JPH0661979A - Diversity gps receiver - Google Patents

Abstract

PURPOSE:To improve a diversity effect when the receiver of a GPS being a position measurement system which uses a satellite with which the entire earth is covered is mounted on a vehicle. CONSTITUTION:A GSP receiver which obtains a position measurement by sequentially receiving a signal from the plural satellites, is equipped with an antenna switching control means 16 which receives the signal sequentially received from one satellite by successively switching plural antennas 1 and 2, level detecting means 17 which detects the level of the signal received by the plural antennas 1 and 2, antenna receiving level judging means 18 which judges the maximum value of the receiving level detected by the level detecting means 17, and position measurement data selecting means 19 which selects one of the received data of the plural antennas 1 and 2 corresponding to the maximum receiving level detected for each satellite, and derives the position measurement.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is a GPS (Global Positionin) which is a satellite-based positioning system that covers the entire globe.
g system) receiver, which can improve the diversity effect when the receiver is mounted on a vehicle and used.

[0002]

2. Description of the Related Art Conventionally, there have been techniques described below as techniques in such a field. When a receiver for using the GPS location system is mounted on a vehicle, satellite signals from a plurality of satellites are obtained by a high-speed sequential reception method, but there are many antennas due to the effect of expanding the spatial reception area. Is preferred. On the other hand, when the antenna is provided outside the vehicle, it is necessary to satisfy the design requirement that the appearance is not damaged. From such a viewpoint, a diversity receiver in which two antennas are installed on the vehicle body is adopted in order to ensure positioning accuracy. That is, positioning is derived by sequential reception of satellite signals from a plurality of satellites, but when one antenna receives a fading effect, it is switched to the other so as not to be affected by this. In this way, the spatial diversity increases the opening area of the antenna for the radio wave input of the two antennas, thereby improving the positioning accuracy.

[0003]

However, there is a problem that the signals from both antennas include fading signals because the arrival directions of a plurality of satellite signals are different. That is, for example, in one antenna, the A satellite signal is subject to fading action, in B antenna signal is not subject to fading action, in the other antenna, A satellite signal is not subject to fading action, B satellite signal is subject to fading action, and other satellites are subject to fading action. If the signal is not subject to fading, correct positioning cannot be derived because the signals of both antennas include the signal subject to fading.

Therefore, in view of the above problems, it is an object of the present invention to provide a diversity GPS receiver which is less likely to be affected by fading effects on a plurality of antennas and which can derive correct positioning.

[0005]

In order to solve the above problems, the present invention provides a GPS receiver that receives signals from a plurality of satellites to obtain positioning, antenna switching control means, level detection means, and antenna reception. A level determination means and a positioning data selection means are provided. The antenna switching control means receives a signal from one satellite to be received by sequentially switching a plurality of antennas.

The level detecting means detects the levels of signals received by the plurality of antennas. The antenna reception level determination means determines the maximum value of the reception levels detected by the plurality of antennas by the level detection means in synchronization with the switching of the antenna switching control means.

The positioning data selection means selects one of the reception data of the plurality of antennas corresponding to the maximum reception level detected by the antenna reception level determination means (18) for each satellite to derive positioning.

[0008]

According to the diversity GPS receiver of the present invention,
A signal from one satellite received by the antenna switching control means is received by sequentially switching a plurality of antennas, and the level detection means detects the level of the signal received by the plurality of antennas, and the antenna The reception level determination means determines the maximum value of the reception levels detected by the plurality of antennas by the level detection means in synchronization with the switching of the antenna switching control means, and the positioning data selection means determines the antenna reception level for each satellite. One is selected from the reception data of the plurality of antennas corresponding to the maximum reception level detected by the determination means, and the positioning is derived by the navigation message decoding means. Therefore, even if each of the multiple antennas is subject to fading effects, it is less likely to be affected by this and correct positioning can be derived.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a diversity G according to an embodiment of the present invention.
It is a figure which shows a PS receiver. Diversity G shown in this figure
The PS receiver first comprises two antennas 1 and 2. The antennas 1 and 2 are attached to, for example, a front portion and a rear portion of a vehicle, and receive transmission signals formed by C / A codes from a plurality of artificial satellites. The C / A code will be described below.

