JPH1048315A - Apparatus and system for reception from satellite - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an apparatus and a system in which an error generated in position data is reduced when radio waves transmitted from an artificial satellite are multipath-received in a plurality of propagation routes. SOLUTION: A GPS receiving apparatus 3 is constituted of an antenna unit 4 which receives radio waves from a plurality of GPS satellites 2, of a GPS body unit 5 which computes a present position on the basis of signals received by the antenna unit 4 and of an operating and display part 6 which displays a map around the present position. The GPS body unit 5 is composed of an RF converter 9 and of a GPS demodulation and computing part 10. A CPU 14 at the GPS demodulation and computing part 10 judges whether a receivable new channel is increased or not. When it is detected that the new channel is increased, the movement speed of a receiving position is computed on the basis of the difference between recently received data and previously received data. When the speed is at a prescribed value or higher, it is judged that received data which is received by the new reception channel is received indirectly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a satellite receiver and a satellite communication system which receive radio waves from artificial satellites and detect the current position based on the received signals.

[0002]

2. Description of the Related Art A global positioning system: GPS (Gl) is used as a satellite receiver for receiving a radio wave from an artificial satellite to determine the current position and a satellite communication system using the satellite receiver.
Product development using an obal positioning system (for example, a surveying system or a navigation system) is underway. This GPS is a non-geostationary satellite communication system that receives radio waves radiated from a non-geostationary satellite launched outside the earth's atmosphere and obtains a reception position. The GPS has an orbit altitude of about 20,000 km, a period of about 12 hours, and an inclination of orbit. Twenty-four satellites are arranged in six orbit planes at an angle of 55 degrees.

[0003] Artificial satellites used in GPS (hereinafter referred to as "GP
S satellite)) is 10 ^-13 /
It is equipped with a highly stable rubidium oscillator (10 nanoseconds / day) and an atomic clock of cesium oscillator. The time signals of all the GPS satellites are synchronized with the time managed as the entire GPS system.

Therefore, the atomic clock mounted on each GPS satellite is constantly monitored by a ground control station.
Periodically updated time correction data is transmitted to each GPS satellite together with the satellite orbit prediction data, and each GPS satellite transmits the orbit prediction data to the ground by radio waves.

[0005] A navigation signal transmitted from a GPS satellite is 1575.42 MHz (L1) as a PSK wave (Phase Shift Keying) subjected to spread spectrum modulation with a PN (Pseudo Noise) code. 1
Two types of radio waves of 227.6 MHz (L2) are transmitted. This code consists of P code (Precision Code) and C /
There are two types of A code (Clear and Acquisition Code). P code is 10.23 Mbps, L1 in one week cycle
And L2 are used to perform ionospheric correction, thereby enabling precise positioning. The C / A code is 1.023Mbp
s, using only L1 with a period of about 1 ms.

There are two types of positioning methods using the GPS, which differ in principle from each other as follows. As
A method to directly calculate the receiving position by receiving radio waves from multiple satellites by direct method positioning and decoding its navigation information (satellite time, orbital elements, etc.) There is a method of receiving radio waves from GPS satellites with a receiver placed and performing relative positioning based on a difference in arrival time between signals reaching the two receivers.

In the above direct method, the receiving device receives navigation signals transmitted from three or more GPS satellites, and calculates the difference between the time of the quartz clock built in the receiving device and the satellite time obtained from the navigation information. The three-dimensional position of the receiving point can be obtained by measuring the distance to the satellite. Actually, since the clock of the receiving apparatus itself may be shifted, the error of the clock can be calculated together with the position coordinates of the receiving apparatus from observation data transmitted from four or more GPS satellites.

The positioning accuracy by the direct method is within 10 m for the P code and about 30 to 100 m for the C / A code. Note that the positioning accuracy of the C / A code is SA (Selective) that intentionally causes an error in the navigation information (orbit, time) of the satellite.
Although the positioning accuracy is degraded due to a usage constraint called “Availability: selective use”, a method using a C / A code is generally used as a method for positioning a mobile body such as an automobile.

