Abstract:
An antenna comprising a reflector ( 20 ) connected to a motor drive ( 30 ), a primary radiator ( 30 ) for transceiving a radio beam at an operating frequency impinged on the reflector ( 20 ) is disclosed. A coarse alignment system comprising a motor drive is connected to the reflector ( 20 ) for driving at least one of the rotation and the tilting of the reflector. The coarse alignment system ( 70; 270; 370; 470 ) comprising an auxiliary antenna ( 50 ) connected to the control device ( 60 ) for communicating with a further auxiliary antenna ( 10   b ), at a second frequency different from the operating frequency. A fine alignment system is also present for electronic adjustment of the radio beam. A control device controls the coarse alignment system and the fine alignment system.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to an antenna system with two antennas being adapted to automatically align with each other and a method for automated alignment of the at least two antennas. 
       BACKGROUND TO THE INVENTION 
       [0002]    Microwave radio relay is a technology for the transmission of digital signals and analog signals, such as telephone calls, television programs, and computer data between two locations using microwave links on a line of sight radio path. The microwaves are transmitted between the two locations along the microwave links using directional antennas. The requirement of a line of sight for the microwave link limits the distance between the two locations up to maximum of about 50 kilometers. 
         [0003]    Microwaves along the microwave link between the two locations have extremely narrow beams. This narrow beam has the advantage that the narrow beam is confined to a line of sight path from the one location to the other location and the microwaves do not therefore interfere with other microwave equipment. The narrow beams are also an advantage for the transmission of maximum power. Similarly, other ones of the microwave links nearby can use the same frequencies, as the microwave links will not interfere with each other. The antennas used in such microwave link systems must be therefore highly directional. The highly directional beam of the microwave link may reduce the risk of interference, but it does complicate the alignment of the radio beams in the microwave link between the two antennas. The direction is highly sensitive to the positioning of the antenna and, in particular, to the positioning of any reflectors in the antenna. 
         [0004]    The issue of aligning microwave antennas is known, for example from U.S. Pat. No. 6,836,675 (Zhang), which teaches a method for aligning antennas during the installation of microwave communications systems. A computerized link quality mechanism monitors the link quality of the link during the aligning of the installation. The link quality comprises the performance of the data communications status, such as the signal strength and the noise test results. 
       SUMMARY OF THE INVENTION 
       [0005]    An antenna system to enable the automatic alignment of two antennas in a microwave relay is disclosed. The antenna system comprises a reflector connected to a motor drive, a primary radiator for transceiving a radio beam at an operating frequency impinged on the reflector; a coarse alignment system comprising a motor drive connected to the reflector for at least one of rotation and tilting of the reflector, a fine alignment system for electronic adjustment of the radio beam; and a control device for controlling the coarse alignment system and the fine alignment system. 
         [0006]    The motor drive is required for the initial coarse alignment of the dish or parabolic antenna. Once the radio beam is directed along the microwave link to the other dish or parabolic antenna, the motor drive can be switched off and, if required, disabled. Any finer and further adjustments to the radio beam are carried out in the primary radiator of the dish or parabolic antenna. The motor drive is generally not required any longer, once the broad alignment has been carried out. The motor drive can be left to rust and it generally requires no maintenance. 
         [0007]    The control device is used in order to drive the motor drive for the rotation and/or tilting of the reflector of the dish or parabolic antenna or for the rotation and/or tilting of the whole dish or parabolic antenna and later make the fine adjustments. The control device can, if required, communicate with the motor drive of the other dish or parabolic antenna of the antenna system. 
         [0008]    The coarse alignment system comprises an auxiliary antenna connected to the control device for communicating with a further auxiliary antenna, at a second frequency different from the operating frequency. 
         [0009]    In a further aspect of the disclosure, the control device is adapted to detect side lobes of the operating frequency for controlling the coarse alignment system. 
         [0010]    In another aspect of the disclosure, the primary radiator comprises a first transceiver, and the fine alignment system comprises an auxiliary transceiver and a commuting system for commuting between the first transceiver and the auxiliary transceiver. 
         [0011]    The present disclosure also teaches an antenna system comprising at least two antennas as described above, and the control devices of the at least two antennas are adapted to exchange control messages concerning alignment of the at least two antennas. 
         [0012]    The present disclosure further teaches a method for aligning a first antenna and a second antenna, the first antenna having a first primary radiator and a first primary reflector, the second antenna having a second primary radiator and a second primary reflector, the method comprising: causing at least one of the first and second reflectors to rotate and/or tilt using a motor drive and thus establishing a communications link with a second one of the two antenna; adjusting the communications link by electronically changing parameters of the radio beam along the communications link. 
         [0013]    The method comprises establishing an auxiliary communication link between a first auxiliary antenna and a second auxiliary antenna of the two antennas. 
         [0014]    In yet another aspect of the disclosure, the method comprises using side lobes of an operating beam between a first primary radiator and a second primary radiator of the two antennas. 
         [0015]    In a further aspect of the disclosure, the method comprises sending a control message from the first one of the two antenna systems to the second one of the two antenna systems during rotation of the reflector indicative of a strength of the communications link. 
         [0016]    In an aspect of the invention, the method may comprise disabling the motor drive after establishment of the communications link. 
         [0017]    In another aspect of the invention, the method further comprises using a first transceiver and a second transceiver when the communication link is established, for adjusting the communication link, and commuting between the first transceiver and the auxiliary transceiver. 
         [0018]    These and other aspects of the invention will be apparent from and elucidated reference to the embodiment(s) described hereinafter. 
     
    
     
       DESCRIPTION OF THE FIGURES 
         [0019]      FIG. 1  shows an antenna system with two dish or parabolic antennas to be automatically aligned using a fixed communication link between the dish or parabolic antennas, according to one aspect of the disclosure. 
           [0020]      FIG. 2  shows an antenna system with two dish or parabolic antennas to be automatically aligned using auxiliary antennas, according to another aspect of the disclosure. 
           [0021]      FIG. 3  shows a preferred embodiment of a primary radiator which can be used with an antenna system according to  FIG. 1  or  FIG. 2 . 
           [0022]      FIG. 4  shows a method for the alignment of two antennas of an antenna system according to one aspect of the disclosure. 
           [0023]      FIG. 5  shows another method for alignment of two antennas of an antenna system according to another aspect of the disclosure. 
           [0024]      FIG. 6  shows an antenna system with two dish or parabolic antennas to be automatically aligned using auxiliary antennas, according to another aspect of the disclosure. 
           [0025]      FIG. 7  shows an embodiment of a primary radiator which can be used with an antenna system according to  FIG. 6 . 
           [0026]      FIG. 8  shows a workflow of a method of alignment an antenna system according to an aspect of the disclosure. 
           [0027]      FIG. 9  shows an alternate embodiment of a primary radiator and adjustment system which can be used with an antenna system in an aspect of the disclosure. 
           [0028]      FIG. 10  shows an alternate embodiment of a primary radiator which can be used with an antenna system in an aspect of the disclosure. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0029]    The invention will now be described on the basis of the drawings. It will be understood that the embodiments and aspects of the invention described herein are only examples and do not limit the protective scope of the claims in any way. The invention is defined by the claims and their references. It will be understood that features of one aspect or embodiment of the invention can be combined with a feature of a different aspect or aspects and/or embodiments of the invention. 
         [0030]      FIG. 1  shows an example of an antenna system  5  of this disclosure. The antenna system  5  comprises a first parabolic antenna  10   a  and a second parabolic antenna  10   b  that have to be aligned with each other. The distance  15  between the two parabolic antennas  10   a  and  10   b  can be between 0.01 or less km and 50 kilometers, but this is not limiting of the invention. Throughout the disclosure, elements which are identical are designated with the same reference number. The letter “a” and “b” are mainly used to distinguish between elements described with reference to a first parabolic antenna (left on the figure) and a letter “b” for the elements described with reference to a second parabolic antenna (right on the figures). 
         [0031]    The antenna system  5  is configured to transmit signals along a communications link  25  (also termed microwave link). In one aspect of the disclosure, the antenna system is configured to transmit radio waves in the microwave band at around 60 GHz. This microwave band is suitable for the transmission of telephone calls, data and television transmissions, but this again is not limiting the invention. 
         [0032]    The first parabolic antenna  10   a  has a first reflector  20   a  and a first primary radiator  30   a . The second parabolic antenna  10   b  has a second reflector  20   b  and a second primary radiator  30   b . The primary radiators  30   a ,  30   b  are adapted to receive radio signals on the communications link  25  between the first parabolic antenna  10   a  and the second parabolic antenna  10   b  and/or to transmit radio signals over the communications link  25 . 
         [0033]    It is known that this transmission is carried out by transmitting a signal from the first primary radiator  30   a  as a signal  70 , which is then reflected in the direction of the second parabolic antenna  10   b  by the first reflector  20   a . Similarly, a signal is received along the communications link  25  by the first reflector  20   a  and focused onto the first antenna array  30   a , where the signal is processed. Similarly the second primary radiator  30   ba  transmits a signal is then reflected in the direction of the first parabolic antenna  10   a  by the second reflector  20   b . A signal is received along the communications link  25  by the second reflector  20   b  and focused onto the second primary radiator  30   b , where the signal is processed. 
         [0034]    The primary radiator may be an antenna array having a plurality of antenna elements, as shown on  FIG. 3 . The primary radiator  30   a  comprises at least one array of radiation elements  32 . In the example of  FIG. 3 , the array comprises eight radiation elements  32 , but this is not limiting the invention. Preferably, the radiation elements  32   a ,  32   b , are individually and independently controllable and addressable. This means that the phase and amplitude of the radiation elements  32  are either individually addressable, or addressable in subsets of radiation elements  32 . 
         [0035]    The array of the primary radiator can be made up of several dielectric antennas, patch antennas, printed dipoles or horn antennas. For the avoidance of doubt, the use of the radiator type is not limiting this invention. Furthermore, the primary radiator may otherwise be a single horn antenna or another single radiator. 
         [0036]    The communications link  25  is highly directional. That means the radiation characteristic of the first and second parabolic antennas comprises a narrow beam in the main radiation direction. Therefore, these narrow beams of the parabolic antennas have to be aligned by substantially aligning the first reflector  20   a  or the whole first parabolic antenna  10   a  with the second reflector  20   b  or the whole second parabolic antenna  10   b  of the antenna system. This alignment is carried out in a two-stage process, as will be described with respect to  FIG. 4 . 
         [0037]    A first coarse adjustment system  42   a  and a second coarse adjustment system  42   b  are provided to align mechanically the first and second parabolic antennas  10   a ,  10   b . The first coarse adjustment system  42   a  comprises a first motor drive  40   a  which is connected to the first reflector  20   a  or the first parabolic antenna  10   a . The second coarse adjustment system  42   b  comprises a second motor drive  40   b  which is connected to the second reflector  20   b  or the second parabolic antenna  10   b.    
         [0038]    The first and/or second motor drive  40   a ,  40   b  are used for broadly aligning the first reflector  20   a  or the whole first parabolic antenna  10   b  with the second reflector  20   b  or the whole second parabolic antenna  10   b.    
         [0039]    The first motor drive  40   a  is adapted to rotate the first reflector  20   a  or the whole first parabolic antenna  10   a  around a main axis Xa, in a plane substantially perpendicular to the direction of the communications link  25 , as shown by rotational arrow  45 . The first motor drive  40   a  is further adapted to tilt the first reflector  20   a  or the entire first parabolic antenna  10   a  in a plane comprising the direction of the communication links, as shown by rotational arrow  46   a . Similarly, the second motor drive  40   b  is adapted to rotate the second reflector  20   b  or the whole second parabolic antenna  10   b  around a main axis Xb, in a plane substantially perpendicular to the direction of the communications link  25 , as shown by rotational arrow  45   b . The second motor drive  40   b  is further adapted to tilt the second reflector  20   b  or the entire second parabolic antenna  10   b  in a plane comprising the direction of the communication links, as shown by rotational arrow  46   b.    
         [0040]    The first motor drive  40   a  is connected to a first control system  60   a , and the second motor drive  40   b  is connected to a second control system  60   b . The first control system  60   a , respectively second control system  60   b , is adapted to control the first motor drive  40   a , respectively second motor drive  40   b , and hence the rotation and/or tilting of the first reflector  20   a  or the whole first parabolic antenna  10   a , respectively the second reflector  20   b  or the whole second parabolic antenna  10   b.    
         [0041]    The control system  60   a ,  60   b  has a receiver to receive the control signals either from a fixed line network  80  (or a further communications network, such as using the GSM, UMTS or LTE protocol) or from the further control system  60   b ,  60   a.    
         [0042]    As will be explained with reference to  FIG. 5 , the first and/or second coarse adjustment system  42   a ,  42   b  is used for a coarse adjustment of the antenna system  5 . Once the direction of the radio beam along the communications link  25  has been broadly aligned by rotation and/or tilting of the reflector  20   a  (and also possibly by the rotation and/or tilting of the further reflector  20   b ), the first and second coarse adjustment system  42   a ,  42   b  together with the motor drive  40   a  can be switched off or disabled. The first motor drive  40   a  and/or the second motor drive  40   b  will no longer be required and can be disconnected from a power supply. The motor drive  40   a  and/or the second motor drive  40   b  will no longer be used and can be allowed to rust if required. 
         [0043]    The first antenna  10   a  comprises a first fine adjustment system  70   a  and the second antenna  10   b  comprises a second fine adjustment system  70   b , to carry out fine adjustments to the direction of the radio beam. The first fine adjustment system  70   a  is adapted to receive control signals from the first control device  60   a . The second fine adjustment system  7   b  is adapted to receive control signals from the second control device  60   b.    
         [0044]    The fine adjustment system is enabled to adjust the direction of the beam, in order to compensate for variations arising from e.g. vibrations of the antenna, as will be explained with reference to  FIG. 4 . 
