JPH0327121B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a dipole-connected folded antenna used as a circularly polarized antenna in the transmission and reception of satellite communications and satellite broadcasting.

[Prior Art and Its Disadvantages] Circularly polarized antennas have been used in radars for a long time, and have recently been rapidly used for communications with moving objects such as satellite communications.

Conventional circularly polarized antennas include cross dipole antennas, helical antennas, patch antennas with notches, and slot antennas.

Among these, the cross dipole antenna has two dipoles of equal length arranged at positions orthogonal to each other, and is the simplest element structure for obtaining circularly polarized waves, since it is easy to form an array. It has been used since ancient times. However, due to the operating principle of this cross dipole antenna, the current of each dipole must have equal amplitude and a phase difference of 90°, which requires a distributor and a transfer device, or requires a reactance connected in series to the feed section. The power supply system has become complicated due to loading and other factors.

[Objective of the Invention] The present invention was made in view of the above-mentioned circumstances, and its purpose is to generate circularly polarized waves using a simple feeding system that has radiation characteristics similar to a cross dipole antenna and does not require a distributor or transfer device. An object of the present invention is to provide a dipole connection type folded antenna that can realize an antenna.

[Summary of the Invention] The dipole-connected folded antenna according to the present invention includes a first dipole antenna and a second dipole antenna installed at a position spatially orthogonal to the first dipole antenna. is connected to one feed point of the second dipole antenna by a conductor that branches from the middle of one antenna element and is folded in parallel at narrow intervals, and is connected to one feed point of the second dipole antenna from the middle of the other antenna element of the first dipole antenna. The second dipole antenna is connected to the other feed point of the second dipole antenna by a conductor that is branched and folded in parallel at narrow intervals, and is fed from one feed point connected to the feed point of the first dipole antenna. This system distributes voltage with the necessary phase difference and amplitude to the two dipole antennas through conductors.

[Embodiments of the Invention] Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a dipole-connected folded antenna of the first embodiment. The dipole-connected folded antenna shown in FIG. 1 consists of conductors (antenna elements) 11 and 12, each of which has a folded conductor 13 branching from the middle,
a first dipole antenna provided with 14;
A conductor (antenna element) 15 arranged at a position spatially orthogonal to this first dipole antenna,
It has a second dipole antenna consisting of 16 antennas. A power feeding section 19 is provided between terminals 17 and 18 of antenna elements 11 and 12, respectively. Folded conductor 1 branched from antenna element 11
3 is folded back in parallel with the antenna element 11 at a narrow interval and is connected to the feeding section 20 of one antenna element 15 of the second dipole antenna. In addition, a folded conductor 1 branched from the antenna element 12
4 is folded back in parallel with the antenna element 12 at a narrow interval and is connected to the feeding section 21 of the other antenna element 16 of the second dipole antenna. Therefore, the first dipole antenna and the second dipole antenna are fed by one feeder 19.

FIG. 2 shows a dipole-connected folded antenna according to a second embodiment. In the second example, the folded conductors 13 and 14 of the first dipole antenna are extended (the portions of the conductors 13a and 14a), the equivalent radii are made equal, and the antenna is installed at a location h above the reflector. As shown in FIG. 2, when the total length of the first dipole antenna is 2L1, the folded width d, the branch position Ls, and the diameter of the conductors 11 and 12 are 2a1, the dipole connection type folded antenna has folded conductors 13 and 14. Since the unbalanced mode current of is attracted to the radiation, the equivalent radius a = √
An equivalent dipole antenna of 2L1 flowing at a1 and d,
It consists of a dipole antenna of 2Ld flowing with radius a2. The distance between these two dipole antennas is Ls
are tied together with shorting stubs. In addition, a1, a2,
The condition d<<λ (wavelength) is required.

The dipole-connected folded antenna of the present invention is
Like the conventional cross dipole antenna for circularly polarized waves, the first dipole antenna and the second dipole antenna are arranged so as to be spatially orthogonal to each other. Therefore, if the dipole-connected folded antenna is configured so that the voltage with the necessary phase difference and amplitude is distributed to the terminals 20 and 21 by only feeding power from the terminals 17 and 18, it will produce the same radiation as a cross dipole antenna. characteristics are obtained. In other words, each antenna element 11, 12, 15, 16 is excited at 90°.
By giving a phase difference of , it is possible to generate circularly polarized waves in the direction perpendicular to the plane of the dipole.

Since the second dipole antenna is fed with power via the folded conductors 13 and 14 branched from the middle of the antenna elements 11 and 12 of the first dipole antenna, a feeding difference occurs. Furthermore, it is assumed that a balanced current and an unbalanced current flow in the folded conductors 13 and 14, and the unbalanced current involved in radiation radiates, but the balanced current has opposite currents flowing, so no radiation occurs. do not have. Therefore, in the dipole-connected folded antenna of the present invention, the folded conductor 1
3, 14 (has the role of a transmission line)
Considering, each antenna element 11, 12, 15,
16, each with a predetermined phase (90°
This can be realized by creating a structure that provides a phase difference of .

Here, a specific structure will be explained using a second embodiment. The structure of the dipole-connected folded antenna is determined based on a1, a2, d, h, L1, L2, Ls, and λ. For example, a1=a2=a
Then, a/λ, d/λ, and h/λ are given in advance, and the values of the remaining conditions L1/λ, L2/λ, and Ls/λ are determined.
For the remaining conditions, set appropriate initial values.
By fixing L1/λ and directly calculating the dipole-connected folded antenna, the axial ratio (the ratio between the maximum and minimum electric field, which indicates how circularly polarized the wave is) is the minimum on the Z-axis. L2/λ, Ls/
It can be found by adjusting λ.

