CN111917452B - Method and system for inhibiting carrier tracking by large frequency offset - Google Patents
Method and system for inhibiting carrier tracking by large frequency offset Download PDFInfo
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- CN111917452B CN111917452B CN202010673973.7A CN202010673973A CN111917452B CN 111917452 B CN111917452 B CN 111917452B CN 202010673973 A CN202010673973 A CN 202010673973A CN 111917452 B CN111917452 B CN 111917452B
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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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- 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
- H04B7/18519—Operations control, administration or maintenance
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2647—Arrangements specific to the receiver only
- H04L27/2655—Synchronisation arrangements
- H04L27/2657—Carrier synchronisation
- H04L27/2659—Coarse or integer frequency offset determination and synchronisation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2647—Arrangements specific to the receiver only
- H04L27/2655—Synchronisation arrangements
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- H04L27/266—Fine or fractional frequency offset determination and synchronisation
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Abstract
The invention discloses a method and a system for restraining carrier tracking by large frequency deviation, wherein the method comprises the steps of carrying out open loop estimation rough synchronization of a first-stage radio frequency analog signal on carrier frequency, and guiding the output of a direct digital frequency synthesizer to control the output frequency of a local oscillation source of a receiver according to the estimation result so as to realize the quick rough synchronization of the carrier frequency; converting the radio frequency analog signal into a digital signal; carrying out closed-loop accurate synchronization of a second-stage digital signal on the carrier frequency, adjusting the output frequency of the integer controlled oscillator, and realizing accurate synchronous tracking of the carrier frequency and the phase; the system comprises an analog front end, a frequency deviation estimation module based on ephemeris, a direct digital frequency synthesizer, an A/D conversion and band-pass filtering module, a digital down-conversion module and a costas loop synchronous carrier module; compared with a full digital suppression carrier tracking scheme, the method has the advantages of wider application occasions and stronger adaptability; under the condition of large frequency offset of a satellite communication system, the method can quickly and accurately perform synchronous tracking processing on the received signal carrier.
Description
Technical Field
The invention belongs to the technical field of carrier synchronization of a satellite communication system, and relates to a method and a system for restraining carrier tracking by large frequency deviation.
Background
Spread spectrum communication technology is widely applied in modern satellite communication systems, and in order to save transmission power and improve the working efficiency of transmitters, a balanced modulator for suppressing carriers is often adopted in the spread spectrum communication systems. The carrier tracking inhibition is a key technology of digital baseband signal processing in spread spectrum communication, and the frequency offset estimation tracking module is added in the carrier synchronization module to effectively cope with the influence of frequency offset and phase jump of a received signal on communication quality caused by Doppler effect, multipath fading and the like in a satellite communication environment. The frequency offset estimation tracking can adopt an open-loop carrier synchronization structure and a closed-loop carrier synchronization structure, the open-loop carrier synchronization mainly directly estimates the carrier frequency and the phase according to a certain estimation algorithm, feedback is not needed, the synchronization time is short, and typical algorithms such as a data auxiliary estimation algorithm, a non-data auxiliary estimation algorithm, a maximum likelihood estimation algorithm and the like. The open-loop carrier synchronization speed is high, but the result obtained by the carrier synchronization is not accurate enough. The closed-loop carrier synchronization can realize accurate tracking synchronization of carriers by using synchronous circuits such as a phase-locked loop, but the synchronous circuits such as the phase-locked loop need a certain time to enter a synchronous state, and the requirement of quick synchronization in the existing satellite communication system cannot be met only by a carrier synchronization mode of a closed-loop structure.
Disclosure of Invention
The invention aims to: the method and the system for restraining carrier tracking by large frequency deviation solve the problems of speed and accuracy of frequency phase tracking of a receiving end on a received signal carrier under large frequency deviation by jointly using an analog signal open-loop carrier synchronization structure and a digital signal closed-loop carrier synchronization structure.
The technical scheme adopted by the invention is as follows:
a method for restraining carrier tracking by large frequency deviation comprises the following steps:
step 1: carrying out open loop estimation rough synchronization of a first-stage radio frequency analog signal on the carrier frequency, and guiding the output of a direct digital frequency synthesizer to control the output frequency of a local vibration source of a receiver according to an estimation result so as to realize rapid rough synchronization of the carrier frequency;
step 2: converting the radio frequency analog signal into a digital signal;
and step 3: and carrying out closed-loop accurate synchronization on the second-stage digital signals on the carrier frequency, adjusting the output frequency of the integer controlled oscillator, and realizing accurate synchronous tracking of the carrier frequency and the phase.
Further, the open-loop estimation rough synchronization of the first-stage radio frequency analog signal adopts the output of the direct digital frequency synthesizer controlled by the satellite ephemeris-based pre-correction and compensation calculation as the reference input of the local vibration source of the receiver.
Further, the satellite ephemeris-based pre-correction and compensation calculation specifically includes: and calculating the relative motion speed between the satellite and the receiver by adopting a geocentric earth-fixed coordinate system, calculating the Doppler frequency shift, and adjusting the output of the direct digital frequency synthesizer as the reference input of the local oscillation source according to the predicted result of the Doppler frequency shift.
Further, the calculation of the relative movement speed specifically includes: and obtaining the satellite position by using the satellite ephemeris, further calculating the instantaneous speed of the satellite in the geocentric geostationary coordinate system, simultaneously obtaining the position and the instantaneous speed of the receiver in the geocentric geostationary coordinate system, and performing projection operation on the speed vector of the receiver and the speed vector of the satellite to the connection vector of the satellite and the receiver.
Further, the doppler frequency is calculated according to the following formula:
wherein c is the speed of light, v S V is a projection of the instantaneous velocity of the satellite in the geocentric geostationary coordinate system onto the satellite-receiver connecting line vector R The projection of the instantaneous speed of the receiver in the geocentric geostationary coordinate system on a connecting line vector of the satellite and the receiver is obtained;
when the satellite and the receiver approach to each other, plus or minus is taken,
The operator above, away from the time ±),
The operator below.
Further, the closed loop accurate synchronization of the digital signal adopts a costas loop carrier synchronization algorithm.
A system for restraining carrier tracking by large frequency deviation comprises an analog front end, a frequency deviation estimation module based on ephemeris, a direct digital frequency synthesizer, A/D conversion and band-pass filtering, digital down-conversion and a costas loop synchronization carrier module, wherein the input end of the analog front end is connected with the output end of an antenna, the input end of the A/D conversion and the band-pass filtering is connected with the output end of the analog front end, the output end of the A/D conversion and the band-pass filtering is connected with the input end of the digital down-conversion, the frequency deviation estimation module based on ephemeris controls the output of the direct digital frequency synthesizer to be used as the reference input of a local oscillation source of the analog front end, and the output of the costas loop synchronization carrier module controls the output frequency of a numerical control oscillator of the digital down-conversion.
Further, the costas loop synchronization carrier module includes a 90 ° phase shifter, a first multiplier, a second multiplier, a first low pass filter, a second low pass filter, a third multiplier and a loop filter, wherein an output signal of the digital down-conversion digitally controlled oscillator is divided into two paths, one path of the output signal is connected to one input end of the first multiplier, the other path of the output signal is connected to one input end of the second multiplier after passing through the 90 ° phase shifter, a digital signal output by a/D conversion and band-pass filtering is divided into two paths which are respectively connected to the other input ends of the first multiplier and the second multiplier, output ends of the first multiplier and the second multiplier are connected to two input ends of the third multiplier after passing through the first low pass filter and the second low pass filter, an output end of the third multiplier is connected to the loop filter, and an output of the loop filter is connected to the digitally controlled oscillator of the digital down-conversion.
Further, the transfer function of the loop filter is as follows:
wherein, C 1 、C 2 For loop filter coefficients:
k is the loop gain of the whole costas loop, xi is the damping coefficient, omega n At natural angular frequency, T s Is the sampling period.
