JPH03291586A - Radar device - Google Patents

Abstract

PURPOSE:To prevent a clutter from being misdetected by calculating a blanking range from the altitude, speed, etc., of an aircraft and blanking the output of a side lobe blanker (SLB) according to the output. CONSTITUTION:A blanking range calculating circuit 8 calculates a range gate number corresponding to a direction wherein the clutter in an area hatched in a figure a detected based on the altitude, speed, diving angle and rolling angle of the air craft as a target possible by mistake and the range of a Doppler frequency number as a blanking range. Then when whether or not there is blanking is outputted to a blanking circuit 7, the circuit 7 removes or passes the target according to the indication. In addition to this constitution, a previously set blanking range table can be selected according to the altitude of the aircraft to decide whether or not there is blanking according to the table. Consequently, even if the ground surface in front of the aircraft is undulated, the possibility that a clutter is misdetected as the target is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to the removal of false targets in radar equipment.

σConventional technology] FIG. 2 is a block diagram of a conventional radar device.

This is similar to the invention described in JP-A-62-119485.

In the figure, ■ is an antenna, 2a and 2b are receivers connected to the antenna 1, and 3a and 3b are receivers 2a and 2b, respectively.
Range gate connected to, 4a.

4b is a Doppler filter connected to the range gates 3a and 3b, 5 is a target detection circuit connected to the Doppler filter 4a, and 6 is a siderobe Bl connected to the Doppler filter 4b and the target detection circuit 5.
anchor).

Next, the operation will be explained.

Consider an aircraft monopulse/pulse Doppler radar system that detects a target approaching from behind as shown in FIG.

The target has a positive Doppler frequency as it approaches the aircraft.

On the other hand, the crank (reflected wave from the ground surface) has a positive Doppler frequency in front of the aircraft as the aircraft approaches, and a negative Doppler frequency in the rear as the aircraft moves away.

In FIG. 2, the operation up to target detection will be explained first.

Target detection is performed in the Σ channel. The targets and clutter received by the antenna 1 are input to a plurality of (N) range gates 3a corresponding to the distances via the receiver 2a. Each output of the range gate 3a is input to a Doppler filter 4a, and a plurality of (M) outputs corresponding to Doppler frequencies are obtained.

When the range gate number is written as #R and the Doppler frequency number is written as #F, (#R, #F) = (1, 1) to (#R,
#F) = NXM outputs up to (N, M) will be obtained. The NXM outputs are the target detection circuit 5.
The target detection process is performed manually.

The target is output to the corresponding range gate number and Doppler frequency number. Since clutter from the rear of the aircraft has a negative Doppler frequency, it is removed by the Doppler filter 4a. This is because the target is a positive Doppler frequency, so no output corresponding to a negative Doppler frequency is provided.

Since clutter from the front of the aircraft has a positive Doppler frequency, it is not removed by the Doppler filter 4a, but most of it is removed by the target detection circuit 5.

The reason is that the target detection circuit 5 normally uses CFAR (C).

n5tant False A1ar++ Rate)
It has a processing function and is detected only when it stands out from the nearby range gate number or Doppler frequency number signal.
This is because clutter from a flat ground surface is not detected.

However, if there are undulations or the like on the ground surface, there is a possibility that clutter will be erroneously detected as a target.

Next, referring to FIG. 2, the operation of the Δ channel and SLB will be explained.

The Δ channel is mainly used for direction detection and secondarily for SLB, but only the parts related to SLB are shown in the block diagram this time.

Similar to the Σ channel, the target and clutter received by the antenna 1 are input to a plurality of range gates 3b corresponding to the distance via the receiver 2b.

Each output of the range gate 3b is input to the Doppler filter 4b, and in order to obtain a plurality of (M) outputs corresponding to the Doppler frequency, (#R, #F) = (1, 1) to (#R, #
F)=(N,M)t7+7)NxM outputs are obtained. The output of the Doppler filter 4b is inputted to 5LB6 of the corresponding range gate number and Doppler frequency number, respectively, and is processed together with the target detection signal of the corresponding Σ channel. 5LB6 compares the amplitude value of the Σ channel and the amplitude value of the Δ channel, and passes or blocks the target detection signal.

The operation of 5LB6 will be explained using FIG. Figure 4 (a
) indicates the antenna gain in the xy plane (horizontal plane) in the coordinate system of FIG. The X7 plane is a plane on which direction detection is performed using the Δ channel. In this case, the orientation θ1□ is 0
° Near (just behind the aircraft) Σ gain > Δ gain,
In the region of 01□ large, Σ gain <Δ gain.

5LB6 is the target signal passing when Σamplitude value>Δamplitude value, Σ
The target signal is cut off when the amplitude value <Δ amplitude value, therefore,
Since the target approaches from behind, it will pass through 5LB6, and clutter in front of the aircraft will be blocked by 5LB6, so that false targets due to unevenness on the ground will not be detected. However, this is a case where attention is paid to the xy plane (horizontal plane).

Next, a case will be described focusing on the xz plane (vertical plane).

As shown in Figure 4), in the X-2,000 plane (vertical plane), Σ gain>Δ gain in almost all directions, and 5LB6
is disabled and all signals pass through.

Therefore, in the direction of the diagonal line shown in Figure 5, clutter has a positive Doppler frequency and SLB is invalid (not removed), so if there are undulations on the ground surface, clutter may be mistakenly targeted. May be detected.

[Problem to be solved by the invention]

Conventional radar equipment is configured as described above, so
There is a problem in that clutter may be mistakenly detected as a target depending on the direction.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a radar device in which clutter is not erroneously detected as a target in any direction.

[Means to solve the problem]

The radar device according to the present invention includes a blanking range calculation circuit and a blanking circuit.

[Effect]

Since the radar device according to the present invention adds blanking within the range calculated from the mother aircraft flight information, clutter will not be erroneously detected as a target in any direction.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of a radar device according to an embodiment of the present invention, and in the figure, numerals 1 to 6 are the same as those of a conventional radar device. 8 is a blanking range calculation circuit, and 7 is a blanking circuit connected to 5LB6 and the blanking range calculation circuit 8.

Next, in the embodiment shown in FIG. 1, only the operations different from those of the prior art will be described.

The blanking range calculation circuit 8 calculates the altitude of the aircraft.

From the velocity, dive angle, and roll angle, calculate the range of the range gate number and Doppler frequency number corresponding to the direction in which clutter in the shaded area in FIG. 5 is likely to be erroneously detected as a target. The blanking range calculation circuit 8 outputs the presence or absence of blanking to the blanking circuit 7. The blanking circuit 7 removes or passes the target according to the instructions.

Next, the formula for calculating the blanking range will be explained.

For simplicity, the dive and roll angles of the aircraft are assumed to be 0 degrees (level flight) in FIG. 6. Set the altitude of the aircraft to H1
If 1 degree is VI, and the angle at which Σ gain>Δ gain is α in the antenna, then distance R0 of point A0 and relative velocity V, . The relationship between is expressed as.

In addition, the distance R0 and relative speed ■ of point A and point are respectively CO3α V 1-1 = V, 6 ((represented by 13α.

From the above, when expressed in a two-dimensional plane of distance and relative velocity,
As shown in Figure 7, from (Ro, V, .) to (R1, V□
) is the blanking range.

When the azimuth angle β in FIG. 6 is changed from 0 degrees to 180 degrees, the range shown by diagonal lines in FIG. 7 is finally calculated as the blanking range. Since the relative velocity and the Doppler frequency have the following relationship: λ f-=Doppler frequency ■, = relative velocity λ : wavelength, the Doppler frequency can be calculated from the relative velocity.

From the above, the blanking range for the range gate number and Doppler frequency number has been calculated. Such an operation eliminates the possibility that clutter will be mistakenly detected as a target even if there are undulations on the ground surface in front of the aircraft.

Note that in the range of distance and relative speed shown by the diagonal line in Figure 7 blanked by the blanking circuit 7, the true target is no longer detected, but the angle α at which Σ gain > Δ gain for the antenna 1 is in front of the aircraft (the antenna The present invention is particularly effective for radar devices that need to prevent detection of false targets because they are small compared to boat fishing.

In addition, in the above embodiment, the blanking range is calculated from the aircraft altitude, etc., but a preset blanking range table is selected based on the aircraft altitude, etc., and the presence or absence of blanking is determined according to the table. It is also possible to have a configuration in which:

FIG. 8 is a bronch diagram of this embodiment, where 9 is a blanking range table and 10 is a blanking range table 9.
A table selection circuit 11 is connected to the table selection circuit 10, and a blanking determination circuit 11 is connected to the full selection circuit 10. The table selection circuit 10 selects the blanking range table 9 based on the aircraft altitude and the like. Blanking determination circuit] 1 determines the presence or absence of blanking from the chifur, range gate number, and Doppler frequency number, and instructs the blanking circuit 7 to perform blanking. Through this processing, the same operation and effect as in FIG. 1 can be obtained.

[Effects of the Invention] As described above, according to the present invention, since the blanking range is calculated based on the altitude, speed, etc. of the aircraft and the blanking is performed, it is possible to prevent clutter from being erroneously detected as a target in any direction. effective.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a radar device according to an embodiment of the present invention, FIG. 2 is a block diagram of a conventional radar device, and FIG.
The figure is an explanatory diagram of the target, clutter, and coordinate axes, Fig. 4 is an explanatory diagram of the antenna gain and SLB, Fig. 5 is an explanatory diagram of the direction in which the crank may be mistakenly detected as a target, and Fig. 6 is an explanatory diagram of the clutter. FIG. 7 is an explanatory diagram of the relationship between distance and relative velocity, FIG. 7 is an explanatory diagram of the blanking range, and FIG. 8 is a block diagram of a radar device in another application example of the present invention. 1 is an antenna, 2 is a receiver, 3 is a range gate, 4 is a Doppler filter, 5 is a target detection circuit, 6 is an SLB, 7 is a blanking circuit, 8 is a blanking range calculation circuit, 9 is a blanking range table, 10 is a table selection circuit, 1
1 is a blanking determination circuit. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) In the radar device, an SLB (Side-lobe Blanker), a blanking range calculation means for calculating a blanking range from the altitude, speed, dive angle, roll angle, etc. of the aircraft, and an output of the blanking range calculation means SL above according to
A radar device comprising: a blanking circuit that performs blanking of B output.