Positioning terminal

Abstract

To provide a positioning terminal capable of efficiently processing both low-chiprate and high-chiprate satellite signals. [Solution] A positioning terminal comprising: a first receiving unit that receives a first satellite signal at a first chip rate transmitted from a first satellite; a second receiving 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 the first satellite signal for a duration of one or more cycles of the identification code of the first satellite included in the first satellite signal received by the first receiving 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 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.

Description

Technical Field

[0001] The present invention relates to a positioning terminal.

Background Art

[0002] Patent Document 1 describes a satellite positioning signal receiving device that includes a GNSS receiving circuit that functions as a master, receives an L1 signal, performs satellite acquisition and satellite tracking to obtain navigation data and satellite observation values, and a GNSS receiving circuit that functions as a slave, receives an L2 / L5 signal, performs satellite acquisition and satellite tracking to obtain navigation data and satellite observation values, and the GNSS receiving circuit of the master performs positioning calculation using the L1 navigation data and satellite observation values obtained by itself and the L2 / L5 navigation data and satellite observation values transferred from the GNSS receiving circuit of the slave.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the satellite positioning signal receiving device described in Patent Document 1, since the GNSS receiving circuit of the master and the GNSS receiving circuit of the slave have the same configuration, there is no difference between 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, and there are problems in optimizing the processing load and circuit size.

Means for Solving the Problems

[0005] One aspect of the positioning terminal according to the present invention is a first receiving unit that receives a first satellite signal with a first chip rate transmitted from a first satellite, A second receiving unit that receives a second satellite signal transmitted from the first satellite at a second chip rate higher than the first chip rate, A first storage unit stores the first satellite signal for a period of time of one or more cycles of the identification code of the first satellite included in the first satellite signal received by the first receiving unit, A first correlation processing unit that performs correlation processing on the first satellite signals stored in the first storage unit, A second correlation processing unit that sequentially performs correlation processing of the second satellite signals received by the second receiving unit, The system includes a control unit that tracks the first satellite signal and the second satellite signal based on the results of the correlation processing performed by the first correlation processing unit and the results of the correlation processing performed by the second correlation processing unit. [Brief explanation of the drawing]

[0006] [Figure 1] A diagram showing an example configuration of a positioning terminal according to the first embodiment. [Figure 2] A diagram showing the structure of L1 band navigation messages in GPS. [Figure 3] A diagram showing the structure of L5 band navigation messages in GPS. [Figure 4] A flowchart illustrating an example of the processing procedure for the positioning terminal in the first embodiment. [Figure 5] A diagram showing an example configuration of a positioning terminal according to the second embodiment. [Figure 6] A flowchart illustrating an example of the processing procedure for the positioning terminal in the second embodiment. [Modes for carrying out the invention]

[0007] Preferred embodiments of the present invention will be described in detail below with reference to the drawings. The embodiments described below are not intended to unduly limit the scope of the present invention as described in the claims. Furthermore, not all of the configurations described below are necessarily essential components of the present invention.

[0008] 1. Embodiment 1-1. Configuration of the positioning terminal Figure 1 shows an example of the configuration of the positioning terminal 1 according to the first embodiment. As will be described in detail below, the positioning terminal 1 receives satellite signals transmitted from satellite 2 and performs positioning based on the received satellite signals.

[0009] As shown in Figure 1, the positioning terminal 1 of the first embodiment includes antennas 51, 52, analog processing unit 10, digital processing unit 20, control unit 30, and positioning unit 40. Note that the positioning terminal 1 may have a configuration in which some of the components shown in Figure 1 are omitted or changed, or other components are added.

[0010] Antennas 51 and 52 are antennas that receive various radio waves, including satellite signals transmitted from each of the multiple satellites 2. Each satellite 2 is an artificial satellite orbiting the Earth in a predetermined orbit and constitutes part of a GNSS. GNSS is an abbreviation for Global Navigation Satellite System. Examples of GNSS include GPS, QZSS, EGNOS, GLONASS, GALILEO, and BeiDou. GPS is an abbreviation for Global Positioning System. QZSS is an abbreviation for Quasi Zenith Satellite System. EGNOS is an abbreviation for European Geostationary Navigation Overlay Service. GLONASS is an abbreviation for Global Navigation Satellite System. The following explanation will use the case where the satellite system to which satellite 2 belongs is GPS as an example.

[0011] Each satellite 2 transmits satellite signals to the ground by superimposing navigation messages onto radio waves in multiple frequency bands, such as the L1 band with a center frequency of 1.57542 GHz and the L2 band with a center frequency of 1.22760 GHz. There are approximately 30 satellites 2 in the GPS system, and to identify which satellite 2 transmitted the satellite signal, the L1 band satellite signal includes an identification code consisting of a unique pattern of 1023 chips. The L1 band identification code is called the C / A code, and each chip is either +1 or -1, appearing as a random pattern and repeating with a period of 1 ms. C / A is an abbreviation for Coarse / Acquisition Code. Thus, the chip rate of the L1 band satellite signal is 1.023 Mcps (= 1023 chips / 1 ms).

[0012] Furthermore, some satellites also transmit satellite signals to the ground by superimposing navigation messages onto L5 band radio waves with a center frequency of 1.17645 GHz. The L5 band satellite signals contain an identification code consisting of a unique pattern of 10230 chips. Similar to the C / A code, each chip in this identification code is either +1 or -1, appearing as a random pattern, and repeating with a 1ms period. Thus, the chip rate of the L5 band satellite signals is 10.23 Mcps (= 10230 chips / 1ms), which is 10 times the chip rate of the L1 band satellite signals.

[0013] As shown in Figure 1, 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 an antenna 51 and receives a first satellite signal of 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 an antenna 52 and receives a second satellite signal of 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.

[0014] Thus, the RF receiving unit 11 and the A / D conversion unit 12 constitute the first receiving unit 101 that receives the first satellite signal, and the RF receiving unit 13 and the A / D conversion unit 14 constitute the second receiving unit 102 that receives 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 satellite signal and the second satellite signal are transmitted from one satellite 2. Hereinafter, it is assumed that the first satellite signal is a satellite signal in the L1 band of GPS, and the second satellite signal is a satellite signal in the L5 band of GPS.

[0015] As shown in FIG. 1, the digital processing unit 20 includes a filter processing unit 21, a sample memory 22, a correlation processing unit 23, a filter processing unit 24, and a correlation processing unit 25.

[0016] The filter processing unit 21 performs a process of attenuating noise components from the first satellite signal converted into a digital signal by the A / D conversion unit 12.

[0017] The sample memory 22 sequentially stores the first satellite signal whose noise components have been attenuated by the filter processing unit 21. In this embodiment, the sample memory 22 stores the first satellite signal for a time period of one cycle or more of the C / A code included in the first satellite signal received by the first receiving unit 101, that is, for a time period of 1 ms or more.

[0018] 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 for a time period of 1 ms or more is stored in the sample memory 22.

[0019] The filter processing unit 24 performs a process of attenuating noise components from the second satellite signal converted into a digital signal by the A / D conversion unit 14.

[0020] 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 the noise component has been attenuated by the filter processing unit 24. In other words, unlike the correlation processing unit 23, the correlation processing unit 25 performs correlation processing on the second satellite signal without using sample memory. The second satellite signal, which is an L5 band satellite signal, has a chip rate 10 times higher than the first satellite signal, which is an L1 band satellite signal, and therefore the amount of data is also 10 times greater. By having the correlation processing unit 25 sequentially perform correlation processing on the second satellite signal, a large sample memory is not required, and costs can be reduced. In addition, the correlation processing unit 25 can efficiently perform correlation processing on the high chip rate second satellite signal.

[0021] As shown in Figure 1, 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 the first satellite signal. When the correlation processing unit 23 is instructed to perform correlation processing for searching the first satellite signal, it generates local codes with the same pattern as the C / A codes of each satellite 2, and performs a process to correlate each C / A code included in the first satellite signal with the local code while shifting the phase of the local code by 1 chip at a time. Because the satellite 2 is moving at high speed, the frequency of the L1 band radio waves received by the antenna 51 fluctuates within a range of approximately ±2 kHz from 1.57542 GHz due to the Doppler effect. Since the Doppler frequency, which is the frequency of this fluctuation, becomes the frequency offset of the first satellite signal, the correlation processing unit 23 also takes the frequency offset of the first satellite signal into consideration when performing correlation processing.

[0022] The search control unit 31 searches for the first satellite signal based on the results of the correlation processing by the correlation processing unit 23. Specifically, if the peak of the correlation value obtained by the correlation processing by the correlation processing unit 23 is greater than or equal to a threshold, the search control unit 31 determines that it has acquired the first satellite signal whose local code corresponding to the peak correlation value is the C / A code. When the search control unit 31 acquires the first satellite signal, it 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 acquisition information including the frequency offset and code phase of the first satellite signal.

[0023] When the search control unit 31 acquires the first satellite signal, the tracking control unit 32, based on the acquisition 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 also 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 acquisition information including the frequency offset and code phase of each tracked satellite signal.

[0024] In this manner, the control unit 30 causes the correlation processing unit 23 to perform correlation processing for searching for the first satellite signal, searches for the first satellite signal based on the results of the correlation processing, and if the first satellite signal is acquired, causes the correlation processing units 23 and 25 to perform correlation processing for tracking the first satellite signal and the second satellite signal based on the acquisition information of the first satellite signal, and tracks the first satellite signal and the second satellite signal based on the results of the correlation processing.

