WO2003016937A1 - Systemes de suivi ameliores - Google Patents
Systemes de suivi ameliores Download PDFInfo
- Publication number
- WO2003016937A1 WO2003016937A1 PCT/AU2002/001094 AU0201094W WO03016937A1 WO 2003016937 A1 WO2003016937 A1 WO 2003016937A1 AU 0201094 W AU0201094 W AU 0201094W WO 03016937 A1 WO03016937 A1 WO 03016937A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- transmitter
- signal
- frequency
- correlograms
- receivers
- Prior art date
Links
Classifications
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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
- G01S5/02—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
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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
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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
- 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
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- 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
Definitions
- the present invention relates generally to improvements in communications systems and in a preferred embodiment the invention is applied to a vehicle location and tracking system employing direct-sequence spread-spectrum (DSSS) transmission techniques.
- DSSS direct-sequence spread-spectrum
- the present invention comprises a method of determining a speed and direction of motion of a mobile transmitter, the method comprising: transmitting a signal from the mobile transmitter; receiving the transmitted signal at three or more receivers positioned at spaced locations on a plane having known positions relative to one another; measuring time of arrival information for the signal received at each receiver; calculating transmission path length differences from the time arrival measurements from the transmitter to each of the receivers and using the path length differences to calculate a location of the transmitter relative to the receivers using multi-lateration; for the signal received at each receiver, determining a frequency offset from a nominal transmission frequency of the transmitter; using the frequency offsets measured at the receivers and the location of the transmitter relative to the receivers to calculate the instantaneous speed and direction of motion of the transmitter relative to the receivers in the plane of the receivers.
- the receivers are located at known fixed positions relative to the earth's surface and spaced such that a plane defined by the receivers approximates the earth's surface, whereby the speed and direction of travel of the transmitter are calculated relative to the earth's surface.
- the following calculations are performed to determine the speed and direction of travel of the transmitte ⁇ -
- the three receivers are located at base stations Bi, B 2 , B 3 ;
- the transmitter T is located such that the angle subtended between the line drawn from the first base station Bi and the transmitter T and the second base station B 2 and the transmitter T is ⁇ , and the angle subtended between the line drawn from the first base station Bi and the transmitter T and the third base station B 3 and the transmitter T is ⁇ ;
- the carrier frequency of the transmitted signal is f c;
- the maximum Doppler shift due to motion of the transmitter is;
- v is the speed of the transmitter in the plane of the base stations and c is the speed of propagation of radio signals;
- v) the measured carrier frequencies fi, f 2 , f 3 of the signals received at the base stations Bi, B 2 , B 3 respectively are related to the maximum Doppler shift by:
- f 2 f c + fdC ⁇ s( ⁇ - ⁇ ) (3)
- f 3 f 0 + f d cos( ⁇ + ⁇ ) (4)
- ⁇ is the angle between the direction of travel of the transmitter T and the line joining the first base station Bi and the transmitter T such that ⁇ and f d can be determined by solving:
- the speed of the transmitter T can then be determined by substituting fd in equation (1 ), while ⁇ gives direction of travel relative to the line Bi - T. Measurements at more than three receivers can be used to provide an over-determined solution to reduce or eliminate the effects of ambiguity and/or random measurement errors.
- the transmission system used is a direct- sequence spread-spectrum system in which the modulating signal is a filtered (band-limited) maximal length pseudo-random binary sequence (PRBS).
- PRBS pseudo-random binary sequence
- the sequence length N (bits) and the chip rate f n (code clock rate) are chosen such that N/f n is greater than the signal propagation delay from the transmitter to the receivers.
