Polarizer and a method of operating the polarizer

Abstract

A polarizer, such as a septum polarizer, which may alter between two states wherein, effectively, the septum is rotated 180 degrees around the longitudinal axis of the waveguide so that the polarization of the signals in the waveguide may easily be altered without having to alter receivers/transmitters connected to the waveguide.

Claims

1. A polarizer comprising: a central waveguide, the central waveguide including, a plane extending through the central waveguide along a longitudinal axis of the central waveguide, an opening, and a polarizing element extending along the longitudinal axis and in the plane, the polarizing element being an electrically conducting element having, when projected on to the plane, a first area on one side of the longitudinal axis and a second area on an opposite side of the longitudinal axis, the second area being smaller than the first area, the polarizer being configured to alter between two states, such that, in a first state, the polarizing element extends in the plane with the first area positioned in a first part of the plane on a first side of the longitudinal axis, and in a second state, the polarizing element extends in the plane with the first area positioned in a second part of the plane on a second side of the longitudinal axis, the second side being opposite to the first side; and a first waveguide and a second waveguide opening into the central waveguide at different sides of the plane extending through the central waveguide.

2. A polarizer according to claim 1, wherein, the polarizing element has a generally triangular shape including, a longitudinal side extending at least substantially parallel to a first side of the central waveguide, a back side extending at least substantially from the first side of the central waveguide to a second, opposite side of the central waveguide, and a third side, and a first part of the polarizing element, positioned where the longitudinal side and the third side intersect, is closer to the opening of the central waveguide than the back side of the polarizing element, wherein, in the first state, the polarizing element of the central waveguide extends in the plane with the longitudinal side extending in the first part of the plane, and in the second state, the polarizing element of the central waveguide extends in the plane with the longitudinal side extending in the second part of the plane.

3. A polarizer according to claim 2, wherein the third side of the polarizing element has a stepped shape, when projected on to the plane.

4. A polarizer according to claim 1, wherein the polarizing element is rotationally provided in the central waveguide.

5. A polarizer according to claim 1, wherein the polarizing element is fixed to the central waveguide and the central waveguide is configured to be rotated in relation to the first and second waveguides.

6. A polarizer according to claim 1, wherein, the polarizing element has a first and a second part, each of the first and second parts being an electrically conducting element having, when projected on to the plane, a first area on one side of the longitudinal axis and a second area, being smaller than the first area, on another, opposite side of the longitudinal axis, and the first areas of both the first and second parts are provided between the second areas of the first and second parts or the second areas are provided between the first areas of the first and second parts.

7. A polarizer according to claim 1, comprising: at least one additional central waveguide in addition to the central waveguide, the central waveguide and the at least one additional central waveguide each being displaceable from an active position, wherein the first and second waveguides open into the central waveguide or the at least one additional waveguide, and an inactive position where the first and second waveguides do not open into any of the central waveguide or the at least one additional waveguide.

8. A method of operating the polarizer according to claim 1, the method comprising: operating the polarizer in the first state, transforming the polarizer to the second state and operating the polarizer in the second state.

9. A method according to claim 8, wherein transforming the polarizer to the second state includes rotating the polarizing element within the central waveguide.

10. A method according to claim 8, wherein, the polarizing element is fixed to the central waveguide, and transforming the polarizer to the second state includes rotating the central waveguide.

11. A method according to claim 8, wherein, the polarizing element has a first part and a second part, each of the first part of the polarizing element and the second part of the polarizing element being an electrically conducting element having, when projected on to the plane, a generally triangular shape with a longitudinal side extending at least substantially parallel to a first side of the central waveguide, a back side, and a third side, the third sides of both the first part of the polarizing element and the second part of the polarizing element, when projected on to the plane, are either both located in a space between the longitudinal sides of the first part of the polarizing element and the second part of the polarizing element, or both located external to the space between the longitudinal sides of the first part of the polarizing element and the second part of the polarizing element, and transforming the polarizer to the second state includes, moving the first part of the polarizing element out of the central waveguide, and moving the second part of the polarizing element into the central waveguide.

12. A method according to claim 8, wherein, the polarizer includes at least one additional central waveguide in addition to the central waveguide, and transforming the polarizer to the second state includes replacing the central waveguide, positioned in an active position in which the first and second waveguides open into the central waveguide, with the at least one additional central waveguide, such that the at least one additional central waveguide second central waveguide is positioned in the active position in which the first and second waveguides open into the at least one additional central waveguide.

