CN108562880A - A kind of reflecting surface Spaceborne SAR System internal calibration network element and internal calibration method - Google Patents
A kind of reflecting surface Spaceborne SAR System internal calibration network element and internal calibration method Download PDFInfo
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- CN108562880A CN108562880A CN201810384341.1A CN201810384341A CN108562880A CN 108562880 A CN108562880 A CN 108562880A CN 201810384341 A CN201810384341 A CN 201810384341A CN 108562880 A CN108562880 A CN 108562880A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
- G01S7/40—Means for monitoring or calibrating
- G01S7/4004—Means for monitoring or calibrating of parts of a radar system
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/88—Radar or analogous systems specially adapted for specific applications
- G01S13/89—Radar or analogous systems specially adapted for specific applications for mapping or imaging
- G01S13/90—Radar or analogous systems specially adapted for specific applications for mapping or imaging using synthetic aperture techniques, e.g. synthetic aperture radar [SAR] techniques
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Abstract
The present invention relates to a kind of SAR system internal calibration network element and matched internal calibration method to realize the internal calibration of ultra wide band reflecting surface satellite-borne SAR by the way that internal calibration network element is added in SAR system.The present invention improves SAR image signal-to-noise ratio by correction channel deviation, achievees the purpose that promote SAR imaging effects.By the present invention in that with interior calibration network, it can realize the magnitude-phase characteristics calibration of whole transmission channels and receiving channel, the consistency that phase alignment ensures phase is first carried out by launch point frequency pulse signal first, then by emitting scanning frequency pulse signal path magnitude-phase characteristics, ensure that the accuracy of calibration.
Description
Technical field
The present invention relates to a kind of ultra wide band Spaceborne SAR System internal calibration network element and its corresponding internal calibration method, belong to
In Space Microwave remote sensing technology field.
Background technology
To realize the high quality imaging of ultrahigh resolution Spaceborne SAR System, need the reality to system transceiver channel in-orbit
Characteristic carries out precise calibration.On the one hand it is that channel characteristic deviation carries out school caused by the factors such as temperature change and aging effect
Just, on the other hand it is that matching template is obtained by the processing of rate-aided signal, ensures imaging effect of the distance to compression.
Due to the characteristic of its ultrahigh resolution, there is ultrahigh resolution satellite-borne SAR ultra wide band, multichannel transmitting and multichannel to connect for it
The characteristics of receiving channel.At the same time, ultrahigh resolution satellite-borne SAR has selected reflector antenna system, it will use centralization hair
The radiation pattern of highpowerpulse signal is penetrated, therefore must be avoided with fiber delay time module in internal calibration network high-power
Leak the influence to rate-aided signal.The above feature determines that the internal calibration method of ultra wide band reflecting surface satellite-borne SAR and tradition are spaceborne
There are larger differences by SAR, cannot directly continue to use the internal calibration method of traditional satellite-borne SAR.How to realize that ultra wide band reflecting surface is spaceborne
The internal calibration of SAR ensures that internal calibration precision is this field technical problem urgently to be resolved hurrily.
Invention content
It is an object of the invention to overcome the deficiencies of the prior art and provide a kind of SAR system internal calibration network element and phases
The internal calibration method answered ensures comprehensive ultra wide band reflecting surface satellite carried SAR inner target, accuracy and convenience.
The object of the invention is achieved by following technical solution：
There is provided a kind of SAR system internal calibration network element, including the first n selects 1 switch including the n switching group switched, the
Two n select 1 switch, radio frequency unit and optical fiber delay unit；
In the case where receiving calibration mode, the pulse signal of transmitter transmitting through the first n select 1 switch, switching group n switch
One is transferred to and one of the n switch corresponding load couplers of SAR all the way；N is the transmission way of SAR load；
In the case where emitting calibration mode, the pulse signal that the conducting access of one of n switch of switching group is coupled out by coupler,
Pulse signal is sent to optical fiber delay unit, is returned after delay after the 2nd n selects 1 switch to be transferred to radio frequency unit regulation power
To radio frequency unit, receiver is forwarded to by radio frequency unit.
Preferably, under with reference to channel magnitude-phase characteristics obtaining mode is calibrated, the pulse signal of transmitter transmitting is through radio frequency list
After first regulation power, it is sent to optical fiber delay unit, radio frequency unit is returned to after delay, receiver is forwarded to by radio frequency unit.
Preferably, further include first switch, second switch, third switch and load；
In the case where receiving calibration mode, the pulse signal of transmitter transmitting is transferred to the first n through first switch and selects 1 switch, the
Two switches and third switch are connected to load；In the case where emitting calibration mode, the conducting of one of n switch of switching group is by coupler coupling
The access pulse signal closed out, pulse signal select 1 switch, third switch, second switch to be transferred to radio frequency unit through the 2nd n, the
One switch is connected to load；Under reference channel magnitude-phase characteristics obtaining mode transmitter emit pulse signal through first switch,
Radio frequency unit is transferred to after second switch, third switch is connected to load.
Preferably, further include power supply and monitoring unit, provide secondary power supply for radio frequency unit and optical fiber delay unit, and supervise
Both controls operating voltage and electric current.
A kind of method carrying out SAR load phase calibrations using the SAR system internal calibration network element is provided, it is special
Sign is, includes the following steps：
(1) it transmitting phase shifter and phase shifter will be received is set as non-phase shift pattern, transmitter launch point frequency pulse signal,
The frequency point of pulse signal is the low-limit frequency of SAR signal subspace bands, and phase isEnable i=1；
(2) pulse signal is divided into the roads n, the i-th road signal is through i-th of transmitting phase shifter (ti) to i-th of traveling wave through power splitter
After pipe amplifier (TWTAi) power amplification, it is transferred to i-th of coupler through i-th of circulator, i-th of coupler believes pulse
Number it is coupled to system internal calibration network element, in the case where emitting calibration mode, i-th of switch conduction access pulse letter of switching group
Number, pulse signal is forwarded to receiver by radio frequency unit, the phase for obtaining receiver output signal isCalculate i-th
Road transmission channel phase
(3) judge whether i is equal to n, enable i=1 if being equal to n and enter step (4)；Then 1 is added to return i if it is less than n
Return step (2)；
(4) system internal calibration network element, which is operated in, receives under calibration mode, the point frequency pulse signal warp of transmitter transmitting
First switch (1), the first n select 1 switch, i-th of switch through switching group again, are transferred to i-th of coupler, i-th of coupler will
Pulse signal is coupled to i-th of circulator, and i-th of circulator transfers signals to i-th of amplitude limit low noise and carry out low noise work(
After rate amplification, phase shifter (ri) is received through i-th, i-th of isolator isolation, is output to receiver after combiner again, is received
Machine carries out reception processing, and the phase of receiver output signal is φi_end, calculate the i-th tunnel receiving channel phase
(5) judge whether i is equal to n, i is then added into 1 return to step (4) if it is less than n；Judge transmitter if being equal to n
The frequency point of the point frequency pulse signal of transmitting, if it is SAR signal subspace band low-limit frequencies, the point frequency pulse signal of transmitter transmitting
Frequency point is set as the centre frequency of SAR signal subspace bands, and phase isEnable i=1, return to step (2)；If it is SAR signal subspace bands
Centre frequency, then the point frequency pulse signal frequency point of transmitter transmitting be set as the highest frequencies of SAR signal subspace bands, phase isEnable i=1, return to step (2)；SAR load phase calibrations are then completed if it is the highest frequency of SAR signal subspace bands.
Preferably, step (1)~(5) K times are repeated, K group receiving channel phases and transmission channel phase are obtained, are calculated
K group receiving channel phases and transmission channel phase error, and each receiving channel and transmission channel phase error mean value are obtained, according to
Phase error mean value adjusts corresponding transmitting phase shifter and receives phase shifter, completes the phase school of each receiving channel and transmission channel
It is accurate.
Preferably, phase calibration will be executed to each subband of SAR system.
A kind of magnitude-phase characteristics scaling method based on the SAR system phase calibration method is provided, each receive is completed and leads to
Magnitude-phase characteristics calibration is carried out after the phase alignment of road and transmission channel, specifically includes following steps：
(1) phase shifter will be emitted and receive phase shifter system phase scaling method progress phase according to claim 6
Position calibration, transmitter emit the pulse signal of SAR actual imagings work, and the phase-frequency characteristic of the transmitting signal isAmplitude versus frequency characte
It is frequency variable for A (f), wherein f；Enable i=1；
(2) pulse signal selects 1 switch to enter power splitter through the 1st, is divided into the roads n through power splitter, the i-th road signal is through i-th
After emitting phase shifter (ti) to i-th of travelling-wave tube amplifier (TWTAi) increase power, i-th of coupling is transferred to through i-th of circulator
Pulse signal is coupled to system internal calibration network element, in the transmission mode, i-th of switching group by clutch, i-th of coupler
Switch conduction accesses pulse signal, and pulse signal is forwarded to receiver by radio frequency unit, obtains the phase of receiver output signal
Frequency characteristic isAmplitude versus frequency characte is Ai_end(f), the magnitude-phase characteristics of the i-th road transmission channel is calculated
(3) judge whether i is equal to n, enable i=1 if being equal to n and enter step (4)；Then 1 is added to return i if it is less than n
Return step (2)；
(4) system internal calibration network element is operated under reference channel magnitude-phase characteristics obtaining mode, the arteries and veins of transmitter transmitting
Signal is rushed after first switch (1) enters system internal calibration network element, is sent out pulse signal by radio frequency unit, passes through
22 select 1 switch to be sent to receiver, and the phase-frequency characteristic for obtaining receiver output signal is ψend(f), amplitude versus frequency characte ACend
(f), the magnitude-phase characteristics for calculating reference channel is
(5) system internal calibration network element, which is operated in, receives under calibration mode, and the pulse signal of transmitter transmitting is through first
Switch (1), the first n select 1 switch, i-th of switch through switching group again, are transferred to i-th of coupler, and i-th of coupler is by pulse
Signal is coupled to i-th of circulator, and i-th of circulator transfers signals to i-th of amplitude limit low noise progress low noise acoustical power and put
After big, phase shifter (ri) is emitted through i-th, i-th of isolator isolation, is output to after combiner selects 1 switch by the 2nd 2 again
Receiver, receiver carry out reception processing, and the phase-frequency characteristic of receiver output signal is φi_end(f), amplitude versus frequency characte ARi_end
(f), the magnitude-phase characteristics that the i-th tunnel receives calibration channel is calculated
(6) judge whether i is equal to n, enable i=1 if being equal to n and enter step (7)；Then 1 is added to return i if it is less than n
Return step (5)；
(7) according to the magnitude-phase characteristics Hi of the roads n transmission channelT, reference channel magnitude-phase characteristics be HrefWith the width in calibration channel
Phase behaviour HiR, calculate the distance matching compression function of SAR system.
Preferably, further include before step (7)：Step (1)~(6) K times are repeated, K groups receiving channel and hair are obtained
Channel magnitude-phase characteristics is penetrated, and obtains each receiving channel and transmission channel magnitude-phase characteristics mean value as final each receiving channel and hair
Penetrate channel magnitude-phase characteristics value.
Preferably, the value of n is 4, calculates the total transfer function H of SAR systemsigMethod be：
(1) equation group of solution formula (1)~(9) composition, obtains the transfer function H of transmittertrans；One 2 selects 1 switch
The transfer function H in power splitter directionswitch11；One 2 selects the transfer function H in 1 switch internal calibration network directionswitch12；Work(point
The transfer function H i of device, transmitting phase shifter and the i-th tunnel of travelling-wave tube amplifier (TWTAi)power；No. i-th circulator direction of the launch passes
Delivery function Hicir1-2；No. i-th circulator receives direction transfer function H icir2-3；No. i-th coupler direction of the launch transmission function
Hicoup1-2；No. i-th coupler receives direction transfer function H icoup2-1；No. i-th coupler couples direction transfer function H icoup1-3；
The inverse coupling direction transfer function H i of No. i-th couplercoup3-1；Amplitude limit low noise, transmitting phase shifter, isolator and combiner i-th
The transfer function H i on roadLNA；2nd 2 selects the interior calibration network of 1 switch to the transfer function H in receiver directionswitch22；2nd 2 selects 1
Combiner is switched to receiver direction transfer function Hswitch21；Transfer function H under internal calibration network launches patternt→r；Internal calibration
Transfer function H under network transmission patternt→c；Transfer function H under the magnitude-phase characteristics obtaining mode of internal calibration network reference channelc→r, connect
Receipts machine transfer function Hrec；
H1T=Htrans·Hswitch11·H1power·H1cir1-2·H1coup1-3·H1c→r·Hswitch22·Hrec (1)
H2T=Htrans·Hswitch11·H2power·H2cir1-2·H2coup1-3·H2c→r·Hswitch22·Hrec (2)
H3T=Htrans·Hswitch11·H3power·H3cir1-2·H3coup1-3·H3c→r·Hswitch22·Hrec (3)
H4T=Htrans·Hswitch11·H4power·H4cir1-2·H4coup1-3·H4c→r·Hswitch22·Hrec (4)
Href=Htrans·Hswitch12·Ht→r·Hswitch22·Hrec (5)
H1R=Htrans·Hswitch12·H1t→c·H1coup3-1·H1cir2-3·H1LNA·Hswitch21·Hrec (6)
H2R=Htrans·Hswitch12·H2t→c·H2coup3-1·H2cir2-3·H2LNA·Hswitch21·Hrec (7)
H3R=Htrans·Hswitch12·H3t→c·H3coup3-1·H3cir2-3·H3LNA·Hswitch21·Hrec (8)
H4R=Htrans·Hswitch12·H4t→c·H4coup3-1·H4cir2-3·H4LNA·Hswitch21·Hrec (9)
(2) transfer function H 1 of four road transceiver channel loops is calculatedsig~H4sigRespectively：
(3) distance matching compression function H is calculatedsig, Hsig=H1sig+H2sig+H3sig+H4sig。
The present invention has the following advantages that compared with prior art：
(1) present invention improves SAR image signal-to-noise ratio by correction channel deviation and acquisition transceiver channel matching template,
Improve SAR imaging effects.
(2) by the present invention in that with interior calibration network, the characteristic calibration of whole transmission channels and receiving channel can be realized,
The consistency that phase alignment ensures phase is first carried out by launch point frequency pulse signal, then by emitting scanning frequency pulse signal path
Magnitude-phase characteristics ensure that the accuracy of calibration.
(3) present invention by the military reconnaissance capability for enhancing ultrahigh resolution satellite-borne SAR, is carried by promoting SAR image effect
High target identification detection probability promotes military weapon strike efficiency, and accurate Information Assurance is provided for military strategy decision.
Description of the drawings
Fig. 1 is the internal calibration loop design schematic diagram of SAR system；
Fig. 2 is the system schema block diagram of internal calibration network element；
Fig. 3 is the detailed system block diagram of ultra wide band reflecting surface SAR system internal calibration loop；
Fig. 4 is the system calibration flow chart of ultra wide band reflecting surface satellite-borne SAR；
Fig. 5 is that step 1 obtains transmitting calibration phaseLoad system signal flow to schematic diagram；
Fig. 6 is that step 1 obtains transmitting calibration phaseInternal calibration network signal flow direction and internal switch state setting
Schematic diagram；
Fig. 7 is that step 2 obtains transmitting calibration phaseLoad system signal flow to schematic diagram；
Fig. 8 is that step 2 obtains transmitting calibration phaseInternal calibration network signal flow direction and internal switch state setting
Schematic diagram；
Fig. 9 is that step 3 obtains transmitting calibration phaseLoad system signal flow to schematic diagram；
Figure 10 is that step 3 obtains transmitting calibration phaseInternal calibration network signal flow direction and internal switch state setting
Schematic diagram；
Figure 11 is that step 4 obtains transmitting calibration phaseLoad system signal flow to schematic diagram；
Figure 12 is that step 4 obtains transmitting calibration phaseInternal calibration network signal flow direction and internal switch state setting
Schematic diagram；
Figure 13 is that step 5 obtains reception calibration phase1_flLoad system signal flow to schematic diagram；
Figure 14 is that step 5 obtains reception calibration phase1_flInternal calibration network signal flow direction and internal switch state set
Set schematic diagram；
Figure 15 is that step 6 obtains reception calibration phase2_flLoad system signal flow to schematic diagram；
Figure 16 is that step 6 obtains reception calibration phase2_flInternal calibration network signal flow direction and internal switch state set
Set schematic diagram；
Figure 17 is that step 7 obtains reception calibration phase3_flLoad system signal flow to schematic diagram；
Figure 18 is that step 7 obtains reception calibration phase3_flInternal calibration network signal flow direction and internal switch state set
Set schematic diagram；
Figure 19 is that step 8 obtains reception calibration phase4_flLoad system signal flow to schematic diagram；
Figure 20 is that step 8 obtains reception calibration phase4_flInternal calibration network signal flow direction and internal switch state set
Set schematic diagram；
Figure 21 is that the calibration pulse of phase alignment emits sequence diagram schematic diagram；
Figure 22 is to flow to schematic diagram with reference to signal of the scanning frequency pulse under calibration mode in SAR load systems；
Figure 23 is to flow to schematic diagram with reference to signal of the scanning frequency pulse under calibration mode in internal calibration network；
Figure 24 is that the calibration pulse that channel characteristic obtains emits sequence diagram schematic diagram.
Specific implementation mode
The technology contents of the present invention include following three：1) first according to the load scheme of ultra wide band reflecting surface satellite-borne SAR
Internal calibration loop and internal calibration network module are devised, ensures comprehensive covering to system transceiver channel；2) secondly, phase is devised
Position calibration obtains the system internal calibration workflow being combined with channel magnitude-phase characteristics；3) it finally, gives and is believed using internal calibration
Number obtain the Processing Algorithm of Range compress matching template.
1. the internal calibration loop and internal calibration network design of ultra wide band reflecting surface SAR
The internal calibration loop of ultra-wide reflecting surface satellite-borne SAR need to meet following three aspects constraints：
(1) calibration loop must assure that each access that covering radar imagery pulse is undergone comprehensively；
(2) access specific to rate-aided signal stream or not scaled signal covering and what radar pulse signal was undergone
Access, it is necessary to have higher temperature and time stability；
(3) rate-aided signal needs have same signal parameter (pulsewidth and bandwidth) with imaging signal.
Based on constraints above condition and ultra wide band reflecting surface SAR load system schemes, the loop design such as attached drawing 1 of internal calibration
Shown, wherein dotted line module realizes the unit that newly introduces of internal calibration for system, includes：1. being located at transmitter in transmission channel
2 between synthesis network front end select 1 switch；2. being located at 2 between feed reception switch matrix and receiver in receiving channel
Select 1 switch；3. the coupler group between circulator and antenna feed array；4. realize calibration loop switching, delays time to control and
The internal calibration network element of gain-adjusted.
Attached drawing 2 gives the scheme block diagram of internal calibration network.Different calibrations are realized inside it by multiple selecting switch
Signal path switching under pattern；Also carry out Regulate signal power with radio frequency unit simultaneously, ensures optical fiber delay unit and reception
The input signal of machine meets corresponding power requirement；Optical fiber delay unit in network is used for emit after rate-aided signal is delayed again
Receiver is inputed to, rate-aided signal is avoided to be interfered by high-power exomonental spatial leaks；Internal calibration network also carries certainly
The power supply and monitoring and controlling unit of body, realization is powered to it and the function of remote-control romote-sensing.
The internal calibration pattern of entire SAR system includes three kinds of transmitting calibration, reception calibration and reference calibration, these three are fixed
Mark pattern forms holonomic system internal calibration process.With the port in attached drawing 1 marked as reference, the calibration letter under three kinds of calibration modes
Number flow direction as listed in table 1：
The rate-aided signal of table 1 ultra wide band reflecting surface, three kinds of internal calibration patterns flows to
| Calibration mode | Rate-aided signal flows to |
| Transmitting calibration | Transmitter → 2 → 7 → 4 → 5 → 6 → 10 → receiver |
| With reference to calibration | Transmitter → 1 → 3 → 6 → 10 → receiver |
| Receive calibration | Transmitter → 1 → 3 → 5 → 4 → 7 → 8 → 9 → receiver |
In emitting calibration mode, transmitter output signal will enter transmission channel.Pulse signal by 2 select 1 switch,
After synthesizing network front end and TWTA groups, low-power level signal all the way is coupled out by the coupler between circulator and feed array
It enters in internal calibration network.In internal calibration network, 1 switch is selected to select the low-power level signal that feed all the way is coupled out by 4,
Then pass through in radio frequency unit and delay cell and does corresponding level conversion and time delay processing, it is defeated finally by radio frequency unit
Go out to reach 2 before receiver and select 1 switch, then receiver is entered by the switch and does reception processing.
In reference loop calibration mode, the output signal of transmitter will select 1 switch to enter internal calibration network by 2.Arteries and veins
It rushes signal and enters radio frequency unit progress level conversion by a series of switches in internal calibration network, then pass through optical fiber delay
Unit carries out carrying out radio frequency unit progress level conversion after accordingly postponing again, is finally exported from radio frequency unit and reaches receiver
1 switch is selected in preceding 2, is entered by the switch and carries out reception processing in receiver.
In the case where receiving calibration mode, transmitter output signal will select 1 switch to enter internal calibration network by 2.Pulse signal
It is exported by port 5 by gating switch in internal calibration network, which reaches the coupling port 4 of coupler group, from the end
It mouthful enters circulator, amplitude limit LNA, select 1 switch to enter finally by 2 to carry out reception processing in receiver.
Carry out frequency spectrum splicing realization distance to ultrahigh resolution, together since ultra wide band reflecting surface SAR will use multi-subband signal
When need branched TWTA and emit the final signal noise ratio (snr) of image of high-power guarantee to synthesize.It is attached by taking 3 sub-band bursts, 4 TWTA as an example
Fig. 3 give involved by internal calibration process synthesis network front end (including 4 power splitters and four transmitting phase shifter t1~
T4), TWTA groups (being made of TWTA1~TWTA4), circulator group (being made of circulator 1~4), coupler group are (by coupler
1~4 composition), amplitude limit LNA modules (including four amplitude limit LNA units, four reception phase shifter r1~r4, four isolators and
One combiner) and internal calibration network detailed composition.
2. system calibration flow
The internal calibration work of system is completed before the imaging begins.The transmitting of four tunnels is obtained first with phase alignment calibration
The phase deviation between phase deviation, four tunnel receiving channels between channel, then by adjusting transmitting phase shifter t1~t4 and connect
The phase shift value for receiving phase shifter r1~r4 is inconsistent to correct the phase between transmission channel and receiving channel.In transmitting-receiving multiplexer channel
Phase alignment on the basis of, then carry out transceiver channel magnitude-phase characteristics calibration.Finally, using corresponding algorithm to channel characteristic mark
Determine signal to be handled, obtains distance and compress template to matching.Attached drawing 4 gives the complete of ultra wide band reflecting surface Spaceborne SAR System
Adjust mark flow.
It can be seen that from flowing chart above, system internal calibration needs to carry out independent phase alignment and channel for each subband
Characteristic obtains.After the channel characteristic for completing all subbands obtains, of each subband is obtained further according to corresponding Processing Algorithm
With template.It is below reference, other 3 subbands, transmitting with subband 1 due to being similar for the calibration process of each subband
Machine emits signal difference, and flow is identical, and detailed calibration flow is given below.
(1) demarcation flow of phase alignment
The phase alignment of transmitter transmitting SAR signal subspaces band 1 includes the phase to four road transmission channels and four tunnel receiving channels
Position calibration.Calibration process will utilize the low-limit frequency f of subband 1L, centre frequency fCWith highest frequency fHIt is obtained etc. multiple frequency points
The phase value in channel, then carry out Combined Treatment to it and obtain the inter-channel phase difference for entire subband, finally utilize the above phase
Potential difference adjusts phase shifter t1~t4 in transmission channel and receiving channel and r1~r4, to achieve the purpose that phase alignment.
The initial phase shift value of four road transmission channel phase shifter t1~t4 and four tunnel receiving channel phase shifter r1~r4 are set as
180o, can positive and negative two-way adjustment.The 1 complete implementation steps of transceiver channel phase alignment of subband are will be given below, it is primary complete
Phase alignment includes 24 steps altogether, and the 1st~8 step, 9~16 steps and 17~24 steps are directed to frequency point f respectivelyL、fCAnd fHExpansion.
Step 1：Emit fLPoint frequency pulse signal, only TWTA1 add power, obtain first via transmission channel phase
In step 1,2 after transmitter select 1 switching gate to synthesize network front end, and only TWTA1 adds power, internal calibration network
In 1 conduction mode of T switches be coupler to receiver, other T switches are all set to load state.2 before receiver select 1 switch to select
Logical internal calibration network come to signal.Attached drawing 5 gives flow direction (dotted line institute of the point-frequency signal inside load system in step 1
Show), attached drawing 6 gives flow direction (dotted line shown in) and therein switch setting side of the point-frequency signal in internal calibration network
Formula.The frequency point of transmitter launch point frequency pulse signal, pulse signal is fLPhase is1 switch is selected to be sent to 4 work(point through 2
Device, is divided into 4 tunnels, and the shifted device t1 of first via signal increases power to the first travelling-wave tube amplifier TWTA1, transmitted through circulator 1
To coupler 1, pulse signal is coupled to T switches 1 by coupler 1, selects 1 switch, No. 3 switches, No. 2 switches to be transferred to radio frequency through 4
Unit is sent to optical fiber delay unit after radio frequency unit Regulate signal power, micro- through optical fiber delay cell delay 40~50
Second, radio frequency unit is returned to, receiver is forwarded to by radio frequency unit, power supply and monitoring unit are radio frequency unit and optical fiber delay list
Member provides secondary power supply, and monitors the two operating voltage.The phase of receiver output signal isIt is complete
At first via transmission channel phase test.
Step 2：Emit fLPoint frequency pulse signal, only TWTA2 add power, obtain the second road transmission channel phase
In step 2, select 1 switching gate state constant with 2 before receiver after transmitter, the T in internal calibration network is opened
The conduction mode for closing 2 is changed to coupler to receiver, and other switches are all set to load state.Attached drawing 7 distinguishes table with dotted line in attached drawing 8
Show that point-frequency signal flows to mode in load system and internal calibration network in step 2.
Step 3：Emit fLPoint frequency pulse signal, only TWTA3 add power, obtain third road transmission channel phase
In step 3, select 1 switching gate state constant with 2 before receiver after transmitter, the switch in internal calibration network
3 conduction mode is changed to coupler to receiver, and other switches are all set to load state.Attached drawing 9 is given respectively with dotted line in attached drawing 10
Go out rate-aided signal in step 3 and flows to mode in SAR load systems and internal calibration network.
Step 4：Emit fLPoint frequency pulse signal, only TWTA4 add power, obtain the 4th road transmission channel phase
In step 4, select 1 gating switch state constant with 2 before receiver after transmitter, the switch in internal calibration network
4 conduction mode is changed to coupler to receiver, and other switches are all set to load state.Attached drawing 11 gives with dotted line in attached drawing 12
Flow direction of the rate-aided signal in load system and internal calibration network in step 4.
Step 5：Emit fLPoint frequency pulse signal, obtains first via receiving channel phase1_fl。
Step 5 starts to obtain the phase characteristic of receiving channel.Whole TWTA no longer add power, and 1 switch is selected in 2 after transmitter
Conduction mode is transmitter to internal calibration network；1 conduction mode of T switches in internal calibration network is transmitter to coupler,
Its four T switch is all set to load state；2 before receiver select 1 switch conduction mode for amplitude limit LNA modules to receiver.Attached drawing
13 give flow direction (dotted line shown in) of the rate-aided signal of step 5 in load system, and attached drawing 14 is rate-aided signal in internal calibration
Flow direction (shown in dotted line) in network and corresponding on off state setting.Transmitter launch point frequency pulse signal, pulse signal
Frequency point be fLPhase isIt selects 1 switch to be sent to interior calibration network through 2, selects 1 switch again through T switches 1 through No. 1 switch, 4,
It is transferred to coupler 1, pulse signal is coupled to circulator 1 by coupler 1, and circulator transfers signals to amplitude limit low noise
LAN1 is exported after carrying out low noise power amplification after shifted device r1 (not shifting to), isolator, combiner, selects 1 switch to pass through 2
Defeated to arrive receiver, receiver carries out reception processing.The phase of receiver output signal isIt completes
First via receiving channel phase test.
Step 6：Emit fLPoint frequency pulse signal, obtains the second tunnel receiving channel phase2_fl。
In step 6, select 1 gating switch state consistent with step 5 with 2 before receiver after transmitter, in internal calibration network
The conduction modes of T switches 2 be changed to transmitter to coupler, other switches are all set to load state.The void of attached drawing 15 and attached drawing 16
Flow direction of the rate-aided signal in load system and internal calibration network in step 6 is set forth in line.
Step 7：Emit fLPoint frequency pulse signal obtains third road receiving channel phase3_fl。
In step 7, select 1 gating switch state consistent with step 5 with 2 before receiver after transmitter, in internal calibration network
The conduction modes of T switches 3 be changed to transmitter to coupler, other switches are all set to load state.The void of attached drawing 17 and attached drawing 18
Flow direction of the rate-aided signal in load system and internal calibration network in step 7 is set forth in line.
Step 8：Emit fLPoint frequency pulse signal, obtains the 4th tunnel receiving channel phase4_fl。
In step 8, select 1 gating switch state consistent with step 5 with 2 before receiver after transmitter, in internal calibration network
The conduction modes of T switches 4 be changed to transmitter to coupler, other switches are all set to load state.The void of attached drawing 19 and attached drawing 20
Flow direction of the point-frequency signal in load system and internal calibration network in step 8 is set forth in line.
By 1~step 8 of procedure described above, four road transmission channels and four tunnel receiving channels are can get in frequency point fL's
Phase value.Step 9~step 16 recycles centre frequency fcPoint frequency pulse signal as rate-aided signal, it is same according to step 1~8
The mode of sample obtains four road transmission channels and four tunnel receiving channels in frequency point fcPhase value；Finally, step 17~step 24 profit
With highest frequency fHPoint-frequency signal obtains whole transceiver channels in frequency point f as rate-aided signalHThe phase value at place.It is given referring to table 2
The phase value of four road transmission channels and receiving channel of three frequency points is gone out.
2 transmission channel of table and phase value of the receiving channel at three frequency points
It is sharp using transmission channel 1 and receiving channel 1 as the reference channel of four road transmission channels and four tunnel receiving channels
It makes of obtained phase in subordinate list 2 and is handled in real time on star, so that it may obtain 1 transmission channel of subband and respectively join with it with receiving channel
The phase difference for examining channel, as listed by subordinate list 3.
3 subband of table, 1 corresponding inter-channel phase difference
For reduction noise jamming, phase alignment precision is provided, single phase calibration process is repeated 512 times or 1024 times,
It is made the difference with standard value, it will be able to obtain 512 groups of transmission channel phase deviationsAnd 512 groups of receiving channel phases are inclined
Poor Δ φ1~Δ φ4.Phase difference is obtained by this 512 times again and seek mean value, and moved using obtained mean value result to adjust transmitting
Phase device t1~t4 and reception phase shifter r1~r4, to ensure the consistency between multichannel transmission channel and multipath reception channel.
Attached drawing 21 gives the impulse ejection sequential of phase calibration process, wherein the transmission interval of two neighboring calibration pulse is Δ T, it is single
Secondary calibration process includes 24 transmitting pulses, this 24 exomonental working methods are as described in 1~step 24 of above step.One
Secondary complete phase calibration process includes 512 single phase alignments altogether.
(2) demarcation flow that channel magnitude-phase characteristics obtains
After as soon as upper section completes the phase alignment of subband 1, system scanning frequency pulse calibration will be carried out in this state, be come
1 corresponding transceiver channel magnitude-phase characteristics of subband is obtained, template is compressed to matching with the distance for 1 echo of Solution operator band.Subband 1
The single acquisition process of channel characteristic includes 9 steps altogether, and step 1~step 4 is transmitting calibration, step 5 is with reference to calibration, step 6
~step 9 is to receive to calibrate.
Step 1：Emit subband 1 scanning frequency pulse signal (transmitting SAR real works signal), only TWTA1 adds power, obtains the
The magnitude-phase characteristics H1 in transmitting calibration channel all the wayT, wherein A (f) withThe amplitude versus frequency characte and phase-frequency characteristic of the 1 scanning frequency pulse signal of subband emitted respectively, A1_end(f) withRespectively
Signal amplitude versus frequency characte and phase-frequency characteristic of 1 scanning frequency pulse of subband after the first via emits calibration channel.Scanning frequency pulse is in SAR systems
Signal flow direction in system and internal calibration network is identical as step 1 in phase alignment.
Step 2：Emit 1 scanning frequency pulse signal of subband, only TWTA2 adds power, obtains the width in the second tunnel transmitting calibration channel
Phase behaviourA2_end(f) withRespectively 1 frequency sweep arteries and veins of subband
Rush the signal amplitude versus frequency characte and phase-frequency characteristic after the second tunnel emits calibration channel.Scanning frequency pulse is in SAR system and internal calibration
Signal flow direction in network is identical as step 2 in phase alignment.
Step 3：Emit 1 scanning frequency pulse signal of subband, only TWTA3 adds power, obtains the width in third road transmitting calibration channel
Phase behaviourA3_end(f) withRespectively 1 frequency sweep arteries and veins of subband
Rush the signal amplitude versus frequency characte and phase-frequency characteristic after third road emits calibration channel.Scanning frequency pulse is in SAR system and internal calibration
Signal flow direction in network is identical as step 3 in phase alignment.
Step 4：Emit 1 scanning frequency pulse signal of subband, only TWTA4 adds power, obtains the width in the 4th tunnel transmitting calibration channel
Phase behaviourA4_end(f) withRespectively 1 frequency sweep arteries and veins of subband
Rush the signal amplitude versus frequency characte and phase-frequency characteristic after the 4th tunnel emits calibration channel.Scanning frequency pulse is in SAR system and internal calibration
Signal flow direction in network is identical as step 4 in phase alignment.
Step 5：Emitting 1 scanning frequency pulse signal of subband, 2 after transmitter select 1 switch to be set as transmitter to internal calibration network,
Swept-frequency signal enters receiver after internal calibration network.This is with reference to calibration in SAR system and the letter in internal calibration network
Respectively as shown in the dotted line of attached drawing 22 and attached drawing 23, the magnitude-phase characteristics for obtaining reference channel is for number flow directionACend(f) and ψend(f) it is respectively that 1 scanning frequency pulse of subband passes through reference
Calibrate the signal amplitude versus frequency characte and phase-frequency characteristic behind channel.
