1. A two-way real-time high-precision distance measurement method for a half-duplex system is used for distance measurement between a terminal A and a terminal B, the terminal A or the terminal B can carry out distance measurement calculation, and when the terminal A carries out distance measurement calculation, the method is characterized by comprising the following steps:

determining that the terminal A is in a first receiving mode or a second receiving mode according to local pseudo ranges measured by the terminal A and the terminal B; when the local pseudo range of the terminal B is smaller than a preset value, the terminal B is used as a second receiving mode, and the rest terminal B is used as a first receiving mode;

when the terminal A is in a receiving mode one, for a set terminal A pseudo range, when a local measurement frame sequence number corresponding to the starting moment of the terminal A pseudo range is equal to a receiving measurement frame sequence number corresponding to the ending moment of the pseudo range of the terminal B, matching the pseudo range of the terminal B with the set terminal A pseudo range;

when the terminal A is in a second receiving mode, for a set terminal A pseudo range, when a local measurement frame number corresponding to the starting moment of the terminal A pseudo range is 1 less than a received measurement frame number corresponding to the ending moment of the pseudo range of the terminal B, matching the pseudo range of the terminal B with the set terminal A pseudo range;

calculating a real-time estimated value and a relative frequency accuracy estimated value of the relative speed of the terminal A and the terminal B according to respective pseudo speed drift measured values of the terminal A and the terminal B;

obtaining a correction value according to a real-time estimation value and a relative frequency accuracy estimation value of the relative speed of the terminals A and B; and obtaining the distance or transmission delay measurement result of the terminals A and B at a certain nominal time according to the pseudo-range measurement value and the correction value of the terminal A and the terminal B respectively.

2. The method of claim 1, wherein the local pseudorange preset value of terminal B is determined according to the measurement frame period of terminal B.

3. The bidirectional real-time high-precision ranging method according to claim 1, wherein high-order dynamic estimation values of the terminals a and B are calculated based on respective pseudo-velocity drift measurement values of the terminals a and B, then real-time estimation values of the relative accelerations of the terminals a and B are calculated, and finally real-time estimation values of the relative velocities of the terminals a and B are calculated.

4. The method of claim 3, wherein the relative frequency accuracy estimation is calculated based on the real-time estimation of the relative velocity and the real-time estimation of the relative acceleration of the terminal A and the terminal B.

5. The bidirectional real-time high-precision ranging method according to any one of claims 1 to 4, wherein a pseudorange difference component is obtained from respective pseudorange measurements of terminal A and terminal B; then, a correction amount is obtained based on a real-time estimated value of the relative velocity of the terminal a and the terminal B, and a relative frequency accuracy estimated value.

6. The utility model provides a two-way real-time high accuracy range unit for half-duplex system for range finding between terminal A and the terminal B, terminal A or terminal B homoenergetic can carry out the range finding and solve, when terminal A carries out the range finding and solves, its characterized in that, two-way real-time high accuracy range unit includes:

the mode determination module is used for determining that the terminal A is in a first receiving mode or a second receiving mode according to the local pseudo ranges measured by the terminal A and the terminal B; when the local pseudo range of the terminal B is smaller than a preset value, the terminal B is used as a second receiving mode, and the rest terminal B is used as a first receiving mode;

the pseudo-range matching module is used for matching the pseudo-range of the terminal B with the set pseudo-range of the terminal A when the local measurement frame sequence number corresponding to the starting moment of the pseudo-range of the terminal A is equal to the received measurement frame sequence number corresponding to the ending moment of the pseudo-range of the terminal B for the set pseudo-range of the terminal A; when the terminal A is in a second receiving mode, for a set terminal A pseudo range, when a local measurement frame number corresponding to the starting moment of the terminal A pseudo range is 1 less than a received measurement frame number corresponding to the ending moment of the pseudo range of the terminal B, matching the pseudo range of the terminal B with the set terminal A pseudo range;

the distance measurement module is used for calculating a real-time estimated value and a relative frequency accuracy estimated value of the relative speed of the terminal A and the terminal B according to respective pseudo speed drift measured values of the terminal A and the terminal B; obtaining a correction value according to a real-time estimation value and a relative frequency accuracy estimation value of the relative speed of the terminals A and B; and obtaining the distance or transmission delay measurement result of the terminals A and B at a certain nominal time according to the pseudo-range measurement value and the correction value of the terminal A and the terminal B respectively.

7. The apparatus according to claim 1, wherein the local pseudorange preset value of terminal B is determined according to the measurement frame period of terminal B.

8. The bidirectional real-time high-precision ranging device as claimed in claim 1, wherein the ranging module calculates high-order dynamic estimation values of the terminals a and B according to respective pseudo-velocity drift measurement values of the terminals a and B, then calculates real-time estimation values of relative accelerations of the terminals a and B, and finally calculates real-time estimation values of relative velocities of the terminals a and B.

9. The bi-directional real-time high precision ranging device according to claim 8, wherein the ranging module calculates the relative frequency accuracy estimation value according to the real-time estimation value of the relative velocity and the real-time estimation value of the relative acceleration of the terminal A and the terminal B.

10. The bidirectional real-time high-precision ranging device according to any one of claims 6 to 9, wherein the ranging module obtains a pseudorange difference component from respective pseudorange measurements of terminal a and terminal B; then, a correction amount is obtained based on a real-time estimated value of the relative velocity of the terminal a and the terminal B, and a relative frequency accuracy estimated value.

Background

The detection radar is used for detecting the small celestial body, acquiring the structure and material components inside the small celestial body and directly observing the deep structure and physical properties. The detection radar adopts common-frequency receiving and transmitting to ensure that the physical effects of electric waves are consistent when the electric waves are transmitted in a star, and the radar adopts two-way one-way ranging (DOWR), so that the influence of time asynchronism between stars can be eliminated, and the distance measurement precision is improved. The DOWR needs to match the local satellite pseudorange with other satellite pseudoranges, and when the a satellite is resolved, it needs to wait for the forward (direction from a to B) one-way pseudorange resolved by the B satellite to be transmitted to the a satellite, and then combine the corresponding time resolved by the a satellite and the backward (direction from B to a) one-way pseudorange to resolve the distance. Under a specific working environment such as a time-sharing working condition, the system cannot obtain the unidirectional pseudo ranges of the A satellite and the B satellite at the same time, the pseudo range measurement time of the A/B satellite has a working time slot difference, and the distance obtained by directly applying DOWR (down-horizon) calculation has distance deviation (constant term) and distance drift (time-varying term) under the influence of the clock characteristic and the motion characteristic of the system.

The prior art is usually based on working conditions such as existence of matched pseudo range, non-consideration of time division, and based on bidirectional measurement, and is not suitable for the requirement of bidirectional measurement under the time division working condition of a half-duplex system by carrying out work in several aspects of improvement of measurement precision and processing under special working conditions or expanding the existing system.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: the method comprises the steps of introducing Doppler drift rate, pseudo-range measurement value and pseudo-speed measurement value as known information, extracting clock characteristics such as relative accuracy and relative drift rate of reference sources at two ends of an A/B satellite, extracting inter-satellite dynamic characteristics such as relative speed and relative acceleration of the A/B satellite, adding clock characteristic correction and dynamic characteristic correction in the DOWR resolving process, and obtaining a high-precision distance measurement result in real time.

The purpose of the invention is realized by the following technical scheme:

a two-way real-time high-precision distance measurement method for a half-duplex system is used for distance measurement between a terminal A and a terminal B, the terminal A or the terminal B can carry out distance measurement calculation, and when the terminal A carries out distance measurement calculation, the method comprises the following steps:

determining that the terminal A is in a first receiving mode or a second receiving mode according to local pseudo ranges measured by the terminal A and the terminal B; when the local pseudo range of the terminal B is smaller than a preset value, the terminal B is used as a second receiving mode, and the rest terminal B is used as a first receiving mode;

when the terminal A is in a receiving mode one, for a set terminal A pseudo range, when a local measurement frame sequence number corresponding to the starting moment of the terminal A pseudo range is equal to a receiving measurement frame sequence number corresponding to the ending moment of the pseudo range of the terminal B, matching the pseudo range of the terminal B with the set terminal A pseudo range;

when the terminal A is in a second receiving mode, for a set terminal A pseudo range, when a local measurement frame number corresponding to the starting moment of the terminal A pseudo range is 1 less than a received measurement frame number corresponding to the ending moment of the pseudo range of the terminal B, matching the pseudo range of the terminal B with the set terminal A pseudo range;

calculating a real-time estimated value and a relative frequency accuracy estimated value of the relative speed of the terminal A and the terminal B according to respective pseudo speed drift measured values of the terminal A and the terminal B;

obtaining a correction value according to a real-time estimation value and a relative frequency accuracy estimation value of the relative speed of the terminals A and B; and obtaining the distance or transmission delay measurement result of the terminals A and B at a certain nominal time according to the pseudo-range measurement value and the correction value of the terminal A and the terminal B respectively.

The bidirectional real-time high-precision ranging method determines a local pseudo-range preset value of the terminal B according to the measurement frame period of the terminal B.

The bidirectional real-time high-precision distance measurement method comprises the steps of calculating high-order dynamic estimation values of a terminal A and a terminal B according to respective pseudo-velocity drift measurement values of the terminal A and the terminal B, then calculating a real-time estimation value of relative acceleration of the terminal A and the terminal B, and finally calculating a real-time estimation value of relative velocity of the terminal A and the terminal B.

The bidirectional real-time high-precision distance measurement method calculates the relative frequency accuracy estimation value according to the real-time estimation value of the relative speed and the real-time estimation value of the relative acceleration of the terminal A and the terminal B.

According to the bidirectional real-time high-precision ranging method, a pseudo-range difference component is obtained according to respective pseudo-range measurement values of a terminal A and a terminal B; then, a correction amount is obtained based on a real-time estimated value of the relative velocity of the terminal a and the terminal B, and a relative frequency accuracy estimated value.

The utility model provides a two-way real-time high accuracy range unit for half-duplex system for range finding between terminal A and the terminal B, terminal A or terminal B homoenergetic can carry out the range finding and solve, when terminal A carries out the range finding and solves, two-way real-time high accuracy range unit includes:

the mode determination module is used for determining that the terminal A is in a first receiving mode or a second receiving mode according to the local pseudo ranges measured by the terminal A and the terminal B; when the local pseudo range of the terminal B is smaller than a preset value, the terminal B is used as a second receiving mode, and the rest terminal B is used as a first receiving mode;

the pseudo-range matching module is used for matching the pseudo-range of the terminal B with the set pseudo-range of the terminal A when the local measurement frame sequence number corresponding to the starting moment of the pseudo-range of the terminal A is equal to the received measurement frame sequence number corresponding to the ending moment of the pseudo-range of the terminal B for the set pseudo-range of the terminal A; when the terminal A is in a second receiving mode, for a set terminal A pseudo range, when a local measurement frame number corresponding to the starting moment of the terminal A pseudo range is 1 less than a received measurement frame number corresponding to the ending moment of the pseudo range of the terminal B, matching the pseudo range of the terminal B with the set terminal A pseudo range;

the distance measurement module is used for calculating a real-time estimated value and a relative frequency accuracy estimated value of the relative speed of the terminal A and the terminal B according to respective pseudo speed drift measured values of the terminal A and the terminal B; obtaining a correction value according to a real-time estimation value and a relative frequency accuracy estimation value of the relative speed of the terminals A and B; and obtaining the distance or transmission delay measurement result of the terminals A and B at a certain nominal time according to the pseudo-range measurement value and the correction value of the terminal A and the terminal B respectively.

The bidirectional real-time high-precision ranging device determines a local pseudo-range preset value of the terminal B according to the measurement frame period of the terminal B.

According to the bidirectional real-time high-precision distance measuring device, a distance measuring module calculates high-order dynamic estimated values of the terminals A and B according to respective pseudo-speed drift measured values of the terminals A and B, then calculates real-time estimated values of relative acceleration of the terminals A and B, and finally calculates real-time estimated values of relative speed of the terminals A and B.

According to the bidirectional real-time high-precision distance measuring device, the distance measuring module calculates the relative frequency accuracy estimation value according to the real-time estimation value of the relative speed and the real-time estimation value of the relative acceleration of the terminal A and the terminal B.

The bidirectional real-time high-precision distance measuring device is characterized in that a distance measuring module obtains a pseudo-range difference component according to respective pseudo-range measurement values of a terminal A and a terminal B; then, a correction amount is obtained based on a real-time estimated value of the relative velocity of the terminal a and the terminal B, and a relative frequency accuracy estimated value.

Compared with the prior art, the invention has the following beneficial effects:

(1) the method breaks through the constraint of the pseudorange measurement simultaneity of the bidirectional distance calculation, realizes the real-time high-precision bidirectional distance calculation under the time-sharing working condition, and expands the application scene of the bidirectional distance calculation method;

(2) the invention provides a receiving mode and an interpretation method, which simplify the pseudo-range matching process in a dynamic scene;

(3) the invention provides a bidirectional comparison calculation formula based on the pseudo-velocity drift rate, and real-time calculation of high-order dynamic quantities such as relative acceleration, relative velocity, relative frequency accuracy and the like of a terminal AB is obtained by using pseudo-velocity drift measurement values and pseudo-velocity measurement values of the terminal AB at different moments, so that the bidirectional calculation is not restricted by measurement simultaneity any more;

(4) the invention provides a correction value calculation formula for bidirectional distance calculation under the time-sharing working condition, and realizes real-time high-precision calculation of the AB relative distance of the terminal under the time-sharing working condition.

Drawings

FIG. 1 is a schematic block diagram of a two-way one-way (DOWR) distance measurement;

FIG. 2 is a two-way one-way (DOWR) dynamic receive mode;

FIG. 3 is a schematic diagram of a working timing sequence of the ranging system under a time-sharing working condition;

FIG. 4 is a DOWR pseudorange sequence schematic under a time-sharing condition;

FIG. 5 is a condition-one algorithm performance verification; wherein (5a) the verification results are compared, and (5b) the verification results are compared in a local graph;

FIG. 6 is a condition two algorithm performance verification.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

A two-way real-time high-precision distance measurement method for a half-duplex system adopts high-order dynamic correction, and solves the problem that the distance measurement can not be completed by matching the receiving and transmitting one-way time delay under the time-sharing receiving and transmitting working condition. The invention introduces Doppler drift rate, combines known information such as pseudo-range measurement value and pseudo-speed measurement value of the A/B satellites, extracts clock characteristics and dynamic characteristics of the A/B satellites, performs clock correction and dynamic correction on an original measurement value on the basis of DOWR incomplete solution, and obtains a high-precision distance measurement result in real time.

1. Description of the parameters

The physical quantities involved in the process and their description are as follows:

γ_a: a star frequency accuracy, defined as γ_a＝(f_a-f₀)/f₀Wherein f is_aRefers to the oscillation frequency, f, of the A-satellite reference source₀Is the nominal oscillation frequency of the reference source.

γ_b: b Star frequency accuracy, defined as γ_b＝(f_b-f₀)/f₀Wherein f is_bReference frequency f of B-satellite reference source₀Is the nominal oscillation frequency of the reference source.

t_a(t): the local time of the A star refers to the local time maintained by the local reference source when the nominal time is t, and meets the requirement

t_b(t): the local time of the B satellite refers to the local time maintained by the local reference source when the nominal time is t, and meets the requirement

clk _ dta (t): the a-satellite local clock difference refers to the degree that the a-satellite local time is ahead of the B-satellite local time when the nominal time is t, and the clk _ dta (t) is t_a(t)-t_b(t)＝(γ_a-γ_b) T. When the oscillation frequency of the A star reference source is greater than that of the B star reference source, the clock difference changes towards the positive direction. The specific implementation mode is analyzed by taking the star A as a reference, the "clock difference" mentioned in the specific implementation mode refers to the local clock difference of the star A, and the symbol clk _ dt (t) is used for replacing clk _ dtA (t).

clk _ dtb (t): the local clock difference of the B satellite means that the local time of the B satellite is advanced by the local time of the A satellite when the nominal time is t, and the clk _ dtB (t) is t_b(t)-t_a(t)＝(γ_b-γ_a) T. When the oscillation frequency of the A star reference source is greater than that of the B star reference source, the clock difference changes towards the negative direction.

v (t): when the nominal time is t, the relative speed of the a/B stars, defined as v (t) ═ dr (t)/dt, is negative when the two stars fly in opposite directions.

V: the average relative speed of A/B stars in the measurement time interval tau is definedWhen the two stars fly in opposite directions, the average relative velocity V is negative.

a (t): when the nominal time is t, the relative acceleration of the a/B stars is defined as a (t) ═ dv (t)/dt, and when the two stars increase toward the flight speed or decrease away from the flight speed, the relative speed a (t) is a negative number.

A: the average relative acceleration of the A/B stars within the measurement time interval tau is definedWhen the flying speed of the two stars in the opposite direction is increased or the flying speed is reduced, the relative average speed A is negative.

fd_A(t): doppler frequency of A-star received signalRate, definitionWherein f is_{RF_B}The carrier frequency for which the signal is transmitted by its satellite, and c the speed of light.

dfd_A(t): doppler frequency shift of A-star received signal, definition dfd_A(t)＝d(fd_A(t))/dt, wherein fd_AAnd (t) is the Doppler frequency of the A star received signal.

fd_B(t): doppler frequency of B-satellite received signal, definitionWherein f is_{RF_A}The carrier frequency for which the signal is transmitted by its satellite, and c the speed of light.

dfd_B(t): doppler frequency shift of B-satellite received signal, definition dfd_B(t)＝d(fd_B(t))/dt, wherein fd_BAnd (t) is the Doppler frequency of the A star received signal.

2. DOWR receive mode

Based on the above definitions, the basic procedure of DOWR ranging is given: respectively transmitting a timing signal by using respective equipment by the A star and the B star for measurement, receiving the timing signal from the opposite side, defining the time difference between the local clock timing signal measured by the A star and the timing signal of the B star as an A star pseudo range, and recording the time difference as pd _ A (ta (t1) and ta (t 4)); wherein ta (t1) is the local starting time of the pseudorange of the a-satellite, ta (t4) is the local ending time of the pseudorange of the a-satellite, and t1 and t4 are respectively the nominal time corresponding to the local starting time and the local ending time of the pseudorange; defining the time difference between the local clock timing signal measured by the B satellite and the received a satellite timing signal as the B satellite pseudorange, denoted as pd _ B (tb (t2), tb (t 3)); tb (t2) is the local start time of the pseudorange of the B satellite, tb (t3) is the local end time of the pseudorange of the B satellite, and t2 and t3 are the nominal times corresponding to the local start time and the local end time of the pseudorange, respectively. The local pseudoranges for a/B stars may be abbreviated as pd _ a and pd _ B, respectively.

The transmission delay between A/B stars at a nominal time t is defined as tau (t). Regardless of the system zero value for range, the expression of pseudorange can be derived from fig. 1 as follows:

obviously, neglecting the difference between the clock difference and the time delay at the time t1 and the time t2, the distance and the clock difference resolved at the satellite a, DOWR, can be obtained:

according to the definition of clock error, when the satellite runs in orbit for a long time, a receiving mode different from that of fig. 1 as shown in fig. 2 may occur: the clock difference of A/B two stars gradually increases, and the clock difference exceeds the propagation delay:

the local pseudoranges are respectively:

the A/B satellite time is divided into several discrete times by the local clock timing signal, which is distinguished by the local measurement frame number. For a star, the local clock timing signal is generated at the period of local time Ta, and the a star local time may be expressed as a time scale sequence { …, (k-1) _ a, k _ a, … } × Ta. Similarly, the B-star local time can be expressed as { …, (k-1) _ B, k _ B, … }. times Tb. Ta and Tb respectively represent the respective measurement frame periods of the AB stars, and Ta ═ 1+ gamma_a)*T_frame、Tb＝(1+γ_b)*T_frameTypical value of the measurement frame period is T_frame0.2 s. Based on this, the one-way pseudoranges may be expressed as follows:

as can be seen from the above equation, in the expression of the local pseudorange pd _ B of the B-satellite, the time scale corresponding to the clock difference is (k-1) _ a, the time scale of the transmission delay is k _ a, and the time scale of the clock difference is not consistent with the time scale of the transmission delay, which is a problem of mismatch between the transmission delay and the clock difference caused in a dynamic environment.

For a specific terminal, taking a satellite as an example, the terminal coexists in three reception modes:

the reception mode I is characterized by a small local pseudorange (pd _ a) and a small remote pseudorange (pd _ B). The receiving mode occurs under the condition that the local clock difference is positive (clk _ dtA >0) and the transmission delay tau is greater than the local clock difference (tau > clk _ dtA), as shown in FIG. 1; or the local clock difference is negative (clk _ dtA < 0) and the transmission delay τ is greater than the absolute value of the local clock difference (τ > ABs (clk _ dtA)), i.e. as shown after AB interchange in fig. 1;

defining the receiving mode II as the local pseudo range (pd _ A) with small value and the foreign pseudo range (pd _ B) with large value; the receiving mode occurs under the condition that the local clock difference is positive (clk _ dtA >0) and the transmission delay tau is smaller than the local clock difference (tau < clk _ dtA), as shown in FIG. 2;

defining a receiving mode III to be characterized by a local pseudo range (pd _ A) with a large value and a remote pseudo range (pd _ B) with a small value; this receive mode occurs under conditions where the local clock difference is negative (clk _ dtA >0) and the propagation delay τ is less than the local clock difference (τ < clk _ dtA), i.e., as shown after AB interchange in fig. 2.

3. Time-sharing measurement of half-duplex system

The detection radar adopts a half-duplex mode to complete measurement, and the terminal A and the terminal B perform time-sharing work according to a time slot T _ slot and a beat which is alternated between transmitting and receiving:

in the Nth time slot, the terminal A transmits the signal received by the terminal B and can establish a forward link, the terminal B extracts real-time forward transmission delay pd _ B (N, k) (pseudo range including system error) and demodulates the real-time forward transmission delay pd _ B (N, k) to obtain the backward transmission delay pd _ A (N-1, k) received by the terminal A in the last time slot (the Nth-1 time slot);

in the N +1 th time slot, the terminal a receives the transmission of the terminal B, establishes a return link, and extracts the real-time return transmission delay pd _ a (N +1, k) (pseudo range, including the system error) from the terminal a, and demodulates the real-time return transmission delay pd _ B (N, k) received by the terminal B in the last time slot (nth time slot).

The above notation for pseudorange is jointly labeled with slot N and frame number k, in the form of pd (N, k), and represents the measurement taken at the kth frame number instant of the nth slot.

The system operation sequence is shown in fig. 3 as follows:

the sequence of pseudoranges obtained at this time is shown in fig. 4, where the dotted arrow indicates that in the receive time slot, the locally generated transmit frame time scale is used for pseudorange resolution only and no signal is transmitted.

Pseudoranges may be labeled jointly with slot and frame number, as follows:

obviously, the self satellite pseudorange and the other satellite pseudoranges are mismatched, and the a satellite pseudorange sequence of the formula (5) and the B satellite pseudorange sequence of the formula (6) cannot directly use the formula (2) to obtain the transmission delay and the clock offset.

The raw measurement also available at this time is the own satellite pseudo-velocity ps _ a, which is the satellite pseudo-velocity ps _ B, as follows:

in addition, the pseudo-speed drift dps _ A of the satellite and the pseudo-speed drift dps _ B of other satellites can be obtained through the tracking loop, the physical meaning of the pseudo-speed drift dps _ A of the satellite is equal to the difference of the pseudo-speed of the formula (5), and the pseudo-speed drift dps _ B is expressed as follows:

4. carrying out the step

The invention solves the problem of inconsistent measurement time of the AB satellite under the condition that the local pseudo range (pd), pseudo speed (ps) and pseudo speed drift (dps) are obtained by the measurement of the A/B satellite respectively, and solves the method for calculating the inter-satellite transmission time delay at the specific time of the A/B satellite. The specific steps are as follows:

step one, receiving mode interpretation:

and according to the section of the DOWR receiving mode, judging the receiving mode:

if the terminal A measures the local pseudo range pd _ A < Ta/2 and pd _ B < Tb/2, the terminal A is considered to be in a receiving mode I;

if the terminal A measures a local pseudo range pd _ A < Ta/2 and pd _ B > Tb/2, the terminal A is considered to be in a receiving mode II;

if the terminal A measures a local pseudo range pd _ A > Ta/2 and pd _ B < Tb/2, the terminal A is considered to be in a receiving mode III;

note that the reception mode determination is performed for a specific terminal, and if the terminal B performs the solution, the local pseudorange pd _ B and the satellite reception pseudorange pd _ a are determined accordingly, as in the above principle.

Step two, DOWR resolving:

and after the mode judgment is completed, incomplete DOWR resolving is carried out.

When the terminal a is in the receiving mode I and the receiving mode III, that is, the terminal a makes a judgment, and when the satellite receiving pseudo range meets pd _ B < Tb/2, the matching criterion is as follows: for a given A-satellite pseudo range pd _ A, recording a local measurement frame sequence number corresponding to the starting time as k, searching the ending time of the B-satellite pseudo range, and matching the pseudo range with the given A-satellite pseudo range when a received measurement frame sequence number corresponding to the ending time of the B-satellite pseudo range is equal to k;

when the terminal a is in the receiving mode II, that is, the terminal a makes a judgment, and when the satellite receiving pseudo range meets pd _ B > Tb/2, the matching criterion is: for a given A-satellite pseudo range pd _ A, recording a local measurement frame sequence number corresponding to the starting time as k, searching the ending time of the B-satellite pseudo range, and matching the pseudo range with the given A-satellite pseudo range when a received measurement frame sequence number corresponding to the ending time of the B-satellite pseudo range is equal to (k + 1);

and after the matching is completed, performing DOWR resolving according to the following step three.

Step three, inter-satellite dynamic calculation:

and calculating a real-time estimated value of the relative acceleration of the terminal AB according to the respective pseudo-velocity drift measured values of the terminal AB. After the pseudo-velocity drift measurement value is differentiated, the influence of clock drift can be removed, the Doppler drift rate, namely the expression of relative jerk is established, and the estimated value of high-order dynamic (relative jerk) is calculated according to the following formula (9)Then, the terminal AB is substituted into the formula (10) to calculate the estimated value a (N, k) of the relative acceleration.

And calculating a real-time estimation value of the relative speed of the terminal AB according to the respective pseudo speed measurement values of the terminal AB. The estimated value a (N, k) of the relative acceleration of the terminal AB is substituted according to the following equation (11), the estimated value V (N, k) of the relative velocity of the terminal AB is calculated, and then the estimated values of the relative acceleration of the terminal AB and the relative velocity of the terminal AB are substituted according to the following equation (12), the estimated value of the relative frequency accuracy (γ) is calculated_a(N,k)-γ_b(N,k))：

Step four, distance calculation:

substituting the estimated value (gamma) of the relative frequency accuracy obtained in the third step into the formula (13)_a(N,k)-γ_b(N, k)) and the terminal AB relative velocity estimation value V (N, k), the correction amounts are obtained as follows:

the expression of the pseudo-range difference component obtained from the pseudo-range measurement value is as follows:

substituting the correction quantity obtained by the formula (13) according to the formula (14) to calculate the terminal AB clock difference clk _ dt (t5) at the nominal time t 5;

the expression of the pseudorange and the component obtained from the respective pseudorange measurement of the terminal AB is as follows:

according to the formula (15), the correction amount obtained by the formula (13) and the calculated value of the clock difference obtained by the formula (14) are substituted, so that the transmission delay τ (t5) at the nominal time t5 can be calculated, namely, the distance of the terminal AB is obtained.

The utility model provides a two-way real-time high accuracy range unit for half-duplex system, adopts above-mentioned range finding method for range finding between terminal A and the terminal B, terminal A or terminal B all can carry out the range finding and solve, when terminal A carries out the range finding and solves, two-way real-time high accuracy range unit includes:

the mode determination module is used for determining that the terminal A is in a first receiving mode or a second receiving mode according to the local pseudo ranges measured by the terminal A and the terminal B; when the local pseudo range of the terminal B is smaller than a preset value, the terminal B is used as a second receiving mode, and the rest terminal B is used as a first receiving mode;

the pseudo-range matching module is used for matching the pseudo-range of the terminal B with the set pseudo-range of the terminal A when the local measurement frame sequence number corresponding to the starting moment of the pseudo-range of the terminal A is equal to the received measurement frame sequence number corresponding to the ending moment of the pseudo-range of the terminal B for the set pseudo-range of the terminal A; when the terminal A is in a second receiving mode, for a set terminal A pseudo range, when a local measurement frame number corresponding to the starting moment of the terminal A pseudo range is 1 less than a received measurement frame number corresponding to the ending moment of the pseudo range of the terminal B, matching the pseudo range of the terminal B with the set terminal A pseudo range;

the distance measurement module is used for calculating a real-time estimated value and a relative frequency accuracy estimated value of the relative speed of the terminal A and the terminal B according to respective pseudo speed drift measured values of the terminal A and the terminal B; obtaining a correction value according to a real-time estimation value and a relative frequency accuracy estimation value of the relative speed of the terminals A and B; and obtaining the distance or transmission delay measurement result of the terminals A and B at a certain nominal time according to the pseudo-range measurement value and the correction value of the terminal A and the terminal B respectively.

5. System performance analysis and verification

The two-way measurement method of time delay is a mature algorithm, and the core of the method is that the received pseudo ranges of two terminals are matched, and then the dynamic error between clock error and satellite is eliminated through two-way calculation, so that the accurate transmission time delay is obtained. In some application scenarios, the terminal AB cannot simultaneously obtain pseudorange measurement values, and at this time, resolving is performed according to a conventional bidirectional measurement method, and measurement results of time delay and clock difference include offsets caused by clock dynamics and inter-device motion, and the resolving value shows that there is an offset from a true value under a static working condition and drifts along with time; under the dynamic working condition, the clock dynamic state and the motion between the devices are superposed.

And (3) establishing a verification environment by using a structure detection radar prototype, wherein the terminal AB is connected by a wire, the receiving and transmitting time slot is 5s, and the measurement frame is 200 ms. Under the first working condition, the distance between the AB devices of the terminal is set to be 76.61m, under the static working condition, the measurement result obtained by using the traditional bidirectional measurement method is shown as a black solid line in a figure 5, the measurement result corrected by using the method is shown as a black + marked curve in the figure 5, and the system truth value is shown as a black dotted line in the figure 5.

Under the second working condition, the distance between the AB initializers of the terminal is set to be 50km, the maximum speed is 100m/s according to sinusoidal dynamic motion, the measurement result obtained by using the traditional bidirectional measurement method is shown as a black solid line in the following graph, the measurement result corrected by using the method is shown as a black + marked curve in the following graph 6, and the system true value is shown as a black dotted line in the graph 6. When DOWR is directly used for resolving under the time-sharing working condition, the deviation of the distance/time delay measured value and the true value can reach 130m at most, and after high-order dynamic correction is adopted, the deviation of the distance/time delay measured value and the true value is less than 0.1 m.

Those skilled in the art will appreciate that those matters not described in detail in the present specification are well known in the art.

Although the present invention has been described with reference to the preferred embodiments, it is not intended to limit the present invention, and those skilled in the art can make variations and modifications of the present invention without departing from the spirit and scope of the present invention by using the methods and technical contents disclosed above.