CN201323567Y - High precision GPS clock used in detection station of time difference between thunder and lightening - Google Patents

Abstract

The utility model relates to a high precision GPS clock used in detection station of time difference between thunder and lightening, which employs a GPS antenna, a GPS receiver, a counter, an external event flip-latch, a constant temperature crystal oscillator, a central process unit (CPU) and a pulse-per-second (PPS) flip-latch, wherein the GPS antenna is connected with the GPS receiver; the GPS receiver is also matched and connected with the PPS flip-latch and the CPU; the PPS flip-latch is connected with the CPU; the counter is connected with the PPS flip-latch and the external event flip-latch respectively; the external event flip-latch is connected with the CPU and is provided with a port for measuring signal input, while the constant temperature crystal oscillator is matched and connected with the counter. The GPS receiver 2 adopts a time service GPS receiver, and the constant temperature crystal oscillator serves as the local frequency source. The high precision GPS clock has the advantages of small error and high time precision.

Description

The high precision GPS clock that is used for thunder and lightning time difference acquisition station

Technical field

The utility model belongs to strange land time synchronized and time service field, relates in particular to the high precision GPS clock that is used for thunder and lightning time difference acquisition station.The Chinese meaning of GPS is global positioning system.

Background technology

Thunder and lightning time difference navigation system is that a whole set of is full-automatic, large tracts of land, high accuracy, lightning monitoring system in real time, and it mainly is made up of four parts: i.e. 1. lightening detection stations; 2. central station; 3. user terminal; 4. lightning information network system.Acquisition station is the core of thunder and lightning time difference navigation system, and its quantity and running quality have determined scale, efficient and the precision of a system.Its major function is to survey the cloud ELECTROMAGNETIC RADIATION SIGNATURE of thunder and lightning over the ground, measures parameters such as time that lightning wave arrives, orientation, intensity, polarity, and with these data in real time be sent to central station.The lightening detection station is distributed in each area, in order to receive airborne electromagnetic wave signal.When thunder and lightning took place, lightning wave was outwards propagated with the light velocity, because each detection website is different with the distance of thunderbolt origination point, the moment that website is respectively surveyed in lightning wave arrival just has difference.To receive the moment of lightning wave when two acquisition stations and deliver to the position analysis instrument, we just can know that lightning wave arrives the time difference at this two station, this time difference, multiply by the light velocity, and can draw the range difference of lightning strike spot to this two station.From how much, the range difference that lightning strike spot to two is surveyed website is known, can obtain a hyperbola, and the position of lightning strike spot is on this hyperbola.If there be the 3rd acquisition station also to receive this lightning wave signal, we can obtain a hyperbola again.Article two, hyp intersection point can draw the particular location of lightning strike spot.Thunder and lightning time difference navigation system is based upon on the chronometer time synchronous foundation, its acquisition station receives the radiated electromagnetic wave that lightning current produced, parameters such as recording electromagnetic wave time of advent are utilized the data of a plurality of acquisition stations that are distributed in the different location, calculate thunder and lightning with time difference method and produce the place.Because propagation velocity of electromagnetic wave is exceedingly fast, and just requires thunderstorm hour difference acquisition station to have the high precision synchronous time.

According to the knowledge of the applicant, thunder and lightning time difference acquisition station all adopts gps clock at present.So-called gps clock, the pps pulse per second signal that utilizes the GPS receiver to be exported is exactly proofreaded local clock, and local clock generally is the electronic clock that is made of a quartz oscillator.Its proofreading method is: with the pulse per second (PPS) rising edge as per second zero point, with the frequency of quartz of the interval correcting local clock between two rising edges.Because the per second check and correction, its blanking time is short, and the error that quartz oscillator was produced in the so short time is very little, so its synchronization accuracy is determined by the output pulse per second (PPS) of GPS receiver fully.The pulse per second (PPS) of GPS receiver output has very high time precision, and its rising edge error generally in 20-1000ns (nanosecond), though error is little, still exists after all.The applicant finds that under study for action the factor that influences error has a lot, mainly is to be subjected to weather influence.Known to the measurement data analysis that obtains, the pulse per second (PPS) error of GPS receiver output becomes normal distribution, and has randomness.In general application scenario, this error is very little, but is measuring the electromagnetic wave occasion of the time of advent, also must be with the gps clock ERROR CONTROL more among a small circle, otherwise be difficult to improve certainty of measurement.

Summary of the invention

The purpose of this utility model is to consider that above-mentioned the deficiencies in the prior art design, and propose and be designed for the high precision GPS clock in the thunder and lightning time difference acquisition station.

