JP3024787B2 - Heading measurement device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention relates to an apparatus for measuring a heading, and more specifically, it utilizes a GPS radio wave (a radio wave transmitted from a Global Positioning System, hereinafter the same). The present invention relates to an apparatus for measuring a heading of a navigating ship or the like.

(Prior art and its problems) In order for a ship or the like to navigate safely on the sea, it is necessary to confirm a correct position of the ship and determine a course based on the position. To this end, various navigational instruments are commonly equipped on ships. The magnetic compass (magnetic compass) and the gyro compass belong to dead reckoning instruments for performing dead reckoning, and can be said to be the most widely used navigation instruments.

The normal magnet compass is based on the principle that if the magnetic needle is suspended freely, it indicates the direction of the earth's magnetic pole.However, the direction of the earth's magnetic pole may correspond to the true north and south of the earth depending on the location. It can be skewed, so the magnetic compass pointer does not always point to true north-south. Also, when the hull is made of a material that is susceptible to magnetic force such as an iron material, or when the cargo itself is an iron material or the like that is easily affected by magnetic force, the reading of the magnetic needle may be deviated. Therefore, such a deviation or self-difference requires correction for the course decision based on experience etc.,
Eventually, the accuracy will be poor.

On the other hand, the gyro compass is based on the principle that the rotation of the earth is applied to the tops that rotate at high speed and the direction of the earth's axis is indicated. It has the drawback that it requires regular maintenance and its service life is not so long.

In addition, ships traveling in the polar region cannot use either a magnet compass or a gyro compass because of their regional characteristics, and there are various problems such as the fact that an inertial navigation system that replaces them is extremely expensive. Was.

(Means for Solving the Problems) Therefore, as a result of intensive studies, the present inventor has found that GPS / NAVSTA
R system (Global Positioning System / Navigatio
n System with Time and Ranges), one of 21 mobile satellites that are built into this system and rotate the universe along a predetermined orbit.
The signals transmitted from the antennas are received by a plurality of omnidirectional antennas for azimuth measurement which are rotated along the circumference or arranged on the circumference and sequentially switched at a fixed period, and the Doppler displacement or phase change of the received radio waves. Is detected in advance by detecting the phase difference between the period of the satellite and the period of rotating or sequentially switching the antenna, and the heading is obtained from the heading of the satellite and the heading of the satellite obtained by the satellite signal. With such a configuration, it has been found that a heading measurement apparatus capable of resolving the above-mentioned inconveniences at once can be obtained.

Accordingly, an object of the present invention is to provide a heading measuring apparatus which is extremely accurate, has an excellent service life, can be used in polar regions, and is easy to handle in determining the heading of its own ship. is there.

Further, in the present invention, a positioning antenna is located at the center of an array of azimuth measuring antennas arranged on the circumference so that the antenna can be easily used even in a small ship or the like where a suitable antenna installation location is extremely limited. The GPS receiver for azimuth measurement and the local oscillation frequency signal generator common to the GPS receiver for positioning are installed, and the positioning with azimuth measurement function is provided. The production of GPS receivers is small and inexpensive, and the structure is simplified, so that the performance is stabilized. Further, by these, the spread spectrum signal for azimuth measurement was stabilized.

Next, a preferred embodiment of a heading measurement apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

(Embodiment) In FIG. 1, reference numeral 10 indicates that the radius is 1/4 of the GPS radio wave.
The figure shows eight dipole antennas arranged on a circumference within a wavelength, and the antenna 10 is electrically connected to an antenna switch 12. The antenna 11 indicates one dipole antenna arranged at the center of the circumferential array of the antennas 10, and the antenna 11 is electrically connected to the positioning GPS receiver 48. The output side of the dipole antenna 10 is connected to the antenna switch 12, and the output terminal of the antenna switch 12 is connected to one input terminal of the frequency converter 14, and the other input terminal of the frequency converter 14. Is connected to the output terminal of the first frequency synthesizer 16. The output terminal of the first frequency synthesizer 16 is connected to a positioning GPS receiver 48. Note that the input terminal of the first frequency synthesizer 16 is connected to the output terminal of the high stability oscillator 18. An output terminal of the frequency converter 14 is connected to an input terminal of the intermediate frequency amplifier 20, and an output side of the amplifier 20 is connected to one input terminal of the multiplier 22. Next, the other input terminal of the multiplier 22 is connected to the output terminal of the modulator 24, and one of the two input terminals of the modulator 24 is connected to a PN code generator (pseudo noise code generator). 26
And the other is connected to the output terminal of the voltage controlled oscillator 28. The output terminal of the multiplier 22 is connected to the input side of the first band pass filter 30, and the output terminal of the first band pass filter 30 is connected to the input side of the multiplier 32. The phase detector 34 receives the output of the multiplier 32 on the one hand and the output of the second frequency synthesizer 36 on the other hand, so that one input terminal thereof is connected to the output terminal of the multiplier 32. The other input terminal is connected to the output terminal of the frequency synthesizer 36. In this case, the input side of the frequency synthesizer 36 is connected to the branched output side of the high stability oscillator 18. Note that the output side of the phase detector 34 is connected to the input side of the voltage controlled oscillator 28 via the loop filter 38. Therefore, the voltage controlled oscillator 28-modulator
24-multiplier 22-first bandpass filter 30-multiplier 32-
The phase detector 34 and the loop filter 38 are connected to each other by a PLL (Phase
Locked Loop).

The output side of the phase detector 34 is branched and connected to the input side of the second band pass filter 40. Phase detector 42
Receives the output of the second bandpass filter 40 and one output of the switched wave generator 44, so that one input terminal is the output terminal of the second bandpass filter 40 and the other input terminal. Is connected to one output terminal of the switching wave generator 44. Here, the other output terminal of the switching wave generator 44 is connected to the input side of the antenna switching device 12.

The heading calculator 46 has one input terminal connected to the output terminal of the phase detector 42, and the other input terminal connected to one output terminal of the positioning GPS receiver 48. I do. Further, the other output terminal of the positioning GPS receiver 48 is connected to the input terminal of the PN code generator 26, and the output side of the heading calculator 46 is connected to the input side of the display 50. .

The device of the present invention is basically configured as described above. Next, the operation and effects of the device of the present invention will be described.

The output of each element constituting the antenna 10 is supplied to the antenna switch 12, while the signal transmitted from one output side of the switching wave generator 44 causes the antenna switch 12 to output any one of the dipole antennas 10. Select one element. Since the selected element receives a GPS radio wave transmitted from a GPS satellite (not shown), the GPS signal of the antenna 10 is introduced into one input terminal of the frequency converter 14 and the other input terminal. Is supplied from the first frequency synthesizer 16 with a local oscillation frequency signal generated in response to the output of the high stability oscillator 18. Therefore, the frequency converter 14 outputs a frequency signal representing the difference between the GPS signal and the local oscillation frequency signal to the intermediate frequency amplifier 20 as an output. In the intermediate frequency amplifier 20, the output signal of the frequency converter 14 is amplified and becomes one input signal of the multiplier 22.
In this case, the signal from the modulator 24 is sent as the other input signal. In this case, the output signal of the modulator 24 is obtained by modulating the output of the voltage controlled oscillator 28 with a PN signal (Psuedo Noisu signal, pseudo noise signal) generated in the PN code generator 26. PN
The signal, that is, the output of the PN code generator 26 is
It is regulated to have an appropriate one satellite code and reception timing within the visibility of the GPS satellite selected by the S receiver 48. Therefore, the output of the multiplier 22 is output to the first band-pass filter 30 whose center frequency is the difference between the intermediate frequency of the intermediate frequency amplifier 20 and the frequency of the voltage controlled oscillator 28.
, The first bandpass filter 30 obtains a signal obtained by demodulating the spread spectrum of the GPS signal received at the antenna 10. Next, the output signal of the first band-pass filter 30 thus demodulated is
The signal is guided to a multiplier 32 for doubling it, and the orbit data and other modulation components contained in the demodulated GPS signal are removed and introduced to one input terminal of a phase detector 34.

Next, the signal sent from the high-stable oscillator 18 is introduced into the first frequency synthesizer 16 on the one hand as described above, and is branched into the second frequency synthesizer 36 on the other hand. The output frequency of the high-stable oscillator 18 is converted into the same frequency as the output frequency of the multiplier 32 by the second frequency synthesizer 36, and is introduced to the other input terminal of the phase detector 34. Here, the output of the phase detector 34 is supplied to the voltage controlled oscillator 28 and the modulator 2 through the loop filter 38 as described above.
4, P including multiplier 22, bandpass filter 30, and multiplier 32
Since it is introduced into the LL, the output signal frequency of the multiplier 32 will be exactly the same as the output frequency of the second frequency synthesizer 36.

By the way, the switching cycle T of the switching wave generator 44 is appropriately selected, and the antenna switching unit is switched via the switching wave generator 44 so that the energization of the eight elements of the antenna 10 is sequentially rotated clockwise from the bow side. Controlling 12 will result in GPS satellites and aerial 10
The relative distance to each element changes sequentially (second
See figure). Accordingly, in response to this, the phase deviation ΔΦ of the received signal of the GPS radio wave changes stepwise connecting the points in FIG. 3 when the projection azimuth of the azimuth of the GPS satellite on the ground plane coincides with the heading azimuth. On the other hand, when the GPS satellite is in the azimuth of Δs from the heading as shown in FIG. 2, it changes stepwise connecting the point X in FIG. Therefore, the switching wave generator
If the switching period T of 44 is selected to be smaller than the time constant of the loop filter 38, the phase deviation generated by sequentially switching each element of the antenna 10 will appear as a change in the output of the phase detector 34. Therefore, such a phase detector 34
Is passed through a second band-pass filter 40 having a center frequency equal to the reciprocal of the switching period T, so that the output of the second band-pass filter 40 is a sine wave of a solid line or a dotted line as shown in FIG. Can be represented. As a result, the difference + (90 ° −360 ° / 16) between the switching phase of the switching wave generator 44 and the output phase of the second band-pass filter 40 is the projection azimuth from the heading to the horizon in the azimuth of the GPS satellite. It will show the direction up to.