[0025] The control unit 30 may search for the first satellite signal based on the correlation processing result of the correlation processing unit 23, and if it acquires the first satellite signal, it may cause the second receiving unit 102 to start receiving the second satellite signal. Specifically, the second receiving unit 102 has a receiving mode in which it receives the second satellite signal and a sleep mode in which it does not receive the second satellite signal, and the tracking control unit 32 may switch the second receiving unit 102 from sleep mode to receiving mode when the search control unit 31 acquires the first satellite signal. In this way, the second receiving unit 102 and the subsequent filter processing unit 24 and correlation processing unit 25 stop processing until the search control unit 31 acquires the first satellite signal, thus reducing power consumption.

[0026] Furthermore, based on a predetermined operation by the user, the control unit 30 may, when high-precision positioning is required, cause the correlation processing units 23 and 25 to perform correlation processing for tracking the first satellite signal and the second satellite signal, and when high-precision positioning is not required, cause 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 processing by the second receiving unit 102, the filter processing unit 24, and the correlation processing unit 25, and thus reducing power consumption.

[0027] When the control unit 30 acquires 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.

[0028] As shown in Figure 1, 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 acquisition information generated by the tracking control unit 32. Specifically, the satellite information processing unit 41 mixes the local code with the same pattern as the identification code and the satellite signal at an appropriate timing based on the frequency offset and code phase of the satellite signal included in each acquisition information, and demodulates the navigation message including the orbital information and time information of each satellite 2.

[0029] Figure 2 shows the structure of L1 band navigation messages. As shown in Figure 2, L1 band navigation messages are composed of data in units of a mainframe with a total of 1500 bits. The mainframe is divided from the beginning into five subframes, the 1st to the 5th subframes, each of 300 bits. The data for one subframe is transmitted from each satellite 2 in 6 seconds. Therefore, the data for one mainframe is transmitted from each satellite 2 in 30 seconds.

[0030] The 300 bits of data contained in each of the five subframes are divided into 10 words, each consisting of 30 bits, starting from the first word. In each subframe, the first word is the TLM word, and the second word is the HOW word. TLM stands for TeLeMetry, and HOW stands for Hand Over Word. Therefore, the TLM word and HOW word are transmitted from satellite 2 at 6-second intervals.

[0031] A TLM word includes preamble data, TLM message, reserved bit, and parity data.

[0032] The HOW word contains time information called TOW or Z count. TOW is an abbreviation for Time Of Week. The Z count data displays the elapsed time in seconds from 0:00 on Sunday each week and resets to 0 at 0:00 on the following Sunday. In other words, the Z count data is information in seconds shown for each week from the beginning of the week, and the elapsed time is expressed in units of 1.5 seconds. Here, the Z count data indicates the time information when the first bit of the next subframe data is transmitted. For example, the Z count data of the first subframe indicates the time information when the first bit of the second subframe is transmitted. The HOW word also contains a 3-bit ID code that indicates the ID of the subframe. That is, the HOW words of the first to fifth subframes contain the ID codes "001", "010", "011", "100", and "101", respectively. The time on satellite 2 can be calculated from the week number data contained in the first subframe and the HOW words contained in each subframe.

[0033] Words 3 through 10 of the first subframe contain satellite correction data such as the week number, satellite 2 status, and clock correction coefficient. Specifically, the week number and satellite 2 status are in word 3, and the clock correction coefficient is in words 8 through 10. Words 3 through 10 of the second and third subframes contain ephemeris parameters, which are detailed orbital information for satellite 2. Words 3 through 10 of the fourth and fifth subframes contain almanac parameters, which are approximate orbital information for all satellites 2. Therefore, satellite correction data, ephemeris parameters, and almanac parameters are transmitted from satellite 2 at 30-second intervals.

[0034] Figure 3 shows the structure of L5 band navigation messages. As shown in Figure 3, L5 band navigation messages are composed of data in units of 300 bits and are transmitted in 6 seconds. The 300 bits of data that make up each message consist of, from the beginning, an 8-bit preamble, a 6-bit satellite number PRN, a 6-bit message type ID, a 17-bit message TOW count, a 1-bit alert flag, a 262-bit message content, and a 24-bit CRC. CRC stands for Cyclic Redundancy Check.

[0035] The message TOW count is a simplified 17-bit TOW count, expressed in units of 6 seconds. The actual TOW count displays the elapsed time in seconds from 0:00 on Sunday each week and resets to 0 at 0:00 on the following Sunday. In other words, the actual TOW count is information in seconds, shown weekly from the beginning of the week, with elapsed time expressed in units of 1.5 seconds. The message TOW count is a simplified 17-bit representation of the actual TOW count.

[0036] Message content varies depending on the message type ID, but it includes information similar to or identical to that contained in L1 band navigation messages.

[0037] Returning to the explanation of Figure 1, the position calculation unit 42 performs positioning calculations using the orbital information and time information of four or more satellites 2 demodulated by the satellite information processing unit 41, and obtains accurate information on the position and time of the receiving points, antennas 51 and 52. Specifically, the positioning terminal 1 calculates the difference between the time of each satellite 2 and the time of the receiving point using the orbital information and time information contained in each satellite signal, calculates a pseudo-distance between each satellite 2 and the receiving point based on this time difference, sets up a four-dimensional equation with the three-dimensional position (x, y, z) and time t of the receiving point as four variables using this pseudo-distance, and finds its solution.

[0038] Note that satellite 2, which transmits the first satellite signal and the second satellite signal, is an example of the "first satellite." Also, sample memory 22 is an example of the "first storage unit." Correlation processing unit 23 is an example of the "first correlation processing unit," and correlation processing unit 25 is an example of the "second correlation processing unit."

[0039] 1-2. Processing procedure for positioning terminals Figure 4 is a flowchart showing an example of the processing procedure of the positioning terminal 1 in the first embodiment. As shown in Figure 4, first, in step S10, the control unit 30 activates the first receiving unit 101. As a result, the first receiving unit 101 starts receiving the L1 band satellite signal, which is the first satellite signal.

[0040] Next, in step S20, the digital processing unit 20 stores the data received by the first receiving unit 101 in the sample memory 22.

[0041] Next, in step S30, the control unit 30 searches for L1 band satellite signals based on the results of the correlation processing by the correlation processing unit 23 until it acquires an L1 band satellite signal in step S40.

[0042] Next, when the control unit 30 acquires an L1 band satellite signal in step S40, if high-precision positioning is not required in step S50, in step S60, it tracks the L1 band satellite signal based on the results of the correlation processing by the correlation processing unit 23.

[0043] On the other hand, if high-precision positioning is required in step S50, in step S70, the control unit 30 activates the second receiving unit 102. This causes the second receiving unit 102 to start receiving the L5 band satellite signal, which is the second satellite signal. Then, in step S80, the control unit 30 tracks the L5 band satellite signal based on the results of the correlation processing by the correlation processing unit 25.

[0044] Next, in step S90, the positioning unit 40 acquires satellite information for each satellite 2 based on the tracked satellite signal.

[0045] Next, in step 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 is completed in step S110.

[0046] Then, when positioning is completed in step S110, the control unit 30 stops the first receiving unit 101 in step S120 and stops the second receiving unit 102 in step S130, thereby ending the process.

[0047] 1-3. Effects As described above, according to the positioning terminal 1 of the first embodiment, for the first satellite signal with a small amount of data and a low chip rate, data for a duration of one or more cycles of the identification code 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 large amount of data and a high chip rate, the correlation processing unit 25 performs correlation processing sequentially without using the sample memory, thereby reducing the processing load and circuit size.

[0048] 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 acquisition information obtained by the search control unit 31, which rapidly searches for the first satellite signal with a small amount of data and a low chip rate. In addition, since the search control unit 31 does not need to search for the second satellite signal with a large amount of data and a high chip rate, the processing load is reduced.

[0049] Furthermore, according to the positioning terminal 1 of the first embodiment, the second receiving unit 102 can be stopped until the tracking control unit 32 acquires the first satellite signal, thereby reducing power consumption.

[0050] Furthermore, according to the positioning terminal 1 of the first embodiment, the positioning unit 40 can perform positioning efficiently or with high accuracy based on the first satellite signal and the second satellite signal.

[0051] 2. Second Embodiment In the following description of the second embodiment, the same reference numerals are used for components similar to those in the first embodiment, and descriptions that overlap with those in the first embodiment are omitted or simplified. The main points to be described are those that differ from the first embodiment.

[0052] Figure 5 shows an example of the configuration of the positioning terminal 1 according to the second embodiment. As shown in Figure 5, the positioning terminal 1 according to the second embodiment includes antennas 51, 52, an analog processing unit 10, a digital processing unit 20, a control unit 30, and a positioning unit 40, similar to Figure 1. Note that the positioning terminal 1 may have a configuration in which some of the components in Figure 5 are omitted or changed, or other components are added.

[0053] As shown in Figure 5, 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, similar to Figure 1. The RF receiver 11 is connected to the antenna 51 and receives a first satellite signal of 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.

[0054] The RF receiver 13 is connected to the antenna 52 and receives the second satellite signal at the second chip rate and the third satellite signal at the third chip rate, which are superimposed on the radio waves received by the antenna 52. For example, the second receiver 102 may switch between receiving the second satellite signal and the third satellite signal based on a predetermined operation by the user. Specifically, the second receiver 102 receives either the second satellite signal or the third satellite signal according to instructions from the control unit 30 based on a predetermined operation.

[0055] Furthermore, the RF receiver 13 may receive the fourth satellite signal at the fourth chip rate, which is superimposed on the radio waves received by the antenna 52. For example, the second receiver 102 may switch the satellite signal it receives between the third satellite signal and the second and fourth satellite signals based on a predetermined operation by the user. Specifically, the second receiver 102 may receive the third satellite signal, or receive the second and fourth satellite signals simultaneously, in accordance with instructions from the control unit 30 based on a predetermined operation.

[0056] The A / D conversion unit 14 converts the satellite signal received by the RF receiving unit 13 into a digital signal.

[0057] Thus, the RF receiver 11 and the A / D converter 12 constitute a first receiver 101 that receives the first satellite signal, and the RF receiver 13 and the A / D converter 14 constitute a second receiver 102 that receives the third satellite signal, or 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. Also, 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 that transmits the first and second satellite signals belongs to the first GNSS, and the satellite 2 that transmits the third and fourth satellite signals belongs to a second GNSS different from the first GNSS.

[0058] In the following, the first GNSS will be GPS and the second GNSS will be Beidou. Furthermore, the first satellite signal will be a GPS L1 band satellite signal, the second satellite signal will be a GPS L5 band satellite signal, the third satellite signal will be a Beidou L1 band satellite signal, and the fourth satellite signal will be a Beidou L5 band satellite signal.

[0059] As shown in Figure 5, the digital processing unit 20 includes a filter processing unit 21, a sample memory 22, a correlation processing unit 23, a filter processing unit 24, and a correlation processing unit 25, similar to Figure 1. Furthermore, in the second embodiment, the digital processing unit 20 includes a sample memory 26.

[0060] The filter processing unit 21 performs a process to attenuate noise components from the first satellite signal, which has been converted into a digital signal by the A / D conversion unit 12.

[0061] The sample memory 22 sequentially stores the first satellite signal from which the noise component has been attenuated by the filter processing unit 21. In this embodiment, the sample memory 22 stores the first satellite signal for a duration of at least one period of the C / A code included in the first satellite signal received by the first receiving unit 101, i.e., for a duration of at least 1 ms.

[0062] The filter processing unit 24 performs a process to attenuate noise components from the third satellite signal, or the second satellite signal and the fourth satellite signal, which have been converted into digital signals by the A / D conversion unit 14.

[0063] The sample memory 26 sequentially stores the third satellite signal, or the second satellite signal and the fourth satellite signal, after the noise component has been attenuated by the filter processing unit 24. In this embodiment, the sample memory 22 stores the third satellite signal for a duration of at least one cycle of the identification code contained in the third satellite signal received by the second receiving unit 102, i.e., for a duration of at least 1 ms.

[0064] The correlation processing unit 23 performs correlation processing on the first satellite signals stored in the sample memory 22. Specifically, the correlation processing unit 23 performs correlation processing on the first satellite signals stored in the sample memory 22 in units of one C / A code cycle, i.e., 1ms. Conversely, the correlation processing unit 23 does not perform correlation processing on the first satellite signals until the sample memory 22 has stored the first satellite signals for a time of 1ms or more.

[0065] Furthermore, the correlation processing unit 23 performs correlation processing on the third satellite signals stored in the sample memory 26. Specifically, the correlation processing unit 23 performs correlation processing on the third satellite signals stored in the sample memory 26 in units of one period of the identification code, i.e., in units of 1 ms. Conversely, the correlation processing unit 23 does not perform correlation processing on the third satellite signals until the sample memory 26 has stored enough of the third satellite signals for a time of 1 ms or more.

[0066] The correlation processing unit 25 sequentially performs correlation processing on the second satellite signal received by the second receiver 102. Furthermore, the correlation processing unit 25 sequentially performs correlation processing on the fourth satellite signal received by the second receiver 102. Specifically, the correlation processing unit 25 sequentially performs correlation processing on the second satellite signal and the fourth satellite signal, each of which has had its noise components attenuated by the filter processing unit 24. In other words, unlike the correlation processing unit 23, the correlation processing unit 25 performs correlation processing on the second satellite signal and the fourth satellite signal without using sample memory. The second and fourth satellite signals, which are L5 band satellite signals, have a higher chip rate than the first and third satellite signals, which are L1 band satellite signals, and therefore have a larger data volume. By having the correlation processing unit 25 sequentially perform correlation processing on the second and fourth satellite signals, a large sample memory is not required, and costs can be reduced. In addition, the correlation processing unit 25 can efficiently perform correlation processing on the high chip rate second and fourth satellite signals.

[0067] As shown in Figure 5, the control unit 30 includes a search control unit 31 and a tracking control unit 32, similar to Figure 1. The search control unit 31 instructs the correlation processing unit 23 to perform correlation processing for searching the first satellite signal and the third satellite signal. When the correlation processing unit 23 is instructed to perform correlation processing for searching the first satellite signal and the third satellite signal, it performs the process of correlating each C / A code contained in the first satellite signal with the local code, and the process of correlating each identification code contained in the third satellite signal with the local code.