Description

(1) In the following, preferred embodiments will be described with reference to the drawing, wherein:

(2) FIG. 1 in general describes the functionality of a septum polarizer,

(3) FIG. 2 illustrates a first embodiment according to the invention, wherein the polarizer element is rotated together with a part of the central waveguide,

(4) FIG. 3 illustrates a second embodiment according to the invention, wherein the polarizer element is rotated within the central waveguide,

(5) FIG. 4 illustrates a third embodiment according to the invention, wherein the polarizer element is a translatable element having two parts translatable into and out of the central waveguide,

(6) FIG. 5 illustrates a fourth embodiment according to the invention, comprising two polarizer elements each provided in a separate waveguide, one of which is translated in position to become the central waveguide,

(7) FIG. 6 illustrates different shapes of polarizing elements for use in the embodiments of the invention,

(8) FIG. 7 illustrates an alternative to the embodiment of FIG. 5, and

(9) FIG. 8 illustrates yet another embodiment according to the invention.

(10) In FIG. 1, communication between two terminals 1, 4, is illustrated, which usually takes place via parabolic antennas 2 and 3. The signal received at the terminal 4 is received in a central waveguide 12 comprising a polarizing element 20, such as a so-called septum. From the central waveguide 12, a first and a second waveguide, 14 and 16, respectively, extend and lead toward a receiver 5 and a transmitter 6, respectively.

(11) The function of the septum or polarizing element 20 is that circularly polarized signals are converted into a linearly polarized signal which is fed to one of the waveguides 14 and 16, depending on whether the received circularly polarized signal is left-hand or right-hand circularly polarized.

(12) When the signals travel in the other direction, the opposite occurs: the transmitter 6 emits a linearly polarized signal, which on its way though the central waveguide 12 is converted by the polarizing element 20 into a circularly polarized signal which is fed to the remote terminal 1.

(13) In one example, the terminal 1 is a satellite and the terminal 4 a ground based terminal, such as an antenna on a vessel, whereby a point-to-point communication is set up.

(14) In FIG. 2, a polarizer 10 according to the invention is seen having the central waveguide 12, the first waveguide 14 and the second waveguide 16 as well as the polarizing element 20. The polarizing element 20 has a generally triangular shape and has a longitudinal side 22, a back side 24 and a third side 26.

(15) The longitudinal side 22 is parallel to a longitudinal axis 18 of the central waveguide 12, and the back side 24 is perpendicular to the longitudinal side 22.

(16) The shape of the polarizing element 20 provides the function of the septum in a septum polarizer as described with reference to FIG. 1.

(17) If a polarizing element 20 was provided in the central waveguide which was rotated 180 degrees, the same received circularly polarized signal would be again converted into a linearly polarized signal but now fed to the other of the first and second waveguides 14/16, respectively.

(18) In this other mode, the polarizing element 20 would still be positioned din the same plane, which comprises the longitudinal axis of the central waveguide, in the central waveguide, but the longitudinal side 22 would shift from one side of the plane, compared to the longitudinal axis, to the other.

(19) In the first embodiment, these two modes are altered between by rotating the central waveguide 12 together with the polarizing element 20, as well as a proximal part 14/16 of the first and second waveguides 14/16, respectively, whereas distal parts 14 and 16 of the first and second waveguides, respectively, may remain fixed and connected to signal receiver/transmitters, for example.

(20) This embodiment has the advantage that the signal connection between the rotating parts 14/16 and the fixed, distal parts 14/16, respectively, may be retained by simple choke arrangements at the junctions. There is therefore no contact issue between the proximal and distal parts 14, 14, 16 and 16. It is noted that before and after rotation, the longitudinal axis remains the same and the plane is the same.

(21) In FIG. 3, another embodiment is seen in which, again, the polarizing element 20 is provided fully within the central waveguide 12. Again, the first and second waveguides 14/16 are provided.

(22) In this embodiment, the polarizing element 20 is rotatable around an axis parallel with the longitudinal axis 18 (see FIG. 2) of the central waveguide, from a first position to a second position wherein, in the drawing, the longitudinal side 22 is at an upper position and a lower position, respectively.

(23) This embodiment has the advantage that only the polarizing element 20 is rotated, which can be accomplished by simple means (e.g. a small motor). Another advantage is that the polarizer can be changed to cover other frequency bands by only replacing the polarizing element 20. The electrical contact along the sides of the polarizing element 20 can be retained by finger stock gaskets or similar arrangements.

(24) In FIG. 4, a third embodiment is illustrated in which the polarizing element 20 is translatable in an up/down movement. The polarizing element 20 has two parts 21 and 21, which may sequentially be positioned within the central waveguide 12.

(25) When the part 21 is provided in the central waveguide, the resulting linearly polarized signal will be fed to e.g. the first waveguide 14, whereas it will be fed to the second waveguide 16, when the other part 21 is provided in the waveguide 12.

(26) In the upper right corner, an element 20 is illustrated where the interchanging of the part 21 with the part 21 is performed using a rotation instead.

(27) This embodiment has the advantage that only the element 20 is moved, which also here can be accomplished by simple means. Another advantage is that the polarizer can be changed to cover other frequency bands by replacing only the element 20 or even providing, in the element 20 elements 21/21 which are adapted to different frequency bands, so that the rotation or translation may be used also for changing frequency bands. The longitudinal slot in the waveguide 12 is shown for illustrative purposes only. This slot preferably is covered by metallic lids which may be attached to the polarizing element 20. The electrical contact along the sides of the polarizing element 20 can be retained by finger stock gaskets or similar arrangements.

