Summary: Introduce satellite location, time service and characteristic and basic principle moving ahead simultaneously; Explain modern the intersection of satellite and the intersection of signal receive and the intersection of hardware and software and design philosophy of system in detail and how imbed, employ accurate object that aeronautical satellite realize make a reservation in the intersection of system and design, clock time service and synchronous data are gathered and controlled.
Keyword: Group’s integrated module satellite location time service of dealing with the chip of LNA RF baseband and moving ahead simultaneously
Utilize the aeronautical satellite, gather and control object localization, time service of the clock and synchronous data, can reach the accurate intensity can’t be obtained of control means of traditional measurement. The synchronous technology of time service of this kind of satellite location is in aviation and navigation, land transportation, scientific investigation, polar region explore and geography measure and weather forecast, apparatus patrol and inspect and person who control application of extensive day by day systematically. In recent years, a lot of manufacturers, such as Atmel, ST, Motorola, Maxim, NEC, Fijitsu, Conexant,etc., have introduced chip group and module that a lot of relevant satellite location time service moves ahead simultaneously in succession, in order to design the stable and reliable, succinct and portable instrument instrument, has offered a lot effective convenient routes. How this text forms various compactly, simple satellite signal receive passway apt to use, of good performance with low costs, how to imbed in different actual application systems to realize that gathers all kinds of controlled and designs paying explaining synthetically in accurate object localization, time service of the clock or synchronous data.
Synchronous summary of time service of a satellite location
The key part in the synchronous technology of time service of satellite location is the artificial earth aeronautical satellite’s group. At present, there are GPS GPS of U.S.A., the whole world of Russia satellite system GLONASS Global Navigation System of navigating in the main aeronautical satellite group , the gal profit of the Big Dipper navigation system of China and European Union is slightly navigation system Galileo in the world. The characteristics and application states of these kinds of navigation satellite systems are set out in Table 1.
Satellite navigation systems are usually made up of three parts: The aeronautical satellite, ground monitor and correct and maintain system, user’s receiver or transceiver. As to the land satellite navigation systems of the Big Dipper office, the ground monitoring center should help users to finish orienting time service and moving ahead simultaneously together. What this text explained especially is that users receive or receive and dispatch some embedded hardwares and softwares to employ and design.
In the civil respect, the localization precision of GPS, GLONASS and the Big Dipper is the rice grade, the clock precision of time service of the satellite is each, the synchronous ability of the data is under 1 μ s. The future Galileo satellite system of navigating, it orients time service synchronous and with precision of GPS and about 10 times civilly. In the above-mentioned several kinds of navigation satellite systems, GPS can be carried on the apparatus all-roundly, all-weatherly, the best satellite whose time service moves ahead simultaneously of satellite location navigates over a long time. At present, U.S.A. is safeguarding GLONASS with Russia, forms GPS GLONASS system, satellite number multiplication together, the precision, range, efficiency and dependability that the time service of satellite location moves ahead simultaneously will get further improvement.
Basic principle that 2 satellite location time service moves ahead simultaneously
The satellite navigates Doppler based on Doppler’s effect moves the law frequently: FΔ=In λ / ν type, fΔ changes for the signal frequency of electromagnetic wave that runs between the objects, λ is the wavelength of its electromagnetic wave of signal, ν is its relative speed.
Have type, explain Doppler, satellite of signal received, move curve and the intersection of satellite and orbit, have one one corresponding relation frequently. That is to say, so long as Doppler who gets the satellite moves the curve frequently, can confirm the orbit of the satellite. On the contrary, known satellite orbit, move the curve frequently according to Doppler received, can confirm that receive the ground position of the body.
The basic principle that the global satellite navigates is: The satellite launches the text of navigating, include, find range the intersection of precision and factor, the intersection of Keppler and parameter, the intersection of orbit and the intersection of perturbation and parameter, the intersection of satellite and the intersection of clock and bad the intersection of parameter and the intersection of ν and ti, atmosphere travel, delay, revise parameter,etc.. The ground receiver, according to code division multiple access CDMA Code Division Multiple Access Or divide much location FDMA Frequency Division Multiple Access frequently Characteristic last every aeronautical satellite, be lasted navigation text on whether it is corresponding, measure spread time Δ ti which sends the signal, utilize a series of parameter of navigating in the text to calculate the position of the satellite xi progressively, yi, zi . Some positions are x, y, z to set up the receiver and await measuring ,It is ν t0 that the clock clock of the receiver is bad, the receiver can only receive 4 satellite signals at least, can position it and the clock is bad:
Under the navigation system in the whole world, the text of navigating of user’s receiver according to the satellite is checking and approving his clock clock badly constantly, can get very high clock precision, this is accurate satellite time service; The regular time sequence characteristic of the text, through the counter, can get the high-accuracy synchronism second pulse PPS Pulse Per Second according to navigating Signal,be used for with /strange land many passway that the data gather and control operations synchronous.
