JPH08278129A - Wave period detection device - Google Patents

Abstract

PURPOSE: To accurately detect a wave period from a flight body or an aircraft flying at high altitude by detecting the wave period from the fluctuation of the intensity of signals reflected from water surface with the lapse of time, and not from the fluctuation of water surface height with the lapse of time. CONSTITUTION: A modulated wave is sent to an oscillator 21 from a sweeping signal generator 20, and a radiowave is transmitted toward water surface from the transmission antenna 22 of an aircraft. A reflected wave from the water surface is received with a receiving antenna 23 and mixed with a part of the transmitted wave through a mixer 24, thereby generating beat signals. Then, the frequency of the beat signals is counted with a beat count circuit 25, and outputted as an altitude detection output signal. On the other hand, beat signals from the mixer 24 are separately inputted to a detector 27, and converted to receiving signal intensity. In addition, the noise-like fluctuation component of receiving signal intensity resulting from the fine fluctuation of wave surface is eliminated via a low pass filter 28, and the receiving intensity on water surface at the fluctuating position is outputted as a receiving intensity output signal 29. As a result, the period of the encounter of waves can be easily detected from the aircraft navigating at high altitude.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wave period detecting device for detecting wave information on a water surface, particularly a wave period, by using radio waves.

[0002]

2. Description of the Related Art Heretofore, the detection period (wave period) of waves on the water surface has been detected by the temporal variation of wave height using a radio altimeter. In this method, a radio altimeter is mounted on a flying vehicle or an aircraft, and while flying, radio waves are transmitted and received on the water surface, and the height of the water surface is continuously detected by the delay in the reception frequency. Since the wave cycle can be detected between mountains on the water surface, it is necessary to detect the time from the appearance of a mountain with a high water surface to the appearance of a mountain with a high water surface after passing through a valley with a low water surface. , Detect the wave cycle from the flight speed at that time.

However, in the conventional wave cycle detecting device using such a radio altimeter, a radio altimeter is mounted on a flying object or an aircraft to detect the appearance of mountains on the water surface by the difference in altitude from the sky to the water surface. Therefore, compared to the altitude of a flying object or an aircraft flying at a high position above the surface of the water, the fluctuation of the height of the wave is very small, and it is not easy to detect the wave cycle. This problem becomes remarkable especially when the weather condition is bad and the flying object or the aircraft has to fly at a high altitude.

[0004]

As described above, the conventional wave period detecting device measures the difference in height due to waves on the water surface using the radio altimeter and detects the wave period by its temporal variation. There is a problem that it is not easy to detect the cycle.

The present invention has been made to solve the above problems, and it is an object of the present invention to provide a wave cycle detecting device capable of accurately detecting a wave cycle even from a flying object or an aircraft flying at a high altitude. Has an aim.

[0006]

The wave cycle detecting apparatus according to the present invention does not detect the wave cycle by the temporal fluctuation of the height of the water surface, but by the temporal fluctuation of the reflected signal intensity from the water surface. By detecting the period, it is possible to detect the wave period without being affected by the position of the flying object or the aircraft at high altitude.

That is, in the wave cycle detecting device according to the present invention, when radio waves are transmitted and received from the sky almost perpendicularly to the water surface, the reception intensity is different between the peaks and valleys forming the waves and the sloped surface. It is characterized by detecting the wave information such as the encounter cycle of waves from the time variation of the reception intensity by transmitting and receiving radio waves while moving over the sky. Further, even if a plurality of waves are combined, the frequency analysis means for analyzing the fluctuation frequency of the output received signal strength is provided, and even if a plurality of waves are combined, the encounter cycle of each combined wave from each spectrum output from the frequency analysis means. It is characterized by detecting wave information such as. Furthermore, it is characterized by being incorporated in a device that uses a radio altimeter to transmit and receive radio waves to and from the water surface to detect wave information such as the encounter cycle of waves from the temporal variation of the height of the water surface.

[0008]

The operation principle of the present invention will be described below.
The present invention does not detect the height of the water surface, but when radio waves are transmitted and received vertically from the sky to the water surface, the received signal strength of the reflected radio waves at the positions of the peaks and valleys where the water surface forming waves is horizontal. The wave period is detected by utilizing the phenomenon that the received signal strength sharply weakens at the slope between the peak and the valley forming the wave. FIG. 1 is a diagram for explaining the operation principle of the present invention, in which 1 is a water surface,
2 is an aircraft, 3a is one wave, 3b is the next wave, 10
Is an inclined surface portion of the wave, 11 is a wave mountain portion, and 12 is a wave valley portion.

The radio wave transmitted from the aircraft 2 is reflected by the water surface 1 and received again by the aircraft 2. Then, when the aircraft 2 is at the position 2a and the radio wave is radiated on the mountain 11 of the wave 3a, and the radio wave is reflected at a substantially right angle on the horizontal plane, a strong reception intensity is obtained. Then, while the aircraft 2a flies to the position 2b, the reception intensity sharply weakens at the slope 10 and becomes strong again at the valley 12, and at the position 2b, the slope 10 decreases.
Then it becomes weak again rapidly. Flying further, mountain 3b of wave 3b
When the sky above 1 is reached, a strong reception strength is obtained again.

Therefore, the time for receiving three strong reception intensities is a wave cycle, and by detecting this, the wave cycle can be detected. The difference in the received signal strength is almost not affected by the flight altitude of the airplane 2 as long as the transmitted beam does not include the inclined surface 10, the ridge 11, and the valley 12 of the wave together. , It becomes possible to easily detect the encounter cycle of waves from a high altitude with a flying object or an aircraft.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a block diagram showing an embodiment of the present invention, in which 20 is a sweep signal generator, 21 is an oscillator, 22 is a transmitting antenna, 23 is a receiving antenna, 24 is a mixer, and 25 is a beat count circuit. , 26 is an altitude detection output, 27 is a detector, 28 is a low pass filter, and 29 is a reception intensity output.

Next, the operation of the embodiment shown in FIG. 2 will be described. The modulated wave is sent to the oscillator 21 by the sweep signal generator 20, a high frequency signal is generated by the oscillator 21, and the radio wave is transmitted toward the water surface via the transmitting antenna 22. Then, the radio wave reflected on the water surface is received by the reception antenna 23, becomes a reception signal, and is mixed with a part of the transmission wave by the mixer 24 to generate a beat signal. Then, the frequency of the generated beat signal is counted by the beat count circuit 25, the distance (altitude) to the water surface is calculated, and output as the altitude detection output 26. The conventional wave cycle detecting device detects the wave cycle by the altitude detection output 26 as described above.

On the other hand, in the apparatus of the present embodiment, the beat signal generated by the mixer 24 is input to the detector 27 separately and detected to be converted into a reception intensity signal, and further, the fine fluctuation of the surface of the wave. The low-pass filter 28 removes the noise-like fluctuation of the reception intensity signal, and the reception intensity of the water surface at that position is output as the reception intensity output 29. Therefore, it is possible to fly the flying object or the aircraft, continuously observe the reception intensity output 29 from the water surface, detect the time of the fluctuation cycle, and detect the wave cycle from the flight speed at that time.

FIG. 3 is a block diagram showing another embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 2 indicate the same or corresponding portions, 30 is a frequency analysis unit, 31 is a fluctuation frequency of the reception intensity. It is a characteristic output. In the embodiment shown in FIG. 2 described above, the wave period is detected by the reception intensity of the received signal, but the temporal fluctuation of the reception intensity is due to a plurality of different water surfaces for a wave having a swell, for example. Since the motions are combined and the frequency fluctuations of the received signals from these are combined, the motion becomes complicated, and it may be difficult to detect the wave period.

Therefore, in this embodiment, the fluctuating frequency of the reception intensity output 29 is input to the frequency analysis unit 30, separated into a frequency spectrum by a frequency analysis method such as FFT, and output as a variation frequency characteristic output 31 of the reception intensity. . Since the reciprocal of the frequency of the spectrum becomes the fluctuation period, the wave period can be detected even for the wave having the above-mentioned undulations. Further, according to the present embodiment, it is possible to obtain more information regarding waves such as the most dominant cycle, the second most dominant cycle, etc., from the strength of the spectrum.

In the above embodiment, the radio altimeter is described as a device in which a means for detecting the wave cycle is added by the temporal fluctuation of the reflected signal intensity from the water surface, but as a separate device different from the radio altimeter. It goes without saying that can also be configured.

[0017]

As described above, the wave cycle detecting device of the present invention detects the wave cycle by the temporal fluctuation of the intensity of the reflected signal from the water surface, so that it is not affected by the flight altitude.
It is possible to easily detect the encounter cycle of waves from a flying object or an aircraft flying above altitude. Further, by adding a frequency analysis means for analyzing the time-varying frequency of the received signal strength, even when a plurality of wave periods are compounded,
It is possible to detect each wave cycle. Furthermore, it is possible to use it together with the conventional device that detects the wave cycle from the temporal fluctuation of the water surface, and in this case, it is easily incorporated into the radio altimeter for detecting the temporal fluctuation of the water surface. There are effects such as being able to.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the operation principle of the present invention.

FIG. 2 is a block diagram showing an embodiment of the present invention.

FIG. 3 is a block diagram showing another embodiment of the present invention.

[Explanation of symbols]

 20 Sweep signal generator 21 Oscillator 22 Transmitting antenna 23 Receiving antenna 24 Mixer 25 Beat count circuit 26 Advanced detection output 27 Detector 28 Low-pass filter 29 Received intensity output 30 Frequency analysis section 31 Frequency characteristic output

Claims (3)

[Claims] 1. A wave period detection device for transmitting and receiving radio waves to and from a water surface to detect wave information such as the encounter frequency of waves, and the like. Taking advantage of the difference in the received intensity between the valley and the slope, the radio wave is transmitted and received on the water surface while moving in the sky, and the wave information such as the encounter frequency of waves is calculated from the temporal fluctuation of the received intensity. A wave cycle detection device characterized by detecting a wave. 2. A frequency analysis means for analyzing the fluctuation frequency of the output received signal strength is provided, and even when a plurality of waves are compounded, each of the waves compounded from each spectrum output from the frequency analysis means is included. The wave cycle detection device according to claim 1, wherein wave information such as an encounter cycle is detected. 3. A radio altimeter, which is incorporated into a device that transmits and receives radio waves to and from the water surface to detect wave information such as the encounter cycle of waves from the temporal fluctuation of the height of the water surface. The wave cycle detection device according to items 1 and 2.