CN111239776A - Efficient multi-system self-adaptive capturing and tracking method for satellite receiver - Google Patents

Efficient multi-system self-adaptive capturing and tracking method for satellite receiver Download PDF

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CN111239776A
CN111239776A CN202010103921.6A CN202010103921A CN111239776A CN 111239776 A CN111239776 A CN 111239776A CN 202010103921 A CN202010103921 A CN 202010103921A CN 111239776 A CN111239776 A CN 111239776A
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carrier
code
frequency
tracking
coarse
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CN111239776B (en
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张传胜
龚高茂
何峰
赵海军
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Hunan Maxwell Electronic Technology Co Ltd
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Hunan Maxwell Electronic Technology 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
    • G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
    • G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/13—Receivers
    • G01S19/24—Acquisition or tracking or demodulation of signals transmitted by the system
    • 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
    • G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/13—Receivers
    • G01S19/24—Acquisition or tracking or demodulation of signals transmitted by the system
    • G01S19/29—Acquisition or tracking or demodulation of signals transmitted by the system carrier including Doppler, related
    • 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
    • G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/13—Receivers
    • G01S19/24—Acquisition or tracking or demodulation of signals transmitted by the system
    • G01S19/30—Acquisition or tracking or demodulation of signals transmitted by the system code related

Abstract

The invention discloses a high-efficiency multi-system self-adaptive capturing and tracking method for a satellite receiver, which comprises the following steps that an antenna at a receiving end receives a signal, the signal enters a baseband part after down-conversion is carried out on the signal, and then: s1, capturing, wherein the capturing step comprises a coarse capturing S11 step and a fine capturing S12 step; s2, tracking of carriers, codes, and data; the invention has strong compatibility, the same set of capturing and tracking system is suitable for various communication systems, seamless switching can be performed between the coexistence of various communication systems, and the real-time performance of communication is better; and the size, the weight and the volume are smaller, the device is suitable for miniaturized and light-weighted satellite-borne application, and has the characteristics of short capture time, high tracking efficiency, small frequency tracking error and the like.

Description

Efficient multi-system self-adaptive capturing and tracking method for satellite receiver
Technical Field
The invention relates to the technical field of satellite receiving, in particular to a high-efficiency multi-system self-adaptive capturing and tracking method for a satellite receiver.
Background
In a satellite communication system, carrier acquisition and tracking are key links for establishing communication with a satellite, and subsequent processing processes such as demodulation, decoding and the like can be performed on satellite signals only after the carrier acquisition and tracking are completed. In the inter-satellite and inter-satellite-ground communication, with the high-speed relative motion of space satellites and the motion to the ground, the signal acquisition and tracking at the receiving end become more complex and difficult. With the development of satellite communication technology, satellite communication tends to adopt multiple communication systems, and in the prior art, when receiving equipment coexists with multiple communication systems, a set of signal capturing and tracking system needs to be independently configured at a receiving end aiming at different communication systems, so that the consumption of the logic resources of the receiving end is large, the receiving equipment is large in size and high in power consumption, and is not suitable for satellite-borne receiving ends and ground receiving equipment with strictly limited size and power, and the prior art has the following problems:
1. the compatibility is poor, and the same set of capturing and tracking system is only suitable for one communication system;
2. when the same receiving end coexists with multiple communication mechanisms, the switching between the communication systems of the receiving end is complex, and the real-time performance and the quality of communication are seriously influenced.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a high-efficiency multi-system self-adaptive capturing and tracking method of a satellite receiver, which has strong compatibility, the same capturing and tracking system is suitable for various communication systems, seamless switching among various communication systems can be realized, and the real-time performance of communication is better; and the size, the weight and the volume are smaller, the device is suitable for miniaturized and light-weighted satellite-borne application, the capturing time is short, the tracking efficiency is high, and the frequency tracking error is small.
