JPH0527011A - Radar signal processing device - Google Patents

Abstract

PURPOSE:To eliminate radar interference signals without erroneous elimination of the target signal due to the level fluctuation without generating inconvenience of non-display between the first two sweeps over the threshold level when a new target signal exists. CONSTITUTION:A radar signal processing device is provided with a level judgement part 101 to make a judgement of the input signal level for every range bin, a level judgement signal memory part 102 to realize consecutive memorization of the level judgement signal of the continuous two sweeps for every range bin, and radar interference judgement means 103, 104 to output the judgement results that the radar interference is made, when in comparison with the level judgement signal for every range bin, a judgement is made that one past sweep exceeds the threshold level, and the present and two past sweeps do not exceed the threshold level. There are in addition provided an input signal memory part 105 to memorize the input signal of one past sweep, and a display signal switching part 106 to output the signal of the same range bin from the input signal memory part 105 as the display signal when no radar interference is made.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal processing device for a detecting device such as a radar device, and more particularly to removing a signal having no correlation between continuous sweeps such as a radar interference signal. At the same time, it relates to a signal processing device for reducing the loss of the target signal as much as possible.

[0002]

2. Description of the Related Art In a radar apparatus, a radar interference signal generated by a radio wave emitted from another radar radio station installed at sea or on land significantly impairs detection of a target signal. It becomes an unnecessary non-target target signal.

For example, like the radar image shown in FIG.
When the radar interference signal is superimposed on the target object signal reflected from the target object and a large number of images are displayed on the radar display screen, the radar interference signal is regarded as the target object signal. You may make a mistake. Therefore, in the signal processing device, removal of the radar interference signal is an indispensable process for detecting the target object signal by the radar device.

In order to remove the radar interference signal, a signal processing device is used which utilizes the difference in the correlation between the radar interference signal and the target object signal in the azimuth direction.

By the way, the target object signals exist continuously in the azimuth direction in the range bins having the same distance, whereas the radar interference signals exist independently in the azimuth direction. The conventional signal processing apparatus utilizes this fact to provide a certain threshold level which is assumed to reliably exceed the radar interference signal, and performs amplitude comparison between the received input signal and the threshold level. By continuously determining the determination result for each range bin in the azimuth direction, the display is performed on the radar image only when the input signal is determined to be the target object signal from the target object. Therefore, the radar interference signal that is not determined to be the target signal is removed. That is, the conventional signal processing device can be said to be a signal processing device focusing on the correlation of the target object signal in the azimuth direction.

This will be described more specifically with reference to FIG. As shown in FIG. 3, the conventional signal processing device includes a level determination unit 301 and a level determination signal storage unit 30.
2, an AND circuit 303, an exclusive OR circuit 304, and a display switching unit 305.

A level determination unit 301 compares the amplitude of a threshold level for determining a radar interference signal with an input signal for each range bin, and outputs a level determination signal. The level determination signal is, for example, a binary value "1" when the amplitude of the input signal is larger than the threshold level and a binary value "0" when the amplitude is smaller than the threshold level.

The level judgment signal storage unit 302 has a capacity for storing data for two sweeps of the level judgment signal, and when the level judgment signal is stored for each range bin,
The stored level determination signal corresponding to the same range bin in the past two sweeps is output.

The AND circuit 303 performs a logical product operation for each range bin having the same distance with respect to the level determination signals in the past two sweeps output from the level determination signal storage unit 302 for each range bin, and the operation is performed. Output the result.
As a result of the calculation, "1" is output when the level determination signals of the range bins having the same distance within the past two sweeps are "1", and "0" is output otherwise.

The exclusive OR circuit 304 is an AND circuit 303.
The operation result output from the above and the level determination signal output from the level determination unit 301 are subjected to an exclusive OR operation for each range bin having the same distance, and the operation result is output as a target determination signal. The target judgment signal is the AND circuit 3
In the range bin in which the calculation result from 03 and the level determination signal output from the level determination unit 301 have the same distance, the value is “0” only when the values are equal, and the value is “1” otherwise. When the target determination signal is “0”, the target target signal is used, and when the target determination signal is “1”, the other non-target target signals are used.

The display switching unit 305 includes an exclusive OR circuit 304.
The display / non-display of the input signal is determined for each range bin based on the target determination signal output from the output target signal, and the input signal is output as a display signal only when the target determination signal is "0".

Here, the sweep number of the present input signal is (N), the previous sweep number is (N-1), and the two previous sweep numbers are (N-2). To do. The sweep number of the sweep to be processed is (N), that is, the input signal sweep. FIG. 7A shows the state of the level determination signal and the state of the target determination signal of three consecutive sweeps in the range bins having the same distance.

With the above construction, as shown in FIG. 4, when all the level judgment signals of the sweep numbers (N-2, N-1, N) are "1", the target judgment signal is "0". Will be displayed and will be displayed. However, it is not displayed in the cases shown in FIG.

As a result, since the target object signal has a strong correlation in the azimuth direction, the level judgment signal of the range bin whose distances are equal in all sweeps of the sweep numbers (N-2, N-1, N). Becomes "1", and the target signal is displayed. Then, the radar interference signal having no correlation in the azimuth direction is not displayed and is removed. In addition,
If the level determination signal is "0" in all sweeps of the group number (N-2, N-1, N), the target determination signal becomes "0" and it is determined as the target signal. ,Is displayed. Therefore, the target signal having an amplitude smaller than the threshold level of the level determination unit is displayed without being removed.

[0015]

In the above-mentioned conventional signal processing apparatus, the state of the level determination signal with respect to the threshold level is changed between three sweeps in which radar interference signals having no correlation in the azimuth direction are consecutive. It was possible to remove the radar interference signal because the condition that the target signal was not determined. However, although the target signal has a correlation in the azimuth direction, no measures have been taken against the constant fluctuation of the amplitude level of the input signal. That is, in the above signal processing device, when the amplitude level of the input signal fluctuates, the level judgment signal of the level judgment unit is judged to be the target signal signal for three consecutive sweeps with respect to the set threshold level. It cannot hold the condition for being killed. Therefore, as shown in FIG. 4 and b ′ in FIG. 6B, the input signal may be removed without being determined as the target signal. Further, as shown in a ′ of FIG. 6B in FIG. 4, when the target signal signal changes from the non-existing region to the existing region, the target signal signal first exceeds the threshold level. The target signal is no longer displayed between the two sweeps. As a result,
There is a disadvantage that the number of target signals displayed at a'is reduced, resulting in a small image of the target signals as a whole and a decrease in detection performance.

The object of the present invention is to erroneously remove the target signal due to fluctuations in the level of the target signal, and for the first two switches exceeding the threshold level when the target signal is newly present. It is an object of the present invention to provide a radar signal processing device capable of removing a radar interference signal without causing an inconvenience of non-display between groups.

[0017]

To achieve the above object, according to one aspect of the present invention, for each sweep, it is determined whether or not the level of the input signal exceeds a preset threshold level. For each range bin, the level determination means for determining each of the past two sweeps are sequentially stored for each range bin, and the level determination signal for each of the past two sweeps is handled. The level determination signal storage means for outputting the level determination signal of the range bin of the distance, and the level determination signals of the current sweep, the one previous sweep, and the two past sweeps are compared for each same range bin, and The input signal of one previous sweep exceeds the threshold level, and the input signals of the present and two previous sweeps exceed the threshold level. Radar interference determination means that determines that there is radar interference and outputs the determination result, input signal storage means that stores an input signal for one previous sweep, and radar interference When there is no radar interference in response to the determination result of the determination means, a signal of the same range bin among the input signals stored in the input signal storage means is output as a display signal, and when there is radar interference, And a display signal switching means for preventing the input signal from being a display signal.

[0018]

A signal that has no correlation with respect to the azimuth direction, such as a radar interference signal, is generated at a constant threshold level.
Residential bins of equal distance will not exceed the threshold level continuously in the azimuth direction. So, for example,
When the amplitude of the input signal exceeds the threshold level, it is set to "1", and when it does not exceed the threshold level, the level is determined. The level judgment result for the level is, for example, [0,0,1,0], and only one sweep exceeds the threshold level.

