JP2539535B2 - Positioning satellite received signal processing method and apparatus and navigation system - Google Patents

Description

The present invention relates to a receiving device for receiving a signal from a NAVSTAR / GPS satellite, a received signal processing method, and a navigation system using the signal.

[Conventional technology]

GPS (Global Positioning System) is a global radio navigation system using artificial satellites that the US Department of Defense is constructing. The system consists of satellite system and ground system. A total of 24 satellites will be finally prepared, and if the system is completed, it will take 24 hours, 3
Dimensional positioning becomes possible.

Signals sent from GPS satellites are less susceptible to interference and obstruction, have high signal concealment capability, distance measurement, time synchronization are possible,
This is a spread spectrum modulation signal that has the excellent capability of code division multiple access.

Spread spectrum modulation is a pseudo-noise signal (Pseudo Noise code: PN code) that is a random code that has a characteristic that the information data signal has a wider band than the frequency band of the information signal, and has high autocorrelation and low cross-correlation. This is a method of transmitting by modulating with (which is called PN spreading). Therefore, the spread spectrum signal receiving apparatus is required to have the following functions. First, the PN used for spreading the information data on the transmitting side
This function demodulates the transmitted information data by generating a PN code with the same pattern as the code inside the receiver, and matching and multiplying the phase of the PN code and the phase of the PN code of the received signal for demodulation. (This is called PN despreading).

 Next, the operation will be described in detail.

After starting up the receiver, change the phase of the PN code until the PN code of the signal to be received matches the phase of the PN code created inside the receiver (phase synchronization). Obtain the spread signal.

Next, since a lot of unnecessary noise signals are mixed in this despread signal, the center frequency of the despread signal and the center frequency of a narrow band filter that removes unnecessary noise from the despread signal are matched. Then, the despread signal is filtered (frequency synchronization). By the above operation, unnecessary noise components are removed, the information signal is demodulated, and PN synchronization is established.

After the PN synchronization is established by the above operation, the phase of the PN code is always matched (for example, as shown in Mitsuo Yokoyama "Spread spectrum communication system" PP.311-325) The PN code generator is controlled based on the signal (PN synchronization tracking) and PN tracking is performed. From the tracking state, the distance between three or more GPS satellites and the receiver is measured, and the self position is calculated.

In the GPS receiving device, processes such as phase synchronization and frequency synchronization are indispensable and time-consuming until positioning is performed after power is turned on. Therefore, in the past, Japanese Patent Laid-Open No. 58-
There is a method of changing the synchronous search speed and shortening the start-up time by the method disclosed in Japanese Patent No. 191552.

[Problems to be solved by the invention]

The signal level of the radio wave transmitted by the GPS satellite greatly changes due to factors such as the elevation angle of the satellite and the deviation of the gain pattern of the antenna used in the receiving device from the elevation angle.

Therefore, it is necessary to optimally select the optimum PN search speed according to the signal level, the bandwidth of the narrow band filter for removing unnecessary noise, and the parameters such as the loop filter in the vibration loop circuit. However, (1) conventionally, since these parameters were made uniform regardless of the signal level, there was a problem that the time required for phase synchronization and frequency synchronization became long. Further, (2) there is a contradictory property between the time required for synchronization and the distance measurement accuracy, and it is difficult to satisfy both characteristics if these parameters are set uniformly. Further, in the vibration loop circuit, there is a problem that the accuracy of distance measurement deteriorates when the data is inverted. Furthermore (3) GPS signal reception availability and signal level
It was used only to change the combination of satellites used for positioning.

An object of the present invention is to shorten the time required for PN search, improve the accuracy of distance measurement, and reduce the positioning error. In addition, it is to realize the navigation system with high positioning accuracy by applying the information of the GPS signal reception availability and the received signal level to the navigation system.

[Means for solving problems]

In order to achieve the above object, the present invention provides (1) the elevation angle of a GPS satellite visible at that time is calculated in advance from the navigation data transmitted from the GPS satellite and the time of positioning, and the antenna gain and GPS at that elevation angle are calculated. S / N ratio of received GPS signal (signal-to-noise ratio) from signal propagation loss
Equipped with the function of seeking. Furthermore, it is equipped with a function that sets the optimum PN search speed from that value, the bandwidth of the filter that removes unnecessary noise from the despread signal, and the parameter of the loop filter in the vibration loop circuit, and capture and follow PN synchronization. It is a thing.

