JP2002181912A - Direction finder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make calculable an azimuth without increasing the dimension of a mast and to accurately measure the azimuth even if an arrival signal is a continuous wave and changes in its frequency, in a direction finder mounted on a moving body such as vessels or the like to calculate the azimuth of the arrival signal. SOLUTION: Non-directional antennas 3a and 3b are mounted on at least two masts 2a and 2b as a pair and RF waveform memories 5a and 5b for storing the waveforms of receiving signals are provided. Since the waveforms 10a and 10b of arrival signals are mutually compared and the calculation of an azimuth is performed on the basis of the time lag of the arrival signals to the antennas 3a and 3b, a direction finder for accurately measuring the azimuth even if the arrival signals are continuous waves and change in frequency without increasing the dimensions of the masts is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direction finding device mounted on a moving body such as a ship to detect the direction of arrival of an RF signal.

[0002]

2. Description of the Related Art A conventional direction finding device will be described. FIG.
FIG. 2 is a block diagram illustrating a configuration of a conventional direction finding device mounted on a ship. In FIG. 9, 22a, 22b, 22c,
22d is a directional antenna, 4g, 4h, 4i, and 4j are receivers. Reference numeral 23 denotes each of the receivers 4g, 4h, 4
An amplitude comparison circuit for comparing the amplitudes of the signals received by i and 4j, and 7e is an azimuth calculation circuit.

Next, the operation will be described. An incoming signal is input to each of the receivers 4g, 4h, 4i, and 4j via each of the directional antennas 22a, 22b, 22c, and 22d. At this time, each directional antenna 22a, 22b, 22c, 22
d each forms a beam in the horizontal direction, and the signal level input to each of the receivers 4g, 4h, 4i, and 4j differs depending on the direction of the incoming signal. Each receiver 4g, 4h, 4
In i and 4j, a reception signal corresponding to the signal level of the input arrival signal is output. Each receiver 4g, 4h, 4i, 4j
Is compared with the amplitude level of each received signal, and the azimuth calculation circuit 7e uses the previously recorded amplitude level difference and the azimuth correspondence data based on the data.
The azimuth of the incoming signal is calculated from the result of the comparison of the amplitude levels.

FIG. 10 is an external view showing a mast portion of a ship on which an antenna which is a component of a conventional direction finding device is mounted.
In FIG. 10, 1f denotes a ship, 2g and 2h denote masts mounted on the ship, and 24 denotes an antenna mounting portion for mounting a directional antenna.

[0005] The directional antennas 22a, 22b, 2 in FIG.
2c and 22d are mounted on the antenna mounting portion 24 of the mast 2g installed on the ship 1f in FIG. FIG. 11 is a schematic structural view showing the structure of the antenna mounting portion. As shown in the drawing, the directional antennas 22a, 22b, 22c, and 22d are mounted on the antenna mounting section 24, and they are equidistantly spaced.

Next, a conventional direction finding device using an omnidirectional antenna will be described. FIG. 12 shows, for example,
FIG. 1 is a block diagram illustrating a configuration of a conventional direction finding device disclosed in Japanese Patent Application Laid-Open No. -1333749. In the figure, 3g, 3h, 3
i and 3j are omnidirectional antennas, 6b and 6c are time difference measurement circuits, and 7f is an azimuth calculation circuit.

Next, the operation will be described. The omnidirectional antennas 3g, 3h, and 3i, 3j are paired and are each arranged at right angles. For example, the omnidirectional antennas 3g and 3h are responsible for measuring the direction of the ship before and after,
j is responsible for left and right. FIG. 13 is a diagram of incoming signals arriving at a pair of omnidirectional antennas 3g and 3h. When a pulse arriving signal arrives as a plane wave from the two omnidirectional antennas 3g and 3h from a direction inclined by θ from the vertical, a time difference τ is generated according to the following formula according to the distance d between the antennas. τ = (d / c) sin θ (c: speed of light) (1) Therefore, the time difference between the received signals received by the omnidirectional antennas 3g and 3h is measured by the time difference measurement circuit 6b, and the angle is applied to τ in the above equation. Calculate θ.

As described above, the omnidirectional antennas 3g, 3g
h, the azimuth of the ship in the front-rear direction is measured, and similarly, the omnidirectional antennas 3i, 3j measure the azimuth of the ship in the left-right direction to determine the true azimuth.

[0009]

As described above, in the case of the conventional direction finding device, it is necessary to install four directional antennas on a single mast at equal azimuthal intervals. When the direction of arrival is detected, the size of the device becomes large, so that there is a problem that the ship cannot be mounted on a ship with limited mast dimensions. Even when an omnidirectional antenna is used, four antennas are required, and when there is a restriction on the mast size, mounting may not be possible. Further, when the incoming signal is a continuous wave and the frequency changes continuously, there is a problem that accurate azimuth measurement cannot be performed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide a direction finding device capable of detecting an azimuth without increasing the size of the device.

[0011]

According to the present invention, there is provided a direction finding device comprising at least two separated mounting units mounted on a moving body such as a ship.
One omnidirectional antenna, at least two receivers for receiving an incoming signal via the antenna, at least two RF waveform memories for storing a waveform of a received signal output from the receiver, and the RF waveform memory A time difference measurement circuit that compares the waveforms stored in each other to measure the time difference between the reception timings of the incoming signals, a self-orientation detection circuit that detects the orientation of the moving object, and the measured time difference and the detected A azimuth calculating circuit for calculating the azimuth of the target from its own azimuth.

[0012] Also, at least one omni-directional antenna mounted on a moving body such as a ship, at least one receiver for receiving an incoming signal via the antenna, and a reference having the same frequency as the incoming signal. A reference signal device that generates a signal, a phase difference detection circuit that detects a phase difference between a reception signal output from the receiver and the reference signal, and stores a phase difference detected at at least two or more different points. A self-position detecting circuit for recognizing the position of the moving object, a self-direction detecting circuit for detecting the direction of the moving object, and at least two or more different signals output from the storing circuit. And an azimuth calculating circuit for calculating the azimuth of the incoming signal from the phase difference at the point (a) and the self position and the self azimuth.

[0013] At least two omni-directional antennas mounted separately on a moving body such as a ship, at least two receivers for receiving an incoming signal via the antenna, and the same frequency as the incoming signal. A reference signal device for generating a reference signal having the same, a phase difference detection circuit for detecting a phase difference between a reception signal output from the receiver and the reference signal, and detecting an orientation in which the moving body is facing. A self-azimuth detection circuit; and a azimuth calculation circuit for calculating the azimuth of the incoming signal from the detected phase difference, the self-azimuth, and the self-position.

Also, an omnidirectional antenna mounted on a moving body such as a ship, a receiver for receiving an incoming signal via the omnidirectional antenna, and a reference signal having the same frequency as the incoming signal are generated. A reference signal device, a synchronous detection circuit that creates a beat signal that is the sum of the received signal output from the receiver and the reference signal, a frequency detection circuit that detects the frequency of the beat signal, A self-orientation detecting circuit for detecting the heading, a self-speed detecting circuit for detecting the moving speed of the moving object, and calculating the frequency of the detected beat signal and the direction of the incoming signal from the self-orientation and the self-speed. And an azimuth calculating circuit.

Further, there is provided an azimuth determining circuit for calculating the azimuth of the incoming signal a plurality of times while changing the azimuth of the moving object, and determining the target azimuth from the plurality of calculation results of the arriving signal. .

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Embodiment 1 of the present invention will be described. FIG. 1 is a block diagram showing a configuration of a direction finding device according to Embodiment 1 of the present invention. In the figure, 1a is a ship, 2a and 2b are masts installed on the ship, 3a and 3b are omnidirectional antennas mounted on each mast 2a and 2b, 4a and 4b are receivers, 5a and 5b are R
F waveform memory, 6 is a time difference measurement circuit, 7a is an azimuth calculation circuit, 8a is a self azimuth detection circuit, and 9 is an incoming signal.

Next, the operation of the first embodiment will be described. When an incoming signal 9 is input from a direction inclined by θ from the vertical with respect to a line connecting the omnidirectional antennas 3a and 3b mounted on the two masts 2a and 2b, two antennas as shown in the conventional example are used. The angle θ is calculated using the relational expression (1) between the distance d and the time difference τ. At this time, the incoming signals 9 input from the omnidirectional antennas 2a and 2b are received by the receivers 4a and 4b, respectively, and the waveforms of the received signals are stored in the RF waveform memories 5a and 5b.

FIG. 2 is a diagram of the RF waveforms 10a and 10b stored in the RF waveform memories 5a and 5b. As shown in the figure, the RF waveforms 10a and 10b are stored with a time difference τ. In the prior art, such an RF waveform memory was not provided, and an accurate time difference τ could not be measured, for example, when the frequency of the arriving signal was a continuous wave, but in the first embodiment, the RF waveform memories 5a and 5b were used. , The time difference τ can be measured even when the incoming signal is a continuous wave and the frequency changes.

