IL201137A - Low profile antenna for satellite communication - Google Patents

Description

201137 p"n | 453597 TAIN w nyft n-nwprf? ^DI-ID ΓΌΙ»3 moan LOW PROFILE ANTENNA FOR SATELLITE COMMUNICATION Abstract A low profile receiving and/or transmitting antenna includes an array of antenna elements that collect and focuses millimeter wave or other radiation. The antenna elements are physically configured so that radiation at a tuning wavelength impinging on the antenna at a particular angle of incidence is collected by the elements and focused in-phase. Two or more mechanical rotators may be disposed to alter the angle of incidence of incoming or outgoing radiation to match the particular angle of incidence.

Field of the Invention The present invention relates generally to antennas and, more particularly, to low profile receiving/transmitting antennas, that may be used in satellite communication systems and intended to be installed at mobile terminals in order to achieve global coverage and/or used at terrestrial wireless communication at platform with constraints on the physical dimensions of the antenna.

BACKGROUND OF THE INVENTION Description of Related Art Satellites are commonly used to relay or communicate electronic signals, including audio, video, data, audio-visual, etc. signals, to or from any portion of a large geographical area. In some cases satellite are used to relay or communicate electronic signals between a terrestrial center and airborne terminals that are usually located inside aircrafts. As an example satellite-based airborne or mobile signal distribution system generally includes an earth station that compiles one or more individual audio/visual/data signals into a narrowband or broadband signal, modulates a carrier frequency band with the compiled signal and then transmits (uplinks) the modulated signal to one or more, for example, geosynchronous satellites. The satellites amplify the received signal, shift the signal to a different carrier frequency band and transmit (downlink) the frequency shifted signal to aircrafts for reception at individual receiving units or mobile terrestrial terminals. Likewise, individual airborne or mobile terminals may transmit a signal, via a satellite, to the base station or to other receiving units.

SUMMARY OF THE INVENTION The present invention discloses an antenna comprising: a support frame, a plurality of antenna panels movably coupled to the support frame and having a variable beam direction relative to the support frame; and at least one actuator adapted to change the beam direction of the plurality of antenna panels, so as to track a transmitter or receiver, such that each pair of adjacent antenna panels substantially border each other as projected onto a plane perpendicular to the beam direction, and wherein when viewed from a predetermined range of the beam direction, none of the antenna panels is covered partially or totally by any other panel. The present invention further discloses a method for receiving or transmitting electrical signals by an antenna, the method comprising providing a plurality of antenna panels having variable beam directions, directing the beam directions of the antenna panels toward a transmitter or receiver, by at least one actuator and changing the beam directions of the antenna panels to define a common beam direction, so as to track the transmitter or receiver, the common beam direction being changed such that each pair of adjacent antenna panels substantially border each other as projected onto a plane perpendicular to the common beam direction, and wherein, when viewed from a predetermined range of the common beam direction, none of the antenna panels is covered partially or totally by any other panel.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a two-dimensional, diagrammatic view of an embodiment of system according to some embodiments of the present invention; FIG. 2 is a three-dimensional, perspective view of an embodiment of a system according to some embodiments of the present invention; FIG. 3 is a diagrammatic view of an embodiment of a system according to some embodiments of the present invention; and FIG. 4 is a diagrammatic illustration of the operation of an antenna arrangement according to some embodiments of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A low profile receiving/transmitting antenna built and operating according to some embodiments of the present invention is described herein below. The low profile receiving/transmitting antenna is described as being constructed for use with a Millimeter Wave (MMW) geosynchronous satellite communication system. It would be apparent, however, to a person with ordinary skills in the art that many kinds of antennas could be constructed according to the principles disclosed herein below, for use with other desired satellite or ground-based, audio, video, data, audio-visual, etc. signal distribution systems including, but not limited to, so-called "C-band" systems (which transmit at carrier frequencies between 3.7 GHz and 4.2 GHz), land-based wireless distribution systems such as multi-channel, multi-point distribution systems (MMDS) and local multi-point distribution systems (LMDS), cellular phone systems, and other wireless communication systems that need low profile antenna due to physical constraints.

In fact, an antenna of the present invention may be constructed according to the principles disclosed herein for use with communication systems which operate also at wavelengths shorter than the MMW range, such as sub-millimeter wave and terra-wave communication systems, or at wavelengths longer than the MMW range, such as microwave communication systems.

Referring now to FIGS. 1 and 2, an antenna 10 according to some embodiments of the present invention is illustrated. Antenna 10 may include plurality of antenna elements 12 disposed on active panels 14 preferably arranged in an array. Antenna element 12 may comprise any type of antenna receiving and/or transmitting units useful for operation in the frequency range intended for use with antenna 10. Antenna element 12 may be disposed on active panel 14 having any desired substantially-plane shape and preferably a rectangular plane. Antenna element 12 may be disposed on active panel 14 in any desired pattern including for example, but not limited to, a 3 x 5 array, a 2 x 4 array, a 5 x 8 array and the like, or any non-rectangular pattern including, for example, any circular, oval or pseudo-random pattern.

Antenna elements 12 may preferably be radiating elements having for example a diameter of one-half of the wavelength (λ) of the signal to which antenna 10 is designed for and may be disposed on active panel 14 in a rectangular pattern such as any one of the above mentioned patterns.

The array of antenna elements 12 is disposed on active panels 14 such that the electrical focus point of each of the antenna elements 12 points in a direction that is substantially at an angle of incidence a with respect to reference plane designated 1 1 in Fig. 1. As illustrated in Figure 1 and FIG. 2, antenna elements 12 are directed in a direction substantially along a line 17, normal to active panel 14 and passing substantially through the center of active panel 14. Each of array of elements 12 may receive radiation arriving at the angle of incidence a with respect to reference plane 1 1. In a transmitting embodiment each of elements 12 may transmit radiation at an angle of incidence a with respect to reference plane 1 1 .

In the embodiment illustrated in FIGS. 1 and 2, antenna 10 is tuned to receive signals having a wavelength of approximately 24 mm, i.e., 12.5 GHz. The width of active panel 14 is denoted as dL With respect to Figure 1 and Fig. 2, the horizontal distance between corresponding points in adjacent active panels 14 may be given by D= dL /sin(a) Wherein: a = the angle between the normal line 17 to the active panel and the reference plane 1 1 that is usually parallel to a body of a mobile platform to which antenna 10 may be attached; CIL = width of the active panel 14.

When the direction of antenna 10 tracks properly the direction of radiation, angle a between the normal 17 to active panels 14 and reference plane 1 1 substantially equals to angle a 1 between the radiation source and the reference plane 1 1 .

For n active panels 14 in antenna 10 the total length D' of antenna 10 may be received from D'=(n-1)*D+ dL.sin(a) The distance D may be determined to be so that when looking at antenna 10 from an angle of incidence a, an active panel 14 shall substantially not cover, partially or totally, any part of an adjacent active panel 14. Furthermore, from an angle a, all active panels 14 will seem to substantially border each other. To allow that for a range of tilting angles a, axis 16 of active panel 14 may be slidably attached to a support construction with possible movement in a direction parallel to reference plane 1 1 so that axis 16 of all active panels 14 remain substantially parallel to each other and perpendicular support construction, thus distance D may be controlled. Said control of distance D may be aimed to follow the adaptation of receive / transmit angle a so that lap of outer lines of adjacent active panels 14, as defined above, is maintained for all values of a.

It has been determined that an antenna configured according to the principles set out herein eliminates the loss of gain of the antenna beam due to the array-plane to array-plane partial coverage. Furthermore, because all the active panels' 14 focus are fully open to the radiation impinging on antenna 10 at the angle of incidence a then the entire active panel apertures across the entire antenna 10 add-up the antenna's total aperture is high and antenna 10 has a relatively high antenna gain, which enables antenna 10 to be used in low energy communication systems, such as satellite communication purposes. Also, an antenna configured according to the principles set out herein eliminates the so-called grating lobes due to the gaps or spacing that may be created between the projection of the said active panels on a plane perpendicular to said preferable angle of incidence.

It is noted that the azimuth pointing angle of the antenna 10 can be changed by rotating it about a center axis which is normal to reference plane and crosses it substantially through its center point. In a similar manner the elevational pointing angle of the antenna 10 can be changed by tilting active panels 14 synchronously, and distance D may be adjusted. Setting the azimuth and elevational angles of antenna 10 and distance D may be done manually or automatically, using any suitable driving actuator 41 , such as but not limited to, pneumatic linear actuator, electrical linear actuator, a motor with a suitable transmission, etc.

Antenna 10 may also be positioned on a rotatable carrying means that may allow to rotate it about an axis that is perpendicular to reference plane 1 1 to any desired azimuth angel. Using any suitable controllable driving means the beam of the antenna 10 may be steered to point to any desired combination of azimuth and elevation angles, thus to receive or to transmit signals from or to a moving source/receiver, or to account for movement of the antenna with respect to a stationary or a moving source/receiver.

Referring to Figure 3, that illustrates antenna 30 built and operating according to some embodiments of the present invention, antenna 30 comprises a limited number of active panels 34, two active panels in the example of Fig. 3. Active panels 34 may be tilted about their tilting axis 32 according to the principles of operation drawn above. Antenna 30 comprises also one or more auxiliary active panels 35, which also may be tilted about their axis 36. Auxiliary active panel 35 may be tilted according to the principle of operation of the operation of active panels 34 when the elevation angle a is within a predefined tilting range. This arrangement may be useful, for example, in cases where the overall longitudinal dimension of antenna 30 is limited, due to constructional constrains for example, hence the distance between active panel 34 and an adjacent auxiliary active panel 35 can not follow the rules dictated above for certain range of titling angle a.

Preferably, driving actuators may be used to provide the maximum beam steering range considered necessary for the particular use of antenna 30. The driving actuators may be of any suitable kind, such as but not limited to, pneumatic linear actuator, electrical linear actuator, a motor with a suitable transmission, etc. As is evident, the maximum beam steering necessary for any particular antenna will be dependant on the amount of expected change in the angle of incidence of the received signal (in the case of a receiving antenna) or in the position of the receiver (in the case of a transmitting antenna) and on the width of the antenna beam, which is a function of the size or aperture of the antenna. The larger the aperture, the narrower the beam.

Referring now to Figure 4, which is a diagrammatic illustration of the construction and operation of an antenna arrangement according to some embodiments of the present invention. An embodiment of low profile antenna 40 is presented. An actuator 41, guiding rails 42, antenna active panel 43, auxiliary antenna active panel 45, an extendible rod 44 and slidable support means 47 are employed. The angle between extendible rod 44 and antenna active panel 43 is rigidly secured to be a predefined angle, approximately 90° in the present example of Fig. - The activation of actuator 41 may cause extendible rods 44 to extend or shorten along the mutual longitudinal axis of extendible rods 44, while the two active panels 43 are maintained substantially parallel to each other as angle a is changed. Similarly, actuator 41 may turn about its central axis 48, thus changing the relative angle between extendible rods 44 and guiding rails 42 so as to change angle a and maintain active panels 43 substantially parallel to each other.

Material described in the specification which is not within the ambit of the claims is not covered by the claims. The scope of protection is as recited by the claims and as stipulated in the Patent Law (5727-1967).

Claims (31)

201 137/2 Claims:

1. An antenna comprising: a support frame; a plurality of antenna panels movably coupled to the support frame and having a variable beam direction relative to the support frame; and at least one actuator adapted to change the beam direction of the plurality of antenna panels, so as to track a transmitter or receiver, such that each pair of adjacent antenna panels substantially border each other as projected onto a plane perpendicular to the beam direction, and wherein when viewed from a predetermined range of the beam direction, none of the antenna panels is covered partially or totally by any other panel.

2. The antenna of claim 1 , wherein the antennal panels are rotatably connected to said support frame on respectively associated parallel axes of rotation and are parallely movable with respect to each other along lines which are perpendicular to said axes of rotation.

3. The antenna of claim 2, further comprising at least one auxiliary panel which can be made active and which is rotatable about an axis parallel to the rotational axes of said antenna panels only for a limited range relative to the elevational angle of rotation of said antenna panels.

4. The antenna of claim 1 , wherein the at least one actuator is adapted to change the beam direction while maintaining the antenna gain substantially the same as for a single antenna with an aperture similar to the sum of all the then active antenna panel apertures.

5. The antenna of claim 1 , wherein the support frame is rotatable under control of the at least one actuator.

6. The antenna of claim 1 , wherein the at least one actuator comprises a pneumatic actuator.

7. The antenna of claim 1 , wherein the at least one actuator comprises an electrical actuator.

8. The antenna of claim 1 , wherein the at least one actuator comprises a linear actuator.

9. The antenna of claim 1 , wherein the at least one actuator comprises a motor.

10. The antenna of claim 1 , wherein a plurality of antenna elements are disposed on each antenna panel.

11. 1 1. The antenna of claim 1 , wherein beam directions of the antenna panels are aligned along a common beam focus direction.

12. The antenna of claim 1 , wherein the plurality of antenna panels comprise at least four antenna panels.

13. A method for receiving or transmitting electrical signals by an antenna, said method comprising: 201 137/2 providing a plurality of antenna panels having variable beam directions; directing the beam directions of the antenna panels toward a transmitter or receiver, by at least one actuator; and changing the beam directions of the antenna panels to define a common beam direction, so as to track the transmitter or receiver, the common beam direction being changed such that each pair of adjacent antenna panels substantially border each other as projected onto a plane perpendicular to the common beam direction, and wherein, when viewed from a predetermined range of the common beam direction, none of the antenna panels is covered partially or totally by any other panel.

14. 1 . The method of claim 13, wherein said antenna panels are parallel to each other and rotated in elevation and azimuth and variably spaced apart from one another using at least one actuator.

15. The method of claim 13, further comprising mounting the antenna panels on an aircraft in a common support structure.

16. An RF antenna array comprising: a plurality of panels, each panel carrying a sub-array of RF antenna elements defining an RF radiation pattern having a principal beam direction; at least one elevational angle driving mechanism; at least one azimuthal angle driving mechanism; at least one linear translation driving mechanism; each said panel being mounted for angular movement by an elevational angle driving mechanism about a respective one of parallel first axes so as to steer elevational angles of corresponding sub-array pattern beams along substantially parallel lines; each said panel also being mounted for movement by an azimuthal angle driving mechanism about a common second axis, substantially perpendicular to said first axes, so as to steer azimuthal angles of corresponding sub-array pattern beams; and at least one of said panels also being mounted for translational movement with respect to at least one other of said panels by a linear translation driving mechanism along a linear axis that is substantially perpendicular to said first axes and to said second axis.

17. An RF antenna array as in claim 16 wherein said driving mechanisms are controlled so as to avoid substantial gaps between projections of said panels along their beam directions over a predetermined range of beam directions.

18. An RF antenna array as in claim 16 wherein said driving mechanisms are controlled so as to avoid substantial overlaps between projections of said panels along their beam directions over a predetermined range of beam directions. 201 137/2

19. An RF antenna array as in claim 16 wherein said driving mechanisms are controlled so as to avoid substantial gaps between projections of said panels along their beam directions over a predetermined range of beam directions and so as to avoid substantial overlaps between projections of said panels along their beam directions over a predetermined range of beam directions.

20. A method of operating an RF antenna array, said method comprising: disposing a sub-array of RF antenna elements defining an RF radiation pattern having a principal beam direction over each of plural individually controllable panels; angularly moving each said panel about a respective one of parallel first axes so as to steer elevational angles of corresponding sub-array pattern beams along substantially parallel lines; angularly moving each said panel about a common second axis, substantially perpendicular to said first axes, so as to steer azimuthal angles of corresponding sub-array pattern beams; and translationally moving at least one of said panels with respect to at least one other of said panels along a linear axis that is substantially perpendicular to said first axes and to said second axis.

21. A method as in claim 20 further comprising moving said panels about and along said axes so as to avoid substantial gaps between projections of said panels along their beam directions over a predetermined range of beam directions.

22. A method as in claim 20 further comprising moving said panels about and along said axes so as to avoid substantial overlaps between projections of said panels along their beam directions over a predetermined range of beam directions.

23. A method as in claim 20 further comprising moving said panels about and along said axes so as to avoid substantial gaps between projections of said panels along their beam directions over a predetermined range of beam directions and so as to avoid substantial overlaps between projections of said panels along their beam directions over a predetermined range of beam directions.

24. An RF antenna array comprising: a plurality of panels, each panel carrying a sub-array of RE antenna elements defining an RF radiation pattern having a principal beam direction; each panel being mounted for coordinated movements in elevational angle, azimuthal angle and separation distance therebetween so as to track an RF target in elevation and azimuth while maintaining mutually parallel principal beam directions for said sub-arrays such that projections of adjacent sub-arrays taken along their respective parallel principal beam 201 137/2 « ■ ·* . directions are approximately contiguous, without substantial gap or substantial overlap, over a range of elevational angles.

25. An RF antenna array as in claim 24 further comprising: at least three movement actuators coupled to said panels for independent control of said movements in elevational angle, azimuthal angle and separation distance respectively.

26. An RF antenna array as in claim 24 wherein the inter-panel separation distance D between corresponding points of adjacent panels having width dL and elevational angle a is substantially D=dL/sin(a) over said range of elevational angles.

27. An RF antenna array as in claim 24 wherein said panels are mounted for linear translational movement along a common linear axis to adjust the inter-panel separation distance.

28. A method of operating an RF antenna array, said method comprising: disposing a sub-array of RF antenna elements defining an RF radiation pattern having a principal beam direction on each of plural panels; controlling coordinated movements of each panel in elevational angle, azimuthal angle and separation distance therebetween so as to track an RE target in elevation and azimuth while maintaining mutually parallel principal beam directions for said sub-array such that projections of adjacent sub-arrays taken along their respective parallel principal beam directions are approximately contiguous, without substantial gap or substantial overlap, over a range of elevational angles.

29. A method as in claim 28 further comprising: controlling at least three movement actuators coupled to said panels for independent control of said movements in elevational angle, azimuthal angle and separation distance respectively.

30. A method as in claim 28 wherein the inter-panel separation distance D between corresponding points of adjacent panels having width dL and elevational angle a is substantially D=dL/sin(a) over said range of elevational angles.

31. A method as in claim 28 wherein said panels are linearly translated along a common linear axis to adjust the inter-panel separation distance.