JPS6022680A - Wave radar observation system - Google Patents

Abstract

PURPOSE:To obtain the direction and the speed of movement of a wave in accordance with the amplitude and the phase by operating a spectrum, namely, a cross-spectrum obtained on a basis of mutual correlation between two pictures of a wave signal each time when a radar antenna is rotated once. CONSTITUTION:In an AD converting circuit 4, a gate setting circuit 5 is used to convert a received signal from a wave to data in a range of one wavelength in case of a long wavelength and convert it to data in a range of five wavelenghts in case of a short wavelength; and the signal is converted to a uniform-intensity linear characteristic by a correcting circuit 6, and polar coordinate data is converted to orthogonal coordinate data by an XY converting circuit 7. Data obtained for every one rotation of the radar antenna is subjected to Fourier transform by a two-dimensional processor 8, and the direction and the speed are obtained in accordance with distributions of the amplitude spectrum and the phase spectrum obtained on a basis of mutual correlation between two pictures of the wave signal and are displayed on a display circuit 9.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a radar observation method for measuring the moving direction and speed of waves by using signals from sea surface reflections that are unnecessary for a marine pulse radar.

Reflections from the sea surface caused by waves can hinder the detection of signals targeted by ships, etc.).

Conventionally, devices have been put into practical use that should be removed as unnecessary signals. However, in recent years, methods have been put into practical use that actively utilize signals reflected from the sea surface caused by waves to calculate wave wavelengths, directions, etc.

This involves taking a J"P I scozo photograph from a radar indicator, scanning this photograph in the X and Y directions using a photosensor, converting it from analog to digital, and calculating the spatial worth vector using two-dimensional Fourier transformation. , is a method of determining the wavelength and direction of waves. (Proceedings of the Japanese Society of Navigation N [L66P, 127-135 May 1980 [
(A method of wave analysis using ship radar) However, this method had the disadvantage that the power spectrum was point symmetrical, making it impossible to determine the direction of the waves and not being able to determine the speed at which the waves were traveling.

The present invention is a wave radar observation method in which the spectrum obtained by two-screen cross-correlation of wave signals, that is, the cross spectrum, is calculated for each revolution of the radar antenna, and the true moving direction and speed of the waves are determined from the amplitude and phase. This will be explained in detail below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the method of the present invention.
is a radar antenna, 2 is a transmitter, 3 is a logarithmic amplification receiver, 4
7.1) is a conversion circuit, 5 is a gate setting circuit, 6 is a correction circuit, 7 is an XY conversion circuit, 8 is a two-dimensional processor, and 9 is a display circuit.

Figure 2 is a PPI photo of the received signal from the waves.

The waves form a striped pattern that spreads in two dimensions, and the fan-shaped black frame uses the gate setting circuit 5 to determine the area where the waves are strongly appearing, based on the wave wavelength distribution, that is, when short wavelengths and long wavelengths coexist. The A/D conversion circuit converts data in one wavelength range for long wavelengths or five wavelength ranges for short wavelengths (long wavelengths are up to about 300 m, and short wavelengths are observed at about 50 m). Step 4 converts from analog to digital. The correction circuit 6 is a circuit that converts the received signal of the radar into a uniform intensity because it becomes stronger at a short distance, and a circuit that converts the signal intensity having a logarithmic characteristic into a linear characteristic. X
The Y conversion circuit 7 is a circuit that converts data input as polar coordinates into rectangular coordinates for convenience of analysis. Figure 3(a)
is the newsletter converted from polar coordinates to rectangular coordinates.

The received signal from the waves spreads in the X direction in the form of a sine wave, and FIG. 3(b) shows that the waves move by φ in the time it takes for the radar antenna to rotate once.

To simplify the equation, if we describe it in one dimension, Fig. 3(a) becomes f + = Asln @%; 1) A: amplitude 1: wave number of the wave, and Fig. 3(b) shows L = Asln 't%t-φ)φ: Phase.

The two-dimensional processor 8 performs the Fourier transform of L and f2 using the 4-year-old FF'L'' process, and obtains Fl and F2, respectively.
Then, the spectrum determined by the cross-correlation of the two screens of the wave signal, that is, the cross spectrum, is S+t=F+"CP* *:?N prime conjugate. Let the real part of Sl be 1.Lc and the imaginary part be 1m. For example, the amplitude Sr and phase Sφ of S12 are Sr-147; 8φ=jan' (Im/H,c).

Figures 4(a) and 4(b) illustrate Sr::Sφ.

Sr is symmetrical and the direction of wave movement is unknown. However, unless φ-0, that is, 1 of the radar antenna
If there is movement of the wave during rotation, the sign of Sφ will not be symmetrical. In FIG. 3, the two waves are moving in the positive direction of χ, so it is sufficient to leave the positive side of the amplitude spectrum. In the two-dimensional case, if the amplitude spectrum is point symmetric and the signs of the phase spectra are different, leave the amplitude spectrum and phase spectrum with negative phase, and if they have the same sign, leave both 1. Next, in order to determine the direction and speed ri from the distribution of the amplitude spectrum and phase spectrum spread two-dimensionally, divide it into 16 directions of 22.5 degrees each, select a few from among those with large amplitudes, and Calculate the average value of the wave number and phase with . 1
The largest direction among the six directions is the direction in which the waves are facing, the average wave number, the average phase φ (degrees), the rotation time of the antenna 1, and the moving speed of the wave V (m/S) are L φ V=(- x-0)/l L is analysis data 1/invitation K
The maximum wavelength of the wave at 360 degrees.

The display circuit 9 is a circuit that displays several directions and velocities in order from the one with the thickest amplitude spectrum among the 16 directional movement velocities thus obtained.

As mentioned above, the wave direction and velocity can be calculated from the wave cross spectrum, but as is well known, if the cross spectrum is subjected to inverse Fourier transform, the cross correlation function can be obtained, and from the direction and deviation of the peak, the wave direction and velocity can be calculated. It is also possible to calculate direction and speed.

As explained above, since the direction in which waves are moving and their speed can be known, it is possible to avoid large waves and select the optimal course for the direction of travel, contributing to the safe and efficient operation of ships. Additionally, since it is possible to obtain stationary data that is more accurate than conventional visual observation, reporting to the Japan Meteorological Agency can be simplified and data reliability can be increased.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the method of the present invention, and FIG.
The figure is for Wave Rator] P-page photograph, Figures 3 (a) and (1)
)) are all diagrams of conversion from polar coordinates to XY orthogonal coordinates,
FIG. 4 (21) and (1)) are diagrams showing the amplitude and phase of the cross spectrum of a sine wave. 1. Antenna, 2. Transmitter, :'). Logarithmic amplification receiver, 4. -Δ/D conversion circuit, 5.. Setting circuit. 6. Correction circuit, 7. Katana 1 O vote Orthogonal 111 votes Figure 4 (a): Number of FL (b)

Claims (1)

[Claims] In a marine pulse radar, signals from sea surface reflections that are unnecessary for the radar obtained from the logarithmic detection output of the received waves are exchanged between analog and digital, and are obtained every rotation of the radar antenna converted from a polar coordinate system to a rectangular coordinate system. Digital calculation of two-dimensional cross-correlation is performed between data within the range of 5 wavelengths to 1 wavelength of the waves on the front, back, left, and right sides of the first two-sided range and the next screen range of the data that is displayed.
A wave radar observation method characterized by determining the wave direction and relative speed to the ship from the amplitude and phase information of the spectrum calculated from ζ.