Technical solution of the present utility model is, adopted gps antenna, the GPS receiver, and counter and external event latch is characterized in that, have also adopted constant-temperature crystal oscillator, CPU and pulse per second (PPS) latch; Wherein, gps antenna links to each other with the GPS receiver, the GPS receiver connects pulse per second (PPS) latch, CPU respectively, the pulse per second (PPS) latch is connected with CPU, counter is connected with the external event latch with the pulse per second (PPS) latch respectively, the external event latch is connected with CPU, and the external event latch is furnished with the port of measuring-signal input, and constant-temperature crystal oscillator and counter connect.

It is characterized in that GPS receiver 2 adopts time service type GPS receiver.

It is characterized in that constant-temperature crystal oscillator is as local frequency source.

The utility model effect is the electromagnetic time of advent of measurement thunder and lightning.When measuring-signal is imported with impulse form, the utility model is started working, will be as the rising edge of the pulse signal of measuring-signal input, provide measurement result with the form of digital quantity, be the high precision time amount, this time parameter is adopted by thunder and lightning time difference acquisition station main control part.

Operation principle of the present utility model is, adopt local frequency source to the GPS receiver pulse per second (PPS) count at interval, the count value of first pulse per second (PPS) correspondence is N ₁, the count value of second pulse per second (PPS) correspondence is N ₂, and the like, the count value of m pulse per second (PPS) is Nm, according to the count value that obtains, closes straight line but get wherein m data making.If make abscissa with the pulse per second (PPS) number, corresponding count value is made ordinate, m the discrete point that just can on plane right-angle coordinate, draw, and these points linearly distribute.

According to mathematical formulae, press down unification bar straight line with least square method, make the error minimum between straight line and the discrete point.Be computing formula below:

1)y＝ax+b

$2),a=\frac{\underset{i=1}{\overset{m}{\mathrm{\Σ}}}(x_i-\stackrel{\‾}{x})(y_i-\stackrel{\‾}{y})}{\underset{i=1}{\overset{m}{\mathrm{\Σ}}}{(x_i-\stackrel{\‾}{x})}^2}$

3)b＝y-ax

Wherein, $\stackrel{\‾}{x}=\frac{1}{n}\underset{i=1}{\overset{m}{\mathrm{\Σ}}}{x}_i,$ $\stackrel{\‾}{y}=\frac{1}{n}\underset{i=1}{\overset{m}{\mathrm{\Σ}}}{y}_i,$ (1) formula is a linear equation, and a is a slope, the frequency of the local frequency source that promptly calculates, and b is an intercept, the pulse per second (PPS) error of the GPS receiver output that promptly calculates.

Key point of the present utility model is that the stability of local frequency source is depended in the improvement of timing tracking accuracy.Stability is high more, but it is many more to add up to the some position of calculating just can obtain, and corresponding timing tracking accuracy is also high more.

The utility model has the advantages that, adopt type GPS receiver when being subjected to, the highly stable frequency source, the high long-time stability when utilizing GPS to be subjected to and the high short-term stability of high stable frequency source are learnt from other's strong points to offset one's weaknesses, and realize a kind of and the split-second precision Greenwich time synchronized.With the frequency source of highly stable frequency source, latch the corresponding numerical value of counter with the pulse per second (PPS) of GPS receiver output as counter.Make ordinate with the latch value, the pulse per second (PPS) number is made abscissa, and available a series of point is represented pulse per second (PPS) on plane right-angle coordinate, but uses least square method match straight line, obtain the slope and the intercept of this straight line, it is pairing to be exactly the frequency of frequency source and the error of pulse per second (PPS).ERROR CONTROL more among a small circle, can be improved time precision.

Description of drawings

Fig. 1, circuit block diagram of the present utility model

But Fig. 2, straight line close schematic diagram

Embodiment

Below, in conjunction with the accompanying drawings specific embodiment of the present utility model is described in further detail.

As shown in Figure 1 and Figure 2, the utility model has adopted gps antenna 1, GPS receiver 2, and counter 4 and external event latch 6 adopt constant-temperature crystal oscillator 3, CPU 7 and pulse per second (PPS) latch 5 again; The utility model is by gps antenna 1, GPS receiver 2, and constant-temperature crystal oscillator 3, counter 4, pulse per second (PPS) latch 5, external event latch 6, CPU more than 7 parts are formed.Wherein, gps antenna 1 links to each other with GPS receiver 2; The pulse per second (PPS) output of GPS receiver 2 connects pulse per second (PPS) latch 5, and the serial ports of GPS receiver 2 connects CPU 7; Constant-temperature crystal oscillator 3 is connected with counter 4; Counter 4 connects with pulse per second (PPS) latch 5, external event latch 6 respectively; Pulse per second (PPS) latch 5, external event latch 6 connect with CPU 7 respectively.External event latch 6 is furnished with the port of measuring-signal input, is connected with external event latch 6 through port as the pulse signal of measuring-signal.Constant-temperature crystal oscillator 3 is as local frequency source.This local frequency source is a highly stable frequency source.GPS receiver 2 adopts time service type GPS receiver.Usually, GPS receiver 2 can be selected the M12T of Motorola for use, and CPU 7 can adopt Intel8051, and constant-temperature crystal oscillator 3 must adopt stability to be higher than 5 * 10 ^-9/ day, frequency is greater than the product of 10Mhz.

GPS receiver 2 meanwhile, with the frequency source of highly stable frequency source as counter 4, latchs 4 corresponding numerical value of counter with the pulse per second (PPS) of GPS receiver 2 outputs with local frequency source---proofread and correct mutually in the highly stable frequency source.Make ordinate with the latch value, the pulse per second (PPS) number is sat abscissa, and available a series of point is represented pulse per second (PPS) on plane right-angle coordinate, but uses least square method match straight line, obtain the slope and the intercept of this straight line, it is pairing to be exactly the frequency of frequency source and the error of pulse per second (PPS).

Measuring-signal adopts (outside) pulse signal of input, (outside) pulse signal is the signal that the thunder and lightning electromagnetic wave is produced after treatment, import by the port that external event latch 6 is furnished with, (outside) pulse signal connects external event latch 6 through port, value by external event latch 6, utilize front institute result calculated again, just can measure the correct time that the thunder and lightning electromagnetic wave arrives.

In concrete the enforcement, time service type GPS receiver is just exported pps pulse per second signal (1PPS), and is attended by rs 232 serial interface signal after receiving four satellite-signals, informs details and some other location and the navigation data of 7 pulse per second (PPS)s of CPU.Constant-temperature crystal oscillator 3 is as local highly stable frequency source, its stability and frequency directly influence synchronization accuracy of the present utility model and resolution, and 4 pairs of constant-temperature crystal oscillators 3 of counter are counted, and are output as N, the 1PPS signal drives the value that pulse per second (PPS) latch 5 latchs counter 4, is output as N _m(m is the 1PPS number), CPU 7 are read N by data wire _m

Obtaining per second latch value N _mAfterwards, CPU 7 is according to the stability of local oscillator, but desirable nearest m data are closed straight line.Oscillator stability is high more, and the m value can obtain big more, and its precision is also high more, if constant-temperature crystal oscillator 3 adopts 1 * 10 ^-9The device in/sky, time precision can improve an order of magnitude.Computational methods as:

1)y＝ax+b

$2),a=\frac{\underset{i=1}{\overset{m}{\mathrm{\Σ}}}(x_i-\stackrel{\‾}{x})(y_i-\stackrel{\‾}{y})}{\underset{i=1}{\overset{m}{\mathrm{\Σ}}}{(x_i-\stackrel{\‾}{x})}^2}$

3)b＝y-ax

Wherein, $\stackrel{\‾}{x}=\frac{1}{n}\underset{i=1}{\overset{m}{\mathrm{\Σ}}}{x}_i,$ $\stackrel{\‾}{y}=\frac{1}{n}\underset{i=1}{\overset{m}{\mathrm{\Σ}}}{y}_i,$ (1) formula is a linear equation, and a is a slope, the frequency of the local frequency source that promptly calculates, and b is an intercept, the pulse per second (PPS) error of GPS receiver 2 outputs that promptly calculate.

It should be noted that: above calculating is carried out in real time, and per second calculates once, guarantees that result of calculation is timely and effective.After frequency that obtains calculating and the pulse per second (PPS) error, its clock synchronization accuracy has just obtained corresponding raising.

Claims (3)

1, the high precision GPS clock that is used for thunder and lightning time difference acquisition station, adopted gps antenna, GPS receiver, counter and external event latch, it is characterized in that, also adopted constant-temperature crystal oscillator (3), CPU (7) and pulse per second (PPS) latch (5); Wherein, gps antenna (1) links to each other with GPS receiver (2), GPS receiver (2) connects pulse per second (PPS) latch (5), CPU (7) respectively, pulse per second (PPS) latch (5) is connected with CPU (7), counter (4) is connected with external event latch (6) with pulse per second (PPS) latch (5) respectively, external event latch (6) is connected with CPU (7), external event latch (6) is furnished with the port of measuring-signal input, and constant-temperature crystal oscillator (3) connects with counter (4).

2, the high precision GPS clock that is used for thunder and lightning time difference acquisition station according to claim 1 is characterized in that, GPS receiver (2) adopts type GPS receiver when being subjected to.

3, the high precision GPS clock that is used for thunder and lightning time difference acquisition station according to claim 1 is characterized in that, constant-temperature crystal oscillator (3) is as local frequency source.

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