Specifically, a/λ=0.006, d/λ=0.032,
If h/λ=0.25 and L1=L2, then
L1/λ=0.208, Ls/λ=0.068. Therefore,
If the design center frequency f0 is f0 = 2GHz, h = 37.5
mm, L1=L2=31.2mm, Ls=10.7mm, a=0.9mm,
It is determined that d=4.8mm.

Note that the element lengths of the first dipole antenna and the second dipole antenna are not limited to being equal lengths (L1=L2), but may also be unequal lengths.

FIG. 3 shows the results of measuring the frequency characteristic of the axial ratio in the Z-axis direction with the center frequency f0 for the dipole-connected folded antenna shown in FIG. 2. In FIG. 3, solid lines indicate theoretical values, and circles indicate measured values. The two are in good agreement. As is clear from this, the dipole-connected folded antenna shown in Figure 2 has an axial ratio of 3 dB.
Below, it has a frequency band of approximately ±5%. In addition,
λ0 indicates a wavelength of 2 GHz, and the power supply unit 19 supplies power using a slit balun (segmented coaxial balun).

FIG. 4 shows the frequency characteristics of the gain in the Z-axis direction. In Figure 4, the solid line indicates the theoretical value,
The circles indicate the measured values; the characteristics are broadband, and the gain is a constant value of approximately 6.5 dB.

FIG. 5 shows the directivity characteristics of the maximum electric field value on the X-Z plane in FIG. 2. As shown in the figure, the theoretical values and measured values agree well.

In this way, by appropriately setting the element values of L1, L2, and Ls, it is possible to give the necessary amplitude ratio and phase difference to the currents flowing through the first dipole antenna and the second dipole antenna. ,
The antenna having the structure shown in the figure can be a circularly polarized antenna.

FIG. 6 and FIG. 7 each show still other embodiments of the present invention. In Figure 6,
The second part of the dipole-connected folded antenna shown in Figure 2
The conductors 15 and 16 of the dipole antenna are connected to the conductors 22 and 23 so as to be parallel to each other. FIG. 7 shows a planar configuration of the antenna shown in FIG. 6. An appropriate load may be connected to the terminals 24, 25 of the conductors 22, 23, or a terminal condition may be provided such that the ends are short-circuited or open. Furthermore, there are antenna configurations that sharpen the directivity and increase the gain using the antenna of the present invention, as shown in FIGS. 8, 9, and 10, respectively. What is shown in FIG. 8 shows the Yagi array method, where 31 is a waveguide, 32 is a radiator using the antenna shown in FIG. 1, and 33 is a reflector. FIG. 9 shows a planar array in which a plurality of radiators 32 are formed by printed conductors on a printed circuit board 34, and a conductive plate 35 on the lower surface of the printed circuit board 34 is used like a reflector. The one shown in FIG. 10 is in the form of a cascaded array. That is, by rotating the plurality of radiators 32 shown in FIG. 1 by 90 degrees,
The feeding points and feeding parts are connected alternately, making it a fully fed circularly polarized directional antenna.

In this way, the folded conductor 1 is branched from the middle of the first dipole antenna and folded back in parallel.
3 and 14, the folded conductor 1 is connected to the second dipole antenna installed spatially orthogonal to the first dipole antenna.
By utilizing the fact that portions 3 and 14 serve as transmission lines, it is possible to distribute voltages with the necessary phase difference and amplitude to each antenna element, thereby generating circularly polarized waves. Therefore, since only one power supply unit is required, the power supply system can be configured easily. Furthermore, since printing technology can be used, a multi-element antenna can be easily constructed and a high gain can be achieved.

[Effects of the Invention] As described above, according to the present invention, it is possible to provide a dipole-connected folded antenna that can realize a circularly polarized antenna without using a power divider or a phase shifter.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the structure of a dipole-connected folded antenna according to an embodiment of the present invention, FIG. 2 is a perspective view showing the structure of an antenna according to a second embodiment of the invention, and FIG. FIG. 4 is a diagram showing the axial ratio characteristics of the antenna shown in FIG. 2, FIG. 4 is a diagram showing the gain of the antenna shown in FIG. 2, FIG. 5 is a diagram showing the directivity shown in FIG. 2, and FIGS. The figures are block diagrams showing still other embodiments of the present invention, FIGS. 8 to 10.
The figure is a diagram showing an antenna configuration using the antenna of the present invention. 11, 12, 15, 16... Conductor (antenna element), 13, 14... Folded conductor, 17, 18,
20, 21...Terminal, 19...Power supply unit.

Claims (1)

[Claims] 1. A first dipole antenna and a second dipole antenna installed at a position spatially orthogonal to the first dipole antenna are branched from the middle of one antenna element of the first dipole antenna and arranged in parallel at narrow intervals. It is connected to one feeding point of the second dipole antenna by a folded conductor, and is connected to the feed point of the second dipole antenna by a conductor that branches from the middle of the other antenna element of the first dipole antenna and is folded in parallel at narrow intervals. A dipole-connected folded antenna characterized in that the antenna is connected to the other feeding point of two dipole antennas and is fed from one feeding part connected to the feeding point of the first dipole antenna.