JPH0537265Y2 - - Google Patents

Description

[Detailed description of the invention] "Industrial application field" This invention expands the video signal in the time axis direction so that small targets can be easily seen. The present invention relates to a radar video signal enlarging circuit.

``Prior Art'' Conventionally, when enlarging a radar video signal, the analog method involved passing the radar video signal through an integrating circuit. For example, the radar video signal shown in FIG. 5A is passed through an integrating circuit consisting of a CR low-pass filter to obtain an enlarged video signal as shown in FIG. 5B. In this case, the signal is delayed by τ ₁ by passing through the integrating circuit. This delay amount τ ₁ could no longer be ignored in the short range, and the radar video signal expansion circuit could not be used in the short range.

JP-A-60-181672 discloses that a monostable multivibrator is driven by the falling edge of a radar video signal pulse, and a pulse of a constant width is added to the trailing edge of the pulse to expand the pulse width. ing. However, in radar, the pulse width is switched in several stages corresponding to the distance range, and the pulse width is narrowed for short ranges, so that the image of the reflected pulse in the radial direction (distance direction) is displayed on the display screen regardless of the distance range. The size is kept constant to some extent to achieve both ease of viewing on the screen and distance resolution performance, but in the case of the one shown in the above publication, pulses of a constant width are added, so when the distance range is short, When the distance range is long, it is magnified to a small extent, so the size of one image on the display screen is not the same, but is inversely proportional to the distance range, and especially when the distance range is short, the distance of the image is As the length in the direction becomes longer, it becomes impossible to distinguish between reflected pulses that are close together, and the distance resolution deteriorates.Furthermore, depending on the distance range, the size of one image becomes smaller as the distance range becomes longer, making it difficult to see.

``Means for solving the problem'' According to this invention, the radar image signal is enlarged by the image enlargement circuit of the analog integration circuit, and
The enlarged video signal and the non-enlarged radar video signal are synthesized by a synthesis circuit.

"Embodiment" FIG. 1 shows an embodiment of this invention. Input terminal 1
The radar image signal from 1 is supplied to the image enlargement circuit 13 through the switch 12, and is also supplied to the synthesis circuit 1.
4. The image enlargement circuit 13 is an analog integrating circuit, and like the conventional one, it is usually a CR
It consists of a low-pass filter, and its output is supplied to the synthesis circuit 14. The output of the combining circuit 14 is supplied to a buffer amplifier 16 through a switch 15. The radar image signal at the input terminal 11 is also supplied to a rain and snow removal circuit 17, and the output of the rain and snow removal circuit 17 is supplied to an image enlargement circuit 13 and a synthesis circuit 14 through a switch 18. Further, the radar image signal at the input terminal 11 is supplied to the buffer amplifier 16 through the switch 19.

When the image is not to be enlarged, the switch 15 is turned off and the switch 19 is turned on. When enlarging the image, the switch 15 is turned on and the switch 19 is turned off. When the rain and snow removal circuit 17 is used, the switch 12 is turned off and the switch 18 is turned on. When the rain and snow removal circuit 17 is not used, the switch 12 is turned on and the switch 18 is turned off.

Switches 12 and 15 are now on, switch 1
8 and 19 are off, and the radar video signal input to the input terminal 11 is as shown in FIG. 2A,
The output of the image enlarging circuit 13 is a signal in which the image signal is enlarged, although its rise is delayed as shown in FIG. 2B. The output of the synthesis circuit 14 is a combination of the waveforms A and B in Figure 2, so as shown in Figure 2C, its rise coincides with the rise of the signal in Figure 2A, and the video signal is expanded. It becomes what is given.

In this case, noise in the original radar image signal is also added to the output of the enlarged image signal in the synthesis circuit 14, but this is ignored. If it is desired to eliminate this noise, it can be done, for example, as shown in Figure 3. In Figure 3, the same reference numerals are used for the parts corresponding to Figure 1. The radar image signal from the input terminal 11 is supplied to the image signal detection circuit 21 and the image delay circuit 22 via the switch 12, and the output of the image delay circuit 22 is supplied to the image enlargement circuit 13 and the synthesis circuit 14 via the switch 23. The image signal detection circuit 21
The delay amount of the video delay circuit 22 is selected according to the time delay required to detect the video signal. The video signal detection output of the video signal detection circuit 21 controls the switch 23 through the switch 24, and the switch 23 is turned on during the period when the video signal is being detected. When the switch 24 is off, the switch 2
The output of the image enlarging circuit 13 is supplied to the synthesizing circuit 14 through a switch 25.
Switches 24 and 25 operate in the opposite manner to switch 19 .

Now assume that switches 12, 24, and 25 are on and switches 18 and 19 are off. When a radar video signal as shown in FIG. 4A is input to the input terminal 11, it is delayed by the video delay circuit 22, resulting in a signal as shown in FIG. 4B. When a video signal is detected by the video signal detection circuit 21 during this delay, the switch 23 is turned on only during this time, so that the video signal shown in FIG. 4C from which noise has been removed is obtained. The video signal from which this noise has been removed is supplied to the video enlarging circuit 13 and the combining circuit 14, and the video enlarging circuit 13 enlarges the video signal as shown in FIG. 4D. The enlarged signal and the non-enlarged signal are synthesized by the synthesis circuit 14, and a synthesized output as shown in FIG. 4E is obtained.

"Effects of the invention" As described above, according to this invention, by combining the enlarged video signal and the non-enlarged video signal, the rise of the enlarged video signal coincides with the rise of the non-enlarged video signal, and the enlarged video signal Therefore, even in a short range, a radar image signal enlarging circuit can be used to display a small target as a large image at the correct distance. Furthermore, even when the pulse width is changed by changing the distance range, a video display of approximately the same size can be obtained regardless of the distance range, making it easy to see, and with little deterioration in distance resolution.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an example of the radar video signal enlarging circuit according to this invention, Fig. 2 is a diagram showing waveforms of each part thereof, and Fig. 3 is a block diagram showing another example of the radar video signal enlarging circuit according to this invention. Figure, 4th
The figure shows the waveforms of each part, and FIG. 5 is a diagram for explaining the occurrence of delay due to the conventional radar image enlargement circuit.

Claims (1)

[Scope of Claim for Utility Model Registration] A video enlarging circuit that enlarges a radar video signal in the time axis direction using an analog integration circuit, and a synthesis circuit that synthesizes the output of the video enlarging circuit and the radar video signal that is not enlarged. Radar video signal expansion circuit.