JP2002122651A - Gps receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a GPS receiver capable of controlling a multipath resistance in an optimal state regardless of the type of an antenna by optimally changing a threshold for selecting a reception signal to be used in a positioning calculation in accordance with whether the antenna is an active antenna or a passive antenna. SOLUTION: It is determined whether the connected antenna is the active antenna or the passive antenna on the basis of a direct current voltage of a power feed line to the antenna. On the basis of the result, the reception signal to be used in the positioning calculation is selected by setting the threshold for selecting the reception signal to an optimal threshold for use of the active antenna when the active antenna is connected and an optimal threshold for use of the passive antenna when the passive antenna is connected. The positioning calculation is performed using only the selected reception signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a GPS receiver for receiving a signal from a GPS satellite and performing a positioning operation, and in particular, a reception level for selecting a reception signal used for the positioning operation according to the type of antenna. Changing the threshold value of.

[0002]

2. Description of the Related Art A GPS receiver measures a distance between a GPS satellite and the GPS receiver itself by tracking a GPS signal transmitted from the GPS satellite (this is called a pseudo distance), and simultaneously measures the distance. It calculates its own position by a geometric operation based on pseudoranges for a plurality of GPS satellites. Furthermore, the GPS receiver measures the rate of change of the carrier frequency of each satellite, calculates its own moving speed and traveling direction, and outputs the calculation results as GPS output data.

[0003] The GPS receiver is tracking G
When the number of PS satellites is three, two-dimensional positioning is performed, and when the number is four or more, three-dimensional positioning is performed. The data calculated in two-dimensional positioning is "latitude, longitude", and in three-dimensional positioning, it is "latitude, longitude, altitude". The number of signals (satellite) that can be simultaneously captured by the GPS receiver is determined by the number of reception channels of the GPS receiver. Generally, the number of reception channels is 8 to 1
It is about 2ch.

FIG. 7 shows a configuration of a general GPS receiver. The GPS receiver 1 includes an RF unit 2, a digital correlation processing unit 3, and a positioning operation unit 4. In the RF unit 2, the signal from the GPS antenna 50 is converted into an intermediate frequency signal by the down converter 21 using the signal from the synthesizer 23 that generates a predetermined frequency based on the reference clock 24, and then the A / D converter 22 , And outputs the signal to the digital correlation processing unit 3. The digital correlation processing unit 3 is a functional block for despreading a GPS signal that has been spread spectrum, a carrier correlation unit 31, a PRN code correlation unit 32, and a carrier NCO3.
3, a plurality of reception channels including a PRN code generator 34 and a code NCO 35. In the positioning operation unit 4, the code generation timing of the PRN code generation unit 34 for each reception channel and the carrier NCO 33
The position, speed, direction, and the like of the GPS receiver 1 itself are calculated based on the phase change amount of the GPS receiver 1 These calculated data are passed to the host system as input / output data 43.

[0005] Incidentally, a GPS receiver and a GPS antenna are generally connected via a connector. The GPS receiver is mounted on various application devices such as a car navigation system and a portable information terminal. GP
The GPS antennas connected to the S receiver and used for these application devices are roughly classified into two types: active antennas and passive antennas. As shown in FIG. 8, the active antenna includes a signal amplifier 52 at a stage subsequent to the antenna element 51. In contrast, a passive antenna refers to a type without a signal amplifier.

The active antenna has a weak GPS signal radiated from a GPS satellite,
In consideration of the fact that the gain of No. 1 is small and that there is a transmission loss to the GPS receiver, it is used for the purpose of keeping the signal level at the RF signal input terminal of the GPS receiver at a certain value or more. On the other hand, a passive antenna is used in an application that does not require a signal amplifier in a case where transmission loss to a GPS receiver is small. Naturally, passive antennas can be expected to have lower costs.

[0007]

The positioning operation unit 4 can know the reception signal level from the output of the digital correlation unit 3 in each reception channel. Since the received signal level can be known, the positioning calculation unit 4 performs the positioning calculation using only the signal having the received signal level equal to or higher than the predetermined threshold, thereby eliminating the signal including the influence of the multipath. Positioning calculation can be performed. This is based on the fact that signals with relatively low received signal levels may be affected by multipath.

[0008] Since the active antenna amplifies and outputs a signal, the optimum threshold value differs depending on whether the antenna used is an active antenna or a passive antenna. FIG. 1A shows an example in which an optimum threshold value (first threshold value) based on an active antenna is applied to a reception signal level in a state where an active antenna is used, and FIG. 1C shows a passive antenna. An example in which an optimal threshold (second threshold) based on a passive antenna is applied to a received signal level in a state where the symbol is used. In addition, the graph of FIG.
This is the case where the S signal is received. The overall received signal level is higher with the active antenna of FIG. 1A and lower with the passive antenna of FIG. 1C. However, since ideal thresholds are applied according to the antennas to be used, signals (satellite B and satellite E) that may be affected by multipath are applied.
It can be seen that the signal of That is, signals not affected by multipath (satellite A, satellite C,
It is possible to execute the positioning calculation using the signals of the satellites D and F).

On the other hand, FIG. 1B shows an example in which an optimum threshold value (first threshold value) on the premise of an active antenna is applied to a received signal using a passive antenna, and FIG. 5 shows an example in which an optimum threshold (second threshold) based on a passive antenna is applied to a reception signal level when an active antenna is used. In the example of FIG. 1B, the threshold value (first threshold value) based on the use of the active antenna is applied in spite of the use of the passive antenna. It can be seen that the received signals (the signals of the satellite D and the satellite F) that can be obtained are excluded. In such a case, the GPS positioning rate is reduced, and the positioning performance is adversely affected.

In the example shown in FIG. 1D, a threshold (second threshold) based on a passive antenna is applied even though an active antenna is used.
Received signal (satellite B) that may include multipath
And the signals of the satellite E) are taken into the positioning calculation. In such a case, the positioning accuracy is adversely affected.

As is clear from the above, if the threshold value for selecting the reception signal used for the positioning calculation does not properly correspond to the type of the antenna, the positioning performance is adversely affected. Therefore, it is necessary to designate or recommend an antenna connected to the GPS receiver so that the GPS receiver can sufficiently exhibit its performance.

The present invention has been made in view of the above circumstances. That is, the present invention optimizes the threshold value for selecting a reception signal used for positioning calculation depending on whether the connected antenna has an amplifier, that is, whether the antenna is an active antenna or a passive antenna. It is an object of the present invention to provide a GPS receiver capable of controlling the multipath tolerance to an optimum state regardless of the type of antenna by changing the value to a suitable value.

[0013]

According to a first aspect of the present invention, there is provided a GPS receiver for performing a positioning operation based on a signal received from a GPS satellite, wherein an antenna connected to the GPS receiver includes an amplifier. With a means for changing a threshold for selecting a signal used for positioning calculation depending on whether the antenna is an active antenna or a passive antenna without an amplifier, using a reception signal selected by exceeding the threshold It is characterized by performing positioning calculation.
By performing a positioning operation by selecting a reception signal whose reception level exceeds the threshold, a reception signal having a low reception level, which is affected by multipath, is excluded and the positioning operation is performed. The threshold to be applied can be changed according to whether the antenna is an active antenna or a passive antenna. Therefore, even if the active antenna is connected and the reception level of the received signal is raised as a whole and the reception level of the signal that may include the influence of multipath is high, the threshold is raised and the antenna is optimized for the active antenna. By setting the threshold value to an appropriate value, it is possible to perform a positioning operation while excluding a signal that may include the influence of multipath. In a state where the passive antenna is connected and the reception level of the received signal is lowered as a whole and the reception level of the signal that may include the influence of multipath is lowered, the threshold is lowered and set to the optimum threshold for the passive antenna. Thus, similarly, it is possible to perform the positioning calculation while excluding a signal that may include the influence of multipath.

According to a second aspect of the present invention, there is provided a GPS receiver for performing a positioning operation based on a signal received from a GPS satellite, wherein the antenna connected to the GPS receiver is an active antenna having an amplifier. Determination means for determining whether the passive antenna has no amplifier, and a threshold change means for changing the reception level threshold according to whether the determination result obtained from the determination means is an active antenna or a passive antenna, Positioning calculation means for selecting a signal in which the received level of the received GPS signal exceeds a threshold value and performing positioning calculation using the selected signal; In the positioning operation means, only the signal level of the received signal exceeding the threshold value set by the threshold value changing means is used for the positioning operation. Therefore, in the positioning calculation, a signal having a low reception signal level, which is likely to include the influence of multipath, is eliminated. In this case, the threshold value changing means can change the threshold value depending on whether the antenna is an active antenna or a passive antenna. Therefore, even if the active antenna is connected and the reception level of the received signal is raised as a whole and the reception level of the signal that may include the influence of multipath is high, the threshold is raised and the antenna is optimized for the active antenna. By setting the threshold value to an appropriate value, it is possible to perform a positioning operation while excluding a signal that may include the influence of multipath. In the state where the passive antenna is connected and the reception level of the received signal is lowered as a whole and the reception level of the signal that may include the influence of multipath is low, the threshold is lowered and set to the optimum threshold for the passive antenna. Thus, similarly, it is possible to perform the positioning calculation while excluding a signal that may include the influence of multipath.

Since the reception level of the signal when the active antenna is used is generally higher than the reception level when the passive antenna is used, the threshold value changing means sets the threshold value when the active antenna is used by the passive antenna. The value is changed so as to be higher than a certain threshold value (claim 3).

Alternatively, the threshold value changing means has a first threshold value which is optimal when an active antenna is used as the antenna, and a second threshold value which is optimal when a passive antenna is used as the antenna. If the antenna is an antenna, the threshold may be the first threshold, and if the antenna is a passive antenna, the threshold may be the second threshold.

Since the reception level of the signal when the active antenna is used is generally higher than the reception level when the passive antenna is used, the first threshold and the second threshold are used.
The threshold value has a relationship of first threshold value> second threshold value (claim 5).

According to a sixth aspect of the present invention, the determination means makes the determination based on the DC voltage of the line on the live line (the line other than the ground) of the RF connector for connecting the antenna to the GPS receiver body. Do.

When an active antenna having an amplifier is connected, the DC voltage of the line on the live side of the RF connector is reduced. Therefore, when the DC voltage of the line is lower than a predetermined reference voltage, the determining means determines It is determined that the active antenna is connected, and when the DC voltage of the line is higher than a predetermined reference voltage, it is determined that the passive antenna is connected (claim 7).

[0020] The determining means may be constituted by a comparator for comparing the analog voltage level of the DC voltage of the line on the live line side of the RF connector with the analog voltage level of a predetermined reference voltage.

Alternatively, the determining means includes an A / D converter for A / D converting the voltage of the line on the live line side of the RF connector;
It is also possible to provide a means for comparing the digital value of the DC voltage of the line obtained by the digital signal output of the / D converter with a predetermined reference voltage as a digital value (claim 9).

[0022]

FIG. 2 is a block diagram showing the configuration of a GPS receiver 100 according to an embodiment of the present invention.
In FIG. 2, the conventional general GP shown in FIG.
Functional blocks having the same functions as the functional blocks of the S receiver 1 are denoted by the same reference numerals.

In FIG. 2, a signal from the GPS antenna 50 is output to the RF unit 2 via an antenna connection state detecting unit 60 provided at a stage preceding the RF unit 2. The antenna connection state detection unit 60 detects whether the GPS antenna 50 is an active antenna or a passive antenna. The GPS receiver 100 includes an antenna connection state detection unit 6
The configuration is such that the detection result at 0 is output to the positioning calculation unit 4a as the antenna connection state detection signal 61.

RF through the antenna connection state detection unit 60
The GPS signal input to the section 2 is
Is down-converted to an intermediate frequency by a signal from the synthesizer 23 that generates a signal of a predetermined frequency based on the signal of the reference clock 24. The down-converted intermediate frequency signal is converted into a digital signal by the A / D converter 22 and output to the digital correlation processing unit 3.

