JPH1194929A - Radar equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain radar equipment by which whether a target is large or small can be discriminated easily and precisely irrespective of whether the distance of the target is far or near by a method wherein a received signal is converted into a received signal in which the component of the distance up to the target contained in the received signal is removed and in which the magnitude of the intensity of the received signal of the target depends on only the effective reflection area of the target and an image is displayed. SOLUTION: An effective-reflection-area conversion part 4 wherein a received signal logV which is digitized by an A/D converter 3 is converted into a received signal logσ in which the component of a distance up to a target contained in the received signal is removed and in which the magnitude of the intensity of the received signal of the target depends on only its effective reflection area and the received signal is supplied to a memory part 5 is installed. In the conversion part 4, the received signal is cleared to an initial value by a trigger signal T from a timing control part 10 by using a distance counting counter 41. After that, a distance clock RCK as a minimum unit in a distance direction is counted so as to be output as the address of a distance-counting output memory 42. The memory 42 outputs value stored in every address. The counter 3 and the memory 42 are added by an addition circuit 43, and the component of the distance is removed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a radar device,
In particular, the present invention relates to a radar device including a ship radar device and a collision prevention assistance device for assisting safe navigation by obtaining position information of a target.

[0002]

2. Description of the Related Art Radar systems are indispensable for ensuring the safety of navigation on ships and the like. FIG. 4 shows a block diagram of a typical conventional example of such a radar apparatus. The radar device receives a pulse-modulated transmission signal from a transmitter 11, emits a pulsed radio wave in a predetermined direction, receives an output of a reflected wave from a target of the radio wave, and outputs the antenna 1. A logarithmic receiver 2 that performs logarithmic amplification detection of the received signal (V) from the antenna 1 and outputs (log V);
A / D converting the received signal (log V) output from the logarithmic receiver 2 and outputting a signal equal to or higher than a predetermined threshold value
Under the control of the D converter 3a and the memory control unit 14, A /
A memory unit 5 for storing and reading out the output signal of the D converter 3a and converting the polar coordinate type signal into a rectangular coordinate type signal;
A D / A converter 6 that D / A converts the signal read from the memory unit 5 and outputs the converted signal, and a display 7 that displays an image of a target or the like based on the output signal of the D / A converter 6. It has a main configuration including:

The antenna 1 is rotated by a motor 8 and has a horizontal beam width of about 0.
It emits 08 degree radio waves and receives reflected waves from targets in that direction. The azimuth signal generator 9 generates an azimuth pulse signal in accordance with the rotation of the motor 8, and generates a relative / true azimuth calculation unit 1.
2 calculates a relative direction or a true direction θ from the direction pulse signal and the gyro signal Gy indicating the reference direction. For example, when mounted on a ship, the relative azimuth is obtained when the bow direction is set as the reference azimuth, and the true azimuth is set with true north as the reference azimuth.

On the other hand, the distance R from the radar device (own ship) to the target can be obtained based on the transmission trigger supplied from the timing control unit 10 and the elapsed time from the time of transmission (radiation emission). The coordinate conversion circuit 13 calculates the distance R thus obtained and the relative / true azimuth calculation unit 12
X, Y orthogonal addresses are generated based on the azimuth .theta. That is, X = X0 + R · sin θ, Y =
Y0 + R · cos θ is calculated, and the X and Y orthogonal addresses are supplied to the memory control unit 14. Here, X0 and Y0 are own ship positions.

[0005] The memory control unit 14 writes the output signal of the A / D converter 3a into a sweep memory included in the memory unit 5, and converts the polar coordinate type signal stored in the sweep memory into an X, Y orthogonal address. Is transferred to a frame memory included in the memory unit 5 and corresponding to one screen of the display 7. Thus, the polar coordinate type is converted to the rectangular coordinate type.

A CRT or LCD is used as the display 7, and the image of the target is displayed in a rectangular coordinate system under the control of the deflecting circuit 15 based on the D / A converted received signal. The image of the target displayed on the display 7 is a signal that is equal to or higher than the threshold value set by the threshold value setting unit 16,
In addition, the level of the displayed target or the like changes by adjusting the sensitivity of the display 7 or the like. The threshold set by the threshold setting unit 16 is a constant level in the distance direction.

Here, the intensity (level) of the received signal of the target
Let V be the effective reflection area of the target and σ be V = Kσ / R
It can be expressed as ⁴ (K is a proportional constant). When this received signal (V) is logarithmically amplified and detected by the logarithmic receiver 2, the output is logV = logK + logσ-4logR. This relationship is shown in FIG. Further, the relationship between the received signal strength at different distances of the target TGa, the received signal strength of the target TGb having an effective reflection area larger than the target TGa, and the relationship between the received signal strength and the set threshold value TH for these are shown. As shown in FIG.

As described above, the received signal strength of the target is inversely proportional to the fourth power of the distance R to the target, and the effective reflection area σ of the target is
Is proportional to Therefore, even if the target is the same target, the received signal strength greatly changes according to the distance, and if the effective reflection area σ is large, the received signal strength becomes large even at a long distance.

[0009]

In this conventional radar device, a signal received by an antenna is subjected to logarithmic amplification detection, then A / D converted, and a signal whose level is equal to or higher than a threshold value is detected. The coordinates are converted and written in the memory unit 5, the written signal is read out, and then D / A converted and displayed on the display 7. The received signal strength of the target is Is inversely proportional to the fourth power of the distance to the object and is proportional to the effective reflection area σ of the target, so that even for the same target, the received signal strength, and therefore the display strength displayed on the display 7 is the target strength. Varies greatly depending on the distance of the target, it is difficult to determine the size of the target, and targets at levels below the threshold are not displayed. Can no longer detect the target of Difficult to avoid a phenomenon that swapping between adjacent target object even, there is a problem in the reliability of safe navigation.

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, the object of the present invention is to set the same display intensity to the same target regardless of the distance of the target, and to set the size of the target (the size of the effective reflection area).
The size of the target can be easily and accurately identified by changing the display intensity according to the distance, and the detection capability for distant targets is improved, and at the same time, swapping between nearby targets is reduced to ensure safety. An object of the present invention is to provide a radar device capable of improving the reliability of navigation.

[0011]

The present invention has the following means in order to achieve the above object. That is, the radar apparatus of the present invention includes a receiving unit that receives a reflected wave from a target, amplifies and detects the output, and outputs a received signal output from the receiving unit to the target included in the received signal. An effective reflection area conversion means for removing a distance component and converting the magnitude of the reception signal intensity of the target into a reception signal depending only on the effective reflection area of the target; and a reception signal from the effective reflection area conversion means. And display means for displaying an image of the target according to the above.

Further, the receiving means includes an antenna for receiving and outputting a reflected wave from the target, and a logarithmic receiver for performing logarithmic amplification detection of a received signal output from the antenna and outputting the signal. , The effective reflection area conversion means,
A distance log output unit that outputs a signal having a value four times a log value of a distance corresponding to a reception timing at each distance in a distance direction of a reception signal output from the log receiver of the reception unit, and a logarithm of the reception unit An addition circuit that adds and outputs the reception signal from the receiver and the output signal of the distance log output unit, and further includes a distance log output unit of the effective reflection area conversion unit, At the reception timing at each distance in the distance direction of the reception signal output from the logarithmic receiver, a distance counter that outputs a distance address corresponding to the reception timing, and a distance address that is output from the distance counter are stored. And a distance log output memory for outputting a signal having a value four times the logarithmic value of the distance. Further, instead of the distance log output memory, there is provided an arithmetic circuit for performing logarithmic operation on the output value of the distance counter and quadrupling the operation result and outputting the result.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention is a receiving means for receiving a reflected wave from a target, amplifying, detecting and outputting the same,
The magnitude of the received signal strength of the target depends only on the effective reflection area of the target by removing the component of the distance to the target included in the received signal from the received signal output from the receiving means. Effective reflection area conversion means for converting to a reception signal, and display means for displaying an image of the target by the reception signal from the effective reflection area conversion means,
The receiving means includes an antenna that receives and outputs a reflected wave from the target, and a logarithmic receiver that performs logarithmic amplification detection of a received signal output from the antenna and outputs the received signal. A distance log output unit that outputs a signal having a value four times a logarithmic value of a distance corresponding to a reception timing at each distance in a distance direction of a reception signal output from the logarithmic receiver of the reception unit; And an adder circuit for adding a reception signal from the logarithmic receiver and an output signal of the distance logarithmic output unit and outputting the added signal.

With such a configuration, there is no component of the distance to the target in the received signal used for image display, and the magnitude of the received signal strength of the target is determined by the effective reflection area of the target. (The proportionality constant part is constant for all targets), so the same target has the same display intensity regardless of the distance to the target, and the size of the target depends on the size of the target. The display can be displayed with the display intensity changed, and the size of the target can be easily and accurately identified.

Further, even a distant target having a level lower than the threshold value, which cannot be detected conventionally, can be detected as long as the target can be distinguished from noise, and the detection capability is improved. Furthermore, since the nearby targets also move on the display screen with the same display intensity, swapping between these targets is reduced. Therefore, the reliability for safe navigation of a ship or the like can be improved.

[0016]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG. 2 is an internal block diagram of an effective reflection area conversion circuit portion of this embodiment. This embodiment is different from the conventional radar apparatus shown in FIG.
Instead of the A / D converter 3a and the threshold setting unit 16, the received signal (log V) output from the logarithmic receiver 2 is A / D
A / D converter 3 for conversion (there is no A / D conversion function but a threshold value discrimination function as in the conventional example), a distance counter 41, a distance log output memory 42, and an addition circuit 4
3, the received signal (log V) digitized by the A / D converter 3 is removed from the received signal (log V) by removing the component of the distance to the target included in the received signal, and the magnitude of the received signal strength of the target is reduced. An effective reflection area conversion unit 4 that converts the reception signal (log σ) that depends only on the effective reflection area and supplies the signal to the memory unit 5 is provided.

The received signal (log V, but digitized) output from the A / D converter 3 is expressed as log K + log σ−4 log R as described above. In the effective reflection area conversion unit 4, first, the distance counting counter 41
Is cleared to the initial value by the trigger signal T sent from the timing control unit 10, and then the distance clock RCK of the minimum unit in the distance direction (corresponding to the reception timing at each distance in the distance direction of the reception signal) is set. It counts and outputs the value as the address of the distance log output memory 42. In the distance log output memory 42 (ROM type memory), a value of 4 log R is stored for each address with respect to the distance R corresponding to these addresses, and for each address given from the distance counting counter 41, Outputs the value stored in the address.

Then, in an adding circuit 43, the received signal (log V) from the A / D converter 3 and the output of the distance logarithmic output memory 42 are added, and the target distance component is removed from the received signal. The magnitude of the received signal depends on the effective reflection area (log σ) of the target only.

Therefore, as shown in FIG. 3, the display intensity of the image of the target displayed on the display unit 7 is the same for the same target regardless of the distance, and the size of the target is small or large. Depending on the size of the effective reflection area), a large one is displayed strong and a small one is displayed weakly.

As a result, the size of the target can be easily and accurately identified, the detection capability for a distant target is improved, and the swapping between the nearby targets is reduced, so that the ship And the like, the reliability for safe navigation can be improved.

In this embodiment, a ROM-type distance logarithmic output memory 42 is used in the circuit for outputting 4 log R, but 4 log R is calculated with respect to the value (R) output from the distance counter 41. It may be an arithmetic circuit that performs the operation. Further, in this embodiment, the present invention is applied to the conventional example in which the rectangular coordinate type display is performed by using the memory unit 5 and the like, but the present invention is also applicable to a polar coordinate type display method.

Further, in this embodiment, the present invention is applied to a radar apparatus having a logarithmic receiver. However, the present invention can be applied to a radar apparatus having no logarithmic receiver.
In this case, a circuit for multiplying the received signal by the fourth power of the distance R is required to remove the distance component from the received signal.

[0023]

As described above, according to the present invention, a reflected wave from a target is received, amplified and detected, and the amplified detected signal is converted into a component of the distance to the target included in the received signal. By removing and converting the received signal strength of the target into a received signal that depends only on the effective reflection area of the target, and displaying the image of the target with the converted received signal, Regardless of the distance to the target, the same target can be displayed with the same display intensity and the display intensity can be changed according to the size of the target, so that the size of the target can be easily changed. In addition, it is possible to accurately and accurately detect, and the detection capability for a distant target can be improved, and the swapping between nearby targets can be reduced. Therefore, the reliability for safe navigation of a ship or the like can be improved. There is an effect that can be.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is an internal block diagram of an effective reflection area conversion unit of the embodiment shown in FIG.

FIG. 3 is a diagram illustrating a relationship between a target distance and a display intensity for explaining an operation and an effect of the embodiment illustrated in FIG. 1;

FIG. 4 is a block diagram illustrating an example of a conventional radar device.

FIG. 5 is a characteristic diagram illustrating a relationship between a received signal strength and a distance of a target in the radar device.

6 is a diagram illustrating a relationship between a distance of a target and a received signal strength for explaining an operation and a problem of the radar device illustrated in FIG. 4;

[Explanation of symbols]

 Reference Signs List 1 antenna 2 logarithmic receiver 3, 3a A / D converter 4 effective reflection area conversion unit 5 memory unit 6 D / A converter 7 display 8 motor 9 azimuth signal generator 10 timing control unit 11 transmitter 12 relative / true Azimuth calculation unit 13 Coordinate conversion circuit 14 Memory control unit 15 Deflection circuit 16 Threshold setting unit 41 Distance counter 42 Distance log output memory 43 Adder circuit

Claims (4)

[Claims] 1. A receiving means for receiving a reflected wave from a target, amplifying and detecting and outputting the received signal, and converting a received signal output from the receiving means into a component of a distance to the target included in the received signal. An effective reflection area conversion means for removing the received signal strength of the target and converting the received signal intensity into a reception signal dependent only on the effective reflection area of the target; and And a display unit for displaying an image. 2. The receiving means includes an antenna for receiving and outputting a reflected wave from the target, and a logarithmic receiver for performing logarithmic amplification detection of a received signal output from the antenna and outputting the signal. A distance logarithm in which the effective reflection area converting means outputs a signal having a value four times a logarithmic value of a distance corresponding to a reception timing at each distance in a distance direction of a reception signal output from the logarithmic receiver of the reception means; 2. The radar apparatus according to claim 1, further comprising: an output unit, and an addition circuit that adds and outputs a reception signal from a logarithmic receiver of the receiving unit and an output signal of the distance logarithmic output unit. 3. A reception log output unit of said effective reflection area converting means outputs a reception timing at each distance in a distance direction of a reception signal output from a log receiver of said reception means, and a distance corresponding to the reception timing. A distance counting counter for outputting an address, and a distance log output memory for outputting a signal having a value four times the logarithmic value of the distance stored in the distance address output from the distance counting counter. Item 3. The radar device according to item 2. 4. A distance log output memory of a distance log output unit of the effective reflection area conversion means according to claim 3,
A radar device provided with an arithmetic circuit for performing logarithmic operation on the output value of the distance counting counter and quadrupling the operation result and outputting the result.