(28) In FIG. 5, a fourth embodiment is illustrated wherein two individual polarizing elements 23 and 23 each is provided in a waveguide 12 and 12, respectively, which are connected to proximal dual waveguide elements 14 and 16 and 14 (not illustrated) and 16, respectively, such that when the upper waveguide 12 and the upper polarizing element 23 is used, the channel 12 receives a circularly polarized signal from a receiving waveguide 17, the polarizing element 23 converts the circularly polarized signal into the linearly polarized signal which is fed to one of the first and second, distal waveguides 14 and 16 via one of the waveguides 14 and 16.

(29) When it is desired to have the linearly polarized signal fed to the other of the distal waveguides 14/16, the waveguide 12 is used wherein the polarizing element 23 is provided, feeding the signal to one of the waveguides 14/16. This shift is provided by shifting the central element with the channels 12, 12, 14, 16, 14 and 16 and polarizing elements 23 and 23 upwardly or downwardly.

(30) This embodiment has the advantage that there is no contact issue between the polarizing element itself and the surrounding waveguide. The contact at the waveguide junctions can be retained by simple choke arrangements. Naturally, the two polarizing elements 23 and 23 may be replaced by the polarizing element 20 of FIG. 4, such that a single element is used instead of the two individual elements.

(31) In FIG. 7, an alternative embodiment is seen in a cross section where the longitudinal axis is right-to-left in the drawing. The two central waveguides 12 and 12 are seen, as are the proximal waveguides 14, 14, 16 and 16 as well as distal waveguides 14 and 16. The polarizing elements 23 and 23 are also illustrated, and it is clear that a rotation around the rotation axis indicated (dot; axis extending out of the plane) will bring the waveguide 12 to the position of the waveguide 12 and thus connect the waveguides 16 and 14 to 14 and 16, respectively.

(32) Naturally, the first and second waveguides may extend in other directions than perpendicular to the central waveguide 12/12, such as parallel thereto or any other direction. These waveguides may be symmetric about a plane defined by the polarizing element or not.

(33) The waveguides are illustrated as quadratic/rectangular, but other shapes may also be used, such as circular, oval, or the like.

(34) In FIG. 6, different shapes of polarizing elements 20/20/23/23 are illustrated. The main shape of the polarizing element to fulfil this function preferably is generally triangular. However, as will also be clear from the following, adaptations to this shape are possible.

(35) In illustration A, the polarizing element 20 is a simple triangle with the longitudinal side 22, the back side 24 and a straight third side 26.

(36) In illustration B, the third side 26 is not straight but step-shaped. Still, the third side is generally approaching the longitudinal side 22 from left to right.

(37) In illustration C, a step-shaped third side 26 is illustrated which, however, has a local maximum 26, i.e. a part which, from left to right, locally increases the distance between the longitudinal side (vertical in the drawing) and the third side.

(38) In illustration D, the third side has a smooth, non-linear shape. Again, a local maximum 26 is illustrated, and again, the operation of the polarizing element is retained.

(39) In illustration E, the third side 26 is again step-shaped, but a longer top part 26 is illustrated. This part 26 is not relevant to the operation of the polarizing element 20, as the main function is that of the height-reducing partillustrated here as the step-shaped part.

(40) Comparing this illustration to FIG. 3, it is seen that the top part 26 may be rotated with the remainder of the polarizing element 20 or may remain fixed in relation to the main waveguide 12, as illustrated in FIG. 3. The polarizing effect is determined by the sloping part of the polarizing element 20, and any extension thereof or dividing of the waveguide 12 subsequent (in the travel direction of the signal in the waveguide 12) is of no or little importance in this respect.

(41) Finally, in illustration F, an elongate element 26 is seen directed along the longitudinal axis but increasing the area of the cross section above the longitudinal axis. The advantages of this type of polarizing element may be seen in U.S. Pat. No. 4,395,685 where also other shapes of this type are illustrated and described. It is seen that the first area, below the longitudinal axis, is generally triangular, as is the first area with a part of the second area (from the bottom to the waist below the part 26).

(42) In FIG. 8, yet another embodiment is illustrated seen along the longitudinal axis into the central waveguide 12 wherein the polarizing element 23 is positioned and from which the first and second waveguides 14 and 16 open. It is seen that the first and second waveguides open at the back of the channel 12.

(43) Two additional sets of channels 14 and 16 are illustrated. These are blinded when the polarizing element 23 is in the illustrated position, but a rotation of 90 degrees will open these into the central channel 12.

(44) Rotation 180 degrees is as that described in relation to e.g. FIG. 3, but a 90 degrees rotation will open into two different channels 14 and 16.