US 3710258 A
A transmission line system having a primarily signal-initiating section and primarily signal-radiating section, along all of which transmission line sections traveling electromagnetic waves may propogate without adverse interference caused by impedance discontinuities, is employed cyclically as an energy storage device and as an impulse radiation device having spacially directive characteristics.
Claims available in
Description (OCR text may contain errors)
United States Patent 1 Strenglein IMPULSE RADIATOR SYSTEM Inventor: Harry F. S'trenglein, Clearwater,
Fla. Assignee: Sperry Rnnd Corp New York,
Filed: Feb. 22, 1971 Appl. No.1 117,270
343/775, 343/912 Int. CL; ..H04b l/04 Field of Search ..325/27, 43, 105-107,
111 3,710,258 [451* Jan. 9, 1973  References Cited UNITED STATES PATENTS 2,407,245 9/1946 Benioff .325/107 2,540,839 2/1951 Southworth..... 3,524,148 8/1970 Bjorke..... 2,688,744 9/1954 Sunstein 2,541,009 2/1951 Tashjian 2,560,541 7/1951 Barrow 3,579,111 5/1971 Johannessen ..325/l4l Primary Examiner-Albert J. Mayer Attorney-S. C. Yeaton  ABSTRACT A transmission line system having a primarily signalinitiating section and primarily signal-radiating section, along all of which transmission line sections traveling electromagnetic waves may propogate without adverse interference caused by impedance discontinuities, is employed cyclically as an energy storage device and as an impulse radiation device having spacially directive characteristics.
13 Claims, 17 Drawing Figures PULSE GENERATOR PATENTEDJAH 9 I975 3.710.258
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PRIOR ART PRIOR ART PULSE GENERATOR V 23 2 r OHMS HORN ANTENNA PRIOR T I/VI/E/VTOR HARRY F. STRE/VGLE/N A TTOR/VEY PATENTED JAN 9 I975 SHEEI 2 OF 4 DISTANCE F|G.5b.
DTSTANCE L DIETANCE (souwcs A) L DISTANCE F|G.6b.
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m E E C C R N U A O T S s ;m M V L O I DISTANCE F l G 8 b.
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V(SOURCE A) A TTOP/VEY PATENTEDJAH 9 192a SHEET 3 BF 4 PULSE GENERATOR FIG.9.
LPULSE GENERATOR ii I/Vl/E/VTO/P HARRY F ST/PE/VGLE/A/ B) F|G.ll.
PATENIEDJAH 9197a 3.710.258 SHEET u 0F 4 14 v INVEIVTOR F l G HARRY F SrRE/vaLE/N ATTORNEY IMPULSE RADIATOR SYSTEM BACKGROUND OF THE INVENTION 1. Field of the Invention The invention pertains to transmission line signal generating and radiating means for the impulse transmission of electromagnetic wave energy and more particularly pertains to such signal generation and radiation elements in which constructive cooperative use is made of the elements of the system both for impulse signal generation and for impulse signal radiation into space.
2. Description of the Prior Art Known prior art antennas are not readily adaptable to the radiation or reception of sharply pulsed or stepped electromagnetic energy signals, even though capable of relatively broad band transmission of ordinary continuous wave signals. For example, the log periodic array, the log-spiral antenna, and many of the known guided or surface wave antenna structures lack properties suitable for the purpose, since they present dispersive impedance discontinuities and because propagation of wave energy on or within the antenna structure is characterized by propagation in TE, TM, or other such dispersive propagation modes. Thus, the phase characteristics of the response of such antennas is not linear.
Furthermore, most known antenna and associated transmitter concepts do not adapt themselves to combination in such a manner that stepped, transient, or sharp impulse radiations are efficiently generated in a compact, inexpensive structure. In the prior art, the structure and function of the transmitter are generally fully separate from the structure and function of the antenna. Balanced transmitter-antenna configurations in which the two substantial parts of the system fully cooperate in determining the nature of the radiated signal are not possible to achieve by employing known design techniques. Absent from the prior art is an effective generator transmitter means for producing immediately successive positive and negative subnanosecond impulse signals so that conventional superheterodyne reception techniques may be employed, as well as receiver systems more specially adapted to processing impulse radiations.
SUMMARY OF THE INVENTION The present invention relates to an improved transmitter-antenna configuration employing an electrically smooth, constant impedance transmission line system for propagating TEM mode waves. The transmission line system is employed cyclically for the cooperative storage of energy on the transmission line and for its release by propagation along the transmission line for radiation at ends of sections of the transmission line formed as flared directive antennas. Thus, cooperative use is made of the transmission line system both for signal generation by cyclically charging the transmission line at a first rate of charging and for signal radiation into space by discharge of the line in a much shorter time than for charging. Discharge of the transmission line causes a voltage wave to travel toward the open ends or radiating apertures of the structure. The process operates to produce, by differentiation, subnanosecond impulses that are radiated in the same direction into space. Pairs of immediately successive positive and negative impulses may be generated and propagated in a given direction in space. They may be detected by using conventional impulse detection receivers or by the use of ordinary superheterodyne or other conventional receivers.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of an antenna structure used in the present invention.
FIGS. 2 and 3 are respectively top and side views of the antenna of FIG. 1 and are useful in explaining its properties.
FIG. 4 is a schematic side view of the antenna of FIG. 1 showing circuit elements for exciting the antenna.
FIGS. 50 to 8b are graphs for explaining the operation of the device of FIG. 4.
FIG. 9 is a circuit arrangement showing one form of the present invention and is useful also in explaining the properties of the invention.
FIG. 10 is a wave form graph illustrating the signal generated by the apparatus of FIG. 9.
FIG. 11 is an alternative embodiment of the invention of FIG. 9 shown in partial cross section in a perspective view.
FIG. 12 illustrates in perspective and partial cross section an alternative structure for use in the embodiment of FIG. 11.
FIG. 13 is a perspective view in: partial cross section of a further alternative construction of the apparatus.
DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1, 2, and 3 illustrate a representative type of balanced impulse antenna system, as described by Gerald F. Ross and David Lamensdorf in U.S. Pat. application Ser. No. 46,079, filed June 15, 1970 issued Apr. 25, 1972 as U.S. Pat. No. 3,659,203 for a Balanced Radiator System and assigned to the Sperry Rand Corp., on which the present novel antenna system is based in general principle and structure. Suitable radiator elements for use in the present invention have a wide instantaneous band width, so that they may radiate a sharp impulse or stepped signal with low distortion of the signal envelope. Further, a suitable antenna for use in the invention has an energy focusing characteristic such that energy radiated in a predetermined direction is maximum.
The modified horn antenna ofYFIGS. l, 2, and 3 is one form of an antenna having such desired characteristics. As will be seen in FIG. I, the antenna 3 com prises a structure which may have mirror image symmetry about a median plane at right angles to the direction of the vector of the electric field propagating within the antenna. The same is true of the transmission line 1, which comprises parallel plate or slab transmission line conductors 4 and 4a of mutually similar shape.
The TEM modified horn antenna 3 consists of a pair of flared, flat, electrically conducting planar members 2 and 2a. Members 2 and 2a are generally triangular in shape, member 2 being bounded by flared edges 6 and 6a and an aperture edge 8. Similarly, member 2a is bounded by flaring edged 7 and 7a and an aperture edge 8a. Edges 8 and 8a may be straight or may be arcuate as shown at 18 and 18a of FIGS. 2 and 3. Each generally triangular member 2 and 2a is slightly truncated at its apex, the truncation being so constructed and arranged that conductor .4 is smoothly joined without overlap at junction 9 to antenna member 2. Likewise, conductor 4a is smoothly joined without overlap at junction 9a to antenna member 20. It is to be understood that the respective junctions 9 and 9a are formed using conventionally available techniques for minimizing any impedance discontinuity corresponding to the junctions S and 9a.
It is also to be understood that the flared members 2 and 2a of antenna-3 are constructed of material highly conductive to high frequency currents. Further, the interior volume of antenna 3 may be filled with an airfoamed dielectric material exhibiting low loss in the presence of high frequency fields. Transmission line 1 may be similarly filled with dielectric material, such material acting to support conductor 4 in fixed relation to conductor 4a and, likewise, to support the flared member 2 relative to member 2a. Alternatively, the conductive elements of transmission line 1 and antenna 3 may be fixed in spaced relation by dielectric walls or spacers such as represented by spacers 1t) and 10a seen located adjacent the aperture edges 8 and 8a of antenna 3.
The general form of the transmission line 1 and of the antenna 3 as illustrated in FIG. 1 is preferred, in part, because TEM mode propagation therein is readily established. The TEM propagation mode is selected, because it is the substantially non-dispersive propagation mode and its use therefore minimizes distortion of the propagating signal. The simple, balanced transmission line structure permits construction of the antenna with minimum impedance discontinuities. Furthermore, it is a property of the symmetric type of transmission line 1 that its characteristic impedance is a function of the dimensional ratio b/h as defined in FIGS. 2 and 3, where it is seen that b is the width dimension of the conductor major surfaces and h is the distance between the inner faces of the conductors. For example the ratio b/h is kept constant in the instance of transmission line 1 because both b and h are arbitrarily made constant.
The antenna 3 is made compatible with transmission line 1 by using the same value of the ratio b/h for both elements. In other words, if b/h is kept constant along the direction of propagation in antenna 3, the characteristic impedance of antenna 3 will be constant along its length L and may readily be made equal to that of line 1. By maintaining a continuously constant characteristic impedance along the structure including line 1 and antenna 3, frequency sensitive reflections are prevented therein. It has been elected, for the sake of simplicity of explanation, to show in FIGS. 1, 2, and 3 flat, triangular flaring and planar configurations for elements 2 and 2a. It should be evident, however, that other configurations may readily be realized which maintain a constant characteristic impedance according to the above rule, andthat such configurations may also be used within the scope of the present invention.
As previously noted, a desirable system for exciting the antenna of FIGS. 1, 2, and 3 has compatible properties, such as being balanced in nature and avoiding the complicating deficiencies of an interface balun or other similar transition element. The system of FIG. 4 achieves such objectives and, in addition, makes beneficial use of the balanced dual-element configuration of antenna 3 as part of the charging line for the excitation generator. It willbe understood that certain liberties have been taken in the drawing of FIG. 4 better to explain the structure and operation of the device disclosed therein. For example, it is seen that FIG. 4 is intended schematically to indicate antenna conductor elements 2 and 2a of FIG. 1 as respective single wire transmission lines 12 and having the same effective electrical characteristics as elements 2 and 2a of FIG. 1 and the same radiating characteristics. As a further example, junctions 9 and 9a in FIG. 1 are represented by junctions l9 and 19a in FIG. 4. The symbols 4 and 4a in FIG. 1 are represented in FIG. 4 by symbols l4 and 14a and identify the opposed conductors of transmission line 1. Dimensions in FIG. 4 are grossly exaggerated, such as the spacing h between conductors l4 and 14a of line 1, merely as a matter of convenience in making the drawing clear.
At the left end of line 1, conductors l4 and 14a are joined by a series circuit having a predetermined time constant and comprising battery 21 coupled between resistors 20 and 20a each having a resistance value of R/2 ohms. At the end of line 1 adjacent junctions l9 and 190, the conductors l4 and 14a are joined by a series circuit comprising a mechanically or electrically actuatable switch 23; the blade terminal 27 of switch 23 is coupled by resistor 22a to conductor 14a, while the contact 26 of the switch is connected through resistor 22 to conductor 14. Resistors 22 and 22a each have a resistance value of r/2 ohms, where r is equal to the characteristic impedance of line 1 (or antenna 3) in ohms, so that they appear in a circuit having a further characteristic time constant.
A square wave pulse generator 24 produces the balanced square pulse wave form 24a and is provided for actuation of switch 23. Switch 23 may take the form of a single pole single throw mercury-wetted reed switch, several varieties of which are readily available on the market. Such reed switches may be closed and opened according to the presence or absence of a static magnetic field in the vicinity of the switch capsule. Thus, pulse generator 24 is adapted to open and close switch 23 by the agency represented by dotted line 25, which may, for example, be a magnetic field excited within a solenoid (not shown) by pulse wave 24a. It will be understood that square wave generator 24 may be replaced by a generator of pulse width modulated waves carrying an intelligence modulation such as voice or code modulation.
In operation, it will be observed that switch 23 is first separated from contact 26 by generator 24 for a time sufficient for the entire structure including the conductors of line 1 and antenna 3 to become charged to a potential difference V equal to that supplied by battery 21. On the next cycle of wave 24a, switch 23 closes with contact 26, forming a conducting circuit path through resistors 22 and 22a. The effect is that of putting a second source B in series with the efiective source A of battery 21, but reversed in polarity relative to the polarity of source A.
FIGS. 5a, 6a, 7a, and 821 show the positive voltage V, contributed by the source A or battery 21, as a positive constant voltage at successive intervals in the system cycle. The same set of figures shows the progress of the negative wave due to the effective source B at the same successive intervals. For example, FIG. 5a shows the situation at the instant switch 23 is closed; note that the wave due to the effective second source B has not yet started to flow.
In FIG. 60, however, the negative wave of voltage V/2 from the effective second source B has'begun to flow toward the aperture of antenna 3. Upon reaching the respective ends 8 and 8a of conductors l2 and 12a of FIG. 4, and upon being reflected, the situation is depicted in FIG. 70. It is seen that when the V/2 wave reaches the respective ends 8, 8a of antenna conductors 12 and 12a, it is reflected and begins to flow back toward antenna junctions 19, 19a. The total contribution of the effective source B, beginning at the instant of reversal, is now V volts. It will be seen that the total potential due to sources A and B between conductors l2 and 12a at the aperture 8, 8 a of the antenna 3 at the instant of reversal suddenly drops from +V volts to zero; this instant of time is one of primaryinterest in the operation of the invention. The wave due to the effective source B continues to travel back toward junctionsl9, 19a until the antenna 3, which has served as part of the charging line for the system, is substantially completely discharged, if the value of r is the characteristic impedance of line 1. The charging cycle is then reestablished by the closure of switch 23 and the system may be repeatedly recycled.
It will be readily appreciated that the total potential difference seen across the aperture 8, 8 a of antenna 3, for the same successive instants of time as described above, may be illustrated as in the respective FIGS. 5b, 6b, 7b, and 8b. It is seen that the potential at the antenna aperture due to source A (battery 21) is progressively eaten away by the travel of the wave due to the effective source B started toward the aperture 8, 80 when switch 23 is closed and then reflected at the aperture ultimately to effect substantial discharge of the line formed by conductors 12 and 12a, the wave having returned to the source resistances 22, 22a.
As previously noted, it is the instant of reflection of the wave from the effective source B at the distance L along conductors 12 and 12a (the aperture of antenna 3) that is of prime interest. Because of the finite characteristic impedance r of the antenna 3, the leading edge of the V/2 wave launched into the aperture of the mouth of the antenna, which is in effect an open circuit, reverses in direction of flow while maintaining its previous polarity. Radiation into space of a single impulse signal proportional in amplitude to dV/dt must occur at this instant of time. No further radiation can obtain until after switch 23 is recycled and conductors 12 and 12a are recharged.
FIG. 9 illustrates an application of the principles of the antenna of FIGS. 1, 2, 3, and 4 according to the present invention. The antenna of FIG. 9 is designed to produce the successive positive and negative impulses 30 and 30a of FIG. 10 in the far field space associated with its radiation pattern. It is seen that the balanced radiator system of FIG. 9 employs a charging-discharging system similar to that shown in association with the antenna of FIG. 4, the corresponding elements of the charging-discharging system having the same reference numerals in FIGS. 4 and 9. These include transmission line 1, resistor pairs 20, 20a and 22, 22a, switch 23, pulse generator 24 and a mechanical or electrical means 25 for actuating switch 23. Battery 21 of FIG. 4
is now composed of similar battery portions 21a and 21b so that a grounded tap may be provided at midpoint 27. While a charging-discharging circuit similar to that of FIG. 4 is illustrated in FIG. 9, it will be recognized that other equivalent circuits such as taught in the above mentioned US. Pat. application Ser. No. 46,079 may readily substituted. In particular, selfpulsing circuits may be used. Transmission line 1 and the oppositely directed antenna conductor elements are illustrated, again as a matter of convenience, as respective single wire transmission line elements.
Propagation of energy leftward from transmission line 1 and its radiation is ensured by antenna 33 composed of transmission line elements 34 and 35. Line element 34 may be connected directly to side 14 of line 1, while its associated line element 35 may be grounded, as at 36, so as to serve as part of a ground plane. The propagating electric field in the space between line components 34, 35 is in the sense of the arrow 37.
Propagation of energy toward the right from trans mission line 1 and its radiation: is enabled by the presence of antenna 33a composed of transmission line elements 34a and 350. Line element 34a may be con nected directly to side 14a of transmission line 1, while its associated line 350 may be connected to grounded line 35 at junction 36. The propagatingelectric field in the space between line components 34a, 35a is in the sense of arrow 370, which is seen to be inverted with respect to arrow 37 and the electric field that the latter represents. It is seen that the assembly of transmission line 1 and the antenna lines 33 and 33a provides an electrically balanced structure having axial symmetry at right angles to the direction of propagation of energy in antenna lines 33 and 33a.
For providing radiation in the direction of the axis of symmetry of the structure of FIG. 9, conductive mirrors 40 and 40a or reflectors of the planar type are provided at the respective apertures of antennas 33 and 33a. Mirrors 40, 40a are aligned at 45 to the direction of energy propagation in antennas 33, 33a, and therefore lie at degrees with respect to each other, so that the radiations are now redirected in the same direction, as indicated by arrows 41 and 41a.
Mirror 40 is placed an average distance d from the aperture formed by the open .ends of antenna line elements 34, 35 for the purpose of redirecting energy along path 4l. Mirror 40a, on the other hand, is placed a slightly greater average distance d c'r from the open ends or antenna radiating aperture formed by antenna line elements 34a, 35a. In the value or, c is the velocity of propagation of energy in lines 33 and 33a and 1- is the width at the base line of the radiated impulse such as at the base of impulse 30 of FIG. 10. By making the paths to a receiver placed in the far field of the radiator system differ by value or, the negative impulse 30a arrives at the receiver immediately following the arrival of the positive impulse 30 and without over-lap.
It is seen that the impulse generator generates an impulse which is radiated simultaneously from each of the two apertures of the radiator system. The M asymmetry serves to delay the polarity reversed portion of the signal by anamount that causes it to appear as if it were the second half of a sinusoidal wave, rather than interfering with the radiation of the first or positive portion of the signal. Accordingly, the single unipolar impulse produced by the antenna of FIG. 1 is now converted into a one cycle signal similar to one cycle of a sinusoidal wave, while also coupling it in a given radiating'direction to free space.
The apparatus of FIG. 9 may be constructed in any of several additional practical forms, including the form illustrated in FIG. 1 1 wherein reference numerals similar to those previously used are employed with i elements 14, 14a, 50, 50a cooperate to form an enclosure about the charging-discharging circuit elements, which latter elements are not shown but which may be similar to those of FIG. 9. The lower end of the enclosure may be similarly sealed by a dielectric wall (not shown) to complete protection of the chargingdischarging circuit elements from dust, water, or corrosive atmospheres.
The oppositely radiating horn transmission line structures 33, 330 may be respectively composed of truncated, triangular, planar conductive metal sheets 34, and 34a, 35a. Sheet 34 may be a folded continuation of transmission line element 14, while the oppositely located sheet 24a may similarly be a folded continuation of transmission line element 14a. Spaced symmetrically above radiator elements 34, 34a are flared conductive sheets 35 and 35a, joined together at junction 36.
The upper elements 35, 35a may be supported in fixed relation with respect to elements 34, 34a, by dielectric walls such as represented by wall portions 51, 51a, and 53. These several wall portions may be integral extensions of the respective dielectric walls 50, 50a, as would be formed by using a pair of dielectric wall elements each having a generally tee shaped configuration. The enclosure for the system may be completed by the use of dielectric antenna aperture or radome walls 52, 52a at the radiating ends of antennas 33, 33a. Mirrors and 40a may be supported by dielectric extensions pending from antennas 33, 33a or by other means well known to those skilled in the mechanical art. Operation of the apparatus of FIG. 11 may be explained in the same manner as in the instance of the apparatus of FIG. 9. Each charging-recharging cycle of the circuit associated with transmission line 1 produces the double impulse 30, 30a shown in FIG. 10 at a receiver illuminated by the radiation patterns represented by arrows 41, 41a.
