JP3179921B2 - Small target detection radar - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small target detecting radar for detecting a small target on the sea surface, such as a submarine periscope or a lifeboat.

[0002]

2. Description of the Related Art Generally, when detecting a small target on the sea surface such as a submarine periscope or a lifeboat, a reflected signal from the target is buried in sea clutter. Therefore, in the small target detection radar, its signal-to-clutter ratio (hereinafter, S / C)
It is necessary to improve the ratio. As a method of improving the S / C ratio in such a case, a method of increasing the range resolution of the radar to reduce the sea surface irradiation area and reducing the clutter power can be considered.

However, as is well known, when the range resolution of a radar is increased, a reflected wave having a large amplitude called a spike increases on the sea surface clutter, and a phenomenon that false alarms increase when a target is detected is increased. Occurs. In order to prevent this phenomenon, a method of maintaining a desired false alarm probability by performing a correlation process has conventionally been adopted. FIG. 4 is a block diagram showing a configuration example of a conventional small target detection radar employing this method.

In FIG. 4, an antenna device 10 radiates power with a predetermined beam width from an antenna and captures the reflected power. The transmission / reception device 12 performs repeated transmission pulse waveform generation, reception power amplification, frequency conversion, and orthogonal conversion.

The antenna device 10 and the transmitting / receiving device 20
Is received by the signal processing device 50. The received signal sent to the signal processing device 50 is divided by a first threshold circuit 51 into a signal having a level equal to or higher than a predetermined threshold value and a signal having a level lower than the predetermined threshold value and is binarized. Correlation processing is performed on the binarized signal for the above-described reason. However, the correlation between sea clutters does not disappear during the normal radar repetition time, so that no processing effect is obtained in the inter-pulse correlation processing.

Accordingly, the inter-scan correlation circuit 53 performs a correlation process at the antenna scan interval so that the sea clutter is sufficiently decorrelated, and a target is detected by the second threshold circuit 54. This target is displayed on a display device 40 generally used in radar devices.

By the way, when performing correlation processing between scans, if processing is performed with high distance resolution, the target moves at its own speed according to its own moving speed and the moving speed of the sea surface such as an ocean current, so that a sufficient processing effect is obtained. I can't get it. Therefore, on the radar side, the stretching circuit 52 must perform the stretching process to degrade the distance resolution in consideration of the target speed and the sea surface moving speed. For this reason, in the conventional configuration, there is a problem that the distance resolution is degraded by the stretching process, and the clutter power is increased, so that the S / C ratio is eventually degraded.

In order to detect a small target having an extremely short exposure time (exposure time), such as a submarine periscope,
It is necessary to increase the number of pulse hits to the target.
Therefore, the conventional small target detection radar shown in FIG. 4 is realized by a high-speed mechanical rotating antenna to increase the number of pulse hits. However, the number of rotations of the high-speed mechanical rotating antenna is mechanically limited, and it is difficult to further increase the number of pulse hits, and there is a limit in improving the S / C ratio.

[0009]

As described above, it is difficult to improve the S / C ratio with the conventionally known small target detection radar.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a small target detection radar which has an improved S / C ratio as compared with the related art and can detect a small target with high accuracy. I do.

[0011]

In order to solve the above-mentioned problems, the present invention provides a transmitting / receiving means for outputting a transmission signal toward a target and receiving a reflected signal, and converting a signal received by the transmitting / receiving means into a binary signal. Binarizing means for converting the range of the received signal binarized by the binarizing means by a range width corresponding to an assumed target speed; A moving speed detecting means for detecting a moving speed amount of the sea surface from the received signal received, and a receiving signal repeatedly sent from the stretching means is input, and the moving amount of the sea surface is corrected by a correction signal sent from the moving speed detecting means. The first characteristic is that a received signal whose range has been corrected by a range width corresponding to the input signal is inputted, and inter-scan correlation detecting means for detecting a correlation of each received signal for each scan. And then, outputs a pulse transmission signal composed of a plurality of different sub-pulse frequency to the target, a receiving means for splitting and outputting for each frequency by receiving the reflected signal, is outputted partitioned this transmitting and receiving means The received signals are respectively input, binarized means for binarization, stretch means for expanding the range width of the received signal repeatedly transmitted from each binarization means, and repeatedly transmitted from the stretch means. received signal is input, a second feature that it is constituted by TWS means for detecting a correlation of each received signal for each scan.

[0012]

In the configuration having the first feature, the stretch width in the stretching process is determined only from the target assumed moving speed. Then, in the inter-scan correlation processing, an error due to the moving speed of the sea surface is corrected. Therefore, the stretch width is reduced by the amount corresponding to the moving speed of the sea surface, so that the S / C ratio is improved.

Further, in the configuration having the second feature, by performing the frequency diversity, the number of pulse hits can be increased by the number of sub-pulses, so that the S / C ratio is improved, and Detection of a small target having a very short time (exposure time) can be performed with high accuracy.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to FIG. In FIG. 1, the same portions as those in FIG. 4 are denoted by the same reference numerals, and different portions will be mainly described here.

FIG. 1 is a block diagram showing the configuration of a small target detecting radar according to the present invention. The drawing differs from FIG. A reception signal received by the antenna device 10 from the transmission / reception means 20 is input to the correction circuit 35. The correction circuit 35 detects a moving speed of the sea surface such as an ocean current from the input signal. Then, a correction signal corresponding to the moving speed of the sea surface is sent to the inter-scan correlation circuit 33.

On the other hand, a received signal from the first threshold circuit 31 is input to a stretch circuit 32, where
The range width is stretched (enlarged) by the range width corresponding to the assumed target speed.

The inter-scan correlation circuit 33 receives the received signal whose range width has been stretched by the stretch circuit 32. The range of this received signal is corrected by the correction signal from the correction circuit 35 by the range width corresponding to the moving amount of the sea surface, and the correlation processing of each received signal is performed for each scan. The processing after the inter-scan correlation processing is performed is the same as that of the related art, and a description thereof will be omitted.

As described above, in the small target detecting radar according to the present embodiment, the stretch width in the stretch processing is determined only from the assumed moving speed of the target. Then, an error due to the moving speed of the sea surface due to the sea current or the like is removed when performing the inter-scan correlation processing. Therefore, the stretch becomes smaller by the stretch width relative to the moving speed of the sea surface than before, and the S / C ratio can be improved. Next, FIG.
An embodiment of the small target detection radar according to the present invention will be described with reference to FIG.

In FIG. 2, the same parts as those in FIG. 4 are denoted by the same reference numerals, and different parts will be mainly described here. In FIG. 2, a transceiver indicated by reference numeral 20 is, for example, a transceiver having a diversity function of two different frequencies. In this transceiver, transmission and reception of pulses composed of sub-pulses having different frequencies f1 and f2 are performed as shown in FIG. This f1, f2
Are set, for example, apart from the frequency band of the transmission pulse.

The received signals received by the antenna device 10 and the transmission / reception device 20 are input to different signal processing systems for each of the sub-pulses f1 and f2. That is, the sub-pulse f1 is binarized in the first threshold circuit 31 by being divided into a signal having a level equal to or higher than a predetermined threshold and a signal having a level lower than the predetermined threshold. The binarized signal is stretched by a stretch circuit 32.

Similarly, the sub-pulse f2 is divided into a signal having a level equal to or higher than a predetermined threshold value and a signal having a level lower than the predetermined threshold value in a second threshold circuit 33, and is binarized. Is made.

The signals sent from the stretch circuits 32 and 34 to the inter-scan correlation circuit 35 are subjected to correlation processing between sub-pulses, and further to inter-scan correlation processing for each scan.

As described above, the small target detection radar shown in FIG. 2 has a frequency diversity function, so that the number of pulse hits is increased by the number of sub-pulses for the same PRI as compared with the conventional one. be able to. Therefore, the S / C ratio is improved in each step, and particularly, a small target with an extremely short exposure time (exposure time) can be detected with high accuracy. The present invention is not limited to the above embodiment.

For example, the correction circuit 35 shown in FIG. 1 may be added to the configuration of the small target detection radar shown in FIG. 2 (not shown). In this case, the received signal transmitted via the antenna device 10 and the transmission / reception device 20 is transmitted to this correction circuit, and detects the moving speed of the sea surface such as an ocean current. Then, a correction signal corresponding to the moving speed of the sea surface is sent to the inter-scan correlation circuit 35. The inter-scan correlation circuit 35 corrects the range of the received signal by the correction signal by the range width corresponding to the moving amount of the sea surface. Is done. As a result, since the error due to the sea surface moving speed is removed when performing the inter-scan correlation processing, the stretch is reduced by the stretch width relative to the sea surface moving speed, and the S / C ratio can be improved. it can. In addition, since the number of pulse hits can be increased by the number of sub-pulses for the same PRI, a small target with an extremely short exposure time (exposure time) can be detected with high accuracy.

[0025]

As described above in detail, according to the present invention, the S / C ratio is improved as compared with the conventional small target detection radar, and a small target on the sea surface can be detected with high accuracy.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a small target detection radar according to the present invention having a first feature.

FIG. 2 is a block diagram showing a configuration of a small target detection radar according to the present invention having a second feature.

FIG. 3 is a diagram for explaining sub-pulses used in the small target detection radar shown in FIG. 2;

FIG. 4 is a block diagram showing a configuration of a conventional small target detection radar.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... antenna apparatus, 20 ... transmission / reception apparatus, 31 ... 1st threshold circuit, 32 ... stretch circuit, 33 ... inter-scan correlation circuit, 34 ... 2nd threshold circuit, 35,
40 ... correction circuit

Continuation of the front page (56) References JP-A-62-88976 (JP, A) JP-A-59-79869 (JP, A) JP-A-54-132191 (JP, A) JP-A-4-157385 (JP) JP-A-3-29881 (JP, A) JP-A-3-17584 (JP, A) JP-A-61-266976 (JP, A) JP-A-60-164275 (JP, A) 4-212082 (JP, A) JP-A-60-381 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01S ⁷ /00-7/42 G01S 13/00-13 / 95

Claims (2)

(57) [Claims] 1. A transmitting / receiving means for outputting a transmission signal toward a target and receiving a reflected signal, a binarizing means for binarizing a signal received by the transmitting / receiving means, and a binary signal generated by the binarizing means. Stretching means for expanding the range width of the converted received signal by a range width corresponding to an assumed target speed, and a moving speed for detecting a moving speed amount of the sea surface from the received signal repeatedly received by the transmitting and receiving means. A detection signal and a reception signal repeatedly sent from the stretching means are input, and a reception signal whose range has been corrected by a range width corresponding to the movement amount of the sea surface by a correction signal sent from the movement speed detection means is input. A small-target detection radar, comprising: inter-scan correlation detection means for detecting a correlation between received signals for each scan. 2. A plurality of sub-paths having different frequencies toward a target.
Transmitting and receiving means for outputting a pulse transmission signal composed of a pulse signal and receiving and distributing the reflected signal for each frequency, and receiving signals distributed and output by the transmitting and receiving means, respectively, and binarized. and binarizing means for the stretching means to expand the range width of the repeating sent come received signals from the respective binarizing means, receiving signals transmitted repeatedly from the stretch means is input, each receiving every scanning A small target detection radar comprising: inter-scan correlation means for detecting signal correlation.