JPH0465687A - Method and device for processing received signal from position measurement satellite and navigation system - Google Patents

Abstract

PURPOSE:To shorten a search time and to improve measurement accuracy by calculating the SN ratio of the signal from a position measurement satellite from necessary parameters, finding an optimum synchronous parameter, and determining the current position of a moving body. CONSTITUTION:The SN ratio of the signal from the position measurement satellite of a worldwide system (GPS) is calculated from a gain pattern corresponding to the elevation angle of an antenna and the synchronous parameter is found according to the arithmetic effect. Then the band of a narrow-band filter is widened up to a high elevation angle where the satellite is seen and psuedo noise (PN) phase synchronization is performed fast. When the elevation angle where the GPS satellite is seen is low, the band of this filter is narrowed down and the PN phase synchronization is performed at a slow speed. Then when the current position of the moving body is determined, high-accuracy distance and position measurement is performed with a short search time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a receiving device for receiving signals from NAVSTAR/GPS satellites, a received signal processing method, and a navigation system using the signals.

[Conventional technology]

GPS (Global 'Positionin'
gSystem (Global Positioning System) is a global radio navigation system using artificial satellites that is being constructed by the United States Department of Defense.

The system consists of a satellite system and a ground system. The satellite system will eventually have a total of 24 units, and once the system is complete, it will be possible to perform 3D positioning around the world 24 hours a day.

Signals sent from GPS satellites are not susceptible to interference or jamming, have high signal concealment ability, and are capable of distance measurement and time synchronization.
It is a spread spectrum modulation signal with excellent capabilities such as code division multiple access.

Spread spectrum modulation uses a pseudo-noise code (Pseu-do-N), which is a random code for transmitting an information data signal in a frequency band wider than the frequency band of the information signal, and has the characteristics of high autocorrelation and low cross-correlation.

i, se code: PN code), and this is called PN spreading). Therefore, the following functions are required for a spread spectrum signal receiving device. First, a PN code with the same pattern as the PN code used to spread information data on the transmitting side is generated inside the receiver, and the phase of the PN code and the phase of the PN code of the received signal are matched and multiplied and demodulated. , is a function of demodulating the transmitted information data (this is called PN despreading).

Next, its operation will be explained in detail.

After the receiving device is started up, the phase of the PN code is changed until the phase of the PN code of the signal to be received matches the phase of the PN code created inside the receiver (phase synchronization), so-called PN search is performed until synchronization is acquired. Get the spread signal.

Next, since this despread signal contains many unnecessary noise signals, the center frequency of the despread signal is matched with the center frequency of a narrowband filter that removes unnecessary noise from the despread signal. to filter the despread signal (frequency synchronization). The above operation removes unnecessary noise components, demodulates the information signal, and establishes PN synchronization.

After PN synchronization is established through the above operations, the PN synchronization from the vibrating loop circuit must be performed so that the PN codes always match in phase (for example, as shown in Mitsuo Yokoyama, "Spread Spectrum Communication System J PP, 311-325"). P based on the signal
The N code generator is controlled by PN synchronization tracking), PN)-racking. Based on the tracking state, the distance between three or more GPS satellites and the receiver is calculated, and the self-position is calculated.

In the above-mentioned GPS receiving device, processes such as phase synchronization and frequency synchronization are indispensable and time consuming until positioning is performed after the power is turned on. Therefore, conventionally, the
There is a method of varying the synchronization search speed and shortening the start-up time using the method disclosed in Japanese Patent No. 191552.

[Problems to be Solved by the Invention 1] The signal level of radio waves transmitted by a GPS satellite varies greatly depending on 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 parameters such as the optimal PN search speed, the bandwidth of the narrow band filter for removing unnecessary noise, and the loop filter in the vibration loop circuit depending on the signal level. However, 1) Conventionally, these parameters were set uniformly regardless of the signal level, which caused a problem in that the time required for phase synchronization and frequency synchronization became long. Furthermore, (2) there are contradictory properties between the time required for synchronization and the accuracy of distance measurement, and it is difficult to satisfy both characteristics if these parameters are set arbitrarily. Furthermore, in the vibration loop circuit, there is a problem in that when the data is reversed, the accuracy of distance measurement deteriorates. Furthermore, (3) whether or not GPS signals can be received and the signal level are
It was only used to change the combination of satellites used for positioning.

An object of the present invention is to shorten the time required for a PN search, improve distance measurement accuracy, and reduce positioning errors. Furthermore, it is an object of the present invention to realize a navigation system with high positioning accuracy by applying information on whether or not a GPS signal can be received and the level of the received signal to the navigation system.

(Means for solving the problem) In order to achieve the above object, the present invention (1) calculates in advance the elevation angle of the GPS satellite visible at that time from the navigation data transmitted from the GPS satellite and the time of positioning. , from the antenna gain and GPS signal propagation loss at that elevation angle,
Equipped with a function to determine the S/N ratio (signal-to-noise ratio) of the received GPS signal. Furthermore, the optimum PN search speed, the filter bandwidth for removing unnecessary noise from the despread signal, and the loop filter parameters in the vibration loop circuit can be set from this value, and the PN synchronization acquisition and tracking functions can be set. It is something.

(2) When there is no navigation data from GPS satellites, when the reliability of that data is extremely low, or when there is no time information, first widen the filter bandwidth and perform synchronized acquisition of the GPS signal, then PN If synchronization is not achieved, the filter bandwidth is narrowed to acquire synchronization and establish PN synchronization.

(3) It is equipped with a function to switch the parameters of the loop filter in the vibration loop circuit before and after synchronous tracking. □ (4) Equipped with a function that estimates the time when the navigation data signal of the GPS satellite reverses from the previous data reversal, and when the data reverses, stops the signal input to the loop filter in the vibration loop circuit and holds the output. It is something that

(5) Equipped with a means to input external information such as the S/N ratio of the GPS signal, and based on that information, determine the optimal PN search speed, the bandwidth of the narrowband 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 that outputs information such as whether or not GPS signals can be received and the level of GPS signal reception, and the navigation system compares this information with the surrounding building conditions recorded in the map data to estimate the current position. It is equipped with the function of

[Effect]

(1) The S/N ratio of GP≦signal is calculated from the GPS signal propagation loss at the visible elevation angle of the GPS satellite and the gain pattern with respect to the antenna elevation angle. When the elevation angle at which a GPS satellite can be seen is high, the band of a narrow band filter that removes unnecessary noise is widened to achieve high-speed PN phase synchronization. Furthermore, when the elevation angle at which the GPS satellite can be seen is low, the band of this filter is narrowed and PN phase synchronization is achieved at low speed.

(2) When there is no navigation data from GPS satellites, or when the reliability of that data is extremely low, or when there is no time information, the level of the apcJt cannot be calculated.
First, a PN search is performed by widening the band of a narrowband filter that removes unnecessary noise from the despread signal. If synchronization is not detected during this process, the level of the GPS signal is low, so
Narrowing the band of this filter improves the S/N ratio. Furthermore, a pN search is performed to establish PN synchronization.

(3) l: The parameters of the loop filter in the dynamic loop should be selected to ensure stable PN tracking in a short period of time from the time when PN synchronization is detected until the start of positioning. After starting positioning, the parameters that minimize the distance measurement error are selected (increasing the constant of the multiplier in the loop filter).

(4) Since the navigation data signal of the GPS satellite is 50 BPS, the data is inverted every 20 m5. Using this property, it calculates when the next data inversion will occur based on the previous data inversion, and when the data inversion occurs, it stops the signal input to the loop filter in the vibration loop and holds the output signal.

(5) When information such as the previously received GPS signal level is received as external data and the signal level is determined to be high based on that information, the band of a narrowband filter that removes unnecessary noise from the despread signal is applied. widen and achieve high-speed PN phase synchronization. Furthermore, 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) GP for measuring self-position with navigation system
When using the S signal, it is checked whether there are any obstacles in the direction in which the GPS satellite can be seen, based on whether or not the GPS signal can be received and the signal level. When it is determined that there is an obstacle, map information and device information constituted by the GPS receiver are compared. Additionally, check the map to see if there are any obstacles in the direction of the GPS satellites. Furthermore, the self-position is determined by map-matching so that it is behind the obstacle.

(Example〕 Hereinafter, one embodiment of the present invention will be described with reference to FIG.

``No. 1'' is an example of a configuration of a GPS receiving device to which the present invention is applied.

In Figure 1, the center frequency 157 transmitted from the GPS satellite
The 5°42MHz spread spectrum signal is transmitted by antenna 1.
is captured and sent to the high frequency section 23.

The high frequency section 23 amplifies this signal with the low noise amplifier 2, and generates a reference oscillator 22 (for example, with an oscillation frequency of 65.472M).
carrier wave (for example, oscillation frequency 1509.948M) created by the first local oscillator 4 whose frequency is controlled by
(z), down conversion is performed at mixer 3, and the first
An intermediate frequency signal Sl is obtained.

Further, unnecessary noise signals are removed from this signal S1 by a bandpass filter 5 (for example, a passband width of about 2 MHz), and the signal is sent to the inverse spectrum spreading section 24.

In the reverse spectrum spreading section 24, the PN code NCO3 and P
The N code generator 7 generates P of the GPS satellite signal to be received.
With the PN code having the same pattern and the same phase as the N code, the spread spectrum signal sent from the high frequency section 23 is despread to obtain the second intermediate frequency signal S2.

This second intermediate frequency signal S2 is branched into two, and the reference oscillator 22
The output phase difference is 90" and the signal is mixed with the signal of 2'":
° Different third intermediate frequency signal S3. Obtain a and b (each called 1 [signal, Q signal).

By performing separate processing on the I and Q signals as described above, processing is possible at a low sampling frequency, and the configuration of the digital signal processing section is simplified.

Furthermore, a low pass filter 12 provided in front of the A/D converter. In a and b, remove the aliased signal which is a frequency component of 172 or more of the sampling frequency of the A/D converter,
Signal S4. Obtain a and b.

Here signal 83. a and b are approximately ±4K due to Doppler effect
Considering the frequency fluctuation of Hz and the frequency fluctuation of the reference oscillator, it is preferable to select the cutoff frequency of the low-pass filter 12, a, 'b to be about 5 to 7 KHz.

Furthermore, in the A/II> converter, this analog signal S4゜a
, b (for example, the reference oscillator signal is output by the branching unit 11 to 4096
15.984375MHz sampling signal) digital signal S5. a, , b and sent to the digital signal processing section 25.

In the digital signal processing section 25, the carrier wave signal output from the third local oscillator 15 constituted by a digital oscillator and the signal S5. Mix a and b with mixer 14°a and b,
Down-converted signal S6. Obtain a and b.

Further, a low-pass filter 16 whose signal cutoff frequency and passband can be adaptively changed according to a signal 816 from the calculation unit 21. a, b, signal 56. a, b
A carrier wave signal S7. from which unnecessary noise has been removed and which contains a navigation data signal. Obtain a and b.

The data demodulator 17 is composed of, for example, a Costas demodulator or a TAN format demodulator, and is a carrier wave signal S7. A carrier wave signal is reproduced from a and b, and the data signal S8 is demodulated by comparing it with the input signal and sent to the arithmetic unit 21.

The detector 18 also detects the input signal S7. The square root of the sum of the squares of a and b is calculated to obtain the amplitude information signal S9 of the input signal.

This signal S9 is sent to the arithmetic unit 21, and if the amplitude of $9 is above the set level, it is determined that the PN synchronization state is determined, and if the amplitude of S9 is below the set level, it is determined that the PN asynchronous state is determined, and the result is determined as the PN synchronization state. It is output as a signal 513.

Further, the amplitude information signal S9 is sent to the vibration loop 19, where it is processed by the dither signal 814 transmitted from the reference oscillator 22 and filtered at a filter frequency set by the reference signal S17 from the calculation section, and is then processed to produce a PN synchronization tracking signal. 510 is output. Note that the data inversion signal S15 is also input to the vibration loop 19 from the calculation unit 21, and controls the input of the signal S9 from the detector 18 to the vibration loop 19.

Further, the switch 20 switches between the PN synchronization acquisition signal SSL and the PN synchronization tracking signal S10.

If the PN synchronization signal 813 from the calculation unit 21 indicates an asynchronous state, it is switched to the PN synchronization acquisition signal Sll output from the calculation unit 21, and if it indicates a synchronous state, it is switched to the PN synchronization and tracking signal S10. .

The control signal S12 output from this switch 20 is PN
It is input to the code NCO3, controls the phase of the PN code, and
Creates a “N same” □ period state.

With the above configuration, GPS signals are demodulated and positioning is performed.
The difference from the conventional method is that the low-pass filter 16. a,
The cutoff frequency of b can be adaptively changed based on the signal S16 from the calculation unit 21, the filter constant of the vibration loop can be changed based on the control signal S17 from the calculation unit 21, and the PN synchronization acquisition signal SSl can be changed. The advantage is that the speed at which the PN synchronization point is searched (search speed) can be changed freely. This PN search uses the PN code chip rate frequency of the received wave and the P
This is achieved by slightly changing the chip rate frequency of the N code 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 difference in chip rate frequency between them.

Next, the processing configuration of the arithmetic unit will be explained using FIG. 2.

The navigation data analysis unit 44 edits navigation data from the demodulated GPS satellite navigation data signal S8.

It performs conversion into Amarnaq data (approximate position information of GPS satellites) and E-homeris data (detailed position information of GPS satellites) necessary for positioning and speed calculations.

Furthermore, information regarding the amount of change in Doppler frequency of the carrier wave is also superimposed on the data signal S8 and sent.

□The filter control calculation unit 45 performs S
/N ratio is estimated, the bandwidth of the low-pass filter is determined, and the filter signal 816 is output to the digital signal processing section 24.

The synchronization determination unit 46 monitors the amplitude information signal S9 of the human input signal, and determines that if the amplitude is above a set level, it is in a PN synchronized state, and if the amplitude is below a set level, it is determined to be a PN asynchronous state. The vibration loop control calculation unit 47 optimizes the loop filter to prevent deterioration of positioning accuracy when the data of the input signal is reversed and to perform stable tracking at high speed, which will be described later. Therefore, the vibration loop control calculation unit 47 predicts the data reversal time. It outputs a data inversion signal S15 and also changes the loop filter's multiplier constant using a control signal S17.

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

The Doppler fluctuation compensator 49 outputs to the third local oscillator a third local oscillation control signal S24 that controls the carrier wave signals S7a, b so as not to be influenced by Doppler fluctuations.

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

The positioning calculation 54 uses the pseudo distance data signal S23 output from the distance measurement counter 44 and the position data of the GPS satellite.
calculates its own three-dimensional position.

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

Next, the processing algorithm of the arithmetic unit 21 will be explained using FIG. After the power is turned on, start-up processing 100 is performed, and the position and speed of the currently visible GPS satellite are determined using the almanac data stored inside the calculation unit 10.
1゜From the combination of the geometric positions, determine the combination of four GPS satellites that can measure the self-position with the highest accuracy (in the case of two-dimensional positioning, a combination of three satellites) 102゜Furthermore, 103. Calculating the Doppler shift frequency amount of the satellite signal from the position and velocity of the GP8th star. After these basic calculations are completed, the settings of the digital signal processing section are performed.

First, the constant of the loop filter of the vibration loop is set to 104°, which is a constant for rapid tracking. Next, the carrier wave signal S7.
In order to remove Doppler frequency fluctuations from a and b, the oscillation frequency of the third local oscillator 15 is set from the calculated Doppler shift amount 105□.

Furthermore, a low-pass filter 16. After the bandwidths of a and b are set to 106° or more using a method described later, a PN synchronization search is started. In 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 has been obtained and positioning is started.

On the other hand, when the amplitude is below a certain identification level, the search is continued until the search for PNI periods is completed.

If 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. If 108° PN synchronization is obtained, the switch control signal section 48 outputs the switch switching signal 513. After 109° synchronization, which synchronizes by changing the PNNCO control signal S12 from the PN search signal Sll to the PN tracking signal S10,
After performing the vibration loop control calculation 110 and changing the loop filter constant to a value that improves the pseudorange measurement accuracy, calculations are performed based on the Doppler frequency obtained from the data demodulator 17 to more accurately measure Doppler frequency fluctuations. low-pass filter 16. to remove and increase pseudorange accuracy.
Narrow the bands of a and b 112゜ Edit the obtained navigation data and obtain almanac data, ehomeris data, etc. 113゜ Furthermore, input the measured values of pseudorange and pseudorange change rate 114 IL1'5. The speed and traveling direction 116 are calculated and output. As long as synchronization is achieved, positioning is continued, and when synchronization is lost, synchronization is regained and positioning is continued.1'17.Next, the operation of each part will be explained.

The navigation data signal S8 output from the data demodulator 17 of the digital signal processing section is edited and analyzed by the calculation section 21, and is processed to include satellite time and position information of each GPS satellite (Almanara, etc.).
data) is obtained.

Based on this almanac data (or previously collected almanac data), time, and current position information, each GP
Calculate the visible elevation angle of the S satellite.

``Furthermore, the gain G (dB) for the elevation angle of the antenna 1 stored in the memory inside the calculation unit 21 is read out, 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: 101101omW), and Od,Bm=1mW), the received GP
Calculated using the S signal level axis formula.

5=PL+G Furthermore, if the noise level N (dBm) is approximated to the thermal noise level, the noise level N can be calculated using the formula.

N=kTB• where k is the Boltzmann constant, T is the equivalent noise temperature, and B is the receiver bandwidth. The signal-to-noise ratio (S/N ratio) of the received GPS satellite can be calculated from this ratio of the GPS signal level and the axial sound level N.

When this S/N ratio is high, the low pass filter 16, a
, b are increased to increase the bandwidth to about 1 (kHz). By widening the bandwidth in this way, frequency synchronization becomes easier.

Furthermore, the PN search speed is increased to obtain phase synchronization in a short time of 5 seconds or less.

Furthermore, when the S/N ratio is low, the low-pass filter L6. a
, b are lowered and the bandwidth is narrowed to about 200 (Hz). By narrowing the bandwidth in this way, the S/N
This improves the ratio and makes it possible to capture GPS signals. Further P
Slow down the N search speed.

To obtain phase synchronization without errors due to the influence of noise.

Therefore, a phase synchronization time of about 10 seconds is required.

The above method was a method that changed each parameter based on almanac data, time, and current position information.
There is also a method of changing each parameter based on external data S18. Next, its operation will be explained.

The calculation unit 21 converts the almanac data into external data S18.
output to an external arithmetic device. The calculation device creates a table of satellite elevation angles with respect to time based on the approximate value of the current position and stores it in memory. If the orbital altitude of the GPS satellite remains the same as it is now, the satellite will pass over the same ground every day, just over four minutes ahead of time. Taking this effect into consideration, the elevation angle of the GPS satellite is determined from the current time and the satellite elevation angle table. The elevation angle value is sent to the calculation unit as external data 818, and the low-pass filter 16. Determine the cutoff frequency and PN search speed of a and b to achieve PN synchronization.

The operations of the external arithmetic device described above can also be stored and executed within the arithmetic unit 21.

Furthermore, another method will be explained.

First, the amplitude information signal S9 is taken into the calculation section and the S/N ratio of the received GPS signal is measured. This is calculated from the difference in amplitude between when no satellite is receiving the signal and when a signal from a GPSI star is being received. This actually measured S/
N ratio and the elevation angle of the satellite.

The S/N ratios calculated from the antenna gains are compared, the calculated S/N ratios are corrected, and the correction values are stored. Further, the S/N ratio axis information part data 818 is outputted to an external arithmetic device (not shown). This external arithmetic device has a S/N
Stores ratio information and time information in memory. When positioning is to be performed at a later date, the S/N ratio of the GPS signal at that time is retrieved from memory and used as external data 818, taking into consideration the effect that GPS satellites pass over the same ground every day, although they are a little over 4 minutes ahead of time. It is output to the arithmetic unit 21. With this information,
Low pass filter 16. The cutoff frequencies of a and b and the PN search speed are determined to reduce the PN synchronization time. The operations of the external arithmetic device described above can also be stored and executed within the arithmetic unit 21.

Further, a processing method when there is no almanac data, time information, or current position information will be described next.

First, when starting to receive GPS signals, the low-pass filter 1
6. The cutoff frequencies of a and b are raised, the passband width is widened, and a PN search is started. By widening the bandwidth in this way, frequency synchronization becomes easier. However, widening the bandwidth in this way deteriorates the S/N ratio, so
There are cases where PS satellites cannot be captured. So GPS
If the signal cannot be captured, a low pass filter 16,a, is applied to improve the S/N ratio.
The cutoff frequency of b is lowered, the passband width is narrowed, and PN search is performed once again to establish PN synchronization.

The capture of c p s 4= has been explained above, but P
In addition to shortening N search time, another desired feature of GPS is positioning accuracy. In order to improve positioning accuracy, the PN code of the input GPS satellite signal.

The vibration loop 19 controls the PN code generated by the PN code generator 7 inside the receiver so that the phases of the PN code are completely matched.
All you need to do is improve the accuracy of distance measurement.

An example of the configuration of a vibration loop to which the present invention is applied is shown in FIG. 4, and details thereof will be explained below.

The input amplitude information signal S9 is the data inverted signal S15.
The signal is switched and held and sent to the switch 25.

This signal is divided by the switch 25 into a lead signal and a delay signal by a dither signal S14. The lead and lag signals each pass through a loop filter and hold 26. which is controlled by a dither signal 814. Data is stored in a and b. Each output is input to the adder/subtractor 27, and the difference is taken, P
N synchronization tracking signal S10 is output.

Next, its operation will be explained.

The amplitude information signal S9 input to the vibration loop is as follows.

There are characteristics as shown in FIG. 5(b). In Figure 5 (a)
indicates the navigation data signal S8, and the horizontal axis is time. In other words, a phenomenon occurs in which the amplitude of 89 drops when the data is inverted.

This is caused by the influence of the filter used in the receiver and cannot be avoided. Moreover, such rapid fluctuations in the amplitude level cause the loop filter 28
．． Passing through a and b will have an adverse effect on PN synchronization and deteriorate positioning performance.

Therefore, the calculation unit 21 calculates the data inversion time of the GPS navigation data signal S8 from the previous data inversion time and the data inversion period 20m5, and the signal level becomes 1 at the time before and after the data inversion time shown in Fig. 5 (C 8 times the data inversion signal S15 shown in ).

When the signal level of S15 is inverted from O to 1, the switch 23 is turned off so that no input is applied to LX, and at the same time, the data before the switch is turned off is stored in the hold 24.

Conversely, when the signal level of 815 is reversed from 1 to 0,
When the switch 23 is connected, the hold 24 function is disabled.

As a result, the amplitude information signal shown in FIG. 5(b) becomes (d
) is converted into the signal shown in Since the fluctuation in the amplitude level when the information signal is inverted is reduced in this way, the distance measurement accuracy and positioning accuracy are improved. Further, the signal is divided into a lead signal S19 and a delay signal S20 under the control of the dither signal S14 by the signal switch 25 shown in (d).

The lead signal and the delay signal are sent to a loop filter and processed. The feature of the present invention is that this loop filter 2
8. The feature is that the multiplier constants inside a and b can be adaptively changed according to the processing process using a control signal 817 from the arithmetic unit.

When performing a PN search and acquiring synchronization, it is necessary to acquire synchronization reliably and to track rapidly.
A small value is selected for the constant of multiplier 29.8 to approximate the characteristics of a first-order loop filter. Further, during PN synchronization tracking, in order to eliminate tracking offset components and improve positioning performance, a large value is selected for the constant of the multiplier 29, b, which is the characteristic of a secondary loop filter.

Furthermore, the values of the constants of the multipliers 30.a, b are switched so as to improve the positioning accuracy.
sent to. If the signal switched by switch 25 has already been output to loop filter 28.8, switch 2
Hold the loop filter output signal just before switching 26.5. Store in b.

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

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

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

The sensor includes a GPS receiver 3 that measures its own absolute position.
11 An optical gyro 39 and a steering angle sensor 37 that measure the rotation angle, a geomagnetic sensor 38 that detects the direction, and a vehicle speed sensor 36 that measures the speed are used.

The display system is an LCD display 32. The information system is a road information receiver 34, and the calculation system is a CD-□ROM that stores road maps.
33, consists of a calculation unit 35 that determines the self-position from the sensor output and controls map matching, display, etc.

Let me briefly explain its operation. The GPS receiver constantly measures its own position and displays the measurement results on the LCD display. However, if the GPS signal cannot be received because it is behind a building, positioning will not be possible. Therefore, navigation is performed using the optical fiber gyro, angle information output from the steering angle sensor, angle information output from the vehicle speed sensor, and azimuth information output from the geomagnetic sensor, and map matching is also used to improve positioning accuracy and the measurement results. is displayed on the LCD display. This configuration allows accurate navigation at all times. It is also possible to perform constant navigation using sensor information such as an optical fiber gyro, a steering angle sensor, a speed sensor, and a geomagnetic sensor, and to make corrections using the positioning results of a GPS receiving device.

Furthermore, this GPS receiving device can also be applied to navigation systems for ships, airplanes, artificial satellites, etc.

Next, FIG. 7 shows an example in which the present GPS receiver is incorporated into a car navigation system having the above configuration and navigation is performed.

In the figure, vector 42 represents the traveling direction of a car 40 traveling on a road, 41 represents a building, and 43 represents a direction vector in which a GPS satellite can be seen.

The positioning accuracy of the GPS system has an error of 30 m to 50 m, depending on the visible placement of the satellites. In order to correct this error, the map and positioning results are compared, and map matching is performed to force the vehicle's location to match the road.

In the case of this figure, travel on the road shown in the figure is selected from the vehicle travel vector 42. However, if the vehicle continues to drive as it is, the a p S signal coming from the direction of the vector 43 will be blocked by the building 41, and the GPS receiving device mounted on the vehicle 4o will no longer be able to receive the GPS signal. This is because the signal level of the amplitude information signal S9 in FIG. 1 decreases,
This is determined when PN synchronization is lost. Therefore, this GPS
Map matching can be performed by using the signal interruption information.

In other words, the CD-ROM 3 that stores the road map shown in FIG.
3, by obtaining information about the building 41 and performing map matching to the location on the road where the direction vector 43 seen by the GPS satellite intersects with the building 41 when the GPS signal is interrupted, the exact location can be determined. .

〔Effect of the invention〕

Since the present invention is configured as described above, it produces the effects described below.

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

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

(3) By switching the parameters of the loop filter in the cystic loop circuit before and after PN synchronization, high-speed and stable synchronization acquisition and improvement in positioning accuracy are achieved.

(4) By estimating the data reversal from the previous data reversal and stopping the control of the vibration loop circuit during that period, it is possible to prevent the deterioration of the positioning error that occurs when the data of the GPS signal is reversed, and improve the positioning accuracy. It will be done.

(5) Provide a means to input/output information such as the elevation angle of the GPS satellite and the S/N ratio of the GPS signal, and remove unnecessary noise signals from the despread signal and the optimum PN search speed for the GPS signal level. By adaptively changing the bandwidth of the filter that performs positioning, the time required for phase synchronization and frequency synchronization can be shortened, and the time required to start positioning can be shortened.

(6) By transmitting whether or not GPS signals can be received to an external device, the navigation device compares this information with the surrounding building conditions recorded in the map data, and performs map matching to determine a more accurate position.

[Brief explanation of drawings]

Figure 1 is a block diagram of the GPS receiver. Figure 2 is a block diagram of the arithmetic processing unit. Figure 3 is a flowchart of the processing of the arithmetic processing unit. Figure 4 is a detailed diagram of the vibration loop circuit. Figure 5 is a diagram of the vibration loop circuit. Signals input and output to the loop circuit, FIG. 6 shows a car navigation system using a GPS receiver, and FIG. 7 shows map data used for map matching. 1... Antenna, 2... Low noise amplifier, 3, 6, 9
．． a, 9. b, 14°a, 14. b...Mixer, 4.
... first local oscillator, 5... bandpass filter, 7.
...PN code generator, 8...PN code NC0110.
...90" hybrid, 11...frequency divider, 12, a
, 12. b, 16. a.16. b - low pass filter,
13, a, 13. b-A/D converter, 15... third local oscillator. 17...Data demodulator, 18...Detector, 19...
Seismic loop. 20. 23, 25... switch, 21... calculation section,
22... Reference oscillator, 24, 26. a, 26. b-H
OL D, 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... Arithmetic unit, 36... Vehicle speed sensor, 37... Rudder angle sensor, 38
...Geomagnetic sensor, 39...Optical fiber gyro,
40... Car (navigator)\, 41... Building, 42... Traveling vector, 43... Direction vector where GPS satellites can be seen, 44... Navigation data analysis, 45.
...Filter control calculation, 46...Synchronization 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

Claims (1)

[Claims] 1. In a positioning satellite reception signal processing method for determining the current position of a moving object by receiving signals from a positioning satellite, the S/S/ of the signal from the positioning satellite is determined from the elevation angle of the satellite and the gain pattern of the antenna. 1. A positioning satellite received signal processing method, comprising calculating an N ratio, determining an optimal synchronization parameter based on the S/N ratio, and determining the current position of a moving object. 2. In claim 1, the synchronization parameters are a synchronization point search speed, a bandwidth of a filter that removes noise from a despread signal from a positioning satellite, and a gain of a loop filter in the vibration loop. Positioning satellite reception signal processing method. 3. In claim 2, the passing time and elevation angle of the satellite are calculated, and the received signal is processed using the synchronization parameter according to the recording time, which is stored in advance together with the S/N ratio and the synchronization parameter. A positioning satellite reception signal processing method characterized by: 4. The positioning satellite received signal processing method according to claim 3, wherein the recorded data is corrected based on actual measurement results, and the correction results are re-recorded. 5. In a positioning satellite received signal processing method for determining the position of a mobile object by receiving a signal from a positioning satellite, when the signal from the positioning satellite is started to be received, noise is removed from the signal from the positioning satellite by despreading. A method for processing a signal received by a positioning satellite, characterized in that the bandwidth of the filter is widened, and if synchronization cannot be obtained in the above state, the bandwidth of the filter is narrowed to perform synchronized acquisition of the signal from the positioning satellite. 6. In a positioning satellite reception signal processing method that receives signals from positioning satellites and calculates the current position of a moving object, the gain of the loop filter in the vibration loop that synchronizes with the received signal and tracks the signal is determined at the time of synchronous acquisition. A positioning satellite reception signal processing method characterized in that the positioning satellite reception signal is changed during synchronous tracking. 7. The positioning satellite received signal processing method according to claim 6, wherein the gain of the vibration loop filter is set so that tracking can be achieved in a short time during synchronous supplementation, and distance measurement accuracy is improved during synchronous follow-up. 8. In a positioning satellite received signal processing method for determining the current position of a mobile object by receiving a signal from a positioning satellite, the data reversal time of the spread spectrum signal sent from the positioning satellite is calculated in advance, and vibration is detected at the predicted time. 1. A positioning satellite received signal processing method, characterized in that the input of a data signal to a loop filter of a loop is stopped, and the value before the output is stopped is output from the vibration loop. 9. In a positioning satellite reception signal processing method that receives signals from positioning satellites and determines the current position of a mobile object, noise is removed from the synchronization point search speed and the despread signal from the positioning satellite based on external input data. filter bandwidth,
A positioning satellite received signal processing method characterized by setting parameters of a loop filter in a vibration loop. 10. In the positioning satellite reception signal processing method for receiving signals from positioning satellites and determining the current position of a mobile object, the synchronization search speed is based on the PN code of the received wave and the PN code inside the receiver.
A positioning satellite received signal processing method characterized by increasing the search speed by increasing the difference in the frequency of codes. 11. In a positioning satellite signal receiving device that receives signals from positioning satellites and determines the current position of a moving object, the receiving device has means for determining synchronization of the positioning satellite signals, and a filter is configured based on the determination result. A positioning satellite signal receiving device characterized by comprising means for varying the bandwidth. 12. In a positioning satellite signal receiving device that receives signals from positioning satellites and determines the current position of a moving object, means for detecting the elevation angle of the satellite and the gain pattern of the antenna, and the S/N ratio of the received signal from the positioning satellite. S/N ratio calculating means for calculating the S/N ratio, search speed determining means for determining the optimum synchronization point search speed from the calculation result, and determining the bandwidth of a filter for removing noise from the despread signal from the positioning satellite. What is claimed is: 1. A positioning satellite signal receiving apparatus comprising: a bandwidth determining means for determining a gain of a loop filter in a vibration loop; and a gain determining means for determining a gain of a loop filter in a vibration loop. 13. In a positioning satellite signal receiving device that receives a signal from a positioning satellite and determines the current position of a mobile object, when starting to receive the signal from the positioning satellite, noise is removed from the despread signal from the positioning satellite. A positioning satellite, characterized in that it is provided with a filter bandwidth determining means that widens the bandwidth of the filter and, if synchronization cannot be obtained in the above state, narrows the bandwidth of the filter to synchronize acquisition of a signal from the positioning satellite. Signal receiving device. 14. In a positioning satellite signal receiving device that receives signals from positioning satellites and determines the current position of a moving object, the receiving device is provided with an external information input terminal, and the receiving device receives signals from positioning satellites and determines the current position of a moving object. , a positioning satellite signal receiving device comprising means for determining an optimal synchronization parameter for synchronizing with a received signal. 15. In a positioning satellite signal receiving device that receives signals from positioning satellites and determines the current position of a moving object, the first processing means processes the signals from the positioning satellites in a short time, and the first processing means processes long-term data. A positioning satellite signal receiving device comprising a second processing means and a storage means for storing the processing result. 16. In claim 15, the first processing means determines the position and speed of the moving body from the signals from the positioning satellite, and the second processing means determines the position, transit time, and synchronization parameters of the positioning satellite. A positioning satellite signal receiving device characterized by: 17. The positioning satellite signal receiving apparatus according to claim 15, wherein the storage means records the processing result of the second processing means. 18. A positioning satellite signal receiving device that receives signals from positioning satellites and determines the current position of a moving object, is equipped with two vibration loop filters, and performs short-time tracking processing and processing that improves distance measurement accuracy. A positioning satellite signal receiving device characterized by: 19. The positioning satellite signal reception according to claim 18, characterized by having a mechanism for switching so that when the PN code generated inside the receiving device is used as a leading signal and a delayed signal, processing is performed by different loop filters respectively. Device. 20. The positioning satellite signal reception according to claim 18, wherein the gain of the loop filter is increased in the case of the short-time tracking process, and the gain is decreased in the case of improving measurement accuracy. Device. 21. In a navigation system comprising a positioning satellite signal receiving device that receives signals from a positioning satellite to determine the current position of a mobile object, and a notification device that reports the current position of the mobile object using other sensor information, The satellite signal receiving device is equipped with a storage means for storing reception availability and reception signal level, and an output terminal for outputting the stored information to a navigation calculation section, and the navigation calculation section is configured to detect the mobile object based on the information from the output terminal. A navigation system characterized by being equipped with a means for determining the status of surrounding buildings. 22. Detecting the moving direction of the moving object using signals from a geomagnetic sensor and a gyro mounted on the moving object, determining the moving speed and distance using the vehicle speed sensor, and calculating the position and traveling direction of the moving object based on the results. In navigation systems that display
From the estimation result, the synchronization point search speed,
A positioning satellite signal receiving device having a function of determining the bandwidth of the noise removal filter and the gain of the loop filter of the vibration loop is added, and the device is used in combination with the geomagnetic sensor and the gyro for self-position detection. navigation system. 23. In a positioning satellite received signal processing method for determining the current position of a moving object by receiving signals from a positioning satellite, the S/N of the signal from the positioning satellite to be received is determined from the elevation angle of the satellite and the directivity and angle of the receiving antenna. 1. A positioning satellite received signal processing method, comprising calculating a ratio, determining various parameters optimal for synchronization based on the S/N ratio, and determining the current position of a moving object. 24. Claim 23, characterized in that the various parameters are a synchronization point search speed, a bandwidth of a filter that removes noise from a despread signal from a positioning satellite, and a gain of a loop filter in the vibration loop. Positioning satellite reception signal processing method. 25. In claim 24, the passing time and elevation angle of the satellite are calculated, and the received signal is stored in advance together with the S/N ratio and the various parameters, and the various parameters are used according to the recording time. A method for processing a positioning satellite received signal. 26. The positioning satellite received signal processing method according to claim 25, wherein the recorded data is corrected based on actual measurement results, and the correction results are re-recorded. 27. In a positioning satellite reception signal processing method that receives signals from positioning satellites and determines the current position of a mobile object, the reception sensitivity of the signals from the positioning satellites to be received is determined from the elevation angle of the satellite and the directivity and angle of the receiving antenna. calculate the optimal synchronization point search speed for synchronization based on the reception sensitivity, the bandwidth of the filter that removes noise from the despread signal from the positioning satellite, and the gain of the loop filter in the vibration loop, and A positioning satellite reception signal processing method characterized in that the current position of a moving object is determined by synchronizing using the determined value.