Abstract:
A radar jamming signal generated by equipment carried by a target aircraft, is launched onto the leading end of a towed single wire transmission line so as to travel the length of the line as a nonradiating surface wave. A drogue radiator is attached to the trailing end of the line for radiating the jamming signal transversely of the towed line so as to be received by and cause jamming of tracking and/or fire control radar. The length of the single wire transmission line is selected so that the trailing radiator causes the jamming signal to emanate from a position sufficiently behind the aircraft so as to be outside the destructive radius of weapon fire directed at the apparent source of the jamming signal by fire control radar. A ventriloqual-like deception of the radar is thus achieved. A wave launcher couples the jamming signal to the leading end of the transmission line and for this purpose includes an electrically conducted horn-shaped structure, a tunable coaxial feed end at the constricted end of the horn structure, an inner transition conductor connecting the inner conductor of the coaxial feed to a leading end of the single wire transmission line, and a plurality of annular dielectric lenses and dielectric guides cooperatively shaped and fitted to the horn structure in a manner that effectively matches the bounded electromagnetic transmission wave characteristics of the coaxial feed cable with the surface wave transmission characteristics of the single wire transmission line.

Description:
BACKGROUND OF THE INVENTION 
   The invention pertains to signal jamming systems, carried by manned or unmanned aircraft including missiles, for the avoidance of position locating, tracking and fire control radar. 
   The present application is related to the subject matter of U.S. application Ser. No. 225,669, filed Jan. 16, 1981, by Walter E. Buehler, Roger M. Whitson and Michael J. Lewis, for ANTI SIGNAL-INTEGRATION APPARATUS AND METHOD FOR COUNTERING INTEGRATION ENHANCEMENT OF RADAR RETURN SIGNALS MASKED BY AIRBORNE VENTRILOQUAL-LIKE NOISE JAMMING. 
   The use of radar signal jamming equipment carried onboard manned and unmanned aircraft to mask the aircraft&#39;s position from position locating, tracking and fire (weaponry) control radar is one of a number of known radar avoidance techniques that fall in the broader field of electronic counter measures (ECMs). Existing jamming techniques are primarily effective in denying the radar equipment range information, i.e., the distance between the radar and the target aircraft. However, the transmission of the jamming signal, emanating as it does from the aircraft, enables some radar systems to home-in on the source of the jamming signal, which is typically a noise signal in the frequency band of the radar, and thereby acquire accurate information representing the angular position of the aircraft. This angle information alone, even without range determination, is sufficient to allow for many types of weaponry, aimed by fire control radar, to reach and destroy the target aircraft. Thus, the mere generation and transmission of a noise jamming signal is not totally effective and providing the desired masking of the aircraft to the tracking radar. 
   Accordingly, an object of the invention is to provide a system for generating and radiating a radar jamming signal from a target aircraft that is to be masked from the radar in such a manner that the jamming signal deceptively emanates from a position which is removed at a safe distance from the target aircraft. 
   More particularly, it is an object of the invention to provide an apparatus for transmitting an onboard generated jamming signal over a transmission line towed by the target aircraft, and radiating the jamming signal from a passive radiator attached to a trailing end of the transmission line. A related object is to provide such a towed transmission line for the jamming signal which is capable of transmitting the jamming signal efficiently over the relatively long distance needed to dispose the point of signal radiation at a safe distance from the target aircraft, and to employ a line having transmission characteristics that preclude excessive radiation leakage at the leading end and along intermediate sections of the line which, if allowed to occur, would cause the emission of a radar trackable signal source at positions dangerously close to the target aircraft. 
   Still another object is to provide a transmission line for the above-mentioned ventriloqual-like radar jamming system, that has high efficiency so as to enable sufficient signal power to reach the radiator at the trailing end of the line so that a jamming signal of adequate strength can be radiated to effectively mask the target aircraft. 
   In accordance with the foregoing objects, it is a feature of the invention to employ a single wire transmission line, which characteristically provides highly efficient signal transmission when in free space or air and to tow such line behind the target aircraft. In connection with this feature, it is another object to provide a broadband, highly efficient, nonleaking electromagnetic wave launcher for launching the onboard generated jamming signals onto the leading end of the towed single wire transmission line. 
   It is also a feature to provide a single wire transmission line that is constructed to accommodate efficient surface wave transmission and that is also sufficiently flexible to allow it to be wound onto and unwound from a line stowage reel carried onboard the target aircraft. 
   A further feature is to provide a radiator in the form of a drogue for attachment to the trailing end of the line for radiating and selectively polarizing the thusly radiated jamming signal, and for causing stable trailing flight of the line consistent with efficient transmission of the jamming signal wave energy along the line. 
   SUMMARY OF THE INVENTION 
   These and other objects, features and advantages are achieved in accordance with the invention by an airborne radar jamming method and apparatus characterized by the provision of a single wire transmission line towed behind a target aircraft, which as the term is used herein includes manned or unmanned aircraft, missiles, rockets, and the like, for causing the jamming signal to be radiated at a “safe” distance behind the aircraft. Briefly, the principal elements of the jamming system include an onboard signal generator for producing a broadband noise (jamming) signal, the above-mentioned single wire transmission line towed by the aircraft, a broadband electromagnetic wave launcher for launching the noise signal produced by the signal generator onto a leading end of the single wire transmission line such that the electromagnetic noise energy is transmitted as a surface wave along the line to a trailing end thereof. A drogue radiator is attached to the trailing end of the single wire transmission line for both aerodynamically stabilizing the line and for radiating the noise signal away from the axis of the line and toward the tracking radar. By using a sufficiently long transmission line relative to the beamwidth of the tracking radar, the latter is deceived by the ventriloqual-like radiation of the noise jamming signal from an apparent source that is at a substantial distance behind the would be target. Thus, the jamming signal masks the radar return signal reflected off the skin of the target aircraft, and if the radar is of a type that upon losing tracking contact with the aircraft skin searches out and homes-in on the angular position of a nearby noise signal source, the ventriloqual-like effect of the trailing radiator denies the tracking radar accurate angle location information of the target&#39;s position. 
   Another aspect of the invention is the provision of a broadband electromagnetic wave launcher that is disposed and connected to couple a broadband noise (jamming) signal onto the leading end of the towed single wire transmission line. The launcher is characterized by a coaxial feed line that extends from the onboard generator to the constricted end of a horn structure where an adjustably slidable impedance matching assembly efficiently couples the electromagnetic energy of the noise signal into the horn structure. The inner conductor of the feed cable is connected to a transition conductor coaxially centered in the horn structure and such transition conductor blends into the single wire transmission line which emerges from the flared end of the horn. Annular dielectric guide and electromagnetic lens structures are coaxially mated to the horn and are fixedly supported thereby for the multipurposes of centering the transition conductor and the leading end of the single wire transmission line and for efficiently compressing the bundle of electromagnetic energy that comprises the signal so that as it emerges from its bounded condition between the flared end of the horn and the transition conductor the signal energy adheres to the line as a surface wave. Such compression of the emerging energy bundle smoothly and gradually reshapes the signal energy so that it matches the impedance and surface wave transmission characteristics of the single wire transmission line without significant energy leakage at the launcher. 
   To provide a complete disclosure of the invention, reference is made to the appended drawings and following description of one particular and preferred embodiment. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a generalized view of the ventriloqual-like radar jamming system illustrating a target aircraft towing the electromagnetic wave launcher, single wire transmission line and drogue radiator for radiating a radar jamming signal from a deceptive distance behind the aircraft position. 
       FIG. 2  is a detailed, block diagram of the noise signal jamming system including the noise generator and power amplifier in combination with a line stowage reel, an electromagnetic wave launcher and the towed single wire transmission line with the drogue radiator. 
       FIGS. 3   a  and  3   b  together show a detailed, axial sectional view of the axisymmetric wave launcher, single wire transmission line and drogue radiator. 
       FIG. 4  is an enlarged, detailed, elevational view of a lengthwise segment of the single wire transmission line. 
       FIG. 5  is a detailed, cross section view of the single wire transmission line of  FIG. 4 . 
       FIG. 6  is a view, partly an axially section, similar to  FIG. 3   b , showing an alternative configuration of the drogue radiator, and an associated delaunching dielectric lens for causing the electromagnetic energy of the radar jamming signal to be efficiently coupled to and thence radiated by the drogue. 
       FIG. 7  is an axial, end view of the drogue radiator of  FIG. 6 , looking aft along the single wire transmission line toward the apex of the conical shaped drogue. 
   

   DETAILED DESCRIPTION 
     FIG. 1  illustrates how the ventriloqual-like jamming system radiates a radar jamming noise signal in a manner that denies radar  11 , angle information of the position of a target aircraft  12 , even though the signal receiving components of radar  11  are capable of homing on and tracking a noise source when the skin-reflected radar return signal is masked by radiating a jamming signal. Attached to aircraft  12  so as to be towed thereby is a single wire transmission line subsystem  14  including a wave launcher  16 , a single wire transmission line  18  extending from a leading end which is mechanically and electrically coupled to the towing aircraft  12  by wave launcher  16 . Line  18  terminates at a substantial distance behind aircraft  12 , and a drogue radiator  20  is attached to the trailing end of the line. 
   As described in greater detail in the section herein dealing with the system&#39;s operation, radar  11  may in the absence of an effective jamming signal function to locate and track the actual position of the aircraft by receiving and processing the radar return signal reflected by the target aircraft. The position of the aircraft is located by its angular coordinates and range (distance) with respect to the location of radar  11 . If in an attempt to defeat skin tracking by radar  11 , a noise jamming signal is radiated by and from target aircraft  12 , many radar tracking systems such as radar  11 , have alternative receiving modes which enable them to home on and track a noise signal source even though the return signal from the aircraft skin is masked by the jamming signal. Hence, radar  11  functioning in such a noise tracking mode will continue to provide the angle information of the position of aircraft  12 , even though the range information is denied because of the masking effect of the jamming signal. 
   With the addition of the single wire transmission line subsystem  14 , a ventriloqual-like radiation of the noise signal is achieved so that the tracking radar  11  is denied both range and angle information. The noise signal generated onboard aircraft  12  is coupled by launcher  16  to the leading end of the single wire transmission line  18  which is characterized by low loss and low leakage transmission. The noise signal energy travels, as a surface wave, the length of line  18  to the trailing end thereof where the energy is intercepted by drogue radiator  20  and radiated thereby transversely outwardly from that location, such that a portion of the radiation propagates toward the tracking radar  11 . The length of transmission line  18  is selected so that the angle error between the actual position of aircraft  12  and the apparent position (because of the noise source) at drogue  12  is, for a typical range from radar  11 , greater than the destruction radius of any anticipated anti-aircraft weaponry. Thus, the angle a that is subtended at the tracking radar  11  by the length of the single wire transmission line  18  should be large enough given the distance (range) of aircraft  12  from radar  11  to dispose drogue radiator  20  far enough behind aircraft  12  so that artillery, armed missiles or rockets, when exploded in the vicinity of the drogue radiator will not inflict disabling damage on aircraft  12 . 
   Now with reference to  FIG. 2 , the single wire transmission line subsystem  14  is driven by an onboard noise signal generator and power amplifier that includes a wideband noise signal source  30  and suitable filtering, preamplification, variable gain control and power amplification provided here respectively by an X-band filter  32 , an amplifier  34 , variable attenuator  36  and a traveling wave tube (TWT) amplifier  38 . Generator  30  provides a source of essentially white noise by tapping the thermal noise existing in a resistor  30   a  and then successively amplifying the thermal noise in a plurality of cascaded, microwave amplifiers  30   b ,  30   c  and  30   d . In this embodiment, these cascaded amplifiers have a one octave wide bandwidth of 6 to 12 gigahertz so as to receive the low level noise signal from resistor  30   a  (at −170 dbm/Hz) and successively raise the signal level by 13 db, 28 db and 42 db to a level of −87 dbm/Hz at the output of generator  30 . 
   The thusly generated noise signal is now applied to an X-bandpass filter  32  that slices from the broadband noise signal, a noise spectrum of several tens of megahertz centered about the mid-frequency of the bandpass of microwave amplifiers  30   b ,  30   c  and  30   d . The slice of noise signal energy from filter  32  is now further amplified by amplifier  34  having a 26 db gain to bring the signal strength up to a level suitable for power amplification by the traveling wave tube amplifier  38 . Variable attenuator  36  serves to adjust the gain of the signal to a desired level prior to power amplification. The output of TWT amplifier  38  brings the signal level up to +23 dbm from the +13 dbm per 50 megahertz at the output of amplifier  34 . The noise signal has now been power amplified to about 200 watts, sufficient to cause approximately 10–20 watts to be radiated by drogue radiator  20  of subsystem  14 . To monitor the power level of the transmit signal, as it exists at the output of power amplifier  38 , a direct microwave coupler  40  is inserted in series between amplifier  38  and the transmission line subsystem  14 , and a power monitor  42  is connected via coupler  40  to provide a measured indication of the transmitter output wattage. 
   From direct coupler  40 , the transmit signal energy is fed through a coaxial cable  44  to subsystem  14 . A junction exists between coaxial cable  44  and the single wire transmission line  18  in a manner described more fully below in connection with  FIGS. 3   a  and  3   b . Between coupler  40  and launcher  16  of subsystem  14 , as schematically shown, a stowage reel  46  is provided including such means as a rotary coaxial joint  45  mounted at the hub of reel  46  for connecting a non-rotating section of cable  44  from coupler  40  to another section of cable  44  which along with line  18  is wound on rotatable reel  46 . A means is thereby provided for stowing single wire transmission line  18  and a feed section of coaxial cable  44  when line  18  is retracted from the extended position as it is shown in  FIGS. 1 and 2  by drawing the line forwardly through a sliding coupling with launcher  16  until drogue  20  is pulled up against launcher  16 . Although not shown in the drawings, stowage reel  46  is mounted onboard aircraft  12  at a location adjacent an opening in the aircraft body in registration with launcher  16  which is mounted on the exterior of the aircraft. Reel  46  is thus positioned for selectively dereeling line  18  to deploy the single wire transmission line subsystem  14  and to retract the line so as to draw drogue radiator  20  up against launcher  16 . 
   As shown in greater detail in  FIG. 3   a , the center conductor of coaxial feed cable  44  is joined by a tapered transition conductor to a leading end of the single wire transmission line  18  and the outer conductor of cable  44  is adapted to be removably connected to the constricted end of launcher  16  when line  18  is fully deployed. Thus, when line  18  is to be retracted, storage reel  46  is adapted to first wind in a short section of coaxial feed cable  44  that is disposed between reel  46  and the constricted end of launcher  16  and thereafter to continue winding in the single wire transmission line  18  until as mentioned above drogue radiator  20  is pulled up against the launcher. In this embodiment, launcher  16  is mounted to the exterior of aircraft  12  by suitable means such as enabled by the mounting bracket  48  illustrated in  FIGS. 2 and 3   a  of the drawings. 
   With reference to  FIGS. 3   a  and  3   b  which show line  18  in its fully deployed position, launcher  16  includes the principal components of a horn structure  50 , and dielectric structures  52 ,  54  and  56 , all of which are axisymmetric about the centerline of transmission line  18 . Horn structure  50  has a constricted end  50   a  including a tubular section  50   b  of substantially uniform diameter for with an adjustable impedance matching coupling  60  that mechanically and electrically joins coaxial feed cable  44  to horn structure  50 . From constricted end  50   a , horn  50  flares outwardly, in accordance with an exponential divergence per unit axial length, terminating at a flared end  50   c  downstream of which the horn bounded electromagnetic noise signal energy is launched as a surface wave onto the conductor provided by line  18 . 
   Adjustable coupling  60  is provided by a tubular member  62  dimensioned so as to slidably (telescopically) fit inside of tubular section  50   b . A stop ring  64  slips over member  62  and can be locked in a fixed axial position on member  62  by screw  65 , so as to abut against an end  63  of the tubular section  50   b  of horn structure  50 . The non-inserted end of tubular member  62  is mechanically and electrically joined to the outer braided conductor of coaxial cable  44  by means such as soldering or brazing. In this manner, coupling  60  provides a slidable adjustment between member  62  and tubular section  50   b  over an adjustment distance Δ1 for impedance matching the coaxial feed cable  44  to the input end of horn  50 . 
   Cable  44  is of a conventional coaxial type, including a center conductor  44   a , a braided outer conductor protective sheath  44   d  which as mentioned above is soldered or brazed to the noninserted end of member  62 , and dielectric body  44   b  disposed between conductors  44   a  and  44   d . To join cable  44  to member  62  the outer braided conductor  44   d  is stripped back a distance somewhat greater than the overall length of tubular member  62 . Member  62  is now slid over the thusly exposed body of dielectric  44   b  so that the end of body  44   b  and the inner conductor  44   a  project beyond the inserted end of member  62 . The braided conductor  44   d  is now soldered or brazed to the opposite end of conductor  62 . 
   Adjacent the inserted end of member  62  dielectric  44   b  of cable  44  is tapered down to inner conductor  44   a  as indicated at  44   e  and the terminal end of inner conductor  44   a  is electrically and mechanically joined as indicated at  66  to the smaller end of a tapered transition conductor  68  of increasing diameter in the direction toward the single wire transmission line  18 . The larger end of transition conductor  68 , which for example may be of solid brass or other conductive metal, is mated to and is mechanically and electrically joined to a matching diameter of a leading end of single wire transmission line  18 . 
   Dielectric structure  52  serves to center transition conductor  68  and the adjoining leading end of single wire transmission line  18  at an axially intermediate position within horn structure  50  and is shaped and mated to horn structure  50  so as to minimize any impedance discontinuity occasioned by the presence of its dielectric body, which has a dielectric in excess of that of free space so as to have a material effect on the electromagnetic signal energy. For this purpose horn structure  50  is shaped as follows. Commencing at a location along the axis of launcher  16  that lies in transverse registration with the taper  44   e  on the body of dielectric  44   b , and hence downstream of tunable coupling  60 , horn structure  50  enlarges in diameter along its axis of symmetry and then with a decreasing amount of divergence until reaching the midsection of  52   a  of dielectric structure  52 , where the interior diameter of horn  50  is approximately constant along the axis. The initial enlargement of horn structure  50  followed by a decreasing amount of divergence along the axis, coincides with the position of a leading taper  52   b  on dielectric structure  52  that commences at an end  52   c  disposed axially downstream of the junction  66  between transition conductor  68  and the inner conductor  44   a  of cable  44 . The initial enlargement of horn structure  50  in registration with the leading taper  52   b  of structure  52  provides a smooth impedance transition in this region. 
   The midsection  52   a  of dielectric structure  52  is fixedly attached to the interior surface of horn structure  50  so that structure  52  is prevented from sliding axially forwardly or rearwardly as line  18  and transition conductor  68  are fed through a central bore  52   e.    
   Continuing toward the flared end  50   c  of horn structure  50  from the midsection  52   a  of dielectric structure  52 , the wall of horn structure  50  again commences to diverge outwardly here in an exponential fashion along the axis of the structure and such outward divergence is in registration with a trailing taper  52   f  on structure  52 . Like the leading taper  52   b , the trailing taper  52   f  of structure  52  provides a smooth, blended impedance transition for the axially propagating electromagnetic energy where the decreasing amount of dielectric material associated with taper  52   f  gradually releases the electromagnetic energy into the lower dielectric volume associated with the air space existing between horn structure  50 , and structure  52 . Taper  52   f  terminates at an end  52   g  at which the electromagnetic energy is contained totally within the air space dielectric. 
   End  52   g  of the trailing taper  52   f  of structure  52  terminates substantially upstream of end  50   c  of horn structure  50  as depicted in the composite of  FIGS. 3   a  and  3   b . Between dielectric structure  52  and end  50   c  of horn structure  50 , the wall of the horn diverges outwardly in an exponential flare. 
   Adjacent end  50   c  of horn  50 , a bulbous shaped dielectric guide structure  54  is disposed to serve as a support structure for maintaining an elongate, double tapered dielectric lens structure  56  coaxial with the centerline of horn structure  50 . A rearward portion  54   a  of guide structure  54  has a circumferential surface mated to the interior flare of horn  50  and terminating at a transverse plane  54   b . Projecting downstream of end  50   c  guide structure  54  has a generally semi-spherical, bulbous portion  54   c  defining an axis of symmetry that is coaxial with the centerline of horn structure  50  and line  18 . Dielectric guide structure  54  is, unlike structure  52 , selected to have a dielectric constant that is approximately that of free space so as to be inert with respect to the transmission of electromagnetic energy. This is achieved by using a material such as rigid, polyurethane foam. In particular, such a foam having a density of 2 lbs/ft 3  has been found suitable for use as dielectric structure  54 . 
   Dielectric lens structure  56  is tapered at both axial ends and is secured in coaxial alignment with the centerline of horn structure  50  by a matingly tapered opening  54   d  provided in foamed dielectric structure  54 . An axial bore  56   a  extends the entire length of lens  56  from an end  56   b  of the leading taper  56   c , through a midsection  56   d  of maximum diameter and through a trailing taper  56   e  that terminates at a trailing end  56   f . The leading taper  56   c  and the dielectric constant of lens structure  56  are selected so as to compensate for the otherwise abrupt impedance transition existing at the termination of flared end  50   c  of horn structure  50  by causing a portion of the electromagnetic energy emerging from the horn to be concentrated in the body of lens structure  56 . In so doing, the radially oriented E (electric) fields of the TEM electromagnetic waves are compressed relative to the radial extent of such fields in the absence of dielectric lens structure  56 . Downstream of the maximum diameter midsection  56   d  of lens structure  56 , the compressed E fields of the wave energy are allowed to expand gradually in the trailing taper  56   e , to blend the emerging wave energy with the steady state surface wave propagation along line  18 . Once launched onto line  18 , the wave energy is in effect “glued” to the conductive surface of the single wire transmission line in accordance with the teachings of A. Sommerfeld and G. J. E. Goubau as disclosed in U.S. Pat. No. 2,685,068 issued to Goubau on Jul. 27, 1954. As described more fully below in connection with  FIGS. 4 and 5 , line  18  in the preferred embodiment has an outer conductive surface in which the propagating electromagnetic wave energy is compressed around the line by the presence of slight DC resistance in the surface conductor, rather than by using a sheathing of dielectric material around a core conductor as in the case of a Goubau transmission line. By using a coaxially cable feed into the constricted end of horn structure  50 , a broadband coupling is achieved between coaxial cable  44  and the horn as compared to the use of a resonant cavity coupling which is inherently narrowband. Additionally, the exponential divergence of horn structure  50  downstream of the midpoint of guide structure  52 , causes the launcher to be less frequency sensitive, enhancing its broadband performance, as does the leading taper  56   c  of dielectric lens structure  56 . Further still, the exponential shaping of horn structure  50  together with the provision of lens structure  56  minimizes the diameter of horn structure  50  at the launching end  50   c  even though line  18  is a Sommerfeld line which, as discussed more fully hereinafter, exhibits a relatively larger diameter energy bundle than a Goubau transmission line, hence suggesting the need for a substantially larger diameter launcher than has been found needed in actual practice. 
   With reference to  FIGS. 4 and 5 , line  18  is formed of an innermost solid nylon tension strand  18   a  surrounded by a braided multifiber cord  18   b  made of synthetic fiber strands which coact with the solid nylon strand  18   a  to provide tension strength for line  18  while also allowing it to remain flexible for coiling on stowage reel  46 . Surrounding cord  18   b  is a homogeneous body  18   c  of foamed synthetic material such as polypropylene to provide a relatively large diameter circumference onto which a thin conductive sheath  18   d  is provided by wrapping a web of aluminum foil around body  18   c  and finishing the wrap with a lengthwise seam  18   e . After the conductive foil  18   d  is applied to the dielectric body  18   c , it is embossed with a herringbone pattern of alternating ridges and furrows indicated at  18   f  such as by initially applying a braided, conductive sheath about line  18  and then removing the braiding to leave the herringbone embossed surface  18   f  on the exterior of line  18  as best shown by  FIG. 4 . In this particular embodiment, the manufacturing steps used in forming line  18  are substantially the same as those used to make a durable, coaxial cable used in closed circuit television transmission except that the outer braided sheath is first applied and then removed in the present embodiment to form the herringbone embossed surface  18   f , whereas in case of the coaxial cable the sheath is permanently retained. Also, in the case of the coaxial cable transmission line, the innermost core of the line is a solid copper conductor, rather than the nonconductive nylon strand  18   a  and braided fiber cord  18   b  shown in  FIG. 5 . 
   Since the transmission mode of line  18  is a surface wave rather than a bounded wave inside a coaxial cable the innermost conductor is omitted in line  18  to reduce the weight of the towed line and to increase its flexibility for coiling on storage reel  46 . The embossed surface  18   f  of conductive foil  18   d  allows the foil to be compressed and stretched so as to avoid an unwanted tendency present in a smooth, unwrinkled conductive foil to shingle and buckle when line  18  twists in flight and when it is coiled even on a relatively large diameter drum of a storage reel. Unlike the uniformity of the herringbone embossed surface  18   f , random shingling of a conductive foil on the line will severely disrupt the surface wave transmission characteristics of the electromagnetic energy and cause some of the energy to be leaked transversely from the line before reaching drogue radiator  20 . By way of example, a line  18  formed in the manner described is capable of being stowed on a one foot diameter drum without causing any permanent deformation of the conductive foil  18   d  that would interfere with the transmission of the electromagnetic energy as a surface wave in accordance with the Sommerfeld principle. 
   The trailing end of line  18  is mechanically and electrically joined as indicated at  70  in  FIG. 3   b  to the apex of a rearwardly divergent conical drogue  20  which is hollow and open to the rear. Air flow perforations  72  are provided in the wall of conical drogue radiator  20  for stabilizing the flight of the drogue and to balance the lift-to-drag ratio of drogue radiator  20  to that of line  18 . It is noted that the flight characteristics of line  18  are substantially dictated by those physical characteristics of line  18  which allow it to function as a transmission line. By aerodynamically configuring drogue radiator  20  to provide a lift-to-drag ratio that approximates that of line  18  itself, the flight of line  18  and drogue radiator  20  attached thereto tends to be stable, without significant bending that would interfere with the transmission characteristics of line  18  as a single wire line transmission system. Also, drogue radiator  20  helps dampen any tendency of air turbulence to induce traveling or galloping waves in the line  18  which also can significantly interfere with its electrical transmission properties. 
   Based on the above-disclosed principles of launcher  16 , line  18  and drogue radiator  20 , a single wire transmission line subsystem  14  has been constructed and tested over a relatively broadband frequency range of 6 to 18 gigahertz. Moreover, it has been demonstrated that the lower limit of the bandwidth is actually about 2 gigahertz, such that the overall bandwidth is several octaves. 
   At these frequencies, the following specifications and dimensions for the coaxial feed cable  44 , launcher  16 , line  18  and drogue radiator  20  were used. Coaxial cable  44  is a conventional 50 ohm coaxial cable while the single wire transmission line  18  has an air space impedance of approximately 400 to 600 ohms. Thus, launcher  16  must provide a low loss broadband coupling between the relatively low impedance of the coaxial feed cable  44  and the substantially higher impedance of single wire transmission line  18 . In this particular embodiment, given the required impedance transition, bandwidth and frequency range, the tubular section  50   b  of horn structure  50  is approximately two inches in length, while the insertable tubular member  62  connected to the shield of cable  44  is one and three-quarters inches long for a tuning distance of Δ1 between locations A and B (indicated in  FIG. 3   a ) of slightly over one-half of an inch. At location B corresponding to the constricted end of horn structure  50 , the inside diameter of the horn wall is approximately 0.25 inches. The distance between locations B and C is approximately 3 inches and the inside horn diameter at location C is about 0.625 inch. Transition conductor  68  is made of brass and is approximately 1.35 inches long and joins the outer conductive foil of line  18  at a junction that is disposed intermediate the ends  52   c  and  52   g  of dielectric  52  when the line is fully deployed as depicted in  FIGS. 3   a  and  3   b . Between locations C and D, horn structure  50  flares outwardly in the above-described exponential fashion from the inside diameter of approximately 0.25 inches at location B to a maximum inside diameter of 4 inches at location D corresponding to end  50   c  of the horn. More generally, horn structure  50  diverges exponentially from an inside diameter of approximately one-quarter of an inch at location B to a maximum diameter of from 2–5 λ 0  (wave lengths) over a length of from 4–8 λ 0  (wave lengths), where λ 0  is the mean wave length of the broadband noise signal. 
   Dielectric guide structure  52  is in this embodiment made from a synthetic material such as polytetrafluoroethylene having a dielectric constant of approximately 2.1, and has an overall length between the leading and trailing ends  52   c  and  52   g  of 3.5 inches and a maximum diameter of 0.625 inches. Each end of structure  52  is tapered down to approximately the diameter of the through bore which is 0.25 inch, or somewhat larger than the diameter of line  18  to permit the line and the larger end of transition conductor  68  to slide through the launcher assembly during deployment and retraction. 
   The size and configuration of guide structure  54  is not critical and need merely be dimensioned and mounted so as to securely center dielectric lens structure  56  coaxially with horn structure  50  and at a fixed axial position with respect to the end  50   c  of the horn. As mentioned, structure  54  has a dielectric constant approximately that of air so as to not alter the propagation of the electromagnetic wave energy other than that which would occur because of the presence of the air dielectric. On the other hand, dielectric lens structure  56  is made of a dielectric material such as polytetrafluoroethylene having a dielectric constant of approximately 2.1 to achieve the above-mentioned gradual compression of the electromagnetic energy as it emerges from the end  50   c  of horn structure  50  followed by a gradual expansion of the bundle of energy as it becomes launched as a steady state surface wave onto single wire transmission line  18 . For this purpose, the maximum diameter of dielectric lens structure  56  at location E is approximately 0.4 inches and its overall length between the leading and trailing ends  56   b  and  56   f  is approximately 16 inches. The midsection  56   d  where the diameter of dielectric lens structure  56  is at a maximum is disposed at approximately 0.5 inch beyond the end  50   c  of horn structure  50 . 
   Single wire transmission line  18  having the above-described configuration is selected in this embodiment to have an overall outer diameter of 0.2 inches measured with respect to the outer surface of foil  18   d . The thickness of foil  18   d  is approximately 0.001 inches. A line  18  constructed thusly has a weight of approximately one pound per 100 feet. The length of line  18  between transition conductor  68  and drogue radiator  20  may vary within the broad constraint of disposing drogue  20  sufficiently behind the aircraft to place the aircraft outside the destructive radius of anti-aircraft weaponry. By way of example, line  18  may be from 100 to 1,000 feet in length. At the greater length of 1,000 feet, the loss in power is less than 8 db at 10 gigahertz. 
   It has been found that a line  18  constructed as a Sommerfeld line and hence without a Goubau dielectric coating on the outer conductive surface, has sufficient resistance in the aluminum foil as used in the preferred embodiment of line  18  to retard the propagation of that portion of the field lying close to the surface of the line. That phenomenon, in accordance with the principles of the Sommerfeld line, compresses or holds the bundle of electromagnetic energy to the line and hence guides the energy without allowing it to radiate radially outwardly from the line. While such a Sommerfled line  18  exhibits a larger radial field than the surface coated Goubau line, nevertheless line  18 , when used in combination with the wave launcher  16 , provides an efficient transmission device together with a low leakage and low weight to length ratio which are desirable in this environment. 
   In this same embodiment, drogue radiator  20  is made of a conductive sheet metal formed to the shape of a cone having a 45° slant. The smaller end of the cone is truncated and mated to the diameter of line  18 , while the larger and trailing end of the cone has a diameter of at least four inches. More specifically, the maximum cone diameter is selected to intercept the bulk of the bundle of electromagnetic energy that is traveling in an imaginary tube along line  18 . A four inch diameter cone is estimated to intercept approximately 96 percent of the wave energy at 9.5 gigahertz. The amount of energy intercepted and hence radiated by the drogue can be enhanced further by using a delaunching dielectric lens at the leading axial end of the conical drogue as described more fully hereinafter in connection with an alternative embodiment of the drogue radiator shown in  FIGS. 6 and 7 . 
   Operation 
   During takeoff and nonstealth flight, the ventriloqual-like jamming system shown in  FIGS. 1 and 2  is disposed in a retracted or stowed configuration by coiling line  18  onto the stowage reel  46 , thereby drawing drogue radiator  20  up against the dielectric lens  56  of launcher  16 . When radar deception is desired, stowage reel  46  is operated to feed out line  18  through the launcher  16  during which time drogue radiator  20  acts as a drag at the trailing end of line  18  to apply tension to the line and assist in pulling the line out into a trolling configuration behind the aircraft. The deployment of single wire transmission line  18  and drogue radiator  20  continues in this manner until the transition conductor  68  between line  18  and the center conductor  44   a  of cable  44  (see  FIG. 3   a ) approaches the constricted end  50   b  of horn structure  50 . At this time, tubular slide member  62 , which is connected to shield  44   b  of cable  44 , slides into the tubular section  50   b  of horn structure  50 . The impedance matching adjustment Δ1 has been previously set by adjusting slidable ring  64  to a position that has been predetermined to provide the optimum impedance match between cable  44  and the impedance at the constricted end of horn structure  50 . And hence, screw  65  has been previously tightened to secure ring  64  to member  62  so that member  62  is at a fixed axial position with respect to tubular section  50   b  when the single wire transmission line  18  is fully deployed. 
   Noise generator  30  and the various amplification stages associated therewith are powered up to transmit the relatively broadband noise signal out over coaxial feed cable  44  to the single wire transmission line subsystem  14 . For radar jamming, a relatively broadband noise signal is used that lies within the frequency range of the anticipated tracking radar and at a radiated power level that is approximately 10 db or greater than the skin reflected radar return signal that is to be masked. For example, a frequency range of from 6 to 18 gigahertz has been transmitted by the embodiment of the invention disclosed herein at a radiated power of about 10–20 watts. This microwave signal is efficiently launched by launcher  16  onto single wire transmission line  18  where the energy is propagated along the line in a surface wave mode with only minimal and tolerable leakage from launcher  16  and line  18 . This minimal leakage is at a power level that is so much lower than the energy radiated by drogue radiator  20 , that the jamming signal from the drogue predominates so as to cause tracking radar to home-in only on radiator  20 . In the preferred embodiment constructed as disclosed above, the leakage from the launcher  16  and intermediate sections of line  18  is at least 20 db below the power level radiated by drogue radiator  20 . 
   When single wire transmission line subsystem  14  is deployed in flight, drogue radiator  20  and line  18  by virtue of matching their lift to drag ratios, cause line  18  to fly in a substantially straight path, with only slight curvature during certain maneuvers and wind conditions. Such minimal curvature has been found to not significantly degrade the characteristically high transmission efficiency of single wire line  18 . Moreover, in most anticipated flight conditions, the line  18  is not interfered with by such earthbound environmental conditions as snow, rain, ice or birds which have tended to detract from the practical applications of such a transmission system when the line is strung on telephone poles or the like. 
   The ventriloqual jamming signal radiated from drogue  20  as shown in  FIG. 1  does not require detailed or particular preknowledge of the tracking radar  11  which may be encountered. The noise energy generated and transmitted by the system masks such information as the range of the towing aircraft  12  from radar  11  and denies angle information that might otherwise be obtained by tracking systems that home-in on a noise source. The ventrilogual jamming signal is thus effective against many radar types and is relatively uncomplex in design and hence is reliable in operation and easy to maintain. Moreover, it is effective against such sophisticated tracking radars as the monopulse type, which is one of the most accurate tracking radar systems in terms of producing angle information. 
   ALTERNATIVE EMBODIMENT 
   With reference to  FIGS. 6 and 7 , an alternative drogue configuration is depicted in which a drogue radiator  20 ′ is formed by a conically shaped conductive body  80  having on its outer and forwardly oriented face, radially outwardly spiraled fluting  82  shaped to effect polarization of the radiated E-fields. Fluting  82  is formed by a plurality of radially outwardly spiraling ridges of metal and/or dielectric material wherein the particular height and degree of spiraling determines the specific type of polarization that is achieved, e.g., circular polarization, slant linear polarizaton or circumferential polarization. By creating such complex polarization in the reflected electromagnetic wave energy, the jamming signal energy radiated by drogue  20 ′ is far less susceptible to being tuned out by tracking systems having the capability of receiving radar return signals of only certain and selected polarization. In other words, it is difficult to tune out such complex polarization as circular, slant linear and circumferential. 
   Additionally, in this embodiment of the drogue radiator  20 ′, the maximum diameter of the conical reflector body  80  is minimized by incorporating a wave delaunching axisymmetric dielectric lens structure  86  adjacent the junction between the trailing end of single wire transmission line  18 ′ and the apex of the drogue&#39;s conical body  80 . More particularly, lens structure  86  is made of a material having a dielectric constant substantially greater than that of air and has an axisymmetric shape that forms a tapered tubular body surrounding the foil conductor of line  18 ′. The taper of lens structure  86  is such as to increase in diameter in a direction toward radiator  20 ′ commencing at a leading end  86   a  where the radial thickness of structure  86  is at a minimum and increasing in thickness to the terminal end  86   b  where both the end of line  18 ′ and the trailing end of lens structure  86  are joined to the apex of conical shaped drogue body  80 . The length of lens structure  86  is approximately 16 inches or 12 λ 0  (wave lengths) and in this embodiment corresponds to the length of the trailing taper  56   e  of dielectric lens structure  56  of launcher  16  ( FIG. 3   b ). 
   Hence delaunching lens structure  86  functions in a manner similar to and as the counterpart of the trailing taper  56   e  of lens structure  56  that projects from the horn of launcher  16  by gradually compressing the cylindrical bundle of electromagnetic energy traveling rearwardly on transmission line  18 ′ into a successively smaller and smaller diameter. By so doing, the maximum diameter of conical body  80  of drogue radiator  20 ′ is minimized while still be large enough in the transverse plane to intercept the major portion of the total transmitted noise energy. While dielectric lens structure  86  is shown in connection with the modified drogue radiator  20 ′ in  FIGS. 6 and 7 , it will be appreciated that a corresponding delaunching lens structure may be incorporated with the above-described drogue radiator  20  and the associated single wire transmission line  18  of  FIG. 3   b . Similarly, the conical body  80  of drogue radiator  20 ′ may be modified by the provision of flight stabilizing air flow apertures  72  as provided on drogue radiator  20  ( FIG. 3   b ). 
   While only particular embodiments have been disclosed herein, it will be readily apparent to persons skilled in the art that numerous changes and modifications can be made thereto including the use of equivalent means, devices, and method steps without departing from the spirit of the invention. For example, the ventriloqual-like radar jamming system may be used in the improved combination jamming and anti-signal integration method and apparatus disclosed and claimed in a copending U.S. Application Ser. No. 225,699, filed Jan. 16, 1982 by Walter E. Buehler, Roger M. Whitson and Michael J. Lewis, for ANTI SIGNAL-INTEGRATION APPARATUS AND METHOD FOR COUNTERING INTEGRATION ENHANCEMENT OF RADAR RETURN SIGNALS MASKED BY AIRBORNE VENTRILOQUAL-LIKE NOISE JAMMING.