Positioning terminal

Abstract

Provided is a positioning terminal capable of efficiently processing a satellite signal at a low chip rate and a satellite signal at a high chip rate. A positioning terminal is provided with: a first reception unit that receives a first satellite signal at a first chip rate transmitted from a first satellite; a second reception unit that receives a second satellite signal at a second chip rate higher than the first chip rate transmitted from the first satellite; a first storage unit that stores a first satellite signal for a time of one or more cycles of an identification code of a first satellite included in the first satellite signal received by the first reception unit; a first correlation processing unit that performs correlation processing on the first satellite signal stored in the first storage unit; a second correlation processing unit that sequentially performs correlation processing on the second satellite signal received by the second receiving unit; and a control unit that tracks the first satellite signal and the second satellite signal on the basis of the result of the correlation processing by the first correlation processing unit and the result of the correlation processing by the second correlation processing unit.

Description

Technical Field

[0001] This invention relates to positioning terminals. Background Technology

[0002] Patent Document 1 describes a satellite positioning signal receiving device comprising: a GNSS receiving circuit that functions as a master unit, receiving L1 signals, performing satellite capture and tracking, and acquiring navigation data and satellite observations; and a GNSS receiving circuit that functions as a slave unit, receiving L2 / L5 signals, performing satellite capture and tracking, and acquiring navigation data and satellite observations. The master unit's GNSS receiving circuit uses its own acquired L1 navigation data and satellite observations, as well as the L2 / L5 navigation data and satellite observations relayed from the slave unit's GNSS receiving circuit, to perform positioning calculations.

[0003] Patent Document 1: International Publication No. 2019 / 155703

[0004] In the satellite positioning signal receiving device described in Patent Document 1, since the GNSS receiving circuit of the host and the GNSS receiving circuit of the slave are the same, there is no difference in the processing of the L1 signal with a relatively low chip rate and the processing of the L5 signal with a relatively high chip rate, which leads to problems in the optimization of processing load and circuit size. Summary of the Invention

[0005] One aspect of the positioning terminal according to the present invention comprises: a first receiving unit for receiving a first satellite signal with a first chip rate transmitted from a first satellite; a second receiving unit for receiving a second satellite signal with a second chip rate higher than the first chip rate transmitted from the first satellite; a first storage unit for storing the first satellite signal for a period of one cycle or more for storing the identification code of the first satellite included in the first satellite signal received by the first receiving unit; a first correlation processing unit for performing correlation processing on the first satellite signal stored in the first storage unit; a second correlation processing unit for performing correlation processing on the second satellite signal received by the second receiving unit in sequence; and a control unit for tracking the first satellite signal and the second satellite signal based on the results of the correlation processing by the first correlation processing unit and the results of the correlation processing by the second correlation processing unit. Attached Figure Description

[0006] Figure 1 This is a diagram showing an example of the configuration of the positioning terminal according to the first embodiment.

[0007] Figure 2 This is a diagram showing the structure of navigation messages in the L1 band of GPS.

[0008] Figure 3This is a diagram showing the structure of navigation messages in the L5 band of GPS.

[0009] Figure 4 This is a flowchart illustrating an example of the processing procedure of the positioning terminal according to the first embodiment.

[0010] Figure 5 This is a diagram showing an example of the configuration of the positioning terminal according to the second embodiment.

[0011] Figure 6 This is a flowchart illustrating an example of the processing procedure of the positioning terminal according to the second embodiment.

[0012] Explanation of reference numerals in the attached figures

[0013] 1: Positioning terminal; 2: Satellite; 10: Analog processing unit; 11: RF receiving unit; 12: A / D conversion unit; 13: RF receiving unit; 14: A / D conversion unit; 20: Digital processing unit; 21: Filtering unit; 22: Sample memory; 23: Correlation processing unit; 24: Filtering unit; 25: Correlation processing unit; 26: Sample memory; 30: Control unit; 31: Search control unit; 32: Tracking control unit; 40: Positioning unit; 41: Satellite information processing unit; 42: Position calculation unit; 51, 52: Antenna; 101: First receiving unit; 102: Second receiving unit. Detailed Implementation

[0014] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that the embodiments described below are not intended to unduly limit the scope of the invention as defined in the claims. Furthermore, not all of the components described below are essential elements of the present invention.

[0015] 1. Implementation Method

[0016] 1-1. Composition of a Positioning Terminal

[0017] Figure 1 This diagram illustrates a configuration example of the positioning terminal 1 according to the first embodiment. As described in detail below, the positioning terminal 1 is a terminal that receives satellite signals transmitted from satellite 2 and performs positioning based on the received satellite signals.

[0018] like Figure 1 As shown, the positioning terminal 1 of the first embodiment includes antennas 51 and 52, an analog processing unit 10, a digital processing unit 20, a control unit 30, and a positioning unit 40. It should be noted that the positioning terminal 1 may be omitted or modified. Figure 1 A composition is formed by adding one or more of its constituent elements.

[0019] Antennas 51 and 52 are for receiving various radio waves, including satellite signals transmitted from each of the multiple satellites 2. Each satellite 2 is an artificial satellite orbiting in a predetermined orbit above the Earth, forming part of GNSS. GNSS is short for Global Navigation Satellite System. Examples of GNSS systems include GPS, QZSS, EGNOS, GLONASS, GALILEO, and BeiDou. GPS is short for Global Positioning System. QZSS is short for Quasi-Zenith Satellite System. EGNOS is short for European Geostationary Navigation Overlay Service. GLONASS is short for Global Navigation Satellite System. The following example illustrates the case where satellite 2 belongs to the GPS satellite system.

[0020] Each satellite transmits navigation messages to the ground by superimposing navigation information onto radio waves in multiple frequency bands, including the L1 band centered at 1.57542 GHz and the L2 band centered at 1.22760 GHz. There are approximately 30 satellites in GPS. To identify which satellite from which the signal originated, the L1 band satellite signal includes an identification code consisting of a unique pattern of 1023 chips. This L1 band identification code is called the C / A code, where each chip is either +1 or -1, appearing as a random pattern and repeating at a 1 ms period. C / A stands for Coarse Acquisition Code. Thus, the chip rate of the L1 band satellite signal is 1.023 Mcps (= 1023 chips / 1 ms).

[0021] In addition, some satellites will transmit navigation messages to the ground by superimposing navigation information onto radio waves in the L5 band centered at 1.17645 GHz. The L5 band satellite signal includes an identification code consisting of a unique pattern of 10230 chips. Similar to the C / A code, each chip is either +1 or -1, appearing as a random pattern repeated at a 1 ms period. Thus, the chip rate of the L5 band satellite signal is 10.23 Mcps (= 10230 chips / 1 ms), which is 10 times the chip rate of the L1 band satellite signal.

[0022] like Figure 1As shown, the analog processing unit 10 includes an RF receiver 11, an A / D converter 12, an RF receiver 13, and an A / D converter 14. The RF receiver 11 is connected to the antenna 51 and receives a first satellite signal with a first chip rate superimposed on the radio waves received by the antenna 51. The A / D converter 12 converts the first satellite signal received by the RF receiver 11 into a digital signal. The RF receiver 13 is connected to the antenna 52 and receives a second satellite signal with a second chip rate superimposed on the radio waves received by the antenna 52. The A / D converter 14 converts the second satellite signal received by the RF receiver 13 into a digital signal.

[0023] Thus, the RF receiver 11 and the A / D converter 12 constitute a first receiver 101 for receiving the first satellite signal, and the RF receiver 13 and the A / D converter 14 constitute a second receiver 102 for receiving the second satellite signal. In this embodiment, the second chip rate of the second satellite signal is higher than the first chip rate of the first satellite signal. For example, the first and second satellite signals are transmitted from one satellite 2. In the following, it is assumed that the first satellite signal is a GPS L1 band satellite signal and the second satellite signal is a GPS L5 band satellite signal.

[0024] like Figure 1 As shown, the digital processing unit 20 includes a filtering processing unit 21, a sample memory 22, a correlation processing unit 23, a filtering processing unit 24, and a correlation processing unit 25.

[0025] The filtering processing unit 21 performs a process to attenuate the noise components from the first satellite signal that has been converted into a digital signal by the A / D conversion unit 12.

[0026] The sample memory 22 sequentially stores the first satellite signal after the noise components have been attenuated by the filtering processing unit 21. In this embodiment, the sample memory 22 stores the first satellite signal received by the first receiving unit 101, which includes a C / A code for a period of more than one cycle, i.e., more than 1 ms.

[0027] The correlation processing unit 23 performs correlation processing on the first satellite signal stored in the sample memory 22. Specifically, the correlation processing unit 23 performs correlation processing on the first satellite signal stored in the sample memory 22 in units of one cycle of the C / A code, that is, in units of 1 ms. Conversely, the correlation processing unit 23 does not perform correlation processing on the first satellite signal until the first satellite signal is stored in the sample memory 22 for a period longer than 1 ms.

[0028] The filtering processing unit 24 performs a process to attenuate the noise components from the second satellite signal that has been converted into a digital signal by the A / D conversion unit 14.

[0029] The correlation processing unit 25 sequentially performs correlation processing on the second satellite signal received by the second receiving unit 102. Specifically, the correlation processing unit 25 sequentially performs correlation processing on the second satellite signal after noise components have been attenuated by the filtering processing unit 24. That is, unlike the correlation processing unit 23, the correlation processing unit 25 performs correlation processing on the second satellite signal without using a sample memory. Since the second satellite signal, which is an L5 band satellite signal, has a chip rate 10 times that of the first satellite signal, which is an L1 band satellite signal, the data volume is also 10 times larger. By sequentially performing correlation processing on the second satellite signal by the correlation processing unit 25, a large sample memory is not required, thus reducing costs. In addition, the correlation processing unit 25 can efficiently perform correlation processing on the high chip rate second satellite signal.

[0030] like Figure 1 As shown, the control unit 30 includes a search control unit 31 and a tracking control unit 32. The search control unit 31 instructs the correlation processing unit 23 to perform correlation processing for searching for the first satellite signal. When instructed to perform correlation processing for searching the first satellite signal, the correlation processing unit 23 performs the following processing: generating a local code of the same pattern as the C / A code of each satellite 2, shifting the phase of the local code chip by chip, and taking the correlation between each C / A code included in the first satellite signal and the local code. Due to the high-speed movement of the satellite 2, the frequency of the radio wave in the L1 band received by the antenna 51 varies within a range of approximately ±2 kHz relative to 1.57542 GHz due to the Doppler effect. Since the Doppler frequency corresponding to this variation is the frequency offset of the first satellite signal, the correlation processing unit 23 also takes into account the frequency offset of the first satellite signal when performing correlation processing.

[0031] The search control unit 31 searches for a first satellite signal based on the results of the correlation processing by the correlation processing unit 23. Specifically, if the peak value of the correlation value obtained through the correlation processing by the correlation processing unit 23 reaches or exceeds a threshold, the search control unit 31 determines that a first satellite signal has been captured, using the local code corresponding to the peak value as the C / A code. Upon capturing the first satellite signal, the search control unit 31 calculates the frequency offset of the first satellite signal based on its chip rate and calculates the code phase based on the phase of the local code, generating capture information including the frequency offset and code phase of the first satellite signal.

[0032] When the search control unit 31 captures the first satellite signal, the tracking control unit 32, based on the capture information generated by the search control unit 31, instructs the correlation processing unit 23 to perform correlation processing for tracking the first satellite signal, and instructs the correlation processing unit 25 to perform correlation processing for tracking the second satellite signal. Then, based on the results of the correlation processing by the correlation processing unit 23 and the correlation processing by the correlation processing unit 25, the tracking control unit 32 tracks the first and second satellite signals and generates capture information including the frequency offset and code phase of each satellite signal being tracked.

[0033] In this way, the control unit 30 causes the correlation processing unit 23 to perform correlation processing for searching for the first satellite signal, and searches for the first satellite signal based on the result of the correlation processing. If the first satellite signal is captured, the correlation processing units 23 and 25 perform correlation processing for tracking the first satellite signal and the second satellite signal based on the capture information of the first satellite signal, and track the first satellite signal and the second satellite signal based on the result of the correlation processing.

[0034] Alternatively, the control unit 30 searches for the first satellite signal based on the correlation processing result of the correlation processing unit 23. If the first satellite signal is detected, the second receiving unit 102 starts receiving the second satellite signal. Specifically, the second receiving unit 102 may have a receiving mode for receiving the second satellite signal and a sleep mode for not receiving the second satellite signal. The tracking control unit 32 switches the second receiving unit 102 from sleep mode to receiving mode when the search control unit 31 detects the first satellite signal. In this case, because the second receiving unit 102 and its subsequent filtering processing unit 24 and correlation processing unit 25 stop processing before the search control unit 31 detects the first satellite signal, power consumption is reduced.

[0035] Alternatively, based on user-specified operations, the control unit 30 may, when high-precision positioning is required, instruct the correlation processing units 23 and 25 to perform correlation processing for tracking the first and second satellite signals; and when high-precision positioning is not required, instruct the correlation processing unit 23 to perform correlation processing for tracking the first satellite signal. In this case, the control unit 30 sets the second receiving unit 102 to sleep mode, thereby stopping the second receiving unit 102, the filtering processing unit 24, and the correlation processing unit 25 from processing, thus reducing power consumption.

[0036] When the control unit 30 captures the first satellite signal and the second satellite signal, the positioning unit 40 performs positioning based on at least one of the first satellite signal and the second satellite signal.

[0037] like Figure 1As shown, the positioning unit 40 includes a satellite information processing unit 41 and a position calculation unit 42. The satellite information processing unit 41 demodulates the navigation message superimposed on the first satellite signal and the second satellite signal based on the capture information generated by the tracking control unit 32. Specifically, the satellite information processing unit 41, based on the frequency offset and code phase of the satellite signals included in each capture information, mixes the local code (which shares the same pattern as the identification code) with the satellite signal at an appropriate time, and demodulates the navigation message including the orbital information and time information of each satellite 2.

[0038] Figure 2 This is a diagram illustrating the structure of navigation messages in the L1 band. (For example...) Figure 2 As shown, the navigation message in the L1 band is structured as a main frame of 1500 bits. The main frame is divided into five subframes of 300 bits each (subframes 1-5). Each satellite transmits one subframe every 6 seconds. Therefore, each satellite transmits one main frame every 30 seconds.

[0039] Each of the five subframes contains 300 bits of data, divided into 30-bit words, starting from the first to the tenth word. In each subframe, the first word is the TLM word, and the second word is the HOW word. TLM is short for Telemetry, and HOW is short for Hand Over Word. Therefore, the TLM word and HOW word are transmitted from satellite 2 at 6-second intervals.

[0040] The TLM word includes preamble data, TLM message, reserved bits, and parity data.

[0041] The HOW word includes time information in TOW or Z count format. TOW stands for Time of Week. Z count data displays the elapsed time in seconds since midnight on Sunday and resets to zero at midnight on the following Sunday. In other words, Z count data is information displayed in seconds for each week starting from the beginning of the week, with elapsed time expressed in 1.5-second increments. Here, the Z count data indicates the start time information for transmitting the next subframe. For example, the Z count data for the first subframe indicates the start time information for transmitting the second subframe. Additionally, the HOW word includes a 3-bit ID code representing the subframe's ID. That is, the HOW words for the first through fifth subframes include ID codes "001", "010", "011", "100", and "101", respectively. The satellite 2's time can be calculated based on the week number data included in the first subframe and the HOW words included in each subframe.

[0042] The third and fourth characters of the first subframe include satellite correction data such as the week number, satellite 2 status, and clock correction factor. Specifically, the week number and satellite 2 status are included in the third character, and the clock correction factor is included in the eighth and fourth characters. The third and fourth characters of the second and third subframes each include ephemeris parameters, which are detailed orbital information for satellite 2. The third and fifth characters of the fourth and fifth subframes each include almanac parameters, which are general orbital information for all satellites of satellite 2. Therefore, satellite correction data, ephemeris parameters, and almanac parameters are transmitted from satellite 2 at 30-second intervals.

[0043] Figure 3 This is a diagram illustrating the structure of navigation messages in the L5 band. (For example...) Figure 3 As shown, L5 band navigation messages are structured as data units of 300 bits each, transmitted every 6 seconds. Each 300-bit message consists of an 8-bit preamble, a 6-bit satellite identifier (PRN), a 6-bit message type ID, a 17-bit message TOW counter, a 1-bit warning flag, a 262-bit message content, and a 24-bit CRC. CRC stands for Cyclic Redundancy Check.

[0044] The message TOW count is a simplified 17-bit TOW count, represented in 6-second increments. The actual TOW count displays the elapsed time in seconds since midnight on Sunday and resets to zero at midnight on the following Sunday. In other words, the actual TOW count is the information displayed in seconds each week from the beginning of the week, with the elapsed time represented in 1.5-second increments. The simplified 17-bit representation of the actual TOW count is the message TOW count.

[0045] The message content varies depending on the message type ID, but includes the same or similar information as navigation messages in the L1 band.

[0046] Return to Figure 1 As explained, the position calculation unit 42 uses the orbital and time information of four or more satellites 2, demodulated by the satellite information processing unit 41, to perform positioning calculations and obtain accurate information on the position and time of the antennas 51 and 52, which serve as receiving points. Specifically, the positioning terminal 1 only needs to use the orbital and time information included in each satellite signal to calculate the difference between the time of each satellite 2 and the time of the receiving point, calculate the pseudorange between each satellite 2 and the receiving point based on the time difference, and use the pseudorange to establish a four-dimensional equation with the three-dimensional position (x, y, z) of the receiving point and the time t as four variables, and then solve it.

[0047] It should be noted that satellite 2, which transmits the first satellite signal and the second satellite signal, is an example of a "first satellite". Additionally, sample memory 22 is an example of a "first storage unit". Correlation processing unit 23 is an example of a "first correlation processing unit", and correlation processing unit 25 is an example of a "second correlation processing unit".

[0048] 1-2. The processing procedure of the positioning terminal

[0049] Figure 4 This is a flowchart illustrating an example of the processing procedure of the positioning terminal 1 according to the first embodiment. For example... Figure 4 As shown, firstly, in process S10, the control unit 30 activates the first receiving unit 101. Thus, the first receiving unit 101 begins receiving satellite signals in the L1 band, which serve as the first satellite signal.

[0050] Next, in process S20, the digital processing unit 20 saves the data received by the first receiving unit 101 into the sample memory 22.

[0051] Next, in process S30, the control unit 30 searches for satellite signals in the L1 band based on the results of the correlation processing by the correlation processing unit 23 until the satellite signals in the L1 band are captured in process S40.

[0052] Next, if the control unit 30 captures a satellite signal in the L1 band in process S40, then in process S60, if high-precision positioning is not required, the satellite signal in the L1 band is tracked based on the correlation processing result of the correlation processing unit 23.

[0053] On the other hand, if high-precision positioning is required in process S50, the control unit 30 activates the second receiving unit 102 in process S70. As a result, the second receiving unit 102 begins receiving satellite signals in the L5 band, which serve as the second satellite signal. Then, in process S80, the control unit 30 tracks the L5 band satellite signal based on the correlation processing results from the correlation processing unit 25.

[0054] Next, in process S90, the positioning unit 40 acquires satellite information of each satellite 2 based on the satellite signal being tracked.

[0055] Next, in process S100, the positioning unit 40 calculates the position of the positioning terminal 1 based on the satellite information of each satellite 2, until the positioning ends in process S110.

[0056] Then, when positioning ends in process S110, the control unit 30 stops the first receiving unit 101 in process S120 and stops the second receiving unit 102 in process S130, thus ending the process.

[0057] 1-3. Effects

[0058] As explained above, according to the positioning terminal 1 of the first embodiment, for the first satellite signal with a low chip rate and small data volume, the data of the identification code for a period of more than one cycle is stored in the sample memory 22, and the correlation processing unit 23 performs correlation processing at high speed; for the second satellite signal with a high chip rate and large data volume, the correlation processing unit 25 performs correlation processing sequentially without using the sample memory, thus reducing the processing load and circuit size.

[0059] Furthermore, according to the positioning terminal 1 of the first embodiment, the tracking control unit 32 can efficiently track the second satellite signal using the capture information obtained by the search control unit 31 through high-speed searching of the first satellite signal with a small data volume and low chip rate. Moreover, since the search control unit 31 does not need to search for the second satellite signal with a large data volume and high chip rate, the processing load is reduced.

[0060] Furthermore, according to the positioning terminal 1 of the first embodiment, the power consumption is reduced because the second receiving unit 102 can be stopped before the tracking control unit 32 captures the first satellite signal.

[0061] Furthermore, according to the positioning terminal 1 of the first embodiment, the positioning unit 40 is capable of performing positioning efficiently or with high precision based on the first satellite signal and the second satellite signal.

[0062] 2. Second Implementation Method

[0063] Hereinafter, regarding the second embodiment, the same reference numerals will be used to mark the same constituent elements as in the first embodiment, and descriptions that are repeated in the first embodiment will be omitted or simplified. The description will mainly focus on the contents that are different from the first embodiment.

[0064] Figure 5 This is a diagram illustrating an example of the configuration of the positioning terminal 1 according to the second embodiment. (See diagram below.) Figure 5 As shown, with Figure 1 Similarly, the positioning terminal 1 in the second embodiment includes antennas 51 and 52, an analog processing unit 10, a digital processing unit 20, a control unit 30, and a positioning unit 40. It should be noted that the positioning terminal 1 may be omitted or modified. Figure 5 A composition is formed by adding one or more of its constituent elements.

[0065] like Figure 5 As shown, with Figure 1Similarly, the analog processing unit 10 includes an RF receiver 11, an A / D converter 12, an RF receiver 13, and an A / D converter 14. The RF receiver 11 is connected to the antenna 51 and receives a first satellite signal with a first chip rate superimposed on the radio waves received by the antenna 51. The A / D converter 12 converts the first satellite signal received by the RF receiver 11 into a digital signal.

[0066] RF receiver 13 is connected to antenna 52 and receives a second satellite signal at a second chip rate and a third satellite signal at a third chip rate superimposed on the radio waves received by antenna 52. For example, second receiver 102 can also switch the received satellite signal between the second satellite signal and the third satellite signal based on a predetermined operation performed by the user. Specifically, second receiver 102 receives either the second satellite signal or the third satellite signal according to an instruction from control unit 30 based on a predetermined operation.

[0067] Furthermore, the RF receiver 13 can also receive a fourth satellite signal with a fourth chip rate superimposed on the radio waves received by the antenna 52. For example, the second receiver 102 can also switch the received satellite signal between a third satellite signal and a second and fourth satellite signal based on a predetermined operation performed by the user. Specifically, the second receiver 102 can also receive a third satellite signal or simultaneously receive a second and fourth satellite signal according to an instruction from the control unit 30 based on a predetermined operation.

[0068] The A / D converter 14 converts the satellite signal received by the RF receiver 13 into a digital signal.

[0069] Thus, the RF receiver 11 and the A / D converter 12 constitute a first receiver 101 for receiving the first satellite signal, and the RF receiver 13 and the A / D converter 14 constitute a second receiver 102 for receiving the third satellite signal or for receiving both the second and fourth satellite signals. In this embodiment, the second chip rate of the second satellite signal is higher than the first chip rate of the first satellite signal. Furthermore, the fourth chip rate of the fourth satellite signal is higher than the third chip rate of the third satellite signal. For example, the first and second satellite signals are transmitted from one satellite 2, and the third and fourth satellite signals are transmitted from another satellite 2. The satellite 2 transmitting the first and second satellite signals belongs to a first GNSS, and the satellite 2 transmitting the third and fourth satellite signals belongs to a second GNSS different from the first GNSS.

[0070] In the following text, it is assumed that the first GNSS is GPS and the second GNSS is Beidou. In addition, the first satellite signal is a satellite signal in the L1 band of GPS, the second satellite signal is a satellite signal in the L5 band of GPS, the third satellite signal is a satellite signal in the L1 band of Beidou, and the fourth satellite signal is a satellite signal in the L5 band of Beidou.

[0071] like Figure 5 As shown, with Figure 1 Similarly, the digital processing unit 20 includes a filtering processing unit 21, a sample memory 22, a correlation processing unit 23, a filtering processing unit 24, and a correlation processing unit 25. Furthermore, in the second embodiment, the digital processing unit 20 includes a sample memory 26.

[0072] The filtering processing unit 21 performs a process to attenuate the noise components from the first satellite signal that has been converted into a digital signal by the A / D conversion unit 12.

[0073] The sample memory 22 sequentially stores the first satellite signal after the noise components have been attenuated by the filtering processing unit 21. In this embodiment, the sample memory 22 stores the first satellite signal received by the first receiving unit 101, which includes a C / A code for a period of more than one cycle, i.e., more than 1 ms.

[0074] The filtering processing unit 24 performs a process that attenuates the noise components from the third, second, and fourth satellite signals that have been converted into digital signals by the A / D conversion unit 14.

[0075] The sample memory 26 sequentially stores the third satellite signal or the second and fourth satellite signals after the noise components have been attenuated by the filtering processing unit 24. In this embodiment, the sample memory 22 stores the third satellite signal received by the second receiving unit 102 for a period of more than one cycle of the identification code included in the third satellite signal, that is, for a period of more than 1 ms.

[0076] The correlation processing unit 23 performs correlation processing on the first satellite signal stored in the sample memory 22. Specifically, the correlation processing unit 23 performs correlation processing on the first satellite signal stored in the sample memory 22 in units of one cycle of the C / A code, that is, in units of 1 ms. Conversely, the correlation processing unit 23 does not perform correlation processing on the first satellite signal until the first satellite signal is stored in the sample memory 22 for a period longer than 1 ms.

[0077] Then, the correlation processing unit 23 performs correlation processing on the third satellite signal stored in the sample memory 26. Specifically, the correlation processing unit 23 performs correlation processing on the third satellite signal stored in the sample memory 26 in units of one cycle of the identification code, that is, in units of 1 ms. Conversely, the correlation processing unit 23 does not perform correlation processing on the third satellite signal until the third satellite signal for a period longer than 1 ms is stored in the sample memory 26.

[0078] The correlation processing unit 25 sequentially performs correlation processing on the second satellite signal received by the second receiving unit 102. Furthermore, the correlation processing unit 25 sequentially performs correlation processing on the fourth satellite signal received by the second receiving unit 102. Specifically, the correlation processing unit 25 sequentially performs correlation processing on the second satellite signal and the fourth satellite signal after noise attenuation by the filtering processing unit 24. That is, unlike the correlation processing unit 23, the correlation processing unit 25 performs correlation processing on the second and fourth satellite signals without using a sample memory. Since the second and fourth satellite signals, which are L5 band satellite signals, have higher chip rates than the first and third satellite signals, which are L1 band satellite signals, the data volume is also larger. By sequentially performing correlation processing on the second and fourth satellite signals by the correlation processing unit 25, a large sample memory is not required, thus reducing costs. Furthermore, the correlation processing unit 25 can efficiently perform correlation processing on the high chip rate second and fourth satellite signals.