Thus, for range bins having the same distance, the level determination result for the threshold level of the amplitude of the input signal is determined in the azimuth direction between three consecutive sweeps, and the level determination result is [0, 1]. , 0], it is possible to remove signals such as radar interference signals that have no correlation in the azimuth direction by removing only the signals of the sweep for which "1" is determined. .

For the target signal, even if there is a change in the level judgment with respect to the threshold level, the above-mentioned level judgment result will not be obtained during three consecutive sweeps. It is not removed and can be displayed as a radar image.

[0021]

Embodiments of the present invention will be described with reference to the drawings.

A signal processing apparatus according to the present invention will be described with reference to FIG.
The case where the device is used for a D / A device will be described. The sweep number of the input signal is (N), the sweep number one past is (N-1), and the sweep number two pasts is (N-2).

The signal processing apparatus according to the present invention comprises a level determining section 1
01, level determination signal storage unit 102, NOR operation unit 10
3, an AND circuit 104, an input signal storage unit 105, and a display switching unit 106.

The level determination unit 101 is provided with an input signal and a preset threshold level (threshold value).
Is compared for each range bin, for example, "1" if the input signal is higher than the threshold level,
Otherwise, "0" is output as the level determination signal. The threshold level that is set must be a level that the radar interference signal exceeds. The level determination unit 101 can be composed of either an analog circuit or a digital circuit. When it is configured with an analog circuit, it can be configured with, for example, an analog level comparator, and when it is configured with a digital circuit, it can be configured with, for example, a digital level comparator.

The level judgment signal storage unit 102 has a capacity for storing data for two sweeps of the level judgment signal,
When the level determination signal is stored for each range bin, the stored level determination signal corresponding to the same range bin in the past two sweeps (N-2, N-1) is output. The level determination signal storage unit 102 can be composed of either an analog circuit or a digital circuit. For example, when it is configured by an analog circuit, it can be realized by connecting two delay circuits having the same transmission repetition period in series, and when configured by a digital circuit, it can be easily configured by a shift register or a memory.

The NOR operation unit 103 outputs 2 from the level determination signal output from the level determination unit and the input signal sweep (N) output from the level determination signal storage unit 102.
For the level determination signals of the previous sweep (N-2), NOR operation is performed for each range bin having the same distance, and the operation result is output. The NOR operation unit 103 can be configured as analog or digital by using a general-purpose general-purpose logic circuit, for example.

The AND circuit 104 includes the operation result output from the NOR operation unit 103 and the level determination signal storage unit 102.
From the input signal sweep (N) output from the device, the level determination signal of the previous sweep (N-1) is AND-operated for each range bin having the same distance, and the operation result is used as the radar interference determination signal. Output. Similarly to the NOR operation unit 103, the AND circuit 104 can be configured by using a general-purpose general-purpose logic circuit regardless of analog or digital.

The input signal storage unit 105 outputs the input signal (N-1) one sweep past from the input signal sweep having the same distance as the range bin of the input signal, and outputs the input signal (N) for each range bin. Is stored for each range bin. The input signal storage unit 105 can be composed of, for example, a delay circuit having an equal transmission repetition period in an analog circuit and a shift register and a memory in a digital circuit.

The display switching unit 106 does not output the input signal as a display signal when it is determined to be a radar interference signal based on the radar interference determination signal output from the AND circuit 104. Only when the determination is not made, the signal output from the input signal storage unit 105 is output as the display signal.

Therefore, the sweep number of the sweep to be processed is (N-1).

Next, the operation of this embodiment will be described with reference to other drawings.

FIG. 2 shows a part of a continuous range bin.
In FIG. 2, when the level determination signal is "1" among the three sweeps having the sweep numbers (N, N-1, N-2),
Is the sweep number (N, N
Since the result of the NOR operation on the level determination signal of -2) is "0", the radar interference determination signal becomes "0", and the signal of the sweep number (N-1) is determined to be the target signal. , The display is done. Also, due to the fluctuation of the input signal, as shown in the case of ', the sweep number (N, N-
Even if the level determination signal of only 2) is "1", it is determined similarly and can be displayed as the target object signal without being erroneously removed.

Further, even when the target object signal is newly present from the sweep number (N-1) as in the case of'in FIG. 2, the sweep number ( Since the result of the NOR operation on the N, N-2) level determination signals is "0", the radar interference determination signal becomes "0", and the signal of the sweep number (N-1) becomes the target signal. The determination is made and the display is performed.
Therefore, the display can be performed without damaging the target signal.

On the other hand, as shown in FIG.
When only the sweep (N-1) exceeds the threshold level, the result of the NOR operation for the level determination signal of the sweep number (N, N-2) becomes "1", so the AND circuit 104 Is the logical product of the operation result output from the NOR operation unit 103 and the level determination signal of the sweep number (N-1) output from the level determination signal storage unit 102 is "1", and the radar Interference judgment signal is "1"
Becomes Therefore, the radar interference signal is removed.

An example of processing for one range bin is shown in FIG. That is, when an input signal as shown in FIG. 6A is input for one range bin, the conventional signal processing apparatus, as shown in a ′ and b ′ of FIG.
Even in the case of the target object signal, a part of the target object signal is not displayed due to an incorrect determination. However, in this embodiment,
As described above, the signal of the sweep number (N-1) is used for display, and the input signal of the sweep number (N, N-2) does not exceed the threshold level, and the sweep number (N −
When only the input signal of 1) exceeds the threshold level, it is determined that there is radar interference, and in other cases, it is determined that there is no radar interference, and the target object signal is displayed. I do. As a result, as shown in a ″ and b ″ of FIG. 6C, the target signal can be displayed without causing the loss. Moreover, the radar interference signal can be removed without inferior to the conventional signal processing device.

The signal processing apparatus according to the present embodiment eliminates the problem of removal of fluctuations in the target object signal without deteriorating the performance of removing non-target object signals such as radar interference signals having no correlation in the azimuth direction. By solving the problem of non-display between the first sweep and the second sweep when a new target signal is present, it is possible to detect the target signal more accurately. This can greatly contribute to the safety of navigation of ships and the like.

FIG. 8 shows an example of a radar device equipped with the above radar signal processing device. The radar apparatus shown in FIG. 8 uses a radar signal receiving apparatus 801 that receives a radar signal received by an antenna (not shown) as input and generates and outputs a radar video signal, and the radar signal processing apparatus of the embodiment shown in FIG. A radar signal processing device 802 that removes the radar interference signal from the radar video signal and outputs it as a display signal; and a radar image display device 803 that displays the display signal output from the radar signal processing device 802 as a radar image. Equipped with.

Next, another embodiment of the radar signal processing apparatus of the present invention will be described with reference to FIG.

The radar signal processing apparatus according to the present embodiment has a level determination unit 901 that determines the level of an input signal by comparing it with a threshold value, and a level that stores the determination signal output from the level determination unit 901 for two sweeps. Judgment signal storage unit 902
An input signal storage unit 904 for storing the input signal for one sweep; a calculation unit 905 for determining whether the input signal is a radar interference signal and outputting a radar interference determination signal;
A display switching unit 906 that outputs the input signal stored in the input signal storage unit 904 as a display signal depending on whether the radar interference determination signal is “1” or “0”.

The level judgment unit 901 compares the set threshold value with the amplitude value of the input signal for each range bin, and judges "1" if the input signal is larger than the threshold value, and judges "0" if it is smaller than the threshold value. Output as.

The level determination signal storage section 902 is, for example,
Shift register 90 for storing and holding one sweep each
2a and 902b. Shift registers 902a, 9
In the case of 02b, assuming that there are M range bins existing in one sweep, an M-stage shift register is used. These shift registers 902a and 902b are connected in series,
The level determination signal between two sweeps can be sequentially stored.

For example, when the level determination signal of the first range bin in the (N) th sweep is output from the level determination unit 901, the signal output from the shift register 902a is the first range bin in the (N-1) th sweep. Of the shift register 90.
The signal output from 2b becomes the level determination signal of the first range bin in the (N-2) th sweep. That is, since all range bins existing in one sweep are M and two M-stage shift registers 902a and 902b are connected in series, by outputting signals from the Mth and 2Mth, (N) The (N−1) th sweep and the (N−) for the mth range bin of the th sweep
2) The level determination signal of each mth range bin of the second sweep is obtained.

The level determination signals of the range bins in the (N) th sweep are sequentially output to the shift register 9
Since it becomes the input signal of 02a, the level determination signal for any three sweeps is output to the calculation unit 905 without being lacking.

The input signal storage section 904 can be composed of, for example, a shift register. If there are M range bins existing in one sweep, it can be configured by using one M-stage shift register. This input signal storage unit 90
When the input signal of the first range bin in the (N) -th sweep is input, the shift register constituting 4 outputs the value of the M-th range bin in the (N-1) -th sweep. In this case, the input signal storage unit 904
The level determination unit 901, the level determination storage unit 902, and the level determination storage unit 902 so that the input signal for the same range bin as the target range for radar interference determination by the calculation unit 905 is output in synchronization with the radar interference determination signal. Arithmetic unit 9
With 05, the operation timing is set.

The calculation unit 905 calculates the (N) th and (N-1) th
When the level determination signal in each range bin of the (N−2) th sweep is input, it is determined whether the input signal of the target range bin is a radar interference signal. If it is determined as a radar interference signal, “1” is set. , Otherwise, "0" is output as a radar interference determination signal.

The display switching unit 906 outputs "0" as a display signal when the radar interference determination signal is "1" according to the radar interference determination signal output from the calculation unit 905,
When the radar interference determination signal is "0", the (N-1) th input signal output from the input signal storage unit 904 is output as a display signal.

In the present embodiment configured as described above, one level judgment section 901 compares the input signal of each range bin of one sweep with the threshold value, and outputs the judgment result as a level judgment signal in sequence. The level determination signal storage unit 902 stores the level determination signal for two sweeps, and the arithmetic unit 905 determines the radar interference signal. Then, when the radar interference determination signal is determined to be radar interference, the display switching unit 906 outputs the display signal as “0”, so that only the radar interference signal is removed.

Next, an embodiment of the arithmetic unit 905 used in the above embodiment will be described with reference to FIG. The present embodiment has a configuration different from that of the NOR operation unit 103 and AND circuit 104 shown in FIG.

The arithmetic unit shown in FIG. 10 is configured using the memory 1001. This memory 1001 is, for example, R
It is composed of an OM (Read Only Memory). However, RAM (random access memory) may be used.

The memory 1001 uses the level determination signal as an address input and the radar interference determination signal as output data. Since the address of the memory indicates the combination of the level determination signals, the radar interference signal determination for the address value is stored in advance as the contents of the memory, and the output data is (N, N-1, N- A radar interference determination signal corresponding to the level determination signal for each range bin in 2) is obtained.

Here, as an example, the address input 3bi
A case where a memory of t and output data of 1 bit is used will be described.

Addresses of 3 bits are A0, A1 and A2. The memory 1001 has addresses A0, A1, A2.
The level determination signal for is stored in advance. Figure 11
An example is shown in. In the example of FIG. 11, the data output is “1” only when the radar interference signal is input, and is “0” otherwise, and the radar interference signal can be detected. An interference determination signal can be output. Note that the level determination signal of the (N) th sweep is input to A0, the level determination signal of the (N-1) th sweep is input to A1, and the (N) th sweep is input to A2.
-2) Input the level determination signal for the second sweep.

In this embodiment, the level judgment signal storage section 90
Although a shift register is used for 2 and the input signal storage unit 904, a semiconductor memory can also be used.

Further, in the above embodiment, the level determination signal storage section 902 and the input signal storage section 904 are provided separately, but they may be provided in common. FIG. 12 shows an example thereof.

The example shown in FIG. 12 is configured by using a parallel-in / parallel-out shift register 903 instead of the shift register 902a shown in FIG. The other components are the same as those shown in FIG. The shift register 903 illustrated in FIG. 12 holds the level determination signal and the input signal in parallel. The level determination signal and the input signal are shifted in synchronization, and the former is sent to the arithmetic unit 905 and the latter is sent to the display switching unit 906.

According to this embodiment, the shift register for the input signal storage section 904 used in the embodiment shown in FIG. 9 can be omitted.

[0057]

As described above, according to the present invention,
If the target signal is erroneously removed due to the level fluctuation of the target signal, or if there is a new target signal, the first 2
It is possible to record without causing the inconvenience of non-display between sweeps.
The interference signal can be removed.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of a radar signal processing device of the present invention.

FIG. 2 is a waveform diagram showing the operation of the radar signal processing device of the above embodiment.

FIG. 3 is a block diagram showing a configuration of a conventional radar signal processing device.

FIG. 4 is a waveform diagram showing the operation of a conventional radar signal processing device.

FIG. 5 is an explanatory diagram showing an example of a radar image of a radar interference signal and a target object signal.

FIG. 6 is an explanatory diagram showing a comparison of processing by a conventional signal processing device and a signal processing device of the present invention in a fixed range bin.

FIG. 7 is a target determination signal according to a state of a level determination signal between three consecutive sweeps in range bins having the same distance,
FIG. 6 is an explanatory view showing the determination result of the radar interference determination signal by comparing the conventional method and the method of the present invention.

FIG. 8 is a block diagram showing the configuration of an example of a radar device equipped with the radar signal processing device of the present invention.

FIG. 9 is a block diagram showing the configuration of another embodiment of the radar signal processing device of the present invention.

FIG. 10 is a block diagram showing an example of a calculation unit that can be used in the above embodiment.

11 is an explanatory diagram showing an example of stored contents of the memory shown in FIG.

12 is a block diagram showing another example of a level determination signal storage section and an input signal storage section used in the embodiment shown in FIG.

[Explanation of symbols]

101, 901 ... Level determination section, 102, 902 ... Level determination signal storage section, 103 ... NOR operation section, 104 ... AND circuit, 105, 904 ... Input signal storage section, 106, 9
06 ... Display switching unit, 801 ... Radar signal receiving device, 80
2 ... Radar signal processing device, 803 ... Radar image display device, 902a, 902b, 903 ... Shift register, 9
05 ... arithmetic unit, 1001 ... memory.

Claims (3)

[Claims] 1. A level determining means for determining, for each range bin, whether or not the level of the input signal of each sweep exceeds a preset threshold level, and the level determination for two consecutive sweeps. Level determination signal storage means for sequentially storing the signals for each range bin, and when the level determination signal is input, outputting the level determination signal of the range bin of the distance corresponding to each of the past two sweeps; For each level judgment signal of sweep, one past sweep, and two past sweeps, the input signal of one past sweep exceeds the threshold level, and the current and two levels are compared for each same range bin. If the input signal of the previous sweep does not exceed the threshold level, it is judged that there is radar interference and the judgment is made. The radar interference determination means for outputting the result, the input signal storage means for storing the input signal for the previous sweep, and the radar interference determination means receiving the determination result of the radar interference determination means. Among the input signals stored in the signal storage means, a signal of the same range bin is output as a display signal, and when there is radar interference, display signal switching means for preventing the input signal from being the display signal is provided. A radar signal processing device, comprising: 2. The radar interference determination means according to claim 1, wherein the radar interference determination means NOR-operates the level determination signals of the current sweep and the two previous sweeps for each range bin having the same distance, and the range bin output from the NOR computation means. An AND operation is performed for each range bin having the same distance and the operation result for each range bin and the level decision signal for each range bin of the previous sweep output from the level decision signal storage means, and the operation result is radar interference. A radar signal processing device having an AND operation means for outputting as a determination signal. 3. The radar interference determining means according to claim 1, wherein the possible combinations of the current sweep, the sweep of one past, and the sweep of two past, with respect to each level determination signal for each range bin having the same distance, Each of the memories has a memory that stores information on a radar interference determination signal indicating whether or not there is radar interference, and the memory determines the level of a current sweep, a previous sweep, and two past sweeps for the same range bin. A radar signal processing device that outputs a radar interference determination signal corresponding to a signal input thereto.