The purpose of the invention is realized by the following technical scheme:
a high-efficiency multi-system self-adaptive capturing and tracking method for a satellite receiver is characterized in that a signal is received by an antenna at a receiving end, and enters a baseband part after being subjected to down-conversion, and the following steps are executed:
s1, capturing, wherein the capturing step comprises a coarse capturing S11 step and a fine capturing S12 step;
s2, tracking of carriers, codes, and data.
Further, in the coarse acquisition S11, the method includes two parts, namely spreading code coarse acquisition and carrier coarse acquisition:
coarse acquisition of spread spectrum codes:
adopts a time domain parallel frequency method and combines with coherent non-coherent operation to jointly complete the coarse capture of the spread spectrum code phase,
the coarse acquisition of the spreading code comprises the following steps:
a) the local counter module generates four interrupts, namely spreading code period interrupt, FFT interrupt, code shift interrupt and fine search interrupt, which are respectively used for capturing tracking code phase alignment, completing one FFT operation, completing one incoherent operation, and performing fine search accumulation to remove high frequency so as to improve frequency resolution;
b) a code NCO (numerical control oscillator, the same below) and a code generator generate spread spectrum codes with different initial phases;
c) the signal processing module despreads the intermediate frequency digital signal, then performs frequency FFT operation and noncoherent operation, detects a correlation result, namely the signal strength through a detector to judge whether the code phase is correct, and if the code phase is correct, sends a capture success mark;
after the coarse acquisition of the spread spectrum code is finished, the carrier coarse acquisition can be carried out:
coherent acquisition by adopting an FFT algorithm, wherein the Fourier transform formula is as follows:
Figure BDA0002387838960000021
wherein x (t) is a time domain signal, e is a natural constant, j is an imaginary part representation of a complex number, t is a time variable, and ω is an angular frequency
In IQ modulation:
Figure BDA0002387838960000027
wherein, ω lo is the local carrier angular frequency;
then:
Figure BDA0002387838960000022
Figure BDA0002387838960000023
as can be seen from the above equation, the acquisition frequency is affected by the symbol modulation, so it is necessary to remove the effect of the symbol modulation on the carrier frequency,
left and right squares:
Figure BDA0002387838960000024
wherein: (I + jQ)2Is unfolded into2-Q2+2IQj；
For BPSK, Q is 0 in this term, for QPSK, I in the above formula2Is equal to Q2The two terms cancel each other, the above equation becomes:
BPSK:
Figure BDA0002387838960000025
QPSK：
Figure BDA0002387838960000026
for BPSK, I2The integral value of (2) is already constant, and for QPSK, the above equation needs to be squared again to eliminate the influence of 2IQj, so for both BPSK and QPSK, the following is obtained for statistical calculation:
BPSK:
Figure BDA0002387838960000031
QPSK：
Figure BDA0002387838960000032
for the above formulaxIf the integral value of the remaining items is a fixed value, which can be set as a, then:
Figure BDA0002387838960000033
in order to eliminate the negative influence in QPSK, the modulus value is taken from the integral result of the above expression,
known as (ω)loω), there is a maximum value, and carrier acquisition can therefore be achieved.
For a 16APSK signal, it can be expressed as:
Figure BDA0002387838960000034
Ri＝R1or R2,
Figure BDA0002387838960000035
Wherein R is1≈0.4336,R2≈1.1272；
The signal with carrier offset can be expressed as:
Figure BDA0002387838960000036
the capture algorithm program is as follows:
1) first, the amplitude | x of the time domain signal is detected(t)|＝Ri；
2) If | x(t)If | is less than 1, the following operation is performed
Figure BDA0002387838960000037
Otherwise
Figure BDA0002387838960000038
Therein are provided with
Figure BDA0002387838960000039
3) The conversion to the frequency domain has:
Figure BDA00023878389600000310
known as (12 omega)loω), there is a maximum value, so carrier acquisition can be achieved by varying the different index ej*mThe m value in the system realizes the carrier capture of a plurality of communication systems, wherein the plurality of communication systems comprise any one of BPSK/QPSK/8PSK/16 APSK.
Further, the fine acquisition is used for calculating a precise carrier doppler value, enabling the phase-locked loop to enter a lock, and performing:
a) the code NCO and the code generator generate a spread spectrum code according to the code phase obtained by the coarse capture;
b) the carrier NCO and the carrier generator generate a current carrier value according to the carrier obtained by the coarse capture;
c) the frequency difference calculation module performs frequency mixing and despreading, then performs accumulation operation to obtain an absolute value, and then performs FFT operation;
d) the carrier NCO and the carrier generator downwards deviate a set frequency by using the captured coarse carrier frequency, carry out frequency mixing and then mix the frequency with an intermediate frequency signal;
e) by arranging a multistage parallel code NCO, a code generator, a carrier NCO and a carrier generator, the multistage parallel code NCO and the carrier generator comprise 2 stages.
Furthermore, tracking of the carrier, the code and the data is used for continuously and stably tracking the captured signal to prevent lock losing.
Further, the method comprises the following steps of tracking carrier waves, pseudo codes and data, wherein correspondingly, a tracking loop consists of a carrier tracking loop, a code tracking loop and a data loop, the carrier tracking loop adopts a Costas loop and uses a two-phase arc tangent phase discriminator and a second-order loop filter; the code tracking loop adopts a delay locked loop, and uses a normalized lead-lag power discriminator and a second-order loop filter; the data tracking loop adopts a data conversion tracking loop.
The invention has the beneficial effects that:
the invention has strong compatibility, the same set of capturing and tracking system is suitable for various communication systems, seamless switching among various communication systems can be realized, and the real-time performance of communication is better; and the size, the weight and the volume are smaller, the device is suitable for miniaturized and light-weighted satellite-borne application, the capturing time is short, the tracking efficiency is high, and the frequency tracking error is small.
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In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a block diagram of a coarse acquisition baseband of the present invention;
FIG. 2 is a fine capture block diagram of the present invention;
FIG. 3 is a block diagram of a second order digital filter according to the present invention;
FIG. 4 is a flow chart illustrating the steps of the present invention.
Detailed Description
The technical solutions of the present invention are further described in detail below with reference to the accompanying drawings, but the scope of the present invention is not limited to the following. All of the features disclosed in this specification, or all of the steps of a method or process so disclosed, may be combined in any combination, except combinations where mutually exclusive features and/or steps are used.
Any feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving equivalent or similar purposes, unless expressly stated otherwise. That is, unless expressly stated otherwise, each feature is only an example of a generic series of equivalent or similar features.
Specific embodiments of the present invention will be described in detail below, and it should be noted that the embodiments described herein are only for illustration and are not intended to limit the present invention. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one of ordinary skill in the art that: it is not necessary to employ these specific details to practice the present invention. In other instances, well-known circuits, software, or methods have not been described in detail so as not to obscure the present invention.
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Before describing the embodiments, some necessary terms need to be explained. For example:
if the terms "first," "second," etc. are used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. Thus, a "first" element discussed below could also be termed a "second" element without departing from the teachings of the present invention. It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may also be present. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements present.
The various terms appearing in this application are used for the purpose of describing particular embodiments only and are not intended as limitations of the invention, with the singular being intended to include the plural unless the context clearly dictates otherwise.
When the terms "comprises" and/or "comprising" are used in this specification, these terms are intended to specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence and/or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
As shown in fig. 1 to 4, a method for high-efficiency multi-system adaptive acquisition and tracking of a satellite receiver includes receiving a signal at an antenna of a receiving end, performing down-conversion on the signal, and entering a baseband part to perform the following steps:
s1, capturing, wherein the capturing step comprises a coarse capturing S11 step and a fine capturing S12 step;
s2, tracking of carriers, codes, and data.
Further, in the coarse acquisition S11, the method includes two parts, namely spreading code coarse acquisition and carrier coarse acquisition:
coarse acquisition of spread spectrum codes:
adopts a time domain parallel frequency method and combines with coherent non-coherent operation to finish the coarse capture of the spread spectrum code phase together,
the coarse acquisition of the spreading code comprises the following steps:
d) the local counter module generates four interrupts, namely spreading code period interrupt, FFT interrupt, code shift interrupt and fine search interrupt, which are respectively used for capturing tracking code phase alignment, completing one FFT operation, completing one incoherent operation, and performing fine search accumulation to remove high frequency so as to improve frequency resolution;
e) the code NCO and the code generator generate spread spectrum codes with different initial phases;
f) the signal processing module despreads the intermediate frequency digital signal, then performs frequency FFT operation and noncoherent operation, detects a correlation result, namely the signal strength through a detector to judge whether the code phase is correct, and if the code phase is correct, sends a capture success mark;
after finishing the coarse capture of the spread spectrum code, entering carrier coarse capture:
coherent acquisition by adopting an FFT algorithm, wherein the Fourier transform formula is as follows:
Figure BDA0002387838960000061
where x (t) is a time domain signal, e is a natural constant, j is an imaginary representation of a complex number, t is a time variable, and ω is an angular frequency.
In IQ modulation:
Figure BDA0002387838960000067
then:
Figure BDA0002387838960000062
Figure BDA0002387838960000063
as can be seen from the above equation, the acquisition frequency is affected by the symbol modulation, so it is necessary to remove the effect of the symbol modulation on the carrier frequency,
left and right squares:
Figure BDA0002387838960000064
wherein: (I + jQ)2Is unfolded into2-Q2+2IQj；
For BPSK, Q is 0 in this term, for QPSK, I in the above formula2Is equal to Q2The two terms cancel each other, the above equation becomes:
BPSK:
Figure BDA0002387838960000065
QPSK：
Figure BDA0002387838960000066
for BPSK, I2The integral value of (2) is already constant, and for QPSK, the above equation needs to be squared again to eliminate the influence of 2IQj, so for both BPSK and QPSK, the following is obtained for statistical calculation:
BPSK:
Figure BDA0002387838960000071
QPSK：
Figure BDA0002387838960000072
for the above formulaxIf the integral value of the remaining items is a fixed value, which can be set as a, then:
Figure BDA0002387838960000073
in order to eliminate the negative influence in QPSK, the modulus value is taken from the integral result of the above expression,
known as (ω)loω), there is a maximum value, so carrier acquisition can be achieved,
for a 16APSK signal, it can be expressed as:
Figure BDA0002387838960000074
Ri＝R1or R2,
Figure BDA0002387838960000075
Wherein R is1≈0.4336,R2≈1.1272；
The signal with carrier offset can be expressed as:
Figure BDA0002387838960000076
the capture algorithm program is as follows:
1) first, the amplitude | x of the time domain signal is detected(t)|＝Ri；
2) If | x(t)If | is less than 1, the following operation is performed
Figure BDA0002387838960000077
Otherwise
Figure BDA0002387838960000078
Therein are provided with
Figure BDA0002387838960000079
3) The conversion to the frequency domain has:
Figure BDA00023878389600000710
known as (12 omega)loω), there is a maximum value, so carrier acquisition can be achieved by varying the different index ej*mThe m value in the system realizes the carrier capture of various communication systems and various communicationsThe system comprises any one of BPSK/QPSK/8PSK/16 APSK.
Further, the fine acquisition is used for calculating a precise carrier doppler value, enabling the phase-locked loop to enter a lock, and performing:
a) a code NCO (namely a numerical control oscillator) and a code generator generate a spread spectrum code according to a code phase obtained by coarse capture;
b) the carrier NCO and the carrier generator generate a current carrier value according to the carrier obtained by the coarse capture;
c) the frequency difference calculation module performs frequency mixing and despreading, then performs accumulation operation to obtain an absolute value, and then performs FFT operation;
d) the carrier NCO and the carrier generator downwards deviate a set frequency by using the captured coarse carrier frequency, carry out frequency mixing and then mix the frequency with an intermediate frequency signal;
e) by arranging a multi-stage parallel code NCO, a code generator, a carrier NCO and a carrier generator, the multi-stage parallel code NCO and the carrier generator comprise stages.
Furthermore, tracking of the carrier, the code and the data is used for continuously and stably tracking the captured signal to prevent lock losing.
Further, the method comprises the following steps of tracking carrier waves, pseudo codes and data, wherein correspondingly, a tracking loop consists of a carrier tracking loop, a code tracking loop and a data loop, the carrier tracking loop adopts a Costas loop and uses a two-phase arc tangent phase discriminator and a second-order loop filter; the code tracking loop adopts a delay locked loop, and uses a normalized lead-lag power discriminator and a second-order loop filter; the data tracking loop adopts a data conversion tracking loop.
The working process of the invention is as follows:
1. capture
The capture is divided into two links of coarse capture and fine capture:
(1) coarse capture:
the coarse acquisition comprises two parts of coarse acquisition of a spreading code and coarse acquisition of a carrier:
coarse acquisition of spread spectrum codes:
and a time domain parallel frequency method is adopted, and coherent and non-coherent operation is combined to finish coarse capture of the spread spectrum code phase together. The block diagram of the coarse trapping baseband part is shown in FIG. 1:
the working process of the coarse acquisition of the spread spectrum code is as follows:
a) the local counter module generates four interrupts, namely spreading code period interrupt, FFT interrupt, code shift interrupt and fine search interrupt, which are respectively used for capturing tracking code phase alignment, completing one FFT operation, completing one incoherent operation, and fine search accumulation to remove high frequency and improve frequency resolution.
b) The code NCO and code generator generate spreading codes of various initial phases.
c) The signal processing module despreads the intermediate frequency digital signal, then performs frequency FFT operation and noncoherent operation, and detects the correlation result, i.e. the signal strength, by a detector to judge whether the code phase is correct, if the code phase is correct, a capture success mark is sent.
Carrier coarse capture: coherent acquisition using an FFT algorithm.
The fourier transform equation is:
Figure BDA0002387838960000081
in IQ modulation:
Figure BDA00023878389600000911
then:
Figure BDA0002387838960000091
Figure BDA0002387838960000092
as can be seen from the above equation, the acquisition frequency is affected by the symbol modulation, so the influence of the symbol modulation on the carrier frequency needs to be removed.
Left and right squares:
Figure BDA0002387838960000093
wherein: (I + jQ)2Is unfolded into2-Q2+j2IQj；
For BPSK, Q is 0 in this term, for QPSK, I in the above formula2Is equal to Q2The two terms can cancel each other out, the above equation becomes BPSK:
Figure BDA0002387838960000094
QPSK：
Figure BDA0002387838960000095
for BPSK, I2The integral value of (b) is already constant, and for QPSK, the above equation needs to be squared again to eliminate the influence of j2IQj, so for the statistical calculation process, for both BPSK and QPSK, the square is again obtained as follows:
BPSK:
Figure BDA0002387838960000096
QPSK：
Figure BDA0002387838960000097
for the above formulaxIf the integral value of the remaining items is a fixed value, which can be set as a, then:
Figure BDA0002387838960000098
in order to eliminate the negative influence in QPSK, the modulus value is then taken from the integration result of the above equation.
Known as (ω)loω), there is a maximum value, and carrier acquisition can therefore be achieved.
For a 16APSK signal, it can be expressed as:
Figure BDA0002387838960000099
Ri＝R1or R2,
Figure BDA00023878389600000910
Wherein R is1≈0.4336,R2≈1.1272；
The signal with carrier offset can be expressed as:
Figure BDA0002387838960000101
the capture algorithm program is as follows:
1) first, the amplitude | x of the time domain signal is detected(t)|＝Ri；
2) If | x(t)If | is less than 1, the following operation is performed
Figure BDA0002387838960000102
Otherwise
Figure BDA0002387838960000103
Here must have
Figure BDA0002387838960000104
3) The conversion to the frequency domain has:
Figure BDA0002387838960000105
known as (12 omega)loω), there is a maximum value, and therefore carrier acquisition can be achieved;
the key of the scheme is that different indexes e are changedj*mThe m value in the method can realize the carrier capture of various communication systems (such as BPSK/QPSK/8PSK/16APSK and the like);
(2) fine capture:
the purpose of fine acquisition is to calculate an accurate carrier doppler (error about 200Hz) to enable the phase-locked loop to enter lock;
a) and the code NCO and the code generator generate a spread spectrum code according to the code phase obtained by the coarse acquisition.
b) The carrier NCO and the carrier generator generate a current carrier value according to the carrier obtained by the coarse capture;
c) the frequency difference calculating module carries out frequency mixing and despreading, then carries out accumulation operation to obtain an absolute value, and then carries out FFT operation, and the calculated frequency difference resolution is about 200Hz and is within the designed traction range of the phase-locked loop.
d) The frequency resolution of the capture is 6kHz, the coarse carrier frequency obtained by the capture is used by the carrier NCO and the carrier generator to shift 40kHz downwards for mixing, and the frequency range of the mixed signal with the intermediate frequency signal is 0-400 kHz.
e) The capture efficiency can be improved by arranging the multi-stage parallel code NCO and the code generator, and the carrier NCO and the carrier generator, the capture time of the carrier and the code can be shortened, the capture time can be shortened to be 1/N of a single stage, and if the capture time is set to be 2 stages, the capture time can be shortened to be half.
2. Tracking of carriers, codes and data
The purpose of tracking is to realize continuous and stable tracking on the captured signal and prevent lock losing. The invention includes the tracking of carrier, pseudo code and data, and correspondingly, the tracking loop consists of a carrier tracking loop, a code tracking loop and a data loop.
The carrier tracking loop adopts a Costas loop and uses a two-phase inverse tangent phase discriminator and a second-order loop filter; the code tracking loop adopts a delay locked loop, and uses a normalized lead-lag power discriminator and a second-order loop filter; the data tracking loop adopts a data conversion tracking loop;
Figure BDA0002387838960000111
wherein the content of the first and second substances,
a)IP(n) and QP(n) is the cumulative sum of the instant branches of the path I and the path Q at the current moment, IP(n-1) and QP(n-1) is the cumulative sum of the instantaneous branches of the path I and the path Q at the previous moment, IPH(n) is the quadrature branch of the data conversion lock loop;
b) e and L are the leading and lagging amplitude envelopes,
Figure BDA0002387838960000112
IE(n) and QE(n) is the cumulative sum of the leading branch of the I path and the Q path at the current moment, IL(n) and QLAnd (n) is the accumulated sum of the I path and the Q path of the lagging branch at the current moment.
c) Loop filter
The above three loops all use a second order loop filter, the block diagram of which is shown in figure 2,
corresponding to the expression between input and output:
Figure BDA0002387838960000113
wherein X (n) is input, Y (n) is output, and T is integration accumulation time; omega0Being the natural circular frequency of the loop filter,
Figure BDA0002387838960000114
BLloop equivalent noise bandwidth, ξ damping coefficient, α2＝2ξ。
Loop parameters:
the loop bandwidth of the phase-locked loop is determined in relation to the update frequency of the phase detector, and the loop can be stabilized generally below the update frequency 1/10. The phase discrimination frequency of the discriminator is kept consistent with the data rate, so that the loop bandwidth changes along with the change of the data rate, the data rate is increased, and the equivalent noise bandwidth is increased in proportion.
