JP2833985B2 - Shaped beam antenna - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shaped beam antenna, and more particularly to a millimeter wave antenna used indoors.

[0002]

2. Description of the Related Art Hitherto, as means for shaping a Kasekant square beam, there are a method using a horn antenna and a method using a waveguide slot array. It is difficult to use these antennas in the millimeter wave band due to the precision of the work. In terms of the precision of the work, a planar printed antenna that manufactures an antenna by etching is effective, but it has been said that it is difficult to realize it in view of the configuration of a feed circuit.
Further, in the case of the conventional waveguide slot array, since the power is supplied from the end of the array, the distance from the end to the end is long, and the structure has a large frequency characteristic.

[0003] Incidentally, these conventional antennas,
"Modified Kasekant square beam antenna using waveguide slot array", 1986 IEICE General Conference 612, "H-plane Kasekant Beamhorn Antenna Design by Ray-Theory", 1979, IEICE General Nationwide Tournament 557, "23GHz Hi-Vision / Shaped Beam Waveguide Slot Array Antenna for Terrestrial Broadcasting" 1
It is shown in the 989 Autumn National Conference of IEICE B-23.

[0004]

The excitation amplitude and phase for realizing the Kasekant square beam can be obtained by numerical simulation. However, the excitation phase of each element varies, and the excitation amplitude also varies for each element. There was a considerable level difference, and it was difficult to realize.

[0005] Further, by using a microstrip line,
In order to realize these phase / amplitude distributions, the phase is adjusted by the line length and the amplitude is adjusted by the line width, which is difficult in terms of accuracy and circuit space. In addition, when series power supply is considered, there is a problem that the frequency characteristics are large.

FIGS. 5 (A), 5 (B) and 5 (C) are diagrams for explaining this problem. In the case of an antenna composed of 28 elements, a cascade beam indicated by a solid line in FIG. (B) shows the excitation phase distribution of the wave source obtained by performing the Fourier transform in order to make, and (C) shows the excitation amplitude. (B)
As shown by, there is a variation in the excitation phase applied to each element in order to obtain a desired secondary beam.

An object of the present invention is to realize a shaped beam antenna having a Kasekant square beam characteristic by a microstrip array antenna having no phase shifter.

[0008]

According to the shaped beam antenna of the present invention, in a shaped beam antenna having Kasecant square beam characteristics, a plurality of array elements are linearly arranged.
Arrangement of arranging the elements at equal intervals symmetrically from the center
Means for arranging a signal supplied from the vicinity of the center to the left and right.
Feeding means for feeding power in series to a plurality of array elements
For multiple array elements arranged on the left and right,
The phase of each array element is the same, and each array element on the left
The phase of the element is opposite to that of each array element on the right.
Means for giving a phase distribution so as to be qualitatively the same . Further, the present invention is characterized in that power is supplied in series from the center of the array to both ends, and a common divider is used in many cases to attenuate the excitation amplitude of each element at a constant rate. A desired shaped beam antenna is obtained.

In the present invention, as a result of performing a simulation for obtaining an excitation phase by performing a Fourier transform on the directivity function to obtain a desired Kasecant beam, the excitation phase is changed when the peak of the Kasekant square beam is appropriately tilted. It can be seen that the left half and the right half take almost constant values.
This allows for a series feed from the center of the array.

FIGS. 2A, 2B and 2C are views for explaining the present invention, wherein FIG. 2A shows a cascant beam obtained by the present invention, and FIG. In FIG. 3, the peak is directed toward the front of the antenna, while the beam is slightly tilted, for example, 2.5 ° to the right. At this time, as shown in (B), the excitation phase distribution of the wave source has a substantially constant phase, and the sign is reversed. From this,
The phase distribution actually given to the radiating element can be realized by giving opposite signs to the left half and the right half and having the same phase. Looking at the amplitude distribution in (C), it can be seen that the amplitude is attenuated at a constant rate except for the two central elements. Since there is a level difference of 30 dB or more between the center element and the end element, it is difficult to realize this distribution by tournament power supply due to the accuracy of the line width in consideration of the distribution ratio. Therefore, considering series power supply from the center and tapering the second element from the center to the end element at the same ratio, many branch circuits can be made the same, and the circuit can be simplified. FIG. 3 shows an example of the characteristics of the Kasecant beam in that case. 5.0 dB for the second element from the center
The level was lowered, and thereafter the taper was tapered by 1.7 dB. The side lobe on the right side has not fallen cleanly, but there is no problem when used indoors.

[0011]

FIG. 1 shows an embodiment of the present invention.

In FIG. 1, a signal supplied from a power supply connector 1 is applied to a first branch 4 of a serial power supply line 3 via a microstrip line 2, where the signal is equally distributed. The series feed line 3 is provided with 14 branches A, B, and C on the left and right sides of the central symmetric line L, from which power is supplied to each radiating element 5. The first branch 4 is shifted to the right by a 1/6 wavelength with respect to the line of symmetry L of the feed line 3 by the wavelength on the line. As a result, the right half array has a phase of 1 with respect to the left half array.
It will advance by 20 °. Since the element interval is set to one wavelength on the line, the phases of the elements of the left and right arrays are the same. In addition, since the left and right arrays are symmetrical with respect to the symmetry line 1, the excitation direction of the antenna is also symmetric with respect to the symmetry line 1, and the phases are opposite. Therefore, the phase of each element of the left half array is relatively +30.
°, the phase of each element of the right half array is -30 °
(+ 30 ° + 60 ° × 2-180 °). Thus, a phase distribution as shown in FIG. 2B can be realized.

Next, the amplitude distribution will be described. Since the power supply circuit is symmetrical on the left and right, only the right half will be described.
After the first branch 4, in the first A branch 6, the energy ratio flowing to the main stream 7 and the branch stream 8 is 0.98: 1, and in the next B branch 9, the energy ratio flowing to the main stream 10 and the branch stream 11 is 1: 0. 48, and then continue the same branch as B branch 9,
As described above, the amplitude distribution close to that of FIG. 2C is realized by equal distribution in the rightmost C branch 12.
In the embodiment, the left and right halves have twelve B-branches, which can use the same distributor, thereby simplifying the power supply circuit. In the embodiment, the element interval is 0.7
3λ ₀ , and the directivity of the element is cos θ.

FIG. 4 is a diagram showing the structure of a radiating element used in the present invention, and uses a slot-coupled microstrip antenna. In the figure, it is composed of three layers: a layer 13 having a radiating element, a layer 14 having a slot, and a layer 15 having a feeding circuit. In this antenna structure, the radiating element and the feed circuit are separated by a ground conductor including a slot, so that unnecessary radiation from the feed circuit does not disturb the radiation pattern. There is an advantage that an adhesive film is laid between two Teflon (registered trademark) substrates and heat-sealed.

[0015]

As described above, the present invention eliminates the dispersion of the excitation phase of each element by appropriately tilting the beam when shaping the Kasekant square beam with the microstrip antenna, thereby reducing the length of the feed line. Phase adjustment due to

Further, since the left half and the right half of the array have the same phase, series power supply from the center becomes possible. For this reason, the shift in the maximum beam direction due to the frequency change can be reduced as compared with the case where power is supplied from the end of the array. In addition, since power can be supplied from the center, a left-right symmetric circuit can be formed by utilizing the left-right symmetry of the amplitude distribution.

Further, since power is supplied from the center having a large amplitude, power distribution can be performed without difficulty. If the attenuation of the amplitude is considered to be constant, many identical distributors can be used, and the power supply circuit can be simplified. Become.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing a current beam characteristic (A), an excitation phase distribution (B) of a wave source, and an excitation amplitude distribution (C) according to the present invention.

FIG. 3 is a diagram showing a radiation pattern when many branch circuits are shared by the present invention.

FIG. 4 is a diagram showing a structure of a radiation element used in the present invention.

FIG. 5 is a diagram showing the conventional beam characteristics (A),
The figure which shows the excitation phase distribution (B) and the excitation amplitude distribution (C) of a wave source.

Claims (2)

(57) [Claims] 1. A shaped beam antenna having Kasecant square beam characteristics, wherein a plurality of beams arranged at equal intervals on a straight line symmetrically from the center to the left and right.
An array element using the microstrip antenna, a signal supplied from the central portion and a power supply circuit for series feed to a plurality of array elements arranged in the left and right, the left half of the plurality of array elements, the right half Excitation phase
The Kasecant square so that the signs are almost the same and the signs are opposite
A shaped beam antenna characterized in that a beam peak is tilted . 2. The shaped beam antenna according to claim 1, wherein the excitation amplitude to each array element fed in series is attenuated at a fixed rate from the center.