JP2993699B2 - GPS receiving system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a global satellite navigation system (GPS).
radio signals from GPS satellites using multiple antennas, and from the received signals, secondary / three-dimensional positions (longitude, latitude, altitude, different directions), time, etc. The present invention relates to a GPS receiving system from which information can be suitably obtained.

[Prior Art] GPS is a passive position information determining means. In a GPS receiving device mounted on a moving body such as an aircraft, a vehicle, a ship, or the like,
L-band navigation signals transmitted from four GPS satellites (hereinafter simply referred to as satellites as necessary) under the control of the ground station (C / A code signal of navigation data, spectrum direct spread by P code signal) Modulation method), which receives GPS radio waves (hereinafter simply referred to as radio waves as necessary). Then, the navigation signal is captured using the PN code generated inside the receiving device from the received signal, distance measurement to the satellite and demodulation of the navigation data are performed, and furthermore, the Doppler measurement value of the received signal, and the pseudo data from the receiving point to the GPS satellite Get the distance. From these values, the position information of the moving object at the receiving point can be obtained.

Such a GPS receiver is composed of three satellites located near the horizon and at an interval close to 120 °, and one satellite located near the zenith among satellites within the visible range of the sky. Must be received at the same time. Because of this, GPS
The antenna installed with the receiving device and attached to the mobile body is located at a location where the obstacle of the shield against the propagation of radio waves from the four satellites is minimized, for example, at the center of the roof in a vehicle. Is common.

The aerial is, for example, a helical type, and has a structure in which four radiating elements are formed in a spiral (helical) below the top feed section, which meets the required circularly polarized and hemispherical radiation characteristics. doing.

[Problem 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, the aerial degrades aesthetic appearance and further causes a problem such as car washing. With inconvenience.
In addition, complicated work is required to prevent water from entering the vehicle from a power supply plug or the like, which is an attachment part of the antenna, and to take measures against water rupture. Therefore, it is conceivable to attach the antenna to the hood or trunk cover. In this case, roadside structures, such as vehicles equipped with a GPS receiver, can easily block radio waves from satellites, especially in the horizontal direction, with a metal roof. Easy to be targeted. Therefore, it is difficult to maintain a stable reception state during traveling. In other words, it has a drawback that position information during traveling cannot be easily obtained.

The present invention has been made in view of the above-described problems, and in order to facilitate mounting of a GPS receiver on a smaller moving object, the degree of freedom of arrangement of a plurality of antennas has been improved, for example, in a part where the feeling of entry is not the highest. An object of the present invention is to provide a GPS receiving system capable of stably obtaining position information from GPS satellites when an antenna is provided.

[Means for Solving the Problems] In order to solve the above problems, the GPS receiving system of the present invention has two antennas for receiving GPS radio waves, and receives a reception signal derived from each antenna. Frequency converter and
At least two reception signal processing means including a PN code demodulation unit, and a PN signal from the at least two reception signal processing means.
A GPS receiving system comprising: a measuring and calculating means for determining a position of a receiving point from an output signal after code demodulation, wherein one local oscillator for supplying a local oscillation signal to each of the frequency conversion units is provided; And determining the position of the receiving point using the higher level of the output signal after demodulation of the PN code from the at least two reception signal processing means.

A plurality of antennas for receiving a GPS radio wave and transmitting a reception signal; a mixer to which at least the reception signal is respectively supplied;
A code demodulator, a detector for transmitting a synchronous detection signal, a carrier NCO for transmitting a carrier signal to the detector, a plurality of reception signal processing systems including an A / D converter for transmitting an orbit information signal of a digital signal, One local oscillator for transmitting a local oscillation signal to a plurality of mixers for a reception signal processing system; and one or more local oscillators for transmitting a PN code signal to the plurality of PN code demodulators. 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 lower than a predetermined level to zero and is larger than the predetermined level. First control means for selecting a trajectory information signal of a certain level or a trajectory information signal of a maximum level; and a PN of a signal processing system for transmitting the selected trajectory information signal
Second control means for controlling the code demodulator and the carrier NCO to obtain the orbit information, the Doppler shift and the pseudorange, and an operation for forming the position information of the receiving point from the orbit information, the Doppler shift and the pseudorange Means are provided.

[Operation] In the above-described GPS receiving system of the present invention, at least 2
A plurality of antennas are arranged in a relatively free part of the moving body so that the directivity angles of the individual hollow lines complement the upper hemisphere and eliminate the dead zone, and radio waves from multiple satellites are received. You. A so-called spatial, diversity reception is formed.

Then, in each of the received signal processing systems, when performing the processing, a local oscillation signal from one local oscillator,
A PN code signal for demodulation to a baseband signal is supplied from a PN code generator provided in one or each of the received signal processing systems.

Furthermore, the maximum level orbit information signal obtained from the reception signal processing system is selected. Alternatively, first, one trajectory information signal is selected and another trajectory information signal is selected by the first control means when the trajectory information signal is equal to or less than the threshold level.
Selective diversity received signal processing means is formed.

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

Further, the position information of the receiving point is calculated by the calculating means from the trajectory information, the Doppler shift and the pseudorange.

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

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

In this example, radio waves W ₁ , W ₂ ,
W ₃ and W ₄ are received by the two antennas A _NT1 and A _NT2 , and thereafter, the received signal processing system A has the same configuration for detecting the detection signal (orbit information signal) by converting the frequency and further demodulating the PN code. , B
And the same local oscillation signal S _{2 for the} reception signal processing systems A and B.
A local oscillator L _osc for delivering a PN code generator P _osc,
A control unit C _C (first control means, second control means) which performs selective control processing of the track information signals S _8a and S _8b in accordance with the state of radio wave reception and sends out position information of the moving vehicle. , Corresponding to the calculation means). The display device D _P to display the location information visually is connected to the control unit C _C.

Hereinafter, the configuration of the reception signal processing systems A and B will be described. The reception signal processing systems A and B have the same configuration and will be described at the same time.
The code in parentheses corresponds to the configuration of the received signal processing system B.

The reception signal processing system A (B) is attached to, for example, one side (the other side) of a side mirror of a small vehicle, and has an antenna A having a configuration (see the above) having circularly polarized and hemispherical radiation characteristics.
_NT1 (A _NT2 ), high-frequency amplifier 12 (32), and mixer 14 (3
4), intermediate frequency amplifier 16 (36) and PN code demodulator 18
(38), baseband lid 20 (40), and detector 22 (4
2) and a carrier NCO that sends out an oscillation signal under numerical control
24 (44) and an A / D converter 26 (46).

The control unit C _C, for example, is a microprocessor M _PU is employed, CPU, RAM, and I / O, functional means such as a ROM storing a program for controlling the device is formed . For allowing the display unit D _P and further selecting the position information and the like, for example, switching means S _W such as a keyboard
And a code NCO50 that sends an oscillation signal under numerical control
And

 Hereinafter, the operation in the above configuration will be described.

The operations of the received signal processing systems A and B are the same and will be described at the same time. The code in parentheses corresponds to the received signal processing system B.

The reception signal S _1a (S _1b ) derived by receiving the radio waves W ₁ , W ₂ , W ₃ , and W ₄ through the antenna A _NT1 (A _NT2 ) is amplified by the frequency amplifier 12 (32). Thereafter, is input to the mixer 14 (34), is supplied with a local oscillation signal S ₂ which is oscillated by the local oscillator L _osc, to be converted into an intermediate frequency signal S _3a (S _3b), followed by intermediate PN code demodulator 18 via frequency amplifier 16 (36)
(38). Further PN code signal S ₅ generated by the PN code generator P _osc is inputted to the PN code demodulator 18 (38), wherein the supplied intermediate frequency signal S _3a and (S _3b) is integrated taking place , The received signal S _1a (S _1b ), that is, the radio wave W ₁
To baseband signals W ₄ it is demodulated. Further baseband signal is supplied to baseband filter 20 (40), an intermediate frequency signal S _3a and (S _3b) only Bezubando signal to the carrier is input to the detector 22 is extracted (42).
In the detector 22 (42), the oscillation signal S having the same frequency as the intermediate frequency signal S _3a (S _3b ) input from the carrier NCO 24 (44)
_{According to 7a} ( _S7b ), synchronous detection is performed to derive a detection signal, which is then supplied to the A / D converter 26 (46). A / D converter
26 (46), the detector 22 (42) orbit information signal detection signal is converted into a digital signal supplied from the S _8a (S _8b) is sent to the control unit C _C.

Here, the level of the A / D converter 26 (46) orbit information signal is fed to the control unit C _C from S _8a (S _8b) (amplitude value) antenna
Among the radio wave W ₁ to W ₄ and Irikan with A _NT1 (A _NT2), is proportional to the captured field strength of the radio wave W ₁ to W ₄ have.

In this manner, the antennas from the reception signal processing systems A and B
The orbit information signals S _8a and S _8b having amplitudes proportional to the electric field strengths of the radio waves W _{1 to} W ₄ sensed by A _NT1 and A _NT2 are transmitted to the A / D converter 26 (4
It is fed to the control unit C _C 6).

Hereinafter, the track information signal S _8a, S _8b is supplied, a description will be given of the control operation of the control unit C _C for sending location information of the mobile vehicle based on Puroguromu.

Code N to the instruction control signal S ₁₀ from the control unit C _C is supplied
Based on the phase and clock cycle of the CO50 oscillation signal,
C / A separately _assigned to satellites by PN code generator _Posc
Signal, i.e., the PN code signal S ₅ is a special pseudo-noise code is generated and subsequently transmitted to the PN code demodulator 18 (38).

Further, an instruction control signal (numerical control) S of the control unit C _{C
According to 12a} (S _12b ), the phase and frequency of the carrier NCO 24 (44) are controlled, and the intermediate frequency signal S _3a (S _3b )
Then, an oscillation signal S _7a (S _7b ) having the same frequency is transmitted.

Here, first, from a particular satellite, for example, if the capture of the radio wave W ₁ is performed, the control unit C _C is PN granted by that C / A the altitude satellite (wave W ₁₎ to be captured first Code generator P
instruct (command signal S ₁₄₎ to _osc, then the level of the track information signal S _8a of the A / D converter 26 while gradually changing the frequency of the oscillation signal S _7a of the clock cycle and the carrier wave NCO24 code NCO50 is so that the maximum closed loop control is performed for varying the frequency of the oscillation signal S _7a of the clock period of the code NCO50 the carrier NCO24 as further maintain the maximum state. Here, the value of the Doppler shift of the radio waves W ₁ from the satellite from the indicated value of the carrier wave NCO24 obtained. Also code NCO50
The pseudo distance from the receiving point to the satellite can be obtained from the indicated value to.

Then, three more radio W ₂ to radio waves W ₄ from the satellite to capture the sequence control of the control unit C _C, the as well as orbital information, Doppler shift, the pseudorange respectively derived. Further, the above-mentioned trajectory information, Doppler shift, performing a calculation process with the pseudorange, the latitude, longitude, at the receiving point of the vehicle,
Obtain position information of speed and moving direction. This position information is visually displayed on the display unit D _p.

Here, radio waves from a particular satellite that Irikan the antenna A _NT1 (1 satellite of W ₁ to W ₄₎ is, if it is blocked by the obstacle, the track information signal S _8a supplied to the control unit C _C Is extremely reduced or not derived. Therefore, although the one position information is not obtained, wherein the control unit C _C is based on A / D conversion of the same control / signal processing and the in received signal processing system B for this particular satellite The trajectory information signal _S8b sent from the device 46 is taken in. Further by the similar sequence control of the control unit C _C by the reception signal processing system A for the remaining three satellites, or radio waves W ₂ from the remaining three satellites
Captures the W _4, wherein as well as orbital information, Doppler shift,
Pseudo distances are respectively derived, and subsequently, positional information of the latitude, longitude, speed, and moving direction at the receiving point of the vehicle is obtained. Similarly, a satellite that cannot be received by the reception signal processing system A is received by the reception signal processing system B.

Thus, with the antennas A _NT1 and A _NT2 arranged at an appropriate position on the vehicle and separated from each other, that is, the radio waves shielded by the roof of the moving body by the space diversity reception
W _{1 to} W ₄ are impressed. Further, the received signals S _1a and S _1b
I am impressed. Further, the received signals S _1a and S _1b are subjected to discriminated signal processing. In this case, it is supplied in common a local oscillation signal S ₂ from the local oscillator L _osc to the mixer 14 and 34. Thus the oscillation signal S _7a carrier NCO24,44, and match the frequency of the S _7b, i.e., the measured value of the Doppler shift is a local oscillation signal of a radio wave from a satellite are received (W ₁ to W _{4) They} will match without being affected by S2.
Therefore, even if diversity reception is performed, the position measurement accuracy is maintained in the best state. Further, the control unit C _C orbit information signal S _8a, determination of the level of S _8b, for example, at the time of the fall below a designated threshold (level), one of the track information signal S _8a large becomes level, the S _8b selected, since control is performed for PN code generator P _osc and code NCO50, the closed-loop control the received signal processing system a, always carried out using the output of the higher-level of B, so-selection And diversity diversity reception signal processing means. Thus, the roof or the like of the moving body, the field strength of the radio wave W ₁ to W ₄ to incoming be received varies intermittently, influence pseudorange measurements can be greatly improved, resulting in vehicle , It is possible to maintain highly accurate position information measurement during traveling.

In this embodiment, an example is shown in which two antennas A _NT1 and A _NT2 are used and the reception signal processing systems A and B are provided, but the present invention is not limited to this. Forming three or more antennas and a reception signal processing system, and using one local oscillator L _osc and one PN code generator P _osc , selective diversity reception signal processing under the control of a control unit similar to the above. Forming the means to obtain the same operation and effect as described above, and obtaining the same operation and effect of the PN code generator are also included in the present invention.

[Effects of the Invention] As can be understood from the above description, according to the GPS receiving system of the present invention, a GPS for a moving object that attaches more importance to aesthetics
The degree of freedom in arranging a plurality of antennas when the receiver is mounted is improved, and for example, stable derivation of position information from GPS satellites when an antenna is installed in a part where the perception situation is not the best It has a possible effect. With such an effect, when the GPS receiving system is adopted in a small passenger car, there is no need to mount an antenna on a roof or the like, and the selection and mounting method of the antenna mounting location becomes easy, and the spread of the GPS receiving system is promoted. There are advantages.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the overall configuration of an embodiment of a GPS receiving system according to the present invention. 14, 34 Mixer 18, 38 PN code demodulator 24, 44 Carrier NCO 50 Code NCO A, B… Received signal processing system A _NT1 , A _NT2 … Antenna C _C … Control Section L _osc …… Local oscillator P _osc …… PN code generator S ₂ …… Local oscillation signal S ₅ …… PN code signal S _7a , S _7b …… Oscillation signal S _8a , S _8b …… Orbit information signal S ₁₀ , S _12a , S _12b …… Instruction control signal

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01S 5/00-5/14 H04J 13/00-13/06 H04B 7/02-7/12

Claims (3)

(57) [Claims] 1. An antenna having two antennas for receiving GPS radio waves,
At least two reception signal processing units each including a frequency conversion unit and a PN code demodulation unit to which a reception signal derived from each antenna is input, and an output after demodulation of the PN code from the at least two reception signal processing units A GPS receiving system comprising: a measuring and calculating means for determining a position of a receiving point from a signal; providing one local oscillator for supplying a local oscillation signal to each of the frequency converters; A GPS receiving system for determining a position of a receiving point using a higher level of an output signal after demodulation of a PN code from said receiving signal processing means. 2. The GPS receiving system according to claim 1, wherein one PN for supplying a PN code signal to said PN code demodulation unit.
A GPS receiving system comprising a code generator. 3. A plurality of antennas for receiving GPS radio waves and transmitting received signals, a mixer to which at least the received signals are respectively supplied, a PN code demodulator, a detector for transmitting a synchronous detection signal, and the detector A plurality of reception signal processing systems including a carrier NCO for transmitting a carrier wave signal, an A / D converter for transmitting an orbit information signal of a digital signal, and a local oscillation signal supplied to a mixer of the plurality of reception signal processing systems. One or more local oscillators, a PN code generator disposed in one or each of the received signal processing systems for transmitting a PN code signal to the plurality of PN code demodulators, and the plurality of received signal processing systems. Are supplied, and when one of the orbital information signals is equal to or less than a predetermined level to zero, the orbital information signal of a level greater than the predetermined level or the orbital information signal of the maximum level is provided. A first control means for selecting, PN of the signal processing system for sending said selected orbit information signal
Second control means for controlling the code demodulator and the carrier NCO to obtain the orbit information, the Doppler shift and the pseudorange, and an operation for forming the position information of the receiving point from the orbit information, the Doppler shift and the pseudorange Means, and a GPS receiving system comprising: