KR101868506B1 - MLAT Receiving Unit Using Local Clock and Driving Method of the Same - Google Patents

Abstract

The MLAT receiver according to the present embodiment includes a precision clock forming unit for forming a local clock synchronized with a time signal provided by a satellite, an RF receiving unit for receiving a signal provided by the transponder and converting the received signal into a baseband, A signal processing unit for forming TOA information from the received signal, and a message processing unit for providing a packet including TOA information to the central processing unit, and is driven by a local clock after synchronization with the satellite.

Description

[0001] The present invention relates to an MLAT receiver using a local clock,

The present invention relates to an MLAT receiver using a local clock and a driving method thereof.

The MLAT (Multilateration) method uses 4 hyperbola or hyperboloid position measurement methods to output signals to a transponder of an aircraft (two-dimensional position can be calculated if three) In the above-mentioned receiver, the position of the aircraft is obtained by measuring the time difference of arrival (TDOA).

The calculation principle is that if one receiver is set as the reference receiver, the TDOA arriving at the remaining receiver is calculated based on this. This TDOA can be viewed as the distance difference between the receivers, and three hyperboloids with a distance difference of a certain size can be obtained, and the point where they meet is the location of the aircraft. The MLAT receiver is a device that receives mode 3 / A, C, S, and 1090ES (ADS-B) signals from an aircraft transponder to locate the aircraft.

A plurality of receivers belonging to the MLAT system provide the time of arrival (TOA) of the signal provided by the aircraft transponder to the central processing unit (CPS), which uses the current position, Calculate the wake. Accordingly, a plurality of receivers are requested to be operated synchronously with the same clock, and time information provided by a satellite such as Global Positioning System (GPS) or GLONASS is used to synchronize the clocks of the MLAT receivers.

The signals received from satellites can be influenced by various factors, such as: (1) ionospheric and tropospheric errors occurring when the signal passes through the atmosphere, (2) signal distortions caused by reflections and refractions due to buildings or terrain, , (3) satellite orbit error caused by the out-of-orbit of the geostationary satellite, (4) non-receivable state caused by the failure of the clock, and (4) propagation disturbance.

One of the technical objects of the present invention is to provide an MLAT receiver which can overcome the influence of the above factors on a received signal, and is robust against disturbance of a satellite signal and can be configured at low cost.

The MLAT receiver according to the present embodiment includes a precision clock forming unit for forming a local clock synchronized with a time signal provided by a satellite, an RF receiving unit for receiving a signal provided by the transponder and converting the received signal into a baseband, A signal processing unit for forming TOA information from the received signal, and a message processing unit for providing a packet including TOA information to the central processing unit, and is driven by a local clock after synchronization with the satellite.

A method of driving an MLAT receiver according to the present embodiment includes the steps of: (a) forming a local clock synchronized with a time signal provided by a satellite; (b) receiving a signal provided by the transponder and converting the received signal into a baseband (C) forming TOA information from a baseband signal, and (d) providing a packet including TOA information to a central processing unit, wherein after the step (a), MLAT A method of driving an MLAT receiver for driving a receiver.

This embodiment provides the advantage of being able to overcome the effects of disturbances that adversely affect the received signal.

1 is a schematic block diagram of an MLAT receiver according to the present embodiment.
2 is a flowchart showing an outline of a method of driving the MLAT receiver according to the present embodiment.
3 is a diagram schematically illustrating a process of synchronizing a time signal provided by a satellite with a local clock.
Fig. 4 is a diagram showing the modification of a signal provided by an aircraft transponder or reference monitoring transponder.
5 is a view schematically showing a process of forming the TOA information by the signal processing unit.
6 is a flowchart illustrating a method of controlling the position of the air vehicle using the TOA provided by the three receivers (RU # 1, RU # 2, RU # 3) and the TOA provided by the reference monitoring transponder, Is determined.

The description of the present invention is merely an example for structural or functional explanation, and the scope of the present invention should not be construed as being limited by the embodiments described in the text. That is, the embodiments are to be construed as being variously embodied and having various forms, so that the scope of the present invention should be understood to include equivalents capable of realizing technical ideas.

Meanwhile, the meaning of the terms described in the present application should be understood as follows.

It should be understood that the singular " include "or" have "are to be construed as including a stated feature, number, step, operation, component, It is to be understood that the combination is intended to specify that it is present and not to preclude the presence or addition of one or more other features, numbers, steps, operations, components, parts or combinations thereof.

Each step may take place differently from the stated order unless explicitly stated in a specific order in the context. That is, each step may occur in the same order as described, may be performed substantially concurrently, or may be performed in reverse order.

All terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs, unless otherwise defined. Terms such as those defined in commonly used dictionaries should be interpreted to be consistent with the meanings in the context of the relevant art and can not be interpreted as having ideal or overly formal meaning unless explicitly defined in the present application .

This specification does not distinguish the types of signal lines. Accordingly, the data bus may be a single line transmitting a single ended signal, or it may be a line pair capable of transmitting a differential signal. Also, each line shown in the drawings can be interpreted as a single signal or a bus signal composed of one or more analog signals or digital signals, and the description can be added if necessary.

Hereinafter, a method of driving the MLAT receiver and the MLAT receiver according to the present embodiment will be described with reference to the accompanying drawings. FIG. 1 is a schematic block diagram of an MLAT receiver according to the present embodiment, and FIG. 2 is a flowchart showing an outline of a driving method of an MLAT receiver according to the present embodiment. The MLAT receiver 1 according to the present embodiment includes an accurate clock forming unit 100 that forms a local clock synchronized with a time signal provided by a satellite, an RF receiver unit 100 which receives a signal provided by the transponder and converts the received signal into a baseband, A signal processing unit 300 for forming TOA information from the baseband converted signal, and a message processing unit 400 for providing packets including TOA information to a central processing unit (not shown) The receiver 1 according to the embodiment is driven by the local clock after synchronization with the satellite.

The driving method of the MLAT receiver according to the present embodiment includes: a step (S100) of forming a local clock synchronized with a time signal provided by a satellite; and (b) a step of receiving a signal provided by the transponder and converting it into a baseband (Step S300) of forming TOA information from the signal converted to the baseband (step S300); and (d) providing the packet including the TOA information to the central processing unit (step S400). a) After the process, run the MLAT receiver with a local clock.

Referring to FIGS. 1 and 2, the precision clock generating unit 100 receives a time signal from a satellite and forms a local clock synchronized with the time signal (S100). In one embodiment, the satellite is a Global Positioning System (GPS) satellite, and the time signal is a 1 PPS (Pulse Per Second) signal transmitted at a cycle of 1 second. In another embodiment, the satellite is a GLONASS satellite and the time signal is a time signal provided by the GLONASS satellite.

In one embodiment, the precision clock forming unit 100 includes a local clock forming unit (not shown) for forming a local clock synchronized with the time signal provided by the artificial satellite, and a local clock generating unit And a first clock shaping portion (not shown) forming a first clock. The local clock shaping unit and the first clock shaping unit may each include a phase locked loop (PLL).

3 is a diagram schematically illustrating a process of synchronizing a time signal provided by a satellite with a local clock. Referring to FIG. 3, the local clock forming unit tracks a time signal provided by the artificial satellite to track and synchronize the phase and the frequency, and outputs a phase and a frequency synchronized with the time signal provided by the artificial satellite. Form a synchronized local clock. When the phase and frequency of the local clock are locked (locked) to the time signal provided by the artificial satellite, the state of the time source state indicating this changes.

When the phase and frequency of the local clock are synchronized with the time signal provided by the artificial satellite, the first clock forming unit included in the precision clock generating unit 100 forms a first clock having a higher frequency than the local clock, ). In one embodiment, the first clock has a frequency of 10 MHz.

The precision clock generator 100 receives a CA code (Coarse Acquisition code), a P code (Precise code), and a navigation message provided by a satellite, receives information on Coordinated Universal Time (UTC) NMEA (National Marine Electronics Association) information including position information of the receiver is formed and provided to the message processing unit 400.

The message processing unit 400 initializes the signal processing unit 300 when the time source state changes. For example, the message processing unit 400 updates the time information of the signal processing unit 300 using the UTC time information included in the provided NMEA information, and initializes a counter (not shown) for calculating the TOA. The time information provided to the signal processing unit 300 forms time of day (TOD) information, which is information on the hour, minute, and second when the signal provided by the transponder of the aircraft is received. When the signal provided by the transponder is received (CPS) (not shown) together with the TOA information, which is information about the TOA. The counter included in the signal processing unit receives the sampling clock as described below and counts the number of sampling clock pulses to form TOA information that is information on the time when the signal provided by the transponder is received. In addition, the message processor 400 may update its own time information using the NMEA information.

The RF receiving unit 200 receives the RF signal provided by the aircraft transponder or the reference monitoring transponder, and converts the RF signal into a baseband signal (S200). 4, a signal provided by an aircraft transponder or a reference monitoring transponder includes a mode 3 / A signal having an identification code (squawk code), a Mode C signal having altitude information, a signal having an ICAO address Bit Mode S signal, and monitoring data, and is a 112-bit 1090ES signal. As shown in the figure, Mode 3 / A signal and Mode C signal have the same form, and Mode S signal and 1090ES signal have the same preamble form.

The RF receiver 200 receives the Mode 3 / A signal, the Mode C signal, the Mode S signal, and the 1090 ES signal provided by the aircraft transponder or the reference monitoring transponder RMT, converts the signal into a baseband signal, ). In one embodiment, the RF receiver 200 includes a down conversion unit (not shown) for converting a received signal into a baseband signal and an envelope detection unit for performing envelope detection on the baseband signal, And a detection unit (not shown). For example, the envelope detector provides the formed envelope to the signal processor 300.

The RF receiving unit 200 receives the first clock formed by the precision clock forming unit 100 and forms a sampling clock SCK having a frequency higher than the frequency of the first clock, . In one embodiment, the RF receiver 200 may further include a sampling clock generator for receiving a first clock to form a sampling clock. For example, the sampling clock may be 100 MHz.

의 해상도를 가질 수 있다. 5 is a diagram schematically illustrating a process of forming the TOA information by the signal processing unit 300. In FIG. 5, the signal processing unit 300 receives the signal converted from the sampling clock (SCK) and the baseband from the RF receiving unit 200, samples the TOA information and the signal converted into the baseband, and outputs the data D (Not shown). The sampler 310 samples the signal converted to the baseband using the sampling clock (SCK). When a preamble of a signal is provided as one input of the sampler, a preamble is received using the number of sampling clock cycles counted from the time the counter (not shown) of the signal processing unit 300 is reset (TOA) is obtained (S300). In one embodiment, the TOA information includes

Of resolution.

의 해상도를 가질 수 있다. The signal processor 300 has UTC time information obtained from the NMEA signal received by the precise clock generator 400 in synchronization with the time signal provided by the artificial satellite and is continuously supplied with a time counter (not shown) The information is updated. Accordingly, the signal processing unit 300 forms time-of-day (TOD) information having information of the hour, minute and second when the preamble of the data is received. As an example, the TOD information

Of resolution.

The message processing unit 400 forms the TOA information formed by the signal processing unit 300 into a packet according to the UDP protocol and transmits it to the central control unit (CPS) (S400). In one embodiment, the message processing unit 400 may transmit TOA information and TOD information in the same packet, and the packet may further include information such as identifier information of the MLAT receiver.

6 shows the TOAs provided by the three central receivers (RU # 1, RU # 2, RU # 3) and the TOA provided by the reference monitoring transponder (RMT) To determine the location of the airline. 6, the central control apparatus includes TOA _RMT , which is TOA information provided by a reference monitoring transponder that receives a signal provided by an aircraft, and TOA _RMT , which is provided by three receivers RU # 1, RU # 2 and RU # TOA1, TOA2, and TOA2.

For example, when a point at which the difference between TOA ₁ and TOA _RMT provided by RU # 1 is calculated, it is shown as a red curve. Likewise, when a point at which the difference between TOA ₂ and TOA _RMT provided by RU # 2 is calculated is shown as a green curve, a point at which the difference between TOA ₃ and TOA _RMT provided by RU # 3 is constant, / RTI > The intersection of the above curves is the position of the aircraft at the corresponding time, and plotting the change of the intersection can be obtained by finding the wake.

The MLAT receiver according to the present embodiment forms a local clock synchronized with the time information provided by the satellite, and operates using the local clock. Therefore, signal distortion caused by reflections and refractions due to buildings or landforms, ionospheric errors and radio disturbances that occur when the satellite is out of orbit, and the ionosphere, tropospheric error, and time signals generated as the time signal of the satellite passes through the atmosphere It is not affected by the error of the time information due to the cause of the error. Further, according to the present embodiment, since a plurality of receivers operate with their own local clocks, it is advantageous that the satellite operates stably even when the satellite deviates from the orbit and forms a time error in a wide area.

In addition, the MLAT receiver according to the present embodiment performs re-synchronization with the satellite in a predetermined period. Therefore, it is possible to prevent accumulation of errors in the local clock due to long-term accumulation of influences of temperature, humidity, etc. of the receiver, and voltage fluctuations provided to the receiver.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of illustration, It will be appreciated that other embodiments are possible. Accordingly, the true scope of the present invention should be determined by the appended claims.

100: precision clock forming unit 200: RF receiving unit
300: signal processing unit 310: sampler
400: message processing unit

Claims (10)

A precision clock forming unit for forming a local clock synchronized with the time signal provided by the artificial satellite;
An RF receiver for receiving a signal provided by the transponder and converting the signal into a baseband;
A signal processor for forming TOA information from the baseband signal;
And a message processing unit for providing a packet including the TOA information to a central processing unit,
Wherein the precise clock generator is driven by the local clock after synchronization with a time signal provided by the satellite,
A local clock synchronized with a time signal provided by the satellite, and a local clock generator for changing state information corresponding to the time signal in synchronization with the time clock, a first clock generator for generating a first clock signal having a frequency higher than the frequency of the local clock, And a first clock shaping portion for forming a clock,
The RF receiver receives the first clock, forms a sampling clock having a higher frequency than the first clock, and provides the sampled clock to the signal processor,
Wherein the signal processing unit includes a sampling unit for sampling the signal converted into the baseband by the sampling clock, and a counter for counting the number of the sampling clock pulses,
Wherein the message processing unit resets the counter when the status information is changed,
Wherein the counter counts a pulse of the sampling clock from a reset time of the counter to obtain a signal reception time (TOA) converted into the baseband and outputs the signal reception time point (TOA) to the central processing unit. delete delete delete The method according to claim 1,
The precision clock forming unit
Receives a CA code (Coarse Acquisition code), a P code (Precise code) and a navigation message provided by the satellite to form a NMEA (National Marine Electronics Association) message and provides it to the message processing unit,
The message processing unit
And initializes the signal processing unit using the NMEA message. The method according to claim 1,
The MLAT receiver comprises:
And resynchronizing the satellite with the satellite in a predetermined period. A method of driving an MLAT receiver, the method comprising:
(a) forming a local clock synchronized with a time signal provided by a satellite, and changing state information indicating synchronization with the time signal;
(b) resetting the counter according to the changed state information, receiving the signal provided by the transponder, and converting the received signal to baseband;
(c) forming TOA information from the baseband signal; and
(d) providing a packet including the TOA information to a central processing unit,
After the step (a), the MLAT receiver is driven with the local clock,
(A) comprises:
(a1) forming a local clock synchronized with a time signal provided by the satellite,
(a2) forming a first clock having a frequency higher than the frequency of the local clock from the local clock, and
(a3) forming a sampling clock having a higher frequency than the first clock,
Wherein the step (c) includes counting pulses of the sampling clock after the counter reset and sampling the signal converted into the baseband with the sampling clock to form TOA information. delete delete 8. The method of claim 7,
Wherein the driving method of the MLAT receiver performs the step (a) by a predetermined period.

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