Patent Document

TECHNICAL FIELD 
     The present invention relates generally to radio frequency directed energy (RFDE) systems, and more particularly to multifunctional type RFDE systems. 
     BACKGROUND OF THE INVENTION 
     Radio frequency directed energy (RFDE) systems are known in the art for directing high power RF, microwave and/or millimeter wave electromagnetic energy to destroy or disrupt a target. Although RFDE systems typically serve as military weapons, RFDE systems need not be limited to weapon systems. For example, RFDE systems of the present invention may be used for non-military purposes such as destroying or disrupting foreign objects, contaminants, undesirable atmospheric conditions, or other types of targets. 
     As for weapon systems, it is important to distinguish between an RFDE weapon system and an electronic warfare system. A primary difference between an RFDE weapon and an electronic warfare system is power and kill mode. An electronic warfare system makes use of a priori knowledge of a target it is designed to jam or disrupt. An electronic warfare system uses such a priori knowledge of a target&#39;s characteristics (e.g., frequency of operation, method of operation, etc.) to disrupt or confuse the target with “finesse”, or a relatively low amount of power. 
     On the other hand, an RFDE weapon system can go after a broad range of targets (electronics, biological, ordinance, structures, etc.) due to its relatively large radiated power. A priori knowledge of the intended target characteristics is typically not required because the RFDE weapon either burns-out or overwhelms its target by the shear amount of power it radiates. 
     An ongoing problem with RFDE systems is targeting—accurately pointing the RF directed energy beam at the intended target and establishing an accurate range from the system to the target. To date, the RFDE system targeting problem has been addressed by using what may be referred to as auxiliary add-on systems. These add-on systems could include a stand-alone radar system, a stand-alone laser range finder, stand-alone optical or infrared imaging system, etc. However, these add-on systems add significant cost to the RFDE system. In addition, these add-on systems add significant complexity by requiring calibration of the alignment between the RFDE system and the stand-alone targeting system. 
       FIG. 1  is a block diagram of a typical RFDE system  10 . In its simplest form, the system  10  includes a high power transmitter  12  transmitting thru a high power antenna  14 . The transmitter  12  operates at RF, microwave or millimeter wave frequencies. The system  10  operates based on a prime power source  16 , such as an AC mains, generator, high capacity battery system, etc. A power conditioning block  18  conditions power delivered from the power source  16  so as to be suitable for powering the transmitter  12 . A cooling system  20  provides appropriate cooling to the power conditioning block  18  and the high power transmitter  12  as needed. A control block  22  provides appropriate control among the various sub-systems. 
     The RFDE weapon system  10  further includes an antenna pointing system  24  for aiming the high power antenna  14 , and thus the high power electromagnetic energy beam transmitted therefrom, at the target. The pointing system  24  typically is driven by coordinate data identifying the direction and range of the intended target. Such coordinate data is provided by a stand-alone targeting system  26 . As is noted above, the targeting system  26  is an add-on often in the form of a stand-alone radar system, a stand-alone laser range finder, stand-alone optical or infrared imaging system, etc. As is also noted above, however, these add-on systems add significantly to the cost and complexity of the RFDE system. 
     In view of the aforementioned shortcomings associated with conventional RFDE systems, there is a strong need in the art for an RFDE system which is not subject to the cost and complexity associated with conventional targeting systems. 
     SUMMARY OF THE INVENTION 
     The RFDE system of the present invention eliminates the need for a separate, stand-alone targeting system by integrating a targeting system within the RFDE system itself. The RFDE system is multi-functional in that all or part of the RFDE system hardware that functions to direct high power electromagnetic energy also functions to obtain and provide targeting information to aim the high power electromagnetic energy beam. For example, the RFDE transmitter is not only used as the source of the directed electromagnetic energy, but is also used as a radar transmitter for targeting an object. A relatively simple radar receiver may then be added to the RFDE system. The cost of the overall system is substantially reduced since an expensive radar transmitter is not required. 
     Moreover, the complexity of the system is reduced as calibration of the alignment between the RFDE system and a stand-alone targeting system becomes unnecessary. 
     According to one aspect of the invention, a multi-functional RFDE system is provided. The RFDE system includes an RFDE transmitter and at least one RFDE antenna. The RFDE transmitter and antenna direct high power electromagnetic energy towards a target sufficient to cause high energy damage or disruption of the target. The RFDE system further includes a targeting system for locating the target. The targeting system includes a radar transmitter and at least one radar antenna for transmitting and receiving electromagnetic energy to locate the target. The RFDE system also includes an antenna pointing system for aiming the at least one RFDE antenna at the target based on the location of the target as ascertained by the targeting system. Moreover, at least a portion of the radar transmitter or the at least one radar antenna is integrated within at least a portion of the RFDE transmitter or the at least one RFDE antenna. 
     According to another aspect of the invention, a method is provided operating an RFDE system. The method includes the steps of utilizing an RFDE transmitter and at least one RFDE antenna to direct high power electromagnetic energy towards a target sufficient to cause high energy damage or disruption of the target; utilizing a targeting system to locate the target, the targeting system including a radar transmitter and at least one radar antenna for transmitting and receiving electromagnetic energy to locate the target; aiming the at least one RFDE antenna at the target based on the location of the target as ascertained by the targeting system; and integrating at least at portion of the radar transmitter or the at least one radar antenna within, at least a portion of the RFDE transmitter or the at least one RFDE antenna. 
     To the accomplishment of the foregoing and related; ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative embodiments of the invention. These embodiments are indicative, however, of but a few of the various ways in which the principles of the invention may be employed. Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of a conventional RFDE system; 
         FIG. 2  is a block diagram of a multi-functional RFDE system in accordance with a first embodiment of the present invention; 
         FIG. 3  is a block diagram of a multi-functional RFDE system in accordance with a second embodiment of the present invention; 
         FIG. 4  is a block diagram of a multi-functional RFDE system in accordance with a third embodiment of the present invention; 
         FIG. 5  is a block diagram of a multi-functional RFDE system in accordance with a fourth embodiment of the present invention; 
         FIG. 6  is a block diagram of a multi-functional RFDE system in accordance with a fifth embodiment of the present invention; 
         FIG. 7  illustrates a multi-functional RFDE system mounted within an aircraft in accordance with an embodiment of the present invention; 
         FIG. 8  illustrates a multi-functional RFDE system mounted within a wheeled vehicle in accordance with an embodiment of the present invention; and 
         FIG. 9  is a schematic diagram of a multi-functional RFDE system incorporating a reflector-type antenna in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention will now be described with reference to the drawings, in which like reference numerals are provided to refer to like elements throughout. 
     The RFDE system of the present invention integrates a targeting system, such as a radar targeting, system, into an otherwise conventional RFDE system. There are several ways that the targeting system can be integrated into the RFDE system as explained herein. The particular embodiments described below are meant to be merely exemplary. The present invention contemplates not only the particular embodiments described herein, but any system in which a targeting system is integrated in part or in whole within the RFDE system. 
     Referring to  FIG. 2 , an RFDE system  30  is shown in accordance with an embodiment of the present invention. Since many of the elements of the RFDE system  30  in  FIG. 3  are similar to those in the conventional system  10  discussed above with respect to  FIG. 1 , only the relevant differences with be discussed herein for sake of brevity. In this particular embodiment, a portion of an otherwise conventional RFDE system (notably the high power transmitter  12  and/or the transmit antenna  14 ) forms part of the targeting system. Specifically, during a targeting mode, the high power RFDE transmitter  12  is controlled by the control block  22  to transmit standard radar tracking signals thru the antenna  14 . The radar tracking signals may be any type of conventional radar signal such a pulse or continuous wave radar. The power level of the tracking signals may be a high powered signal, such as the RFDE signal itself, or a relatively low powered signal as more typical in radar tracking applications. 
     In the embodiment of  FIG. 2 , a separate radar receiver  32  and radar receive antenna  34  are used in conjunction with the integrated RFDE/radar transmitter  12 . In one embodiment, the RFDE high power output beam intended to destroy or disturb a target is transmitted using the RFDE/radar transmitter  12  and antenna  14 . The radar receive antenna  34  receives portions of the RFDE output beam reflected by the target back towards the system  30 . The radar receiver  32  processes the reflected return signals using conventional techniques in order to identify the location of the target. For example, the radar receiver  32  can be coherently linked to the transmitted RFDE output waveform (represented by line  36 ) so that Doppler processing can be achieved and the direction and range of the target identified. 
     The radar receiver  32  provides the target location information to an integrated targeting system block  38  which feeds the location information to the antenna pointing system  24 . Such operation allows the antenna  14  to be directed in both search and track radar functions. 
     As will be appreciated, the RFDE system  30  in  FIG. 2 , as with the various other embodiments of the invention described herein, can operate in both an RFDE mode and a tracking mode. Both modes may be carried out simultaneously as described above, for example, where the high power electromagnetic energy output waveform of the RFDE system also serves as the radar tracking system transmit signal. Alternatively, the RFDE system  30  may switch between the RFDE mode and the tracking mode using a separate RFDE high power beam and lower power radar transmit signals, respectively. So long as the system  30  switches between the two modes rapidly enough so as not to lose track of the target, operation between RFDE mode and tracking mode may be time-division multiplexed. 
     Typically the radar transmitter is one of the most expensive portions of a radar tracking system. Therefore, by using the RFDE transmitter  12  and antenna  14  to function as the radar transmitter and antenna for targeting, the cost of the targeting system can be drastically reduced. Also, using the radar return of the RFDE high power beam itself to determine the target location can substantially improve the beam pointing accuracy of the RFDE system  30 . By using the RFDE high power beam to determine the location of the target, the power density on target will be maximized when standard radar tracking techniques are employed (e.g., monopulse, continuous scan, etc.). 
     Those of ordinary skill will appreciate that the RFDE transmitter  12  can be any transmitter suitable for transmitting an RFDE high power beam. For example, the RFDE transmitter  12  may be a single or multiple tube source, or solid state source. Moreover, it will be appreciated that the antenna  14  can be any type of suitable high power antenna which can be mechanically and/or electronically pointed and scanned via the antenna pointing system  24 . The transmitter/antenna can also be comprised of an active electronically steered array (AESA), for example, where an array of high power amplifiers/antennas is utilized. The radar receive antennas  34  can be any type of suitable antenna for receiving the radar return signals. As with the antenna  14 , the radar receive antenna  34  is mechanically and/or electronically pointed and scanned via the antenna pointing system  24 . The antenna pointing system  24  can be a mechanical gimbal or a beam steering computer controlling phase shifters in an electronically steerable array. 
       FIG. 3  illustrates another embodiment representing how a tracking system can be integrated with an RFDE system. The embodiment of  FIG. 3 , as with the other embodiments described herein, shares many of the same elements as  FIG. 2 , and thus again only the relevant differences between the embodiments will be discussed for sake of brevity. 
     Specifically,  FIG. 3  illustrates an RFDE system  40  in which the power amplifier of the tracking system is integrated within the power amplifier of the RFDE system. More particularly, the RFDE transmitter  12  includes a low power RFDE signal source  42  operating at a first frequency and input to an adder  44 . The output of the adder  44  is input to a power amplifier  46  which amplifies the output before being radiated by the transmit antenna  14 . A low power radar signal source  48  at a second frequency is also input to the adder  44 . In addition, the low power radar signal source  48  is input to the radar receiver  32  to provide for coherent processing. The adder  44  thus outputs the combined RFDE signal source and radar signal source to the power amplifier  46 . The power amplifier  46  can be any suitable type of amplifier including, for example, an injection locked magnetron, a klystron, a solid-state amplifier, etc., or an array of any of these types of amplifiers in an AESA embodiment. 
     In the embodiment of  FIG. 3 , a separate low power radar signal from the signal source  48  is used. This signal is combined with the RFDE signal from the RFDE signal source  42  prior to the combined signal being amplified by the power amplifier  46 . The frequencies of the RFDE signal and the radar signal do not have to be at the same frequency. In fact, they can be completely independent of each other within the bandwidth constraints of the power amplifier  46  and the RFDE transmit antenna  14 . It will be appreciated that significant isolation can be achieved between the RFDE and radar signals by filtering out the RFDE signal at the receive antenna  34  and/or radar receiver  32 . 
     Again, it will be appreciated that the RFDE system  40  of  FIG. 3  may operate in an RFDE mode and a targeting mode. As in the other embodiments described herein, such modes may be carried out simultaneously or in time-multiplexed fashion. In the case where the RFDE signal source  42  and radar signal source  48  are different, one may consider such operation as frequency-multiplexed as will be appreciated. 
       FIG. 4  illustrates yet another embodiment of the present invention. In this embodiment, the RFDE system  50  integrates the radar receive antenna into the same antenna  14  serving as the RFDE and radar transmit antenna. This is accomplished by means of a high power circulator  52  which routes the RFDE/radar transmit signals from the shared transmitter  12  through to the antenna  14 . Reflected signals received by the antenna are routed by the circulator  52  to the receiver  32  for processing. In this example, as in the others discussed herein, the RFDE transmit signal may also be the radar transmit signal. The return signal is received by the same antenna  14  and coupled through the circulator  52  to the receiver  32 . The radar system thus can provide target information feedback to the antenna pointing system  24 . 
     The high power circulator  52  can be problematic in that it can be difficult to design a circulator that can handle the typical total power radiated by an RFDE system. Nevertheless, with improvements in materials and technologies such a circulator may someday be commercially feasible. Furthermore, the embodiment of  FIG. 4  certainly is very suitable for an AESA system where the output power is broken-up among an array of transmit elements as discussed in more detail below. 
     In some integrated RFDE/targeting applications it may be desirable only to share the antenna between the RFDE and targeting systems. The RFDE system and the targeting system otherwise operate independently. An example of such an embodiment is shown in  FIG. 5 . 
     Specifically, the embodiment of  FIG. 5  illustrates a radar system  32 ′ which functions essentially independently of the RFDE system  60  with the exception of sharing a dual polarized antenna  14 . The RFDE system transmits the RFDE high power beam from the transmitter  12  via the dual polarized antenna  14  using one polarization (e.g., vertical, right hand circular, etc.). The radar system  32 ′, with its own transmitter/receiver, transmits the radar transmit signal via the antenna  14  using the orthogonal polarization (e.g., horizontal, left hand circular, etc.). The reflected radar return signal received by the antenna  14  is processed by the radar system  32 ′ to provide target location information, again using conventional techniques. As in the other embodiments, the location information is provided to the integrated targeting system  38  which provides the information to the antenna pointing system  24 . The embodiment of  FIG. 5  can be used to provide tracking information and/or is especially suitable for providing range information for the RFDE system. 
       FIG. 6  illustrates an embodiment in which AESAs or phased array antennas may be incorporated within the present invention. The embodiment of  FIG. 6  is fundamentally the same as the embodiment of  FIG. 3 , with the exception that the power amplifier  46  is represented by an array of power amplifiers  46 ′ included with the RFDE/radar transmit AESA antenna  14 . The radar receive antenna  34  may similarly comprise an AESA antenna. 
     As is shown in  FIG. 6 , the combined signal from the adder  44  is input to a power splitter  72  within the AESA antenna  14 . The power splitter  72  separates the signal and provides the split signal to respective phase shifters  74  and power amplifiers  46 ′ corresponding to respective radiator elements  14 ′ in the antenna  14 . The antenna pointing system  24  may steer the antenna  14  by adjusting the phase of the phase shifters  74 , as will be appreciated. 
     Continuing to refer to  FIG. 6 , it will further be appreciated that the radar source  48  and RFDE source  42  can be at different frequencies and still radiate in the same direction. As long as the phase shifters  74  are selected to provide a true time delay (which is fairly common in the art), the antenna  14  may be steered concurrently for both frequencies. 
     A multifunctional RFDE system of the present invention can be employed on a variety of platforms. For example,  FIG. 7  illustrates an embodiment in which the system is employed on an aircraft. The combined RFDE/radar transmitter  12  and antenna  14  (not shown), for example, are mounted to radiate out the side of the aircraft. A pod is then mounted beneath the aircraft, containing the radar receiver  32  and receive antenna  34  (also not shown). 
       FIG. 8  shows an embodiment in which the RFDE system of the present invention can be employed on a wheeled vehicle. For example, the RFDE and radar systems are mounted in the back of the vehicle and share a common antenna. One possible such system  80  is shown in  FIG. 9 . A high power RFDE source  12  radiates into a beam transport system comprised of mirrors (e.g.,  82 ) suitable for the frequency of operation. A cross-polarized radar transmit signal from the radar system  32 ′ is then injected into the RFDE beam path by means of a beam combiner/splitter  84 . The RFDE and radar transmit signal are then simultaneously transmitted from the common antenna  14 , in this embodiment a reflector-type antenna. The radar return signal is received by the antenna  14  and directed back to the cross-polarized radar system  32 ′ via the mirrors  82  and beam combiner/splitter  84 . 
     Although the invention has been shown and described with respect to certain preferred embodiments, it is obvious that equivalents and modifications will occur to others skilled in the art upon the reading and understanding of the specification. For example, although the present invention has been described primarily in the context of a conventional radar based targeting system, other types of radar-like targeting systems which rely on the transmission and return of electromagnetic energy (e.g., laser-based, infrared, etc.) can also be used without departing from the scope of the invention. 
     The present invention includes all such equivalents and modifications, and is limited only by the scope of the following claims.

Technology Category: 5