JPS6025468A - Wave radar observation system - Google Patents

Abstract

PURPOSE:To maintain the real time of processing and prevent the range of data itself from being spoiled by taking a direct polar coordinate two-dimensional frequency analysis of a sea surface reflected signal, and displaying the image of a calculated spectrum. CONSTITUTION:The sea surface reflected signal from a radar antenna 1 is received by a receiver 3, and inputted to and stored in a memory 6 for polar coordinate data through an A/D converter 4 and an intensity correcting circuit 5 which makes correction by distance. A signal read out of this memory 6 is processed by the 1st azimuth direction FFT circuit 7, a Bessel function weighting circuit 8, and the 2nd azimuth direction FFT circuit 9, and then an adjustment limiter 10 makes a level adjustment and supplies the resulting signal to a polar coordinate spectrum display device 12.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a radar system for measuring the direction and wavelength of waves using sea surface reflection signals in a marine radar.

Reflection from the sea surface caused by waves hinders the detection of signals aimed at ships, etc., and thus devices have been put into practical use that should be removed as unnecessary signals. However, in the past few years, waves have actively utilized the signals reflected from the sea surface caused by waves, and the signals reflected from the sea surface caused by waves have been actively utilized. Methods for calculating directions, etc. are being put into practical use.

This takes a PPI scope photo from the radar indicator,
From this photograph, the spatial spectrum can be calculated using orthogonal two-dimensional Fourier transform for the orthogonal data that was scanned in the X and Y directions using a photo sensor and converted from analog to digital, or the radar receiver output can be directly converted into analog data.
After making the data density uniform by interpolating and thinning the polar coordinate system data obtained by digital conversion, a rectangular part is cut out and a spatial spectrum is calculated using orthogonal two-dimensional Fourier transform, and the wave direction and wavelength are calculated. It is.

However, in the former method mentioned above, since data is obtained from the photographic medium, real-time processing cannot be expected, and the dynamic range of the data itself is significantly impaired.
In addition, the latter method requires processes such as interpolation and thinning, and has the disadvantage that only a portion of the data can be used.In addition, the direction and wavelength of waves and their reciprocal wavenumbers can be calculated from Cartesian coordinates by the direction and wavelength in that direction. There was the inconvenience of having to read the

The present invention provides a wave radar observation system that can eliminate these drawbacks. Specifically, the present invention aims to provide an analog wave radar observation system that uses sea surface reflection signals obtained every rotation of the radar antenna.
Direct polar coordinate two-dimensional frequency analysis is performed on digitally converted polar coordinate data without the process of interpolation, thinning, or data cutting. Polar coordinates where the R axis is the wavelength or the wave number of the reciprocal of the wavelength and the Z axis is the direction of the spectrum.

Alternatively, in addition to the R-axis and y-axis, the amplitude spectrum can be displayed as an overhead view of two axes and one square in polar coordinates.
Because it is an armor, it aims to ensure not only real-time processing but also the speed of observation without compromising the range of the data itself.

Ding This will be explained in detail above based on the drawings.

FIG. 1 is a block diagram showing an embodiment of the method of the present invention. 1 is radar antenna, 2 is transmitter, 3 is receiver, 4 is A
,/I) is a converter. 5 is an intensity correction circuit based on distance, which means that the signal intensity from waves is approximately 3 of the distance.
Since it is inversely proportional to the power of the wave signal, this characteristic is corrected to make the wave signal linear. 6 is a memory for polar coordinate data, 7 is a first azimuth direction FFT circuit, 8 is a cell function recording ROM and distance direction Bessel function weighting circuit, 9 is a second azimuth direction FFT circuit, 10 is a spectrum above the set level Adjustment limiter for outputting 11
1 is an adjustment knob for setting the adjustment limiter 100 level, and 12 is a polar coordinate spectrum display.

FIG. 2 is a model diagram of the PPI display of the received signal from waves. The waves are a two-dimensionally spread striped pattern. The polar coordinate data shown in FIG. The signal is converted from analog to digital, passed through an intensity correction circuit 5 based on the distance of the signal from the radar wave, and recorded in a data memory 6.

Here, we will explain the Wankel transformation of two-dimensional frequency analysis in polar coordinates. 5. Expressing the quadratic redundant Fourier transformation in the polar j position, ・r−dr・dθ (−j kO)−exp(jk$ , lexp(km/2
) ・drdθ. Here, f(θ) is the radar PPI data shown in FIG. 2, and F(R, In) is the polar coordinate two-dimensional spectral distribution.

In a discrete system, the polar coordinate two-dimensional frequency analysis described above consists of three parts.

1; F for the azimuth direction regarding data with a constant range
I(" T 11; ■ Regarding the azimuth data, Bessel function and distance weighting Ill in the distance direction; Regarding the constant range data determined by IT, F F 'J' again in the azimuth direction. Here, each term in the above equation We will touch on the correspondence between this and each component in Figure 1.

(2) corresponds to the first azimuth direction FFT circuit 7, (2) corresponds to the Bessel function recording ROM and distance direction Bessel function weighting circuit 8, and m corresponds to the second azimuth direction FFT circuit 9.

The number of data processed by each FFT circuit and the usage range of the Bessel function recording ROM correspond to the processing of the number of data included in the radar repetition frequency and the predetermined distance range and azimuth width.

1 (, OM includes the Bensel function, but the meaning of this is that the calculation of This is to perform high-speed processing by separately preparing the Bessel function values and arithmetic expressions necessary for calculation and outputting the necessary values.

2. If the received signal model from the waves shown in Figure 2 is a complete sine wave train. The above polar coordinate two-dimensional frequency analysis results are
As shown in Figure 3, the spectrum has peaks at two points symmetrical to the origin.8 If the number of data in the distance direction is N, the sampling distance is Δr, and the distance from the origin is R, the direction of the waves is indicated by the arrow in Figure 3. and the wavelength is t.

Incidentally, the received signal from actual waves is not a sine wave train as shown in Fig. 2, but is also affected by reflected signals such as frequencies, and the above frequency analysis results are also directional and directional as shown in Fig. 4. The spectrum also broadens in terms of frequency. FIG. 4 shows the results of actual measurements of an actual sea surface reflection signal, which was subjected to Wankel transformation for polar coordinate frequency analysis using this device.

For a spectrum with a large amplitude as shown in Fig. 4, the wave number or its reciprocal wavelength can be determined by the distance R from the origin, and the direction of the wave can be visually read by the polar coordinate display spectrum display 12 by the direction D. can be recognized.

The numbers shown in the figure represent the amplitude of the spectrum with 9 being the maximum value. Polar coordinate display spectrum display J2 displays this value as an amplitude value corresponding to the three-dimensional Z axis.
It is possible to display a polar coordinate value diagram.

Further, the polar coordinate display spectrum display device 12 can also display the spectrum amplitude in different colors on a color cathode ray tube using a B scope in which the direction of polar coordinates is extended along the horizontal axis.

There are too many spectra to display.

To prevent overcrowding on the screen, turn the adjustment dial 11 left and right while looking at the display screen 12. Polar coordinate spectrum display 1
2/\ Just output it.

According to this method, as shown in Figure 4, the same pattern will be displayed in two directions that are 1800 degrees symmetrical in the direction in which waves approach and the direction in which waves move away, but the signals for each antenna rotation are compared and selected. By doing this, it can be limited to one direction.

As explained above, according to the present invention, the direction of the waves and the wave number or the wavelength, which is the reciprocal thereof, can be quantitatively read directly on the screen. This information can be reported not only to one's own ship, but also to other ships.By doing so, it is possible to prevent marine accidents for other ships, select the optimal course, and widely contribute to the safe navigation of ships. This has a remarkable effect.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an embodiment of the method of the present invention; Fig. 2 is a model diagram of a PP■ display of a signal received from waves; Fig. 3 is a diagram showing the results of polar coordinate frequency analysis of the model signal of Fig. 2; FIG. 4 is a diagram showing the results of polar coordinate frequency analysis of an actual sea surface reflection signal. 1...Radar antenna, 2...Transmitter 3...Receiver
4... A/D converter 5... Intensity correction circuit based on distance, 6... Memory for polar coordinate data 7... First azimuth direction FFT circuit 8... Bessel function recording ROM and distance direction Bessel function weight Hige circuit patent applicant Japan Radio Co., Ltd.

Claims (2)

[Claims] (1) In a marine radar, the signal from the sea surface reflection is converted from analog to digital, and polar coordinate two-dimensional frequency analysis is performed on the polar coordinate data obtained every rotation of the radar antenna.
・In order to perform the Nckel transformation, a Benssel function is stored in the ROM in advance in correspondence with the number of polar coordinate data, and a spectrum is calculated using the read Bessel function and the polar coordinate data, and several amplitudes that can be recognized on the screen are calculated. The spectrum of the image is displayed in polar coordinates with the R axis representing the wavelength or the wave number of the reciprocal of the wavelength and the X axis representing the direction of the waves.1-
Stone wave radar observation method. (2) In ship radar, signals from sea surface reflections are converted from analog to digital, and the polar coordinate data obtained every rotation of the radar antenna is subjected to Wankel transformation of polar coordinate two-dimensional frequency analysis, so that the number of polar coordinate data corresponds to the number of polar coordinate data. The cell function is stored in ROM in advance, and spectra are calculated using the read Bessel function and the polar coordinate data, and for the spectra of several amplitudes that can be recognized on the screen, the wavelength or the reciprocal of the wavelength is calculated. A wave radar observation method characterized by displaying an image as polar coordinate data with the wave number as the R axis, the wave direction as the φ axis, and the spectrum amplitude as the Z axis.