[0068] The search control unit 31 searches for the first satellite signal and the third satellite signal based on the results of the correlation processing by the correlation processing unit 23. Specifically, if the peak of the correlation value obtained by the correlation processing of the first satellite signal by the correlation processing unit 23 is greater than or equal to a threshold, the search control unit 31 determines that the first satellite signal, whose local code corresponding to the peak correlation value is the C / A code, has been captured. Similarly, if the peak of the correlation value obtained by the correlation processing of the third satellite signal by the correlation processing unit 23 is greater than or equal to a threshold, the search control unit 31 determines that the third satellite signal, whose local code corresponding to the peak correlation value is the identification code, has been captured. When the search control unit 31 captures the first satellite signal, it 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 search control unit 31 captures the third satellite signal, it 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.

[0069] When the search control unit 31 acquires the first satellite signal, the tracking control unit 32 causes the correlation processing unit 23 to perform correlation processing for tracking the first satellite signal based on the acquisition information of the first satellite signal generated by the search control unit 31. Furthermore, the tracking control unit 32 may cause the correlation processing unit 25 to perform correlation processing for tracking the second satellite signal based on the acquisition information of the first satellite signal generated by the search control unit 31. Then, the tracking control unit 32 may track the first satellite signal and the second satellite signal based on the results of the correlation processing by the correlation processing unit 23 and the results of the correlation processing by the correlation processing unit 25, and generate acquisition information including the frequency offset and code phase of each satellite signal being tracked.

[0070] Thus, the control unit 30 may have the correlation processing unit 23 perform correlation processing for searching for the first satellite signal, search for the first satellite signal based on the results of the correlation processing, and if the first satellite signal is acquired, have the correlation processing units 23 and 25 perform correlation processing for tracking the first satellite signal and the second satellite signal based on the acquisition information of the first satellite signal, and track the first satellite signal and the second satellite signal based on the results of the correlation processing.

[0071] Furthermore, when the search control unit 31 acquires the third satellite signal, the tracking control unit 32 causes the correlation processing unit 23 to perform correlation processing for tracking the third satellite signal based on the acquisition information of the third satellite signal generated by the search control unit 31. In addition, the tracking control unit 32 may cause the correlation processing unit 25 to perform correlation processing for tracking the fourth satellite signal based on the acquisition information of the third satellite signal generated by the search control unit 31. Then, the tracking control unit 32 may track the third satellite signal and the fourth satellite signal based on the results of the correlation processing by the correlation processing unit 23 and the results of the correlation processing by the correlation processing unit 25, and generate acquisition information including the frequency offset and code phase of each satellite signal being tracked.

[0072] Thus, the control unit 30 may have the correlation processing unit 23 perform correlation processing for searching for the third satellite signal, search for the third satellite signal based on the results of the correlation processing, and if the third satellite signal is acquired, have the correlation processing units 23 and 25 perform correlation processing for tracking the third satellite signal and the fourth satellite signal based on the acquisition information of the third satellite signal, and track the third satellite signal and the fourth satellite signal based on the results of the correlation processing.

[0073] If high-precision positioning is requested based on a predetermined operation by the user, the control unit 30 may cause the correlation processing unit 23 to perform correlation processing for tracking the first satellite signal and the second satellite signal, and the correlation processing unit 25 to perform correlation processing for tracking the third satellite signal and the fourth satellite signal. Alternatively, if high-precision positioning is not requested based on a predetermined operation by the user, the control unit 30 may cause the correlation processing unit 23 to perform correlation processing for tracking the first satellite signal, but may not cause the correlation processing unit 25 to perform correlation processing for tracking the third satellite signal and the fourth satellite signal.

[0074] If high-precision positioning is not required, the positioning unit 40 will perform positioning based on at least one of the first satellite signal and the second satellite signal when the control unit 30 has acquired the first satellite signal and the second satellite signal. Alternatively, if high-precision positioning is required, the positioning unit 40 may perform positioning based on at least one of the third satellite signal and the fourth satellite signal when the control unit 30 has acquired the third satellite signal and the fourth satellite signal.

[0075] As shown in Figure 5, the positioning unit 40 includes a satellite information processing unit 41 and a position calculation unit 42, similar to Figure 1. The satellite information processing unit 41 demodulates navigation messages superimposed on the first satellite signal, second satellite signal, third satellite signal, and fourth satellite signal based on acquisition information generated by the tracking control unit 32. Specifically, the satellite information processing unit 41 mixes local codes with the same pattern as the identification code and the satellite signals at appropriate timings based on the frequency offset and code phase of the satellite signals included in each acquisition information, and demodulates navigation messages including orbital information and time information of each satellite 2.

[0076] The position calculation unit 42 performs position calculations using the orbital information and time information of four or more satellites 2 demodulated by the satellite information processing unit 41, thereby obtaining accurate information on the position and time of the receiving points, antennas 51 and 52.

[0077] Note that satellite 2 transmitting the first and second satellite signals is an example of the "first satellite," and satellite 2 transmitting the third and fourth satellite signals is an example of the "second satellite." Also, sample memory 22 is an example of the "first storage unit," and sample memory 26 is an example of the "second storage unit." Correlation processing unit 23 is an example of the "first correlation processing unit," and correlation processing unit 25 is an example of the "second correlation processing unit."

[0078] Figure 6 is a flowchart showing an example of the processing procedure of the positioning terminal 1 in the second embodiment. As shown in Figure 6, first, in step S210, the control unit 30 activates the first receiving unit 101. This causes the first receiving unit 101 to start receiving the GPS L1 band satellite signal, which is the first satellite signal.

[0079] Next, in step S220, the digital processing unit 20 stores the data received by the first receiving unit 101 in the sample memory 22, which is the first sample memory.

[0080] Next, in step S230, the control unit 30 searches for GPS L1 band satellite signals based on the results of the correlation processing by the correlation processing unit 23 until it acquires GPS L1 band satellite signals in step S240.

[0081] Furthermore, in step S250, the control unit 30 activates the second receiving unit 102. This causes the second receiving unit 102 to begin receiving the third satellite signal, which is the Beidou L1 band satellite signal.

[0082] Next, in step S260, the digital processing unit 20 stores the data received by the second receiving unit 102 in the sample memory 26, which is the second sample memory.

[0083] Next, in step S270, the control unit 30 searches for Beidou's L1 band satellite signals based on the results of the correlation processing by the correlation processing unit 23, until it acquires Beidou's L1 band satellite signals in step S280.

[0084] Next, if the control unit 30 acquires GPS L1 band satellite signals in step S240 and Beidou L1 band satellite signals in step S280, then in step S290, if high-precision positioning is not required, in step S300, it tracks the GPS L1 band satellite signals based on the results of the correlation processing by the correlation processing unit 23. Furthermore, in step S310, it tracks the Beidou L1 band satellite signals based on the results of the correlation processing by the correlation processing unit 23.

[0085] On the other hand, if high-precision positioning is required in step S290, in step S320, the control unit 30 tracks the GPS L1 band satellite signal. Also, in step S330, the digital processing unit 20 stops saving data to the second sample memory, the sample memory 26. Furthermore, in step S340, the control unit 30 tracks the second satellite signal, the GPS L5 band satellite signal, and in step S350, it tracks the fourth satellite signal, the Beidou L5 band satellite signal.

[0086] Next, in step S360, the positioning unit 40 acquires satellite information for each satellite 2 based on the tracked satellite signal.

[0087] Next, in step 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 is completed in step S380.

[0088] Then, when positioning is completed in step S380, the control unit 30 stops the first receiving unit 101 in step S390 and the second receiving unit 102 in step S400, and terminates the process.

[0089] According to the positioning terminal 1 of the second embodiment described above, for the first and third satellite signals with a small amount of data and a low chip rate, data for a duration of one or more cycles of the identification code is stored in the sample memories 22 and 26, and the correlation processing unit 23 performs correlation processing at high speed. For the second and fourth satellite signals with a large amount of data and a high chip rate, the correlation processing unit 25 performs correlation processing sequentially without using sample memories, thereby reducing the processing load and circuit size.

[0090] 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 using the acquisition information obtained by the search control unit 31, which rapidly searches for the first and third satellite signals, which have a small amount of data and a low chip rate. In addition, the processing load is reduced because the search control unit 31 does not need to search for the second and fourth satellite signals, which have a large amount of data and a high chip rate.

[0091] Furthermore, according to the positioning terminal 1 of the second embodiment, the positioning unit 40 can perform positioning efficiently or with high accuracy based on the first satellite signal and the second satellite signal of the first GNSS and the third satellite signal and the fourth satellite signal of the second GNSS.

[0092] The present invention is not limited to this embodiment, and various modifications can be implemented within the scope of the gist of the present invention.

[0093] The embodiments and variations described above are merely examples and are not limiting. For example, the embodiments and variations can be combined as appropriate.

[0094] The present invention includes configurations substantially identical to those described in the embodiments, for example, configurations with the same function, method, and results, or configurations with the same purpose and effect. Furthermore, the present invention includes configurations in which non-essential parts of the configurations described in the embodiments are replaced. Furthermore, the present invention includes configurations that produce the same effects or achieve the same purpose as those described in the embodiments. Finally, the present invention includes configurations that add known technology to the configurations described in the embodiments.

[0095] The following can be derived from the embodiments and modifications described above.

[0096] One form of a positioning terminal is: A first receiving unit that receives a first satellite signal at a first chip rate transmitted from the first satellite, A second receiving unit that receives a second satellite signal transmitted from the first satellite at a second chip rate higher than the first chip rate, A first storage unit stores the first satellite signal for a period of time of one or more cycles of the identification code of the first satellite included in the first satellite signal received by the first receiving unit, A first correlation processing unit that performs correlation processing on the first satellite signals stored in the first storage unit, A second correlation processing unit that sequentially performs correlation processing of the second satellite signals received by the second receiving unit, The system includes a control unit that tracks the first satellite signal and the second satellite signal based on the results of the correlation processing performed by the first correlation processing unit and the results of the correlation processing performed by the second correlation processing unit.

