JPH01235883A - False image signal processor for radar - Google Patents

Abstract

PURPOSE:To stably remove a false image without affecting tracking operations by reading out the data on the previously stored positions and sections where the false image is possibly generated corresponding to the position of the actually detected target echo and generating a false image gate signal in the corresponding data reception time. CONSTITUTION:The data on the position and section where the false image is possibly generated from the target in the position assigned by the target detection bearing and distance of a radar are previously stored in a false image information memory device 2. The position data of the target echo detected by the radar are successively detected and are supplied to the memory device 2. The data on the positions and sections where the false image is possibly generated corresponding to said position are read out and outputted from the memory device 2 by a false image information readingout controller 5. The false image gate signal 3 is generated 3 in the radar reception time zone corresponding to this data and in addition, the tracking gate signal for the tracking target of the radar is generated 4. The output of the reception signal is removed as the false image signal in a gate circuit 1 when the false image gate signal exists and the tracking gate signal does not exist.

Description

[Detailed Description of the Invention] [Industrial Field of Application] This invention relates to a radar false image signal processing device, and particularly to a radar false image signal processing device capable of generating false images caused by a target existing at a position specified by the target object detection direction and distance of the radar. When a target echo is detected at the specified position, a false image gate signal is generated in a time period corresponding to the position and interval data where a false image can occur, and the false image is detected. The present invention relates to a radar artifact signal processing device that removes image signals.

[Conventional technology] First, the cause of radar false images will be explained.

In radar, in addition to the primary reflected echo, a false image may occur due to the secondary reflection of electromagnetic waves that are reflected from the primary reflecting target and then reflected from the next reflecting object (this is called a secondary reflecting object). .

Figure 3 is an explanatory diagram of the occurrence of radar artifacts, and in the figure 1
0 is a radar on land, 11 is a ship on the sea, 12 is a false image located at a distance a behind the ship 11, 13 is a false image located at a distance a behind the ship 11, 14 is 2 on the shoreline of land
The next reflecting object is the embankment.

The operation shown in FIG. 3 will be explained. It is assumed that the sea is monitored by a radar 10 installed near the coast of land, and a primary echo of a ship 11 is detected. At this time, the coastline embankment 14
becomes a secondary reflector of electromagnetic waves reflected from the ship 11,
False images 12 and 13 are generated at distances a and b behind the real image echo of the ship. The characteristics of such false images occur depending on the positional relationship between the position of the ship and the secondary reflecting object, and therefore they often appear or disappear suddenly. In other words, the primary echo of a ship above the detectable level is always detected at the current position of the ship, but false images due to secondary reflections may suddenly appear or disappear due to changes in the positional relationship with the secondary reflecting object. I do things. Although false images are theoretically generated by secondary and higher order reflections, since the reflected power of secondary and higher orders is attenuated, it is practically sufficient to consider up to the secondary reflections.

[Problems to be Solved by the Invention] As a method for removing the above-mentioned radar artifacts, for example, a correlation technique such as sweep correlation or frame correlation of the radar can be used, taking advantage of the characteristic that false images occur suddenly. A method was used to remove echoes that suddenly occurred.

However, in cases where the false image continues for a certain period of time, or in the case of small ships where primary echoes occur and disappear, there are problems such as insufficient removal of the false image.

The object of the present invention is to eliminate the above-mentioned problems and provide a radar image signal processing device having a sufficient artifact removal function.

[Means for Solving the Problems] The radar false image signal device according to the present invention detects the position and section where a false image can occur due to a target existing at a position specified by the target object detection direction and distance of the radar. A false image information storage device stores data in advance, and sequentially detects position data of target object echoes detected by radar, supplies position data of the detected target object echoes to the false image information storage device, a false image information readout controller that reads and outputs data on a position and section where a false image can occur corresponding to the position of the target echo from the false image information storage; and a false image generation controller that is supplied from the false image information readout controller. a false image gate generator that generates a false image gate signal during a radar reception time period corresponding to possible position and section data; and a tracking gate generator that tracks the radar target and generates a tracking gate signal for the tracked target. and a gate circuit that prohibits output of a received signal input when a false image gate signal from the false image gate generator is present and a tracking gate from the tracking gate generator is not present. This solves the above problem.

[Operation] In this invention, data of the position and section where a false image can occur due to a target existing at a position specified by the target object detection direction and distance of the radar is stored in advance, and the data of the position and section where a false image can be generated is stored in advance. Using the position data of the target echo,
The data of the stored position and section where a false image can occur corresponding to the position of this target echo is read out, and a false image gate is set in the radar reception time period corresponding to the read position and section data where a false image can occur. A signal is generated, and received echoes during the generation period of the false image gate signal are regarded as false image signals and are removed. However, when the radar is tracking a target, it is determined whether or not this tracking gate signal is being generated at the same time, and even if the false image gate signal is being generated, the tracking gate signal is being generated. During this period, the removal of received echoes is stopped and the tracking operation is not hindered.

[Embodiment] FIG. 1 is a block diagram of a radar artifact signal processing device showing an embodiment of the present invention, in which 1 is a gate circuit, 2 is an artifact information storage device, 3 is an artifact gate generator, and 4 is a tracking gate generator,
5 is a false image information readout controller. Each device configuring FIG. 1 will be explained. Gate circuit 1 has an input signal of 81
The output signal is S41, and the gate control signals are S2 and S3, and the gate operation is performed as follows. First, when the gate control signal S2 is at L level (S2-0), the gate is open.

Gate control signal S is at H level (S2-1) and S
When the signal is also at H level (33-1), the gate is open. The gate is closed only when the gate control signal S2 is at H level (S2-1) and S is at L level (S3-0). When each gate is open, the input signal S1 passes through the gate to obtain the output signal S4. On the other hand, when the gate is closed, the input signal S does not pass through the gate and the output signal S4 is not obtained. The false image information storage device 2 stores data on the position and section where a false image can occur due to the influence of the primary reflection target existing at the position specified by the target detection direction and distance of the radar (from the target at the specified position). Rear distance r to r + Δ
The interval from r to r2+Δr2... from rn to r
n+Δr) for a required number of specified positions, and when the position data specified by the target direction and distance of the radar is supplied (for example, the specified position data is (when supplied as address data), it is possible to read out the data of the position and section where a false image can occur, which is stored in correspondence with the specified position data. Therefore, it may be a read-only memory or a writable memory. The false image information readout controller 5 always retains the current position data (azimuth and distance data) of the received signal based on the distance calculated from the input antenna azimuth signal and radar trigger signal, and is supplied from the gate circuit 1 at the same time. When a target echo signal is input, the current position data of this target echo is stored in the false image information storage 2.
For example, the data is supplied as address data to the false image information storage device 2, and the data is read out from the false image information storage device 2 regarding the position and section where a false image can occur, which is stored in correspondence with the current position data of the target object echo, and the data is read out from the false image information storage device 2. This device has a readout control function for the false image information supplied to the computer. Even if the current position data of the target echo is supplied to the false image information storage device 2, if false image information corresponding to the current position data of the target echo is not stored (i.e., the current position of the target echo is is not a position where a false image can occur), naturally the position and section data where a false image can occur are not read out. The false image gate generator 3 is a device that generates a false image gate signal S2 during the radar reception time period corresponding to the position and section data in which a false image can occur, which is inputted from the false image information readout controller 5. When there are multiple positions and sections where false images can occur, false image gate signal S
2 is also generated multiple times. The tracking gate generator 4 is a device that generates a tracking gate for capturing and tracking radar target echoes based on the input radar trigger signal, radar azimuth signal, and radar reception signal S1.
This is a device that generates a tracking pulse signal S3 in an interval from distance R to R+ΔR at ±Δθ.

FIG. 2 is a timing chart for explaining the operation of FIG. 1.

The operation of FIG. 1 will be explained with reference to FIG. The gate circuit 1 shown in FIG. 1 is supplied with a radar reception signal S from a radar receiver. As shown at 81 in FIG. 2, the radar received signal S1 has A, BSC, and D manually input as target objects or false image echoes from different distances in the azimuth θ. When the echo A is now input to the gate circuit 1, the false image gate signal S2 shown in FIG. Obtain echo A'. now echo A'
is input to the false image information readout controller 5 on the assumption that a position where a false image can occur has been detected for one day. The false image information readout controller 5 supplies data on the current position of the echo A' calculated from the input radar azimuth signal and radar trigger signal to the false image information storage 2, and reads the echo from the false image information storage 2. Corresponding to the current position of A', the position and section data where a false image can occur (r, r + Δ "Al) and (r A21
At Al r +Δ "A2)" is read out and supplied to the false image gate generator 3.The false image gate generator 3 reads out the false image generation time period during radar reception corresponding to the two sets of input position and interval data. A1, indicated by P and PA2 in Figure 2, generates a false image gate signal S2 and supplies it to the gate circuit 1.When the echo B of the radar reception signal S1 is input to the gate circuit 1, the false image gate signal S2 is Since it is at the L level, it passes through the gate circuit 1 and becomes an echo B' of the signal S4 from which the false image has been removed.The detection position of this echo B' is again a position where a false image can occur, and the false image information is stored. The vessel is Echo B
Assuming that the data of the position and section where a false image can occur corresponding to the detected position of ' is stored, the false image gate signal S shown by P and PB in FIG. Ru. Next, when the echo C of the radar reception signal/signal S1 is input to the gate circuit 1, the false image gate signal S2 becomes H.
Since the tracking gate signal S3 is at L level, it does not pass through the gate circuit 1, and no echo C' is obtained in the output signal S4 from which the false image has been removed. In other words, echo C was removed as a false image. When the echo D of the radar reception signal Sl is input to the gate circuit 1, the false image gate signal S2 is at H level, but at the same time, the tracking gate signal S3 is also at H level, so it passes through the gate circuit 1 and the false image gate signal S2 is at H level. An echo D' that is being tracked is obtained from the removed output signal S4. Therefore, the radar echo being tracked will not be mistakenly removed as a false image.

If the radar is a land-based fixed station radar as shown in Figure 3, the secondary reflection target that causes false images and its position are known, and the secondary reflection target and its position within the radar signal processing area are known. The position and section where a false image can occur can be calculated from the positional relationship with the reflective target. In the present embodiment, it has been explained that all the position and section data where a false image can occur corresponding to this predetermined position are stored in advance in the false image information storage device 2 for a required number of predetermined positions. However, if this false image information storage device 2 is constructed from a read-only storage device (for example, a ROM IC), the storage capacity may become excessive. Therefore, only data such as the position and shape of the secondary reflection target are stored in a read-only memory, and when a received echo is detected at the predetermined position, (
In reality, the radar transmission pulse is the received echo of the previous one,
When a received echo is detected at a predetermined position before the antenna rotates one rotation), calculate the position and section data where a false image can occur,
A memory device (e.g. RAM IC) in which this calculation result can be written
) may be stored. In this case, a small capacity read-only memory is sufficient.

[Effects of the Invention] As explained above, this invention stores in advance the position and section data where a false image is expected to occur when a target echo exists at a specified position where a false image may occur.
When a target echo is actually detected at the specified position, a false image gate signal is immediately generated in the corresponding time period from the stored position and section data, making it possible to remove the false image. This method has the effect of stably removing false images compared to .

Also, for the target being tracked, a tracking gate signal is used to
Since the logic circuit is configured to prevent false images from being removed by mistake, it is possible to remove false images without affecting the tracking operation.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a radar artifact signal processing device according to the present invention, FIG. 2 is a timing chart for explaining the operation of FIG. 1, and FIG. 3 is a diagram illustrating generation of radar artifacts. In the figure, 1 is a gate circuit, 2 is a false image information storage, 3 is a false image gate generator, 4 is a tracking gate generator, and 5 is a false image information read controller. For OAA death 8; 4-claw fishing, 41 nails village girl]

Claims (1)

[Claims] In a signal processing device for the purpose of removing radar false images, there is provided a signal processing device for detecting a position and a section where a false image can occur due to a target existing at a position specified by the target object detection direction and distance of the radar. A false image information storage device that stores data for a required number of specified positions in advance; and a false image information storage device that calculates the direction and distance of a target echo detected by a radar, and stores the position specified by the direction and distance of the target object echo. a false image information read controller that supplies data to the false image information storage device and reads and outputs data of a position and section where a false image can occur corresponding to the designated position data from the false image information storage device; a false image gate generator that generates a false image gate signal during a radar reception time period corresponding to position and section data where a false image can occur, which is supplied from the false image information readout controller; and a false image gate generator that tracks the radar target. , a tracking gate generator that generates a tracking gate signal in a distance range in a direction in which the tracking target is received; a false image gate signal is generated from the false image gate generator;
A radar artifact signal processing device comprising: a gate circuit that removes an input radar reception signal as a artifact signal when the tracking gate signal is not generated from the tracking gate generator.