The digital correlation processing unit 3 performs processing for despreading the GPS signal which has been spread spectrum. The signal output from the A / D converter 22 to the carrier correlator 31 is a carrier NCO which is a numerically controlled transmitter.
The multiplication result is multiplied by the signal from 33, and the result of the multiplication is integrated, whereby the correlation calculation is performed. The positioning operation unit 4a controls the carrier NCO 33 via the carrier tracking loop 42 so that a peak value by this correlation calculation is obtained, that is, synchronization with the carrier is established.

The signal from carrier correlation section 31 is further output to PRN code correlation section 32. In the PRN code correlator 32, the signal from the carrier correlator 31 and the same pseudo random code as the GPS satellite to be captured
The signal is multiplied by a signal from the PRN code generator 34 generated based on the signal from the CO 35, and the multiplication result is integrated, thereby performing the correlation calculation. The positioning calculation unit 4a controls the code NCO 35 via the code tracking loop 41 so that a peak value obtained by this correlation calculation is obtained, that is, synchronization with the PRN code signal included in the GPS signal is established. .

By the above signal processing, the GPS signal is despread, and a baseband signal is obtained from the correlation output 36. The positioning calculation unit 4a acquires a GPS message including satellite position information and the like from the obtained baseband signal. Further, the positioning calculation unit 4a determines the G based on the generation timing of the PRN code signal generated on the GPS receiver side.
The time of flight of the PS signal is obtained, the pseudo distance is measured based on the time, and the speed, direction, and the like of the GPS receiver 100 itself are calculated based on the amount of phase change of the carrier NCO 33.

In the digital correlation processing section 3, a carrier correlation section 31, a PRN code correlation section 32, a carrier NCO 33, a PRN code generation section 34, and a code NC
There are a plurality of reception channels constituted by O35. For example, assume that the number of reception channels is eight in FIG. The positioning calculation unit 4a performs a geometric calculation based on the pseudoranges obtained from four or more of the received signals received on each reception channel, and performs a geometric calculation on the GPS receiver 100.
Executes a positioning operation to find its own position. The data such as the positioning result, speed, and direction are input / output data 43
It is passed to the host system as a.

The positioning operation section 4a applies a threshold value to signals received in each reception channel, selects only signals whose reception level exceeds the threshold value, and uses them for positioning operation. Further, the positioning calculation unit 4a sets the threshold to be applied at this time to an optimal value for use of the active antenna when the antenna status detection signal 61 indicates that the antenna is the active antenna based on the antenna status detection signal 61. Set to. In addition, when the antenna state detection signal 61 indicates that the antenna is a passive antenna, the positioning calculation unit 4a sets the threshold to an optimal value for use of the passive antenna.

Therefore, the antenna connection state detecting section 60
However, if it is determined that the GPS antenna 50 connected to the GPS receiver 100 is an active antenna, a threshold (first threshold) state as shown in FIG. 1A is realized. . When the antenna connection state detection unit 60 determines that the GPS antenna 50 connected to the GPS receiver 100 is a passive antenna, the threshold (second threshold) shown in FIG. The state will be realized. That is, the GPS antenna 50
Is an active antenna, the signal from the antenna is amplified and the reception level of the received signal is high, and accordingly, the threshold value is set to a higher value than that of the passive antenna. Note that these thresholds (first threshold,
The second threshold value) is a value stored in the ROM included in the positioning calculation unit 4a.
It is preferable to hold them at the like.

Since the threshold value is switched in this manner, regardless of which type of antenna is connected, a received signal (highly likely to be affected by multipath) in the positioning calculation in the positioning calculation unit 4a. Satellites B and E) are eliminated. That is, the influence of the multipath on the positioning result is eliminated irrespective of the type of the connected antenna, and the positioning accuracy is improved.

Next, details of the antenna connection state detecting section 60 will be described. FIG. 3 shows details of a circuit for supplying power to the antenna in the GPS receiver 100. Antenna 5
The GPS signal from 0 is input to the RF connector 62 of the GPS receiver 100 and then output to the down converter 21 via the capacitor 63a and the band-pass filter 63. In FIG. 3, there may be an example of a circuit in which a signal amplifier is inserted between the band-pass filter 63 and the down converter 21.

When the GPS antenna 50 is an active antenna, the power required by the antenna amplifier is supplied to the antenna. The power supply from the GPS receiver 100 side to the active antenna
This is done via the reverse path of the PS signal. That is, GPS
Power is supplied to the antenna 50 from the antenna power supply 65 via the protection resistor 64 and the inductor 64a.

The antenna power supply 65 on the GPS receiver 100
A protection resistor 64 is inserted between the antenna and the RF connector 62 in preparation for a short circuit at the antenna input terminal. FIG. 4 illustrates an equivalent circuit in a state where the antenna power supply 65 supplies power to the active antenna. Signal amplifier 52 provided in active antenna (FIG. 8)
Since a certain amount of power is consumed in this case, it can be regarded as a resistance on an equivalent circuit. Therefore, it is represented as an antenna unit equivalent resistance 68 in FIG.

With the above consideration, when the power supply 65 is supplied to the active antenna, the potential of the line sandwiched between the protection resistor 64 and the antenna unit equivalent resistor 68 is equal to the live line (ground) of the RF connector 62. The potential of the line on the other side) can be uniquely determined from the power supply voltage of the antenna power supply 65 and the resistance values of the protective resistance 64 and the antenna unit equivalent resistance 68.

FIG. 5 shows a voltage state in the equivalent circuit of FIG. In the state of FIG. 5, that is, in the state where the active antenna is connected, the line voltage 71 which is the potential of the line 68 a sandwiched between the protection resistor 64 and the antenna unit equivalent resistance 68 is the antenna power supply voltage which is the potential of the antenna power supply 65. It takes a certain value lower than 72 and higher than the ground potential (0 V). On the other hand, the line voltage 71 when the passive antenna is connected to the GPS receiver 100 or when the antenna is not connected (open state) becomes the same potential as the antenna power supply voltage 72.

FIG. 6 shows an antenna connection state detection circuit 60a added to the antenna power supply circuit shown in FIG. 3 for detecting an antenna based on the above.
It is. The circuit shown in FIG. 6 forms the antenna connection state detection unit 60. 6, in order to obtain the line voltage 71 shown in FIG.
4 and the input terminal of the comparator 66 are connected. The line voltage 71 input to the comparator 66 is compared with the reference voltage 67.

The reference voltage 67 may be set to an intermediate voltage between the line voltage 71 in the state where the active antenna is connected and the antenna power supply voltage 72 as shown in FIG. 5, for example. Therefore, the comparator 66 determines that the active antenna is connected when the line voltage 71 is lower than the reference voltage 67, and determines whether the passive antenna is connected when the line voltage 71 is higher than the reference voltage 67, Alternatively, it can be determined that it is in an open state where nothing is connected. The determination result is output to the positioning calculation unit 4a as the antenna connection state detection signal 61.

Therefore, the positioning calculation unit 4a can know whether the connected antenna is an active antenna or a passive antenna, and as described above,
It becomes possible to set the threshold of the reception level for selecting the reception signal used for the positioning calculation to an optimum value.

In FIG. 6, although the comparator 66 is used to know the state of the line voltage 71, an A / D converter is used in place of the comparator 66, and the A / D conversion is performed to obtain a digital value. By passing the line voltage 71 to the positioning calculation unit 4, the positioning calculation unit 4 compares the line voltage 71 as a digital value with the reference voltage as a digital value,
It is also possible to adopt a configuration for performing the same determination.

[0041]

As described above, according to the present invention, G
Depending on whether the PS antenna is an active antenna or a passive antenna, a reception level threshold for selecting a signal used for positioning calculation is set to an optimal value, and a reception signal having a high possibility of including multipath is set. Is eliminated, and the positioning accuracy can be improved. That is, it is possible to control the multipath resistance to an optimum state regardless of the type of the antenna. A user using the GPS receiver of the present invention has an advantage that it is not necessary to consider what kind of recommended GPS antenna is used.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a relationship between a received signal level and a threshold.

FIG. 2 is a diagram illustrating a configuration of a GPS receiver as an embodiment of the present invention.

FIG. 3 is a circuit diagram showing details of an antenna power supply circuit in the GPS receiver of the present invention.

FIG. 4 shows a state in which an active antenna is connected;
It is a figure showing the equivalent circuit of an antenna power supply line.

FIG. 5 is a diagram illustrating a relationship among an antenna power supply voltage, a line voltage of an antenna power supply line, and a reference voltage.

FIG. 6 is a circuit diagram showing details of an antenna connection state detection unit in the GPS receiver of the present invention.

FIG. 7 is a diagram showing a general configuration of a GPS receiver as a conventional technique.

FIG. 8 is a diagram showing a configuration of an active antenna.

[Explanation of symbols]

 Reference Signs List 2 RF unit 3 Digital correlation processing unit 4a Positioning operation unit 21 Down converter 22 A / D converter 23 Synthesizer 24 Reference clock 31 Carry correlation unit 32 PRN code correlation unit 33 Carrier NCO 34 PRN code generation unit 35 Code NCO 50 GPS antenna 60 Antenna Connection state detection unit 61 Antenna connection state detection signal 62 RF connector 64 Protective resistor 66 Comparator 68 Antenna unit equivalent resistance

Continued on front page F-term (reference) 5J021 AA02 AA13 CA06 DB04 EA04 FA14 FA15 FA16 FA17 FA20 FA29 FA30 FA31 FA32 GA02 GA08 HA05 HA06 HA10 5J062 AA02 AA11 AA12 CC07 DD15 GG02 5K061 AA11 BB12 CC02 CC45 CD01 AB05BA01 BE03

Claims (9)

[Claims] 1. A GPS receiver for performing a positioning operation based on a signal received from a GPS satellite, wherein an antenna connected to the GPS receiver is an active antenna having an amplifier or a passive antenna having no amplifier. A GPS receiver, comprising: means for changing a threshold value for selecting a signal to be used for positioning calculation depending on whether the signal is present, and performing positioning calculation using a reception signal selected when the signal exceeds the threshold value. 2. A GPS receiver for performing a positioning operation based on a signal received from a GPS satellite, wherein an antenna connected to the GPS receiver is an active antenna having an amplifier or a passive antenna having no amplifier. Determining means for determining whether or not the received GPS signal is a threshold value for changing the reception level threshold value according to whether the determination result obtained from the determining means is an active antenna or a passive antenna. And a positioning calculation means for selecting a signal having a reception level exceeding the threshold value and performing a positioning calculation using the selected signal. 3. The apparatus according to claim 2, wherein the threshold changing unit changes a threshold when the antenna is an active antenna so as to be higher than a threshold when the antenna is a passive antenna. The GPS receiver as described. 4. The threshold changing unit has a first threshold that is optimal when an active antenna is used as the antenna, and a second threshold that is optimal when a passive antenna is used as the antenna, The method according to claim 2, wherein the threshold is the first threshold when the antenna is an active antenna, and the threshold is the second threshold when the antenna is a passive antenna. GPS receiver. 5. The method according to claim 1, wherein the first threshold and the second threshold are a first threshold and a second threshold.
5. The GPS receiver according to claim 4, wherein a relationship of threshold> second threshold is satisfied. 6. The antenna according to claim 6, wherein the determining unit is configured to connect the antenna to the G antenna.
6. The determination according to claim 2, wherein the determination is performed based on a DC voltage of a line on a live line (a line that is not grounded) of the RF connector for connection to a main body of the PS receiver.
The GPS receiver according to any one of the above. 7. The determination means determines that an active antenna is connected when the DC voltage of the line is lower than a predetermined reference voltage, and the DC voltage of the line is higher than the predetermined reference voltage. 7. When it is high, it is determined that the passive antenna is connected.
The GPS receiver according to 1. 8. The apparatus according to claim 6, wherein said determining means comprises a comparator for comparing an analog voltage level of a DC voltage of said line with an analog voltage level of said predetermined reference voltage. The GPS receiver according to 1. 9. The method according to claim 8, wherein the determining unit determines a voltage of the line as A / A.
An A / D converter for performing D / D conversion, and means for comparing a digital value of a DC voltage of the line obtained by a digital signal output of the A / D converter with the predetermined reference voltage as a digital value. The GPS receiver according to claim 6, wherein: