Polarization converter system

Description

[0001] This invention is directed to a system comprising a polarization converter according to the preamble of claim 1.

[0002] Such a system is known from the EP-A 0 198 982. In the known system the optimization of the energy flow between the waveguides is not necessarily given.

[0003] From the US-A 3 622 921 a polarization rotator is known which comprises a conducting vane rotated about the longitudinal axis of symmetry of a circular wave guide by a drive.

[0004] Therefore it is an object of the invention to optimize the energy flow between the waveguides of a system of the initially described type.

[0005] This object is solved according to the invention by a system with the features of claim 1.

[0006] The invention herein is particularly useful is converting commercial satellite communications transmitted as circular polarized signals to linearly polarized signals so that home TV receivers may conveniently receive such signals. With the polarization converter of this invention it is also possible to receive linearly polarized signals if desired.

[0007] The present system may be remotely operated by the home owner (operator) to switch between different polarized transmissions from different or the same satellites, for example, from a satellite in the U.S.A. eastern time zone transmitting left hand circularly polarized microwave TV signals to a satellite in the U.S.A. central time zone transmitting right hand circularly polarized microwave TV signals. The system is not only inexpensive but also it provides polarization conversion with only about 1/10 of a db losses at the primary frequencies of interest, 10.0 GHz to 15.0 GHz, but also unexpectedly provides reception separation between left hand and right hand circularly polarized signals of at least about 15 to 20 db received by the converter at the same frequency.

[0008] It is to be understood that the system of the invention will operate over a broad range of microwave frequencies.

[0009] The converter may also be used for transmitting both circular or linear polarized signals.

Fig. 1 is a side elevational view of the polarization converter supported by an antenna;

FIG. 2 is a sectional view of the converter taken from the top thereof;

Fig. 3 is a view taken along line 3-3 of Fig. 2;

Fig. 4 is a view taken along line 4-4 in Fig. 2;

Fig. 5 is a view taken along line 5-5 in Fig. 2;

Figs. 6A to 6D are views showing various angular positions that the fin is movable about the axis of the circular waveguide with respect to the center line of the rectangular waveguide.

[0010] The polarization converter system of the invention includes a circular waveguide having a rectangular waveguide opening into the side thereof and forming a passage for microwave energy to pass between said waveguides. In proximity to said opening of said rectangular waveguide into said circular waveguide, there is positioned a metal fin and shorting member adjacent thereto for converting circularly polarized microwave energy entering said circular waveguide to linearly polarized microwave energy for transmission through the rectangular waveguide or converting linearly polarized microwave energy entering the rectangular waveguide and converting the same to circularly polarized microwave energy for transmission from said circular waveguide.

[0011] The fin may if desired also be rotated to permit linearly polarized signals to be transmitted between waveguides without conversion.

[0012] Reference should now be had to Figures 1 to 5 which disclose a system for receiving microwave energy. At 20 there is shown an antenna system for receiving microwave energy transmitted, for example, by a communications satellite. The antenna 20 includes a dish 20-1 for collecting the transmitted microwave energy and focussing the collected energy at the horn 20-4. The horn 20-4 has a wide tapered mouth 20-4a gradually defining smaller interior circles and a narrower circular waveguide portion 20-4b. Both portions 20-4a and 20-4b have inner walls which are circularly shaped. The horn 20-4 is coupled by conventional flange connections to a circular waveguide 22 which is supported by members 20-3 coupled to the dish 20-1. The entire antenna complex is supported by a conventional tripod member 20-2 which may, e.g. be ground or roof- mounted. The circular waveguide 22 has a center line shown at 22-1. Extending from and opening into the circular waveguide 22 is a rectangular waveguide 23 (normally called a 90° port) having a center line 23-1 which is substantially perpendicular to the circular waveguide center line 22-1.

[0013] Microwave energy entering the horn 20-4 travels into the circular waveguide 22 and leaves from the rectangular waveguide outlet 23-3. The outlet end of the rectangular waveguide is coupled to a conventional receiver-down converter 28 which in turn is connected via a coax cable 28-1 to the user's receiver.

[0014] The receiver-down converter 28 conventionally used requires linear polarized microwave signals for operation, whereas satellites often transmit signals as circularly polarized signals (either left or right hand polarized). Accordingly, to convert the circularly polarized signal to a linearly polarized signal, an assembly 26 including a fin 26-1 of electrically conductive material, e.g. copper or aluminum, is positioned for rotation about the center line (axis) 22-1 of the circular waveguide 22. The face of the fin 26-1 a is substantially flat and is at substantially a right angle to the axis 22-1 of the circular waveguide 22. In the preferred embodiment the fin 26-1 is conveniently mounted in a di-electric material 26-2, e.g. polystyrene, etc. for rotation about the axis 22-1. The di-electric material support 26-2 is positioned on a coupling member 24-3 which is itself coupled to a shaft 24-2 driven by an electric motor 24 (e.g. step or continuous) to position the fin 26-1 about the axis 22-1.

[0015] In the preferred embodiment the fin edge 26-1 a is positioned preferably at 1/4 (one quarter) of a wavelength from a circularly shaped metal shorting plate 27, e.g. copper, aluminum, etc. at the frequency to be converted to obtain the best conversion ratio. Where a band of frequencies is to be received, the 1/4 of a wavelength distance is usually based on the center frequency of the band. If the fin surface 26-1 a is inwardly of the rectangular waveguide wall 23-5 i.e. to the left of Fig. 2, the bandwidth performance is unsatisfactory and if the fin 26-la surface is positioned beyond the center line 23-1, i.e. to the right of Fig. 2, the incoming wave form is reflected to such a degree that the converter performance is unsatisfactory.

[0016] The fin 26-1 is positionable with respect to the shorting plate by adjusting the position of the coupler 24-3 on the shaft 24-2 by use of a set screw 24-3a. The shorting plate 27 as shown is mounted in a slidable manner in the circular waveguide portions 22-2 as shown by arrows 22-3 to position the shorting plate 27 and the fin 26-1 with respect to the inlet 23-4. In order to allow the flow of microwave energy without substantially reducing the amount of energy flow between waveguides, the fin face 26-1 a is positioned between waveguide center line 23-1 and the proximal inner wall 23-5 of the rectangular waveguide 23.

[0017] The member 25 also supports the motor by way of flanges 25-1 and the coupling member is rotatable in a bearing sleeve 27-1. Thus in practice the fin surface 26-1 a is always positioned between the center line 23-1 and the proximal wall 23-5 and the shorting plate 27 is preferably positioned to the left of the proximal wall 23-5 as shown in Fig. 2, however it may be positioned forward of the wall 23-5 and back of the center line 23-1. Figs. 6A to 6D show four positions to which fin 26-1 is rotatably positionable about axis 22-1. In Figs. 6A and 6D the fin 26-1 is 90_° to the center line 23-1 or parallel thereto and in such positions linearly polarized microwave energy entering the horn 20-4 will travel through circular waveguide 22 and be directed into rectangular waveguide 23 without having its polarization changed. With the fin 26-1 as shown in Figs. 6A and 6D, circularly polarized signals entering the horn 20-4 will be substantially reflected back with the remainder entering the rectangular waveguide.

[0018] When the fin 26-1 is at ± 45_° to the center line 23-1 as shown in Figs. 6B and 6C, circularly polarized microwave energy signals (LH and RH) entering the horn 20-4 will be converted to linearly polarized microwave energy. With the fin 26-1 positioned as in FIG. 6B (45_° to the center line 23-1) right hand (RH) circularly polarized microwave signals will be converted to linearly polarized microwave signals and the fin 26-1 as positioned in Fig. 6C left hand (LH) circularly polarized microwave signals will be converted to linearly polarized signals, thus providing the linearly polarized signals which then pass through the rectangular waveguide and are accepted by the receiver 28. It should be understood that the converter of this invention may also be used in a transmitter mode by replacing the receiver 28 with a transmitter. Thus linearly polarized transmitted microwave signals now entering rectangular waveguide at 23-3 may be converted to circularly polarized microwave energy by positioning the fins as shown in either Figs. 6B or 6C for transmission from the circular waveguide 22 through horn 20-4 against the dish 20-1 for beaming at e.g. a communications satellite.

[0019] Likewise, transmitted linearly polarized microwave signals entering the rectangular waveguide 23 may be transmitted as linearly polarized signals by the antenna without a change in polarization by positioning the fin as shown in either Figs. 6A or 6D.

[0020] It has been found that for a bandwidth of 11.7-12.7 GHz with a center frequency of 12.2 GHz the fin face 26-1a should be .525 inches from the shorting plate 27 and it is preferred that the fin face be positioned to the right of wall 23-5 about .105" inches. It should also be understood that the fin may be directly driven by the coupling member by the shaft. The plate 27 may be of a thickness of 25 mils and a fin 26 having a width dimension (w) of .020 inches, a length (1) dimension of .605 inches and a thickness (t) of .225 inches has been found adequate using a circular waveguide 22 of an inner diameter .622 inches and a rectangular waveguide 23 of an inner length dimension (1) .750 inches between walls 23-5 and 23-6 and width (w) dimension .093 inches is satisfactory.

[0021] It should also be understood that the fin thickness as well as the other dimensions may be varied as will be appreciated, and it is understood that the dimensions given are only by way of example for the preferred embodiment at this time.

Claims

1. A system comprising a polarization converter including a circular waveguide (22) having a first open extremity and a second extremity having a rectangular opening in its side wall proximal to the second extremity, a rectangular waveguide (23) having an opening for receiving or transmitting a signal, connected to the circular waveguide at the rectangular opening thereof, the center line (23-1) of the rectangular waveguide (23) being substantially perpendicular to the center line (22-1) of the circular waveguide (22), a unit (26) closing the second extremity having a metal fin (26-1) and a shorting member (27), said fin (26-1) being at a preset distance from said shorting member (27), said fin (26-1 ) being movable with respect to the center line (23-1) of the rectangular waveguide (23) about the axis (22-1) of the circular waveguide (22) with the face thereof (26-1 a) substantially at right angles to the axis (22-1) of the circular waveguide (22), and means at the first open extremity providing circular polarized microwave signals to the circular waveguide (22), characterized in that the shorting member (27) and the fin (26-1) are positioned in the circular waveguide (22) at the opening of the rectangular waveguide (23) into the circular waveguide (22) and that the fin (26-1) has a front edge positioned between the center line (23-1) of the rectangular waveguide and a wall (23-5) of the rectangular waveguide (23) being farthest from the circular waveguide opening (20-4a).

2. The system according to claim 1 in which a re- ceiverdown converter (28) is coupled to the rectangular waveguide (23) at the outlet thereof.

3. The system according to claim 1 or 2 in which an antenna horn (20-4) is coupled to the opening to the circular waveguide (22).

4. The system according to claim 3 comprising a dish reflector (20-1), the horn (20-4) positioned to receive reflected microwave energy from said reflector (20-1) or provide microwave energy to be reflected by said reflector (20-1).

5. The system according to one of claims 1 to 4 in which the shorting member (27) is spaced from the metal fin (26-1) positioned at the opening of said rectangular waveguide (23) into said circular waveguide (22) with the shorting member (27) being positioned with respcet to said metal fin (26-1 ) so that microwave energy traveling in said waveguides in either direction initially encounters said fin (26-1), said shorting member (27) being positioned inwardly of said wall (23-5).

6. The system of one of claims 1 to 5 including means (24) for rotating said fin (26-1 ) about the axis (22-1) of said circular waveguide (22).

7. The system according to one of claims 1 to 6 in which a circularly polarized input microwave signal is converted to a linear polarized signal, comprising a polarization converter, said fin (26-1) being spaced a predetermined distance from said shorting member (27) depending upon the wavelength of the frequency of the signal whose polarization is to be converted.

Revendications

1. Dispositif comprenant un convertisseur de polarisation incluant un guide d'ondes circulaire (22) présentant une première extrémité ouverte et une deuxième extrémité dans laquelle est ménagée une ouverture rectangulaire dans une paroi latérale, proximale à la deuxième extrémité, un guide d'ondes rectangulaire (23) présentant une ouverture pour recevoir ou émettre un signal, connecté au guide d'ondes circulaire à l'endroit de l'ouverture rectangulaire, la ligne médiane (23-1) du guide d'ondes rectangulaire (23) étant essentiellement perpendiculaire à la ligne médiane (22-1) du guide d'ondes circulaire (22), une unité (26) présentant une ailette de métal (26-1) et un organe servant à la mise en court- circuit (27), ladite ailette (26-1) étant à une distance prédéterminée dudit organe servant à la mise en court-circuit (27), ladite ailette (26-1) étant mobile par rapport à la ligne médiane (23-1) du guide d'ondes rectangulaire (23) autour de l'axe (22-1) du guide d'ondes circulaire (22) et sa face (26-1 a) étant essentiellement à angle droit par rapport à l'axe (22-1) du guide d'ondes circulaire (22), et des moyens situés à l'endroit de la première extrémité ouverte fournissant des signaux micro-onde à polarisation circulaire au guide d'ondes circulaire (22), caractérisé en ce que l'organe servant à la mise en court- circuit (27) et l'ailette (26-1) sont positionnés dans le guide d'ondes circulaire (22) à l'ouverture du guide d'ondes rectangulaire (23) dans le guide d'ondes circulaire (22) et en ce que l'ailette (26-1) a un bord avant positionné entre la ligne médiane (23-1) du guide d'ondes rectangulaire et une paroi (23-5) du guide d'ondes rectangulaire (23) la plus éloignée de l'ouverture du guide d'ondes circulaire (20-4a).

2. Dispositif selon la revendication 1, caractérisé en ce qu'un convertisseur abaisseur de fréquence (28) est couplé au guide d'ondes rectangulaire (23) à sa sortie.

3. Dispositif selon la revendication 1 ou 2, caractérisé en ce qu'un cornet d'antenne (20-4) est couplé à l'ouverture du guide d'ondes circulaire (22).

4. Dispositif selon la revendication 3, caractérisé en ce qu'il comprend un réflecteur parabolique (20-1) et le cornet (20-4) positionné de manière à recevoir une énergie micro-onde réfléchie par ledit réflecteur (20-1) ou à fournir une énergie micro-onde qui doit être réfléchie par ledit réflecteur (20-1 ).

5. Dispositif selon l'une des revendications 1 à 4, caractérisé en ce que l'organe servant à la mise en court-circuit (27) est écarté de l'ailette en métal (26-1) positionnée à l'ouverture dudit guide d'ondes rectangulaire (23) à l'intérieur dudit guide d'ondes circulaire (22), l'organe servant à la mise en court- circuit (27) étant positionné par rapport à ladite ailette en métal (26-1 ) de telle sorte que de l'énergie micro-onde se déplaçant dans lesdits guides d'ondes dans l'une ou l'autre direction rencontre ladite ailette (26-1) au début, ledit organe servant à la mise en courtcircuit (27) étant positionné à l'intérieur de ladite paroi (23-5).

6. Dispositif selon l'une des revendications 1 à 5, caractérisé en ce qu'il comprend des moyens (24) servant à faire tourner ladite ailette (26-1) autour de l'axe (22-1) dudit guide d'ondes circulaire (22).

7. Dispositif selon l'une des revendications 1 à 6, dans lequel un signal micro-onde d'entrée à polarisation circulaire est converti en un signal à polarisation linéaire, comportant un convertisseur de polarisation, caractérisé en ce que ladite ailette (26-1) est écartée dudit organe servant à la mise en court- circuit (27) d'une distance prédéterminée dépendant de la longueur d'onde de la fréquence du signal dont la polarisation doit être convertie.

Ansprüche

1. Gerät mit einem Polarisationswandler mit einem kreisförmigen Wellenleiter (22) mit einem ersten offenen Ende und einem zweiten Ende und einer rechteckigen Öffnung in seiner Seitenwand in der Nähe des zweiten Endes, einem rechteckigen Wellenleiter (23) mit einer Öffnung zum Empfangen oder Übertragen eines Signales, der mit dem kreisförmigen Wellenleiter an dessen rechteckiger Öffnung verbunden ist, wobei die Mittellinie (23-1) des rechteckigen Wellenleiters (23) im wesentlichen senkrecht zu der Mittellinie (22-1) des kreisförmigen Wellenleiters (22) steht, einer das zweite Ende schließenden Einheit (26) mit einer Metallrippe (26-1) und einem Kurzschlußteil (27), wobei die Rippe (26-1) in einem voreingestellten Abstand von dem Kurzschlußteil (27) angeordnet ist, die Rippe (26-1) bewegbar in bezug auf die Mittellinie (23-1) des rechteckigen Wellenleiters (23) um die Achse (22-1) des kreisförmigen Wellenleiters (22) ist und deren Vorderfläche (26-1a) im wesentlichen in rechten Winkeln zu der Achse (22-1) des kreisförmigen Wellenleiters (22) liegt, und einer Einrichtung an dem ersten offenen Ende, die zirkularpolarisierte Mikrowellensignale an den kreisförmigen Wellenleiter (22) abgibt, dadurch gekennzeichnet, daß das Kurzschlußteil (27) und die Rippe (26-1) in dem kreisförmigen Wellenleiter (22) an der Öffnung des rechteckigen Wellenleiters (23) in den kreisförmigen Wellenleiter (22) angeordnet sind und daß die Vorderkante der Rippe (26-1 ) zwischen der Mittellinie (23-1) des rechteckigen Wellenleiters und einer Wand (23-5) des rechteckigen Wellenleiters (23) angeordnet ist, die am weitesten von der Öffnung (20-4a) des kreisförmigen Wellenleiters entfernt ist.

2. Gerät nach Anspruch 1, bei dem ein Empfänger-Abwärtswandler (28) mit dem rechteckigen Wellenleiter (23) an dessen Auslaß verbunden ist.

3. Gerät nach Anspruch 1 oder 2, bei dem ein Antennenhorn (20-4) mit der Öffnung des kreisförmigen Wellenleiters (22) verbunden ist.

4. Gerät nach Anspruch 3 mit einem Schüsselreflektor (20-1), bei dem das Horn (20-4) zum Empfangen von von dem Reflektor (20-1) reflektierter Mikrowellenenergie oder zum Vorsehen von von dem Reflektor (20-1) zu reflektierender Mikrowellenenergie angeordnet ist.

5. Gerät nach einem der Ansprüche 1 bis 4, bei dem das Kurzschlußteil (27) in einem Abstand von der Metallrippe (26-1) angeordnet ist, die an der Öffnung des rechteckigen Wellenleiters (23) in den kreisförmigen Wellenleiter (22) angeordnet ist, wobei das Kurzschlußteil (27) in bezug auf die Metallrippe (26-1) so angeordnet ist, daß die in den Wellenleitern in eine der Richtungen wandernde Mikrowellenenergie zuerst die Rippe (26-1) trifft und das Kurzschlußteil (27) inwärts von der Wand (23-5) angeordnet ist.

6. Gerät nach einem der Ansprüche 1 bis 5 mit einer Einrichtung (24) zum Drehen der Rippe (26-1 ) um die Achse (22-1) des kreisförmigen Wellenleiters (22).

7. Gerät nach einem der Ansprüche 1 bis 6, bei dem ein zirkularpolarisiertes Eingangsmikrowellensignal in ein linearpolarisiertes Signal gewandelt wird, mit einem Polarisationswandler, wobei die Rippe (26-1) in einem vorbestimmten Abstand von dem Kurzschlußteil (27) angeordnet ist, der von der Wellenlänge der Frequenz des Signales abhängt, dessen Polarisation zu wandeln ist.

Drawing