CN111856524A

CN111856524A - Method and system for continuous high-precision measurement in two directions at same frequency

Info

Publication number: CN111856524A
Application number: CN202010580490.2A
Authority: CN
Inventors: 蒙艳松; 杨瑞强; 徐连军; 王登峰; 郑先安; 王延光; 胡涛
Original assignee: Xian Institute of Space Radio Technology
Current assignee: Xian Institute of Space Radio Technology
Priority date: 2020-06-23
Filing date: 2020-06-23
Publication date: 2020-10-30
Anticipated expiration: 2040-06-23
Also published as: CN111856524B

Abstract

The invention relates to a method and a system for measuring the same-frequency bidirectional continuous high precision, which comprises three methods: completing time synchronization; respectively establishing local reference time sequences at an active end and a passive end; calculating transmission time delay, wherein the time delay can be calculated and obtained through track forecast information, or can be measured and obtained by adopting a bidirectional time comparison method, and then time slot adjustment is carried out at a passive end to obtain a local adjustment time sequence; and respectively carrying out signal reconstruction and continuous measurement at the active end and the passive end. The third method specifically comprises the following steps: the first step is to configure the time slot length and generate a local reference time sequence; and a second step of setting a staggered time sequence, so that the active end time sequence TA and the passive end time sequence TB meet the condition that TA, TB and M, N are equal, wherein M is not equal to N. The same-frequency bidirectional link basically eliminates the additional time delay of the ionosphere/troposphere, and improves the measurement precision of the microwave link.

Description

Method and system for continuous high-precision measurement in two directions at same frequency

Technical Field

The invention relates to a method and a system for continuous high-precision measurement in a same-frequency two-way manner, belongs to the technical field of precision measurement of inter-satellite/inter-satellite links, and can be applied to tasks with high-precision requirements on measurement, such as inter-satellite/inter-satellite high-precision time-frequency transmission.

Background

The time-frequency cabinet task of the manned space engineering space station is an atomic clock experiment based on the microgravity environment of the space station, and comprises a space clock group, a ground high-precision atomic clock network and a satellite-ground time-frequency transmission link. The main task of the satellite-ground microwave link is to complete ultra-high precision time-frequency transmission between a space clock group and a ground atomic clock, and the time stability @1 day of the microwave link is expected to reach ps magnitude. The microwave time-frequency transmission link is in satellite-ground transmission, and additional time delay is generated when microwave signals penetrate through an ionized layer and a troposphere, so that the improvement of the system performance of the measurement link is restricted. The additional delay can be expressed as an integral of the signal propagation path, the value of which is determined by the signal frequency, the signal propagation path, and the path characteristics such as temperature, water vapor pressure, and Total Electron Content (TEC). The current typical correction algorithm comprises model correction and double-frequency/three-frequency ionosphere correction, and the correction precision is about 0.2TECU (4cm) by taking a navigation constellation as an example, so that the time delay stability requirement of subps/day cannot be met.

For the additional delay characteristic, if the frequencies of the transmission links are the same and the uplink and downlink signals are transmitted simultaneously, the additional delay of the uplink and the additional delay of the downlink are completely equal, the additional delay of the ionosphere/troposphere can be completely cancelled theoretically, and the accuracy of the link is greatly improved.

The current research on the same-frequency transceiving system mainly focuses on two directions: 1) the method comprises the steps of receiving and transmitting in a same frequency time-sharing mode, realizing bidirectional receiving and transmitting through receiving and transmitting time slot switching, and being mature in Ka inter-satellite links and TDD time division multiple access communication systems in the Beidou navigation system; 2) Co _ frequency Co _ time Full Duplex (Co _ frequency Co _ time Full Duplex) simultaneous receiving and transmitting, realizing Full Duplex transmission, solving the problem of same frequency self-interference and having more applications in communication systems.

However, in the conventional time division system, the time slot is generally set to be ms magnitude or s magnitude, the uplink and downlink time slots of LTE-TDD support ms level switching at the fastest speed, the switching time slot of the link between the beidou satellites is 1.5s, and the time division switching makes signals discontinuous, so that the time division switching cannot adapt to an application scenario with high-precision measurement requirements; the same-frequency simultaneous receiving and transmitting system is applied to a 5G communication system, the same-frequency self-interference suppression is about 30 dB-60 dB for signals with the bandwidth within 20MHz, and the same-frequency self-interference suppression performance is reduced along with the expansion of the signal bandwidth; according to the budget of the satellite measurement link, the basic requirement of the link on local same-frequency self-interference is larger than 100dB, and the current same-frequency self-interference cancellation technology cannot meet the requirement of the current satellite measurement link.

Disclosure of Invention

The technical problem solved by the invention is as follows: the method and the system overcome the defects of the prior art, provide a same-frequency bidirectional continuous high-precision measurement method and system, and solve the problems that when a time-sharing system is adopted in the traditional same-frequency transceiving system, signals are discontinuous, when the same-frequency transceiving system is adopted, self-interference is large, and the high-precision requirement of the measurement system cannot be met.

The technical scheme of the invention is as follows: a method for continuous high-precision measurement in two directions with same frequency comprises the following steps:

(1-1) respectively carrying out time synchronization processing on the active end and the passive end to synchronize the local time of the active end and the passive end to obtain synchronous second pulse;

(1-2) respectively generating local reference time sequences by the active end and the passive end on the synchronous pulse per second reference;

(1-3) windowing and sending the time continuous measurement signal at the transmission time slot by the active end according to the local reference time sequence, and ensuring the time correlation of the measurement signal; receiving a measuring signal sent by a passive end in a receiving time slot;

(1-4) the passive terminal estimates the transmission time delay between the active terminal and the passive terminal, and carries out time slot adjustment according to the transmission time delay to obtain a local adjustment time sequence; according to the local adjustment time sequence, windowing the time continuous measurement signal in the transmission time slot and sending the time continuous measurement signal, and ensuring the time correlation of the measurement signal; receiving a received measurement signal sent by an active end in a receiving time slot, wherein the carrier frequencies of the measurement signal sent by the passive end and the active end are the same, so that a same-frequency bidirectional link is established;

And (1-5) the active end and the passive end respectively rebuild the received measuring signals to recover the measuring signals with continuous time, and the time-frequency synchronization between the active end and the passive end is realized according to the carrier phase measuring value of the measuring signals of the opposite side, so that the high-precision carrier phase measurement based on the continuous signals is completed.

The local reference timing can be established according to the following two rules:

the first rule is:

(1-2.1a) alternately forming a receiving time slot and a transmitting time slot, wherein the time length of the transmitting time slot is less than the estimated maximum transmission time delay between the active end and the passive end;

(1-2.2a), the local reference timing sequence time slot length is configurable, the transmission time slot time length is defined as Tx, the receiving time slot time length Tr, and the switching period T is the transmission time slot time length plus the receiving time slot time length, namely: T-Tx + Tr, the receive slot length is greater than the transmit slot, i.e.: tr is more than or equal to Tx;

(1-2.3a) aligning the local reference time sequence to a local synchronous second pulse, namely aligning the leading edge of a local transmitting time slot with the rising edge of the synchronous second pulse;

(1-2.4a) defining the time slot numbers in 1s to be 1-N in sequence, wherein the odd-numbered time slots in the local reference time sequence of the active end and the passive end are transmitting time slots, and the even-numbered time slots are receiving time slots.

