WO2019001415A1 - 一种可替代传统无线电导航***的大区域高精度定位方法 - Google Patents
一种可替代传统无线电导航***的大区域高精度定位方法 Download PDFInfo
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- WO2019001415A1 WO2019001415A1 PCT/CN2018/092823 CN2018092823W WO2019001415A1 WO 2019001415 A1 WO2019001415 A1 WO 2019001415A1 CN 2018092823 W CN2018092823 W CN 2018092823W WO 2019001415 A1 WO2019001415 A1 WO 2019001415A1
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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
- G01S5/0009—Transmission of position information to remote stations
- G01S5/0045—Transmission from base station to mobile station
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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
- G01S5/0009—Transmission of position information to remote stations
- G01S5/009—Transmission of differential positioning data to mobile
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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
- G01S5/14—Determining absolute distances from a plurality of spaced points of known location
- G01S5/145—Using a supplementary range measurement, e.g. based on pseudo-range measurements
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W56/00—Synchronisation arrangements
- H04W56/001—Synchronization between nodes
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W64/00—Locating users or terminals or network equipment for network management purposes, e.g. mobility management
- H04W64/003—Locating users or terminals or network equipment for network management purposes, e.g. mobility management locating network equipment
Definitions
- the invention relates to the field of radio positioning.
- a new high-precision radio positioning method which can replace most radio navigation systems is proposed.
- radio navigation technology has formed a relatively complete theoretical system and a very wide range of applications.
- the existing radio navigation systems mainly include compass, Volt (VOR), range finder (DME), Tacom (TACAN), Roland (LORAN-C), satellite navigation system and its augmentation system.
- the radio compass system uses the amplitude zero point of the 8-shaped directional antenna to automatically track the base station for direction finding, which is a single-station direction and multi-station positioning layout.
- the base station transmits power several hundred watts to kilowatts.
- the signal frequency is 100-1800kHz and the coverage is 250-350km.
- the direction finding accuracy is 2°, so that the position deviation is 3489.95m at 100Km; the position deviation is 348.99m at 10Km.
- Unlimited capacity and weak anti-interference ability is possible to be used to calculate the base station for direction finding.
- the Volta system uses antenna rotation to establish the correspondence between signal phase and azimuth, and measures the azimuth of the aircraft by measuring the phase.
- the VOR power of the route is 100-200w, and the terminal VOR is 50w. To automatically track the measurement method.
- the operating frequency is 108-117.95MHz.
- the route VOR coverage is 200nmile and the terminal VOR is 25nmile.
- the normal VOR accuracy is 2°-3°, and the Doppler VOR accuracy is less than 1° (at 100Km, the position deviation is 174.52m; at 10Km, the position deviation is 17.45m).
- the capacity is infinite, the ordinary Voller has strong anti-interference performance, and the Doppler Volt is strong.
- the characteristic is that the precision is general, slightly better than the compass system, and the anti-interference performance is strong.
- the response ranging system measures the distance from the aircraft to the ground station by measuring the round-trip propagation time of the signal (pulse) from the aircraft to the ground station, adopting the single station layout ranging and multi-station layout positioning.
- the power of the terminal station is 100w, and the power of the route station is 1Kw.
- the ranging method of inquiry-response is adopted.
- the inquiry frequency is 1025-1150MHz, and the response frequency is 962-1213MHz.
- the DME station coverage is greater than 200nmile, the terminal DME station is greater than 60nmile, and the precision DME (landing station) is greater than 22nmile.
- the accuracy of ordinary DME is less than 370m, and the standard 1 and standard 2 are less than 30m and 12m respectively. Limited capacity, up to 100 aircraft. Anti-interference ability is general.
- the characteristics are high power, low update rate, high precision and limited capacity.
- Tacom is a composite radio navigation system consisting of DME and improved VOR.
- the improved VOR improves the resolution of the azimuth by increasing the measurement of the smaller phase change period.
- the layout mode is single station layout, DME ranging, VOR direction finding, and joint polar coordinate positioning.
- the power of the mobile station is greater than 500w, and the power of the fixed station is 3000w.
- the direction finding is automatic tracking, and the ranging uses a query-response method.
- the operating frequency is 963-1213MHz.
- the coverage of the fixed platform is 350-370Km
- the mobile station is 185km
- the headspace has a cone-shaped signal dead zone of 90° ⁇ 30°.
- the actual accuracy of the direction finding is 0.5° (the position deviation is 872.65m at 100Km; the position deviation is 87.27m at 10Km), and the ranging accuracy can reach 0.1km.
- the azimuth measurement capacity is unlimited, and the distance measurement capacity is 110.
- Anti-interference ability DME is generally, VOR is strong.
- the layout method consists of a plurality of adjacent launching stations forming a positioning platform chain, and also includes a work area monitoring station and a chain control center.
- the power is 165-1800 KW, and the positioning rate is 10-20 times/min.
- the working frequency is 100KHz and the coverage is 600-1500 nautical miles.
- the positioning accuracy of the near zone is 460m (0.25n mile), the far zone is 1.2nmile, and the relative positioning accuracy is 18-90m. Unlimited capacity and strong anti-interference ability.
- the satellite navigation system achieves positioning by multi-star pseudo-code correlation peak ranging or carrier phase ranging.
