Abstract: The invention is a magnetron 10 and a method of operation of a magnetron. A magnetron in accordance with the invention comprises an anode cylinder (14); a cathode (12) disposed within the anode cylinder; a plurality of vanes (16) extending inward into the anode cylinder so as which form a plurality of resonant cavities; an electrically insulative magnetron chamber wall (20) coupled to the anode; an antenna (18) coupled to at least one of the vanes which provides an output of microwaves passing through the electrically insulative magnetron chamber wall when the magnetron is operating; and at least one baffle (102, 202 and 302) disposed in lines of sight (40, 42, 44 and 46) between the cathode and the electrically insulative magnetron chamber wall on which material emitted from the cathode is deposited instead of on the electrically insulative magnetron chamber wall.

Abstract: An apparatus for the heating of pressed stock in the manufacture of boards of material or in the manufacture of veneer panels. The apparatus includes a microwave preheating device having rod antennae disposed in series, reflective shields, and a heating cell configured as a continuous oven in which the introduction of microwaves into the pressed stock takes place via the rod antennae. The rod antennae are attached to lie horizontally and transversely to the direction of production above, below, or above and below the pressed stock within the heating cell. The reflective surfaces are assigned to the rod antennae on the opposite sides of the pressed stock.

Abstract: A microwave delivery system for a cooking appliance includes a toroidal waveguide, a launching zone and a waveguide cover. The launching zone includes opposing top, bottom and side walls that form a pathway for a microwave energy field to travel from a magnetron through the waveguide and into a cooking chamber. In accordance with one aspect of the overall invention, the bottom wall of the launching zone is aligned with a bottom surface of the waveguide to establish a direct conducting surface for the microwave energy field. The waveguide cover shields a hollow interior portion of the waveguide from cooking byproducts generated in the cooking chamber during a cooking process. The waveguide cover is preferably constituted by a metallic conductor having a finish that enhances the microwave energy field distribution in the cooking chamber.

Abstract: A microwave delivery system for a cooking appliance having a cooking chamber includes a toroidal-shaped waveguide, a magnetron, a tubular feed member interconnecting the magnetron with the toroidal-shaped wave guide and a field flux generator positioned about the tubular feed member. The flux field generator shifts a microwave energy field produced by the magnetron in the tubular feed member. The shifted microwave field focuses high energy standing waves that are directed into the toroidal-shaped wave guide and, ultimately, the cooking chamber. The field flux generator produces either magnetic or electrical fields and is driven by a pulsed DC current, a rectified AC current or a pure AC signal energy source.

Abstract: A microwave oven includes openings and microwave dispersing apparatuses which are arranged to align with a magnetron in a row below a cooking cavity so as to reduce the overall size of a waveguide and uniformly reflect high-frequency electromagnetic waves to all regions of the cooking cavity. The center of a first opening is disposed at a downstream location away from the magnetron by a distance corresponding to one of odd numbers times a half-wavelength of a standing wave in the waveguide, while the center of a second opening is disposed at an upstream location which is offset from another distance away from the magnetron corresponding to another one of the odd numbers times the half-wavelength of the standing wave in the waveguide.

Abstract: An instrument is disclosed for microwave-assisted chemical processes that avoids tuning discrepancies that otherwise result based upon the materials being heated. The instrument includes a source of microwave radiation, a waveguide in communication with the source, with at least a portion of the waveguide forming a cylindrical arc, a cylindrical cavity immediately surrounded by the cylindrical arc portions of the waveguide, and at least three slotted openings in the circumference of the circular waveguide that provide microwave communication between the waveguide and the cavity.

Abstract: Cleaning a microwave device, in particular for drying print substrate in a printing machine, with a microwave source providing an irradiation field and a resonator chamber, wherein a microwave-penetrable material on the inside surfaces of the resonator chamber for forming a material layer that allows any dirt accumulated on it to protrude into the irradiation field.

Abstract: A method is disclosed for carrying out microwave assisted chemical reactions. The method includes the steps of placing reactants in a microwave-transparent vessel, placing the vessel and its contents into a microwave cavity, applying microwave radiation within the cavity and to the vessel and its contents while concurrently externally cooling the vessel conductively.

Abstract: The present invention relates to an apparatus and methods for performing chemical reactions. In particular, the present invention relates to an apparatus for heating chemical reaction mixtures. The apparatus applies one or more semiconductor based microwave generators making the apparatus suitable for parallel processing of chemical reaction mixtures. The invention further relates to methods for performing chemical reactions, e.g. methods for heating a plurality of samples simultaneously or sequentially, methods for monitoring a microwave heated chemical reaction, and methods where the optimum conditions with respect to parameters, such frequency and applied power can be determined for the system consisting of apparatus plus sample.

Abstract: A microwave oven effectively and uniformly cooks large-sized food even though the food inhibits a proper rotation of a cooking tray in a cooking cavity of the microwave oven. An upper wave dispersing unit is provided at a top wall of the cooking cavity and primarily disperses microwaves from the top wall into the cooking cavity. A side wave dispersing unit is provided at a second sidewall of the cooking cavity opposite to a first sidewall of the cooking cavity. The first sidewall partitions the cooking cavity from a machine room of the microwave oven. The side wave dispersing unit secondarily disperses the primarily dispersed microwaves in the cooking cavity. The second sidewall of the cooking cavity has a recess which receives a fan of the side wave dispersing unit. A cover is installed in front of the recess to cover the fan of the side wave dispersing unit. The cover is made of a transparent material and allows a user to view a rotational operation of the side wave dispersing unit.

Abstract: A microwave delivery system for a cooking appliance includes an electronic control unit and a plurality of magnetrons arranged in a spaced relationship for the introduction of various energy fields into an oven cavity. The electronic control unit creates a phase angle shift between each of the microwave energy fields such that a constructive standing wave propagates about the oven cavity. In this manner, localized hot and cold spots, which can detrimentally affect cooking efficiency, are eliminated without the need for mode stirring or turntables. With this system, the total energy delivered to the oven cavity is the combined energy level of the various microwave energy fields.

Abstract: A microwave delivery system for a cooking appliance includes a toroidal waveguide and a launching zone. The launching zone has an interior metallic surface into which a microwave energy field is introduced. The microwave energy field couples with the interior metallic surface of the launching zone thus increasing the efficiency of the energy field as it enters the waveguide. Additionally, a tuning form section is provided in the waveguide which further enhances the microwave energy field, thereby creating a maximum energy node around the inside and outside of the waveguide. Insulation is provided both in the interior of the waveguide and in a central, exterior depression defined by the waveguide.

Abstract: A microwave oven effectively and uniformly cooks large-sized food even though the food inhibits a proper rotation of a cooking tray in a cooking cavity of the microwave oven. An upper wave dispersing unit is provided at a top wall of the cooking cavity and primarily disperses microwaves from the top wall into the cooking cavity. A side wave dispersing unit is provided at a second sidewall of the cooking cavity opposite to a first sidewall of the cooking cavity. The first sidewall partitions the cooking cavity from a machine room of the microwave oven. The side wave dispersing unit secondarily disperses the primarily dispersed microwaves in the cooking cavity. The second sidewall of the cooking cavity has a recess which receives a fan of the side wave dispersing unit. A cover is installed in front of the recess to cover the fan of the side wave dispersing unit. The cover is made of a transparent material and allows a user to view a rotational operation of the side wave dispersing unit.

Abstract: A safety apparatus for an output level-adjustable microwave oven includes a fuse disposed in a power supply line that connects a high power relay or a low power relay with a primary coil of a high voltage transformer of the microwave oven. Where a wrong operation occurs due to defects in the relays, such as a melting of any one of the relays, the fuse disposed in the power supply line connected to the primary coil of the high voltage transformer is cut off. Accordingly, a potential fire resulting from the wrong operation is prevented.

Abstract: A microwave delivery system for a cooking appliance includes a toroidal waveguide having a ring diameter twice that of the wavelength of the microwaves produced by a magnetron, and a cross-sectional diameter equal to one-half of the produced microwaves. The waveguide includes a plurality of cavity excitation ports through which the microwaves enter a cooking cavity. The delivery system further includes a rotating stirrer positioned within the waveguide. The stirrer includes a plurality of openings which become aligned with the cavity excitation ports when the stirrer is rotated to create a uniform, high energy pattern of microwave energy to enter the cooking cavity. Finally, the waveguide includes a plurality of openings along spaced portions thereof to allow a flow of air through the waveguide.

Abstract: A microwave oven is provided which allows electrical components to be cooled separately from the cooking chamber. The microwave oven includes a front plate and a back plate which is spaced a distance from, and opposite to the front plate. The microwave oven also includes a base plate between the front plate and the back plate, and a partition wall for isolating a cooking chamber from an electric outfit room. A wave guide is attached to a rear part of the partition wall and a magnetron is mounted on an upper surface of the wave guide. An electric outfit plate is fitted at approximately the same height as the upper surface of the cooking chamber. Electrical components such as a transformer and a capacitor can be mounted on the electric outfit plate. With this arrangement, the electric components are all mounted above and to the side of the cooking chamber, which allows them to be easily cooled.

