JPH0378594B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a ground ranging radar mounted on an aircraft or the like to measure the distance to the ground, and particularly to improving the accuracy thereof.

[Conventional technology]

Figure 3 is a diagram showing the configuration blocks of a conventional ground ranging radar. In the figure, 1 is a phased array antenna, 2 is an excitation/receiver, 3 is a beam controller, 4 is a navigation sensor, and 5 is a diver. The angle input section 6 is a signal processor. Further, 10 in the signal processor 6 is a beam data calculation unit, which calculates the phased array antenna 1 based on the attitude angle data from the navigation sensor 4 and the ranging dive angle data set from the dive angle input unit 5. Beam directivity angle data is calculated and sent to the beam controller 3.

A conventional ground ranging radar is configured as described above. For example, the transmitted wave from the excitation/receiver 2 is irradiated to the ground or sea surface in the ranging direction via the phased array antenna 1, and the reflected wave is reflected from the phased array antenna 1. The monopulse sum pattern and difference pattern are obtained as received signals through an aided array antenna, and further excitation and
After being converted into a digital signal by the receiver 2, the signal processor 6 detects the distance of the null point of the difference pattern from the two digital signals to determine that the null point of the difference pattern is oriented in the ranging direction. Ground distance measurement is achieved using .

Here, we will discuss the fourth example of operation of ground ranging radar.
Supplement with figures. In FIG. 4, 20 is a ground ranging radar, 21 is an aircraft, 22 is the ground or sea surface, 23 is a difference pattern of the phased array antenna 1, 24 is a ranging axis, 25 is a horizontal axis, and 26 is a phased door. mechanical boresight axis of ray antenna 1;
27 is a distance measurement dive angle, and 28 is a distance measurement angle. In this case, in the signal processor 6, the digital signal corresponding to the sum/difference pattern of the phased array antenna is stored in the range memory, and the two reception data stored in this range memory are combined (differenced) in the calculation unit. Phase detection of pattern data using sum pattern data)
Then, find range bins that change from positive to negative, find the distance to the zero point, that is, the null point of the difference pattern 23 by linear approximation, etc. from these range bin data, and confirm that the null point angle of the difference pattern 23 matches the distance measurement angle 28. It is used to measure distance.

[Problem that the invention seeks to solve]

As mentioned above, in conventional ground ranging radar, the distance where the received signal of the phase-detected difference pattern is zero is set as the ranging point, so when the ranging dive angle is large and the altitude is low, As shown in FIG.
The number of range bins 30 in which a exists is two or less, and since the received signal 31b due to the side lobe and the received signal 31a due to the main beam are present in the same range bin 30, the distance between the zero point 33 and the null point 32 is shifted, There was a problem that the distance measurement accuracy was poor.

The present invention was made to solve these problems, and an object of the present invention is to obtain a ground ranging radar with good ranging accuracy.

[Means for solving problems]

In the ground ranging radar according to the present invention, the beam width of the phased array antenna 1 is widened under conditions where the ranging dive angle is large and the altitude is low, and the difference pattern 2 is
The number of range bins 30 in which reception signals 31a of the three main beams exist is increased.

[Effect]

In this invention, the range bin 3 in which the received signal 31a by the main beam of the difference pattern 23 exists under the conditions of a large ranging dive angle and a low altitude.
Since the number of zeros is increased and the received signals due to side lobes are separated from the range bin of the null point, accurate null point detection, that is, distance measurement, can be performed using these increased range bin data.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of the present invention, and numerals 1 to 5 in the figure are exactly the same as the conventional ground ranging radar described above. Reference numeral 6a denotes a signal processor, which differs from the conventional one in that a beam width correction value calculation 12 is added to the beam data calculation section 10a. In the beam width correction value calculation 12, the inertial sensor 4
The beam width correction value α is calculated from the altitude data, attitude angle data, and ranging dive angle data set by the dive angle input unit 5.