- a plurality of satellites form a navigation constellation covering the whole world; the ground monitoring station ensures the constellation operation.
- the transmitting power of GPS is 478.63w, and the update rate can reach 50Hz.
- the operating frequency is L1:1575.42MHz; L2: 1227.60MHz; L5: 1176.45MHz. Coverage is global and part of space.
- Positioning accuracy P code 10m (50%); C / A code: 20m (50%); carrier phase positioning accuracy: cm level (but need to be differential, there is full-circumference ambiguity). Unlimited capacity.
- the Wide Area Augmentation System is a GPS satellite-based augmentation system.
- the GPS signals are monitored and evaluated by a plurality of ground monitoring stations in a large area, and the positioning accuracy and availability of the navigation are improved by the difference, and the navigation risk is reduced by the integrity monitoring.
- the current radio navigation systems have their shortcomings or defects, and the main versatility problems include:
- the object of the present invention is to solve the above problems, and to provide a large-area high-precision positioning method which can replace the traditional radio navigation system.
- the positioning method of the invention has the characteristics of independence, large area and high precision, and can completely replace the compass, VOR, DME.
- the TACAN and LORAN-C systems can coexist with GPS, but the accuracy and anti-interference ability are superior to GPS. It can also be applied to indoor and outdoor continuous positioning without power background, and on this basis, a corresponding large-area indoor and outdoor continuous radio positioning system can be built.
- a large-area high-precision positioning method that can replace the traditional radio navigation system, including the following steps:
- Step 1 Based on the principle that each base station covers 300 km (radius), select a regional high point to establish a base station, and determine the geographical location of the base station;
- Step 2 Clock synchronization between base stations using atomic clock, fiber synchronization, time comparison or RTK technology
- Step 3 Determine a radio navigation signal system, including selection of a carrier frequency and determination of a modulation mode, and each base station transmits a positioning signal;
- Step 4 The receiving terminal performs positioning solution according to the radio navigation signal transmitted by the base station, and the positioning terminal measurement method is a combination of pseudo-random code pseudo-range measurement and carrier phase pseudo-range measurement.
- the method of the present invention is intended to replace the systems of compass, VOR, DME, TACAN, LORAN-C, WAAS, etc., and the required base stations can be established at the original site (including the airport) of these system base stations, or newly built. It can coexist with GPS and meet the high-precision positioning requirements of most navigation users in a large area. If this goal is achieved, its obvious advantages are as follows:
- the alternative systems of the present invention include Compass, DME, VOR, TACAN, LORAN-C, WAAS, and the releasable frequency bands are 100-1800 kHz, 108-117.95 MHz, 1025-1150 MHz, 962-1213 MHz, and the like.
- the present invention occupies only a frequency range of less than 5 MHz, and frequency resources of other frequency bands can be released for other services.
- the navigation system can replace the compass, VOR, DME, TACAN, LORAN-C, WAAS and other systems, coexist with GPS, so the radio navigation device can be simplified to 2-3 units. Due to the wide coverage of the single system of the present invention, land-based stations can also be greatly reduced.
- the present invention does not use a WAAS-like enhancement technique, and uses only pseudo-code coarse measurement to determine the full-circumference ambiguity, and then performs accurate measurement by carrier phase ranging.
- the combination of the two enables high-precision distance measurement, and a single system can achieve an accuracy of about 1 meter.
- the GPS transmitting power is 478.63w. After more than 20,000 kilometers of propagation, the received signal is very weak (-166dbm), which has been annihilated by noise; the transmitting power of the present invention can be equivalent or even stronger than GPS, only After hundreds of kilometers to thousands of kilometers of propagation, the received signal is stronger and less susceptible to interference. Therefore, the anti-interference ability of the present invention is strong, and there is no vulnerability of GPS.
- the invention adopts pseudo-random code spread spectrum communication, and has high spread spectrum gain due to good self-correlation property of the signal, so that the system can receive weak signals with high sensitivity. Therefore, the signal propagation distance can be very long, up to several thousand km or more, and the coverage is wide.
- the invention comprehensively considers the propagation performance of electromagnetic waves in the outdoor space and the indoor building wall, the transmission performance of the electromagnetic wave at the interface, the positioning precision requirement and the hardware realization difficulty, etc., selects the low frequency carrier, can spread widely on the surface of the earth, and can be worn. Through the building. Therefore, continuous positioning of large areas indoors and outdoors can be realized.
- the high complexity of the GPS system is self-evident, and the present invention requires only four base stations to achieve a wide range of high-precision targets with greatly reduced complexity. Since the GPS system operates in space, the ground monitoring section cannot make absolutely accurate measurements of the satellite's orbit and clock drift, there will be star clock errors and ephemeris errors; the propagation to the ground receives opportunities to cross the atmosphere, with ionospheric and tropospheric errors. The base station of the system is on the ground, and the above error is avoided, so the accuracy is further improved.
- the present invention has the characteristics of simple system, wide coverage, high precision, and strong anti-interference ability.
- Figure 1 is a schematic diagram of a radio positioning method for large area positioning
- Figure 2 is a schematic diagram of the steps of implementing radiolocation in a large area
- FIG. 3 shows the signal generation and transmission block diagram
- FIG. 4 is a block diagram of the CPM modulator
- FIG. 6 is a block diagram of the CPM demodulator
- Figure 7 is a schematic diagram of base station layout and coverage capabilities
- Figure 8 is a comparison of power spectra of CPM modulation and BPSK, BOC modulation
- Fig. 9 is a schematic diagram of the solution of the full-circumference ambiguity of the carrier phase and the realization of high-precision ranging.