The basic principle that the land satellite of the Big Dipper office navigates is: As the centre of a circle with 2 known satellites in position, each in order to determine this star is to the subscriber computer before forming 2 spheres for the radius. The ground control centre offers one to regard the earth’s core as ball heart, ball heart to nonuniform sphere as the radius of the earth surface height through the electron high Cheng’s map. The points of intersect of three spheres are user’s position. The concrete localization course is: Sent out the signal by centre on the ground at first, reflect and reach user’s receiver through 2 satellites separately, reflect, pass the intersection of ground and centre back separately by 2 satellite by receiver and then, ground centeral station calculate two the intersection of route and time t1 and t2 taken, set position of the satellite as xi, yi, zi ,The intersection of ground and in the center is Ri to the distance of the satellite, xi, yi, zi , Ri can confirm, can calculate the position to be examined and is clicked x through the following equation groups by centre on the ground, y, z :
Above-mentioned a series of complicated operation, for global navigation system, receive the side, go on in user; To land navigation system of the Big Dipper office, carry on in the centre on the ground. After centre on the ground positions user, pass localization and clock information to users through the satellite.
Receiving the end to design of 3 global aeronautical satellite signals
3.1 Basic composition of the signal receive end of satellite
The signal receive end of global aeronautical satellite is mainly made up of following part: Satellite reception antenna, low in noise amplifier LNA Lower Noise Amplifier , the radio frequency of front plays frequency converter EndFront RF EndFront Radio Frequency Down Converter , signal the intersection of passway and relevant device, digital the intersection of signal and operation deal with the controller DSP, real-time clock RTC Real Time Clock , the memory Memory of the data and inputting and exporting I/O interface to make up, the whole system.
Can be found out from Fig. 1: The core of the signal receive end of satellite is DSP, the determination from text of navigating to position of satellite, reach receiving the end and awaiting measuring a little more positions and receive and carry the bad determination of the clock of the clock, and satellite passway data whole to it controls to be DSP this finish definitely. Often select 32′s common digital signal processor or one-chip computer of ARM7 kernel for use in practical application, to carry out this line of complicated operation and control.
Receive the end and output the accurate localization / data result and PPS second pulse signal of time service outwards, and can receive external communication to dispose.
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3.2 Choose the appropriate satellite signal to receive and dispatch the aerial?
The satellite signal reception antenna are that satellites receives the key part of the end.
Choose the satellite signal reception antenna, should have appropriate signals to gain, and also look at its shape and size. The satellite signal reception antenna that the fixed occasion uses, can select for use and gain the first aerial of the large volume high; The satellite reception antenna of portable mobile devices can select miniature flat aerial and spiral aerial of four arms for use. The common miniature dull and stereotyped aerial is that the ceramic microwave porcelain lies between the aerial. The ceramic microwave porcelain lies between the aerial economically and practically, can already be regarded as the passive antenna and has been connected to the front RF and played the changer directly at short range, also can form the active long feeder car-mounted aerial together with LNA. Four arm spiral aerial performance is better than the dull and stereotyped aerial, position is not required; But costly, the pole is large in length, do not employ more.
The satellite signal received is that the dextrorotation garden polarises the wave, requires the anticlockwise garden to polarise the wave for the signal of the satellite. Use the intersection of land and the intersection of user and receiver of aeronautical satellite, office of the Big Dipper, need complicated operation can get the intersection of ground and accurate localization time service result that in the center offer, but it should receive the intersection of satellite and signal as well as transmit signal to satellite, ideal of aerial its choose it is miniature the intersection of pen arm and form that have the intersection of source and pairs of the intersection of frequency band and spiral satellite receive and dispatch aerial. ?
3.3 Select the integrated assembly for use and construct the signal receive end of satellite
Select appropriate CPU and peripheral device for use, the principle according to the show of Fig. 1, can design the hardware circuit of the signal receive end of satellite very easily; But because involve a large amount of complicated and tedious operation, CPU software design task is very strenuous.
Design the signal receive end of satellite, often select to put up with integrated assembly. Available LNA assembly, such as MAX2641/ 2654/2655,etc. of ATR0610 of Atmel, Maxim. The available front RF plays the frequency converter, ATR0600 such as Atmel, MB15H156 of μ PB1029R, Fujitsu of μ N1005/8021C, NEC of STB5600 of MAX2742/4/5 of Maxim, ST, μ Nav,etc..
A lot of famous semi-conductive manufacturers integrate passway relevant device, DSP operation controller, data memory,etc. in a chip, some orient the time service algorithm to include the passway relevant algorithm, satellite position and confirm algorithms, await measuring, output information such as time service of localization and PPS second pulse every second through one bunch of mouths of RS232 externally, and RS232 that can receive users through one bunch of mouths of RS232 communicates and disposes the message, this kind of chip is the baseband processor Base Band Processor . The baseband processor contains 8~16 satellite passway numbers, it is stable and reliable to work, cheap. Can avoid users and select the DSP digital signal processor or ARM7 one piece organization at a high speed for use and build circuit and design satellite signal operation and deal with the trouble of the software while using this kind of chip. Common satellite signal baseband processor, such as MB87Q2040 of μ PD77538, Fujitsu of μ N8031B, NEC of ST20GP6 of CXD2932 of ATR0620 of Atmel, Sony, ST, μ Nav,etc..
Carry the structural block diagram in global aeronautical satellite signal receive of Fig. 1
Receiving the end block diagram of satellite signal that the integrated assembly of Fig. 2 constructs
Fig. 2 is GPS satellite signal receive end block diagram formed by ATR0610, ATR0600 and ATR0620.
While selecting LNA, front RF for use and playing the frequency converter, baseband processor and constructing the signal receive end of satellite, should pay attention to selecting the device of a manufacturer for use as much as possible; If can’t accomplish, should select the devices of the ripe different manufacturers that match for use. Table 2 has listed several kinds of devices with stable and reliable commonly used job to match and make up.
The best matching association of the integrated satellite signal receive assembly of Table 2
There are some famous semi-conductive manufacturers, further integrate, for instance, ST makes RF frequency converter and baseband processor to integrate the multi-functional form chip STB2056 introduced together, Motorola makes LNA, RF frequency converter and baseband processor to integrate the module chip MG4000/MG4100/MG4200 of multi-functional form introduced together. Fig. 3 is the satellite signal receive end block diagram formed by MG4200. The gradual improvement of the integrated level of end chip function of signal receive of the satellite, has offered the effective shortcut for simplifying and designing.
3.4 Use the integrated module to construct the signal receive end of satellite
It is simple, distinct in end to use the integrated assembly to construct the signal receive of satellites, but if the circuit design of the radio frequency has inadequate experience, in PCB Print Circuit Board At the plate making, overall arrangement, connect up unreasonable, often can interfere with, cause the intersection of satellite location and the intersection of time service and synchronous data or signal float seriously because of noise, cause the too big deviation. In a situation that design the signal receive end of satellite for the first time or the radio frequency circuit design has inadequate experience, designing the best route of the end of signal receive of satellite is to use the satellite signal receive OEM Original Equipment Manufacturer Board or receiving the module. Satellite signal receive whether some famous semiconductor design manufacturer utilize the intersection of module and the intersection of satellite and the intersection of signal receive and end that integrated assembly design in board or module in OEM, work stable and reliable, accurate intensity high, interface standardize the standard. RCBLJ on OEM board such as μ Blox, SBRLS, Jupiter Receiver of Conexant, ancient and wild GN77,etc.. Receive TIMLP of the module such as μ Blox, TIMLS, FS Oncore of Motorola, GSU16 of Koden, TU30 of Rackwell, Trax02 of TastraX,etc.. Receive module physique smallly and exquisitely, many are low consumption products, the embedded system of the especially suitable portable apparatus is designed and develops. These satellite signal receive OEM boards or module, source or active aerial does not to match the appropriate one, can form the field type or car-mounted type with steady performance portably and receive the end. Aerial and receive module, integrate little size together, integrate and receive the module, such as SAMLS of μ Blox, it is more convenient to employ and design. The satellite signal receive end that Fig. 4 is formed with TIMLP, can use the passive antenna carried at random to use in the field directly, can also insert the active car-mounted aerial to use in advancing outside.
3.5 The special design while only moving ahead simultaneously with the satellite signal?
In practical application, use the intersection of aeronautical satellite and signal, in strange land or gather, in pace with accuracy controlled purpose with many the intersection of passway and data only, for example the trouble in the power system records wave, phase place measuring, trouble to sentence to the distance, relay protection etc., needn’t use the satellite signal receive assembly costing an arm and a leg, OEM board or receive the module, and select the regular device for use and construct and receive the circuit and combine software recognition and pulse to the signal to count, get the accurate synchronous PPS pulse signal directly. Fig. 5 is a typical embodiment of this kind of plot.