Further, in the above-described interference method, relative positioning is performed based on the arrival time difference between signals arriving at the two receivers. Since it has the advantage of being able to cancel and can be positioned with higher accuracy than positioning by the direct method, development for geodetic and surveying is under way.

[0010]

SUMMARY OF THE INVENTION In this way, the GPS
In a satellite receiving system that obtains the current position based on the time from when a radio wave is transmitted from a satellite to when it is received, each GPS
While a satellite has a precise atomic clock, the satellite receiver only has a clock with a crystal oscillator. Therefore, a clock offset easily occurs in the time information of the satellite receiver.

Therefore, in a satellite receiver, three or more (4
(About 12 pieces) of GPS satellites are received at the same time, and the pseudo-range data including the clock offset between each GPS satellite and the receiving point and the orbital position data of each receiving satellite are used to determine the receiving point. The position is calculated. Therefore, the satellite receiver is provided with 4 to 12 reception channels.

Further, radio waves from a GPS satellite do not travel straight but curve at a certain curvature when passing through the ionosphere, stratosphere, and troposphere. Therefore, the distance from the receiving point to the GPS satellite is calculated as a pseudo distance. In addition, since the GPS satellites emit radio waves toward the ground while moving, they can receive radio waves from the same satellite over a wide area on the ground.

However, since radio waves transmitted from GPS satellites are radiated over a wide range, there are cases where the radio waves are directly received by an antenna of a satellite receiving device, and cases where they are indirectly reflected by a building or the like. As described above, when a so-called multipath in which radio waves transmitted from the same GPS satellite are multiplexed and received on a plurality of propagation paths occurs, a signal of the same frequency is received a plurality of times with a certain time difference. , An accurate distance (pseudorange) from the receiving point to the GPS satellite cannot be obtained, and the current position displayed on the display becomes inaccurate.

As described above, in a satellite receiving apparatus and a satellite receiving system which perform positioning by receiving a radio wave transmitted from a GPS satellite, if there is a multipath, the distance (pseudo distance) to the GPS satellite can be accurately obtained. In particular, when displaying the current position of the moving object, frequent multipaths occur, so that there is a problem that the error of the current position displayed on the display increases.

The present invention has been made in view of the above problems, and has as its object to provide a satellite receiving apparatus and a satellite receiving system that solve the above problems.

[0016]

Means for Solving the Problems The present invention has the following features in order to solve the above problems. According to the first aspect of the present invention, a receiver that locks a reception channel that has received a radio wave from an artificial satellite among a plurality of reception channels, and calculates a current position based on reception data received by the reception channel of the receiver. A speed calculating means for calculating a moving speed of a receiving position based on a difference between current reception data received by the reception channel and previous reception data; and And an indirect reception determining means for determining that the received data received by the receiving channel is due to indirect reception when the speed is equal to or higher than a predetermined value.

Therefore, according to the first aspect, the moving speed of the receiving position is calculated based on the difference between the current received data received by the receiving channel and the previous received data, and the calculated speed is equal to or higher than a predetermined value. Sometimes, in order to determine that the received data received by the receiving channel is due to indirect reception, even if the radio wave transmitted from the artificial satellite is multiplexed and received on a plurality of propagation paths, the receiving channel is obtained by indirect reception. Excluding the received data, the receiving frequency of the receiving channel is searched again, and the current position with a small error obtained by the direct receiving can be obtained.

According to a second aspect of the present invention, there is provided a receiver for locking a reception channel of a plurality of reception channels that has received radio waves from an artificial satellite, and a receiver which locks a reception channel based on reception data received by the reception channel of the receiver. In a satellite receiving apparatus having a calculating means for calculating a position, a new receiving channel determining means for determining whether or not a new receiving channel that has become receivable has increased, and the new receiving channel determining means increasing the new receiving channel. If it is detected that the moving speed of the receiving position is calculated based on the difference between the current received data received by the plurality of receiving channels and the previous received data, the speed calculating unit calculates the moving speed of the receiving position. When the received speed is equal to or higher than a predetermined value, the received data received by the new reception channel is due to indirect reception. Indirect reception determination means for determining, is characterized in that it has a.

Therefore, according to the present invention, when it is detected that the number of new reception channels has increased, the reception position shifts due to the difference between the current reception data received by a plurality of reception channels and the previous reception data. When the speed is calculated and the calculated speed is equal to or higher than a predetermined value, it is determined that the received data received by the new reception channel is due to indirect reception. Even if the reception channel is multiplexed, the reception data obtained by indirect reception of the reception channel is excluded and the reception frequency of the reception channel is searched again, so that the current position with a small error obtained by direct reception can be obtained.

According to the third aspect of the present invention, a plurality of artificial satellites and a receiving channel among the plurality of receiving channels that receive radio waves from the artificial satellite are locked, and based on received data received by the receiving channel. In a satellite receiving system having a satellite receiving device for calculating a current position, the satellite receiving device calculates a moving speed of a receiving position based on a difference between current received data received by the receiving channel and previous received data. Speed calculation means, and indirect reception determination means for determining, when the speed calculated by the speed calculation means is equal to or more than a predetermined value, the reception data received by the reception channel is due to indirect reception. It is characterized by the following.

Therefore, according to the third aspect, similarly to the first aspect, the moving speed of the receiving position is calculated based on the difference between the current reception data received by the reception channel and the previous reception data. When the speed is equal to or higher than a predetermined value, it is determined that the received data received by the receiving channel is due to indirect reception. Reception data obtained by indirect reception is excluded, and the reception frequency of the reception channel is searched again, so that the current position with a small error obtained by direct reception can be obtained.

According to the fourth aspect of the present invention, a plurality of artificial satellites and a receiving channel for receiving radio waves from the artificial satellite among the plurality of receiving channels are locked, and based on received data received by the receiving channel. A satellite receiving system for calculating a current position, the satellite receiving device comprising: a new receiving channel determining means for determining whether or not a new receiving channel has become receivable; Speed calculating means for calculating the moving speed of the receiving position based on the difference between the current reception data received by the plurality of reception channels and the previous reception data when the increase in the number of new reception channels is detected by the determination means; When the speed calculated by the speed calculating means is equal to or higher than a predetermined value, the speed is received by the new reception channel. Shin data is characterized in that it has an indirect reception determination means determines that due indirectly receiving the.

Therefore, according to the fourth aspect, similarly to the second aspect, when it is detected that the number of new reception channels has increased, the present reception data and the previous reception data received by a plurality of reception channels are used. Calculates the moving speed of the receiving position from the difference, and when the calculated speed is equal to or higher than a predetermined value, it is determined that the received data received by the new receiving channel is due to indirect reception. Even if the received radio wave is multiplex-received on multiple propagation paths, the received data obtained by indirect reception of the receiving channel is excluded, the receiving frequency of the receiving channel is searched again, and the error obtained by the direct reception is small. The position can be determined.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing one embodiment of the present invention. GPS receiving system (satellite receiving system) 1
Is a non-geostationary satellite communication system that receives a radio wave transmitted from a non-geostationary satellite launched out of the earth's atmosphere and obtains a reception position.
GPS satellites 2 are arranged.

The GPS receiver (satellite receiver) 3 includes an antenna unit 4 for receiving radio waves from at least four GPS satellites 2 (2a to 2d), and an antenna unit 4
A GPS main unit (receiver) 5 for calculating the current position from the signal received by the controller 5 and an operation / display unit 6 for displaying a map around the current position.

The antenna unit 4 is connected to the GPS satellite 2 (2
The antenna 7 includes an antenna 7 for receiving radio waves from a to 2d) and an LNA (low noise amplifier) 8 for amplifying a signal received by the antenna 7. In addition, the GPS main unit 5
An RF converter 9 for converting an RF signal into an intermediate frequency signal (IF), and an intermediate frequency signal (I
After generating digital data obtained by demodulating F), arithmetic processing is performed using the digital data to obtain position data,
It comprises a GPS demodulation / arithmetic unit 10 for generating positioning data such as speed data.

Therefore, radio waves radiated from the GPS satellites 2 (2a to 2d) to the ground are received by the antenna unit 4, amplified, and then supplied to the RF converter 9. R
Although not shown, the F converter 9 includes an RF amplifier, first and second mixers, first and second IF circuits, VCO and P
An LL circuit and the like are provided. And the RF converter 9
Converts an RF signal into an intermediate frequency signal (IF),
It is supplied to the S demodulation / arithmetic unit 10.

Further, the GPS demodulation / arithmetic unit 10 outputs positioning data such as position data and speed data for specifying the current position to the operation / display unit 6, and the operation / display unit 6
Positioning data (reception position) supplied from the GPS demodulation / arithmetic unit 10 in response to an operation performed on the keyboard of the operation unit
Is displayed. When the GPS receiver 3 has map data by a memory card or the like, the operation / display unit 6
And the current location on the map.

FIG. 2 is a block diagram showing the configuration of the GPS demodulation / arithmetic unit 10. The GPS demodulation / arithmetic unit 10 has a CP
U14, a custom LSI 15, and a TCXO (temperature compensated crystal oscillator) 16. The CPU 14 performs satellite search control, carrier synchronization control, and C / A code synchronization control by operating the keys on the operation / display unit 6, and displays the GPS satellites 2 (2 a to 2 d) and the current position of the user on the operation / display unit 6. The pseudo distance data indicating the distance (without correction) is output. The custom LSI 15 receives an intermediate frequency signal (IF) from the RF converter 9 and a temperature-compensated clock from the TCXO 16, and includes a baseband converter, a carrier synchronization circuit, a correlation processing circuit,
It includes a C / A code generation circuit, a C / A code synchronization circuit, a baseband filter, a PSK (phase shift keying) data demodulation circuit, and CPU peripheral logic.

The TCXO 16 has a built-in temperature sensor 17 for performing temperature compensation in a housing, and an output terminal 18 for outputting a temperature signal detected by the temperature sensor 17 is provided on a side surface of the housing. The lead wire 19 drawn from the output terminal 18 is
It is connected to the input terminal 20 of U14.

For this reason, the CPU 14 performs a temperature compensation calculation process based on a temperature signal output from the temperature sensor 17 built in the TCXO 16 as described later.
The temperature of the XO 16 can be accurately detected. FIG. 3 is a block diagram showing a circuit configuration for performing frequency conversion of a signal received by the antenna 7.

A VCO (Voltage Controlled Oscillator) 22 is provided in the RF converter 9 and changes the oscillation frequency according to the voltage output from the TCXO 16. Also, NCO 23
It is provided in the GPS demodulation / arithmetic unit 10 and performs tuning by varying the frequency oscillated from the TCXO 16.

In this configuration, the frequency conversion of the RF converter 9 is fixed, and tuning is performed by the NCO 23.
Then, the reception frequency is obtained by the following equation. Receiving frequency = VCO + TCXO + NCO = 84.5 × TCXO + TCXO + Tune × TCXO (1) The nominal oscillation frequency of TCXO16 is 18.414 MH.
z, the IF of the RF converter 9 is 1.023 MHz.

Here, when trying to receive a radio wave emission frequency of 1575.42 MHz from the GPS satellite 2, GP
The value when locking the radio wave from S satellite 2 is Tune =
1.023 / 18.414. However, TCXO
When the deviation ΔF is included in the 16 reference frequencies, it can be expressed as the following equation.

TCXO = tcxo + ΔF (2) The reference frequency is tcxo = 18.414 MHz. Therefore, the actual reception frequency is 1575.42 + 8
It stops at 5.555 × ΔF [MHz]. However, TCXO
Since the deviation is unknown, it is necessary to search the reception frequency error range caused by the TCXO deviation.

The initial frequency search is performed in the same manner as in the conventional case. However, when the first GPS satellite 2 is locked, the TCXO deviation can be known from the oscillation frequency of the NCO 23 and the Doppler shift prediction (Dopp) of the channel locking the radio wave from the GPS satellite 2 based on the following equation. it can. 1575.42 + Dopp = 85.5 × TCXO + Tune × TCXO (3) Then, the search center frequency of another channel which is not locked yet is set to a value including the TCXO deviation correction. As a result, it is possible to reduce the time from locking the first GPS satellite 2 to locking the second and subsequent GPS satellites 2.

The satellite receiving system 1 which receives the radio waves transmitted from the GPS satellites 2 and obtains the current position as described above
In each of the GPS satellites 2 (2a to 2d), a precise atomic clock is mounted, while the GPS receiver 3 has a TC clock.
Only a crystal oscillation clock using the clock from the XO 16 is mounted. Therefore, a clock offset easily occurs in the time information of the GPS receiver 3.

Therefore, the GPS receiving device 3 simultaneously receives radio waves transmitted from three or more GPS satellites 2 and includes a pseudo-clock offset between each GPS satellite 2 (2a to 2d) and the receiving point. The position of the receiving point is calculated from the distance data and the orbital position data of each of the received GPS satellites 2 (2a to 2d).

By the way, in the GPS receiver 3,
Immediately after the power is switched from off to on, the oscillation frequency sharply changes due to the temperature characteristics of the oscillation frequency of the TCXO 16 as the reference signal generation source.
When radio waves from (2a to 2d) are captured, TCXO1
It is necessary to capture the radio wave by expanding the range of the frequency for searching the signal only until the oscillation frequency of No. 6 is stabilized.

However, if the range of the search frequency is widened and radio waves are captured, an accurate current position cannot be obtained until the oscillation frequency of the TCXO 16 becomes stable, and it takes a considerable time until the current position is calculated. Will be. Therefore, in the GPS receiver 3, the temperature characteristic of the oscillation frequency of the TCXO 16 is stored in the memory 21 of the CPU 14, and the temperature sensor 17 built in the TCXO 16 is used.
The predicted frequency related to the temperature characteristic of the TCXO 16 stored in the memory 21 is read out based on the temperature information derived from. Thereby, the CPU 14 can reduce the time from when the power is turned on until the radio wave from the GPS satellites 2 (2a to 2d) is captured.

Thus, in the memory 21 of the CPU 14,
As frequency setting means for reading temperature information detected by a temperature sensor 27 incorporated in the TCXO 16 and setting a frequency search range of radio waves from the GPS satellites 2 (2a to 2d) based on a frequency corresponding to a temperature characteristic of the TCXO 16 A frequency setting program is stored.

Further, the memory 21 of the CPU 14 is capable of receiving a calculation program for calculating a pseudo distance from the receiving point to the GPS satellite 2 based on the signal received by the receiving channel and calculating the current position, and receiving the program. A new reception channel judgment program (new reception channel judgment means) for judging whether or not a new reception channel has increased, and this reception received by a plurality of reception channels when it is detected that the new reception channel has increased. A speed calculating program (speed calculating means) for calculating the moving speed of the receiving position based on a difference between the data and the previous received data, and when the calculated speed is equal to or more than a predetermined value, the received data received by the new receiving channel is Indirect reception determination program (indirect reception determination means) that determines that the reception is due to indirect reception
Are stored.

When the power supply voltage Vcc is supplied, the CPU 14 starts the above-described receiving operation, performs an operation based on the pseudo distance data of the demodulated signal supplied from the RF converter 9, and obtains position data, It generates positioning data such as speed data and time data. Further, the CPU 14 performs image processing based on the main program and data from a map CD-ROM (not shown).

FIG. 4 is a view from the GPS satellites 2 (2a to 2d).
Radio signals are locked on each receiving channel and positioning is performed
FIG. The CPU 14 controls each GPS satellite 2 (2a
2d) is defined as a receiving point A.
Transmitted from each GPS satellite 2 (2a to 2d)
Each GPS satellite 2 from the receiving point A from the time until it is transmitted
Pseudo distance L to (2a to 2d) ₁~ L_FourIs calculated.
Radio waves transmitted from each GPS satellite 2 (2a to 2d)
When received by the antenna 7 of the GPS receiver 3
Means that radio waves of the same frequency are multiplexed (multipath)
Because there is no such thing, the simulation with each GPS satellite 2 (2a to 2d)
Similar distance L₁~ L_FourSince there is only one intersection,
The position of the point A can be obtained accurately.