In summary, due to the adoption of the technical scheme, the invention has the beneficial effects that:
compared with the traditional analog carrier synchronization processing mode realized by a phase-locked loop or the mode of inhibiting a carrier tracking loop in a full digital mode, the method adopts open-loop estimation rough synchronization in the analog signal processing link, and the estimation result guides the output of a direct digital frequency synthesizer to control the output frequency of a local oscillation source of a receiver to realize rapid rough synchronization of carrier frequency; then, in the digital signal processing link, accurate frequency phase tracking is carried out on the carrier wave of the received signal by using a costas loop carrier synchronization algorithm; compared with the full digital carrier synchronization processing technology, the medium frequency bandwidth is narrower, the corresponding noise level is lower, the requirement on the A/D conversion frequency is lower, the application occasion is wider than that of the full digital inhibition carrier tracking scheme, and the adaptability is stronger; under the condition of large frequency deviation of a satellite communication system, rapid and accurate synchronous tracking processing can be carried out on a received signal carrier, reference can be provided for the design of carrier synchronization equipment at a satellite communication receiving end, and the method is particularly suitable for but not limited to application in the direction of an airborne narrowband satellite communication system.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and that for those skilled in the art, other relevant drawings can be obtained according to the drawings without inventive efforts, wherein:
FIG. 1 is a functional block diagram of the present invention;
FIG. 2 is a schematic diagram of the open loop carrier synchronization of analog signals in the present invention;
FIG. 3 is a schematic diagram of the calculation of Doppler frequency offset in the present invention;
FIG. 4 is a schematic diagram of digital signal closed loop carrier synchronization in the present invention;
FIG. 5 is a schematic diagram of a loop filter in a costas loop synchronous carrier module;
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
Thus, the following detailed description of the embodiments of the present invention, as presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.
It is noted that relational terms such as "first" and "second," and the like, may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrases "comprising one of 8230; \8230;" 8230; "does not exclude the presence of additional like elements in a process, method, article, or apparatus that comprises the element.
Some of the terms used in the present invention are explained below:
DDS: the DDS signal generator adopts Direct Digital Synthesis (DDS) technology, namely a Direct Digital frequency synthesizer for short, improves the frequency stability and the accuracy of the signal generator to the same level as the reference frequency, and can carry out fine frequency adjustment in a wide frequency range. The signal source designed by the method can work in a modulation state, can adjust the output level and can output various waveforms.
NCO: a Numerically Controlled Oscillator (NCO) is an important component of a software radio, a Direct Digital Synthesizer (DDS), a Fast Fourier Transform (FFT), and the like, and is also one of the main factors determining the performance thereof, and is used to generate a controllable sine wave or cosine wave. Along with the improvement of the integration level of the chip, the chip is widely applied to the fields of signal processing, digital communication, modulation and demodulation, frequency conversion and speed regulation, guidance control, power electronics and the like.
DDC: the digital down-conversion is divided into two basic modules, a numerically controlled Oscillator NCO (NU-mechanical Control Oscillator) mixing module and a decimation filtering module. The NCO module generates sine and cosine wave sample values, and then the sample values are multiplied by input data respectively to finish frequency mixing.
LPF: a low-pass filter is an electronic filtering device that allows signals below a cutoff frequency to pass, but does not allow signals above the cutoff frequency to pass.
PD: a phase detector (phasedetector) refers to a device capable of detecting a phase difference of an input signal, and is a circuit that makes an output voltage have a definite relationship with a phase difference between two input signals.
VCO: the voltage-controlled oscillator is an oscillating circuit with output frequency corresponding to input control voltage, the frequency of the oscillator is a function of input signal voltage, and the working state of the oscillator or the element parameters of an oscillating circuit are controlled by the input control voltage to form the voltage-controlled oscillator.