- Step 1 Select a geographical high point to establish a station according to the coverage of the base station, and determine the precise geographical location of the base station.
- the base station layout is planned based on the principle that each base station covers 300 kilometers (radius).
- the signal transmission base station is set up at the regional high point (or the original navigation station), and the base station needs to be guaranteed when it is set up.
- the user in the service area receives at least four signals from different base stations at the same time, and the linear distance between the base stations is several hundred kilometers to thousands of kilometers.
- the positioning network composed of each base station should make the DOP value of the service area as small as possible; after the base station is set up, it is necessary to know the exact geographical location of the base station, and the geographical coordinates can be obtained by prior calibration or by using GNSS differential technology;
- Step 2 The clock synchronization between the base stations is implemented by a precision atomic clock, or a time comparison technique or a differential technique of satellite navigation.
- the ground base station is mainly composed of two parts: a clock synchronization part and a signal generation transmission part.
- the reference frequency is provided by an atomic clock to ensure accuracy and stability.
- Fiber synchronization, time comparison techniques, or satellite navigation differential positioning techniques can also be employed to synchronize the clocks of the sources between the base stations.
- Step 3 Each base station transmits a positioning signal. Determine the radio navigation signal system suitable for large-area, indoor and outdoor continuous positioning, including the selection of carrier frequency and the determination of modulation mode.
- the radio positioning signal mainly includes a ranging code signal, a navigation message and a carrier signal, and the baseband signal is directly sequence-spread modulated by a ranging code signal (also called a spreading code) and a navigation message, and then modulated to a certain modulation mode. Select carrier.
- a ranging code signal also called a spreading code
- each base station transmits a signal on the same carrier frequency in the form of CDMA (Code Division Multiple Access).
- CDMA Code Division Multiple Access
- One of the 20 MHz-200 MHz bands is selected as the carrier frequency band of the radio navigation signal (with a bandwidth of 5 MHz or less).
- the selection of this frequency range takes into account the propagation properties of electromagnetic waves in large outdoor space and indoor building walls, the transmission performance of electromagnetic waves at the interface, the need for positioning accuracy, and the difficulty of hardware implementation.
- the radio signal of the present invention adopts a CPM (Continuous Phase Modulation) modulation method, and the modulation mode is selected to comprehensively consider the available bandwidth, the degree of attenuation of signal side lobes, and the like.
- CPM Continuous Phase Modulation
- the modulation mode is selected to comprehensively consider the available bandwidth, the degree of attenuation of signal side lobes, and the like.
- CPM signal power concentration is higher, sidelobe attenuation is faster, and out-of-band interference is smaller, so that the higher the signal-to-noise ratio is obtained, the adjacent frequency band is The signal interference is also small and can effectively save frequency resources.
- ⁇ is the signal symbol energy
- T is the symbol interval width
- f c is the carrier frequency
- ⁇ 0 is the initial phase.
- a time-varying phase function that represents modulated signal information.
- the system performs serial-to-parallel conversion (conversion to quaternary symbol I k );
- Step 4 The receiving terminal performs positioning solution according to the radio navigation signal transmitted by the base station, and the positioning terminal positioning method is a method combining pseudorange measurement of pseudorandom code and carrier phase pseudorange measurement.
- the receiving antenna receives the radio frequency signal, and is subjected to down-conversion filtering, and the A/D sampling is converted into a digital intermediate frequency signal, and the decoded pseudo-range and carrier pseudo-range information are captured and tracked, and the position information is calculated.
- the receiving block diagram of the signal is shown in Figure 5.
- bandpass filtering is performed on the intermediate frequency signal r(t) by the bandpass filter BPF to filter out-of-band noise;
- the filtered signals are separately frequency-divided by two orthogonal carrier frequencies, and then passed through the low-pass filter LPF to obtain two orthogonal low-pass signal components;
- the distance coarse test can provide support for the solution of the carrier phase full-circumference ambiguity, such as the condition of the chip length of 150 meters (pseudo-code rate 2MHz). The measurement accuracy of 1.5 to 3 meters can be achieved (0.01 to 0.02 chips).
- accurate measurement by carrier phase ranging If the carrier wavelength is 6 meters (carrier frequency is 50MHz), the carrier phase ranging accuracy will be better than 0.2m (about 3% wavelength), so that there is no whole
- the high-precision pseudo-range measurement of the ambiguity of the week or the ambiguity of the whole week is small and easy to solve), and then the high-precision positioning data is obtained.
- Figures 7, 8, and 9 are illustrations of some of the technical means involved in the present invention.
- the frequency band signal selected by the present invention propagates on the surface of the earth, and its attenuation is greatly reduced, so the coverage is greatly increased.
- the signal transmitting base station is set up on the ground high point. Under the condition that the user in the service area receives at least four positioning and navigation signals from different base stations at the same time, the linear distance between the base stations can reach several hundred kilometers to thousands of kilometers. .
- the radio navigation signal modulation method designed by the present invention is CPM modulation
- FIG. 8 is a comparison diagram of the MSK signal (one of the CPM signals) and the power spectrum of the BPSK signal and the BOC signal.
