KR102424784B1 - eLORAN receiver system to minimize a receiving time delay in an eLORAN system - Google Patents

Abstract

An eLORAN receiver system for minimizing a reception time delay in an eLORAN system is disclosed. The eLORAN receiver system for minimizing the reception time delay in the eLORAN system, wherein the eLORAN system includes a control station, a dLORAN reference station, and a plurality of eLORAN transmission stations, comprises: a plurality of eLORAN transmission stations connected to the control station and having eLORAN transmitters; and eLORAN receivers receiving eLORAN signals including position, navigation and timing (PNT) information transmitted in all directions from m eLORAN transmitters. In the eLORAN receiver, an omnidirectional antenna is used so as to minimize the reception time delay in accordance with a gain and a phase change of an antenna in the eLORAN signals including the PNT information, and a monopole antenna or a dipole antenna is used as the omnidirectional antenna.

Description

{eLORAN receiver system to minimize a receiving time delay in an eLORAN system}

The present invention relates to an eLORAN system, and more particularly, in an eLORAN system including a control station, a dLORAN calibration reference station, and a plurality of eLORAN transmitting stations, a PNT (Position, Navigation, Timing - having an eLORAN receiver that receives an eLORAN signal including location, navigation, and time information, wherein the eLORAN transmitter and the eLORAN receiver have an omni-directional antenna (monopole antenna, or dipole antenna), to an eLORAN receiver system that minimizes reception time delay in an eLORAN system.

Currently, GPS in Korea, GLONASS in Russia, Galileo in the European Union, BeiDou in China, Michibiki and MSAS in Japan are used in Korea, all of which are foreign GNSS systems.

Global Navigation Satellite System (GNSS) mainly uses GPS. A GPS receiver that receives signals from three or four GPS satellites is inexpensive and provides high positioning accuracy, but is vulnerable to 'interference' caused by a GPS jammer attack by a jammer. A jammer is a device used to disrupt, limit, or downgrade the use of a communications or radar system, and includes broadband, noise, discontinuous frequency repeaters, and deceptive equipment. If GPS signal reception is interrupted using a jammer, location and time information is lost, and operation of airplanes, fighters, warships, and missiles is disrupted.

Recently, many cases of damage have occurred in the fields of mobile communication base stations, aircraft, and ships that use GPS signals due to GPS radio wave disturbance in Korea. GPS signals are being used. However, the received signal of the GPS receiver received on the ground from three or four GPS satellites at an altitude of 20,000 km is very low, so it is exposed to various radio disturbance problems.

For this reason, the Federal Aviation Administration (FAA) announced in 1998 that the International Civil Aviation Organization (ICAO) needed a radio navigation technology capable of backing up GPS.

As an alternative navigation to GNSS, the need for a backup system that is completely independent and provides PNT (Position, Navigation, Timing - Position, Navigation, Time) information and can be used in air, sea, and land was required. was considered for use.

The Long Range Navigation (LORAN) system was developed in the United States and Britain during World War II. After the LORAN-A, LORAN-B, and LORAN-C systems, an enhanced long-distance navigation system (eLORAN: enhanced LORAN) is being developed.

Terrestrial radio navigation technology can easily measure PNT (position, navigation, visual information) through radio positioning using electromagnetic waves. In particular, PNT information is widely used as eLORAN radio navigation technology in ships sailing the sea and airplanes in the aviation field.

South Korea needs a terrestrial radio navigation system that can replace or back up a satellite navigation system using GNSS satellites, prevent North Korean GPS jamming attacks, operate ships in aviation and ports that directly require an eLORAN radio navigation system, and Visual information of positioning accuracy will be used.

LORAN-A

During World War II in 1943, the LORAN-A was developed in the United States as a navigation system for long-distance flights over the Pacific. LORAN-A uses 1950kHz in a 200kW class transmitter, and its location accuracy is frequently changed by location, time delay, terrain and weather, and it shows very low accuracy.

LORAN-B

LORAN-B, developed to compensate for the disadvantage of LORAN-A, which has poor positioning accuracy, added phase matching to LORAN-A. The LORAN-B system tested between 1948 and 1955 sought to improve the positional accuracy through phase synchronization, and as a result, the accuracy could be increased compared to the LORAN-A.

LORAN-C

The LORAN-A and LORAN-B systems using terrestrial waves have a problem in that their stability is greatly reduced when used over long distances. The US Coast Guard (USCG) conducted radio transmission tests with long-range phase pulses that became the basis of Loran-C in 1965. Based on the experiments, the first transmitting stations were established in the Mediterranean and Northeast Atlantic in 1958, and the LORAN-C service was launched. In addition to location, LORAN-C can provide visual information and is used as an aid to GNSS in air navigation systems in the Instrument Flight Regulations (IFR) and Visual Flight Regulations (VFR). Although the location accuracy of LORAN-C is quite low (over 400m), when the eLORAN system, the latest technology of LORAN-C, is applied, the location accuracy is increased to 20m within a range of 30km.

Enhanced Long Range Navigation (eLORAN) is a terrestrial radio navigation system that improves the performance of GNSS as an auxiliary navigation device based on the existing LORAN-C. The advantage of LORAN is that it uses a pulsed signal with less radio interference and a low-frequency carrier with large transmission energy as it is, and serves as an auxiliary to navigation performance and GNSS, and users of existing LORAN-C receivers can continue to use the system.

Since the GPS uses three or four satellite signals, the strength of the received signal is weak, and the signal is not received in the tunnel. Due to this characteristic, GPS is vulnerable to radio wave disturbance and has a disadvantage in that it is difficult to use if the satellite is not visible in the field of view of the GPS receiver in an indoor or tunnel environment. The eLORAN system is a terrestrial radio navigation system developed as an alternative GPS navigation system by supplementing the disadvantages of using only the existing GPS. The main characteristics of the eLORAN system are high transmission output, strong resistance to radio wave disturbance, and use of long-wavelength terrestrial waves, so positioning is possible even if line-of-sight is not secured. At least three transmitters are required to operate the eLORAN system, and Korea has the Pohang and Gwangju transmitters of the existing LORAN-C system. It can operate its own eLORAN system covering some regions. The eLORAN transmission station has a transmission system including a high transmission antenna of 100 m or more, and the installation cost is high. Performance prediction simulation of the eLORAN system that predicts the positioning accuracy performance in the deployment situation of 4 eLORAN transmitting stations is required. Based on the SNR data collected through the actual measurement of the Loran-C signal, the error of the SNR prediction value used for the eLORAN accuracy simulation is evaluated. analysis is needed In addition, the standard deviation of the signal is obtained using the actually measured SNR value of the LORAN-C signal and compared with the SNR predicted value, thereby further improving the navigation performance prediction accuracy.

Table 1 summarizes the performance of the LORAN-C system specified in the United States.

[Table 1]

The eLORAN system is a LORAN system that improves the positional accuracy and performance of the existing LORAN-C system with an error of 400m or more in air, sea, and land, and is used as an auxiliary backup system for GPS.

Table 2 compares the characteristics of LORAN-C and eLORAN.

[Table 2]

LORAN navigation uses a hyperbolic method (USCG, 1992) using Time Difference (TD) to find a navigation solution, whereas eLORAN (enhanced LORAN) navigation uses TOA (time of arrival) to find a user's location.

LORAN-C is resistant to signal interference due to the high transmission power of the transmitting station, and all-in-view using multiple measurement values is possible because all transmitting stations achieve time synchronization by implementing TOT (Time of Transmission) control. do .

Since the time of radio wave transmission of all transmitting stations can be known through time synchronization, the eLORAN system uses a Time Of Arrival (TOA)-based distance measurement, not a Time Differential of Arrival (TDOA) measurement, unlike LORAN-C.

Since the TOA measurement of eLORAN includes a positioning error proportional to the distance, a compensation method according to each error element should be applied to improve the positioning accuracy of the location estimation result. In eLORAN, the correction value obtained through the error model equation or the actual measurement process is reflected in the position estimation. In general, according to the HEA (Harbor and Entrance Approach) standard, the size of the error of the navigation result of the eLORAN that has undergone the positioning error correction corresponds to 10 to 20 m, which is similar to the position accuracy of the GNSS.

In the United States, the eLORAN plan has been suspended, and in Korea, where there is no GPS alternative navigation system, eLORAN (enhanced LORAN), which has improved the performance of LORAN-C, is an alternative navigation system, and it is necessary to secure the technology of the GNSS backup system.

The eLORAN system is a terrestrial radio navigation system using a low frequency operating in the frequency band of 90 ~ 110 kHz. The eLORAN system transmits LORAN-type navigation RF pulses at a center frequency of about 100 kHz, and differs from LORAN-C in that the eLORAN transmission is synchronized to UTC similar to GPS; It includes transmission time control, differential compensation similar to differential GPS, use of 'full view' tracking, and one or more eLORAN data channels providing low-speed data messaging and differential compensation and almanac information.

In the field of aviation, the US FAA can use it in take-off and air navigation compared to the existing L ORAN-C, but its use in airport approach and landing was not approved due to a large position error. However, since eLORAN provides higher positioning accuracy and integrity compared to LORAN-C, it is likely to be used in ports and military fields.

In the maritime field, especially in ports, the eLORAN technology that provides usable positioning accuracy and the eLORAN system complements GNSS is expected to use Korea's independent radio navigation system. In the maritime field, eLORAN is expected to be used for port entry and departure and vessel approach. Positional accuracy of 8-20m satisfies the conditions of IMO A915, and a position error of about 8m within a complex port will be of great help to ships' safe passage and entry/exit port.

In the military field, the eLORAN system, which has a strong advantage in GPS jamming attacks, can be applied to the navigation system of warships at sea or used in military weapons and military vehicles required for radar-operated guided missiles.

Table 2 shows that the positioning performance of eL ORAN required by the US Coast Guard (USCG) is 8-20m, which is much higher than 460m of LORAN-C. A dLORAN reference station is essential to ensure an accuracy of 8-20m in the eLORAN system. In particular, the dLORAN reference station plays a key role in increasing the location accuracy in the eLORAN system. The dLORAN reference station receives the signal transmitted from the eLORAN transmitting station, finds the positioning error due to propagation delay due to the terrain or other environment, and generates correction information to correct the error. And, by transmitting it to the eLORAN transmitting station and transmitting the correction information data in the eLORAN signal, the positioning accuracy of the eLORAN system is greatly improved.

