CN115296725B - Down-guiding low-orbit satellite-ground transmission large Doppler compensation method - Google Patents
Down-guiding low-orbit satellite-ground transmission large Doppler compensation method Download PDFInfo
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- CN115296725B CN115296725B CN202211219121.6A CN202211219121A CN115296725B CN 115296725 B CN115296725 B CN 115296725B CN 202211219121 A CN202211219121 A CN 202211219121A CN 115296725 B CN115296725 B CN 115296725B
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- 238000012545 processing Methods 0.000 claims abstract description 18
- 238000005259 measurement Methods 0.000 claims abstract description 14
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/14—Relay systems
- H04B7/15—Active relay systems
- H04B7/185—Space-based or airborne stations; Stations for satellite systems
- H04B7/1851—Systems using a satellite or space-based relay
- H04B7/18517—Transmission equipment in earth stations
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/14—Relay systems
- H04B7/15—Active relay systems
- H04B7/185—Space-based or airborne stations; Stations for satellite systems
- H04B7/1851—Systems using a satellite or space-based relay
- H04B7/18513—Transmission in a satellite or space-based system
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- 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
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- 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
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Abstract
The invention discloses a downlink-guided large Doppler compensation method for satellite-ground transmission of a low-orbit satellite, and relates to a channel transmission technology in the field of low-orbit satellite communication. The invention adopts continuous measurement of the active guide signal of the low orbit satellite to generate Doppler correction carrier and Doppler compensation carrier, adopts the Doppler correction carrier to eliminate the Doppler effect of the downlink, and adopts the Doppler compensation carrier to compensate the Doppler effect of the uplink, thereby improving the Doppler effect resistance of the whole system. The method improves the Doppler effect resistance of the whole system without improving the satellite processing complexity of the low-orbit satellite, and is particularly suitable for the high-dynamic-resistance design of the low-orbit satellite.
Description
Technical Field
The invention relates to the field of low-orbit satellite communication and low-orbit satellite internet, which is suitable for the design and realization of a low-orbit satellite-ground transmission system for on-satellite regeneration processing.
Background
For a low-orbit satellite, the satellite has high running speed and generates a large Doppler effect, so that the error rate is increased in the communication process, and the system performance is directly reduced. In order to ensure the reliability of communication, doppler frequency offset and frequency offset change rules of the satellite in a visual range must be analyzed, so that Doppler effect is compensated, and communication quality is improved.
Currently, there are two general methods for resisting doppler effect in satellite communication: firstly, a signal receiving end analyzes a signal, estimates Doppler frequency offset generated by a proper algorithm, and corrects uplink and downlink frequency offset through corresponding control aspects based on a frequency offset estimation value; secondly, according to the motion information of the satellite (or the terminal), the Doppler frequency offset and the Doppler change rate are converted, and then the carrier wave is compensated. For low earth orbit satellites, the Doppler effect is severe, the scene is complex, and the two methods both occupy more satellite processing load resources and increase satellite processing load complexity.
Disclosure of Invention
In view of this, the present invention provides a downlink-guided large doppler compensation method for satellite-to-ground transmission of low-orbit satellites. The method can distribute complex signal analysis functions to be borne by the ground terminal, simplifies the complexity of satellite processing load, and accordingly reduces the dependence on the high performance of the satellite processing load platform.
The technical scheme adopted by the invention is as follows:
a downlink-guided low-orbit satellite-to-ground transmission large Doppler compensation method comprises the following steps:
step 1, processing a load on a satellite to generate and send an active guide signal;
step 2, the ground terminal performs sampling measurement processing on the active pilot signal to generate a digital Doppler correction carrier;
step 3, the ground terminal performs digital mixing on the downlink carrier wave and the digital Doppler correction carrier wave, and eliminates the downlink Doppler frequency offset and the Doppler change rate, so that the ground terminal can demodulate normally;
step 4, the ground terminal converts the Doppler correction carrier wave into a Doppler compensation carrier wave according to the uplink and downlink frequency relation;
step 5, the ground terminal carries out digital mixing on the Doppler compensation carrier and the uplink carrier to realize Doppler compensation, and then the low-orbit satellite-borne demodulator carries out normal demodulation;
therefore, the correction compensation of the satellite-ground high dynamic large Doppler effect of the low orbit satellite is completed.
Further, the specific manner of step 2 is as follows:
step 201, a ground terminal performs sampling processing on an active pilot signal to generate a sampling sequence;
step 202, measuring the sampling sequence in a continuous, crossed and parallel mode, and increasing the number of samples and the measuring frequency of single measurement;
step 203, loop filtering is carried out on the measurement result;
and step 204, generating a Doppler correction carrier wave according to the loop filtering result.