(2) When there is no GPS satellite navigation data, or when the reliability of that data is extremely poor, or when there is no time information, the bandwidth of the filter is first widened to synchronously capture the GPS signal, and then PN When the synchronization is not obtained, the filter bandwidth is narrowed to perform the synchronization acquisition and the PN synchronization is established.

(3) It has a function of switching the parameter of the loop filter in the vibration loop circuit before and after the synchronous tracking.

(4) Estimate the time when the navigation data signal of the GPS satellite reverses from the previous data inversion, and when the data reverses, stop the signal input to the loop filter in the vibration loop circuit,
It has a function to hold the output.

(5) A means for inputting external information such as the S / N ratio of GPS signals is provided, and based on that information, the optimum PN search speed is set. The bandwidth of the narrow band filter that removes unnecessary noise from the despread signal. It has a function to set the parameters of the loop filter in the vibration loop circuit.

(6) It has a function to output information such as GPS signal reception availability and GPS signal reception level to the outside. The navigation system compares the information with the surrounding building conditions recorded in the map data to estimate the current position. It has a function to do.

[Action]

(1) The S / N ratio of the GPS signal is calculated from the GPS signal propagation loss of the elevation angle seen by the GPS satellite and the gain pattern with respect to the elevation angle of the antenna. When the elevation angle of the GPS satellite is high, widen the band of the narrow band filter that removes unnecessary noise to increase the speed.
PN phase synchronization is achieved. When the elevation angle of the GPS satellite is low, the band of this filter is narrowed and PN phase synchronization is achieved at low speed.

(2) When there is no GPS satellite navigation data, or when the reliability of the data is extremely poor, or when there is no time information, the level of the GPS signal cannot be calculated, so unnecessary noise is first removed from the despread signal. Widen the band of the narrow band filter and perform PN search. If synchronization is not detected in this process, the level of the GPS signal is low, so the band of this filter is narrowed to improve the S / N ratio. Further, PN search is performed to establish PN synchronization.

(3) Select the parameter of the loop filter in the vibration loop that is stable for PN tracking in a short time from the time when PN synchronization is detected to when positioning is started. After the positioning is started, it works to select a parameter that minimizes the distance measurement error (increase the constant of the multiplier in the loop filter).

(4) Since the GPS satellite navigation data signal is 50 BPS, the data is inverted every 20 ms. Utilizing this property, it calculates when the next data inversion occurs from the previous data inversion, and when the data inversion occurs, it acts to hold the output signal while stopping the signal input to the loop filter in the vibration loop.

(5) A narrow band filter band that receives unnecessary information from the despread signal when it is judged that the signal level is high because it receives information such as the GPS signal level previously received as external data. And PN phase synchronization at high speed. When it is determined that the signal level is low, the band of this filter is narrowed and PN phase synchronization is achieved at low speed.

(6) GPS in the depth of self position with the navigation system
When using a signal, check whether there is an obstacle in the direction in which the GPS satellite can be seen from the signal reception level and signal level of the GPS signal. When it is determined that there is an obstacle, the map information is matched with the position information output from the GPS receiving device. In addition, check the map for obstacles in the direction in which the GPS satellites are visible. Furthermore, the self-position is determined by map matching so as to be behind the obstacle.

〔Example〕

 An embodiment of the present invention will be described below with reference to FIG.

FIG. 1 is an example of the configuration of a GPS receiving device to which the present invention is applied.

In Fig. 1, the center frequency of 1575.42 transmitted from the GPS satellite
The spread spectrum signal of MHz is captured by the antenna 1 and sent to the high frequency unit 23.

The high frequency unit 23 amplifies this signal by the low noise amplifier 2 and creates a carrier wave (for example, an oscillation frequency of 1509.948MHz) generated by the first local oscillator 4 whose frequency is controlled by the reference oscillator 22 (for example, an oscillation frequency of 65.472MHz). ) By mixer 3
Down conversion is performed to obtain a first intermediate frequency signal S1.

Further, an unnecessary noise signal is removed from the signal S1 by a band pass filter 5 (for example, a pass band width of about 2 MHz), and the inverse spread spectrum unit 24 is sent.

In the inverse spread spectrum unit 24, the PN code NCO8 and the PN code generator 7 generate a spread spectrum signal sent from the high frequency unit 23 with the same pattern and the same phase as the PN code of the GPS satellite signal to be received. Despread and obtain the second intermediate frequency signal S2.

This second intermediate frequency signal S2 is branched into two, mixed with two signals having an output phase difference of 90 ° of the reference oscillator 22 and frequency-converted (down conversion), and a third intermediate frequency signal having a phase difference of 90 °. Obtain S3, ab (called I signal and Q signal, respectively).

By separating the I and Q signals as described above, the processing can be performed at a low sampling frequency and the configuration of the digital signal processing unit is simplified.

Furthermore, a low-pass filter provided in front of the A / D converter 1
In 2.ab, the aliasing signal, which is a frequency component of 1/2 or more of the sampling frequency of the A / D converter, is removed, and signals S4.a, b are obtained.

Here, the signal S3.a, b has a frequency fluctuation of about ± 4KHz due to the Doppler effect, and considering the frequency fluctuation of the reference oscillator, the cutoff frequency of the low-pass filter 12.a, b is about 5-7KHz.
Good to choose.

Furthermore, this analog signal S4.a, b is converted by the A / D converter (for example, the reference oscillator signal is divided by 4096 by the frequency divider 11 to 15.98437).
It is converted to a digital signal S5.a, b (with a sampling signal of 5 MHz) and sent to the digital signal processing unit 25.

In the digital signal processing unit 25, the carrier signal output from the third local oscillator 15 composed of a digital oscillator and the signals S5.a, b are mixed by the mixers 14.a, b, and the down-converted signal S6. Get a and b.

Furthermore, by the signal S16 from the calculation unit 21, the low-pass filter 16.a, b capable of adaptively changing the signal cutoff frequency and changing the pass band, removes unnecessary noise from the signal S6.a, b, Obtain carrier signals S7.a, b containing navigation data signals.

The data demodulator 17 is composed of, for example, a Costas demodulator or a TAN format demodulator, reproduces a carrier signal from the carrier signal S7.a, b containing the desired data, and compares it with the input signal to obtain the data. The signal S8 is demodulated and sent to the calculation unit 21.

The detector 18 also calculates the square root of the sum of squares of the input signals S7.a, b to obtain the amplitude information signal S9 of the input signal.

This signal S9 is sent to the calculation unit 21, and if the amplitude of S9 is equal to or higher than the set level, it is determined to be the PN synchronous state, and if the amplitude of S9 is equal to or lower than the set level, it is determined to be the PN asynchronous state.
Output as the synchronization signal S13.

Further, the amplitude information signal S9 is sent to the vibration loop 19, frequency-divided by the reference oscillator 22, processed by the dither signal S14 transmitted from the PN code generator 7, and the filter frequency set by the reference signal S17 from the arithmetic unit. The PN synchronization tracking signal S10 is output after being filtered by. In addition, vibration loop 1
The data inversion signal S15 is also input from the arithmetic unit 21 to the detector 9.
It controls the input of signal S9 from 18 to seismic loop 19.

The switch 20 switches between the PN synchronization prompting signal S11 and the PN synchronization tracking signal S10. If the PN synchronization signal S13 from the calculation unit 21 indicates the asynchronous state, it is switched to the PN synchronization acquisition signal S11 output from the calculation unit 21, and if it indicates the synchronization state, it is switched to the PN synchronization tracking signal S10.

The control signal S12 output from the switch 20 is the PN code N
It is input to CO8 and controls the position of the PN code to create the PN synchronization state.

With the above configuration, GPS signals are demodulated and positioning is performed.
The difference from the conventional method is that the cutoff frequencies of the low-pass filters 16.a and b can be adaptively changed based on the signal S16 from the arithmetic unit 21, and the control signal S1 from the arithmetic unit 21 is also changed.
The filter constant of the vibration loop can be changed based on 7, and the PN synchronization acquisition signal S11 can be changed, and the speed (search speed) for searching for the PN synchronization point can be changed freely.
This PN search is realized by slightly changing the PN code chip rate frequency of the received wave and the chip rate frequency of the PN code created inside the receiver, and equivalently changing the phase of the PN code. For example, if the chip rate frequency of the received wave PN code is 1.023 MHz and the chip rate frequency of the PN code generated inside the receiver is 1.0232 MHz, the search speed is 200 BIT / Sec. Therefore, in order to speed up the search, it is sufficient to increase the chip rate frequency difference between them.

 Next, the processing configuration of the arithmetic unit will be described with reference to FIG.

The navigation data analysis unit 44 edits the navigation data from the demodulated GPS satellite navigation data signal S8 to obtain the Amarnac data (GPS satellite approximate position information) and ephemeris data (detailed GPS satellite position information) required for positioning and speed calculation. ). In addition, information regarding the Doppler frequency change amount of the carrier wave is also superimposed and transmitted to the data signal S8.

The filter control calculation unit 45 estimates and calculates the S / N ratio of the GPS signal described later, determines the bandwidth of the low pass filter, and outputs the filter signal S16 to the digital signal processing unit 25.

The synchronization determination unit 46 monitors the amplitude information signal S9 of the input signal, and determines that the amplitude is equal to or higher than the set level and the PN asynchronous state if the amplitude is equal to or lower than the set level. The vibration loop control calculation unit 47 optimizes the loop filter for preventing the positioning accuracy from deteriorating at the time of data inversion of the input signal, which will be described later, and for stable tracking at high speed. Therefore, the data inversion time is predicted and the data inversion signal S15 is output, and is changed by the control signal S17 of the multiplier constant of the loop filter.

The switch control signal section 48 outputs a PN synchronization signal S13 for switching between the synchronization acquisition mode and the synchronization tracking mode.

The Doppler fluctuation compensator 49 outputs a third station oscillation control signal S24 for controlling the carrier wave signals S7.a, b so as not to be affected by the Doppler fluctuation, to the third local oscillator.

The satellite selection unit 53 selects the combination of satellites that provides the highest positioning accuracy.

The positioning calculation 54 uses the pseudo range data signal S23 output from the distance measurement counter 44 and the own 3 from the position data of the GPS satellites.
Calculate the dimensional position.

The speed calculation unit 55 calculates its own speed and heading direction from pseudorange change rate data (this is obtained from the frequency change amount of the carrier), GPS satellite position data, and the like.

Next, the processing algorithm of the arithmetic unit 21 will be described with reference to FIG. After the power is turned on, start-up processing 100 is performed, and the position and speed of the GPS satellite currently visible are obtained 101 using the almanac data stored in the arithmetic unit 101.

Based on the combination of the geometrical positions, a combination of four GPS satellites capable of positioning its own position with the highest accuracy is determined (in the case of two-dimensional positioning, a combination of three satellites) 102.

Further, the Doppler shift frequency amount of the satellite signal is calculated from the position and velocity of the GPS satellite 103.

After completing these basic operations, the digital signal processing unit is set.

First, the constant of the loop filter of the vibration loop is set as a constant for rapid tracking 104.

Next, in order to remove the Doppler frequency fluctuation from the carrier signals S7.a, b, the oscillation frequency of the third local oscillator 15 is set 105 from the calculated Doppler shift amount.

Further, the bandwidths of the low pass filters 16.a and 16b are set 106 by the method described later.

After the above settings are completed, start PN synchronization search.
In the synchronization determination 107, the amplitude level of the GPS signal is monitored, and when it exceeds a certain level, it is determined that PN synchronization is obtained and positioning is started.

On the other hand, when the amplitude is below a certain level, the search is continued until the search for the PN1 cycle is completed, and if the PN synchronization is still not achieved, the oscillation frequency of the third local oscillator 15 is slightly changed and the PN synchronization search is performed again. Do 108.

When PN synchronization is obtained, the switch control signal section 48 outputs the switch switching signal S13 and the PNNCO control signal S12 to P
The N synchronization acquisition signal S11 is changed to the PN synchronization tracking signal S10 for synchronization 109. After synchronization, after changing the loop filter constant for performing the seismic loop control calculation 110 to a value that improves the accuracy of pseudorange measurement, the calculation 111 is performed based on the Doppler frequency obtained from the data demodulator 17 to further improve Doppler accuracy. The band of the low-pass filters 16.a and b is narrowed 112 in order to remove frequency fluctuations and improve the accuracy of the pseudorange. Also, the obtained navigation data is edited to obtain almanac data, ephemeris data, etc. 113. Further, the measured value of the pseudo distance or the pseudo distance change rate is input, 114 is used to calculate and output the self-position 115, the speed and the traveling direction 116. Positioning is continued while synchronization is maintained, and if synchronization is lost, synchronization is regained and positioning is continued 117.

 The operation of each unit will be described below.

The navigation data signal S8 output from the data demodulator 17 of the digital signal processing unit is edited and analyzed by the calculation unit 21 to obtain satellite time and position information (almanac data) of each GPS satellite. From this almanac data (or previously collected almanac data), time, and current position information, the elevation angle that each GPS satellite can see is calculated.

Further, the antenna 1 stored in the memory inside the arithmetic unit 21
The gain G (dB) with respect to the elevation angle is read, and the amount L (dB) of the GPS signal attenuated in the atmosphere at that elevation angle is calculated. Here, the effective power of the GPS signal is P (dBm: 101ogP
(MW) and 0 dBm = 1 mW), the received GPS signal level S is calculated by the following equation.

S = P−L + G Further, if the noise level N (dBm) is approximated to the thermal noise level, the noise level N is calculated by the following equation.

N = kTB where k is the Boltzmann constant, T is the equivalent noise temperature, and B is the bandwidth of the receiver. Depending on the ratio of the GPS signal level S and the noise level N, the signal-to-noise ratio (S
/ N ratio) can be calculated.

When this S / N ratio is high, the cutoff frequency of the low pass filters 16.a and 16b is increased to widen the bandwidth to about 1 (kHz).
By thus widening the bandwidth, frequency synchronization becomes easier.

In addition, the PN search speed should be increased to obtain phase synchronization within 5 seconds or less.

When the S / N ratio is low, the cutoff frequency of the low pass filters 16.a and 16b is lowered to narrow the bandwidth to about 200 (Hz).
By narrowing the bandwidth in this way, the S / N ratio improves and it becomes possible to capture GPS signals. In addition, the PN search speed is slowed down so that phase synchronization can be obtained without error due to the influence of noise. Therefore, the phase synchronization time needs to be around 10 seconds.

The above is a method of changing each parameter according to the information of almanac data, time, and current position, but there is also a method of changing each parameter based on the external data S18. Next, the operation will be described.

The calculation unit 21 outputs the almanac data to the external calculation device as the external data S18. The computing device creates a table of satellite elevation angles against time from the approximate value of the current position,
Store in memory. If the GPS satellite's orbital altitude remains the same, the satellite will pass over the same ground every day, with a little more than four minutes in time. Considering the effect, the elevation angle of the GPS satellite is calculated from the current time and the elevation angle table of the satellite. The elevation value is sent to the calculation unit by the external data S18, the cutoff frequency of the low-pass filters 16.a and b and the PN search speed are determined by the above-described method, and PN synchronization is achieved. Operation of the external computing device
It can also be stored and executed within 21.

 Still another method will be described.

First, the amplitude information signal S9 is taken into the calculation unit, and the S / N ratio of the GPS signal being received is measured. This is calculated from the difference in amplitude when no satellite is receiving and when a signal from a GPS satellite is received. The measured S / N ratio is compared with the S / N ratio calculated from the elevation angle of the satellite and the antenna gain, the calculated S / N ratio is corrected, and the correction value is stored. Further, the S / N ratio information is output as external data S18 to an external arithmetic unit (not shown). This external computing device is S /
Store N ratio information and time information in memory. When performing positioning at a later date, considering the effect that the GPS satellites pass over the same ground every day while being 4 minutes faster, the GPS signal S / N ratio at that time is called from the memory External data S18
To the arithmetic unit 21. Based on this information, the cutoff frequency of the low-pass filters 16.a and 16b and the PN service speed are determined, and the PN synchronization time is shortened. The operation of the external arithmetic device can be stored and executed in the arithmetic unit 21.

A processing method when there is no almatic data, time information, or current position information will be described next. First, at the start of GPS signal reception, the cutoff frequency of the low-pass filters 16.a and 16b is increased to widen the pass band width and start the PN search. By thus widening the bandwidth, frequency synchronization becomes easier. However, if such bandwidth is expanded, S / N
As the ratio deteriorates, it may happen that GPS satellites with low elevation angles cannot be captured. Therefore, if the GPS signal could not be captured, in order to improve the S / N ratio, the low-pass filter 16.a,
Lower the cutoff frequency of b, narrow the passband width, and set P again.
Perform N search and establish PN synchronization.

Although the acquisition of the GPS signal has been described above, positioning accuracy is another function desired by the GPS in addition to shortening the PN search time. In order to improve the positioning accuracy, the vibration loop 19 should be set so that the phase of the PN code of the input GPS satellite signal and the phase of the PN code created by the PN code generator 7 inside the receiver are completely matched.
The distance measurement accuracy may be improved by controlling with.

Therefore, the fourth example of the configuration of the vibration loop to which the present invention is applied is
As shown in the figure, the details will be described below.

The input amplitude information signal S9 is switched and held by the data inversion signal S15 and sent to the switch 25. In the switch 25, this signal is divided into a lead signal and a lag signal by the dither signal S14. The lead signal and the lag signal respectively pass through the loop filter, and the data are stored in the holds 26.a and b controlled by the dither signal S14. Each output is input to the adder / subtractor 27, the difference is taken, and the PN synchronization tracking signal S10 is output.

 Next, the operation will be described.

The amplitude information signal S9 input to the vibration loop has the characteristics shown in FIG. 5 (b). In FIG. 5, (a) shows the navigation data signal S8, and the horizontal axis is time. In other words, there is a phenomenon that the amplitude of S9 drops when the data is inverted. This is caused by the filter used in the receiver and cannot be avoided. When such abrupt fluctuation of the amplitude level passes through the loop filters 28.a and 28b, the PN synchronization is adversely affected and the positioning performance deteriorates.

Therefore, the data inversion time of the GPS navigation data signal S8 is calculated by the calculation unit 21 from the previous data inversion time and the data inversion frequency of 20 ms, and the signal level becomes 1 before and after the data inversion time in FIG. Data inversion signal shown in
Outputs S15.

When the signal level of S15 is inverted from 0 to 1, the switch 23 is cut off so that the input is not applied, and at the same time, the data before the switch is cut off is stored in the hold 24.

Conversely, when the signal level of S15 is inverted from 1 to 0,
The hold 24 to which the switch 23 is connected works so as to be invalid.

As a result, the amplitude information signal shown in FIG.
It is converted into the signal shown in (d). In this way, the fluctuation of the amplitude level at the time of inversion of the information signal is reduced, so that the distance measurement accuracy and the positioning accuracy are further improved. Furthermore (d)
The signal shown in (1) is divided into a lead signal S19 and a delay signal S20 under the control of the dither signal S14 by the switch 25.

The lead signal and the lag signal are sent to a loop filter and processed. The feature of the present invention is that this loop filter
28.a, b The multiplier constant inside the control signal S17
The feature is that it can be adaptively changed according to the processing process.

When performing a PN search and acquiring synchronization, it is necessary to reliably acquire synchronization and to track more rapidly.
Select a small value for the constant of the multiplier 29.a to approximate the characteristics of the first-order loop filter. Further, when PN synchronization is followed, a large value is selected for the constant of the multiplier 29.b as the characteristic of the secondary loop filter in order to eliminate the tracking offset component and improve the positioning performance.

Further, the constants of the multipliers 30.a and 30b are also switched so that the positioning accuracy is improved. The signal output from the loop filter by the above method is sent to the holds 26.a and 26b. When the signal switched by the switch 25 is output to the loop filter 28.a, the loop filter output signal immediately before the switch 25 is switched is stored in the hold 26.b.

Further switch to output to loop filter 28.b
When 25 is switched, hold 26.b is released and conversely the loop filter output signal immediately before switch 25 is switched is stored in hold 26.a. The signals S21 and S22 thus obtained are added and subtracted by the adder 27 to obtain the PN synchronization tracking signal.

Next, FIG. 6 shows an example in which the GPS receiver described above is incorporated into an automobile navigation system.

The system consists of a sensor system, display system, information system, and arithmetic system.

GPS receiver that measures its own absolute position as a sensor 3
1. An optical fiber gyro 39 / steering angle sensor 37 for measuring a rotation angle, a geomagnetic sensor 38 for detecting a direction, and a vehicle speed sensor 36 for measuring a speed are used.

The display system is composed of an LCD display 32, the information system is a road information receiver 34, the operation system is a CD-ROM 33 which stores a road map, and an operation unit 35 which obtains its own position from sensor output and controls map matching / display etc. It

The operation will be briefly described. The GPS receiver constantly measures its own position and displays the measurement result on the LCD display. However, if the GPS signal cannot be received due to the shadow of the building, etc., positioning cannot be performed. So an optical fiber gyro,
Navigation is performed based on the angle information output from the rudder angle sensor, the angle information output from the vehicle speed sensor, and the azimuth information output from the geomagnetic sensor, and map matching is also used to improve positioning accuracy, and the measurement results are displayed on an LCD display. indicate. With such a configuration, accurate navigation is always possible. In addition, navigation is always performed using sensor information such as an optical fiber gyro, rudder angle sensor, speed sensor, geomagnetic sensor, and GPS.
It is also possible to make a correction based on the positioning result of the receiving device.

Furthermore, this GPS receiver is applicable to navigation systems for ships, airplanes, artificial satellites, etc.

Next, FIG. 7 shows an example in which the present GPS receiving device is incorporated into the automobile navigation system having the above-mentioned configuration to perform navigation.

In the figure, the traveling direction of the automobile 40 traveling on the road is represented by a vector 42, the building is represented by 41, and the direction vector in which the GPS satellite is viewed is represented by 43.

The positioning accuracy of the GPS system has an error of 30m to 50m, depending on the visible position of the satellite. To correct the error,
Map matching is performed by comparing the map with the positioning result and forcing the self-position to be on the road.

In the case of this figure, the traveling on the road shown in the figure is selected from the traveling vector 42 of the automobile. However, if the vehicle continues running as it is, the GPS signal coming from the direction of the vector 43 is blocked by the building 41, so that the GPS receiving device mounted on the vehicle 40 cannot receive the GPS signal. This is determined by the fact that the signal level of the amplitude information signal S9 in FIG. 1 decreases and the PN synchronization is lost. Therefore, map matching can be performed by using this GPS signal blocking information. In other words, when the information on the building 41 is obtained from the CD-ROM 33 storing the road map shown in FIG. 7 and the GPS signal is cut off, the location on the road where the direction vector 43 seen by the GPS satellite intersects with the building 41. You can know the exact position by map matching with.

〔The invention's effect〕

Since the present invention is configured as described above,
The following effects are achieved.

(1) The S / N ratio of the signal sent from the GPS satellite is calculated from the gain pattern with respect to the elevation angle of the GPS satellite and the elevation angle of the antenna used for the GPS receiver, and the optimum PN search speed and despreading for that signal level are calculated. By adaptively changing the bandwidth of the filter that removes unnecessary noise signals from the signal, the time required for phase synchronization and frequency synchronization is shortened,
The time to start positioning can be shortened.

(2) PN synchronization can be performed in the shortest time even if there is no information such as the position of the GPS satellite, its own approximate position, and time, so the time to start positioning can be shortened.

(3) By switching the parameters of the loop filter in the vibration loop circuit before and after PN synchronization, high-speed and stable synchronization acquisition and positioning accuracy can be improved.

(4) Estimating the data inversion from the previous data inversion, and by stopping the control of the vibration loop circuit during that period, it is possible to prevent the deterioration of the positioning error that occurs during the data inversion of the GPS signal, and improve the positioning accuracy. To be

(5) The elevation angle of the GPS satellites and the S / N ratio of the GPS signal are provided as an external input / output means to eliminate unnecessary noise signals from the PN search speed and despread signal that are optimal for the GPS signal level. By adaptively changing the bandwidth of the filter to be used, the time required for phase synchronization and frequency synchronization can be shortened, and the time until the start of positioning can be shortened.

(6) By outputting the availability of GPS signal reception to the outside, the navigation device collates the information and the surrounding building situation recorded in the map data, and performs map matching to determine a more accurate position.

[Brief description of drawings]

FIG. 1 is a block diagram of a GPS receiver, FIG. 2 is a configuration diagram of an arithmetic processing unit, FIG. 3 is a flowchart of processing of the arithmetic processing unit, FIG. 4 is a detailed diagram of a vibration loop circuit, and FIG. Signals input to and output from the loop circuit are shown in FIG. 6, which is an automobile navigation device using a GPS receiver, and FIG. 7 is map data used for map matching. 1 ... Antenna, 2 ... Low noise amplifier, 3,6,9.a, 9.b, 1
4.a, 14.b ... Mixer, 4 ... First local oscillator, 5 ... Band pass filter, 7 ... PN code generator, 8 ... PN code NC
O, 10 …… 90 ° hybrid, 11 …… divider, 12.a, 12.
b, 16.a, 16.b …… Low pass filter, 13.a, 13.b …… A / D
Converter, 15 ... 3rd local oscillator, 17 ... Data demodulator,
18 …… Detector, 19 …… Vibration loop, 20,23,25 …… Switch, 21 …… Computer, 22 …… Reference oscillator, 24,26.a, 26.b…
… HOLD, 27 …… Adder, 28.a, 28.b …… Loop filter, 29.a, 29.b, 30.a, 30.b …… Multiplier, 31 …… GPS receiver, 32… ... LCD display, 33 ... CD-ROM, 34 ... road information receiver, 35 ... computing unit, 36 ... vehicle speed sensor, 37 ...
… Steering angle sensor, 38 …… Geomagnetic sensor, 39 …… Optical fiber gyro, 40 …… Car (navigator), 41 …… Building, 42 …… Driving level, 43 …… Direction vector from which GPS satellite is visible, 44 …… Rudder data analysis, 45 ... Filter control calculation, 46 ... Synchronous judgment, 47 ... Vibration loop control calculation, 48 ...
… Switch control signal, 49 …… Doppler fluctuation compensation, 50 ……
Start-up processing, 51 …… Satellite position / speed calculation, 52 …… Doppler shift change amount calculation, 53 …… Satellite selection, 54 …… Positioning calculation, 55 …… Speed calculation

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-1-175321 (JP, A) JP-A-52-75917 (JP, A) JP-A-58-191552 (JP, A)

Claims (9)

(57) [Claims] 1. A positioning satellite reception signal processing method for receiving a signal from a positioning satellite to obtain a current position of a mobile body, wherein a signal from the positioning satellite is obtained from an elevation angle of the positioning satellite and an antenna gain pattern at the elevation angle. Estimate the S / N ratio, the phase of the PN spread signal of the signal sent from the positioning satellite according to the estimated S / N ratio and the phase of the PN spread signal generated inside the receiver of the mobile A positioning satellite reception signal processing method, characterized in that a signal from the positioning satellite is received by changing a sync point search speed, which is a change rate of a phase difference. 2. The positioning satellite reception signal processing method according to claim 1, wherein a bandwidth of a filter for removing noise from the despread signal from the positioning satellite is changed based on the sync point search speed. . 3. The positioning satellite reception signal processing method according to claim 2, wherein the filter is a low-pass filter that enhances the S / N ratio of the despread signal. 4. A positioning satellite reception signal processing apparatus for receiving a signal from a positioning satellite to determine the current position of a mobile body, wherein the signal from the positioning satellite is detected from the elevation angle of the positioning satellite and the antenna gain pattern at the elevation angle. Estimating means for estimating the S / N ratio, and the PN spread signal phase of the signal transmitted from the positioning satellite according to the S / N ratio estimated by the estimating means and the PN generated inside the receiver of the mobile body. A positioning satellite reception signal processing device, comprising means for receiving a signal from the positioning satellite by changing a sync point search speed, which is a change rate of a phase difference from the phase of the spread signal. 5. The positioning satellite reception signal processing device according to claim 4, wherein a bandwidth of a filter for removing noise from the despread signal from the positioning satellite is changed based on the sync point service speed. . 6. The positioning satellite reception signal processing device according to claim 5, wherein the filter is a low-pass filter for increasing the S / N ratio of the despread signal. 7. A positioning satellite reception signal processing device for receiving a signal from a positioning satellite to obtain a current position of a moving body, a vehicle speed sensor for obtaining a moving speed and a moving distance of the moving body, and the positioning satellite received signal. In a navigation system including a processing device and means for calculating and displaying a position and a traveling direction of the moving body based on outputs from the vehicle speed sensor,
The positioning satellite reception signal device is an elevation angle of the positioning satellite and an estimating means for estimating the S / N ratio of the signal from the positioning satellite from the gain pattern of the antenna at the elevation angle, and the S / N estimated by the estimating means. By changing the sync point search speed, which is the rate of change of the phase difference between the phase of the PN spread signal of the signal sent from the positioning satellite and the phase of the PN spread signal generated inside the receiver of the mobile unit according to the ratio. And a means for receiving a signal from the positioning satellite. 8. The navigation system according to claim 7, wherein a bandwidth of a filter for removing noise from a despread signal from the positioning satellite is changed based on the sync point search speed. 9. The navigation system according to claim 8, wherein the filter is a low-pass filter that enhances the S / N ratio of the despread signal.