US2901748A - Antenna lobe switching system - Google Patents

Description

Aug. 25, 1959 J. A. SIRONS 2,901,748

ANTENNA LOBE SWITCHING SYSTEM Filed Jan. 26, 1956 3 Sheets-Sheet 1 y /am Aug. 25, 1959 .1. A. SIRONS ANTENNA LOBE SWITCHING SYSTEM 3 Sheets-Sheet 2 Filed Jan. 26, 1956 r R. 7 WM MN Wm 06 7Q W 7 A 4 l i V.

3 Sheets-Sheet 3 BY WM A7770 )i 2 key/V7 Aug. 25, 1959 .1. A. SIRONS ANTENNA LOBE swmcmuc SYSTEM Filed Jan. 26, 1956 uwmm United States Patent 2,901,748 ANTENNA LOBE SWITCHING SYSTEM Janis A. Sirons, Springfield, Ohio, assignor to the United StatesofAmerica as represented by the Secretary of the Air-Force Application January 26, 1956, Serial Ne. 561,693 13 Claims. (Cl. 343-733) (Granted .under Title 35, U.S. Code (1952), see. 266) The. invention described herein maybe manufactured and used by or' for the United-States Government for governmental purposes without payment to me of any royalty thereon.

Thisinvention relates to radio frequency switches and particularly to a switch for alternately connecting a coaxial transmission line to either of two other coaxial transmission lines carrying high frequency currents. It is an object of the invention to provide a radio frequency switch of this type that is capable of a relatively fast switching rate and that introduces a minimum of discontinuities in the transmission paths through the switch.

The switch finds particular utility as an antenna lobe switch in radio compass circuits such as disclosed and claimedin my application Serial No. 561,694, filed January 26, 1956. In this radio comp-ass circuit a rhombic antenna is used as the directional receiving device and its field patternis periodically switched from a directional patternan'gularly displaced to one side of the antenna axis to a similar, pattern equally displaced to the other side of the antenna axis. The pattern switching is accomplis'hed by interchanging the feed and terminating points ofthe antenna. The circuit compares the outputs of the radio' compass receiver, fed by the antenna, for each of the two conditions, and produces a direct current output having an amplitude directly related to the magnitude of the difference in-the two receiver outputs and a polarity determined by the relative amplitudes of the two receiver outputs. The receiver output comparisons are accomplished-bye phase sensitive detector which is synchronized with the antenna lobe' switch by energizing both from a common source of alternating current. Further objects of the invention, therefore, are to provide an antenna lobe switch capable of periodically changing the feed and terminating points of a rhombic antenna and also-capable of'being driven by and in.synchronism with a source of alternating current.

A more detailed description of the invention will be givenin connection-with thespecific embodiments thereof shown in the accompanying drawings in which Fig. 1 is a schematic diagram of the switch connected to a rhombic' antenna;

Figs. 2 and 3 are plan and elevation views of one embodiment of the switch;

Figs. 4 and 5 are sectional views'of-the switch shown in- Figs. 2 and 3;

Fig. 6shows thedetails of the'switch contacts;

Fig. 7'is an alternate driving'mechanism for the switch; and

Fig; 8 isa time motion chart for the switch.

The antenna lobe switch and the manner of connecting it to a rhombic antenna areshown schematically in Fig. 1; In thisfigure, conductors 1, 2, 3 and 4 comprise a rhombic antenna. If point- A is made the feed point and point B isterminatedto ground through a proper terminating resistor, 50 ohms in the example shown, the fieldpattern of the antenna is as shown by the dashed line. If the feed and terminating points are now interchanged, the pattern becomes that shown indotted outline; In radiocompass circuits, signals received over thetwopatternsare compared to yield information as to thepo'sitiomof a source of. radio signals-relative to-the 'ice antenna axis perpendicular to the 1ine.A'--B. The man her of accomplishing this, comparison forms no part of the present invention and willnot be discussed further. The switch shown schematically inFig, 1 serves tope-riodically interchange the feed and terminating points of the rhombic antenna and operates ata relatively high rate, for example, c./s. Theswitch' comprises contacts 5 and 6' connected, respectively-to points B and A of the antenna. The contact 7"is actuated by an electro magnetic drive generally illustratedby the armature 8 and coil 9. The armature 8operates to move contact 7 in opposite directions duringj opposite half cycles of the energizing alternating current appliedto coil 9. In'the neutral position of'theswitch (coil 9deenergized) contact 7 is in electrical connection withboth contacts- 5 and 6. Also contacts -1'0"and" 11 make electrical connection with contacts 5 and 6, respectively. During operation, contact 7 is moved up and. down by armature 8 periodically insynchronisnrwith the energizing alternating current in coil 9. When, contact7 moves upward contacts 7-6 and'10--5 are broken, the latter by upward movement of contact;5. I'nthis condition receiver 12,is connected to point B'of the antenna through contacts 75 and'point A' of, the antenna is connected to ground through contacts6-11 and 50 ohm resistor 13. During the next half cycleofthe. alternating current in coil 9, armature 8*moves contact-7' downward opening contacts 75 and 6'-11, thelatter'by pushing contact 6 downward. In this conditionthe receiver is connected to point A through,contacts*7-6- and point B. is connected to ground'through contacts 5-10 and 50 ohm-resistor 14.

The mechanical and electricaldetails'of-the lobe switch 'are shown in Figs. 2 to 6. Referring-firstto' Fig. 4, this figure is a view taken along section line 4--4 of Fig. 2. Short sections of'coaxial transmission line 15 and 16, terminating in coaxial connectors 17'-and 18, enter opposite sides of switch'contact housing block 19. The axes of these sections lie in acommon verticalplane and their outer conductors extend 'to the-center of block 19. Spring contacts 5 and 6, which may be made of beryllium copper, are extensions of center conductors 20 and 21 to which they may be attached by any method providing good electrical contact, such as by silver soldering. The construction of the spring contacts- Sand 6 is shown more clearly in Fig. 6. These contacts' are preferably silver plated to increase surface conductivity. The free ends of spring contacts 5 and 6 overlap; slightly and contact 7 is situated between theoverlappingends; The axes-ofcoaxial sections 15 and 16"a're" vertically displaced by an amount sufiicientto accommodatecontact 7. Contacts 10 and 11 are inthe form of met'allicpins, preferably silver or silver plated, which-extend intocavities in screw plugs 22-and 23 filled with'a resistive material such as carbon. Plug 23 isshown iii-section and illustrates clearly the resistive filling 13 wuien forms the resistance 13- of Fig. l, the body 19 being grounded} Resistor 14 is similarly provided'in plug 22.

Means, to be explainedlate'r, are provided for moving contact7 both upand down:from the neutral position shown in Fig. 4 in a direction substantially normal to contacts 5 and 6. With contact 7 in its neutral position-the switch is initially adjustedby'screwing contact 10 up and contact 11 down until electricaloontact is made with spring cont-acts 5 and 6 without breaking contacts 5-7 and 6-7. This is possible because-ofthe initial spring bias in contacts 5 and-6 which causes the former to bow downward and-the-latter-upward;

After proper adjustment of contacts 10 and 11 disturbance of the setting may; be prevented by pouring sealing waxor. other suitablev compound in the space above thescrew plugsikand Alsohthe screw caps shown offer further protection against disturbance of the contact settings. Upward movement of contact 7 from its neutral position breaks contacts 6-7 and -4.0 while leaving contacts 5-7 and 6-11 closed. Downward movement breaks contacts '5-7 and 6-11 and leaves contacts 6-7 and 510 closed.

, The details of contact 7 and the mechanism for oscillating it about its neutral position are shown in Fig. 5. The section shown in this figure is taken along section lines 55 of Fig. 2 and 5'-5 of Fig. 4. A third coaxial line section 24, terminating in coaxial connector 25, enters the block 19 in a direction normal to the directions of line sections 15 and 16. The cylindrical opening forming the outer conductor of this line section extends completely through block 19. Contact 7 is an extension of the center conductor of line section 24 to which it is attached through a short spring section 26. The spring 26 may be made of beryllium copper like spring contacts 5 and 6 and may be attached to contact 7 and center conductor 27 by means of silver solder. There should be no tension in spring 26 when contact 7 is in its neutral position, the nature of spring 26 being more that of a flexible coupling.

An electromagnetic drive is provided for oscillating contact 7 about its neutral position. This drive mechanism is contained in and supported by a housing 28 of nonmagnetic material to which block 19 is attached and with which it communicates through opening 29. The drive mechanism comprises a permanent magnet 30 held, together with pole pieces 31 and 32, between straps 33 and 34 of nonmagnetic material. Straps 33 and 34 are attached to each other by screws 35 and strap 33 supports the whole magnet assembly in housing 23 to which it is attached by screws 36. An armature 37, made of a material having high magnetic permeability, is attached to an angle member 38 by means of throughbolts 39 and plates 40 and 41 and the angle member is attached to housing 28 by screws 42. The angle memher, which is preferably made of a nonmagnetic material of good elasticity such as beryllium copper, acts as a torsion support for the armature and effectively resists any movement of the armature other than movements producing torsion in the angle member. An advantage of the inherent stiffness of this type mounting is its weli defined neutral position. The short end of the armature engages a slot 70 in an insulating cap 43 on contact 7.

The armature 37 is surrounded by a coil 44 which is suitably supported within the housing 28 as by wedges 45 and 46. Leads from the coil go to a gas-tight connector 47. Housing 28 is provided with a cover 48 (removed in Figs. 2 and 3). If the switch is to be evacuated or pressurized, it may be made gas-tight by soldering the cover to the housing body 28.

When an alternating current flows in coil 44, end 49 changes its magnetic polarity on each half-cycle of the alternating current. Since the magnetic polarity of poles 5t and 51 does not change, an alternate attraction and repulsion exists between each of these poles and the end 49 of armature 37 causing this end of the armature to vibrate in a vertical direction.

This oscillation is transmitted through the short end of armature 37 and coupling 43 to contact 7 causing it to oscillate about its neutral point and actuate the switch in the manner already described.

Another suitable driving mechanism for contact 7 of the switch is shown in Fig. 7. The operating principle is very similar to that of a permanent magnet electrodynamic loudspeaker. Permanent magnet 52 and circular yoke 53 operate to establish a strong magnetic field across the circular air gap between the lower end of magnet 52 and the circular pole piece 54 surrounding it. A coil of fine wire 55, wound on sleeve 56, is accurately positioned within the air gap with freedom of movement in the vertical direction. This is accomplished .by two resilient diaphragm type mounts 57 and 58 which are interconnected to move in unison by structural member 59 and spiders 6t and 61, the latter having sleeve 56 attached thereto. The member 59 also carries an insulating coupling 62 for transmitting its motion to contact 7. Resilient mountings 57 and 58 restrain member 59 from any motion other than in a vertical direction and resiliently oppose any movement of this member away from its neutral position in the vertical direction. When an alternating current is passed through coil 55 alternate up and down forces act on this coil which are transmitted to member 59 through sleeve 56. The resulting oscillation of member 59 about its neutral position is transmitted through coupling 62 to contact 7.

The spider 66) carries a weight 63 which may conveniently be made of solder. This weight is made such as to give the mass of the oscillating system the required value with respect to the resilience of mounts 57 and 58 to produce mechanical resonance at the frequency of the driving current in coil 55. The apparatus of Fig. 7 is also sealed and suitable for evacuation or pressurization of the switch.

In radio housing systems it is desirable that antenna lobe switching occur at a rate of at least c./ s. The switch described, with either the drive of Fig. 5 or that of Fig. 7, can easily attain this or higher rates. A time and motion chart of the switch contacts is shown in Fig. 8 for an operating frequency of 100 c./s.

I claim:

1. A switching device for coaxial transmission lines comprising first and second cantilever spring contacts anchored to spaced fixed points and extending toward each other, in the general direction of a line joining said points, with their free ends in proximity; a third contact situated between the free ends of said first and second contacts, said third contact having a pair of contact surfaces facing in opposite directions substantially normal to said first and second contacts and having a neutral position in which said contact surfaces are engaged by free ends of said first and second contacts; and means for displacing said third contact in a direction substantially normal to said first and second spring contacts until electrical contact with one of said first and second contacts is broken said first, second and third contacts being extensions of the center conductors of three separate coaxial lines.

2. Apparatus as claimed in claim 1 in which there are provided fourth and fifth fixed contacts, said fourth fixed contact being on the same side of said first contact as the associated contact surface of said third contact and said fifth contact being on the same side of said second contact as the associated contact surface of said third contact, said fourth and fifth contacts being in engagement with said first and second contacts, respectively, when said third contact is in its neutral position.

3. Apparatus as claimed in claim 2 in which said first and second spring contacts are biased toward the respective surfaces of said third contact which they engage.

4. A switching device for coaxial transmission lines comprising first and second cantilever spring contacts anchored to spaced fixed points and extending toward each other, in the general direction of a line joining said points, with their free ends overlapping, a third contact situated between the overlapping ends of said first and second contacts and having a neutral position in which it makes electrical contact with both said first and second contacts, and means for displacing said third contact in a direction substantially normal to said first and second contacts until electrical contact with one of said first and second contacts is broken said first, second and third contacts being extensions of the center conductors of three separate coaxial lines.

5. Apparatus as claimed in claim 4 in which there are provided a pair of fixed contacts positioned on opposite sides of the overlapping portion of said first and second contacts and on the same sides of said first and second spring contacts as said third contact, one of said fixed contacts being in electrical contact with said first contact and the other being in electrical contact with said second contact when said third contact is in its neutral position.

6. Apparatus as claimed in claim 5 in which said first and second cantiliver spring contacts are biased toward said third contact.

7. Apparatus as claimed in claim 1 in which the last named means comprises a coil, means for energizing said coil with alternating current for producing an alternating magnetic field, and means responsive to said alternating field for oscillating said third contact about its neutral position in a direction substantially normal to said first and second contacts.

8. Apparatus as claimed in claim 4 in which the last named means comprises a coil, means for energizing said coil with alternating current for producing an alternating magnetic field, and means responsive to said alternating field for oscillating said third contact about its neutral position in a direction substantially normal to said first and second contacts.

9. A switching device comprising first and second cantiliver spring contacts anchored to spaced fixed points and extending toward each other with their free ends overlapping, a third cantiliver contact anchored to a fixed point and having its free end situated between the overlapping ends of said first and second contacts and having a neutral position in which it makes electrical contact with both said first and said second contacts, a pair of fixed contacts positioned on opposite sides of the overlapping portion of said first and second contacts and on the same sides of said first and second contacts as said third contact, one of said fixed contacts being in electrical contact with said first contact and the other being in electrical contact with said second contact when said third contact is in its neutral position, and means situated on the opposite side of said first and second contacts with respect to said third contact anchor point for oscillating said third contact about its neutral position in a direction substantially normal to said first and second contacts, said oscillating means comprising an elongated armature element pivoted at a point between its ends and having a spring biased neutral position in which it is in alignment with said third contact in its neutral positon, an insulating mechanical coupling between one end of said armature and said third contact, a permanent magnet having two poles located adjacent to the other end of said armature and on either side of the longitudinal axis of said armature in its neutral position, a fixed coil surrounding said armature between said pivot point and said other end, and means for applying alternating current energization to said coil.

10. An electromechanical oscillatory drive comprising an elongated armature of high magnetic permeability, a torsion bar made of an elastic metal and having a right angle cross section, means anchoring the outer ends of said torsion bar, means for rigidly attaching said armature at a point intermediate its ends to said bar in a transverse direction, fixed permanent magnet means having its poles adjacent one end of said armature and located equal distances on either side of the longitudinal axis of said armature when said torsion bar is unstressed, a fixed coil surrounding said armature between said torsion bar and said one end, and means for applying alternating current energization to said coil.

11. A rhombic antenna lobe switch operating to periodically interchange the feed and terminating points of the antenna, said switch comprising first and second cantilever spring contacts anchored to spaced fixed points and extending toward each other with their free ends overlapping, a third contact situated between the overlapping ends of said first and second contacts and having a neutral position in which it makes electrical contact with both said first and second contacts, said first and second spring contacts being biased toward said third contact, a pair of fixed contacts positioned on opposite sides of the overlapping portion of said first and second contacts and on the same sides of said first and second contacts as said third contact, one of said fixed contacts being in electrical contact with said first contact and the other being in electrical contact with said second contact when said third contact is in its neutral position, means for oscillating said third contact about its neutral position in a direction substantially normal to said first and second contacts, equal terminating resistances connected between said fixed contacts and the ground for said antenna, means for connecting the feed point of said antenna to one of said first and second contacts and the terminating point of said antenna to the other of said first and second contacts, and means for connecting an external circuit to said third contact.

12. A rhombic antenna lobe switch operating to periodically interchange the feed and terminating points of the antenna, said switch comprising: a body of conductive material, said body being at the potential of the antenna ground; a first bore extending through said body; second and third bores extending into said body from opposite directions and intersecting said first bore, the axes of said second and third bores being parallel to each other, being in a plane normal to the axis of said first bore and being slightly ofiset from said third bore axis by equal amounts in opposite directions; means for attaching a first coaxial transmission line serving as an external circuit, a second coaxial transmission line having its center conductor connected to the feed point of said antenna and a third coaxial transmission line having its center conductor connected to the terminating point of said antenna, to said body so that said first, second and third bores, respectively, form extensions of the inner surfaces of the outer conductors of said lines; first and second cantilever spring contacts attached to the center conductors of said second and third transmission lines and extending toward each other through said second and third bores with their free ends overlapping; a third contact, having a thickness substantially equal to the sum of said offsets, situated between the overlapping ends of said first and second contacts, said third contact extending through a portion of said first bore and being flexibly attached to the center conductor of said first transmission line for movement in a direction normal to the axes of said second and third bores and having a neutral position in which it makes electrical contact with both said first and second contacts; a pair of fixed contacts positioned on opposite sides of the overlapping portion of said first and second contacts and on the same side of said first and second contacts as said third contact, one of said fixed contacts being in electrical contact with said first contact and the other being in electrical contact with said second contact when said third contact is in its neutral position; equal terminating resistances connected between said fixed contacts and said body; and means extending through that part of said first bore not containing said third contact for oscillating said third contact about its neutral position in a direction normal to the axes of said second and third bores.

13. Apparatus as claimed in claim 12 in which each of said fixed contacts is attached to said body by means of a resistive material providing the terminating resistance.

References Cited in the file of this patent UNITED STATES PATENTS 2,523,768 Knutsen Sept. 26, 1950 2,600,247 Huetlen June 10, 1952 2,618,717 Westin Nov. 18, 1952 2,790,129 Barnes Apr. 23, 1957 2,820,910 Barnes Jan. 21, 1958 FOREIGN PATENTS 1,013,353 France Apr. 30, 1952

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