- the present invention comprises a method of determining a speed and direction of motion of a mobile transmitter, the method comprising: transmitting a signal from the mobile transmitter; receiving the transmitted signal at four or more receivers positioned at spaced locations having known positions relative to one another in space, and which are not contained in a single plane; measuring time of arrival information for the signal received at each receiver; calculating relative transmission path length differences from the time arrival measurements from the transmitter to each of the receivers and using the path length differences to calculate a location of the transmitter relative to the receivers using multi-lateration; for the signal received at each receiver, determining a frequency offset from a nominal transmission carrier frequency of the transmitted signal; using the frequency offsets at the receivers and the location of the transmitter relative to the receivers to calculate the instantaneous speed and direction of motion of the transmitter relative to the receivers.
- the following calculations are performed to determine the speed and direction of travel of the transmitte ⁇ -
- the transmitter T is located such that an angle subtended between lines drawn respectively from the first base station Bi to the transmitter T and from the second base station B 2 to the transmitter T is ⁇ , an angle subtended between lines drawn respectively from the first base station Bi to the transmitter T and from the third base station B 3 to the transmitter T is ⁇ , and an angle subtended between lines drawn respectively from the first base station Bi to the transmitter T and from the fourth base station B 4 to the transmitter T is ⁇ ;
- the carrier frequency of the transmitted signal is f c; iv) the maximum Doppler shift due to motion of the transmitter is;
- v is the speed of motion of the transmitter and c is the speed of propagation of radio signals;
- v) the measured carrier frequencies f-i, f 2 , f 3 , of the signals received at the base stations Bi, B 2 , B 3 , B 4 respectively are related to the maximum Doppler shift by:
- f ⁇ fo + fdF ⁇ ( ⁇ , ⁇ , ⁇ , ⁇ , ⁇ ) (7)
- f 2 f c + fdF 2 ( ⁇ , ⁇ , ⁇ , ⁇ , ⁇ ) (8)
- f 3 fc + fdF 3 ( ⁇ , ⁇ , ⁇ , ⁇ , ⁇ ) (9)
- f 4 f c + f d F 4 ( ⁇ , ⁇ , ⁇ , ⁇ , ⁇ ) (10)
- ⁇ is the angle between the direction of travel of the transmitter T and the line joining the first base station Bi and the transmitter T, and ⁇ is the angle between the direction of travel of the transmitter T and the line joining the first base station B 2 and the transmitter T; vi) , ⁇ and fd are determined by solving equations 7, 8, 9 and 10, where fi, f 2 , f 3 , , ⁇ , ⁇ and ⁇ are known; and vii) the speed of the transmitter T is determined by substituting f d in equation (1 ), and ⁇ and ⁇ give direction of travel relative to the lines Bi - T and B 2 - T.
- measurements at more than four receivers can be used to provide an over-determined solution to reduce or eliminate the effects of ambiguity and/or random measurement errors.
- the present invention comprises a method of determining a frequency error in a signal received by a direct sequence spread- spectrum communications receiver, the method comprising: mixing a received signal to an intermediate frequency signal; successively making a plurality of samples of the intermediate frequency signal over predetermined measurement periods of time to produce a plurality of sample points for each measurement period; processing the sample points from each measurement period to produce a contiguous set of complex correlograms; from the set of complex correlograms, determining a set of target points amongst the complex points in the correlogram which best represent the received signal, (typically the position of peaks or the leading edges of those peaks (target points) in a composite correlogram); monitoring the phase angle of the corresponding target points in successive complex correlograms to determine a sequence of phase changes (rotations) in the received signal; determining the mean rate of change of phase of the target points, and
- the frequency error is preferably used to compensate the mixing frequency to match the received frequency and thereby achieve an intermediate frequency signal closely matched to the intended intermediate frequency of the receiver.
- the intermediate frequency signal is sampled at a frequency fs equal to the chip rate fc times number of samples n s per predetermined measurement period t s divided by the product of the spreading code length Nc and the number of spreading code cycles Cs per predetermined measurement period ts
- the number of samples n s per predetermined measurement period t s is a power of 2 selected to give a sampling frequency greater than or equal to the Nyquist Rate, and where the predetermined measurement periods have a period length ts which is a period over which coherence is generally assured and ts is an integer number of spreading code cycle periods.
- the intermediate frequency signal is sampled at approximately 4MHz over successive approximately 4 msec periods to produce sets of 16384 complex samples. These sample sets undergo processing to produce the correlograms for each respective period.
- the generated correlograms are complex, but in general only the magnitude is considered to determine the index (time offset) of the set of points which best represent the received signal (usually the peaks in the correlograms). This time offset (determined as an average or other suitable function over the complete set of sample correlograms) is used as a measure of time of arrival of the signal for position determination.
- the effect of any frequency error in the received signal is to induce a rotation in the phase of the peak values of the correlograms.
- the rate of rotation and hence the frequency error in the original signal can be estimated.
- the present invention comprises a method of improving the signal to noise ratio of a spread-spectrum receiver by reducing the effects of random noise and noise due to multi-path reception, the method comprising: mixing a received signal to an intermediate frequency signal; successively making a plurality of samples of the intermediate frequency signal over predetermined periods of time to produce a plurality of sample points for each period; processing the sample points from each period to produce a succession of complex correlograms; monitoring the phase of the peak values in successive correlograms to determine a rate of phase rotation of the received signal; determining from the rate of rotation of the received signal the frequency error of the received signal relative to the nominal or expected frequency of the signal; reprocessing the signal with compensation for the determined frequency error to modify the correlograms such that the phase of the signal peaks in successive correlograms is aligned; and performing a complex accumulation of the correlograms to provide some amount of cancellation of noise due to its randomly distributed phase.
- the intermediate frequency signal is sampled at a frequency fs equal to the chip rate fc times number of samples ns per predetermined measurement period ts divided by the product of the spreading code length Nc and the number of spreading code cycles Cs per predetermined measurement period ts
- the number of samples ns per predetermined measurement period ts is a power of 2 selected to give a sampling frequency greater than or equal to the Nyquist Rate, and where the predetermined measurement periods have a period length t s which is a period over which coherence is generally assured and ts is an integer number of spreading code cycle periods.
- the intermediate frequency signal is sampled at approximately 4MHz over successive approximately 4 msec periods to produce sets of 16384 sample points. These sample sets undergo processing to produce the complex correlograms for each respective period.
- the effect of any frequency error in the received signal is to induce a rotation in the phase of the peak value(s) of the correlograms.
- Usual signal processing utilises accumulation (or averaging) of successive correlograms in order to improve the signal to noise ratio. Because of the inherent phase rotation of correlogram data, this processing is done using magnitude information only (incoherent accumulation). The effect of taking the correlogram magnitude is to rotate all data (noise plus signal) into a common plane and thus both noise and signal magnitude become linearly additive in the accumulation process. A net SNR improvement is achieved because the noise magnitude at any point in the correlograms varies randomly in amplitude with successive correlograms whereas the signal amplitude is generally large and constant.
- the normal signal processed in the receive site comprises the direct path signal plus a number of reflected signals.
- reflected signals must, by definition, have taken a different path they will exhibit different Doppler frequency shifts if the transmitter and/or the reflecting body is in motion.
- the received correlogram is de-rotated to align the phase of the primary (direct path) signal
- the multipath signals may be rotated out of the primary signal plane, resulting in a decrease in observed multi-path amplitude when correlograms are accumulated.
- the present invention comprises a method of determining the angle of arrival of a signal, the method comprising: mixing the received signals from two spaced antennas at a single receiver site to intermediate frequency signals; successively making a plurality of samples of the intermediate frequency signals over predetermined periods of time to produce a plurality of complex sample points for each period for each of the signals; processing the complex sample points from each period to produce a succession of correlograms for each of the two signals; comparing the phases of the peak values of the correlograms of the two signals; determining from the difference in phase between the two signals the difference in time of arrival of the two signals and hence, from the geometry of the location of the two antennas, the angle of arrival of the signal from the transmitter.
- the rate of phase rotation between successive correlogram measurements was determined in order to estimate the transmission frequency error.
- the phase difference between correlograms calculated for each measurement represents the difference in path length of the signal from transmitter to antenna. Differential path length measurement allows calculation of the angle of arrival of the transmission relative to the antenna baseline.
- the present invention provides a method of determining a frequency error between two signals received by a spread-spectrum communications receiver from two transmitters separated in distance from each other, the method comprising: mixing each received signal to an intermediate frequency signal; successively making a plurality of samples of the intermediate frequency signals over predetermined measurement periods of time to produce a plurality of sample points for each measurement period; processing the sample points from each measurement period to produce a contiguous set of complex correlograms; from the set of complex correlograms, determining a set of target points amongst the complex points in each correlogram which best represent the received signals; monitoring the phase angle of the corresponding target points in successive complex correlograms of each received signal to determine a sequence of phase changes in the received signals relative to each other; determining the mean rate of change of phase of the target points, and translating the mean rate of change of phase to a frequency representing the frequency error of one of the received signals relative to the other received signal; and using the frequency error information to synchronise to the received signals.
- Figure 1 generally illustrates a vehicle tracking system in which the improvements to a communication system according to the present invention might be used; and Figure 2 is a diagram showing the trigonometry used to calculate a speed and direction of a moving transmitter from frequency shifts in received signals.
- FIG. 3 is a block diagram illustrating the receiver processing used in the preferred embodiment.
- the receiver extracts information transmitted by cross-correlating the incoming composite stream with the spreading code associated with the transmission.
- the spread-spectrum signal is folded (condensed) into a small number of adjacent points in the correlogram whilst all other non-matching signals (generally noise) remain spread across the whole correlogram.
- the value of the cross-correlation between the incoming signal and the noise-free version of the spreading code as a function of relative time delay (epoch) over one complete cycle of the spreading code is termed the correlogram.
- the transmitter on 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 well-spaced 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.
- Inverse hyperbolic navigation techniques then may be used to compute the position of the transmitter at the central computer 13 which then sends this information to an operator terminal.
- the spreading code is a 511 bit, maximal length pseudo-random binary sequence (PRBS) and is clocked at a rate of 1 Mbit sec. In this case there is one complete cycle of the spreading code every 511 microsecs.
- PRBS maximal length pseudo-random binary sequence
- Embodiments of the present invention use a novel technique to estimate the carrier frequency f , / 2 , f 3 on transmitter transmissions received at a receiver site 12. Generally this frequency will be in error compared to its nominal value due to:
- the technique employed to estimate frequency error involves estimating the phase angle rotation in the peaks of the successive complex correlograms used to generate time-of-arrival data at a site. As a side benefit, once this phase rotation is known, the rotation may be removed from the original data, leading to improvements in the correlogram signal to noise ratio and hence improved tracking accuracy.
- the same technique may be used to measure the carrier phase difference between a signal received at diverse receive antennas, allowing for the calculation of the angle of arrival of the direct-path signal and hence the direction vector of the transmitter relative to the antenna baseline.
- the receive site signal processing assumes that the transmitter is transmitting on the correct frequency and mixes the received signal to an intermediate frequency (IF) signal appropriately.
- the IF is sampled at approximately 4MHz over approximately 4 msec periods to produce sample sets of 16384 complex points.
- This sample set undergoes processing to produce a correlogram.
- This processing comprises taking the Fourier Transform of the sample sets, multiplying the resulting complex frequency spectrum by a template comprising the complex conjugate of the Fourier Transform of the expected signal (with zero frequency error and known reference epoch), and then taking the inverse Fourier Transform of the result. (This process is illustrated in figure 3.)
- all operations following analog to digital conversion may be performed in a general purpose computer processing apparatus.
- the generated correlogram contains complex correlation values, but in general only the magnitude of these values is considered to determine the epoch (peak position) of the signal, which is used for position fitting.
- the effect of any frequency error in the received signal is to induce a rotation, or progressive variation in the phase, of the complex correlogram samples.
- the mean rate of phase rotation and hence the frequency error in the received signal may be estimated.
- the transmission frequency error measured at each receive site comprises a fixed error due to frequency offsets in the transmitter, plus a random measurement error plus the error due to Doppler shift of the frequency due to the component of the transmitter velocity vector in the direction of the receiving site.
- the common frequency error may be estimated given the transmitter and receive site locations and the observed frequency error at 3 or more receive sites. Once the common component is removed, the remaining residual errors may be used to calculate the relative motion between the transmitter and the receive sites. Measurements at more than 3 sites can be used to provide an over-determined solution to reduce or eliminate the effect of ambiguities and/or random measurement error.
- the effect of taking the correlogram magnitude is to rotate all data (noise plus signal) into a common plane and thus both noise and signal become additive in the accumulation process.
- a net signal-to-noise ratio improvement is achieved because the noise magnitude is random in amplitude whereas the signal amplitude is generally large and constant.
- the normal signal processed in the remote site comprises the direct path signal plus a number of reflected signals.
- reflected signals must, by definition, have taken a different path they will exhibit different Doppler frequency shifts if the transmitter and/or the reflecting body is in motion.
- the received correlogram is de-rotated to align the phase of the primary (direct path) signal
- the phase of the multipath signals will typically exhibit phase rotation.
- the coherent accumulation of such phase rotating multipath signals will typically exhibit constructive and destructive accumulation and therefore not increase linearly with each accumulation step. This results in a decrease in observed multi-path amplitude when complex correlograms are accumulated.
- the rate of phase rotation between successive correlogram measurements was determined in order to estimate the transmission frequency error.
- the (carrier) phase difference between signal peaks in corresponding correlograms represents the difference(s) in path length of the common signal from its transmitter to each antenna. Differential path length measurement allows calculation of the angle of arrival of the transmission relative to the antenna baseline.
- the transmitter T is located such that the angle subtended between the line drawn from the first base station Bi and the transmitter T and the second base station B 2 and the transmitter T is ⁇ , and the angle subtended between the line drawn from the first base station Bi and the transmitter T and the third base station B 3 and the transmitter T is ⁇ ;
- the carrier frequency of the transmitted signal is f c;
- the maximum Doppler shift due to motion of the transmitter is;
- v is the speed of the vehicle and c is the speed of propagation of radio signals;
- v) the measured carrier frequencies f-i, f 2 , f 3 of the signals received at the base stations B-i, B 2 , B 3 respectively are related to the maximum Doppler shift by:
- ⁇ is the angle between the direction of travel of the transmitter T and the line joining the first base station Bi and the transmitter T;
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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
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP02752893A EP1428037A1 (fr) | 2001-08-13 | 2002-08-13 | Systemes de suivi ameliores |
KR10-2004-7002191A KR20040019407A (ko) | 2001-08-13 | 2002-08-13 | 추적 시스템 개선 방법 |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AUPR6971A AUPR697101A0 (en) | 2001-08-13 | 2001-08-13 | Improvements to tracking systems |
AUPR6971 | 2001-08-13 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2003016937A1 true WO2003016937A1 (fr) | 2003-02-27 |
Family
ID=3830927