Example 1
The invention provides a method for restraining carrier tracking by large frequency deviation, which comprises the following steps:
step 1: carrying out open loop estimation rough synchronization of a first-stage radio frequency analog signal on the carrier frequency, and guiding the output of a direct digital frequency synthesizer to control the output frequency of a local vibration source of a receiver according to an estimation result so as to realize rapid rough synchronization of the carrier frequency;
preferably, the open-loop estimation rough synchronization of the first-stage radio frequency analog signal adopts satellite ephemeris-based pre-correction and compensation calculation to control the output of the direct digital frequency synthesizer as the reference input of the local vibration source of the receiver.
The satellite ephemeris-based pre-correction and compensation calculation specifically comprises the following steps: and calculating the relative motion speed between the satellite and the receiver by adopting a geocentric geostationary coordinate system, calculating Doppler frequency shift, and adjusting the output of the direct digital frequency synthesizer as the reference input of the local oscillation source according to a Doppler frequency shift prediction result.
As shown in fig. 3, the calculation of the relative movement speed specifically includes: and obtaining the position of the satellite by using the satellite ephemeris, further calculating the instantaneous speed of the satellite in the geocentric geostationary coordinate system, simultaneously obtaining the position and the instantaneous speed of the receiver in the geocentric geostationary coordinate system, and performing projection operation on the speed vector of the receiver and the speed vector of the satellite to the connection line vector of the satellite and the receiver.
In the scheme, the Doppler frequency is calculated according to the following formula:
wherein c is the speed of light, v S Is the projection of the instantaneous speed of the satellite in the geocentric geostationary coordinate system on the connecting line vector of the satellite and the receiver, v R The projection of the instantaneous speed of the receiver in the geocentric coordinate system on the connecting line vector of the satellite and the receiver is obtained;
when the satellite and the receiver approach each other, plus or minus is taken,
The operator above, away from the time ±),
The operator below.
And adjusting the output frequency of the direct digital frequency synthesizer to be f'/f times of the output frequency without Doppler effect according to the calculation result, and using the adjusted output frequency as the reference input of the local vibration source of the receiver, so that the frequency offset of the center frequency output by the frequency conversion component is subjected to preliminary compensation, as shown in fig. 2.
And 2, step: converting the radio frequency analog signal into a digital signal; a/D conversion is typically used to convert the radio frequency analog signal to a digital signal.
And 3, step 3: and carrying out closed-loop accurate synchronization on the second-stage digital signals on the carrier frequency, adjusting the output frequency of the integer controlled oscillator, and realizing accurate synchronous tracking of the carrier frequency and the phase.
Preferably, the closed loop precise synchronization of the digital signal adopts a costas loop carrier synchronization algorithm. During implementation, the frequency of the output signal is adjusted according to the frequency offset result, so that the frequency of the output signal of the numerically controlled oscillator is close to the carrier frequency of the received signal.
In summary, compared with the traditional analog carrier synchronization processing mode realized by a phase-locked loop or the mode of inhibiting a carrier tracking loop in a full digital way, the invention adopts open loop estimation coarse synchronization in the analog signal processing link, and the estimation result guides the output of the direct digital frequency synthesizer to control the output frequency of the local vibration source of the receiver to realize the fast carrier frequency coarse synchronization; then, in the digital signal processing link, accurate frequency phase tracking is carried out on the received signal carrier by using a costas loop carrier synchronization algorithm; compared with the full digital carrier synchronization processing technology, the medium frequency bandwidth is narrower, the corresponding noise level is lower, the requirement on the A/D conversion frequency is lower, the application occasion is wider than that of the full digital inhibition carrier tracking scheme, and the adaptability is stronger; under the condition of large frequency deviation of a satellite communication system, rapid and accurate synchronous tracking processing can be carried out on a received signal carrier, reference can be provided for the design of carrier synchronization equipment at a satellite communication receiving end, and the method is particularly suitable for but not limited to application in the direction of an airborne narrowband satellite communication system.
Example 2
The embodiment provides a system for suppressing carrier tracking with large frequency deviation, as shown in fig. 1, the system includes an analog front end, a frequency deviation estimation module based on ephemeris, a direct digital frequency synthesizer, an a/D conversion and band-pass filtering, a digital down-conversion, and a costas loop synchronization carrier module, an input end of the analog front end is connected to an output end of an antenna, an input end of the a/D conversion and band-pass filtering is connected to an output end of the analog front end, an output end of the a/D conversion and band-pass filtering is connected to an input end of the digital down-conversion, the frequency deviation estimation module based on ephemeris controls an output of the direct digital frequency synthesizer to serve as a reference input of a local oscillation source of the analog front end, and an output of the costas loop synchronization carrier module controls an output frequency of a digitally controlled oscillator of the digital down-conversion.
Specifically, as shown in fig. 4, the costas loop synchronization carrier module includes a 90 ° phase shifter, a first multiplier, a second multiplier, a first low pass filter, a second low pass filter, a third multiplier, and a loop filter, where an output signal of the digitally-downconverted digitally-controlled oscillator is divided into two paths, one path of the output signal is connected to one input end of the first multiplier, the other path of the output signal is connected to one input end of the second multiplier after passing through the 90 ° phase shifter, a digital signal output by the a/D conversion and the bandpass filtering is divided into two paths of the output signal and respectively connected to the other input ends of the first multiplier and the second multiplier, output ends of the first multiplier and the second multiplier are connected to two input ends of the third multiplier after passing through the first low pass filter and the second low pass filter, an output end of the third multiplier is connected to the loop filter, and an output end of the loop filter is connected to the digitally-downconverted digitally-controlled oscillator. The costas loop carrier synchronization module adjusts the frequency of the output signal according to the frequency offset result, so that the frequency of the output signal of the numerically controlled oscillator is close to the carrier frequency of the received signal.
In this scheme, as shown in fig. 5, a principle of a loop filter in a costas loop synchronization carrier module is shown, where a transfer function of the loop filter is as follows:
wherein, C 1 、C 2 For the loop filter coefficients:
k is the loop gain of the whole costas loop, xi is the damping coefficient, omega n At natural angular frequency, T s Is the sampling period.
The beneficial effects of the system are the same as those of the method embodiment, and are not described again.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and should not be taken as limiting the scope of the present invention, and any modifications, equivalents and improvements made by those skilled in the art within the spirit and scope of the present invention should be included in the present invention.
Claims (7)
1. A method for restraining carrier tracking by large frequency deviation is characterized in that: the method comprises the following steps:
step 1: carrying out open loop estimation rough synchronization of a first-stage radio frequency analog signal on the carrier frequency, and guiding the output of a direct digital frequency synthesizer to control the output frequency of a local vibration source of a receiver according to an estimation result so as to realize fast rough synchronization of the carrier frequency; the open loop estimation rough synchronization of the first-stage radio frequency analog signal adopts the output of a satellite ephemeris-based precorrection and compensation calculation control direct digital frequency synthesizer as the reference input of a local oscillation source of a receiver;
and 2, step: converting the radio frequency analog signal into a digital signal;
and 3, step 3: carrying out closed-loop accurate synchronization of a second-stage digital signal on the carrier frequency, adjusting the output frequency of the integer controlled oscillator, and realizing accurate synchronous tracking of the carrier frequency and the phase; and the closed loop accurate synchronization of the second-stage digital signal adopts a costas loop carrier synchronization algorithm.
2. The method of claim 1, wherein the large frequency offset suppressed carrier tracking is performed by: the satellite ephemeris-based pre-correction and compensation calculation specifically comprises the following steps: and calculating the relative motion speed between the satellite and the receiver by adopting a geocentric earth-fixed coordinate system, calculating the Doppler frequency shift, and adjusting the output of the direct digital frequency synthesizer as the reference input of the local oscillation source according to the predicted result of the Doppler frequency shift.
3. The method of claim 2, wherein the large frequency offset suppressed carrier tracking is characterized by: the calculation of the relative movement speed is specifically as follows: and obtaining the position of the satellite by using the satellite ephemeris, further calculating the instantaneous speed of the satellite in the geocentric geostationary coordinate system, simultaneously obtaining the position and the instantaneous speed of the receiver in the geocentric geostationary coordinate system, and performing projection operation on the speed vector of the receiver and the speed vector of the satellite to the connection line vector of the satellite and the receiver.
4. The method of claim 3, wherein the large frequency offset suppressed carrier tracking is performed by: the doppler frequency is calculated according to the following formula:
wherein c is the speed of light, v S V is a projection of the instantaneous velocity of the satellite in the geocentric geostationary coordinate system onto the satellite-receiver connecting line vector R The projection of the instantaneous speed of the receiver in the geocentric geostationary coordinate system on a connecting line vector of the satellite and the receiver is obtained;
when the satellite and the receiver approach to each other, plus or minus is taken,
The operator above, when far away from, takes ±),
The operator below.
5. A system for suppressing carrier tracking by large frequency offset is characterized in that: the frequency offset estimation module based on the ephemeris controls the output of the direct digital frequency synthesizer to be used as the reference input of a local oscillation source of the analog front end, and the output of the costas loop synchronous carrier module controls the output of a numerically controlled oscillator of the digital down-conversion.
6. The system according to claim 5, wherein the system for large frequency offset suppressed carrier tracking comprises: the costas loop synchronization carrier module comprises a 90-degree phase shifter, a first multiplier, a second multiplier, a first low-pass filter, a second low-pass filter, a third multiplier and a loop filter, wherein an output signal of the digital down-conversion numerically-controlled oscillator is divided into two paths, one path of the output signal is connected to one input end of the first multiplier, the other path of the output signal is connected to one input end of the second multiplier after passing through the 90-degree phase shifter, a digital signal output by A/D conversion and band-pass filtering is divided into two paths which are respectively connected to the other input ends of the first multiplier and the second multiplier, output ends of the first multiplier and the second multiplier are connected to two input ends of the third multiplier after passing through the first low-pass filter and the second low-pass filter, an output end of the third multiplier is connected to the loop filter, and an output of the loop filter is connected to the numerically-controlled oscillator of the digital down-conversion.
7. The system of claim 6, wherein the system for large frequency offset suppressed carrier tracking comprises: the transfer function of the loop filter is as follows:
wherein, C 1 、C 2 For loop filter coefficients:
k is the loop gain of the whole costas loop, xi is the damping coefficient, omega n At natural angular frequency, T s Is the sampling period.
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| CN101441259A (en) * | 2008-12-18 | 2009-05-27 | 中国科学院微电子研究所 | Automatic auxiliary tracking system and tracking method of global position system receiver |
| CN104702547A (en) * | 2014-09-25 | 2015-06-10 | 上海欧科微航天科技有限公司 | Pilot frequency information and satellite ephemeris joint Doppler frequency shift estimation and compensation method |
| CN107566107A (en) * | 2017-09-21 | 2018-01-09 | 河海大学 | A kind of quick precise synchronization method and system of the digital carrier signal of big frequency deviation |
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| US9020087B2 (en) * | 2012-05-15 | 2015-04-28 | Exar Corporation | All digital burst-mode clock and data recovery (CDR) |
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| CN101441259A (en) * | 2008-12-18 | 2009-05-27 | 中国科学院微电子研究所 | Automatic auxiliary tracking system and tracking method of global position system receiver |
| CN104702547A (en) * | 2014-09-25 | 2015-06-10 | 上海欧科微航天科技有限公司 | Pilot frequency information and satellite ephemeris joint Doppler frequency shift estimation and compensation method |
| CN107566107A (en) * | 2017-09-21 | 2018-01-09 | 河海大学 | A kind of quick precise synchronization method and system of the digital carrier signal of big frequency deviation |
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