Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.