Have a facelift in the circuit to realize in Fig. 5 that obtain the strongest satellite signal; Have a facelift and pare the wave part and catch and navigate the spread frame very beginning of the text, starting the counter in the one-chip computer will count to pulse of having a facelift of another No.; The speed characteristic that the text propagates according to navigating of the one-chip computer calculated and produced the accurate PPS second pulse signal.
Satellite signal receive end block diagram that Fig. 3 is formed by MG4200
Fig. 4 is by ” aerial receiving module ” Satellite signal receive end formed
The principle picture happens in the pulse the simple and easy satellite signal second of Fig. 5
Expand noise reduction select NE570/571 for use frequently, take open to strain wave and signal amplify select LM1450 for use, signal have a facelift or sharpen wave and have a facelift and select LM311 for use in the 5 Fig., the one-chip computer selects MCS51 for use.
4 is employed and designed
4.1 The synchronous data of the applied satellite signal are gathered and controlled
The signal of navigating of the applied satellite carries on the accurate strange land or with collection and control of industry’s data of the passway, mainly use PPS pulse signal second got by the signal receive end of satellite directly or use again therefore PPS signal gets PPM Pulse Per Minute , 100PPS, PPH Pulse Per Hour Pulse signal, gather the modulus converter ADC, numerical control and count the converter of the mould in data starting many passways synchronously, open or close each passway switch synchronously; Have used for measuring judging, make accurate the intersection of time and label, localization of fault, the intersection of work and the intersection of corner and measurement,etc. in the power system. Besides needing to use the synchronous pulse to start and judge measurement, also need to get the accurate measurement time value. Need to subdivide the time interval among PPS with the timer of the high-resolution at this moment, for CPU to catch and use. In order to get accurate clk clock The clock will select the high-frequency thermostatical crystal oscillator for use. Model of this kind.
The synchronous data of the applied satellite signal of Fig. 6 gathered and controlled the model block diagram
In Fig. 6, CPU can choose to use programmable logic device PLD, digital signal processor DSP or one-chip computer MCU. Speed, type, specification of CPU, ADC, DAC,etc.,etc. should be according to designing the systematic state to determine actually.
4.2 applied satellite signals carry on object localization and clock time service
The applied satellite signal carries on the object localization and general course of the clock time service: Design the intersection of satellite and the intersection of signal receive and end, obtain from it await measuring some three-dimensional the intersection of position and message longitude, latitude, above sea level With UTC Universal Coordinate Time of international standard time ,Store, reveal, pass the time service passway RS232, RS485, CAN,etc. Broadcast the clock outwards or propagate the real seat of the object of this moment outwards through wireless communication GSM/CDMA.
The distinguishing value of localization / clock precision got: By /unit in that latitude fen for value can reach decimal point the last 5,can reach decimal point the last 2 above sea level rice values unit, the unit value can reach the last 2 of the decimal point second of the clock.
The intersection of applied satellite and the intersection of signal receive and the intersection of chip and group or the intersection of OEM and board or receive whom module design, receive the end, the serial data form that fails outside usually uses U.S.A. national marine electronic association NMEA National Marine Electronics Association NMEA183 standard,is it every to last end send out second by one of PPS pulse and a messages such as localization, clock,etc. seconds outwards. PPS second pulse and the intersection of anecdotes and the intersection of data and information have strict the intersection of time and relation, deduct, allow the intersection of pulse and time sequence jump, become, can receive accurate the intersection of clock and value along read the intersection of clock and data second such as PPS. While using, need to convert the time of resulting UTC to.
Carry on the object localization and model of the clock time service.
Object localization and clock time service model block diagram of the applied satellite signal of Fig. 7
4.3 attentive matters
1 Receiving losing the step of satellite signal
When not applying widening or apt region influenced by the sun storm,etc. to mountain area, polar region,etc. in design system, should add the software and hardware measure of preventing the signal receive of the satellite from losing the step into design. The concrete method is often to design here accurate PPS to produce circuit, real-time clock RTC circuit, as discerning in NMEA form message that the end makes from receiving
References
A high Cheng Fa. GPS measurement. Beijing: People’s Transportation Press, 2001
2 Motorola Co. GPS Products PREVIEW Instant GPS MG4200. Rev1.0. 200412
3 uBlox Co. Component catalogue of GPS’s positioning. Rev3. 200410