CN103792535B - A kind of method utilizing SAR Satellite observation ionized layer TEC value - Google Patents

Abstract

The invention discloses a kind of method utilizing SAR Satellite observation ionized layer TEC value.After satellite-borne SAR transponder pulse signal passes through ionosphere, in its phase place, comprise ionized layer TEC information complete on travel path.The method chooses some sub-bands from the SAR signal with certain bandwidth, to provide the degree of freedom needed for Used for Unwrapping Phase Ambiguity.By technological means such as optimal design sub-band parameters, while taking into account TEC value estimated accuracy, eliminate the impact of electromagnetic wave propagation distance phase place on Used for Unwrapping Phase Ambiguity process.Finally build Used for Unwrapping Phase Ambiguity equation, final realization is estimated the high precision of ionized layer TEC value.Ionized layer TEC value estimated by utilization compensates satellite-borne SAR phase of echo, effectively can improve Space-borne SAR Imaging quality and interferometry precision.

Description

A kind of method utilizing SAR Satellite observation ionized layer TEC value

Technical field

The present invention relates to a kind of method measuring ionized layer TEC value, particularly relate to a kind of method that the SAR of utilization satellite realizes high-acruracy survey ionized layer TEC value, belong to geostationary orbit SAR system development field.

Background technology

Satellite-borne SAR is launched and is received electromagnetic wave after passing through ionosphere, the propagation effects such as group delay, phase drift, dispersion and faraday's polarized rotation can be there is, thus the SAR image quality of low-frequency range is impacted, for geostationary orbit SAR (GEOSAR) because its synthetic aperture time is long, the impact that ionospheric change in time and space causes GEOSAR imaging is further serious.Many research structures (as U.S. NASAJPL, Cranfield university of Britain, the Chinese Academy of Space Technology, Chinese Academy of Sciences electron institute, Beijing Institute of Technology) have carried out the correlative study of GEOSAR both at home and abroad at present.Subsidize the U.S. jet propulsion laboratory (JPL) of carrying out GEOSAR research by U.S. NASA to point out: accurately understanding the impact of atmospheric disturbance on SAR signal is the key issue obtaining meaningful conclusion.Britain's Cranfield (Cranfield) university has carried out passive double-basis GEOSAR systematic study, and points out that the impact of air is most important to GEOSAR imaging.

For ionosphere, the main method that GEOSAR impact corrects to be comprised both at home and abroad at present: based on Phase gradient autofocus (PGA) method, weighted least require method and Minimum entropy method etc. of orientation to process; Based on distance to the adaptive matched filter method of process and distance multiple look processing method; Existing measurement means is utilized ionized layer TEC value to be carried out to the method etc. measured in real time.The impact of Ionospheric variability on azimuth focus can be compensated to the PGA method processed for orientation, but it needs on the one hand to exist in the picture an isolated spy and shows a little, the method can only estimate the time dependent high-order term in ionosphere on the other hand, be unable to estimate constant term and the once item of the change of ionized layer TEC value, even if therefore realize the azimuth focus of image, but still cannot solve for the positioning error of image and follow-up interferometry error.Similar with PGA method, orientation can be compensated to a certain extent to dispersion problem for weighted least require method and Minimum entropy method, but all be difficult to accurately estimate TEC value, thus cannot accurate phase compensation be carried out.The bandwidth simultaneously transmitted due to SAR is usually relatively little compared with its carrier frequency, for distance to adaptive matched filter method estimate that the precision of ionized layer TEC value is very low, be difficult to the requirement meeting high imaging quality.For apart from many vision methods, it is by becoming two parts by spectrum imaging, delay inequality is therebetween estimated respectively after imaging, and then estimate ionized layer TEC value, the method is subject to the restriction of SAR signal bandwidth equally, time delay estimation precision is lower, and (take carrier frequency as 1GHz, bandwidth is 40M is example, and the delay inequality that 1TECU causes only has 10 ^-10the magnitude of second), be therefore difficult to the size accurately estimating ionized layer TEC value.Due to ionosphere on the impact of Electromagnetic Wave Propagation on the one hand with space electronic density and distribute relevant, on the other hand and electromagnetic wave propagation path-dependent.And the pulse signal of SAR institute launching and receiving is constantly change in time with space, guarantee is difficult to identical with the time with the path of SAR transmitting and receiving signal for ionospheric measurement, there is certain deviation in the TEC value therefore measured, thus can not fine compensation ionosphere on the impact of SAR image quality.

The domestic and international research for GEOSAR is all at the early-stage at present, and to overcome ionosphere for the impact of GEOSAR imaging be the most key and one of the problem that must solve of GEOSAR research.This problem has become the hot issue of SAR area research both at home and abroad at present.

Summary of the invention

The technical matters that the present invention solves is: overcome the deficiencies in the prior art, a kind of method utilizing SAR Satellite observation ionized layer TEC value is provided, satellite-borne SAR its own signal is utilized to carry the feature of complete ionosphere information, extract the phase information of multiple selected sub-band, ionized layer TEC value is estimated by technological means such as multifrequency ambiguity solutions, thus compensate the impact of ionosphere on Space-borne SAR Imaging and interferometry, improve image quality and interferometry precision.

Technical scheme of the present invention is: a kind of method utilizing SAR Satellite observation ionized layer TEC value, comprises the steps:

(1) at ground configuration SAR signal receiver for receiving the pulse signal of SAR satellite launch;

(2) from the SAR satellite pulse signal that step (1) receives, choose three sub-band signals, be respectively sub-band 1, sub-band 2 and sub-band 3, sub-band 1, sub-band 2 are respectively f with the carrier frequency of sub-band 3 three sub-band signals ₁, f ₂, f ₃, the carrier frequency of three sub-bands meets f ₃>f ₂>f ₁, and f ₂-f ₁=f ₃-f ₂=Δ f;

(3) frequency spectrum of three sub-band signals step (2) chosen is moved respectively, its spectral centroid frequency is made all to be positioned at zero-frequency, then utilize matched filtering to carry out process of pulse-compression to three sub-band signals respectively, obtain the phase place Φ at three sub-band signal peak point places _n(n=1,2,3);

(4) the phase place Φ at three the sub-band signal peak point places obtained according to step (3) _n(n=1,2,3) calculate the interferometric phase of sub-band 1 and sub-band 2 signal peak value point, and computing formula is Φ ₁₂=angle [exp (j Φ ₁) × exp (-j Φ ₂)]; Calculate the interferometric phase of sub-band 2 and sub-band 3 signal peak value point, computing formula is Φ ₂₃=angle [exp (j Φ ₂) × exp (-j Φ ₃)]; Wherein defining angle [exp (j (α+2k π))]=α, α ∈ [-π, π], k is integer,

(5) the interferometric phase Φ that step (4) obtains is utilized ₁₂and Φ ₂₃solve ionized layer TEC value, computing formula is as follows:

$\mathrm{TEC}=\frac{((f_2-f_1){\mathrm{\Φ}}_{23}-(f_3-f_2){\mathrm{\Φ}}_{12})c}{2\mathrm{\π}40.3((f_2-f_1)(\frac{1}{f_2}-\frac{1}{f_3})-(f_3-f_2)(\frac{1}{f_1}-\frac{1}{f_2}))}$

Wherein, c is the light velocity.

Utilize a method for SAR Satellite observation ionized layer TEC value, it is characterized in that comprising the steps:

(1) at ground configuration SAR signal receiver for receiving the pulse signal of SAR satellite launch;

(2) from the SAR satellite pulse signal that step (1) receives, choose three sub-band signals, be respectively sub-band 1, sub-band 2 and sub-band 3, sub-band 1, sub-band 2 are respectively f with the carrier frequency of sub-band 3 three sub-band signals ₁, f ₂, f ₃, the carrier frequency of three sub-bands meets f ₃>f ₂>f ₁, f ₂-f ₁≠ f ₃-f ₂;

(3) frequency spectrum of three sub-band signals step (2) chosen is moved respectively, its spectral centroid frequency is made all to be positioned at zero-frequency, then utilize matched filtering to carry out process of pulse-compression to three sub-band signals respectively, obtain the phase place Φ at three sub-band signal peak point places _n(n=1,2,3);

(4) relevant ephemeris information is utilized to obtain the rough estimate evaluation of electromagnetic wave true propagation distance R utilize respectively to the phase place Φ of three sub-band signal peak points that step (3) obtains _n(n=1,2,3) compensate, and can be compensated the phase place of rear three sub-band signals:

${\mathrm{\Φ}}_n^{\′}=\mathrm{angle}\left[\exp \left(j({\mathrm{\Φ}}_n+\frac{2\mathrm{\π}\hat{R}{f}_n}{c})\right)\right],n=\mathrm{1,2,3};$

Wherein, definition angle [exp (j (α+2k π))]=α, α ∈ [-π, π], k are integer,

(5) judge whether the carrier frequency of three sub-bands meets following constraint condition:

$\left\{\begin{array}{c}-\mathrm{\&pi;}<{\mathrm{\&Phi;}}_2^{\&prime;}+2\mathrm{\&pi;}\frac{\mathrm{\&Delta;R}}{c}(f_2-f_1)<\mathrm{\&pi;}\\ -\mathrm{\&pi;}<{\mathrm{\&Phi;}}_2^{\&prime;}+2\mathrm{\&pi;}\frac{\mathrm{\&Delta;R}}{c}(f_2-f_3)<\mathrm{\&pi;}\end{array}\right.$

If meet, enter (6), otherwise re-execute step (2)-(5), wherein Δ R is electromagnetic wave true propagation distance R and its rough estimate evaluation between evaluated error, c is the light velocity;

(6) the phase place Φ ' at three the sub-band signal peak point places obtained according to step (4) _n(n=1,2,3) calculate the interferometric phase of sub-band 1 and sub-band 2 signal peak value point, and computing formula is Φ ₁₂=angle [exp (j Φ ' ₁) × exp (-j Φ ' ₂)]; Calculate the interferometric phase of sub-band 2 and sub-band 3 signal peak value point, computing formula is Φ ₂₃=angle [exp (j Φ ' ₂) × exp (-j Φ ' ₃)]; Wherein defining angle [exp (j (α+2k π))]=α, α ∈ [-π, π], k is integer,

(7) the interferometric phase Φ that step (6) obtains is utilized ₁₂and Φ ₂₃solve ionized layer TEC value, computing formula is as follows:

$\mathrm{TEC}=\frac{((f_2-f_1){\mathrm{\&Phi;}}_{23}-(f_3-f_2){\mathrm{\&Phi;}}_{12})c}{2\mathrm{\&pi;}40.3((f_2-f_1)(\frac{1}{f_2}-\frac{1}{f_3})-(f_3-f_2)(\frac{1}{f_1}-\frac{1}{f_2}))}$

Wherein, c is the light velocity.

The present invention compared with prior art has following beneficial effect:

(1) the present invention proposes the solution that two kinds overcome distance phase effect, can take into account the estimated accuracy of TEC value, effectively eliminate again the impact of distance phase place;

(2) the present invention is by the phase interference between multiple sub-band signal, solves phase fuzzy problem, thus can estimate ionized layer TEC value accurately;

(3) the ionized layer TEC value measured by the present invention is identical with the exomonental travel path of SAR and time, thus can accurate compensation SAR phase of echo error, improves image quality and interferometry precision.

Accompanying drawing explanation

Fig. 1 is the processing flow chart of the inventive method scheme 1;

Fig. 2 is the processing flow chart of the inventive method scheme 2.

Embodiment

After satellite-borne SAR transponder pulse signal passes through ionosphere, in its phase place, comprise ionized layer TEC information complete on travel path.The present invention chooses some sub-bands from the SAR signal with certain bandwidth, to provide the degree of freedom needed for Used for Unwrapping Phase Ambiguity.By technological means such as optimal design sub-band parameters, while taking into account TEC value estimated accuracy, eliminate the impact of electromagnetic wave propagation distance phase place on Used for Unwrapping Phase Ambiguity process.Finally build Used for Unwrapping Phase Ambiguity equation, final realization is estimated the high precision of ionized layer TEC value.Ionized layer TEC value estimated by utilization compensates satellite-borne SAR phase of echo, effectively can improve Space-borne SAR Imaging quality and interferometry precision.The present invention utilizes phase information to realize high-precision TEC value completely and measures, and as depicted in figs. 1 and 2, embodiment is as follows for realization flow figure:

The first step: at ground configuration SAR signal receiver, directly receives the pulse signal of SAR satellite launch, to eliminate the impact that ground scatter point is estimated TEC value.

Second step: choose three sub-bands from the SAR echo signal received.

Because the phase place receiving SAR signal is not only subject to ionosphere effect, and be subject to the impact of propagation distance R.Therefore choosing in sub-band process, overcome the impact of distance phase place by the method for choose reasonable sub-band centre frequency.Provide two sub-band centre frequency selection schemes below:

Scheme 1: the centre frequency of three sub-bands selected by supposing is respectively f ₁, f ₂, f ₃, and f ₃>f ₂>f ₁, then, when choosing three sub-band signals, between centre frequency, demand fulfillment constraint condition is: f ₂-f ₁=f ₃-f ₂=Δ f.

Scheme 2: when not selecting the constraint condition of scheme 1, i.e. f ₃>f ₂>f ₁, f ₂-f ₁≠ f ₃-f ₂time, then following methods can be adopted to eliminate the impact of distance phase place:

(1) relevant ephemeris information is utilized to obtain the rough estimate evaluation of electromagnetic wave true propagation distance R then evaluated error $\mathrm{\&Delta;R}=R-\hat{R}.$

(2) frequency spectrum of choose three sub-band signals is moved respectively, make its spectral centroid frequency all be positioned at zero-frequency, then utilize matched filtering to realize process of pulse-compression respectively, the phase place Φ at three sub-band signal peak point places can be obtained _n(n=1,2,3), utilize compensate the phase place of three sub-band signal peak points respectively, the distance phase place at compensated peak point place is the phase place of rear three sub-band signals can be compensated:

${\mathrm{\&Phi;}}_n^{\&prime;}=\mathrm{angle}\left[\exp \left(j({\mathrm{\&Phi;}}_n+\frac{2\mathrm{\&pi;}\hat{R}{f}_n}{c})\right)\right],n=\mathrm{1,2,3}$

Wherein, definition angle [exp (j (α+2k π))]=α, α ∈ [-π, π], k are integer, the now centre frequency demand fulfillment of sub-band:

$\left\{\begin{array}{c}-\mathrm{\&pi;}<{\mathrm{\&Phi;}}_2^{\&prime;}+2\mathrm{\&pi;}\frac{\mathrm{\&Delta;R}}{c}(f_2-f_1)<\mathrm{\&pi;}\\ -\mathrm{\&pi;}<{\mathrm{\&Phi;}}_2^{\&prime;}+2\mathrm{\&pi;}\frac{\mathrm{\&Delta;R}}{c}(f_2-f_3)<\mathrm{\&pi;}\end{array}\right.$

Therefore the program needs the f constantly selected by adjustment ₁, f ₂, f ₃size, until meet above-mentioned constraint condition.Wherein Δ R is electromagnetic wave true propagation distance R and its rough estimate evaluation between evaluated error, $\mathrm{\&Delta;R}=R-\hat{R}$ C is the light velocity.

3rd step: calculate the interferometric phase between sub-band signal.

(1) if adopt the constraint condition of scheme 1 in second step, the frequency spectrum of choose three sub-band signals is moved respectively, its spectral centroid frequency is made all to be positioned at zero-frequency, then utilize matched filtering to realize process of pulse-compression respectively, the phase place Φ at three sub-band signal peak point places can be obtained _n(n=1,2,3), then calculate the interferometric phase of sub-band 1 and sub-band 2 signal peak value point: Φ ₁₂=angle [exp (j Φ ₁) × exp (-j Φ ₂)], the interferometric phase of sub-band 2 and sub-band 3 signal peak value point: Φ ₂₃=angle [exp (j Φ ₂) × exp (-j Φ ₃)], wherein defining angle [exp (j (α+2k π))]=α, α ∈ [-π, π], k is integer, for the constraint condition in scheme 1, interferometric phase Φ ₁₂, Φ ₂₃meet respectively:

$\left\{\begin{array}{c}{\mathrm{\&Phi;}}_{12}+2\mathrm{M\&pi;}=2\mathrm{\&pi;}\frac{40.3\mathrm{TEC}}{c}(\frac{1}{f_2-\mathrm{\&Delta;f}}-\frac{1}{f_2})+\frac{2\mathrm{\&pi;R\&Delta;f}}{c}\\ {\mathrm{\&Phi;}}_{23}+2\mathrm{M\&pi;}=2\mathrm{\&pi;}\frac{40.3\mathrm{TEC}}{c}(\frac{1}{f_2}-\frac{1}{f_2+\mathrm{\&Delta;f}})+\frac{2\mathrm{\&pi;R\&Delta;f}}{c}\end{array}\right.---\left(1\right)$

Wherein M is an integer, represents fuzzy number.

(2) if adopt the constraint condition of scheme 2 in second step, through moving to zero-frequency, matched filtering and distance phase compensation to selected three sub-band signal spectral centroid, according to the Φ ' obtained _n(n=1,2,3) calculate the interferometric phase of sub-band 1 and sub-band 2 signal peak value point: Φ ₁₂=angle [exp (j Φ ' ₁) × exp (-j Φ ' ₂)], the interferometric phase of sub-band 2 and sub-band 3 signal peak value point: Φ ₂₃=angle [exp (j Φ ' ₂) × exp (-j Φ ' ₃)], wherein defining angle [exp (j (α+2k π))]=α, α ∈ [-π, π], k is integer, for the constraint condition in scheme 2, interferometric phase Φ ₁₂, Φ ₂₃meet respectively:

$\left\{\begin{array}{c}{\mathrm{\&Phi;}}_{12}=2\mathrm{\&pi;}\frac{40.3\mathrm{TEC}}{c}(\frac{1}{f_1}-\frac{1}{f_2})-\frac{2\mathrm{\&pi;\&Delta;R}(f_1-f_2)}{c}\\ {\mathrm{\&Phi;}}_{23}=2\mathrm{\&pi;}\frac{40.3\mathrm{TEC}}{c}(\frac{1}{f_2}-\frac{1}{f_3})-\frac{2\mathrm{\&pi;\&Delta;R}(f_2-f_3)}{c}\end{array}\right.---\left(2\right)$

4th step: can the formula of derived for solving ionized layer TEC value according to formula (1) or (2) is as follows:

$\mathrm{TEC}=\frac{((f_2-f_1){\mathrm{\&Phi;}}_{23}-(f_3-f_2){\mathrm{\&Phi;}}_{12})c}{2\mathrm{\&pi;}40.3((f_2-f_1)(\frac{1}{f_2}-\frac{1}{f_3})-(f_3-f_2)(\frac{1}{f_1}-\frac{1}{f_2}))}$

Utilize the interferometric phase Φ that the 3rd step obtains ₁₂and Φ ₂₃try to achieve ionized layer TEC value according to above formula, wherein c is the light velocity.

Because the interferometric phase calculated value between sub-band has certain error, so according to formula $\mathrm{TEC}=\frac{((f_2-f_1){\mathrm{\&Phi;}}_{23}-(f_3-f_2){\mathrm{\&Phi;}}_{12})c}{2\mathrm{\&pi;}40.3((f_2-f_1)(\frac{1}{f_2}-\frac{1}{f_3})-(f_3-f_2)(\frac{1}{f_1}-\frac{1}{f_2}))}$ The reality calculated is the estimated value of ionized layer TEC but the two schemes that the present invention proposes overcomes the estimated accuracy can taking into account TEC value apart from the impact of phase place, effectively eliminate again the impact of distance phase place, by the phase interference between multiple sub-band signal, solve phase fuzzy problem, although interferometric phase has certain error, still ionized layer TEC value can be estimated accurately.

Reach the prerequisite of different between guarantee carrier frequency under, the frequency spectrum of sub-band signal can be overlapping to increase the bandwidth of sub-band, is convenient to that raising is follow-up carries out the output Y-PSNR after matched filtering process to each sub-band.

The non-detailed description of the present invention is known to the skilled person technology.

Claims (2)

1. utilize a method for SAR Satellite observation ionized layer TEC value, it is characterized in that comprising the steps:

(1) at ground configuration SAR signal receiver for receiving the pulse signal of SAR satellite launch;

(2) from the SAR satellite pulse signal that step (1) receives, choose three sub-band signals, be respectively sub-band 1, sub-band 2 and sub-band 3, sub-band 1, sub-band 2 are respectively f with the carrier frequency of sub-band 3 three sub-band signals ₁, f ₂, f ₃, the carrier frequency of three sub-bands meets f ₃>f ₂>f ₁, and f ₂-f ₁=f ₃-f ₂=Δ f;

(3) frequency spectrum of three sub-band signals step (2) chosen is moved respectively, its spectral centroid frequency is made all to be positioned at zero-frequency, then utilize matched filtering to carry out process of pulse-compression to three sub-band signals respectively, obtain the phase place Φ at three sub-band signal peak point places _n, n=1,2,3;

(4) the phase place Φ at three the sub-band signal peak point places obtained according to step (3) _n, n=1,2,3, calculate the interferometric phase of sub-band 1 and sub-band 2 signal peak value point, computing formula is Φ ₁₂=angle [exp (j Φ ₁) × exp (-j Φ ₂)]; Calculate the interferometric phase of sub-band 2 and sub-band 3 signal peak value point, computing formula is Φ ₂₃=angle [exp (j Φ ₂) × exp (-j Φ ₃)]; Wherein defining angle [exp (j (α+2k π))]=α, α ∈ [-π, π], k is integer,

(5) the interferometric phase Φ that step (4) obtains is utilized ₁₂and Φ ₂₃solve ionized layer TEC value, computing formula is as follows:

$TEC=\frac{\left(\right(f_2-f_1){\mathrm{\&Phi;}}_{23}-(f_3-f_2\left){\mathrm{\&Phi;}}_{12}\right)c}{2\&times;\mathrm{\&pi;}\&times;40.3\left(\right(f_2-f_1\left)\right(\frac{1}{f_2}-\frac{1}{f_3})-(f_3-f_2\left)\right(\frac{1}{f_1}-\frac{1}{f_2}\left)\right)}$

Wherein, c is the light velocity.

2. utilize a method for SAR Satellite observation ionized layer TEC value, it is characterized in that comprising the steps:

(1) at ground configuration SAR signal receiver for receiving the pulse signal of SAR satellite launch;

(2) from the SAR satellite pulse signal that step (1) receives, choose three sub-band signals, be respectively sub-band 1, sub-band 2 and sub-band 3, sub-band 1, sub-band 2 are respectively f with the carrier frequency of sub-band 3 three sub-band signals ₁, f ₂, f ₃, the carrier frequency of three sub-bands meets f ₃>f ₂>f ₁, f ₂-f ₁≠ f ₃-f ₂;

(3) frequency spectrum of three sub-band signals step (2) chosen is moved respectively, its spectral centroid frequency is made all to be positioned at zero-frequency, then utilize matched filtering to carry out process of pulse-compression to three sub-band signals respectively, obtain the phase place Φ at three sub-band signal peak point places _n, n=1,2,3;

(4) relevant ephemeris information is utilized to obtain the rough estimate evaluation of electromagnetic wave true propagation distance R utilize respectively to the phase place Φ of three sub-band signal peak points that step (3) obtains _n, n=1,2,3, compensates, and can be compensated the phase place of rear three sub-band signals:

${\mathrm{\&Phi;}}_n^{\&prime;}=angle\&lsqb;\exp \left(j\right({\mathrm{\&Phi;}}_n+\frac{2\mathrm{\&pi;}\hat{R}{f}_n}{c}\left)\right)\&rsqb;,n=1,2,3;$

Wherein, definition angle [exp (j (α+2k π))]=α, α ∈ [-π, π], k are integer,

(5) judge whether the carrier frequency of three sub-bands meets following constraint condition:

$\left\{\begin{array}{c}-\mathrm{\&pi;}<{\mathrm{\&Phi;}}_2^{\&prime;}+2\mathrm{\&pi;}\frac{\mathrm{\&Delta;}R}{c}(f_2-f_1)<\mathrm{\&pi;}\\ -\mathrm{\&pi;}<{\mathrm{\&Phi;}}_2^{\&prime;}+2\mathrm{\&pi;}\frac{\mathrm{\&Delta;}R}{c}(f_2-f_3)<\mathrm{\&pi;}\end{array}\right.$

If meet, enter (6), otherwise re-execute step (2)-(5), wherein Δ R is electromagnetic wave true propagation distance R and its rough estimate evaluation between evaluated error, c is the light velocity;

(6) the phase place Φ ' at three the sub-band signal peak point places obtained according to step (4) _n, n=1,2,3, calculate the interferometric phase of sub-band 1 and sub-band 2 signal peak value point, computing formula is Φ ₁₂=angle [exp (j Φ ' ₁) × exp (-j Φ ' ₂)]; Calculate the interferometric phase of sub-band 2 and sub-band 3 signal peak value point, computing formula is Φ ₂₃=angle [exp (j Φ ' ₂) × exp (-j Φ ' ₃)]; Wherein defining angle [exp (j (α+2k π))]=α, α ∈ [-π, π], k is integer,

(7) the interferometric phase Φ that step (6) obtains is utilized ₁₂and Φ ₂₃solve ionized layer TEC value, computing formula is as follows:

$TEC=\frac{\left(\right(f_2-f_1){\mathrm{\&Phi;}}_{23}-(f_3-f_2\left){\mathrm{\&Phi;}}_{12}\right)c}{2\&times;\mathrm{\&pi;}\&times;40.3\left(\right(f_2-f_1\left)\right(\frac{1}{f_2}-\frac{1}{f_3})-(f_3-f_2\left)\right(\frac{1}{f_1}-\frac{1}{f_2}\left)\right)}$

Wherein, c is the light velocity.