- the MSK signal (CPM signal) energy is more concentrated at the center frequency, and the sidelobe attenuation is faster, so it is more suitable for the carrier frequency is low, the available bandwidth is narrow, 20MHz- A band in the 200MHz range.
- the accuracy of the ranging is described by taking a pseudo-code rate of 2 MHz (chip length of 150 m) and a carrier wavelength of 6 m (carrier frequency of 50 MHz) as an example.
- the code phase pseudorange measurement is carried out, which can realize the coarse measurement accuracy of 1.5m, and solve the whole-circumference ambiguity of the carrier phase fine measurement; then, by the carrier phase measurement, the pseudo-range fine measurement of about 0.2m can be realized. Finally, the positioning accuracy of 1m is achieved.
- the invention transmits the radio navigation signal with strong penetration and wide coverage designed by the present invention through a plurality of ground high-altitude base stations in a large area, and each base station performs layout according to the preferred GDOP according to the target area, and the geographical coordinate position of the base station is known in advance. Or for accurate calibration, the time synchronization between the base stations is achieved by fiber synchronization, time comparison technology, satellite navigation differential technology or precision atomic clock.
- the indoor and outdoor integrated positioning terminal receives the radio navigation signal radiated by the plurality of base stations, and extracts the navigation message information, and finally calculates the high-precision positioning information of the terminal user by using the pseudo-code coarse ranging and the phase fine ranging of the radio signal. Specific technical innovations include:
- the system adopts a low frequency carrier of 100MHz.
- the signal propagates on the surface of the earth, and the propagation distance is farther than the high frequency signal.
- the signal of this frequency range greatly increases the penetration ability of the building wall and the floor, so the coverage of indoor and outdoor will be greatly increased. rise.
- the system adopts the way of stationing at the ground high point in the area.
- the precise location of the ground base station is known, the clock is an atomic clock, and the time reference is accurate.
- the satellite's ephemeris clock and ionospheric and tropospheric errors during atmospheric propagation are avoided.
- the invention selects reasonable transmission power, which can be several tens of watts, several hundred watts or even stronger, and only propagates through several hundred kilometers to thousands of kilometers (far less than the propagation distance of satellite navigation signals), and the received signal is strong and anti-interference ability. Strong.
- the invention adopts a pseudo-random code spread spectrum communication system, and has a high spread spectrum gain due to good self-correlation characteristics of the signal, and can receive weak signals with high sensitivity. Therefore, the signal has a long transmission distance and a wide coverage.
- the system uses pseudo-range coarse ranging to determine the full-circumference ambiguity; then accurate measurement by carrier phase ranging.
- the combination of the two enables high-precision distance measurement.
- the radio navigation signal modulation method designed by the invention is CPM modulation, the signal energy is more concentrated at the center frequency, and the side lobe attenuation is faster, thereby reducing the effective bandwidth of the signal.
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Abstract
一种可替代传统无线电导航***的大区域高精度定位方法,包括:步骤一,以每个基站覆盖300公里(半径)左右为原则,选择地域高点建立基站,确定基站的地理位置;步骤二,基站之间利用原子钟、光纤同步、时间比对或RTK技术进行时钟同步;步骤三,确定无线电导航信号体制,包括载波频率的选择以及调制方式的确定,各基站发射定位信号;步骤四,接收终端根据基站发射的无线电导航信号进行定位解算,定位终端测量方法为伪随机码的伪距测量和载波相位伪距测量相结合的方法。该方法拟替代罗盘、VOR、DME、TACAN、LORAN-C、WAAS等***,所需基站可以在这些***基站原址(包括机场)建立,或者新建。能够与GPS并存,在大区域内满足大多数导航用户的高精度定位需求。
Description
本发明涉及到无线电定位领域,在分析传统无线电导航***性能及优缺点的基础上,提出一种可替代大多数无线电导航***的大区域高精度无线电定位新方法。
无线电导航技术发展到今天,已经形成了较为完备的理论体系和非常广泛的应用领域。现有的无线电导航***主要有罗盘、伏尔(VOR)、测距器(DME)、塔康(TACAN)、罗兰(LORAN-C)、卫星导航***及其增强***等。
2001年,美国联邦无线电导航计划认为,随着GPS及其增强***的建成使用,其他的无线电导航服务将由于需求的降低而逐步减少。该计划预计现用的传统无线电导航***VOR、DME、TACAN和一类精密进近ILS等提供的导航服务将在2010年开始减少。但是在GPS及其广域增强***WAAS提供导航服务期间,暴露出卫星导航***的一些弱点,比如电离层闪烁(风暴)和无线电干扰等,这些弱点对卫星导航的服务性能产生了重大影响。
由于尚未克服卫星导航***的上述弱点,在2008年的美国联邦无线电导航计划中,不再将卫星导航服务作为唯一的航空导航手段,并对传统无线电导航服务计划进行了调整,其中DME和TACAN计划长期提供服务,而一类精密进近ILS将在2015年以后开始减少。
由于导航性能约束理念的改变,2014年的美国联邦无线电导航计划进一步调整了,其中VOR将在2020年缩减站点以维持最基本的工作网络,DME将进一步扩展以支持RNAV。此外,WAAS将从GPSL2切换到GPSL5,从而提高LPV服务的可用率。同时,FAA将继续开展局域增强***LAAS提供二类和三类精密进近服务的研究。
虽然无线电导航***还将继续提供服务,但在应用中有其固有的缺陷或问题,下面对传统的无线电导航***的技术特点分析如下:
一、罗盘测向***
无线电罗盘***利用8字形方向性天线的振幅零值点自动跟踪基站进行测向,为单站测 向、多站定位的布局方式,基站发射功率几百瓦到上千瓦。信号频率在100-1800kHz,覆盖范围达250-350km。测向精度2°,这样在100Km处,位置偏差达3489.95m;在10Km处,位置偏差达348.99m。容量无限,抗干扰能力较弱。
特点是大功率发射,测向精度低,定位精度更低。
二、伏尔(VOR)
伏尔***利用天线旋转,建立信号相位与方位的对应关系,通过测量相位实现对飞机方位的测量。采用单站布局测方位,多站布局定位。航路VOR功率为100-200w,终端VOR为50w。为自动跟踪测量方式。工作频率为108-117.95MHz。航路VOR覆盖范围为200nmile,终端VOR为25nmile。普通VOR精度为2°-3°,多普勒VOR精度小于1°(在100Km处,位置偏差达174.52m;在10Km处,位置偏差达17.45m)。容量无限,普通伏尔抗干扰性能较强,多普勒伏尔强。
特点是精度一般,略优于罗盘***,抗干扰性能较强。