[0079] like Figure 5 As shown, with Figure 1 Similarly, the control unit 30 includes a search control unit 31 and a tracking control unit 32. The search control unit 31 instructs the correlation processing unit 23 to perform correlation processing for searching for the first satellite signal and the third satellite signal. When instructed to perform correlation processing for searching for the first satellite signal and the third satellite signal, the correlation processing unit 23 performs correlation processing of each C / A code included in the first satellite signal with the local code and correlation processing of each identification code included in the third satellite signal with the local code.

[0080] The search control unit 31 searches for the first satellite signal and the third satellite signal based on the correlation processing results of the correlation processing unit 23. Specifically, if the peak value of the correlation value obtained by the correlation processing of the first satellite signal by the correlation processing unit 23 reaches or exceeds a threshold, the search control unit 31 determines that the first satellite signal with the local code corresponding to the peak value as the C / A code has been captured. Similarly, if the peak value of the correlation value obtained by the correlation processing of the third satellite signal by the correlation processing unit 23 reaches or exceeds a threshold, the search control unit 31 determines that the third satellite signal with the local code corresponding to the peak value as the identification code has been captured. When the first satellite signal is captured, the search control unit 31 calculates the frequency offset of the first satellite signal based on its chip rate, calculates the code phase based on the phase of the local code, and generates capture information including the frequency offset and code phase of the first satellite signal. Similarly, when the third satellite signal is captured, the search control unit 31 calculates the frequency offset of the third satellite signal based on its chip rate, calculates the code phase based on the phase of the local code, and generates capture information including the frequency offset and code phase of the third satellite signal.

[0081] When the search control unit 31 captures a first satellite signal, the tracking control unit 32, based on the capture information of the first satellite signal generated by the search control unit 31, instructs the correlation processing unit 23 to perform correlation processing for tracking the first satellite signal. Furthermore, the tracking control unit 32 can also, based on the capture information of the first satellite signal generated by the search control unit 31, instruct the correlation processing unit 25 to perform correlation processing for tracking a second satellite signal. Then, the tracking control unit 32 can also track the first and second satellite signals based on the results of the correlation processing by the correlation processing unit 23 and the correlation processing by the correlation processing unit 25, and generate capture information including the frequency offset and code phase of each satellite signal being tracked.

[0082] Alternatively, the control unit 30 may cause the correlation processing unit 23 to perform correlation processing for searching for the first satellite signal, and search for the first satellite signal based on the result of the correlation processing. If the first satellite signal is captured, the correlation processing units 23 and 25 may perform correlation processing for tracking the first satellite signal and the second satellite signal based on the capture information of the first satellite signal, and track the first satellite signal and the second satellite signal based on the result of the correlation processing.

[0083] Furthermore, when the search control unit 31 captures a third satellite signal, the tracking control unit 32, based on the capture information of the third satellite signal generated by the search control unit 31, instructs the correlation processing unit 23 to perform correlation processing for tracking the third satellite signal. Furthermore, the tracking control unit 32 can also, based on the capture information of the third satellite signal generated by the search control unit 31, instruct the correlation processing unit 25 to perform correlation processing for tracking a fourth satellite signal. Then, the tracking control unit 32 can also track the third and fourth satellite signals based on the results of the correlation processing by the correlation processing unit 23 and the correlation processing by the correlation processing unit 25, and generate capture information including the frequency offset and code phase of each satellite signal being tracked.

[0084] Alternatively, the control unit 30 may cause the correlation processing unit 23 to perform correlation processing for searching for the third satellite signal, and search for the third satellite signal based on the result of the correlation processing. If the third satellite signal is captured, the correlation processing units 23 and 25 may perform correlation processing for tracking the third satellite signal and the fourth satellite signal based on the capture information of the third satellite signal, and track the third satellite signal and the fourth satellite signal based on the result of the correlation processing.

[0085] The control unit 30 can also, based on user-defined operations, in situations where high-precision positioning is required, instruct the correlation processing unit 23 to perform correlation processing for tracking the first and second satellite signals, and instruct the correlation processing unit 25 to perform correlation processing for tracking the third and fourth satellite signals. Alternatively, the control unit 30 can, based on user-defined operations, in situations where high-precision positioning is not required, instruct the correlation processing unit 23 to perform correlation processing for tracking the first satellite signal, without instructing the correlation processing unit 25 to perform correlation processing for tracking the third and fourth satellite signals.

[0086] When high-precision positioning is not required, the positioning unit 40 performs positioning based on at least one of the first and second satellite signals when the control unit 30 acquires the first and second satellite signals. Alternatively, when high-precision positioning is required, the positioning unit 40 performs positioning based on at least one of the third and fourth satellite signals when the control unit 30 acquires the third and fourth satellite signals.

[0087] like Figure 5 As shown, with Figure 1Similarly, the positioning unit 40 includes a satellite information processing unit 41 and a position calculation unit 42. The satellite information processing unit 41 demodulates the navigation messages superimposed on the first, second, third, and fourth satellite signals based on the capture information generated by the tracking control unit 32. Specifically, the satellite information processing unit 41, based on the frequency offset and code phase of the satellite signals included in each capture information, mixes the local code (which shares the same pattern as the identification code) with the satellite signals at an appropriate time, and demodulates the navigation messages including the orbital and time information of each of the satellites 2.

[0088] The position calculation unit 42 uses the orbital and time information of four or more satellites 2 demodulated by the satellite information processing unit 41 to perform positioning calculations and obtain accurate information on the position and time of the antennas 51 and 52, which serve as receiving points.

[0089] It should be noted that satellite 2, which transmits the first and second satellite signals, is an example of a "first satellite," and satellite 2, which transmits the third and fourth satellite signals, is an example of a "second satellite." Furthermore, sample memory 22 is an example of a "first storage unit," and sample memory 26 is an example of a "second storage unit." Correlation processing unit 23 is an example of a "first correlation processing unit," and correlation processing unit 25 is an example of a "second correlation processing unit."

[0090] Figure 6 This is a flowchart illustrating an example of the processing procedure of the positioning terminal 1 according to the second embodiment. For example... Figure 6 As shown, firstly, in process S210, the control unit 30 activates the first receiving unit 101. Consequently, the first receiving unit 101 begins receiving satellite signals in the L1 band of GPS, which serve as the first satellite signal.

[0091] Next, in process S220, the digital processing unit 20 saves the data received by the first receiving unit 101 into the sample memory 22, which serves as the first sample memory.

[0092] Next, in process S230, the control unit 30 searches for satellite signals in the L1 band of GPS based on the results of the correlation processing of the correlation processing unit 23, until the satellite signals in the L1 band of GPS are captured in process S240.

[0093] Additionally, in process S250, the control unit 30 activates the second receiving unit 102. As a result, the second receiving unit 102 begins receiving satellite signals in the L1 band of Beidou, which serves as the third satellite signal.

[0094] Next, in process S260, the digital processing unit 20 saves the data received by the second receiving unit 102 into the sample memory 26, which serves as the second sample memory.

[0095] Next, in process S270, the control unit 30 searches for satellite signals in the L1 band of Beidou based on the results of the correlation processing by the correlation processing unit 23, until the satellite signals in the L1 band of Beidou are captured in process S280.

[0096] Next, if the control unit 30 captures GPS L1 band satellite signals in step S240 and Beidou L1 band satellite signals in step S280, then in step S300, if high-precision positioning is not required in step S290, it tracks GPS L1 band satellite signals based on the correlation processing results of the correlation processing unit 23. Furthermore, in step S310, it tracks Beidou L1 band satellite signals based on the correlation processing results of the correlation processing unit 23.

[0097] On the other hand, when high-precision positioning is required in process S290, the control unit 30 tracks the GPS L1 band satellite signal in process S320. Furthermore, in process S330, the digital processing unit 20 stops saving data to the sample memory 26, which serves as the second sample memory. Then, in process S340, the control unit 30 tracks the GPS L5 band satellite signal, which serves as the second satellite signal, and in process S350, it tracks the Beidou L5 band satellite signal, which serves as the fourth satellite signal.

[0098] Next, in process S360, the positioning unit 40 acquires satellite information of each satellite 2 based on the satellite signal being tracked.

[0099] Next, in process S370, the positioning unit 40 calculates the position of the positioning terminal 1 based on the satellite information of each satellite 2, until the positioning ends in process S380.

[0100] Then, when positioning ends in process S380, the control unit 30 stops the first receiving unit 101 in process S390, stops the second receiving unit 102 in process S400, and ends the process.

[0101] According to the positioning terminal 1 of the second embodiment described above, for the first and third satellite signals with low chip rates and small data volume, the data of the identification code for a period of more than one cycle is stored in the sample memory 22 and 26, and the correlation processing unit 23 performs correlation processing at high speed; for the second and fourth satellite signals with high chip rates and large data volume, the correlation processing unit 25 performs correlation processing sequentially without using the sample memory, thus reducing the processing load and circuit size.

[0102] Furthermore, according to the positioning terminal 1 of the second embodiment, the tracking control unit 32 can efficiently track the second and fourth satellite signals by using the capture information obtained by the search control unit 31 through high-speed searching of the first and third satellite signals with low chip rates and small data volumes. Moreover, since the search control unit 31 does not need to search for the second and fourth satellite signals with high chip rates and large data volumes, the processing load is reduced.

[0103] Furthermore, according to the positioning terminal 1 of the second embodiment, the positioning unit 40 is capable of performing positioning efficiently or with high precision based on the first and second satellite signals of the first GNSS and the third and fourth satellite signals of the second GNSS.

[0104] This invention is not limited to this embodiment, and various modifications can be implemented within the scope of the spirit of this invention.

[0105] The above-described embodiments and modifications are merely examples and are not intended to limit the scope. For instance, the embodiments and modifications may be appropriately combined.

[0106] This invention includes configurations that are substantially the same as those described in the embodiments, such as configurations with the same functions, methods, and results, or configurations with the same purpose and effects. Additionally, this invention includes configurations obtained by replacing non-essential parts of the configurations described in the embodiments. Furthermore, this invention includes configurations that can achieve the same effects as those described in the embodiments, or configurations that can achieve the same purpose. Additionally, this invention includes configurations obtained by incorporating known techniques into the configurations described in the embodiments.

[0107] The following content is derived from the above implementation methods and variations.

[0108] One aspect of the positioning terminal is:

[0109] The first receiving unit receives a first satellite signal at a first chip rate transmitted from the first satellite.

[0110] The second receiving unit receives a second satellite signal transmitted from the first satellite at a second chip rate that is higher than the first chip rate.

[0111] The first storage unit stores the first satellite signal, which includes the identification code of the first satellite in the first satellite signal received by the first receiving unit, for a period of more than one cycle.

[0112] The first correlation processing unit performs correlation processing on the first satellite signal stored in the first storage unit;

[0113] The second correlation processing unit sequentially performs correlation processing on the second satellite signal received by the second receiving unit; and

[0114] The control unit tracks the first satellite signal and the second satellite signal based on the results of the correlation processing by the first correlation processing unit and the results of the correlation processing by the second correlation processing unit.

[0115] According to this positioning terminal, for the first satellite signal with a low chip rate and small data volume, the identification code data for more than one cycle is stored in the storage unit for high-speed correlation processing; for the second satellite signal with a high chip rate and large data volume, the storage unit is not used and correlation processing is performed sequentially. Therefore, the processing load and circuit size can be reduced.

[0116] In one aspect of the positioning terminal, it could also be that...

[0117] The control unit causes the first correlation processing unit to perform correlation processing for searching for the first satellite signal, and searches for the first satellite signal based on the result of the correlation processing. If the first satellite signal is captured, the control unit causes the first correlation processing unit and the second correlation processing unit to perform correlation processing for tracking the first satellite signal and the second satellite signal based on the capture information of the first satellite signal.

[0118] According to this positioning terminal, it is possible to efficiently track the second satellite signal using the capture information obtained by searching the first satellite signal with a small data volume and low chip rate at high speed, and it is not necessary to search the second satellite signal with a large data volume and high chip rate, so the processing load is reduced.

[0119] In one aspect of the positioning terminal, it could also be that...

[0120] The control unit searches for the first satellite signal based on the result of the correlation processing of the first correlation processing unit, and if the first satellite signal is captured, causes the second receiving unit to start receiving the second satellite signal.

[0121] According to this positioning terminal, there is no need to search for a second satellite signal or to have a storage unit for storing the second satellite signal, thus reducing processing load and circuit size. Furthermore, according to this positioning terminal, the control unit can stop the second receiver before the first satellite signal is acquired, thereby reducing power consumption.

[0122] One side of the positioning terminal may also include a positioning unit, which performs positioning based on at least one of the first satellite signal and the second satellite signal captured by the control unit.

[0123] According to this positioning terminal, positioning can be performed efficiently or with high precision based on at least one of the first satellite signal and the second satellite signal.

[0124] In one aspect of the positioning terminal, it could also be that...

[0125] The first satellite belongs to the first GNSS.

[0126] The second receiving unit receives signals from a third satellite transmitted by a second satellite belonging to a second GNSS different from the first GNSS.

[0127] The first correlation processing unit performs correlation processing on the third satellite signal.

[0128] This positioning terminal can be used to perform positioning efficiently or with high precision using satellite signals from two GNSS systems.

[0129] Alternatively, one side of the positioning terminal may include a second storage unit, which stores the third satellite signal received by the second receiving unit. The third satellite signal is a signal with a duration of more than one cycle of the identification code of the second satellite.

[0130] The first correlation processing unit performs the correlation processing on the third satellite signal stored in the second storage unit.

[0131] According to this positioning terminal, regarding third satellite signals, it is also possible to store data of identification codes for a period of more than one cycle in the storage unit for high-speed related processing.

[0132] In one aspect of the positioning terminal, it could also be that...

[0133] The second receiving unit switches the received satellite signal between the second satellite signal of the first satellite and the third satellite signal of the second satellite based on a predetermined operation.

[0134] According to this positioning terminal, its versatility is improved because it can switch the satellite signals received by the second receiving unit.

Claims

1. A positioning terminal, characterized by have: The first receiving unit receives a first satellite signal at a first chip rate transmitted from the first satellite. The second receiving unit receives a second satellite signal transmitted from the first satellite at a second chip rate that is higher than the first chip rate. The first storage unit stores the first satellite signal, which includes the identification code of the first satellite in the first satellite signal received by the first receiving unit, for a period of more than one cycle. The first correlation processing unit performs correlation processing on the first satellite signal stored in the first storage unit; The second correlation processing unit sequentially performs correlation processing on the second satellite signals received by the second receiving unit; as well as The control unit tracks the first satellite signal and the second satellite signal based on the results of the correlation processing by the first correlation processing unit and the results of the correlation processing by the second correlation processing unit.

2. The positioning terminal according to claim 1, characterized in that, The control unit causes the first correlation processing unit to perform correlation processing for searching for the first satellite signal, and searches for the first satellite signal based on the result of the correlation processing. If the first satellite signal is captured, the control unit causes the first correlation processing unit and the second correlation processing unit to perform correlation processing for tracking the first satellite signal and the second satellite signal based on the capture information of the first satellite signal.

3. The positioning terminal according to claim 1, characterized in that, The control unit searches for the first satellite signal based on the result of the correlation processing of the first correlation processing unit, and if the first satellite signal is captured, causes the second receiving unit to start receiving the second satellite signal.

4. The positioning terminal according to claim 3, characterized in that, The positioning terminal includes a positioning unit, which performs positioning based on at least one of the first satellite signal and the second satellite signal captured by the control unit.

5. The positioning terminal according to claim 4, characterized in that, The first satellite belongs to the first GNSS. The second receiving unit receives signals from a third satellite transmitted by a second satellite belonging to a second GNSS different from the first GNSS. The first correlation processing unit performs correlation processing on the third satellite signal.

6. The positioning terminal according to claim 5, characterized in that, The positioning terminal includes a second storage unit that stores the third satellite signal received by the second receiving unit. The third satellite signal is a signal with a duration of more than one cycle of the identification code of the second satellite. The first correlation processing unit performs the correlation processing on the third satellite signal stored in the second storage unit.

7. The positioning terminal according to claim 6, characterized in that, The second receiving unit switches the received satellite signal between the second satellite signal of the first satellite and the third satellite signal of the second satellite based on a predetermined operation.

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