Abstract: In a microwave oven system comprising at least one magnetron of a given operating frequency and a mains unit for the at least one magnetron, the at least one magnetron of a given operating frequency is replaceable by a magnetron of another operating frequency. The magnetrons of the different operating frequencies have at least approximately the same mechanical dimensions so that they can be easily replaced quickly. The mains unit can be used for the different magnetrons in unchanged form or in a form involving minor modifications, without any change in the electrical parameters or with a slight change therein, thereby affording interchangeability of the various magnetrons.

Abstract: A microwave cooking appliance includes a sheathed resistive electric heating element including an outer portion, an inner portion and a cross-over portion electrically interconnecting the outer and inner portions. The heating element is arranged in a cooking chamber of the microwave cooking appliance in a manner which effects an impedance characteristic of the cooking chamber. The cross-over portion is arranged such that the heating element acts like an RF antenna moving a microwave energy field to portions of the cooking chamber in which low electric fields occur. In this manner, the broil element helps increase the operational efficiency of the cooking applaince by minimizing any hot and cold spots within the cooking chamber.

Abstract: A surgical and dental instrument sterilizer is described. Liquid water is rapidly vaporized by microwave heating and steam is generated to attain a steam pressure of approximately 47 psi and a temperature of approximately 135° C. in the region of the articles to be sterilized. Micron-size water-droplets are intermittently sprayed onto the articles which are arranged on a tray, from both the top and from underneath thereof so as to thoroughly wet the surfaces. A 30-90 s duration of droplet spray is followed by pulsed microwave irradiation of the top and underneath surfaces for a similar period, as an example; this is followed by a plurality of spray/microwave cycles.

Abstract: An elliptical exposure chamber has an extended focal region. A plurality of cylindrical reactors (25) form the extended focal region. Reducing the size of the opening (58) to each reactor (25) reduces the amount of energy reflected and increases the overall heating. In order to efficiently deliver the electromagnetic energy to the reduced opening (58), a tapered waveguide (55) has a concave end (56). A power splitter (42) divides power from a central waveguide (52) to the plurality of reactors (25). The power that is delivered to each reactor (25) can be adjusted by adjusting the impedance of each reactor (25), the width of each reactor (25) or the width of the opening (58) to each reactor (25). The width of the opening (58) to each reactor (25) can be controlled by a movable metal plate (44). A dielectric wheel can be used to shift hot spots along the focal region.

Abstract: The invention relates to a device for adjusting the distribution of microwave energy density in an applicator which forms a resonator chamber and in which the radiation generated by microwave generators is guided to the applicator wall by waveguides; and to a use for this device. According to the invention, several electroconductive coupling pins (31) are used, each of these extending preferably vertically into both the waveguide chamber and the applicator resonator chamber, in order to feed in the microwaves with as little loss as possible and to enable the field distribution in the resonator chamber to be modified. The invention is especially suitable for producing a plasma.

Abstract: Microwave heating apparatus comprising a dielectric microwave applicator provided with a microwave coupling device adapted to feed microwave energy to the applicator. The applicator is provided with a load chamber 8 extending coaxially with regard to the centre axis of the applicator from an upper end to a predetermined distance from a lower end of the applicator, the load chamber is adapted to receive a load to be heated. The dielectric applicator comprises two sections, an upper section 4 provided with the load chamber and a lower section 6 for impedance matching between the coupling device and upper section. In a preferred embodiment the lower section has an increasing cross-sectional area from the coupling device to the intersection to the upper section.

Abstract: A furnace is provided for microwave sintering of nuclear fuel. A stationary wave is generated in an antenna cavity and used to extract microwaves through slots into a resonance chamber containing the nuclear fuel. A position of the slots is adjusted in such a way that a predetermined temperature profile is produced in the nuclear fuel.

Abstract: The microwave applicator for microwaves outputs from a guide (1) comprises an envelope (3) that forces microwaves to converge towards a focal point (16) by means of a complementary central reflector (4). A fraction of the waves reaches this point after reflection on two facets (11, 13), usually curved and concave, of the reflector (4) and the envelope (3), while the other fraction is reflected three times on three facets (10, 12 and 14), the last two facets of which form part of the envelope and one of which is concave for focussing. These devices can be used for removing a concrete surface, because the microwaves cause vaporisation at the focal point (16).

Abstract: A microwave oven includes openings and microwave dispersing apparatuses which are arranged to align with a magnetron in a row below a cooking cavity so as to reduce the overall size of a waveguide and uniformly reflect high-frequency electromagnetic waves to all regions of the cooking cavity. The center of a first opening is disposed at a downstream location away from the magnetron by a distance corresponding to one of odd numbers times a half-wavelength of a standing wave in the waveguide, while the center of a second opening is disposed at an upstream location which is offset from another distance away from the magnetron corresponding to another one of the odd numbers times the half-wavelength of the standing wave in the waveguide.

Abstract: An instrument is disclosed for microwave-assisted chemical processes that avoids tuning discrepancies that otherwise result based upon the materials being heated. The instrument includes a source of microwave radiation, a waveguide in communication with the source, with at least a portion of the waveguide forming a cylindrical arc, a cylindrical cavity immediately surrounded by the cylindrical arc portions of the waveguide, and at least three slotted openings in the circumference of the circular waveguide that provide microwave communication between the waveguide and the cavity.

Abstract: A volatiles analyzer is disclosed that includes a source of microwave radiation that can selectively produce at least one predetermined frequency of microwave radiation. A cavity is in communication with the source. The walls of the cavity form a twelve faced polyhedron in which eight faces form a regular octagon and having two faces that are both non-parallel and non-perpendicular to the eight faces of the regular octagon. The polyhedron focuses microwave energy of the predetermined frequency on a balance pan while supporting a plurality of TM and TE modes in the cavity.

Abstract: The invention relates to a device for adjusting the distribution of microwave energy density in an applicator which forms a resonator chamber and in which the radiation generated by microwave generators is guided to the applicator wall by waveguides; and to a use for this device. According to the invention, several electroconductive coupling pins (31) are used, each of these extending preferably vertically into both the waveguide chamber and the applicator resonator chamber, in order to feed in the microwaves with as little loss as possible and to enable the field distribution in the resonator chamber to be modified. The invention is especially suitable for producing a plasma.

Abstract: A furnace is provided for microwave sintering of nuclear fuel. A stationary wave is generated in an antenna cavity and used to extract microwaves through slots into a resonance chamber containing the nuclear fuel. A position of the slots is adjusted in such a way that a predetermined temperature profile is produced in the nuclear fuel.

Abstract: A compact and highly controllable impedance-varying-unit, a microwave device using the same unit, and a high-frequency-heating appliance using the same unit are provided. The impedance varying unit includes a rectangular waveguide-section as a main body made of metallic material, an open end of waveguide-section working on microwave in a microwave cavity, a terminal end of waveguide-section closed by metallic material, a rotary movable body made of non-metallic material, and a driver for the movable body. A rotating angle or a position of the movable body is controlled, so that an impedance at the open end is varied and transmission status of microwave is changed, thereby variably controlling a standing wave distribution. Controlling the standing wave distribution allows an object in the cavity to be selectively heated or uniformly heated. Further, the standing wave produced in the microwave cavity is sequentially varied, so that the object can be selectively heated or uniformly heated.

Abstract: This invention relates to a dielectric heating device. More particularly, it relates to a dielectric heating device which employs microwave heating, suitable for heating or cooking foodstuffs and suitable for, but not restricted to, use as a domestic or institutional microwave oven.

Abstract: The microwave applicator for microwaves outputs from a guide (1) comprises an envelope (3) that forces microwaves to converge towards a focal point (16) by means of a complementary central reflector (4). A fraction of the waves reaches this point after reflection on two facets (11, 13), usually curved and concave, of the reflector (4) and the envelope (3), while the other fraction is reflected three times on three facets (10, 12 and 14), the last two facets of which form part of the envelope and one of which is concave for focussing. These devices can be used for removing a concrete surface, because the microwaves cause vaporisation at the focal point (16).

Abstract: Disclosed herein is a microwave oven with a magnetic field detecting device. The microwave oven includes a magnetron for generating microwaves and a wave guide for guiding the microwaves to a cooking chamber. A detection opening is formed in one side of the wave guide to allow a magnetic field generated by standing waves formed in the wave guide to be discharged from the wave guide. The magnetic field detecting device is formed on a board mounted on the wave guide to detect the magnetic field discharged through the detection opening.

Abstract: A microwave oven has an oven cavity with a wall (2) formed with a hole (6) covered on an external side of the wall by a metal launch box (8) and choke plate (7). A metal match plate (10) is mounted on the internal side of the wall (2) so that the match plate (10) and the launch box (8) form a launch cavity for delivering microwave energy to the cavity. The choke plate (7) has a peripheral choke channel which prevents leakage of microwave energy between the launch box (8) and choke plate (7), enabling the choke plate (7) and match plate (10) to be bolted to the wall (2).

Abstract: A microwave heating apparatus including a cavity for heating food, a first antenna, which projects into the cavity and is arranged to pass into or through the food in order to irradiate the food internally, and a second antenna arranged to supply microwave radiation into the cavity in order to irradiate the food externally. Microwave energy is supplied to the first and second antennae in such a way that the user can independently control the levels of microwave energy irradiated by the first and second antennae.

Abstract: The present invention relates to an apparatus and methods for performing chemical reactions. In particular, the present invention relates to an apparatus for heating chemical reaction mixtures. The apparatus applies one or more semiconductor based microwave generators making the apparatus suitable for parallel processing of chemical reaction mixtures. The invention further relates to methods for performing chemical reactions, e.g. methods for heating a plurality of samples simultaneously or sequentially, methods for monitoring a microwave heated chemical reaction, and methods where the optimum conditions with respect to parameters, such frequency and applied power can be determined for the system consisting of apparatus plus sample.

Abstract: A combination convection/microwave oven in which a food product is cooked by microwave energy from a source thereof and by a heated airflow provided by a thermal energy source and a blower. The food product is located in the near field of the microwave energy. The oven includes a controller that operates the thermal energy source and/or the blower according to temperature and or time to improve cooking results. The cooking procedure includes a soak interval during which the thermal energy source, the blower and/or the microwave energy source is turned off, whereby the temperature of the food product is permitted to equilibrate and thereby provide more uniform cooking. The food product may be located directly on the rack or in a microwave transparent or reflective container.

Abstract: A path for a material passes through an opening and along a segment through an off-peak region of an electric field. An E-plane bend delivers an electromagnetic wave to the segment. A standing wave is used to heat the material. The peaks or valleys are pushed or pulled by a movable surface or by changing the frequency of the electromagnetic wave. A rectangular choke flange is used at the opening to the segment. A curved segment connects the segment to another segment for heating the material. According to another aspect of the invention, a segment is used to heat just the edge of a planar material.

Abstract: The invention provides a dielectric heating device. The device includes a plurality of electrically conductive side walls which are electrically interconnected in use and arranged in series to define a heating cavity. At least one pair of adjacent side walls has its walls inclined to each other at a corner having an included angle selected from the group consisting of acute angles and obtuse angles. At least one electromagnetic power source capable of emitting electromagnetic radiation suitable for dielectric heating is arranged to feed waves of such radiation into the cavity with circular polarization of the waves, to cause the cavity to act as a multimode resonant heating cavity.

Abstract: A uniform heating structure for a microwave oven is provided. The structure of the invention includes: a magnetron for generating microwaves, a wave guide for guiding the microwaves generated by the magnetron, a pair of openings for radiating the microwaves guided by the wave guide in the form of circular polarized waves, and a cavity which is shaped in a polyhedron more than a rectangular and in which more than one interior walls constructing the polyhedron slope at a predetermined angle (&thgr;1) excepting a right angle with respect to a neighboring interior wall. With this structure, the microwaves generated by the magnetron are reflected to be delivered to food through a sloping interior wall of the cavity while being radiated to the cavity through the wave guide and the openings, thus ensuring a uniform distribution of the microwaves throughout the food and making the food uniformly cooked.

Abstract: A grain containment vessel equipped with one or more antennas and a vapor extraction system is disclosed. An electromagnetic heating pattern is established throughout the grain volume elevating the bulk temperature, while an air flow is applied throughout the grain volume. The electromagnetic energy desorbs the water and increases the vapor pressure and the air flow carries the heat and water from the containment vessel. A controlled amount of electromagnetic energy is introduced into the grain volume to reduce or eliminate fungus infestation and increase insect mortality.

Abstract: A device and a method for microwave feeding of an oven cavity by means of a coupling slot (1) which is fed by a waveguide. The a-dimension of the waveguide is significantly larger than the effective a-dimension of the slot. The slot comprised a radiating main slot part (5) and slot extensions (6,7) projecting from it at its respective sides, which extension have a substantially smaller cross-dimension than the b-dimension of the main slot part.

Abstract: A volatiles analyzer is disclosed that includes a source of microwave radiation that can selectively produce at least one predetermined frequency of microwave radiation. A cavity is in communication with the source. The analyzer includes an analytical pan balance with at least its balance pan in the cavity. The walls of the cavity form a polyhedron that focuses microwave energy of the predetermined frequency on the balance pan while supporting a plurality of TM and TE modes in the cavity.

Abstract: A volatiles analyzer is disclosed that includes a source of microwave radiation that can selectively produce at least one predetermined frequency of microwave radiation. A cavity is in communication with the source. The analyzer includes an analytical pan balance with at least its balance pan in the cavity. The walls of the cavity form a polyhedron that focuses microwave energy of the predetermined frequency on the balance pan while supporting a plurality of TM and TE modes in the cavity.

Abstract: A microwave heating system is provided including a microwave generator, a fluid pipeline having an upstream section and a downstream section, and a waveguide assembly connected to the microwave generator. The waveguide assembly includes a microwave distributor positioned in the fluid pipeline at a junction between the upstream section and the downstream section. The microwave distributor is in substantially straight line alignment with the upstream section proximal to the junction, while the downstream section is in substantially right angle alignment with the upstream section proximal to the junction. The microwave heating system substantially prevents or remediates gas hydrate blockages in the upstream section of the fluid pipeline at extended distances from the microwave generator. The microwave heating system may also simultaneously control a function of a device remotely positioned on the upstream section or power the remote device.

Abstract: The present invention relates to a microwave oven including a cavity having a certain area for cooking, a magnetron installed at the outside of the cavity for generating microwave, a waveguide installed at the side of the magnetron and its end extended inside of the cavity for transmitting the microwave inside of the cavity. The microwave oven comprises a bidirectional flow channel formed inside of the waveguide for transmitting microwave selectively inside of the cavity in accordance with cooking function, a microwave plate combined to inside of the waveguide so as to be rotational for guiding the microwave to selected direction between the two direction of the flow channel, and a plasma lamp installed adjacent to the side of the bidirectional flow channel for generating radiant energy by being heated by the microwave.

Abstract: A source provides an electromagnetic wave that has a range of frequencies. The source sweeps the frequency of the electromagnetic wave between a cutoff frequency and double the cutoff frequency. The location, angle, or effective angle of an opening is adjusted by an opening adjuster. A path for an electromagnetic wave has a short for creating a standing wave. The path has a movable surface that can push and pull the peaks and valleys of the standing wave so as to achieve more uniform heating of the material. A dielectric wheel pushes and pulls the peaks and valleys of a standing wave so as to achieve more uniform heating of a material. A dielectric structure has a surface that has a short side and a long side. A motor rotates the dielectric structure to push and pull the peaks and valleys of a standing wave so as to achieve more uniform heating of a material. A path has a first choke flange that has a width w1 and a second choke flange that has a width w2.

Abstract: A path for a material passes through an opening and along a segment through an off-peak region of an electric field. An E-plane bend delivers an electromagnetic wave to the segment. A standing wave is used to heat the material. The peaks or valleys are pushed or pulled by a movable surface or by changing the frequency of the electromagnetic wave. A rectangular choke flange is used at the opening to the segment. A curved segment connects the segment to another segment for heating the material. According to another aspect of the invention, a segment is used to heat just the edge of a planar material.

Abstract: A feed that provides circularly polarized microwave energy such as for energizing a microwave oven cavity. The feed includes a transformer to match a linearly polarized rectangular waveguide to a polarization waveguide section which may be circular or square in cross section. The polarization waveguide section contains an asymmetrical element that provides symmetry about a plane only. The asymmetrical element therefore introduces a difference in microwave electrical phase for polarizations which are respectively parallel to and perpendicular to the symmetry plane. A second waveguide section having a bend is also used in the feed assembly. The second waveguide section, which may for example be a bent section of circular waveguide, also presents an electromagnetic symmetry about a plane only. As a result, the two waveguide sections operating together provide circularly polarized energy at constant magnitude but continually rotating phase.

Abstract: A high frequency heating apparatus for heating an object to be heated is provided with an electromagnetic wave emission device for emitting electromagnetic waves, a local heating device capable of heating an optional portion of the object by the electromagnetic waves emitted from the emission device, and a control device for controlling the local heating device. The high frequency heating apparatus is further provided with a stage on which the object is placed, a protecting device for protecting the local heating device, a setting device and a detection device, so that the local heating device, the electromagnetic wave emission device or the stage is controlled in accordance with the setting device or detection device.