JPH05129822A - High gain antenna with molding lobe - Google Patents

Abstract

PURPOSE: To provide a high gain antenna having a shaped lobe. CONSTITUTION: The high gain antenna includes a conformed array on a surface of a rotating body with an optional profile, the surface is in existence on a plane passing through a rotary shaft Δ, includes a plurality of generating lines 12 consisting of radiating elements 13 and a shaped lobe is provided in which all the radiation elements 13 on a same generating line 12 are connected to a single control point. The antenna is especially used for space communication.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to high gain antennas having shaped lobes.

[0002]

2. Description of the Related Art Antennas of this type are extremely useful in the field of space. For example, a low-orbit mobile satellite has an extremely wide-angle cone for ground observation, and has an altitude of 800k.
In m, the apex angle of the cone is 63 °. The distance from the satellite to one station inside the cone is various values ranging from 800 km (nadir) to 2300 km (corner edge). When performing missions such as telemetry or telecommands between this satellite and this station, it is necessary to ensure an equal beam link regardless of the relative position of this station inside the cone. Therefore, the antennas used for such missions are
The standard model of P (equivalent isotropic radiated power) must have a directivity diagram with a maximum at the edge of the cone and a gradual decrease towards the nadir. In this case, the dynamic range is about 12 dB. Such a standard model may further include low level preparation (at the nadir the dynamic range is reduced to about 10 dB), or conversely, compensation for atmospheric attenuation (proportional to distance) Is over 13 dB. These standard models are azimuth-based rotating bodies and have the shape of concave containers. Therefore, it is necessary to use an antenna with shaped lobes.

[0003]

Some known techniques for obtaining such a standard model can be broadly divided into two groups: conformed reflectors and array antennas.

Conformal reflector: A conformed reflector consists of a rotating body with a profile optimized to follow a standard model formed on the basis of elevation. The problem with this type of mirror is that it must have a rotational directivity diagram because it is necessary to ensure the link of the entire cone. Therefore, it is difficult to obtain high gain with a reflecting mirror having a reasonable size. This type of reflector is described in a paper by Bridges, Shafai & Kishk, "Method of Moment Analysis of Cavity-Fed Shaped Beam Reflector Antenna.
nt analysis of a cavity-f
ed shaped beam reflector a
ntenna "(Antenna'90 conference
nce processes, August 15
~ 17, 1991, Winnipeg, Canada)
Has been analyzed by.

Array antenna: Based on the above recognition, the idea was born to use a high gain electronically scanned array antenna with directional antenna lobes and to move this antenna under electronic control. Such an antenna is described in the document "Antenna Engineer".
ing handbook ", (RC Johnso
n & H. Jasik, MacGraw-Hill;
chapitre 20 "PhasedArrays"
R. Tang & R.M. W. Burns, Pages2
0-1 to 20-5). It is not necessary to secure links for the entire cone at the same time, only for the direction of the target station. The antennas are further divided into two groups, planar arrays and conformed arrays.

Planar array: A lobe of a prior art array, which determines the array size based on the pitch, ie the spacing between two adjacent sources, could be obtained with a shaped mirror with similar size if the problem could be solved. It is possible to obtain a directivity far superior to the specified directivity. Since the feeding phase of each source is controlled by the phase shifter, the directivity diagram is moved by changing these phases. This solution has two major drawbacks.

It is necessary to correct the elevation-based lobe by more than about ± 60 ° even at very low altitudes. This requires the sources to be very close together.

It is very difficult to obtain a radiation maximum at about 60 ° and a minimum on the axis. Therefore, even when the radiation pattern of the source has the shape of the standard model, that is, even when it has the radiation maximum at 60 ° (eg, helix),
It is necessary to use a source having a high directivity in °.
As a result, if it is desired to obtain a high gain (eg> 20 dBi), a relatively large size is required, and thus a large number of sources and phase shifters (50 to 50 depending on the basic directivity of 60 °). 100) is required. Therefore, this type of antenna requires a large number of control points.

Conformed array: To obtain a 60 ° cone emission maximum, the source is placed on a conformed surface (eg a hemisphere). The lobes are scanned based on elevation and azimuth by controlling each source with one phase shifter. However, with such an array, it is possible to use radiating elements with a directivity maximum at 0 ° -not all sources available at the same time, but they must also be direction-correctable to 60 °.

An object of the present invention is to provide an antenna which can remedy these drawbacks, ie an antenna which can reduce the number of control points of said antenna and at the same time effectively ensure the desired mission.

[0011]

To this end, the present invention provides a high gain antenna having a shaped lobe. Features of the antenna of the present invention include a conformed array on a conformed surface of any profile having an axis of symmetry,
The surface includes a plurality of busbars existing in a plane passing through an axis of symmetry of the antenna, and the radiating element is arranged on the busbars,
All radiating elements on the same bus are connected to a single control point of phase and amplitude, and the scanning of the lobes and orientations of the shaping lobes can be obtained based solely on the control of the phase of the bus by these control points. is there.

Preferably, all radiating elements on the same bus are connected to a passive distributor and a controllable phase shifter. The amplitude and phase limits of the radiating element of each busbar are determined by the non-electric characteristic value of the passive distributor of each busbar. Adjusting the elevation pattern of the antenna by controlling the phase shifter. Azimuth scanning is ensured by bus switching.

Since the conformed array of the present invention is present on the conformed surface of any profile that preferably has an axis of symmetry, the profile is optimized to determine the shape of the radiation directivity diagram of the busbar. .. Because of this, the orientation of the normal to the generatrices in the plane passing through the axis of symmetry will be variable depending on the position on the generatrices, so that the radiating elements lying above the generatrix will have different directions. .. In other words, the gradient of the radiating element with respect to the axis of symmetry is optimized in order to obtain the desired radiation directional pattern of the busbar.

Such an antenna has the important advantage that it can scan two planes using only unidirectional control distributed in the azimuth plane. Further, the required number of controls is reduced (to one per busbar) compared to conventional antennas which required one control per radiating element.

Furthermore, the shape of the radiation lobes can be optimized by adjusting the variable gradient of the passive distributor and the radiating element with respect to the axis of symmetry.

In this way, a third degree of freedom is obtained in the processing of a row of radiating elements present on the same bus. For this reason, the radiating element can be effectively utilized in the working direction. This becomes more important as the scanning range becomes wider and the direction correction becomes larger, for example, when the direction correction becomes ± 60 ° or more. This capability of the present invention is a significant advantage over a solution planaire which ensures a large range of travel and which results in loss of directional efficiency at high points.

[0017]

The features and advantages of the invention will be more fully understood from the following description, which is based on non-limiting examples illustrated in the accompanying drawings.

The antenna of the present invention has a conformed array arranged on a conformed surface 11 having an axis of symmetry and having any profile (conical, spherical, elliptical, parabolic, hyperbolic, etc.). Including 10. The array consists of a bus bar 12 containing a plurality of sources or radiating elements 13. Each busbar 12 is a conformed surface 1
It is a line of intersection between 1 and a plane passing through the axis of symmetry Δ (for example, the axis of the nadir). In FIG. 1, the surface 11 is a conical surface,
Each of the busbars 12 includes three radiating elements 13.

The antenna of the embodiment of FIG. 1 includes one phase shifter 14 per bus 12 and a passive divider 15 that divides the amplitude and phase of the signal between the sources is the output of the phase shifter 14 and each source. It is arranged between 13 inputs. This distributor 15 is similar for each busbar, so that the antenna geometry of the embodiment of FIG. 1 is completely rotator. This distributor 15 is provided so that several directivity diagrams of the radiation emitted by the sources 13 of each busbar 12 are obtained and that one directivity diagram is created which combines all the sources 13 of the antenna. Has been calculated to.

In order to obtain sufficient directivity, one or a plurality of adjacent bus bars are simultaneously radiated. The rotation of the busbar has two effects on the phase of the radiation.

The first effect is to rotate the plane of polarization by ψ about the rotation axis Δ. This rotation is constant. This rotation is related to the geometry of the array as shown in FIG.

The second effect is that the propagation delay is generated in proportion to the relative distance of the source with respect to the standard model plane P perpendicular to the sighting direction. For a given standard model plane P,
The distance from the source of the same bus to the surface has various values.

The function of the phase shifter is to compensate for these effects. However, since there is only one phase shifter per bus and this propagation delay compensation must be the same for all sources, the average delay must be calculated. This propagation delay depends on the aiming elevation angle direction. That is, it depends on the inclination of the standard model plane P. In FIG. 3, for example, all the busbars are phase-aligned in the direction corresponding to the nadir axis Δ (θ = 0 °). The phase shifter need only compensate for the azimuthal rotation of the plane of polarization. On the contrary, when the aiming axis is 60 ° (θ = 60 °), the fluctuation is large. Therefore, the phases of a plurality of adjacent bus lines cannot be summed at the same time in the entire range of elevation angle. Therefore, the directivity diagram outside the aiming direction deteriorates.

Therefore, even if the directivity diagram of one bus bar 12 perfectly matches the standard model, if the propagation delay in the direction of 60 ° is compensated, the correct directivity diagram is obtained when θ = 60 °. However, the correct directivity diagram cannot be obtained in other cases. Especially when θ = 0 °, the obtained directivity diagram is significantly lower than the standard model.

To compensate for this degradation, it is possible to increase the size of the busbar, ie to increase the energy delivered to the source of the busbar in order to obtain a directivity diagram that is significantly higher than the standard model envisaged. It is possible.

It is also possible to modify the directivity diagram and adjust the phase shifter to adapt it to the elevation angle of the aiming station. When the aiming station is at θ = 60 °, the propagation delay in this direction is compensated. As the elevation angle decreases, the directional diagram is deformed by adjusting the phase shifter. For example, in practice, when the station is at θ = 30 °, the directivity diagram of 30 ° is above the standard model, even though the directivity diagram of 60 ° is below.
The same is true up to °. At 0 °, the directivity diagram does not correspond to the standard model at 60 °.