         [0045]    In particular, when the primary radiator is an array of radiation elements, the fine adjustment system is adapted to adjust the phase and amplitude of the radiation elements. When the primary radiator is a horn antenna, the fine adjustment system comprises lenses or a separate actuator at the feed. 
         [0046]      FIG. 2  shows an example of an antenna system  205  according to another aspect of this disclosure. 
         [0047]    The antenna system  205  comprises a first parabolic antenna  210   a  and a second parabolic antenna  210   b  that have to be aligned with each other. The first parabolic antenna  210   a  has a first reflector  220   a  and a first primary radiator  230   a . The second parabolic antenna  210   b  has a second reflector  220   b  and a second primary radiator  230   b . The primary radiators  230   a ,  230   b  are adapted to receive radio signals on a communications link  225  between the first parabolic antenna  210   a  and the second parabolic antenna  210   b  and/or to transmit radio signals over the communications link  225 . 
         [0048]    A first coarse adjustment system  242   a  and a second coarse adjustment system  242   b  are provided to align mechanically the first and second parabolic antennas  210   a ,  210   b . The first coarse adjustment system  242   a  comprises a first motor drive  240   a  which is connected to the first reflector  220   a  or the first parabolic antenna  210   a . The second coarse adjustment system  242   b  comprises a second motor drive  240   b  which is connected to the second reflector  220   b  or the second parabolic antenna  210   b.    
         [0049]    The first and/or second motor drive  240   a ,  240   b  are used for broadly aligning the first reflector  220   a  or the whole first parabolic antenna  210   b  with the second reflector  220   b  or the whole second parabolic antenna  210   b.    
         [0050]    The first motor drive  240   a  is adapted to rotate the first reflector  220   a  or the whole first parabolic antenna  210   a  around a main axis Xa, in a plane substantially perpendicular to the direction of the communications link  225 , as shown by rotational arrow  246   a . The first motor drive  240   a  is further adapted to tilt the first reflector  220   a  or the entire first parabolic antenna  210   a  in a plane comprising the direction of the communication links, as shown by rotational arrow  246   a . Similarly, the second motor drive  240   b  is adapted to rotate the second reflector  220   b  or the entire second parabolic antenna  210   b  around a main axis Xb, in a plane substantially perpendicular to the direction of the communications link  225 , as shown by rotational arrow  245   b . The second motor drive  240   b  is further adapted to tilt the second reflector  220   b  or the entire second parabolic antenna  210   b  in a plane comprising the direction of the communication links, as shown by rotational arrow  246   b.    
         [0051]    The first motor drive  240   a  is connected to a first control system  260   a , and the second motor drive  240   b  is connected to a second control system  260   b . The first control system  260   a , or the second control system  260   b , is adapted to control the first motor drive  240   a , or respectively the second motor drive  240   b , and hence to control the rotation and/or the tilting of the first reflector  220   a  or the entire first parabolic antenna  210   a , or respectively the second reflector  220   b  or the entire second parabolic antenna  210   b.    
         [0052]    A first auxiliary antenna  250   a  and a second auxiliary antenna  250   b  are positioned at the location of the first parabolic antenna  210   a  and of the second parabolic antenna  210   b , respectively, and are connected to the first control system  260   a  and the second control system  260   b . The first auxiliary antenna  250   a  and the second auxiliary antennas  250   b  can establish an auxiliary radio beam or radio link in general between the location of the first parabolic antenna  210   a  and the second parabolic antenna  210   b  for a coarse adjustment of the first parabolic antenna  210   a  and the second parabolic antenna  210   b.    
         [0053]    The first auxiliary antenna  250   a  can transmit the auxiliary radio beam to the second auxiliary antenna  250   b , at a much lower frequency, for example 5.6 GHz, but this is not limiting of the invention, in order to control the broad adjustment of the radio beam along the communications path  225 . The 5.6 GHz beam is not highly directional and does not need any adjustment. Hence, the coarse adjustment of the antenna system may be facilitated. 
         [0054]    Alternately, the first auxiliary antenna  250   a  and the second auxiliary antenna  250   b  may be adapted to exchange control signals using different communication standards from the communication standard used by the radio signals to be established between the main antennas  210   a  or  210   b . Examples of different communication standards comprise, but are not limited thereto, a ZigBee protocol or a proprietary standard at 433 MHz. 
         [0055]    The first auxiliary antenna  250   a  and the second auxiliary antenna  250   b  are therefore part of the first coarse adjustment system  242   a  or the second coarse adjustment system  242   b . The first auxiliary antenna  250   a  and/or the second auxiliary antenna  250   b  can receive and/or send information to and from the first controller  260   a  and/or the second controller  260   b , e.g. on a level of received power for each position of the mobile reflector. 
         [0056]      FIG. 4  shows an example of a method of this disclosure, with reference to the antenna system  5  described in  FIG. 1 . 
         [0057]    In a first step S 200 , the first and second parabolic antennas  10   a  and  10   b  are erected at their locations. The locations are within line of sight of each other and the first and second reflectors  20   a  and  20   b  will be mounted on the mounts connected to the first and second motor drives  40   a  and  40   b.    
         [0058]    The control system  60   a  and  60   b  will then start in step  210  the rotation of at least one of the first reflector  20   a  and the second reflector  20   b  in order to align the first reflector  20   a  and the second reflector  20   b  with each other. 
         [0059]    The skilled person will understand that a first one of the two reflectors  20   a ,  20   b  may be fixed whilst the other one of the two reflectors  20   b ,  20   a  is rotated and/or tilted during alignment. Alternately, both of the reflectors  20   a ,  20   b  may be rotated and/or tilted during alignment. 
         [0060]    The first reflector  20   a  and the second reflector  20   b  may be aligned by using an alignment beam signal which is transmitted from one antenna to the other antenna. The received power may be measured for each position of the first reflector  20   a  and/or the second reflector  20   b  (step S 220 ). The first control system  60   a  and the second control system  60   b  can determine a position where the received power is higher, for example using an iterative process until a position of at least one of the two reflectors  20   a  or  20   b  corresponding to a maximum received power is determined. 
         [0061]    The rotation and/or tilting of the two reflectors  20   a ,  20   b  is controlled by the two control systems  60   a ,  60   b . The two control systems  60   a ,  60   b  may therefore exchange control or/and status messages in step S 220  by the fixed link  80 . Alternatively, the communication link between the two control systems  60   a ,  60   b  can be established by using the sidelobes of the reflector antennas radiation pattern. The communication of the control messages or/and the status messages does not need a link with high data rates, which are only possible using the main beam. So, if the receivers of the control systems are sensitive enough, the sidelobes of the reflector antennas radiation pattern can be used for communicating the control messages or/and the status messages. 
         [0062]    The first reflector  20   a  and the second reflector  20   b  may be aligned by using an alignment beam signal which is transmitted from one antenna to the other antenna. The received power may be measured for each position of the first reflector  20   a  and/or the second reflector  20   b . The first control system  60   a  and the second control systems  60   b  can determine a position where the received power is higher, for example using an iterative process until a position of at least one of the reflectors corresponding to a maximum received power is determined (step S 230 ). 
         [0063]    The rotation and/or tilting of the two reflectors  20   a ,  20   b  is controlled by the two control systems  60   a ,  60   b . Once the two control systems  60   a ,  60   b  determine in step S 230  that the both of the two reflectors  20   a  and  20   b  are substantially aligned with each other such that the directional radio beam on the communications link  225  is well received, the control system  260   a  and  260   b  can disable the motor drives  40   a  and  40   b  in step S 240 . 
         [0064]    The motor drive  40   a ,  40   b , will no longer be used and can be allowed to rust, if required. 
         [0065]    Fine adjustments of the radio beam along the communications link  25  are carried out in step S 250  using the antenna array  30 . It is known that these adjustments can be adapted by using active components and/or software control to adjust the phase and amplitude of the signals for every antenna element of the array for forming the radio beam along the communications link  25 . This fine adjustment can cope with any small movement of the parabolic antennas  10   a  and  10   b.    
         [0066]      FIG. 5  shows another example of a method of this disclosure, with reference to the antenna system  205  described in  FIG. 2 . 
         [0067]    In a first step S 2200 , the first parabolic antenna  210   a  and the second parabolic antennas  210   b  are erected at their locations. The locations are within line of sight of each other and the first reflector  220   a  and the second reflectors  220   b  will be mounted on the mounts connected to the first motor drive  240   a  and the second motor drive  240   b.    
         [0068]    An alignment beam will then be emitted and the control system  260   a  and  260   b  will then start, in step S 2210 , the rotation and possibly the tilting of at least one of the first reflector  220   a  and the second reflector  220   b  in order to align both of the two reflectors  220   a  and  220   b  with each other. 
         [0069]    The first reflector  220   a  and the second reflector  220   b  may be aligned by using an alignment beam signal which is transmitted from one antenna to the other antenna. The received power may be measured for each position of the first reflector  220   a  and/or the second reflector  220   b  (step S 2220 ). The first control system  260   a  and the second control systems  260   b  can determine a position where the received power is higher, for example using an iterative process until a position of at least one of the two reflectors  220   a ,  220   b  corresponding to a maximum received power is determined. 
         [0070]    The rotation and/or the tilting of the first reflector  220   a  is controlled by the first control system  260   a  and the rotation and/or tilting of the second reflector  220   b  is controlled by the second control system  260   b . In this aspect of the invention, a second link between the first auxiliary antenna  250   a  and the second auxiliary antenna  250   b  is used for adjusting the position of the first antenna and the second antenna of the antenna system. 
         [0071]    The control messages may comprise information and command relating to an amount of rotation or tilting. The status message may comprise information relating to an amount of received power measured on the antenna configured in reception during the antenna alignment. 
         [0072]    Once both of the control systems  260   a  and  260   b  determine in step S 2230  that both of the reflectors  20   a  and  20   b  are substantially aligned with each other such that the directional radio beam on the communications link  225  is well received, the two control systems  260   a  and  260   b  can disable the two motor drives  240   a  and  240   b  in step S 2240 . 
         [0073]    The two motor drives  240   a ,  240   b , will no longer be used and can be allowed to rust if required. 
         [0074]    Fine adjustments of the radio beam along the communications link  225  are carried out in step S 2250  using the antenna array  230 . It is known that these adjustments can be adapted by using active components and/or software control to adjust the phase and amplitude of the signals for every antenna element of the array for forming the radio beam along the communications link  225 . This fine adjustment can cope with any small movement of the parabolic antennas  210   a  and  210   b.    
         [0075]      FIG. 6  shows another example of an antenna system  305  according to one aspect of the disclosure, and  FIG. 7  is a detailed view of the primary radiator with a transmission system of  FIG. 6 . The antenna system  305  differs substantially from the antenna system  5  of  FIG. 1  in that the antenna system  305  comprises a primary transceiver  371  and auxiliary transceiver  373  as part of a fine adjustment system  370  for the fine adjustment of the antenna alignment. 
         [0076]    The antenna system  305  comprises a first parabolic antenna  310   a  and a second parabolic antenna  310   b  that have to be aligned with each other. The first parabolic antenna  310   a  has a first reflector  320   a  and a first primary radiator  330   a . The second parabolic antenna  310   b  has a second reflector  320   b  and a second primary radiator  330   b . The two primary radiators  330   a ,  330   b  are adapted to receive radio signals on a communications link  325  between the first parabolic antenna  310   a  and the second parabolic antenna  310   b  and/or to transmit radio signals over the communications link  325 . 
         [0077]    A first coarse adjustment system  342   a  and a second coarse adjustment system  342   b  are provided to align mechanically the first parabolic antenna  310   a  and the second parabolic antennas  310   b . The first coarse adjustment system  342   a  comprises a first motor drive  340   a , which is connected to the first reflector  320   a  or the first parabolic antenna  310   a . The second coarse adjustment system  342   b  comprises a second motor drive  340   b , which is connected to the second reflector  320   b  or the second parabolic antenna  310   b.    
         [0078]    A first fine adjustment system  370   a  is provided for the further finer adjustments of the antennas  310   a ,  310   b , and comprises a commuting system  375   a  as will be explained later in the disclosure. 
         [0079]    The first motor drive  340   a  and/or the second motor drive  340   a ,  340   b  are used for broadly aligning the first reflector  320   a  or the whole first parabolic antenna  310   b  with the second reflector  320   b  or the entire second parabolic antenna  310   b.    
         [0080]    The first motor drive  340   a  is adapted to rotate the first reflector  320   a  or the entire first parabolic antenna  310   a  around a main axis Xa, in a plane substantially perpendicular to the direction of the communications link  325 , as shown by rotational arrow. The first motor drive  340   a  is further adapted to tilt the first reflector  320   a  or the entire first parabolic antenna  310   a  in a plane comprising the direction of the communication links, as shown by rotational arrow  346   a . Similarly, the second motor drive  340   b  is adapted to rotate the second reflector  320   b  or the entire second parabolic antenna  310   b  around a main axis Xb, in a plane substantially perpendicular to the direction of the communications link  325 , as shown by rotational arrow  345   b . The second motor drive  340   b  is further adapted to tilt the second reflector  320   b  or the entire second parabolic antenna  310   b  in a plane comprising the direction of the communication links, as shown by rotational arrow  346   b.    
         [0081]    The first motor drive  340   a  is connected to a first control system  360   a , and the second motor drive  340   b  is connected to a second control system  360   b . The first control system  360   a , or the second control system  360   b , is adapted to control the first motor drive  340   a , or respectively the second motor drive  340   b , and hence the rotation and/or tilting of the first reflector  320   a  or the entire first parabolic antenna  310   a , or the second reflector  320   b  or the entire second parabolic antenna  310   b.    
         [0082]      FIG. 7  shows a detailed view of the primary radiator  330   a . In this aspect of the disclosure, the primary radiator  330   a ,  330   b  comprises at least one array of radiation elements  332   a ,  332   b . The radiation elements  332   a  are individually and independently controllable and addressable. This means that the phase and amplitude of the radiation elements  332  are either individually addressable, or addressable in subsets of radiation elements  332  by the fine adjustment system  370   a.    
         [0083]    A primary transceiver  371   a  comprises a primary power amplifier for transmitting and a primary low noise amplifier for receiving signals to/from the radiation elements of the primary radiator  330   a . Therefore the primary transceiver is coupled to a primary feeding network  372   a  which connects the primary transceiver to the respective antenna elements of the primary radiator  330   a.    
         [0084]    An auxiliary transceiver  373   a  comprises an auxiliary power amplifier for transmitting and an auxiliary low noise amplifier for receiving signals to/from the radiation elements of the primary radiator  330   a . Therefore the auxiliary transceiver  373   a  is coupled to a auxiliary feeding network  374   a  which connects the auxiliary transceiver to the respective antenna elements of the primary radiator  330   a.    
         [0085]    The auxiliary transceiver  373   a  and the respective auxiliary feeding network  374   a  are arranged parallel to the primary transceiver  371   a  and the respective primary feeding network  372   a.    
         [0086]    The primary feeding network  372   a  and the auxiliary feeding network  374   a  are adapted to form flexible radiation beams by changing the phase and amplitude of the feeding signals or by switching antenna elements on or off. 
         [0087]    The auxiliary transceiver  373   a  is part of said fine adjustment system  370   a.    
         [0088]      FIG. 8  shows a workflow of a method of alignment, which will now be described, with reference to the antenna system as shown in  FIG. 6 . 
         [0089]    In a first step S 3200 , the first parabolic antennas  310   a  and the second parabolic antennas  310   b  are erected at their locations. The locations are within line of sight of each other and the first reflectors  320   a  and the second reflectors  320   a  will be mounted on the mounts connected to the first motor drives  340   a  and the second motor drives  340   a.    
         [0090]    An alignment beam will then be emitted and the two control systems  360   a  and  360   b  will then start, in step S 3210 , the rotation and possibly the tilting of at least one of the first reflector  320   a  and the second reflector  320   b  in order to align the first reflector  320   a  and the second reflector  320   b  with each other. 
         [0091]    The coarse adjustment system  342   a ,  342   b  may be similar to the coarse adjustment system  42   a ,  42   b  of the antenna system  5  or to the coarse adjustment system  242   a ,  242   b  of the antenna system  205 . The first control system  360   a  and the second control system  360   b  can determine a position where the received power is higher, for example using an iterative process until a position at least one of the two reflectors  320   a ,  320   b  corresponds to a maximum received power is determined. 
         [0092]    Once the two control systems  360   a  and  360   b  determine in step S 3230  that the both of the reflectors  320   a  and  320   b  are substantially aligned with each other such that the directional radio beam on the communications link  325  is well received, the two control systems  360   a  and  360   b  can disable their corresponding motor drives  340   a  and  340   b  in step S 3240 . 
         [0093]    Suppose now that, after the coarse mechanical alignment, the signals are exchanged and processed via the primary transceiver  371   a  using the primary radiator  330   a.    
         [0094]    The fine adjustment system  370   a  adjusts the phase and amplitude of the primary feeding network  372   a  of the primary radiator  330   a  and checks a signal quality from the radiation elements  332   a  for a plurality of phase and amplitude configurations (step S 3250 ). When the fine adjustment has been done, the communication link is established via the primary transceiver  371   a.    
         [0095]    After some time, a misalignment of the two antennas  310   a  and  310   b  with respect to each other may occur. 
         [0096]    It is determined, by the auxiliary transceiver  373   a , that other second amplitude and phase parameters of the auxiliary feeding network  374   a  leads to a better signal quality of signal than the amplitude and phase parameters of the primary feeding network  372   a  of the primary radiator  330  (step S 3260 ). The determination is done by changing the amplitude and phase parameters of the auxiliary feeding network  374   a  until better phase and amplitude parameter are found. 
         [0097]    The commuting system  375   a  of the fine adjustment system  370   a  may therefore decide to commute the functions of the primary transceiver  371   a  and of the auxiliary transceiver  373   a  and to switch the communication to the auxiliary transceiver  373   a  with the auxiliary feeding network  374   a  having the better phase and amplitude parameters (step S 3270 ). 
         [0098]    The commuting of primary transceiver  371   a  and of the auxiliary transceiver  373   a  occurs on the fly, whilst the primary transceiver  371   a  and the auxiliary transceiver  373   a  are in use, therefore avoiding loosing some signal information. Once the commuting is achieved, the primary transceiver  371   a  is used for quality of signal investigation, whilst the auxiliary transceiver  373   a  is used as a main transceiver. 
         [0099]      FIG. 9  shows another example of primary radiator  430   a  with a fine adjustment system  470   a  which can be used with the antenna system of  FIG. 6 . 
         [0100]    The primary radiator  430   a  comprises a plurality of radiation elements  432   a , which are individually and independently controllable and addressable. 
         [0101]    A primary transceiver  471   a  comprises a primary power amplifier for transmitting and a primary low noise amplifier for receiving signals from the radiation elements of the primary radiator  430   a . Therefore the primary transceiver is coupled to a primary feeding network  472   a  which connects the primary transceiver to the respective antenna elements of the primary radiator  430   a.    
         [0102]    An auxiliary transceiver  473   a  comprises a auxiliary power amplifier for transmitting and an auxiliary low noise amplifier for receiving signals from the radiation elements of the primary radiator  430   a . Therefore the auxiliary transceiver  473   a  is coupled to a auxiliary feeding network  474   a  which connects the auxiliary transceiver to the respective antenna elements of the primary radiator  430   a.    
         [0103]    The auxiliary transceiver  473   a  and the respective auxiliary feeding network  474   a  is arranged parallel to the primary transceiver  471   a  and the respective primary feeding network  472   a.    
         [0104]    The primary feeding network  472   a  and the auxiliary feeding network  474   a  are adapted to form different radiation beams by changing the phase and amplitude of the feeding signals or by switching antenna elements on or off. 
         [0105]    The fine adjustment system  470   a  checks a signal quality transmitted from the auxiliary subset  433   a  of the radiation elements and the commuting system  475   a  may commute and switch from the primary subset  431   a  to the auxiliary subset  433   a , depending on the signal quality check. 
         [0106]    The steps S 3260  and S 3270  of the adjustment process described with reference to  FIG. 8  may be modified as follows. It is determined that the auxiliary subset  433   a  of the radiation elements  432   a  leads to a better signal quality than the primary subset  431   a  of the radiation elements  432   a . The signal quality can be determined using amplitude of the signal. 
         [0107]    The commuting system  475   a  of the fine adjustment system  470   a  commutes the functions of the primary transceiver  471   a  and of the auxiliary transceiver  473   a . Once the commuting has been carried out, the primary transceiver  471   a  in conjunction with the primary subset  431   a  of the radiation elements is used for investigating the quality of the signal, whilst the auxiliary transceiver  473   a  in conjunction with the auxiliary subset  431   a  of the radiation elements is used as a primary transceiver. The commuting system  475   a  may comprise a commuting matrix for the primary subset  431   a  of the radiation elements and the auxiliary subset  433   a  of the radiation elements  432   a . The commuting may be carried out in the intervals between the transmission and reception intervals in TDD (Time Division Duplexing) process. The commuting may be carried out in less than 100 ns. 
         [0108]    In contradistinction to the fine adjustment system  370   a  of  FIG. 7 , which was adapted to adjust the phase and amplitude parameters for the radiating elements  332   a  of the primary radiator  330   a , the fine adjustment system  470  of  FIG. 9  is adapted to commute from one of the primary subset  431   a  or the auxiliary subset  433   a  to the other one of the primary subset  431   a  or the auxiliary subset  433   a  which would lead to a better quality of signals, and vice versa. 
         [0109]      FIG. 10  shows yet another example of a primary radiator that can be used with the antenna system of  FIG. 6 . In this aspect of the disclosure, the primary radiator comprises at least two horn elements  532 ,  535 . 
         [0110]    A primary transceiver  571  is coupled to a primary amplifier  572  and is designed to transmit signals to a first horn element  532 . An auxiliary transceiver  573  is coupled to an auxiliary amplifier  574  and is designed to transmit signals to a second (auxiliary) horn element  535 . The fine adjustment of the horn elements can be done by using an actuator. Alternatively, an antenna array can be used instead of the horn antennas. 
         [0111]    Suppose now that, after a coarse mechanical alignment, the signals are exchanged and processed via the first horn element  532 . After some time, a misalignment of the antennas  310   a ,  310   b  with respect to each other may occur. This may be the case when one or both of the two antennas  310   a ,  310   b  have slightly moved, e.g. due to vibrations. 
         [0112]    It is determined that the second horn element  535  should be used and lead to a better signal quality of the signal than the first horn element  532 . 
         [0113]    A commuting system  575  carries out the commuting from the first horn element  532  to the second (auxiliary) horn element  535 . The commuting may occur whilst the primary transceiver  571  and the auxiliary transceiver  572  are in use, therefore avoiding losing some signal information during the passage from the first horn element  532  to the second (auxiliary) horn element  535 . Once the commuting is achieved, the primary transceiver  571  may be shut down. 
         [0114]    As noted above, the fine alignment of the radio beam can be carried out on the fly whilst the radio beam on the communication link  25  is being transmitted.