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/AU2002/001094 WO2003016937A1 (fr) | 2001-08-13 | 2002-08-13 | Systemes de suivi ameliores |
Country Status (5)
Country | Link |
---|---|
EP (1) | EP1428037A1 (fr) |
KR (1) | KR20040019407A (fr) |
CN (1) | CN1541338A (fr) |
AU (1) | AUPR697101A0 (fr) |
WO (1) | WO2003016937A1 (fr) |
Cited By (14)
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WO2004086078A1 (fr) * | 2003-03-28 | 2004-10-07 | Commonwealth Scientific And Industrial Research Organisation | Dispositif et procede de determination d'un epoque au moyen d'un signal desetale de spectre etale |
EP1868304A1 (fr) * | 2005-03-31 | 2007-12-19 | NEC Corporation | Terminal radio mobile et son procédé de détection de vitesse de déplacement |
US7667647B2 (en) | 1999-03-05 | 2010-02-23 | Era Systems Corporation | Extension of aircraft tracking and positive identification from movement areas into non-movement areas |
US7739167B2 (en) | 1999-03-05 | 2010-06-15 | Era Systems Corporation | Automated management of airport revenues |
US7777675B2 (en) | 1999-03-05 | 2010-08-17 | Era Systems Corporation | Deployable passive broadband aircraft tracking |
US7782256B2 (en) | 1999-03-05 | 2010-08-24 | Era Systems Corporation | Enhanced passive coherent location techniques to track and identify UAVs, UCAVs, MAVs, and other objects |
US7889133B2 (en) | 1999-03-05 | 2011-02-15 | Itt Manufacturing Enterprises, Inc. | Multilateration enhancements for noise and operations management |
US7908077B2 (en) | 2003-06-10 | 2011-03-15 | Itt Manufacturing Enterprises, Inc. | Land use compatibility planning software |
EP2307905A1 (fr) * | 2008-07-08 | 2011-04-13 | Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung | Procédé et dispositif de détermination de la position changeante d'un émetteur mobile |
US7965227B2 (en) | 2006-05-08 | 2011-06-21 | Era Systems, Inc. | Aircraft tracking using low cost tagging as a discriminator |
US8072382B2 (en) | 1999-03-05 | 2011-12-06 | Sra International, Inc. | Method and apparatus for ADS-B validation, active and passive multilateration, and elliptical surveillance |
US8203486B1 (en) | 1999-03-05 | 2012-06-19 | Omnipol A.S. | Transmitter independent techniques to extend the performance of passive coherent location |
US8446321B2 (en) | 1999-03-05 | 2013-05-21 | Omnipol A.S. | Deployable intelligence and tracking system for homeland security and search and rescue |
DE102015221836A1 (de) * | 2015-11-06 | 2017-05-11 | Pepperl + Fuchs Gmbh | Fördereinrichtung |
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KR101785113B1 (ko) | 2011-03-08 | 2017-10-13 | 엘에스산전 주식회사 | 측위 시스템 및 위치 측정 방법 |
CN102768309B (zh) * | 2012-08-02 | 2014-08-20 | 西北工业大学 | 采用频率差分技术消减天线测试环境中多径干扰的方法 |
CN102768310B (zh) * | 2012-08-02 | 2014-09-03 | 西北工业大学 | 采用距离偏移技术消减天线测试环境中多径干扰的方法 |
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CN105572659A (zh) * | 2014-08-27 | 2016-05-11 | 美国频顺通讯科技公司 | 使用射频信号确定对象距离 |
DE102015121724A1 (de) * | 2015-12-14 | 2017-06-14 | Symeo Gmbh | System und Verfahren mit zumindest drei Signale empfangenden Stationen |
CN112327252B (zh) * | 2020-10-12 | 2022-07-15 | 中国海洋大学 | 一种基于多扬声器和多麦克风声波多目标追踪方法 |
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- 2001-08-13 AU AUPR6971A patent/AUPR697101A0/en not_active Abandoned
-
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- 2002-08-13 KR KR10-2004-7002191A patent/KR20040019407A/ko not_active Application Discontinuation
- 2002-08-13 EP EP02752893A patent/EP1428037A1/fr not_active Withdrawn
- 2002-08-13 CN CNA028159322A patent/CN1541338A/zh active Pending
- 2002-08-13 WO PCT/AU2002/001094 patent/WO2003016937A1/fr not_active Application Discontinuation
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Also Published As
Publication number | Publication date |
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EP1428037A1 (fr) | 2004-06-16 |
AUPR697101A0 (en) | 2001-09-06 |
CN1541338A (zh) | 2004-10-27 |
KR20040019407A (ko) | 2004-03-05 |
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