Metcal, Inc.

Other

United States of America As Represented by the Secretary of the Air Force

Watkins- Johnson Company

Iris Associates

Philip S Carter, Jr

John F Krumme

Frank Anthony Doljack

Harry Goldie

Steven N Stitzer

John P Ekstrand

Mark J Cowell

Andrew Tomlinson

Michael Hodges

Kevin Ladd

A small loop antenna employs circuits for increasing the power output and bandwidth of such antennas by employing coaxial cable or wide antenna elements on which the coaxial cable may be mounted or use microstrip, both for the purpose of reducing the inductance and resistance of the antenna structure in a fixed ratio so that the reduced terminating resistance increases the level of signal output. This method applies to both receiving and transmitting antennas for cases where the terminating resistance is much larger than the radiation resistance plus the antenna and tuner loss resistances.

Electrically small receiving antennas

A heater employs a ferromagnetic or like material heated by a varying magnetic field to heat the ferromagnetic material wherein the ferromagnetic material has a large cross-section comprised of many members of small cross-section insulated from one another and wherein for medical applications each member may be surrounded by a heat conductive electrically conductive coating.

Thermal induction heater

A temperature self-regulating heater has a thin first layer of high magnetic permeability, a second layer of electrially conductive non-magnetic material forming a substrate and a heat conductive dielectric disposed between the layers. A varying (preferably r.f.) magnetic field is imposed upon the exposed surface of the first layer and the material to be heated may be placed in contact with an exposed surface of the second layer or may be the dielectric. The heater may be employed with an induction stove wherein the first layer is disposed above the stove's induction coil and the second layer can be the bottom of a cooking utensil.

Transverse electric heater

A heater (seed) and system for subjecting body tissue to closely controlled hyperthermia or higher temperatures includes a core of ferromagnetic material having a high resistivity or resistivity of a non-conductor enclosed with a bio-compatible non-magnetic conductive sheath and excited by a coil positioned to establish a magnetic field coupled to the seed. The core is dimensioned so as to reduce demagnetizing effects to acceptable levels. The thickness of the conductive sheath is optimized to maximize heat generation to achieve a heat generating capacity which is considerably greater than that of the bare ferromagnetic material.

Thermal seed for treatment of tumors

A single constant voltage power supply concurrently supplies a plurality of independent loads each with an independently selectable constant current load without interaction between the loads (currents) by employing a plurality of parallel connected circuits of electrical lengths equal to (2n-1)90.degree. each connected between the constant voltage source and a different one of said loads.

Parallel supply for multiple loads from a single power supply

A self regulating heater comprises a non-conductive, magnetic core having a coil wound about it and providing pole pieces extending into contact or very near contact with a surrounding ferromagnetic member which in turn may be surrounded by and in intimate contact with a non-magnetic low resistance member; the magnetic member having an effective Curie temperature at the temperature to be maintained.

Self regulating heater

An improved performance ferromagnetic self-regulating heater. Constant alternating current is applied to a layered structure including at least one ferromagnetic layer. One or more layers of non-magnetic material is added to the ferromagnetic layer in such a way that the power factor of the heater is very significantly increased above its value in the absence of at least one of the layers. The alternating current flows through the different layers in varying quantities depending on layer composition, temperature and Curie point of the ferromagnetic layer. The structure generates heat by resistive heating as a function of the power applied. In one embodiment a single layer of non-magnetic, high-resistance material is in intimate electrical and thermal contact with one surface of the ferromagnetic material. Below the effective Curie temperature of the ferromagnetic layer the current is mainly confined in the non-magnetic layer which heats with greater efficiency due to better resistive and impedance chararacteristics. In a second embodiment a further non-magnetic, low-resistance layer is added to the opposite surface of the ferromagnetic material. Here the majority of the current is switched from the high-resistance to the low-resistance layer as the heater approaches effective Curie. Accordingly, impedance matching circuit losses can be substantially reduced and energy is saved in high power systems based on the power factor.

High power self-regulating heater

A temperature control system is disclosed for controlling heating current to a heater having an impedance which varies substantially with temperature. The change in impedance of the heater changes the degree of mismatch between the power transmission system and the heater resulting in a change in the voltage which is reflected back to the power transmission system. The reflected voltage is monitored and its magnitude compared to a reference source and the power to the heater is controlled in response to this comparison.

Temperature control in which the control parameter is the degree of

The impedance of an autoregulating heater is greatly increased by employing in one embodiment a return conductor in the form of a helix surrounded by and insulated from a magnetic conductor; the two conductors connected in series or as a transformer across an a.c. source whereby the current in the magnetic material is forced to follow a helical path. In a preferred embodiment, a multilayered coil is wrapped about and insulated from a magnetic sleeve disposed about a copper rod; the sleeve and rod forming the secondary of a transformer. The helical path of the current in the secondary plus the impedance transformation effect of the transformer greatly enhances the impedance of the load as presented to a current source. The winding is enclosed within another magnetic sleeve which provides another magnetic shield about the heater and if connected at one end to the inner magnetic layer increases the width to thickness ratio for purposes to be described.

High efficiency autoregulating heater

A heating structure is described having both a return conductor and a heating element consisting of a substrate of a non-magnetic material having high thermal and electrical conductivity, clad with a surface layer of a ferromagnetic material of relatively low electrical conductivity.

Shielded heating element having intrinsic temperature control

The heating element consists of a substrate or core of a non-magnetic material having high thermal and electrical conductivity, clad with a surface layer of a ferromagnetic material of relatively low electrical conductivity. When the heating element is energized by a source of high frequency alternating current, the skin effect initially confines current flow principally to the surface layer of ferromagnetic material. As temperature rises into the region of the Curie temperature of the ferromagnetic material, however, the decline in magnetic permeability of the ferromagnetic material causes a significant lessening of the skin effect, permitting migration of current into the high conductivity non-magnetic core, thereby simultaneously enlarging the cross-sectional area of the current flow path and expanding it into the highly conductive material; the resistance of the heating element becomes less due to both causes. By selecting the proper frequency for energization, by regulating the source to produce constant current, and by selecting dimensions and material parameters for the heating element, temperature regulation in a narrow range around the Curie temperature of the ferromagnetic material can be produced, despite considerable fluctuations in thermal load.

Alternating current electrically resistive heating element having

Two sectoral radial resonators coupled at their centers of radii by a strip transmission line and doubly loaded with opposing ferrimagnetic spheres between the said strip transmission line and the ground planes provides a frequency selective power limiter.

Frequency selective ferrimagnetic power limiter

An electron-bombarded semiconductor (EBS) source including plural EBS diodes connected in series at the fundamental radio frequency operating range delivers power to a load. A single voltage supply is provided and radio frequency isolation means is connected between the series connected diodes and said supply to effectively connect the diodes in parallel with respect to said supply voltage and current.

Growing community of inventors

Palo Alto, CA, United States of America

Philip S Carter, Jr