JPS5828553B2 - Meteorological echo intensity measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for measuring the intensity of weather echoes obtained in weather radars and air traffic control radars.

Meteorological observation using radar has the advantage of being able to obtain weather information over a wide area from time to time, and is indispensable for weather observation and forecasting.

In recent years, various types of automation have been promoted in order to speed up and improve weather observation using radar, but automation requires measuring the intensity of weather echoes received by radar.

Generally, the intensity of weather echoes is measured by dividing the radar coverage area into unit areas of a predetermined size and measuring the average intensity of the received video for each unit area.The results can be used to observe rainfall intensity. Used to detect thunderclouds.

In addition, since it is necessary to measure the intensity of meteorological echoes over a wide range of radar and video to be measured, a video having a logarithmic characteristic (log video) is generally used.

An example of a conventional weather echo intensity measuring device is shown in FIG.

Radar and video are sampled at regular intervals by a sample and hold circuit 1, and converted into digital values by an A/D converter 2.

This situation is shown in FIG.

In FIG. 2, 11 is a radar video, 12 is a sampling period, 13 is a sampling hold circuit, and the output of 1 is shown.

The amplitude information of the video digitized by the above A/D conversion is further converted into log-linear (Log-L 1nea
r) It is converted into linear amplitude information by the converter 3, and integrated over a certain distance section by the distance integrator 4.

The distance integrated result is further integrated over a certain azimuth section by an azimuth integrator 5, and as a result, an average value of video intensity in a unit area is obtained.

The result of the azimuth integration is further integrated in the time averaging circuit 6 with the measurement results up to the previous scan stored in the memory 7, time-wise averaging is performed, and the results are output to a computer or the like.

Conventionally, in this type of measurement equipment, the factors that determine measurement accuracy are the human-powered radar and the A/D converter that converts the video amplitude into digital values. This method requires a D converter and has the disadvantage of being expensive.

Also, since the converted digital value is the amplitude value of the log video, it is necessary to convert it to a value converted to a straight line video for distance integration and azimuth integration.
This method has the disadvantage that it requires the following:

Furthermore, in order to prevent overflow from occurring during calculations for distance integration and azimuth integration, arithmetic units and registers that can handle several bits more than the number of A/D converted bits are required, making them large and expensive. There was a drawback.

The present invention has been made to eliminate the drawbacks of these conventional devices, and provides an inexpensive and highly accurate weather echo intensity measuring device that utilizes the characteristics of weather echoes in radar.

Hereinafter, one embodiment of the present invention will be described in detail based on the drawings.

In Fig. 3, 8 is a radar, a video quantizer that quantizes the video, and 4 is a video quantizer that integrates (counts) the video (hit) quantized by the video quantizer 8 over a certain distance segment. A distance integrator 5 is an azimuth integrator which further integrates (counts) the output from the distance integrator 4 over a constant azimuth section.

As a result, the total number of hits in the unit area is obtained.

A quantization level controller 9 compares a predetermined reference value with the total number of hits in a unit area obtained by the azimuth integrator 5, and if it is larger than the reference value, the total number of hits is stored in the memory 7. Control is performed to increase the quantization level of the corresponding unit area, and to lower the quantization level if it is smaller than the reference value.

The control results are output as measurement results to an external computer, etc., and are also stored in the memory 7 and read out when the next corresponding unit area is processed.

A D/A converter 10 generates a voltage corresponding to the quantization level value read from the memory 7, and a video quantizer 8.
Output to.

Now, suppose that the radar and video indicated by 11 in FIG. 11 is compared with its quantization level 16,
Those exceeding the quantization level are quantized at a fixed quantization timing 14, and the quantized video (hint) 15 and Namo's quantized video 15 are counted by a distance integrator 4 and an azimuth integrator 5 to form a unit area. The total number of hits is obtained.

The total number of hits is compared with a reference value by the quantization level controller 9, and if the total number of hits is greater than the reference value, the quantization level 16 of the corresponding unit area stored in the memory 7 is increased, and vice versa. If it is small, control it to lower it.

That is, if the quantization level 16 is increased, the portion of the video 11 that exceeds the quantization level 16 will be reduced, and the number of detected quantized videos 15 will be reduced, and if the quantization level 16 is decreased, the number of detected quantized videos 15 will be increased. A feed back loop is formed to control the quantization level in each unit area so that the probability of detecting a hit is constant, and the quantization level at that time is used as the measurement value.

By repeating the above operation every time the antenna rotates (scans), the number of detected quantized videos in each unit area can be made approximately equal to the reference value given to the quantization level controller 9.

Note that control of the quantization level 16 is performed based on the number of quantized videos 16 detected in the previous scan, so strictly speaking it is not real-time processing, but since the temporal fluctuations of weather echoes are relatively gradual, this is particularly problematic. No error will occur.

The reference value for the number of detected quantized videos 15 is calculated from the intensity distribution of the echo to be measured.

That is, in general, the transmission wavelength of weather radar and air traffic control radar is from several digits to several tens of C1rI, while clouds and rain that are the cause of weather echoes are aggregates of minute water droplets and ice with a diameter of several cylinders or less. .

It is known that the intensity of reflected echoes from objects that are smaller than the wavelength has a Rayleigh distribution.

When the Rayleigh distributed video 11 is quantized at a constant quantization level 16, the detection probability and the average signal intensity have a relationship as shown in FIG.

In FIG. 5, the vertical axis represents the detection probability of the quantized video 15, and the horizontal axis represents the ratio of the quantization level 16 to the average level of the video 11.

According to Figure 5, for example, is the detection probability 60%? If the quantization level 16 is controlled in such a manner, the quantization level 16 at that time becomes equal to the average level of the video 15 (quantization level/video average level=1).

Therefore, in this case, the quantization level indicates the intensity of the echo.

In this case, the reference value may be obtained by multiplying the total number of quantized videos in a unit area by 0.6.

The video quantizer 8 used in the present invention only needs to have a level comparator and some digital circuits.

In addition, for distance integration and azimuth integration, it is only necessary to count the number of hits, and compared to the conventional method, which integrates amplitude values, it is constructed with a simpler circuit, and the Log-Lin
There is also no need to convert ear.

Furthermore, since the D/A converter 10 is cheaper and faster than an A/D converter, it is easier to achieve the required quantization accuracy.

As described above, according to the present invention, when measuring the intensity of meteorological echoes by radar, the reference value to be compared with the count value of the quantized video is set to the quantization level, and the average intensity of the echo whose intensity probability distribution is known is set to the quantization level. By choosing the quantization level to be equal to the detection probability of the quantized video when quantized as , the quantization level can be used as the average intensity of the echo in a unit area. This has the advantage that a certain level of accuracy can be achieved with an inexpensive and small-scale circuit.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of a conventional meteorological echo intensity measuring device, Fig. 2 is a diagram showing the A/D conversion processing process in the conventional method, and Fig. 3 is a diagram showing an embodiment of the present invention. FIG. 4 is a block diagram showing the video quantization process in the present invention, and FIG. 5 is a diagram showing the relationship between the detection probability of a Rayleigh distributed signal and the quantization level. In the figure, 4... distance integrator, 5...
Azimuth integrator, 7...Memory, 8...Video quantizer, 9...Quantization level controller, 1
0...D/A converter, 11...Radar video, 14...Quantization timing, 15...
...Quantized video, 16...Quantization level. In the figures, the same or corresponding parts are designated by the same reference numerals.

Claims (1)

[Claims] 1 Radar, a means for comparing the amplitude of the video with a quantization level given for each fixed distance division and generating a quantized video for those exceeding the quantization level, and calculating the number of generated quantized videos for each unit area. and means for controlling the quantization level for each unit area based on the counting result of the quantized video for each unit area to maintain the count value of the quantized video for each unit area at a reference value. , by selecting the reference value to be equal to the detection probability of the quantized video when quantizing an echo with a known intensity probability distribution using the average intensity of the echo as the quantization level. A weather echo intensity measuring device characterized in that a quantization level controlled for each unit area is used as the average intensity of echoes in the unit area.