[0097] According to this positioning terminal, for the first satellite signal with a small data volume and low chip rate, data equivalent to more than one cycle of the identification code is stored in the memory unit and correlation processing is performed at high speed. For the second satellite signal with a large data volume and high chip rate, correlation processing is performed sequentially without using the memory unit, thereby reducing processing load and circuit size.

[0098] In one embodiment of the positioning terminal, The control unit may cause the first correlation processing unit to perform correlation processing for searching the first satellite signal, search for the first satellite signal based on the results of the correlation processing, and if the first satellite signal is acquired, cause 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 acquisition information of the first satellite signal.

[0099] This positioning terminal allows for efficient tracking of the second satellite signal by using acquisition information obtained from rapidly searching for the first satellite signal, which has a small amount of data and a low chip rate. Furthermore, it eliminates the need to search for the second satellite signal, which has a large amount of data and a high chip rate, thus reducing the processing load.

[0100] In one embodiment of the positioning terminal, The control unit may search for the first satellite signal based on the results of the correlation processing of the first correlation processing unit, and if it acquires the first satellite signal, it may cause the second receiving unit to start receiving the second satellite signal.

[0101] This positioning terminal eliminates the need to search for a second satellite signal and also eliminates the need for a memory unit to store the second satellite signal, thus reducing processing load and circuit size. Furthermore, this positioning terminal allows the control unit to shut down the second receiving unit until it acquires the first satellite signal, thus reducing power consumption.

[0102] One embodiment of the positioning terminal is: The control unit may also include a positioning unit that performs positioning based on at least one of the first satellite signal and the second satellite signal captured by the control unit.

[0103] This positioning terminal allows for efficient and highly accurate positioning based on at least one of the first satellite signal and the second satellite signal.

[0104] In one embodiment of the positioning terminal, The aforementioned first satellite belongs to the first GNSS, The second receiving unit receives a third satellite signal transmitted from a second satellite belonging to a second GNSS different from the first GNSS. The first correlation processing unit may perform correlation processing on the third satellite signal.

[0105] This positioning terminal can perform positioning efficiently and with high accuracy using signals from two GNSS satellites.

[0106] One embodiment of the positioning terminal is: The second receiving unit has a second storage unit that stores the third satellite signal for a duration of one or more cycles of the identification code of the second satellite, The first correlation processing unit may perform the correlation processing of the third satellite signals stored in the second storage unit.

[0107] According to this positioning terminal, data for the third satellite signal, equivalent to more than one cycle of the identification code, can be stored in the memory unit and correlation processing can be performed at high speed.

[0108] In one embodiment of the positioning terminal, The second receiving unit may, based on a predetermined operation, switch the satellite signal it receives between the second satellite signal of the first satellite and the third satellite signal of the second satellite.

[0109] This positioning terminal allows the second receiver to switch the satellite signal it receives, thus improving its versatility. [Explanation of symbols]

[0110] 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…Filter processing unit, 22…Sample memory, 23…Correlation processing unit, 24…Filter processing 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

Claims

1. A first receiving unit that receives a first satellite signal at a first chip rate transmitted from the first satellite, A second receiving unit that receives a second satellite signal transmitted from the first satellite at a second chip rate higher than the first chip rate, A first storage unit stores the first satellite signal for a period of time of one or more cycles of the identification code of the first satellite included in the first satellite signal received by the first receiving unit, A first correlation processing unit that performs correlation processing on the first satellite signals stored in the first storage unit, A second correlation processing unit that sequentially performs correlation processing of the second satellite signals received by the second receiving unit, A positioning terminal comprising: a control unit that tracks the first satellite signal and the second satellite signal based on the results of the correlation processing performed by the first correlation processing unit and the results of the correlation processing performed by the second correlation processing unit.

2. In claim 1, The control unit causes the first correlation processing unit to perform correlation processing for searching the first satellite signal, searches for the first satellite signal based on the results of the correlation processing, and, if the first satellite signal is acquired, 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 acquisition information of the first satellite signal, in a positioning terminal.

3. In claim 1, A positioning terminal in which the control unit searches for the first satellite signal based on the results of the correlation processing of the first correlation processing unit, and when the first satellite signal is acquired, causes the second receiving unit to start receiving the second satellite signal.

4. In claim 3, A positioning terminal comprising a positioning unit that performs positioning based on at least one of the first satellite signal and the second satellite signal captured by the control unit.

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

6. In claim 5, The second receiving unit has a second storage unit that stores the third satellite signal for a duration of one or more cycles of the identification code of the second satellite, The first correlation processing unit performs the correlation processing on the third satellite signals stored in the second storage unit, which is a positioning terminal.

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

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