JPH083053Y2 - Array antenna - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to an array antenna, and more particularly to improvement of an array antenna using a directional coupler in a feeding circuit.

(Prior Art) Conventionally, array antennas have been widely used in radar devices because they are excellent in terms of high gain, low sidelobe, and the like. In the array antenna, it is important to reduce the phase error of the excitation power to the radiating element to reduce the side lobe.

FIGS. 3 (a) and 3 (b) show configuration diagrams of this type of array antenna for an example using four radiating elements and a series feeding circuit.

In the array antenna shown in FIG. 3 (a), the power input from the power feeding unit 1 is distributed by the directional couplers 2a to 2d,
Electric power is supplied to the corresponding radiating elements 6a to 6d. Here, the delay lines 4a to 4c are inserted to compensate for the time difference until the power supplied from the power feeding unit 1 reaches each of the radiating elements 6a to 6d, and to make the excitation phases of the radiating elements 6a to 6d in phase. 3a to 3e are terminators.

In the array antenna having such a configuration, the directional couplers 2a to
The output terminal on the coupling side of 2d is connected to the radiating elements 6a to 6d, and the error of the excitation phase in the used frequency band can be ignored. On the other hand, power loss occurs because the power supply line is terminated. This power loss usually has a value of about 0.1 dB to 0.3 dB.

The array antenna shown in FIG. 3 (b) has a configuration in which the directional coupler 2d in FIG. 3 (a) is deleted and the main line of the final stage directional coupler 2c is connected to the radiating element 6d. ing. With this configuration, the above-mentioned power loss does not occur. However, since the main line and the coupling side line of the directional coupler 2c are connected to the radiating elements 6c and 6d, the frequency characteristic of the excitation phase of the radiating element has a phase error 7b as shown in FIG. This is because the relative phase between the main line of the directional coupler and the line on the coupling side generally has a phase difference of approximately 90 degrees in the used frequency band. In FIG. 4, 8b shows the phase characteristic of the radiating element 6d, and 9b shows the phase characteristic of the radiating elements 6a-6c.

(Problems to be Solved by the Invention) Since the above-described conventional array antenna has a structure in which the feed line is terminated, there is a drawback that power loss occurs. Further, in order to eliminate this power loss, if a structure in which a radiating element is attached to the terminal portion is adopted, there is a drawback that an error occurs in the antenna aperture phase due to the frequency characteristic of the directional coupler and the side lobe of the antenna is increased.

(Means for Solving the Problems) An array antenna according to the present invention includes first to (n-1) th directional couplers (n is an integer of 2 or more) connected in series, and the first antenna. To 1st to (n-1) th radiating elements that respectively receive the outputs of the coupling side lines of the (n-1) th directional couplers via the 1st to (n-1) th delay lines, An n-th radiating element that receives an output of the output-side main line in the (n-1) th directional coupler,
In the array antenna receiving the radiation power of the feeding circuit in the input side main line of the directional coupler, the n-th radiating element is connected to the (n-th) via a phase shifter.
Receiving the output of the output side main line of the directional coupler of 1),
The phase frequency characteristic of the phase shifter is substantially the same as the phase frequency characteristic of the coupling line in the (n-1) th directional coupler with respect to the main line. )
Each delay time in the delay line is selected such that the output of the feeding circuit feeds the first to n-th radiating elements in the same phase.

(Example) Next, this invention is demonstrated with reference to drawings.

FIG. 1 shows an embodiment of an array antenna according to the present invention,
FIG. 3 is a diagram showing a four-element array antenna, which is a feeding circuit including a feeding unit 1, directional couplers 2a to 2c, terminators 3a to 3c, delay lines 4a to 4c, and phase shifter 5 and radiating elements 6a to 6d.
Composed of.

The electric power input from the power feeding unit 1 is directional couplers 2a to 2c.
Are distributed by the phase shifter 5 or the delay lines 4a to 4c.
Power is supplied to the radiating elements 6a to 6d through the radiating elements. Here, the phase shifter 5 is set to a phase shift characteristic similar to the phase characteristic of the coupling side line of the directional coupler 2c with respect to the main line side. The delay lines 4a to 4c are set to have the same length as the length of the power feeding line between the power feeding unit 1 and the radiating element 6d.

FIG. 2 shows the aperture phase characteristics of the array antenna having such a configuration.

As is apparent from FIG. 2, the phase characteristic of the radiating element 6d approaches that of the other radiating elements 6a to 6c, and the phase error 7a
Is smaller than the phase error 7b in FIG. 4 when the phase shifter 5 is not provided. In the figure, 8a indicates the phase characteristic of the radiating element 6d, and 9a indicates the phase characteristic of the radiating elements 6a to 6c.

(Effect of the Invention) As described above, the present invention can reduce the aperture phase error of the array antenna and suppress the rise of the antenna side lobe by providing the phase shifter on the main line side of the directional coupler. effective.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an array antenna according to the present invention, FIG. 2 is a diagram showing aperture phase characteristics of the array antenna shown in FIG. 1, and FIGS. 3 (a) and 3 (b) are conventional ones. FIG. 4 is a configuration diagram of the array antenna, and FIG. 4 is a diagram showing aperture phase characteristics of the array antenna shown in FIG. 1 ... Feeder, 2a-2d ... Directional coupler, 3a-3d ... Terminator, 4a-4c ... Delay line, 5 ... Phase shifter, 6a ...
6d ... Radiating element, 7a, 7b ... Phase error, 8a, 8b ... Phase characteristic of radiating element 6d, 9a, 9d ... Phase characteristic of radiating elements 6a-6c.

Claims (1)

[Scope of utility model registration request] 1. First to (n-1) th directional couplers (n is an integer of 2 or more) connected in series, and the first
To 1st to (n-1) th radiating elements that respectively receive the outputs of the coupling side lines of the (n-1) th directional couplers via the 1st to (n-1) th delay lines, The above (n-
1) An n-th radiating element that receives an output of an output side main line in the directional coupler, and an input side main line of the first directional coupler that receives the radiation power of the feeding circuit In the above, the n-th radiating element is connected to the (n-th) via a phase shifter.
Receiving the output of the output side main line of the directional coupler of 1),
The phase frequency characteristic of the phase shifter is substantially the same as the phase frequency characteristic of the coupling line in the (n-1) th directional coupler with respect to the main line. )
The array antenna is characterized in that each delay time in the delay line is selected to a value at which the output of the feeding circuit is fed to the first to n-th radiating elements in the same phase.