JPH0336322B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an array antenna with improved response characteristics to high frequency pulse signals.

Generally, as shown in Fig. 1, a series-fed array antenna consists of one feeding point 1 and a series of radiating elements E1 to EN (N is 50 to 100) arranged in series to absorb residual power. Consisting of a terminator 2,
By appropriately setting the amplitude and phase of each radiating element, the high frequency signal input from the signal source 3 is distributed and radiated to achieve desired directivity. This type of array antenna has the advantage that the array feed line can be configured simply, and is therefore widely used as a radar antenna.

On the other hand, in order to increase the angular resolution in a pulse radar, it is necessary to narrow the beam width by increasing the aperture of the antenna, and to increase the distance resolution, it is necessary to narrow the transmission and reception pulse width.
However, in a radar with a narrow beam width and narrow pulse width using a series-fed array antenna shown in Figure 1, it takes a certain amount of time for the pulse signal to propagate within the antenna. There may be cases where a desired high frequency power distribution cannot be obtained. This is equivalent to using only a portion of the antenna aperture, so high-frequency CW (continuous wave)
Compared to the case where signals are transmitted and received, directivity deteriorates, such as a decrease in gain, an increase in beam width, and an increase in side lobes. For example, in an antenna with a cosine aperture amplitude distribution, the relationship between the pulse width T _S required to suppress the drop in gain to within 0.3 dB and the radio wave propagation time T _A in the antenna is given by MISkolnik
According to the author's book “RADAR HANDBOOK” pages 13-23, it is expressed by the formula (1).

T _A /T _S <0.2 ...(1) In other words, in the case of a series-fed array antenna,
Since the radio wave propagation time T _A within the antenna increases approximately in proportion to the size of the antenna aperture, the pulse width T _S must also be wide enough to satisfy the relationship in equation (1).

As explained above, when a conventional series-fed array antenna is used in a radar, there is a drawback that there is a certain limit to improving both the angular resolution and the distance resolution.

An object of the present invention is to provide an array antenna with improved response characteristics to high-frequency pulse signals by dividing a conventional array antenna into a plurality of parts and shortening the radio wave propagation time within the array antenna.

The configuration of the present invention is that, in an array antenna for a pulse radar that is fed with a high-frequency pulse signal, a radiating section in which a plurality of radiating elements directed in the same direction are arranged in series is divided into a plurality of parts, and the divided radiation is a plurality of sub-array antennas, each of which has a feeding section, and the feeding points and terminal ends of these feeding sections are arranged in substantially the same direction; a high-frequency pulse signal is fed in parallel to each feeding section of these sub-array antennas; a distributor; a plurality of feed lines respectively connecting the divider and the feed points of each of the sub-array antennas; adjacent feed points and terminations of each of the feed sections included in these feed lines or the distributor; and a phase shift means for setting the phase difference of the high-frequency pulse signal supplied between the two and the two to approximately 2nπ radians (n is an integer).

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 2 is a schematic diagram illustrating the first embodiment of the present invention. In this embodiment, an array antenna of length L (L is an arbitrary length) is connected to a first series-fed sub-array antenna (hereinafter referred to as sub-array antenna) 4 of length L1 and a second series-fed sub-array antenna (hereinafter referred to as sub-array antenna) 4 of length L2. The sub array antenna 5 is divided into two sub array antennas 4 and 5.
Terminators 6 and 7 are provided at the ends of the signal source 11, and the high-frequency signal from the signal source 11 is divided into two parts by a divider 8, and power is fed to the sub array antennas 4 and 5 via feed lines 9 and 10 in the same phase. be.

FIGS. 3a and 3b show phase distribution diagrams within the series-fed array antennas of the conventional and the present embodiment, each expressed as a relative phase with respect to the phase of the feeding point of each array antenna. In the case of a conventional array antenna of length L, the phase distribution within the array antenna increases continuously as shown in Figure 3a, whereas in this embodiment, which is divided into two sub-array antennas, In this case, as shown in FIG. 3b, a discontinuity with a phase difference φ occurs at the boundary between the sub array antennas 4 and 5, and the directivity deteriorates. However, this phase difference φ
φ=2nπ (radians) (n=0, 1, 2, 3,...
...) ...(2) If so, the phase at the boundary between the sub array antennas 4 and 5 will be continuous, and no deterioration of directivity will occur. Therefore, in this embodiment, means for setting a phase difference between the sub array antennas 4 and 5 is required so as to satisfy the condition of equation (2).

By dividing the array antenna into two in this way and inputting the divided high-frequency signals into each of the sub-array antennas 4 and 5 in the same phase, the radio wave propagation time within the array antenna is approximately Since it can be shortened by half, there is no possibility of directivity deterioration.

FIG. 4 is a configuration diagram illustrating a specific example of FIG. 2. In this embodiment, the feed line 9 in FIG.
Phase shifters 15 and 16 are inserted into phase shifter 10, and the amount of phase shift of phase shifters 15 and 16 is set so as to satisfy the condition of equation (2). Therefore, in the embodiment, the lengths L1 and L2 of the sub array antennas 4 and 5 can be set arbitrarily. In this embodiment, instead of providing the phase shifters 15 and 16, the lengths of the feed lines 9 and 10 may be changed.
(2) can be satisfied, and the phase shifter 1
Even if one of 5 and 16 is removed, the condition of equation (2) can be satisfied in the same way.

FIG. 5 is a block diagram of a second embodiment of the present invention, in which a series-fed array antenna is divided into three sub-array antennas 17, 18, and 19. Each of these sub-array antennas 17, 18, 19 is provided with a terminator 20, 21, 22, and the signal source 1
The high frequency signal from 1 is divided into three parts by a distributor 23, and is fed to each of the sub array antennas 17, 18, 19 via feed lines 24, 25, 26 in the same phase. In this case as well, the sub array antennas 17, 18,
Since the length of each of the sub array antennas 17, 18, and 19 is determined, the radio wave propagation time within the array antenna can be shortened without deteriorating the directivity due to phase discontinuity at the boundaries of the sub array antennas 17, 18, and 19. The propagation time in this case is approximately 1/3 compared to the configuration using one array antenna.

FIG. 6 is a block diagram of a third embodiment of the present invention, in which phase shifters 27, 28, and 29 are provided in the feed lines 24, 25, and 26 of the second embodiment. In this case as well, the phase shifters 27, 28,
By setting the phase shift amount of 29, each length of the sub array antennas 17, 18, and 19 can be set arbitrarily. Further, as in the second embodiment, a phase shifter 27,
28, 29 instead of providing feed lines 24, 25,
Even if the length of 26 is changed, the phase shifters 27, 28,
Even if any one of 29 is omitted, the conditions of formula 2 can be satisfied in the same way.

Above, in each embodiment, the case of two or three sub-array antennas has been explained, but even when the number of sub-array antennas is further increased, the radio wave propagation time within the array antenna is similarly reduced by the number of sub-array antennas. Therefore, the response characteristics to high frequency pulse signals can be improved.

As explained above, the present invention shortens the radio wave propagation time within the array antenna by distributing high-frequency signals in parallel to each of the feeding sections of a series-fed array antenna in which the feeding section is divided into a plurality of sections. , the response characteristics to high-frequency pulse signals are significantly improved, and both the angular resolution and distance resolution, which are the basic performance of radar, can be improved.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing the configuration of a conventional series-fed array antenna, FIG. 2 is a schematic diagram explaining the first embodiment of the present invention, and FIGS. FIG. 4 is a diagram of the phase distribution within the feed type array antenna, FIG. 4 is a configuration diagram explaining the specific example of FIG. 2 of the present invention, FIG. FIG. 3 is a configuration diagram of a third embodiment of the invention. In the figure, 1... Feeding point of array antenna, 2, 6, 7,
20, 21, 22... Terminator, 3, 11... Transmission source, E1, E2, E3,..., EN... N radiating element rows, 4, 5, 17, 18, 19... Series feeding type sub-array antenna, 8, 23...distributor,
9, 10, 24, 25, 26... feed line, 1
5, 16, 27, 28, 29...phase shifters.

Claims (1)

[Claims] 1 In a pulse radar array antenna to which a high-frequency pulse signal is fed; a radiating section in which a plurality of radiating elements directed in the same direction are arranged in series is divided into a plurality of sections, and a feeding section is connected to each of these divided radiating sections. a plurality of sub-array antennas in which the feed points and terminal ends of each of these feed sections are arranged in substantially the same direction; a distributor that feeds high-frequency pulse signals in parallel to each of the feed sections of these sub-array antennas; a plurality of feed lines each connecting between the antenna and the feed point of each of the sub-array antennas;
Phase shifting means included in each of these feed lines or distributors and setting the phase difference of the high frequency pulse signals fed between adjacent feed points and terminations of each of the feed sections to approximately 2nπ radians (n is an integer); An array antenna comprising: