KR100300937B1 - Spiral antenna device - Google Patents

Abstract

It is an object of the present invention to simultaneously receive signals with different polarizations by a helical feeder without gain reduction compared to prior art devices. According to the invention two or more helical feeders are provided for each polarization direction. The invention can be used, for example, in a DBS system.

Description

Spiral antenna

The present invention relates to an antenna device having a spiral feeder. The spiral feeder antenna consists of a single conductor or multiple conductors wound in a spiral. Except for some other possible modes, helical antennas are generally used in so-called axial mode or shin mode. The axial mode provides maximum radiation along the spiral axis, which occurs when the helical circumference is approximately one wavelength. The normal mode of generating radiation along the helix axis occurs when the diameter of the helix is smaller than the wavelength. Axis mode is a concern in the present invention.

The use of spiral antennas for antenna devices is widely known. For example, US Pat. No. 3,184,747 describes a coaxial feed spiral antenna having an aiming disc between a feed and a spiral and forming an endfire radiation from the disc. In the above-mentioned US patent, the dimensions of the helix for the antenna device are known.

US Pat. No. 4,742,359 describes an antenna device using a spiral antenna having two ends, wherein the first end is connected to the feeder line. For the following description, the feeder line is aligned with the axis of the spiral antenna. The helical antenna is manufactured as a so-called endfire helical antenna, and under maximum reception power, the direction of signal power flow at the first end is in the same direction as the received radiation. The helical antenna is also manufactured as a so-called backfire helical antenna, the direction of signal power flow at the first end under maximum reception power is in the same direction as the received radiation.

The US patent describes an antenna device comprising a reflector and a primary helical antenna, wherein the primary helical antenna has a coil having a pair of ends, the coil such that the axis of the spiral antenna is substantially coincident with the axis of the reflector. It is arranged at the focus of the reflector. The feeder line connects the antenna device and the external circuit, so that the primary spiral antenna is a backfire spiral antenna connected to the feeder line at an end closer to the reflector, and the other end of the spiral antenna is free, The feeder line is a coaxial cable.

The use of one or more spiral feeders with dielectric lenses is also known in WO 92/13373. This allows signals from different directions to be received at the same time.

In axis mode, spirals wound like the right screw receive right circular polarization, while spirals wound like the left screw receive left circular polarization.

In order for both polarization directions to be received simultaneously, at least two helices must be provided. If these spirals are part of an antenna device using focusing means, it is impossible to have two feeders simultaneously in the focus of the focusing means. This results in an unacceptable gain reduction for at least one polarization direction. Also, if the spirals are too close to each other, crosstalk may occur due to undesirable defocusing and / or strong coupling between the spirals.

It is an object of the present invention to provide an antenna device having a focusing means and a spiral feeder and capable of receiving at least two different circularly polarized radiation simultaneously without reducing the gain as compared to known antenna devices.

According to the invention, only one spiral feeder is provided for each polarization direction, and two or more are provided. This spiral feeder preferably operates in axial backfire mode.

The principle of the present invention is described below.

For example, focusing means, such as parabolic reflectors, and dielectric lenses, such as Luneburg-type lenses, have a focal point to focus incident radiation. In order to receive radiation with two opposite polarizations, two spiral feeders must be provided near the focal point. This means that two helices cannot be placed together at the focal point. Two or more spirals are provided in accordance with the present invention for each polarization direction to compensate for the gain reduction thereby.

Other features, advantages and details of the invention are described below with reference to the accompanying drawings.

1 is a side view of a preferred embodiment;

2 is a front view of the preferred embodiment;

3 shows a preferred embodiment of a power coupler.

In FIG. 1 the parabolic reflector 10 acts as a focusing means and has a reflector shaft 10a and a focus 11. Two spiral feeders 12a and 12b exist around the focal point 11, which feeders have the same winding scheme and mainly receive radiation with the same circular polarization. Each spiral feeder 12 has a collimator disc 13a, 13b, respectively. The signal received by the feeder 12 is directed to the circuit board through respective feeder lines 14a, 14b, for example coaxial cable, semi-cured cable, etc., which circuit board is included in the housing 15 Not shown in FIG.

There is also a second spiral feeder pair 22a, 22b provided in a winding manner opposite to the feeder 12. These feeders 22 are not shown in FIG. 1 but are shown in FIG. 2 which provides a front view of this embodiment. Each feeder 22 has a collimator disk 23a, 23b, respectively.

Diameter 61 of aiming disks 13 and 23 is approximately

0.25 * La,

Where La is the wavelength of the radiation to be received.

In a preferred embodiment the diameter 62 of the helix 12, 22 is about

0.3 * La,

The spacing 63 between the centers of two spirals 12a, 12b or 22a, 22b, each of the same pair,

0.7 * La or so.

In this embodiment, the housing 15 is approximately

0.8 * La Inn

Basic round tube-like shape with diameter.

For each room spirals 12 or 22 are arranged symmetrically on both sides of the focal point 11, respectively, so that the center of the segment F-F 'or f-f' is each of the focusing means 10. To match the focus (11).

Input power for each direction of polarization is added into the housing 15 using the corresponding power coupler. A preferred embodiment of such a power coupler is shown only in one polarization direction in FIG. 3. The inner conductors of the feeder line 14 are connected to microstrip lines 16a and 16b, each having a common junction 17. Outer line 18 leads to the other end (not shown) of the low noise converter (LNC). If the signal to be received is a television broadcast signal, the information of the signal is indicated by the corresponding TV set.

For other polarization directions, other power couplers may be provided, which may be of the same kind as shown in FIG.

In order to process the signals received by the feeders 12, 22, two LNC circuit boards can be provided which can be orthogonal to one another, for example, formed of crosses, "T", etc. Is housed in a housing 15 which may be round, triangular or square tubular.

Variations of the preferred embodiment may include at least one of the following modifications:

It is possible to provide two or more spiral feeders for reception in each polarization direction. In this case, the phase centers F and f form a triangle, a square, or the like. It is preferable to arrange the helical feeder such that the center of the triangle, square, etc. coincides with the focal point 11;

Instead of the reflector 10 other focusing means acting by reflection, refraction and / or diffraction may be used. Another preferred focusing means is a Luneburg-type lens, which may be cylindrical, bicylindrical, quadrant cylindrical;

By connecting the first pair of helical feeders 12 with the second pair of helical feeders 22 a linear polarized signal can be received. The linear polarization direction can be selected by the corresponding phase shifter means;

The antenna device can be used for the reception of broadcast signals such as television signals, audio broadcast signals and the like, which can be transmitted directly or indirectly from satellites. Antenna devices may also be used for the reception of other radio frequencies with different polarizations.

Claims (2)

In the antenna device having the focusing means 10 and the helical feeder 11 operating in the axial backfire mode, the first group of two or more helical feeders 12 is provided for reception in the first polarization direction, The second group 22 of two or more helical feeders is provided for reception in a second polarization direction, wherein the first group 12 of the helical feeders is wound opposite to the second group 22 of the helical feeders, And the feeder is positioned such that the center point of the phase center (F; f) of the spiral feeders (12, 22) of each group coincides with the focal point (11) of the focusing means (10). 2. An antenna device according to claim 1, wherein a circuit board is provided for processing signals of each polarization to be received, wherein the circuit boards are orthogonal to each other.