CN112311449A - Low-earth-orbit satellite communication dynamic time delay and Doppler simulation method - Google Patents

Low-earth-orbit satellite communication dynamic time delay and Doppler simulation method Download PDF

Info

Publication number
CN112311449A
CN112311449A CN202011276417.2A CN202011276417A CN112311449A CN 112311449 A CN112311449 A CN 112311449A CN 202011276417 A CN202011276417 A CN 202011276417A CN 112311449 A CN112311449 A CN 112311449A
Authority
CN
China
Prior art keywords
signal
time delay
dynamic
low
filter
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
CN202011276417.2A
Other languages
Chinese (zh)
Other versions
CN112311449B (en
Inventor
王闻今
孙港乐
李灵瑄
陈婷婷
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Southeast University
Original Assignee
Southeast University
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Southeast University filed Critical Southeast University
Priority to CN202011276417.2A priority Critical patent/CN112311449B/en
Publication of CN112311449A publication Critical patent/CN112311449A/en
Application granted granted Critical
Publication of CN112311449B publication Critical patent/CN112311449B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • 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
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B17/00—Monitoring; Testing
    • H04B17/30—Monitoring; Testing of propagation channels
    • H04B17/391—Modelling the propagation channel
    • 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
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/0014—Carrier regulation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/0014—Carrier regulation
    • H04L2027/0024—Carrier regulation at the receiver end
    • H04L2027/0026—Correction of carrier offset

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • Astronomy & Astrophysics (AREA)
  • Aviation & Aerospace Engineering (AREA)
  • General Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Radio Relay Systems (AREA)

Abstract

The invention discloses a low-earth orbit satellite communication dynamic time delay and Doppler simulation method, which calculates dynamic transmission time delay and dynamic Doppler frequency offset according to the real-time communication distance between a low-earth orbit satellite and a ground terminal, and designs a corresponding dynamic time delay simulation system according to a low-earth orbit satellite signal transmission model. The satellite-end transmitted signal can be simulated through the dynamic time delay simulation system to obtain a ground received signal in a real-time dynamic time delay scene. The dynamic time delay filter in the dynamic time delay simulation system does not need to calculate the filter coefficient in real time, and the filter coefficient can be updated only by inputting the real-time delay by utilizing the Farrow structure. Meanwhile, the frequency band of the satellite transmission signal is positioned in the working frequency band of good amplitude-frequency response of the time delay filter by adopting up-sampling and down-sampling processing, so that the error of the time delay simulation system is further reduced.

Description

Low-earth-orbit satellite communication dynamic time delay and Doppler simulation method
Technical Field
The invention belongs to the field of communication, and particularly relates to a low-orbit satellite communication dynamic time delay and Doppler simulation method realized by utilizing a fractional time delay filter.
Background
The height of the low-orbit satellite is about 600 km-1500 km, and the period of one circle of the low-orbit satellite around the earth is less than 24 hours. Thus, a low earth orbit satellite cannot remain relatively stationary with a ground-based receiver like a geostationary orbit satellite, but rather has relative motion with the ground-based receiver. The period of time during which the low-earth satellite passes over and communicates with the ground-based receiver is referred to as the low-earth satellite over-the-top process. In the process of the low-earth orbit satellite passing the top, the communication distance between the low-earth orbit satellite and the ground receiving end is changed continuously, so that the communication transmission delay is changed continuously. Meanwhile, the communication in the relative motion process also causes doppler frequency offset, and the doppler frequency offset corresponding to different moments is also constantly changed, so that the actual received signal of the ground terminal is difficult to accurately simulate.
Disclosure of Invention
The purpose of the invention is as follows: in order to overcome the defects in the prior art, the invention provides a dynamic time delay and Doppler simulation method for low-orbit satellite communication, which adopts up-sampling and down-sampling processing to ensure that a satellite transmission signal frequency band is in a working frequency band with good amplitude-frequency response of a time delay filter, and further reduces the error of a time delay simulation system.
The technical scheme is as follows: in order to achieve the purpose, the invention adopts the technical scheme that:
a low-earth-orbit satellite communication dynamic time delay and Doppler simulation method is based on that the communication distance of a low-earth-orbit satellite in a process of passing through the top is constantly changed, so that the signal transmission time delay and Doppler frequency offset are also changed in real time. The method calculates dynamic transmission delay and dynamic Doppler frequency offset according to the real-time communication distance between the low-earth orbit satellite and the ground terminal, and designs a corresponding dynamic delay simulation system according to a low-earth orbit satellite signal transmission model. The satellite-end transmitted signal can be simulated through the dynamic time delay simulation system to obtain a ground received signal in a real-time dynamic time delay scene. The dynamic time delay filter in the dynamic time delay simulation system designed by the invention does not need to calculate the filter coefficient in real time, and the filter coefficient can be updated only by inputting real-time delay by utilizing a Farrow structure, so that compared with other schemes, the dynamic time delay simulation system has the advantages of simple structure, low implementation complexity and accurate simulation result, and specifically comprises the following steps:
step 1, calculating a real-time dynamic communication distance of a low-orbit satellite in a process of passing through a top by utilizing a space geometric position relation between a low-orbit satellite operation orbit and a ground terminal, and further obtaining a dynamic transmission delay TD(t) and a doppler shift Δ f (t).
And 2, designing a dynamic time delay simulation system by using the low-earth orbit satellite signal transmission model, and updating the coefficient of a dynamic time delay filter in the simulation system according to the dynamic transmission time delay in the low-earth orbit satellite signal transmission process.
Step 2.1, establishing a low-orbit satellite signal transmission model under dynamic time delay and Doppler scenes:
let the QAM baseband signal sent by the low earth orbit satellite be u (t), whose expression is:
u(t)＝sI(t)+jsQ(t)
wherein s isI(t) is the I-band signal, sQ(t) is Q baseband signal, and the baseband signal u (t) has a frequency fcThe carrier frequency of (a) is modulated to obtain a sending signal s (t), and the expression of the sending signal s (t) is as follows:
Figure BDA0002779196220000021
where Re is an operation taking a real number, j0Is composed of
Figure BDA0002779196220000022
Transmitting signal s (T) through dynamic transmission delay TDAnd (t) receiving the signal by the ground terminal. The receiving signal r (t) received by the ground terminal under the condition of not considering signal attenuation and multipath propagation factors and only considering transmission delay is expressed as follows:
Figure BDA0002779196220000023
the received signal r (T) has a period TsAfter sampling, getTo a discrete signal r (nT)s) Then, the signal is demodulated to become a discrete baseband signal u' (nT)s) The expression is as follows:
Figure BDA0002779196220000024
where N is 1, 2.., N is a discrete baseband signal u' (nT)s) The number of samples.
Defining a transmission time delay multiple D (n) to express the transmission time delay T of the nth sampling momentD(nTs) And the sampling interval TsIs expressed as
Figure BDA0002779196220000025
Wherein I (n) represents an integer part of D (n), and d (n) represents a decimal part of D (n).
When d (n) is 0, discrete baseband signal u' (nT)s) U (nT) in the expressions-TD(nTs) Is the n-D (n) discrete baseband signal u (nT) of the transmitting ends-D(n)Ts). However, when d (n) ≠ 0, u (nT)s-TD(nTs) Is not directly available for a discrete signal at the transmitting end, and each discrete baseband signal u (nT) transmitted by the satellite end is requireds) And (4) showing. Consider u (nT)s-TD(nTs) Is a discrete baseband signal u (nT) transmitted from the satellite sides) The pass frequency response is H (e)jω)≈e-jωD(n)The output signal after the FIR filter. Assuming that the coefficients of the causal FIR filter of order M are h (i), i is 0,1,., M-1, the low-orbit satellite signal transmission model in the dynamic time delay scenario is:
Figure BDA0002779196220000031
step 2.2, designing a dynamic time delay simulation system: when the transmission delay multiple d (n) is larger, the integer part and the decimal part in the transmission delay multiple d (n) are respectively realized by cascading two modules, and the method specifically comprises the following three steps:
step 2.2.1, designing a queue structure to realize that an integer part I (n) in a transmission delay multiple D (n): in order to realize the integer part I (n) in the transmission delay multiple D (n), the method can be realized by only delaying the transmission signal of the satellite end by I (n) sampling intervals. Therefore, the transmitting signal of the satellite end is correspondingly delayed and output through a first-in first-out structure in the queue, and the transmitting signal u (nT) of the satellite end is outputs) Transmitting the output signal u to the queue structureI(nTs) The specific expression is as follows:
uI(nTs)＝u((n-I(n))·Ts)
step 2.2.2, designing a dynamic delay filter to realize the fractional part d (n) in the transmission delay multiple D (n): the Lagrange interpolation filter with good frequency response performance is used as a dynamic time delay filter, and the frequency response of the dynamic time delay filter is H (e) because only the fractional part d (n) in the transmission time delay multiple D (n) is needed to be realizedjω)≈e-jωd(n)Thus, the M-order lagrange interpolation filter coefficient expression is:
Figure BDA0002779196220000032
the M-order lagrange interpolation filter is implemented with a Farrow structure, i.e. the FIR filter coefficients are written in polynomial form with respect to the fractional part d (n). Thus, the expression of the M-order Lagrangian interpolation filter coefficients implemented with the Farrow structure is written as:
Figure BDA0002779196220000033
wherein, d (n)jJ power of d (n), M order Lagrange interpolation filter coefficient h (i) in polynomial d (n)jCoefficient a before itemi,jThe method is obtained by expanding an M-order Lagrange interpolation filter coefficient expression. In addition, ai,jBy calculating order MThe inverse of the van der Mond matrix, derived from ai,jThe expression of the M-order real number square matrix A is as follows:
Figure BDA0002779196220000041
the M-order real number square matrix A is only related to the order M of the filter and is not related to the transmission delay. Therefore, when updating the dynamic delay filter, the value of the matrix a is pre-calculated, and then the fractional part d (n) in the transmission delay multiple d (n) is input to the dynamic delay filter, so as to obtain the real-time dynamic filter coefficient, and the expression is:
Figure BDA0002779196220000042
step 2.2.3, designing a multiplier to realize an exponential part in a signal transmission model: multiplying the coefficients by a multiplier
Figure BDA0002779196220000043
Multiplying the signal by the output signal of the fractional delay filter to realize the exponential part in the signal transmission model:
and 2.2.4, substituting the low-orbit satellite signal transmission model in the step 2.1 by combining the step 2.2.1, the step 2.2.2 and the step 2.2.3 to obtain a dynamic time delay simulation system:
Figure BDA0002779196220000044
and 3, performing up-sampling filtering processing on the transmitting signal of the satellite end, passing the signal through a dynamic time delay simulation system, and performing down-sampling processing simulation on the output signal of the dynamic time delay simulation system to obtain a ground receiving signal after dynamic time delay and Doppler frequency offset.
Preferably: obtaining the dynamic transmission time delay T in the step 1D(t) and doppler shift Δ f (t):
acquiring real-time communication distance L (t) between low-earth satellite and ground terminal in the process of passing through topAnd calculating the dynamic transmission time delay T of the low-orbit satellite in the process of passing the topD(t) and doppler shift Δ f (t), expressed as:
Figure BDA0002779196220000051
Figure BDA0002779196220000052
wherein c is the speed of light, f is the carrier frequency of the satellite transmission signal, v is the linear velocity of the low-orbit satellite running around the earth, and theta (t) is the included angle between the running speed direction of the low-orbit satellite and the connecting line from the low-orbit satellite to the ground terminal.
Preferably: the method for performing upsampling filtering processing in the step 3 comprises the following steps:
the up-sampling rate is assumed to be p times the signal sampling rate, i.e. the up-sampling has a sampling period of
Figure BDA0002779196220000053
Satellite transmission signal after up-sampling processing
Figure BDA0002779196220000054
Writing into:
Figure BDA0002779196220000055
wherein the content of the first and second substances,
Figure BDA0002779196220000056
the l-th data, l 1,2, p n, representing the up-sampled processed signal.
Up-sampling processed satellite transmission signal
Figure BDA0002779196220000057
Through MLPAfter low-pass filtering of order, a low-pass filtered signal is obtained
Figure BDA0002779196220000058
The expression is written as:
Figure BDA0002779196220000059
wherein h isLP(i0) Is MLPCoefficient of order low-pass filter i0＝0,1,...,MLP-1。
Low pass filtered signal
Figure BDA00027791962200000510
The delayed signals are input into a dynamic time delay filter and then are multiplied to obtain received signals
Figure BDA00027791962200000511
Comprises the following steps:
Figure BDA00027791962200000512
wherein, I '(l) and D' (l) are respectively integer part and fractional part of the up-sampled transmission delay multiple D '(l), and the expression of the up-sampled transmission delay multiple D' (l) is
Figure BDA00027791962200000513
Preferably: the method for performing down-sampling processing in the step 3 comprises the following steps: output signal
Figure BDA0002779196220000061
Obtaining a down-sampled signal u' (nT) after down-sampling processing with the rate p times of the sampling rates) The expression is as follows:
Figure BDA0002779196220000062
preferably: in that
Figure BDA0002779196220000063
At the time of the up-sampling and low-pass filtering of the signal
Figure BDA0002779196220000064
And writing into a queue data structure. Meanwhile, the down-sampling module reads the received signal at the output port of the dynamic time delay simulation system
Figure BDA0002779196220000065
Dynamic time delay simulation system at each
Figure BDA0002779196220000066
And finishing corresponding operation according to the value change condition of I' (l) in the interval:
(a) if I' (l) is kept unchanged, the dynamic time delay simulation system is
Figure BDA0002779196220000067
One of the data in the queue is removed from the queue during the interval and sent to the input of the dynamic delay filter. Will be provided with
Figure BDA0002779196220000068
The fractional delay part of the time, d' (l), is input to the corresponding input of the Farrow structure, updating the filter coefficients.
(b) If I' (l) is increased by 1, the dynamic delay filter is in
Figure BDA0002779196220000069
In the interval will
Figure 1
The fractional delay part of the time, d' (l), is input to the corresponding input of the Farrow structure, updating the filter coefficients.
(c) If I' (l) is decreased by 1, the dynamic delay filter is in
Figure BDA00027791962200000611
Two data in the queue are removed from the queue in the interval and are sequentially transmittedTo the input of a dynamic delay filter. Will be provided with
Figure BDA00027791962200000612
The fractional delay part of the time, d' (l), is input to the corresponding input of the Farrow structure, updating the filter coefficients.
Preferably: by calculating an analogue received signal
Figure BDA00027791962200000613
And ideal received signal ynMean square error MSE between estimates the simulated ground received signal accuracy, whose expression is:
Figure BDA00027791962200000614
and N is the total number of sampling points of the ground terminal.
Compared with the prior art, the invention has the following beneficial effects:
1. the invention can simulate the ground terminal receiving signal under the real-time dynamic time delay scene, and has wide application range.
2. The filter coefficient adopted by the invention does not need to be repeatedly calculated in a large quantity, the filter coefficient can be updated in real time by inputting the real-time transmission delay through the Farrow structure, and the design is simple and easy to realize.
3. The design of the up-sampling, down-sampling and dynamic time delay simulation system adopted by the invention ensures that the received signals obtained by the transmission time delay and Doppler frequency offset simulation system are accurate and the signal distortion degree is lower.
Drawings
FIG. 1 is a flow chart of an embodiment of the present invention;
FIG. 2 is a diagram of a queue structure for implementing integer part I (n) of D (n) according to an embodiment of the present invention;
FIG. 3 is a diagram of a Farrow structure of a 5 th order Lagrangian interpolation filter for implementing fractional part d (n) of D (n) according to an embodiment of the present invention;
fig. 4 is a schematic structural diagram of a dynamic delay simulation system according to an embodiment of the present invention.
Fig. 5 is a schematic diagram of the overall system framework according to the embodiment of the invention.
Detailed Description
The present invention is further illustrated by the following description in conjunction with the accompanying drawings and the specific embodiments, it is to be understood that these examples are given solely for the purpose of illustration and are not intended as a definition of the limits of the invention, since various equivalent modifications will occur to those skilled in the art upon reading the present invention and fall within the limits of the appended claims.
A method for simulating dynamic delay and doppler for low earth orbit satellite communication, as shown in fig. 1-5, specifically comprising the following steps:
step 1, calculating a real-time dynamic communication distance of a low-orbit satellite in a process of passing through a top by utilizing a space geometric position relation between a low-orbit satellite operation orbit and a ground terminal, and further obtaining a dynamic transmission delay TD(t) and a doppler shift Δ f (t).
Obtaining the real-time communication distance L (T) between the low-orbit satellite and the ground terminal in the process of passing the top, and calculating the dynamic transmission time delay T of the low-orbit satellite in the process of passing the topD(t) and doppler shift Δ f (t), expressed as:
Figure BDA0002779196220000071
Figure BDA0002779196220000072
wherein c is the speed of light, f is the carrier frequency of the satellite transmission signal, v is the linear velocity of the low-orbit satellite running around the earth, and theta (t) is the included angle between the running speed direction of the low-orbit satellite and the connecting line from the low-orbit satellite to the ground terminal.
And 2, designing a dynamic time delay simulation system by using the low-earth orbit satellite signal transmission model, and updating the coefficient of a dynamic time delay filter in the simulation system according to the dynamic transmission time delay in the low-earth orbit satellite signal transmission process.
Step 2.1, establishing a low-orbit satellite signal transmission model under dynamic time delay and Doppler scenes: the specific derivation process of the low-earth-orbit satellite signal transmission model is as follows:
let the QAM baseband signal sent by the low earth orbit satellite be u (t), whose expression is:
u(t)＝sI(t)+jsQ(t)
wherein s isI(t) is the I-band signal, sQ(t) is Q baseband signal, and the baseband signal u (t) has a frequency fcThe carrier frequency of (a) is modulated to obtain a sending signal s (t), and the expression of the sending signal s (t) is as follows:
Figure BDA0002779196220000081
transmitting signal s (T) through dynamic transmission delay TDAnd (t) receiving the signal by the ground terminal. Without considering factors such as signal attenuation and multipath propagation, and only considering transmission delay, the expression of r (t) of the signal received by the ground terminal can be written as follows:
Figure BDA0002779196220000082
the received signal r (T) has a period TsObtaining a discrete signal r (nT) after samplings) Then, the signal is demodulated to become a discrete baseband signal u' (nT)s) The expression can be written as:
Figure BDA0002779196220000083
where N is 1, 2.., N is a discrete baseband signal u' (nT)s) The number of samples.
Defining a transmission delay multiple d (n) to indicate the nth sampling time (i.e. t ═ nT)s) Transmission delay T ofD(nTs) And the sampling interval TsThe expression of the ratio of (a) to (b) is:
Figure BDA0002779196220000084
wherein I (n) represents an integer part of D (n), and d (n) represents a decimal part of D (n).
When d (n) is 0, discrete baseband signal u' (nT)s) U (nT) in the expressions-TD(nTs) Is the n-D (n) discrete baseband signal u (nT) of the transmitting ends-D(n)Ts). However, when d (n) ≠ 0, u (nT)s-TD(nTs) Is not directly available for a discrete signal at the transmitting end, and each discrete baseband signal u (nT) transmitted by the satellite end is requireds) And (4) showing. Can be regarded as u (nT)s-TD(nTs) Is a discrete baseband signal u (nT) transmitted from the satellite sides) The pass frequency response is H (e)jω)≈e-jωD(n)The output signal after the FIR filter. . The specific FIR filter is designed in step (2.2.2), where it is assumed that coefficients of a causal FIR filter of order M are h (i), i is 0,1,., M-1, and a low-orbit satellite signal transmission model in a dynamic time delay scenario is as follows:
Figure BDA0002779196220000091
step 2.2, designing a dynamic time delay simulation system: when the transmission delay multiple d (n) is larger, generally, when the transmission delay multiple d (n) is larger than 1, the transmission delay multiple d (n) is considered to be larger, and when the transmission delay multiple d (n) is larger, the frequency response of the FIR filter of the system becomes non-ideal, and larger simulation errors are generated. Therefore, the integer part and the decimal part in the transmission delay multiple D (n) are respectively realized by cascading two modules, and the method specifically comprises the following three steps:
step 2.2.1, designing a queue structure to realize that an integer part I (n) in a transmission delay multiple D (n): in order to realize the integer part I (n) in the transmission delay multiple D (n), the method can be realized by only delaying the transmission signal of the satellite end by I (n) sampling intervals. For this purpose, the transmitted signal of the satellite end is output with corresponding delay through the structure of "first-in first-out" in the queue, the structure of the queue is as shown in fig. 2As shown. Transmitting signal u (nT) of satellite ends) Transmitting the output signal u to the queue structureI(nTs) The specific expression is as follows:
uI(nTs)＝u((n-I(n))·Ts)
step 2.2.2, designing a dynamic delay filter to realize the fractional part d (n) in the transmission delay multiple D (n): since the integer part I (n) in D (n) is realized by the step 2.2.1, the step only needs to realize the fractional part d (n) in D (n). To design the frequency response mentioned in step 2.1 to be H (e)jω)≈e-jωD(n)The FIR filter adopts a Lagrange interpolation filter with good frequency response performance as a dynamic time delay filter, and only needs to realize a fractional part d (n) in a transmission time delay multiple D (n), so that the frequency response of the dynamic time delay filter is H (e)jω)≈e-jωd(n)Thus, the M-order lagrange interpolation filter coefficient expression is:
Figure BDA0002779196220000092
the M-order lagrange interpolation filter is implemented with a Farrow structure, i.e. the FIR filter coefficients are written in polynomial form with respect to the fractional part d (n). Therefore, the coefficient expression of the M-order lagrangian interpolation filter implemented by the Farrow structure can be rewritten as follows:
Figure BDA0002779196220000093
wherein, M order Lagrange interpolation filter coefficient h (i) in polynomial d (n)jCoefficient a before itemi,jThe method is obtained by expanding an M-order Lagrange interpolation filter coefficient expression. In addition, ai,jOr by calculating the inverse of the M-order van der Mond matrix, from ai,jThe expression of the M-order real number square matrix A is as follows:
Figure BDA0002779196220000101
it can be found that the M-order real number square matrix a is only related to the filter order M, and is not related to the transmission delay. Therefore, when updating the dynamic delay filter, the value of the matrix a is pre-calculated, and then the fractional part d (n) in the transmission delay multiple d (n) is input to the dynamic delay filter, so as to obtain the real-time dynamic filter coefficient, and the expression is:
Figure BDA0002779196220000102
FIG. 3 shows a Farrow structure diagram of a 5 th order Lagrangian interpolation filter.
Step 2.2.3, designing a multiplier to realize an exponential part in a signal transmission model: multiplying the coefficients by a multiplier
Figure BDA0002779196220000103
Multiplying the signal by the output signal of the fractional delay filter to realize the exponential part in the signal transmission model:
and 2.2.4, substituting the low-orbit satellite signal transmission model in the step 2.1 by combining the step 2.2.1, the step 2.2.2 and the step 2.2.3 to obtain a dynamic time delay simulation system:
Figure BDA0002779196220000104
and 3, performing up-sampling filtering processing on the transmitting signal of the satellite end, passing the signal through a dynamic time delay simulation system, and performing down-sampling processing simulation on the output signal of the dynamic time delay simulation system to obtain a ground receiving signal after dynamic time delay and Doppler frequency offset.
The method adopts up-sampling and down-sampling processing to the satellite transmission signal, improves the simulation accuracy, and specifically comprises the following two steps:
step 31, a method for performing upsampling filtering processing:
the up-sampling rate is assumed to be p times the signal sampling rate, i.e. the up-sampling has a sampling period of
Figure BDA0002779196220000111
Satellite transmission signal after up-sampling processing
Figure BDA0002779196220000112
Writing into:
Figure BDA0002779196220000113
wherein the content of the first and second substances,
Figure BDA0002779196220000114
the l-th data, l 1,2, p n, representing the up-sampled processed signal.
Up-sampling processed satellite transmission signal
Figure BDA0002779196220000115
Through MLPAfter low-pass filtering of order, a low-pass filtered signal is obtained
Figure BDA0002779196220000116
The expression is written as:
Figure BDA0002779196220000117
wherein h isLP(i0) Is MLPCoefficient of order low-pass filter i0＝0,1,...,MLP-1。
Low pass filtered signal
Figure BDA0002779196220000118
The delayed signals are input into a dynamic time delay filter and then are multiplied to obtain received signals
Figure BDA0002779196220000119
Comprises the following steps:
Figure BDA00027791962200001110
wherein, I '(l) and D' (l) are respectively integer part and fractional part of the up-sampled transmission delay multiple D '(l), and the expression of the up-sampled transmission delay multiple D' (l) is
Figure BDA00027791962200001111
Step 32, a method for performing down-sampling processing: output signal
Figure BDA00027791962200001112
Obtaining a down-sampled signal u' (nT) after down-sampling processing with the rate p times of the sampling rates) The expression is as follows:
Figure BDA00027791962200001113
according to the steps, a time delay simulation system structure and an integral framework of the patent can be designed, and are respectively shown in fig. 4 and fig. 5. In that
Figure BDA0002779196220000121
At the time of the up-sampling and low-pass filtering of the signal
Figure BDA0002779196220000122
And writing into a queue data structure. Meanwhile, the down-sampling module reads the received signal at the output port of the dynamic time delay simulation system
Figure BDA0002779196220000123
Dynamic time delay simulation system at each
Figure BDA0002779196220000124
And finishing corresponding operation according to the value change condition of I' (l) in the interval:
(a) if I' (l) is kept unchanged, the dynamic time delay simulation system is
Figure BDA0002779196220000125
One of the data in the queue is removed from the queue during the interval and sent to the input of the dynamic delay filter. Will be provided with
Figure BDA0002779196220000126
The fractional delay part of the time, d' (l), is input to the corresponding input of the Farrow structure, updating the filter coefficients.
(b) If I' (l) is increased by 1, the dynamic delay filter is in
Figure BDA0002779196220000127
In the interval will
Figure BDA0002779196220000128
The fractional delay part of the time, d' (l), is input to the corresponding input of the Farrow structure, updating the filter coefficients.
(c) If I' (l) is decreased by 1, the dynamic delay filter is in
Figure BDA0002779196220000129
Two data in the queue are removed from the queue in the interval and are sequentially sent to the input end of the dynamic delay filter. Will be provided with
Figure BDA00027791962200001210
The fractional delay part of the time, d' (l), is input to the corresponding input of the Farrow structure, updating the filter coefficients.
Preferably: by calculating an analogue received signal
Figure BDA00027791962200001211
And ideal received signal ynMean square error MSE between estimates the simulated ground received signal accuracy, whose expression is:
Figure BDA00027791962200001212
and a down-sampling module in the system frame performs down-sampling processing on the output signal of the dynamic time delay filter according to the sampling rate p times, so that the analog value of the final ground terminal receiving signal can be obtained.
In order to estimate the accuracy of the ground receiving signal simulated by the patent, the simulated receiving signal can be calculated
Figure BDA00027791962200001213
And ideal received signal ynMean square error MSE between, expressed as:
Figure BDA00027791962200001214
and N is the total number of sampling points of the ground terminal. To simulate the received signal
Figure BDA00027791962200001215
And ideal received signal ynThe expressions are respectively:
Figure BDA00027791962200001216
Figure BDA0002779196220000131
the invention adopts the up-sampling and down-sampling processing to ensure that the frequency band of the satellite transmission signal is in the working frequency band with good amplitude-frequency response of the time delay filter, thereby reducing the error of the time delay simulation system.
The above description is only of the preferred embodiments of the present invention, and it should be noted that: it will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the principles of the invention and these are intended to be within the scope of the invention.

Claims (6)

1. A low earth orbit satellite communication dynamic time delay and Doppler simulation method is characterized by comprising the following steps:
step 1, calculating a real-time dynamic communication distance of a low-orbit satellite in a process of passing through a top by utilizing a space geometric position relation between a low-orbit satellite operation orbit and a ground terminal, and further obtaining a dynamic transmission delay TD(t) and doppler shift Δ f (t);
step 2, designing a dynamic time delay simulation system by using a low-earth orbit satellite signal transmission model, and updating the coefficient of a dynamic time delay filter in the simulation system according to the dynamic transmission time delay in the process of transmitting signals by the low-earth orbit satellite;
step 2.1, establishing a low-orbit satellite signal transmission model under dynamic time delay and Doppler scenes:
let the QAM baseband signal sent by the low earth orbit satellite be u (t), whose expression is:
u(t)＝sI(t)+jsQ(t)
wherein s isI(t) is the I-band signal, sQ(t) is Q baseband signal, and the baseband signal u (t) has a frequency fcThe carrier frequency of (a) is modulated to obtain a sending signal s (t), and the expression of the sending signal s (t) is as follows:
Figure FDA0002779196210000011
where Re is an operation taking a real number, j0Is composed of
Figure FDA0002779196210000012
Transmitting signal s (T) through dynamic transmission delay TD(t) then receiving by the ground terminal; the receiving signal r (t) received by the ground terminal under the condition of not considering signal attenuation and multipath propagation factors and only considering transmission delay is expressed as follows:
Figure FDA0002779196210000013
the received signal r (T) has a period TsObtaining a discrete signal r (nT) after samplings) After demodulationBecomes a discrete baseband signal u' (nT)s) The expression is as follows:
Figure FDA0002779196210000014
where N is 1, 2.., N is a discrete baseband signal u' (nT)s) The number of samples of (a);
defining a transmission time delay multiple D (n) to express the transmission time delay T of the nth sampling momentD(nTs) And the sampling interval TsIs expressed as
Figure FDA0002779196210000021
Wherein I (n) represents the integer part of D (n), and d (n) represents the fractional part of D (n);
when d (n) is 0, discrete baseband signal u' (nT)s) U (nT) in the expressions-TD(nTs) Is the n-D (n) discrete baseband signal u (nT) of the transmitting ends-D(n)Ts) (ii) a However, when d (n) ≠ 0, u (nT)s-TD(nTs) Is not directly available for a discrete signal at the transmitting end, and each discrete baseband signal u (nT) transmitted by the satellite end is requireds) Represents; consider u (nT)s-TD(nTs) Is a discrete baseband signal u (nT) transmitted from the satellite sides) The pass frequency response is H (e)jω)≈e-jωD(n)The output signal after the FIR filter of (1); assuming that the coefficients of the causal FIR filter of order M are h (i), i is 0,1,., M-1, the low-orbit satellite signal transmission model in the dynamic time delay scenario is:
Figure FDA0002779196210000022
step 2.2, designing a dynamic time delay simulation system: when the transmission delay multiple d (n) is larger, the integer part and the decimal part in the transmission delay multiple d (n) are respectively realized by cascading two modules, and the method specifically comprises the following three steps:
step 2.2.1, designing a queue structure to realize that an integer part I (n) in a transmission delay multiple D (n): in order to realize the integer part I (n) in the transmission time delay multiple D (n), the method can be realized only by delaying the sending signal of the satellite end by I (n) sampling intervals; therefore, the transmitting signal of the satellite end is correspondingly delayed and output through a first-in first-out structure in the queue, and the transmitting signal u (nT) of the satellite end is outputs) Transmitting the output signal u to the queue structureI(nTs) The specific expression is as follows:
uI(nTs)＝u((n-I(n))·Ts)
step 2.2.2, designing a dynamic delay filter to realize the fractional part d (n) in the transmission delay multiple D (n): the Lagrange interpolation filter with good frequency response performance is used as a dynamic time delay filter, and the frequency response of the dynamic time delay filter is H (e) because only the fractional part d (n) in the transmission time delay multiple D (n) is needed to be realizedjω)≈e-jωd(n)Thus, the M-order lagrange interpolation filter coefficient expression is:
Figure FDA0002779196210000023
the M-order Lagrange interpolation filter is implemented with a Farrow structure, i.e., the FIR filter coefficients are written in polynomial form with respect to the fractional part d (n); thus, the expression of the M-order Lagrangian interpolation filter coefficients implemented with the Farrow structure is written as:
Figure FDA0002779196210000031
wherein, d (n)jJ power of d (n), M order Lagrange interpolation filter coefficient h (i) in polynomial d (n)jCoefficient a before itemi，jThe coefficient expression of the M-order Lagrange interpolation filter is expanded to obtain the coefficient expression; in addition, ai，jObtained by calculating the inverse of the M-order van der Mond matrix, from ai，jThe expression of the M-order real number square matrix A is as follows:
Figure FDA0002779196210000032
the M-order real number square matrix A is only related to the order M of the filter and is not related to transmission delay; therefore, when updating the dynamic delay filter, the value of the matrix a is pre-calculated, and then the fractional part d (n) in the transmission delay multiple d (n) is input to the dynamic delay filter, so as to obtain the real-time dynamic filter coefficient, and the expression is:
Figure FDA0002779196210000033
step 2.2.3, designing a multiplier to realize an exponential part in a signal transmission model: multiplying the coefficients by a multiplier
Figure FDA0002779196210000034
Multiplying the signal by the output signal of the fractional delay filter to realize the exponential part in the signal transmission model:
and 2.2.4, substituting the low-orbit satellite signal transmission model in the step 2.1 by combining the step 2.2.1, the step 2.2.2 and the step 2.2.3 to obtain a dynamic time delay simulation system:
Figure FDA0002779196210000035
and 3, performing up-sampling filtering processing on the transmitting signal of the satellite end, passing the signal through a dynamic time delay simulation system, and performing down-sampling processing simulation on the output signal of the dynamic time delay simulation system to obtain a ground receiving signal after dynamic time delay and Doppler frequency offset.
2. The low earth orbit satellite communication dynamic time delay and Doppler simulator of claim 1The method is characterized in that: obtaining the dynamic transmission time delay T in the step 1D(t) and doppler shift Δ f (t):
obtaining the real-time communication distance L (T) between the low-orbit satellite and the ground terminal in the process of passing the top, and calculating the dynamic transmission time delay T of the low-orbit satellite in the process of passing the topD(t) and doppler shift Δ f (t), expressed as:
Figure FDA0002779196210000041
Figure FDA0002779196210000042
wherein c is the speed of light, f is the carrier frequency of the satellite transmission signal, v is the linear velocity of the low-orbit satellite running around the earth, and theta (t) is the included angle between the running speed direction of the low-orbit satellite and the connecting line from the low-orbit satellite to the ground terminal.
3. The method of claim 2, wherein the method comprises: the method for performing upsampling filtering processing in the step 3 comprises the following steps:
the up-sampling rate is assumed to be p times the signal sampling rate, i.e. the up-sampling has a sampling period of
Figure FDA0002779196210000043
Satellite transmission signal after up-sampling processing
Figure FDA0002779196210000044
Writing into:
Figure FDA0002779196210000045
wherein the content of the first and second substances,
Figure FDA0002779196210000046
the first data, l 1,2,., pN, representing the up-sampled signal;
up-sampling processed satellite transmission signal
Figure FDA0002779196210000047
Through MLPAfter low-pass filtering of order, a low-pass filtered signal is obtained
Figure FDA0002779196210000048
The expression is written as:
Figure FDA0002779196210000049
wherein h isLP(i0) Is MLPCoefficient of order low-pass filter i0＝0，1，...，MLP-1；
Low pass filtered signal
Figure FDA00027791962100000410
The delayed signals are input into a dynamic time delay filter and then are multiplied to obtain received signals
Figure FDA00027791962100000411
Comprises the following steps:
Figure FDA0002779196210000051
wherein, I '(l) and D' (l) are respectively integer part and fractional part of the up-sampled transmission delay multiple D '(l), and the expression of the up-sampled transmission delay multiple D' (l) is
Figure FDA0002779196210000052
4. The method of claim 3, wherein the method comprises: the method for performing down-sampling processing in the step 3 comprises the following steps: output signal
Figure FDA0002779196210000053
Obtaining a down-sampled signal u' (nT) after down-sampling processing with the rate p times of the sampling rates) The expression is as follows:
Figure FDA0002779196210000054
5. the method of claim 4, wherein the method comprises: in that
Figure FDA0002779196210000055
At the time of the up-sampling and low-pass filtering of the signal
Figure FDA0002779196210000056
Writing into a queue data structure; meanwhile, the down-sampling module reads the received signal at the output port of the dynamic time delay simulation system
Figure FDA0002779196210000057
Dynamic time delay simulation system at each
Figure FDA0002779196210000058
And finishing corresponding operation according to the value change condition of I' (l) in the interval:
(a) if I' (l) is kept unchanged, the dynamic time delay simulation system is
Figure FDA0002779196210000059
Removing a data queue from the queue in the interval and sending the data queue to the input end of the dynamic delay filter; will be provided with
Figure FDA00027791962100000510
Inputting a time delay fractional part d' (l) into a corresponding input end of a Farrow structure, and updating a filter coefficient;
(b) if I' (l) is increased by 1, the dynamic delay filter is in
Figure FDA00027791962100000511
In the interval will
Figure FDA00027791962100000512
Inputting a time delay fractional part d' (l) into a corresponding input end of a Farrow structure, and updating a filter coefficient;
(c) if I' (l) is decreased by 1, the dynamic delay filter is in
Figure FDA00027791962100000513
Removing the queues of the two data in the queues in the interval, and sequentially sending the queues to the input end of the dynamic time delay filter; will be provided with
Figure FDA00027791962100000514
The fractional delay part of the time, d' (l), is input to the corresponding input of the Farrow structure, updating the filter coefficients.
6. The method of claim 5, wherein the method comprises: by calculating an analogue received signal
Figure FDA0002779196210000061
And ideal received signal ynMean square error MSE between estimates the simulated ground received signal accuracy, whose expression is:
Figure FDA0002779196210000062
and N is the total number of sampling points of the ground terminal.
CN202011276417.2A 2020-11-16 2020-11-16 Low-earth-orbit satellite communication dynamic time delay and Doppler simulation method Active CN112311449B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202011276417.2A CN112311449B (en) 2020-11-16 2020-11-16 Low-earth-orbit satellite communication dynamic time delay and Doppler simulation method

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202011276417.2A CN112311449B (en) 2020-11-16 2020-11-16 Low-earth-orbit satellite communication dynamic time delay and Doppler simulation method

Publications (2)

Publication Number Publication Date
CN112311449A true CN112311449A (en) 2021-02-02
CN112311449B CN112311449B (en) 2022-02-01

Family

ID=74334501

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202011276417.2A Active CN112311449B (en) 2020-11-16 2020-11-16 Low-earth-orbit satellite communication dynamic time delay and Doppler simulation method

Country Status (1)

Country Link
CN (1) CN112311449B (en)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113109772A (en) * 2021-04-07 2021-07-13 成都信息工程大学 Ultra-wideband high-dynamic target signal simulation method
CN113411149A (en) * 2021-05-20 2021-09-17 东南大学 Low-orbit satellite mobile communication ground experiment system
CN113472464A (en) * 2021-09-06 2021-10-01 中国人民解放军国防科技大学 Method and system for real-time simulation of high dynamic satellite channel Doppler characteristics
CN116094630A (en) * 2023-04-07 2023-05-09 湖南国天电子科技有限公司 High-precision signal delay calculation method
CN116260506A (en) * 2023-05-09 2023-06-13 红珊科技有限公司 Satellite communication transmission delay prediction system and method

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104316938A (en) * 2014-09-25 2015-01-28 上海欧科微航天科技有限公司 Novel satellite simulator for low-earth-orbit satellite quasi-synchronous communication system
CN109343081A (en) * 2018-10-10 2019-02-15 中国人民解放军国防科技大学 GPS signal dynamic receiving environment simulation method and system
CN111064503A (en) * 2019-12-30 2020-04-24 长光卫星技术有限公司 Satellite channel high dynamic time delay Doppler simulation system
WO2020200396A1 (en) * 2019-03-29 2020-10-08 Nokia Technologies Oy Apparatus for doppler shift compensation, corresponding method and computer program

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104316938A (en) * 2014-09-25 2015-01-28 上海欧科微航天科技有限公司 Novel satellite simulator for low-earth-orbit satellite quasi-synchronous communication system
CN109343081A (en) * 2018-10-10 2019-02-15 中国人民解放军国防科技大学 GPS signal dynamic receiving environment simulation method and system
WO2020200396A1 (en) * 2019-03-29 2020-10-08 Nokia Technologies Oy Apparatus for doppler shift compensation, corresponding method and computer program
CN111064503A (en) * 2019-12-30 2020-04-24 长光卫星技术有限公司 Satellite channel high dynamic time delay Doppler simulation system

Non-Patent Citations (4)

* Cited by examiner, † Cited by third party
Title
KIM, H 等: "Use of Cyclone Global Navigation Satellite System (CyGNSS) Observations for Estimation of Soil Moisture", 《GEOPHYSICAL RESEARCH LETTERS》 *
WENJIN WANG 等: "Near Optimal Timing and Frequency Offset Estimation for 5G Integrated LEO Satellite Communication System", 《IEEE ACCESS》 *
沙海 等: "VFD滤波器的导航信道模拟器动态时延模拟方法", 《国防科技大学学报》 *
齐巍 等: "高动态信号模拟器中的多普勒模拟算法", 《航空学报》 *

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113109772A (en) * 2021-04-07 2021-07-13 成都信息工程大学 Ultra-wideband high-dynamic target signal simulation method
CN113109772B (en) * 2021-04-07 2024-01-30 成都信息工程大学 Ultra-wideband high-dynamic target signal simulation method
CN113411149A (en) * 2021-05-20 2021-09-17 东南大学 Low-orbit satellite mobile communication ground experiment system
CN113411149B (en) * 2021-05-20 2022-04-22 东南大学 Low-orbit satellite mobile communication ground experiment system
CN113472464A (en) * 2021-09-06 2021-10-01 中国人民解放军国防科技大学 Method and system for real-time simulation of high dynamic satellite channel Doppler characteristics
CN113472464B (en) * 2021-09-06 2021-11-12 中国人民解放军国防科技大学 Method and system for real-time simulation of high dynamic satellite channel Doppler characteristics
CN116094630A (en) * 2023-04-07 2023-05-09 湖南国天电子科技有限公司 High-precision signal delay calculation method
CN116094630B (en) * 2023-04-07 2023-08-08 湖南国天电子科技有限公司 High-precision signal delay calculation method
CN116260506A (en) * 2023-05-09 2023-06-13 红珊科技有限公司 Satellite communication transmission delay prediction system and method
CN116260506B (en) * 2023-05-09 2023-07-04 红珊科技有限公司 Satellite communication transmission delay prediction system and method

Also Published As

Publication number Publication date
CN112311449B (en) 2022-02-01

Similar Documents

Publication Publication Date Title
CN112311449B (en) Low-earth-orbit satellite communication dynamic time delay and Doppler simulation method
US5309484A (en) Method and apparatus for asynchronous timing recovery using interpolation filter
US8611762B2 (en) System and method for frequency-domain chromatic dispersion and polarization mode dispersion compensation with time-domain channel estimation
EP0300449B1 (en) Digital automatic line equalizer with means for controlling tap gains of transversal filter on mean power of output from the filter
CN110752870B (en) Timing recovery method and device for roll-off coefficient variable broadband satellite transmission system
US9954514B2 (en) Output range for interpolation architectures employing a cascaded integrator-comb (CIC) filter with a multiplier
CN102801674A (en) Incoherent detection method and device of continuous phase modulation signals
CN107332539B (en) High-speed parallel multi-path fractional delay filter implementation method
Duhamel et al. Multi-channel high resolution blind image restoration
CN106357323A (en) Satellite channel group delay compensation method and device
CN100525267C (en) Channel estimating and balancing apparatus for time domain known array OFDM system and method thereof
JPH10270945A (en) Device and method for modulating digital residual-sideband wave
DE19606102A1 (en) Mobile base station receiver signal DC voltage equalisation method
Alimohammad et al. FPGA Implementation of isotropic and nonisotropic fading channels
CN113541825B (en) Phase control array ground system test platform
US11888538B2 (en) Receiving apparatus
CN101304495B (en) Ghost cancellation equalizer
EP0244057B1 (en) Communication system, receiver and transmitter and method of data retrieval
US7098836B2 (en) Signal-processing device with real-time and reprocessing operating modes
JP3149236B2 (en) Receiving system
CN112422103B (en) Method for reducing number of raised cosine filter multipliers and FIR raised cosine filter
CN107800405B (en) Radial basis function neural network self-adaptive enhancer circuit based on FPGA design
Ogawa et al. Sampling theorem with optimum noise suppression
CN107809400B (en) High-speed low-complexity parallel blind equalization realization method based on FPGA
US20020114380A1 (en) Combined pre-equalizer and nyquist filter

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant