Abstract:
An apparatus for determining the integrity of an antenna system, including a controller, at least one valve operationally connected to the controller, a source of pressurized gas, at least one microwave antenna and a pressure sensor. The at least one microwave antenna is fluidly connected to the pressurized gas by way of the at least one valve. The pressure sensor is in communication with the controller. The pressure sensor senses the pressure of the pressurized gas. The controller is configured to check for a gas leak in the at least one microwave antenna by checking for a change in the pressure with the at least one valve being alternatively opened and closed.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an antenna system, and, more particularly, to an air leak detection device for an antenna system. 
     2. Description of the Related Art 
     Typical microwave antenna systems include a transmission line, a feed horn and a reflector dish. There are many types of configurations of these components depending upon the antenna type and frequency range. The transmission line conducts radio frequency signals to and from the feed horn. The feed horn operation is critical to the proper operation of the entire antenna system. The fundamental purpose of the feed horn is to match the impedance of the transmission, which may typically be 50 ohms to that of free space, which is approximately 377 ohms. At typical microwave frequencies, such as in the C band and above, the transmission line is also commonly called a waveguide that is normally hollow. The feed horn itself, often called the feed, includes a conical structure that is hollow and is connected to the waveguide. 
     Often the feed horn is mounted so that it is offset from the center of the reflector. The reflector may be a section of a parabola and the offset feed scheme prevents the feed and the feed support from shading the reflector and thus reducing its effective aperture for other performance problems. 
     The offset feed scheme often requires the feed horn to be positioned such that rain, water or snow may enter therein. If water enters the feed horn it causes corrosion and signal loss. This problem is further exasperated by the flow of water into the radio frequency components used in the receiver/transmitter. Typically the opening in the feed horn is covered with a membrane, such as a plastic membrane to shield the system and to prevent the entry of water thereby. The plastic membrane must pass radio frequency energy with minimum attenuation. This imposes a limit on the material that can be used for constructing the membrane. Typical membranes are sensitive to sunlight and more particularly to the ultraviolet light that causes the membrane to become brittle and crack. 
     The radio frequency components are substantially hermetically sealed and while leakage often occurs through the membrane it is also understood that other portions of the feed horn, waveguide or radio frequency components can also allow ambient air to leak into the interior thereof. Leakage can be the result of leaking gaskets, fatigue cracks in the transmission line or other components as well. Ambient air contains gaseous water and when the ambient temperature falls to or below the dew point, condensation will occur within the system. Water that condenses therein is typically too viscous to escape and it remains trapped inside of the radio frequency components causing corrosion damage and it also modifies the impedance of the transmission line and feed horn. The most popular method of keeping the interior of the radio frequency components from the radio/transmitter all the way to the feed horn is to pressurize the system with low-pressure dry air. The pressurized dry air may slowly leak through the various openings in the antenna system but this prevents moist ambient air from leaking thereinto. Typical pressures range from 0.25 to 6 lbs per square inch above the ambient pressure. The supply of the dry air will typically have a dew point that is below −50° C. 
     The pressurized air may be supplied by way of a small compressor and an air-drying system. A typical installation may have four to eight or more antenna systems that utilize the pressurized dried air from the single supply source. 
     A leak in one of the antennas can compromise the ability of the rest of the antennas to be adequately protected since the compromise depletes the supply of dried pressurized air. A substantial leak in one antenna then can lead to the eventual failure or degradation of the rest of the antennas since they are all then starved for the necessary pressurized dry air. 
     What is needed in the art is a device and system that will detect and isolate a leak of air in an antenna system. 
     SUMMARY OF THE INVENTION 
     The present invention provides a microwave antenna leak detection system and method. 
     The invention in one form is directed to an apparatus for determining the integrity of an antenna system, including a controller, at least one valve operationally connected to the controller, a source of pressurized gas, at least one microwave antenna and a pressure sensor. The at least one microwave antenna is fluidly connected to the pressurized gas by way of the at least one valve. The pressure sensor is in communication with the controller. The pressure sensor senses the pressure of the pressurized gas. The controller is configured to check for a gas leak in the at least one microwave antenna by checking for a change in the pressure with the at least one valve being alternatively opened and closed. 
     An advantage of the present invention is that a multi antenna system having one or more air leaks can be protected by the isolation of the leaky systems. 
     Another advantage of the present invention is that the leak detection system communicates the problem to an operator so that maintenance can be scheduled and affected. 
     Yet another advantage of the present invention is that the pressurized gas and dehydrator systems are preserved by keeping the capacity of the gas and dehydrating systems from being over taxed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1  illustrates a single antenna system utilizing an embodiment of the present invention and method; 
         FIG. 2  is another view of a feed horn utilized in the antenna system of  FIG. 1 ; 
         FIG. 3  is a schematized illustration of an embodiment of the present invention; and 
         FIG. 4  is a flow chart illustrating an embodiment of the method utilized in the antenna system illustrated in  FIG. 3 . 
     
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates one embodiment of the invention, in one form, and such exemplification is not to be construed as limiting the scope of the invention in any manner. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings, and more particularly to  FIGS. 1 and 2 , there is shown an antenna system  10  having a reflective dish  12 , a support  14 , a feed horn  16 , a waveguide  18  and a membrane  20 . Although antenna system  10  is illustrated as a single system in  FIGS. 1 and 2  it is to be understood that a multitude of antennas are included in antenna system  10 . Each antenna includes a reflective dish  12  with a feed horn  16  oriented to receive and transmit a signal reflected off of reflective dish  12 . The shape of reflective dish  12  is chosen to focus the energy received to an entry port of feed horn  16  and in a like manner to reflect the signal issuing from feed horn  16 . The positioning of reflective dish  12  directs the direction of the signal coming therefrom. Waveguide  18  is connected to feed horn  16  and directs the radio frequency energy to or from a receiver/transmitter, not shown. Whereas waveguide  18  as well as feed horn  16  is hollow, membrane  20  is positioned over the end of feed horn  16  in order to prevent or at least reduce the amount of ambient air that can enter into hollow portions of feed horn  16  and waveguide  18 . As discussed above membrane  20  may be considered a weak link in the pressurized air that is supplied to feed horn  16  and  18  but the leakage of air from system  10  is not limited thereto. 
     Now, additionally referring to  FIG. 3 , there is shown an embodiment of the present invention configured for dealing with three antenna systems represented by feed horns  16 ,  22  and  24 . It is to be understood that any number of antenna systems can be utilized in this system by paralleling additional valves and antennas as illustrated in  FIG. 3 . Additionally, even though feed horns  16 ,  22  and  24  are shown it is to be understood that they each represent an entire antenna, waveguide and transmitter/receiver sections that are pressurized by the device and method of the present invention. Antenna system  10  includes feed horns  16 ,  22  and  24 , valves  26 ,  28 ,  30  and  32 , a controller  34 , a communication device  36 , a pressure sensor  38 , a pressure level setting device  40 , a time delay setting device  42 , indicators  44 ,  46 ,  48  and  50 , switches  52 ,  54  and  56 , dehydrator  58  and a pressurized gas source  60 . The electronic connections to feed horns  16 ,  22  and  24  are not separately illustrated and a line connected to each of feed horns  16 ,  22  and  24  are illustrative of the gas coupling thereto. Although referred to herein as a gas, the gas may simply be ambient air that is pressurized and subsequently dehydrated. Valves  26 ,  28 , and  32  are all under the control of controller  34  and are electro-magnetically actuated. The valves are illustrated as having two positions although other types of valves are also contemplated. Further, line restrictions of a predetermined amount may be positioned in the lines following valve  32  or preceding valve  32 . The restrictions would limit the gas flow therethrough to a predetermined amount. Valve  32  may be omitted, but is included to illustrate one manner in which the present invention can be carried out. 
     Communication device  36  is connected to controller  34  for the purpose of conveying problems detected by controller  34  to a user by way of telecommunications, Internet or other communication method. Pressure sensor  38  is fluidly coupled to the line that supplies gas to feed horn  16 ,  22  and  24 . Line  62  can be understood to be a manifold  62 . Pressure sensor  38  detects a pressure in line  62  and sends a signal to controller  34  representative thereof. 
     Pressure level setting device  40  allows the setup technician to select a particular pressure representative of a minimum pressure that would indicate failure of the system if the pressure is detected to be below that level. Although illustrated as a potentiometer, the value may also be digitally entered into controller  34 . In a like manner time delay setting device  42  is illustrated as a potentiometer and provides that controller  34  may check the system after suitable time delay as set by time delay setting device  42 . 
     Indicators  44 ,  46  and  48  are separately illuminated when a problem is detected in feed horns  16 ,  22  and  24 , respectively. For example, if feed horn  16  is found to have developed a leak then indicator  44  is illuminated to indicate a problem to indicate a problem therewith. This allows for ease of troubleshooting and shows that a particular antenna has been isolated from pressurized gas system  60 . 
     Switches  52 ,  54 ,  56  allow the setup technician to select which of the antenna systems are active. For example, if system  10  has the capability of detecting leaks in ten antenna systems and the particular installation utilizes six antenna systems then the operator, by selecting the switches indicates to controller  34 , which of several valves, to leave in an off position and those particular valves are not connected to antennas. 
     As previously mentioned, pressurized gas source  60  may be a compressor or alternatively another source of pressurized gas such as pressurized gas contained in a cylinder. If the gas is already dehydrated then dehydrator  58  is not needed. In a normal installation the source of pressurized gas  60  is a compressor system with dehydrator  58  removing water therefrom. 
     Now, additionally referring to  FIG. 4  there is illustrated a method  100  that utilizes the elements of  FIG. 3  to check the pressure in antenna system  10 . At step  102 , gas pressure in manifold  62  is checked by isolating or turning valves  26 ,  28  and  30  to an off position. This allows method  100  to check the functionality of pressurized gas source  60  and its ability to supply gas to manifold  62 . If the manifold pressure is not acceptable at step  104  then the manifold pressure problem is communicated at step  106  by way of communication device  36 . The communication alerts the operator that the manifold pressure is below an acceptable level selected by pressure level setting device  40 . If the manifold pressure is inadequate, not only is it communicated by way of communication device  36 , but also indicator  50  is illuminated indicating that manifold pressure is too low, which may be caused by a failure of pressurized gas source  60 . 
     If the pressure in manifold  62  is satisfactory then method  100  proceeds to step  108  in which one of the feed horns is connected by way of a respective valve to manifold  62 . Once the feed horn that is selected, such as feed horn  16 , then valve  26  is activated allowing pressure in manifold  62  to be supplied to feed line  16 . Pressure sensor  38  again is used to detect the pressure in manifold  62  to see if the flow of air to feed horn  16  causes the pressure in manifold  62  to drop below the predetermined value. If the feed horn pressure is acceptable at step  110  then method  100  determines whether all the feed horns had been checked at step  116 . If not all the feed horns had been checked then an internal counter is incremented at step  118  causing the next installed feed horn to be checked starting back at step  108 . 
     If the feed horn pressure is not satisfactory as determined at step  110  then that particular feed horn is isolated at step  112  by turning the respective valve off and then communicating the feed horn pressure problem at step  114 , by way of communication device  36  to an operator. 
     Method  100  may be initiated upon a periodic predetermined timing such as selected by time delay setting device  42 . Additionally, method  100  may be carried out more than one time to verify the malfunction of feed horn pressure before communicating the problem by way of communication device  36 . 
     Another method contemplated is to utilize valve  32  in which valves  26 ,  28 ,  30  are initially shut off thereby isolating feed horns  16 ,  22  and  24 . Valve  32  may be positioned in an off position with pressure sensor  38  then monitoring the pressure in manifold  62 . This allows the integrity in manifold  62  to be checked to determine if a drop in pressure within a specified time is less than a predetermined value. If the pressure in manifold  62  is satisfactory then a similar test is done by activating, one at a time, each of valves  26 ,  28  and  30  while keeping the rest of the valves in the isolated position. Pressure supplied by opening valve  32  and then valve  32  is closed and then bleed off pressure in manifold  62  is sensed by pressure sensor  38  to determine if the loss rate due to a particular feed horn satisfactory or whether there is an unacceptable gas leak. 
     Control circuitry may include semiconductor devices such as metal oxide field effect transistors that drive solenoids to allow direct control of the solenoids by way of controller  34 . The control of indicators  44 - 50 , while described in a negative sense in that they are illuminated when a problem occurs, can be utilized in an opposite sense where they are illuminated when the system is functioning normally. When a problem is detected indicators  44 - 50  may then blink or display a different color. When a leak is detected in antenna system  10  and the leak is due to a single feed horn that particular feed horn is isolated from system  10  with the rest of the feed horns receiving pressurized air in a normal fashion. The information transmitted by controller  34 , by way of communication device  36 , may include information that is transmitted in a preamble-data-postamble format. This may be communicated to a communication device that receives and then translates the information into a message sent to an operator. Additionally, communication device  36  may receive instructions from the operator to initiate controller  34  to retest or alternately to configure system  10  by way of the instructions received therefrom. For example, controller  34  may report a low pressure in the manifold system, and further communication from the operator may require controller  34  to keep one feed horn supplied with air and to isolate all others therefrom allowing a priority system to be established. The priority system would determine which of the feed horns is of a higher importance than the others. 
     The present invention advantageously allows configuring of the antenna system as well as monitoring of the pressurized system and isolating of the particular antenna(s) that may cause a leak in the air supplying system and thereby degrading the performance of potentially all of the antennas. 
     While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.