At the data rate RbEquivalent noise bandwidth B at 2kHzL≤0.1Rb＝200Hz。
The quick-catching belt is
Figure BDA0002387838960000121
If the damping coefficient is selected to be ξ -0.707
Figure BDA0002387838960000122
In other technical features of the embodiment, those skilled in the art can flexibly select and use the features according to actual situations to meet different specific actual requirements. However, it will be apparent to one of ordinary skill in the art that: it is not necessary to employ these specific details to practice the present invention. In other instances, well-known algorithms, methods or systems have not been described in detail so as not to obscure the present invention, and are within the scope of the present invention as defined by the claims.
For simplicity of explanation, the foregoing method embodiments are described as a series of acts or combinations, but those skilled in the art will appreciate that the present application is not limited by the order of acts, as some steps may occur in other orders or concurrently depending on the application. Further, those skilled in the art should also appreciate that the embodiments described in the specification are preferred embodiments and that the acts and elements referred to are not necessarily required in this application.
Those of skill in the art would appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware or combinations of computer software and electronic hardware. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
The disclosed systems, modules, and methods may be implemented in other ways. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units may be only one logical division, and there may be other divisions in actual implementation, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be referred to as an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.
The units described as separate parts may or may not be physically separate, and the parts displayed as units may or may not be physical units, may be located in one place, or may also be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.
The functions, if implemented in the form of software functional units and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present invention may be embodied in the form of a software product, which is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: various media capable of storing program codes, such as a usb disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk, or an optical disk.
It will be understood by those skilled in the art that all or part of the processes in the methods for implementing the embodiments described above can be implemented by instructing the relevant hardware through a computer program, and the program can be stored in a computer-readable storage medium, and when executed, the program can include the processes of the embodiments of the methods described above. The storage medium may be a magnetic disk, an optical disk, a ROM, a RAM, etc.
The foregoing is illustrative of the preferred embodiments of this invention, and it is to be understood that the invention is not limited to the precise form disclosed herein and that various other combinations, modifications, and environments may be resorted to, falling within the scope of the concept as disclosed herein, either as described above or as apparent to those skilled in the relevant art. And that modifications and variations may be effected by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (5)

1. A high-efficiency multi-system self-adaptive acquisition and tracking method for a satellite receiver is characterized in that a signal is received by an antenna at a receiving end, and enters a baseband processing part after being subjected to down-conversion, and the following steps are executed:
s1, capturing, wherein the capturing step comprises a coarse capturing S11 step and a fine capturing S12 step;
s2, tracking of carriers, codes, and data.
2. The method as claimed in claim 1, wherein the coarse acquisition S11 includes two parts, namely, spreading code coarse acquisition and carrier coarse acquisition:
coarse acquisition of spread spectrum codes:
adopts a time domain parallel frequency method and combines with coherent non-coherent operation to finish the coarse capture of the spread spectrum code phase together,
the coarse acquisition of the spreading code comprises the following steps:
a) the local counter module generates four interrupts, namely spreading code period interrupt, FFT interrupt, code shift interrupt and fine search interrupt, which are respectively used for capturing tracking code phase alignment, completing one FFT operation, completing one incoherent operation, and performing fine search accumulation to remove high frequency so as to improve frequency resolution;
