CN106773615B - A kind of pulsar photon timing method based on APD detector - Google Patents
A kind of pulsar photon timing method based on APD detector Download PDFInfo
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Abstract
The invention discloses a kind of pulsar photon timing method based on APD detector is realized using APD to 0.5~10keV weak pulse star photon detection.On the one hand have many advantages, such as that detection efficient is high, the response time is fast, energy resolution is high；On the other hand, photo-generated carrier is along pn-junction to drift inside detector, smaller by detector bring gitter itself, therefore is highly suitable for pulsar photon timing；Using constant fraction discriminator and single threshold triggering method, while suppressing noise, further eliminate due to different X-ray energy bring amplitude autokinetic effects；TDC timing accuracy is kept, pulsar photon timing error is further decreased by long steady, the high precision clock frequency of correction principle output in conjunction with the long steady and short steady advantage of atomic clock of GPS second pulse signal.
Description
Technical field
The invention belongs to the technical fields such as deep space exploration navigation, aerospace, information remote sensing, and in particular to one kind is based on
The pulsar photon timing method of APD detector.
Background technique
Pulsar navigation is a kind of independent navigation mode dependent on the natural clock of pulsar, it is completely independent of ground
The support stood is realized the time service of spacecraft using the pulsar X-ray band pulse in detection universe, determines appearance, positioned, and then complete
At the independent navigation of spacecraft.The basic principle of X-ray pulsar navigation is: when measurement pulsar pulse reaches spacecraft
Phase, form the pulsion phase for the difference of the phase of solar system mass center, which is the letter of position of aircraft and pulsar position
Number, it is assumed that the position of known pulsar can be obtained observation moment spacecraft with respect to the sun by certain navigation algorithm
It is the position coordinates of mass center.
Pulsar pulse arrival time TOA (Time of Arrival) measurement is the key that realize pulsar navigation.TOA
It is relatively to be obtained by the nominal contour of observation profile and high s/n ratio.Spacecraft detects arteries and veins by installation X-ray detector
Rush the x-ray photon of star radiation, record photon arrival time, through integral after a period of time, fit pulse profile, and with arrive
Nominal contour up to solar system mass center relatively determines TOA.
Therefore, high-precision photon arrival time is the basic observation of detector, directly affects TOA measurement and navigation essence
Degree.Photon timing accuracy is related to the X single-photon detector and timing method of selection.Pulsar navigation is as a kind of novel navigation
Technology, relevant report is less both at home and abroad at present in terms of pulsar photon timing research.
Summary of the invention
In view of this, the object of the present invention is to provide a kind of pulsar photon timing method based on APD detector, it can
Technical support is provided for the development of X-ray pulsar navigation detector, pulsar photon pulse arrival time TOA measurement.
A kind of pulsar photon timing method based on APD detector, includes the following steps:
Step 1, using APD detector direct impulse starlight, obtain photonic pulsed signals；
Step 2 carries out preposition amplification and filtering forming processing to the photonic pulsed signals that step 1 obtains, so that after filtering
The pulse signal of output keeps original rising edge as far as possible, wherein photonic pulsed signals rising time 100ns~200ns it
Between；
The pulse signal of step 3 is divided into two-way by step 3, to wherein decaying all the way, in addition prolonging all the way
Late, the intersection point of two paths of signals waveform is found by trigger, while generating a positive pulse；
Step 4 exports the positive pulse that the pulse per second (PPS) that 50M pulse clock and GPS are exported generates step 3 using atomic clock
It is timed, pulsar photon arrival time is finally located in nanosecond.
Preferably, being put before using pressure sensitive to the preposition enhanced processing of photonic pulsed signals progress in the step 2, electric current
Put before sensitive or charge-sensitive before the mode of putting handled.
Preferably, filtering forming processing uses CR- (RC) in the step 2mFiltering or active SK filtering are realized.
Preferably, in the step 2, using CR- (RC)mWhen filtering, by selecting the RC value of suitable filter circuit, make
The pulse exported after must filtering keeps original rising edge.
Preferably, in the step 3, the method that finds the intersection point of two paths of signals waveform are as follows: assuming that the pulse signal of input
The triangular signal for being A for slope:
Vin=At (3)
The then signal all the way after q times of decaying are as follows:
Va=Aqt (4)
The another way signal of delayed Δ t are as follows:
Vd=A (t- Δ t) (5)
Waveform intersection point time t is determined by formula (4) and (5)CIt indicates are as follows:
tC=Δ t/ (1-q) (6)
Preferably, the amplitude of decaying road signal is between 0.4~0.6 times of original signal.
Preferably, the delay time of postpones signal is between 20ns~30ns.
Preferably, the GPS pulse per second (PPS) exported is corrected by sliding Mean Method in the step 4, it will be by school
Positive GPS second pulse and 50M pulse clock, is input in TDC module, is timed to photon, specifically:
If the pulse per second (PPS) time series of GPS receiver output is X={ x1,x2,…xn}；If the pulse period of atomic clock is
T is counted with the pulse per second (PPS) time of the pulse pair GPS of the atomic clock, then pulse per second (PPS) time series is expressed as Y={ y1,y2,…
yn, in which:
yi=yi-1+niT-εi(7) wherein, i=1,2 ..., n；N indicates element number in sequence；niFor atom in 1s
The count value of clock；εiFor the sum of GPS second pulse random error and the accumulated error of atomic clock, meet Gaussian Profile；
Long-time counting is carried out to GPS pulse using atomic clock, obtains long-term averaged countAs next pulse per second (PPS)
The estimated value of countingPass through yiThe estimated value of lower one-second burst error is obtained compared with xi in time series XIt willInstead of ni
And it willInstead of εi, substitute into (7) formula obtain revised pulse per second (PPS) time series.
Preferably, when atomic clock is corrected GPS second pulse, to counting number N > 10000 of GPS second pulse.
Preferably, the TDC module is finely divided using the pulse clock that time split-phase method exports atomic clock, and by
This will be applied in photon timing subdivision time.
Preferably, by atomic clock clock subdivision at 0 °, 90 °, 180 ° and 270 ° of 4 split-phase clocks, final timing accuracy
For 5ns.
The invention has the following beneficial effects:
(1) it is realized using APD to 0.5~10keV weak pulse star photon detection.On the one hand there is detection efficient height, ring
Fast between seasonable, the advantages that energy resolution is high；On the other hand, photo-generated carrier is along pn-junction to drift inside detector, by visiting
It is smaller to survey device bring gitter itself, therefore is highly suitable for pulsar photon timing；
(2) constant fraction discriminator and single threshold triggering method are used, while suppressing noise, is further eliminated due to different X
Photon energy bring amplitude autokinetic effect；
(3) the long steady and short steady advantage of atomic clock of GPS second pulse signal is combined, it is steady, high-precision by correction principle output length
Clock frequency is spent, TDC timing accuracy is kept, further decreases pulsar photon timing error.
Detailed description of the invention
Fig. 1 is the pulsar photon timing method functional block diagram of the invention based on APD detector；
Fig. 2 is APD single-photon detector basic principle of the invention；
Fig. 3 is constant fraction discriminator module of the invention；
Fig. 4 is the time keeping module of the invention based on atomic clock.
Specific embodiment
The present invention will now be described in detail with reference to the accompanying drawings and examples.
A kind of pulsar photon timing method based on APD detector, main operational principle are as shown in Figure 1, comprising:
(1) APD detector: the principle amplified by snowslide is converted to by photoelectric effect incident x-ray fluorescence micro-
Weak electric signal.
(2) signal extraction module: comprising circuits such as preposition amplification, shaping filters, the APD small-signal exported is converted to
It can be used for the pulse signal of timing；
(3) constant fraction discriminator module: being triggered using constant fraction discriminator and single threshold, guarantees useful signal acquisition, while eliminating not
Co-energy photon bring amplitude travelling；
(4) clock keeps module: miniature atomic clock is used, in conjunction with GPS second pulse, export high surely clock frequency to FPGA,
Guarantee the precision of TDC timing；
(5) TDC (Time-Digital Convert) module: realizing inside FPGA, by GPS second pulse as starting
Signal carries out time-to-digital converter to the positive pulse of constant fraction discriminator circuit output.
It is of the invention that detailed process is as follows:
(1) basic principle of APD single-photon detector
APD detector may be implemented highly sensitive and fast-response unification, be very suitable for pulsar using flow-through structure is drawn
Weak photon detection.Draw flow-through APD structure and distribution map of the electric field as shown in Fig. 2, using P+IPN+Multilayered structure.
When applying reverse biased appropriate to APD, the entire area PI all exhausts, therefore is referred to as depletion layer.In depletion layer
Portion can be divided into multiplication region and drift region again.PN+Knot is held since built in field effect is there are high field region, also known as multiplication region
By most of pressure drop of reverse biased added by APD.The area ratio P, the area I is much broader, but its electric field is also more much weaker than high field region, but foot
So that carrier keeps certain drift velocity, the of short duration transition time is only needed in the wider area I, therefore the area I also known as drifts about
Area.
Enter to inject in semiconductor material when incident light penetrates antireflection layer, generates photo-generated carrier electron hole pair.Electronics is empty
Cave accelerates the very high energy of acquisition to make the concentration of carrier at double by continuous ionization by collision in multiplication region by High-Field
Ground increases, and generates avalanche multiplication effect.Then photo-generated carrier after multiplication is quickly getted in drift region, until by the electricity at both ends
It collects pole.
A branch of in this way, avalanche photodide can obtain fast response speed and certain gain, reduce simultaneously
Noise.
In specific implementation, the APD007 model that X-ray APD detector can select FMB-Oxford company to produce, response
Time is less than 10ns, and energy resolution is better than 300eV@6keV, reverse biased 0-400V.Detector window selects 70 μm of Kapton
Material only allows X-ray of 0.5-20KeV to pass through.
(2) preposition amplification and filtering wave-shaping circuit
Preposition amplification is put before can choose pressure sensitive according to different detector models, is put before current sensitive, charge-sensitive
Before put.Here since APD detector itself has the characteristics of high-gain, fast-response, therefore it can choose simplest parallel connection
Structure is put before negative feedback current is sensitive, output voltage can be expressed as
Vo(t)=iD(t)Rf (1)
Wherein Vo(t) to put output voltage, i before current sensitiveDIt (t) is APD detection output electric current, RfBefore current sensitive
Put negative feedback resistor.
Filtering wave-shaping circuit can use CR- (RC)mFiltering or active SK filtering are realized.Here CR- (RC) is usedmFiltering
Mode first passes through CR differential, integrates using 2 grades or more of RC.CR-(RC)mOnly selectively RC constant is related for filter shape,
The pulse exported after filtering can indicate are as follows:
Reach peak value in t=m τ, at this timeVomFor the peak value of pulse exported after filtering.
By selecting suitable RC value, so that the pulse exported after filtering keeps original rising edge as far as possible, and after being able to satisfy
The needs of continuous timing.Rising time is between 100ns~200ns.Meanwhile for subsequent timing needs, forming amplification
Signal amplitude need between 1V~5V.
(3) constant fraction discriminator method
Since APD detector response time is fast, internal photo-generated carrier is along pn-junction to drift, by detector band itself
The gitter come is smaller.But the signal amplitude that different X-ray energy will lead to APD output is variant.Therefore, for APD
The signal of output can use constant fraction discriminator method.
As shown in figure 3, constant fraction discriminator is a kind of timing method with constant triggering ratio, it is suitable for signal leading edge difference not
Greatly, the different signal of amplitude can eliminate the difference due to input signal amplitude and the Time walk effect that introduces.
The input pulse signal of constant fraction discriminator is first divided into two-way, to wherein decaying all the way, in addition all the way into
Two paths of signals, is then added to the input terminal of zero-cossing discriminator by row delay, obtains time detection digital signal.Here for letter
It is single, it is assumed that input signal is the triangular signal that slope is A
Vin=At (3)
Then signal is all the way after q times of decaying
Va=Aqt (4)
The another way signal of delayed Δ t is
Vd=A (t- Δ t) (5)
The time t determined by two above formula, comparatorCIt can be expressed as
tC=Δ t/ (1-q) (6)
Then the intersection point t of two paths of signals waveform is foundC, while generating a positive pulse；It can be seen that comparator determined
Time is unrelated with signal amplitude, eliminates the difference due to input signal amplitude and the Time walk effect that introduces.
Here according to the signal characteristic after forming, postpone road signal delay time between 20~30ns, road signal of decaying
It is between 0.4~0.6 times of original signal.
(4) time based on atomic clock keeps
Using sliding Mean Method to atomic clock frequency marking and GPS second synthetic impulse, the GPS and 50MHz that output calibration is crossed are former
Secondary clock frequency is used to subsequent TDC module.
Since the random error of GPS second signal meets the normal distribution that mean value is zero, can be filtered out by sliding mean algorithm.
By the mean operation to preceding N seconds error, the accumulated error estimated value of atomic frequency is obtained, next second atomic clock is counted
Value compensates, to generate high-precision second pulse signal.
Concrete operations principle is as follows: setting the pulse per second (PPS) time series of GPS receiver output as X={ x1,x2,…xn}.If former
The pulse period of secondary clock is T, is counted with the atomic clock to the GPS second burst length, then pulse per second (PPS) time series can indicate
For Y={ y1,y2,…yn}
yi=yi-1+niT-εi (7)
Wherein, niIt is counter in 1s to the count value of atomic clock.εiFor the random error and atomic clock of GPS second pulse
The sum of accumulated error meets Gaussian Profile.By (7) formula it is found that pulse per second (PPS) sequence Y is by niAnd εiIt determines, if can accurately forecast down
One second niAnd εi, then can produce high-precision pulse per second (PPS) time series.
As shown in figure 4, being counted respectively using atomic clock to (N > 10000) GPS pulse for a long time, obtain long-term flat
Equal count valueThe estimated value counted as next pulse per second (PPS)It is lesser using atomic clock error within the unit time simultaneously
Characteristic passes through yiWith xiCompare to obtain the estimated value of lower one-second burst errorIt willWith(7) formula of substitution can be obtained by high-precision
The pulse per second (PPS) time series of degree.
Commercial CPT atomic clock can be used in atomic clock, has small-sized advantage, general to export 10MHz frequency, needs to pass through
Frequency multiplication chip exports 50MHz atomic frequency standard, uses to subsequent TDC.
(5) TDC module
Time digital transformation TDC module is the rise time for the positive pulse signal for obtaining time detecting circuit to carry out number
Change.TDC can realize that, using the GPS second pulse of input as the start signal of starting, constant proportion is fixed inside FPGA according to demand
When the positive pulse that exports as the stop signal terminated, Tstart+(Tstop-Tstart) it is photon arrival time.(Tstop-Tstart)
It is measured by the time Time_bin of TDC inside modules.When specific TDC method can use counter-type TDC, carry chain
Between interpolation type TDC, multiphase clock interpolation type TDC.
It here is the method combined using " thick " counting and the measurement of " thin " time by taking time split-phase TDC as an example.Thick count section
Divide and obtained by the clock-driven high precision timer of the external atomic clock CLK (50MHz) of FPGA, time resolution Time_bin is
20ns。
Thin time portion is obtained by clock phase-splitting, and by the PLL module inside FPGA, CLK (50MHz) clock is divided into 4
A phase (0 °, 90 °, 180 ° and 270 °) carries out time measurement using this 4 split-phase clocks, can achieve the Time_ of thick clock
Bin is segmented to 1/4, and final photon positioning time differentiates up to 5ns.
In conclusion the above is merely preferred embodiments of the present invention, being not intended to limit the scope of the present invention.
All within the spirits and principles of the present invention, any modification, equivalent replacement, improvement and so on should be included in of the invention
Within protection scope.
Claims (10)
1. a kind of pulsar photon timing method based on APD detector, which comprises the steps of:
Step 1, using APD detector direct impulse starlight, obtain photonic pulsed signals；
Step 2 carries out preposition amplification and filtering forming processing to the photonic pulsed signals that step 1 obtains, so that exporting after filtering
Pulse signal keep original rising edge as far as possible, wherein photonic pulsed signals rising time is between 100ns~200ns；
The pulse signal of step 3 is divided into two-way by step 3, to wherein decaying all the way, in addition postponing all the way, is led to
The intersection point that trigger finds two paths of signals waveform is crossed, while generating a positive pulse；
Step 4 exports the positive pulse progress that the pulse per second (PPS) that 50M pulse clock and GPS are exported generates step 3 using atomic clock
Periodically, pulsar photon arrival time is finally located in nanosecond；
In the step 4, the GPS pulse per second (PPS) exported is corrected by sliding Mean Method, by corrected GPS second arteries and veins
Punching and 50M pulse clock, are input in TDC module, are timed to photon, specifically:
If the pulse per second (PPS) time series of GPS receiver output is X={ x1,x2,…xn}；If the pulse period of atomic clock is T, with
The pulse per second (PPS) time of the pulse pair GPS of the atomic clock is counted, then pulse per second (PPS) time series is expressed as Y={ y1,y2,…yn,
Wherein:
y1=yi-1+niT-εi (7)
Wherein, i=1,2 ..., n；N indicates element number in sequence；niFor the count value of atomic clock in 1s；εiFor GPS second pulse
The sum of random error and the accumulated error of atomic clock, meet Gaussian Profile；
Long-time counting is carried out to GPS pulse using atomic clock, obtains long-term averaged countIt is counted as next pulse per second (PPS)
Estimated valuePass through yiThe estimated value of lower one-second burst error is obtained compared with xi in time series XIt willInstead of niAnd
It willInstead of εi, substitute into (7) formula obtain revised pulse per second (PPS) time series.
2. a kind of pulsar photon timing method based on APD detector as described in claim 1, which is characterized in that described
Preposition enhanced processing is carried out using putting, put before current sensitive or charge spirit before pressure sensitive to photonic pulsed signals in step 2
The mode of putting is handled before quick.
3. a kind of pulsar photon timing method based on APD detector as described in claim 1, which is characterized in that described
In step 2, filtering forming processing uses CR- (RC)mFiltering or active SK filtering are realized.
4. a kind of pulsar photon timing method based on APD detector as described in claim 1, which is characterized in that described
In step 2, using CR- (RC)mWhen filtering, by selecting the RC value of suitable filter circuit, so that the pulse exported after filtering
Keep original rising edge.
5. a kind of pulsar photon timing method based on APD detector as described in claim 1, which is characterized in that described
In step 3, the method that finds the intersection point of two paths of signals waveform are as follows: assuming that the pulse signal of input is the triangle letter that slope is A
Number:
Vin=At (3)
The then signal all the way after q times of decaying are as follows:
Va=Aqt (4)
The another way signal of delayed Δ t are as follows:
Vd=A (t- Δ t) (5)
Waveform intersection point time t is determined by formula (4) and (5)CIt indicates are as follows:
tC=Δ t/ (1-q) (6).
6. a kind of pulsar photon timing method based on APD detector as described in claim 1, which is characterized in that decaying
The amplitude of road signal is between 0.4~0.6 times of original signal.
7. a kind of pulsar photon timing method based on APD detector as described in claim 1, which is characterized in that delay
The delay time of signal is between 20ns~30ns.
8. a kind of pulsar photon timing method based on APD detector as described in claim 1, which is characterized in that atom
When clock is corrected GPS second pulse, to counting number N > 10000 of GPS second pulse.
9. a kind of pulsar photon timing method based on APD detector as described in claim 1, which is characterized in that described
TDC module is finely divided using the pulse clock that time split-phase method exports atomic clock, and is thus applied to the subdivision time
In photon timing.
10. a kind of pulsar photon timing method based on APD detector as claimed in claim 9, which is characterized in that will be former
For secondary clock clock subdivision at 0 °, 90 °, 180 ° and 270 ° of 4 split-phase clocks, final timing accuracy is 5ns.
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| CN109443557B (en) * | 2018-12-26 | 2020-11-06 | 合肥工业大学 | Single photon pulse arrival time detection device |
| CN110286405B (en) * | 2019-07-10 | 2020-09-15 | 中国科学院近代物理研究所 | Application of calibration device of deep space detector system |
| CN110346755B (en) * | 2019-07-10 | 2023-06-27 | 四川中电昆辰科技有限公司 | Signal amplitude detection device and method and arrival time correction method thereof |
| CN110686702B (en) * | 2019-09-27 | 2022-10-11 | 中国科学院上海光学精密机械研究所 | Pulsar photon flow simulation system and method based on light field high-order correlation |
| CN111983656B (en) * | 2020-08-17 | 2023-10-27 | 电信科学技术第五研究所有限公司 | Method, device and computer medium for optimally estimating GNSS time in GNSS time system equipment |
| CN112379381B (en) * | 2020-09-01 | 2023-12-19 | 南京理工大学 | Laser ranging circuit |
| CN117434820A (en) * | 2023-12-19 | 2024-01-23 | 杭州谱育科技发展有限公司 | Time-to-digital converter and time-of-flight mass spectrometer |
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