Accordingly, in the phase detector 42, the phase difference between the output of the switching wave generator 44 and the output of the second bandpass filter 40 is extracted, and the signal is then introduced into one input terminal of the heading calculator 46. Is done. On the other hand, a heading signal of a GPS satellite including the PN code of the positioning GPS receiver 48 is transmitted to the other input terminal of the heading calculator 46. As a result, in the heading calculator 46, the output of the phase detector 42+ (90 ° −360 ° / 1
6) is calculated to be subtracted, so that the heading is determined, which will be displayed by the display 50. By the way, since the positioning antenna 11 that supplies the GPS signal to the positioning GPS receiver 48 is arranged at the center of the circumferential array of the azimuth measuring antenna 10, by sequentially switching each element of the antenna 10 The phase deviation of the generated GPS signal will change exactly symmetrically with respect to the GPS signal received by the positioning antenna 11, and the output of the first frequency synthesizer 16 will be the positioning GPS receiver 48. Are supplied in common to the GPS antenna 48 for positioning, and are supplied from the antenna 11 for positioning.
Since the GPS signal is used as a local oscillation frequency signal for converting to an intermediate frequency, the timing of the PN code transmitted from the positioning GPS receiver 48 to the PN code generator 26 is accurately received by the antenna 10 for azimuth measurement. This coincides with the center of the timing of the PN code of the GPS signal, so that the output of the first band-pass filter 30 has the largest demodulation output and a stable spread spectrum demodulated signal is obtained.

In another embodiment of the present invention, a single dipole antenna can be used instead of the antenna 10 and the antenna switch 12. When this dipole antenna is rotated on the circumference at the period T, a Doppler shift Δf appears in the antenna 10, and as a result, a sine-wave output corresponding to the Doppler shift Δf is output to the second bandpass filter 40. (See FIG. 4). Here, in the figure, the solid line shows the output obtained when the projection of the GPS satellite on the ground plane coincides with the heading, while the dotted line shows the projection of the GPS satellite's orientation on the ground plane from the heading. The output obtained as a result of the Θs deviation is shown. In this case, the heading calculator 46 uses the positioning GPS
Phase detector 4 based on the direction of the GPS satellite sent from receiver 48
The heading is obtained by subtracting the output of 2 + 180 °, and is similarly displayed by the display 50.

(Effects of the Invention) Accordingly, even with one dipole antenna, the same effect as that obtained when eight dipole antennas are used can be obtained by changing the calculation elements.

As described above, the present invention has been described with reference to the preferred embodiments. However, the present invention is not limited to the embodiments of the present invention, and various modifications can be made without departing from the spirit of the present invention. is there.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the structure of a heading measuring apparatus according to the present invention, FIG. 2 is an explanatory diagram showing a correlation between a bow and a satellite, and FIG. 3 is a phase deviation of a GPS radio wave reception signal. FIG. 4 is an explanatory diagram showing a correlation between the position and the time, and FIG. 4 is an explanatory diagram showing a correlation between the Doppler deviation and the time that appear when one dipole antenna is used. 10… azimuth measurement antenna, 11… positioning aerial, 12…
Antenna switcher, 14 frequency converter, 16 first frequency synthesizer, 18 oscillator, 20 intermediate frequency amplifier, 22
… Multiplier, 24 …… Modulator, 26 …… PN code generator, 28…
... voltage controlled oscillator, 30 ... first bandpass filter, 32
... Multiplier, 34 ... Phase detector, 36 ... Second frequency synthesizer, 38 ... Loop filter, 40 ... Second band pass filter, 42 ... Phase detector, 44 ... Switching wave generator , 46 ……
Heading calculator, 48… GPS receiver, 50 …… Display.

Claims (1)

(57) [Claims] 1. A plurality of omnidirectional antennas for azimuth measurement which are rotated along the circumference or are arranged on the circumference and are sequentially switched at a constant period, and the omnidirectional antenna for azimuth measurement are rotated or sequentially rotated. Switching means, a positioning antenna installed at the center of the omnidirectional antenna array for azimuth measurement, and a GPS receiver that receives GPS radio waves by the positioning antenna to obtain the position of the ship and the azimuth of the GPS satellite. The PN code given to the GPS satellite transmitted from the GPS receiver, the reception timing of the PN code and the GPS signal obtained from the positioning antenna, the Doppler change or phase change of the received radio wave of the predetermined GPS satellite. A means for extracting, a local oscillation frequency signal is supplied in common to the GPS receiver and the means for extracting the Doppler change or the phase change, and the omnidirectional antenna for azimuth measurement and the GPS received by the positioning antenna are received. Means for generating a local oscillation frequency signal for converting each signal to an intermediate frequency, and detecting a phase difference between a cycle of the Doppler change or phase change and a cycle of rotating or sequentially switching the antenna to detect a GPS satellite with respect to the heading. Means for detecting a heading, means for obtaining a heading from a heading of a GPS satellite with respect to the heading and a heading of a GPS satellite obtained from the GPS receiver, and a display for displaying the heading. Heading measurement device.