US2892983A - Antenna system and switch therefor - Google Patents

Description

United States Patent() ANTENNA SYSTEM AND Vswrrcn rHEnEFoR Rodger G. Larson, Horseheads, N.Y. assignor, 'by .mesne assignments, to the vUnited States of America as represented b y theSecretary of the Navy Application October 20, 1953, .SerialNm 387,335

10 Claims. (Cl. S33-'13) This invention relates to 'antenna systems and more particularly to antenna systems in which it is possible to sequentially yenergize individual antennas of a group, and tto :a novel yswitch for controlling 4antenna energization.

In many installations, particularly those of =radio echo devices vin which a plurality of antennas are used for scanning, ronly one 'antenna is energized at any instant, but all of `the vantennas must be available for the reception vof low power reflected energy. In the past, uncontrolled gas tubes were inserted in the'wave guides feeding `,the antennas 'for the purpose ofdisconnec'ting the antennas from the transmitter, but lit has been lfound that uncontrolled gas tubes often 4fail to switch properly. Mechaniy.cal switches vsuch as vrotating `toothed disks contacting stationary brushes yare subject to mechanical breakdowns and introduce noise into the signals.

.It :is an object of this `invention to provide a new and improved antenna system .in which switching is positively controlled.

.It .is yanother object of this invention to provide a new and improved switch forcontrolling high power radio -frequency energy.

Other objects and advantages of the invention will hereinafter become more fully apparent from the following description of the annexeddrawings, which illustrate a preferred embodiment, and wherein:

Fig. 1 is .a sectional view of an antenna array which `incorporates the s'wiitch :of vthis invention, and

Fig. vr2 :is a sectional view of a portion of the array `of lFig. 1 showing ydetails of structure of the switch of this invention.

Referring now to the drawings and more particularly to Fig. l, .the .reference numeral 10 designates a' source fof radio ,frequency energy 'shown fin :block form and con- 'nected lto :one Vend of Ia main wave guide 11. The main waveguide .11 .is connected atits other 'end to a distributing -wave guide .12 `to which `branch `wave guides 13, '14, 15 and 16 are connected. Antennas 22, 23, 24 and 25, shown in Iblock form, are connected to the branch wave guides 13, '14, 15 fand 16 iin which switches 17, 18, 19 and 21 respectively are interposed.

In operation, radio frequency energy is `transmitted `from thepsource 10i, to the antennas 22, 23, 24 and 25 by the wave guides 11, '12, 13, 14, 15 and 16. At any instant, only one of the four antennas shown is to be energized, and the switches 'in the branch wave guides of the other three antennas are actuated to prevent the transmission of energy through their respective branch waive guides. For example, if the antenna 22 is to be energized at any instant, the switches 18, 19 and 21 are actuated to prevent radio frequency energy from reaching the antennas 23, 24 and 25.

Referring now to Fig. 2, a portion of the distributing wave guide 12 is shown connected to a portion of the branch wave guide 14 in which the switch 18 is interposed. The switch 18 comprises an envelope 31 of insulating material such as glass in the form of a hollow ice cylinder. A cylindrical 'anode 32 having an Aend closure disk 30 with a central opening ltherein is sealed 'in one end of the envelope 31 and a hollow cylindrical cathode support '33 is sealed in the other end of the envelope 31.

The cathode support 33 has a portion, reduced in cross-section, which portion extends outside the envelope 31. A wire 39 is positioned within the support 33 by a surrounding `glass sleeve 36 which also fonms a seal between the wire 39 and the reduced portion of the support 33. A quartz cylinder 35, which is ilared at one end, surround-s `and is sealed to the sleeve 36 `so ythat its Vllared end faces the center of the envelope l31. A rdisk 34 having a central opening is secured across the end of the support 33 within the envelope 31 and supports a small vmass of a radio-active material 38, such as radium bromide, within the support 33. A thorium cup 37 is supported on the end of the lead wire 39 inside lthe flared end of the quartz cylinder 35.

A -tube 41 for exhausting the envelope 31 and for lling it with an ionizable Igas such as helium is sealed within the anode 32 about the opening in the disk 30. After the envelope 31 has been filled with the gas at the 'desired pressure, the tube 41 -is ,sealed to complete the hermetic sealing of the switch 18. A source of pulses 42 is connected across the anode 32 and the wire 39 by wires 44 and 43 respectively. The ends of the switch 18 protrude lfrom the sides of the wave guide 14 so that ythe anode 32 and the cathode support 33 do not extend into the conduction path of the high frequency energy. The space between the vanode 32 and the disk 34 is the vdischarge space in which the discharge through n the switch 18 takes place.

In operation, `the radio-active material 38 continually emits ions and electrons. which tend to be confined within the ionizing space dened by the disk 34, the 'ared portion of the quartz cylinder 35 and the end of the wire 39. The `small opening in the disk 34 allows very 4few ions or electrons to escape into the discharge space between the anode 32 and thedisk 34. For this reason, lthe ion and electron concentration in the discharge space is normally very small, too small to produce general ionization of the gas within the envelope 31 when a radio frequency pulsev traverses the switch 18. AImmediately preceding the transmission of a high frequency radio pulse which is not to be radiated by the antenna 23, a direct'voltage pulse from the source 42 is Vapplied vacross the anode 32 and the wire 39 with the wire 39 negative. The direct voltage pulse causes the electrons which have been `emitted by the radio-active material 38 to be exvpelled from 'the ionizing space through the openingin the disk 34 into the ydischarge space. This raises the concentration of electrons within the discharge space and la` high frequency `radio pulse of high power passing through the wave guide 14 will accelerate these electrons, causing-them to collide with the molecules ofthe gas within the envelope 31 and ionize the gas. The 'large concentration of free ions and electrons in the discharge Ispace provides low impedance paths for the radio fre- 'quency energy and the wave guide 14 becomes virtually short-circuited.

Since there is always a supply of free electrons in the ionizing space, the switch 18 is always ready for operation and needs only to be primed by the application of a voltage. As a result, the response is rapid, and since the gas in the envelope 31 deionizes readily and rapidly, high switching rates are possible. If radio-active materials having long half-lives are used, the supply of free ions and electrons is practically inexhaustible, and since there is no heater to consume energy and the direct voltage pulses are of very low current, power losses are small and the switch 18 is cool in its operation. The level of attenuation of the switch is, in part, a function of the diameter of the envelope 31, and may therefore be controlled and designed at any value over a Wide range. The wave guide in which the switch is interposed is open for the conduction oflow power reflected pulses at `all times that the switchris not actually conducting.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1.7In a switching system for controlling the flow of high power radio frequency energy along a wave guide to an antenna, an airtight envelope having an axis, a rst end anda second end; said envelope being disposed with its axis transverse to said wave guide and with said first Aand said second ends extendingbeyond opposite side walls of said wave guide; an anode secured with said first end Y of said envelope; a cathode structure .secured in said second end but without said wave guide; and an ionizable atmosphere contained within said envelope; s aid cathode structure comprising a hollow metal shell lpositioned with one end within andthe other `end without said second end of said envelope and coaxial therewith; said envelope being sealed about -saidb shell; an insulating cylinder secured within said shell coaxial therewith; a wire located within vsaid insulating cylinder coaxial therewith; said insulating cylinder being sealed to both said shell and said wire; a perforated disk affixed across the end of said shell within said envelope; said-insulating cylinder having its end adjacent said disk flared outwardly; and a quantity of radioactive material affixed to said disk within said cylinder; and means for selectively causing electrons to be expelled from within said shell through said perforationin said disk. Y

2. The system defined in claim 1in which said anode is positioned without said wave guide.

3. An electron discharge device. for controlling'high power radio frequency energy, which device comprises an envelope filled with an ionizable atmosphere; an anode `and a cathode mounted within said envelope; said cath- Odefcomprising a hollow shell; a diaphragmv having a small perforation therein secured to one end of said shell as a closure therefor; said shellbeing positioned in said envelope such that said end with' said closure faces said anode; a radio-active material which emits electrons affixed within said shell to provide a reservoir'of electrons; and means for connecting said anode and said cathode to a source of electrical potential for expelling said electrons from within said shell through said perforation and into the space between said closure and said anode.

4. An electron discharge device for controlling high power radio frequency energy, which device comprises an envelope filled withean ionizable atmosphere, a source of free electrons, means for maintaining said electrons from said source within a prescribed volume, means for j expelling said electrons from said prescribed volume into the interior of said envelope, and means for establishing a potential gradient across at least a portion of the 1in- .terior of s aid envelope to accelerate said electrons,

` 5. An electron discharge device for controlling high frequency radio energy, said devicecomprising an envelope of insulating material; said envelope having a first end and a second end and being filled with an ionizable atmosphere; an anode hermetically sealed in said first end; a cathode structure hermetically sealed in said second end; said cathode structure comprising a wire extending into said envelope; a hollow insulating bushing surrounding and sealed to said wire and having a flared end extending into said envelope beyond the end of said wire; a hollow support surrounding and sealed to said bushing and extending into said envelope to the end of said bushing; a diaphragm having a small perforation therein secured as a closure to the end of said support adjacent said bushing; said wire, said bushing, and said diaphragm defining a space within said support; and a radio-active material which emits electrons affixed to said diaphragm within said space.

6. The devicedened in claim 5 further including means for expelling said electrons from said space and through said perforation, said means comprising a source of electrical potential connected across said anode and said wire.' t

7. Avcontrollable switch for short-circuiting a wave guide, which switch comprises'an envelope formed of insulating material and having a first end and a second end, said envelope being filled withan ionizable atmosphere and being positioned'transverse of said wave guide with said first and said sec'ond'ends protruding from the side walls of said wave guide, a first electrode structure .hermetically sealed Iwithin said rst end but without said wave guide, a second electrode structure sealed within said second end but without 'said wave guide, a source of free electrons contained within said second electrode structure, means for maintaining said electrons Without said wave guide, and controllableY means connected across said electrodes for projecting said electrons into the conduction path of said wave guide to be accelerated by the passage of radio frequency energy passing through said wave guide to ionize said atmosphere.

8. A controllable switch for short-circuiting a wave guide adapted to conduct high frequency radio energy, said switch comprising a first electrode positioned outside a first side wall of said wave guide; a second electrode positioned outside a second side wall of said wave guide, said wavev guide being filled with an ionizable atmosphere between said electrodes, a source of free electrons adjacent said second electrode outside said wave guide, and controllable means connected across said electrodes for projecting said electrons into said wave guide in the conduction path thereof to be accelerated by radio frequency energy passing therethrough and to ionize said atmosphere therein.

9. The switch defined in claim 8 wherein said source of electrons comprises a radio-active material.

l0. The switch defined in claim 8 wherein said means for projecting said electrons comprises a source of direct electrical potential, the. potential output of said source of electrical potential being capable of control in amplitude and polarity.

References Cited the file of this patent UNITED STATES PATENTS Hall et al.- Dec. 20,

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