JP4092317B2 - Satellite positioning method and satellite positioning system - Google Patents

Description

  The present invention relates to a satellite positioning method and a satellite positioning system that calculate a self-position by obtaining a pseudorange 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.
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. 19, the receiving unit 104 includes an RF-to-IF converter 106 equipped with a GPS receiving antenna 105, an A / D converter 107 that converts 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. 20 (A) to FIG. 20 (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. 20 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. 20A, the phase of each frame (FRAME: 1 msec each) 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. 20B is a diagram for explaining the case where a GPS signal (C / A code signal) is extracted from the rising point (data head) where 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). In the operation of FIG. 20B, the reception signal (C / A code) is started from a certain point of time, and the reception signal (C / A code) is added and averaged by 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. 20 (B), the continuous reception signals captured from a certain point in time are synchronously added and averaged every four periods (four C / A codes). Next, FIG. 20 (C) shows the correlation calculation result of the replica PN code (replica C / A code) inside the receiver and the result of FIG. 20 (B). The polarity of the peak value of the correlation calculation is positive if the polarity obtained as a result of the respective synchronous additions in FIG. 20B and the polarity of the replica PN code in the receiver match, and negative if they differ.

  FIG. 20 (D) is a diagram showing the absolute value of the correlation result of FIG. 20 (C). That is, the absolute value of each correlation calculation is taken in FIG. In FIG. 20 (E), each correlation calculation obtained as 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.
Therefore, 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 FIGS. 20 (D) and 20 (E) and adding them synchronously does not reduce the white noise itself, so the sensitivity (S / N) cannot be improved. There is a problem that it is sufficient.

  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. 20B 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. When 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, and therefore 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.

That is, the receiver terminal is connected to the external base station via, for example, the Internet line, and information such as the satellite position is periodically transmitted from the base station. However, even if the calling side is periodic, if such a communication line is interposed, a time shift (time delay) occurs at the receiving side with respect to the time of transmission, and the amount of shift varies depending on the congestion state of the line. To do. Accordingly, the satellite information received from the base station by the receiver terminal and the received signal from the satellite that has started processing at the same time are not simultaneous, and the satellite information from the base station is in the past. If the position is calculated based on the past satellite position, a large error occurs and the accuracy is low.
In order to eliminate the time shift, a means using an atomic clock is conceivable. However, in this case, the configuration is complicated and expensive, and there is a problem in that it cannot be completely matched.

  Therefore, the present invention is capable of knowing the self-position even if a signal from a satellite is received in a building or the like, that is, even if it is a weak satellite reception signal that is attenuated, and has a very high sensitivity and responsiveness. The present invention provides a satellite positioning method and a satellite positioning system with extremely high detection accuracy.

Satellite positioning method according to the present invention, satellite positioning that calculates self-position calculated pseudorange between the receiver terminal to the information communication between the external base station and the satellite as well as receiving signals from satellites In the method, the time corresponding to one bit of navigation data of the satellite reception signal received by the receiver terminal from the satellite is defined as the acquisition time of the front part and the processing time of the remaining rear part from the start of data acquisition, The reception signal acquired within the acquisition time is subjected to arithmetic processing including correlation calculation during the subsequent processing time, and a predetermined number of reception signals corresponding to the acquisition time are acquired after sequentially delaying the start of data acquisition step by step. In addition, each of the received signals is subjected to the arithmetic processing including correlation calculation during each subsequent processing time, a delay value is obtained by detecting a peak value in the result of the arithmetic processing, The navigation data of the satellite reception signal received by the receiver terminal is compared with the external navigation data received by the receiver terminal from the external base station to calculate the delay time of the external navigation data, and based on the delay time The receiver terminal estimates the satellite position when processing the satellite reception signal, calculates the pseudorange based on the estimated satellite position and the delay value, and calculates its own position.
Further, the arithmetic processing performed during the processing time applies a pseudo pattern prepared in advance by the receiver terminal to the synchronous addition signal obtained by synchronously adding the reception signals from the satellite acquired within the acquisition time. Is applied to the synchronous addition signal to make the polarity by the navigation data the same, and the signal obtained in the polarity correction calculation step and the replica PN code prepared in advance by the receiver terminal And a correlation calculation step for performing correlation calculation.

In addition, the calculation of the delay time is performed by causing the navigation data having the predetermined number of bits acquired from the satellite and the external navigation data having the same number of bits as the navigation data to interact with each other while shifting each bit. the time corresponding to a shift bit number to the pattern matches Ru determined as the delay time.

Furthermore, the satellite positioning system according to the present invention includes a receiver terminal that receives a signal from a satellite and communicates information with an external base station to calculate a pseudorange with the satellite and calculate a self-position. In the satellite positioning system, the receiver terminal compares the navigation data of the satellite reception signal received from the satellite with the external navigation data received from the external base station, and calculates the delay time of the external navigation data. A delay time calculation unit; a satellite position correction calculation unit that estimates a satellite position when the receiver terminal processes a satellite reception signal based on the delay time; and a self-position for obtaining a pseudorange based on the estimated satellite position of and a position calculator that performs calculations, moreover, the delay time calculation unit, the one of the external navigation data of the same bit number as the predetermined number of bits of the navigation data and該航method data A first operation unit that sequentially performs a combination operation on each part while shifting each bit, a second operation unit that calculates a sum of the results of the combination operation, and a maximum value obtained when a maximum value is obtained And a third calculation unit that obtains a time corresponding to the number of shifted bits as the delay time.

According to the present invention, the amount of data required for arithmetic processing can be reduced, and even a memory with a small capacity can be used. Further, the circuit in the receiver terminal 11 can be simplified, and the processing speed can be increased. By increasing the processing speed, it is possible to output information in real time.
Furthermore, PN signals buried in noise can be detected with significantly improved S / N even in signals at the polarity reversal of navigation data, and GPS signals (GPS radio waves) can be detected in buildings and buildings. Even in a place where the attenuation is, the sensitivity can be remarkably improved, the pseudorange with the satellite S can be detected, and the self-position can be calculated with high accuracy and responsiveness.

Furthermore, even if there is a time delay in the communication network (network) between the external base station and the receiver terminal, and the time delay amount fluctuates, the satellite position is corrected to an accurate position and estimated. This enables position detection with high accuracy.
In addition, even if Doppler is present in the signal from the satellite (even if it remains), the time delay can be obtained reliably, the true position of the satellite can be estimated, and the accuracy of position detection can be improved. Can do.

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, a receiver terminal 11 that receives a signal from a satellite S and communicates information with an external base station 1 via a communication means L (communication network) obtains a pseudorange with the satellite S. A satellite positioning method and a satellite positioning system for calculating a self-position.
2 and 3, S ₁ , S ₂ , S ₃ , and S ₄ are target positioning satellites that travel around the earth, and 1 is an external base station provided on the ground. 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, base station position, each satellite position, pseudo distance between each satellite and the receiving antenna 2 position, and the like from the received satellite received signal (GPS signal). These pieces of information are transmitted to the receiver terminal 11 by the transmitter 5 via the communication means L (by information communication). This transmission is generally performed by broadcasting. The communication means L may be a mobile phone line, terrestrial broadcast, or satellite broadcast. Alternatively, an Internet line may be used, and all possible communication means L (by an electromagnetic method) are targeted.

  11 is a GPS receiver terminal. Information such as Doppler information and base station position, each satellite position, and pseudo distance between each satellite and the base station is 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 seen directly, but also in the shade of trees (in addition to normal outdoor reception) or the center of a building (due to reinforced concrete) We also assume places where the strength of is quite weak.
The GPS receiver 13 (RF tuner) has an A / D conversion portion that converts an analog signal of a GPS reception signal ----- PN signal ---- to a digital signal. The digitized PN signal is sent to the next signal processing unit 21.
The above configuration is widely used in general with conventional GPS technology, and detailed description thereof is omitted.

  The receiver terminal 11 includes a pseudo pattern unit 22 that stores a pseudo pattern A (described later), a signal processing unit 21, a pseudo distance detection unit 19, and a position calculation unit 20. The signal processing unit 21 includes an I / Q signal conversion carrier removal units 35 and 36, a Doppler correction unit 16, a PN polarity correction calculation unit 25, a (synchronous addition /) correlation calculation unit 10, a delay time calculation unit 40, and a position correction calculation unit. 41.

As described above, the external base station 1 transmits external navigation data including various information to the receiver terminal 11 via the communication means L. As shown in FIG. 4, information from the base station server of the external base station 1 is periodically transmitted and transmitted as a pulse signal (for example, at 1 pps). That is, the information is transmitted as a pulse signal for each information of a predetermined time (for 1 second). However, since a time delay occurs in the communication means L between the external base station 1 and the receiver terminal 11, the information received by the receiver terminal 11 from the base station 1 is different from the transmission time from the base station 1. Will occur. As a result, as shown in FIG. 4, the receiver terminal 11 that has started to receive a signal from the satellite S by the trigger receives the information from the base station 1 and at the same time starts collecting and calculating the satellite received signal. Even if the position is calculated, the information received from the base station 1 is about the past. That is, this information is about the past position of the satellite S for which the pseudorange is to be obtained, and is different from the true satellite position when the receiver terminal 11 starts the arithmetic processing.
This will be explained with reference to FIG. 3. Each satellite S moves at a high speed from T ₁ to T ₂ during the predetermined time (1 sec), and the signal from the satellite S processed by the receiver terminal 11 is transmitted from the satellite S to Tx. In contrast, the information received from the base station 1 is for the position of the satellite S at the position T ₁ .

Therefore, the receiver terminal 11 of the satellite positioning system of the present invention includes a delay time calculation unit 40 that self-detects this time delay at the receiver terminal 11, and a satellite position correction calculation unit that obtains the true satellite S position by the time delay. 41 and a position calculation unit 7 for calculating the position based on the true satellite S.
In other words, the delay time calculation unit 40 compares the navigation data of the satellite reception signal received by the receiver terminal 11 from the satellite S and the external navigation data received by the receiver terminal 11 from the external base station 1 to determine the external navigation data. Calculate the delay time. Then, the satellite position correction calculation unit 41 corrects the position information from the base station 1 based on the delay time, estimates the satellite position when the receiver terminal 11 processes the satellite reception signal, and the position calculation unit 7 Based on the estimated satellite position and a delay value (delay amount τ) (to be described later), a pseudorange is obtained and the self position is calculated.

First, the main part of the present invention will be described in general. FIG. 6 shows a flowchart for calculating the self-position from the signal received by the GPS receiver 13.
In the satellite positioning method in the satellite positioning system according to the present invention, first, a time (20 msec) corresponding to one bit of the navigation data of the satellite reception signal received by the receiver terminal 11 from the satellite S is calculated from the start of data acquisition. the acquisition time T ₁ of the, considered as remaining after part of the processing time T _2. The start of data acquisition is not limited to the boundary of polarity inversion, but can be started from an arbitrary position (see FIG. 10) with respect to the satellite reception signal.
This will be described with reference to FIG. 10. Of 20 msec, for example, 15 msec from the start of data acquisition is set as the acquisition time T _1, and the remaining 5 msec is set as the processing time T ₂ . If (acquisition time T ₁ ) + (processing time T ₂ ) = 20 msec, these times can be set freely, but the processing time T ₂ is a divisor of the time corresponding to 1 bit of navigation data. Value.

A carrier wave is removed from the satellite reception signal digitalized by the GPS receiving unit 13 and Doppler correction is performed, and acquisition of data from the satellite S is started for the signal to perform arithmetic processing. That is, in FIG. 10, the received signal acquired within the acquisition time T ₁ is processed after that, and a predetermined number of reception signals for the acquisition time T ₁ are acquired after the start of data acquisition is sequentially delayed by the minute time i. At the same time, each received signal is subjected to arithmetic processing thereafter.
That is, the reception signal acquired within the acquisition time T ₁ is subjected to arithmetic processing including correlation calculation (described later) during the subsequent processing time T ₂ , and the acquisition start time is sequentially delayed by the minute time i. A predetermined number of T ₁ received signals are acquired, and each received signal whose acquisition start is sequentially delayed is subjected to arithmetic processing including correlation calculation during each subsequent processing time T ₂ , and the peak value in the result of the arithmetic processing The delay value is obtained by detecting.

This will be explained in detail with reference to FIG. 10. For satellite reception signals whose navigation data polarity changes periodically, data acquisition starts from an arbitrary position (arrow X), and reception signals are acquired for 15 msec. To do. This acquired signal is processed in the next consecutive 5 msec (→ 1.). Furthermore, the received signal is acquired for 15 msec (arrow X ₂ ) after a minute time i (5 msec) from the start of this data acquisition (arrow X), and the acquired signal is subjected to the same arithmetic processing in the next consecutive 5 msec. (→ 2.). Further, a received signal is acquired for 15 msec after a delay of 10 msec from the start of data acquisition (arrow X) (arrow X ₃ ), and the acquired signal is subjected to the same arithmetic processing in the next consecutive 5 msec (→ 3 .) Further, a received signal is acquired for 15 msec after a delay of 15 msec from the start of data acquisition (arrow X) (arrow X ₄ ), and the acquired signal is subjected to the same arithmetic processing in the next consecutive 5 msec (→ 4 .)

Thus, the timing of the data acquisition start delaying sequentially (3 times), separate (four) data string acquired respectively acquisition time T ₁ sentence of the received signal as the respective process time arithmetic processing of each data T Do it in _two . That is, with respect to one satellite reception signal, four separate data strings with different data acquisition start timings are acquired, and each is processed. The data string of each acquisition time T ₁ is subjected to synchronous addition in units of 1 frame (1 msec).
The number of data strings (four) is a value obtained by dividing the time corresponding to one bit of the navigation data by the processing time T ₂ (that is, 20 msec ÷ 5 msec = 4). Note that the minute time i for sequentially delaying the start of data acquisition is the same as the processing time T ₂ (ie, 5 msec).

By starting the acquisition of data as described above, for navigation data whose polarity changes in units of 1 bit, a data string having the same polarity over the entire acquisition time T ₁ (which does not change in the middle) is always obtained. It is done. That is, in the case of FIG. 10, the data acquisition (arrow X ₄ ) data sequence (→ 4.) That started 15 ms after the first data acquisition start X (X ₁ ) is the first, second, third In both rounds, the polarity of the received signal during the acquisition time T ₁ does not change midway. In other words, a data string of the acquisition time T ₁ that does not cross the boundary of polarity inversion of the navigation data is obtained. This data string acts as effective in peak value detection.

Then, the peak value is detected and the delay value is obtained by the same operation as before according to the result of the calculation process (correlation calculation) in each of the four data strings, and the delay time calculation unit 40 and the satellite position correction calculation unit 41 work. Thus, the true position of the satellite S is obtained at the receiver terminal 11, the pseudo distance is obtained from the delay value, and the self position is calculated.
The arithmetic processing performed during the processing time T ₂ will be described. A pseudo-preparation prepared in advance by the receiver terminal 11 is added to the synchronous addition signal obtained by synchronously adding the reception signal from the satellite S acquired within the acquisition time T ₁ . A pattern correction operation step in which the pattern A is further applied to the synchronous addition signal to make the polarity by the navigation data identical, and the signal (polarity correction data) obtained in the polarity correction calculation step and the receiver A correlation calculation step of calculating a correlation with a replica PN code prepared in advance by the terminal 11.

That is, in FIG. 2, the calculation processing performed during the processing time T ₂ is performed in the calculation block unit 23 included in the signal processing unit 21, and the calculation block unit 23 includes the polarity correction calculation unit 25 and the correlation calculation unit 10. .
The polarity correction calculation unit 25 multiplies or divides the synchronous addition signal obtained by synchronously adding the received signal from the satellite S acquired within the acquisition time T ₁ by the pseudo pattern A prepared in advance by the receiver terminal 11. The calculation unit 25a (see FIG. 17), an average calculation unit 25b that averages the results in the multiplication / division calculation unit 25a, and a polarity correction unit 25c that further multiplies the synchronous addition signal by the results in the average calculation unit 25b.
Further, the correlation calculation unit 10 performs correlation calculation using the signal obtained by the polarity correction calculation unit 25 and the replica PN code prepared in advance by the receiver terminal 11.

The polarity correction calculation unit 25 will be further described. The pseudo pattern A for correcting (changing) the polarity of the received signal prepared (stored) in advance in the pseudo pattern unit 22 of the receiver terminal 11 is sequentially delayed in the start of data acquisition. Then, each of the plurality of received signals obtained is applied to data obtained by synchronous addition in units of one frame (1 msec), and the polarity of the received signals is corrected (for the same purpose).
Note that the synchronous addition performed in units of one frame with respect to a plurality of acquired signals by sequentially delaying the start of data acquisition may be performed simultaneously with acquisition (step by step) during the acquisition time T ₁ , or processing after the acquisition time T ₁ the function of the synchronization addition and correlation calculation unit 10 at time T _2, may be carried out, the calculation processing performed during the processing time T _2, in addition to the correlation calculation include polar modification.

  The pseudo pattern A is used in this polarity correction calculation step, and is a data string having a predetermined number of bits corresponding to a unit frame (one frame) of a signal from the satellite S (as will be described later). It consists of the same number of groups as a predetermined number of bits displaced (shifted) in order.

The correlation calculation unit 10 performs correlation calculation on the data whose polarity is changed (identified), and then detects the value (delay amount τ) from which the correlation calculation peak value becomes the maximum value. The delay time calculation unit 40 obtains the delay time of the external navigation data, the position correction calculation unit 41 corrects the position of the true satellite S, and the pseudorange detection unit 19 receives the receiver terminal 11 and the satellite S. Is detected.
Moreover, noise reduction by synchronous addition and correlation calculation is improved to the maximum by the PN signal having the same polarity. Then, the pseudo distance detection unit 19 can detect the pseudo distance in a state where the noise reduction is improved to the maximum.

That is, the receiver terminal 11 includes a calculation block unit 23 that performs a calculation process including correlation calculation on the received signal acquired within the acquisition time T ₁ and detects a peak value during the subsequent processing time T ₂ , and a calculation block unit A position calculation unit 7 that obtains a delay value from the result of 23, calculates a pseudo-range from the delay value and the true satellite position obtained by the position correction calculation unit 41, and calculates its own position. Furthermore, the operation block 23, the processing time after T ₁ each acquisition time in the received signal each to acquire a predetermined number of received signals ₁ sentence acquisition time T the data acquisition starts sequentially delayed by a minute time i T ₂ to perform the above calculation processing including correlation calculation. The position calculation unit 7 includes a pseudo distance detection unit 19 and a position calculation unit 20.

Further, in the present invention, the result of the arithmetic operation performed during processing time T ₂ (correlation calculation), when the peak value only required for self-location calculation is not detected is attenuated signals from (satellite In this case (when the peak value cannot be detected), the received signal of the previous acquisition time T ₁ that is the target of the calculation process in this case (for example, the first acquisition time T ₁₎ The received signal having the acquisition time T ₁ out of the next (second) navigation data 1-bit signal is accumulated synchronously added, and then the calculation process including the correlation calculation is performed. That is, the arithmetic processing performed during the processing time T ₂ includes (cumulative) synchronous addition in addition to the correlation calculation.

This operation will be described in detail. In FIG. 10, even if four separate data strings are acquired from the start of data acquisition (arrow X) and processed, the peaks necessary for self-position calculation (for example, buried in noise) If a value cannot be detected, after the first acquisition time T ₁ and processing time T ₂ have elapsed from the start of data acquisition (arrows X ₁ , X ₂ , X ₃ , X ₄ ) in each of the four data strings. After the first acquisition time T ₁ , the signal acquisition is performed after the first processing time T ₂ .
Then, a received signal acquired by the acquisition time T ₁ of the second round, the received signal that has already been acquired in the first round of acquisition time T _1, synchronous addition (cumulative synchronous addition) to the subsequent first An arithmetic process including a correlation calculation is performed using the data obtained by cumulative synchronous addition during the _second processing time T2.
As shown in the flowchart of FIG. 6, this cumulative synchronous addition is repeated a plurality of times until a peak value necessary for position calculation can be detected, and when a predetermined peak value necessary for self-position calculation is obtained, The next position calculation unit 7 calculates the self position.

  When this cumulative synchronous addition is performed, the result is stored in the memory and processed, but the past received signal is no longer needed and is deleted. That is, since the received signals are cumulatively added and only four data strings are required, it can be said that a small-capacity memory is sufficient.

That is, the calculation block unit 23 includes a determination processing unit 24 (see FIG. 6) that determines whether or not the peak value necessary for self-position calculation has been detected based on the result of the calculation processing by the calculation block unit 23. in case it's not peak value detected by determining parts 24, the arithmetic processing including from acquisition time T ₁ sentence of the received signal of the following navigation data 1 bit sentence signal and by accumulating synchronous addition, the correlation calculation The calculation block unit 23 is configured to perform the above.

Next, the delay time calculation unit 40 and the satellite position correction calculation unit 41 will be described. First, FIG. 11 (a) shows navigation data received by the receiver terminal 11 from the satellite S. FIG. 11 (b) shows the polarity when the navigation data is synchronously added in a 20 msec section, and there is no Doppler.
FIG. 11 (c) shows the external navigation data received by the receiver terminal 11 from the external base station 1, and shows the polarity for each 20 msec section as in FIG. 11 (b). Note that FIG. 11 (B) and FIG. 11 (C) show a state in which the mutual polarity patterns coincide with each other.
FIG. 11 (d) shows the navigation data received by the receiver terminal 11 from the satellite S, in which Doppler exists (the Doppler remains), and the range surrounded by the broken line is reversed in polarity by the Doppler. ing. However, in FIGS. 11 (d) and 11 (c), the polarities are partially inverted, but it can be said that the mutual polar patterns are in agreement.

Therefore, the calculation of the delay time performed by the delay time calculation unit 40 is performed while shifting either the navigation data having a predetermined number of bits acquired from the satellite S or the external navigation data having the same number of bits as the navigation data bit by bit. The time (corresponding to the number of shifted bits until the mutual polarity patterns coincide with each other) is obtained as a delay time through interaction (combined operation and sum operation described later).
That is, the navigation data received from the satellite S and the external navigation data received from the external base station 1 are compared, and even if the polarity patterns do not match (shift), for example, the navigation data is 1 bit (20 msec). ) If you shift the external navigation data one by one in order, the mutual polarity patterns will always match. That is, the time corresponding to the number of bits to be shifted until the polarity patterns match can be obtained as the delay time of the external navigation data.

Then, the satellite position estimation based on the delay time performed in the satellite position correction calculation unit 41 is calculated by the position and orbit of the satellite S based on the external navigation data received from the external base station 1 and the delay time, This is done by estimating the satellite position after the delay time. Specifically, in FIG. 3, the position where the satellite S has moved after the delay time since the information indicating that the position of the satellite S is T ₁ is transmitted from the external base station 1 is Tx. From the position T ₁ , the ratio of the time (1 sec) until the external base station 1 next transmits the information that the position of the satellite S is T ₂ after a predetermined time (1 pps) and the delay time, trajectory of the satellite S from ₁ to the position T ₂ be to allocate, it can estimate the position Tx satellite. Since the satellite S has a circular orbit, the trajectory can be calculated by time distribution as an arc shape. For simplification of calculation, the trajectory may be linearly distributed as a straight line.

  The above is a description of the entire main part of the present invention. Next, referring back to FIG. 2 and FIG. 5, referring to the hardware block diagram of the GPS receiver terminal 11, the entire satellite positioning system and satellite positioning method are described. This will be described more specifically.

The code of each block in FIG. 2 corresponds to the code of each block in FIG. The Doppler correction unit 16, the polarity correction calculation unit 25, the (synchronization addition) correlation calculation unit 10, the delay time calculation unit 40, the position correction calculation unit 41, the pseudo distance detection unit 19, and the position calculation unit 20 in FIG. 2 are functional blocks. is there.
The means for configuring the functional block may be a hardware configuration, a software configuration, or a mixed configuration. In FIG. 5, a hardware configuration for executing software processing, which is a means constituting this functional block, is indicated by a signal processing unit 21 and a CPU unit 8.

In FIG. 5, 14 is a receiving antenna unit, 13 is a GPS receiving unit, and the GPS receiving unit 13 includes a high frequency amplifying unit 32, a frequency converting unit 33 for down-converting the frequency, a frequency synthesizer unit 34, an intermediate frequency amplifying unit 38, An A / D converter unit 39 is included. The signal processing unit 21 includes an I signal conversion carrier removal unit 35, a Q signal conversion carrier removal unit 36, a 90-degree phase shifter 37, a Doppler correction unit 16, a polarity correction calculation unit 25 (not shown), ) A correlation calculation unit 10, a delay time calculation unit 40, and a position correction calculation unit 41. Further, as shown in FIG. 2, a pseudo pattern portion 22 composed of a ROM for storing or generating the pseudo pattern A is provided.
The CPU unit 8 includes a CPU 42, a RAM 45 and a ROM 46 connected to the CPU 42. Reference numeral 12 denotes a receiving unit for obtaining information from the base station 1 of FIG.

Next, an outline of the operation will be described with reference to FIG.
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. A / D conversion is performed by the A / D converter 39 through the intermediate frequency amplifier 38, and the satellite reception signal is converted from an analog signal into a digitized discrete signal.

  The received signal down-converted and digitized by the frequency conversion unit 33 into the 70 MHz band 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 fluctuation of the satellite signal captured by the antenna unit 14.

  Then, the carrier removal units 35 and 36, the Doppler correction unit 16, the polarity correction calculation unit 25, the (synchronous addition /) correlation calculation unit 10, the delay time calculation unit 40, the satellite position correction calculation unit 41, the pseudo distance detection unit 19, and the position The functional block of the calculation unit 20 is executed. A case where this functional block is executed by digital signal processing by software will be described.

  FIG. 6 shows a flowchart for executing the functional blocks in FIG. 2 by software. In FIG. 6, carrier wave removal units 35 and 36, Doppler correction unit 16, polarity correction calculation unit 25 (not shown), (synchronous addition /) correlation calculation unit 10, delay time calculation unit 40, satellite position correction calculation unit, which are functional blocks in FIG. 6. 41, the pseudo distance detecting unit 19, and the position calculating unit 20 correspond to the functional blocks in the digital signal processing unit 21, the position calculating unit 7 and the CPU unit 8 of FIG.

  FIG. 7 is a diagram showing an outline of operations of the I signal conversion carrier removal unit 35 and the Q signal conversion carrier removal unit 36. The frequency synthesizer unit 34 and the 90 degree phase shifter 37 convert the received signal into 90 degrees. The parts multiplied by the 70 MHz carrier waves having different phases, that is, the I signal conversion carrier removal unit 35 and the Q signal conversion carrier removal unit 36 extract the I and Q PN received signals orthogonal to each other (to each other with the carrier 70 MHz removed). It is. Reference numerals 47 and 48 denote multiplication units. 49 and 50 are low-pass filters.

A signal from the frequency synthesizer 34 in FIG. 5 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 A / D converter 39 are multiplied by the multipliers 47 and 48 and passed through the low-pass filters 49 and 50, 0.5 PN. cos (Δwt + Φ), −0.5PN.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 orthogonally received signals (digital signals) from which the carrier waves have been removed are continuously (subsequently) Doppler corrected without being stored in the memory.
The above-described high frequency amplifier 32, frequency converter 33, synthesizer 34, intermediate frequency amplifier 38, A / D converter 39, I signal conversion carrier removal unit 35, Q signal conversion carrier removal unit 36, phase shift The container 37 is a general-purpose device and is generally widely used.

The digital data 0.5PN.cos (Δwt + Φ) and −0.5PN.sin (Δwt + Φ) of the I and Q signals includes a Doppler component. The Doppler frequency Δw is taken from the outside (base station 1).
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 42 and stored in the RAM 45.

Doppler correction is performed by the following algorithm. FIG. 8 shows an operation for performing Doppler correction on the digital data 0.5PN.cos (Δwt + Φ) and −0.5PN.sin (Δwt + Φ) of the I and Q signals with the Doppler correction information Δw.
FIG. 8 is a functional block diagram performed by a program. Reference numerals 26, 27, 28, and 29 denote multiplication units, 30 denotes an addition unit, and 31 denotes a subtraction unit. 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 received signals (data) of the I signal and the Q signal, which are discretized and the carrier wave is removed, are represented by input signals 0.5PN.cos (Δwt + Φ) and −0.5PN.sin (Δwt + Φ) as shown in FIG.
These signals are multiplied by cos (Δwt) and sin (Δwt) from the Doppler frequency Δw obtained from the receiving unit 12 by the multiplying units 26, 27, 28, and 29, and then passed through the adding unit 30 and the subtracting unit 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. 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 input to the operation block unit 23 without being stored in the memory. This input data does not include the Doppler component Δw.

FIG. 9 shows another embodiment for explaining the Doppler correction unit 16. According to this, the Doppler correction can be simplified. 9A shows a Doppler correction unit for the I signal unit, and FIG. 9B shows a Doppler correction unit for the Q signal unit. In this embodiment, cos (Δwt) and sin (Δwt) from the Doppler frequency Δw are converted to one bit. That is, as shown in the drawing, cos (Δwt) and sin (Δwt) are each made +1 or −1 (0).
In FIG. 9A, the input signals are output in the order of (1), (3), (2), and (4), and this is repeated. In FIG. 9B, the data are output in the order of (3) (2) (4) (1), and this is repeated.

Next, with respect to the received signal subjected to Doppler correction, the polarity is changed (corrected), the synchronous addition is performed, and the correlation calculation is performed, and the delay time of the external navigation data from the external base station 1 is set. The operation for obtaining and estimating the true position of the satellite S at the time of data processing will be described.
That is, the operations of the polarity correction calculation unit 25, the (synchronization addition /) correlation calculation unit 10, the delay time calculation unit 40, and the satellite position correction calculation unit 41 are entered.

FIG. 14 is a general view for explaining the functional block operations of the polarity correction calculation unit 25 and the (synchronous addition /) correlation calculation unit 10 in FIG. 2, and FIGS. 16, 17 and 18 are detailed diagrams of the respective blocks. . FIG. 15 is a diagram illustrating the delay time calculation unit 40 and the satellite position correction calculation unit 41.
First, the pseudo pattern A of the pseudo pattern portion 22 for correcting the polarity is a set of pattern groups of 1023 types from A ₁ to A ₁₀₂₃ in FIG. As described above, the pseudo 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 (shifted) bit by bit. ) And a predetermined number of bits (1023).

Specifically, the pseudo pattern A is the same pattern as the CA code (PN code) from the satellite, and has a data string in which 0 and 1 are continued in a predetermined (fixed) order. The sum of the number and the number of 1s consists of 1023 bits. Then, a pseudo pattern A is obtained by composing one group of 1023 bits of one data string of 1023 bits. These 1023 data strings are all different from each other, and values from A ₁ to A ₁₀₂₃ are shifted one bit at a time (shifted). 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.
These pseudo patterns A may be 1 instead of 0 and -1 instead of 1.

  The operation in FIG. 14 will be described. Actually, although the blocks (first inputs) in FIG. 14 are the same blocks for the I signal and Q signal, respectively, and the operations are the same, only one of the signals will be described here. Hereinafter, the signal of 0.25PN.cos (Φ) will be described.

Signals to be input to the multiplication / division calculation unit 25a and the polarity correction unit 25c of FIG. 17 included in the polarity correction calculation unit 25 are prepared by the processing shown in FIGS. That is, with respect to the Doppler-corrected received signal, a predetermined number (four) of acquisition signals of acquisition time T ₁ are sequentially delayed by 5 msec up to a maximum of 15 msec.
When the correlation calculation is completed for the received signal within the _first acquisition time T ₁ and no peak value is obtained, the reception signal is acquired for the second acquisition time T ₁ (for example, As shown in FIG. 10, when receiving signals from the first time to the third time are required to obtain the peak value, data of 15 × 3 = 45 msec is obtained).

As shown in FIG. 16, the received signal (first signal) acquired at each acquisition time T ₁ (for 15 msec) is synchronously added 15 times in units of 1 msec to obtain the second signal. Since a predetermined number of received signals are obtained by sequentially delaying the start of data acquisition, second signals from the first (→ 1.) To the fourth (→ 4.) Are obtained.

Then, as shown in FIG. 17, a polarity correction calculation step is further performed in which the pseudo signal A prepared in advance by the receiver terminal 11 is applied to the second signal, and further applied to the second signal.
Specifically, as illustrated in FIG. 17, the polarity correction calculation unit 25 includes a multiplication / division calculation unit 25a that multiplies or divides the second signal by a pseudo pattern A prepared in advance by the receiver terminal 11, and a multiplication / division calculation unit 25a. An average calculation unit 25b that averages the results and a polarity correction unit 25c that further multiplies the second signal by the result in the average calculation unit 25b.
This process will be specifically described as follows.

The second signal to be input is “INPUT SIGNAL”, the navigation data is “DATA”, the CA code is “CA”, the noise is “NOISE”, and the second signal is expressed by the equation (1). It becomes like this.
INPUT SIGNAL = DATA x CA + NOISE (1)

Then, pseudo patterns A ₁ to A ₁₀₂₃ are applied to this second signal. That is, each divided by A ₁₀₂₃ each second signal from the pseudo pattern A ₁ at multiplicative calculation unit 25a. In FIG. 17, the multiplication / division calculation unit 25a is a division unit.
If {CA / A} = 1, that is, if the CA code of the second signal and the pseudo pattern A coincide (although the polarity is normal or reverse), the multiplication / division operation The result in the part 25a can be expressed as in Expression (2) and Expression (3).
INPUT SIGNAL / A = DATA × CA / A + NOISE / A (2) INPUT SIGNAL / A = DATA + NOISE ′ (3)

Then, when the obtained signal is averaged DD in the average calculation unit 25b, it can be expressed as in Expression (4). Note that N is a real number and can be, for example, 15, but may be another real number. Thereby, the polarity (D ′) of the navigation data in the second input signal can be estimated.
DD = 1 / N × Σ {INPUT SIGNAL / A}
= 1 / N × Σ {DATA + NOISE ′}
= D '+ NOISE "(4)

Then, when this result is further acted (multiplied) on the second signal by the polarity correcting unit 25c and rearranged, it can be expressed as in Expression (5).
DD × INPUT SIGNAL
= (D '+ NOISE ") x (DATA x CA + NOISE)
= [D ′ × DATA] × CA + NOISE ″ × DATA × CA
+ NOISE x (D '+ NOISE ")
= CA + (NOISE "xDATAxCA)
+ {NOISE × (D ′ + NOISE ″)} (5)

  That is, in equation (5), [D ′ × DATA] is obtained by multiplying the polarity of navigation data (D ′ = 1 or −1) in the second signal by the navigation data (DATA) of the second signal. is there. Therefore, if the polarity (estimated) of the navigation data in the second signal is D ′ = + 1, the navigation data (DATA) is also +1, and the result of mutual multiplication is +1. On the other hand, when the polarity of the navigation data in the second signal estimated (calculated) is D ′ = − 1, the navigation data (DATA) is also −1, and the multiplication result is +1. That is, the polarity according to the navigation data is made the same for all the second signals.

As described above, in this step, the received signal acquired for the acquisition time T ₁ is synchronously added 15 times to obtain a new input signal (second input signal), which has the same polarity (phase) (same phase). Alternatively, it can be said that the division is performed by the pseudo pattern A which is opposite (reverse phase) and coincides. Further, in order to satisfy the condition where the polarities are the same or opposite, 1023 patterns in which the pseudo pattern is shifted bit by bit are prepared, and parallel arithmetic processing in 1023 cases is performed.

Then, as shown in FIG. 18, the correlation calculation is performed on the signal obtained in the polarity correction calculation step, and whether or not the peak value necessary for the calculation of the self-position can be detected by the determination processing unit 24 included in the calculation block unit 23. Make a decision. If the peak value cannot be detected, the reception signal at the acquisition time T ₁ that has already been subjected to this correlation calculation and the reception signal at the next acquisition time T ₁ (with the same polarity). Are accumulated synchronously and correlation is calculated again.

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 as shown in Expression (6).
1 / m × {ΣD (M, N)} (where M = 1 to m) (6)

  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. For this reason, in the present invention, cumulative reduction is accelerated, noise reduction is accelerated, and peak values can be detected.

  Next, the correlation calculation will be described. The correlation calculation unit 10 calculates the correlation with the replica PN code (replica C / A code signal) prepared in advance by the receiver terminal 11. The replica PN code and the correlation calculation are widely known contents, but will be briefly described below.

In general, a plurality of GPS satellites S travel around the earth, and each satellite S transmits a carrier wave of 1575.42 MHz by spread spectrum modulation with a PN signal corresponding to each individual satellite S and transmitted to the earth. 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 (demodulating the satellite reception signal) is stored in advance in the ROM of the signal processing unit 21 provided in the GPS receiver terminal 11.

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, 7).
y (k) = ΣX (n) h (n + k) (where n = 0 to N−1) (7)

  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 equation (8) by this correlation calculation.
1 / √ (m · N) (8)

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 = 1 to N = 1023 is assumed.
Therefore, the noise reduction amount can produce the effect of the result of the above equation (8) by cumulatively adding the received signals. That is, the delay amount τ can be obtained even for a very weak signal that is muddy by noise.

  The operation of the pseudo distance detection unit 19 will be described. The pseudo distance detection unit 19 searches for the data having the maximum absolute value in the data obtained as a result of the correlation calculation unit 10, and detects the absolute value of the correlation peak value having the maximum absolute value and the delay amount τ. It is a result.

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. At this time, the true position of the satellite S when the receiver terminal 11 processes the satellite reception signal is detected by the functions of the delay time calculation unit 40 and the satellite position correction calculation unit 41. Note that the correlation calculation performed by the correlation calculation unit 10, 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.
In the present invention, the pseudo distance is not limited to a general term used as a GPS term, but is defined as including a distance measured by another method.

The delay time calculation unit 40 will be described. The navigation data having a predetermined number of bits in the received satellite signal received from the satellite S shown in FIG. 11 (b) is digitized (replaced by +1 or -1) ) Is {A (n)} shown in FIGS. 12 (A) and 12 (B), and {B (n)} is obtained by digitizing the external navigation data received from the external base station 1 in the same manner. It is assumed that {A (n)} and {B (n)} have the same number of bits.
Then, {A (n)} and {B (n)} are aligned and compared as shown in FIG. {A (n)} in FIG. 12 (a) is obtained by digitizing the navigation data in FIG. 11 (b), and the external navigation data {B (n) received from the external base station 1 in FIG. )} Is acquired with a phase shift of 1 bit from {A (n)}.

  The delay time calculation unit 40 multiplies each of the {A (n)} and {B (n)} multiplied by the (n−1) th polarity and the next nth polarity. For the absolute value of the sum of the values (combination calculation), the sum of n = 1 to N is calculated (summation calculation). Then, this operation is sequentially combined for each part while shifting either the navigation data or the external navigation data bit by bit, and the sum is calculated. That is, the state in which the external navigation data {B (n)} is shifted by 1 bit (shifted to the left) from the state of FIG. 12 (a) is {B (n)} of FIG. Are those in which the polar patterns of {A (n)} and {B (n)} match each other. In this way, the combination operation and the sum operation are sequentially performed while shifting one bit at a time, and the time corresponding to the number of shifted bits when the maximum value of the sum operation is obtained is detected as the delay time. In other words, as is clear from FIGS. 12 (a) and 12 (b), the maximum value (value of 26) is obtained in a state where the polarity patterns match.

  FIGS. 13A and 13B show a case where Doppler remains in the navigation data received from the satellite S, and {A (n)} corresponds to FIG. 11D. Even in this case, the polarity patterns are matched by performing the same combination calculation and summation calculation for each part while shifting either the navigation data or the external navigation data bit by bit (see FIG. )) Gives the maximum value (24). That is, according to the present invention, the delay time can be reliably obtained even when Doppler remains in the navigation data received and processed by the receiver terminal 11 from the satellite S.

That is, the delay time calculation unit 40 according to the present invention performs a first calculation for sequentially combining each portion of the navigation data having a predetermined number of bits and the external navigation data having the same number of bits as the navigation data while shifting one bit at a time. And a second arithmetic unit for obtaining the sum of the results of the combination operation, and a third arithmetic unit for obtaining the maximum value of the result of the sum and obtaining a time corresponding to the number of shifted bits when the maximum value is obtained as the delay time It can be said that
In FIG. 12 and FIG. 13, the combination calculation in the first calculation unit is performed with two adjacent polarity values as one set, but may be performed with three consecutive polarity values. That is, the (n−1) th, nth, and (n + 1) th values may be calculated as a set.

The receiver terminal 11 processes the signal from the satellite S based on the satellite position of the external navigation data received by the receiver terminal 11 from the external base station 1 in the satellite position correction calculation unit 41 based on the obtained delay time. The receiver terminal 11 calculates and corrects the true position of the satellite S at the time.
Then, the pseudo distance detection unit 19 of the receiver terminal 11 obtains the pseudo distance from the true position of the satellite S.
Thereafter, in the block of the position calculation unit 20 in FIG. 2, the self position is determined based on the detection result of the true satellite position. The method for determining the self position in the position calculation unit 20 is generally well known and can be easily realized.

  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.

Next, another embodiment of the present invention will be described. Functions of the parts of the Doppler correction unit 16, the polarity correction calculation unit 25, the (synchronous addition /) correlation calculation unit 10, the delay time calculation unit 40, the position correction calculation unit 41, the pseudo distance detection unit 19, and the position calculation unit 20 in FIG. Although the block has been described with an algorithm by software, the Doppler correction unit 16 and the operation block unit 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 uses the code prepared in advance in the receiver terminal 11 to make the polarity of the navigation data of the received signal (PN signal) the same, and perform synchronous addition and correlation calculation. Or by performing synchronous addition, it is completely excluded that signal components cancel each other out due to different polarities in synchronous addition or the like and the improvement in sensitivity (S / N) deteriorates.
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) using a pseudo pattern prepared in advance in the receiver terminal 11. It is intended to obtain a high-sensitivity satellite positioning means (method) capable of stable positioning even in a house, behind a building, inside a building, etc.

  In addition, since the present invention performs processing based on satellite reception signals (PN signals), it is different from the method of taking navigation data from an external base station in order to obtain a delay value as in the prior art. It can be opened from an 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, without depending on the navigation data from the outside by the communication means L, all the polarities of the PN signal are made the same, and the PN signal buried in the noise emerges from the noise by synchronous addition and correlation calculation. Get super high sensitivity.
Further, by increasing the number of samplings, the sensitivity (S / N ratio) is remarkably improved in the correlation calculation, and the pseudorange with the satellite S can be detected accurately and quickly even in a building or the like.
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 signals are effectively synchronized in all the satellite reception signals at the predetermined time T in which the polarity of the navigation data is changed, that is, in the signal at the boundary of the polarity inversion of the navigation data. A PN signal buried in noise can be detected with significantly improved S / N. In addition, the number of samplings increases, 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 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.

Then, with the navigation data from the satellite S, the receiver terminal 11 can determine the true position of the satellite S from the data obtained from the external base station 1, and there is Doppler in the data to be processed ( Even if it remains, it is possible to estimate the exact position of the satellite S. Therefore, the receiver terminal 11 can detect the self-position with higher accuracy.
That is, in an asynchronous communication network (communication means L) such as the Internet where time delay exists, it is possible to achieve pseudo time synchronization at the receiver terminal 11, and errors due to time delay can be eliminated.

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 explanatory drawing explaining the position of the satellite at the time of signal processing with a receiver terminal. It is a time chart figure which shows the information transmitted from an external base station, and the information received in a receiver terminal. It is a block diagram which shows the structure of a GPS receiver terminal. It is a flowchart until it acquires a pseudorange from the received signal input from the GPS receiving part. It is operation | movement explanatory drawing of an I * Q signal conversion carrier removal part. It is operation | movement explanatory drawing which performs a Doppler correction from I and Q signal after a carrier wave removal, and obtains a signal. It is explanatory drawing which shows other embodiment of Doppler correction. It is explanatory drawing explaining operation | movement which delays every minute time and obtains a received signal. It is explanatory drawing which shows the navigation data from a satellite, and the navigation data from an external base station. It is explanatory drawing explaining delay time calculation. It is explanatory drawing explaining the delay time when there exists polarity inversion by Doppler. It is explanatory drawing explaining the operation | movement which obtains the correlation calculation result from a received signal, and calculates | requires delay amount. It is explanatory drawing explaining the operation | movement which acquires the delay time of the navigation data from an external base station. It is explanatory drawing explaining the operation | movement which carries out synchronous addition of the received signal. It is explanatory drawing explaining a polarity correction calculating part. It is explanatory drawing explaining a cumulative synchronous addition part and a correlation calculation part. 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

1 External base station 7 Location calculator
11 Receiver terminal
25 Polarity correction calculator
25a Multiplication / division calculator
25b Average calculator
25c Polarity correction section
40 Delay time calculator
41 Satellite position correction calculation unit A Pseudo pattern S Satellite T ₁ acquisition time T ₂ processing time i Minute time

Claims (4)

A receiver terminal (11) that receives a signal from the satellite (S) and communicates information with the external base station (1) calculates a pseudorange with the satellite (S) and calculates its own position. In the satellite positioning method, the time corresponding to one bit of navigation data of the satellite reception signal received by the receiver terminal (11) from the satellite (S) is set as the acquisition time (T ₁ ) and the processing time (T ₂ ) of the remaining rear part, the received signal acquired within the acquisition time (T ₁ ) is subjected to arithmetic processing including correlation calculation during the subsequent processing time (T ₂ ), and Then, after the start of data acquisition is sequentially delayed by a minute time (i) , a predetermined number of reception signals corresponding to the acquisition time (T ₁ ) are acquired, and each received signal is also processed during each subsequent processing time (T ₂ ). Perform the above calculation process including correlation calculation, and add the result of the calculation process. The delay value is obtained by detecting the peak value, and the navigation data of the satellite reception signal received by the receiver terminal (11) from the satellite (S) and the receiver terminal (11 ) from the external base station (1). ) Is compared with the received external navigation data to calculate the delay time of the external navigation data, and based on the delay time, the receiver terminal (11) estimates the satellite position when the satellite received signal is processed. A satellite positioning method characterized in that a pseudorange is obtained based on the estimated satellite position and the delay value and the self-position is calculated. The arithmetic processing performed in the above processing time (T ₂₎ is a synchronous addition signal a received signal obtained by synchronously added from the acquisition time (T ₁₎ the satellite to get in (S), said receiver What is obtained by applying the pseudo pattern (A) prepared in advance by the terminal (11) to the synchronous addition signal to make the polarity by the navigation data the same is obtained, and the polarity correction calculating step. The satellite positioning method according to claim 1, further comprising: a correlation calculation step of calculating a correlation between the received signal and a replica PN code prepared in advance by the receiver terminal (11) . The delay time is calculated by causing the navigation data having a predetermined number of bits acquired from the satellite (S) and the external navigation data having the same number of bits as the navigation data to interact with each other while shifting one bit at a time. satellite positioning method according to claim 1 or 2, wherein determining the time corresponding to the shift bit number to the polarity pattern is matched as the delay time. A receiver terminal (11) that receives a signal from a satellite (S) and communicates information with an external base station (1) to calculate a pseudorange with the satellite (S) and calculate a self-position. In the satellite positioning system, the receiver terminal (11) compares the navigation data of the satellite reception signal received from the satellite (S) with the external navigation data received from the external base station (1). A delay time calculation unit (40) for calculating a delay time of the external navigation data, and a satellite position correction calculation for estimating a satellite position when the receiver terminal (11) processes a satellite reception signal based on the delay time Part (41), and a position calculation part (7) that calculates a pseudo-range based on the estimated satellite position and calculates the self-position, and the delay time calculation part (40) has a predetermined number of bits. The above navigation data and the same number of bits as the navigation data A first calculation unit that sequentially performs a combination operation on each part while shifting any one of the external navigation data bit by bit, a second calculation unit that calculates a sum of the results of the combination calculation, and a maximum value of the sum result A satellite positioning system, comprising: a third calculation unit that obtains a time corresponding to the number of shifted bits when the maximum value is obtained as the delay time.

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