JP3787592B2 - Satellite positioning method and satellite positioning system - Google Patents

Description

The present invention relates to a satellite positioning method and a satellite positioning system for obtaining a pseudo distance between a satellite and a receiver terminal based on a signal from the satellite.

  Positioning satellites travel around the earth many times, and signals are continuously transmitted at the same carrier frequency. Each satellite is assigned a PN code (referred to as a C / A code in the case of GPS) and is different for each satellite, and is continuously transmitted from each satellite as a pseudo-noise signal. Navigation data including information such as the orbit of the satellite is transmitted from the satellite, and the polarity of the PN code is inverted with this navigation data and PSK modulated with the same carrier wave and continuously transmitted.

In the case of a GPS signal, the PN code (C / A code) is 1 msec (1 millisecond) as a 1PN frame as shown in FIG. 1, and this 1PN frame is transmitted as a periodic continuous signal.
That is, the navigation data is 1 bit {20 msec (50 bps)}, and the polarity of the C / A code is inverted according to the polarity of the navigation data. That is, if the navigation data is 1, the polarity of the C / A code remains unchanged, and if the navigation data is -1, the polarity of the C / A code is also inverted.

  An assist type GPS is known as a satellite positioning system that improves reception sensitivity (see, for example, Patent Document 1). As shown in FIG. 11, the receiving unit 104 includes an RF-to-IF converter 106 having a GPS receiving antenna 105, an A / D converter 107 for converting an analog signal from the converter 106 into a digital signal, A memory (digital snapshot memory) 108 for recording the output from the A / D converter 107 and a general-purpose programmable digital signal processing circuit (hereinafter abbreviated as a DSP circuit) 109 for processing a signal from the memory 108 are provided.

  In addition, a program EPROM (ROM, memory) 110, a frequency synthesizer 111, a power regulator circuit 112, an address writing circuit 113, a microprocessor 114, a RAM (memory) 115, an EEPROM (ROM, memory) connected to the DSP circuit 109. 116) having a modem 118 with a transceiver antenna 117 and connected to a microprocessor 114;

Next, the operation will be described. The base station 101 issues a command to the receiving unit 104 to perform the measurement via the message transmitted by the data communication link 119. The base station 101 transmits the Doppler data of the satellite information for the target satellite in this message.
The Doppler data has a frequency information format, and the message specifies the target satellite. This message is received by modem 118 which is part of receiving unit 104 and stored in memory 108 coupled to microprocessor 114. The microprocessor 114 handles the transmission of data information between the DSP circuit 109, the address writing circuit 113 and the modem 118 and controls the power management function in the receiving unit 104.

  When the receiving unit 104 receives an instruction for GPS processing and Doppler information (eg, from the base station 101), the microprocessor 114 activates the power regulator circuit 112 according to the instruction. The power regulator circuit 112 provides functions to the RF-to-IF converter 106, the A / D converter 107, the memory 108, the DSP circuit 109, and the frequency synthesizer 111 via the power lines 120a to 120e. Thereby, the signal from the GPS satellite received via the GPS receiving antenna 105 is down-converted to the IF frequency and then digitized.

The signal to be processed usually corresponds to a time of 100 msec to 1 sec (or longer). Such a continuous data set is stored in the memory 108.
The DSP circuit 109 performs sword range calculation. In addition, the DSP circuit 109 performs a number of correlation operations between the locally generated reference and the received signal quickly, thereby enabling a fast Fourier transform (FFT) that enables extremely fast computation of the sword range. ) Allows the use of algorithms. The Fast Fourier Transform algorithm searches for all such locations simultaneously in parallel, accelerating the computation process.

When the DSP circuit 109 completes the calculation of the sword range for each of the target satellites, it transmits this information to the microprocessor 114 via the interconnect bus 122. The microprocessor 114 then uses the modem 118 to transmit the sword range data to the base station 101 via the data communication link 119 for the final position calculation.
In addition to the sword data, a time lag indicating the elapsed time from the initial data collection in the memory 108 to the time of transmission of the data through the data communication link 119 can be transmitted to the base station 101 at the same time. This time lag increases the ability of base station 101 to perform position calculations. This is because GPS satellite position can be performed at the time of data collection.

  Modem 118 utilizes a separate transmit / receive antenna 117 for transmitting and receiving messages over data communication link 119. It is understood that the modem 118 includes a communication receiver and a communication transmitter, both of which are alternately coupled to the transmit / receive antenna 117. Similarly, the base station 101 can use separate transmit and receive antennas 103 to transmit and receive data link messages, and therefore, the base station 101 continuously transmits GPS signals via the GPS receive antenna 102. Can be received automatically.

The position calculation in the DSP circuit 109 is expected to take several seconds or less depending on the amount of data stored in the memory 108 and the speed of the DSP circuit 109 or some DSP circuits. As described above, the memory 108 captures records corresponding to relatively long times.
Effective processing of large blocks of data using the first convolution method contributes to the performance of processing signals at low reception levels (for example, when reception levels decrease due to significant obstruction by buildings, trees, etc.) ). All sword ranges for visible GPS satellites are calculated using this same buffered data. This has improved performance for continuously tracking GPS receivers in situations where the amplitude of the signal changes rapidly (such as an urban fault condition).

  For the signal processing performed in the DSP circuit 109, the purpose of the processing is to determine the timing of the received waveform with respect to the locally generated waveform, and to obtain higher sensitivity, a very long portion of the waveform, Usually, the part from 100msec to 1sec is processed. The received GPS signal (C / A code) is composed of 1023 bits = 1 msec repetitive sword random (PN frame).

  Therefore, the previous and next PN frames are added to each other. For example, there are 1000 PN frames per second, so the first frame is added coherently to the next second frame and the resulting is added to the third frame. Hereinafter, as shown in FIG. 12 (A) to FIG. 12 (E), they are sequentially added. As a result, a signal having a duration of 1PN frame = 1023 bits is obtained. By comparing the phase of this sequence with the local reference sequence, the relative timing between the two, that is, the sword range (pseudorange) can be determined. The signal processing performed by the DSP circuit 109 will be described with reference to FIG.

  FIG. 12 is different from an actual GPS signal, and is drawn as a pseudo explanatory diagram for explanation. In the interval (20 msec) where the navigation data is 0 (-1) or 1, 20 frames (20 C / A code periods) actually exist, but for the sake of explanation, it is shown as 4 frames. In FIG. 12A, the phase of each frame (FRAME: 1 msec) is reversed between DATA = 0 and DATA = 1. In this state, a GPS signal (C / A code signal) is input to the receiving antenna.

FIG. 12B is an explanatory diagram when a GPS signal (C / A code signal) is extracted from a rising point (data head) at which DATA becomes 0. It should be noted that this figure is captured at the timing of a special condition written for easy explanation.
That is, it is a diagram when a very special condition is established when the data is captured from the rising point where DATA becomes 0 (the leading portion of the data). The operation shown in FIG. 12 (B) starts taking a received signal (C / A code) from a certain point of time, and adds and averages the received signal (C / A code) for every four frames.

  However, it should be noted that if the received signal (C / A code) starts from the beginning of the first DATA = 0 frame 2 (FRAME 2), the result of addition and averaging is zero. Actually, it is almost impossible to successfully extract from the head of DATA when the receiver starts to acquire signals. In other words, it is actually to start taking data from the middle of the navigation data and from the middle of the frame.

  In FIG. 12 (B), the continuous reception signals captured from a certain point in time are synchronously added every four periods (four C / A codes) and averaged. Next, FIG. 12C shows the correlation calculation result of the replica PN code (replica C / A code) inside the receiver and the result of FIG. The polarity of the peak value of the correlation calculation is positive if the polarity of the result of synchronous addition in FIG. 12B and the polarity of the replica PN code in the receiver match, and negative if they are different.

  FIG. 12 (D) shows a diagram of the absolute value of the correlation result of FIG. 12 (C). That is, the absolute value of each correlation calculation is taken in FIG. In FIG. 12E, each correlation calculation obtained with an absolute value is synchronously added. The sensitivity (S / N) is improved by adding the PN (C / A code) signal, which is a periodic signal, many times by the above synchronous addition and correlation calculation.

Other conventional satellite positioning systems include the following.
The C / A code of the GPS reception signal is temporarily stored in a memory for a certain period of time by an A / D converter. This C / A code signal has a place where the polarity is inverted by GPS navigation data. In this patent, the C / A code signal buried in noise is obtained from the external navigation data in order to emerge from the noise, and the synchronous addition and correlation calculation are performed with the C / A code signal having the same polarity. To perform high-sensitivity reception.

  In this system, navigation data is received from a server of an external base station into a receiver terminal via a communication line and received at the receiver terminal, and the phase of the navigation data and the C / A code signal in the received signal of the receiver terminal are added. The phase of the C / A code signal is completely matched, and the polarity of the received PN code is changed with this navigation data to make all the C / A code signals have the same polarity. Is gaining super sensitivity by making it appear in the noise.

  In this system, the phase of the C / A code signal in the received signal received by the server of the external base station and the receiver terminal and the phase of the navigation data obtained by incorporating the navigation data from the server of the external base station into the receiver via the communication line. Does not match. The reason is that there are variations and delays in communication time in the communication line.

For this purpose, the GPS terminal of the GPS positioning system sends its own time signal to a time server that outputs an accurate time signal, and receives the time signal from this time server so as to know the communication time to the time server. .
By knowing this communication time, the phase difference of the navigation data taken from the server of the external base station to the receiver via the communication line is reduced as much as possible, and the navigation data from the outside is scanned to determine the phase difference. They are completely matched (for example, see Patent Document 2).
US Pat. No. 5,663,734 US Pat. No. 6,329,946

The conventional GPS positioning system is configured as described above. However, the phase of the PN signal included in the GPS received signal is inverted in the navigation data section and polarity depending on the content of the navigation data.
For this reason, in such processing, the polarity of the PN signal changes depending on the navigation data. Therefore, when synchronous addition is performed according to the polarity of the PN signal, the signal components cancel each other out in the process of FIG. N) There was a drawback that it was not sufficient for improvement. In other words, the boundary of polarity reversal of navigation data was not detected. Therefore, there is a problem that the improvement in sensitivity (S / N) is insufficient.
Also, taking the absolute value of the correlation calculation value in the process of FIG. 12 (D) and FIG. 12 (E) and performing synchronous addition does not lead to the reduction of white noise itself, so the sensitivity (S / N) is not improved. There is a problem that it is sufficient.

  Further, in the conventional GPS positioning system (Patent Document 2), when synchronous addition is performed, signal components cancel each other out in the process of FIG. 12B due to the polarity of the PN signal, which is not sufficient for improving the sensitivity (S / N). The problem of not being solved. Specifically, in order to make the polarity of the received signal (PN signal) the same, the navigation data is received from the base station, and the received signal (PN signal) is multiplied to make the polarity the same. Then, by performing synchronous addition, an ideal noise reduction effect is obtained.

  However, it has the following problems. In this case, the communication time from the base station to the receiver terminal is not zero. If the communication line is the Internet or packet communication, etc., the communication time also varies considerably, and the phase error becomes extremely large, so the scan time also increases, so the delay variation in the communication line becomes the position measurement response time. It will be greatly involved. That is, in order to realize high-sensitivity positioning, there is a serious drawback that the receiver cannot be measured with a practical response time unless strict requirements are imposed on the communication time standard in the communication line.

  Therefore, the present invention provides a satellite positioning method and satellite positioning which can receive a signal from a satellite in a building or the like, that is, an attenuated satellite reception signal, and can know the reception position with high sensitivity and good response. A system is provided.

The satellite positioning method according to the present invention is a satellite positioning method in which a receiver terminal receives a signal from a satellite, and the receiver terminal obtains a pseudo distance to the satellite from the received satellite reception signal for a predetermined time. Then, the receiver terminal calculates the polarity of the navigation data in the unit frame by processing the pseudo code pattern prepared in advance by the receiver terminal in the unit frame of the satellite reception signal, and further receives the polarity. A polarity discrimination calculation step that is applied to the signal frame is sequentially performed on the satellite reception signals for the predetermined time period so that the polarity of the navigation data of the satellite reception signals for the predetermined time period is the same, and A satellite reception signal is synchronously added with a unit frame as one unit, and a correlation calculation is performed between the synchronously added PN signal and the replica PN code prepared in advance by the receiver terminal. Detects a delay value corresponding to the correlation peak value and a correlation peak value from results of correlation calculation is a method of obtaining the pseudo-range from the delay value.

Also, the pseudo-code pattern in the polarity determination operation step is a predetermined number of bits of the data string corresponding to a unit frame of a signal from the satellite, yet the predetermined number of bits as many of displacing one by one bit It consists of a group.
The predetermined time of the satellite reception signal received and processed by the satellite receiver terminal is 0.5 seconds or more and 3 seconds or less.

  The satellite positioning system according to the present invention is a satellite positioning system in which a receiver terminal receives a signal from a satellite, and the receiver terminal obtains a pseudorange with the satellite based on the received satellite reception signal for a predetermined time. The receiver terminal includes a pseudo code pattern unit that stores a pseudo code pattern in advance, and causes the unit frame of the satellite reception signal to process the pseudo code pattern, thereby generating navigation data in the unit frame. A polarity discrimination calculator for which polarity is required, a polarity calculator for applying the determined polarity to a received signal frame, and the polarity determination calculator and the polarity calculator for the satellite reception signal for a predetermined time in sequence. A first arithmetic unit for making the polarity of the navigation data of the satellite reception signal for the predetermined time equal, and the satellite for the predetermined time having the same polarity of the navigation data A second arithmetic unit that synchronously adds a unit frame of the received signal as one unit, a third arithmetic unit that performs a correlation calculation using the synchronously added synchronous PN signal and a replica PN code prepared in advance by the receiver terminal, And a pseudo distance detecting device that detects a correlation peak value and a delay value corresponding to the correlation peak value from a result of the correlation calculation and obtains the pseudo distance from the delay value.

The polarity discriminating arithmetic unit is configured to multiply or divide the unit frame of the satellite reception signal by the pseudo code pattern to obtain a data string having a predetermined number of bits having a positive or negative polarity, and the predetermined bit An average computing unit that takes an average of a number of data strings and obtains a positive or negative unit numerical value.
The pseudo code pattern is stored in a pseudo code pattern section of the receiver terminal, and the pseudo code pattern is a data string having a predetermined number of bits corresponding to a unit frame of a signal from the satellite. It consists of the same number of groups as the predetermined number of bits displaced one bit at a time.

  According to the present invention, the number of samplings can be increased and the sensitivity can be significantly improved. As in the prior art, data from an external base station is not required, processing can be performed with a signal received by itself, and a PN signal (PN signal) buried in noise can be detected with significantly improved S / N. That is, the PN signal can be efficiently raised from the noise, and the pseudo-range with the satellite S can be accurately and even in a place where the GPS signal (GPS radio wave) is significantly attenuated, such as in a building or a building. Measure with good response.

FIG. 1 is an explanatory diagram illustrating the structure of a PN signal (also referred to as a C / A code, hereinafter referred to as a PN signal) in a GPS satellite reception signal, and FIG. 2 is a block diagram illustrating an overview of the satellite positioning system. .
In the present invention, either a received PN signal on which a carrier wave (carrier) is superimposed or a received PN signal on which a carrier wave is not superimposed may be used.

In the present invention, the receiver terminal 11 receives a signal from the satellite S, and the receiver terminal 11 obtains a pseudo distance from the satellite S based on the received satellite signal for a predetermined time T (0.5 sec to 3 sec). A satellite positioning system and method.
In FIG. 2, S ₁ , S ₂ , S ₃ , and S ₄ are target positioning satellites that travel around the earth, and 1 is a base station. The base station 1 includes a receiving antenna 2 installed in an environment with a good view, and a GPS signal is received by a GPS reference signal server receiver 3.

  The GPS reference signal server receiver 3 extracts Doppler information 4 from the received satellite reception signal (GPS signal). Further, the base station position, each satellite position, and the pseudo distance between each satellite and the receiving antenna 2 position are extracted. These pieces of information are transmitted to the receiver terminal 11 by the transmitter 5 via the communication means L. This transmission is generally performed by broadcasting. The communication means L may be a mobile phone line, terrestrial broadcast, or satellite broadcast. Or you can use the internet line, and all possible means (by electromagnetic means) are covered.

11 is a GPS receiver terminal. The Doppler information 4 and information on the base station position, each satellite position, and the pseudo distance 6 between each satellite and the base station are received by the receiving unit 12 of the GPS receiver terminal 11 from the base station 1.
If the frequency of the broadcast radio wave is a frequency band near the GPS radio wave (signal), the receiving unit 12 may be shared with the GPS receiving unit 13. In the present invention, it is assumed that many terminals 11 receive simultaneously by means of communication means L (line, broadcast, mobile phone, Internet, etc.). FIG. 2 shows one GPS receiver terminal 11.

Reference numeral 14 denotes an antenna unit of the GPS receiver terminal 11. The location of the GPS receiver terminal 11 (antenna unit 14) is not only where the satellite S can be directly seen, but also the strength of GPS radio waves, such as in the shade of trees (inside outdoor reception) and in buildings. We assume weak places.
The reception unit 13 is an A / D conversion part that converts an analog signal of a GPS reception signal ---- PN signal --- to a digital signal. The digitized PN signal is stored in a memory (RAM) 15-GPS signal storage unit.
The above configuration is widely used in general with conventional GPS technology, and detailed description thereof is omitted.

  More specifically, the receiver terminal 11 includes a pseudo code pattern unit 22 in which a pseudo code pattern A (to be described later) is stored in advance, and a unit frame of a satellite reception signal that is processed by the pseudo code pattern A. A polarity discriminating calculator 24 for determining the polarity of the navigation data and a polarity calculator 25 for calculating the calculated polarity as a frame of the received signal (the next unit frame of the unit frame).

Further, a first computing unit 8 for operating the polarity discrimination computing unit 24 and the polarity computing unit 25 sequentially for the satellite reception signal for a predetermined time T to make the polarity of the navigation data of the satellite reception signal for the predetermined time T, A second arithmetic unit 9 that synchronizes and adds a unit frame as a unit for a satellite reception signal of a predetermined time T with the same polarity of the navigation data, a synchronous addition PN signal that is synchronously added, and a replica prepared in advance by the receiver terminal 11 A third computing unit 10 that performs a correlation calculation with a PN code, and a pseudo distance for detecting a correlation peak value and a delay value (delay amount τ) corresponding to the correlation peak value from the result of the correlation calculation and obtaining a pseudo distance from the delay value And a detection device 19.
Hereinafter, the polarity discriminating arithmetic unit 24, the polarity arithmetic unit 25, and the first arithmetic unit 8 are referred to as a polarity changing device 17, and the second arithmetic unit 9 and the third arithmetic unit 10 are referred to as a synchronous addition / correlation calculating device 18. .

An embodiment in the case of accumulating GPS signals in the 1 sec section will be described. As will be described later, the present invention can be applied to any accumulation time.
Of the signals from successive satellites S, the 20 msec section has the same time as the 1-bit section of the navigation data. Therefore, 1 sec is the same time as the 5-bit section of the navigation data.
In FIG. 2, reference numeral 21 denotes a signal processing unit included in the receiver terminal 11. Among them, the Doppler correction unit 16, the polarity change device 17, the synchronous addition / correlation calculation device 18, and the pseudo distance detection device 19 indicate functional blocks, and the receiver terminal 11 (signal processing unit 21) receives and accumulates for 1 second. The navigation data of the PN signal (satellite reception signal) at (predetermined time T) is made the same polarity, the satellite reception signals for 1 second (predetermined time T) with the same polarity are added synchronously, The pseudo value is obtained by calculating the delay value.

The PN code polarity changing device 17 stores the pseudo code pattern A for equalizing the polarity of the satellite reception signal prepared (stored) in advance in the pseudo code pattern unit 22 of the receiver terminal 11 and stored in the memory 15 for 1 sec. It is a device that acts on the satellite reception signal----------------to make the polarity of the navigation data of the signal the same.
Further, the pseudo code pattern A is a data string having a predetermined number of bits corresponding to a unit frame (one frame) of a signal from the satellite S, and is composed of a group having the same number as the predetermined number of bits displaced sequentially by one bit. is there.

  The synchronous addition / correlation calculation device 18 performs synchronous addition and correlation calculation on the PN signals having the same polarity as the navigation data. Thereafter, the pseudorange detection device 19 detects the pseudorange between the receiver terminal 11 and the satellite S by detecting a value (delay amount τ) at which the correlation calculation peak value becomes the maximum value.

Noise reduction by synchronous addition and correlation calculation is improved to the maximum by the PN signal having the same polarity within 1 sec. The pseudo distance detection device 19 detects the pseudo distance in a state where noise reduction is improved to the maximum by making the polarity of the PN signal within 1 sec the same.
The position calculation device 20 can know the self-position of the receiver terminal 11 based on the pseudo distance obtained here and the information on the base station position from the receiving unit 12, each satellite position, and the pseudo distance between the base station and each satellite. it can.

FIG. 3 is a detailed hardware block diagram of the GPS receiver terminal 11. The code | symbol of each block of FIG. 2 respond | corresponds with the code | symbol of the block of FIG. The Doppler correction unit 16, the polarity changing device 17, the synchronous addition / correlation calculation device 18, the pseudo distance detection device 19, and the position calculation device 20 in FIG. 2 are functional blocks.
The means for configuring the functional block may be a hardware configuration, a software configuration, or a mixed configuration. The signal processing unit 21 shows a hardware configuration for executing software processing, which is means for configuring this functional block.

In FIG. 3, 14 is a receiving antenna unit, 13 is a GPS receiving unit, a high frequency amplifying unit 32, a frequency converting unit 33 that down-converts the frequency, a frequency synthesizer unit 34, an I signal converting (carrier wave removing) unit 35, and a Q signal. Conversion (carrier wave removal) unit 36, 90 degree phase shifter 37, A / D converters 38 and 39, 15 is a memory (RAM) for temporarily storing information, and 21 is a signal processing unit A DSP unit 41, a CPU unit 42, a pseudo code pattern unit (ROM) 22 for storing or generating a pseudo code pattern A, a DSP ROM 44, a RAM 45, a ROM 46 of the DSP unit 41, and a storage unit connected to the CPU unit 42 7
Reference numeral 12 denotes a receiving unit for obtaining information from the base station 1 of FIG. Further, the memory arrangement in the RAM 45 of the signal processing unit 21 is shown in FIG.

Next, an outline of the operation in FIG. 3 will be described.
A 1.5 GHz _Z band GPS signal that has been subjected to spread spectrum modulation with a PN signal is received by the high frequency amplifier 32 from the receiving antenna unit 14. The signal is down-converted by the frequency synthesizer unit 34 and the frequency conversion unit 33 and converted into, for example, a frequency region of 70 MHz band. The frequency synthesizer unit 34 and the 90-degree phase shifter 37 multiply by a carrier of 70 MHz having a phase difference of 90 degrees, that is, an I signal conversion (carrier wave removal) unit 35 and a Q signal conversion (carrier wave removal) unit 36, The I and Q PN codes that are orthogonal to each other (with the carrier wave of 70 MHz removed) are extracted.
This operation is shown in FIG. FIG. 5 is a diagram showing an outline of operations of the I signal conversion (carrier wave removal) unit 35 and the Q signal conversion (carrier wave removal) unit 36. In FIG. 5, the I signal conversion (carrier wave removal) unit 35, the Q signal conversion (carrier wave removal) ) Part 36, phase shifter 37, A / D converter 38, A / D converter 39, and memory 15 correspond to the reference numerals in FIG.
47 and 48 are multipliers. 49 and 50 are low-pass filters.

  The GPS reception signal down-converted to the 70 MHz band by the frequency conversion unit 33 is represented by PN.cos ((w + Δw) t + Φ). Δw is the Doppler frequency. Δw is a combination of the Doppler frequency fluctuation of the satellite signal captured by the antenna unit 14 and the frequency fluctuation of the frequency synthesizer 34. Here, the description will be made assuming that there is no frequency variation of the frequency synthesizer 34. In this case, Δw is only the Doppler frequency variation of the satellite signal captured by the antenna unit 14.

A signal from the frequency synthesizer 34 in FIG. 3 and a signal having a phase difference of 90 degrees in the 90-degree phase shifter 37 are expressed by carrier waves cos (wt) and sin (wt) orthogonal to each other. When these orthogonal signals and the signal PN.cos ((w + Δw) t + Φ) from the frequency converter 33 are multiplied by the multipliers 47 and 48 and passed through the low-pass filters 49 and 50, PN.cos (Δwt + Φ ), −PN.sin (Δwt + Φ) is obtained. These conversions are generally used as I and Q converters.
In this embodiment, in each of the I and Q converters, the carrier waves cos (wt) and sin (wt) that are orthogonal to the signal PN.cos ((w + Δw) t + Φ), that is, the carrier frequency w is the same. The carrier wave has been removed.

  The signals (analog signals) orthogonal to each other from which the carrier waves have been removed are converted from analog signals into digitized discrete signals by A / D converters 38 and 39, respectively. These two signals are stored in the memory (RAM) 15 for 20 msec (the length of the navigation data 1-bit section). The high frequency amplifier 32, frequency converter 33, synthesizer 34, I signal conversion (carrier wave removal) unit 35, Q signal conversion (carrier wave removal) unit 36, phase shifter 37, A / D converter 38, Each of the A / D converters 39 is general-purpose and widely used.

  The (digital) signal processing unit 21 in FIG. 3 has a CPU unit 42 connected to the receiving unit 12, a memory (RAM) 45 connected thereto, and a memory (ROM) in order to take in the data obtained through the receiving unit 12. 46, a DSP section 41 connected to a memory (RAM) 45, a memory (ROM) 44 connected to the DSP section 41, and a pseudo code pattern section 22. The pseudo code pattern portion 22 is a storage portion (ROM) for storing the pseudo code pattern A in advance. The CPU unit 42 and the DSP unit 41 are connected to each other. The CPU unit 42, the RAM 45, and the ROM 46 operate as a microprocessor.

  The ROM 46 is a part that also stores a digital signal processing execution program, and the configuration of the hardware part of the digital signal processing unit 21, that is, the DSP unit 41, the CPU unit 42, the RAM 45, the ROM 46, and the ROM 44 is a conventional CPU, A general-purpose digital signal processing configuration using a DSP and a memory (RAM, ROM) is widely used and known.

  Then, the digital signal processing unit 21 causes the functional blocks of the Doppler correction unit 16, the polarity changing device 17, the synchronous addition / correlation calculation device 18, the pseudo distance detection device 19, and the position calculation device 20 shown in FIG. A case where this functional block is executed by digital signal processing by software will be described.

FIG. 8 is a diagram for explaining functional block operations of the polarity changing device 17, the synchronous addition / correlation calculating device 18, and the pseudo distance detecting device 19 in FIG.
Pseudo code pattern A pseudocode pattern portion 22 is a set of patterns in a 1023 type from A ₁ to A ₁₀₂₃ in FIG. As described above, the pseudo code pattern A is a data string of a predetermined number of bits (1023 bits) corresponding to a unit frame (one frame) of a signal from the satellite S, and the data is sequentially displaced bit by bit ( It consists of the same number of groups as the predetermined number of shifted bits (1023).

Specifically, the pseudo code pattern A is the same pattern as the PN code from the satellite, has a data string in which 0 and 1 are continuous in a predetermined (fixed) order, and the number of 0s and 1 The sum of the numbers consists of 1023 bits. A pseudo-code pattern A is obtained by forming one group of 1023 bits of one data string of 1023 bits. These 1023 data strings are all different from each other, and the values from A ₁ to A ₁₀₂₃ are shifted one bit at a time. That is, one frame sentence of the PN code is assumed to be [0100110001110 ... 11111], A ₁ is a [10100110001110 ... 1111], A ₂ is [110100110001110 ... 111] next, A ₁₀₂₃ and [0100110001110 ... 11111] . That is, A ₁ to A ₁₀₂₃ are all composed of 1023 bits.
Further, these pseudo code patterns A may be 1 instead of 0 and -1 instead of 1.

Next, the operation of the digital signal processing unit 21 will be described.
FIG. 7 shows a flowchart for executing the functional blocks of the digital signal processing unit 21 in FIG. 2 by software. In FIG. 7, the Doppler correction unit 16, the polarity changing device 17, the synchronous addition / correlation calculation device 18, the pseudorange detection device 19, and the position calculation device 20, which are functional blocks, correspond to the functional blocks in the digital signal processing unit 21 in FIG. 2. is doing. F ₁ to F _{10 in} FIG. 7 are software blocks (processes) processed by the respective functional blocks.

First, a received signal of 1 sec is fetched from the memory 15 (process F ₁ ). The digital data 0.5PN.cos (Δwt + Φ) and −0.5PN.sin (Δwt + Φ) of the I and Q signals stored in the memory 15 from the A / D converters 38 and 39 in FIG. 3 include Doppler components. Next, the Doppler frequency Δw is taken from the outside (base station 1) (step F ₂ ).
The Doppler frequency Δw can be obtained from the base station 1 (server) in FIG. 2 by the receiving unit 12 of the GPS receiver terminal 11. This Δw is received by the CPU unit 42 and stored in the RAM 45.

Next, Doppler correction is performed by the following algorithm (step F ₃ ). FIG. 6 shows an operation for performing Doppler correction on the digital data 0.5PN.cos (Δwt + Φ) and −0.5PN.sin (Δwt + Φ) of the discretized I and Q signals stored in the memory 15 with the Doppler correction information Δw. Show.
FIG. 6 is a functional block diagram performed by a program. 26, 27, 28, and 29 are multipliers, 30 is an adder, and 31 is a subtractor. t is a discretized value and is t = 0: Δt: W × T, and t is a value discretized from 0 to W × T at a sample interval Δt. Sampling frequency is fKHz. Here, f = N will be described. T = 1 msec; W = 1023. The sampling interval Δt is Δt = 1 / f.

The discretized I and Q signals (data) stored in the memory 15 of FIG. 5 are input signals 0.5PN.cos (Δwt + Φ) and −0.5PN.sin (Δwt + Φ) as shown in FIG. expressed.
These signals are multiplied by cos (Δwt) and sin (Δwt) from the Doppler frequency Δw obtained from the receiving unit 12 by the multipliers 26, 27, 28, and 29, and then passed through the adder 30 and the subtractor 31. -0.25PN.sin (Φ) and 0.25PN.cos (Φ).

The multipliers 26, 27, 28, 29, the adder 30, and the subtractor 31 can be easily realized by a program (calculation means). That is, the following calculation is performed.
I / Q signal digital data PN.cos (Δwt + Φ) and −PN.sin (Δwt + Φ) are set to SIin = −0.5PN.sin (Δwt + Φ) and SQin = 0.5PN.cos (Δwt + Φ), −SIin Xcos (Δwt) + SQin × sin (Δwt) and SQin × cos (Δwt) −SIin × sin (Δwt) are calculated. As a result of the calculation, -0.25PN.sin (Φ) and 0.25PN.cos (Φ) are obtained.
The thus obtained I and Q PN signals orthogonal to each other are stored in the memory units 51 and 61 of FIG. 4 (step F ₄ ). This accumulated data does not include the Doppler component Δw.

FIG. 9 shows an example of data in which one of the I and Q signals is accumulated. FIG. 9 is a matrix of 1000 rows and N columns. N is preferably 1023 to 2046 and is 1023 in FIG.
In this figure, one row and N column on the horizontal axis corresponds to one C / A code period per 1023 lines because one C / A code period (1 msec) was sampled at 1023 KHz. That is, one line is one period of C / A code (corresponding to one frame). And since 1 second of data is collected, it shows that it consists of 1000 lines.

These matrixes will be described below by defining the matrix with the following expression. D (M1: M2, N1: N2) is defined as a matrix from the M1st row to the M2th row and from the N1th column to the N2th column. NI: N2 is described as indicating a natural number from N1 to N2. D (A, B: C) indicates the Bth column to the Cth column of the A row. Therefore, the matrix of FIG. 9 can be expressed by D (1: 1000,1: N) (FIG. 9 indicates N = 1023) ).
An operation for obtaining the results of synchronous addition and correlation calculation by making the polarities of the carrier waves the same with respect to the discretized I and Q PN signals (data) of 1000 rows and N columns will be described below.
That is, the operation of the polarity changing device 17, the synchronous addition / correlation calculating device 18, and the pseudo distance detecting means 19 in the flowchart of FIG.

This operation will be described with reference to FIG. Although the blocks in FIG. 8 are actually the same blocks for the I signal and Q signal, and the operations are the same, only one of the signals will be described here.
In FIG. 8, 22 is a pseudo code pattern portion. A ₁ , A ₂ ,..., A ₁₀₂₃ are a set of pseudo code patterns composed of 1023 pieces.
The respective signals of −0.25PN.sin (Φ) and 0.25PN.cos (Φ), which are the outputs of FIG. 6, are stored in the memory units 51 and 61 (FIG. 4). Hereinafter, a signal of 0.25PN.cos (Φ) will be described (the operation is the same for −0.25PN.sin (Φ)).

The polarity discriminating calculator 24 multiplies or divides the unit frame of the satellite reception signal and the pseudo code pattern A to obtain a data string having a predetermined number of bits with positive or negative polarity, and a predetermined bit. And an average calculator 24b that takes the average of the number of data strings and obtains a positive or negative unit numerical value.
Then, when a unit frame (one frame) in the signal to be processed is expressed as IN (t), the following equation is obtained. Note that t, M, and N are integers.

Then, the data corresponding to the first frame of the 1 sec signal is made to correspond to the data of each row from P ₁ to P ₁₀₂₃ , that is, the multiplication / division calculator 24a divides (Equation 2). The result is stored in the memory units 52 and 62 (FIG. 4) (step F ₆ ).
If {PN (m) / A} = 1 (that is, if one frame of the signal coincides with the pseudo code pattern A), Equation 2 can be expressed as Equation 3.

  Note that Equation 3 is 1023 pieces of data per row. Next, when the average calculator 24b takes the 1023 (N) average DDs, Equation 4 is obtained.

  Then, the average value DD is multiplied by the polarity calculator 25 by the next one frame data --- IN (t + Δt): Δt is 1 msec ---- Formula 5). Further, the equation of Equation 5 can be the equation of Equation 6.

Then, this operation is sequentially performed for a signal of 1 second. In addition, although the case where {PN (m) / A} = 1 was described above, {PN (m) / A} = − for a signal when the navigation data is negative (−1). 1 is obtained.
Accordingly, when the navigation data in the processed signal of one frame is positive, the average value DD is obtained as a positive value (1) by this processing, and the positive value (1) is obtained as the following ( (Navigation data will be positive) Multiply one frame and that one frame will be positive. However, when the average value DD is obtained as a negative value (−1) and the negative value (−1) is multiplied by the next frame (the navigation data will be negative), that one frame is positive. It becomes.
In other words, the navigation data is exactly the same for 1 second.

  Note that this identification operation is not performed in one frame including a portion where the navigation data is displaced from positive to negative or from negative to positive. Therefore, the identification of the polarity of the navigation data in the satellite positioning method and system of the present invention excludes the portion where the navigation data is displaced from positive to negative or from negative to positive. And since this excluded part is small as seen from the total number of data, it is not affected at all by the accuracy. Further, as can be seen from the above equation, the value of noise is extremely small.

FIG. 10 is a model diagram in which 1 sec signals are rearranged vertically for each frame (unit frame).
Next, the second arithmetic unit 9 performs synchronous addition for each of 1023 pieces and 1000 rows of data. In general, synchronous addition is widely known as a method for reducing noise in a periodic signal in a digital signal processing circuit. To describe this calculation, in general, when one cycle of a periodic signal is sampled with s sampling pulses and data for m cycles is obtained, data of D (1: m, 1: s) can be obtained ( s is the number of samples, m is the number of additions). At this time, the synchronous addition average result of the Mth row is expressed by the equation (7).

  Assuming that the noise superimposed on the signal is Gaussian with a statistical property, the noise component is known to be reduced to 1 / √m by m additions. In the embodiment of the present invention, m = 1000. Therefore, noise reduction by the synchronous addition of the present invention is 1 / √1000.

The results of the synchronous addition are stored in the memory units 53 and 63 (FIG. 4) (step F ₆ ). Then, the correlation calculation is performed using the synchronously added data and the replica PN code (C / A code signal) that the receiver terminal 11 of FIG. 8 has in advance. The replica PN code (C / A code signal) and the correlation calculation are widely known contents, but will be briefly described below.

In general, a plurality of GPS satellites S travels on the earth, and each satellite S transmits a 1557.42 MHz carrier wave to the earth by performing spread spectrum modulation with a PN signal signal corresponding to each individual satellite S. . For example, it is assumed that 1575.42 MHz is transmitted with spectrum spread modulation by satellite S _{1 using} PN signal a and satellite S _{2 using} PN signal b. In order to take out (demodulate) the signal of the satellite S ₁ at the receiver terminal 11, the receiver terminal 11 side stores in advance the PN signal a 'identical to the PN signal a, and the PN signal a' is used to store the satellite. In S ₁ , the receiver terminal 11 demodulates the PN signal a.

In order to receive the satellite S ₂ , the same PN signal b ′ as the PN signal b must be stored in advance on the receiver terminal 11 side. Therefore, if the receiver terminal 11 does not have all the PN signals corresponding to each satellite S emitted from each satellite S in advance, the signal of each satellite S cannot be received. In the present invention, the PN signal prepared in advance is used as a replica PN code.
Each replica PN code corresponding to each GPS satellite S (which demodulates the satellite reception signal) is stored in advance in the ROM 46 of the signal processing unit 21 provided in the GPS receiver terminal 11. Yes.

  In general, when data X is x (n) (where n = 0: N), data Y is h (n) (where n = 0: N), k is an integer, and 0 ≦ k ≦ N, Equation 8 It is expressed as

  Then, y (1), y (2), y (3)... Y (N) is calculated. Here, in the calculation of y (k), the number of data additions is N. Accordingly, it is known that the noise component is reduced to 1 / √N by adding N times if the noise superimposed on the signal at this time is Gaussian with a statistical property. Therefore, the noise reduction by this calculation is 1 / √N. This calculation is called correlation calculation. (Equivalent correlation calculation is a well-known method that uses FFT as a high-speed operation. Here, a general calculation method is shown for explaining the principle.)

If y (1), y (2), y (3) ... y (N) are the absolute values of y (nn), the absolute value of y (nn) Is a correlation peak value (where 0 ≦ nn ≦ N). Nn at this time is called a delay amount τ. Further, obtaining the delay amount τ and the peak value y (nn) is called obtaining the correlation peak.
If the data X is x (n) obtained by synchronously adding the signal m times, the noise reduction amount is expressed by the equation (9) by this correlation calculation.

In the present invention, the PN signal is x (n), the replica PN code is h (n), m is the number of synchronous additions, N is the number of samples for one period of the PN signal, and m = 1000, N = 1023 as an embodiment. Is assumed.
Therefore, the noise reduction amount can bring about the effect of the above equation (8) only by acquiring the GPS data for 1 sec. That is, the delay amount τ can be obtained even for a very weak signal that is muddy by noise.

Data resulting from the synchronous addition is stored in the memory units 53 and 63 (FIG. 4), and the correlation calculation unit C performs correlation calculation with the replica PN code of FIG.
Although the correlation calculation of the I signal is performed, the same calculation is performed for the Q signal.

The correlation calculation result of the I signal is stored in the memory unit 54 (FIG. 4), and the correlation calculation result of the Q signal is stored in the memory unit 64 (FIG. 4).
Next, I and Q signals are synthesized and stored in the memory unit 70 (FIG. 4).

  The operation of the pseudo distance detection device 19 in FIG. 8 will be described. The pseudo-range detecting device 19 is the result obtained by the correlation calculation unit C, and searches for the data having the maximum absolute value in the data stored in the memory unit 70, and the absolute value of the correlation peak value having the maximum absolute value is obtained. The value and the delay amount τ are detection results.

If this delay amount τ is obtained, a pseudo distance (a distance between the satellite S and the GPS receiver terminal 11) can be obtained from the delay amount τ. Note that the correlation calculation performed by the correlation calculation unit C, the synthesis of the I signal and the Q signal, and the means for obtaining the pseudo distance from the delay amount τ are generally known and will not be described.
Thereafter, in the block of the position calculation device 20 in FIG. 2, information on the base station position from the base station 1, each satellite position, and the pseudorange between each satellite and the base station is acquired by the receiver 12 of the receiver terminal 11. Self-position is determined. In addition, the position calculation device 20 is generally well known and can be easily realized from the pseudorange obtained here, the base station position, each satellite position, and the pseudorange between each satellite and the base station. .

In a GPS positioning system, in the past, it was almost impossible to determine its own position in a building or the like. However, according to the present invention, the sensitivity that can be received by the GPS receiver terminal 11 has been referred to as impossible in the past. Even if the signal is very weak, such as in a building, the sensitivity can be dramatically improved and position measurement is possible.
Basically, ultra-high sensitivity is achieved only by acquiring 1 second of GPS data.

That is, in the present invention, the receiver terminal 11 calculates the polarity of the navigation data in the unit frame by calculating the pseudo code pattern A prepared in advance by the receiver terminal 11 in the unit frame of the satellite reception signal. The polarity discrimination calculation step for calculating the polarity of the satellite reception signal frame (the next unit frame of the unit frame) is sequentially performed on the satellite reception signal of the predetermined time T, and the navigation data of the satellite reception signal at the predetermined time T And the satellite reception signals of a predetermined time T are synchronously added with a unit frame as one unit.
Then, the correlation addition is performed with the synchronous addition PN signal and the replica PN code prepared in advance by the receiver terminal 11, and the correlation peak value and the delay value corresponding to the correlation peak value are detected from the result of the correlation calculation, The pseudorange is obtained from the delay value.
The predetermined time T of the satellite reception signal received and processed by the satellite receiver terminal 11 is not less than 0.5 sec (seconds) and not more than 3 sec (seconds). Particularly preferred is 2 sec (seconds) or less.
If it is less than the lower limit, improvement in sensitivity cannot be expected, and if it exceeds the upper limit, the processing time becomes long and the practicality becomes poor.

Next, another embodiment of the present invention will be described. The functional blocks of the parts of the Doppler correction unit 16, the polarity changing device 17, the synchronous addition / correlation calculation device 18, and the pseudo-range detection device 19 in FIG. 2 have been described with the algorithm by software, but the Doppler correction unit 16 and FIG. For the six functional blocks, the multipliers 26, 27, 28, 29, the adder 30, and the subtractor 31, the functional blocks of the multiplier P and the correlation calculation unit C in FIG. 8 may be configured by hardware.
Moreover, you may comprise by mixing software and hardware.

As a result, the present invention solves the conventional problems, and makes the polarity of the navigation data of the received signal (PN signal) the same with the code prepared in advance in the receiver terminal 11 so that the synchronous addition and correlation By performing the calculation or synchronous addition, it is completely excluded that the signal components cancel each other in the synchronous addition and the sensitivity (S / N) improvement is deteriorated.
That is, dramatic sensitivity (S / N) is obtained by performing synchronous addition and correlation calculation with the same polarity of the navigation data of the received signal (PN signal) with a pseudo code pattern prepared in advance in the receiver terminal 11. ) To obtain a highly sensitive satellite positioning means (method) capable of stable positioning even in a house, behind a building, in a building, etc.

  In addition, since the present invention performs processing based on a satellite reception signal (PN signal) and is different from the method of taking navigation data from an external base station as in the prior art, it can be released from the external base station. In other words, the information of the external base station is unnecessary in order to make the polarity of the satellite reception signal (PN signal) the same, and the polarity of the reception signal (PN signal) is made the same and then the synchronous addition is performed. The noise can be reduced effectively.

That is, even if the navigation data is not received from the external base station by the communication means L, for example, from the received signal received by the receiver terminal 11 existing in the building, the navigation data of the satellite S from the external base station is used. The receiver terminal 11 itself makes the polarity of the navigation data of the PN signal the same and performs synchronous addition. Therefore, all the PN signal signals have the same polarity without depending on the navigation data from the outside by the communication means L, and the PN signal signal buried in the noise emerges from the noise by synchronous addition and correlation calculation. By doing so, ultra-high sensitivity is obtained.
In the present invention, the sensitivity (S / N ratio) is remarkably improved in the correlation calculation by increasing the number of samplings in the A / D converters 38 and 39 only by receiving a short-time continuous signal. The pseudo-range with the satellite S is detected accurately and quickly even in the middle.
The PN signal can also be applied to a GPS signal PN, a Gallileo reception PN signal, or the like.

  As described above, according to the present invention, the number of samplings can be increased, and the sensitivity can be remarkably improved. As in the prior art, data from an external base station is not required, processing can be performed with a signal received by itself, and a PN signal (PN signal) buried in noise can be detected with significantly improved S / N. That is, the PN signal can be efficiently raised from the noise, and the pseudo-range with the satellite S can be accurately and even in a place where the GPS signal (GPS radio wave) is significantly attenuated, such as in a building or a building. Measure with good response.

It is explanatory drawing explaining the PN signal structure in a GPS received signal. It is a block diagram which shows the outline | summary of one Embodiment of this invention. It is a block diagram which shows the structure of a GPS receiver terminal. It is explanatory drawing which shows the memory content of a memory part. It is operation | movement explanatory drawing of the memory part which memorize | stores the I * Q signal conversion carrier wave removal part, an A / D converter, and its output. It is operation | movement explanatory drawing which performs a Doppler correction from I and Q signal after a carrier wave removal, and obtains a PN signal. It is a flowchart from receiving a GPS signal to obtaining a pseudorange. It is explanatory drawing explaining the operation | movement which makes a pseudo code pattern act on a PN signal, and obtains a correlation calculation result. It is a memory | storage state figure of the memory part which memorize | stored the result obtained by sampling a signal. It is the model figure which rearranged the signal vertically for every unit frame. It is a block diagram which shows the conventional GPS positioning system. It is explanatory drawing explaining the conventional GPS positioning system.

Explanation of symbols

8 First operator 9 Second operator
10 Third operator
11 Receiver terminal
19 Pseudo distance detector
22 Pseudo code pattern section
24 Polarity discrimination calculator
24a Multiplication / division calculator
24b Average calculator
25 Polarity calculator A Pseudo code pattern S Satellite T Predetermined time

Claims (6)

  The receiver terminal (11) receives a signal from the satellite (S), and the receiver terminal (11) determines a pseudo distance between the satellite (S) and the satellite terminal (11) by the received satellite signal at a predetermined time (T). A satellite positioning method to be obtained, wherein the receiver terminal (11) performs arithmetic processing on a pseudo code pattern (A) prepared in advance by the receiver terminal (11) in a unit frame of the satellite reception signal, and The polarity determination calculation step for obtaining the polarity of the navigation data in the unit frame and applying the polarity to the received signal frame is sequentially performed on the satellite reception signals for the predetermined time (T), and the predetermined time (T) The polarity of the navigation data of the satellite reception signal is made the same, and the satellite reception signal of the predetermined time (T) is synchronously added with a unit frame as one unit, and the synchronous addition PN signal obtained by synchronous addition and the receiver Terminal (11) is used in advance Correlation calculation is performed with a replica PN code, a correlation peak value and a delay value corresponding to the correlation peak value are detected from the result of the correlation calculation, and the pseudo distance is obtained from the delay value Satellite positioning method. The pseudo code pattern (A) in the polarity discrimination calculation step is a data string of a predetermined number of bits corresponding to a unit frame of a signal from the satellite (S), and the predetermined number of bits displaced in order bit by bit. satellite positioning method according to claim 1, wherein comprising a same number group with. The satellite positioning method according to claim 1 or 2 , wherein the predetermined time (T) of the satellite reception signal received and processed by the satellite receiver terminal (11) is 0.5 seconds or more and 3 seconds or less.   The receiver terminal (11) receives a signal from the satellite (S), and the receiver terminal (11) determines a pseudo distance between the satellite (S) and the satellite terminal (11) by the received satellite signal at a predetermined time (T). In the satellite positioning system to be obtained, the receiver terminal (11) includes a pseudo code pattern unit (22) in which a pseudo code pattern (A) is stored in advance, and the pseudo code in a unit frame of the satellite reception signal. A polarity discrimination calculator (24) for calculating the polarity of the navigation data in the unit frame by calculating the pattern (A), a polarity calculator (25) for applying the determined polarity to the frame of the received signal, The polarity discrimination computing unit (24) and the polarity computing unit (25) are sequentially operated for a predetermined time (T) of the satellite reception signal to change the polarity of the navigation data of the satellite reception signal for the predetermined time (T). First computing unit to be identical (8) A second arithmetic unit (9) for synchronously adding the unit frame as one unit for the satellite reception signal of the predetermined time (T) with the same polarity of the navigation data, the synchronous addition PN signal and the synchronous addition A third computing unit (10) that performs correlation calculation with a replica PN code prepared in advance by the receiver terminal (11), and detects a correlation peak value and a delay value corresponding to the correlation peak value from the result of the correlation calculation And a pseudorange detecting device (19) for obtaining the pseudorange from the delay value. The polarity discrimination computing unit (24) multiplies and divides to obtain a data string of a predetermined number of bits whose polarity is positive or negative by multiplying or dividing the unit frame of the satellite reception signal and the pseudo code pattern (A). 5. The satellite positioning system according to claim 4 , further comprising: a calculator (24a); and an average calculator (24b) that averages the data string of the predetermined number of bits and obtains a positive or negative unit numerical value. The pseudo code pattern (A) is stored in the pseudo code pattern section (22) of the receiver terminal (11), and the pseudo code pattern (A) is a unit of a signal from the satellite (S). 6. The satellite positioning system according to claim 4 or 5, comprising a data string of a predetermined number of bits corresponding to a frame and a group having the same number as the predetermined number of bits displaced in order by one bit.

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