b) the code NCO and the code generator generate spread spectrum codes with different initial phases;
c) the signal processing module despreads the intermediate frequency digital signal, then performs frequency FFT operation and noncoherent operation, detects a correlation result, namely the signal strength through a detector to judge whether the code phase is correct, and if the code phase is correct, sends a capture success mark;
after finishing the coarse capture of the spread spectrum code, entering carrier coarse capture:
coherent acquisition by adopting an FFT algorithm, wherein the Fourier transform formula is as follows:
Figure FDA0002387838950000011
wherein, x (t) is a time domain signal, e is a natural constant, j is an imaginary part representation mode of a complex number, t is a time variable, omega is an angular frequency, and omega lo is a local carrier angular frequency;
in IQ modulation:
Figure FDA0002387838950000012
then:
Figure FDA0002387838950000013
Figure FDA0002387838950000014
as can be seen from the above equation, the acquisition frequency is affected by the symbol modulation, so it is necessary to remove the effect of the symbol modulation on the carrier frequency,
left and right squares:
Figure FDA0002387838950000021
wherein: (I + jQ)2Is unfolded into2-Q2+2IQj；
For BPSK, Q is 0 in this term;
for QPSK, I in the above formula2Is equal to Q2The two terms cancel each other, the above equation becomes:
BPSK:
Figure FDA0002387838950000022
QPSK：
Figure FDA0002387838950000023
for BPSK, I2The integral value of (2) is already constant, and for QPSK, the above equation needs to be squared again to eliminate the influence of 2IQj, so for both BPSK and QPSK, the following is obtained for statistical calculation:
BPSK:
Figure FDA0002387838950000024
QPSK：
Figure FDA0002387838950000025
for the above formulaxIf the integral value of the remaining items is a fixed value, which can be set as a, then:
Figure FDA0002387838950000026
in order to eliminate the negative influence in QPSK, the modulus value is taken from the integral result of the above expression,
known as (ω)loω), there is a maximum value; so that it is possible to achieve carrier acquisition,
for a 16APSK signal, it can be expressed as:
Figure FDA00023878389500000212
Ri＝R1or R2,
Figure FDA0002387838950000027
Wherein R is1≈0.4336,R2≈1.1272；
The signal with carrier offset can be expressed as:
Figure FDA0002387838950000028
the capture algorithm program is as follows:
1) first, the amplitude | x of the time domain signal is detected(t)|＝Ri；
2) If | x(t)If | is less than 1, the following operation is performed
Figure FDA0002387838950000029
Otherwise
Figure FDA00023878389500000210
Therein are provided with
Figure FDA00023878389500000211
3) The conversion to the frequency domain has:
Figure FDA0002387838950000031
known as (12 omega)loω), there is a maximum value; thus carrier acquisition can be achieved by varying the different indices ej*mThe m value in the system can realize carrier capture of a plurality of communication systems, wherein the plurality of communication systems comprise any one of BPSK/QPSK/8PSK/16 APSK.
3. The method as claimed in claim 1, wherein in the step of fine acquisition S12, the method is used to calculate a precise carrier doppler value, enable a phase-locked loop to enter lock, and perform:
a) the code NCO and the code generator generate a spread spectrum code according to the code phase obtained by the coarse capture;
b) the carrier NCO and the carrier generator generate a current carrier value according to the carrier obtained by the coarse capture;
c) the frequency difference calculation module performs frequency mixing and despreading, then performs accumulation operation to obtain an absolute value, and then performs FFT operation;
d) the carrier NCO and the carrier generator downwards deviate a set frequency by using the captured coarse carrier frequency, carry out frequency mixing and then mix the frequency with an intermediate frequency signal;
e) by arranging a multi-stage parallel code NCO, a code generator, a carrier NCO and a carrier generator, the multi-stage parallel code NCO and the carrier generator comprise stages.
4. The method as claimed in claim 1, wherein the carrier, code and data tracking is used to continuously and stably track the acquired signal and prevent lock loss.
5. The method as claimed in claim 4, wherein the method comprises tracking carrier, pseudo code and data, and the tracking loop comprises carrier tracking loop, code tracking loop and data loop, the carrier tracking loop adopts Costas loop, and uses two-phase inverse tangent phase detector and second-order loop filter; the code tracking loop adopts a delay locked loop, and uses a normalized lead-lag power discriminator and a second-order loop filter; the data tracking loop adopts a data conversion tracking loop.
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