CN101464508B - Method for capturing C/A code signal of GPS - Google Patents
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Abstract
The invention discloses a method for acquiring the C/A code signals of a GPS in the GPS communication technical field. The method comprises a rough acquisition process and a precise acquisition process. The rough acquisition process comprises the following steps: searching a plurality of parallel satellites set by a system and obtaining a rough code phase and carrier frequency by using code phase search based on FFT; and the precise acquisition process comprises the following steps: setting a precise acquisition carrier frequency step according to the code phase and the carrier frequency obtained from rough acquisition and determining the search scope of precise acquisition; and removing the correlation between input signals and local carrier signals influenced by the code phase and comparing a correlation value and a resetting threshold value to determine whether satellite signals can be really acquired. Compared with the prior GPS acquiring method, the invention improves the acquisition performance of GPS signals, ensures the GPS fast acquisition, and simultaneously achieves the high-accuracy requirements of the GPS acquisition.
Description
Technical field
The invention belongs to the GPS communication technical field, relate in particular to the catching method of the C/A coded signal of a kind of GPS.
Background technology
GPS (Global Positioning System) GPS is used by the US military exploitation and for the armies of navy, army and air force at first as the new generation satellite navigation positioning system.Through years development, the Current GPS system has become a kind of dual-use system that is widely adopted, its application and application prospect head and shoulders above this system designer imagination originally, in nearly all field such as Aeronautics and Astronautics, military affairs, traffic, transportation, resource exploration, communication, meteorology, all be used as a very important technological means and method, be used for navigating, regularly, location, geophysical parameters measure and atmospheric physics parametric measurement etc.
The GPS GPS is a radio space positioning system, it utilizes Navsat and land station to provide round-the-clock, high precision, continuous, real-time three-dimensional coordinate (latitude for the whole world, longitude, height above sea level), three-dimensional velocity and locating information, earth surface is taken up an official post where to put and all can be used for location and navigation.Gps system comprises three parts: space segment-gps satellite constellation; Ground Control part-ground monitoring system, customer equipment part-gps signal receiver.The GPS space segment uses the satellite of 24 highly about 2.02 ten thousand kms to form satellite constellation, wherein form the gps satellite constellation at the rail backup satellite by 21 work satellites and 3, the distribution of satellite makes and all can observe satellite more than four Anywhere, any time in the whole world, and can keep the geometric figure of good location calculation accuracy, continuous in time worldwide navigation ability is provided.Ground monitoring partly comprises between four monitoring, a upload station and a master station, is used to monitor, control, revise and inject the navigation data of each gps satellite.The GPS receiver can receive following information: the accurate temporal information to nanosecond that is used for time service; Be used to forecast the forecast ephemeris of satellite general location of living in coming few months; The broadcast ephemeris of required co-ordinates of satellite when being used for compute location, precision are several meters to tens meters (each satellite difference changes at any time); And gps system information, as satellite situation etc.
The carrier signal of two kinds of frequencies of gps satellite emission, promptly frequency is the L1 carrier wave of 1575.42 megahertzes and the L2 carrier wave that frequency is 1227.60 megahertzes, modulates multiple signal respectively.Mainly contain:
(1) C/A (Coarse/Acquisition: thick/as to catch) sign indicating number
The C/A sign indicating number is modulated on the L1 carrier wave, is that (Pseudo-randomNumber, PRN), its code length is 1023 (cycle is 1ms) for the Pseudo-Random Noise Code of 1MHz.Because the C/A sign indicating number of every satellite is all different, therefore, we distinguish them through their PRN number commonly used.The C/A sign indicating number is that domestic consumer is in order to measure a kind of main signal of survey station to intersatellite distance.
(2) P sign indicating number
The P sign indicating number is otherwise known as smart yard, is modulated on L1 and the L2 carrier wave, and be the Pseudo-Random Noise Code of 10MHz, the cycle is seven days.Because privacy restriction, domestic consumer can't utilize the P sign indicating number to carry out navigator fix.
(3) navigation information
Navigation information is that numeric data code is modulated on the L1 carrier wave, and its signal frequency is 50 hertz, comprises orbit parameter, satellite clock correction number and some other systematic parameter of gps satellite.The user generally need utilize this navigation information to calculate the position of a certain moment gps satellite on Earth's orbit, and navigation information is also referred to as broadcast ephemeris.
For domestic consumer, gps system provides the standard setting service, and (Standard PositioningService, SPS), this generally realizes by the C/A sign indicating number information that parsing is modulated at the different satellites on the L1 carrier wave.Because the position of satellite knows in advance, and according to the distribution of gps satellite constellation, random time anywhere at the earth's surface generally can receive the signal of 4 to 11 satellites simultaneously.And under three-dimensional situation, utilize 3 satellites can form 3 equations, parse current location coordinate (X, Y, Z).In fact consider the clocking error between satellite and the receiver, therefore need to introduce the 4th satellite, form 4 equations, find the solution the coordinate figure and the clocking error of current point, thereby obtain the longitude and latitude and the elevation of current location.Certainly, in fact receiver can receive the satellite-signal that surpasses more than 4, therefore can further revise the result that the signal resolution by 4 satellites goes out, to reduce error as far as possible.
By top introduction as can be known, the standard setting service that provides of GPS needs the information on the C/A sign indicating number on the demodulation L1 carrier wave.Signal on the frequency of L1 can be expressed as
S
L1＝A
pP(t)D(t)cos(2πf
1t+φ)+A
cC(t)D(t)sin(2πf
1t+φ) (1)
S in the formula
L1Be the signal on the carrier wave L1, A
pBe the amplitude of P sign indicating number, the phase place of P (t)=± 1 expression P sign indicating number, i.e. P sign indicating number pseudo-random sequence, D (t)=± 1 represents numeric data code, i.e. navigation message information, f
1Be the frequency on the L1, i.e. 1575.42MHz, φ is an initial phase, A
cBe the amplitude of C/A sign indicating number, the phase place of C (t)=± 1 expression C/A sign indicating number, i.e. C/A sign indicating number pseudo-random sequence.Synthetic gps signal is launched to the whole world, resolves navigator fix information for receiver whenever and wherever possible and uses.
Fig. 1 is the ultimate principle figure of GPS receiver, the signal of gps satellite emission is received by antenna, by radio frequency (Radio Frequency, RF) chain input signal is amplified to suitable amplitude and with frequency inverted to the output frequency of needs, by A/D converter (ADC) output signal is become digital signal again, enter numeric field and handle, calculate through signal capture, tracking, subframe identification, ephemeris and pseudorange parsing, satellite position and customer location.Wherein, catch the signal that is meant the some satellites of discovery; Tracking is the phase change that obtains navigation data; And, can obtain subframe and navigation data according to the phase hit of navigation data, in navigation data, just can obtain ephemeris and pseudorange; The last position that goes out the user according to the position and its computation of pseudoranges of satellite.
In order to follow the tracks of gps signal and to carry out information decoding, just must be earlier with catching the existence of handling detection signal.Start the satellites in view of prize procedure searching,, perhaps can calculate the signal of usable satellite, at this moment, only need the several satellites of search by the broadcast ephemeris of nearest record if roughly know the rough position and the time of satellite with respect to receiver.Certainly, if the satellite of initial setting up is wrong, then the time of satnav can be long, because this moment, prize procedure was searched at the beginning is wrong satellite, said method is called warm start.Also have a kind of satellite signal reception method that is called cold start-up in addition, promptly receiver is not known the specifying information of satellite, must catch all satellites, and this can be very consuming time, the method that therefore general always glad selection can be caught fast.
In case prize procedure detects signal, just must offer some necessary parameter of tracking module, as the reference position in C/A sign indicating number cycle and the carrier frequency of input signal.The data that generally collect comprise the signal of several satellites, the C/A sign indicating number reference position difference of each signal, and the start time difference, Doppler shift is also different.Trapping module need find the reference position of C/A sign indicating number, and collects mail with this information butt joint and number to carry out despreading, exports a continuous wave signal, obtains carrier frequency.In order to accelerate acquisition speed, receiver can carry out parallel capture to a plurality of satellites, promptly simultaneously N satellite is caught.Simultaneously, the acquisition procedure of gps signal is a two-dimensional search process, as shown in Figure 2, each square is represented the signal of specific C/A sign indicating number reference position and specific carriers skew, receiver produces this locality reproduction signal of each square correspondence, and carry out relevantly with received signal, by the correlated results of received signal relatively, judge whether signal catches with local reproduction signal.
Catching method commonly used at present has following several:
1. sequential search prize law
As shown in Figure 3, after the later intermediate frequency input signal of process ADC multiplies each other with the local PRN sign indicating number that produces, in-phase component and quadrature component with local carrier multiplies each other again, form homophase I road signal and quadrature Q road signal, then respectively through integration-removing, square summation link, compare with predetermined threshold value at last, judge whether signal catches,, then enter the subsequent treatment link if catch; If do not catch, then adjust the phase place and the carrier frequency of local code by the synchro control link, carry out said process again.
By above-mentioned introduction as can be known, the sequential search method is in code phase and the enterprising line scanning search of two directions of carrier frequency, with code phase and the carrier frequency that finds coupling.Have and just have negatively because cause Doppler shift that carrier wave changes,,, scan successively to positive and negative both direction generally from nominal frequency therefore in the carrier frequency direction; And, without any the information of relevant phase place, therefore can begin scanning during owing to beginning from any phase place in the code phase direction, and generally select from start-phase certainly, travel through all phase places successively, until capturing signal.The principle of this method is very simple, and is also more convenient to achieve, but the combination of code phase that need scan and carrier frequency is too many, causes consuming time longer.
2. carrier frequency parallel search prize law
The code phase that above-mentioned sequential search need be searched for and the combination of carrier frequency are too many, consuming time oversize, if therefore all code phases or all carrier frequencies can be able to be judged whether and the input signal coupling by a search procedure, then can save time greatly, improve performance.
The frequency parallel search is caught by Fast Fourier Transform (FFT) (FFT), processing procedure is become frequency domain by time domain, as shown in Figure 4.After input signal multiplies each other with the local PRN sign indicating number that produces, transform to frequency domain by FFT, if this moment, local code phase and the input signal that produces was complementary, then there is a significant peak value position of carrier frequency correspondence on frequency domain, surpass default thresholding, if this moment code phase and input signal do not match, then the position of each frequency correspondence does not have significant peak value on the frequency domain, therefore enter the synchro control link and adjust the local code phase that produces, repeat said process.Promptly by FFT, all frequencies once can be searched for and finish, therefore can reduce searching times.
3. code phase parallel search prize law
The said frequencies parallel search is all frequencies once to be searched for finish, equally also all code phases once can be searched for and be finished, and owing to the searching times of code phase search number of times much larger than frequency, finish if therefore code phase once can be searched for, then search efficiency will be much larger than the frequency parallel search.
In sequential search, input signal multiplies each other with the local code of different code phases, and in fact can calculate input signal and the circular correlation that does not have the PRN sign indicating number of phase shifts, obtain the correlated results of all code phases by relevant and convolution operation getting in touch between time domain, frequency domain.Fig. 5 is the synoptic diagram of code phase parallel search.The in-phase component and the quadrature component of input signal and local carrier multiply each other respectively, obtain I road and Q road signal, pass through FFT then, multiply each other with PRN sign indicating number through FFT, then the result is transformed into time domain by IFFT (Fourier inversion), its result's the absolute value representation input signal and the correlativity of PRN sign indicating number.If a tangible peak value is arranged in the correlated results, promptly peak value surpasses default thresholding, and then Dui Ying code phase is exactly the code phase of input signal.
More than in three kinds of methods, sequential search need search successively on code phase and carrier frequency two dimension pattern; And the carrier frequency parallel search only needs search successively on code phase one dimension pattern; The code phase parallel search only needs search successively on carrier frequency one dimension pattern; And the code phase number of steps is more much bigger than carrier frequency number of steps, and therefore, the required searching times of the third method is minimum, and second kind is taken second place, and first kind at most.
The acquisition procedure of gps signal is except the needs capture time is short, and it is high as far as possible also to need to catch precision, and it is low to make that promptly mistake is caught probability, and this is relevant with concrete acquisition algorithm, and is especially relevant with thresholding preset value in the said method.Current, catch probability in order to reduce mistake, usually need confirm initial acquisition, such as: code phase and carrier frequency that initial acquisition obtains are carried out catching affirmation N time continuously, if the correlated results that wherein surpasses M time represents then that greater than default thresholding initial acquisition is effective, otherwise, current initial acquisition is invalid, restarts acquisition procedure.Again such as, preset value A and K, if correlation greater than default thresholding, then K adds 1, judges whether K equals A, if, then represent signal capture, otherwise do not adjust code phase and carrier frequency, continue to catch; If correlation is not more than default thresholding, then K subtracts 1, judge whether K equals zero or whether surpass the maximal correlation time correlation time, if not, then do not adjust code phase and carrier frequency, continue to catch, otherwise the expression signal is not caught, adjust code phase and carrier frequency, and reset K, continue to catch.
Need to prove that relevant hardly between thick/catch code that each satellite uses, the correlation between the promptly different C/A sign indicating numbers is very little; The autocorrelation performance of C/A is fine, if promptly same C/A sign indicating number does not have code phase offset, then correlation is very big, if there is code phase offset, then correlation is very little.
In sum, the acquisition procedure of gps signal require the speed catch fast, catch the precision height.And the each have their own relative merits of existing method.In order to improve the acquisition performance of gps signal, accelerate acquisition speed, need improve said method.Though utilize the method for FFT can reduce the number of times of search, the operand of FFT operation is bigger, therefore need manage to reduce the number of times of FFT operation; And because good autocorrelation performance and the their cross correlation of C/A sign indicating number can reduce the use number of FFT by once searching for the signal of a plurality of satellites; In addition, the setting and the acquisition performance of thresholding are closely related, and therefore threshold setting method and relevant parameter reasonable in design is very important.
Summary of the invention
The object of the present invention is to provide the catching method of the C/A coded signal of a kind of GPS, solve the problem that the present gps signal catching method that uses can't be accomplished fast and precisely have both.
Technical scheme of the present invention is that the catching method of the C/A coded signal of a kind of GPS comprises thick acquisition procedure and smart acquisition procedure, it is characterized in that described thick acquisition procedure comprises the following steps:
Step 11: the local PRN sign indicating number that produces L satellite-signal correspondence, and carry out mould 2 add with, then the result is carried out FFT and gets conjugate operation, obtain signal C (k);
Step 12: this locality is created in the carrier frequency signaling s (n) in the carrier frequency hunting zone, and multiplies each other with one section input signal, passes through the FFT computing then, obtains signal X (k);
Step 13: C (k) and X (k) are multiplied each other, obtain R (k), carry out the IFFT computing then, obtain r (n), and delivery | r (n) |;
Step 14: find out | r (n) | the L of a middle maximum value, and compare with predetermined threshold value, determine greater than predetermined threshold value | and r (n) | corresponding code phase and carrier frequency;
Step 15: do relevant with input signal the local signal of every pair of code phase and each satellite of carrier frequency correspondence, the result compares with predetermined threshold value, if greater than predetermined threshold value, represent that then this this satellite-signal to code phase and carrier frequency correspondence exists, and slightly catches and finishes; Otherwise jumping to step 11 slightly catches again;
Described smart acquisition procedure comprises the following steps:
Step 21:, essence is set catches the carrier frequency stepping according to code phase of slightly catching acquisition and carrier frequency;
Step 22: catch the stepping of carrier frequency according to essence, determine the hunting zone that essence is caught;
Step 23: according to slightly catching the code phase that obtains, input signal is handled, removed the influence of code phase;
Step 24: in the hunting zone, the input signal that the removal code phase is influenced is relevant with local carrier signal, and correlation is compared with predetermined threshold value, to determine whether really to capture satellite-signal;
Step 25: if in the hunting zone, do not catch satellite-signal, then jump to step 11, continue the acquisition procedure of aforementioned each step; If capture satellite-signal, then with the code phase of this satellite correspondence and carrier frequency output, this satellite catch end, continue the acquisition procedure of other satellites.
The described local PRN sign indicating number that produces L satellite-signal correspondence, L is predefined value.
In described step 14 and the step 15, predetermined threshold value is for fixing empirical value or according to the value of noise size setting.
Described basis is slightly caught the code phase and the carrier frequency of acquisition, essence is set catches the method for carrier frequency stepping and is, the code phase of search volume is defined as the code phase of slightly catching acquisition, carrier frequency is defined as each F hertz of carrier frequency both sides of slightly catching acquisition, and F is for slightly catching the stepping of carrier frequency; Essence is caught the carrier frequency stepping and is set to the G hertz, and G=F/J, J are positive integer.
In the described step 24, predetermined threshold value is for fixing empirical value or according to the value of noise size setting.
The described input signal that will remove code phase influence is relevant with local carrier signal, and correlation compared with default thresholding, to determine whether that the method that really captures satellite-signal is, in the N continuous correlations value that local carrier signal and the input signal correlation of removing the code phase influence begin greater than predetermined threshold value for the first time, if have M greater than predetermined threshold value, then represent satellite signal acquisition; Wherein M, N are positive integer, and N is more than or equal to M.
The catching method of the C/A coded signal of a kind of GPS provided by the invention is compared with existing GPS catching method, has improved the acquisition performance of gps signal, when guaranteeing that GPS catches fast, realizes that GPS catches high-precision requirement.
Description of drawings
Fig. 1 is GPS receiver ultimate principle figure.
Fig. 2 is that the two dimension in the GPS receiver is caught master drawing.
Fig. 3 is a sequential search prize law synoptic diagram.
Fig. 4 is a carrier frequency parallel capture method synoptic diagram.
Fig. 5 is a phase acquisition method synoptic diagram.
Fig. 6 is the thick catching method process flow diagram of the C/A coded signal of GPS of the present invention.
Fig. 7 is the thick catching method synoptic diagram of the C/A coded signal of GPS among the present invention.
Fig. 8 is the smart catching method process flow diagram of the C/A coded signal of GPS of the present invention.
Fig. 9 is the smart catching method synoptic diagram of the C/A coded signal of GPS of the present invention.
Embodiment
Below in conjunction with accompanying drawing, preferred embodiment is elaborated.Should be emphasized that following explanation only is exemplary, rather than in order to limit the scope of the invention and to use.
The invention provides the catching method of the C/A coded signal of a kind of GPS, comprise thick acquisition procedure and smart acquisition procedure.Thinking of the present invention is: at first, the L satellite parallel is searched for, L is by default; Use obtains rough code phase and carrier frequency based on the code phase search of FFT; Judge whether the empirical value that the employed predetermined threshold value of acquisition success is set to fix, perhaps the value that is provided with according to the noise size; If greater than predetermined threshold value, then need each is further verified greater than the code phase and the carrier frequency of the correlation correspondence of predetermined threshold value, be which satellite with what determine to catch based on the correlation of the code phase search of FFT output.Carrying out essence according to the above-mentioned rough code phase that obtains and carrier frequency catches; The code phase of search volume is defined as and slightly catches the rough code phase that has obtained, and carrier frequency is defined as and slightly catches each the F hertz of rough carrier frequency both sides that has obtained, the stepping of slightly catching carrier frequency that F is; Essence is caught the carrier frequency stepping and is set to the G hertz, satisfies G=F/J, and J is a positive integer; Judge whether the empirical value that the employed predetermined threshold value of acquisition success is set to fix, perhaps the value that is provided with according to the noise size; Confirm whether really to catch the following method that adopts: N continuous time input signal is with during local signal is relevant, is correlated with and value is not less than M greater than the number of times of predetermined threshold value, and wherein M, N are that positive integer and N are more than or equal to M.
In an embodiment, be without loss of generality, get L=2, F=200, G=20, J=10, N=10, M=8.
Fig. 6 is the thick catching method process flow diagram of the C/A coded signal of GPS of the present invention.Among Fig. 6, step 601: the local PRN sign indicating number that produces 2 satellite-signal correspondences, and carry out that mould 2 adds and, then the result is carried out FFT and gets conjugate operation, obtain signal C (k).
Step 602: this locality is created in the carrier frequency signaling s (n) in the carrier frequency hunting zone, and multiplies each other with one section input signal, passes through the FFT computing then, obtains signal X (k).
Step 603: C (k) and X (k) are multiplied each other, obtain R (k), carry out the IFFT computing then, obtain r (n), and delivery | r (n) |.
Step 604: find out | r (n) | 2 values of middle maximum, and compare with default thresholding, determine greater than thresholding | and r (n) | corresponding code phase and carrier frequency;
Step 605: do relevant with input signal the local signal of every pair of code phase and each satellite of carrier frequency correspondence, the result compares with default thresholding, if greater than thresholding, represent that then this this satellite-signal to code phase and carrier frequency correspondence exists, and slightly catches and finishes; Otherwise need get back to step 601 searches for again.
Fig. 7 is the thick catching method synoptic diagram of the C/A coded signal of GPS among the present invention.Fig. 7 has illustrated the implementation procedure of thick catching method of the C/A coded signal of GPS from another aspect.
Fig. 8 is the smart catching method process flow diagram of the C/A coded signal of GPS of the present invention.Among Fig. 8, step 801:, essence is set catches the carrier frequency stepping according to code phase of slightly catching acquisition and carrier frequency.
Step 802: catch the stepping of carrier frequency according to essence, determine the hunting zone that essence is caught.
Step 803: according to slightly catching the code phase that obtains, input signal is handled, removed the influence of code phase.
Step 804: in the hunting zone, the input signal that the removal code phase is influenced is relevant with local carrier signal, and correlation is compared with predetermined threshold value, to determine whether really to capture satellite-signal.
Step 805: if in the hunting zone, do not catch satellite-signal, then jump to step 601, continue the acquisition procedure of aforementioned each step; If capture satellite-signal, then with the code phase of this satellite correspondence and carrier frequency output, this satellite catch end, continue the acquisition procedure of other satellites.Determine whether really to capture satellite-signal, the method of taking is: from the continuous 10 correlations values that this local signal and input signal correlation begin greater than default thresholding for the first time, if have 8, then represent satellite signal acquisition, otherwise continue search greater than threshold value.
Fig. 9 is the smart catching method synoptic diagram of the C/A coded signal of GPS of the present invention.Fig. 9 has illustrated the implementation procedure of smart catching method of the C/A coded signal of GPS from another aspect.The above; only for the preferable embodiment of the present invention, but protection scope of the present invention is not limited thereto, and anyly is familiar with those skilled in the art in the technical scope that the present invention discloses; the variation that can expect easily or replacement all should be encompassed within protection scope of the present invention.Therefore, protection scope of the present invention should be as the criterion with the protection domain of claim.
Claims (5)
1. the catching method of the C/A coded signal of a GPS comprises thick acquisition procedure and smart acquisition procedure, it is characterized in that described thick acquisition procedure comprises the following steps:
Step 11: the local PRN sign indicating number that produces L satellite-signal correspondence, and carry out mould 2 add with, then the result is carried out FFT and gets conjugate operation, obtain signal C (k);
Step 12: this locality is created in the carrier frequency signaling s (n) in the carrier frequency hunting zone, and multiplies each other with one section input signal, passes through the FFT computing then, obtains signal X (k);
Step 13: C (k) and X (k) are multiplied each other, obtain R (k), carry out the IFFT computing then, obtain r (n), and delivery | r (n) |;
Step 14: find out | r (n) | the L of a middle maximum value, and compare with predetermined threshold value, determine greater than predetermined threshold value | and r (n) | corresponding code phase and carrier frequency;
Step 15: do relevant with input signal the local signal of every pair of code phase and each satellite of carrier frequency correspondence, the result compares with predetermined threshold value, if greater than predetermined threshold value, represent that then this this satellite-signal to code phase and carrier frequency correspondence exists, and slightly catches and finishes; Otherwise jumping to step 11 slightly catches again;
Described smart acquisition procedure comprises the following steps:
Step 21:, essence is set catches the carrier frequency stepping according to code phase of slightly catching acquisition and carrier frequency;
Step 22: catch the stepping of carrier frequency according to essence, determine the hunting zone that essence is caught;
Step 23: according to slightly catching the code phase that obtains, input signal is handled, removed the influence of code phase;
Step 24: in the hunting zone, the input signal of removing the code phase influence is relevant with local carrier signal, and correlation compared with predetermined threshold value, to determine whether really to capture satellite-signal, specifically be, in the N continuous correlations value that local carrier signal and the input signal correlation of removing the code phase influence begin greater than predetermined threshold value for the first time,, then represent satellite signal acquisition if having M greater than predetermined threshold value; Wherein M, N are positive integer, and N is more than or equal to M;
Step 25: if in the hunting zone, do not catch satellite-signal, then jump to step 11, continue the acquisition procedure of aforementioned each step; If capture satellite-signal, then with the code phase of this satellite correspondence and carrier frequency output, this satellite catch end, continue the acquisition procedure of other satellites.
2. the catching method of the C/A coded signal of a kind of GPS according to claim 1 is characterized in that the described local PRN sign indicating number that produces L satellite-signal correspondence, and L is predefined value.
3. the catching method of the C/A coded signal of a kind of GPS according to claim 1 is characterized in that in described step 14 and the step 15, and predetermined threshold value is for fixing empirical value or according to the value of noise size setting.
4. the catching method of the C/A coded signal of a kind of GPS according to claim 1, it is characterized in that described basis slightly catches the code phase and the carrier frequency of acquisition, essence is set catches the method for carrier frequency stepping and is, the code phase of search volume is defined as the code phase of slightly catching acquisition, carrier frequency is defined as each F hertz of carrier frequency both sides of slightly catching acquisition, and F is for slightly catching the stepping of carrier frequency; Essence is caught the carrier frequency stepping and is set to the G hertz, and G=F/J, J are positive integer.
5. the catching method of the C/A coded signal of a kind of GPS according to claim 1 is characterized in that in the described step 24, and predetermined threshold value is for fixing empirical value or according to the value of noise size setting.
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| CN102759741B (en) * | 2011-04-29 | 2014-12-10 | 安凯(广州)微电子技术有限公司 | GPS (Global Position System) receiver |
| CN102185628A (en) * | 2011-05-04 | 2011-09-14 | 北京航空航天大学 | Spread spectrum code phase capture equipment based on adaptive power accumulation and capture method thereof |
| CN102426367B (en) * | 2011-08-31 | 2013-07-17 | 北京时代民芯科技有限公司 | Capturing method of satellite navigation signal in adjustable carrier wave doppler frequency searching range |
| TW201310936A (en) * | 2011-08-31 | 2013-03-01 | Keystone Semiconductor Corp | Method for improving ensemble auto searching efficiency and device thereof |
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