A TDOA positioning method and system based on optical fiber delay correction

Abstract

The application discloses a TDOA positioning method and system based on optical fiber delay correction, and the method comprises the following steps: S1: a positioning station calculates a local oscillator frequency according to a signal frequency band, and sends a same local oscillator signal to all superheterodyne observation stations through optical fibers; S2: intermediate frequency signals of the superheterodyne observation stations are transmitted into the positioning station through the optical fibers, and the positioning station simultaneously collects multiple signals of the same superheterodyne observation station through different radio frequency switch arrays; S3: the positioning station corrects the local oscillator phase in the signals according to the delay parameter of the optical fiber and the local oscillator frequency, and estimates the time difference of arrival of the multiple signals; S4: a plurality of hyperbolic equations are constructed by selecting different combinations of superheterodyne observation stations, and the position of a static radiation source is obtained through a least mean square error algorithm. The clock synchronization problem of the TDOA observation station is solved through the optical fiber communication mode.

Description

Technical Field

[0001] This invention relates to the field of outdoor wireless positioning technology, and in particular to a TDOA positioning method and system based on fiber optic delay correction. Background Technology

[0002] TDOA positioning is a method of positioning that utilizes time difference. By measuring the time it takes for a signal to arrive at a monitoring station, the distance to the signal source can be determined. Using the distances from the signal source to each monitoring station (drawing circles with the monitoring station as the center and the distance as the radius), the signal's location can be determined. However, absolute time is generally difficult to measure. By comparing the absolute time differences of the signal's arrival at each monitoring station, a hyperbola can be plotted with the monitoring station as the focus and the distance difference as the major axis. The intersection of the hyperbola is the signal's location.

[0003] Currently, TDOA high-precision radio positioning requires clock synchronization between observation stations. For high-precision TDOA positioning in large outdoor areas, the farther apart the observation stations are, the smaller the positioning geometric error. The clock synchronization problem of distant and dispersed observation stations usually adopts high-cost satellite common-view equipment.

[0004] Currently, most TDOA positioning observation stations use high-cost digital technology to sample signals at the front end, and then use data communication to aggregate the sampled signals to the positioning station for time difference estimation. The real-time performance of positioning is closely related to the transmission speed of the communication link, and high-speed communication also leads to increased system costs. Summary of the Invention

[0005] The purpose of this invention is to provide a TDOA positioning method and system based on fiber optic delay correction to solve the technical problem of clock synchronization difficulties for large-scale outdoor TDOA positioning observation stations.

[0006] The objective of this invention is achieved through the following technical solution: a TDOA positioning method based on fiber optic delay correction, comprising the following steps:

[0007] S1: The positioning station calculates the local oscillator frequency based on the signal frequency band and sends the same local oscillator signal to all superheterodyne observation stations via optical fiber;

[0008] S2: The intermediate frequency signal of the superheterodyne observation station is transmitted to the positioning station through optical fiber. The positioning station simultaneously acquires multiple signals from the same superheterodyne observation station through different radio frequency switch arrays.

[0009] S3: The positioning station corrects the local oscillator phase in the signal based on the delay parameters of the optical fiber and the local oscillator frequency, and estimates the arrival time difference of multiple signals.

[0010] S4: Select different combinations of superheterodyne observation stations to construct multiple hyperbolic equations, and use the minimum mean square error algorithm to obtain the location of the static radiation source.

[0011] Furthermore, in step S1, the method for calculating the local oscillator frequency of the positioning station based on the signal frequency band is: fo = fc + fi, where fo is the local oscillator frequency, fc is the center frequency of the acquired signal frequency band, and fi is the intermediate frequency center frequency of the front-end superheterodyne observation station.

[0012] Furthermore, in step S1, the step of sending the same local oscillator signal to all superheterodyne observation stations via optical fiber specifically involves the positioning station generating a highly stable local oscillator frequency fo from the GPSDO clock via a phase-locked loop, and then transmitting it to all superheterodyne observation stations via optical fiber through a power divider.

[0013] Furthermore, step S2 specifically involves: after all superheterodyne observation stations downconvert their antenna signals to intermediate frequency signals, they transmit the signals back to the positioning station via optical fiber. The positioning station then simultaneously acquires two signals from the same superheterodyne observation station through a radio frequency switch array.

[0014] Furthermore, the intermediate frequency signal of each superheterodyne observation station is connected to two multiple-choice RF switch arrays via a power divider. Each time, the positioning station selects two different branch signals and connects them to two ADCs for synchronous sampling.

[0015] Furthermore, in step S3, the calculation method for the local oscillator phase in the correction signal is: phase(i) = 2 * pi * fo * delay(i), where phase(i) is the pre-phase value of the i-th branch, fo is the local oscillator frequency, pi is pi, and delay(i) is the delay of the fiber in the i-th branch.

[0016] Furthermore, in step S3, the method for calculating the estimated arrival time difference of multiple signals is as follows: TDE(i,j) = TD(i,j) - (delay(i) - delay(j)), where delay(i) is the delay of the i-th branch optical fiber, delay(j) is the delay of the j-th branch optical fiber, TD(i,j) is the time difference between the arrival of the i-th and j-th branch signals at the positioning value, and TDE(i,j) is the time difference between the arrival of the signals at the i-th and j-th superheterodyne observation station antennas.

[0017] Furthermore, step S4 specifically involves: when there are N+1 superheterodyne observation stations, one of them is selected as the primary observation station, and the other N are secondary observation stations. The primary and secondary stations are combined into N groups of observations. N time differences (TDEs) are estimated by collecting data in N time segments. These TDEs are multiplied by the speed of light to convert them into the distance difference between the signal and the antenna. N hyperbolic equations are constructed by combining the coordinates of all antennas. The position of the static radiation source is obtained by using the minimum mean square error algorithm.

[0018] A TDOA positioning system based on fiber optic delay correction includes a positioning station, a fiber optic transceiver, and a superheterodyne observation station. The positioning station calculates the local oscillator frequency based on the signal frequency band and transmits the same local oscillator signal to all superheterodyne observation stations via the fiber optic transceiver. The intermediate frequency signal from the superheterodyne observation station is transmitted to the positioning station via the fiber optic transceiver. The positioning station simultaneously acquires multiple signals from the same superheterodyne observation station through different RF switch arrays. The positioning station corrects the local oscillator phase in the signal based on the delay parameters of the fiber optic cable and the local oscillator frequency, and estimates the arrival time difference of the multiple signals. The positioning station selects different combinations of superheterodyne observation stations to construct multiple hyperbolic equations and obtains the position of the static radiation source through the minimum mean square error algorithm.

[0019] The beneficial effects of this invention are as follows: This invention solves the clock synchronization problem of TDOA observation stations through optical fiber communication; centralized sampling of positioning stations reduces the cost of independent stations and improves the real-time positioning performance. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0021] Figure 1 This is a flowchart of the present invention;

[0022] Figure 2 This is a system block diagram of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0024] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0025] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0026] Example 1:

[0027] See Figure 1 A TDOA positioning method based on fiber delay correction includes the following steps:

[0028] S1: The positioning station calculates the local oscillator frequency based on the signal frequency band and sends the same local oscillator signal to all superheterodyne observation stations via optical fiber;

[0029] S2: The intermediate frequency signal of the superheterodyne observation station is transmitted to the positioning station through optical fiber. The positioning station simultaneously acquires multiple signals from the same superheterodyne observation station through different radio frequency switch arrays.

[0030] S3: The positioning station corrects the local oscillator phase in the signal based on the delay parameters of the optical fiber and the local oscillator frequency, and estimates the arrival time difference of multiple signals.

[0031] S4: Select different combinations of superheterodyne observation stations to construct multiple hyperbolic equations, and use the minimum mean square error algorithm to obtain the location of the static radiation source.

[0032] In this embodiment, the local oscillator frequency calculated by the positioning station based on the signal frequency band refers to the fact that all front-end superheterodyne observation receivers are broadband receivers ranging from 20MHz to 18GHz, with an intermediate frequency center frequency of fi and an intermediate frequency bandwidth of fb. When the center frequency of the acquired signal frequency band is fc, the local oscillator frequency fo is calculated as fo = fc + fi. The transmission of the same local oscillator signal to all superheterodyne observation stations via optical fiber specifically involves the positioning station generating a highly stable local oscillator frequency fo from the 10MHz clock of GPSDO through a phase-locked loop, and transmitting it to all superheterodyne observation stations via optical fiber through a power divider. The initial value of the signal phase can be set to 0.

[0033] In this embodiment, step S2 specifically involves: all superheterodyne observatories downconverting their antenna signals to intermediate frequency (IF) signals and transmitting the signals back to the positioning station via optical fiber. The positioning station then simultaneously acquires two signals from the same superheterodyne observatory using an RF switch array. Furthermore, the IF signals from each superheterodyne observatory are connected to two multiplexer RF switch arrays via power dividers. The positioning station selects two different branch signals each time and connects them to two ADCs for synchronous sampling (IF digital quantization acquisition). For a scenario with N superheterodyne observatories, there are N-1 possible combinations.

[0034] In this embodiment, in step S3, the positioning station corrects the local oscillator phase in the signal based on the delay parameters and local oscillator frequency of the optical fiber. Specifically, before using the positioning system, the delay parameters of each optical fiber are measured with a calibration instrument. The local oscillator phase correction value is: phase(i) = 2 * pi * fo * delay(i), where fo is the local oscillator frequency, pi is pi, delay(i) is the delay of the i-th branch optical fiber, and phase(i) is the pre-phase value of the i-th branch, which can be subtracted from the sampled signal.

[0035] Furthermore, estimating the arrival time difference of multiple signals specifically involves subtracting the intermediate frequency delay in the optical fiber and estimating the arrival time difference of two signals. This refers to calculating the time difference TD(i,j) between the two branch signals arriving at the positioning station using a cross-correlation algorithm, and then compensating for it with the optical fiber delay parameter. The time difference of the signal arriving at the antenna is calculated using the following formula: TDE(i,j) = TD(i,j) - (delay(i) - delay(j)), where delay(i) is the delay of the i-th branch optical fiber, delay(j) is the delay of the j-th branch optical fiber, TD(i,j) is the time difference between the i-th and j-th branch signals arriving at the positioning value, and TDE(i,j) is the time difference between the signal arriving at the i-th and j-th superheterodyne observation station antennas.

[0036] In this embodiment, step S4 specifically involves: selecting different combinations of superheterodyne observation stations from multiple references to construct multiple hyperbolic equations, and using the minimum mean square error algorithm to obtain the location of the static radiation source. This means that a superheterodyne positioning station can only estimate the time difference between the signal arrival at the antennas of two superheterodyne observation stations at the same time interval. When there are N+1 superheterodyne observation stations, one is selected as the primary observation station, and the other N are secondary observation stations. These primary and secondary stations are combined into N groups of observations. N time differences (TDEs) are estimated by collecting data in N time intervals, multiplying them by the speed of light to convert them into the distance difference between the signal arrival at the antenna, and then using all antenna coordinates to construct N hyperbolic equations. The location of the static radiation source is then obtained using the minimum mean square error algorithm.

[0037] See Figure 2A TDOA positioning system based on fiber optic delay correction is disclosed to implement the aforementioned TDOA positioning method based on fiber optic delay correction. The system includes a positioning station, a fiber optic transceiver, and a superheterodyne observation station. The positioning station calculates the local oscillator frequency based on the signal frequency band and transmits the same local oscillator signal to all superheterodyne observation stations via fiber optic transceiver. The intermediate frequency signal from the superheterodyne observation station is transmitted to the positioning station via fiber optic transceiver. The positioning station simultaneously acquires multiple signals from the same superheterodyne observation station using different RF switch arrays. The positioning station corrects the local oscillator phase in the signal based on the fiber delay parameter and the local oscillator frequency, estimating the arrival time difference of the multiple signals. The positioning station selects different combinations of superheterodyne observation stations to construct multiple hyperbolic equations and obtains the location of the static radiation source using a minimum mean square error algorithm.

[0038] Furthermore, a multi-channel power divider is installed between the positioning station output and the fiber optic transceiver input. An intermediate frequency (IF) digital quantization acquisition unit, an RF switch array, and a power divider are sequentially installed between the positioning station input and the fiber optic transceiver output. The IF digital quantization acquisition unit includes IF digital quantization acquisition unit 1 and IF digital quantization acquisition unit 2; the RF switch array includes RF switch array 1 and RF switch array 2. IF digital quantization acquisition unit 1 is located between RF switch array 1 and the positioning station, and IF digital quantization acquisition unit 2 is located between RF switch array 2 and the positioning station. The power divider is connected to each superheterodyne observation station to transmit the IF signals from the superheterodyne observation stations to RF switch array 1 and RF switch array 2, respectively, and then back to the positioning station via IF digital quantization acquisition unit 1 and IF digital quantization acquisition unit 2.

[0039] This invention has at least the following technical effects:

[0040] This invention solves the clock synchronization problem of TDOA observation stations through optical fiber communication; centralized sampling of positioning stations reduces the cost of independent stations and improves the real-time positioning performance.

[0041] It should be noted that, for the sake of simplicity, the foregoing embodiments are all described as a series of actions. However, those skilled in the art should understand that this application is not limited to the described order of actions, because according to this application, some steps can be performed in other orders or simultaneously. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions involved are not necessarily essential to this application.

[0042] The above embodiments describe the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Modifications and variations made by those skilled in the art without departing from the spirit and scope of the invention should be within the protection scope of the appended claims.

Claims

1. A TDOA positioning method based on optical fiber delay correction, characterized in that, Includes the following steps: S1: The positioning station calculates the local oscillator frequency based on the signal frequency band and sends the same local oscillator signal to all superheterodyne observation stations via optical fiber; S2: The intermediate frequency signal of the superheterodyne observation station is transmitted to the positioning station through optical fiber. The positioning station simultaneously acquires multiple signals from the same superheterodyne observation station through different radio frequency switch arrays. S3: The positioning station corrects the local oscillator phase in the signal based on the delay parameters of the optical fiber and the local oscillator frequency, and estimates the arrival time difference of multiple signals. S4: Select different combinations of superheterodyne observation stations to construct multiple hyperbolic equations, and use the minimum mean square error algorithm to obtain the location of the static radiation source.

2. The TDOA positioning method based on optical fiber delay correction according to claim 1, characterized in that, In step S1, the method for calculating the local oscillator frequency of the positioning station based on the signal frequency band is: fo = fc + fi, where fo is the local oscillator frequency, fc is the center frequency of the acquired signal frequency band, and fi is the intermediate frequency center frequency of the front-end superheterodyne observation station.

3. The TDOA positioning method based on optical fiber delay correction of claim 1, wherein, In step S1, the step of sending the same local oscillator signal to all superheterodyne observation stations via optical fiber is specifically as follows: the positioning station generates a highly stable local oscillator frequency fo from the GPSDO clock via a phase-locked loop, and transmits it to all superheterodyne observation stations via optical fiber through a power divider.

4. The TDOA positioning method based on optical fiber delay correction of claim 1, wherein, Step S2 is as follows: After all superheterodyne observation stations downconvert the antenna signals to intermediate frequency signals, they transmit the signals back to the positioning station through optical fiber. The positioning station simultaneously acquires two signals from the same superheterodyne observation station through an RF switch array.

5. A TDOA positioning method based on optical fiber delay correction according to claim 4, characterized in that, The intermediate frequency signal of each superheterodyne observation station is connected to two multiple-choice RF switch arrays via a power divider. Each time, the positioning station selects two different branch signals and connects them to two ADCs for synchronous sampling.

6. The TDOA positioning method based on optical fiber delay correction of claim 1, wherein, In step S3, the calculation method for the local oscillator phase in the correction signal is: phase(i) = 2 * pi * fo * delay(i), where phase(i) is the pre-phase value of the i-th branch, fo is the local oscillator frequency, pi is pi, and delay(i) is the delay of the fiber in the i-th branch.

7. The TDOA positioning method based on optical fiber delay correction of claim 1, wherein, In step S3, the method for calculating the estimated arrival time difference of multiple signals is as follows: TDE(i,j) = TD(i,j) - (delay(i) - delay(j)), where delay(i) is the delay of the i-th branch optical fiber, delay(j) is the delay of the j-th branch optical fiber, TD(i,j) is the time difference between the arrival of the i-th and j-th branch signals at the positioning value, and TDE(i,j) is the time difference between the arrival of the signals at the i-th and j-th superheterodyne observation station antennas.

8. The TDOA positioning method based on optical fiber delay correction of claim 1, wherein, Step S4 is as follows: When there are N+1 superheterodyne observation stations, select one as the master observation station and the other N as secondary observation stations. The master and secondary stations are combined into N groups of observations. N time differences (TDEs) are estimated by collecting data in N time segments. These TDEs are multiplied by the speed of light to convert them into the distance difference between the signal and the antenna. N hyperbolic equations are constructed by combining the coordinates of all antennas. The position of the static radiation source is obtained by using the minimum mean square error algorithm.

9. A TDOA positioning system based on optical fiber delay correction, for implementing the TDOA positioning method based on optical fiber delay correction according to any one of claims 1 to 8, characterized in that, The positioning station calculates the local frequency according to the signal frequency band, and sends the same local signal to all the superheterodyne observation stations through the optical transceiver; the intermediate frequency signal of the superheterodyne observation station is transmitted into the positioning station through the optical transceiver, and the positioning station simultaneously collects the multiple signals of the same superheterodyne observation station through different radio frequency switch arrays; the positioning station corrects the local phase in the signal according to the delay parameter of the optical fiber and the local frequency, and estimates the time difference of the multiple signals; the positioning station selects different combinations of superheterodyne observation stations to construct multiple hyperbolic equations, and obtains the position of the static radiation source through the least mean square error algorithm.

Images