Abstract: A system and method for detecting the state and thickness of water accumulation on a surface incorporates a plurality of spaced, thin, electrically resonant circuits bonded to the surface and a radio frequency transmitter for exciting the circuits to resonance. A receiver detects the resonant signal from each circuit, determines the resonant frequency and quality factor of the circuit and correlates that information with predetermined data representing changes in resonant frequency and quality factor as a function of liquid water and ice accretion to thereby establish the state and thickness of water overlaying the circuits.

Abstract: A continuous conductor pattern applied to a dielectric cooking utensil improves the distribution of microwave energy to the bottom surface of food being cooked. The energy is coupled from the electromagnetic field within the oven cavity by metal strip pickup probes on the hand grips or side walls which are part of the embedded metal layer. The conductor pattern on the bottom wall couples energy from the pickup probes to the central region of the utensil.

Abstract: A power supply for controlling the duty-cycle of a microwave oven magnetron and the like power-energizing load, includes a parallel combination of a non-linear resistance element, such as a varistor and the like, and a gateable semiconductor switching device, such as a triac and the like, in series with a power supply voltage-doubler diode, connected in parallel across the magnetron. The flow of current through the magnetron is substantially reduced or prevented when the semiconductor switching device is gated to an "off" condition and is substantially enabled to a normal current flow value when the semiconductor switching device is gated to an "on" condition, typically by high frequency squarewaves provided at the gate electrode.

Abstract: A circuit for controlling power consumption of a load, by controlling the flow of current thereto, utilizes at least one parallel combination of non-linear resistance elements, such as a varistor and the like, and a gateable semiconductor switching device, such as a triac and the like, to substantially reduce or prevent current flow when the semiconductor switching device is gated to an "off" condition and to enable normal current flow to a load when the semiconductor switching device is gated to an "on" condition. Embodiments of the power circuits for control of magnetron power, in a microwave oven, are illustrated.

Abstract: A high impedance four wire temperature sensing system is comprised of a thermistor or other sensor and four leads such that a constant current is impressed on the sensor via two leads and the voltage across the sensor is read via the other two. The sensor and leads have microwave surface resistivity much higher than impedance levels in microwave ovens so that negligible microwave energy is coupled to the sensing system. The high resistance leads in a rigid probe to be inserted into the food and in a flexible cable are electrically conductive iron oxide magnetic tape or are deposited conductors.

Abstract: A module board comprised of a microstrip transmission line, terminating resistors and detectors is mounted over two coupling apertures spaced one quarter guide wavelength along a rectangular waveguide. The microstrip line has a length of five quarters of a wavelength as measured in the secondary line system. Output signals representing forward and reflected power flow in the waveguide are developed by the two detectors. This power sensor is low cost and compact and is suitable for a microwave oven.

Abstract: A cut-off tubular housing has flat surfaces for mounting multiple solid state microwave oscillators using microstrip circuitry, each exciting a wire-like resonant coupler wound on a central dielectric support tube for receiving a frankfurter or other material body. The couplers are longitudinally spaced and angularly staggered so that energy coupled to different regions of the body is absorbed by the material to thereby isolate couplers and hence sources even at close spacings. In a rectangular configuration, a non-resonant box has a planar array of serpentine or spiral resonant couplers with adjacent couplers oriented orthogonally to minimize coupling.