CN1541338A - Improvements to tracking systems - Google Patents

Improvements to tracking systems Download PDF

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Publication number
CN1541338A
CN1541338A CNA028159322A CN02815932A CN1541338A CN 1541338 A CN1541338 A CN 1541338A CN A028159322 A CNA028159322 A CN A028159322A CN 02815932 A CN02815932 A CN 02815932A CN 1541338 A CN1541338 A CN 1541338A
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China
Prior art keywords
signal
transmitter
frequency
correlogram
base station
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CNA028159322A
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Chinese (zh)
Inventor
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格雷戈里·查尔斯·赫斯特
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韦恩·诺曼·阿古特
罗伯特·申克
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威廉·马克·卡尼
÷
查尔斯·利·霍梅斯
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QUICKTRAK NETWORKS Ltd
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QUICKTRAK NETWORKS Ltd
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Publication of CN1541338A publication Critical patent/CN1541338A/en
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
    • G01S5/01—Determining conditions which influence positioning, e.g. radio environment, state of motion or energy consumption
    • G01S5/011—Identifying the radio environment
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
    • G01S5/02—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using radio waves
    • G01S5/10—Position of receiver fixed by co-ordinating a plurality of position lines defined by path-difference measurements, e.g. omega or decca systems
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S11/00—Systems for determining distance or velocity not using reflection or reradiation
    • G01S11/02—Systems for determining distance or velocity not using reflection or reradiation using radio waves
    • G01S11/10—Systems for determining distance or velocity not using reflection or reradiation using radio waves using Doppler effect
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
    • G01S5/02—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using radio waves
    • G01S5/0246—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using radio waves involving frequency difference of arrival or Doppler measurements
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/08—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Position Fixing By Use Of Radio Waves (AREA)

Abstract

A spread-spectrum location and tracking system, is provided in which the vehicle (10) or object to be located emits a continual direct sequence spread spectrum radio signal (11). This transmission is received at a number of wellspaced receiving stations (12) in the coverage area and the differences in the times of arrival of the signals at these receivers are measured by determining the epoch corresponding to the correlogram peak. The carrier frequencies f1, f2, f3 of transmitter transmissions received at a receiver site (12), are estimated and frequency errors apart from those due to relative motion between the transmitter and a particular receive site, will be seen as a common offset by all receive sites, and may thus be eliminated by suitable processing, allowing estimate of the velocity vector of a moving transmitter from a single set of measurements at (3) or more remote sites.

Description

The improvement of tracker
Technical field
The present invention relates generally to the improvement of communication system, and in a preferred embodiment, the present invention is applied to use the vehicle location and the tracker of direct sequence spread spectrum (DSSS) transmission technology.
In this instructions, word " comprises (comprise) " or is interpreted as representing to comprise element, integer or the step of regulation such as the distortion of " comprising (comprises) " or " comprising (comprising) ", perhaps element set, integer group or step group, but element, integer or the step of not getting rid of any other, perhaps element set, integer group or step group.
Any discussion to file included in this instructions, effect, material, device, object etc. only is for applied environment of the present invention is provided.And this should not thought admitting to following inference: promptly, because any or all foregoings occurred in Australia before the priority date of each claim of the application, therefore these contents have constituted the part on prior art basis, perhaps become the common practise of association area of the present invention.
Summary of the invention
According to first aspect, the present invention includes a kind of the determine speed of mobile transmitter motion and the method for direction, this method comprises:
Send signal from mobile transmitter;
On three or more the receiver that is disposed on the plane, receive the signal that is sent with known position toward each other;
Information time of arrival of measurement received signal on each receiver;
It is poor to the path-length of each receiver to calculate the self-emission machine from the measurement result of time of arrival, and utilizes path length difference and utilize polygon method (multi-lateration) to come the position of transmitter computes with respect to described a plurality of receivers;
To the signal that each receiver received, determine frequency shift (FS) with the nominal transmission frequency of transmitter;
Frequency shift (FS) that utilization records at receiver and transmitter are with respect to the position of described a plurality of receivers, and transmitter computes is with respect to transient motion speed and the direction of described a plurality of receivers in the receiver plane.
Preferably, described a plurality of receiver is positioned at the known a plurality of fixed positions with respect to earth surface, and be spaced apart setting, make the plane approximation that limits by receiver, thereby the speed and the direction of coming transmitter computes to advance with respect to earth surface in earth surface.
Preferably, in the two-dimensional case of utilizing 3 receivers, carry out following calculating for determining speed and direction that transmitter is advanced:
Wherein:
I) three receivers are positioned at base station B 1, B 2, B 3
Ii) the position of transmitter T makes the base station B that wins 1The line and the second base station B to transmitter T 2To the angle between the line of transmitter T is θ, and the first base station B 1Line and the 3rd base station B to transmitter T 3To the angle between the line of transmitter T is δ;
Iii) the carrier frequency of signal transmitted is f c
Iv) the maximum doppler frequency that produces owing to the motion of transmitter is;
f d＝f c·v/c (1)
Wherein v is the speed of transmitter in the plane, base station, and c is the velocity of propagation of radio signal;
V) at base station B 1, B 2, B 3The mensuration carrier frequency f of the signal that receives 1, f 2, f 3Be respectively with the relation of maximum doppler frequency:
f 1＝f c+f d?cos(α) (2)
f 2＝f c+f d?cos(θ-α) (3)
f 3＝f c+f d?cos(α+δ) (4)
Wherein α is the direct of travel and the first base station B of transmitter T 1And the angle between the line of transmitter T, α and f like this dCan pass through following equation solution is determined:
f 1-f 1＝f d(cosα-cos(α-θ)) (5)
And f 1-f 3=f d(cos α-cos (α+δ)) (6)
F wherein 1, f 2, f 3, θ and δ be known.
Then pass through f dCan determine the speed of transmitter T in the substitution equation (1), and α provides transmitter T with respect to line B 1The direction that-T advances.
Can utilize more than the measurement result of three receivers and separate to reduce or the influence of disambiguation and/or random meausrement error with (over-determined) that an overdetermination is provided.
This speed can be determined that technology is applied in any diversity machine communication system that wherein can clearly determine the position.Yet in this preferred embodiment, employed transmission system is a Resistant DS Spread Spectrum System, and wherein modulation signal is filtering (limit band) maximum length pseudo-random binary sequence (PRBS).Sequence length N (position) and chip-rate (chip rate) f nThe selection of (sign indicating number clock frequency) makes N/f nGreater than signal propagation delays from transmitted from transmitter to receiver.
According to second aspect, the present invention includes a kind of movement velocity of definite mobile transmitter and the method for direction, this method comprises:
Send signal from mobile transmitter;
What be provided with at interval in the space has four of known position toward each other or more receives the signal that is sent on the receiver, and these receivers are not included in the single plane;
Information time of arrival of measurement received signal on each receiver;
It is poor to the relative path-length of each receiver to calculate the self-emission machine from the measurement result of time of arrival, and utilizes polygon method and utilize path length difference to come the position of transmitter computes with respect to described a plurality of receivers;
To the signal that each receiver received, determine to transmit the frequency shift (FS) of carrier frequency with the nominal of signal transmitted;
Utilization is in the frequency shift (FS) of receiver and the transmitter position with respect to described a plurality of receivers, and transmitter computes is with respect to the instantaneous velocity and the direction of described a plurality of receivers motions.
Preferably, in the three-dimensional situation of utilizing 4 receivers, carry out following calculating for determining speed and direction that transmitter is advanced:
Wherein:
I) four receivers are positioned at base station B 1, B 2, B 3, B 4
Ii) the position of transmitter T makes the base station B that wins 1The line and the second base station B to transmitter T 2To the angle between the line of transmitter T is θ, and the first base station B 1Line and the 3rd base station B to transmitter T 3To the angle between the line of transmitter T is δ, the first base station B 1Line and the 4th base station B to transmitter T 4To the angle between the line of transmitter T is φ;
Iii) the carrier frequency of signal transmitted is f c
Iv) the maximum doppler frequency that produces owing to the motion of transmitter is;
f d＝f c·v/c (1)
Wherein v is the speed of transmitter motion, and c is the velocity of propagation of radio signal;
V) at base station B 1, B 2, B 3, B 4The mensuration carrier frequency f of the signal that receives 1, f 2, f 3, f 4Be respectively with the relation of maximum doppler frequency:
f 1＝f c+f dF 1(α，β，θ，δ，φ) (7)
f 2＝f c+f dF 2(α，β，θ，δ，φ) (8)
f 3＝f c+f dF 3(α，β，θ，δ，φ) (9)
f 4＝f c+f dF 4(α，β，θ，δ，φ) (10)
Wherein α is the direct of travel and the first base station B of transmitter T 1And the angle between the line of transmitter T, and β is the direct of travel and the second base station B of transmitter T 2And the angle between the line of transmitter T;
Vi) can determine α, β and f by solving equation 7,8,9 and 10 d, f wherein 1, f 2, f 3, f 4, θ, δ and φ be known; And
Vii) pass through f dSubstitution equation (1) is determined the speed of transmitter T, and α and β provide transmitter T with respect to line B 1-T and B 2The direct of travel of-T.
In three-dimensional situation, can utilize more than the measurement result of four receivers so that the separating to reduce or the influence of disambiguation and/or random meausrement error an of overdetermination to be provided.
According to the third aspect, the present invention includes the method for the frequency error in a kind of signal of determining to be received by the direct sequence spread spectrum communication control processor, this method comprises:
With the signal mixing that receives is intermediate-freuqncy signal;
In a plurality of intermediate-freuqncy signals sampling of continuous drawing in the cycle of predetermined a plurality of Measuring Time, with to producing a plurality of sample points each measuring period;
Processing is from the sample point of each measuring period, to produce a plural correlogram of organizing continuously.
Organize plural correlogram from this, determine one group of impact point (being generally the position of peak value in the plural correlogram or the forward position of those peak values (impact point)) of representing received signal best in the complex points in correlogram;
Monitor the phasing degree of the corresponding impact point in the continuous plural correlogram, to determine phase change (rotation) sequence in the received signal;
Determine the average phase rate of change of impact point, and (directly) the average phase rate of change is changed into frequency, this frequency representation received signal is with respect to the nominal frequency of received signal or the frequency error of expected frequency.
This frequency error is preferably used for mixing is compensated with the frequency that received of coupling, thereby and realizes the intermediate-freuqncy signal that conforms to very much with the expection intermediate frequency of receiver.
In general, for typical embodiment, this intermediate-freuqncy signal is with frequency f sSampling, this frequency f sEqual chip-rate f cMultiply by every predetermined measurement period t sSampling number n sAnd divided by the extended code length N cWith every predetermined measurement period t sExtended code loop number C sProduct:
f s＝f c·n s/(N C·C s)
This makes every predetermined measurement period t sSampling number n sBe 2 exponential, it is selected obtaining being greater than or equal to the sampling frequency of nyquist rate, and wherein the Cycle Length of predetermined measurement period is t s, in this Cycle Length, can guarantee the coherence usually, and t sIt is an integer extended code cycle period.
In a preferred embodiment, continuous a plurality of being similar in 4 millisecond periods to be similar to the 4MHz frequency, to produce the groups of a plurality of 16384 plural number sampling to the intermediate frequency signal sampling.These groups of samples are processed to produce the correlogram of each respective cycle.The correlogram that is produced is a plural number, but usually only considers that amplitude determines that organizes the index (time migration) (the normally peak value in the correlogram) of the point of representing received signal best.This time migration (being confirmed as average or other the suitable functions to whole sampling correlogram group) is used as the measuring to be used for the position of time of arrival of this signal and determines.
Yet the influence of any frequency error in the received signal is, causes the rotation in the phase place of peak value of correlogram.Phase place by monitoring the peak value in serial correlation figure poor can be estimated speed of rotation and therefore estimate frequency error in the original signal.
According to fourth aspect, the present invention includes a kind of by reducing because the influence of noise that multipath reception produces and random noise improves the method for the signal noise ratio of band spread receiver, this method comprises:
With the signal mixing that is received is intermediate-freuqncy signal;
The a plurality of intermediate-freuqncy signal sampling of continuous drawing in predetermined a plurality of time cycles are to produce a plurality of sample points to each cycle;
Processing is from the sample point in each cycle, to produce continuous a plurality of plural correlogram;
Monitor the phase place of the peak value among the serial correlation figure, to determine the phase place speed of rotation of received signal;
From the speed of rotation of received signal, determine that received signal is with respect to the nominal frequency of this signal or the frequency error of expected frequency;
Utilization to the compensation of definite frequency error come signal is handled again, to revise correlogram, make the phase place of the signal peak among the serial correlation figure obtain calibration; And
Correlogram is carried out plural number add up, so that provide some counteractings to noise owing to the phase place of its stochastic distribution.
Equally, in general, for typical embodiment, intermediate-freuqncy signal is with frequency f sSampling, this frequency f sEqual chip-rate f cMultiply by every predetermined measurement period t sSampling number n sAnd divided by the extended code length N cWith every predetermined measurement period t sExtended code loop number C sProduct:
f s＝f c·n s/(N C·C s)
Make every predetermined measurement period t like this sSampling number n sBe 2 exponential, it is selected obtaining being greater than or equal to the sampling frequency of nyquist rate, and wherein the Cycle Length of predetermined measurement period is t s, in this Cycle Length, can guarantee the coherence usually, and t sIt is an integer extended code cycle period.
In a preferred embodiment, continuous a plurality of being similar in 4 millisecond periods to be similar to 4MHz to the intermediate frequency signal sampling, to produce the group of a plurality of 16384 sample points.These groups of samples are processed to produce the plural correlogram of each respective cycle.The influence of any frequency error in received signal is to cause the rotation of the peak phase of correlogram.Phase place by monitoring serial correlation figure peak value poor can be estimated speed of rotation and therefore estimate frequency error in the original signal.
Common signal Processing is utilized add up (perhaps average) of serial correlation figure, to improve signal noise ratio.Because the rotation of the proper phase of correlogram data, this processing only utilizes amplitude information (noncoherent accumulation) and finishes.
The effect of getting the correlogram amplitude is all data (noise plus signal) to be rotated in the common plane and therefore make the amplitude of noise and signal become linear, additive in cumulative process.Since the noise amplitude of arbitrfary point in correlogram on amplitude with serial correlation figure random variation, and signal amplitude is big usually and be constant, therefore can realize the improvement of clean SNR.
Yet, if remove rotation among the serial correlation figure, make signal peak be carried out phase alignment by the phase place of regulating serial correlation figure, can carry out plural number and add up, the noise phase of stochastic distribution will produce some counteractings in this case.In fact, noise is root mean square when each accumulation increase, and signal is linear increase at every turn when adding up.
Go potential advantages of rotation (de-rotation) technology to be embodied in the minimizing of multipath effect.The normal signal of handling at receiving position comprises that the direct-path signal adds a plurality of reflected signals.Because according to its definition, reflected signal must be taked different paths, if therefore transmitter and/or reflecting body are at the volley, then reflected signal can show different Doppler shifts.When the correlogram that is received is gone rotation when calibrating the phase place of main (direct-path) signal, multipath signal may rotate outside the main signal plane, therefore causes the minimizing in viewed multipath amplitude when correlogram is added up.
According to the 5th aspect, the present invention includes a kind of method of the angle of arrival of definite signal, this method comprises:
To be mixed down intermediate-freuqncy signal from the received signal of two isolated antennas at an independent receiver website;
A plurality of sampling of continuous drawing intermediate-freuqncy signal in predetermined a plurality of time cycles produce a plurality of plural sample points with each cycle to each signal;
Processing is from the plural sample point in each cycle, so that each signal in these two signals is produced continuous a plurality of correlograms;
The phase place of the peak value of the correlogram of these two signals of comparison;
Determine time of arrival poor of these two signals from these two phase difference between signals, and therefore determine the angle of arrival from the signal of transmitter from the geometric relationship of the position of these two antennas.
In first to file,, determined the phase place speed of rotation between the serial correlation figure measurement result for estimation transmission frequency error.In the situation that the synchronous signal that receives at discrete antenna place, space is measured, the phase differential between the correlogram that calculates for each measurement result represents to send to from transmitter path poor of the signal of antenna.The measurement result of different paths allows to calculate the transmission angle of arrival with respect to the antenna baseline.
Aspect the 6th, the invention provides a kind of definite receiver for spread spectrum communication from the method for the frequency error between two of discrete setting two signals that transmitter received each other on the distance, this method comprises:
Each received signal is mixed down intermediate-freuqncy signal;
In a plurality of sampling of predetermined a plurality of Measuring Time continuous drawing intermediate-freuqncy signal in the cycle, with to producing a plurality of sample points each measuring period;
Processing is from the sample point of each measuring period, to produce a plural correlogram of organizing continuously;
Organize plural correlogram from this, determine one group of impact point of representing received signal best in the complex points in each correlogram;
Monitor the phasing degree of the corresponding impact point in the continuous plural correlogram of each received signal, to determine the phase change sequence relative to each other of received signal;
Determine the mean change speed of the phase place of impact point, and the mean change speed of phase place is converted into a signal in the expression received signal with respect to the frequency of the frequency error of other received signals; And
Utilize frequency error information to come synchronous received signal.
Description of drawings
Utilize example to describe embodiments of the invention now in conjunction with the accompanying drawings, wherein:
Fig. 1 illustrates vehicle tracking system prevailingly, wherein can adopt according to the improvement to communication system of the present invention; And
Fig. 2 is that demonstration is used for calculating the speed of a mobile transmitter and the trigon figure of direction from the frequency displacement of received signal.
Fig. 3 shows the block diagram of the processing of employed receiver in a preferred embodiment.
Embodiment
To describe the present invention in conjunction with example and with reference to many vehicle locations and tracker shown in general among the figure 1, this system has adopted a direct sequence spread spectrum communication system as the means of determining vehicle location.
In the direct sequence spread spectrum transmission system, receiver extracts the information that is sent by the extended code of importing combined-flow and be associated with transmission is carried out simple crosscorrelation.When the time of occurrence (spochs) of clock frequency and this input and the local extended code that produces mated, spread-spectrum signal was folded a small amount of consecutive point in (compression) one-tenth correlogram, and every other non-matched signal (being generally noise) still spreads all over whole correlogram.Cross correlation value between the extended code of input signal and noiseless form is called as correlogram as the function that the relative time in a complete cycle of extended code postpones (time of occurrence).
With reference to figure 1, can find in a spread-spectrum location and tracker the continuous direct sequence spread spectrum radio signal 11 of transmitter emission on vehicle 10 or object to be positioned.This is transmitted in receiving station 12 places that a plurality of appropriate intervals in the overlay area open and is received, and by determining to measure the poor of time of arrival (toa) on these receivers corresponding to the time of occurrence of correlogram peak value.Can use anti-hyperbolic airmanship to come the position of transmitter computes in central computer 13 then, central computer 13 sends to operator's terminal with this information then.In a preferred embodiment, extended code is that 511 maximum length pseudo-random binary sequence (PRBS) and its clock frequency are per second 1Mbit.In this case, per 511 microseconds have a complete extended code circulation.
Embodiments of the invention adopt a kind of new technology to estimate the carrier frequency f of the transmitter transmission signals that is received at receiver website 12 1, f 2, f 3Usually this frequency has been compared error with its nominal value, and reason is as follows:
Frequency shift (FS) in the transmitter that causes owing to the measurement in the synthetic control loop of carrier frequency and quantization error;
Frequency shift (FS) in the transmitter that causes owing to the error in the frequency reference oscillator on the transmitter;
The Doppler who causes owing to the relative motion between transmitter and the receiving station changes the frequency shift (FS) in the received signal at receiving station place that causes.
Except that the frequency error that causes owing to the relative motion between transmitter and the specific receiving station, all frequency errors all will be considered as a public skew by all receiving stations, therefore can it be eliminated by suitable processing, can estimate the velocity of a mobile transmitter from single group measurement result at 3 or more a plurality of remote sites.
The technology that is used for the estimation frequency error relates to the phasing degree rotation of peak value that estimation is used to produce the continuous plural correlogram of website data time of arrival.As subsidiary benefit,, then can from raw data, remove rotation, thereby cause improving the signal noise ratio in the correlogram, and therefore improve tracking accuracy in case this phase place rotation is known.
Can adopt identical technology to measure carrier phase difference between the signal that receives in different receiving antenna place, thereby can calculate the angle of arrival of direct-path signal, and therefore calculate the direction vector of transmitter with respect to the antenna baseline.
The estimation of the frequency error that is received
Receiving station signal Processing hypothesis transmitter sends signal and received signal suitably is mixed down intermediate frequency (IF) signal with correct frequency.In a plurality of approximate 4 milliseconds cycles, IF is sampled, to produce the groups of samples of a plurality of 16384 complex points with approximate 4MHz.This groups of samples is processed to produce correlogram.This processing comprises carries out Fourier transform to groups of samples, multiply by the complex spectrum of gained with a template, this template comprises the complex conjugate (having zero frequency error and known benchmark time of occurrence) of the Fourier transform of wanted signal, then the result is carried out inverse fourier transform (Fig. 3 illustrates this process).In the preferred embodiment, all operations can carry out in a general calculation machine treating apparatus after the analog to digital conversion.The correlogram that is generated comprises plural correlation, but the amplitude of usually only considering these values is determined the time of occurrence (peak) of signal, and this peak is used for carrying out position match (position fitting).
Yet the influence of any frequency error in received signal is to introduce the rotation or the gradual change of the phase place of plural correlogram sampling.Phase place by monitoring serial correlation figure peak value poor, therefore mean speed that can the evaluation phase rotation also estimates frequency error in the received signal.
Be applied to velocity estimation
The transmission frequency error measured at each receiving station comprises the fixed error that causes because of the frequency shift (FS) in the transmitter, and random meausrement error and the error that Doppler shift caused that causes frequency because of the transmitter velocity at the component of receiving station direction.The public frequency error can be estimated according to transmitter and receiving station position and at the frequency error that 3 or more receiving station are observed.In case the removal component common then can utilize remaining residual error to come relative motion between transmitter computes and the receiving station.Can utilize in measurement result separating of an overdetermination is provided, to reduce or to remove the influence of ambiguousness and/or random meausrement error more than three websites.
Being applied to SNR improves
For adding up of 4 milliseconds of sampling producing the data that serial correlation figure carries out causes 8 complete code round-robin coherent accumulations for each correlogram.This coherent accumulation provides the improvement of maximum signal noise ratio (SNR), but only can be applied to a certain period, and it is relevant that signal kept in this period.This period, to be that the frequency of the caused carrier signal of error that produced by carrier frequency error and Doppler shift is uncertain determined, and in fact in this preferred embodiment this period be defined as about 4 milliseconds.
Common signal Processing utilizes the noncoherent accumulation (perhaps average) of serial correlation figure further to improve signal noise ratio.Because the rotation of the proper phase of correlogram data, this processing can only only utilize amplitude information to carry out (that is noncoherent accumulation).
The effect of getting the correlogram amplitude is all data (noise plus signal) to be rotated in the common plane and therefore make noise and signal become addition in cumulative process.Because noise amplitude random variation on amplitude, and signal amplitude is big usually and be constant, therefore can realize the improvement of net signal noise ratio.
Yet, if the rotation among the removal serial correlation figure makes signal peak (time of occurrence of representation signal) be carried out phase alignment, can carry out plural number and add up, the noise phase of stochastic distribution will produce some counteractings in this case.In fact, noise is root mean square at every turn when adding up increase, and signal is linear increase at every turn when adding up.In fact, coherence time by infinite expanding with provide coherent accumulation benefit.
Go an application-specific of rotation technique to be embodied in minimizing multipath effect aspect.The normal signal of handling at remote site comprises direct-path signal and a plurality of reflected signal.Because according to its definition, reflected signal has been taked different paths, if therefore transmitter and/or reflecting body are kept in motion, then reflected signal can show different Doppler shifts.When the correlogram that will be received goes rotation when calibrating the phase place of main (direct-path) signal, the phase place of multipath signal will show the phase place rotation usually.The coherent accumulation of this phase place rotation multipath signal will show long mutually and adding up of disappearing mutually usually, and therefore linear the increasing with every accumulation step.This causes reducing of when adding up plural correlogram viewed multipath amplitude.
Be applied to measure the angle of arrival
In formerly using, determined the phase place speed of rotation between the serial correlation figure measurement result for estimating the transmission frequency error.When the common signal measured in the reception simultaneously of the discrete antenna in a plurality of spaces institute, (carrier wave) phase differential between the signal peak in the corresponding correlogram is represented the poor of common signal path to each antenna from its transmitter.The feasible transmission angle of arrival that can calculate of different path measurement results with respect to the antenna baseline.
Being applied to common frequencies measures
The technology that is used for measuring the frequency error of present embodiment previously discussed can be applied even more extensively in measuring any two errors between frequency source discrete on the distance, and can be therefore as long-range frequency synchronization method.
Determine speed and direction
With reference to figure 2, vehicle direct of travel in the tracker of this preferred embodiment and speed determine that operation carries out according to the following steps:
Wherein:
I) three receivers are positioned at base station B 1, B 2, B 3
Ii) the position of transmitter T makes the base station B that wins 1The line and the second base station B to transmitter T 2To the angle between the line of transmitter T is θ, and the first base station B 1Line and the 3rd base station B to transmitter T 3To the angle between the line of transmitter T is δ;
Iii) the carrier frequency of signal transmitted is f c
Iv) the maximum doppler frequency that produces owing to the motion of transmitter is;
f d＝f c·v/c (1)
Wherein v is the speed of vehicle, and c is the velocity of propagation of radio signal;
V) at base station B 1, B 2, B 3The mensuration carrier frequency f of the signal that the place receives 1, f 2, f 3Be respectively with the relation of maximum doppler frequency:
f 1＝f c+f d?cos(α) (2)
f 2＝f c+f d?cos(θ-α) (3)
f 3＝f c+f d?cos(α+δ) (4)
Wherein α is the direct of travel and the first base station B of transmitter T 1And the angle between the line of transmitter T;
α and f like this dCan pass through following equation solution is determined:
f 1-f 2＝f d(cosα-cos(α-θ)) (5)
And f 1-f 3=f d(cos α-cos (α+δ)) (6)
F wherein 1, f 2, f 3, θ and δ be known.
By with f dCan determine the speed of transmitter T in the substitution equation (1), and α provides transmitter T with respect to line B 1The direct of travel of-T.
It will be understood by those skilled in the art under the situation of the spirit and scope that do not depart from generalized description of the present invention and can the present invention shown in specific embodiment be changed in a large number and/or improve.Therefore, aspect all, all should be considered as present embodiment indicative and nonrestrictive.

Claims (29)

1. determine the speed of mobile transmitter T motion and the method for direction for one kind, this method comprises:
Send signal from mobile transmitter;
On three or more the receiver that is disposed on the plane, receive the signal that is sent with known position toward each other;
Determine information time of arrival of received signal on each receiver;
It is poor to the path-length of each receiver to calculate the self-emission machine, and utilizes path length difference and utilize polygon method to come the position of transmitter computes with respect to described a plurality of receivers;
To the signal that each receiver received, determine to transmit the frequency shift (FS) of carrier frequency with the nominal of signal transmitted;
Utilization is in the frequency shift (FS) of described a plurality of receivers and the transmitter position with respect to described a plurality of receivers, and transmitter computes is with respect to the instantaneous velocity and the direction of the motion of described a plurality of receivers in the receiver plane.
2. method according to claim 1, wherein said a plurality of receiver is positioned at the known a plurality of fixed positions with respect to earth surface, and be spaced apart, make the plane approximation that limits by receiver in earth surface, thus the speed and the direction of coming transmitter computes to advance with respect to earth surface.
3. method according to claim 1 and 2, wherein:
I) three receivers are positioned at base station B 1, B 2, B 3
Ii) the position of transmitter T makes the base station B that wins 1The line and the second base station B to transmitter T 2To the angle between the line of transmitter T is θ, and the first base station B 1Line and the 3rd base station B to transmitter T 3To the angle between the line of transmitter T is δ;
Iii) the carrier frequency of signal transmitted is f c
Iv) the maximum doppler frequency that produces owing to the motion of transmitter is;
f d＝f c·v/c (1)
Wherein v is the speed that transmitter moves in the plane, base station, and c is the velocity of propagation of radio signal;
V) at base station B 1, B 2, B 3The mensuration carrier frequency f of the signal that receives 1, f 2, f 3Be respectively with the relation of maximum doppler frequency:
f 1＝f c+f dcos(α) (2)
f 2＝f c+f dcos(θ-α) (3)
f 3＝f c+f dcos(α+δ) (4)
Wherein α is the direct of travel and the first base station B of transmitter T 1And the angle between the line of transmitter T;
Vi) α and f dCan pass through following equation solution is determined:
f 1-f 2＝f d(cosα-cos(α-θ)) (5)
And f 1-f 3=f d(cos α-cos (α+δ)) (6)
F wherein 1, f 2, f 3, θ and δ be known; And
Vii) with f dDetermine the speed of transmitter T in the substitution equation (1), and α provides transmitter T with respect to line B 1The direction that-T advances.
4. according to claim 1,2 or 3 described methods, wherein measuring more than three receivers so that separating of an overdetermination to be provided, to reduce the influence of ambiguousness and/or random meausrement error.
5. according to claim 1,2,3 or 4 described methods, wherein, described transmission system is a Resistant DS Spread Spectrum System, and wherein modulation signal is filtering (limit band) maximum length pseudo-random binary sequence (PRBS), its sequence length N (position) and chip-rate f nThe selection of (clock frequency) makes N/f nGreater than signal propagation delays from transmitted from transmitter to receiver.
6. determine the movement velocity of a mobile transmitter T and the method for direction for one kind, this method comprises:
Send signal from mobile transmitter;
What be provided with at interval in the space has four of known position toward each other or more receives the signal that is sent on the receiver, and these receivers are not included in the single plane;
Determine information time of arrival of received signal on each receiver;
It is poor to the relative path-length of each receiver to calculate the self-emission machine, and utilizes this path length difference and utilize polygon method to come the position of transmitter computes with respect to described a plurality of receivers;
To the signal that each receiver received, determine to transmit the frequency shift (FS) of carrier frequency with the nominal of signal transmitted;
Utilization is in the frequency shift (FS) of described a plurality of receivers and the transmitter position with respect to described a plurality of receivers, and transmitter computes is with respect to the instantaneous velocity and the direction of described a plurality of receivers motions.
7. method according to claim 1 and 2, wherein:
I) four receivers are positioned at base station B 1, B 2, B 3, B 4
Ii) the position of transmitter T makes the base station B that wins 1The line and the second base station B to transmitter T 2To the angle between the line of transmitter T is θ, and the first base station B 1Line and the 3rd base station B to transmitter T 3To the angle between the line of transmitter T is δ, the first base station B 1Line and the 4th base station B to transmitter T 4To the angle between the line of transmitter T is φ;
Iii) the carrier frequency of signal transmitted is f c
Iv) the maximum doppler frequency that produces owing to the motion of transmitter is;
f d＝f c·v/c (1)
Wherein v is the speed of transmitter motion, and c is the velocity of propagation of radio signal;
V) at base station B 1, B 2, B 3, B 4The mensuration carrier frequency f of the signal that receives 1, f 2, f 3, f 4Be respectively with the relation of maximum doppler frequency:
f 1＝f c+f dF 1(α，β，θ，δ，φ) (7)
f 2＝f c+f dF 2(α，β，θ，δ，φ) (8)
f 3＝f c+f dF 3(α，β，θ，δ，φ) (9)
f 4＝f c+f dF 4(α，β，θ，δ，φ) (10)
Wherein α is the direct of travel and the first base station B of transmitter T 1And the angle between the line of transmitter T, and β is the direct of travel and the second base station B of transmitter T 2And the angle between the line of transmitter T;
Vi) determine α, β and f by solving equation 7,8,9 and 10 d, f wherein 1, f 2, f 3, f 1, θ, δ and φ be known; And
Vii) pass through f dSubstitution equation (1) is determined the speed of transmitter T, and α and β provide transmitter T with respect to line B 1-T and B 2The direct of travel of-T.
8. according to claim 6 or 7 described methods, wherein measuring more than four receivers so that separating of an overdetermination to be provided, to reduce the influence of ambiguousness and/or random meausrement error.
9. according to claim 6,7 or 8 described methods, wherein, described transmission system is a spread spectrum system, wherein the chip-rate f of the length N position of PN sign indicating number and PN sign indicating number nThe selection of (sign indicating number clock frequency) makes N/f nGreater than signal propagation delays from transmitted from transmitter to receiver.
10. the method for the frequency error in the signal of determining to be received by the direct sequence spread spectrum communication control processor, this method comprises:
With the signal mixing that receives is intermediate-freuqncy signal;
In a plurality of intermediate-freuqncy signals sampling of continuous drawing in the cycle of predetermined a plurality of Measuring Time, with to producing a plurality of sample points each measuring period;
Processing is from the sample point of each measuring period, to produce a plural correlogram of organizing continuously;
Organize plural correlogram from this, determine one group of impact point of representing received signal best in the complex points in correlogram;
Monitor the phasing degree of the corresponding impact point in the continuous plural correlogram, to determine the phase change sequence in the received signal;
Determine the average phase rate of change of impact point, and the average phase rate of change is changed into frequency, this frequency representation received signal is with respect to the nominal frequency of received signal or the frequency error of expected frequency.
11. method according to claim 10, the position of the impact point in the wherein plural correlogram are to locate by the peak value of the amplitude of discerning each plural correlogram.
12. method according to claim 11, wherein said groups of samples is processed to produce the correlogram of each respective cycle, the correlogram that is produced is added up, and the position of the point by determining one group of peak amplitude with the correlogram that is added up is identified for the time of arrival (toa) that the position is determined.
13. according to claim 11 or 12 described methods, wherein by positioning the position of selecting the impact point in each plural correlogram to first in that group point of the peak value that is confirmed as representing corresponding correlogram.
14. according to claim 12 or 13 described methods, the difference of the phase place by monitoring serial correlation figure peak value and come the estimation frequency error wherein by the Measurement Phase rate of change, thus measure the influence of the frequency error in the received signal.
15., wherein measured frequency error is used to compensate the mixing frequency, thereby intermediate-freuqncy signal to mate the frequency that is received and to realize conforming to very much with the expectation intermediate frequency of receiver according to claim 10,11,12,13 or 14 described methods.
16. according to claim 10,11,12,13,14 or 15 described methods, wherein intermediate-freuqncy signal is with frequency f sSampled this frequency f sEqual chip-rate f cMultiply by every predetermined measurement period t sSampling number n sAnd divided by the extended code length N cWith every predetermined measurement period t sExtended code loop number C sProduct:
f s＝f c·n s/(N C·C s)
This makes every predetermined measurement period t sSampling number n sBe 2 exponential, it is selected obtaining being greater than or equal to the sampling frequency of nyquist rate, and wherein the Cycle Length of predetermined measurement period is t s, in this Cycle Length, can guarantee the coherence usually, and t sIt is an integer extended code cycle period.
17. one kind by reducing random noise and because the The noise that multipath reception produces is improved the method for the signal noise ratio of band spread receiver, this method comprises:
With the signal mixing that is received is intermediate-freuqncy signal;
The a plurality of intermediate-freuqncy signal sampling of continuous drawing in predetermined a plurality of time cycles are to produce a plurality of sample points to each cycle;
Processing is from the sample point in each cycle, to produce continuous a plurality of plural correlogram;
Monitor the phase place of the peak value among the serial correlation figure, to determine the phase place speed of rotation of received signal;
From the speed of rotation of received signal, determine that received signal is with respect to the nominal frequency of this signal or the frequency error of expected frequency;
Utilization is handled institute's estimation frequency compensation of error again, to revise correlogram, makes the phase place of the signal peak among the serial correlation figure be calibrated; And
Plural correlogram is added up, so that noise is offset owing to the phase place of its stochastic distribution.
18. method according to claim 17, wherein the position of the point by determining one group of peak amplitude with correlogram is identified for the time of arrival (toa) that the position is determined.
19., wherein, select the position of the impact point in each plural correlogram at first in that group point of the peak value that is confirmed as representing corresponding correlogram by positioned according to claim 17 or 18 described methods.
20. according to claim 17,18 or 19 described methods, the difference of the phase place by monitoring serial correlation figure peak value and come the estimation frequency error wherein by the Measurement Phase rate of change, thus measure the influence of the frequency error in the received signal.
21. according to claim 17,18,19 or 20 described methods, wherein measured frequency error is used to compensate the mixing frequency,, thereby and realizes the intermediate-freuqncy signal that conforms to very much with the expectation intermediate frequency of receiver with coupling institute receive frequency.
22. according to claim 17,18,19,20 or 21 described methods, wherein intermediate-freuqncy signal is with frequency f sSampling, this frequency f sEqual chip-rate f cMultiply by every predetermined measurement period t sSampling number n sAnd divided by the extended code length N cWith every predetermined measurement period t sExtended code loop number C sProduct:
f s＝f c·n s/(N C·C s)
This makes every predetermined measurement period t sSampling number n sBe 2 exponential, it is selected obtaining being greater than or equal to the sampling frequency of nyquist rate, and wherein the Cycle Length of predetermined measurement period is t s, in this Cycle Length, can guarantee the coherence usually, and t sIt is an integer extended code cycle period.
23. according to each the described method in the claim 17 to 22, the frequency error of wherein said estimation is used to regulate the phase place of serial correlation figure, thereby signal peak is carried out phase alignment, and accumulation step is to utilize the plural number of correlogram to add up to carry out.
24. method according to claim 23, wherein adding up of plural correlogram is used to reduce multipath effect.
25. the method for the angle of arrival of a definite signal, this method comprises:
To be mixed down intermediate-freuqncy signal from the received signal of two isolated antennas at an independent receiver website;
A plurality of sampling of continuous drawing intermediate-freuqncy signal in predetermined a plurality of time cycles produce a plurality of plural sample points with each cycle to each signal;
Processing is from the plural sample point in each cycle, so that each signal in these two signals is produced continuous a plurality of correlograms;
The phase place of the peak value of the correlogram of these two signals of comparison;
Determine time of arrival poor of these two signals from these two phase difference between signals, and therefore determine the angle of arrival from the signal of transmitter from the geometric relationship of the position of these two antennas.
26. method according to claim 25, wherein intermediate-freuqncy signal is with frequency f sSampling, this frequency f sEqual chip-rate f cMultiply by every predetermined measurement period t sSampling number n sAnd divided by the extended code length N cWith every predetermined measurement period t sExtended code loop number C sProduct:
f s＝f c·n s/(N C·C s)
This makes every predetermined measurement period t sSampling number n sBe 2 exponential, it is selected obtaining being greater than or equal to the sampling frequency of nyquist rate, and wherein the Cycle Length of predetermined measurement period is t s, in this Cycle Length, can guarantee the coherence usually, and t sIt is an integer extended code cycle period.
27. a definite receiver for spread spectrum communication is from the method for the frequency error between two of discrete setting two signals that transmitter received each other on the distance, this method comprises:
Each received signal is mixed down intermediate-freuqncy signal;
In a plurality of sampling of predetermined a plurality of Measuring Time continuous drawing intermediate-freuqncy signal in the cycle, with to producing a plurality of sample points each measuring period;
Processing is from the sample point of each measuring period, to produce a plural correlogram of organizing continuously;
Organize plural correlogram from this, determine one group of impact point of representing received signal best in the complex points in each correlogram;
Monitor the phasing degree of the corresponding impact point in the continuous plural correlogram of each received signal, to determine the phase change sequence with respect to other received signals of a received signal;
Determine the mean change speed of the phase place of impact point, and the mean change speed of phase place is converted into frequency, this frequency representation received signal is with respect to the frequency error of other received signals; And
Utilize frequency error information to come the synchronous signal that receives.
28. method according to claim 27, wherein the position of the impact point in plural correlogram is to locate by the peak value in the amplitude of discerning each plural correlogram.
29. according to claim 27 or 28 described methods, wherein intermediate-freuqncy signal is with frequency f sSampling, this frequency f sEqual chip-rate f cMultiply by every predetermined measurement period t sSampling number n sAnd divided by the extended code length N cWith every predetermined measurement period t sExtended code loop number C sProduct:
f s＝f c·n s/(N C·C s)
Make every predetermined measurement period t like this sSampling number n sBe 2 exponential, it is selected obtaining being greater than or equal to the sampling frequency of nyquist rate, and wherein the Cycle Length of predetermined measurement period is t s, in this Cycle Length, can guarantee the coherence usually, and t sIt is an integer extended code cycle period.
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