CN113341368B - DOR beacon generation method suitable for deep space exploration - Google Patents

DOR beacon generation method suitable for deep space exploration Download PDF

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Publication number
CN113341368B
CN113341368B CN202110503402.3A CN202110503402A CN113341368B CN 113341368 B CN113341368 B CN 113341368B CN 202110503402 A CN202110503402 A CN 202110503402A CN 113341368 B CN113341368 B CN 113341368B
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dor
beacon
formula
frequency
signal
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CN113341368A (en
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杜检来
徐锡超
李巧玲
张慧
熊勇华
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Shanghai Aerospace Electronics Co ltd
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Shanghai Aerospace Electronics Co ltd
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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
    • G01S1/00—Beacons or beacon systems transmitting signals having a characteristic or characteristics capable of being detected by non-directional receivers and defining directions, positions, or position lines fixed relatively to the beacon transmitters; Receivers co-operating therewith
    • G01S1/02—Beacons or beacon systems transmitting signals having a characteristic or characteristics capable of being detected by non-directional receivers and defining directions, positions, or position lines fixed relatively to the beacon transmitters; Receivers co-operating therewith using radio waves
    • 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
    • G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
    • G01S19/38—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system
    • G01S19/39—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system the satellite radio beacon positioning system transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/40—Correcting position, velocity or attitude
    • G01S19/41—Differential correction, e.g. DGPS [differential GPS]
    • 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
    • G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
    • G01S19/38—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system
    • G01S19/39—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system the satellite radio beacon positioning system transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/42—Determining position
    • G01S19/43—Determining position using carrier phase measurements, e.g. kinematic positioning; using long or short baseline interferometry
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D30/00—Reducing energy consumption in communication networks
    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

Abstract

The invention provides a DOR beacon generation method suitable for deep space exploration, which is realized by adopting an FPGA (field programmable gate array), does not need a complex circuit structure, and particularly in a digital measurement and control transponder, a DOR beacon generation part and a measurement and control transponder intermediate-frequency signal processing part share an FPGA chip without additionally adding a circuit; the DOR beacon generation mode is expressed by a hardware description language (VHDL or Verilog HDL) of the FPGA, so that coherent/incoherent instructions, sine wave/square wave waveform selection, modulation parameter adjustment, DOR beacon switching and other instructions can be flexibly responded, and the realization form of a hardware circuit is not influenced; DOR beacon generation is realized in a digital circuit mode, the modulation index of a generated signal is accurate, the frequency spectrum symmetry is good, the influence of temperature is small, and the consistency is good.

Description

DOR beacon generation method suitable for deep space exploration
Technical Field
The invention relates to the technical field of deep space measurement and control, in particular to a DOR beacon generation method suitable for deep space detection.
Background
When the satellite runs in orbit, the orbit of the satellite needs to be accurately determined, and support is provided for the orbit control of the satellite. In the low earth satellite, a GPS or a beacon of a measurement and control transponder can be adopted for measuring the orbit; for the satellite in the deep space exploration field, the above method for determining the orbit is not suitable any more, and is influenced by the transmission distance, and the received signal is extremely weak and can generate the distance ambiguity problem. Very Long base line Interferometry (VLBI) technology is used in the united states, europe and us as the primary approach to rail determination during deep space exploration and has been applied in-orbit.
Very long baseline interferometry techniques require the transmission of DOR (Differential One-way Ranging) beacon signals on the satellite, which are typically generated and transmitted by measurement and control transponders, to the surface using the same link as the telemetry signals. In order to realize accurate measurement of VLBI, a general DOR beacon is composed of a low frequency beacon and a high frequency beacon, frequencies of the two beacons are coherent with a carrier signal frequency, and for X-band deep space sounding, a frequency relationship between the beacon frequency and a main carrier signal is generally as follows:
f dor1 ＝f downstream /2200 (formula 1)
f dor2 ＝f Downstream /440 (formula 2)
According to the actual requirement of VLBI measurement, a DOR beacon sent in downlink has two modes of coherence and noncoherence, and in the noncoherence mode, the downlink frequency is a nominal frequency; in the coherent mode, the downlink frequency is also correlated to the uplink doppler frequency. Meanwhile, the waveform of the DOR beacon can be selected from sine waves and square waves, the modulation degree can be adjusted possibly, the DOR beacon can be controlled in an on-off mode, and the frequency of the DOR signal can be changed when necessary.
The patent 'a deep space exploration is with one-way range finding signal generation method of X frequency channel and device (CN 10491441B)' and 'X frequency channel deep space transponder DOR circuit (CN 201418010702J)' all relate to the method of generating the DOR signal, but all adopt the circuit form to realize, need adopt special circuit, do not utilize the miniaturized design of satellite-borne product, and be inconvenient in modification, not flexible enough when to DOR beacon relevant parameter change.
Disclosure of Invention
The invention aims to provide a DOR beacon generation method suitable for deep space exploration, which is realized in an FPGA (field programmable gate array), can flexibly modify parameters and modes, is suitable for various application occasions of VLBI (very long term evolution bi) measurement, and is particularly suitable for the field of deep space exploration.
In order to solve the technical problems, the technical scheme of the invention is as follows: a DOR beacon generation method suitable for deep space exploration is provided, and comprises the following steps:
s1, calculating the frequency value of the DOR beacon:
let the frequency of the downlink signal be f down If the Doppler frequency of the uplink signal is Δ f, then
In the coherent mode:
f 1 ＝(f down + Δ f)/2200 formula 3
f 2 ＝(f down + Δ f)/440 formula 4
In the non-coherent mode:
f 1 ＝f down /2200 formula 5
f 2 ＝f down /440 type 6
After the frequency value of the DOR beacon is obtained through calculation, the DOR beacon needs to be converted into a frequency control word during internal processing of the FPGA, and the working frequency is set to be f s If the bit width of the clock control word is N, then
f1_contol＝round(2 N *f 1 Fs) formula 7
f2_contol＝round(2 N *f 2 Fs) formula 8;
s2, generating a DOR beacon waveform:
and calculating according to the frequency control word to obtain phase words, wherein the phase words of the two DOR beacons are calculated respectively, and the calculation formula is as follows:
NCO1 ═ NCO1+ f1_ contol formula 9
NCO2 ═ NCO2+ f2_ contol formula 10
When a sine wave beacon is required to be output, performing table lookup through the phase control word to obtain a corresponding sine value; when a sine wave needs to be output, the highest bit of the phase control word is output;
s3, modulation degree control:
setting a modulation degree coefficient m1 of the DOR according to a preset value; when an uplink remote control instruction modifies the DOR modulation factor, placing a new factor in the DOR modulation factor m 1; multiplying the DOR beacon signal obtained in the step S2 by a modulation factor m1 to obtain a signal after modulation control;
s4, DOR switch control:
DOR1 and DOR2 are respectively controlled by different remote control commands; setting corresponding switch flags k1 and k2 according to the instructions of DOR1 and DOR2, respectively, wherein a signal '1' indicates that the beacon is in an on state; signal "0" indicates that the beacon is in an off state;
s5 PM modulation
After the DOR signal is generated according to the instruction, the DOR signal is modulated together with signals such as telemetry subcarrier and the like, and the modulation system is PM (phase modulation), and the expression is as follows:
Data_out＝Sin(2πf 0 t+m0*sin(2πf TM t)+k1*DOR_OUT 1 +k2*DOR_OUT 2 ) Formula 11.
Further, in step S2, when performing table lookup through the phase control word to obtain a corresponding sine value, a 1/4 sine table is selected.
Further, in step S4, the DOR beacon can be turned on and off by remote control command according to the use requirement.
The DOR beacon generation method suitable for deep space exploration provided by the invention adopts the FPGA to generate the DOR beacon without an additional circuit, thereby being beneficial to the miniaturization design of a satellite-borne product; the implementation mode is flexible, and the expected beacon signal can be generated by modifying the configuration parameters or external instructions; the generated DOR beacon has good quality, the modulation error is within 0.05rad, the frequency spectrum symmetry is within 0.1dB range, and the influence of the environment temperature is small.
Drawings
The invention is further described with reference to the accompanying drawings:
FIG. 1 is a block diagram of a DOR generation implementation suitable for deep space exploration according to an embodiment of the present invention;
fig. 2 is a flowchart of DOR generation suitable for deep space exploration according to an embodiment of the present invention.
Detailed Description
The following describes the DOR beacon generation method suitable for deep space exploration according to the present invention in further detail with reference to the accompanying drawings and specific embodiments. Advantages and features of the present invention will become apparent from the following description and from the claims. It is to be noted that the drawings are in a very simplified form and are all used in a non-precise ratio for the purpose of facilitating and distinctly aiding in the description of the embodiments of the invention.
The DOR beacon generation method suitable for deep space exploration, provided by the invention, adopts the FPGA to generate the DOR beacon, does not need an additional circuit, and is beneficial to the miniaturization design of a satellite-borne product; the implementation mode is flexible, and the expected beacon signal can be generated by modifying the configuration parameters or external instructions; the generated DOR beacon has good quality, the modulation error is within 0.05rad, the frequency spectrum symmetry is within 0.1dB range, and the influence of the environment temperature is small.
FIG. 1 is a block diagram of DOR generation implementation suitable for deep space exploration, including DOR1/DOR2 two-way beacon generation and PM signal modulation, and the generated signals are finally output through a D/A conversion circuit. Fig. 2 is a detailed implementation flowchart of the present invention.
1. Frequency values for the DOR beacons are calculated.
The frequency value of the DOR beacon is related to the coherent/non-coherent mode and the uplink signal doppler frequency. Generally, the frequency relation between the DOR beacon frequency of the X-band deep space measurement and control and the main carrier signal is shown as formula (1) and formula (2). Let the frequency of the downlink signal be f down If the Doppler frequency of the uplink signal is Δ f, then
In the coherent mode:
f 1 ＝(f down + Δ f)/2200 (formula 3)
f 2 ＝(f down + Δ f)/440 (formula 4)
In the non-coherent mode:
f 1 ＝f down /2200 (formula 5)
f 2 ＝f down /440 (type 6)
After the frequency value of the DOR beacon is obtained through calculation, the DOR beacon needs to be converted into a frequency control word during internal processing of the FPGA, and the working frequency is set to be f s If the bit width of the clock control word is N, then
f1_contol＝round(2 N *f 1 Fs) (formula 7)
f2_contol＝round(2 N *f 2 Fs) (type 8)
2. A DOR beacon waveform is generated.
The DOR beacon waveform is generally selected by both sine and square waves according to external commands. Firstly, a phase word is obtained through calculation according to the frequency control word, and the phase words of the two DOR beacons are calculated respectively. The calculation formula is as follows:
NCO1 ═ NCO1+ f1_ contol (formula 9)
NCO2 ═ NCO2+ f2_ contol (formula 10)
When a sine wave beacon needs to be output, a table is looked up through the phase control words to obtain a corresponding sine wave value, and in order to save register resources, an 1/4 sine wave table is adopted. When the sine wave needs to be output, the highest bit of the phase control word is output.
3. And (5) controlling the modulation degree.
Setting a modulation degree coefficient m1 of the DOR according to a preset value; and when an uplink remote control command modifies the DOR modulation factor, setting a new factor to the DOR modulation factor m 1. And (3) multiplying the DOR beacon signal obtained in the step (2) by a modulation factor m1 to obtain a signal with a modulated degree controlled.
4. And (4) controlling a DOR switch.
The DOR beacon can be controlled to be turned on and off through a remote control command according to the use requirement. DOR1 and DOR2 are controlled separately by different remote commands. Setting corresponding switch flags k1 and k2 according to the instructions of DOR1 and DOR2, respectively, wherein a signal '1' indicates that the beacon is in an on state; signal "0" indicates that the beacon is in an off state.
5. PM modulation
After the DOR signal is generated according to the instruction, the DOR signal is modulated together with signals such as telemetry subcarrier and the like, and the modulation system is PM (phase modulation), and the expression is as follows:
Data_out＝Sin(2πf 0 t+m0*sin(2πf TM t)+k1*DOR_OUT 1 +k2*DOR_OUT 2 ) (formula 11)
The steps 1 to 5 are all realized in the FPGA. After the DOR beacon signal is generated and modulated, the DOR beacon signal is converted into an analog signal through a D/A conversion chip, and finally the analog signal is up-converted into an X frequency band or other radio frequency working frequency bands and is sent to the ground through an antenna.
The DOR beacon generation method suitable for deep space exploration provided by the embodiment has the following beneficial effects:
1. the beacon generation method is realized by adopting the FPGA, a complex circuit structure is not needed, particularly in a digital measurement and control responder, a DOR beacon generation part and a measurement and control responder intermediate-frequency signal processing part share an FPGA chip, and no additional circuit is needed;
2. the DOR beacon generation mode is expressed by a hardware description language (VHDL or Verilog HDL) of the FPGA, so that coherent/incoherent instructions, sine wave/square wave waveform selection, modulation parameter adjustment, DOR beacon switching and other instructions can be flexibly responded, and the realization form of a hardware circuit is not influenced;
3. DOR beacon generation is realized in a digital circuit mode, the modulation index of a generated signal is accurate, the frequency spectrum symmetry is good, the influence of temperature is small, and the consistency is good.
Those not described in detail in this specification are within the skill of the art. It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims (3)

1. A DOR beacon generation method suitable for deep space exploration is characterized by comprising the following steps:
s1, calculating the frequency value of the DOR beacon:
let the frequency of the downlink signal be f down If the Doppler frequency of the uplink signal is Δ f, then
In the coherent mode:
f 1 ＝(f down + Δ f)/2200 formula 3
f 2 ＝(f down + Δ f)/440 formula 4
In the non-coherent mode:
f 1 ＝f down /2200 formula 5
f 2 ＝f down /440 type 6
After the frequency value of the DOR beacon is obtained through calculation, the DOR beacon needs to be converted into a frequency control word during internal processing of the FPGA, and the working frequency is set to be f s And the bit width of the frequency control word is N, then
f1_contol＝round(2 N *f 1 Fs) formula 7
f2_contol＝round(2 N *f 2 Fs) formula 8;
s2, generating a DOR beacon waveform:
and calculating according to the frequency control word to obtain phase words, wherein the phase words of the two DOR beacons are calculated respectively, and the calculation formula is as follows:
NCO1 ═ NCO1+ f1_ contol formula 9
NCO2 ═ NCO2+ f2_ contol formula 10
When a sine wave beacon is required to be output, performing table lookup through the phase control word to obtain a corresponding sine value; when square waves need to be output, the highest bit of the phase control word is output;
s3, modulation degree control:
setting a modulation degree coefficient m1 of the DOR according to a preset value; when an uplink remote control instruction modifies the DOR modulation factor, placing a new factor in the DOR modulation factor m 1; multiplying the DOR beacon signal obtained in the step S2 by a modulation factor m1 to obtain a signal with a modulated degree controlled;
s4, DOR switch control:
DOR1 and DOR2 are respectively controlled by different remote control commands; setting corresponding switch flags k1 and k2 according to the instructions of DOR1 and DOR2, respectively, wherein a signal '1' indicates that the beacon is in an on state; signal "0" indicates that the beacon is in an off state;
s5 PM modulation
After the DOR signal is generated according to the instruction, the DOR signal is modulated together with signals such as telemetry subcarrier and the like, and the modulation system is PM (phase modulation), and the expression is as follows:
Data_out＝Sin(2πf 0 t+m0*sin(2πf TM t)+k1*DOR_OUT 1 +k2*DOR_OUT 2 ) Formula 11.
2. A DOR beacon generating method for deep space exploration, as claimed in claim 1, wherein in step S2, when the phase control word is used to look up the table to obtain the corresponding sine value, the table 1/4 is selected.
3. A DOR beacon generating method for deep space exploration, according to claim 1, wherein in step S4, the DOR beacon is controlled to be turned on and off by remote control command according to the use requirement.
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US6674687B2 (en) * 2002-01-25 2004-01-06 Navcom Technology, Inc. System and method for navigation using two-way ultrasonic positioning
WO2004051908A2 (en) * 2002-11-27 2004-06-17 U-Nav Microelectronics Corporation System and method for providing secure communication between network nodes
GB2480311A (en) * 2010-05-13 2011-11-16 Univ Bangor Optical OFDM synchronisation using clock signal transmitted outside OFDM symbol frequency band
CN103368638B (en) * 2012-03-29 2016-08-24 中国科学院空间科学与应用研究中心 A kind of TTC & DT Systems for deep space probe and method
KR20180058896A (en) * 2016-11-24 2018-06-04 김경수 Apparatus for SDR-MRSP processor
US10433260B1 (en) * 2018-07-02 2019-10-01 Arris Enterprises Llc Antenna-parameter control in a distributed system
WO2019010143A1 (en) * 2017-07-01 2019-01-10 Ruckus Wireless, Inc. Antenna-parameter control in a distributed system
CN108173589A (en) * 2017-12-25 2018-06-15 航天东方红卫星有限公司 A kind of moonlet TT＆C system and method suitable for survey of deep space
CN108462523B (en) * 2018-02-12 2022-06-10 上海航天电子有限公司 General digital USB responder baseband software design method
CN109633574B (en) * 2018-10-25 2020-12-22 上海无线电设备研究所 Wide-range high-precision Doppler measurement method for deep space exploration
CN111786720B (en) * 2020-07-23 2022-03-15 中国科学院微小卫星创新研究院 Measurement and control communication system and method for deep space exploration small satellite
CN112422167B (en) * 2020-10-27 2022-12-09 北京空间飞行器总体设计部 Zero-value calibration method for multi-channel high-precision distance measuring transceiver
CN112666548B (en) * 2020-12-11 2023-09-29 中国人民解放军63921部队 Method, device and system for determining working mode of speed measuring transponder

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