The second rule is:

(1-2.1b) alternately forming a receiving time slot and a transmitting time slot, wherein the time length of the transmitting time slot is less than the estimated maximum transmission time delay between the active end and the passive end;

(1-2.2b), the local reference timing sequence time slot length is configurable, the transmission time slot time length is defined as Tx, the receiving time slot time length Tr, and the switching period T is the transmission time slot time length plus the receiving time slot time length, namely: T-Tx + Tr, the receive slot length is greater than the transmit slot, i.e.: tr is more than or equal to Tx;

(1-2.3b), adding a protection time slot Ts to the receiving time slot on the original basis, and prolonging the time length of the local receiving time slot to ensure that the time length of the receiving time slot becomes Tr' ═ Tr + Ts, and the following conditions are met: tr' is more than or equal to 3Tx, so that a local reference timing sequence is obtained;

(1-2.4b) aligning the local reference time sequence to a local synchronous second pulse, namely aligning the leading edge of a local transmitting time slot with the rising edge of the synchronous second pulse;

(1-2.5b) defining the time slot numbers in 1s to be 1-N in sequence, wherein the odd-numbered time slots in the local reference time sequence of the active end and the passive end are transmitting time slots, and the even-numbered time slots are receiving time slots.

The relative deviation of the local reference timing of the transmitting end and the receiving end does not exceed 20 ns.

The sending end and the receiving end complete time synchronization by referring to GNSS time or realize time synchronization by adopting a bidirectional time comparison method.

The bidirectional time comparison method is realized by adopting two one-way pseudo range measurement links, wherein the link from an active end to a passive end is a forward link, and the working frequency point of the forward link is f₁The passive end to the active end is a return link, and the working frequency point of the return link is f₂So that f₁≠f₂The active end and the passive end respectively obtain a unidirectional pseudo range measured value locally, and the passive end obtains a unidirectional pseudo range measured value pd _ B locally and a unidirectional pseudo range measured value pd _ A returned by the active end according to a formula

And acquiring the relative time deviation dt, and then adjusting the local second pulse according to the relative time deviation dt to synchronize the local second pulse with the local second pulse of the active end and record the local second pulse as a synchronous second pulse.

The specific method for the sending end and the receiving end to complete time synchronization according to the GNSS time comprises the following steps:

the sending end and the receiving end acquire the second pulse given by the GNSS receiver and adjust the synchronization of the local second pulse signal and the second pulse output by the GNSS receiver.

When the active end and the passive end are respectively positioned on two satellites, or the active end is positioned on the satellites and the passive end is positioned on the ground station.

When the active end and the passive end are respectively located on two satellites, the passive end obtains the transmission time delay of the active end and the passive end by the following method, specifically:

(4.1-1a), respectively reading the orbit prediction information of each satellite by the active end and the passive end, and calculating the position of the satellite at the current moment under an ECEF coordinate system or an ECI coordinate system according to the orbit prediction information; the orbit forecast information is six orbits and corresponding reference time thereof, or motion state vectors of the satellite in an ECEF coordinate system or an ECI coordinate system and corresponding reference time thereof, wherein the motion state vectors comprise the position and the speed of the satellite;

(4.1-2a), the active end and the passive end acquire the position of the phase center of each terminal antenna under the satellite body coordinate system;

(4.1-3a), the active end and the passive end respectively convert the phase center position of each microwave terminal antenna into an ECEF coordinate system or an ECI coordinate system according to the position of the satellite in which the current time is located in the ECEF coordinate system or the ECI coordinate system, and the transfer matrix from each satellite body coordinate system to the ECEF coordinate system or the ECI coordinate system;

(4.1-4a), the active end sends the position of the antenna phase center of the microwave terminal at the current moment in an ECEF coordinate system or an ECI coordinate system to the passive end, the passive end makes a difference between the positions of the antenna phase center of the active end and the antenna phase center of the passive end in the ECEF coordinate system or the ECI coordinate system, and the distance R (k) between the antenna phase centers of the active end and the passive end is calculated, so that the transmission delay tau (k) can be obtained.

When the active end is located in a satellite and the passive end is located in a ground station, the passive end obtains the transmission time delay of the active end and the passive end by the following method, specifically:

(4.1-1b), the active end reads the orbit forecast information of the satellite, and calculates the position of the satellite in the ECEF coordinate system or the ECI coordinate system at the current moment according to the orbit forecast information; the orbit forecast information can be six orbital numbers and corresponding reference time thereof, or motion state vectors of the satellite in an ECEF coordinate system or an ECI coordinate system and corresponding reference time thereof, wherein the motion state vectors comprise the position and the speed of the satellite;

(4.1-2b), the active end acquires the position of the terminal antenna phase center under the satellite body coordinate system;

(4.1-3b), the active end converts the phase center position of each microwave terminal antenna into an ECEF coordinate system or an ECI coordinate system according to the position of the satellite in the ECEF coordinate system or the ECI coordinate system at the current moment, and a transfer matrix from the satellite body coordinate system to the ECEF coordinate system or the ECI coordinate system;

(4.1-4b), the active end sends the position of the antenna phase center position of the microwave terminal at the current moment under an ECEF coordinate system or an ECI coordinate system to the passive end;

(4.1-4b), the passive end acquires the position of the antenna phase center position of the microwave terminal at the current moment under an ECEF coordinate system or an ECI coordinate system and sends the position to the passive end, the positions of the antenna phase center positions of the active end and the passive end under the ECEF coordinate system or the ECI coordinate system are differenced, and the distance R (k) between the antenna phase centers of the active end and the passive end is calculated, so that the transmission delay tau (k) can be obtained.

The passive end obtains the transmission time delay between the active end and the passive end by adopting a bidirectional time comparison method, the active end and the passive end are defined as a forward link, and the working frequency point of the forward link is f₁The passive end to the active end is a return link, and the working frequency point of the return link is f₂So that f₁≠f₂The active end and the passive end respectively obtain a unidirectional pseudo range measured value locally, and the passive end obtains a unidirectional pseudo range measured value pd _ B locally and a unidirectional pseudo range measured value pd _ A returned by the active end according to a formula

And acquiring the transmission time delay between the active end and the passive end, wherein C is the speed of light.

The update period T _ orb for the passive terminal to estimate the transmission delay between the active terminal and the passive terminal must satisfy the following condition:

(T_orb×V+R)≤t×C

wherein, R track forecast precision, V is relative motion speed of the active end and the passive end, t is precision requirement of transmission time delay, and C is light speed.

The time slot adjusting period of the passive terminal is greater than the transmission time slot duration Tx and not greater than the transmission delay updating period T _ orb.

For the local reference time sequence under the first rule, the time slot adjustment is performed by the passive end, and the method for obtaining the local adjustment time sequence comprises the following steps:

(1-4.1a), calculating a residual value delta tau (k) of the transmission time delay tau (k) between the active end and the passive end, which is obtained by rounding a local reference timing switching period T (Tx + Tr) to 2 Tx;

(1-4.2a), generating local adjustment timing: when delta tau (k) belongs to (0, Tx/2) or delta tau (k) belongs to [ Tx/2,2Tx), adjusting the local reference time sequence, and inverting the local reference time sequence to obtain a local adjustment time sequence; when Δ τ (k) e (Tx/2, Tx), then the local reference timing is not adjusted, i.e.: the local adjustment timing is made the same as the reference timing.

For the local reference time sequence under the first rule, the time slot adjustment is performed by the passive end, and the method for obtaining the local adjustment time sequence is as follows:

(1-4.1b), calculating a transmission delay tau (k) between the active end and the passive end, and taking a residue value delta tau (k) after the switching period T '═ Tr' + Tx of the adjusted receiving time slot duration is completed;

(1-4.1b), generating local adjustment timing: delaying the local reference timing by 2Tx in its entirety when Δ τ (k) e (0, Tx) or Δ τ (k) e (T '-Tx, T') to get the local adjusted timing, otherwise, keeping the local reference timing unchanged, i.e.: the local adjusted timing is made the same as the local reference timing.

The invention provides another same-frequency bidirectional continuous high-precision measurement method, which comprises the following steps:

(44.1) setting the reference switching period of the local reference timing as T_base；

(44.2) setting the active endSwitching period T_AIs composed of

Switching period T of passive terminal_BIs composed of

M≠N；

(44.3) the active terminal according to the switching period T_AGenerating a local reference time sequence, and the passive terminal according to the switching period T_BGenerating a local reference timing sequence; the local reference time sequence consists of alternate transmission time slots and receiving time slots, and the duty ratio of the transmission time slots is 50%.

Based on the method, the invention also provides a same-frequency bidirectional continuous high-precision measurement system, which at least comprises two terminals, wherein each terminal has the same physical composition and comprises a transmitting-receiving shared antenna, a transmitting-receiving switching unit, a transmitting channel, a receiving channel and a signal processing unit;

the receiving and transmitting shared antenna is used for transmitting the radio frequency signal of the terminal and receiving the radio frequency signals transmitted by other terminals;

the receiving and transmitting switching unit is used for carrying out receiving and transmitting switching according to the switching control signal sent by the signal processing unit, and transmitting the radio-frequency signal of the transmitting channel to the receiving and transmitting common antenna or forwarding the radio-frequency signal received by the receiving and transmitting common antenna to the receiving channel;

The transmitting channel performs transceiving switching according to the switching control signal sent by the signal processing unit; in the receiving time slot, the receiving and the sending are isolated, and the same frequency interference is avoided; in the sending time slot, receiving a baseband signal from a signal processing unit, carrying out up-conversion on the baseband signal to a frequency point to be sent, carrying out power amplification on the baseband signal, and sending the baseband signal to a receiving and sending switching unit;

the receiving channel receives the radio frequency signal from the receiving and transmitting switching unit, down-converts the radio frequency signal to an intermediate frequency and then sends the radio frequency signal to the signal processing unit;

the signal processing unit sets the terminal as an active end or a passive end; the active end and the passive end are subjected to time synchronization processing to obtain synchronous second pulses, and local reference time sequences are respectively generated on the synchronous second pulse reference; the local reference time sequence consists of a receiving time slot and a transmitting time slot which are alternately arranged, and the time length of the transmitting time slot is less than the estimated maximum transmission time delay between the active end and the passive end; in addition, the active end generates a switching control signal according to the local reference time sequence and outputs the switching control signal to the receiving and transmitting switching unit and the transmitting channel to generate a time continuous measuring signal, and the time continuous measuring signal is windowed in a transmitting time slot and sent to the transmitting channel; carrying out pseudo code tracking and carrier tracking on the intermediate frequency signal sent by a receiving channel in a receiving time slot, reconstructing a measuring signal with continuous time, and realizing high-precision carrier phase measurement based on the continuous signal; the passive end estimates the transmission time delay between the active end and the passive end, adjusts the time slot according to the transmission time delay to obtain a local adjustment time sequence, and generates a switching control signal according to the local adjustment time sequence to output the switching control signal to the transceiving switching unit and the transmitting channel; generating a time continuous measuring signal, windowing the time continuous measuring signal in a transmitting time slot and sending the time continuous measuring signal to a transmitting channel; and carrying out pseudo code tracking and carrier tracking on the intermediate frequency signal sent by the receiving channel in the receiving time slot, reconstructing a time-continuous measuring signal, and realizing high-precision carrier phase measurement based on the continuous signal according to the carrier phase measurement value of the measuring signal of the opposite side.

The second same-frequency bidirectional continuous high-precision measurement system provided by the invention at least comprises two terminals, wherein each terminal has the same physical composition and comprises a receiving and transmitting shared antenna, a receiving and transmitting switching unit, a transmitting channel, a receiving channel and a signal processing unit;

the signal processing unit sets the terminal as an active end or a passive end; the active end and the passive end are both subjected to time synchronization processing to obtain synchronous second pulse, and on the basis of the synchronous second pulse, the transmission time slot duration is defined as Tx, the receiving time slot duration Tr, and the switching period T is the sum of the transmission time slot duration and the receiving time slot duration, namely: T-Tx + Tr, the receive slot length is greater than the transmit slot, i.e.: tr is more than or equal to Tx; the receiving time slot and the transmitting time slot are alternately formed, and the time length of the transmitting time slot is less than the estimated maximum transmission time delay; adding a protection time slot Ts on the original basis of a receiving time slot, prolonging the time length of a local receiving time slot, and changing the time length of the receiving time slot into Tr' ═ Tr + Ts, wherein the following conditions are met: tr' is more than or equal to 3Tx, so that a local reference timing sequence is obtained; the active end generates a switching control signal according to the local reference time sequence and outputs the switching control signal to the receiving and transmitting switching unit and the transmitting channel to generate a time continuous measuring signal, and the time continuous measuring signal is windowed in a transmitting time slot and sent to the transmitting channel; carrying out pseudo code tracking and carrier tracking on an intermediate frequency signal sent by a receiving channel in a receiving time slot, reconstructing a measuring signal with continuous time, and realizing time-frequency synchronization between an active end and a passive end according to a carrier phase measuring value of the measuring signal of the opposite side; the passive end estimates the transmission time delay between the active end and the passive end, adjusts the time slot according to the transmission time delay to obtain a local adjustment time sequence, and generates a switching control signal according to the local adjustment time sequence to output the switching control signal to the transceiving switching unit and the transmitting channel; generating a time continuous measurement signal, windowing the time continuous measurement signal in a transmission time slot and sending the time continuous measurement signal to a transmission channel; and carrying out pseudo code tracking and carrier tracking on the intermediate frequency signal sent by the receiving channel in the receiving time slot, reconstructing a measuring signal with continuous time, and realizing time-frequency synchronization between the active end and the passive end according to the carrier phase measuring value of the measuring signal of the opposite side.

The third same-frequency bidirectional continuous high-precision measurement system provided by the invention at least comprises two terminals, wherein each terminal has the same physical composition and comprises a receiving and transmitting shared antenna, a receiving and transmitting switching unit, a transmitting channel, a receiving channel and a signal processing unit;

the signal processing unit sets the terminal as an active end or a passive end; setting a reference switching period of a local reference timing sequence to T _base(ii) a The active end is according to the switching period T_AGenerating a local reference time sequence, and the passive terminal according to the switching period T_BGenerating a base reference time sequence; the switching period T of the active terminal_AIs composed of

Switching period T of passive terminal_BIs composed of

M is not equal to N; the local reference time sequence consists of alternate transmitting time slots and receiving time slots, and the duty ratio of the transmitting time slots is 50%; the active end and the passive end generate switching control signals according to the local reference time sequence and output the switching control signals to the receiving and transmitting switching unit and the transmitting channel to generate time continuous measurement signals, and the signals are transmittedThe time slot windows the time continuous measurement signal and sends the time continuous measurement signal to a transmitting channel; and performing pseudo code tracking and carrier tracking on the intermediate frequency signal sent by the receiving channel in the receiving time slot, reconstructing a measuring signal with continuous time, and realizing time-frequency synchronization between the active end and the passive end according to the carrier phase measuring value of the measuring signal of the opposite side.

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

(1) the invention adopts a common-frequency bidirectional link to realize high-precision carrier phase measurement based on continuous signals, and completes high-precision time-frequency synchronization between an active end and a passive end by the influence of forward and backward common-frequency high-precision measurement on the cancellation transmission environment, particularly the additional time delay introduced by a troposphere/an ionosphere;

(2) The first method provided by the invention introduces auxiliary information or a bidirectional time comparison method, realizes flexible time slot adjustment, reduces the integral loss of a same-frequency link compared with a frequency division link, and can approximate the signal integral time to T/2;

(3) the time slot configuration method based on the protection time slot provided by the second method reduces the performance constraint on auxiliary information or bidirectional time comparison, and has redundant design of a system and higher reliability;

(4) the time slot configuration method based on the staggered time sequence is suitable for asymmetric links, and avoids transceiving conflicts in a simple method under the condition that link budget is met; the method does not need time synchronization, so that external information assistance is not needed, and bidirectional time comparison is not needed; the method has no restriction on dynamic conditions such as transmission delay variation and relative speed of the active end and the passive end, and is generally suitable for various space missions such as satellite-ground space, near-ground space and deep space;

(5) the method of the invention ensures that the synchronous deviation of the uplink and downlink signals is not more than 2 times (typical value is 20us) of the transmitting time slot, realizes the large-amplitude cancellation of the additional time delay of the ionized layer/the troposphere, and improves the measurement precision of the microwave link to subps/day.

(6) The method enables the time slot length to be adaptable to nanosecond-millisecond magnitude, the time slot length is not limited by transmission delay any more, and the time slot length can be larger than the transmission delay or smaller than the transmission delay;

(7) the measurement system provided by the invention has the advantages of simple structure, strong universality of used devices, easy realization of the system, strong accessibility and suitability for various application scenes.

Drawings

FIG. 1 is a schematic diagram of steps of a first and second methods for realizing same-frequency bidirectional continuous high-precision measurement according to the present invention;

FIG. 2 is a schematic diagram of the third method for realizing the same-frequency bidirectional continuous high-precision measurement according to the present invention;

FIG. 3 is a schematic diagram of the timing sequence adjustment of a first method for realizing the same-frequency bidirectional continuous high-precision measurement according to the present invention;

FIG. 4 is a schematic diagram of the timing sequence of the second method for realizing the same-frequency bidirectional continuous high-precision measurement according to the present invention;

FIG. 5 is a schematic diagram of the timing sequence adjustment of a third method for realizing the same-frequency bidirectional continuous high-precision measurement according to the present invention;

FIG. 6 is a block diagram of a same-frequency bidirectional continuous high-precision measurement method of the invention;

FIG. 7 is a block diagram of a terminal of the co-frequency bi-directional continuous high-precision measurement system according to the embodiment of the present invention;

FIG. 8 is a diagram of performance simulation of a co-frequency bi-directional continuous high-precision measurement system according to an embodiment of the present invention;

FIG. 9 is a diagram of performance verification of a co-frequency bi-directional continuous high-precision measurement system according to an embodiment of the present invention.

Detailed Description

The invention is further illustrated by the following examples.

As shown in fig. 1 and fig. 2, the present invention realizes continuous high-precision measurement of the same frequency, and provides 3 feasible methods and a system with strong universality.

The processing steps of the 1 st method and the 2 nd method can be seen in fig. 1, and specifically are as follows: firstly, time synchronization is completed through a GNSS or bidirectional time comparison method; secondly, local reference time sequences are respectively established at the active end and the passive end; thirdly, firstly, calculating transmission time delay, wherein the time delay can be obtained by calculating track forecast information or by measuring by adopting a bidirectional time comparison method, and then carrying out time slot adjustment at a passive end to obtain a local adjustment time sequence; and fourthly, respectively carrying out signal reconstruction and continuous measurement on the active end and the passive end.

The processing steps of the method 3 do not require time synchronization, as shown in fig. 2, which specifically includes: the method comprises the steps of firstly, configuring the time slot length and generating a local reference time sequence; and a second step of setting a staggered time sequence, so that the active end time sequence TA and the passive end time sequence TB meet the condition that TA, TB and M, N are equal, wherein M is not equal to N.

The invention is further illustrated below with reference to examples.

One-time same-frequency bidirectional continuous measurement method with 50% of receiving and transmitting duty ratio

As shown in fig. 1, the first method for continuous high-precision measurement in two directions at the same frequency provided by the present invention comprises the following steps:

the sending end and the receiving end can complete time synchronization by referring to GNSS time or realize time synchronization by adopting a two-way time comparison method.

(a) The specific method for the sending end and the receiving end to complete time synchronization according to the GNSS time comprises the following steps:

(b) The bidirectional time comparison method is realized by adopting two one-way pseudo range measurement links, wherein the link from an active end to a passive end is a forward link, and the working frequency point of the forward link is f₁The passive end to the active end is a return link, and the working frequency point of the return link is f₂So that f₁≠f₂The active end and the passive end respectively obtain a unidirectional pseudo range measured value locally, and the passive end obtains a unidirectional pseudo range measured value pd _ B locally and a unidirectional pseudo range measured value pd _ A returned by the active end according to a formula

(1-2) respectively generating local reference time sequences by the active end and the passive end on the synchronous pulse per second reference; the local reference time sequence consists of a receiving time slot and a transmitting time slot which are alternately alternated, and the time length of the transmitting time slot is less than the estimated maximum transmission time delay between the active end and the passive end; the relative deviation of the local reference timing of the transmitting end and the receiving end does not exceed 20 ns.

The rules for generating the local reference timing are as follows:

(1-2.1), the local reference timing sequence time slot length is configurable, the transmission time slot time length is defined as Tx, the receiving time slot time length Tr, and the switching period T is the transmission time slot time length plus the receiving time slot time length, namely: T-Tx + Tr, where Tx ∈ (100ns,10ms), Tr ∈ (100ns,10ms), the receive slot length is greater than the transmit slot, i.e.: tr is greater than or equal to Tx.

(1-2.2) aligning the local reference time sequence to a local synchronous second pulse, namely aligning the leading edge of a local transmission time slot with the rising edge of the synchronous second pulse;

(1-2.3), defining the time slot numbers in 1s to be 1-N in sequence, wherein the time slots with odd numbers (1,3, 5.) -in the local reference time sequence of the active end and the passive end are transmission time slots, and the time slots with even numbers (2,4, 6.) -are reception time slots.

the active end and the passive end are respectively positioned on two satellites, or the active end is positioned on the satellites and the passive end is positioned on the ground station.

(1.4-1a), respectively reading the orbit prediction information of each satellite by the active end and the passive end, and calculating the position of the satellite at the current moment under an ECEF coordinate system or an ECI coordinate system according to the orbit prediction information; the orbit forecast information can be six orbital numbers and corresponding reference time thereof, or motion state vectors of the satellite in an ECEF coordinate system or an ECI coordinate system and corresponding reference time thereof, wherein the motion state vectors comprise motion and speed;

(1.4-2a), the active end and the passive end acquire the position of the phase center of each terminal antenna under a satellite body coordinate system (Masscenter-coordinates):

wherein the content of the first and second substances,

the position of the active terminal antenna phase center under a satellite body coordinate system (Masscenter-coordinates) is shown;

the position of the passive terminal antenna phase center under a satellite body coordinate system (Masscenter-coordinates) is shown;

(1.4-3a), the active end and the passive end respectively convert the phase center position of each microwave terminal antenna into an ECEF coordinate system or an ECI coordinate system according to the position of the satellite in which the current time is located in the ECEF coordinate system or the ECI coordinate system, and the transfer matrix from each satellite body coordinate system to the ECEF coordinate system or the ECI coordinate system;

wherein the content of the first and second substances,

the position of the active end microwave terminal antenna phase center position under an ECEF coordinate system or an ECI coordinate system;

R_AMCCtoECEFtransferring a matrix from a satellite body coordinate system where an active end is located to an ECEF coordinate system or an ECI coordinate system;

R_BMCCtoECEFtransferring a matrix from a satellite body coordinate system where the passive end is located to an ECEF coordinate system or an ECI coordinate system;

(x_sA,y_sA,z_sA) The position of the satellite of the active terminal at the current moment under an ECEF coordinate system or an ECI coordinate system (x) _sB,y_sB,z_sB) The position of the satellite of the passive end at the current moment under an ECEF coordinate system or an ECI coordinate system

(1.4-4a), the active end sends the position of the antenna phase center position of the microwave terminal at the current moment under an ECEF coordinate system or an ECI coordinate system to the passive end, the passive end makes the position difference of the antenna phase center positions of the active end and the passive end under the ECEF coordinate system or the ECI coordinate system, and the distance R (k) between the antenna phase centers of the active end and the passive end is calculated, so that the transmission delay tau (k) can be obtained:

τ(k)＝R(k)/c。

(1.4-1b), the active end reads the orbit forecast information of the satellite, and calculates the position of the satellite in the ECEF coordinate system or the ECI coordinate system at the current moment according to the orbit forecast information; the orbit forecast information can be six orbital numbers and corresponding reference time thereof, or motion state vectors of the satellite in an ECEF coordinate system or an ECI coordinate system and corresponding reference time thereof;

(1.4-2b), the active end acquires the position of the terminal antenna phase center under a satellite body coordinate system (Masscenter-coordinates):

Wherein the content of the first and second substances,

(1.4-3b), the active end converts the phase center position of each microwave terminal antenna into an ECEF coordinate system or an ECI coordinate system according to the position of the satellite in which the current time is located in the ECEF coordinate system or the ECI coordinate system, and a transfer matrix from the satellite body coordinate system to the ECEF coordinate system or the ECI coordinate system;

wherein the content of the first and second substances,

(x_sA,y_sA,z_sA) The position of the satellite where the active end is located at the current moment is in an ECEF coordinate system or an ECI coordinate system;

(1.4-4b), the active end sends the position of the antenna phase center position of the microwave terminal at the current moment under an ECEF coordinate system or an ECI coordinate system to the passive end;

(1.4-5b), the passive end acquires the position of the antenna phase center position of the microwave terminal at the current moment under an ECEF coordinate system or an ECI coordinate system and sends the position to the passive end, the positions of the antenna phase center positions of the active end and the passive end under the ECEF coordinate system or the ECI coordinate system are differenced, and the distance R (k) between the antenna phase centers of the active end and the passive end is calculated, so that the transmission delay tau (k) can be obtained:

τ(k)＝R(k)/c。

The method for the passive end to adjust the time slot and obtain the local adjustment time sequence comprises the following steps:

(1-4.1a), calculating a residual value delta tau (k) of the transmission delay tau (k) between the active end and the passive end after the local reference timing switching period T (Tx + Tr) is rounded to 2 Tx:

Δτ(k)＝mod(τ(k),T)

wherein mod (-) is remainder operation;

The generation process of the above adjustment timing is shown in fig. 3. The active end (terminal a) and the passive end (terminal B) establish a synchronous local reference timing, as shown in the first line in the figure, obtain the transmission delay and find the remainder Δ τ (k) of the switching period. Tx in the figure satisfies Δ τ (k) e (0, Tx/2), so at the passive end (terminal B), the local reference timing is inverted as described in (1-4.2) to obtain the local adjustment timing, as shown in the third row of the figure, in this case, terminal A transmits a signal with an integral time ≧ Tx/2 at terminal B, as shown in the third row of the figure, and terminal B transmits a signal with an integral time ≧ Tx/2 at terminal A, as shown in the fifth row of the figure, and during a complete transceiving period, the signal integral time ≧ T/4, a bidirectional link can be established.

(T_orb×V+R)≤t×C

wherein, R is the track forecasting precision, V is the relative motion speed of the active end and the passive end, t is the precision requirement of the transmission time delay, and C is the light speed.

Taking the space station satellite-ground link as an example, the transmission delay of the satellite-ground link is about 1ms, and when the emission width of the local time slot is set to be 10us, the precision tau of the transmission delay is expected to be better than 1 us. The space station orbit prediction error R is counted by 100m, and the maximum dynamic V of the satellite and the earth is 7km/s, so that the updating period T _ orb does not exceed 28ms according to the formula. The time slot adjusting period of the passive end is more than 10us and less than 28 ms.

And (1-5) the active end and the passive end respectively reconstruct the received measurement signals, recover the measurement signals with continuous time and realize high-precision carrier phase measurement based on the continuous signals. The high-precision carrier phase measurement of the continuous signals is realized through the forward and backward co-frequency high-precision measurement, the influence on the cancellation transmission environment, particularly the additional time delay introduced into the troposphere/ionosphere, the high-precision time-frequency synchronization between the active end and the passive end is completed, and the time difference and the time delay between the active end and the passive end are obtained.

After the above steps, discontinuous reception signals are obtained at the local receiving end of each of the active end (terminal a) and the passive end (terminal B), and the characteristics are as follows: repeating according to the period T, the signal is visible within the period Tr time, and the signal is invisible within the period Tx time. At this time, if the discontinuous signal is directly measured, the accuracy is limited. In the method, a 3-order phase-locked loop is adopted for tracking, and a continuous receiving signal is locally reconstructed, as shown in fig. 6. A tracking channel is established for an input intermittent receiving signal, coherent integration time is set to be ms magnitude (a typical value is 1ms), and phase-locked loop closed-loop tracking is used through integration-clearing, phase discrimination and loop filtering links. With the continuous phase information characterized by the NCO, a continuous signal can be locally reconstructed. Then, the locally reproduced received signal is sent to a carrier phase extraction module to obtain a high-precision carrier phase measurement result.

Second, transmitting-receiving duty ratio non-50% same frequency bidirectional continuous measuring method

The difference between the second same-frequency bidirectional continuous high-precision measurement method provided by the invention and the first method is that:

(1) the rule of the local reference time slot in the step is as follows:

(1-2.5b), defining the time slot numbers in 1s to be 1-N in sequence, wherein the time slots with odd numbers (1,3, 5.)) in the local reference time sequence of the active end and the passive end are transmission time slots, and the time slots with even numbers (2,4, 6.)) are reception time slots.

(2) The method for adjusting the time slot by the passive end to obtain the local adjustment time sequence comprises the following steps:

(1-4.1b), calculating a transmission delay tau (k) between the active end and the passive end, and taking a residue value delta tau (k) after the switching period T '═ Tr' + Tx of the adjusted receiving time slot duration is completed:

Δτ(k)＝mod(τ(k),(Tx+Tr'))

wherein mod (-) is remainder operation;

(1-4.2b), generating local adjustment timing: delaying the local reference timing by 2Tx in its entirety when Δ τ (k) e (0, Tx) or Δ τ (k) e (T '-Tx, T') to get the local adjusted timing, otherwise, keeping the local reference timing unchanged, i.e.: the local adjusted timing is made the same as the local reference timing.

The generation process of the above adjustment timing is shown in fig. 4. The active end (terminal a) and the passive end (terminal B) establish a synchronized local reference timing, as shown in the first row in the figure, obtain a transmission delay and obtain a remainder Δ τ (k) for a switching period, where Δ τ (k) satisfies the condition of Δ τ (k) e (0, Tx) or Δ τ (k) e (T '-Tx, T'), so that the local reference timing is entirely delayed by 2Tx at the passive end (terminal B) according to (2-5.2) to obtain a local adjustment timing, as shown in the third row in the figure. In this case terminal a transmits a signal that can be integrated over the Tx time in terminal B, as shown in the third line of the figure; terminal B transmit signal can also get a complete integration of Tx time at terminal a as shown in the fifth row of the figure. During a complete transceiving period, the signal integration time is T'/4, and a bidirectional link can be established.

And (2-6) the active end and the passive end respectively rebuild the received measuring signals, recover the measuring signals with continuous time, and realize time-frequency synchronization between the active end and the passive end according to the carrier phase measuring value of the measuring signals of the opposite side.

Common-frequency bidirectional continuous measurement method for three-step spread time sequence

The third same-frequency bidirectional continuous high-precision measurement method provided by the invention comprises the following steps of:

(44.1) setting the reference switching period of the local reference timing as T_base。

(44.2) setting the switching period T of the active terminal_AIs composed of

PassiveSwitching period T of terminal_BIs composed of

M≠N；

The generation process of the above adjustment timing is shown in fig. 5. The active end (terminal a) and the passive end (terminal B) establish the same local reference timing, as shown in the first row in the figure, and the local reference timing is subdivided at the active end (terminal a) and the passive end (terminal B) according to (44.2) to obtain a local adjustment timing, where N is 1 and M is 2, as shown in the third row in the figure. In this case, the time when the transmission signal of the active terminal (terminal a) reaches the passive terminal (terminal B) is shown in the second row of the figure, and the time when the transmission signal of the passive terminal (terminal B) reaches the active terminal (terminal a) is shown in the fourth row of the figure; the integration time of the active end and the passive end is respectively

As shown in the third and fifth rows of the figure. During a complete transceiving period, the signal integration time is T/4, and a bidirectional link can be established.

In the staggered timing setting, N and M may occur at any ratio, and the signal integration time will converge to T/4 during a complete transceiving period. Typically, a typical value N ═ 1, M ═ 2; the values of N and M may be increased when the system demands higher transmission rates.

After the above steps, discontinuous reception signals are obtained at the local receiving end of each of the active end (terminal a) and the passive end (terminal B), and the characteristics are as follows: repeating according to the period T, the signal is visible within the period Tr time, and the signal is invisible within the period Tx time. At this time, if the discontinuous signal is directly measured, the accuracy is limited. In the method, a 3-order phase-locked loop is adopted for tracking, and a continuous receiving signal is locally reconstructed. A tracking channel is established for an input intermittent receiving signal, coherent integration time is set to be ms magnitude (typical value is 1ms), and phase-locked loop closed-loop tracking is used through links of integration-clearing, phase discrimination and loop filtering. With the continuous phase information characterized by the NCO, a continuous signal can be locally reconstructed. And then, sending the locally reproduced received signal to a carrier phase extraction module to obtain a high-precision carrier phase measurement result.

Four-and-same-frequency bidirectional continuous measuring system

Based on the method, the invention provides a same-frequency bidirectional continuous high-precision measurement system, which at least comprises two terminals, wherein each terminal has the same physical composition and comprises a transmitting-receiving shared antenna, a transmitting-receiving switching unit, a transmitting channel, a receiving channel and a signal processing unit. A same-frequency two-way measurement system is shown in FIG. 7

(1) Antenna for transmitting and receiving

The receiving and transmitting common antenna is used for transmitting the radio frequency signal of the terminal and receiving the radio frequency signals transmitted by other terminals;

(2) and a transmitting/receiving switching unit

The receiving and transmitting switching unit performs receiving and transmitting switching according to the switching control signal sent by the signal processing unit, and transmits the radio frequency signal of the transmitting channel to the receiving and transmitting common antenna or forwards the radio frequency signal received by the receiving and transmitting common antenna to the receiving channel;

the receiving and transmitting switching unit is connected with the antenna and the receiving and transmitting channel, is a key component for realizing system common-frequency measurement, and particularly can be realized by adopting a PIN switch or a circulator, and is required to support quick switching, short tailing time and larger receiving and transmitting isolation. The indexes are as follows:

a) switching period: 100 ns-5 s;

b) tail time: less than or equal to 10 ns;

c) Isolation of transmitting and receiving: not less than 20dB

(3) Emission channel

The transmitting channel performs transceiving switching according to the switching control signal sent by the signal processing unit; in the receiving time slot, carrying out receiving and transmitting isolation to avoid same frequency interference; and in the sending time slot, receiving the baseband signal from the signal processing unit, carrying out up-conversion on the baseband signal to a radio frequency point to be sent, carrying out power amplification on the baseband signal, and sending the baseband signal to the transceiving switching unit. The receiving and transmitting isolation can be carried out by adopting various technical means such as radio frequency signal quitting, final stage power amplification closing and the like. The radio frequency signal cancellation means that a local oscillator signal in the transmitting channel is turned off, so that the transmitting channel does not generate a transmitting signal in a receiving time slot; the final stage power amplifier is that when a plurality of amplifiers are arranged in a transmitting channel, the amplifier of the final stage is turned off, and at the moment, a modulated transmitting signal is generated, but the amplitude is smaller.

(4) Receiving channel

Receiving a radio frequency signal from the receiving and transmitting switching unit, down-converting the radio frequency signal to an intermediate frequency, and transmitting the radio frequency signal to the signal processing unit;

(5) signal processing unit

Based on the three methods, the signal processing unit of the invention has three different implementation modes respectively:

the first implementation mode comprises the following steps:

setting the terminal as an active end or a passive end; the active end and the passive end are both subjected to time synchronization processing to obtain synchronous second pulses, and local reference time sequences are respectively generated on the synchronous second pulse reference; the local reference time sequence consists of a receiving time slot and a transmitting time slot which are alternately arranged, and the time length of the transmitting time slot is less than the estimated maximum transmission time delay between the active end and the passive end; in addition, the active end generates a switching control signal according to the local adjusting time sequence and outputs the switching control signal to the receiving and transmitting switching unit and the transmitting channel to generate a time continuous measuring signal, and the time continuous measuring signal is windowed in the transmitting time slot and sent to the transmitting channel; and performing pseudo code tracking and carrier tracking on the intermediate frequency signal sent by the receiving channel in a receiving time slot, reconstructing a measuring signal with continuous time, and realizing high-precision carrier phase measurement based on the continuous signal according to a carrier phase measuring value of the measuring signal of the opposite side. The high-precision carrier phase measurement of the continuous signals is realized through forward and backward co-frequency high-precision measurement, the influence on the cancellation transmission environment, particularly the additional time delay introduced into a troposphere/ionosphere, and the high-precision time-frequency synchronization between the active end and the passive end is completed to obtain the time difference and the time delay between the active end and the passive end; the passive end estimates the transmission time delay between the active end and the passive end, adjusts the time slot according to the transmission time delay to obtain a local adjustment time sequence, and generates a switching control signal according to the local adjustment time sequence to output the switching control signal to the transceiving switching unit and the transmitting channel; generating a time continuous measuring signal, windowing the time continuous measuring signal in a transmitting time slot and sending the time continuous measuring signal to a transmitting channel; and performing pseudo code tracking and carrier tracking on the intermediate frequency signal sent by the receiving channel in a receiving time slot, reconstructing a measuring signal with continuous time, and realizing high-precision carrier phase measurement based on the continuous signal according to the carrier phase measuring value of the measuring signal of the opposite side. The high-precision carrier phase measurement of the continuous signals is realized through forward and backward co-frequency high-precision measurement, influences on a transmission environment, particularly additional time delay introduced into a troposphere/ionosphere, are completed, high-precision time-frequency synchronization between an active end and a passive end is completed, and time difference and time delay between the active end and the passive end are obtained. .

The second implementation mode comprises the following steps:

the signal processing unit sets the terminal as an active end or a passive end; the active end and the passive end are both subjected to time synchronization processing to obtain synchronous second pulse, and on the basis of the synchronous second pulse, the transmission time slot duration is defined as Tx, the receiving time slot duration Tr, and the switching period T is the sum of the transmission time slot duration and the receiving time slot duration, namely: T-Tx + Tr, the receive slot length is greater than the transmit slot, i.e.: tr is more than or equal to Tx; the receiving time slot and the transmitting time slot are alternately formed, and the time length of the transmitting time slot is less than the estimated maximum transmission time delay; adding a protection time slot Ts on the original basis of a receiving time slot, and prolonging the time length of a local receiving time slot to ensure that the time length of the receiving time slot is changed into Tr' ═ Tr + Ts, and the following conditions are met: tr' is more than or equal to 3Tx, so that a local reference timing sequence is obtained; the active end generates a switching control signal according to the local reference time sequence and outputs the switching control signal to the receiving and transmitting switching unit and the transmitting channel to generate a time continuous measuring signal, and the time continuous measuring signal is windowed in a transmitting time slot and sent to the transmitting channel; carrying out pseudo code tracking and carrier tracking on an intermediate frequency signal sent by a receiving channel in a receiving time slot, reconstructing a measuring signal with continuous time, and realizing time-frequency synchronization between an active end and a passive end according to a carrier phase measuring value of the measuring signal of the opposite side; the passive end estimates the transmission time delay between the active end and the passive end, adjusts the time slot according to the transmission time delay to obtain a local adjustment time sequence, and generates a switching control signal according to the local adjustment time sequence to output the switching control signal to the transceiving switching unit and the transmitting channel; generating a time continuous measurement signal, windowing the time continuous measurement signal in a transmission time slot and sending the time continuous measurement signal to a transmission channel; and carrying out pseudo code tracking and carrier tracking on the intermediate frequency signal sent by the receiving channel in the receiving time slot, reconstructing a measuring signal with continuous time, and realizing time-frequency synchronization between the active end and the passive end according to the carrier phase measuring value of the measuring signal of the opposite side.

The third implementation mode comprises the following steps:

the signal processing unit sets the terminal as an active end or a passive end; setting a reference switching period of a local reference timing sequence to T_base(ii) a The active end is according to the switching period T_AGenerating a local reference time sequence, and the passive terminal according to the switching period T_BGenerating a local reference timing sequence; the switching period T of the active terminal_AIs composed of

Switching period T of passive terminal_BIs composed of

M is not equal to N; the local reference time sequence consists of alternate transmitting time slots and receiving time slots, and the duty ratio of the transmitting time slots is 50%; the active end and the passive end generate switching control signals according to the local reference time sequence and output the switching control signals to the receiving and transmitting switching unit and the transmitting channel to generate time continuous measuring signals, and the time continuous measuring signals are windowed in the transmitting time slot and sent to the transmitting channel; and performing pseudo code tracking and carrier tracking on the intermediate frequency signal sent by the receiving channel in the receiving time slot, reconstructing a measuring signal with continuous time, and realizing time-frequency synchronization between the active end and the passive end according to the carrier phase measuring value of the measuring signal of the opposite side.

Five, same frequency two-way continuous measurement embodiment

The method realizes the same-frequency bidirectional continuous high-precision measurement, can overcome the disturbance of atmospheric environment such as an ionized layer and a troposphere in the microwave transmission process, and can greatly reduce the additional time delay introduced by the ionized layer/the troposphere compared with the traditional model correction or double-frequency/triple-frequency correction method. The system adopts time-sharing reception and local reconstruction, and realizes bidirectional continuous measurement; compared with a typical frequency division bidirectional link, the method has the advantages that the effective integration time in a fixed period is reduced, so that the signal accumulation capacity is reduced, the carrier-to-noise ratio of an equivalent received signal is deteriorated, and the worst condition system carrier-to-noise ratio deterioration degree is considered as follows:

10*log10(1/4)＝6dB

And performing system performance simulation according to the carrier-to-noise ratio, taking a space station satellite-to-ground link as an example, wherein the satellite-to-ground distance is 400km, the carrier-to-noise ratio threshold of a bidirectional link is 57dBHz, and the carrier-to-noise ratio is reduced to 51dBHz when the scheme is adopted. The simulation results are given in fig. 8 below, and in the context of high-precision measurement application, the phase measurement precision of the bidirectional link is 0.256 °, and the measurement precision of the method is 0.511 °, and it can be seen that the phase measurement precision reaches 1.42e-3 weeks at a threshold level (51dBHz) by using the same-frequency bidirectional measurement method described herein. When the same-frequency bidirectional links transmit and receive basically simultaneously, the accuracy which can be achieved after the ionosphere/troposphere additional time delay is cancelled by using the method can be estimated to be about: 0.946ps @ freq ═ 1.5 GHz; 0.047ps @ freq ═ 30 GHz. The precision can reach sub-mm magnitude after the L wave band is offset, and is greatly improved compared with the current typical level.

By using a certain communicator verification platform, setting a communicator inlet signal as a threshold level, corresponding to 57dBHz received by a typical bidirectional link, respectively verifying the system performance of the typical frequency division bidirectional link (old system) and the same frequency bidirectional link (new system) by adopting a balanced duty ratio method under an ideal condition (the carrier-to-noise ratio is reduced by 6dB), as shown in FIG. 9, the phase measurement result obtained by the same frequency bidirectional method is deteriorated by 0.273 degrees, compared with the simulation result, the precision of the same frequency bidirectional link is reduced by about 0.255 degrees, and the measured value is basically equivalent to the theoretical simulation value.

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 modifications and variations of the present invention without departing from the spirit and scope of the present invention.

Claims

1. A method for continuously measuring high precision in a same-frequency two-way mode is characterized by comprising the following steps:

(1-4) the passive terminal estimates the transmission time delay between the active terminal and the passive terminal, and performs time slot adjustment according to the transmission time delay to obtain a local adjustment time sequence; according to the local adjustment time sequence, windowing and sending the time continuous measurement signal in the transmission time slot, and ensuring the time correlation of the measurement signal; receiving a received measurement signal sent by an active end in a receiving time slot, wherein the carrier frequencies of the measurement signal sent by the passive end and the active end are the same, so that a same-frequency bidirectional link is established;

2. The same-frequency bidirectional continuous high-precision measurement method according to claim 1, characterized by comprising the steps of: the rules of the local reference timing are as follows:

(1-2.2a), the local reference timing sequence time slot length is configurable, the transmission time slot time length is defined as Tx, the receiving time slot time length Tr, and the switching period T is the transmission time slot time length plus the receiving time slot time length, namely: t is Tx + Tr, the length of the receive slot is greater than the transmit slot, i.e.: tr is more than or equal to Tx;

3. The same-frequency bidirectional continuous high-precision measurement method according to claim 1, characterized by comprising the steps of: the rules of the local reference timing are as follows:

(1-2.2b), the local reference timing sequence time slot length is configurable, the transmission time slot time length is defined as Tx, the receiving time slot time length Tr, and the switching period T is the transmission time slot time length plus the receiving time slot time length, namely: t is Tx + Tr, the length of the receive slot is greater than the transmit slot, i.e.: tr is more than or equal to Tx;

(1-2.3b), adding a protection time slot Ts to the receiving time slot on the original basis, and prolonging the time length of the local receiving time slot, so that the time length of the receiving time slot becomes Tr' ═ Tr + Ts, and the following conditions are met: tr' is more than or equal to 3Tx, so that a local reference timing sequence is obtained;

4. The method according to any one of claims 2 or 3, wherein the local reference timing of the transmitting end and the receiving end has a relative deviation of no more than 20 ns.

5. The method according to any one of claims 2 or 3, wherein the sending end and the receiving end complete time synchronization with reference to GNSS time or implement time synchronization by using a two-way time comparison method.

6. The method according to claim 5, wherein the bidirectional time alignment is performed by using two single-pass pseudorange measurement links, the active end to the passive end are forward links, and the forward link frequency point is f₁The passive end to the active end is a return link, and the working frequency point of the return link is f₂So that f₁≠f₂The active end and the passive end respectively obtain a unidirectional pseudo range measured value locally, and the passive end obtains a unidirectional pseudo range measured value pd _ B locally and a unidirectional pseudo range measured value pd _ A returned by the active end according to a formula

And acquiring a relative time deviation dt, and then adjusting the local second pulse according to the relative time deviation dt to enable the local second pulse to be synchronous with the local second pulse of the active end and to be recorded as a synchronous second pulse.

7. The method according to claim 5, wherein the specific method for the sending end and the receiving end to complete time synchronization according to GNSS time comprises:

8. The method according to any one of claims 2 or 3, wherein when the active end and the passive end are located on two satellites respectively, or the active end is located on a satellite and the passive end is located on a ground station.

9. The method according to claim 8, wherein when the active end and the passive end are located on two satellites respectively, the passive end obtains the transmission delays of the active end and the passive end by the following method, specifically:

(4.1-1a), the active end and the passive end respectively read orbit prediction information of each satellite, and the position of the satellite at the current moment in an ECEF coordinate system or an ECI coordinate system is calculated according to the orbit prediction information; the orbit forecast information is six orbits and corresponding reference time thereof, or motion state vectors of the satellite in an ECEF coordinate system or an ECI coordinate system and corresponding reference time thereof, wherein the motion state vectors comprise the position and the speed of the satellite;

10. The same-frequency bidirectional continuous high-precision measurement method according to claim 8, characterized in that when the active end is located at a satellite and the passive end is located at a ground station, the passive end obtains the transmission delay of the active end and the passive end by the following method, specifically:

(4.1-1b), the active end reads the orbit forecast information of the satellite, and calculates the position of the satellite in the ECEF coordinate system or the ECI coordinate system at the current moment according to the orbit forecast information; the orbit prediction information can be six orbital numbers and reference time corresponding to the six orbital numbers, or motion state vectors of the satellite in an ECEF coordinate system or an ECI coordinate system and reference time corresponding to the six orbital numbers, wherein the motion state vectors comprise the position and the speed of the satellite;

11. The same-frequency bidirectional continuous high-precision measurement method according to claim 8, characterized in that: the passive end obtains the transmission time delay between the active end and the passive end by adopting a bidirectional time comparison method, the active end and the passive end are defined as a forward link, and the working frequency point of the forward link is f ₁The passive end to the active end is a return link, and the working frequency point of the return link is f₂So that f₁≠f₂The active end and the passive end respectively obtain a unidirectional pseudo range measured value locally, and the passive end obtains a unidirectional pseudo range measured value pd _ B locally and a unidirectional pseudo range measured value pd _ A returned by the active end according to a formula

12. The method according to any one of claims 9 to 11, wherein the update period T _ orb for the passive terminal to estimate the transmission delay between the active terminal and the passive terminal must satisfy the following condition:

(T_orb×V+R)≤t×C

13. The method according to claim 12, wherein the period of time slot adjustment performed by the passive end is greater than the transmission time slot duration Tx and not greater than the transmission delay update period T _ orb.

14. The method according to claim 2, wherein the time slot adjustment is performed at the passive end, and the method for obtaining the local adjustment timing sequence comprises:

15. The method according to claim 3, wherein the time slot adjustment is performed at the passive end, and the method for obtaining the local adjustment timing sequence comprises:

(1-4.1b), calculating a transmission time delay tau (k) between the active end and the passive end, and taking an integral residual value delta tau (k) of a switching period T '═ Tr' + Tx after the receiving time slot duration is adjusted;

16. A method for continuously measuring high precision in a same-frequency two-way mode is characterized by comprising the following steps:

(44.2) setting the switching period T of the active terminal_AIs composed of

Switching period T of passive terminal_BIs composed of

M≠N；

17. A same-frequency bidirectional continuous high-precision measurement system is characterized by at least comprising two terminals, wherein the physical composition of each terminal is completely the same and comprises a transmitting-receiving shared antenna, a transmitting-receiving switching unit, a transmitting channel, a receiving channel and a signal processing unit;

the transmitting channel performs transceiving switching according to the switching control signal sent by the signal processing unit; in the receiving time slot, carrying out receiving and transmitting isolation to avoid same frequency interference; in the sending time slot, receiving a baseband signal from a signal processing unit, carrying out up-conversion on the baseband signal to a frequency point to be sent, carrying out power amplification on the baseband signal, and sending the baseband signal to a receiving and sending switching unit;

the signal processing unit sets the terminal as an active end or a passive end; the active end and the passive end are both subjected to time synchronization processing to obtain synchronous second pulses, and local reference time sequences are respectively generated on the synchronous second pulse reference; the local reference time sequence consists of a receiving time slot and a transmitting time slot which are alternately arranged, and the time length of the transmitting time slot is less than the estimated maximum transmission time delay between the active end and the passive end; in addition, the active end generates a switching control signal according to the local reference time sequence and outputs the switching control signal to the receiving and transmitting switching unit and the transmitting channel to generate a time continuous measuring signal, and the time continuous measuring signal is windowed in a transmitting time slot and sent to the transmitting channel; carrying out pseudo code tracking and carrier tracking on the intermediate frequency signal sent by a receiving channel in a receiving time slot, reconstructing a measuring signal with continuous time, and realizing high-precision carrier phase measurement based on the continuous signal; the passive end estimates the transmission time delay between the active end and the passive end, adjusts the time slot according to the transmission time delay to obtain a local adjustment time sequence, and generates a switching control signal according to the local adjustment time sequence to output the switching control signal to the transceiving switching unit and the transmitting channel; generating a time continuous measuring signal, windowing the time continuous measuring signal in a transmitting time slot and sending the time continuous measuring signal to a transmitting channel; and performing pseudo code tracking and carrier tracking on the intermediate frequency signal sent by the receiving channel in the receiving time slot, reconstructing a measuring signal with continuous time, and realizing high-precision carrier phase measurement based on the continuous signal according to the carrier phase measuring value of the measuring signal of the opposite side.

18. A same-frequency bidirectional continuous high-precision measurement system is characterized by at least comprising two terminals, wherein the physical composition of each terminal is completely the same and comprises a transmitting-receiving shared antenna, a transmitting-receiving switching unit, a transmitting channel, a receiving channel and a signal processing unit;

the signal processing unit sets the terminal as an active end or a passive end; the active end and the passive end are both subjected to time synchronization processing to obtain synchronous second pulse, and on the basis of the synchronous second pulse, the transmission time slot duration is defined as Tx, the receiving time slot duration Tr, and the switching period T is the sum of the transmission time slot duration and the receiving time slot duration, namely: t is Tx + Tr, the length of the receive slot is greater than the transmit slot, i.e.: tr is more than or equal to Tx; the receiving time slot and the transmitting time slot are alternately formed, and the time length of the transmitting time slot is less than the estimated maximum transmission time delay; adding a protection time slot Ts on the original basis of a receiving time slot, and prolonging the time length of a local receiving time slot to ensure that the time length of the receiving time slot is changed into Tr' ═ Tr + Ts, and the following conditions are met: tr' is more than or equal to 3Tx, so that a local reference timing sequence is obtained; the active end generates a switching control signal according to the local reference time sequence and outputs the switching control signal to the receiving and transmitting switching unit and the transmitting channel to generate a time continuous measuring signal, and the time continuous measuring signal is windowed in a transmitting time slot and sent to the transmitting channel; carrying out pseudo code tracking and carrier tracking on an intermediate frequency signal sent by a receiving channel in a receiving time slot, reconstructing a measuring signal with continuous time, and realizing time-frequency synchronization between an active end and a passive end according to a carrier phase measuring value of the measuring signal of the opposite side; the passive end estimates the transmission time delay between the active end and the passive end, adjusts the time slot according to the transmission time delay to obtain a local adjustment time sequence, and generates a switching control signal according to the local adjustment time sequence to output the switching control signal to the transceiving switching unit and the transmitting channel; generating a time continuous measuring signal, windowing the time continuous measuring signal in a transmitting time slot and sending the time continuous measuring signal to a transmitting channel; and performing pseudo code tracking and carrier tracking on the intermediate frequency signal sent by the receiving channel in the receiving time slot, reconstructing a measuring signal with continuous time, and realizing time-frequency synchronization between the active end and the passive end according to the carrier phase measuring value of the measuring signal of the opposite side.

19. A same-frequency bidirectional continuous high-precision measurement system is characterized by at least comprising two terminals, wherein the physical composition of each terminal is completely the same and comprises a transmitting-receiving shared antenna, a transmitting-receiving switching unit, a transmitting channel, a receiving channel and a signal processing unit;

the signal processing unit sets the terminal as an active end or a passive end; setting a reference switching period of a local reference timing sequence to T _base(ii) a The active end is according to the switching period T_AGenerating a local reference time sequence, and the passive terminal according to the switching period T_BGenerating a local reference timing sequence; the switching period T of the active terminal_AIs composed of

Switching period T of passive terminal_BIs composed of