[Table 3]

On land, the eLORAN receiver (Hybrid receiver: GPS receiver + eLORAN receiver) can be integrated and used in the vehicle's navigation system, which relied on the existing GNSS receiver. In an environment where satellites and mobile communication base stations are installed, eLORAN using a low frequency band of 90 ~ 110 kHz is too expensive to use with a GNSS receiver showing weakness in a building forest area, so it is difficult.

eLORAN is expected to play a major role as Korea's independent navigation system and GNSS backup system. However, in order to satisfy the performance requirements suggested by the USCG, there are still many issues to be solved, from the selection of the optimal eLORAN transmitting station location to the correction information calculation algorithm of the dLORAN reference station and the time synchronization method. The eLORAN system service will be started as Korea's independent terrestrial radio navigation system, which calculates the hardware or correction information responsible for transmitting and receiving radio waves, designing, implementing, and testing the system control software.

As a related prior art 1, Patent Publication No. 10-2013-0024300 (published on March 08, 2013) discloses "eLORAN receiver and positioning method of eLORAN receiver", and positioning method of eLORAN receiver and eLORAN receiver To provide an eLORAN receiver and a positioning method of the eLORAN receiver, which improve positioning performance by effectively removing errors included in the eLORAN measurement.

The eLORAN receiver includes: a receiver for receiving each signal transmitted from four or more LORAN (Long Range Navigation) transmitters; a distance measuring unit that calculates a distance measurement value by multiplying the speed of light by the difference between the time each signal is transmitted and the time each signal is received; and the error of the distance measurement is calculated as cB + r*D (c is the speed of light, B is the clock error, r is the distance between the transmitter and the eLO RAN receiver, D is the unknown), and the coordinates of each distance measurement value and the reference point, and a position extracting unit for calculating a position based on a value B0 of the clock error at the reference point and an unknown value D0 at the reference point.

As the related prior art 2, in Patent Registration No. 10-1594322 (registration date February 05, 2016), "a system for monitoring maritime radio navigation signals and providing their reliability" is registered.

The eLORAN/GNSS integrated receiver is a representative example of using eLoran as a backup system for GNSS. However, while GNSS receivers have already been commercialized and sold by many companies, eLoran/GNSS integrated receivers are only marketed in Reelektronika in the Netherlands and CrossRate in the United States, and research in Korea is still lacking.

If the demand for alternative navigation due to the signal interference problem of GNSS such as jamming increases, it is expected that the demand for the eLoran/GPS integrated navigation receiver will increase.

1 and 2 are block diagrams of a harbor maritime radio navigation signal monitoring system.

Maritime radio navigation signal monitoring and reliability providing system

GNSS, eLORAN, and DGNSS receivers (14, 15, 16) connected to GNSS, eLORAN, and DGNSS antennas (11, 12, 13) respectively;

It is additionally connected to the GNSS antenna 11 using the divider 17, and performs an FFT sampling function to check whether the GNSS signal input to the GNSS receiver 14 is a jamming signal (USRP) ( 18) and

an integrated PNT module (10) comprising a rubidium oscillator (19) for frequency and time synchronization with the GNSS receiver (14);

It is connected to the GNSS receiver, eLORAN receiver, DGNSS receiver 14, 15, 16, USRP 18, and rubidium oscillator 19 to analyze whether a jamming signal is input, and input the GNSS signal of the ship 70 It receives and analyzes whether it is a normal signal, and generates reliability evaluation information with each analysis data or a combination of analysis data made by analyzing whether the TOA received from the eLORAN receiver 15 and the receiving location is normal data Industrial PC (20) for transmitting to (70); includes,

The reliability evaluation information is provided to the ship 70 by selecting any one of the reliability indices including good, available, caution, and risk based on the set reference value according to a set period,

The communication network includes a medium-wave beacon (RTCM header, RTCM #16), a mobile communication network, an AIS message, a DMB channel, a fishery information communication network, and a TRS communication network, any one of them,

The industrial PC 20 receives the FFT sampling file generated by the USRP 18, extracts as much as a data size of a predetermined size to perform FFT, performs FFT, and uses the result to obtain a jamming signal Recognition is determined using the average of in-band energy, and is applied to the port navigation of the vessel (70).

As a related prior art 3, Patent Publication No. 10-2020-0135732 (published on December 03, 2020) discloses "eLORAN receiver and antenna with ferromagnetic material and winding and a related method".

A low-frequency transmission station for a Long Range Navigation (LORAN) system is more specifically, eLORAN is a low-frequency radio navigation system operating in a frequency band of 90 to 110 kHz. Low-frequency eLORAN transmissions can be propagated by terrestrial waves, which are a type of surface wave embracing the Earth. Ionospheric reflection, or airwaves, is another important mechanism of eLORAN wave propagation. In a typical low-frequency antenna, the tower itself is used as a unipolar antenna. Because of the tower's height, which can be over 600 feet as a result of the operating wavelength, many upper wires are connected to the top of the tower to form a resonant capacitor. These wires, known as Top Loading Elements (TLEs), can approximate a solid cone.

The eLORAN receiver may include an antenna and an eLORAN receiver circuit connected thereto. The antenna includes a ferromagnetic core comprising a ferromagnetic central portion and a ferromagnetic arm extending outwardly from the ferromagnetic central portion; each electrically conductive winding surrounding each of the ferromagnetic arms; and an electrically conductive patch element adjacent the ferromagnetic core.

The ferromagnetic core and each electrically conductive winding are configured to respond to a plurality of H-field signals, and the electrically conductive patch element is configured to respond to an E-field signal.

The eLORAN receiver circuitry is configured to correct position based on a plurality of H-field signals and E-field signals.

wherein the eLORAN receiver circuit is configured to calculate an E-field to H-field amplitude ratio, an E-field to H-field phase difference, and an E-field to H-field pulse arrival time difference, wherein the eLORAN receiver circuit is configured to: and correct the position based on the field-to-H-field amplitude ratio, the E-field to H-field phase difference, and the E-field to H-field pulse arrival time difference.

However, since the antenna of the eLORAN transmitter of the transmitting station of the eLoran system is radiated at a peak power of 200-1500kW at a low frequency of 100kHz band, it is not easily disturbed by radio wave interference. Therefore, the eLoran system is used as an auxiliary means to overcome the GPS interference and vulnerability to interference.

The structure of the eLoran transmit antenna consists of a monopole connected with an upper load element, a monopole antenna fed from one point by tying an inverted triangle wire, and an inverted pyramid monopole antenna. Generally, it has a height of 0.05-0.15 wavelength and low radiation of about 1-2Ω. have resistance

The antenna of the eLORAN receiver may use an electric field (E-field) antenna, a loop antenna, or a magnetic field (H-field) antenna. E-field antenna has constant omnidirectional reception characteristics from all directions and has excellent signal reception performance, but it is affected by surrounding electronic equipment and must be grounded.

The H-field antenna improves the antenna radiation efficiency and compensates the phase by arranging two loop antennas in which the antenna radiation patterns are orthogonal to each other in pairs.

However, the H-field antenna does not need grounding, is relatively robust against noise from surrounding electronic equipment, and uses two loop antennas that are orthogonal to each other. There is a change and it does not have a constant circular directivity, so a positioning error occurs. In particular, in the case of the H-field antenna and the loop antenna having directivity, the strength of the eLORAN signal is changed according to the directionality of the antenna, so that the reception time delay occurs according to the gain and phase change of the antenna of the eLORAN receiver.

Patent Publication No. 1 0-2013-0024300 (published on March 08, 2013), "eLORAN receiver and positioning method of eLORAN receiver", Hanyang Navicom Co., Ltd. Patent Registration No. 10-1594322 (Registration date: February 05, 2016), "Sea radio navigation signal monitoring and reliability providing system", Korea Institute of Ocean Science and Technology Patent Publication No. 10-2020-0135732 (published on December 03, 2020), "eLORAN receiver and antenna with ferromagnetic material and winding and related method", Eagle Technology, LLC

It is an object of the present invention to solve the above problems, in an eLORAN system including a control station, a dLORAN calibration reference station, and a plurality of eLORAN transmitting stations, PNT (Position, Navigation, Timing - It has an eLORAN receiver that receives an eLORAN signal including location, navigation, and time) information. Provided is an eLORAN receiver system that minimizes the reception time delay of the eLORAN signal, which minimizes the reception time delay in the eLORAN system.

In order to achieve the object of the present invention, an eLORAN receiver system that minimizes reception time delay in an eLOR AN system is an eLORAN system including a control station, a dLORAN reference station, and a plurality of eLORAN transmitting stations: connected to the control station, , a plurality of eLORAN transmitting stations having an eLORAN transmitter; and an eLORAN receiver for receiving an eLORAN signal including PNT (Position, Navigation, Timing - Position, Navigation, Time) information transmitted in all directions from the transmitters of the m eLORAN transmitting stations,

The eLORAN receiver uses an omni-directional antenna to minimize a reception time delay according to a gain and phase change of an antenna of the eLORAN signal including the PNT information, and the omni-directional antenna uses a monopole antenna or a dipole antenna.

The eLORAN receiver system that minimizes the reception time delay in the eLORAN system of the present invention is an eLORAN system including a control station, a dLORAN reference station, and a plurality of eLORAN transmitting stations in all directions (omni) from the transmitter of the LORAN-C system or the eLORAN transmitter. -directional) and an eLORAN receiver that receives an eLORAN signal including PNT (Position, Navigation, Timing - position, navigation, time) information transmitted in omni-directional directions, the eLORAN transmitter and the eLORAN receiver are Antenna, or dipole antenna) is used, and the reception time delay of the eLORAN receiver with 20mm positioning accuracy is minimized.

In particular, eLORAN receivers are mounted on ships, ships, and special ships belonging to the Coast Guard, as a backup device for GPS receivers related to positioning and navigation to military and government ships, and are used to control the entry and departure of ships into and out of ports and maritime safety management. It was used for positioning.

In addition, the eLORAN system is strong against GPS jamming attacks by transmitting a 100kHz high-output signal from the transmitting station. It can be used for Johan guided weapon systems and military vehicles.

1 and 2 are diagrams of a port maritime radio navigation signal monitoring system.
3 is a conceptual diagram of an eLORAN system that blocks GPS jamming interference.
4 is an eLORAN system configuration diagram for implementing the present invention.
5 is a block diagram of an eLORAN receiver system having an omni-directional antenna (monopole antenna, or dipole antenna) that minimizes reception time delay in the eLORAN system according to the present invention.

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings, the configuration and operation of the invention. In the description of the present invention, if it is determined that a detailed description of a related known function or a known configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. In addition, when the drawing numbers indicate the same configuration, the same reference numbers are given in different drawings.

The eLORAN system consists of three eLORAN transmitting stations, a dLORAN calibration reference station (Monitor Site), and a control station (Control Center).

The eLORAN transmitting station serves to transmit the eLORAN signal together with the dLORAN correction information, and the dLORAN correction reference station corrects the error information of the eLORAN signal.

The dLORAN calibration reference station is installed at specific reference point coordinates (X0, Y0), and the module (Differential eLoran Reference Station) that calculates the calibration information processes it to generate the calibration information and transmits it to the eLORAN transmitting station.

Receive the eLORAN signal after time synchronization through the eLORAN receiver,

3 is a conceptual diagram of an eLORAN system that blocks GPS jamming interference.

4 is an eLORAN system configuration diagram for implementing the present invention.

5 is a block diagram of an eLORAN receiver system having an omni-directional antenna (monopole antenna or dipole antenna) that minimizes reception time delay in the eLORAN system according to the present invention.

The eLORAN receiver system that minimizes the reception time delay in the eLORAN system is

A control station 200 connected to the monitoring PC 210 , a dLORAN calibration reference station 220 connected to the control station 200 , a LORAN-C system transmitter or an eLORAN transmitter connected to the control station 200 . In the eLORAN system used as a terrestrial navigation system including the eLORAN transmitting station 230 of:

a control station 200 connected to the monitoring PC 210;

a dLORAN calibration reference station 220 coupled to the control station 200;

Connected to the control station 200, a cesium atomic clock is used to synchronize the eLORAN transmitter within ±100 ns, and modulates and transmits the eLORAN transmitter using a low frequency of 90 to 110 kHz. A plurality of eLORAN transmission stations 230 or more having a; and

An eLORAN receiver for receiving an eLORAN signal including PNT (Position, Naviagt ion, Timing-position, navigation, time) information transmitted in all directions from the transmitter of the m eLORAN transmitting stations 230 in all directions (omni-directional) (300k) is provided,

The eLORAN receiver 300k uses an omni-directional antenna to minimize the reception time delay according to the gain and phase change of the antenna of the eLORAN signal including the PNT information.

The eLORAN transmitting station 230 includes an additional pulse that transmits Differential-Global Positioning System (D-GPS) correction data.

The eLORAN transmitting station 230 electrically accurately matches the main power switchboard, the control console, the amplification unit (PGA, Pules Generator Assembly), the output network, and the transmitter and the antenna to efficiently radiate the maximum output. It includes an output network, a group I or group II output, a switch network that connects the output of the coupling network and an antenna input, and an antenna part, and the antenna is a top-loading monopole type (TLM) Use a vertical antenna.

The eLORAN transmitting station 230 may synchronize a Loran-C signal or an eLORAN signal with universal time (UTC) in a coordinated universal time (UTC) synchronization system and use it as a standard time.

The eLORAN transmitter 230 is synchronized with the UTC synchronization system provided in the control station 200, calculates a location using time of arrival (TOA), and an eLORAN receiver 300k provided in an airplane, ship, car, etc. receives the eLORAN signal of the transmitting station through the LDC (Loran Data Channel) from the eLORAN transmitting station 230, measures the TOA value after being synchronized with the eLORAN signal at a fixed location, and time according to the signal propagation path (ASF) It has delay and positioning error. Two or three or four UTC synchronized transmitting stations operate on the principle of measurement of the time difference of arrival of radio waves, which can provide a hyperbolic position line. Position measurement is possible with the intersection of two or more position lines, and the measurement of the time difference between each position line is UTC synchronized between the master station (control station) and the slave station (eLORAN transmitting station), and the received pulse envelope or It is determined by the comparison of the cycle leading edges. The master station transmits at regular intervals and the slave station starts after receiving these signals and is synchronized with each other. The delay time between successive master signals shall be sufficient to allow a receiver within coverage to receive the last transmission before the master's next transmission. The LORAN chain is usually composed of a triangular, star-connected, or rectangular array of transmitters, and each configuration has advantages and disadvantages in terms of system coverage and accuracy.

In order to simply measure the pulse arrival time difference (TD), the master station and the slave station of the transmitting station may transmit only one pulse each, but in reality, a large number of (8-9) pulse groups are transmitted. This is to supply more energy to the receiver side without increasing the output. The pulse group emitted from the main station consists of 9 pulses, and the first 8 pulses are transmitted at intervals of 1000 μs, and finally the 9th pulse is located 2000 μs behind the 8th pulse. In the case of the final station, only 8 pulses are transmitted and 100kHz is used as the carrier frequency to improve Loran-C precision, which is called cycle matching.

At the receiving end, the TD value should be measured within the first few cycles of the carrier frequency in order to obtain maximum accuracy, because the rear part of the pulse is interfered with by the late arriving space wave. Therefore, the pulse is designed to rise rapidly in order to make an accurate measurement within the first few cycles.

The Loran-C band is 90-110 kHz and is designed so that 99% of the transmit energy of the radiated pulse form is distributed within this 20 kHz band.

The eLORAN receiver 300k calculates a distance measurement by multiplying the signal's Time of Arrival (TOA) measurement by the speed of light. The distance between the transmitter (Xi, Yi) and the receiver (Xk, Yk) of the eLORAN transmitting station is calculated by time x speed.

TOA measurements are the actual distance between the transmitter (Xi, Yi) and the receiver (Xk, Yk) of the eLORAN transmitting station 230, the receiver's clock error (B), the primary factor (PF), the secondary factor ( Secondary Factor (SF), an additional secondary factor (Additional Secondary Factor, ASF), etc. may include errors and noise.

The eLORAN receiver 300k is

An antenna unit 310 having an eLORAN antenna, a GPS antenna, and a D-GPS antenna;

The eLORAN reception signal input unit 311, the GPS receiver unit 312, the D-GPS receiver unit 313 and the GPS signal inputted to the GPS receiver unit 312 respectively connected to the eLORAN antenna, the GPS antenna, and the D-GPS antenna. A rubidium oscillator (not shown) for frequency and time synchronization with a USRP (USRP) 317 that performs FFT sampling to check the presence of a jamming signal included in the GPS signal input unit 311 include

In addition, the eLORAN receiver 300k,

a receiver circuit unit 321 for receiving and demodulating each signal transmitted from the LORAN-C transmitter or eLORAN (Long Range Navigation) transmitter of three or more transmitting stations; error compensating unit 322; and a control unit 324 connected to the location extraction unit 323; It further includes a control processor (AD board, DSP board, CPU board) 320 having a time synchronization unit 327, a communication unit 328, and a storage unit 329 respectively connected to the control unit.

The control processor 320 of the eLORAN receiver,

a control unit 324 for controlling to provide UTC time synchronization and PNT information including location, navigation, and time information;

a receiver circuit unit 321 that receives an eLORAN signal, additionally a GPS signal or a D-GPS signal, receives an eLORAN signal through an eLORAN reception signal input unit 311, and includes a jamming signal removing unit (filter);

a distance measuring unit (not shown) that calculates a distance measurement value by multiplying the speed of light by the difference between the time each signal is transmitted and the time each signal is received;

It is connected to the control unit 324, and in the distance measurement, a Primary Factor (PF), a Secondary Factor (SF), an Additional Secondary Factor (ASF), an Ellipsoidal Factor (EF) ) an error compensating unit 322 for compensating for at least one of the errors; and

It is connected to the control unit 324, and based on the measured distance to each transmitting station, the coordinates (x,y) of the dLORAN reference point, and the value of the clock error (B) at the dLORAN reference point, the position is determined by triangulation. It includes a position extraction unit 323 to calculate.

The control processor 320 includes an AD board, a DSP board, and a CPU board.

The eLORAN receiver 300k is connected to the control unit 324 and further includes an Ethernet communication unit 328 connected to a PC through a LAN.

The eLORAN receiver 300k has a receiver circuit 321 connected to the control unit 324, and when there is a jamming signal included in the GPS signal by the USRP 317, the It further includes a jamming signal removing unit for driving an anti-jamming frequency signal processing unit (with a filter circuit) provided in the receiver circuit unit 321 to remove the jamming signal with a filter.

Currently, the measured value of the eLORAN receiver has errors (eg, errors due to PF, SF, ASF, and EF) according to various factors in addition to the large value of the receiver clock error (B).

The eLORAN transmitter of the transmitting station uses an omni-directional antenna with a size of 100m to 210m that receives the eLORAN signal in all directions, and the omni-directional antenna uses a monopole antenna.

The eLORAN receiver 300k uses the omni-directional antenna for receiving the eLORAN signal in all directions, and the omni-directional antenna is an E-field antenna and uses a monopole antenna or a dipole antenna.

In an embodiment, a number of vessels entering a port are equipped with eLORAN receivers.

The transmitter of the eLORAN transmitting station 230 transmits an omnidirectionally modulated eLORAN signal through a Loran Data Channel (LDC), and an omni-directional antenna (monopole antenna) without delay between the transmission time of the eLORAN transmitter and the reception time of the eLoran signal. Or, the distance between the eLORAN transmitting station and each receiver is measured by the time of arrival (TOA) of the eLORAN receiver having a dipole antenna), and the eLORAN receiver provided on the ship according to the triangulation of three eLORAN transmitting stations. measure the position of

Since the frequency of Loran signal is 100 KHz, it is transmitted from the ground, so Jamming is difficult. The eLoran system can provide excellent location information because it receives D-GPS Data, dLoran Data, and UTC Data from three or four transmitting stations through an LDC (Loran Data Channel) to the eLORAN receiver.

In the eLORAN system, the antenna of the eLORAN receiver 300k uses an E-field antenna or an H-field antenna suitable for use environment.

The E-field antenna has constant omni-directional reception characteristics from all directions and has excellent signal reception performance, but it is affected by surrounding electronic equipment and must be grounded.

On the other hand, the H-field antenna, which does not require grounding and is relatively resistant to noise from surrounding electronic equipment, consists of two loop antennas orthogonal to each other and does not have a constant circular directivity due to the phase and gain difference between the loop antennas. Therefore, since the measurement value changes depending on the direction of the received signal, it is necessary to correct the error according to the direction of the received signal when using the H-field antenna.

The eLORAN receiver 300k has a positioning error within 10m in a dynamic environment when an E-field antenna is used, but a positioning error up to 20m occurs when an H-field antenna is used. Although the H-field antenna is theoretically composed of two loop antennas orthogonal to each other, it does not have circular isotropic property due to the phase and gain difference between the loop antennas, and a directivity error of the H-field antenna occurs.

The measured value TOA (time of arrival) is

TOA = TTOR - TTOT = τ(RX-TX) + PF + SF + ASF + ΔRx

Here, TTOR: Time of Reception,

TTOT: Time of Transmission,

τ(RX-TX) : Synchronization error of the receiver clock relative to the transmitter clock

PF: 1st delay element (time delay by distance)

SF: Secondary delay factor (time delay due to sea)

ASF: Additional delays caused by land

ΔRx : Receiver internal delay

In an embodiment, the eLORAN system comprises one control station 200 , one dLORAN calibration reference station 220 , and three eLORAN transmitting stations 230 ,

The eLORAN receiver 300k includes an eLORAN receiver having an omni-directional antenna and a D-GPS or S-GPS receiver, and includes an eLORAN antenna unit, a receiver circuit unit, a control processor (AD board, DSP board, CPU board), and a storage unit. and PNT (GPS, eLoran) receiving equipment having a time synchronization unit 327 is used.

The DSP board of the control processor 320 uses a fast Fourier transform (FFT) to block a radio disturbance signal included in the GNSS frequency band by a filter. The filter can use BPF or HPF.

The eLORAN system performs triangulation by receiving eLoran signals from one dLORAN calibration reference station and three eLORAN transmitting stations. Thus, the positioning accuracy can be improved.

The calibration information generated by the dLORAN calibration reference station can be positioned within a relatively short distance within 30 km, so it is used mainly at major bases such as ports.

When the eLORAN receiver 300k uses an H-field antenna, the actual Loran measurement time of arrival (TOA) may be expressed as Equation (1) (Hartnett et al, 2003).

Here, ρ is the distance between the transmitting station and the receiver, Primary Factor (PF) is the signal transmission delay error in the atmosphere, and the Secondary Factor (SF) is the signal transmission delay error when crossing the sea level. estimated through In addition, the Additional Secondary Factor (ASF) is a signal propagation delay error when passing through the ground surface. It is removed using the value obtained by subtracting the distance between the transmitting station and the receiver, PF, and SF from the TOA calculated or actually measured through simulation modeling. δ is the signal noise. Here, ASF is divided into ASF _S which is an error that occurs in the spatial domain, ASF _T which is an error that occurs with time, and ASF _D which is an error that occurs due to the characteristics of the H-field antenna.

로 나타낼 수 있다.In addition, when the eLORAN receiver 300k uses the H-field antenna, H _τ due to the loop antenna time delay according to the rotation of the antenna and the directivity error due to the loop phase delay

can be expressed as

Here, A is the amplitude of the sine wave in the signal of the eLORAN receiver received from the eLORAN transmitting station, and θ is the angle between the transmitting station and the receiver antenna.

The eLORAN receiver system that minimizes the reception time delay in the eLORAN system of the present invention is an eLORAN system including a control station, a dLORAN calibration reference station, and a plurality of eLORAN transmitting stations, in all directions (omni - It has an eLORAN receiver that receives an eLORAN signal including PNT (Position, Navigation, Timing - Position, Navigation, Time) information transmitted in all directions from a directional), and the eLORAN transmitter and eLORAN receiver are Antenna or dipole antenna) is used, and the reception time delay of the eLORAN receiver with 20mm positioning accuracy is minimized.

In particular, eLORAN receivers are mounted on ships, ships, and special ships belonging to the Coast Guard, and used as a backup device for GPS receivers related to positioning and navigation in military and government ships, and are used to control the entry and departure of ships into and out of ports and maritime safety management. It was used for positioning. Realistically, the eLORAN receiver can be used on a ship in a port or a military plane.

In addition, the eLORAN system is strong against GPS jamming attacks by transmitting a 100kHz high-output signal from the transmitting station. It can be used in guided weapon systems and military vehicles.

As described above, the method of the present invention is implemented as a program and is readable using computer software in the form of a recording medium (CD-ROM, RAM, ROM, memory card, hard disk, magneto-optical disk, storage device, etc.) ) can be stored in

Although described with reference to a specific embodiment of the present invention, the present invention is not limited only to the same configuration and operation as the specific embodiment to illustrate the technical idea as described above, and within the limit not departing from the technical spirit and scope of the present invention. can be implemented with various modifications, and the scope of the present invention should be determined by the claims to be described later.

100: GPS satellite 200: control station
210: PC 220: dLORAN calibration reference station
230: eLORAN transmitter 300k: eLORAN receiver

Claims (9)

In an eLORAN system comprising a control station, a dLORAN reference station, and a plurality of eLORAN transmitting stations:
a plurality of eLORAN transmitting stations connected to the control station and having an eLORAN transmitter; and
Equipped with an eLORAN receiver for receiving an eLORAN signal including PNT (Position, Navigation, Timing - position, navigation, time) information transmitted in all directions from transmitters of m eLORAN transmitting stations,
The eLORAN receiver uses an omni-directional antenna to minimize the reception time delay according to the gain and phase change of the antenna of the eLORAN signal including PNT information,
The eLORAN receiver is
An antenna unit including an eLORAN antenna, a GPS antenna, and a D-GPS antenna;
The eLORAN antenna, the GPS antenna, and the eLORAN reception signal input unit connected to the D-GPS antenna, the GPS receiver unit, the D-GPS receiver unit, and the GPS signal inputted to the GPS receiver unit to check the presence of jamming signals It includes a rubidium oscillator for frequency and time synchronization with a USRP (USRP) that performs FFT sampling and a GPS reception signal input unit,
a receiver circuit unit for receiving and demodulating each signal transmitted from a LORAN-C transmitter or an eLORAN (Long Range Navigation) transmitter of m or more transmitting stations; error compensation unit; and a control unit connected to the location extraction unit; Further comprising a control processor having a time synchronization unit, a storage unit, and a communication unit respectively connected to the control unit,
The control processor of the eLORAN receiver,
a control unit for controlling to provide PNT information including location, navigation, and time information to be synchronized with UTC time;
a receiver circuit unit for receiving an eLORAN signal, additionally a GPS signal or a D-GPS signal, receiving an eLORAN signal through an eLORAN receiving signal input unit, and having a jamming signal removing unit;
a distance measuring unit calculating a distance measurement value by multiplying the difference between the time each signal is transmitted and the time at which each signal is received;
It is connected to the control unit, and in the distance measurement value, a Primary Factor (PF), a Secondary Factor (SF), an Additional Secondary Factor (ASF), an Ellipsoidal Factor (EF) error of an error compensating unit compensating for at least one; and
It is connected to the control unit, and based on the measured distance from each transmitting station, the coordinates (x,y) of the dLORAN reference point, and the value of the clock error (B) at the dLORAN reference point. Position extraction for calculating the position by triangulation includes wealth,
Loran measurement TOA (Time Of Arri val) can be expressed as the following formula,
TOA = ρ + PF + SF + ASF _S + ASF _T + ASF _D + δ
Here, ρ is the distance between the transmitting station and the receiver, Primary Factor (PF) is the signal propagation delay error in the atmosphere, Secondary Factor (SF) is the signal propagation delay error when crossing the sea level, and Additional Secondary Factor (ASF) is the spatial ASF _S , which is an error occurring in the region, ASF _T , which is an error that occurs over time, ASF _D, δ, which is an error caused by the characteristics of an H-field antenna, is signal noise,
In the eLORAN receiver 300k, the relationship between ASF _D, which is an error occurring when an H-field antenna is used, H _τ due to loop antenna time delay due to antenna rotation, and directional error H _θ due to loop phase delay, can be expressed by the following equation there is,
ASF _D, = H _τ + H _θ, H _θ = A cos (π + θ)
A is the amplitude of the sine wave in the signal of the eLORAN receiver received from the eLORAN transmitting station, θ is the angle of the transmitting station and the receiver antenna,
The eLORAN receiver is mounted on ships, ships belonging to the Coast Guard, and special boats for port entry and departure, and is used as a backup device for GPS receiving equipment related to positioning and navigation on military and government ships. will do,
The eLORAN system is strong against GPS jamming attacks by transmitting a 100kHz high-output signal from the transmitting station, and the eLORAN system is applied to the navigation system of ships in harbors or warships of naval bases at sea, or guided weapons required for radar operation guided missiles on land. The eLORAN receiver system that minimizes the reception time delay in the eLORAN system, characterized in that it can be utilized in systems and military vehicles.
According to claim 1,
The eLORAN system comprises one control station, one dLORAN reference station, and three eLORAN transmitting stations,
An eLORAN receiver system that minimizes reception time delay in the eLORAN system.
According to claim 1,
The eLORAN transmitter uses a cesium atomic clock to synchronize the eLORAN transmitter within ±100 ns, and modulates and transmits using a low frequency of 90 to 110 kHz,
An eLORAN receiver system that minimizes reception time delay in the eLORAN system.
According to claim 1,
The eLORAN receiver includes an eLORAN receiver having an omni-directional antenna and a D-GPS or S-GPS receiver, and measures time with an antenna, a receiver circuit, a control processor (AD board, DSP board, CPU board), and a storage unit Using PNT (GPS, eLoran) receiving equipment having a timer to
An eLORAN receiver system that minimizes reception time delay in the eLORAN system.
According to claim 1,
The eLORAN receiver uses the omni-directional antenna for receiving the eLORAN signal in all directions,
The omni-directional antenna is an E-field antenna, using a monopole antenna or a dipole antenna,
An eLORAN receiver system that minimizes reception time delay in the eLORAN system.
delete delete According to claim 1,
The eLORAN receiver is connected to the control processor, further comprising an Ethernet communication unit connected to the PC through a LAN,
An eLORAN receiver system that minimizes the reception time delay in the eLORAN system.
According to claim 1,
The eLORAN receiver is
The receiver circuit unit is connected to the control unit, and when there is a jamming signal included in the GPS signal by the USRP, anti-jamming provided in the receiver circuit unit to remove the jamming signal included in the GPS signal with a filter Further comprising a jamming signal removing unit for driving the frequency signal processing unit,
An eLORAN receiver system that minimizes reception time delay in the eLORAN system.

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