Step 6：Emit 1 scanning frequency pulse signal of subband, whole TWTA are not added with power, obtain the first via and receive calibration channel
Magnitude-phase characteristicsAR1_end(f) and φ1_end(f) it is respectively that subband 1 is swept
Signal amplitude versus frequency characte and phase-frequency characteristic of the frequency pulse after the first via receives calibration channel.Scanning frequency pulse is in SAR system and interior
The signal flow direction calibrated in network is identical as step 5 in phase alignment.
Step 7：Emit 1 scanning frequency pulse signal of subband, whole TWTA are not added with power, obtain the second tunnel and receive calibration channel
Magnitude-phase characteristicsAR2_end(f) and φ2_end(f) it is respectively that subband 1 is swept
Signal amplitude versus frequency characte and phase-frequency characteristic of the frequency pulse after the second tunnel receives calibration channel.Scanning frequency pulse is in SAR system and interior
The signal flow direction calibrated in network is identical as step 6 in phase alignment.
Step 8：Emit 1 scanning frequency pulse signal of subband, whole TWTA are not added with power, obtain third road and receive calibration channel
Magnitude-phase characteristicsAR3_end(f) and φ3_end(f) it is respectively that subband 1 is swept
Signal amplitude versus frequency characte and phase-frequency characteristic of the frequency pulse after third road receives calibration channel.Scanning frequency pulse is in SAR system and interior
The signal flow direction calibrated in network is identical as step 7 in phase alignment.
Step 9：Emit 1 scanning frequency pulse signal of subband, whole TWTA are not added with power, obtain the 4th tunnel and receive calibration channel
Magnitude-phase characteristicsAR4_end(f) and φ4_end(f) it is respectively that subband 1 is swept
Signal amplitude versus frequency characte and phase-frequency characteristic of the frequency pulse after the 4th tunnel receives calibration channel.Scanning frequency pulse is in SAR system and interior
The signal flow direction calibrated in network is identical as step 8 in phase alignment.
To reduce noise jamming, promoting the channel magnitude-phase characteristics precision obtained, the single that step 1~step 9 is formed
Flow repeats 512 times, and obtained result is averaging processing, so that it may obtain accurate four tunnels transmitting calibration channel, reference
It calibrates channel and four tunnels receives the magnitude-phase characteristics in calibration channel.Attached drawing 24 gives channel magnitude-phase characteristics and obtains calibration process
The transmission interval of impulse ejection sequential, two neighboring calibration pulse is Δ T, and single calibration process includes 9 transmitting pulses, this 9
A exomonental working method is as described in 1~step 9 of above step.Once complete channel characteristic acquisition process includes altogether
512 times single characteristic obtains.
(3) Processing Algorithm of rate-aided signal
It completes the phase alignment in channel and on this basis after the magnitude-phase characteristics of Acquisition channel, i.e., will utilize corresponding
Processing Algorithm can be applied to matching template of the distance to compression processing to calculate.
Subordinate list 4 gives the transmission function of unit module involved by system calibration process.
The transmission function of different units module in 4 system of table
After the demarcation flow obtained according to channel characteristic completes step 1~step 9, the biography in 9 obtained calibration channels
Delivery function is represented by：
H1T=Htrans·Hswitch11·H1power·H1cir1-2·H1coup1-3·H1c→r·Hswitch22·Hrec (1)
H2T=Htrans·Hswitch11·H2power·H2cir1-2·H2coup1-3·H2c→r·Hswitch22·Hrec (2)
H3T=Htrans·Hswitch11·H3power·H3cir1-2·H3coup1-3·H3c→r·Hswitch22·Hrec (3)
H4T=Htrans·Hswitch11·H4power·H4cir1-2·H4coup1-3·H4c→r·Hswitch22·Hrec (4)
Href=Htrans·Hswitch12·Ht→r·Hswitch22·Hrec (5)
H1R=Htrans·Hswitch12·H1t→c·H1coup3-1·H1cir2-3·H1LNA·Hswitch21·Hrec (6)
H2R=Htrans·Hswitch12·H2t→c·H2coup3-1·H2cir2-3·H2LNA·Hswitch21·Hrec (7)
H3R=Htrans·Hswitch12·H3t→c·H3coup3-1·H3cir2-3·H3LNA·Hswitch21·Hrec (8)
H4R=Htrans·Hswitch12·H4t→c·H4coup3-1·H4cir2-3·H4LNA·Hswitch21·Hrec (9)
What formula (1)~formula (4) indicated to be obtained when the subband demarcates the road transmission channel of its 1st tunnel~the 4th respectively
Demarcation signal, formula (6)~formula (9) indicate that the subband carries out its first via (LNA1)~the 4th tunnel (LNA4) receiving channel respectively
The demarcation signal obtained when calibration, formula (5) indicate the reference calibration loop signals of the subband.
During image forming job, the undergone transmission function of pulse signal is system in transceiver channel all the way：
Hsig=HtransHswitch11·(HpowerHcir1-2Hcoup1-2Hcoup2-1Hcir2-3HLNA)·Hswitch21Hrec (10)
Based on the analysis result of formula (1)~formula (10), the transmission function of the corresponding four roads transceiver channel of the subband can be obtained
H1sig~H4sigRespectively：
Since system imaging is that four road transceiver channels work at the same time, the total transfer function H of systemsigIt is above four
The sum of a transmission function, you can be expressed as：
Hsig=H1sig+H2sig+H3sig+H4sig (15)
Formula (15) obtains HsigBe the subband accordingly distance matching compression function.Utilize the function and the subband
SAR echo signal carries out matched filtering.
It can be seen that by formula (11)~(14), to obtain Range compress matching template, not only need every road transmission channel, connect
Receive channel and the rate-aided signal with reference to loop, it is also necessary to which the transfer function characteristics between each each port of coupler are (such as 5 institute of subordinate list
Row), each channel pass through internal calibrator transfer function characteristics.Coupler is passive module, and transmission function is stablized, is not easy relatively
It changes, the transmission function between its multiport can be measured on ground.H1 in internal calibration networkt→c~H4t→cThis four transmission
Function only includes multiple electronic switches, therefore transmission function is also comparatively stablized, and Ht→rWith H1c→r~H4c→rBe required for through
Radio frequency unit and optical fiber delay module are crossed, this two parts all can all generate variation with temperature, will ginseng when sequential is calibrated in design
Most enough small (Δ T=are arranged in the time interval examined between calibration and transmitting calibration
0.2ms), to ensure to stablize in this intersegmental Property comparison between interior radio frequency unit and optical fiber delay module.This
The H1 of up-to-date style (11)sig=Ht→r/H1t→cIt is represented by
Wherein HswitchFor the internal calibration network input port 3 that is connected with transmitter in attached drawing 22 to radio frequency unit input terminal
The transfer function characteristics of mouth, HdelayFor the transmission letter from radio frequency unit input port to internal calibrator to receiver output port 6
Number characteristic is (since interval delta T is very short between transmitting calibration and reference calibration, therefore, it is considered that the H that they are includeddelayUnanimously),
H1switchFor the internal calibrator input port 5 that is connected with ultrahigh resolution mode coupler 1 in attached drawing 6 to rf inputs mouth
Transfer function characteristics.
Due to HswitchWith H1switchOnly include electronic switch, therefore stability is preferable, so that Ht→r/H1t→cAlso same
There is sample higher stability (similarly to also have Ht→r/H2t→c、Ht→r/H3t→c、Ht→r/H4t→c), it can be tested in face of it on ground
The acquisition of later stage Range compress template is used for after calibration.
Transfer function characteristics between 5 each port of each coupler of table
| Serial number | Transfer function characteristics | Symbol |
| 1. | 1 → port of port, 3 transmission function of coupler 1 | H1coup1-3 |
| 2. | 3 → port of port, 1 transmission function of coupler 1 | H1coup3-1 |
| 3. | 1 → port of port, 2 transmission function of coupler 1 | H1coup1-2 |
| 4. | 2 → port of port, 1 transmission function of coupler 1 | H1coup2-1 |
| 5. | 1 → port of port, 3 transmission function of coupler 2 | H2coup1-3 |
| 6. | 3 → port of port, 1 transmission function of coupler 2 | H2coup3-1 |
| 7. | 1 → port of port, 2 transmission function of coupler 2 | H2coup1-2 |
| 8. | 2 → port of port, 1 transmission function of coupler 2 | H2coup2-1 |
| 9. | 1 → port of port, 3 transmission function of coupler 3 | H3coup1-3 |
| 10. | 3 → port of port, 1 transmission function of coupler 3 | H3coup3-1 |
| 11. | 1 → port of port, 2 transmission function of coupler 3 | H3coup1-2 |
| 12. | 2 → port of port, 1 transmission function of coupler 3 | H3coup2-1 |
| 13. | 1 → port of port, 3 transmission function of coupler 4 | H4coup1-3 |
| 14. | 3 → port of port, 1 transmission function of coupler 4 | H4coup3-1 |
| 15. | 1 → port of port, 2 transmission function of coupler 4 | H4coup1-2 |
| 16. | 2 → port of port, 1 transmission function of coupler 4 | H4coup2-1 |
The above, best specific implementation mode only of the invention, but scope of protection of the present invention is not limited thereto,
Any one skilled in the art in the technical scope disclosed by the present invention, the change or replacement that can be readily occurred in,
It should be covered by the protection scope of the present invention.
The content that description in the present invention is not described in detail belongs to the known technology of professional and technical personnel in the field.
Claims (10)
1. a kind of SAR system internal calibration network element, it is characterised in that：1 switch including the n switch switched are selected including the first n
Group, the 2nd n select 1 switch, radio frequency unit and optical fiber delay unit；
In the case where receiving calibration mode, the pulse signal of transmitter transmitting selects one of the n switch of 1 switch, switching group to pass through the first n
It is defeated to arrive and one of the n switch corresponding load couplers of SAR all the way；N is the transmission way of SAR load；
In the case where emitting calibration mode, the pulse signal that the conducting access of one of n switch of switching group is coupled out by coupler, pulse
Signal is sent to optical fiber delay unit after the 2nd n selects 1 switch to be transferred to radio frequency unit regulation power, returns to and penetrates after delay
Frequency unit is forwarded to receiver by radio frequency unit.
2. SAR system internal calibration network element as described in claim 1, which is characterized in that mutually special with reference to calibration channel width
Property obtaining mode under, transmitter transmitting pulse signal after radio frequency unit regulation power, be sent to optical fiber delay unit, postpone
Radio frequency unit is returned to afterwards, and receiver is forwarded to by radio frequency unit.
3. SAR system internal calibration network element as claimed in claim 2, which is characterized in that further include first switch (1),
Two switches (2), third switch (3) and load；
In the case where receiving calibration mode, the pulse signal of transmitter transmitting is transferred to the first n through first switch (1) and selects 1 switch, and second
Switch (2) and third switch (3) are connected to load；In the case where emitting calibration mode, the conducting of one of n switch of switching group is by coupling
The access pulse signal that device is coupled out, pulse signal select 1 switch, third switch (3), second switch (2) to be transferred to and penetrate through the 2nd n
Frequency unit, first switch (1) are connected to load；The pulse signal that transmitter emits under reference channel magnitude-phase characteristics obtaining mode
Radio frequency unit is transferred to after first switch (1), second switch (2), third switch (3) is connected to load.
4. SAR system internal calibration network element as claimed in claim 1 or 2, which is characterized in that further include that power supply and monitoring are single
Member provides secondary power supply for radio frequency unit and optical fiber delay unit, and monitors the two operating voltage and electric current.
5. a kind of method that SAR system internal calibration network element using described in claim 3 carries out SAR load phase calibrations,
It is characterised in that it includes following steps：
(1) transmitting phase shifter and reception phase shifter are set as non-phase shift pattern, transmitter launch point frequency pulse signal, pulse
The frequency point of signal is the low-limit frequency of SAR signal subspace bands, and phase isEnable i=1；
(2) pulse signal is divided into the roads n through power splitter, and the i-th road signal is put through i-th of transmitting phase shifter (ti) to i-th of travelling-wave tubes
After big device (TWTAi) power amplification, i-th of coupler is transferred to through i-th of circulator, i-th of coupler is by pulse signal coupling
System internal calibration network element is closed, in the case where emitting calibration mode, i-th of switch conduction of switching group accesses pulse signal, by
Pulse signal is forwarded to receiver by radio frequency unit, and the phase for obtaining receiver output signal isCalculate the transmitting of the i-th tunnel
Channel phases
(3) judge whether i is equal to n, enable i=1 if being equal to n and enter step (4)；Then 1 return is added to walk i if it is less than n
Suddenly (2)；
(4) system internal calibration network element, which is operated in, receives under calibration mode, and the point frequency pulse signal of transmitter transmitting is through first
Switch (1), the first n select 1 switch, i-th of switch through switching group again, are transferred to i-th of coupler, and i-th of coupler is by pulse
Signal is coupled to i-th of circulator, and i-th of circulator transfers signals to i-th of amplitude limit low noise progress low noise acoustical power and put
After big, phase shifter (ri), i-th of isolator isolation are received through i-th, is output to receiver after combiner again, receiver into
Row reception is handled, and the phase of receiver output signal is φi_end, calculate the i-th tunnel receiving channel phase
(5) judge whether i is equal to n, i is then added into 1 return to step (4) if it is less than n；Judge that transmitter emits if being equal to n
Point frequency pulse signal frequency point, if it is SAR signal subspaces band low-limit frequency, the point frequency pulse signal frequency point of transmitter transmitting
It is set as the centre frequency of SAR signal subspace bands, phase isEnable i=1, return to step (2)；If it is in SAR signal subspace bands
Frequency of heart, then the highest frequency of transmitter transmitting put frequency pulse signal frequency point and be set as SAR signal subspace bands, phase areEnable i
=1, return to step (2)；SAR load phase calibrations are then completed if it is the highest frequency of SAR signal subspace bands.
6. SAR system phase calibration method according to claim 5, which is characterized in that repeat step (1)~(5) K
It is secondary, K group receiving channel phases and transmission channel phase are obtained, K group receiving channel phases and transmission channel phase error are calculated, and
Each receiving channel and transmission channel phase error mean value are obtained, corresponding transmitting phase shifter is adjusted according to phase error mean value and connects
Phase shifter is received, the phase alignment of each receiving channel and transmission channel is completed.
7. SAR system phase calibration method according to claim 6, which is characterized in that each subband of SAR system
Execute phase calibration.
8. a kind of magnitude-phase characteristics scaling method based on the SAR system phase calibration method described in claim 6, feature exist
In completing to carry out magnitude-phase characteristics calibration after the phase alignment of each receiving channel and transmission channel, specifically include following steps：
(1) phase shifter will be emitted and receive phase shifter system phase scaling method progress phase school according to claim 6
Standard, transmitter emit the pulse signal of SAR actual imagings work, and the phase-frequency characteristic of the transmitting signal isAmplitude versus frequency characte is A
(f), wherein f is frequency variable；Enable i=1；
(2) pulse signal selects 1 switch to enter power splitter through the 1st, is divided into the roads n through power splitter, the i-th road signal emits through i-th
After phase shifter (ti) increases power to i-th of travelling-wave tube amplifier (TWTAi), i-th of coupling is transferred to through i-th of circulator
Pulse signal is coupled to system internal calibration network element by device, i-th of coupler, and in the transmission mode, i-th of switching group is opened
Conducting access pulse signal is closed, pulse signal is forwarded to receiver by radio frequency unit, obtains the phase frequency of receiver output signal
Characteristic isAmplitude versus frequency characte is Ai_end(f), the magnitude-phase characteristics of the i-th road transmission channel is calculated
(3) judge whether i is equal to n, enable i=1 if being equal to n and enter step (4)；Then 1 return is added to walk i if it is less than n
Suddenly (2)；
(4) system internal calibration network element is operated under reference channel magnitude-phase characteristics obtaining mode, the pulse letter of transmitter transmitting
Number after first switch (1) enters system internal calibration network element, pulse signal is sent out by radio frequency unit, passes through the 2nd 2
1 switch is selected to be sent to receiver, the phase-frequency characteristic for obtaining receiver output signal is ψend(f), amplitude versus frequency characte ACend(f), it counts
Calculate reference channel magnitude-phase characteristics be
(5) system internal calibration network element, which is operated in, receives under calibration mode, and the pulse signal of transmitter transmitting is through first switch
(1), the first n selects 1 switch i-th through switching group switch again, is transferred to i-th of coupler, and i-th of coupler is by pulse signal
It is coupled to i-th of circulator, after i-th of circulator transfers signals to i-th of amplitude limit low noise progress low noise power amplification,
Emit phase shifter (ri) through i-th, the isolation of i-th isolator, after combiner selects 1 switch by the 2nd 2 be output to reception again
Machine, receiver carry out reception processing, and the phase-frequency characteristic of receiver output signal is φi_end(f), amplitude versus frequency characte ARi_end(f),
Calculate the magnitude-phase characteristics that the i-th tunnel receives calibration channel
(6) judge whether i is equal to n, enable i=1 if being equal to n and enter step (7)；Then 1 return is added to walk i if it is less than n
Suddenly (5)；
(7) according to the magnitude-phase characteristics Hi of the roads n transmission channelT, reference channel magnitude-phase characteristics be HrefIt is mutually special with the width in calibration channel
Property HiR, calculate the distance matching compression function of SAR system.
9. magnitude-phase characteristics scaling method according to claim 8, which is characterized in that further include before step (7)：Repetition is held
Row step (1)~(6) K times obtains K groups receiving channel and transmission channel magnitude-phase characteristics, and obtains each receiving channel and emit logical
Road magnitude-phase characteristics mean value is as final each receiving channel and transmission channel magnitude-phase characteristics value.
10. magnitude-phase characteristics scaling method according to claim 9, which is characterized in that the value of n is 4, calculates SAR system
Total transfer function HsigMethod be：
(1) equation group of solution formula (1)~(9) composition, obtains the transfer function H of transmittertrans；One 2 selects 1 switch work(point
The transfer function H in device directionswitch11；One 2 selects the transfer function H in 1 switch internal calibration network directionswitch12；Power splitter, hair
Penetrate the transfer function H i on the i-th tunnel of phase shifter and travelling-wave tube amplifier (TWTAi)power；No. i-th circulator direction of the launch transmission function
Hicir1-2；No. i-th circulator receives direction transfer function H icir2-3；No. i-th coupler direction of the launch transfer function H icoup1-2；
No. i-th coupler receives direction transfer function H icoup2-1；No. i-th coupler couples direction transfer function H icoup1-3；I-th road coupling
The inverse coupling direction transfer function H i of clutchcoup3-1；Amplitude limit low noise, the transmission for emitting phase shifter, the i-th tunnel of isolator and combiner
Function HiLNA；2nd 2 selects the interior calibration network of 1 switch to the transfer function H in receiver directionswitch22；2nd 2 selects 1 switch to be combined
Device is to receiver direction transfer function Hswitch21；Transfer function H under internal calibration network launches patternt→r；Internal calibration network transmission
Transfer function H under patternt→c；Transfer function H under the magnitude-phase characteristics obtaining mode of internal calibration network reference channelc→r, receiver transmit
Function Hrec；
H1T=Htrans·Hswitch11·H1power·H1cir1-2·H1coup1-3·H1c→r·Hswitch22·Hrec (1)
H2T=Htrans·Hswitch11·H2power·H2cir1-2·H2coup1-3·H2c→r·Hswitch22·Hrec (2)
H3T=Htrans·Hswitch11·H3power·H3cir1-2·H3coup1-3·H3c→r·Hswitch22·Hrec (3)
H4T=Htrans·Hswitch11·H4power·H4cir1-2·H4coup1-3·H4c→r·Hswitch22·Hrec (4)
Href=Htrans·Hswitch12·Ht→r·Hswitch22·Hrec (5)
H1R=Htrans·Hswitch12·H1t→c·H1coup3-1·H1cir2-3·H1LNA·Hswitch21·Hrec (6)
H2R=Htrans·Hswitch12·H2t→c·H2coup3-1·H2cir2-3·H2LNA·Hswitch21·Hrec (7)
H3R=Htrans·Hswitch12·H3t→c·H3coup3-1·H3cir2-3·H3LNA·Hswitch21·Hrec (8)
H4R=Htrans·Hswitch12·H4t→c·H4coup3-1·H4cir2-3·H4LNA·Hswitch21·Hrec (9)
(2) transfer function H 1 of four road transceiver channel loops is calculatedsig~H4sigRespectively：
(3) distance matching compression function H is calculatedsig, Hsig=H1sig+H2sig+H3sig+H4sig。
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