Abstract:
A communication system with an antenna array having a respective antenna for each of a multitude of communication modules and a control system which seiectiyely reassigns communication over a first of said multitude of communication modules to a second communication module of said multitude of communication modules in response to identification of a predicted interference within a predetermined interference matrix.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to a communication system, and more particularly to management of an antenna array. 
   Aircraft communications systems usually include a receiver-transmitter, a digital interface of the control panel mechanism to and from the receiver transmitter, and an antenna system. The antenna system of a typical communications system is connected to the receiver-transmitter by a coaxial cable, sometimes known as a transmission line. This basic arrangement can be found in aircraft and in ground installations. 
   Some conventional communications systems connect the receiver-transmitter and the antenna as a dedicated, matched pair, and the antenna is tuned to operate efficiently over the particular receiver-transmitter&#39;s operating range. In more complex applications, a receiver-transmitter may be connected to a second antenna by a control mechanism and a coaxial relay. A typical application may be an upper antenna and a lower antenna, each mounted on an aircraft. This type of dual antenna design allows the crew to direct the radio to the preferred antenna so as to increase coverage for the upper hemisphere or the lower hemisphere (or fore/aft, etc.) according to the operational requirements at that time. Such antenna switching is performed by switching the antenna control lines and the RF coaxial lines via a combination of coax switches and conventional control line switching usually performed by relays. The result is an effective communications system that provides a desired spatial coverage, but may frequently results in some interferences due to the practical limitations of space available to locate antennas. 
   As receiver-transmitters have become capable of covering a wider spectrum of frequencies, the design of the antenna hardware has become more complex and more expensive. Active impedance tuning elements in the antenna are digitally switched in or out of the antenna&#39;s internal impedance matching mechanisms to adjust the effective impedance of the antenna for optimum/efficient transmission. 
   Furthermore, as the capabilities of radios continue to increase, or as the number of radios installed on the airborne platform (eg; helicopter or fixed wing) increase, the potential for mutual interference increases. Close spacing of dedicated antennas can result in the radiated power of one radio interfering with another radio whose antenna is in proximity to the other antenna that is transmitting. The nature of the interference may be caused by transmit power of a level such that the receiving radio/antenna&#39;s receiver bandwidth processes the RF energy at the edges of its receiver bandwidth. This is sometimes referred to as the skirts of the receiver. This undesired interference problem is further increased when the radios are wideband units that cover a broad portion of the RF spectrum. When wideband transmitters of any kind are utilized such as for communications, navigation, IFF, etc., the harmonic content of each transmitter may also interfere with any of the receiving devices located in proximity. 
   Aircraft may typically have from three to as many as fifty antennas on the fuselage. Each antenna is installed to achieve proper coverage and the correct ground plane. The ability to locate an antenna at any arbitrary location to avoid interference may not be possible due to lack of ground plane, interference with maintenance access, or ground clearance. Interference of one transmitter with another receiver is most often a compromise to balance coverage, pattern efficiency, and mutual interference. As the number of antennas increases, so does the difficulty in locating antennas. These types of considerations must be addressed for ground stations, fixed wing aircraft, and helicopters. 
   Accordingly, it is desirable to provide a communication system which provides desired spatial coverage while minimizing interference due to the practical limitations associated with the space available to locate a multiple of antennas. 
   SUMMARY OF THE INVENTION 
   A communication system according to an exemplary aspect of the present invention includes an antenna array having a respective antenna for each of a multitude of communication modules and a control system which selectively reassigns communication over a first of said multitude of communication modules to a second communication module of said multitude of communication modules in response to identification of a predicted self-induced interference within a predetermined interference matrix. 
   A method of managing a communication system according to an exemplary aspect of the present invention includes identifying a predicted self-induced interference within a predetermined interference matrix between a first communication module with a first antenna and a second communication module with a second antenna; and reassigning the first communication module with the first antenna to a third communication module with a third antenna in response to the predetermined interference matrix to avoid the predicted interference. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows: 
       FIG. 1  is a general perspective view an exemplary rotary wing aircraft embodiment for use with the present invention; 
       FIG. 2  is a block diagram of communication system of the present invention; and 
       FIG. 3  is a simplified schematic representation of an interference matrix according to the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1  illustrates a general perspective view of an aircraft  10  having a communication system  12  with an antenna array  14 . Although the present invention is described hereinbelow in terms of a particular aircraft configuration as illustrated in the disclosed embodiment, it should be understood that the present invention may be modified for use with other aircraft and ground systems and sites. It should be understood that the “communication system” as used herein includes other navigation, identification, alert systems and the like which have an antenna within the antenna array  14  ( FIG. 1 ). Such other systems will also benefit from the present invention. 
   Referring to  FIG. 2 , the antenna array  14  includes a multiple of antennas A 1 -An each located in a particular location on the aircraft  10  ( FIG. 1 ). Due to the fixed location, each antenna A 1 -An may also be subject to interference from, and subject other antennas, to interference. Each antenna A 1 -An provides dedicated transmission and/or reception for a respective communication modules R 1 -Rn over a transmission line L 1 -Ln. It should be understood that “communication module” as utilized herein includes single-use receiver-transmitters, multifunction broadband transceivers as well as other alert systems such as radar warning receivers, IFF systems and the like which require an antenna within the antenna array. 
   Typically, the aircraft  10  often includes duplicate communication modules, here for example, communication modules R 1 -R 3  are of an equivalent type and communication modules R 4 -R 5  are equivalent. It should be understood that various systems and combinations of systems may be used with the present invention, and the systems disclosed in the illustrated embodiment are for descriptive purposes only and are not limited to those alone. 
   Each of the duplicate communication modules R 1 -R 3 , R 4 -R 5  although providing equivalent capabilities typically have their respective antennas A 1 -A 3  and A 4 -A 5  located in different fixed positions on the aircraft  10  ( FIG. 1 ). Having the antennas A 1 -An located in different fixed positions results in different potential interference interactions between any pair of antennas A 1 -An. 
   Each communication module R 1 -Rn communicates with a data bus  16  which provides communication between each communication modules R 1 -Rn and a control system  18 . The control system  18  includes a crew interface system  20  and a communication interface  22 . 
   The crew interface system  20  includes a display  24  such as a high resolution LCD or flat panel display, which depicts antenna array allocation and communication module R 1 -Rn distribution information to the crew such that the crew may interact with the communication system  12 . The crew interface system  20  further includes an input device  28 , a plurality of buttons and directional keypad, but alternatively including a mouse, keyboard, keypad, remote device or microphone. Alternatively, the display  24  can be a touch screen display. 
   The crew interface system  20  further includes a CPU  32  and storage device  34  connected to the CPU  32 . The storage device  34  may include a hard drive, CD ROM, DVD, RAM, ROM or other optically readable storage, magnetic storage or integrated circuit. The storage device  34  contains a database  36  (illustrated schematically) with a Dynamic Antenna Allocation (DAA) algorithm and an interference matrix  30  (also illustrated schematically in  FIG. 3 ). Other operational software for the CPU  32  may also be stored in storage device  34  or alternatively in ROM, RAM or flash memory. 
   The communication interface  22  provides an input/output to crew audio systems  38  which may include a helmet mounted microphone and headphone speaker systems as well as other audio and voice systems. Multiple crewmembers are accommodated by the communication interface  22 . 
   The DAA algorithm achieves equivalent flexibility, redundancy, and functionality to antenna sharing through software-controlled reconfiguration by the control system  18 . The DAA manages the multiple of communication module R 1 -Rn and their dedicated antennas A 1 -An in response to the interference matrix  30  which has been preprogrammed with the potential interactions of all the communication modules R 1 -Rn. The Interference matrix is determined by a combination of analyses and testing for each particular aircraft  10  and is a look-up table stored as a portion of the database  36  ( FIG. 3 ). The look up table is itself dynamic in that it must make decisions related to potential interference as a function of the frequency differential between radios, and the harmonic interaction potential. Both harmonic and “in-band” interference combinations are defined in the interference matrix via a priori analyses and measurements of the communication module R 1 -Rn and associated antenna array  14  for the particular aircraft  10  ( FIG. 1 ). Additionally, interferences that may be determined after predefining the interference matrix are selectively added to the interference matrix upon acceptance by the crew through the crew interface system  20 . That is, interference variability such as operating environments and equipment upgrades which have not been predefined and are identified by engineering design as a result of predictive analysis, or by the crew, and are later added to the interference matrix to account for these variabilities. 
   In operation, when a discrete radio frequency, combined with an antenna A 1 -An located at a fixed point, and further combined with the frequency of any other communications device is selected for use simultaneously, the DAA algorithm will “look-up” that particular combination in the interference matrix to determine if the desired combination may result in an interference. When the desired combination of the discrete radio frequency, combined with an antenna A 1 -An located at a fixed point, and further combined with the frequency of any other communications device is predicted to result in an interference therebetween, the communication system  12  will alert the crew through the crew interface system  20 . The crew may then reassign the interacting pair of communication modules R 1 -Rn to another pair of communication module R 1 -Rn that utilize other dedicated antennas A 1 -An such that then antenna A 1 -An provides improved electronic isolation. The newly defined allocation then is checked to see if a subsequent interference potential may be generated as a result of the intended reallocation. Using this sequential technique, unintended secondary interferences are avoided prior to the automatic or manual reassignment. This process can repeat until all the interference conditions are resolved. Such reassignment may also occur automatically in response to the interference matrix  30 . 
   In one non-limiting operational example, if particular conditions cause transmissions at frequency F from antenna A 1  to interfere with reception on antenna A 2 , the DAA will reassign transmission on frequency F from transceiver R 1  to, for example, module R 4  which has dedicated antenna A 4 . The interference matrix, through predetermined analyses and/or testing, having determined that antenna A 2  will not be interfered with by transmission on Frequency F from antenna A 4  thereby provides virtual switching between module R 1 /antenna A 1  and module R 4 /antenna A 4  over the data bus  16 . Such virtual switching of hardware may be performed automatically in a manner transparent to the crew and the results displayed to the crew on the crew interface system  20 . Alternatively, or additionally, the crew interface system  20  displays a multiple of alternative selections which may be manually selected. It should be understood that the interference matrix  30  illustrated in  FIG. 3  is vastly simplified and that significant quantities of information are stored within the interference matrix  30  to define the interaction between each module/antenna with every other module/antenna at expected frequencies when utilized for transmitting and receiving from particular directions, operational environments and instructions for which module/antenna is the preferred re-assignment. 
   As much of the RF energy generated as possible must be efficiently transferred to the antennas to secure the maximum radiated power from a transmitter. Also, for best reception, maximum transfer of energy from the antenna to the receiver must occur. Efficient transmission and reception conditions prevail whenever the transmitter (or receiver) is properly matched to the transmission line and the transmission line is properly matched to the antenna. That is, this system solution maintains a dedicated antenna A 1 -An for each communication module R 1 -Rn and intended function, maximizing isolation between the modules and emphasizing flexible reassignment rather than additional antenna complexity and/or selective antenna RF transmission line switching. 
   Through transceiver/antenna selection and frequency management, DAA enhances redundancy, increases performance, and mitigates cosite interference. DAA also improves reliability and reduces weight by eliminating hardware heretofore required for RF transmission line switching. Furthermore, DAA reduces pilot workload by automating the process of antenna allocation, which requires operator intervention in conventional designs 
   It should be understood that relative positional terms such as “forward,” “aft,” “upper,” “lower,” “above,” “below,” and the like are with reference to the normal operational attitude of the vehicle and should not be considered otherwise limiting. 
   Although particular step sequences are shown, described, and claimed, it should be understood that steps may be performed in any order, separated or combined unless otherwise indicated and will still benefit from the present invention. 
   The foregoing description is exemplary rather than defined by the limitations within. Many modifications and variations of the present invention are possible in light of the above teachings. The preferred embodiments of this invention have been disclosed, however, one of ordinary skill in the art would recognize that certain modifications would come within the scope of this invention. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. For that reason the following claims should be studied to determine the true scope and content of this invention.