JPH0367595B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention detects the Doppler frequency transition of a target using a transmitting/receiving antenna mounted on a missile to obtain approach speed information necessary for guiding the missile. This invention relates to an active radar guidance control system.

[Conventional technology]

The conventional active radar guidance control system will be explained below.

In Figure 3, 1 is a missile, 2 is a target aircraft, and 3 is the missile 1 for target tracking.
This is the transmitting/receiving antenna mounted on the. 4 and 5 are the velocity vectors M of missile 1 and target 2, respectively.
VT is shown, 6 is a line drawn from missile 1 in the direction of target 2 (called the line of sight), and 7 is a line fixed to the inertial coordinate system, translated in parallel to pass through the center of gravity of missile 1. , the angle σ formed by 6 and 7 above
is called the visual angle. 8 shows an example of a radio wave path in which radio waves radiated from the transmitting/receiving antenna 3 of the missile 1 are reflected on the ground or sea surface 9 and return through the same route.

Here, the angle between 4 and 6 in the figure is ψMT, and 5 and 6
The angle formed by ψTM is the angle formed by 4 and 8, that is,
Let ψM be the incident angle of the radio wave passing through the path 8 to the antenna 3.

Proportional navigation, which is the mainstream of current guided navigation for missiles, generates an acceleration of the magnitude aM=NeVcσ〓 (1) in the direction perpendicular to the missile axis in proportion to the rate of change σ〓 of the line of sight angle σ. This guides the missile and brings it to the target.
10 in FIG. 3 indicates this acceleration vector M.
Furthermore, Ne in equation (1) is called the effective navigation constant, and Vc is the approach speed between missile 1 and target 2.

FIG. 4 shows a block diagram of a typical mechanism mounted on the missile 1 shown in FIG. 3 to detect the above-mentioned σ and Vc. In the figure, 11 is the LO (local oscillator), and the oscillation frequency here is the transmission frequency 1 of the transmitted radio wave.
2 and MIX (mixer) 13, AFC
(Automatic frequency adjuster) IF (intermediate frequency) by 14
Tune in to 15. On the other hand, the reflected wave from the target received by the transmitting/receiving antenna 3 is mixed with the above LO11 output and MIX16 to become the IF17 signal.
IF15 and IF17 are mixed by MIX18 and DA
(Doppler amplifier) 19, and SG (speed gate) 2 to further improve the S/N ratio.
0 through which the approach speed signal Vc is obtained. on the other hand,
The transmitting/receiving antenna 3 is statically stabilized in an inertial coordinate system by mounting a gyro, etc., and when it is tracked by the antenna tracking device 21 with a first-order delay characteristic in the direction of the target 2, the boresight error (in the direction of the antenna center Since ε is approximately proportional to the rate of change σ〓 of the eye line angle σ, using σ〓 and Vc obtained from this, (1)
Determine the magnitude of aM in Eq. The missile 1 is guided by controlling the steering wing of the missile 1 based on the aM obtained from equation (1).

[Problem that the invention seeks to solve]

As described above, the conventional method detects the Doppler frequency transition of the reflected wave received by missile 1 from the transmitted wave to determine the approach speed between missile 1 and target 2. There is a problem that the target is subject to clutter failure. This will be explained below. FIGS. 5a and 5b show typical antenna envelopes of the transmitting and receiving antenna 3 as a transmitting antenna and a typical receiving antenna, respectively. Here, the vertical axis is antenna gain (DB),
The horizontal axis indicates the angle from the center of the antenna. 22 and 24 are called main lobes, 23 and 25
are called side lobes. The antenna envelope typically remains constant with respect to rotation around the central axis of the antenna, but may be partially deformed. While tracking target 2,
The transmitting/receiving antenna 3 is directed toward the target 2.

At this time, the transmitted wave is not only reflected by the target but also from all over the ground or sea surface 9, and this reflected wave is also received by the transmitting/receiving antenna 3. This is called Kuratsuta. Since clutter undergoes different Doppler frequency transitions depending on the path the radio waves take, this will be distributed over a certain band. This situation is shown in FIG. The figure shows the calculation of clutter power at one point in a missile guidance simulation, and the wavelength of the transmitted wave is 10GHz. The vertical axis is the clutter power (DBM), and the horizontal axis is the Doppler frequency transition (KHz). 26 is the cluster power, and the main lobe 24 (fifth) of the transmitting/receiving antenna 3
27 received by Figure b) is particularly called the main lobe clutter. 28 is the target signal level simultaneously received through the same main lobe 24. As can be seen from FIG. 6, when the clutter power is large, the target signal is buried in the clutter, making it impossible to detect Vc by the circuit of FIG. 4. In particular, if the target 2 is at a lower altitude than the missile 1, the transmitting/receiving antenna 3 of the missile 1 will be directed downward, and the clutter power will increase, making it impossible to track the target.

This invention was made to eliminate the problems of the conventional systems as described above, and aims to improve guidance accuracy by making it possible to track targets at low altitudes.

[Means for solving problems]

The active radar guidance control method according to the present invention includes a calculation means for calculating an incident angle of an antenna corresponding to a clutter path showing a frequency transition equal to a target Doppler frequency transition, and a control means for controlling an envelope of the antenna, The side lobe gain of the antenna corresponding to the above angle of incidence is reduced.

[Effect]

In this invention, by reducing the sidelobe gain of the antenna corresponding to the angle of incidence determined by the calculation means, the influence of clutter can be eliminated and the target Doppler frequency transition can be easily detected. become.

〔Example〕

The principle and one embodiment of this invention will be explained below.

In FIG. 3, the clutter frequency transition fdc reciprocating along the clutter path 8 and the frequency transition fdT of the target signal reciprocating along the path 6 are calculated as follows.

fdc=2/λVMCOSψM (2) fdT=1/λ(VMCOSψMT+VTCOSψTM) (3) From equations (2) and (3), ψM (incidence angle to antenna 3) at which fdc=fdT is determined by the following equation.

ψM=COS ^-1 (1/2COSψMT+1/2VT/VM COSψTM) (4) Therefore, if all values of VM, VT, ψMT, and ψTM are known, ψM that satisfies equation (4) can be found. The obtained value of ψM is plotted on the horizontal axis in Figure 5b, and the transmitting and receiving antenna envelopes are adaptively changed to reduce the sidelobes at the corresponding positions, thereby reducing the clutter power near the Doppler frequency transition of the target signal. If so, the target signal can be clearly detected as shown in FIG. For example, the following is known as an antenna envelope adaptive control method.

(1) Side rope canceller (2) Power−Inversion (Howell−Applebaum)
Method adaptive antenna (3) LMS (widrow) method adaptive antenna (4) Sample Matrix Inversion method adaptive antenna Theoretically, it is possible to use these methods to control the antenna so that it has the optimal envelope from moment to moment. However, it is difficult to implement it with a small device such as one mounted on a missile. However, in a roll-stabilized missile (a system that controls the missile so that it does not rotate around its axis), the part that points downward is limited, and in the present invention, it is necessary to suppress a part of the side lobe that points downward. , the purpose can be achieved, and it is relatively easy to carry out because it is sufficient to prepare several antenna envelope patterns in that case.

As mentioned above, to determine the value of ψM, VM,
The values of VT, ψMT, and ψTM must be known. Concerning this, there may be a method of observing everything from the missile 1, a method of using part of the information from the ground antenna, etc., but in one embodiment, a method of observing everything from the missile 1 will be described.

An embodiment of the present invention will be described below. In FIG. 1, numerals 29 and 30 are a rate gyro and an accelerometer mounted on the missile 1, respectively. M is determined by processing the angular velocity and acceleration around the axis of the missile obtained from this in the first arithmetic processing unit 31. On the other hand, transmitting and receiving antenna 3
The distance to the target can be determined by the radar distance meter 32, which detects the phase shift of the reflected wave of the transmitted wave toward the target, and when the antenna angle control system 21 performs antenna angle control, the direction of the target can be determined from the angle of the antenna. As I understand, these information and the above M
T, ψMT, ψTM are obtained by processing the information in the second arithmetic processing section 33 using, for example, a known Kalman filter, which are further processed by the third arithmetic processing section 34 (4). ) ψM is found by processing according to the equation. The desired objective can be achieved by operating the antenna envelope control mechanism 35 in accordance with the determined value of ψM and suppressing the sidelobe gain of the transmitting and receiving antenna 3. The first, second, and third arithmetic processing sections 31, 33, and 34 constitute the arithmetic means of the present application, and the antenna envelope control mechanism 35 constitutes the control means.

In the above example, the values of VM, VT, ψMT, and ψTM necessary for determining the value of ψM were all determined by the onboard equipment on the missile 1. This information may be detected and transmitted to the missile 1.

Furthermore, the above description has been made regarding a two-dimensional vertical plane model that includes the missile 1 and the target 2. General 3
In the dimensional model, the direction of ψM that satisfies equation (4) will draw an arc, but even in that case, a sufficient effect can be expected by reducing the sidelobes around the direction determined by the above model.

〔Effect of the invention〕

As described above, the active radar guidance control method according to the present invention includes a calculation means for determining the angle of incidence of the antenna corresponding to the clutter path showing a frequency transition that is equal to the target Doppler frequency transition, and a control means for controlling the envelope of the antenna. By reducing the sidelobe gain of the antenna corresponding to the above incident angle, the envelope of the transmitting and receiving antenna can be adaptively adjusted to control the clutter power having a frequency transition near the target Doppler frequency transition. Since it can be changed, it becomes possible to track even low-altitude targets, which has the effect of greatly improving guidance accuracy.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the main part of an embodiment of the present invention, FIG. 2 is a diagram showing the clutter power and target signal according to the above embodiment, and FIG. 3 is a diagram showing a typical communication between a missile and a target using this method. A schematic diagram showing the positional relationship, FIG. 4 is a block diagram showing an example of a detection mechanism for Vc and σ in the same method, FIGS. 5 a and b are diagrams showing antenna envelopes on the transmitting side and receiving side of the transmitting and receiving antenna, FIG. 6 is a diagram showing the clutter power and target signal according to the conventional method. 1... Missile, 2... Target, 3... Transmitting/receiving antenna, 8... Kuratsuta route, 9... Ground or sea surface, 3
1, 33, 34... Arithmetic processing unit (arithmetic means), 35
...Antenna envelope control mechanism (control means).
Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] 1 A transmitting/receiving antenna mounted on the missile emits radio waves toward a fast-moving target, receives the reflected waves, detects the target's Doppler frequency transition, and obtains information on the approach speed to the target necessary for guidance. In the activuda guidance control system that guides the missile to automatically track the target, the angle of incidence of the antenna corresponding to the clutter path that exhibits a frequency transition that is equal to the Doppler frequency transition of the target is determined. 1. An active radar guidance control method, comprising: a calculation means; and a control means for controlling an envelope of the antenna; the sidelobe gain of the antenna corresponding to the incident angle is reduced.