CN102654580A - Realizing method and device of fast Fourier transform algorithm during signal capturing process - Google Patents
Realizing method and device of fast Fourier transform algorithm during signal capturing process Download PDFInfo
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- CN102654580A CN102654580A CN2012101382625A CN201210138262A CN102654580A CN 102654580 A CN102654580 A CN 102654580A CN 2012101382625 A CN2012101382625 A CN 2012101382625A CN 201210138262 A CN201210138262 A CN 201210138262A CN 102654580 A CN102654580 A CN 102654580A
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Abstract
The invention provides a realizing method of fast Fourier transform algorithm during signal capturing process, wherein the method comprises the following steps: receiving a satellite signal; calculating operating point number D according to a selected integral time T and a frequency offset coverage range F; and performing fast Fourier transform according to the operating point number D. According to the technical scheme provided by the invention, a mechanism of dynamically calculating the operating point number is adopted and the corresponding operating point number is used to perform the fast Fourier transform according to different environments and demands to improve the efficiency of the fast Fourier transform algorithm so as to improve the signal capturing efficiency.
Description
Technical field
The present invention relates to the satellite navigation signals processing technology field, relate in particular to the implementation method and the device of FFT in a kind of satellite signal acquisition (Fast Fourier Transform, Fast Fourier Transform (FFT)) algorithm.
Background technology
GLONASS (Global Navigation Satellite System; GNSS) utilize Navsat to carry out timing, location and range finding, can in worldwide, realize round-the-clock, comprehensive three dimensions, speed and the temporal information that real-time high-precision is provided for sea, land and aerial user continuously.At present, GNSS has comprised GPS of USA, Muscovite GLONASS, the Galileo system of European Union, the triones navigation system of China, is example with the gps system, and this system mainly is made up of three parts, i.e. space segment, Ground Control part and user's set part.Space segment is made up of 24 satellites, is distributed on the plane, 6 roads.Ground Control part is by the master station of the work of being in charge of, coordinating whole ground control system, under the control of master station, injects the ground-plane antenna of seeking text, forms as the monitoring station and the communication backup system of automatic data acquisition center to satellite.The user's set part mainly is made up of GPS receiver and satellite antenna.
Signal capture is claimed the synchronous of signal again, is meant from white noise, to detect the known waveform signal, and be an input processing procedure.Being used for the optimum receiver of lock-on signal is correlation receiver, and this correlation receiver carries out input signal and local reproduction waveform related operation and result is carried out threshold judgement.When signal is not caught, can only adopt the exploration mode to carry out relevant treatment, promptly travel through various code phase possibilities until finding out relevant peaks.
In order to capture satellite-signal, need reappear the sign indicating number and the carrier wave of satellite-signal simultaneously, this is a two-dimensional search process in fact.Different according to catching method on sign indicating number and Doppler territory are divided into following four kinds with the Acquisition Scheme of satellite-signal: the serial of pseudo-code serial carrier wave, pseudo-code serial carrier wave are parallel, the parallel carrier wave serial of pseudo-code, the parallel carrier wave parallel search scheme of pseudo-code.
At present; The application of satellite signal receiver has expanded in the complex environment (indoor, high building city in) gradually; Change in signal strength is bigger in these environment, and the receiver that needs that has is done long stack accumulative total, the stack accumulative total that only need do the short time that has; Therefore, can conform and searching method is very crucial to satellite signal receiver fast.
Satellite-signal is caught fast generally has two kinds of methods, a kind of a large amount of correlators, a kind of Fast Fourier Transform (FFT) (FFT) unit that uses special use of being to use.The method resource cost of a large amount of correlators is serious, therefore, uses the method for special-purpose FFT more welcome.FFT has reduced the time of calculating discrete Fourier transformation (DFT), and determines the length of computing time by counting of its calculating.In the general receiver; Counting that FFT calculates all fixed, no matter which type of RST, it all uses a kind of point value to calculate; Such as 2048 points, a kind of like this way of fixedly counting can cause the reception of satellite-signal under better RST also can be slower.
Along with the miniaturization and the positioning requirements of receiver are increasingly high, the higher method of capture rate need occur and catch satellite-signal, the efficient of fast fourier transform algorithm seems and is even more important when improving signal capture.
Summary of the invention
The purpose of this invention is to provide a kind of implementation method and device of fast fourier transform algorithm efficient when improving satellite signal acquisition, can effectively improve operation efficiency and can not influence catching of satellite-signal.。
The implementation method of fast fourier transform algorithm when the present invention provides a kind of signal capture, said method comprises: receiving satellite signal; According to the T and the frequency shift (FS) coverage F calculation operations D that counts integral time that chooses; Carry out Fast Fourier Transform (FFT) according to the computing D that counts.
Further, said integral time, T can be at 5ms, 10ms, 20ms, 40ms, in the 80ms scope from small to large circulation choose and periodically calculate the said computing D that counts, till signal is successfully caught.
Further, said frequency shift (FS) coverage is 20000Hz.
Further, calculate the count span DF of D of said computing, judgement formula and confirm that condition is according to the judgement formula: DF* (1000/T) >=F, choose among the said span DF minimum 2 geometry multiple value as the count value of D of said computing.
The present invention also provides a kind of implement device of fast fourier transform algorithm during the signal capture of fast fourier transform algorithm implementation method when using said signal capture.
Further, said integral time, T can be at 5ms, 10ms, 20ms, 40ms, in the 80ms scope from small to large circulation choose and periodically calculate the said computing D that counts, till signal is successfully caught.
Further, said frequency shift (FS) coverage is 20000Hz.
Further, calculate the count span DF of D of said computing, judgement formula and confirm that condition is according to the judgement formula: DF* (1000/T) >=F, choose among the said span DF minimum 2 geometry multiple value as the count value of D of said computing.
After adopting technical scheme of the present invention; The mechanism that adopts the dynamic calculation computing to count according to different environment and needs, adopts corresponding operation to count and carries out Fast Fourier Transform (FFT); Improve the efficient of fast fourier transform algorithm, thereby improve the efficient of signal capture.
Description of drawings
Fig. 1 is an embodiment of the invention implementation method schematic flow sheet;
Fig. 2 is an embodiment of the invention implement device structured flowchart.
Embodiment
In order to make the object of the invention, technical scheme and advantage clearer,, the present invention is further elaborated below in conjunction with accompanying drawing and embodiment.Should be appreciated that specific embodiment described herein only in order to explanation the present invention, and be not used in qualification the present invention.
Accompanying drawing 1 is an embodiment of the invention implementation method schematic flow sheet; Accompanying drawing 2 is embodiment of the invention implement device structured flowcharts.
In embodiments of the present invention; Shown in accompanying drawing 1; The implementation method flow process of fast fourier transform algorithm is following during signal capture: at first; Receiving satellite signal 101, the satellite-signal that is received is the digital medium-frequency signal through the radio-frequency front-end sampling, the bit wide of intermediate-freuqncy signal can be 2 bits or more.
Calculate the FFT computing and count 102, according to integral time T and frequency shift (FS) coverage D, the computing that calculating FFT needs is counted, and concrete the realization: integral time, T was from 5ms; 10ms, 20ms, 40ms circulates successively from small to large in the 80ms scope and chooses; For example, calculate for the first time, integral time T=5ms, frequency shift (FS) coverage F=20000Hz; Be updated in the judgement formula count span DF:DF* (1000/T) >=F of D of calculation operations, that is, and DF* (1000/5) >=20000, DF >=100; Just, the count span DF of D of computing is >=100, chooses that to satisfy among the span DF be the minimum value of how much multiples of 2, i.e. D=100.Change the FFT computing and count 103, count to the computing of FFT 100 assignment, carry out FFT computing 104, according to operation result; Whether decision signal acquisition success 105, is, then finishes FFT computing 106, not; Then return and calculate the FFT computing and count 102, carry out calculating second time, at this moment, integral time T=10ms; Calculate the new computing D102 that counts, continue next step, till the signal capture success.
In embodiments of the present invention, shown in accompanying drawing 2, the implement device structure of fast fourier transform algorithm is following during signal capture.
The control module 201 of counting is counted according to the computing of T and frequency shift (FS) coverage F calculating integral time FFT, and wherein integral time, T was from 5ms, 10ms, 20ms; 40ms circulates successively from small to large in the 80ms scope and chooses, for example; Calculate for the first time, integral time T=5ms, frequency shift (FS) coverage F=20000Hz; Be updated in the judgement formula count span DF:DF* (1000/T) >=F of D of calculation operations, that is, and DF* (1000/5) >=20000; The result is DF >=100, and just, the count span DF of D of computing is >=100; Choose among the span DF that to satisfy be the minimum value of how much multiples of 2, i.e. D=100 is transferred to the value of D and carries out the FFT computing in the arithmetic element 202.The computing of control module 201 of counting can be periodic; According to the result of arithmetic element 202 feedbacks, if the result of feedback does not successfully catch for signal, the control module of then counting is chosen next one option integral time successively as T integral time; For example integral time T=10ms; And recomputate the count value of D of new computing, deliver to again and carry out the FFT computing in the arithmetic element 202, till the result of arithmetic element feedback successfully catches for signal.
The data that data preparatory unit 203 needs from the storer acquisition according to the indication of the control module 201 of counting, are divided combination with data then on request, and the data after the division combination will become the input data of arithmetic element 202.
The above is merely preferred embodiment of the present invention, not in order to restriction the present invention, all any modifications of within spirit of the present invention and principle, being done, is equal to and replaces and improvement etc., all should be included within protection scope of the present invention.
Claims (8)
1. the implementation method of fast fourier transform algorithm during a signal capture is characterized in that said method comprises: receiving satellite signal; According to the T and the frequency shift (FS) coverage F calculation operations D that counts integral time that chooses; Carry out Fast Fourier Transform (FFT) according to the computing D that counts.
2. the implementation method of fast fourier transform algorithm according to claim 1 is characterized in that, said integral time, T was at 5ms; 10ms, 20ms, 40ms; In the 80ms scope from small to large circulation choose and periodically calculate the said computing D that counts, till signal is successfully caught.
3. the implementation method of fast fourier transform algorithm according to claim 1 is characterized in that, said frequency shift (FS) coverage is 20000Hz.
4. according to the implementation method of the described fast fourier transform algorithm of claim 1 to 3; It is characterized in that; Calculate the count span DF of D of said computing according to the judgement formula; Judgement formula and confirm that condition is: DF* (1000/T) >=F, choose among the said span DF minimum 2 geometry multiple value as the count value of D of said computing.
5. the implement device of fast fourier transform algorithm when an application rights requires the signal capture of 1 said method.
6. according to the implement device of the said fast fourier transform algorithm of claim 5, it is characterized in that said integral time, T was at 5ms; 10ms, 20ms, 40ms; In the 80ms scope from small to large circulation choose and periodically calculate the said computing D that counts, till signal is successfully caught.
7. the implement device of fast fourier transform algorithm according to claim 5 is characterized in that, said frequency shift (FS) coverage is 20000Hz.
8. according to the implement device of the described fast fourier transform algorithm of claim 5 to 7; It is characterized in that; Calculate the count span DF of D of said computing according to the judgement formula; Judgement formula and confirm that condition is: DF* (1000/T) >=F, choose among the said span DF minimum 2 geometry multiple value as the count value of D of said computing.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN2896304Y (en) * | 2006-02-27 | 2007-05-02 | 凹凸科技（中国）有限公司 | Device for providing estimation to signal-to-noise ratio of spread spectrum signal |
| CN101324658A (en) * | 2008-08-04 | 2008-12-17 | 哈尔滨工业大学 | Method for capturing full bit of GPS weak signal |
| CN101910859A (en) * | 2007-11-30 | 2010-12-08 | 高通股份有限公司 | Sequential tracking and offline demodulation in receiver |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN2896304Y (en) * | 2006-02-27 | 2007-05-02 | 凹凸科技（中国）有限公司 | Device for providing estimation to signal-to-noise ratio of spread spectrum signal |
| CN101910859A (en) * | 2007-11-30 | 2010-12-08 | 高通股份有限公司 | Sequential tracking and offline demodulation in receiver |
| CN101324658A (en) * | 2008-08-04 | 2008-12-17 | 哈尔滨工业大学 | Method for capturing full bit of GPS weak signal |
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Application publication date: 20120905 |