Transmission line r.-f. lobing unit

April 19, 1960

D. H. LANCTOT

2,933,701

TRANSMISSION LINE R.-F. LOBING UNIT

Filed April 8, 1957

Sheets-Sheet 1

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April 19, 1960 d. h. lanctot 2,933,701

TRANSMISSION LINE R.-F. LOBING UNIT

Filed April 8, 1957

Sheets-Sheet 2

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CONNECTOR )2 OUTPUT CONNECTOR 13 OUTPUT

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TIME

Fie. IO

INVENTOR.

DONALD H. LANCTOT

BY

ATTORNEYS

2,933,701

Patented Apr. 19, 1960

United States Patent Office

2,933,701

TRANSMISSION LINE R.-F. LOBING UNIT 5

Donald H. Lanctot, Malibu, Calif., assignor, by mesne assignments, to Electronic Specialty Co., a corporation of California

Application April 8, 1957, Serial No. 651,537

Claims. (CI. 333—7)

This invention relates generally to high frequency electrical switches and more particularly to an improved electro-mechanical lobing unit for switching high frequency electrical energy from an input transmission line to two or more output transmission lines. For convenience of terminology, the transmission lines discussed are in the form of co-axial cables, although it should be understood that parallel wire lines and wave guides could be employed as transmission carriers for the electrical energy involved.

High frequency lobing switches of the type under consideration are particularly well adapted for switching high power, high frequency electrical energy between two or more antennas such as employed in radar systems. In some instances, there may be provided a single reflecting type antenna structure fed by two separate co-axial lines arranged to deliver energy pulses alternately to the antenna from different focus points whereby the beam of the antenna is shifted between two limits. In other instances, there may be a plurality of antennas which are sequentially energized to provide an effective lobe sweeping characteristic. It is important in all such lobing switches that minimum losses occur during the switching operation and that a proper impedance match be retained between the input and the various output lines to which the energy is directed.

The problem of minimizing power losses from leakage and poor impedance matching is generally overcome by providing a positive connection as by metal to metal contact in the switching medium between the various inner conductors of the co-axial lines. In addition, the switching medium itself is designed from a dimensional standpoint to insure relatively uniform and proper impedance matching.

In order to effect switching of energy from an input line to two or more output lines at a desired rate of speed; for example, five hundred times per second, however, the problem of insuring positive connection by metal to metal contact is rendered extremely difficult. Therefore, in instances wherein a relatively rapid cyclic switching is desired, resort is had to a capacitive coupling between the various inner conductors whereby no mechanical friction is introduced as a result of metal to metal contact. By means of such capacitive coupling, a relatively friction free unit may be provided with little mechanical difficulties. On the other hand, considerable losses are incurred as a result of capacitive coupling, and further, the various energy portions distributed among the output lines are not positively defined.

In attempting to provide relatively rapid cyclic switching by means of metal to metal contacts between the various inner conductors, there is, in addition to friction, the problem of wear between the metal to metal contact surfaces and the consequent problem of engineering a switch with sufficiently close tolerances to insure a satisfactory degree of reliability.

Bearing the above in mind, it is a primary object of the present invention to provide a greatly improved type of lobing switch in which the inner conductors of the various co-axial lines are positively connected by a metal to metal engagement to enable discrete and equal or proportioned amounts of energy to be distributed between the various lines with a minimum of electrical losses and mechanical friction and at a rate of anywhere from zero cycles to five or six hundred cycles per second.

More particularly, it is an object to provide a switch of the above type which is positive throughout in operation and in which any wear of metal to metal contact points automatically compensates itself whereby an extremely reliable and substantially maintenance free unit results.

These basic objectives as well as many other objects and advantages of the present invention are attained, briefly, by providing a hollow metal casing for receiving a center co-axial connector and at least two outside coaxial connectors. The center co-axial connector is adapted to be connected to an input co-axial line carrying power to the unit and the two outside co-axial connectors, are adapted to be respectively connected to two output, co-axial lines between which the energy in the input line is to be periodically switched. The various co-axial connectors extend into one side of the casing and terminate in the interior thereof.

A plurality of switching members respectively associated with the co-axial connectors are rotatably mounted on a bearing plate within the housing. These switching members include tapered probes extending from a central conducting disc for the center co-axial connector switching member, and two conducting sector plates respectively associated with the outside co-axial conductors to terminate in point contact means at the ends of the respective inner conductors for the co-axial connectors. The central disc and sector plates are positively geared together for rotation by a motor extending from the rear of the housing. The disc and sector plates themselves are substantially co-planar and arranged such that the sector plates overlap peripheral portions of the disc. Each sector plate includes at least one sector element arranged to make a metal to metal contact with the periphery of the central disc, the sectors associated with each of the sector plates being of such relative position with respect to each other that the various connections between the sectors and the central disc are made alternately upon rotation of the plates and disc by the driving motor. With this arrangement, it is possible to alternately switch electrical energy received in the center co-axial connector between the two outside co-axial connectors at an extremely rapid rate. The casing for the various switching components is designed in a manner to co-operate with the probes leading from the point contact means to insure a proper impedance match between the various connectors. Further, the entire unit is hermetically sealed and filled with oil of given dielectric constant.

A better understanding of the invention and its various features and advantages will be had by referring to a more complete description of a specific embodiment thereof as illustrated in the accompanying drawings, in which:

Figure 1 is a perspective view of the lobing unit for switching electrical energy from an input co-axial line between two output co-axial lines;

Figure 2 is a plan view taken in the direction of the arrows 2—2 illustrating the various switching components employed in the unit of Figure 1;

Figure 3 is an enlarged elevational view partly in cross section of one of the point contact means employed in the unit of Figure 2;

Figure 4 is an enlarged perspective view of one of the' elements of the point contact means;

Figure 5 is a cross sectional schematic view of a por-

0,033,701 tion of the switching means taken in the direction of the arrows 5—5 of Figure 2;

Figure 6 is an enlarged cross section taken in the direction of the arrows 6—6 of Figure 5;

Figure 7 illustrates a modified type of sector plate 5 which could be employed in the switching apparatus of Figure 5;

Figure 8 is another schematic diagram illustrating one possible relationship of the driving gears for operating the switching unit, taken in the direction of the arrows 10 8—8 of Figure 2;

Figure 9 is an elevational view of the driving gears taken in the direction of the arrows 9—9 of Figure 8; and,

Figure 10 is a time graph illustrating the output energy 15 distribution effected by the switching unit of this invention.

Referring to Figure 1, there is illustrated a hollow casing 10 on the front face of which is mounted a center co-axial connector 11 and two outside co-axial connectors 20 12 and 13. In the embodiment shown in Figure 1 for the sake of illustration, the center co-axial connector 11 is adapted to be connected to an input co-axial line from a high frequency oscillator such as a magnetron or other source of high frequency electrical energy, while 25 the two outside co-axial connectors 12 and 13 are adapted to be respectively connected to two output co-axial lines leading to a pair of antennas or other type radiating or transmitting device. The switching arrangement within the casing 10 is such that energy entering the center co- ³⁰axial connector 11 will be alternately switched between the output co-axial connectors 12 and 13. A portion of the unit also includes a driving motor 14 extending from the rear of the casing 10 for effecting this switching operation. The motor 14 is provided at its. rear with ³“ an inlet 15 for connection to an electrical source to drive the motor. Preferably, the motor 14 is of the synchronous type such that it will rotate at a precise, constant speed.

Referring now to the partial cross sectional plan view of Figure 2, it will be noted that the outer conductors of the various co-axial connectors 11, 12 and 13 are all electrically connected together through the medium of the metal casing 10 while the inner conductors associated with these connectors are isolated from the casing by ⁴⁵suitable dielectric material. As shown in Figure 2, the hollow interior of the casing 10 is divided by a metallic bearing plate 16 extending completely across the unit to provide a first compartment 17 serving to house the various switching units to be described shortly and a sec- ⁵⁰ond compartment 18 serving to house various gearing associated with the switching units and driven by the motor 14.

The bearing plate 16 also serves as a mounting means for rotatably mounting a center switching member 19 and two outside switching members 20 and 21 in co-axial alignment respectively with the center co-axial connector 11 and the two outside co-axial connectors 12 and 13. The manner in which these switching members are mounted in the bearing plate 16 is identical and, therefore, de- ⁶⁰scription of the mounting arrangement and components of one will suffice for all. Referring to the lower switching member 21 of Figure 2, for example, there are provided ball bearings 22 for mounting the rear portion of θ the switching member to the bearing plate 16 and ball bearings 23 mounting the forward portion of the member 21 to the casing 10 adjacent the output co-axial connector 13. The switching member 21 itself includes a tapered electrically conducting probe 24 extending in the γθ first compartment 17 towards the output eo-axial connector 13. The interior walls of the housing 10 include similarly tapered portions as at 25, the angle of the interior taper 25 being slightly greater than the taper 24 such that proportionate spacing between the housing 10, 75 serving as the outer conductor, and the tapered probe 24, serving as the inner conductor, with respect to the varying diameter of the inner conductor, is maintained. By this arrangement, a proper impedance match is provided from the output co-axial connector 13 to the switching member 21.

As shown in Figure 2, the tapering probe 24 terminates in a reduced diameter end portion 26 providing an end point contact surface arranged to make metal to metal contact with a point contact means 27 positioned at the end of the inner conductor 28 of the output co-axial connector 13. The reduced end portion 26 of the probe 24 corresponds in diameter to the diameter of the inner conductor 28 of the co-axial connector 13. Suitable dielectric material serves to support the inner conductor 28 and end portion of the probe 26 in proper co-axial alignment, and the inner metal ball bearing race of the bearings 23 serves to co-operate with the tapered metallic wall portions of the housing 10 to provide an effective outer conductor for these inner conductors. The switching member 21 is rotatably mounted in the plate 16 such that rotation takes place about the central axis of the tapering probe 24 whereby the extreme end portion 26 of this probe rotates against the point contact means 27 at the end of the stationary inner conductor 28. Similar tapered probes and point contact means are included in the other two switching members 19 and 20.

As shown in Figure 2 and in greater detail in Figure 5, the tapered probe for the center switching member 19 merges in and is electrically connected to a central conducting disc 29. The tapered probes for the switching members 20 and 21 similarly are electrically connected to sector plates 30 and 31. The sector plates are co-planar with the central disc and dimensioned to overlap the periphery of the disc when the rotatable switching members 19, 20 and 21 are rotated. These sector plates and central disc constitute a transfer means for alternately passing electrical energy from the central co-axial connector to the outside co-axial connectors all as will become clearer as the description proceeds.

As shown in Figure 2, the switching members 20 and 21 include co-axial stubs including inner conductors 32 and 33 electrically connected to the tapered probes, such as the probe 24 for the switching member 21, and extending into and terminating within the second compartment 18. These stubs 32 and 33 respectively co-operate with the mounting bearings for the respective outside switching members 20 and 21 and the bearing plate 16 itself to provide a substantially uniform end wall for R.-F. energy being transferred between the center co-axial connector and the outside co-axial connectors, whereby electrical losses are minimized when energy is being passed through the transfer means.

The various switching means 19, 20 and 21 are rotated by a suitable gear train in the second compartment 18. This gear train, as clearly shown in Figures 2, 8 and 9, may comprise, for example, a pinion 34 connected directly to the shaft 35 of the motor 14 and meshing with a spur gear 36 in turn connected to a second pinion 37 meshing with a center spur gear 38 directly secured to the center switching member 19. The center spur gear 38 is arranged to mesh directly with two outside spur gears 39 and 40 directly secured to the switching members 20 and 21 respectively. Rotation of the center spur gear 38 will, therefore, rotate the spur gears 39 and 40 in the same direction and at exactly the same speed in a positive manner whereby the sector plates on the other side of the partition bearing plate 16 will also be rotated exactly in synchronism with respect to the center conducting disc 29. The gears 34, 36, and 37 are merely reduction gears to provide a proper operating speed for the switching members.

Figure 3 shows in enlarged detail view the point contact means associated with the inner conductor 28 and tapering probe 24 for the outside coaxial connector 13.,

2,933,701

This point contact means is characteristic of the other two connections to tapered probes for the switching members 19 and 20 and, therefore, description of one will suffice for all. As shown in Figure 3, the inner conductor 28 has a tapered surface portion 41 conical in shape and thence merging into a reduced diameter nose portion 42. The point contact means 27 itself comprises a highly conductive cup element having a plurality of slots in its sides to define fingers 43, 44, 45 and 46 as best seen in Figure 4. The ends of these figures are adapted to ride on the conical surface 41 and are biased laterally inwardly thereby tending to move the element 27 in an axial direction as indicated by the arrow to the right, such that the bottom of the element 27 engages the contact surface 47 of the end portion 26 of the probe. The nose portion 42 serves as a guide for this axial movement. This bottom portion of the cup 27 is made with precious metal to insure a long wearing contact with the probe end. Because of the biasing of the spring fingers in engagement with the conical surface 41, any wearing of the inner engaging surfaces at 47, which may result under ordinary conditions in a loss of contact, is accommodated by the constant urging of the cup bottom towards the probe and by the action of the fingers against the conical surface 41. Thus, there is provided an automatic adjustment which is continuously in action to insure positive electrical contact between the inner conductor 28 and the probe end portion 26.

The manner in which the transfer means comprising the various sector plates 30 and 31 and the central disc 29 as described in connection with Figure 2 operate, will now be described in detail with reference to Figures 5 and 6. In Figure 5, it will be noted that the sector plate 30 includes two sectors 48 and 49. In the embodiment shown for illustrative purposes, these sectors may have an arcuate peripheral extent of substantially fortyfive . degrees each and extend diametrically as shown. Similarly, the sector plate 31 includes two diametrically oppositely extending sectors 50 and 51 each of substantially forty-five degrees of arc. The sectors 50 and 51 are positioned at ninety degrees relative to the sectors 48 and 49 such that alternate contact with the central conducting disc 29 will be made by the respective sectors. The overall diameters of the sector plates 30 and 31 are such that their peripheries will overlap the periphery of the conducting disc 29. As shown best in Figure 6, the central disc 29 in a preferred embodiment, actually includes two coaxial discs 52 and 53 secured together at their hubs to define a peripheral slot 54. The overlapping of the sectors is accommodated by reception of the sectors between the discs in the slot 54. As a result of the differential speed created by the overlapping, a wiping contact will be made between the sector plates and the central conducting disc comprising the dual discs 52 and 53.

If it is assumed that the gear train drives the central conducting disc 29 in a counter clockwise direction as viewed in Figure 5, then the sector plates 30 and 31 will be driven in a clockwise direction simultaneously and at the same rate of speed, all as indicated by the arrows. In this event, the sector portion 49 as shown will be entering the peripheral slot 54 and thus while so sandwiched within this slot electrical energy will be passed from the center coaxial connector 11 to the outside coaxial connector 12.

Just prior to termination of contact of the sector 49 with the inner side walls of the discs defining the slot 54 in the conducting disc 29, the sector 51 associated with the sector plate 31 will enter the slot 54 to make contact with the conducting disc 29. The arcuate extent and degree of overlapping of the various plates and central disc may be designed such that one contact will be made before the other contact is broken. By having a contact made before the other is broken, possible arcing occasioned by open circuits is avoided.

In the cross sectional view of Figure 6 taken in the ⁶ .

direction of the arrows 6—6 of Figure 5, it will be noted that the peripheral disc surfaces for the discs 52 and 53 defining the slot 54 are directed inwardly slightly to enable introduction of a spring bias so that the discs 52 and 53 tend to grip opposite sides of the sector 49 thereby providing a positive engagement as at 55 and 56. To facilitate entry of the sectors, the edge and end portions thereof such as at 57 for the sector 49 are tapered slightly.

This manner of interconnection of the sector plates with the conducting disc 29 is an important feature of the invention. By sandwiching the sector within the slot 54 to provide consistent contact pressure coupled with the natural differential speeds introduced as a result of the overlapping, there is provided a self cleaning action between these engaged metal to metal surfaces. Further, the inherent additional advantages of capacitance coupling is realized because of the relatively large contact area between the metal contacting portions of the dual discs 52 and 53 sector 49.

The duration of the electrical connection between any one sector and the disc may be varied by altering the arcuate extent of the sector. Further, the sectors on one sector plate may be dimensioned differently from the sectors on the other sector plate in order to provide a distinguishing characteristic in the electrical signal transmitted to one of the coaxial connectors as compared to the other.

In Figure 7, for example, there is illustrated a sector plate 58 having sector portions 59 and 60 provided with notches 61 such that several make and break connections are effected while the sectors 59 and 60 are sandwiched within the slot 54. Thus, the output energy from the corresponding coaxial connector is distinguished over that fed to the other coaxial connector. As an alternative to the notching such as at 61, the overall arcuate extent of the sectors 59 and 60 may be made different from that of the sectors on the other sector plate whereby a distinguishing means is provided for the two output signals.

The overall operation of the entire lobing unit will be apparent from the above description. Referring once again to Figure 2 and to the plot in Figure 10, a source of electrical energy is connected to the electrical inlet 15 for the motor 14 to drive the motor at a constant rate of speed. An inlet co-axial line passing from an electrical energy source (not shown) is connected to the center co-axial connector 11, and two output co-axial lines (not shown), leading to other units such as antennas between which the energy from the input co-axial line is to be switched, are connected to the outside co-axial connectors 12 and 13. The input high frequency energy in the co-axial connector 11 is passed through the inner conductor thereof and the point contact cup means such as illustrated in Figures 3 and 4 to the center probe associated with the switching member 19 so that this energy appears on the conducting disc 29. This disc is being rotated at a given speed through the medium of the gear train by motor 14 and simultaneously the outer sector plates 30 and 31 are similarly being rotated. As best shown in Figure 5, the sector plates 30 and 31 will thus alternately make electrical contact with the conducting disc 29 thereby passing the high frequency energy at disc 29 to one or the other of the sector plates 30 and 31. From the sector plates 30 and 31, this electrical energy will pass down a corresponding tapered probe and point contact cup to the corresponding inner conductor of the outside co-axial connectors 12 and 13 to pass to the output co-axial lines. The provision of the bearing plate partition 16 as described heretofore, in co-operation with the co-axial stubs 32 and 33 minimizes electrical losses during the transferring operation between the disc and sectors and defines essentially, with the remaining walls of the first compartment 17, an R.-F. cavity. This portion of the unit is thiis isolated from the various gears in the second compartment 18.

2,933,701

As mentioned heretofore, the unique point contact means 27 in the form of the split cup of Figures 3 and 4 insures substantially maintenance free and reliable operation of the unit. Further, the sandwiching provision in the central conducting disc 29 provided by the dual disc construction with the peripheral portions of the sector plates, insures positive electrical contact during the switching operation. Any wear during these contacting periods is accommodated by biasing in of the side of the walls of the discs 52 and 53 against the sector therewithin. The differential speed as a result of the overlapping of the sectors and central disc provides wiping action as well as a cleaning action between these contacting surfaces.

Because of the positive mechanical gearing and constant speed of the motor 14 as well as the positive arcuate dimensioning of the various sectors, a discrete proportioning of the input electrical energy is maintained. In Figure 10, for example, the distribution of this high frequency energy between the two output co-axial connectors 12 and 13 is illustrated. Thus, with respect to time, the output of electrical energy from the co-axial connector 12 is indicated by the shaded wave form 62 and the output of the co-axial connector 13 is indicated by the shaded portion 63. It will be noted that the duration of each of the energies distributed between the output connectors is exactly equal as indicated by P. Each output of the lobing unit thus provides a substantially perfect square wave, and to this end the lobing unit may readily be employed as a square wave generator.

As mentioned heretofore, it may be desirable that the output from one of the co-axial connectors be distinguishable from the output from the other co-axial connector, and to this end one of the sector plates may be dimensioned differently from the other. In the event such dimensioning took the form of decreasing the arcuate extent of the sectors on the sector plate, this would effectively change the period P for the particular energy coming from one of the outputs as compared with the period P for the energy from the other output.

In the actual embodiment of the lobing switch unit, the entire interior of the casing 10 as illustrated in Figure 2 is filled with oil 64 of given dielectric constant and the whole unit is hermetically sealed. Sealing between the first and second compartments 17 and 18 insofar as the oil is concerned, however, is not necessary nor desirable. Actually, the oil will permeate the motor 14 itself and serve to lubricate all the gearing as well as the various ball bearings and will provide an excellent operating and lubricating medium for the sector plates and conducting disc. Any sparking, for example, will be immediately quenched by the oil and any generated heat will be readily transferred to the casing 10 and properly dissipated. Further, the given dielectric constant of the oil is such as to provide a uniform impedance between the tapered probes and interior tapering of the case 10 such that impedance matching is maintained throughout.

While the instant invention has been described with respect to a particular embodiment in which a center coaxial connector is arranged to switch electrical energy between only two output co-axial connectors, it should be readily understood that additional output co-axial connectors and associated tapered probes and switching units including properly designed sector plates may be incorporated without departing from the spirit of the invention. Thus, for example, because of the symmetry of the unit with respect to the central axis thereof passing through the center co-axial connector 11, two additional co-axial connectors similar to 12 and 13. could be arranged above and below the connector 11 as viewed in Figure 1 whereby electrical energy may be uniformly distributed between four output co-axial connectors. It is also possible to serially connect another set of switching members in co-axial tandem fashion with the switching members 19, 20, and 21 and employ the same motor driving means for rotating these members on common shafts. Other such modifications falling within the scope and spirit of this invention will readily occur to those skilled in the art. The transmission line R.-F. lobing switch is, therefore, not to be thought of as limited to the particular embodiment described and shown for illustrative purposes.