However, when the radio wave reflected on a building or the like provided around the receiving point A is indirectly received, the receiving time is delayed by that amount, and each GPS satellite 2 (2a to 2d) is delayed.
Pseudo distance to the L ₁ '~L _4', and the error occurs in the current position. For example, the pseudo distance is L ₁ ′ by multipath.
'When it becomes, the pseudorange L _1' ~L ₄ intersections of ~L ₄ 'ends up plurality of, which intersections can not be determined whether a legitimate receiving point A. Since the pseudo distances L ₁ ′ to L ₄ ′ obtained by receiving radio waves from the respective GPS satellites 2 (2a to 2d) are larger than the original pseudo distances L _{1 to} L ₄ , the pseudo distance L ₁ When obtaining an intersection of ₁ '~L _4', so that the plurality of intersections within the error range B are scattered.

However, since it is unlikely that all of the receiving channels are affected by multipath, the receiving position moves and the pseudo distances L ₁ to L _{1 for} each receiving channel are changed.
L ₄ is complicatedly changed in pseudorange L ₁ '~L _4' by multipath. For example, when a multipath occurs only on the reception channel A that receives a signal from the GPS satellite 2a, the pseudo distance of the reception channel A is L ₁ ′, and the pseudo distances of the other reception channels B to D are L ₂ to L. It becomes ₄ .

Therefore, in this embodiment, since it is extremely unlikely that all the received radio waves are multipath, when one reception channel is locked and the pseudo distance is calculated, the value of the other pseudo distance is calculated. The correction distance corrected based on is calculated to determine whether the difference between the pseudo distance and the correction distance is within an allowable range, and when the difference between the pseudo distance and the correction distance is outside the allowable range, Unlock the receiving channel and repeat the frequency search. As a result, the pseudo distance of one reception channel is changed to a value that is not affected by multipath.

If the value of the pseudo distance L ₁ ′ is close to the correction distance calculated from the other pseudo distances L _{2 to} L ₄ , the difference between the pseudo distance and the correction distance is within the allowable range. ,
Continue to lock one receiving channel. This allows
The error range B formed by the pseudo distances L ₁ ′ to L ₄ ′ is reduced to the correction range C close to the original reception point A. As a result, the error due to multipath is reduced, and a position within the error range B close to the original receiving point A can be displayed as the current position.

FIG. 5 is a flowchart for explaining a process for displaying the current position based on the received data obtained from the GPS satellite 2. In step S1 (hereinafter, “step” is omitted), the CPU 14 searches for a reception frequency of one reception channel A. And GPS satellite 2
When receiving the signal from a, the receiving channel CH1 is locked. In S2, it is determined whether or not the reception channel is locked. If the channel is not locked, the reception channel cannot be received. Therefore, the flow shifts to S3 to update the search frequency to the next reception channel CH2. Then, the process returns to S1 to search for the reception frequency of the reception channel CH2.

As described above, S1 to S3 are repeated to search for a reception frequency while switching the reception channel until a radio wave from one GPS satellite 2 is received. Also, S2
If the receiving channel is locked in step S4, the process proceeds to step S4, and it is determined whether the receiving channel can be received on another receiving channel. Then, if reception is possible on another reception channel, the process proceeds to S3 and the search frequency is updated to the next reception channel CH3. Thereafter, the process returns to S1 to search for the reception frequency of the reception channel CH3.

However, if all the receivable reception channels are locked in S4, the process proceeds to S5, where all the reception frequencies of the currently locked reception channels are stored. In the next step S6, the pseudo position La to the GPS satellite 2 is calculated from the received data received in each reception channel to calculate the reception position (current position).

Then, the current position and the positioning time are stored in the memory 21 in S7. Subsequently, the process proceeds to S8, where the reception channel received last time is compared with the reception channel received this time. In the next step S9, it is determined whether or not the number of new reception channels has increased from the result of comparing the previous reception channel with the current reception channel. This is because when the vehicle is moving, when passing by a building, a mountain, or the like, the number of receivable GPS satellites 2 changes and the GPS satellites 2 themselves are also moving, so that new reception is possible. GPS
The number of satellites 2 increases, or it becomes impossible to receive radio waves from GPS satellites that could be received until then. Therefore, the number of receivable GPS satellites 2 and the reception channel change every moment.

If the number of new reception channels has not increased in S9, the process proceeds to S10, where the currently calculated coordinate position is displayed on the display of the operation / display unit 6. Thereafter, the process returns to S1, and the processes of S1 to S10 are repeated. However, if the number of new reception channels has increased in S9, the process proceeds to S11, and the difference between the reception position calculated in the previous process and the reception position (current position) calculated in the current process is determined by comparing the difference between the previous position and the current position. The moving speed is calculated by dividing by the time difference.

In the next S12, the moving speed becomes, for example, 300
Judge whether it is over km / h. If the calculated moving speed is equal to or less than 300 km / h, it is determined that the moving speed is normal, and the process proceeds to S10. However, the calculated moving speed is 30
If the speed is 0 km / h or more, the speed is normally unthinkable, so it is determined that the speed is abnormal, and the flow shifts to S13 to determine that the error due to the new reception channel is large. That is, S1
In 2, when the calculated moving speed is 300 km / h or more, it is determined that an error due to multipath (indirect reception) is large.

In this case, since the currently calculated reception position (current position) is an abnormal value having a large error, the process proceeds to S14, and the previously calculated coordinate position is displayed on the display of the operation / display unit 6. Then, the lock of the new reception channel is released in S15. Then, in S16, the receiving frequency of the new receiving channel is searched again. Subsequently, in S17, it is determined whether or not the new reception channel has been locked by receiving radio waves from the GPS satellites 2. Then, the search of the reception frequency of the new reception channel is performed until the new reception channel is locked. When the new reception channel is locked, the process returns to S6 described above, and the processing after S6 is executed.

As described above, when the number of new receivable channels that can be received increases, the moving speed is calculated from the difference between the previous and current reception positions, and when the moving speed is higher than a predetermined speed (for example, 300 km / h), the multi It is determined that the error due to the path (indirect reception) is large. Therefore, even if the radio wave transmitted from the GPS satellite 2 is multiplexed (multipath) on a plurality of propagation paths, if the error is large (the amount of deviation S exceeds the allowable range C), the reception data of the new reception channel is transmitted. By ignoring and re-searching the reception frequency of the new reception channel, it is possible to obtain reception data with less error due to multipath and to obtain a more accurate reception position. as a result,
An accurate distance (pseudo distance) from the receiving point to the GPS satellite 2 can be obtained, and the current position can be accurately displayed.

For this reason, radio waves transmitted from the same GPS satellite 2 are multiplexed and received (multipath) through a plurality of propagation paths, and if the error is large, the received data is ignored and the reception frequency of the reception channel is changed again. By performing a search, an accurate reception position can be obtained.

In the above embodiment, when the number of new reception channels increases, the moving speed is calculated from the difference between the previous and current reception positions, and it is determined whether or not an error due to multipath (indirect reception) is large. Regardless of whether or not the number of new reception channels has increased, it is also possible to calculate the moving speed from the difference between the previous and current reception positions and determine whether or not the error due to multipath (indirect reception) is large.

[0059]

As described above, according to the first and third aspects, the moving speed of the receiving position is calculated by calculating the difference between the current received data received by the receiving channel and the previous received data. If the speed is equal to or higher than a predetermined value, the receiving channel is determined to be the result of indirect reception. Can exclude the received data obtained by the indirect reception and search the reception frequency of the reception channel again to obtain the current position with a small error obtained by the direct reception. For this reason, radio waves transmitted from the same artificial satellite are multiplexed (multipath) through multiple propagation paths,
If the error is large, an accurate reception position can be obtained by ignoring the data received from the artificial satellite and searching again for the reception frequency of the reception channel.

According to the second and fourth aspects, when it is detected that the number of new reception channels has increased, the difference between the current reception data received by a plurality of reception channels and the previous reception data is calculated. The moving speed of the receiving position is calculated, and when the calculated speed is equal to or higher than a predetermined value, the radio wave transmitted from the artificial satellite is used to determine that the received data received by the new receiving channel is due to indirect reception. Even if multiplex reception is performed on a plurality of propagation paths, the reception data obtained by indirect reception of the reception channel is excluded, and the reception frequency of the reception channel is searched again to obtain a current position with a small error obtained by direct reception. be able to.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a GPS demodulation / arithmetic unit in FIG. 1;

FIG. 3 is a block diagram showing a circuit configuration for performing frequency conversion of a received signal.

FIG. 4 is a diagram for explaining a pseudo distance, an error range, and an allowable range between each GPS satellite and a reception point.

FIG. 5 is a flowchart illustrating a process of displaying a current position based on received data obtained from a GPS satellite 2.

[Explanation of symbols]

 Reference Signs List 1 GPS receiving system 2 (2a to 2d) GPS satellite 3 GPS receiving device 4 Antenna unit 5 GPS main unit 7 Antenna 9 RF converter 10 GPS demodulation / arithmetic unit 14 CPU 15 Custom LSI 16 TCXO (Temperature compensated crystal oscillator) 21 Memory

Claims (4)

[Claims] 1. A receiver for locking a reception channel of a plurality of reception channels that has received radio waves from an artificial satellite, and a calculation unit for calculating a current position based on reception data received by a reception channel of the receiver. A speed calculating means for calculating a moving speed of a reception position based on a difference between current reception data received by the reception channel and previous reception data; and a speed calculated by the speed calculation means. A satellite receiving apparatus comprising: an indirect reception determining unit that determines, when the value is equal to or more than a predetermined value, reception data received by the reception channel to be obtained by indirect reception. 2. A receiver for locking a reception channel of a plurality of reception channels that has received a radio wave from an artificial satellite, and a calculation means for calculating a current position based on reception data received by the reception channel of the receiver. A new receiving channel determining means for determining whether or not a new receiving channel that has become receivable has increased, and when the new receiving channel determining means detects that the new receiving channel has increased. Speed calculation means for calculating the moving speed of the reception position based on the difference between the current reception data received by the plurality of reception channels and the previous reception data, and the speed calculated by the speed calculation means is not less than a predetermined value. In some cases, an indirect reception determination method for determining that the reception data received by the new reception channel is due to indirect reception. A satellite receiver comprising: a stage; 3. A satellite receiver which locks a plurality of artificial satellites and a receiving channel out of the plurality of receiving channels that receives radio waves from the artificial satellite, and calculates a current position based on received data received by the receiving channel. A satellite receiving system, comprising: a speed calculating unit configured to calculate a moving speed of a receiving position based on a difference between current reception data and previous reception data received by the reception channel; A satellite receiving system, comprising: when the speed calculated by the calculating means is equal to or higher than a predetermined value, determining that the received data received by the receiving channel is due to indirect receiving. . 4. A satellite receiver which locks a plurality of artificial satellites and a receiving channel out of the plurality of receiving channels that has received radio waves from the artificial satellite, and calculates a current position based on received data received by the receiving channel. A satellite receiving system comprising: a new receiving channel determining unit that determines whether a new receiving channel that has become receivable has increased; and a new receiving channel determined by the new receiving channel determining unit. When the increase is detected, speed calculation means for calculating the moving speed of the receiving position based on the difference between the current reception data received by the plurality of reception channels and the previous reception data; When the received speed is equal to or higher than the predetermined value, the reception data received by the new reception channel is indirectly received. A satellite receiving system comprising: