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Variable Inductor

IP.com Disclosure Number: IPCOM000093926D
Original Publication Date: 1966-Apr-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

French, WK: AUTHOR

Abstract

This variable inductor is different from the usual structure employing a magnetic slug movable into and out of the coil in a tank circuit to vary its inductance. This inductor employs ferrite particles suspended in a viscous liquid. By virtue of the smallness of the particles and their constant agitation in the presence of an oscillating field, the inductor is particularly suited for use in an automatic frequency control circuit with feedback to adjust the inductor to maintain the frequency.

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Variable Inductor

This variable inductor is different from the usual structure employing a magnetic slug movable into and out of the coil in a tank circuit to vary its inductance. This inductor employs ferrite particles suspended in a viscous liquid. By virtue of the smallness of the particles and their constant agitation in the presence of an oscillating field, the inductor is particularly suited for use in an automatic frequency control circuit with feedback to adjust the inductor to maintain the frequency.

A capped hollow tube of nonmagnetic material is filled with magnetic particles suspended in oil or other viscous liquid. The L and C coils are wound about the tube as a core. Coil L is connected in an oscillator as part of its tank circuit. The alternating field from this coil maintains the suspended magnetic particles in constant excitation and causes the particles to migrate toward the left end of the tube. Thus the Q of the oscillator circuit is altered.

By feedback arrangement in the oscillator circuit, a DC is generated which energizes the coil C to resist the migration of particles and thus stabilize the frequency of the oscillator. Through use of colloidal size particles responsive to the AC oscillator field, this construction obviates the usual dead-space associated with automatic frequency control circuits using movable slug tuners with feedback control.

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