In certain applications, a less abrupt transition or junction between the charging-discharging transmission line elements 14, 14a and the respective radiation transmission line 33 and 33a is desirable. FIG. 12 illustrates an example of an improved transmission line junction which may be used with the device shown in FIG. 11. The junction is a tee or triple port junction having symmetric arms for connection to radiator systems 33, 33a. It is observed that the branching radiators 33 and 33a stem from a symmetric mutual coupling region 60 having oppositely directed arcuate regions 61, 61a. Regions 61, 61a form smoothly curved energy transmission paths which may ultimately become substantially parallel to one another, being bound by the conductively continued transmission line elements 34, 35 and 34a, 35a.
The parameter or, previously mentioned, has been established in the field of microwave transient signal research as a useful parameter for identifying the behavior of transmission line elements exposed to short duration or impulse electromagnetic signals. For example, it has been reported in the literature as being of value in the qualitative evaluation of signal distortion in terms of the length of a tapered transmission line. For example, if or is very small compared to the length of a tapered line, only a negligible distortion will be suffered by signals traversing the tapered line. The parameter or is also of particular interest in qualitatively defining the character of the junction region 60 where branch line regions 61 and 61ajoin the elements 14, 14a of line 1. Here, for transmission of a relatively undistorted transient or impulse signal, the general area commonly regarded as the junction region needs to be great compared to e r. The region 60 then behaves like a simple resistive discontinuity to transient or impulse signals, rather than having distributed dispersive characteristics that cause signal distortion. With 01- very small by comparison the dispersion or smearing of a very short pulse passing through region 60 is small compared to 1..
While the junction 60 itself is not readily defined in purely geometrical terms, it is readily defined in terms of the electromagnetic fields propagating across the junction. In essence, it has been described as involving an area centered on junction 60 where there are TEM and other propagation modes present. Departure a short distance from the actual junction region discovers the presence only of the TEM mode fields normally associated with propagation in transmission lines 1, 33,
FIG. 13 illustrates an alternative form of the invention that avoids the use of the mirrors 40, 40a shown in FIGS. 9 and 11. In the system of FIG. 13, radiators 133, 133a are aligned in generally parallel fashion with their radiating apertures both directed at any distant cooperating receiver. The upper elements 135, 135a of the respective radiators 133, 133a are smoothly joined at junctions 165, 16511 to the ends of a conducting strip having portions 200, 200a mutually joined above junction 60. In FIG. 13, antenna radiators 133 and 133a have respective apertures and junctions 165, 175 and a, a lying in the same respective planes. The upper element 135 of antenna 133 is joined at junction 165 to a transmission line element that is, in turn, joined at junction 165a to the upper element 135a of antenna 133a. The transmission element serving to join antenna elements 135 and 1350 may have a pair of straight portions 200 and 200a joined by a semi-circular portion 202, all lying substantially in the same horizontal plane. The respective junctions 175, 175a of the lower antenna elements 134, 134a may be similarly joined through conductive strips 201, 201a and semicircular parts 203, 204. Parts 203, .204 are separated, however, in order to permit formation of junction 60. At junction 60, the charging-discharging line element 14 is joined to lower arcuate portion 203, while element 14a is similarly joined to arcuate portion 204. It is observed that the latter junctures are formed so that the coupling region 60 is offset by the value c-r/Z from the true axis of symmetry 210 of the apparatus. It will be appreciated that the improved junction of FIG. 12 may be as equally well used in the configuration of FIG. 13 as it is used in the arrangement of FIG. 11. Further, it will be understood that the several embodiments of the invention may each have dielectric walls for supporting the elements of the embodiment in closed relation. For example, such walls may be employed in the structure of FIG. 13 or the regions between cooperating conductors may be filled with a dielectric substance such as an air-foamed dielectric material.
If the improved junction of FIG. 12 is used in the device of FIG. 13, the transmission lines constituted of elements 14, 14a, of the respective doubly arcuate elements 202, 203, and 204 and of radiators 133 and 1330 form an impedance matched system so as to avoid undesired reflections at the region 60, at junctions I65, 175 and 165a, 1750, in the arcuate interconnection system, and elsewhere. Dispersive propagation is also avoided. The several regions generally defined by the arcuate cooperating conductors may particularly be arranged to have radii large compared to the value or to avoid dispersive smearing of the impulse shape. Similarly, the junction region 60 will preferably be large compared to the value cr.
lt will be seen upon inspecting FIG. 13 that the ap paratus shown therein is generally symmetric about an axis parallel to the direction of energy radiation. Symmetry is not complete, however, as a path differential of Cr is again introduced so that a far field receiver is illuminated by the dual impulse wave of FIG. 10. Asymmetry of the required degree is introduced bymaking the signal propagation path from junction 60 to the antenna aperture at 166 of antenna 133 longer by an appropriate value than the propagation path from junction 60 to aperture at 1660 of antenna 133a.
While the invention has been described in its preferred embodiments, it is to be understood that the words which have been used are words of description rather than of limitation and thatchanges within the purview of the appended claims may be made without departure from the true scope andspirit of the invention in its broader aspects.
1. Apparatus for radiating base band duration impulses of electromagnetic energy comprising:
three-port transmission line meanshaving first and second radiating aperture port means and input port means coupled thereto between said aperture port means,
current source means adjacent said input port means switching circuit means adjacent said charging means having conducting and non conducting states and having a second time constant substantially shorter than said first time constant for causing field collapsing waves to propagate toward said aperture ports for substantially discharging said transmission line means, and means for re-directing said base band duration impulses radiated by said aperture port means along a substantially common space path upon arrival of said collapsing fields at said aperture ports. a 2. Apparatus as described in claim 1 wherein said current source means and said switching circuit means are so constructed and arranged as to cause, when said switching circuit means is activated, field-collapsing waves to propagate along said transmission line means to said first and second radiating aperture port means for the purpose of causing directional radiation from said first and second radiating aperture port means of base band duration electromagnetic energy impulses of amplitude substantially proportional to the rate of change with time of the collapsing fields at said first and second radiating aperture port means.
3. Apparatus as described in claim 2 wherein the wave pattern of said impulses of electromagnetic energy comprises opposed-polarity first and second impul ses, the second impulse substantially immediately following the first impulse in substantially non-overlapping relation.
4. Apparatus as described in claim 3 wherein said transmission line means comprises first and second substantially planar electrical conductor means with opposed major conducting surfaces.
5. Apparatus as described in claim 4 wherein said substantially planar conducting means is adapted to propagate traveling electromagnetic waves in the TEM mode.
6. Apparatus as described in claim 1 wherein said three-port transmission line means comprises:
junction means having first, second, and third port means,
dual-element transmission line means coupled between said junction means and said input port means, and
first and second dual-element transmission line means respectively coupled between said second junction port means and said first aperture port means and between said third junction port means and said second aperture port means.
7. Apparatus as described in claim 6 wherein said elements of said dual-element transmission line means coupled to said aperture port means comprise first and second substantially planar electrical conductor means having opposed major conducting surfaces.
8. Apparatus asdescribed in claim 7 wherein said major conducting surfaces have a width b and a separation 11, where the ratio b/h is held substantially constant.
9. Apparatus as described in claim 7 wherein said major conducting surfaces have a region adjacent said aperture port means in which the value of b progressively expands for the purpose of defining said radiating aperture port means.
10. Apparatus as described in claim 9 wherein said means for re-directing impulse energy radiated by said aperture port means comprises reflector means.
said second reflector means being located an arbitrary average distance d from said second radiating aperture port means plus an incremental distance or, where c is velocity of propagation within said transmission line means and 'r is the time duration of said impulse of electromagnetic energy. 13. Apparatus as described in claim 12 wherein said first reflector means lies at an angle of substantially 90 with respect to said second reflector means.