FIG. 2 is a diagram for explaining the C / A code in the satellite transmission signal. As shown in the figure, radio waves of 1575.42 MHz are transmitted from each satellite and phase-modulated by a digital code called C / A code. This C /
The A code is called a pseudo noise (PN) code, and a different code is assigned to each satellite. The spectrum is spread by modulating each code so that each satellite can be identified even at the same frequency. Has become.
There are 36 types of C / A codes, the chip rate is 1.023 Mbps, and the code length is 1023 bits (1 ms). On the C / A code, data necessary for positioning calculation called "navigation message" is superposed. Navigation message has a chip rate of 50 bps
So, one mainframe is constructed in 30 seconds.

Returning to FIG. 1, the switch 3 is the antenna 1
And 2 are switched alternately. The RF amplifier 4 amplifies the RF signal switched by the switch 3. The oscillator 5 is a temperature compensation crystal oscillator. PLL (Phase Locked Loo
p) 6 forms a signal for local oscillation using the oscillator 5 as a reference signal. The mixer 7 is about 1.5 from the RF amplifier 4.
The RF signal of GHz is frequency-converted (IF signal) to the intermediate frequency of 4.092 MHz. The intermediate frequency filter amplifier 8 amplifies the signal converted by the mixer 7 by about 110 dB.
An A / D converter 9 (Analog to Digital Converter) converts the analog signal amplified by the intermediate frequency filter amplifier 8 into a 1-bit digital signal. C / A synchronizing means 10 for inputting the digital signal of the A / D converter 9
Simultaneously demodulates the data by matching the frequency with the satellite radio wave and at the same time matching the phase of the C / A code to despread the spectrum. At this time, C / A from each satellite
Since the code is sent at the timing exactly synchronized with the atomic clock mounted on the satellite, the pseudo distance RP from the phase shift amount of the C / A code at the time of synchronization at the receiving side.
Is derived. The C / A code generator 11 generates a C / A code corresponding to a satellite to generate the C / A code synchronizing means 1
Supply to 0. The C / A synchronizing means 10 and the C / A code generator 11 are formed by a digital signal processor (DSP). The frequency divider 12 frequency-divides the clock signal from the oscillator 5 and is used as a sampling signal for the A / D converter 9 and further for forming the C / A code of the C / A code generator 11.

Next, the navigation message decoding means 13 to which the data demodulated by the C / A synchronization means 10 is input, the orbit information of each satellite, the correction value of the atomic clock mounted on the satellite, and the correction coefficient of the propagation delay due to the ionosphere. , The satellite and the receiving position are represented by three-dimensional coordinates from the general orbit information of all satellites. here,
If x, y, and z are the coordinates of the receiving point and u, v, and w are the coordinates of the satellites, the pseudoranges RPi, ui,
Assuming vi and wi (i = 1,2,3,4), the following equation holds.

[0013]

[Equation 1]

Here, ui, vi and wi (i = 1,2,3,4) are obtained by solving the Kepler equation from the orbital parameters in the navigation message. C indicates the speed of light, and Δtr indicates the deviation between the GPS reference time and the receiver clock. Therefore, the receiving points x, y, and z are obtained by solving the above equation, and three-dimensional positioning (latitude, longitude, altitude) becomes possible. When receiving three satellite radio waves, two-dimensional positioning (latitude, longitude) is possible. The display unit 14 displays the three-dimensional positioning (latitude, longitude, altitude) of the reception position thus obtained.

The control means 15 is the C / A code generator 1
1 controls to sequentially generate the C / A code corresponding to each satellite. Further, the control means 15 is provided with an antenna switching control means 16 for controlling switching between the antennas 1 and 2. The antenna switching control means 16 will be described below.
The switching timing of will be described. FIG. 3 is a diagram showing selection of a signal to be used based on the switching timing of the antenna and the detection signal level. The minimum time required to obtain the C / A code and the pseudo distance RP is 10 as described above.
23 bits × 1.023 Mbps = 1 ms, and it is assumed that this is 2 ms in consideration of timing adjustment.
As shown in FIG. 3, by the antenna switching control means 16,
For example, reception of 5 channels (1 channel spare) from 5 satellites is sequentially performed by alternately switching the antennas 1 and 2 in each channel. That is, 1ch
The antenna 1 first receives 2 ms, and then the antenna 2 receives 2 ms. Continuing, the antenna 1 receives 2 ms for 2 ch, and then the antenna 2 receives 2 ms. In this way, when the reception of 5 channels is completed, the process returns to 1 channel and the above reception is repeated. The time required from 1ch to 5ch is 20ms. The chip rate of the navigation message is 50 bps, and 20 ms per bit is required to extract the satellite signal, and this 20 ms is within a range that can be sufficiently used for division considering the number of satellites and antenna switching.

The level detecting means 17 detects the level of the output signal of the intermediate frequency filter amplifier 8. As shown in FIG. 3, it is assumed that the signal level received by the antenna 1 is detected as SV1a and the signal level received by the antenna 2 is detected as SV1b in the reception of 1 channel. Similarly, 2ch
Assume that SV2a, SV2b to SV5a, and SV5b are detected for ~ 5ch. Antenna reception level determination means 1
Reference numeral 8 determines the magnitude of the received signal level detected by the level detecting means 17 in synchronization with the switching of the antenna switching control means 16 in order to determine the magnitude of the signal level detected by the antennas 1 and 2. For example, SV1a = 4
0, if SV1b = 30, then SV1a> SV1b, so 1c
The signal from the antenna 2 of h may be subject to fading. Therefore, the antenna reception level determining means 1
SV1a from 8 to the navigation message decoding means 13
When the information> SV1b is output, the navigation message decoding means 13 needs to adopt the data from the antenna 1 for the data of 1ch and use it as the data for deriving the pseudorange RP. Similarly, 2ch, 3c
The levels of the reception levels of the antennas 1 and 2 are determined for h, 4ch, and 5ch, and the data with the higher level is adopted to derive the pseudorange RP. Therefore, the antenna switching control means 16 synchronizes the data from the C / A synchronizing means 10 with 1ch, 2ch, in synchronization with the antenna switching.
Data D1a, D1b, D2a, D2b, D3a, D3b, D4a, D4 obtained from 3ch, 4ch, 5ch antennas 1 and 2.
b, D5a, D5b are temporarily stored, and one of the data obtained from the antennas 1 and 2 is selected according to the level judgment information from the antenna reception level judgment means 18 and the pseudo distance RP is set to the navigation message decoding means 13. The positioning data selecting means 19 to be derived is the navigation message decoding means 13
To be installed. The navigation message decoding means 13, the control means 15, and the antenna switching control means 16 are formed by a microcomputer, and the microcomputer is the DSP.
Control unit, central processing unit for positioning calculation, interface for external communication, ROM (Read Only Memory), RA
It is composed of M (Random Access Memory) and the like. In the above description, the number of antennas is two, but the number of antennas is not limited to this and may be three or more. In that case, the antenna reception level determination means 18 searches for the maximum signal level among the reception levels of the plurality of antennas, and uses the signal from the antenna that receives the maximum level as data for positioning derivation. Although the number of satellites is 5, the number is not limited to this.

[0017]

As described above, according to the present invention, a signal from one satellite that is sequentially received is received by sequentially switching a plurality of antennas, and the level of the received signal is detected and detected. The maximum value of the received level is determined and one of the received data of multiple antennas is selected according to the maximum received level to derive the positioning. Difficult and accurate positioning can be derived

[Brief description of drawings]

FIG. 1 is a diagram showing a diversity GPS receiver according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a C / A code in a satellite transmission signal.

FIG. 3 is a diagram showing selection of a signal to be used based on a switching timing of an antenna and a detection signal.

[Explanation of symbols]

 1, 2 ... Antenna 3 ... Switch 10 ... C / A synchronization means 11 ... C / A code generator 13 ... Navigation message decoding means 16 ... Antenna switching control means 17 ... Level detection means 18 ... Antenna reception level determination means 19 ... Positioning Data selection means

Claims (1)

[Claims] 1. A GPS receiver that receives signals from a plurality of satellites to obtain positioning, and antenna switching control for receiving a signal from a single satellite that is received by sequentially switching a plurality of antennas. Means (1
6), level detection means (17) for detecting the levels of signals received by the plurality of antennas, and the plurality of level detection means (17) synchronized with the switching of the antenna switching control means (16). Antenna reception level determining means (18) for determining the maximum value of the reception level detected by the antenna, and the antenna reception level determining means (1) for each satellite.
A diversity GPS receiver comprising: positioning data selecting means (19) for deriving positioning by selecting one from the reception data of the plurality of antennas corresponding to the maximum reception level detected in 8).