Abstract:
An optical LNB capable of fast position-adjusting is employed in an LNBF. The optical LNB includes a down-converting device coupled to an OMT of the LNBF for down-converting a polarized signal for generating a first intermediate frequency signal, a branching device for branching the first intermediate frequency signal for generating a second and a third intermediate frequency signals, an electrical/optical converting device coupled to the branching device for converting the second intermediate frequency signal into an optical signal, and a power end for receiving power from a power supply and outputting the third intermediate frequency signal.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a satellite communication receiving system, and more particularly, to a satellite communication receiving system capable of fast position-adjusting. 
     2. Description of the Prior Art 
     Satellite communication technology has advantages of wide coverage area and long distance linking, which is applied in many domains, such as in satellite broadcasts or communication systems. Thus, wherever you are (even on the ocean or in the desert), the satellite signal may be received by a corresponding antenna. 
     Please refer to  FIG. 1 .  FIG. 1  is a diagram illustrating a satellite communication receiving system  100  in the prior art during position-adjusting. The satellite communication receiving system  100  comprises a dish antenna  110 , a Low Noise Block Down-converter with Integrated Feed (LNBF)  120 , and a power supply  130 . In the satellite communication receiving system  100 , the paraboloid dish antenna  110  reflects the satellite signal onto the LNBF  120  located on the focal point of the dish antenna  110 . The satellite signal is polarized and down-converted to an intermediate frequency (IF) signal by the LNBF  120 . After that, the IF signals are converted to optical signals and outputted through an optical fiber cable. The power supply  130  provides power to the LNBF  120  through a coaxial cable. In the prior art, when a engineer installs the dish antenna  110  and adjusts the position of the dish antenna  110  for the satellite, a multiple dwelling unit (MDU)  140  has to be utilized for converting the optical signals outputted by the LNBF  120  to electrical signals and transmitting the electrical signals to the demodulating device  150 , e.g. set-top box (STB). In this way, the engineer can determine if the position of the dish antenna  110  is correct. However, generally the satellite communication receiving system  100  is disposed on the roof or the exterior wall of a building, where no power socket or power source is available, and therefore the engineer has to use power from the interior of the building for powering the MDU  140 . Such environmental disadvantage increases the difficulty for the installation and thus the time required for adjusting the satellite communication receiving system  100  to the correct position prolongs as well. 
     SUMMARY OF THE INVENTION 
     The present invention provides an optical Low Noise Block down-converter (LNB) capable of fast position-adjusting utilized in a Low Noise Block Down-converter with Integrated Feed (LNBF) of a satellite communication receiving system. The optical LNB comprises a down-converting device, coupled to an Orthomode Transducer (OMT) of the LNBF, for down-converting a polarized signal so as to generate a first Intermediate Frequency (IF) signal; a branching device, for branching the first IF signal, so as to generate a second and a third IF signals; an electrical/optical converting device, coupled to the branching device, for converting the second IF signal to an optical signal; and a power end for receiving power and outputting the third IF signal. 
     These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram illustrating a satellite communication receiving system in the prior art during position-adjusting. 
         FIG. 2  is diagram illustrating a satellite communication receiving system of the present invention during position-adjusting. 
         FIG. 3  is a functional block diagram illustrating the LNBF of the satellite communication receiving system of the present invention. 
         FIG. 4  is a diagram illustrating an embodiment of the down-converting device in  FIG. 3 . 
         FIG. 5A  through  FIG. 5G  are diagrams illustrating different embodiments of the branching device in  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION 
     Please refer to  FIG. 2 .  FIG. 2  is diagram illustrating a satellite communication receiving system  200  of the present invention during position-adjusting. The satellite communication receiving system  200  comprises a dish antenna  210  and a LNBF  220 . The LNBF  220  receives power from the demodulating device  250  through the coaxial cable and the power end of the LNBF  220 . The LNBF  220  polarizes the satellite signals received by the dish antenna  210 , down-converts the polarized signals to the IF signals, converts the IF signals to optical signals, and outputs the optical signals through the optical fiber cable. Additionally, the LNBF  220  also outputs the IF signals through the power end of the LNBF  220  and the coaxial cable. In this way, when the engineer execute position-adjusting for the dish antenna  210 , the IF signals transmitted through the coaxial cable can be transmitted to the demodulating device  250 , and the engineer can determine if the position of the dish antenna  210  is correct simply by the signal output from the demodulating device  250 , without the need of optical/electrical conversion by the MDU. 
     Simply speaking, since in the satellite communication receiving system  200 , the LNBF  220  directly outputs the IF signals through the power end of the LNBF  220  and the coaxial cable, the engineer can determine if the position of the dish antenna  210  is correct simply according to the signal output from the demodulating device  250 . In such condition, the MDU is no longer required for optical/electrical conversion. More importantly, the engineer executes position-adjusting with convenience. 
     Please refer to  FIG. 3 .  FIG. 3  is a functional block diagram illustrating the LNBF  220  of the satellite communication receiving system  200 . As shown in  FIG. 3 , the LNBF  220  comprises an Orthomode Transducer (OMT)  310 , a down-converting device  320 , a branching device  330 , and an electrical/optical converting device  340 . Additionally, the LNBF  220  comprises a feedhorn for receiving the satellite signals reflected by the dish antenna  210 . The OMT  310  polarizes the satellite signal S S  into the vertical polarized signal S V  and the horizontal polarized signal S H . The down-converting device  320  down-converts the vertical polarized signal S V  and the horizontal polarized signal S H  to an IF signal S R  within a predetermined frequency band. The branching device  330  branches the IF signal S R  to the IF signals S R1  and S R2 . The IF signals S R1  and S R2  are equivalent to the IF signal S R , wherein the IF signal S R1  is provided to the electrical/optical converting device  340  for converting to the optical signal S O , and the optical signal S O  is outputted to the optical fiber coaxial cable. The IF signal S R2  is outputted to the coaxial cable through an F connector  360 . In this way, the engineer can connect the demodulating device  250  to the coaxial cable carrying the IF signal S R2  for position-adjusting. Additionally, preferably, the IF signal S R2  is carried on the coaxial cable which connects the LNBF  220  and the power supply  130 . 
     It is noticeable that  FIG. 3  only describes the functions of the LNBF  220 , and the detailed realization for the LNBF  220  should be modified according to the system requirement. For example, please refer to  FIG. 4 .  FIG. 4  is a diagram illustrating an embodiment of the down-converting device  320  in  FIG. 3 . As shown in  FIG. 4 , the down-converting device  320  comprises two down-converting circuits B 1  and B 2 , an IF diplexer  430 , and an amplifier  440 . The down-converting circuits B 1  and B 2  down-convert the vertical and the horizontal polarized signals S V  and S R  to a predetermined frequency band, e.g. 0.95 GHz˜1.95 GHz˜3.0 GHz and 3.4 GHz˜4.4 GHz˜5.45 GHz. More specifically, in the down-converting circuit B 1 , the vertical polarized signal S V  passes the low-noise amplifier  411  and the band-pass filter  412  with the pass-band of 10.7˜12.75 GHz, then passes the mixer  413  for mixing with the oscillation signal with frequency of 9.75 GHz generated from the oscillator  414 , and finally passes the band-pass filter  415  with the pass-band of 0.95˜3 GHz and the IF amplifier  416 , to output an IF signal S RV . In the down-converting circuit B 2 , the horizontal polarized signal S H  passes the low-noise amplifier  421  and the band-pass filter  422  with the pass-band of 10.7˜12.75 GHz, then passes the mixer  423  for mixing with the oscillation signal with frequency of 7.3 GHz generated from the oscillator  424 , and finally passes the band-pass filter  425  with the pass-band of 3.4˜5.45 GHz and the IF amplifier  426 , to output an IF signal S RH . The IF diplexer  430  combines the IF signals S RV  and S RH  and transmits to the amplifier  440  so that the amplifier  440  accordingly outputs the IF signal SR to the branching device  330 . 
     Besides, for product integrity, the down-converting device  320  can be integrated with the electrical/optical converting device  340  and the branching device  330 , as an Optical Low Noise Block Down-converter (Optical LNB)  400 . By the above integration, the optical LNB  400  not only has the functions of down-converting and converting the IF signals to optical signals for output, but also is able to directly output the IF signals through the power ends for position-adjusting. 
     On the other hand, in the present invention, the disposition of the branching device  330  can be varied. Since the signals outputted from the branching device  330  are provided for position-adjusting, and in fact, the IF signals S RV  or S RH  in  FIG. 4  can be also utilized for position-adjusting, the branching device  330  can be accordingly disposed at the nodes N 1  or N 2  for branching the IF signals S RV  or S RH  respectively. 
     Moreover, because the branching device  330  is only used for branching the IF signal S R , the realization of the branching device  330  should be well-known to those skilled in the art. For example, please refer to  FIG. 5A through 5G .  FIG. 5A  through  FIG. 5G  are diagrams illustrating different embodiments of the branching device  330  in  FIG. 4 , which respectively represent a direct coupler, a T-type power divider, a resistant power divider, a Wilkinson power divider, a quadrature hybrid power divider, and a ring hybrid power divider. It is also noticeable that the realizations of the branching device  330  can be designed according to user requirements and should not be limited to only embodiments disclosed in  FIG. 5A  to  FIG. 5G . 
     To sum up, by the satellite communication receiving system of the present invention, when a engineer executes position-adjusting, he/she can directly reads the IF signals outputted from the LNBF through the demodulating device for determining if the dish antenna is in the correct position, without the need of the MDU for optical/electrical conversion, which provides great convenience. 
     Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention.