Abstract:
A low noise block converter feedhorn (LNBF) is disclosed. The LNBF comprises a PCB, a dielectric resonator oscillator (DRO), a chamber, a tuning screw, and a cover. The DRO is placed on the PCB. The chamber has a first partition, and the first partition is used to cover up the DRO. The chamber further comprises a round hole. The tuning screw passes through the round hole and is then used to adjust the oscillating frequency of the DRO. The cover is used to cover up the tuning screw in order to restrain the DRO from power leakage through the gap in between the round hole and the tuning screw.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a low noise block converter feedhorn (LNBF), and more particularly, to an LNBF which can restrain power leaked out from a dielectric resonator oscillator (DRO). 
     2. Description of the Related Art 
     Due to technology advancement and improvement on the standard of living, satellite antennas have become prevalent and have been widely installed. Generally, after satellite signals are reflected by a round satellite dish, the reflected signals are received and gathered by a Low Noise Block Converter Feedhorn (LNBF), which are then transmitted to other receivers such as televisions. 
     The LNBF comprises a Dielectric Resonator Oscillators (DRO). The DRO is used to adjust the oscillating frequency of the signals received from the satellites; the signals are then transmitted to the other receivers. In the prior art, the DRO employs a tuning screw to tune the oscillating frequency. However, there is a high possibility of power leakage from the DRO through the aforesaid method. The power radiation of power leakage will be reabsorbed by the satellite antenna and will cause signal interferences. 
     A method is disclosed in the prior art to solve the aforesaid problems. Refer to  FIG. 1  for the diagram relating to an LNBF of the prior art. As shown in the prior art, a large shield  91  is used by an LNBF  90  to cover up a DRO  92  and other electronic elements in order to restrain power leakage from DRO  92 . However, the covering method through the use of shield  91  is expensive and the tuning process of DRO  92  is difficult. 
     Therefore, a new design is needed to resolve the problems in the prior art. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to provide a LNBF which will be able to restrain power leakage from a DRO. 
     In order to achieve the aforementioned objective, the invention provides an LNBF which comprises a PCB, a dielectric resonator oscillator (DRO), a chamber, a tuning screw, and a cover. The DRO is placed on the PCB. The chamber has a first partition, and the first partition is used to cover up the DRO. The chamber further comprises a round hole. The tuning screw passes through the round hole and is used to adjust the oscillating frequency of the DRO. The cover is used to cover up the tuning screw to restrain power leakage from the DRO through the gap between the round hole and the tuning screw. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an LNBF of the prior art. 
         FIG. 2A  is an exterior view of an LNBF according to an embodiment of the invention. 
         FIG. 2B  is an internal circuit diagram of an LNBF according to an embodiment of the invention. 
         FIG. 3A  shows an LNBF without a tuning screw according to an embodiment of the invention. 
         FIG. 3B  shows an LNBF with a tuning screw according to an embodiment of the invention. 
         FIG. 3C  shows an LNBF with a cover according to an embodiment of the invention. 
         FIG. 4  shows the relative radiation efficiency for different structure of an LNBF in accordance with the invention. 
         FIG. 5  shows the relationship between the relative radiation efficiency and the radius of the tuning screw of an LNBF for the invention. 
         FIG. 6  shows the relationship between the relative radiation efficiency and the quantities of the via holes of an LNBF for the invention. 
         FIG. 7A  is an embodiment of an LNBF for the invention which connects the first partition to the ground. 
         FIG. 7B  is an embodiment of an LNBF for the invention which connects the second partition to the ground. 
         FIG. 7C  is an embodiment of an LNBF for the invention which connects the edge of the PCB boarder to the ground. 
         FIG. 8  shows the relationship between the relative radiation efficiency and the grounding methods of an LNBF for the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The advantages and innovative features of the invention will become more apparent from the following preferred embodiments. 
     Refer to  FIG. 2A  and  FIG. 2B  for the diagrams relating to an LNBF for the invention.  FIG. 2A  is an exterior view of the LNBF according to an embodiment of the invention;  FIG. 2B  is an internal circuit diagram of the LNBF according to an embodiment of the invention. 
     As shown in  FIG. 2A  and  FIG. 2B , an LNBF  10  according to an embodiment of the invention is used for receiving wireless signals reflected from a round dish (not shown). For example, for receiving satellite signals, but the invention is not only limited to the satellite signals. The LNBF  10  comprises a PCB  11 , a DRO  20 , a chamber  31 , a tuning screw  41 , a cover  42  and a plurality of via holes  12 . The DRO  20  is made from ceramic compounds, but the invention is not limited to this material. The DRO  20  which is placed on the PCB  11  is used for adjusting the oscillating frequency of the wireless signals received. The chamber  31  comprises a first partition  311  and a second partition  312 . The first partition  311  covers up the DRO  20  so as to restrain power leakage from the DRO  20 . The second partition  312  covers up the entire PCB  11 . A round hole  311   a  is located on partition  31  (as shown in  FIG. 3A ). The tuning screw  41  passes through the round hole  311   a  to tune the DRO  20 . 
     The cover  42  is placed on top of the tuning screw  41 . In the embodiment, the cover  42  is an F type screw or other standardized screws, but the invention is not limited to these screws. The cover  42  is deployed to cover the gap between the tuning screw  41  and the chamber  31 ; this can prevent the DRO  20  from power leakage through the gap. There are a plurality of via holes  12  placed on the PCB  11  which surround the DRO  20 . 
     The via holes  12  on the PCB  11  are small holes filled or coated with metal, which are used to connect the grounding metal on both sides of the PCB  11  (not shown). Power will be radiated through the gap between the via holes  12  at the pressing boundary when the chamber  31  is pressed against the PCB  11 . Therefore, radiation of power can be restrained by a high density of via holes  12 . 
     Next, please refer to  FIG. 3A˜FIG .  3 C for the diagrams relating to an LNBF of the invention, and refer to  FIG. 4  for the diagram showing the relative radiation efficiency for different structure of the LNBF in accordance with the invention.  FIG. 3A  is a diagram showing the embodiment of an LNBF without a tuning screw.  FIG. 3B  is a diagram showing the embodiment of an LNBF with a tuning screw.  FIG. 3C  is a diagram showing the embodiment of an LNBF with a cover. 
     As for the embodiments shown in  FIG. 3A  and  FIG. 4 , the relative radiation efficiency measured is approximately negative 8 dB if the first partition  311  of the chamber  31  does not connect with the tuning screw  41 . It means that some of the power from the DRO  20  is radiated through the round hole  311   a . For the embodiment as shown in  FIG. 3B , the relative radiation efficiency measured is reduced to approximately negative 20 dB if the tuning screw  41  is inserted at the round hole  311   a . However, some of the power is radiated through the gap between the round hole  311   a  and the tuning screw  41 . Therefore, an embodiment of the invention is shown in  FIG. 3C . As shown in  FIG. 3C , power leakage from the DRO  20  is restrained by covering the tuning screw  41  with the cover  42 . The relative radiation efficiency measured is reduced to approximately negative 30 dB. In the invention, the cover  42  is a standardized screw nut which simplifies the assembly and the removal process, and it is therefore convenient to tune the DRO  20 . 
     Next, refer to  FIG. 5  which shows the relationship between the relative radiation efficiency and the radius of the tuning screw of the LNBF for the invention. 
     The invention has set a constraint on the radius of tuning screw  41 . As shown in  FIG. 5 , it can be seen that when the radius of the tuning screw  41  is shorter, the relative radiation efficiency measured will be less, which means that less power will be radiated from the gap between the tuning screw  41  and the chamber  31 . In the embodiment of the invention, the radius of tuning screw  41  ranges from 1 mm to 2 mm. 
     Next, refer to  FIG. 6  which shows the relationship between the relative radiation efficiency and the quantities of the via holes of the LNBF for the invention. 
     The quantities and density of via holes  12  have an effect on the relative radiation efficiency measured. Power will be radiated through the gap between the via holes  12  at the pressing boundary when the chamber  31  is pressed against the PCB  11 . As shown in  FIG. 6 , the higher the density of the via holes  12  at the pressing boundary, the less relative radiation efficiency will be measured and power leakage from the DRO  20  through the sides of the PCB  11  will also be reduced. Therefore, as shown in  FIG. 2B , the embodiment of the invention consists of a high density of the via holes  12 . 
     Next, refer to  FIG. 7A˜7C  which show the grounding methods for a LNBF of the invention and refer to  FIG. 8  which shows the relationship between the relative radiation efficiency and the grounding methods of an LNBF for the invention.  FIG. 7A  shows the embodiment which connects the first partition to the ground.  FIG. 7B  shows the embodiment which connects the second partition to the ground.  FIG. 7C  shows the embodiment which connects the PCB edges to the ground. 
     Refer to the embodiments shown in  FIG. 7A  and in  FIG. 8 , which show the relationship between the relative radiation efficiency and the grounding methods of the LNBF for the invention. If the pressing boundary  51  between the first partition  311  of the chamber  31  and the PCB  11  is coated with metal, a separation layer can be formed when the chamber  31  and the PCB  11  are pressed together, which will be used for grounding purpose. However, this configuration is not very effective in terms of restraining power leakage, as the relative radiation efficiency measured is approximately 6 dB. Refer to the embodiment shown in  FIG. 7B . If the pressing boundary  52  between the second partition  312  and the PCB  11  is coated with metal, a second sealed separation layer will be formed which can then be used for grounding purpose. Power could be prevented from radiating through the sides of the PCB  11  and the relative radiation efficiency measured will be reduced to approximately 25 dB. The embodiment is shown in  FIG. 7C , where the edges  11   a  of the PCB  11  are coated with metal for grounding purposes. The relative radiation efficiency measured is reduced to approximately 29 dB, thus the optimal power restraining effect will be obtained. 
     Through the embodiments of the LNBF for the invention, power can be prevented from radiating through the gap between the round hole  311   a  and the tuning screw  41 , or through the sides of the PCB  11 . Therefore power leakage from the DRO  20  will be minimized. 
     Although the present invention has been explained in relation to its preferred embodiment, it is also to be understood that many other possible modifications and variations can be made without departing from the spirit and scope of the invention as hereinafter claimed.