JPH03205580A - Gps reception system - Google Patents

Abstract

PURPOSE:To stably obtain position information from a GPS satellite even if antennas are not arranged at the best positions by equipping one local oscillator and a PN code generator in frequency conversion part and a PN code demodulation part respectively. CONSTITUTION:The two antennas ANT1 and ANT2 are arranged at relatively free positions on a moving body so that the directional angle cover an upper hemisphere complementarily to eliminate a blind area, and then receive radio waves W1 - W4 from the satellite. Received signal processing systems A and B when performing processing are supplied with a local oscillation signal S2 from a local oscillator LOSC and a PN code signal S5 from a PN code generator POSC. The microprocessor MPU of a control part CC selects one of trajectory information signals S8a and S8b supplied from the processing systems A and B and selects the other one when the selected signal is lower than a threshold level. Then the MPU controls the PC code demodulator (18 or 38) of the selected processing system and a carrier NCO (24 or 44) to obtain trajectory information, a Doppler shift, and a dummy distance, from which position information on a reception point is obtained.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is applicable to the global satellite navigation system (GPS: Gl
obal Positioning System)
, radio waves from GPS satellites are received using multiple antennas, and location information such as secondary/three-dimensional position (longitude, latitude, altitude, direction of movement) and time at the receiving point is preferably obtained from the received signal. The present invention relates to the resulting GPS reception system.

[Prior Art] GPS is a passive position information determining means, and in a GPS receiving device mounted on a mobile object such as an aircraft, vehicle, or ship, four GPS satellites (hereinafter referred to as ,
GPS radio waves (hereinafter simply referred to as radio waves as necessary) are L-band navigation signals (direct spread spectrum modulation waves using C/A code signals of navigation data and P code signals) transmitted from satellites (hereinafter simply referred to as satellites). ).

Then, the navigation signal is captured using a PN code generated inside the receiver from the received signal, and the distance to the satellite is measured and the navigation data is demodulated. Get pseudorange.

From these values, position information of the mobile object at the receiving point can be obtained.

This type of GPS receiver receives radio waves from three satellites located near the horizon and at intervals of approximately 120 degrees, and one satellite located near the zenith, out of the satellites within the visible range of the sky. must be received at the same time. For this reason, G
The antenna attached to a mobile object equipped with a PS receiver is placed in a location where there is minimal interference with the propagation of radio waves from the four satellites mentioned above, for example, one is placed in the center of the roof of a vehicle. is common.

For example, the antenna adopts a helical method, and has a structure in which four radiating elements are formed in a helical shape downward from the top feeding part, and supports the required circularly polarized wave and hemispherical radiation characteristics. are doing.

[Problems to be Solved by the Invention] However, the above-mentioned antenna is a structure having a certain thickness and size, and when attached to a moving body such as a small vehicle, it spoils the aesthetic appearance, and furthermore, it is difficult to wash the car. accompanied by inconvenience. In addition, complicated work is required to prevent water from entering the vehicle from the power supply plug, etc. where the antenna is attached, and to take measures to prevent water from breaking. Therefore, attaching an antenna to the bonnet or trunk cover may be considered. In this case, radio waves from satellites in the horizontal direction are likely to be blocked by roadside structures such as vehicles equipped with GPS receivers, especially metal roofs, and the presence of people (reception) is intermittent when driving in urban areas. It's easy to become a target. Therefore, it becomes difficult to maintain a stable reception state while driving. In other words, the vehicle has the disadvantage that position information cannot be easily obtained while the vehicle is running.

The present invention was made in view of the above problems, and in order to facilitate the installation of a GPS receiver in a smaller moving object, the present invention improves the degree of freedom in the placement of multiple antennas, for example, in areas where the sensing situation is not the best. An object of the present invention is to provide a GPS receiving system that can stably obtain position information from GPS satellites when an antenna is installed.

[Means for Solving the Problems] In order to solve the above problems, the GPS reception system of the present invention has two antennas for receiving GPS radio waves, and the reception signal derived from each antenna is transmitted manually. GPS comprising at least two received signal processing means each having a frequency conversion section and a PN code demodulation section, and measurement calculation means for determining the position of a receiving point from the output signal from each received signal processing means.
The receiving system is characterized in that one local oscillator is provided for supplying a local oscillation signal to each of the frequency converters.

Furthermore, the present invention is characterized in that it includes one PN code generator that supplies a PN code signal to the PN code demodulation section.

Also, a plurality of antennas that receive GPS radio waves and send out received signals, and a mixer, a PN, to which at least the received signals are respectively supplied.
a plurality of received signal processing systems including a code demodulator, a detector that sends out a synchronous detection signal, a carrier NCO that sends a carrier signal to the detector, and an A/D converter that sends out a digital trajectory information signal; one local oscillator for sending a local oscillation signal to the mixers of the plurality of received signal processing systems; and one local oscillator for sending a PN code signal to the plurality of PN code demodulators, distributed to one or each of the received signal processing systems. A plurality of trajectory information signals derived from the plurality of reception signal processing systems are supplied, and one of the trajectory information signals is below a predetermined level to zero and is greater than the predetermined level. a first control means for selecting a trajectory information signal with a level of
a second control means for controlling a code demodulator and a carrier wave NCO to obtain orbit information, a Doppler shift, and a pseudorange; and an operation for forming position information of a receiving point from the orbit information, Doppler shift, and pseudorange. It is characterized by comprising means.

[Operations] In the above GPS receiving system of the present invention, at least two
A plurality of antennas are arranged in a relatively free part of a moving body so that the beam angles of the individual hollow wires cover the upper hemisphere complementary to each other, eliminating dead areas, and radio waves from multiple satellites are received. Ru. So-called spatial diversity reception is formed.

In each receiving signal processing system, when performing the processing, a local oscillation signal from one local oscillator and a paceband signal from a PN code generator disposed in one or each receiving signal processing system are used. A PN code signal for demodulating is supplied.

Furthermore, the orbit information signal with the highest level obtained from the received signal processing system is selected. Alternatively, first, one trajectory information signal is selected, and if the signal is below a threshold level, another trajectory information signal is selected by the first control means, so-called.
Selective diversity received signal processing means are formed.

Thereafter, the second control means controls the PN code demodulator and carrier NCO of the received signal processing system selected by the first control means to obtain orbit information, Doppler shift, and pseudorange.

Furthermore, the positional information of the receiving point is calculated by the calculation means from the orbit information, Doppler shift, and pseudorange.

[Embodiment] Next, an embodiment of the GPS receiving system according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing the overall structure of an embodiment of a GPS receiving system according to the present invention.

In this example, radio waves W+, W2 transmitted from four satellites
, Wl , W4 to two antennas A N 7 1, A
Receive at N T 2, then frequency conversion and further P
Receiving signal processing systems A and B having the same structure that demodulate the N code and detecting the detection signal (trajectory information signal), and a local oscillator L that sends the same local oscillation signal S2 to the receiving signal processing systems A and B. . 5c, and a PN code generator P. 5C, and a control unit C that performs selective control processing of the trajectory information signal S8as s8b in response to the radio wave reception situation and sends out position information of the moving vehicle. (corresponding to the first control means, second control means, and calculation means). Note that the control section C
. A display device Dp that visually displays position information is connected to.

The structure of the received signal processing systems A and B will be explained below. The received signal processing systems A and B are the same system and will be explained at the same time.

The symbols in parentheses correspond to the structure of the received signal processing system B.

The reception signal processing system A (B) is installed, for example, on one (other) of the side mirrors of a small vehicle, and uses an antenna ANTI (see above) that has circularly polarized waves and a hemispherical radiation characteristic.
ANT2), high frequency amplifier 12 (32), and mixer 1
4 (34), intermediate frequency amplifier 16 (36), PN code demodulator 18 (38), and baseband filter 20
(40), a detector 22 (42), a carrier NCO 24 (44) that sends out an oscillation signal under numerical control, and an A/D converter 26 (46).

Control part C. is, for example, a microprocessor M p l
, is adopted, and includes a CPU, RAM, I/O, and a ROM that stores programs for controlling this device.
Functional means such as the following are formed. Furthermore, it has a switching means Sw, such as a keyboard, for selecting position information etc. and displaying it on the display D, and a code NCO 50 for sending out an oscillation signal under numerical control.

The operation in the above structure will be explained below.

Note that the operations of the received signal processing systems A and B are the same, and will be explained at the same time. The symbols in parentheses correspond to the received signal processing system B.

Radio waves W1, W2, W3, W4 are antenna A N 7 1 (
The received signal S la (S
+b) is amplified by the high frequency amplifier 12 (32).

Thereafter, it is input to the mixer 14 (34) and the local oscillator L. The local oscillation signal S2 oscillated by 5c is supplied, converted into an intermediate frequency signal S3- (S3b), and then supplied to the PN code demodulator 18 (38) via the intermediate frequency amplifier 16 (36). Ru. Furthermore, the PN code signal S5 generated by the PN code generator posc is inputted to the PN code demodulator 18 (38), and is integrated with the intermediate frequency signal S3a (S31,) supplied here. The received signals s, a (S.b), that is, the baseband signals of the radio waves W1 to W, are demodulated. Furthermore, the baseband signal is supplied to the baseband filter 20 (40), and only the baseband signal having the intermediate frequency signals S3, (S3b) as carrier waves is extracted and the detector 22 (42
) is entered.

The detector 22 (42) receives the intermediate frequency signal s. oscillation signal S7.a (S3.) and the same frequency as S7.a (S3.). (Stb), synchronous detection is performed to derive a detected signal, and then the A/D converter 26
(46). The A/D converter 26 (46) converts the detection signal supplied from the detector 22 (42) into a digital signal, and sends the trajectory information signal ssa (S8b) to the controller C. Send to.

Here, the level (amplitude value) of the orbit information signal ssa (Seb) sent from the A/D converter 26 (46) to the control unit Cc is the radio wave W detected by the antenna ANTI (ANT2).
1 to W4, it is proportional to the electric field strength of the captured radio waves W1 to W.

In this way, from the receiving signal processing systems A and B, the antenna A is
NTI, an orbit information signal Seas having an amplitude proportional to the electric field strength of the radio waves W1 to W4 received by ANT2.
8b is the controller C from the A/D converter 26 (46). will be sent to

Hereinafter, the orbit information signal S [1 a z S 8 b
A control unit C is supplied with the information and sends position information of the moving vehicle based on the program. The control operation will be explained below.

The PN code generator POS based on the phase and clock period of the oscillation signal of the code NCO 50 to which the instruction control signal SIO from the control unit Cc is supplied. A C/A signal that is separately applied to the satellite, that is, a PN code signal S5 which is a special pseudo-noise code, is generated and then sent to the PN code demodulator 18 (38).

Furthermore, the control section C. Instruction control signal (numerical control) Sl
2- (S12b), the carrier wave N C 024 (4
In 4), the phase and frequency are controlled, and the intermediate frequency signal S3- (S3-) and the oscillation signal S7 of the same frequency are
．． (S7.) is sent.

Here, first, when capturing, for example, radio waves W1 from a specific satellite, the control unit C. Instructs the PN code generator POSC to the C/A code assigned to the satellite (radio wave W+) to be captured first (instruction signal Sl4) L, then the clock cycle of code NCO50 and carrier wave NCO2
A while gradually changing the frequency of the oscillation signal S7a of 4.
Closed loop control is performed to change the clock cycle of the code NCO 50 and the frequency of the oscillation signal Sea of the carrier NCO 24 so that the level of the orbit information signal 38a of the /D converter 26 becomes maximum and maintains the maximum state. . Here, the value of the Doppler shift of the radio wave w1 from the satellite is obtained from the instruction value to the carrier wave NCO 24. Furthermore, the pseudo distance from the reception point to the satellite can be obtained from the instruction value for the code N C 050.

Next, the control section C. Through sequence control, radio waves W2 to W4 from three more satellites are captured, and orbit information, Doppler shift, and pseudorange are respectively derived in the same manner as above. Furthermore, arithmetic processing is performed using the above-mentioned trajectory information, Doppler shift, and pseudorange to obtain positional information such as latitude, longitude, speed, and moving direction at the receiving point of the vehicle. This position information is visually displayed on the display DP.

? Here, if the radio waves from a specific satellite (W+ to W, one satellite) that enter the antenna A N T I are blocked by an obstacle, the control unit C. The orbit information signal S8a supplied to the orbit information signal S8a is extremely reduced or not derived. Therefore, position information cannot be obtained, but the control unit Cc transmits an A/D converter to this particular satellite in the reception signal processing system B under the same control/signal processing as described above. The orbit information signal S8b sent from 46 is taken in.

Furthermore, for the remaining three satellites, the received signal processing system A has a control section C similar to that described above. Through sequence control, the radio waves W2 to W4 from the remaining three satellites are captured, and the orbit information, Doppler shift, and pseudorange are respectively derived in the same way as above, and then the latitude and Obtain location information such as longitude, speed, and direction of movement. Similarly, for satellites that cannot be received by reception signal processing system A, reception signal processing system B
Receive at.

In this way, by using the antennas ANTI and ANT■ placed separately at appropriate parts of the vehicle, that is, by using spatial diversity reception, the radio waves W1 to W4 that are shielded by the roof of the moving object are made to be felt by the human body. . Furthermore, differential signal processing of the received signals Sla and Slb is performed.

In this case, the local oscillator L. Local oscillation signal S2 from sc
is commonly supplied to mixers 14 and 34. As a result, the frequencies of the oscillation signals S7a and S'lb of the carrier waves NCO24 and 44 match, that is, the measured value of the Doppler shift of the radio waves (W1 to W4) from the satellite being received is the same as that of the local oscillation signal S2. It will be consistent without being affected. Therefore, position measurement accuracy is maintained at the best level even with diversity reception. Furthermore, the control section C. is the determination of the level of the orbit information signals S8a and S8b, for example, when the level falls below a predetermined darkness value (level), one of the orbit information signals S s a % S s b is at a higher level.
is selected to control the PN code generator Posc and the code NCO 50, so this closed loop control is performed using the output of the receiving signal processing system A or B, which always has a higher level. A so-called selective diversity received signal processing means is formed. As a result, even if the electric field strength of the incoming radio waves W1 to W changes intermittently due to the roof of a moving object, the influence on pseudo-range measurement is greatly reduced, and as a result, the It is possible to maintain highly accurate measurement of position information while driving.

In addition, in this embodiment, two antennas A Nt +, A
Although an example has been shown in which N T 2 is used and reception signal processing systems A and B are provided, the present invention is not limited to this. Three or more antennas and a receiving signal processing system are formed, and one local oscillator L. ,. , one PN code generator P. ,. A selective diversity reception signal processing means is formed under the control of a control section similar to that described above to obtain the same effects as described above, and furthermore, a PN code generator is provided in each reception signal processing system. The present invention also includes obtaining the same effects as those of the above embodiments.

[Effects of the Invention] As can be understood from the above explanation, the GPS reception system of the present invention provides GPS access to moving objects that place greater emphasis on aesthetics.
The degree of freedom in arranging multiple antennas when the S receiver is installed is improved, and for example, stable derivation of position information from GPS satellites when the antennas are installed in areas where the sensing conditions are not optimal. This has the effect of making it possible. With these effects, when adopting a GPS reception system in a small passenger car, there is no need to install an antenna on the roof etc., making it easier to select the antenna installation location and installation method, and to reduce the
This has the advantage of promoting the spread of PS reception systems.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the overall structure of an embodiment of a GPS receiving system according to the present invention. 14, 34... Mixer 18, 38... PN code demodulator 24, 44... Carrier wave NGO 50... Code NCO ASB... Reception signal processing system ANTI, ANT2... Antenna Cc...・Control unit L O 'a C... Local oscillator P o sc... PN code generator S2... Local oscillation signal S5... PN code signal S7a, S7b... Oscillation signal

Claims (2)

[Claims] (1) At least two received signal processing means each having two antennas for receiving GPS radio waves, each comprising a frequency conversion section and a PN code demodulation section into which received signals derived from the respective antennas are input. In a GPS receiving system, the GPS receiving system includes measurement calculation means for determining the position of a receiving point from an output signal from the received signal processing means, wherein a local oscillation signal is supplied to each of the frequency conversion sections. G characterized in that one local oscillator is provided to
PS reception system. (2) The GPS receiving system according to claim 1, further comprising one PN code generator that supplies a PN code signal to the PN code demodulating section. (3) A plurality of antennas that receive GPS radio waves and send out received signals, and a mixer and a PN to which at least the received signals are respectively supplied.
a plurality of received signal processing systems including a code demodulator, a detector that sends out a synchronous detection signal, a carrier NCO that sends a carrier signal to the detector, and an A/D converter that sends out a digital trajectory information signal; one local oscillator for sending a local oscillation signal to the mixers of the plurality of received signal processing systems; P set up
A plurality of trajectory information signals derived from the N code generator and the plurality of received signal processing systems are supplied, and one of the trajectory information signals is below a predetermined level to zero, and when the level is higher than the predetermined level. a first control means for selecting an orbit information signal; and a signal processing system P for transmitting the selected orbit information signal.
a second control means for controlling an N-code demodulator and a carrier wave NCO to obtain orbit information, a Doppler shift, and a pseudorange; and forming position information of a receiving point from the orbit information, Doppler shift, and pseudorange. A GPS reception system comprising: a calculation means.