To give an example of the calculation method, if the beam width at a beam direction angle of 0 degrees is θ _BO , the beam direction angle is θ, and the distance dive angle is θ _D (assuming the ground or sea surface is horizontal), then the beam width is θ _B is θ _B ≒ θ _BO / cos θ・α [However, α is the beam width correction value, α = 1/(cos θ _D ) ⁿ or n is the altitude parameter, n ≥ 1], and the distance measurement dive angle is large. The beam width is also set to widen at low altitudes.

In the ground ranging radar configured as described above, the beam width is widened under conditions where the ranging dive angle is large and the altitude is low, so the number of range bins in which signals received by the main beam exist can be increased. The received signals due to side lobes can be separated from the range bin near the null point.

In this invention, FIG. 2 shows the received signal 31 of the phase-detected difference pattern when n=4 under the same operating conditions as in FIG. 5, but there is a received signal 31a due to the main beam of the difference pattern. range bin 30
Since the number has increased four times compared to the conventional one, the range bin 30 near the null point 32 is not affected by the received signal 31b due to the side lobe.
By averaging a plurality of data from these range bins 30, a zero point 33 that coincides with the null point 32 is obtained, making accurate distance measurement possible.

Let me explain why this is possible.

In other words, the condition that the number of data in the range bin 30 is small is that the distance is short and the ground reflection coefficient is large, and a sufficient signal-to-noise ratio is obtained.
On the other hand, the beam width of the phased array antenna 1 can be arbitrarily widened to some extent by changing the number of elements or the aperture phase.

Therefore, the beam width can be widened under conditions where the ranging dive angle is large and the altitude is low. The noise ratio has been adequately addressed.

Incidentally, in the above explanation, this invention was described in terms of a method using a monopulse type phased array antenna 1, but this invention switches the main beam of the sum pattern up and down with respect to the distance measurement point, and the received signals are Needless to say, the present invention can also be used when using a beam switching type phased array antenna in which a zero point is formed at a distance measurement point through processing.

〔Effect of the invention〕

As explained above, this invention has the effect that highly accurate ground processing data can be obtained and ranging accuracy can be improved by a simple method of widening the beam width under conditions where the ranging dive angle is large and the altitude is low. be.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing reception signals of the present invention, FIG. 3 is a block diagram showing a conventional ground ranging radar, and FIG. 4 is a block diagram showing a conventional ground ranging radar. A diagram showing an example of operation of a ground ranging radar,
FIG. 5 is a diagram showing received signals of a conventional ground ranging radar. In the figure, 1 is a phased array antenna;
2 is an excitation/receiver, 3 is a beam controller, 4 is a navigation sensor, 5 is a dive angle input section, 6, 6a is a signal processor, 10, 10a is a beam data calculation section, 11
is beam direction angle calculation, 20 is ground ranging radar, 2
1 is the aircraft, 22 is the ground or sea surface, 23 is the difference pattern, 24 is the ranging axis, 25 is the horizontal axis, 26 is the mechanical boresight axis, 27 is the ranging dive angle, 28 is the ranging angle, 30 is the reception Nos. 31a and 31b are received signals due to the main lobe and side lobes, 32
is a null point, and 33 is a zero point. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A phased array antenna that forms an entrance and exit for transmitted waves and received waves in space, an excitation/receiver that forms a source of transmitted waves and converts received waves into digital signals, and a phased array antenna that forms an entrance and exit for transmitted waves and received waves in space; A beam controller that controls the beam direction and shape of the phased array antenna, a navigation sensor that detects the attitude angle of the phased array antenna, a dive angle input unit that inputs the ranging dive angle, and a phased array antenna. The range memory for storing the digital signal reception waves corresponding to the sum and difference patterns and the range memory data of the stored sum and difference patterns are synthesized (phase detection of the difference pattern is performed using the sum pattern), and A signal processor consisting of an arithmetic unit for calculating the distance (range bin position that changes negatively from ), and the signal processor includes attitude angle data from the navigation sensor and distance measuring dive data from the dive angle input unit. Beam data for calculating beam correction values to widen the beam width of the phased array antenna in the vertical direction of the ranging dive angle based on the angle, at a low altitude and with a large ranging dive angle. A ground ranging radar characterized by comprising a calculation section.