JP3288076B2 - Diversity GPS receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a GPS (Global Positioning System) which is a satellite-based positioning system covering the whole earth.
g system), which can improve a diversity effect when the receiver is mounted on a vehicle and used.

[0002]

2. Description of the Related Art Heretofore, there have been the following 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. However, a large number of antennas are required due to an effect of expanding a spatial reception area. Is preferred. On the other hand, when the antenna is provided outside the vehicle, it is necessary to satisfy a design requirement that the appearance is not impaired. From such a viewpoint, a diversity receiver in which two antennas are installed on a vehicle body is employed to secure 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 to prevent the influence. In this way, the spatial aperture increases the aperture area of the antennas for radio wave input to the two antennas to improve the positioning accuracy.

[0003]

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

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a diversity GPS receiver which is less likely to be affected by a plurality of antennas even if each antenna is subjected to a fading effect and can derive a correct positioning.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems , the present invention provides a GPS receiver that receives signals from a plurality of satellites with a plurality of antennas and obtains positioning. detecting means, data demodulating means, antenna reception level determining hands stage, measurement position data selection means, and the synchronization signal
Ru der those provided No. generation means. The antenna switching control means receives signals from a plurality of satellites to be received by sequentially switching a plurality of antennas.

The level detecting means stores the levels of the signals from the same satellite received by the plurality of antennas in synchronization with the switching of the antenna switching control means, and stores the stored signal levels of the respective antennas. Is detected. Said de
The data demodulation means is synchronized with the switching of the antenna switching control means.
From the same satellite received by the plurality of antennas.
Demodulate the signal. The antenna reception level determining means,
The level detector determines a maximum value of the reception levels detected by the plurality of antennas.

[0007] The positioning data selection means is provided with the data recovery means.
Temporary storage of the demodulated data from the
In addition, for each satellite , one of the stored reception data of the plurality of antennas is selected and the positioning is derived in accordance with the maximum reception level detected by the antenna reception level determination means. The synchronizing signal generation means is configured to switch the antenna
Means, the level detection means and the data storage means
And an oscillator for generating a synchronization signal for
And a frequency divider for dividing the frequency of the signal. And
With the above configuration, the diversity GPS receiver of the present invention
Is an antenna switching timing by the antenna switching means.
The connection duration of one antenna is the C / A code
Extra time for timing adjustment was added to the acquisition time of
Is defined as

[0008]

According to the diversity GPS receiver of the present invention,
Signals from a plurality of satellites received by the antenna switching control means, a plurality of antennas are sequentially switched,
The levels of the signals received from the same satellite and received by the plurality of antennas are stored in synchronization with the switching of the antenna switching control unit by the level detection unit, and the stored signal level of each antenna is stored. The level is detected, and the data demodulation means performs the antenna switching control operation.
Synchronized with the switching of the stage, received by the plurality of antennas
Signals from the same satellite are demodulated, and 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,
The positioning data selection means, the data demodulation means
When demodulated data from is temporarily stored as received data
Both corresponding to the maximum reception level sensed in the antenna reception level determining means for each satellite, one from the stored reception data of the plurality of antennas has been the positioning is derived by the selected navigation message decoding means. At this time,
Antenna switching means, said level detection means, and said data storage
The synchronization signal for the synchronization of the means comprises an oscillator and the signal of the oscillator.
And a frequency divider for dividing the signal.
Generated. In addition, the antenna switching means
The tenor switching timing is the connection duration of one antenna
Is used to adjust the timing at the acquisition time of the C / A code.
It is stipulated that the time is added . Therefore, even if a plurality of antennas are each subjected to a fading effect, the effects can be made hard to be affected, so that a 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 showing a PS receiver. Diversity G shown in this figure
The PS receiver first has two antennas 1 and 2. The antennas 1 and 2 are attached to, for example, a front part and a rear part of a vehicle, and receive transmission signals formed by C / A codes from a plurality of artificial satellites. Hereinafter, the C / A code will be described.

FIG. 2 is a diagram for explaining a C / A code in a satellite transmission signal. As shown in the figure, a radio wave of 1755.42 MHz is transmitted from each satellite and phase-modulated by a digital code called a 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 code is modulated by each code to spread the spectrum, so that each satellite can be identified even at the same frequency. Has become.
The C / A code has 36 patterns, a chip rate of 1.023 Mbps, and a code length of 1023 bits (1 ms). On the C / A code, data required for positioning calculation called "navigation message" is superimposed. Navigation message has a chip rate of 50 bps
Thus, one main frame is formed in 30 seconds.

Returning to FIG. 1, the switch 3 is connected to the antenna 1
And 2 are alternately switched. The RF amplifier 4 amplifies the RF signal switched by the switch 3. The oscillator 5 is a temperature compensated 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 receives about 1.5 from the RF amplifier 4.
The RF signal of GHz is frequency-converted (IF signal) to an 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 synchronization means 10 for inputting a digital signal of the A / D converter 9
Performs demodulation of data by performing spectrum despreading by adjusting the frequency to the satellite radio wave and simultaneously adjusting the phase of the C / A code. At this time, C / A from each satellite
Since the code is sent at a timing precisely synchronized with the atomic clock mounted on the satellite, the pseudo distance RP is calculated from the phase shift amount of the C / A code at the time of synchronization on the receiving side.
Is derived. The C / A code generator 11 generates a C / A code corresponding to the satellite and outputs the C / A code synchronization means 1
Supply 0. The C / A synchronization means 10 and the C / A code generator 11 are formed by a digital signal processor (DSP). The frequency divider 12 divides the frequency of the clock signal from the oscillator 5 and uses it 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 for inputting the data demodulated by the C / A synchronizing means 10 includes the orbit information of each satellite, the correction value of the atomic clock mounted on the satellite, and the correction coefficient of the ionospheric propagation delay. The satellite and the receiving position are represented by three-dimensional coordinates from the approximate orbit information of all the satellites. here,
Let x, y, z be the coordinates of the receiving point and u, v, w be the coordinates of the satellite, for each of the four satellites, the pseudoranges RPi, ui,
Assuming that vi and wi (i = 1, 2, 3, 4), the following equation is established.

[0013]

(Equation 1)

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

The control means 15 controls the C / A code generator 1
1 controls so as to sequentially generate C / A codes corresponding to the respective satellites. The control means 15 is provided with an antenna switching control means 16 for controlling the switching of the antennas 1 and 2. The antenna switching control means 16 will be described below.
Will be described. FIG. 3 is a diagram showing selection of a signal to be used based on antenna switching timing and a detection signal level. The minimum time for obtaining the C / A code and the pseudo distance RP is, as described above, 10 times.
23 bits × 1.023 Mbps = 1 ms, and it is sufficient that this is 2 ms in consideration of timing adjustment.
As shown in FIG. 3, the antenna switching control means 16
For example, reception of five channels (one channel reserve) from five satellites is performed sequentially by switching the antennas 1 and 2 alternately in each channel. That is, 1ch
, The antenna 1 first receives 2 ms, and then the antenna 2 receives 2 ms. Subsequently, for the reception of 2 ch, the antenna 1 receives 2 ms and then the antenna 2 receives 2 ms. In this way, go to the reception of 5ch
Then, it returns to 1ch and repeats the above reception. 5c from 1ch
The time required for h is 20 ms. The chip rate of the navigation message is 50 bps, and it takes 20 ms per bit to extract the satellite signal.
The ms is in a range that can be sufficiently used to divide in consideration of 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 1ch reception. Similarly, 2ch
It is assumed that the channels 5 to 5 are detected as SV2a and SV2b to SV5a and SV5b. Antenna reception level determining means 1
Numeral 8 judges 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 levels detected by the antennas 1 and 2. For example, SV1a = 4
0, if SV1b = 30, then SV1a> SV1b, so 1c
There is a possibility that the signal from the antenna 2 at h is subjected to a fading effect. Therefore, the antenna reception level determining means 1
8 to SV1a for the navigation message decoding means 13.
When the information of> 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 data for deriving the pseudo distance RP. Similarly, 2ch, 3c
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 pseudo distance RP. Therefore, the demodulated data from the C / A synchronizing means 10 is synchronized with the antenna switching by the antenna switching control means 16 to 1ch, 2c
h, received data D1a, D1b, D2a, D2b, D3a, D3b, obtained from antennas 1 and 2 of 3ch, 4ch and 5ch,
D4a, D4b, D5a, and D5b are temporarily stored, and one of the reception data obtained from the antennas 1 and 2 is selected based on the level determination information from the antenna reception level determination unit 18 and the pseudo data is sent to the navigation message decoding unit 13. Distance RP
Is provided in the navigation message decoding means 13. The navigation message decoding means 13, the control means 15, and the antenna switching control means 16 are formed of a microcomputer, which is a central processing unit for controlling the DSP, performing positioning calculation, an interface for communicating with the outside, a ROM. (Read Only M
emory), RAM (Random Access Memory) and the like. In the above description, two antennas are used. However, the number of antennas is not limited thereto, and three or more antennas may be used. In this case, the antenna reception level determining 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 and deriving. Although the number of satellites is set to five, the number is not limited to five.

[0017]

As described above, according to the present invention, sequentially received signals from a plurality of satellites are received by sequentially switching a plurality of antennas, and receiving the received signals.
Demodulate and use the demodulated data as received data for each antenna
Temporarily stores and detects the level of the received signal, determines the maximum value of the detected reception level, and selects one from the stored reception data of multiple antennas corresponding to the maximum reception level to derive positioning Therefore, even if a plurality of antennas are subjected to the fading effect, the influence is less likely to be obtained, and correct positioning can be derived.

[Brief description of the drawings]

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

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

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

[Explanation of symbols]

 DESCRIPTION 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 judgment means 19 ... Positioning Data selection means

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04B ⁷ /02-7/12 H04L 1/02-1/06 G01S 5/00-5/14

Claims (1)

(57) [Claims] 1. A GPS receiver for receiving signals from a plurality of satellites with a plurality of antennas to obtain positioning, wherein the GPS receiver receives signals from the plurality of satellites by sequentially switching the plurality of antennas. In synchronization with the switching of the antenna switching control means (16),
Level detecting means (17) for storing the levels of signals from the same satellite received by the plurality of antennas and detecting the stored signal levels of the respective antennas; And the plurality
Demodulate signals from the same satellite received by different antennas
A data demodulation means (10), an antenna reception level judgment means (18) for judging a maximum value of reception levels detected by the plurality of antennas by the level detection means (17), and a data demodulation means
Temporarily store demodulated data from (10) as received data
To Rutotomoni, corresponding to the maximum reception level sensed for each said antenna reception level determining means for satellite (18), the serial
Positioning data selection means for deriving the positioning by selecting one from the reception data of the plurality of antennas that憶 (1
9), the antenna switching means (16) and the level detection means
(17) for synchronizing the data storage means (19)
Oscillator (5) for generating a synchronization signal and said oscillator
Synchronization consisting of a frequency divider (12) for dividing the signal of (5)
Signal generation means, and an antenna switching tie by said antenna switching means (16).
The connection duration of one antenna is C / A
Add time for timing adjustment to the acquisition time
A diversity GPS receiver characterized in that it is defined as: