JP2001102847A - Antenna device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antenna device of high system gain at low cost by simplifying the configuration. SOLUTION: An antenna 3 is spatially moved by a drive part 5 and signals received at respective positions are applied to a composite aperture processing part 6. In this composite aperture processing part 6, components in a desired direction are calculated by multiplying the respective received signals provided at respective receiving points by a weighing coefficient, and by adding these components, a synthetic aperture beam is formed in the relevant direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an antenna device used for, for example, a radar device.

[0002]

2. Description of the Related Art In a search radar, a tracking radar, and the like, in order to target a small target or a target at a long distance, it is necessary to increase the system gain to increase the gain of the received echo. For this reason, in general, a technique such as using a reflector as shown in FIG. 9A or using an array antenna as shown in FIG. 9B is employed.

However, in the above method, the smaller the intensity of the received echo, the larger the size of the reflector and the array antenna must be. As the size of the reflector increases, its mass also increases, and it is necessary to cover it with a large radome to avoid wind pressure. For this reason, the impact on the facility is increased, and it is inevitably disadvantageous in terms of operation and cost. In addition, when the size of the array antenna becomes large, the number of phase shifters and transmission / reception modules increases, which also causes problems such as an increase in weight and cost.

[0004]

As described above, in the conventional antenna apparatus, the antenna aperture is increased by increasing the size of the reflector and the array antenna, so that the reception gain is obtained. For this reason, there have been various adverse effects such as an impact on the equipment side, an increase in weight, and an increase in cost due to the enlargement of the equipment.

[0005] The present invention has been made in view of the above circumstances,
An object of the present invention is to provide an antenna device having a high system gain at a low cost with a simple configuration.

[0006]

In order to achieve the above object, the present invention provides an antenna unit for receiving an incoming radio wave, a moving unit for moving the antenna unit to a different position, and a moving unit for the antenna unit. And a synthetic aperture forming means for multiplying each received signal by a weighting coefficient to calculate a desired direction component of the received signal, and combining the multiplied signals to form a received beam in a desired direction. I do.

In this way, the desired direction components of the received signal obtained at each position of the moving antenna unit are calculated, and the components are combined to form a reception beam in the desired direction. As a result, an antenna aperture corresponding to the space area in which the antenna section is moved is formed, and it is possible to obtain performance that is apparently equivalent to that of a large aperture antenna. As a result, a large receiving gain can be obtained with a small and lightweight antenna, and an antenna device with a high system gain can be realized. In addition, since the resolution of the antenna beam can be increased, the effect can be exerted when searching for and tracking a long-distance target or a small target.

[0008]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of a radar device to which an antenna device according to an embodiment of the present invention is applied. This radar device emits the radar transmission signal generated by the transmission unit 1 from the antenna unit 3 to the space via the circulator 2, and
The arriving radar echo is received by the antenna unit 3 and guided to the receiving unit 4 via the circulator 2. The antenna unit 3 is attached to a driving unit 5, and the driving unit 5 moves the position of the antenna unit 3.

As a method of moving the antenna unit 3 by the driving unit 5, the antenna unit 3 may be rotated around a predetermined position as shown in FIG. 2A, or may be moved linearly as shown in FIG. 2B. You may make it do. In addition, you may make it move along an arbitrary route.

The received signal transmitted from the receiving section 4 is supplied to a synthetic aperture processing section 6. The synthetic aperture processing unit 6 calculates a component in a desired direction by multiplying a received signal obtained at each reception point by a weighting coefficient, and forms a synthetic aperture beam in the direction by adding the components. It is.

It is needless to say that the present invention can be used as an antenna device having only a receiving function except for the transmitting section 1 and the circulator 2 from the above configuration.

Next, the operation of the above configuration will be described with reference to FIGS. FIG. 3 is a diagram showing a state of formation of a synthetic aperture beam when the antenna unit 3 is rotationally moved along a circular path. X ₁ , X ₂ ,..., X _M , and X _N indicate reception at each position. Indicates a signal.

When a synthetic aperture process is performed based on each received signal X _i (i = 1, 2,..., N), a synthetic aperture beam output B _i
Can be represented by the following equation.

[0014]

(Equation 1)

Here, _Wi is a complex weight for forming a synthetic aperture beam in a desired direction, and is a function of position. According to the above equation, it can be seen that a higher beam output can be obtained as the number of reception points is increased and M is increased.
The processing time required to form one synthetic aperture (that is, the observation time) increases. For this reason, the target moves within the time required for processing, and the accuracy in the distance direction deteriorates depending on the moving speed. Therefore, it is necessary to calculate the optimum value of M based on the desired angular resolution and distance accuracy. .

Now, in order to obtain a desired angular resolution by the synthetic aperture processing when the antenna unit 3 is rotated and moved, it is necessary to set each parameter as follows.
First, there is a relationship expressed by the following equation between the angular resolution θ _B and a desired aperture length L.

[0017]

(Equation 2)

Here, K is a constant determined by the side lobe level of the antenna section 3. On the other hand, when the synthetic aperture processing is performed with the rotation angular velocity ω and the observation time T as shown in FIG. 3B, the following relationship exists between the desired aperture length L and the rotation radius R.

[0019]

(Equation 3)

By substituting equation (1) into equation (2), the following equation (3) is obtained.

[0021]

(Equation 4)

From equation (3), it can be seen that the relationship between the desired angular resolution θ _B and the observation time T has been obtained. Therefore, the reception points M and observation time T because of the proportional relationship, it is possible to obtain the optimum value of M by the desired angular resolution theta _B.

Considering the distance accuracy due to the movement of the target, if the accuracy of the distance is required to be ± ΔR [m] or less, the target speed is assumed to be V [m / s].

[0024]

(Equation 5)

The following equation can be established. Since the relationship between the observation time T and the distance accuracy ΔR is obtained from Expression (4), the optimum value of M can be obtained from the distance accuracy.

By the way, the relationship between the distance accuracy ΔR and the desired angular resolution theta _B is the formula (4) is substituted into equation (3) can be obtained as the following equation (5). Therefore, to calculate the optimum value of M and a desired angular resolution theta _B and the distance accuracy [Delta] R.

[0027]

(Equation 6)

As described above, the antenna unit 3 is rotated,
By performing the synthetic aperture processing based on the signals received over a certain angle range, it is possible to obtain the same effect as increasing the apparent aperture of the antenna in a desired direction. That is, by multiplying each received signal by a weighting coefficient corresponding to the angle between the desired measurement direction and the antenna directivity direction and then combining the signals, the components of the element beams in the measurement direction are combined, and the components are sharp in this measurement direction. A synthetic aperture beam having a peak can be obtained. Thereby, even if the antenna section 3 itself is small and lightweight, it is possible to obtain a system gain in a desired direction.

Next, consider the case where the antenna unit 3 is moved along an arbitrary route including a straight line. FIG. 4 is a diagram showing how a synthetic aperture beam is formed when the antenna unit 3 is periodically moved along a straight path.

In this case, the required angular resolution θB is
Like (1),

[0031]

(Equation 7)

## EQU1 ##

By the way, the antenna 3 along the straight path
Is moved at the moving speed _VL , the following equation (7) is obtained.

[0034]

(Equation 8)

The relationship between the desired angular resolution θ _B and the observation time T at this time is obtained by substituting equation (7) into equation (6).

[0036]

(Equation 9)

## EQU3 ##

[0038] That is, in order to generally obtain a desired angular resolution theta _B it is seen that it is necessary to determine the moving synthetic aperture length L as shown in equation (7). Since the relationship between the previously described distance accuracy ΔR and the observation time T is as (4), the distance is the relationship between the accuracy ΔR and angular resolution theta _B (4)
Substituting the equation into equation (8),

[0039]

(Equation 10)

## EQU4 ## Therefore, to calculate the optimum value of M from the angular resolution theta _B and the distance accuracy [Delta] R.

As described above, in the present embodiment, the antenna unit 3
Are spatially moved by the drive unit 5 and the received signals received at the respective positions are given to the synthetic aperture processing unit 6.
The synthetic aperture processing unit 6 calculates a component in a desired direction by multiplying a received signal obtained at each reception point by a weighting coefficient, and adds the components to form a synthetic aperture beam in the direction. I have to.

With this configuration, a synthetic aperture beam having a sharp peak in a desired direction can be formed. As a result, a system gain in a desired direction can be obtained even if the antenna unit 3 is small and lightweight. Becomes

According to this embodiment, since the antenna section 3 is moved spatially, a cooling effect by air can be naturally obtained. In other words, a conventional large array antenna requires a cooling blower to use large power. On the other hand, according to the present embodiment, the power consumption itself of the antenna unit 3 can be reduced, and a dedicated cooling due to the air cooling effect is achieved. There is no need to provide equipment. Thus, the configuration can be simplified, energy can be saved, and the cost can be reduced.

Furthermore, since the size of the antenna section 3 can be reduced, the influence of the wind pressure can be reduced, thereby eliminating the need for a radome. This also contributes to simplification of the configuration and space saving.

The present invention is not limited to the above embodiment. For example, various configurations can be considered as the configuration of the antenna unit 3. For example, as shown in FIG. 5, the antenna section 3 may be an array antenna in which a plurality of antenna elements are arranged. In particular, by combining with a phased array antenna, three-dimensional search and tracking can be performed, which is more effective. As shown in FIG. 6, the antenna unit 3 may further include a plurality of receiving antennas to receive radio waves having different wavelengths, or to receive different polarized waves as shown in FIG. good. Further, by turning the antenna aperture in three different directions as shown in FIG. 8 and rotating it, the rate of acquired data is tripled. For this reason, the efficiency of data acquisition can be significantly improved.

In addition, various modifications can be made without departing from the spirit of the present invention.

[0047]

As described above in detail, according to the present invention, the antenna section is moved spatially, and the received signals at the respective positions are multiplied by the respective weighting coefficients and then synthesized to form a synthetic aperture beam in a desired direction. Since the antenna device is formed, an antenna device having a high system gain can be provided with a simple configuration at a low cost.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of a radar device to which an antenna device according to an embodiment of the present invention is applied.

FIG. 2 is a diagram showing an example of how to move an antenna unit 3;

FIG. 3 is a diagram showing a state of forming a synthetic aperture beam when the antenna unit 3 is rotationally moved along a circular path.

FIG. 4 is a diagram showing a state of formation of a synthetic aperture beam when the antenna unit 3 is periodically moved along a linear path.

FIG. 5 is a schematic diagram showing another configuration of the antenna device according to the present invention.

FIG. 6 is a schematic diagram showing another configuration of the antenna device according to the present invention.

FIG. 7 is a schematic diagram showing another configuration of the antenna device according to the present invention.

FIG. 8 is a schematic diagram showing another configuration of the antenna device according to the present invention.

FIG. 9 is a schematic diagram showing a configuration of a conventional antenna device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Transmission part 2 ... Circulator 3 ... Antenna part 4 ... Reception part 5 ... Drive part 6 ... Synthetic aperture processing part

Claims (10)

[Claims] 1. An antenna unit for receiving an incoming radio wave, a moving unit for moving the antenna unit to a different position, and each receiving signal for calculating a desired directional component of the receiving signal obtained at each of the different positions. An antenna apparatus comprising: a synthetic aperture forming means for multiplying each of the weighting coefficients and synthesizing the multiplied signals to form a reception beam in a desired direction. 2. The antenna device according to claim 1, wherein said moving means rotates the antenna section around a predetermined rotation axis. 3. When the radius of rotation of the antenna section around the rotation axis is R, θ _B = K · λ / (2R · sin (ωT / 2)) where K is determined by the side lobe level. 3. The antenna device according to claim 2, wherein a constant λ: wavelength [m] θ _B : angular resolution (beam width) [rad] ω: angular velocity [rad / s] T: observation time [s]. 4. When the radius of rotation of the antenna section around the rotation axis is R, θ _B ≧ K · λ / (2R · sin (ω · ΔR / V)) where K: side lobe level Λ: wavelength [m] θ _B : angular resolution (beam width) [rad] ω: angular velocity [rad / s] ± ΔR: distance accuracy [m] V: target velocity [m / s] The antenna device according to claim 2, wherein: 5. The antenna device according to claim 1, wherein the moving means moves the antenna section along a straight path. 6. The moving synthetic aperture distance of the antenna unit is L.
Θ _B = K · (λ / L) where K: a constant determined by the side lobe level, λ: wavelength [m] θ _B : angular resolution (beam width) [rad] Item 6. The antenna device according to item 5. 7. The antenna device according to claim 1, wherein the antenna unit is an array antenna in which a plurality of antenna elements are arranged. 8. The antenna device according to claim 1, wherein the antenna unit includes a plurality of receiving antennas for independently receiving radio waves. 9. The antenna device according to claim 8, wherein the plurality of receiving antennas receive radio waves having different frequencies from each other. 10. The antenna device according to claim 8, wherein the plurality of receiving antennas receive radio waves having different polarizations.