US3001151A - Electromagnetic wave modulating devices - Google Patents

Electromagnetic wave modulating devices Download PDF

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Publication number
US3001151A
US3001151A US720892A US72089258A US3001151A US 3001151 A US3001151 A US 3001151A US 720892 A US720892 A US 720892A US 72089258 A US72089258 A US 72089258A US 3001151 A US3001151 A US 3001151A
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Prior art keywords
waveguide
tube
modulating
slot
tubes
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Expired - Lifetime
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US720892A
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English (en)
Inventor
Morris Arthur Langley
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National Research Development Corp UK
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Nat Res Dev
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P1/00—Auxiliary devices
    • H01P1/165—Auxiliary devices for rotating the plane of polarisation
    • H01P1/175—Auxiliary devices for rotating the plane of polarisation using Faraday rotators
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03C—MODULATION
    • H03C7/00—Modulating electromagnetic waves
    • H03C7/02—Modulating electromagnetic waves in transmission lines, waveguides, cavity resonators or radiation fields of antennas
    • H03C7/022—Modulating electromagnetic waves in transmission lines, waveguides, cavity resonators or radiation fields of antennas using ferromagnetic devices, e.g. ferrites

Definitions

  • the invention relates to electromagnetic wave modulating devices of the kind in which gyro-magnetic material is carried in a length of waveguide and modulation of a wave propagated in the waveguide is obtained by varying that component of the magnetic flux in the material which lies in the direction of propagation along the waveguide.
  • a material of the ferrite type is often employed as the gyro-magnetic material, hence the name ferrite modulator which is generally used. Ferrite materials can be found which have low loss at microwave frequencies and accordingly modu lating devices using them can be made to operate at these frequencies.
  • One method of applying a modulating signal to vary the flux is to provide a solenoid wound around the waveguide; in that case eddy currents are induced in the waveguide walls by the modulating field and set a limit to the modulating frequency.
  • the solenoid is wound inside the waveguide there is difiiculty owing to the presence in the wave propagating path of the Winding of the solenoid.
  • the Wall of the waveguide defines a current path for a modulating signal extending in onehanded direction around the axis of propagation of the waveguide and along the length thereof.
  • FIG. 1 shows a partly sectioned view of one form of ferrite modulator
  • I FIG. 2 shows a further form of ferrite modulator.
  • a thin conducting circular tube 1 carries a narrow helical slot 2 which progresses along the tube 1.
  • the tube '1 is supported by a body 3 of plastic material which is conveniently an epoxy resin such as that known under the registered trademark Araldite.
  • the body 3 is transparent and hence in the drawing it has been possible to indicate the tube 1 as visible through the body 3.
  • An end flange 4 is provided at the left-hand end of the tube 1 as shown in the drawing and is in electrically conducting engagement with it except where a short longitudinal slot 5 continues the helical slot 2 from the end of its helical path to the end of the tube 1.
  • a second end flange 6 is similarly fixed except that it does not make conducting contact with the end of the tube 1.
  • a terminal 7 is mounted on the plastic body 3 and connected via a lead 8 on the body 3 to the end of the spiral Which'the tube 1 now forms owing to the slot 2.
  • the end of the slot 2 continues to the end of the tube 1 by means of a further short longitudinal slot; in the drawing this is obscured by the flange '6.
  • a red 9 of ferrite material for example a magnesiummanganese ferrite is located coaxially of the tube 1 by means of an annular foam spacer 10.
  • the device of FIG. 1 is secured into a desired waveguide transmission system by the flanges 4 and 6 at its ends; suitable circular to rectangular waveguide transformers are provided if necessary and an earthed source of high frequency modulating signal is connected to the terminal '7.
  • a modulating signal current flows along the spiral of the tube 1 from the terminal 7 to the end flange 4; the end flange 4 is effectively earthed to the rest of the waveguide system; but the flange 6, although connected to the waveguide system, is insulated from the tube 1 and does not form part of the modulating signal current circuit.
  • the modulating signal current thus flows helically about the ferrite rod; and the flux in the ferrite rod 9 varies according to the modulating signal current flowing round it.
  • the slot 2 is made small to minimise radiation outwards from inside the tube 1.
  • the thickness of the tube 1 is made small; it should be thick enough to allow waves to propagate along the Waveguide system of which it forms part; on the other hand it should be small to reduce eddycurrent losses in it.
  • the number of turns of the coil which is effectively formed by the slot 2 in the tube 1 is chosen from considerations of the modulation signal frequency and the frequency of the wave propagated down the tube 1, bearing in mind the magnitude of the modulating current which flows during operation of the device.
  • the circular tube 1 was 0.9 in. in diameter; the overall length of the tube section was 5.5 in. and con1prisedl4 turns pitched at 3 turns per inch.
  • the diameter of the magnesium-manganese ferrite rod was 0.25 in.
  • a wave of frequency 9375 mc./s. propagated along the tube 1 was modulated when a current of 1 amp. at 7 mc./s. was fed to the tube ll at the terminal 7.
  • the insertion loss was 0.5 db. t
  • the preferred method of manufacture for the tube 1 is that due to E. B. Cowley & G. W. Fynn and is described in copending patent application No. 8,593/57. Briefly, the method involves a stainless steel mandrel of a length and outside diameter corresponding to the length and inside diameter of the tube which provides the helix. A helical track and longitudinal lead tracks at each end are cut in the mandrel and filled with an insulating plastic filler, e.g. an epoxy resin such as Araldite, to bring them flush with the surface again. A layer of copper is then deposited on the mandrel in an elcctroforming bath. deposited over the plastic-filled track and the required tube is thus formed having a helical slot along its length.
  • an insulating plastic filler e.g. an epoxy resin such as Araldite
  • FIG. 2 A further form of modulator is shown in FIG. 2 where two circular tubes 1A, 1B each carry a helical slot 2A, 23 respectively; the helical slots 2A, 2B are arranged so that they are wound about the axis of the tubes 1A, 1B in opposite-handed directions.
  • the tubes 1A, 1B abut together at a common edge 12. but are insulated there from each other.
  • the two tubes 1A, 1B are connected in a waveguide system at their end flanges 4A, 43 again respectively.
  • the flanges 4A, 4B are electrically connected to their respective tubes 1A, 1B and provide an earthed connection because they are connected to the tubes 11 of the waveguide system.
  • the tubes 1A, 1B are supported by a body 3 of an epoxy resin.
  • the tubes EA, 1B similarly enclose an annular foam spacer and a rod of ferrite material, both of which extend between the flanges 4A, 4B.
  • a terminal '7 is held in the resin body 3 and is connected at the abutment edge 12 to the tubes 1A, 1B. 7
  • an earthed source of high frequency modulating signal M is connected at the terminal 7 and the tubes ill of the waveguide system feed microwave energy through the tubes 1A, 18; a circuit is thus completed from the earthed source of modulating signal via the connection to the terminal 7 and the contrary-wound helices formed in the tubes 1A, 113 to the earthed flanges 4A, 4B.
  • the result is that the microwave energy in the waveguide system is modulated by the signal from the source M.
  • This construction has the advantage that the flanges are at earth potential and that there is no completely annular break in the waveguide system; only one feed, the terminal 7, is required for the two tubes 1A, 1B and no flanges are required where they abut. This simplifies the electrical arrangement of the modulator.
  • the manufacture of the modulator it is proposed to make the tubes 1A, 1B in one operation, that is, on a single mandrel by electroforming.
  • a tube of 'high dielectric constant material can be substituted for the annular foam spacer 10 f FIG. -1.
  • Suitable materials are polystyrene and 'polytetrafluorethylene ('P.T.F.E. boron nitride would also be suitable and would be of additional advantage owing to greater thermal conductivity. It is' proposed to extend this arrangement toprovide for increased cooling by using a fluid dielectric instead of the dielectric tube; dielectric bu1kheads would be provided across the waveguide to contain the fluid dielectric.
  • a silicone oil or possibly carbon tetrachloride, as a liquid dielectric to provide a means of cooling the modulator.
  • Suitable circulation and cooling arrangements could also be provided for the fluid.
  • a cooling radiator would be connected to the waveguide by fluid-carrying connections through small holes in the wall of the waveguide.
  • a modulating device of the kind-referredto comprising a waveguide and a mass of gyromagnetic mate,-
  • the wall of the waveguide defines a current path for a modulating signal extending in one-handed direction around the axis of propagation of the waveguide and along the length thereof.
  • a modulating device of the kind referred to comprising a waveguide and a mass of gyromagnetic material located within the waveguide wherein the wall of the waveguide defines two current paths for a modulating signal each extending from a common point in opposite- 4 handed directions around the waveguide and in opposite directions along the length thereof.
  • a modulating device as claimed in claim 2 wherein the length of waveguide is terminated by flanges connected electrically with the waveguide wall and constituting ends of the current paths remote from the common point, and a connection is made at the common point, whereby, in operation with the modulator connected at its flanges into an associated waveguide system, the current paths are fed in parallel from a modulating current source connected between the common earth connection formed by the waveguide system and the connection at the common point.
  • a modulating device as claimed in claim 2 wherein the current paths are of helical form in the wall of a circular waveguide, said helical paths being delineated by helical slots in said waveguide wall, said slots being wider'on the inside of the waveguide wall than on the outside.
  • An electromagnetic wave modulating device in which a wave propagated in a waveguide is modulated by vsrymaterial in the waveguide which lies in the direction of propagation along the waveguide comprising, a waveguide, a mass of gyromagnetie material located within the waveguide, the'wall of the Waveguide defining a current path for a modulatin'g signal extending in one-handed direction around the axis of'pjropagation of thewaveguide and longitudinally of the waveguide, and connections to the waveguideat each end of the current path defined thereby for connection to a modulating signal source.
  • An electromagnetic wave modulating device in which a wave propagated in a waveguide is modulated by varying that component of magnetic flux in -a gyromagnetic material in the waveguide which lies in the direction of propagation along the waveguide comprising, a waveguide, a mass of gyromagnetic material located within'the' waveguide, the wall of the waveguide defining two current paths for'a modulating signal each extending from a common 'point in opposite-handed directions around the waveguide and in opposite directions alo'ng'the length thereof.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Waveguide Aerials (AREA)
  • Non-Reversible Transmitting Devices (AREA)
US720892A 1957-03-15 1958-03-12 Electromagnetic wave modulating devices Expired - Lifetime US3001151A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB8592/57A GB846288A (en) 1957-03-15 1957-03-15 Improvements in or relating to electromagnetic wave modulating devices

Publications (1)

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US3001151A true US3001151A (en) 1961-09-19

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US720892A Expired - Lifetime US3001151A (en) 1957-03-15 1958-03-12 Electromagnetic wave modulating devices

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US (1) US3001151A (en(2012))
DE (1) DE1060924B (en(2012))
FR (1) FR1193259A (en(2012))
GB (1) GB846288A (en(2012))
NL (1) NL225886A (en(2012))

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3217272A (en) * 1961-05-16 1965-11-09 Adams Russel Co Inc High-speed high-power r-f switching
US3245011A (en) * 1961-05-31 1966-04-05 Raytheon Co Ferroelectric signal-translating device having voltage-controlled signal delay
US3340483A (en) * 1965-11-30 1967-09-05 Hughes Aircraft Co Controllable ferrite phase shifter having means to cool the ferrite
US3501716A (en) * 1968-12-03 1970-03-17 Bell Telephone Labor Inc Gyrator network using operational amplifiers

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2562921A (en) * 1945-03-10 1951-08-07 Standard Telephones Cables Ltd High power ultra high frequency load device
US2773245A (en) * 1951-06-18 1956-12-04 Itt Gyrator methods and means
US2784382A (en) * 1952-04-05 1957-03-05 Thompson Prod Inc Magnetic high frequency attenuator
US2820952A (en) * 1953-12-29 1958-01-21 Collins Radio Co High power ladder network attenuator for frequencies from zero to over one thousand megacycles
US2832938A (en) * 1952-08-18 1958-04-29 George T Rado Polarization plane rotator for microwave energy
US2850705A (en) * 1955-04-18 1958-09-02 Herman N Chait Ridged ferrite waveguide device
US2873370A (en) * 1955-08-15 1959-02-10 Levinthal Electronics Products Microwave pulse generator

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2562921A (en) * 1945-03-10 1951-08-07 Standard Telephones Cables Ltd High power ultra high frequency load device
US2773245A (en) * 1951-06-18 1956-12-04 Itt Gyrator methods and means
US2784382A (en) * 1952-04-05 1957-03-05 Thompson Prod Inc Magnetic high frequency attenuator
US2832938A (en) * 1952-08-18 1958-04-29 George T Rado Polarization plane rotator for microwave energy
US2820952A (en) * 1953-12-29 1958-01-21 Collins Radio Co High power ladder network attenuator for frequencies from zero to over one thousand megacycles
US2850705A (en) * 1955-04-18 1958-09-02 Herman N Chait Ridged ferrite waveguide device
US2873370A (en) * 1955-08-15 1959-02-10 Levinthal Electronics Products Microwave pulse generator

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3217272A (en) * 1961-05-16 1965-11-09 Adams Russel Co Inc High-speed high-power r-f switching
US3245011A (en) * 1961-05-31 1966-04-05 Raytheon Co Ferroelectric signal-translating device having voltage-controlled signal delay
US3340483A (en) * 1965-11-30 1967-09-05 Hughes Aircraft Co Controllable ferrite phase shifter having means to cool the ferrite
US3501716A (en) * 1968-12-03 1970-03-17 Bell Telephone Labor Inc Gyrator network using operational amplifiers

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Publication number Publication date
NL225886A (en(2012))
GB846288A (en) 1960-08-31
DE1060924B (de) 1959-07-09
FR1193259A (fr) 1959-11-02

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