JP2674380B2 - Radar equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radar device for forming a low sidelobe beam in real time.

[0002]

2. Description of the Related Art FIG. 5 shows the structure of a conventional digital beam forming (DBF) radar device. In FIG. 5, 1 is a plane element antenna for receiving radio waves, and 2 is a reception from this plane element antenna. A receiver for converting a microwave signal into a video signal, and 3 is a former for forming a beam by inputting a video signal output from the receiver and a beam pointing weight output from an ideal beam pointing weight memory,
Reference numeral 4 is a signal processor for processing the output from the beam former to determine the next beam pointing direction, and 5 is an ideal beam pointing holding a beam pointing weight for pointing the beam in the beam pointing direction from this signal processor. It is a wait memory.

In the case of forming a beam in this conventional DBF radar device, the signal u _i from the receiver is expressed by "Equation 3" by the beam pointing direction weight a _i and the theoretical weight T _i such as Taylor for pattern formation. The pattern is synthesized by performing a complex product sum operation based on The pattern synthesized in this way does not have a sufficiently low side lobe as the solid line pattern in FIGS.

[0004]

(Equation 3)

[0005]

In the conventional DBF radar device, the beam former 3 forms a reception beam by performing a complex product sum operation of the input signal and the beam pointing weight and the pattern formation theory weight. However, in the planar element antenna 1, there is a problem that the formed beam obtained by the above-described conventional method does not have a low sidelobe pattern due to mutual coupling between elements or the like.

The present invention has been made in order to solve such a problem, and forms a reception beam pattern of a low side lobe which is directed in a beam directing direction provided with a small memory amount and a small calculation amount in real time. The purpose is to do.

[0007]

A radar device according to the present invention includes a beam pointing weight memory for outputting a beam pointing direction weight designated by a signal processor and a theoretical null point direction (for example, a null point direction of Taylor distribution). , A pattern memory that holds the pattern measured in advance,
A weight calculator for calculating weights for low sidelobe patterns using these patterns by an arithmetic expression approximating the plane wave synthesis method is added to the radar device.

[0008]

The radar device according to the present invention reverses the null point direction so as to make a null point in the theoretical null point direction (for example, the null point direction of Taylor distribution) with respect to the beam pointing direction instructed by the signal processor. A pattern is created by combining the plane waves of the phases. By doing so, a low sidelobe pattern close to the theoretical low sidelobe pattern can be obtained even under the mutual coupling environment between elements. At this time, the pattern data E _x (θ _y ) measured in advance, which is coarser than the required beam pointing resolution Δθ _s , is held in the memory, and the interference between the synthetic waves for creating the null point is ignored. A low sidelobe pattern can be obtained in real time by approximating an arithmetic expression for obtaining the low sidelobe weight.

[0009]

【Example】

Embodiment 1 FIG. FIG. 1 shows an embodiment of the present invention, in which 1 to 4 are exactly the same as the conventional device. 6
Receives the beam pointing direction θ _s from the signal processor 4 and θ _s
Beam steering weights memory for outputting the weight A _si for beam pointing direction, the weights B _mi for beam pointing in the direction of the null point direction theta _m when (m = 1 to n) obtained by beam pointing in that direction Is. Reference numeral 7 denotes a pattern memory, which is a memory that holds a beam pattern E _x (θ _y ) measured in advance when the beam is directed in each direction. 8 is this A _si , B _mi , E _s (θ _s ), E _s
It is a weight calculator that calculates weights from (θ _m ) and E _m (θ _m ) by the approximate expression shown in “Equation 9” below.

The operation of the thus constructed radar apparatus will be described in detail. First, the plane wave synthesis method will be described as a general theory for forming a low sidelobe pattern. The beam pointing direction instructed from the signal processor 4 is θ _s , and the theoretical null point direction at this time is θ _m (m = 1 to n).
When plane waves are combined so as to create a null point in the theoretical null point direction θ _m , the sidelobe level also approaches the theoretical low sidelobe pattern. The formation patterns when the beam is directed in the θ _s and θ _m directions are E _s (θ) and E _m (θ). Assuming that complex weights for forming E _s (θ) and E _m (θ) are A _si and B _mi (i = 1 to N: the number of N elements),
The weight for forming a null point in the θ _m direction by directing the beam in the θ _s direction is a linear combination of A _si and B _mi.
Is represented by

[0011]

(Equation 4)

Here, α _m satisfies “Equation 5”.

[0013]

(Equation 5)

Here, E _s (θ _j ): a θ _j direction composite pattern when the beam is directed in the θ _s direction. Here, E _m (θ _j ): a θ _j direction composite pattern when the beam is directed in the θ _m direction. α _m : The amount of contribution in the θ _j direction when the beam is directed in the θ _m direction.

However, in order to obtain this α _m , an n-th order inverse matrix operation is required, and it is very difficult to secure real-time property. As the first method of the present invention, the above "Equation 5" is approximated to "Equation 6".

[0016]

(Equation 6)

This is because only E _m (θ _m ) is considered with respect to E _s (θ) in order to create a null point in the θ _m direction as shown in FIG. 3, and the null point is set in the θ = θ _m ′ direction. E _m (θ _m for making
The mutual contribution of ´) is neglected. Here, θ _m ′ is a theoretical null point direction other than the θ _m direction. The level difference Δm in the θ = θ _s and θ = θ _m directions thus approximated is represented by “Equation 7”.

[0018]

(Equation 7)

[Mathematical formula-see original document] When this is solved for α _m , "Equation 8" is obtained.

[0020]

(Equation 8)

In this way, the weight A _i for forming the low side lobe is obtained by "Equation 9".

[0022]

(Equation 9)

Embodiment 2 FIG. FIG. 2 shows another embodiment of the present invention, in which 1 to 4 are exactly the same as the conventional device. _{Reference numeral} 9 denotes a weight _Asi for directing the beam in the beam directing direction θ _s from the signal processor 4 and a null point direction θ _m (m = 1 to n) when the beam is directed in the direction.
This is a beam pointing weight memory that outputs a weight B _mi ′ for pointing a beam having a low far sidelobe level in the direction (1). Reference numeral 10 denotes a second pattern memory, which has a low main beam side pattern E _x (θ _y ) which has been measured in advance when the beam is directed in each direction and a far side lobe which has been measured in advance to be combined with the null point. It is a memory that holds the pattern R _x (θ _y ). 11 The _{A si, B mi ', E} s (θ s), E s (θ m), R m
It is a weight calculator that calculates weights from (θ _m ) using the approximate expression shown in “Equation 10” below.

Next, the operation of the radar device according to the second embodiment of the present invention will be described. Difference from the first embodiment in FIG. 1, a pattern to be combined with the direction of making the null point E _m (θ _m) (E
It is considered that (θ) is not a pattern based on Taylor distribution etc.) but a pattern having a low far sidelobe level as shown in FIG. 4 has a smaller main beam gain loss. The weight that gives such a pattern is B _mi
If the pattern is expressed as R _x (θ _y ), the weight A _i ′ to be obtained is expressed as “Equation 10”.

[0025]

(Equation 10)

[0026]

The present invention has the following effects by being configured as described above.

Even under the influence of mutual coupling between elements in the array antenna, a pattern memory that requires a comparatively small amount of memory and an approximate calculation of weights by using the pattern memory can realize a low side lobe in real time with a small hardware scale. Can be formed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a block diagram showing a second embodiment of the present invention.

FIG. 3 is a beam pattern diagram showing the concept of beam combining in the first embodiment of the present invention.

FIG. 4 is a beam pattern diagram showing the concept of beam combining in the second embodiment of the present invention.

FIG. 5 is a block diagram showing a conventional radar device.

[Explanation of symbols]

 1 planar element antenna 2 receiver 3 beam former 4 signal processor 5 ideal beam pointing weight memory 6 beam pointing weight memory 7 pattern memory 8 weight calculator 9 beam pointing weight memory 10 pattern memory 11 weight calculator

Claims (2)

(57) [Claims] 1. A planar element antenna for receiving radio waves, a receiver for converting a microwave signal received from the planar element antenna into a video signal, an output video signal of the receiver and a weight A based on the following equation. A beam forming weight input from a weight calculator for calculating _i , a beam forming device for beam forming, a signal processor for processing the output from the beam forming device to determine the next beam pointing direction, and this signal processing device A beam pointing weight memory for inputting a beam pointing direction θ _{s from the above,} and outputting a beam weight _Asi for beam pointing in that direction and a weight B _mi for beam pointing in the theoretical null point direction θ _m ; The pattern data E _s (θ _s ), E _s (θ _m ), E _m (θ
_m ) is provided and a pattern memory is provided. (Equation 1) 2. A plane element antenna for receiving radio waves, a receiver for converting a microwave signal received from the plane element antenna into a video signal, an output video signal of the receiver and a weight calculator based on the following equation. A beam former for inputting a beam forming weight from the beam former, a signal processor for processing the output from the beam former to determine the next beam pointing direction, and a beam pointing direction θ _s from this signal processor enter the directional weights B for directing the directional weights a _si and less far side lobes theoretically null point direction theta _m beam for directing the beam to that direction
_The beam pointing weight memory for outputting _mi ′ and the pattern data E _s (θ _s ), E _s (θ _m ) and the pattern data R _m (θ) having a low far side lobe are output to the weight calculator by the output of the beam pointing weight memory. _m ) is provided and a pattern memory is provided. (Equation 2)