JPH0829516A - Gps receiver - Google Patents

Abstract

PURPOSE:To reduce the error detection rate of a demodulated data when the receiving signals of positioning radio wave from GPS satellites have low and high levels. CONSTITUTION:When a receiving/processing section 12 receives a signal of predetermined level or above from a GPS satellite, a navigation message for each GPS is outputted along with a demodulated data, e.g. the time within the GPS satellite. A receiving position is operated from the demodulated data through a satellite position calculating section 13, a receiving position calculating section 14, and a distance/angle of elevation calculating section 15 before being presented at a display section 16. In this regard, a section 17 calculates a receiving signal level corresponding to the field strength at the receiving position based on the distance between the receiving position and the GPS satellite calculated at the section 15. A receiving detection level (threshold value for demodulation) corresponding to a predicted receiving signal level is then set at the receiving/processing section 12 and a corresponding demodulation data is delivered therefrom.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to an on-vehicle navigation system or the like, and based on the received signal level (electric field strength) of positioning radio waves from a GPS satellite (Navstar),
The present invention relates to a GPS receiver that performs such demodulation.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram showing the structure of a conventional GPS receiver. In FIG. 4, the GPS receiver includes a planar antenna 1 for receiving positioning radio waves from GPS satellites, and a signal received from the antenna 1 is processed to, for example, high frequency amplification, frequency conversion, and intermediate frequency. A reception processing unit 2 is provided which outputs the demodulation data of the navigation message and the GPS satellite time by performing the spectrum despreading demodulation processing on the amplification and C / A code. Further, a satellite position calculation unit 3 for calculating the positions of three or four GPS satellites in the sky from the demodulated data from the reception processing unit 2.
And a reception position calculation unit 4 for calculating reception positions, for example, two-dimensional position information of latitude and longitude or three-dimensional position information of latitude, longitude and altitude based on the GPS satellite position data from the satellite position calculation unit 3. And are provided. Further, a distance / elevation angle calculation unit 5 for calculating the distance to three or four GPS satellites in the sky and the elevation angle thereof, and a display unit for displaying information (positioning information) of the two-dimensional reception position or the three-dimensional reception position. 6 and 6. The satellite position calculation unit 3 to the reception position calculation unit 4 are generally configured by using a microcomputer or the like.

The operation of the GPS receiver having the above structure will be described below.

The antenna 1 receives positioning radio waves from three or four GPS satellites, and the received signals are input to the reception processing unit 2. When the received signal level is equal to or higher than a predetermined level, in other words, when the electric field strength is equal to or higher than the predetermined level, demodulation processing is performed and a navigation message for each GPS satellite and demodulated data such as GPS satellite time are output.
From this demodulated data, the satellite position calculation unit 3 calculates the positions of three or four GPS satellites, respectively. The distance / elevation angle calculation unit 5 calculates the distance and elevation angle between the reception position and the GPS satellite from the position information of each GPS satellite and the reception position information calculated last time by the reception position calculation unit 4. Alternatively, the estimated movement amount for the time from the previous position calculation to the current position calculation is added to the previous reception position, and the distance and elevation angle between the reception position and the GPS satellite are calculated from the approximate position to the distance / elevation angle calculation unit 5. Is calculated. Next, the reception position calculated by the distance / elevation angle calculation unit 5, the distance and elevation angle to each GPS satellite, the GPS satellite time from the reception processing unit 2,
The reception position calculation unit 4 calculates the reception position of the GPS reception device based on the time in the GPS reception device, and the two-dimensional or three-dimensional reception position information (positioning information) is displayed on the display unit 6 on the screen. To do.

As described above, even in the conventional GPS receiving apparatus described above, when the received signal level from the GPS satellite is predetermined,
By performing the demodulation process, two-dimensional or three-dimensional position information indicating the reception position is obtained.

[0006]

However, in the GPS receiver of the conventional example, when the reception processing unit 2 performs the inverse spread spectrum demodulation processing, the reception signal level (electric field strength) is obtained.
Since the reception detection level (threshold value) of whether or not to demodulate the received signal is set to be low so that the radio wave from the GPS satellite with low When demodulating radio waves from a high GPS satellite, there is a drawback that erroneous detection occurs with respect to the noise.

As described above, the present invention solves the conventional problem, and when the received signal of the positioning radio wave from the GPS satellite is at the low level and the high level, the false detection rate of the demodulated data can be reduced. An object is to provide an excellent GPS receiver.

[0008]

In order to achieve the above object, the invention according to claim 1 is a reception detection level of whether to demodulate a reception signal according to a distance between a reception position and a GPS satellite. In a GPS receiving device that changes the number, a receiving means that outputs a navigation message and demodulated data of satellite time when the received signal level of a radio wave transmitted from a GPS satellite exceeds a set reception detection level, and the device. From the demodulated data, the position calculating means for calculating the position of the GPS satellite from the demodulated data, and the distance between the GPS satellite and the receiving position from the position of the GPS satellite and the receiving position calculated by the position calculating means. And the distance / elevation angle calculating means for calculating the elevation angle, and the reception position and GP calculated by the distance / elevation angle calculating means.
A receiving position calculating means for calculating a receiving position based on a distance and an elevation angle from the S satellite, a satellite time from the receiving means and a time from the time measuring means, and a receiving position calculated by the distance / elevation angle calculating means and a GPS satellite. And a detection level calculation means for calculating a reception detection level for determining whether or not the reception means performs signal detection based on the reception signal level expected from the distance.

According to a second aspect of the invention, the reception position and GPS
A GPS receiving apparatus that changes a reception detection level of whether to demodulate a reception signal according to a distance from a satellite,
Receiving means that outputs a navigation message and demodulated data of satellite time when the received signal level of the radio wave transmitted from the PS satellite exceeds the set reception detection level, a clocking means that clocks the time in the device, and demodulated data Position calculating means for calculating the position of the GPS satellite from the position, and distance / elevation angle calculating means for calculating the distance and elevation angle between the GPS satellite and the receiving position from the position of the GPS satellite and the receiving position calculated by the position calculating means. A receiving position calculating means for calculating a receiving position based on a distance between the receiving position calculated by the distance / elevation angle calculating means and a GPS satellite, an elevation angle, a satellite time from the receiving means, and a time from the clocking means; Receiving sensitivity calculating means for calculating receiving sensitivity based on the directivity of the antenna from the elevation angle of the GPS satellite at the receiving position calculated by the elevation angle calculating means, and receiving sensitivity calculation Detection level calculation for calculating a reception detection level for determining whether or not to perform signal detection by the receiving means based on the sensitivity calculated by the step and the distance between the receiving position calculated by the distance / elevation angle calculating means and the GPS satellite And means.

[0010]

With this structure, the GPS according to claim 1
The receiving device outputs a navigation message and demodulated data of satellite time when the received signal level of the radio wave transmitted from the GPS satellite exceeds the set reception detection level. The reception detection level in this case is GP from the demodulated data.
The position of the S satellite is calculated, and further the distance and elevation angle to the receiving position are calculated, and the receiving position is calculated based on the satellite time and the time from the time measuring means, and the receiving position and the GPS satellite are It is calculated based on the received signal level expected from the distance.

Further, in the GPS receiving apparatus according to the second aspect, the position of the GPS satellite is calculated from the demodulated data, and the distance and elevation angle from this receiving position are calculated. further,
The reception position is calculated based on the satellite time and the time from the time measuring means, and the reception sensitivity due to the directivity of the antenna is calculated from the elevation angle of the GPS satellite at the reception position. The reception sensitivity, the reception position and the GPS satellite The reception detection level is calculated based on the distance from

Therefore, when the signal detection level is changed according to the distance between the GPS satellite and the receiving position and the received signal of the positioning radio wave from the GPS satellite is at the low level and the high level, the false detection rate of the demodulated data is detected. Is reduced.

[0013]

Embodiments of the GPS receiving apparatus of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of the first embodiment of the GPS receiving apparatus of the present invention. In FIG. 1, in the first embodiment, a planar antenna 11 for receiving positioning radio waves from GPS satellites and a received signal from the antenna 11 are processed, for example, high frequency amplification, frequency conversion,
The reception processing unit 12 that performs the intermediate frequency amplification and the spectrum despreading demodulation processing for the C / A code based on the reception detection level described below and outputs the demodulation data of the navigation message and the GPS satellite time is provided. Has been. Furthermore, a satellite position calculation unit 13 that calculates the positions of three or four GPS satellites in the sky from the demodulated data from the reception processing unit 12, and a GPS from this satellite position calculation unit 13
A reception position calculation unit 14 that calculates a reception position, for example, two-dimensional position information of latitude and longitude, or three-dimensional information of latitude, longitude, and altitude based on satellite position data is provided. Further, a distance / elevation angle calculation unit 15 that calculates the distances to the three or four GPS satellites in the sky and their elevation angles, and a display unit 16 that displays two-dimensional or three-dimensional reception position information (positioning information). , And a detection level calculation unit 17 for calculating the reception detection level. The satellite position calculator 1
3 to the reception position calculation unit 14 include a microcomputer (MPU) and a digital signal processor (DS).
It is generally configured using P) or the like.

Next, the operation of the first embodiment will be described. The antenna 11 receives respective positioning radio waves from three or four GPS satellites, and the received signals are input to the reception processing unit 12. When this received radio wave is equal to or higher than a predetermined electric field strength, the detection level calculation unit 1 described in detail below.
Based on the reception detection level set from No. 7, the demodulation processing is performed to obtain the navigation message and GPS for each GPS satellite.
Outputs demodulated data such as satellite time. From this demodulated data, the satellite position calculation unit 13 calculates the positions of three or four GPS satellites, respectively. Based on the position information of each GPS satellite and the reception position information previously calculated by the reception position calculation unit 14, the distance / elevation angle calculation unit 15 determines the reception position and the GPS position.
Calculate the distance to the satellite and the elevation angle. Alternatively, the reception position and the GPS can be calculated from the approximate position obtained by adding the estimated movement amount for the time from the previous position calculation to the current position calculation to the previous reception position.
The distance / elevation angle calculation unit 15 calculates the distance and elevation angle from the satellite. Next, the reception position calculated by the distance / elevation angle calculation unit 15 and the distance and elevation angle between each GPS satellite are calculated. Furthermore, based on the time in the GPS satellite from the reception processing unit 12 and the time in the GPS receiving apparatus, the GP
The reception position calculation unit 14 calculates the two-dimensional or three-dimensional reception position of the S reception device, and the positioning information is displayed on the screen of the display unit 16. In this case, from the distance between the reception position calculated by the distance / elevation angle calculation unit 15 and the GPS satellite, the detection level calculation unit 17 calculates the reception reception signal level based on the electric field strength at the reception position based on this distance.

FIG. 2 is a diagram showing the relationship between the distance between the receiving position and the GPS satellite and the elevation angle. In FIG. 2, the radius R of the earth is 6000 km, the orbit of the GPS satellite is the earth center O
And the radius of this orbit is 26000 km. When the satellite angle of the satellite at the receiving position is 0 degree and the radio wave of the GPS satellite is received, the distance between the receiving position and the GPS satellite is the shortest, when the elevation angle is 90 degrees, the distance is 20,000 km, and the longest angle is 0.
In the case of degrees, it becomes 25,000 km. Since the electric field strength is inversely proportional to the square of the distance, when the received signal level at a distance of 25000 km is "1", the received signal level is obtained by the following [Equation 1].

[0017]

[Equation 1]

From this [Equation 1], it is expected that the reception signal level at the reception position and the GPS satellite of 20,000 km will be about 1.6 times. Here, in order to detect the radio wave from the GPS satellite whose distance to the receiving position is 25000 km, which is the longest, the reception detection level at the distance of 25000 km is used as a reference and set to 0.80 (hereinafter, two significant digits). . The shortest distance between the receiving position and GPS satellite is 20,000
In the case of km, if the received signal level is multiplied by 1.6 and 0.8 is multiplied by 1.6 to obtain 1.3 as the received signal level, the false detection rate for noise can be reduced. it can.

As described above, by setting the reception detection level according to the expected reception signal level, it is possible to detect a signal even for a radio wave having a low reception signal level which is far from the GPS satellite, and the GPS satellite It is possible to reduce erroneous detection of noise of a radio wave having a high received signal level due to a short distance from. That is, since the reception detection level can be expressed as a function [Equation 1] of the distance between the reception position and the GPS satellite, the reception detection level can be expressed as the reception position and the GPS satellite.
It can be expressed as the following [Equation 2] as a function of the satellite distance. Based on this [Equation 2], the detection level calculation unit 1
7 determines the signal detection.

[0020]

[Equation 2]

The reception detection level is calculated from the distance between the reception position and the GPS satellite by [Equation 2]. The reception detection level is a function of the distance between the reception position and the GPS satellite. It should be.

[0022]

(Equation 3)

As described above, according to the first embodiment, the detection level calculating section 17 calculates the reception detection level according to the distance between the reception position and the GPS satellite, so that even a radio wave having a low reception signal level is obtained. The signal detection can be performed, and the false detection rate for noise of radio waves having a high received signal level can be reduced.

FIG. 3 is a block diagram showing the configuration of the second embodiment of the GPS receiver of the present invention. In FIG. 3, the second embodiment is different from the first embodiment shown in FIG.
A reception sensitivity calculation unit 20 for calculating the reception sensitivity at the reception position based on the distance and elevation angle between the reception position and the GPS satellite detected by the distance / elevation angle calculation unit 15 is added.

Next, the operation of the second embodiment will be described. In FIG. 3, the operation from the antenna 11 to the display unit 16 and the detection level calculation unit 17 is the same as that of the first embodiment shown in FIGS. Here, the sensitivity of received radio waves due to the directivity of the antenna 11 is calculated by the reception sensitivity calculation unit 20 from the reception position detected by the distance / elevation angle calculation unit 15 and the elevation angle of the GPS satellite, and further, the distance / elevation angle calculation unit 15 is calculated.
The reception signal level from the current GPS satellite is predicted from the reception position detected by the GPS satellite and the distance between the GPS satellite and the reception processing unit based on the reception detection level calculated by the detection level calculation unit 17 based on this prediction. 12 outputs the demodulated data. Similar to the description in FIG. 2 described above, the reception position and the GP
The distance to the S satellite and the received signal level are given by [Equation 1]. For the received signal level where the distance between the receiving position and the GPS satellite is 25000 km, the received signal where the distance between the receiving position and the GPS satellite is 20000 km It is expected that the level will increase about 1.6 times. Further, the planar antenna 11 also has directional characteristics, and the reception sensitivity of this antenna 11 can be obtained by the following [Equation 4].

[0026]

[Equation 4]

From this [Equation 4], the reception sensitivity varies depending on the elevation angle between the reception position and the GPS satellite, and the reception signal level also changes. Receiving sensitivity is 1/2 and elevation angle is 90 at elevation angle 0 degree
The reception sensitivity of the antenna 11 that is “1” in degrees is represented by the following [Equation 5].

[0028]

(Equation 5)

From [Equation 5], the received signal level when the distance between the receiving position and the GPS satellite is 25000 km is 0.5 because the elevation angle is 0 degree, and the receiving distance when the distance between the receiving position and the GPS satellite is 20000 km. The signal level is 90
Due to the degree, it is expected to be 1.6 as it is.
Here, the longest distance between the receiving position and the GPS satellite is 2500
In order to be able to detect the signal from the radio wave of the GPS satellite where the received signal level is 0km and the elevation angle of the GPS satellite is 0 degree, the level is set to 0.40 based on the reception detection level at the elevation angle of 0 degree and the distance of 25000km. If the distance between the receiving position and the GPS satellite is the shortest, 20,000 km,
The received signal level increases 1.6 times from the distance between the receiving position and the GPS satellite. Corresponding to this 1.6 times, if 0.44 obtained by multiplying 0.40 by 1.6 is set as the reception detection level, the false detection rate for noise decreases.

Further, when the elevation angle is 90 degrees, the antenna 11
In consideration of the fact that the received signal level is doubled compared to the elevation angle of 0 degree due to the directivity of, the reception detection level is set to 1.3, which is obtained by multiplying 0.64 by 2. As a result, the false detection rate for noise is further reduced.

As described above, if the reception detection level is set according to the distance between the reception position and the GPS satellite and the reception signal level predicted from the directional characteristics of the antenna 11, the reception sensitivity is poor and the reception position and the GPS satellite. It becomes possible to detect signals even for radio waves with a low received signal level due to the fact that the distance between Can be reduced. The false detection rate can be further reduced with respect to the noise of radio waves having a high electric field strength. The reception detection level can be expressed as a function of the expected reception signal level and reception sensitivity. The reception sensitivity is calculated by the reception sensitivity calculation unit 20 based on [Equation 5], and the reception detection level is represented by the following [Equation 6] which is a function of the reception position, the distance between the GPS satellites and the reception sensitivity. .

[0032]

(Equation 6)

The detection level calculation unit 17 calculates the reception detection level based on this [Equation 6], and the reception processing unit 12 determines the signal detection based on the calculated reception detection level. In the second embodiment, the reception detection level is calculated from the reception position, the distance between the GPS satellites and the reception sensitivity [Equation 6].
Then, the calculation is performed, but the reception detection level may be a function of the reception sensitivity depending on the reception position, the distance between the GPS satellites, and the directional characteristics of the antenna 11, which satisfies the following [Equation 7].

[0034]

(Equation 7)

Thus, according to the second embodiment described above,
Distance between the receiving position and GPS satellites, and G for the receiving position
Since the detection level calculating unit 17 calculates the reception detection level according to the reception sensitivity due to the directional characteristics of the antenna 11 obtained from the elevation angle of the PS satellite, it is possible to detect a signal even for a radio wave having a low reception signal level and the reception signal level is It is possible to reduce the false detection rate with respect to high radio wave noise.

[0036]

As is apparent from the above description, according to the GPS receiving apparatus of the first aspect, when the received signal level of the received radio wave from the GPS satellite exceeds the set reception detection level. Outputs navigation messages and demodulated data of satellite time.

Further, in the GPS receiving apparatus according to the second aspect, the position of the GPS satellite is calculated from the demodulated data, and the distance and elevation angle from this receiving position are calculated, and the satellite time and the time from the timekeeping means are calculated. The receiving position is calculated based on the elevation angle of the GPS satellite at the receiving position, and the receiving sensitivity due to the directivity of the antenna is calculated from the elevation angle of the GPS satellite. The receiving detection level is calculated based on this receiving sensitivity and the distance between the receiving position and the GPS satellite. It is calculated.

As a result, the signal detection level is GPS
It is changed according to the distance between the satellite and the receiving position, and when the received signal of the positioning radio wave from the GPS satellite is at the low level and the high level, the false detection rate of the demodulated data can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a first embodiment of a GPS receiving apparatus of the present invention.

FIG. 2 is an explanatory diagram showing a relationship between a distance between a reception position and a GPS satellite and an elevation angle in the first embodiment.

FIG. 3 is a block diagram showing the configuration of a second embodiment of the GPS receiver of the present invention.

FIG. 4 is a block diagram showing a configuration of a conventional GPS receiver.

[Explanation of symbols]

 11 antenna 12 reception processing unit 13 satellite position calculation unit 14 reception position calculation unit 15 distance / elevation angle calculation unit 16 display unit 17 detection level calculation unit 20 reception sensitivity calculation unit

Claims (2)

[Claims] 1. A GPS receiving apparatus for varying a reception detection level of whether or not to demodulate a reception signal according to a distance between a reception position and a GPS satellite, wherein a reception signal of a transmission radio wave from the GPS satellite. When the level exceeds the set reception detection level, a receiving unit that outputs a navigation message and demodulated data of satellite time, a time measuring unit that measures the time in the device, and a GPS satellite position is calculated from the demodulated data. Position calculating means and GP calculated by the position calculating means
Distance / elevation angle calculation means for calculating the distance and elevation angle between the GPS satellite and the reception position from the position of the S satellite and the reception position;
Receiving position calculating means for calculating a receiving position based on the distance and elevation between the receiving position calculated by the distance / elevation angle calculating means and a GPS satellite, the elevation angle, the satellite time from the receiving means, and the time from the clocking means; Detection level for calculating a reception detection level for determining whether or not to perform signal detection by the reception means based on the reception signal level expected from the distance between the reception position calculated by the distance / elevation angle calculation means and the GPS satellite A GPS receiving apparatus comprising: a calculating unit. 2. A GPS receiving apparatus for varying a reception detection level for demodulating a reception signal according to a distance between a reception position and a GPS satellite, wherein a reception signal of a transmission radio wave from the GPS satellite is provided. Receiving means for outputting a navigation message and demodulated data of satellite time when the level exceeds the set reception detection level, time measuring means for measuring the time in the device, and position for calculating the position of the GPS satellite from the demodulated data. Calculating means and GPS calculated by the position calculating means
Distance / elevation angle calculating means for calculating the distance and elevation angle between the GPS satellite and the receiving position from the satellite position and receiving position, and the distance and elevation angle between the receiving position and the GPS satellite calculated by this distance / elevation angle calculating means. The receiving position calculating means for calculating the receiving position based on the satellite time from the receiving means and the time from the clocking means, and the antenna from the elevation angle of the GPS satellite at the receiving position calculated by the distance / elevation angle calculating means. Reception sensitivity calculation means for calculating the reception sensitivity based on the directivity of, and the reception means based on the sensitivity calculated by the reception sensitivity calculation means and the reception position calculated by the distance / elevation angle calculation means and the GPS satellite. And a detection level calculating means for calculating a reception detection level for determining whether or not to perform signal detection in the GPS receiving device.