Patent Publication Number: US-9419342-B2

Title: Low noise block converter and outdoor unit

Description:
TECHNICAL FIELD 
     The present disclosure relates to a low noise block converter and an outdoor unit and more particularly to a low noise block converter and an outdoor unit having a consistent communication quality. 
     DISCUSSION OF THE BACKGROUND 
     Satellite communications require equipment such as ground stations, low noise block down converters, transmission cables, and modulator/demodulators. The ground station receives radio frequency signals from satellites; the low noise block down converter amplifies the received radio frequency signals and converts the amplified radio frequency signals to intermediate frequency signals; and the transmission cables transmit the intermediate signals to the modulator/demodulator. 
     Generally, the low noise block down converter may include a radio frequency circuit and an intermediate circuit electrically connecting to the radio frequency circuit. The radio frequency circuit receives radio frequency signals, converts the radio frequency signals to intermediate signals, and transmits the intermediate signals to the intermediate circuit. 
     The ground station uses a highly directional receiving device, i.e., dish antenna, which has to be precisely directed toward satellites in orbit at 36,000 kilometers in altitude. For example, if a dish antenna with a 180 cm diameter shifts 2 cm horizontally, or 3 cm vertically, the signals will become weak or even disappear. In addition, if the dish antenna is configured to use electromagnetic waves in a frequency band of 26-40 GHz, an accuracy of 0.1 degree is needed, and the tolerance has to be within 0.02 degrees for aiming precisely at satellites. 
     This “Discussion of the Background” section is provided for background information only. The statements in this “Discussion of the Background” are not an admission that the subject matter disclosed in this “Discussion of the Background” section constitutes prior art to the present disclosure, and no part of this “Discussion of the Background” section may be used as an admission that any part of this application, including this “Discussion of the Background” section, constitutes prior art to the present disclosure. 
     SUMMARY 
     One aspect of the present disclosure provides a low noise block converter and an outdoor unit having a consistent communication quality. 
     A low noise block converter comprises a housing, a feed cap disposed on top of the housing, and an air permeable membrane disposed on a bottom portion of the housing. The housing includes a base portion, at least one feed horn protruding from the base portion, and a bottom cover attached to a bottom of the base portion so as to form a housing cavity, wherein the bottom cover has a vent hole forming a flow path between the housing cavity and an external environment. The feed cap is disposed on a feed portion of the at least one feed horn and the air permeable membrane is disposed over the vent hole and coupled to the bottom cover via an adhesive, wherein the membrane is configured to permit egress of a gas from the housing cavity therethrough. 
     An outdoor unit comprises a dish antenna and a low noise block converter positioned at a focus point of the dish antenna. The low noise block converter comprises a housing, a feed cap disposed on top of the housing, and an air permeable membrane disposed on a bottom portion of the housing. The housing includes a base portion, at least one feed horn protruding from the base portion, and a bottom cover attached to a bottom of the base portion so as to form a housing cavity, wherein the bottom cover has a vent hole forming a flow path between the housing cavity and an external environment. The feed cap is disposed on a feed portion of the at least one feed horn and the air permeable membrane is disposed over the vent hole and coupled to the bottom cover via an adhesive, wherein the membrane is configured to permit egress of a gas from the housing cavity therethrough. 
     Due to the design for the bottom cover with the vent hole forming the flow path between the housing cavity and the external environment, the height variation of the feed cap caused by the air pressure imbalance between the housing cavity and the environment can be decreased. Consequently, the electronic characteristics of the low noise block converter and the outdoor unit can be well controlled so as to have a consistent communication quality even if the temperature or pressure of the environment changes. 
     The foregoing has outlined rather broadly the features and technical advantages of the present disclosure in order that the detailed description of the disclosure that follows may be better understood. Additional features and advantages of the disclosure will be described hereinafter, which form the subject of the claims of the disclosure. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures or processes for carrying out the same purposes of the present disclosure. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the disclosure as set forth in the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete understanding of the present disclosure may be derived by referring to the detailed description and claims when considered in connection with the Figures, where like reference numbers refer to similar elements throughout the Figures, and: 
         FIG. 1  shows a three-dimensional view of an outdoor unit according to one embodiment of the present invention; 
         FIG. 2  is an assembled view of a low noise block converter according to one embodiment of the present invention; 
         FIG. 3  and  FIG. 4  are disassembled views of the low noise block converter in  FIG. 2  from the top side and the bottom side respectively; 
         FIG. 5  is a close-up view of a bottom cover of the low noise block converter in  FIG. 2  according to one embodiment of the present invention; 
         FIG. 6  illustrates a full view of a feed horn structure according to one exemplary embodiment of the present invention; 
         FIG. 7  illustrates a top view of the feed horn structure shown in  FIG. 6 ; 
         FIG. 8  illustrates a cross-sectional view of the feed horn structure along a sectional line  1 - 1  in  FIG. 7 ; 
         FIG. 9  illustrates a cross-sectional view of the feed horn structure along a sectional line  2 - 2  in  FIG. 7 ; 
         FIG. 10  shows comparative waveforms of the height variation of ten (10) comparative feed caps after temperature cycling testing, wherein the comparative feed caps are attached to low noise block converters having a bottom cover with no vent hole; 
         FIG. 11  shows comparative waveforms of the height variation of ten (10) comparative feed caps after ALT (accelerated life testing); wherein the comparative feed caps are attached to low noise block converters having a bottom cover with no vent hole; 
         FIG. 12  shows comparative waveforms of the cross polarization isolation (also referred to as x-polarization or XPOL isolation) of the comparative low noise block converters equipped with the ten (10) feed caps in  FIG. 11  after ALT; 
         FIG. 13  shows exemplary waveforms of the height variation of five (5) exemplary feed caps after several types of environmental tests, wherein the five (5) exemplary feed caps are attached to low noise block converters having a bottom cover with a vent hole; 
         FIGS. 14-16  are exemplary waveforms showing the frequency-drift of the low noise block converters equipped with a bottom cover having a vent hole after several types of environmental tests, wherein the specification has a bottom limit of −5 MHz and an upper limit of 5 MHz on the frequency-drift characteristic; and 
         FIG. 17  shows exemplary waveforms of the cross polarization isolation (XPOL isolation) of ten (10) exemplary low noise block converters equipped with the bottom cover having a vent hole after ALT. 
     
    
    
     DETAILED DESCRIPTION 
     The following description of the disclosure accompanies drawings, which are incorporated in and constitute a part of this specification, and illustrate embodiments of the disclosure, but the disclosure is not limited to the embodiments. In addition, the following embodiments can be properly integrated to complete another embodiment. 
     References to “one embodiment,” “an embodiment,” “exemplary embodiment,” “other embodiments,” “another embodiment,” etc. indicate that the embodiment(s) of the disclosure so described may include a particular feature, structure, or characteristic, but not every embodiment necessarily includes the particular feature, structure, or characteristic. Further, repeated use of the phrase “in the embodiment” does not necessarily refer to the same embodiment, although it may. 
     The present disclosure is directed to a low noise block converter and an outdoor unit having consistent communication quality. In order to make the present disclosure completely comprehensible, detailed steps and structures are provided in the following description. Obviously, implementation of the present disclosure does not limit special details known by persons skilled in the art. In addition, known structures and steps are not described in detail, so as not to limit the present disclosure unnecessarily. Preferred embodiments of the present disclosure will be described below in detail. However, in addition to the detailed description, the present disclosure may also be widely implemented in other embodiments. The scope of the present disclosure is not limited to the detailed description, and is defined by the claims. 
       FIG. 1  shows a three-dimensional view of an outdoor unit  100  according to one embodiment of the present invention. In one embodiment of the present disclosure, the outdoor unit  100  comprises a dish antenna  101  and a low noise block converter  10  positioned at a focus point of the dish antenna  101 . 
       FIG. 2  is an assembled view of a low noise block converter  10  according to one embodiment of the present invention, and  FIG. 3  and  FIG. 4  are disassembled views of the low noise block converter  10  from the top side and the bottom side respectively. In one embodiment of the present disclosure, the low noise block converter  10  comprises a housing  11  and a feed cap  17  disposed on top of the housing  11 . In one embodiment of the present disclosure, the housing  11  includes a base portion  12 , at least one feed horn structure  13  protruding from the base portion  12 , and a bottom cover  19  attached to a bottom of the base portion  12  so as to form a housing cavity  21 . In one embodiment of the present disclosure, the low noise block converter  10  further comprises a circuit board  23  disposed within the housing cavity  21 , and a plastic cover  25  attached to a bottom portion of the housing  10 , wherein the feed cap  17  is disposed on a feed portion  15  of the at least one feed horn structure  13 . 
       FIG. 5  is a close-up view of a bottom cover  19  of the low noise block converter  10  according to one embodiment of the present invention. In one embodiment of the present disclosure, the bottom cover  19  has a vent hole  19 A forming a flow path between the housing cavity  21  and the external environment, and an air permeable membrane  19 B is disposed over the vent hole  19 A and coupled to the bottom cover via an adhesive  19 C, wherein the membrane  19 B is configured to permit egress of a gas from the housing cavity  21  therethrough. In one embodiment of the present disclosure, the plastic cover  25  includes an aperture  25 A corresponding to the vent hole  19 A of the bottom cover  19 . 
     In one embodiment of the present disclosure, the air permeable membrane  19 B is an aqueous liquid impermeable membrane such as a hydrophobic membrane, and configured to at least meet an ingress protection rating of IEC IP65 and TEC IP67. In one embodiment of the present disclosure, the air permeable membrane  19 B is a PTFE (Polytetrafluoroethene). 
       FIG. 6  illustrates a full view of the feed horn structure  13  according to one exemplary embodiment of the present invention.  FIG. 7  illustrates a top view of the feed horn structure  13  shown in  FIG. 6 .  FIG. 8  illustrates a cross-sectional view of the feed horn structure  13  along a sectional line  1 - 1  in  FIG. 7 , and  FIG. 9  illustrates a cross-sectional view of the feed horn structure  13  along a sectional line  2 - 2  in  FIG. 7 . 
     Referring to  FIG. 6  to  FIG. 9 , in one embodiment of the present invention, the feed horn structure  13  comprises two first feed horns  111  each having a first upper aperture  113 , with a first wall  121  surrounding the first upper aperture  113 ; a second feed horn  115  disposed between the two first feed horns  111 , and the second feed horn  115  having a second upper aperture  117 ; a second wall  123  surrounding the first wall  121 , with a first groove  131  between the second wall  123  and the first wall  121 ; a third wall  125  surrounding the second wall  123  and the second upper aperture  117 , with a second groove  133  between the third wall  25  and the second wall  123 ; a fourth wall  127  surrounding the third wall  125 , with a third groove  135  between the fourth wall  127  and the third wall  125 ; and a plurality of ribs  151  connecting the first wall  121  and the second wall  123 . 
     In one embodiment of the present invention, the center feed horn  115  receives electromagnetic waves in a frequency band of 12.2-12.7 GHz (Ku  101 ) from a satellite located at 101 degrees west longitude. The left feed horn  111  receives a beam in a frequency band of 18.3-18.8 and 19.7-20.2 GHz (Ka  103 ) from a satellite located at 102.8 degrees west longitude. The right feed horn  111  receives a beam in a frequency band of 18.3-18.8 and 19.7-20.2 GHz (Ka  99 ) from a satellite located at 99.2 degrees west longitude. 
     In one embodiment of the present invention, the third wall  125  comprises at least one non-circular groove  137  between the second upper aperture  117  and the third groove  125 . In one preferred embodiment of the present invention, the non-circular groove  137  is an arc-shaped groove, as shown in  FIG. 7 . In one embodiment of the present invention, the first upper aperture  113  is rectangular with round corners, and the second upper aperture  117  is also rectangular with round corners. In another embodiment of the present invention, the first upper aperture can be circular or elliptical, and the second upper aperture can be circular or elliptical, as well. 
     In one embodiment of the present invention, the feed horn structure  13  comprises a first plate  141  disposed in a first bottom aperture of the first feed horn  111 . In one preferred embodiment of the present invention, the first plate  141  has a multi-step shape, as shown in  FIG. 8 . In one preferred embodiment of the present invention, the feed horn structure  13  comprises a second plate  143  disposed in a second bottom aperture of the second feed horn  115 . In one preferred embodiment of the present invention, the second plate  145  has a multi-step shape, as shown in  FIG. 9 . In one embodiment of the present invention, the first plate  141  in the first feed horn  111  and the second plate  145  in the second feed horn  115  are disposed in a perpendicular manner, as shown in  FIG. 7 . 
     Referring to  FIG. 7 , in one embodiment of the present invention, the feed horn structure  13  comprises four ribs  151  separated by 90 degrees. In one preferred embodiment of the present invention, the four ribs  151  are disposed at 45 degrees relative to a horizontal line  153 . In one preferred embodiment of the present invention, the rib  151  has a tapered shape with an inner curve and an outer curve, and the width of the rib  151  is preferably 4 degrees. In addition, the four ribs  151  can be positioned at other angles in order to achieve similar effects. 
     In one embodiment of the present invention, the circuit board  23  is disposed on a terminal portion  13 B of the feed horn structure  13 , the feed horns  111  include a horn cavity  111 A communicating with the housing cavity  21 , and the feed horns  113  include a horn cavity  113 A communicating with the housing cavity  21 . 
     The temperature variation may increase the volume of the air inside the housing cavity  21 , which communicates with the horn cavity  113 A and  115 A, thereby causing a warp of the feed cap  17  on top of the feed horn structure  13 . The nonplanar characteristic (warp) of the feed cap  17  may cause return loss and insertion loss degradation, and the return loss and insertion loss may also vary with respect to the magnitude of the nonplanar characteristic (warp) of the feed cap  17 . 
       FIG. 10  shows comparative waveforms of the height variation of ten (10) comparative feed caps after temperature cycling testing, wherein the comparative feed caps are attached to low noise block converters having a bottom cover with no vent hole. As shown in  FIG. 10 , without the vent hole, the air pressure imbalance between the housing cavity and the environment will cause the height variation of the feed cap to be about 1.5 mm (from 1 mm to 2.5 mm) after temperature cycling testing. 
       FIG. 11  shows comparative waveforms of the height variation of ten (10) comparative feed caps after ALT (accelerated life testing); wherein the comparative feed caps are attached to low noise block converters having a bottom cover with no vent hole. As shown in  FIG. 11 , without the vent hole, the air pressure imbalance between the housing cavity and the environment will cause the height variation of the feed cap to be about 2 mm (from 1.5 mm to 3.5 mm) after ALT. 
       FIG. 12  shows comparative waveforms of the cross polarization isolation (also referred to as x-polarization or XPOL isolation) of the comparative low noise block converters equipped with the ten (10) feed caps in  FIG. 11  after ALT. For the XPOL isolation characteristics, the more negative in amplitude (dB), the better the performance of the low noise block converters; and the performance of the low noise block converters degrades as the amplitude (dB) shift from the negative toward zero. As shown in  FIG. 12 , the XPOL isolation characteristics of the ten comparative low noise block converters all degrade by about 2-3 dB, which is caused by the height variation of the feed cap due to the air pressure imbalance between the housing cavity and the environment. 
       FIG. 13  shows exemplary waveforms of the height variation of five (5) exemplary feed caps after several types of environmental tests, wherein the five (5) exemplary feed caps are attached to low noise block converters having a bottom cover with a vent hole. The environmental tests include temperature-humidity testing (THT), temperature cycling (TC), impacting dust (ID), impacting water (IW), mechanical vibration (MV), mechanical shock (MS), corruption (CR), and accelerated life testing (ALT). As clearly shown in  FIG. 13 , with the vent hole in the bottom cover of the low noise block converters, the air pressure imbalance between the housing cavity and the environment can be decreased, and the height variations of the five (5) exemplary feed caps are all well controlled within 0-0.5 mm after performing all environmental tests. 
       FIGS. 14-16  are exemplary waveforms showing the frequency drift of the low noise block converters equipped with a bottom cover having a vent hole after several types of environmental tests, wherein the specification has a bottom limit of −5 MHz and an upper limit of 5 MHz on the frequency-drift characteristic. As shown in  FIGS. 14-16 , with the vent hole in the bottom cover of the low noise block converters, the air pressure imbalance between the housing cavity and the environment can be decreased, the height variations of the five (5) exemplary feed caps are all well controlled within 0-0.5 mm after performing all environmental tests, and the frequency-drift characteristic for the feed horns  111  (Ka  99  and Ka  103 ) and the feed horns  115  (Ku  105 ) are all well controlled within the specification after performing all environmental tests. 
       FIG. 17  shows exemplary waveforms of the cross polarization isolation (XPOL isolation) of ten (10) exemplary low noise block converters equipped with the bottom cover having a vent hole after ALT. As shown in  FIG. 17 , the XPOL isolation characteristics of the ten comparative low noise block converters all remains substantially at the same level, even after 30-days, because the design for the bottom cover with the vent hole effectively decreases the height variation of the feed cap due to the air pressure imbalance between the housing cavity and the environment. 
     Due to the design for the bottom cover with the vent hole forming the flow path between the housing cavity and the external environment, the height variation of the feed cap caused by the air pressure imbalance between the housing cavity and the environment can be decreased. Consequently, the XPOL isolation characteristics of the low noise block converter and the outdoor unit can be well controlled so as to have a consistent communication quality even if the temperature or pressure of the environment changes. 
     Although the present disclosure and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the disclosure as defined by the appended claims. For example, many of the processes discussed above can be implemented in different methodologies and replaced by other processes, or a combination thereof. 
     Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present disclosure, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed, that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present disclosure. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.