Due to the geometrical shape of the rotator, azimuthal scanning is ensured by simple switching of the busbars.

In such an embodiment, the number of phase shifters can be reduced to the same number as the sources on the bus, as compared to the conventional conformed structure. Very few control points can simultaneously excite the phase shifters on the bus 12 to perform azimuth and elevation scans of the antenna. Therefore, using a busbar having a weak directivity and a small dimension, the azimuth-based directivity diagram follows a standard model and a conformed solution (c) is obtained by simply switching the azimuth.
onformee) is obtained.

For example, in one application example, the telemetry mission is performed according to the standard model of EIRP (Equivalent Isotropically Radiated Power) of FIG. 4 (maximum value curve 16 and minimum value curve 17). FIG. 4 shows a standard model of TMCU (effective telemetry load for optical or radar observation satellite). The purpose of this application is to maintain the standard model of EIRP with minimum radiated power. For example, it is necessary to obtain a maximum gain value of 21 dBi with a radiated power of 10 W. Considering the loss of 1 dB, the directivity would be 22 dBi. The size of the pseudo-conical antenna 20 is determined as shown in FIG. This antenna comprises 36 busbars 21 each having four sources 22.
Have. Each of the sources 22 is made of print technology. A copper block is printed on a conformed dielectric substrate that provides a pseudo-conical surface with a profile inclined from the top to the first source by α = 10 ° rather than a linear profile. Distributors in the form of copper tracks are printed between four sources 22 of the same busbar and on the same substrate as these sources.
The distributor is connected to the phase shifter. Only 9 of the 36 buses are excited at the same time. Therefore the total radiation is controlled by nine phase shifters at a time.

FIG. 6 shows a directivity diagram 26 obtained by compensating for the propagation delay in the direction of the standard model minima 25 and 62 °. FIG. 7 shows the same standard model minimum 27 and the resulting directivity diagram 28. It is only necessary to adjust the values of the nine phase shifters to compensate for the delay in the direction of elevation of 5 ° (FIGS. 6 and 7 show the directivity Di in dBi).

Although the preferred embodiments of the present invention have been described above with reference to the drawings, it will be understood, of course, that equivalent elements may be substituted for the elements described within the scope of the present invention.

In particular, the conformed surface may be of any profile with any axis of symmetry.

In the described embodiment, the surface comprises an axis of rotational symmetry, but the surface may have a quadratic symmetry (reflection in the plane), such as an ellipse, a parabola or a hyperbola, or It may have higher symmetries that give more complex surfaces.

[Brief description of drawings]

FIG. 1 is a schematic view of an embodiment of an antenna of the present invention.

2 is an explanatory diagram showing some characteristic values of the antenna of FIG. 1. FIG.

3 is an explanatory diagram showing some characteristic values of the antenna of FIG. 1. FIG.

FIG. 4 is an explanatory diagram of another embodiment of the antenna of the present invention.

FIG. 5 is an explanatory diagram of another embodiment of the antenna of the present invention.

FIG. 6 is an explanatory diagram of another embodiment of the antenna of the present invention.

FIG. 7 is an explanatory diagram of another embodiment of the antenna of the present invention.

[Explanation of symbols]

 10 conformed array 11 conformed surface 12 bus bar 13 radiating element 14 phase shifter 15 distributor

Claims (5)

[Claims] 1. A conformed array on a conformed surface of any profile having at least one axis of symmetry, said conformed surface intersecting said surface perpendicular to said surface and said Including a plurality of busbars defined by the intersection of a plane containing the axis of symmetry with the conformed surface, each busbar including a plurality of radiating elements, all radiating elements of the same busbar belonging to said busbars Connected to a single control point for phase and switching, scanning of points and azimuths in a plane perpendicular to the axis of symmetry is only phase control of the busbar through the single control point of each busbar. High-gain antenna with shaped lobes, characterized in that it is obtained based on 2. Further comprising one passive distributor for each busbar, said radiating elements of the same busbar being connected to said single control point by said passive distributor, the amplitude between said elements of said busbar and The antenna according to claim 1, wherein the phase rule is determined by a non-electric characteristic value of the passive distributor. 3. The normal to a generatrix in the plane including the generatrix has a constant or variable direction for all elements of the same generatrix depending on the shape of the conformed surface of any profile. And the direction of the normal is optimized to determine the shape of the radiation directivity diagram of the bus and to obtain the desired shape of the radiation directivity diagram. Antenna described in. 4. The conformed surface of any profile comprises a surface of revolution about an axis, the axis being parallel to the mean axial direction of the forming lobes. The antenna according to any one of claims. 5. The conformed surface of any profile comprises only a portion of a surface of revolution about an axis, the axis being parallel to the mean axial direction of the forming lobe. The antenna according to any one of Items 1 to 3.