US2883605A - Modulator - Google Patents

Description

April 21, 1959 H. T. MORTIMER 2,883,605

MoDULAToR Filed Marsh 27', 1957 2 meets-sheet z INVENTOR HARRY T. MORTIMER Annnnnnnnnnn ATTORNEY5 United States Patent O MODULATR Harry T. Mortimer, Anaheim, Calif. Application March 27, 1957, Serial No. 648,982

8 Claims. (Cl. 321-68) (Granted under Title 35, U.S. Code (1952), sec. 266) whichlare magnetically coupled with each other; the firstcore has an input Winding disposed thereon for receiving an alternating signal while the second core has an output'winding and aV biasing winding disposed thereon. A unidirectional current is applied to the biasing windingy for producing a longitudinal flux in the second core substantially parallel to the direction of grain orientation while an alternating signal is applied to the input windingv disposed on the other core. The time varying magnetic flux produced in the first core by the alternating signal induces a voltage in the second core. The second core is constructed of magnetic material which is a good con-v ductor so that the induced voltage causes a current to flow around the core longitudinally along essentially the same path as the unidirectional flux created by the' biasing current. second core which is substantially perpendicular to the longitudinal flux and to the direction of grain orientation. The transverse flux causes the component of the longitudinal flux which is perpendicular to the output winding to vary at twice the frequency of the alternating signal applied to the first core, and hence an output voltage is induced in the output winding which has a frequency twice that of the alternating signal. The magnitude of the output voltage can be controlled by the amount of biasing current applied to the second core, and the phase of the output voltage depends on the polarity of the lbiasing current.

The invention is capable of amplifying the direct current applied to the biasing winding and the amplified signal which is of an alternating current nature can be furtheramplified without the difliculties inherent in the amplification of direct current signals. Further the apparatus of the invention has a fast response time limited only by the speed of magnetization of the core for a given signal, is more eicient and can carry a heavier load than conventional second harmonc modulators.

An object of the present invention is the provision of a magnetic second harmonc modulator.

Another object is vto provide a fast response second harmonc modulator utilizing grain oriented magnetic materials.

A further object of the invention is the provision of a fast response second harmonc modulator utilizing grain oriented magnetic materials in which the output voltage is directly Proportional to a direct current biasing signal applied to the device.

Still another object is to provide a magnetic second harmonc modulator which has a fast response time, is

eflicient and is capable of carrying a heavy load.

This current sets up a transverse flux in the= Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description When considered in connection with the accompanying drawings in Which like reference numerals designate like parts throughout the figures thereof and wherein:

Fig. 1 shows a schematic representation of a typical embodiment of the magnetic second harmonc modulator of the present invention;

Fig. 2 discloses another embodiment of the invention in which an E core is used to produce flux ynecessary to induce a voltage in the toroidal core; and

Figs. 3 and 4 show vector diagrams of the flux and the magnetic fields present in the grain oriented core of the present invention.

Referring'now to the drawings, in which like reference characters designate like or corresponding parts throughout the second views, there is shown in Fig. 1 (Which illustrates one embodiment) a magnetic core 11 having a Winding 12 disposed thereon for the reception of an alternating signal supplied from signal source 13. Magnetically linked with the core 11 is another magnetic core 14 constmcted of a grain Oriented magnetc material such as Hypersil in which the direction of grain orientation is tangent to the curve of the core 14 at every point in the core. Core 14 could, for example, be wound from thin Hypersil tape in which the direction of grain orientation is parallel to the longitudinal direction of the tape. Although core 14 is preferably of grain oriented material, core 11 need not be of such material.

A control or biasing winding 15 is disposed upon the core 14, and a Variable unidirectional current source comprising, for example, a battery 16 and a Variable resistor 17 is connected thcreto for producing a magnetomotive force in the winding 15 which produces a longitudinal flux in the core 14 in the direction of the grain orientation of the magnetic material. An inductor 18 and a capacitor 19 is provided to present a high impedance to second and higher harmonics of the alternating signal from source 13 in order to isolate the unidirectional current source from such harmonics.

An output winding 21 disposed on the core 14 has a load circuit 22 connected thereto and a voltage varying at twice the frequency of the signal -from source 13 Will be induced therein and delivered to the load 22.

A theory of operation of the device is as follows, however, it is not intended that the invention in any way be restricted by this explanation. The unidirectional current from the battery 16 creates a non-varying longitudinal flux in the core 14 in the direction of the grain orientation of the magnetic material. Since this flux is non-varying, that is, there is no change in the flux linking the output winding 21 with respect to time, no voltage will be induced therein and no output will result. When an alternating current is applied to the winding 12 from the source 13 a time varying magnetic field is set up in and around the core 11. The core 14 cuts this time varying field in the same manner as a winding in a transformer and a voltage is induced therein which causes current to flow around the core 14 along the same aXis as the non-varying longitudinal flux and the grain orientation. Since a current creates a magnetic field perpendicular to its direction, a transverse magnetic flux is set up in the core which is perpendicular to the constant flux produced by the winding 15. This transverse field varies at the same frequency as the signal from the source 13, but as can be appreciated by reference to Fig. 1, this flux is parallel to the turns of the winding 21 and hence no voltage is induced because of this field acting alone. However, this transverse field 'causes thec omponent of the effective longitudinal flux,

assaeos whichl links with the output winding 21 to vary at twice the frequency of the alternating signal from the source 13.

Referring now to Pigs. 3 and 4, there is shown a vector representation of the magnetic forces acting on the core 14 as well as the longitudinal flux set up in the core. The vector HL represents the magnetic field intensity created by a current flowing in the winding 15, and it is assumed that HL is positive, as shown in Pig. 3, when the battery has a polarity as shown in Pig. 1. This magnetic field HL creates a longitudinal flux qbL in the direction of grain orientation of the magnetic material in core 14. The alternating current produced by the induced voltage in the core 14 creates a transverse field of intensity designated by HT which acts to rotate the flux vector (pr, so that it lines up with the resultant magnetic field designated by resultant H. The flux magnitude qbL will remain essentially constant and hence the flux linking the winding 21 will be bL cos and the change in flux is represented by -dom and a negative voltage will be induced in the output winding 21. When the alternating current in the core goes through zero the vector 42:, will return to its original position, a change of flux -l-doL will link the output winding 21 and a positive voltage will be induced therein. Tracing this action through a complete current cycle, the vector oh will be in line with HL and there will be no field cornponent HT when the current has zero value. As the current goes positive -t-I-IT will increase and the vector cpi, will be rotated clockwise until HT and qL have reached the position shown in Pig. 3 when the current has reached a maximum value. The reduction in flux linking the winding 21, -d4 L will cause a negative voltage to be induced therein. As the current again returns to a zero value HT reduces to zero, pL returns to its original position and a positive voltage is induced in the output winding because of an increase of flux -l-dtp-L linking the output Winding. As the current goes negative a negative transverse magnetic field designated by -HT is created in the core which rotates the vector bL in a counterclockwise direction until it reaches the position shown in Pig. 3 and a change of flux designated by -d pL is linked with the output winding 21 inducing a negative voltage therein. When the current returns to zero, -HT is reduced to zero, the vector pl, is aligned with HL, and a change in fiux +d pL links the winding 21 inducing a positive voltage therein.

Thus the output voltage induced in the winding 21 varies at twice the frequency of the current in the core 14 Which alternates at a frequency equal to that of the signal from the source 13. If the battery 15 shown in Pig. l is reversed, the magnetic field in the core 14 will be negative as shown in Pig. 5, that is, a magnetic field -I-lL and a magnetic flux -4 L will exist in the core. When the current produced by the induced voltage goes positive the vector -qsL is rotated counterclockwise by the magnetic field -l-HT, the flux which links with the output winding 21 is increased by an amount -I-doL and a positive voltage is induced in the winding. When the current comes back to zero the flux changes by an amount -doL inducing a negative voltage in the output winding. Similarly, when the current goes negative first a positive and then a negative voltage is induced in the output winding. Thus it is manifest that the phase of the output voltage is shifted through 180 when the flux qbL is changed from positive to negative by a change in the polarity of the unidirectional current source 16.

lt can also be readily deduced from an inspection of Pigs. 3 and 4 that the magnitude of the output voltage induced in the winding 21 is dependent o-n the magnitude of the longitudinal flux qsL as this voltage is proportional to and dqL is qL-oL cos 6. Thus if the frequency and the peak value of the magnitude of the signal from signal source 13 is maintained constant, the maximum value of HT and -HT will remain unchanged and the time required for the vector oL to be rotated to the position indicated in Pigs. 4 and 5 and return to its normal position will remain constant, thus the value of the induced voltage in the output winding will be directly proportional to the magnitude of the flux qbL.

Pig. 2 illustrates an embodiment of the invention in which a three legged magnetic core 23 is used in lieu of the core 11 in Pig. 1. In this case the signal source 13 supplies an alternating signal to the winding 12 which in turn creates a time varying flux in the middle leg of the core. The core 14 is placed around this middle leg and the time varying magnetic field induces a voltage in the core which causes a time varying current to flow circumferentially thus producing the time varying transverse field in the core 14. The functioning of the device is the same as that of the embodiment illustrated in Pig.v 1.

Westinghouse Type C Hypersil cores can be conveniently used to construct the embodiment shown in Pig.w 1. These C-shaped cores are constructed of laminated grain Oriented material and are designed to be pressed together by a banding strap after the windings have been positioned thereon. Alternatively the core 14 having windings 15 and 21 positioned thereon can be constructed of continuously wound grain Oriented magnetic tape and it has been found that this is frequently preferable inorder to reduce the number of ampere turns necessary to control the flux in the core.

Thus the present invention provides a magnetic second harmonic modulator which utilizes certain Characteristics of grain Oriented material and which has a fast response time, is efiicient and is capable of carrying a heavy load.

It should be understood, of course, that the foregoing disclosure relates to only preferred embodiments of the invention and that it is intended to cover all changes and modifications of the examples of the invention herein chosen for the purposes of the disclosure, which do not constitute departures from the spirit and scope of the invention.

What is claimed is:

1. A second harmonic modulator comprising a core of grain Oriented magnetic material, means for producing a unidirectional magnetic flux in said core in the direction of grain orientation, means for producing a time varying magnetic field in said core in a direction perpendicular to the direction of grain orientation, and a frequency selective output means magnetically coupled to said core tuned to twice the frequency of said time varying magnetic field.

2. A second harmonic modulator comprising a core of grain Oriented magnetic material, a control winding disposed upon said core, means applying a unidirectional current to said control winding for producing a unidirectional flux in said core inthe direction of grain orientation, means for producing a time varying magnetic field in said core perpendicular to the direction of grain orientation and a frequency selective output means magnetically coupled to said core tuned to twice the frequency of said time varying magnetic field.

3. A second harmonic modulator comprising a first core of grain Oriented conductive magnetic material,

means for producing a unidirectional magnetic flux iny said core in the direction of grain orientation, means adjacent said first core for inducing alternating current to flow in said first core in the direction of grain orientation, said alternating current producing a time varying 4. A second harmonic modulator comprising a first core of grain oriented magnetic material, means for producing a unidirectional magnetic flux in said core in the direction of grain orientation, a second magnetic core magnetically coupled to said first core, means for producing a time varying magnetic field in and around said second core oriented and intersecting said first core in a direction perpendicular to the direction of grain orientation and a frequency selective load magnetically coupled to said first core tuned to twice the frequency of said time varying magnetic field.

5. A second harmonic modulator comprising, a first toroidal core of grain oriented magnetic material, the grain being oriented in a circumferential direction, means for producing a steady unidirectional flux in said core in the direction of the grain orientation, a second toroidal core, means for producing a time varying flux in said second core in a circumferential direction, said second core being interlinked with said first core with a portion of said second core located substantially at the center of said first core, and a frequency selective output means magnetically coupled to said first core and tuned to a frequency harmonically related to the frequency of said time varying flux.

6. A second harmonic modulator comprising, at least first and second separate interlinked continuous paths of magnetic material having a permeability greater than air, means adjacent said first path for producing a varying strength magnetic flux in said first path along the length thereof, means adjacent said second path for producing a steady strength unidirectional magnetic flux along the length thereof, output means magnetically coupled to the flux of said second path for extracting energy from said unidirectional flux When said unidirectional fluX is varied, said second path consisting of grain oriented material With the grain oriented along the length of said second path.

7. The modulator according to claim 6 Wherein the grain oriented material is electrically conductive.

8. The modulator according to claim 6 Wherein at least one additional path of magnetic material having a permeability greater than air is connected in parallel With a portion of said first path to form a third continuous path interlinked With said second path.

References Cited in the file of this patent UNITED STATES PATENTS 2,445,s57 Mccreary July 27, 1948 2,46l,992 McCreary Feb. 15, 1949 FOREIGN PATENTS 886,159 Germany Aug. 10, 1953

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