antenna

Abstract

An antenna of the ADE type, operating at frequencies between approximately 59 GHz and 71 GHz, comprises a main reflector (12, 112), a feeder (16, 116) and a sub-reflector (14, 114), which is kept at a predetermined distance from the feeder by a sub-reflector support (18, 118) and has such dimensions that the total spatial requirement thereof is less than 10x10x10 cm.

Description

Field of the invention

[0001] The present invention relates to an antenna.

[0002] The invention has been developed with particular regard, though in a non-limiting manner, to an antenna for telecommunications operating at frequencies between approximately 59 GHz and 71 GHz.Technological background

[0003] Recently, there has emerged the opportunity to use the 60 GHz band more widely both for 6G telecommunications and for communications between the Earth and instruments or vehicles which are used on space missions. To this end, it has become necessary to have an antenna which can be relatively economical both to produce and to launch into space.

[0004] WANG YANXUN ET AL "Design of the axially displaced ellipse antenna with low profile at W band", 2015 INTERNATIONAL WORKSHOP ON ANTENNA TECHNOLOGY (IWAT), discloses an antenna of the ADE type, comprising a main reflector, a feeder and a sub-reflector.

[0005] PENCHEL RAFAEL A ET AL: "Design of Wideband Omnidirectional Dual-Reflector Antennas in Millimeter Waves", IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS, published on 3 May 2019 discloses another antenna of the ADE type, comprising a main reflector, a feeder and a sub-reflector.

[0006] PRATA A ET AL: "Displaced-axis-ellipse reflector antenna for spacecraft communications", MICROWAVE AND OPTOELECTRONICS CONFERENCE, 2003. discloses yet another ADE antenna.Statement of invention

[0007] An object of the invention is therefore to provide an antenna which can be produced and launched with contained costs. Another object is to provide an antenna with small dimensions but with a high gain. Another object is to provide an antenna which is economical to manufacture.

[0008] According to a first aspect, there is described an ADE antenna (Axially Displaced Ellipse) having overall dimensions which are less than 10 cm x 10 cm x 10 cm. Such an antenna is suitable for being housed in a CubeSat 1U. CubeSat satellites are miniature satellites with forms and dimensions which are standardized. In particular, a CubeSat 1U is cubic and has sides which are conventionally defined as 10 cm long, while other CubeSat models have dimensions equal to a multiple of a 10 cm cube. An antenna which is suitable for being used in a CubeSat is economically more sustainable than a larger antenna both in terms of production and particularly in terms of being launched. The antenna may operate at frequencies between approximately 59 GHz and 71 GHz. The antenna may comprise a main reflector, a feeder and a sub-reflector, which is kept at a predetermined distance from the feeder by a sub-reflector support.

[0009] According to the first aspect, there is described an antenna of the ADE type, wherein the main reflector is obtained by the geometric rotation about a rotation axis of a portion of a branch of a parabola having an axis which is translated with respect to the rotation axis. A clearance angle, which is defined between the axis of the parabola and a segment which joins an edge of the sub-reflector and the focus of the parabola, is in the range from 10° to 20°, preferably in the sub-range from 16° to 17° and even more preferably it is 16.3°.

[0010] According to another aspect, there is described an antenna of the ADE type, wherein the main reflector is formed by two semi-reflectors which can selectively be moved relative to each other between an open configuration, in which the two semi-reflectors are close together so as to form the main reflector, and a closed configuration. The antenna which is formed in this manner may therefore be in an open, operative configuration or in a closed, more compact configuration.

[0011] According to a preferred embodiment, the two semi-reflectors are hinged together, preferably with rotoidal joints. Each semi-reflector may be hinged to a sliding support, which is able to slide on tracks. The semi-reflectors are preferably fixed to the sliding supports by means of rotoidal joints.Brief description of the drawings

[0012] Additional features and advantages will be appreciated from the following detailed description of two embodiments of the invention with reference to the appended drawings which are provided purely by way of non-limiting example and in which: Figure 1 is a perspective view of an antenna according to the invention, Figure 2 is a perspective view of the rear of the antenna of Figure 1, Figure 3 is a cross-section of the antenna of Figure 1, Figure 4 shows a cross-section along a plane which is positioned at 90° with respect to the plane of section of Figure 3, Figure 5 schematically shows the profiles which, rotated about the axis z, define the surfaces of the main reflector and the sub-reflector, Figure 6 shows the parameters of an inclined ellipse which, rotated about the axis z, defines the surface of the sub-reflector, Figure 7 is a perspective view of the rear of an antenna according to a second embodiment of the invention, Figure 8 is a perspective view of the front of the antenna of Figure 1, Figure 9 is a side view of the antenna of Figure 7, in a closed configuration, Figure 10 is a side view of the antenna of Figure 7, in an intermediate configuration, and Figure 11 is a side view of the antenna of Figure 7, in an open configuration. Detailed description

[0013] Now with reference to the drawings, an antenna 10 according to the invention is an ADE antenna, that is to say, an Axially Displaced Ellipse antenna. The antenna comprises a main reflector 12, a sub-reflector 14 and a feeder 16 which is positioned at the centre of the reflector. A sub-reflector support 18 keeps the sub-reflector at a suitable distance from the feeder. There is provided at the rear of the main reflector 12 a feeding network 20, which is preferably subdivided into two half-shells, as can be seen in Figure 2. There is provided therein a power supply network which is formed by two adapted sections in a rectangular guide 26, which can be seen in the cross-section of Figure 3, in order to direct the radiation towards the feeder 16.

[0014] There is provided between the feeding network and the feeder a septum polarizer 22 with a stepped blade 24, as can clearly be seen in the cross-section of Figure 4, in order to circularly polarize the linear signal originating from each adapted section in the rectangular guide 26. In this manner, the septum polarizer 22 simultaneously provides a right-handed circular polarization (RHCP) to a signal and a left-handed circular polarization (LHCP) to the other signal. This allows the antenna to transmit and receive at the same time. The sub-reflector support 18 is preferably made from a material which is substantially transparent with respect to the frequencies concerned, for example, rohacell frequencies.

[0015] The design of an ADE antenna will now be briefly described with reference to the drawing of Figure 5 which shows the profile of half an antenna, with the respective profiles 32 and 34 being defined on the reflective surfaces 36, 38 of the main reflector 12 and the sub-reflector 14. The configuration is symmetrical by rotation about the axis which passes through the centre of the main reflector and which is designated A s in the Figure. D M , D S and D B denote the diameters of the main reflector, the sub-reflector and a blocking area, respectively. The main reflector is generated by the rotation of a section of parabola with focus P, which is laterally translated with respect to the axis of symmetry A s of the antenna. Consequently, the focus P of the parabola forms a ring around the axis A s .

[0016] The sub-reflector 14 is generated by the rotation of a section of an ellipse with an inclined axis A E about the axis of symmetry A s . The ellipse has one of the foci O thereof on the axis of symmetry A S of the antenna while the other focus P coincides with the focus of the section of parabola. The focus O of the ellipse on the axis of symmetry is also indicated as the focus of the antenna.

[0017] In a generic antenna ADE, the blocking area of the antenna may coincide with the diameter of the sub-reflector (D B = D S ) . In that case, however, the Applicant has found that, in an antenna with extremely reduced dimensions, such as the one being discussed, a specific portion of rays return back into the feeder, resulting in unacceptable S parameters. The Applicant has discovered that this may be prevented or in any case limited with an angle θ L different from zero, where θ L is a clearance angle which is defined between the axis of the parabola and a segment which joins the edge of the sub-reflector and the focus of the parabola. In particular, the Applicant has determined that better performance levels are obtained when θ L is in the range from 10° to 20° and preferably in the sub-range from 16° to 17°. Even more preferably, θ L is equal to 16.3°; the optimum illumination angle is θ E = 40.2°.

[0018] With particular reference to Figure 6, the sub-reflector 14 has a radius D S / 2 of preferably 5 mm. The sub-reflector 14 is characterized by an ellipse with axes A1 and A2 which are preferably of 9 mm and 11.1 mm, respectively.

[0019] The above-described antenna is capable of ensuring a high gain, greater than 30 dB in the band of operation, while being very small and therefore able to be housed in a CubeSat, with the economic advantages which result. Furthermore, the antenna is preferably produced with a combination of CNC and 3D printing in order to make it particularly economical and to obtain the high level of precision required. The above-described configuration, with a feeding network 20 subdivided into two half-shells, is particularly suitable for being produced with CNC technology. If, however, it is chosen to produce it with 3D printing, the subdivision is not necessary, though possible.

[0020] The antenna is preferably made of metal, specifically aluminium.

[0021] Now with reference to Figures 7 to 11, there will now be described a foldable antenna 110. The foldable antenna 110 is, when open, entirely similar to the antenna 10 described above. It is an ADE antenna, with a main reflector 112 and a sub-reflector 114 having the same geometries as the reflectors 12 and 14 of the antenna described above, with particular reference to the angles θ L and θ E . The main difference with respect to the antenna 10 is that the main reflector 112 is formed by two semi-reflectors 113. The two semi-reflectors 113 are hinged to each other, preferably with rotoidal joints 115, and, when placed side by side, form a reflector 112 which differs from the main reflector 12 only by the gap between the two semi-reflectors 113. Furthermore, each semi-reflector is hinged to a sliding support 117, which can slide on tracks 119. The two sliding supports 117 are suitable for sliding towards each other or away from each other. The semi-reflectors 113 are fixed to the sliding supports 117 by means of rotoidal joints 121.

[0022] The antenna 110 can therefore change from a closed configuration, which is shown in Figure 9, to an open configuration, which is shown in Figure 11, moving through an intermediate configuration which can be seen in Figure 10. In the open configuration, the sliding supports 117 are at the minimum possible distance apart from each other while, in the closed configuration, they are spaced apart.

[0023] The advantage of this foldable variant is that, while maintaining the total dimensions in the closed configuration less than 10 cm x 10 cm x 10 cm, so as to ensure the possibility of housing it in a CubeSat, it may comprise a main reflector which is slightly larger with respect to the version with a single-piece reflector. The Applicant has carried out simulations in order to evaluate the performance levels of the foldable variant, finding that there are no substantial changes in the performance levels, even when assuming a gap between the two semi-reflectors of 0.1 mm.

[0024] The foldable antenna 110 is provided with a feeder 116, a sub-reflector support 118 and a feeding network 120 which are generally similar to the ones described above for the antenna 10, to the description of which reference may therefore be made.

[0025] Naturally, the principle of the invention remaining the same, the forms of embodiment and details of construction may be varied widely with respect to those described and illustrated, without thereby departing from the scope of the invention as defined by the appended claims.

Claims

1. An antenna of the axially displaced ellipse, ADE, type, configured to operate at frequencies between approximately 59 GHz and 71 GHz, comprising a main reflector (12, 112), a feeder (16, 116) and a sub-reflector (14, 114), which is kept at a predetermined distance from the feeder by a sub-reflector support (18, 118), wherein the antenna is dimensioned such that the total spatial requirement thereof is less than 10 cm x 10 cm x 10 cm, wherein the main reflector (12, 112) is obtained by the geometric rotation about a rotation axis (AS) of a portion of a branch of a parabola having an axis (AP) which is translated with respect to the rotation axis, wherein a clearance angle (θL), which is defined between the axis of the parabola and a segment which joins an edge of the sub-reflector and the focus of the parabola (P), is in the range from 10° to 20°.

2. An antenna of the ADE type according to the preceding claim, wherein the clearance angle (θL) is in the sub-range from 16° to 17°.

3. An antenna of the ADE type according to the preceding claim, wherein the clearance angle (θL) is 16.3°.

4. An antenna of the ADE type according to any one of the preceding claims, wherein the main reflector (112) is formed by two semi-reflectors (113) which can selectively be moved relative to each other between an open configuration, in which the two semi-reflectors are close together so as to form the main reflector, and a closed configuration.

5. An antenna of the ADE type according to the preceding claim, wherein the two semi-reflectors (113) are hinged together, preferably with rotoidal joints (115).

6. An antenna of the ADE type according to claim 4 or 5, wherein each semi-reflector is hinged to a sliding support (117), which is able to slide on tracks (119).

7. An antenna of the ADE type according to claim 7, wherein the semi-reflectors (113) are hinged to the sliding supports (117) by means of rotoidal joints (121).

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