The invention has the beneficial effects that:
1. the invention takes simplified satellite processing complexity as a basic starting point, and a ground terminal carries out multiple, accurate and high-frequency measurement on an active guide signal sent on a satellite to generate a digital Doppler correction carrier; doppler frequency mixing is carried out on the Doppler correction carrier and the downlink carrier, and the Doppler effect of a downlink is eliminated; and generating a Doppler compensation carrier according to the Doppler correction carrier and the relationship between the uplink and the downlink frequencies, mixing the Doppler compensation carrier with the uplink carrier, and offsetting the Doppler effect of the uplink on a satellite receiving end, thereby realizing the Doppler resistance of the whole satellite-ground transmission uplink and downlink large loop.
2. Compared with the traditional method, the method reduces the processing complexity of the uplink on-satellite demodulation end, and can effectively reduce the on-satellite processing complexity, thereby reducing the dependence on the high performance of an on-satellite processing platform.
Drawings
Fig. 1 is a schematic diagram of an operating principle of a downlink-guided large doppler compensation method for satellite-to-ground transmission of a low-orbit satellite in an embodiment of the present invention.
Fig. 2 is a flow chart of doppler correction in an embodiment of the invention.
Detailed Description
The invention is described in further detail below with reference to the figures and the detailed description.
A downlink-guided low-orbit satellite-to-satellite large-Doppler compensation method aims at the following problems:
the low orbit satellite moves at high speed, generates Doppler effect, and reflects the Doppler effect to signal transmission, namely, larger frequency offset and frequency offset change rate.
Therefore, the method continuously measures the active pilot signal of the low orbit satellite to generate a Doppler correction carrier and a Doppler compensation carrier, eliminates the Doppler effect of the downlink by adopting the Doppler correction carrier, and performs Doppler compensation on the uplink by adopting the Doppler compensation carrier, thereby improving the Doppler effect resistance of the whole system.
Specifically, referring to fig. 1 and 2, in the method, the low-earth satellite load transmits an active pilot signal and a downlink signal, and receives an uplink signal; the ground terminal receives the downlink signal, measures the active pilot signal and transmits an uplink signal; the ground terminal generates a digital doppler correction carrier and a doppler compensation carrier according to the measurement result of the active pilot signal, and performs the cancellation of the downlink doppler effect and the compensation of the uplink doppler effect, as shown in fig. 1. The ground terminal performs continuous, cross and parallel methods on the active pilot signal, so as to improve the accuracy of doppler measurement and the number of measurements, as shown in fig. 2.
The method comprises the following flow steps:
(1) Processing load on the satellite of the low-orbit satellite to generate and transmit an active guide signal;
after the low earth orbit satellite communication system is started, an active pilot signal and a downlink signal are transmitted at a frequency point preset by the system, wherein the active pilot signal is a single-tone signal.
(2) And the ground terminal performs sampling measurement processing on the active pilot signal to generate a digital Doppler correction carrier. The concrete method is as follows:
step 201, a ground terminal performs sampling processing on an active pilot signal to generate a sampling sequence;
step 202, measuring the sampling sequence in a continuous, crossed and parallel mode, and increasing the number of samples and the measuring frequency of single measurement;
step 203, loop filtering is carried out on the measurement result;
and step 204, generating a Doppler correction carrier wave according to the loop filtering result.
The specific implementation scheme of step (2) is shown in FIG. 2, and is detailed as follows:
determining the time length of the sample of the measuring active signal as Δ t in the unit: s, the rate of change of the Doppler frequency offset is Δ f, in units: hz/s, the sampling sample time length should satisfy:
∆t=(1/∆f) 1/2
in the embodiment, the downlink signal symbol rate is Sys _ rate, unit: sps, the measured frequency should satisfy:
∆k=1/(0.03*Sys_rate)
in the embodiment, the FFT is performed on the sample with the sampling time Δ t, the frequency is estimated, the filtering is performed through the second order loop, and then the doppler correction carrier is performed:
x Correction (t)=cos(2*pi*f*t)
wherein,fis the second order loop filtered frequency.
(3) The ground terminal adopts digital Doppler correction carrier waves and downlink carrier waves to carry out digital frequency mixing, the elimination of Doppler frequency offset and change rate is completed, and the ground terminal demodulates normally;
in the embodiment, the downlink signal is subjected to doppler cancellation by digital mixing, and the carrier after cancellation is obtained as follows:
y cancellation of (t)=y(t)*x(t)
Wherein,x(t) is the Doppler cancellation carrier,y(t) is a downlink signal, and,y cancellation of (t) is a signal after Doppler correction.
(4) The ground terminal converts the Doppler correction carrier into a Doppler compensation carrier according to the relation between the uplink frequency and the downlink frequency;
in one embodiment, the downlink active pilot signal has a frequency off1, the uplink signal frequency point isfDoppler compensation carrier frequency generated by the ground terminal:
f compensating for =f* f2/ f1
In an embodiment, the doppler compensation carrier is:
x compensation (t)=cos(2*pi*f Compensating for *t)
(5) The ground terminal carries out digital mixing on the Doppler compensation carrier and the uplink carrier to realize Doppler compensation, and the satellite-borne demodulator can normally demodulate after receiving the compensation signal;
in the embodiment, digital mixing is adopted for the uplink signal to perform doppler compensation, and a carrier wave after doppler compensation is adopted:
z compensation (t)=z(t)* x Compensating for (t)
Wherein,x compensation (t)The carrier is cancelled for the purpose of doppler cancellation,z(t) is an uplink signal and (d),z compensating for And (t) is the Doppler compensated signal.
The steps are continuously carried out, and communication under the satellite-ground strong Doppler effect is completed.
In a word, the invention is an effective method for solving the problem of large Doppler effect between each satellite of the low-orbit satellite and the low-orbit satellite internet constellation and the ground terminal.
Claims (1)
1. A downlink-guided low-orbit satellite-ground transmission large Doppler compensation method is characterized by comprising the following steps:
step 1, a low-orbit satellite transmits an active guide signal;
step 2, the ground terminal performs sampling measurement processing on the active pilot signal to generate a digital Doppler correction carrier; the concrete mode is as follows:
step 201, a ground terminal performs sampling processing on an active pilot signal to generate a sampling sequence;
step 202, measuring the sampling sequence in a continuous, crossed and parallel mode, and increasing the number of samples and the measuring frequency of single measurement; determining the time length of the sample of the measuring active signal as Δ t in the unit: s, the rate of change of the Doppler frequency offset is Δ f, in units: hz/s, the sampling sample time length satisfies the following conditions:
∆t=(1/∆f) 1/2
the downlink signal symbol rate is Sys _ rate, unit: sps, the measured frequency satisfies:
∆k=1/(0.03*Sys_rate)
step 203, loop filtering is carried out on the measurement result;
step 204, generating a Doppler correction carrier wave according to a loop filtering result;
step 3, the ground terminal performs digital frequency mixing by adopting a digital Doppler correction carrier and a downlink carrier to complete the elimination of Doppler frequency offset and change rate, and then the ground terminal performs normal demodulation;
step 4, the ground terminal converts the Doppler correction carrier wave into a Doppler compensation carrier wave according to the uplink and downlink frequency relation;
step 5, the ground terminal carries out digital mixing on the Doppler compensation carrier and the uplink carrier to realize Doppler compensation, and then the satellite-borne demodulator carries out normal demodulation;
and finishing the correction compensation of the satellite-ground high dynamic large Doppler effect of the low orbit satellite.
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103116038A (en) * | 2013-01-21 | 2013-05-22 | 中国人民解放军国防科学技术大学 | Acceleration-measuring method by satellite receiver carrier tracking l |
| CN112039579A (en) * | 2020-09-10 | 2020-12-04 | 上海清申科技发展有限公司 | Signal synchronization method and device for satellite communication |
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| CN104297765B (en) * | 2014-09-25 | 2017-04-26 | 上海欧科微航天科技有限公司 | Ground terminal simulator used for low-orbit satellite synchronous communication system |
| CN110187368B (en) * | 2019-06-24 | 2023-05-16 | 中国电子科技集团公司第二十九研究所 | Doppler frequency offset processing method between low-orbit satellite and ground terminal |
| CN112019252B (en) * | 2020-08-03 | 2022-04-19 | 航天科工空间工程发展有限公司 | Method and system for correcting return frequency offset of low-earth-orbit satellite communication system |
| CN112965089B (en) * | 2021-02-05 | 2024-03-19 | 重庆两江卫星移动通信有限公司 | Method and system for acquiring high-precision signal of integrated low-orbit satellite |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103116038A (en) * | 2013-01-21 | 2013-05-22 | 中国人民解放军国防科学技术大学 | Acceleration-measuring method by satellite receiver carrier tracking l |
| CN112039579A (en) * | 2020-09-10 | 2020-12-04 | 上海清申科技发展有限公司 | Signal synchronization method and device for satellite communication |
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