The time difference measurement circuit 6 measures the time difference τ based on the waveforms 10a and 10b stored as described above. Further, the self-azimuth detecting circuit 8a detects the direction in which the ship 1 is facing (hereinafter, self-azimuth). Direction calculation circuit 7a
Then, the direction of arrival to the antenna is calculated from the measured time difference τ based on the above equation, and the antenna direction is calculated from the detected self direction and the installation positions of the masts 2a and 2b. The arrival direction of the arrival signal 9 is obtained from the antenna direction and the arrival direction with respect to the antenna.

As described above, in the first embodiment, in the direction finding apparatus using the omni-directional antenna, the RF waveform memory for storing the waveform of the arriving signal is provided, and the waveforms of the arriving signals are compared with each other to make it possible to control the antenna. Provided is a direction finding device for performing accurate azimuth measurement even when the arrival signal is not only a pulse signal but also a continuous wave and the frequency changes in order to measure an arrival time difference.

Embodiment 2 In Embodiment 2, only one mast of a ship or the like is used, and a single omnidirectional antenna mounted on the mast is used. A direction finding device that compares the azimuth and the phase difference between the arriving signals and calculates the azimuth of the arriving signal will be described.

FIG. 3 is a block diagram showing a configuration of the direction finding apparatus according to the second embodiment. 1b is a ship, 2c is a mast installed on the ship, 3c is an omnidirectional antenna mounted on the mast 2c, 4c is a receiver, 7b is an azimuth calculation circuit,
8b is a self-orientation detection circuit, and 9 is an incoming signal. Also,
11a is a reference signal device, 12a is a phase difference detection circuit, 13 is a storage circuit, and 14 is a self-position detection circuit.

FIG. 4 is a diagram showing a method of azimuth measurement according to the second embodiment. 100a is the ship at the time T1, which is located at the position P1. 100b is a self-position at time T2, and is located at a position P2 separated from the self-position at time T1 by a distance d. 9 is time T1,
It is an arrival signal to the ship 1 at T2.

Next, the operation will be described. At time T1, an incoming signal 9 input from the omnidirectional antenna 3 mounted on the mast 2 is received by the receiver 4c. The reference signal device 11a generates a signal having the same frequency as the received signal. The phase difference detection circuit 12a detects a phase difference δ1 between the received signal received by the receiver 4 and the reference signal generated from the reference signal device 11a. The recording circuit 13 includes the phase difference detection circuit 1
The phase difference δ1 detected in 2a is stored. Further, the self-position detection circuit 14 detects the position (hereinafter referred to as “self-position”) P1 of the ship 1 using GPS or the like.

Next, the ship 1 moves to the self-position P2 at the time T2, compares the incoming signal 9 with the reference signal generated at the time T1 in the same manner as described above, and detects the phase difference δ2 by the phase difference detection circuit 12a.
Is detected and stored in the storage circuit 13. Further, the self-position detecting circuit 14 detects the self-position P2.

The azimuth calculation circuit 7b calculates the times T1 and T
2, the arrival direction is calculated from the self-positions P1 and P2 in FIG. 2 and the phase differences δ1 and δ2 stored in the storage circuit 13. The distance between the positions P1 and P2 is d, the wavelength of the arriving signal is λ, and the phase difference between the two points of the arriving signal is δ (= δ2−δ).
Assuming 1), the arrival direction θ is as follows: δ = (2πd / λ) sin θ (2) The azimuth calculation circuit 7 calculates θ using the above equation.
The azimuth of the incoming signal is calculated from the azimuth of the straight line connecting the position P1 and the position P2 and the calculated θ.

As described above, according to the second embodiment, in the direction finding device used for ships and the like, one omnidirectional antenna mounted on the mast is used, and the moving distance, direction, and arrival signal of the moving ship are provided. Since the azimuth of the arriving signal is calculated by comparing the phase differences, it takes time to detect the azimuth, but a direction finding device that can be configured with one mast is obtained.

Embodiment 3 In Embodiment 3 of the present invention, a direction finding apparatus that uses at least two omnidirectional antennas and calculates the azimuth of an incoming signal based on the phase difference of the incoming signal will be described.

FIG. 5 is a block diagram showing the configuration of the direction finding apparatus according to the third embodiment. In the figure, different from the second embodiment shown in FIG. 3, masts 2d and 2e, omnidirectional antennas 3d and 3e, and two receivers 4d and 4e are configured.

Next, the operation of the third embodiment will be described. The point that the azimuth is calculated using the phase difference of the arriving signal is the same as that in the second embodiment. However, in the second embodiment, the measurement is performed by changing the self-position with only one omnidirectional antenna. In the third embodiment, two masts are provided, 2d and 2e, and two omnidirectional antennas 3d and 3e are provided respectively.
e. Then, the incoming signals 9d and 9e arriving at the omnidirectional antennas 3d and 3e are simultaneously measured, and the phase difference δ of the received signal is detected by the phase difference detection circuit 12b.
The azimuth calculation circuit 7c uses the detected phase difference δ to determine the angle θ from the direction perpendicular to the line connecting the antennas according to the equation (2) used in the second embodiment. At this time, d is the distance between antennas, and λ is the wavelength of the incoming signal. The direction of the incoming signal is calculated from the obtained angle θ and the self direction detected by the self direction detection circuit 8.

As described above, in the third embodiment, one omnidirectional antenna 3d,
3e, and the azimuth is obtained by using the phase difference between the incoming signals input to the antennas 3d and 3e.
Compared to the conventional example in which two pairs of antennas are mounted on one mast, the mast size can be reduced and the azimuth can be detected instantaneously.

Embodiment 4 FIG. In the fourth embodiment of the present invention, only one mast such as a ship is used, and one omnidirectional antenna mounted on the mast is used.
A description will now be given of a direction finding device that obtains an azimuth from a speed and a frequency shifted by the Doppler effect of a received signal.

FIG. 6 is a block diagram showing an apparatus configuration of a direction finding apparatus according to the fourth embodiment. In the figure, 1d is a ship, 2f is a mast installed on the ship, 3f is a mast 2
omnidirectional antenna mounted on f, 4f receiver, 7d
Is an azimuth calculation circuit, 8d is a self azimuth detection circuit, 9 is an incoming signal, and 11c is a reference signal device. Reference numeral 15 denotes a synchronous detection circuit, 16 denotes a frequency detection circuit, and 17 denotes a self-speed detection circuit.

Next, the operation will be described. Ship 1d
Is moving at a speed v. The incoming signal 9 input from the omnidirectional antenna 3f mounted on the mast 2f is received by the receiver 4f. At this time, the frequency of the received signal shifts according to the arrival direction component of the ship speed. For example, when the incoming signal comes from the direction of travel of the ship, the incoming signal shifts to the highest frequency side, shifts from the high frequency side to the low frequency side as it deviates from the direction of travel of the ship, and the incoming signal from right behind is the lowest. Shift to the frequency side. That is,
The direction of the incoming signal can be calculated by measuring the shift of the frequency of the incoming signal with respect to the speed of the ship.

Based on the received signal output from the receiver 4f, the reference signal 11c generates a signal having the same frequency as the received signal when the ship stops. This reference signal 11
The reference signal generated from c and the received signal received by the receiver 4f are synchronized by the synchronous detection circuit 15, and a beat signal that is the sum of the reference signal and the received signal is output. The frequency of the output beat signal is detected by the frequency detection circuit 16. The self-azimuth detecting circuit 8d detects the direction in which the ship 1 travels, and the self-speed detecting circuit 17 detects the speed v at which the ship 1 moves. The azimuth calculation circuit 7d refers to azimuth data corresponding to the frequency of the beat signal stored in advance, and obtains the arrival azimuth based on the detected frequency of the beat signal, the azimuth in which the ship 1 moves, and the moving speed of the ship 1.

As described above, in the fourth embodiment, one omnidirectional antenna is used, and the azimuth is obtained from the moving azimuth and speed of the moving ship and the shift frequency of the received signal. It is possible to obtain a direction finding device that can be configured and that can instantaneously determine a bearing.

Fifth Embodiment The First to Fourth Embodiments
Until then, for example, when the direction in the front-back direction was determined, there was a disadvantage that ambiguity remained in the left-right direction,
In the fifth embodiment of the present invention, the direction finding apparatus according to the first to fourth embodiments is provided with a new azimuth determining circuit, and the azimuth calculation of the incoming signal is performed a plurality of times while changing the self azimuth, so that the antenna A direction finding apparatus that performs accurate azimuth calculation without increasing the number will be described.

FIG. 7 is a block diagram showing a configuration of a direction finding apparatus according to Embodiment 5 of the present invention. In the figure, the same reference numerals as those in the first embodiment denote the same or corresponding parts. Reference numeral 18 denotes an azimuth determination circuit which is a feature of the fifth embodiment.

For operations other than the azimuth determination circuit 18,
The azimuth is calculated as in the first embodiment. FIGS. 8A and 8B are diagrams illustrating the azimuth calculation method according to the fifth embodiment. 1e is a ship, 3a and 3b are omnidirectional antennas, 9
Is the incoming signal, 19a is the target that fires the incoming signal, 19
Reference numerals b and 19c denote virtual signal emission sources arising from ambiguity in calculating the azimuth, 20a and 20b denote virtual signals, and 21 a reference line for determining the azimuth. At certain times T1 and T2, the azimuth of the incoming signal is calculated by changing the self azimuth. First, at a certain time T1, the self orientation Φ1
When the angle of the target with respect to the straight line connecting the antennas 3a and 3b is θ1a, in the device configuration of the direction finding device according to the first embodiment, in addition to the angle θ1a, the target is also set in a direction inclined by θ1a to the opposite side of the ship 1. There is a possibility that it is determined that there is a direction, and both the azimuth θ2a and the azimuth θ2b are calculated as θ2a = θ1a−Φ1 θ2b = θ1a + Φ1.

In order to determine one of these, the self-azimuth is changed at time T2 and the azimuth is calculated again. In the self-azimuth Φ2, the arrival direction θ1b at the antenna is calculated, and the arrival directions θ2c and θ2d are obtained.
Then, the azimuth determination circuit 18 determines that θ2a and θ2c are equal from the azimuths obtained above, and
The target azimuth is determined in consideration of the calculation error. As described above, by adding the azimuth determination circuit 18, a direction finding device in which the azimuth calculation accuracy is improved without increasing the number of antennas is obtained.

In the above example, the azimuth determination circuit is added to the direction finding device of the first embodiment. However, the azimuth determination circuit is added to the direction finding device of the second, third, or fourth embodiment. It may be. In this case, as in the above example, the azimuth calculation is performed a plurality of times by the respective methods, and from the plurality of results calculated by the azimuth determination circuit, the true signal emission source is determined from the possibility of two signal emission sources in the same manner as described above. Is determined, and the target direction is determined in consideration of the calculation error.

[0042]

As described above, the direction finding device according to the present invention comprises a pair of two non-directional antennas and an RF waveform memory in a direction finding device mounted on a moving body such as a ship. With the configuration, when using the time difference of the arriving signals input to the paired antennas, it is possible to calculate the azimuth even if the frequency of the arriving signal changes, and to reduce the mast size and average. Obtain a direction finding device that can do it.

A direction finding apparatus mounted on a moving body such as a ship, wherein one omnidirectional antenna is used, and the azimuth is obtained from the own moving distance and azimuth and the phase difference between the arriving signals before and after the movement. Therefore, a direction finding device that can be configured with only one mast is obtained.

Also, two omnidirectional antennas are paired,
Since the azimuth of the arriving signal is obtained from the phase difference and the self azimuth of the arriving signal to the paired antenna, a direction finding device capable of reducing the mast size is obtained.

Also, since one omnidirectional antenna is used and the azimuth is obtained based on the moving azimuth and speed of the self and the shift frequency of the received signal, it can be configured with one mast.
Moreover, a direction finding device that can instantaneously determine the direction is obtained.

In addition, a direction finding device is provided which includes a direction determining circuit and performs a plurality of times while changing its own direction, and determines a target from a plurality of calculation results, thereby improving the direction accuracy without increasing the number of antennas.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a direction finding device according to Embodiment 1 of the present invention.

FIG. 2 is a diagram showing a time difference measurement method of the direction finding apparatus according to Embodiment 1 of the present invention.

FIG. 3 is a block diagram showing a configuration of a direction finding device according to Embodiment 2 of the present invention.

FIG. 4 is a diagram showing a measurement method based on a phase difference of the direction finding apparatus according to Embodiment 2 of the present invention.

FIG. 5 is a block diagram showing a configuration of a direction finding device according to Embodiment 3 of the present invention.

FIG. 6 is a block diagram showing a configuration of a direction finding apparatus according to Embodiment 4 of the present invention.

FIG. 7 is a block diagram showing a configuration of a direction finding device according to Embodiment 5 of the present invention.

FIG. 8 is a diagram showing a measurement method of a direction finding apparatus according to Embodiment 5 of the present invention.

FIG. 9 is a block diagram showing a configuration of a conventional direction finding device.

FIG. 10 is an external view showing a mast section on which a conventional antenna in a direction finding device is mounted.

FIG. 11 is a schematic structural view showing a structure of a mounting portion of an antenna in a conventional direction finding device.

FIG. 12 is a block diagram showing a configuration of another conventional direction finding device.

FIG. 13 is a diagram illustrating the principle of a conventional direction finding device.

[Explanation of symbols]

1a, 1b, 1c, 1d, 1e, 1f Ships, 2a, 2
b, 2c, 2d, 2e, 2f, 2g, 2h Mast, 3
a, 3b, 3c, 3d, 3e, 3f, 3g, 3h, 3
i, 3j omnidirectional antenna, 4a, 4b, 4c, 4
d, 4e, 4f, 4g, 4h, 4i, 4j Receiver, 5
a, 5b RF waveform memory, 6a, 6b, 6c time difference measurement circuit, 7a, 7b, 7c, 7d, 7e, 7f direction calculation circuit, 8a, 8b, 8c, 8d self-direction detection circuit, 9 incoming signal, 10a, 10b RF waveform memory waveform, 11a, 11b, 11c Reference signal device, 12
a, 12b phase difference detection circuit, 13 storage circuit, 14
Self-position detection circuit, 15 Synchronous detection circuit, 16
Frequency detection circuit, 17 self-speed detection circuit, 18 azimuth determination circuit, 19a signal emission source, 19b, 19c
Virtual signal emitting source, 20a, 20b virtual incoming signal, 2
1 reference line, 22 directional antenna, 23 amplitude comparison circuit, 24 antenna mounting part, 100a time T1
, Ship position at 100b time T2.

Claims (5)

[Claims] At least two omni-directional antennas mounted separately on a moving body such as a ship, at least two receivers for receiving an incoming signal via the antennas, and output from the receivers At least two RF waveform memories for storing received signal waveforms, a time difference measurement circuit for comparing waveforms stored in the RF waveform memories and measuring a time difference between reception timings of the incoming signals, and A direction finding device comprising: a self-orientation detecting circuit for detecting an azimuth of the vehicle; and an azimuth calculating circuit for calculating the target azimuth from the measured time difference and the detected self-azimuth. 2. An at least one omni-directional antenna mounted on a moving body such as a ship, at least one receiver for receiving an incoming signal via the antenna, and a reference having the same frequency as the incoming signal. A reference signal device that generates a signal, a phase difference detection circuit that detects a phase difference between a reception signal output from the receiver and the reference signal, and stores a phase difference detected at at least two or more different points. A self-position detecting circuit for recognizing the position of the moving object, a self-direction detecting circuit for detecting the direction of the moving object, and at least two or more different signals output from the storing circuit. And a direction calculation circuit for calculating the direction of the incoming signal from the phase difference at the point (a) and the self position and the self direction. 3. At least two omni-directional antennas mounted on a moving body such as a ship at a distance, at least two receivers for receiving an incoming signal via the antenna, and the same frequency as the incoming signal. A reference signal device for generating a reference signal having the same, a phase difference detection circuit for detecting a phase difference between a reception signal output from the receiver and the reference signal, and detecting an orientation in which the moving body is facing. A direction finding device comprising: a self-azimuth detecting circuit; and a direction calculating circuit that calculates a direction of the incoming signal from the detected phase difference, the self-direction, and the self-position. 4. An omni-directional antenna mounted on a moving body such as a ship, a receiver for receiving an incoming signal via the omni-directional antenna, and a reference signal having the same frequency as the incoming signal. A reference signal device, a synchronous detection circuit that creates a beat signal that is the sum of the received signal output from the receiver and the reference signal, a frequency detection circuit that detects the frequency of the beat signal, A self-orientation detecting circuit for detecting the heading, a self-speed detecting circuit for detecting the moving speed of the moving object, and calculating the frequency of the detected beat signal and the direction of the incoming signal from the self-orientation and the self-speed. And a bearing calculation circuit. 5. An azimuth determination circuit for calculating an azimuth of an incoming signal a plurality of times while changing an azimuth of a moving object, and determining a target azimuth from a plurality of calculation results of the arriving signal. The direction finding device according to any one of claims 1 to 4, wherein