer’s specific objectives, and these decisions may vary as the embodiments differ.

[0026] It should also be noted that, in order to avoid obscuring this application with unnecessary details, only the device structure closely related to the solution of this application is shown in the accompanying drawings, while other details that are not closely related to this application are omitted.

[0027] It should be understood that this application is not limited to the described embodiments by virtue of the following description with reference to the accompanying drawings. In this document, embodiments may be combined with each other, features may be substituted or borrowed between different embodiments, and one or more features may be omitted in one embodiment, where feasible.

[0028] To measure the ionosphere, dual-frequency SAR payloads are required to share the same signal source, undergoing different frequency conversion processes to obtain dual-frequency signals; the dual-frequency SAR payloads simultaneously transmit dual-frequency signals. The time delay and phase of the SAR signal received by the ground station are related to the carrier frequency; therefore, the ionospheric TEC value can be estimated based on the dual-frequency SAR signal.

[0029] This application provides a data processing method for measuring the ionosphere using a dual-frequency ground station with non-synchronous satellite-to-ground communication. Figure 1 A schematic diagram illustrating the data processing method for ionospheric measurements using a dual-frequency ground station with non-synchronous satellite-to-ground communication is shown. (See attached diagram.) Figure 1 The method mainly includes the following steps: Step S1: The ground station receives a dual-frequency SAR signal, which includes two SAR signals with different carrier frequencies, referred to as the first SAR signal and the second SAR signal; each SAR signal in the dual-frequency SAR signal is divided into data packets to obtain multiple data packets.

[0030] The received data volume is in the terabyte range, making it difficult to process on a regular computer. Therefore, the data (Data_all) needs to be divided into packets.

[0031] The criteria for data packetization are as follows: (1) It is necessary to ensure that the data packets before and after the data packets overlap, for example, overlap for 1 second.

[0032] (2) In order to determine the correct location of the full pulse pressure peak, the overlapping data is stored separately as a data packet, i.e., the overlapping data packet.

[0033] Here, based on the characteristics of continuous data reception and signal processing, a data packetization criterion is proposed, which resolves the contradiction between massive data and existing computer configuration, ensuring the continuity of signal processing while meeting the capabilities of existing computers.

[0034] Step S2: Perform pulse compression on the data packets of each SAR signal to determine the location of all pulse compression peaks.

[0035] Here, pulse compression is performed on each data packet to obtain the peak values ​​of each pulse compression.

[0036] Data packetization may result in the same pulse signal received by the ground station from the satellite being divided into two adjacent data packets, referred to as the first data packet and the second data packet, respectively. This makes the last pulse pressure peak of the first data packet and the first pulse pressure peak of the second data packet incomplete pulse pressure peaks, and thus the position of the pulse pressure peak is also inaccurate.

[0037] To accurately determine the location of the last pulse pressure peak in the first data packet, the sequence number of the last pulse pressure peak in the overlapping data packet is first determined, and the pulse pressure peak with the corresponding sequence number is found in the second data packet. The location of this pulse pressure peak is the location of the last pulse pressure peak in the first data packet.

[0038] Step S3: Determine the time delay difference based on the positions of all pulse compression peaks of the first SAR signal and the positions of all pulse compression peaks of the second SAR signal; determine the absolute value of the ionospheric TEC based on the time delay difference.

[0039] Specifically, methods for determining time delay differences include: For the positions of all pulse compression peaks of the first SAR signal and the positions of all pulse compression peaks of the second SAR signal, the positions corresponding to the same pulse are subtracted to obtain the position difference; then, based on the position difference and the sampling frequency, the time delay difference is obtained. Here, the position difference is divided by the sampling frequency to obtain the time delay difference.

[0040] Specifically, the absolute value of the ionospheric TEC is determined using the following formula:

[0041] in, Due to time delay differences, It is the absolute value of the ionospheric TEC. At the speed of light, The carrier frequency of the first SAR signal. This is the carrier frequency of the second SAR signal.

[0042] Step S4: For each SAR signal, determine the number of phase ambiguity integers based on the signal phase change at adjacent pulse compression peak positions; determine the amount of phase change introduced into the signal by the ionospheric TEC value change based on the number of phase ambiguity integers.

[0043] According to existing technology, Because of the noise in the signal, Not equal to Therefore, setting a threshold .

[0044] Determine all that satisfy the following formula , :

[0045] in, The integer number of phase ambiguity cycles corresponding to the first SAR signal. The integer number of phase ambiguity cycles corresponding to the second SAR signal. This represents the signal phase change at the adjacent pulse compression peak positions of the first SAR signal. This represents the signal phase change at the adjacent pulse compression peak positions of the second SAR signal. The carrier frequency of the first SAR signal. The carrier frequency of the second SAR signal. For threshold; for The unambiguous phase, for The unambiguous phase.

[0046] like , If the value of is not unique, the final phase ambiguity integer number corresponding to the first SAR signal is determined according to the following formula. The final integer number of phase ambiguity corresponding to the second SAR signal : .

[0047] Specifically, the phase change introduced into the signal by the change in ionospheric TEC value is determined based on the integer number of phase ambiguity cycles, using the following formula:

[0048]

[0049] in, The phase change is introduced into the signal by the change in the ionospheric TEC value corresponding to the first SAR signal. This represents the integer number of phase ambiguity cycles corresponding to the final first SAR signal. This represents the signal phase change at the adjacent pulse compression peak positions of the first SAR signal. The phase change is introduced into the signal by the change in the ionospheric TEC value corresponding to the second SAR signal. This represents the integer number of phase ambiguity cycles corresponding to the final second SAR signal. This represents the signal phase change at the adjacent pulse compression peak position of the second SAR signal.

[0050] Here, the phase deambiguation method of dual-frequency SAR signals is used, so that there is no upper limit to the measurement of the change in ionospheric TEC value.

[0051] Step S5: Calculate the change in ionospheric TEC value, i.e., the change in TEC value of the ionosphere at adjacent pulse times, based on the phase change introduced into the signal according to the change in ionospheric TEC value corresponding to each SAR signal.

[0052] Specifically, the following formula can be used:

[0053]

[0054]

[0055] in, The change in ionospheric TEC value obtained from the first SAR signal. At the speed of light, The carrier frequency of the first SAR signal. The phase change is introduced into the signal by the change in the ionospheric TEC value corresponding to the first SAR signal. The change in ionospheric TEC value obtained from the second SAR signal. The carrier frequency of the second SAR signal. The phase change is introduced into the signal by the change in the ionospheric TEC value corresponding to the second SAR signal. This is an estimate of the change in the ionospheric TEC value.

[0056] To further verify the effectiveness of the method in this application, the following simulation analysis was conducted.

[0057] Simulation parameters:

[0058] Figure 2 The estimated results of the absolute value of TEC are shown. Figure 3 The estimation error of the absolute value of TEC is shown. Figure 4 The estimated results of the change in TEC value are shown. Figure 5 The estimation error of the change in TEC value is shown.

[0059] according to Figures 2-5 It is evident that the method of this application can accurately estimate the absolute value of TEC and the change in TEC value.

[0060] Based on the same inventive concept as the data processing method for ionospheric measurements using a dual-frequency ground station with non-synchronous satellite-to-ground communication, this embodiment also provides a corresponding data processing apparatus for ionospheric measurements using a dual-frequency ground station with non-synchronous satellite-to-ground communication, including: The data packetization module is used by the ground station to receive dual-frequency SAR signals, which include two SAR signals with different carrier frequencies, referred to as the first SAR signal and the second SAR signal; and to divide each SAR signal in the dual-frequency SAR signal into data packets to obtain multiple data packets. The pulse compression peak location determination module is used to perform pulse compression on the data packets of each SAR signal and determine the location of all pulse compression peaks; The absolute value determination module for TEC is used to determine the time delay difference based on the positions of all pulse compression peaks of the first SAR signal and the positions of all pulse compression peaks of the second SAR signal; and to determine the absolute value of the ionospheric TEC based on the time delay difference. The phase change determination module is used to determine the number of phase ambiguity integers for each SAR signal based on the signal phase change at adjacent pulse compression peak positions; and to determine the amount of phase change introduced into the signal by the ionospheric TEC value change based on the number of phase ambiguity integers. The TEC value change calculation module is used to calculate the ionospheric TEC value change based on the phase change introduced into the signal by the ionospheric TEC value change corresponding to each SAR signal.

[0061] The data processing device for measuring the ionosphere using a dual-frequency ground station with non-synchronous space-to-ground communication in this embodiment has the same inventive concept as the data processing method for measuring the ionosphere using a dual-frequency ground station with non-synchronous space-to-ground communication described above. Therefore, the specific implementation of this device can be found in the embodiment section of the data processing method for measuring the ionosphere using a dual-frequency ground station with non-synchronous space-to-ground communication described above, and its technical effects correspond to the technical effects of the above method, so it will not be repeated here.

[0062] The above descriptions are merely various embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A data processing method for measuring ionosphere by a non-time-synchronized dual-frequency ground station of satellite-ground, characterized in that, The method comprises the following steps: The ground station receives a dual-frequency SAR signal, wherein the dual-frequency SAR signal comprises two SAR signals with different carrier frequencies, denoted as a first SAR signal and a second SAR signal; Data packets are obtained by performing data packeting on each SAR signal in the dual-frequency SAR signal; The positions of all pulse compression peaks of each SAR signal are determined by performing pulse compression on the data packets of each SAR signal; The time delay difference is determined according to the positions of all pulse compression peaks of the first SAR signal and the positions of all pulse compression peaks of the second SAR signal; The absolute amount of ionospheric TEC value is determined based on the time delay difference; For each SAR signal, the phase ambiguity integer number is determined according to the amount of signal phase change at adjacent pulse compression peak positions; The amount of phase change of the ionospheric TEC value introduced into the signal is determined according to the phase ambiguity integer number; The amount of ionospheric TEC value is calculated according to the amount of phase change of the ionospheric TEC value introduced into the signal corresponding to each SAR signal.

2. The method of claim 1, wherein, Wherein, The data packeting is performed on each SAR signal in the dual-frequency SAR signal, and the criterion adopted is: It is necessary to ensure that the data packets before and after overlap; the overlapping data is stored as an overlapping data packet.

3. The method of claim 1, wherein, The positions of all pulse compression peaks are determined, including: The position of the last pulse compression peak of each data packet is determined by the following method: The two adjacent data packets before and after are denoted as a first data packet and a second data packet; the overlapping data of the first data packet and the second data packet is stored as an overlapping data packet; The serial number of the last pulse compression peak in the overlapping data packet is determined, and the pulse compression peak with the corresponding serial number in the second data packet is found, and the position of the pulse compression peak is the position of the last pulse compression peak of the first data packet.

4. The method of claim 1, wherein, Wherein, The time delay difference is determined according to the positions of all pulse compression peaks of the first SAR signal and the positions of all pulse compression peaks of the second SAR signal, including: For the positions of all pulse compression peaks of the first SAR signal and the positions of all pulse compression peaks of the second SAR signal, the positions corresponding to the same pulse are subtracted to obtain the position difference; The time delay difference is obtained according to the position difference and the sampling frequency.

5. The method of claim 1, wherein, Wherein, The absolute amount of ionospheric TEC value is determined based on the time delay difference, and the following formula is adopted: wherein, is a time delay difference, is an absolute value of ionospheric TEC, is a speed of light, is a carrier frequency of the first SAR signal, is a carrier frequency of the second SAR signal.

6. The method of claim 1, wherein, Wherein, For each SAR signal, the phase ambiguity integer number is determined according to the amount of signal phase change at adjacent pulse compression peak positions, including: determining all of the , : wherein, is a phase ambiguity integer number corresponding to the first SAR signal, is a phase ambiguity integer number corresponding to the second SAR signal, is a signal phase variation amount at a position of an adjacent pulse compression peak value of the first SAR signal, is a signal phase variation amount at a position of an adjacent pulse compression peak value of the second SAR signal, is a carrier frequency of the first SAR signal, is a carrier frequency of the second SAR signal, is a threshold; If , is not unique, the final phase ambiguity integer number corresponding to the first SAR signal is determined according to the following formula , and the final phase ambiguity integer number corresponding to the second SAR signal is determined according to the following formula : 。 7. The method of claim 1, wherein, Wherein, The amount of phase change of the ionospheric TEC value introduced into the signal is determined according to the phase ambiguity integer number, and the following formula is adopted: wherein, is a phase change amount introduced into the signal by an ionospheric TEC value change amount corresponding to the first SAR signal, is a final phase ambiguity integer number corresponding to the first SAR signal, is a signal phase change amount at a position of an adjacent pulse compression peak value of the first SAR signal, is a phase change amount introduced into the signal by an ionospheric TEC value change amount corresponding to the second SAR signal, is a final phase ambiguity integer number corresponding to the second SAR signal, is a signal phase change amount at a position of an adjacent pulse compression peak value of the second SAR signal.

8. The method of claim 1, wherein, Wherein, The amount of ionospheric TEC value is calculated according to the amount of phase change of the ionospheric TEC value introduced into the signal corresponding to each SAR signal, and the following formula is adopted: wherein, is an ionospheric TEC value variation quantity obtained according to the first SAR signal, is the speed of light, is a carrier frequency of the first SAR signal, is a phase variation quantity introduced into the signal by the ionospheric TEC value variation quantity corresponding to the first SAR signal, is an ionospheric TEC value variation quantity obtained according to the second SAR signal, is a carrier frequency of the second SAR signal, is a phase variation quantity introduced into the signal by the ionospheric TEC value variation quantity corresponding to the second SAR signal, is an estimated value of the ionospheric TEC value variation quantity.

9. A data processing device for measuring ionosphere by a non-time-synchronized dual-frequency ground station of satellite-ground, characterized in that, The method comprises the following steps: A data packeting module is configured to receive a dual-frequency SAR signal by a ground station, wherein the dual-frequency SAR signal comprises two SAR signals with different carrier frequencies, denoted as a first SAR signal and a second SAR signal; and data packets are obtained by performing data packeting on each SAR signal in the dual-frequency SAR signal; a pulse compression peak position determination module configured to pulse compress each data packet of the SAR signals and determine positions of all pulse compression peaks; a TEC value absolute amount determination module configured to determine a time delay difference according to the positions of all pulse compression peaks of the first SAR signal and the positions of all pulse compression peaks of the second SAR signal; determine an absolute amount of ionospheric TEC value based on the time delay difference; a phase change amount determination module configured to determine, for each SAR signal, a phase ambiguity integer number according to a phase change amount of signals at adjacent pulse compression peak positions; determine a phase change amount of ionospheric TEC value change introduced into signals according to the phase ambiguity integer number; a TEC value change amount calculation module configured to calculate an ionospheric TEC value change amount according to the phase change amount of ionospheric TEC value change introduced into signals corresponding to each SAR signal.

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