三、测距器(DME)
应答测距***通过测量飞机到地面站的信号(脉冲)的往返传播时间,进行飞机到地面站距离的测量,采用单站布局测距,多站布局定位的方式。终端台功率100w,航路台功率1Kw。采用询问-应答的测距方式。询问频率1025-1150MHz,应答频率962-1213MHz。航路DME台覆盖范围大于200nmile,终端DME台大于60nmile,精密DME(着陆台)大于22nmile。普通DME精度小于370m,标准1、标准2分别小于30m、12m。容量有限,最多100架飞机左右。抗干扰能力一般。
特点是功率大,更新率低,精度一般,容量有限。
四、塔康(TACAN)
塔康是复合无线电导航***,由DME和改进的VOR组成,改进的VOR通过增加对更小的相位变化周期的测量,提高对方位的分辨率。布局方式为单站布局,DME测距,VOR测向,联合进行极坐标定位。机动台的功率大于500w,固定台的功率为3000w。测向为自动跟踪,测距采用询问-应答的方式。工作频率为963-1213MHz。固定台的覆盖范围在350-370Km,机动台为185km,顶空存在90°±30°的锥形信号盲区。测向实际精度0.5° (在100Km处,位置偏差达872.65m;在10Km处,位置偏差达87.27m),测距精度可达0.1km。方位测量容量无限,距离测量容量110架。抗干扰能力DME一般,VOR较强。
特点是大功率发射,***复杂,测量精度较高。
五、罗兰(LORAN-C)
罗兰C是复合无线电导航***,在进行脉冲测距差的同时,通过对脉冲载波相位的测量,实现对距离差的精测。布局方式为多个临近的发射台组成定位台链,还包括工作区监测站和台链控制中心。功率是165-1800KW,定位速率:10-20次/min。工作频率为100KHz,覆盖范围达600~1500海里。近区定位精度为460m(0.25n mile),远区1.2nmile,相对定位精度18-90m。容量无限,抗干扰能力较强。
特点是超大功率发射,定位精度低,更新率低,覆盖范围广。
六、卫星导航***
卫星导航***通过多星的伪码相关峰测距或载波相位测距,实现定位。多颗卫星组成导航星座,覆盖全球;地面测控站保障星座运行。GPS的发射功率为478.63w,更新率可达50Hz。工作频率为L1:1575.42MHz;L2:1227.60MHz;L5:1176.45MHz。覆盖范围为全球及部分太空。定位精度P码:10m(50%);C/A码:20m(50%);载波相位定位精度:cm级(但需差分,有整周模糊度)。容量无限。
特点是***复杂,覆盖全球,精度高(差分后更高),抗干扰能力弱,室内不行。
七、WAAS
广域增强***(WAAS)属于GPS星基增强***。利用在大区域内的多个地面监测站监测评估GPS信号,通过差分提高导航的定位精度和可用性,通过完好性监测降低导航的风险。
特点是精度和完好性较高,但需依赖于卫星导航***和GEO卫星才能工作。
由以上分析可知,目前的无线电导航***都有其不足或缺陷,存在的主要通用性问题包括:
(1)定位精度低(罗盘、VOR、DME、TACAN、LORAN-C);
(2)抗干扰能力弱(GPS、WAAS);
(3)以及发射功率大、覆盖范围小、***复杂、容量有限、不适用于室内等。
发明内容
本发明的目的是为了解决上述问题,提出一种可替代传统无线电导航***的大区域高精度定位方法,本发明定位方法具有独立、大区域和高精度的特点,能够完全替代罗盘、VOR、DME、TACAN、LORAN-C***,能够与GPS并存,但精度和抗干扰能力比GPS优越。也能够应用于无电力背景下的室内外连续定位,可以在此基础上建成相应的大区域室内外连续无线电定位***。
一种可替代传统无线电导航***的大区域高精度定位方法,包含以下几个步骤:
步骤一:以每个基站覆盖300公里(半径)左右为原则,选择地域高点建立基站,确定基站的地理位置;
步骤二:基站之间利用原子钟、光纤同步、时间比对或RTK技术进行时钟同步;
步骤三:确定无线电导航信号体制,包括载波频率的选择以及调制方式的确定,各基站发射定位信号;
步骤四:接收终端根据基站发射的无线电导航信号进行定位解算,定位终端测量方法为伪随机码的伪距测量和载波相位伪距测量相结合的方法。
本发明的优点在于:
本发明方法拟替代罗盘、VOR、DME、TACAN、LORAN-C、WAAS等***,所需基站可以在这些***基站原址(包括机场)建立,或者新建。能够与GPS并存,在大区域内满足大多数导航用户的高精度定位需求。如该目标得以实现,其明显的优势如下:
(1)释放大量频率资源。
选择20MHz-200MHz中的一个频段作为无线电导航信号的载波频段(宽度为5MHz以内)。根据定位精度分析,本发明可替代的***有罗盘、DME、VOR、TACAN、LORAN-C、WAAS,可释放的频段为100-1800kHz、108-117.95MHz、1025-1150MHz、962-1213MHz等。本发明仅占用一个小于5MHz的频率范围,其他频段的频率资源可以被释放,用于其它服务。
(2)简化大量无线电导航设备至2-3台,陆基台站可大大减少。
因为该导航***可替代罗盘、VOR、DME、TACAN、LORAN-C、WAAS等***,与GPS并存,所以无线电导航设备简化至2-3台即可。由于本发明单***的覆盖范围广,所以陆基台站也可以大大减少。
(3)不用任何增强技术,无整周模糊度,单***即可达到精度1m左右。
本发明不用类似WAAS的增强技术,仅使用伪码粗测确定整周模糊度,再以载波相位测距进行精确测量。二者结合实现高精度距离测量,单***即可达到1米左右的精度。
(4)抗干扰能力强,避免GPS脆弱性。
本发明与GPS相比:GPS发射功率478.63w,经过两万多千米的传播,导致接收信号十分微弱(-166dbm),已经被噪声湮没;本发明发射功率可与GPS相当甚至更强,只经过几百km至上千km的传播,接收信号更强,更不易受干扰。因此,本发明的抗干扰能力强,不存在GPS的脆弱性。
(5)覆盖范围广,接收灵敏度高。
本发明采用伪随机码扩频通信,由于信号良好的自相关特性,具有很高的扩频增益,使***可以高灵敏接收微弱信号。因此信号传播距离可以很远,最高可达到几千km以上,覆盖范围很广。
(6)兼顾室内外大区域定位。
本发明综合考虑了电磁波在室外空间和室内建筑墙体中的传播性能、电磁波在界面的透射性能、定位精度需求和硬件实现难度等,选择低频载波,可在地球表面大范围传播,以及可穿透建筑物。所以可实现室内外大区域连续定位。
(7)避免GPS***的高复杂性,并且不具有GPS大部分的定位误差(如星钟、星历、电离层、对流层)。
GPS***的高复杂性不言自明,而本发明仅需4个基站,即可实现大范围、高精度的目标,复杂性大大降低。由于GPS***在太空运行,地面监控部分不能对卫星的运行轨道和时钟漂移做绝对准确的测量,会有星钟误差和星历误差;传播到地面接收机会穿越大气层,有电离层和对流层误差。而本***基站在地面,避免了上述误差,因此精度进一步提高。
结论:
通过以上分析,可知本发明兼具了***简单、覆盖范围广、精度高、抗干扰能力强等特 点。
图1大区域定位的无线电定位方法示意图;
图2大区域无线电定位实现步骤示意图;
图3信号产生与发射框图;
图4 CPM调制器原理框图;
图5信号接收框图;
图6 CPM解调器原理框图;
图7基站布局与覆盖范围能力的示意图;
图8 CPM调制与BPSK、BOC调制的功率谱比较图;
图9载波相位整周模糊度的解算及高精度测距的实现示意图。
下面将结合附图和实施例对本发明作进一步的详细说明。进行大区域、室内外连续的高精度无线电定位,示意如图1所示,实现过程如图2所示,包含4个步骤:
步骤一:根据基站覆盖范围选择地域高点建站,确定基站的精确地理位置。
根据被服务区域大小及环境特征,以每个基站覆盖300公里(半径)左右为原则,规划基站布局,在地域高点(或原导航台站)架设信号发射基站,基站在架设时需保证被服务区域用户在同一时间内至少收到4个不同基站发出的信号,基站之间的直线距离为几百km至上千km。为保证定位精度,各基站组成的定位网络应使服务区域的DOP值尽量小;基站架设完成后,需知道基站准确的地理位置,其地理坐标可通过事先标定,或采用GNSS差分技术获取;
步骤二:基站之间的时钟同步,采用精密原子钟实现,或者采用时间比对技术或卫星导航的差分技术。
地面基站主要由两部分构成:时钟同步部分和信号产生发射部分。采用原子钟提供基准频率,以保证其精度和稳定性。也可以采用光纤同步、时间比对技术或卫星导航差分定位技术,以同步各基站间信号源的时钟。
步骤三:各基站发射定位信号。确定适用于大区域、室内外连续定位的无线电导航信号体制,包括载波频率的选择以及调制方式的确定。
1)信号的发射过程
无线电定位信号主要包括测距码信号、导航电文和载波信号,基带信号由测距码信号(又称扩频码)和导航电文进行直接序列扩频调制,然后再以一定的调制方式调制到所选载波上。因此各基站以CDMA(码分多址)的形式在相同的载波频率上发射信号。信号发射框图如图3。
2)频率的确定
选择20MHz-200MHz中的一个频段作为无线电导航信号的载波频段(带宽为5MHz以内)。选择该频率范围,是综合考虑了电磁波在室外大区域空间和室内建筑墙体中的传播性能、电磁波在界面的透射性能、定位精度的需求和硬件实现难度等。信号在地球表面障碍物、建筑墙体中的衰减公式为
其中ε″=ε,ε'=σ/ω,μ为磁导率、ε为墙体的介电常数、σ为电导率、ω为角频率,可以看出,该频率范围的信号相比500MHz-20GHz范围内的信号,无论在地球表面还是在建筑墙体内,其衰减会大大降低,因此其在室内外的覆盖范围会大幅上升。
3)调制方式
本发明的无线电信号采用CPM(ContinuousPhaseModulation)调制方式,选择该调制方式综合考虑了可用带宽、信号旁瓣的衰减程度等。相比于卫星导航的BPSK和BOC信号的调制频谱,CPM信号功率集中度更高、旁瓣衰减更迅速、对带外干扰更小,这样在得到较高的信噪比的同时,对邻近频带的信号干扰也较小,并且可有效节省频率资源。
CPM调制信号的波形表达式为
实现该表达式的调制器原理框图如图4所示。调制过程如下:
(1)制信息进行串并转换(转换为四进制码元I
k);
(3)再对相位值取余弦(cos)和正弦(sin),得到两路正交低频分量;
步骤四:接收终端根据基站发射的无线电导航信号进行定位解算,定位终端定位方法为伪随机码的伪距测量和载波相位伪距测量相结合的方法。
1)信号的接收过程
接收天线接收射频信号,经下变频滤波,A/D采样转化成数字中频信号,捕获、跟踪解算出码伪距和载波伪距信息,再计算出位置信息。信号的接收框图如图5所示。
2)CPM解调器原理图图6所示,解调器的解调步骤为:
(1)首先,由带通滤波器BPF对中频信号r(t)进行带通滤波以滤除带外噪声;
(2)然后,用两路正交载频分别对经滤波的信号进行差频,再经过低通滤波器LPF,就得到两路正交的低通信号分量;
(3)对两路正交低通信号分量进行“附加增量计算”,便可得到增量;
(4)对增量进行Viterbi译码,输出即为信息码元;
(5)最后,对信息码元进行串并转换,便可得到所需要的信息比特流。
3)定位数据解算
首先,采用伪随机码测距,除了可以得到扩频增益外,进行距离粗测可为载波相位整周模糊度的解算提供支持,如在码片长度150米(伪码速率2MHz)的条件下能实现1.5~3米的测距精度(0.01~0.02码片)。其次,再以载波相位测距进行精确测量,如载波波长为6米(载波频率为50MHz)时,载波相位测距精度会优于0.2m(约3%波长),这样就可以 实现不存在整周模糊度(或整周模糊度很小易解算)的高精度的伪距测量,进而得到高精度的定位数据。
其中,图7、8、9均是对本发明涉及的某些技术手段进行的图解说明。
1.如图7所示:
本发明选择的频段信号,在地球表面传播,其衰减会大大降低,因此覆盖范围会大幅上升。在地面高点架设信号发射基站,在保证被服务区域内用户在同一时间内至少收到4个不同基站发出的定位导航信号的条件下,基站之间的直线距离可达几百km至上千km。
2.如图8所示:
本发明设计的无线电导航信号调制方式为CPM调制,图8为MSK信号(CPM信号的一种)与BPSK信号、BOC信号功率谱的对比图。从图中可看出,相比于BPSK信号和BOC信号,MSK信号(CPM信号)能量更集中于中心频率处,旁瓣衰减更快,因此更适合于载波频率低、可用带宽窄、20MHz-200MHz范围中的某个频段。
3.如图9所示:
以2MHz的伪码速率(码片长度150米)和6m的载波波长(载波频率为50MHz)为例,进行测距精度的说明。首先进行码相位伪距测量,可实现1.5m的粗测精度,解决载波相位精测时的整周模糊度;然后通过载波相位测量,可实现约0.2m的伪距精测。最终实现1m的定位精度。
总结说明
本发明通过大区域多个地面高点基站发射本发明设计的穿透力强、覆盖范围广的无线电导航信号,各基站根据目标区域按照较优的GDOP进行布局,基站的地理坐标位置事先已知或进行精确标定,各基站之间的时间同步采用光纤同步、时间比对技术、卫星导航的差分技术或精密原子钟实现。室内外一体定位终端通过接收多个基站辐射的无线电导航信号,进行导航电文信息提取,通过对无线电信号的伪码粗测距和相位精测距,最终解算出终端用户的高精度定位信息。具体的技术创新点包括:
(1)采用低频载波
***采用100MHz上下的低频载波,信号在地球表面传播,传播距离比高频信号远;该频率范围的信号对建筑墙体及楼板的穿透能力大大增加,因此其在室内外的覆盖范围会大幅上升。
(2)地面布站
根据基站的覆盖范围(300公里左右),***采用在区域内地面高点布站的方式,地面基站的精确位置已知,时钟是原子钟,时间基准精确。避免了卫星的星历星钟和大气传播过程中的电离层和对流层误差。
(3)采用合理发射功率
本发明选用合理的发射功率,可为几十瓦、几百瓦甚至更强,只经过几百km至上千km的传播(远小于卫星导航信号的传播距离),接收的信号强壮、抗干扰能力强。
(4)采用伪随机码体制
本发明采用伪随机码扩频通信体制,由于信号良好的自相关特性,具有很高的扩频增益,可以高灵敏接收微弱信号。因此信号传播距离远,覆盖范围广。
(5)采用伪码加载波相位的混合测距方式
本***采用伪距粗测距,确定整周模糊度;再以载波相位测距进行精确测量。二者结合实现高精度的距离测量。
(6)采用CPM调制
本发明设计的无线电导航信号调制方式为CPM调制,信号能量更集中于中心频率处,旁瓣衰减更快,因此降低了信号有效带宽。
Claims (2)
- 一种可替代传统无线电导航***的大区域高精度定位方法,包含以下几个步骤:步骤一:根据基站覆盖范围选择地域高点建站,确定基站的精确地理位置;根据被服务区域大小及环境特征,以每个基站覆盖300公里(半径)左右为原则,规划基站布局,在地域高点(或原导航台站)架设信号发射基站,基站在架设时需保证被服务区域用户在同一时间内至少收到4个不同基站发出的信号,基站之间的直线距离为几百km至上千km。为保证定位精度,各基站组成的定位网络应使服务区域的DOP值尽量小;基站架设完成后,需知道基站准确的地理位置,其地理坐标可通过事先标定,或采用GNSS差分技术获取;步骤二:基站之间进行时钟同步,采用精密原子钟实现,或者采用时间比对技术或卫星导航的差分技术;地面基站主要由两部分构成:时钟同步部分和信号产生发射部分。采用原子钟提供基准频率,以保证其精度和稳定性。也可以采用光纤同步、时间比对技术或卫星导航差分定位技术,以同步各基站间信号源的时钟。步骤三:确定无线电导航信号体制,包括载波频率的选择以及调制方式的确定,各基站发射定位信号;(1)确定频率无线电导航信号的载波频段为20MHz-200MHz,带宽小于等于5MHz;(2)调制方式本发明的无线电信号采用CPM(ContinuousPhaseModulation)调制方式,选择该调制方式综合考虑了可用带宽、信号旁瓣的衰减程度等。相比于卫星导航的BPSK和BOC信号的调制频谱,CPM信号功率集中度更高、旁瓣衰减更迅速、对带外干扰更小,这样在得到较高的信噪比的同时,对邻近频带的信号干扰也较小,并且可有效节省频率资源。步骤四:接收终端根据基站发射的无线电导航信号进行定位解算,定位终端测量方法为伪随机码的伪距测量和载波相位伪距测量相结合的方法;(1)CPM解调器的解调步骤为:中频信号通过带通滤波器滤除带外噪声,再用两路正交载频对滤波的信号进行差频,然后译码出信息码元,最后进行串并转换,得到信息比特流。(2)定位数据解算首先,采用伪码测距进行距离粗测;其次,再以载波相位测距进行精确测量,最终得到高精度的定位数据。
- 本发明通过大区域多个地面高点基站发射本发明设计的穿透力强、覆盖范围广的无线电导航信号,各基站根据目标区域按照较优的GDOP进行布局,基站的地理坐标位置事先已知或进行精确标定,各基站之间的时间同步采用光纤同步、时间比对技术、卫星导航的差分技术或精密原子钟实现。室内外一体定位终端通过接收多个基站辐射的无线电导航信号,进行导航电文信息提取,通过对无线电信号的伪码粗测距和相位精测距,最终解算出终端用户的高精度定位信息。具体的技术创新点包括:(1)采用低频载波***采用100MHz上下的低频载波,信号在地球表面传播,传播距离比高频信号远;该频率范围的信号对建筑墙体及楼板的穿透能力大大增加,因此其在室内外的覆盖范围会大幅上升。(2)地面布站根据基站的覆盖范围(300公里左右),***采用在区域内地面高点布站的方式,地面基站的精确位置已知,时钟是原子钟,时间基准精确。避免了卫星的星历星钟和大气传播过程中的电离层和对流层误差。(3)采用合理发射功率本发明选用合理的发射功率,可为几十瓦、几百瓦甚至更强,只经过几百km至上千km的传播(远小于卫星导航信号的传播距离),接收的信号强壮、抗干扰能力强。(4)采用伪随机码体制本发明采用伪随机码扩频通信体制,由于信号良好的自相关特性,具有很高的扩频增益,可以高灵敏接收微弱信号。因此信号传播距离远,覆盖范围广。(5)采用伪码加载波相位的混合测距方式本***采用伪距粗测距,确定整周模糊度;再以载波相位测距进行精确测量。二者结合实现高精度的距离测量。(6)采用CPM调制本发明设计的无线电导航信号调制方式为CPM调制,信号能量更集中于中心频率处,旁瓣衰减更快,因此降低了信号有效带宽。
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