A joint search system based on time difference measurement

Abstract

The present invention discloses a joint search system based on time difference measurement, including a distress signal transmitting device and multiple search devices. The distress signal transmitting device is used to transmit a frequency-swept signal to the multiple search devices, and the multiple search devices are used to receive the frequency-swept signal and transmit interactive information to each other; this method calculates the position of the distress signal transmitting device through the position information of any two search devices and the time difference information of the distress signal transmitting device. This device greatly simplifies the complexity of the device to be searched and rescued, and also avoids the device management problems caused by using high-level Beidou devices, making it possible to widely popularize and apply this device.

Description

Technical Field

[0001] The present invention relates to the field of rescue, and particularly to a joint search system based on time difference measurement. Background Art

[0002] When conducting target search, due to technical limitations, the search accuracy of a single machine search is limited. It can only perform simple direction finding, and the search equipment is also relatively complex, requiring multiple directional antennas, which brings inconvenience to the use of the search equipment. Summary of the Invention

[0003] The technical problem solved by the present invention is to provide a joint search system based on time difference measurement that facilitates the miniaturization and lightweight of equipment and improves the search speed and accuracy.

[0004] The technical solution adopted by the present invention to solve its technical problems is: a joint search system based on time difference measurement, including a distress signal transmitting device and multiple search devices. The distress signal transmitting device is used to transmit a frequency-swept signal to the multiple search devices, and the multiple search devices are used to receive the frequency-swept signal and transmit interaction information to each other;

[0005] The calculation method for obtaining the position of the device to be searched through any two search devices is as follows:

[0006] (1);

[0007] Wherein, is the coordinate point of one of the search devices, is the coordinate point of the second search device. Assume is the coordinate point of the distress signal transmitting device, C is the speed of light, that is , represents the time difference of the electromagnetic wave arriving at the two joint search devices A and B;

[0008] (2);

[0009] Wherein, is the coordinate point of the third search device;

[0010] By equations (1) and (2), the above binary quadratic equation can be solved to obtain the coordinate value of point P.

[0011] Furthermore: The distress signal transmitting device includes a first ARM module, a first temperature-compensated crystal oscillator module for providing a reference clock to the first ARM module, and further includes a first PLL-VCO module signal-connected to the first ARM module and the first temperature-compensated crystal oscillator module and a first antenna connected to the first PLL-VCO module.

[0012] Further, the search device includes a second ARM module, a Beidou module signal-connected to the second ARM module, a data link device signal-connected to the second ARM module for transmitting interaction information, and further includes a mixing and filtering module signal-connected to the second ARM module, a second PLL-VCO module connected to the mixing and filtering module, and a VHF antenna connected to the mixing and filtering module, and further includes a second temperature-compensated crystal oscillator module connected to the second ARM module and the second PLL-VCO module;

[0013] The second temperature-compensated crystal oscillator module is used to provide a reference clock for the second ARM module and the second temperature-compensated crystal oscillator module;

[0014] The second temperature-compensated crystal oscillator module is used to synthesize a local oscillator signal and send it to the mixing and filtering module;

[0015] The mixing and filtering module is used to frequency-shift the received swept-frequency signal to the intermediate low frequency;

[0016] The second ARM module is used to perform ADC sampling on the received intermediate low-frequency signal and perform frequency discrimination processing on the sampled data to obtain a sawtooth swept-frequency signal identical to that of the transmitting end, then find the mutation point of the swept-frequency signal, and record the corresponding sampling time point.

[0017] Further, the interaction information includes the search device number information, the search device intensity information, the search device GPS information, the second information of the data corresponding to the current frame of the search device, and the relative offset value relative to the current second number.

[0018] Further, perform a smoothing calculation on the sampling time point data, specifically:

[0019] ;

[0020] The represents the time when the electromagnetic wave reaches the A search device at the i-th sampling, and the represents the time when the electromagnetic wave reaches the B search device at the i-th sampling.

[0021] Further, the swept-frequency signal is a triangular wave or a sine wave;

[0022] The swept-frequency signal includes a start field, a synchronization sequence field, a user ID field, a check field, and an end field.

[0023] Further, calculate the coordinate values of multiple P points and perform a smoothing calculation on them. The specific calculation method is:

[0024] ;

[0025] .

[0026] The beneficial effects of the present invention are as follows:

[0027] 1. It greatly simplifies the complexity of the searched and rescued device, and also avoids the device management problems caused by using high-level Beidou devices, making it possible to widely popularize and apply this device;

[0028] 2. Due to the simplification of functions, the cost and power consumption of the searched and rescued device are greatly reduced, which brings convenience to the popularization and use of this device;

[0029] 3. In the searching device, multiple-point joint measurement is used, which greatly reduces the complexity of the searching device. Only a simple whip antenna needs to be used, instead of an antenna array or a directional antenna, greatly simplifying the structure of each searching device and facilitating installation and use;

[0030] 4. The multiple smoothing algorithm is adopted to reduce the requirements for the sampling clock and the single measurement accuracy, greatly reducing the device cost and power consumption, and improving the accuracy at the same time;

[0031] 5. In the searching device, high-level Beidou technology is used to improve the anti-interference ability of the system, ensuring that the searching device can still work stably during extraordinary times, providing a solid foundation for the searching work. Brief Description of the Drawings

[0032] Figure 1 It is a framework diagram of a joint searching system based on time difference measurement according to an embodiment of the present application.

[0033] Figure 2 It is a schematic diagram of trajectory calculation based on two-point positioning.

[0034] Figure 3 It is a framework diagram of a distress signal transmitting device of a joint searching system based on time difference measurement according to an embodiment of the present application.

[0035] Figure 4 It is a framework diagram of a searching device of a joint searching system based on time difference measurement according to an embodiment of the present application.

[0036] Figure 5 It is a schematic diagram of a zigzag frequency-swept signal of a joint searching system based on time difference measurement according to an embodiment of the present application.

[0037] Figure 6 It is a schematic diagram of a forward and reverse frequency-swept signal with information-carrying ability of a joint searching system based on time difference measurement according to an embodiment of the present application.

[0038] Figure 7 It is a recording diagram of the inflection point moment of a searching device of a joint searching system based on time difference measurement according to an embodiment of the present application. Detailed Implementation Modes

[0039] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following will describe the detailed implementation modes of the present invention in conjunction with the accompanying drawings. Many specific details are set forth in the following description to facilitate a thorough understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0040] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly on the other element or there can also be an intermediate element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intermediate element at the same time.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this invention belongs. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0042] As Figure 1 shown, an embodiment of the present application discloses a joint search system based on time difference measurement, including a distress signal transmitting device and a plurality of search devices. The distress signal transmitting device is used to transmit a frequency-swept signal to the plurality of search devices, and the plurality of search devices are used to receive the frequency-swept signal and transmit interactive information to each other;

[0043] Specifically, as Figure 2 shown, the method for calculating the position of the device to be searched by any two search devices is as follows:

[0044] (1);

[0045] Among them, is the coordinate point of one of the search devices, is the coordinate point of the second search device. Assuming is the coordinate point of the distress signal transmitting device, C is the speed of light, that is , represents the time difference between the arrival of the electromagnetic wave at the two joint search devices A and B;

[0046] The above formula (1) is a hyperbola in a two-dimensional plane. When is 0, the hyperbola degenerates into a perpendicular bisector between points A and B. Therefore, using the data of the third point, another equation can be obtained:

[0047] (2);

[0048] wherein, is the coordinate point of the third search device;

[0049] By equations (1) and (2), the above binary quadratic equation can be solved to obtain the coordinate value of point P .

[0050] The above calculation method greatly simplifies the complexity of the search and rescue device, and also avoids the device management problems caused by using high-level Beidou devices, making the large-scale popularization and application of this device possible. At the same time, the cost and power consumption of the search and rescue device are greatly reduced, bringing convenience to the popular use of this device.

[0051] In this embodiment, as Figure 3 shown, the distress signal transmitting device includes a first ARM module, a first temperature compensated crystal oscillator module for providing a reference clock to the first ARM module, and further includes a first PLL-VCO module signal-connected to the first ARM module and the first temperature compensated crystal oscillator module, and a first antenna connected to the first PLL-VCO module.

[0052] As Figure 4 shown, the search device includes a second ARM module, a Beidou module signal-connected to the second ARM module, a data link device for transmitting interactive information signal-connected to the second ARM module, and further includes a mixing and filtering module signal-connected to the second ARM module, a second PLL-VCO module connected to the mixing and filtering module, and a VHF antenna connected to the mixing and filtering module, and further includes a second temperature compensated crystal oscillator module connected to the second ARM module and the second PLL-VCO module;

[0053] The second temperature compensated crystal oscillator module is used to provide a reference clock to the second ARM module and the second temperature compensated crystal oscillator module;

[0054] The second temperature compensated crystal oscillator module is used to synthesize a local oscillator signal and send it to the mixing and filtering module;

[0055] The mixing and filtering module is used to shift the frequency of the received swept signal to the intermediate low frequency;

[0056] The second ARM module is used to perform ADC sampling on the received intermediate low frequency signal and perform frequency discrimination processing on the sampled data to obtain a sawtooth swept signal identical to the transmitting end, then find the mutation point of the swept signal, and record the corresponding sampling time point, as Figure 7 shown.

[0057] Specifically, in the above structure, the Beidou module can be used to achieve high-precision time synchronization (better than 10 ns) and positioning (positioning accuracy better than 0.1 m). The Beidou module provides a second synchronization signal to the ARM system through the PPS second pulse. At the same time, the second temperature-compensated crystal oscillator module can be calibrated through the PPS signal to ensure an accuracy better than 0.1 PPM. Thus, it can be ensured that within 100 ms, the clock error of the temperature-compensated voltage-controlled crystal oscillator is not greater than 10 ns, which is equivalent to the time synchronization accuracy of GNSS. The calibration of the temperature-compensated voltage-controlled crystal oscillator here is completed by the calibration module inside the ARM. The second temperature-compensated voltage-controlled crystal oscillator also provides a reference clock for the second PLL + VCO module to ensure that the synthesized local oscillator signal has high precision. Using the mixing and filtering circuits, the frequency shift of the swept-frequency signal is realized, and it is shifted to the low intermediate frequency, such as 450 kHz or 480 kHz, etc.

[0058] For the 450 kHz intermediate frequency signal, it is sampled by the built-in ADC of the ARM. In principle, the higher the sampling rate, the higher the time resolution, which is beneficial to the accurate measurement of the time difference. According to the system accuracy requirements and the resource configuration of the ARM, in this system, depending on the different resource configurations, 1800 kHz, 600 kHz, 360 kHz, etc. can be adopted.

[0059] Inside the ARM, the sampled data is subjected to frequency discrimination processing to obtain the same sawtooth-shaped swept-frequency signal as the transmitting end. Then, the mutation point of the swept-frequency signal is found, and the corresponding sampling time point is recorded.

[0060] To ensure the accuracy of the sampling point time, the PPS signal can be used to synchronize the ADC sampling, so that the time difference of each joint search device can be ensured to be < 10 ns.

[0061] In this embodiment, the interaction information includes the search device number information, the search device strength information, the search device GPS information, the second information of the data corresponding to the current frame of the search device, and the relative offset value relative to the current second number. The unit of the above offset value is 1 / fs.

[0062] Specifically, the search device number information includes the number of the search device and the number of the device to be searched, each 24 bits, a total of 48 bits;

[0063] The search device strength information represents the signal strength of the device to be searched received by the current device

[0064] The search device GPS information represents the GPS information of the location where the current device is located;

[0065] The above information frame is sent every few seconds, and the specific interval can be set according to the actual situation.

[0066] In this embodiment, the smoothing calculation is performed on the data at the sampling time point, specifically:

[0067] ;

[0068] The represents the time when the electromagnetic wave arrives at the A search device at the i-th sampling, and the represents the time when the electromagnetic wave arrives at the B search device at the i-th sampling.

[0069] Through the above smoothing calculation, the time resolution can be improved, thereby improving the positioning accuracy.

[0070] Theoretically, according to statistics, 4th-order smoothing is equivalent to doubling the sampling clock, and 16th-order smoothing is equivalent to quadrupling the clock sampling accuracy. If all 72 data acquisition points of the SYN field are used for smoothing, it is equivalent to times the sampling clock, with a corresponding maximum measurement error of 65 ns and an average error of 32.5 ns, and the equivalent average error is about 10 m.

[0071] Of course, the more smoothing times, the more time is required. Therefore, multiple smoothing is suitable for scenarios with slow movement, such as 36 km / h. Otherwise, due to the change of the spatial position, the final accuracy cannot be guaranteed.

[0072] In the case of limited system resources, the sampling rate and the number of smoothing times can be appropriately reduced to reduce the system overhead.

[0073] ;

[0074] Among them, represents the expected average error, C represents the speed of light, represents the sampling frequency, N represents the order of smoothing, that is, sampling N points and then calculating the geometric mean. When setting the number of smoothing times, it can be set according to the error range requirement according to the above formula.

[0075] In this embodiment, the swept-frequency signal can be a triangular wave or a sine wave. The sawtooth swept-frequency signal is as Figure 5 shown. The swept-frequency signal is divided into two types: forward swept-frequency and reverse swept-frequency, corresponding to bit 1 and bit 0 respectively, so that it can carry information. The signal diagram is as Figure 6 shown;

[0076] The swept-frequency signal includes a start field, a synchronization sequence field, a user ID field, a check field, and an end field.

[0077] In this embodiment, the coordinate values of multiple P points are calculated and smoothed. The specific calculation method is as follows:

[0078] ;

[0079] 。

[0080] The above steps use multiple reference points for multiple calculations and smooth the calculation results, thereby obtaining more accurate position parameters of the target to be searched. Then, taking the coordinates of the selected point as a reference, direction finding calculation is carried out, and further rapid positioning of the target to be searched is performed.

[0081] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A joint search system based on time difference measurement, characterized in that: It includes a distress transmitting device and a plurality of search devices, wherein the distress transmitting device is used to transmit a sweep frequency signal to the plurality of search devices, and the plurality of search devices are used to receive the sweep frequency signal and transmit interactive information to each other; The calculation method for obtaining the position of the device being searched by any two searching devices is: Among them, (x A , y A ) is the coordinate point of one of the search devices, (x B , y B ) is the coordinate point of the second search device. Assuming (x P , y P ) is the coordinate point of the distress signal transmitting device, C is the speed of light, that is, 3×10 8 m / s, and ΔT A,B represents the time difference for the electromagnetic wave to reach the two combined search devices A and B; Among them, (x C ,y C ) is the coordinate point of the third search device; By using equations (1) and (2), we can solve the above quadratic equation and obtain the coordinates of point P. The search device includes a second ARM module, a Beidou module connected to the second ARM module signal, a data link device connected to the second ARM module signal for transmitting interactive information, a frequency mixing and filtering module connected to the second ARM module signal, a second PLL-VCO module connected to the frequency mixing and filtering module, and a VHF antenna connected to the frequency mixing and filtering module, and a second temperature-compensated crystal oscillator module connected to the second ARM module and the second PLL-VCO module; The second temperature-compensated crystal oscillator module is used to provide a reference clock to the second ARM module and the second temperature-compensated crystal oscillator module; The second temperature compensated crystal oscillator module is used to synthesize the local oscillator signal and send it to the mixing and filtering module; The mixing and filtering module is used to shift the frequency of the received sweep signal to a medium or low frequency; The second ARM module is used to perform ADC sampling on the received medium and low frequency signals and perform frequency discrimination processing on the sampled data to obtain the same sawtooth sweep frequency signal as the transmitting end, then find the mutation point of the sweep frequency signal and record the corresponding sampling time point; The interaction information includes search device number information, search device strength information, search device GPS information, search device current frame corresponding to the data of the second information and the relative offset value relative to the current second number; Smoothing calculation is performed on the data at the sampling time point, specifically: The T A,i represents the time when the electromagnetic wave arrives at the A search device at the i-th sampling, and the T B,i represents the time when the electromagnetic wave arrives at the B search device at the i-th sampling.

2. The joint search system based on time difference measurement according to claim 1, characterized in that: The distress transmitting device includes a first ARM module, a first temperature-compensated crystal oscillator module for providing a reference clock to the first ARM module, a first PLL-VCO module signal-connected to the first ARM module and the first temperature-compensated crystal oscillator module, and a first antenna connected to the first PLL-VCO module.

3. The joint search system based on time difference measurement according to claim 1, wherein: The frequency sweep signal is a triangle wave or a sine wave; The frequency sweep signal includes a start field, a synchronization sequence field, a user ID field, a check field and an end field.

4. The joint search system based on time difference measurement according to claim 1, wherein: Calculate the coordinate values of multiple P points and perform smoothing calculations on them. The specific calculation method is as follows:

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