Device for supplying microwaves to a treatment chamber

Abstract

The invention relates to a device (1) for supplying microwaves to a treatment chamber (2), comprising a treatment chamber (2) and at least one waveguide (4) for supplying the microwaves to the treatment chamber (2). The waveguide (4) opens into a radiation element (8), which is designed such that circularly polarised electromagnetic waves can be radiated from the waveguide into the treatment chamber (2).

Description

[0001] DESCRIPTION

[0002] Device for supplying microwaves into a treatment room

[0003] The invention relates to a device for supplying microwaves into a treatment chamber, wherein the device comprises a treatment chamber and at least one waveguide for supplying the microwaves to the treatment chamber.

[0004] Numerous different devices are known in practice in which microwaves are fed into a treatment chamber in order to treat objects there using the energy supplied via the microwaves. The energy supplied via the microwaves can be used, for example, to warm or heat objects. It is also known that microwaves can be used to generate a plasma, which can then be used to treat objects, for example, to apply a coating to an object or to modify its surface.

[0005] The treatment room is usually surrounded by an electrically conductive enclosure to prevent unwanted leakage of the microwaves previously supplied to the treatment room. Various methods are known in practice for supplying the microwaves to the treatment room in order to carry out the intended treatment in the treatment room.

[0006] Some treatment rooms have a shape and dimensions adapted to the microwaves intended for the treatment, thus forming a resonance chamber for the supplied microwaves. Within the resonance chamber, standing waves and areas with a very high power density can then advantageously form within the treatment room.

[0007] In such resonance chambers, the microwaves can be fed into the treatment room, for example, via waveguides that open into the treatment chamber or its enclosure. It is also known for a treatment room to have one or more windows and horn antennas arranged outside the treatment room, through which the microwaves are radiated and then beamed through the windows into the treatment room.

[0008] The spatial distribution of the field strengths, and thus also the power density of the radiated microwaves, within the treatment room is largely determined by the resonance conditions within the treatment room, independent of the microwave supply. Changing this intensity distribution and the resulting adaptation to different objects to be treated with the microwaves in the treatment room is not possible with such resonance chambers, or only with considerable effort.

[0009] DE 10 2017 121 732 A1 and DE 10 2017 121 731 A1 describe various variants of a device for treating a product with microwaves. The microwaves are fed into a treatment chamber via a coaxial conductor. One end of the coaxial conductor extends into the treatment chamber. The microwaves are coupled out of the coaxial conductor through a lateral opening in the coaxial conductor and radiated into the treatment chamber. In this way, microwaves can be radiated within the treatment chamber in a direction predetermined by the opening in the coaxial conductor and used specifically to treat an object located in the treatment chamber.The intensity distribution of the microwaves within the treatment room is determined, regardless of the spatial design of the treatment room, not primarily by any resonance conditions that may not exist within the treatment room, but predominantly by the directed radiation of the microwaves from the coaxial conductors projecting into the treatment room.

[0010] For many treatments, it is considered advantageous to be able to supply the highest possible microwave power to the treatment room. Microwave generating devices are known that can generate sufficiently high microwave power to be supplied to the treatment room. However, the method of supply often limits the maximum microwave power that can be supplied when the device is used as intended.

[0011] It is therefore considered an object of the present invention to design a device for feeding microwaves into a treatment room in such a way that the treatment room can be supplied with the highest possible microwave power.

[0012] This object is achieved according to the invention in that the waveguide is connected at one end to a radiating element or opens into a radiating element, wherein the radiating element is designed such that circularly polarized electromagnetic waves are radiated from the waveguide via the radiating element into the treatment room. By appropriately designing the radiating element, high power can be fed into the treatment room from the waveguide and used to perform a treatment in the treatment room.

[0013] The inventive design of the radiating element significantly reduces the coupling of electromagnetic waves from the treatment chamber back into the waveguide. This is no longer relevant in many applications, since only circularly polarized and aligned electromagnetic waves that match the radiating element could couple back into the waveguide via the radiating element, and the proportion of these waves in the treatment chamber is negligible. Therefore, the radiating element should preferably be designed so that the electromagnetic waves emitted by the radiating element contain a high proportion of circularly polarized electromagnetic waves. It is advantageous if predominantly or exclusively circularly polarized electromagnetic waves are emitted by the radiating element.A person skilled in the art is familiar with various design options for a radiating element that emits circularly polarized electromagnetic waves, in particular predominantly or exclusively circularly polarized waves. Any necessary adaptation of known radiating elements to the properties of microwaves with a vacuum wavelength between 35 cm and 1 mm, as well as to the highest possible power outputs radiated by the radiating element, can be carried out with the specialist knowledge of a person skilled in the art.

[0014] The use of a suitably designed radiating element offers further advantages. According to an advantageous embodiment of the inventive concept, the device comprises a microwave generating device connected to the treatment chamber via the waveguide without an additional protective device, which would protect the microwave generating device from microwaves propagating from the treatment chamber via the waveguide toward the microwave generating device. With conventionally known methods of supplying microwaves via a waveguide into the treatment chamber, it must generally be expected that a significant portion of the power generated by the microwave generating device will couple back into the waveguide after being supplied to the treatment chamber and be transmitted to the microwave generating device.To prevent damage to the microwave generating device, protective devices such as an isolator are regularly placed between the microwave generating device and the treatment chamber. These devices reduce or prevent unwanted propagation of microwaves toward the microwave generating device. Due to the radiating element, which emits circularly polarized electromagnetic waves, a portion of the electromagnetic waves that can be coupled back into the waveguide from the treatment chamber is largely reduced to a power range that is no longer relevant, thus eliminating the need for a separate protective device to protect the microwave generating device from feedback microwaves.

[0015] This allows both the required installation space and the manufacturing costs for a device according to the invention to be significantly reduced.

[0016] According to a particularly advantageous embodiment of the inventive concept, the microwave generating device is designed such that it can generate a microwave power of more than 250 watts. It has been shown that with a suitably designed radiating element, such a high power can be readily supplied to the treatment chamber. In order to supply a high overall power to the treatment chamber, only one microwave generating device with a waveguide, or at least only a few microwave generating devices, is required, which further reduces the space required compared to conventional devices.

[0017] Optionally, the microwave generation device may include at least one solid-state microwave generator. Solid-state microwave generators are already known in practice, capable of generating and emitting microwaves with a sufficiently high power for many applications. Compared to a magnetron or a magnetron-based microwave generation system, a solid-state microwave generator or a solid-state microwave generation system requires less installation space, is considerably easier to operate, and can be better adapted to the properties of a device with a treatment chamber relevant for microwave transmission over a wider range.

[0018] To facilitate easy adaptation of the supplied microwaves to the treatment room, the microwave generating device can optionally be configured to allow the phase and / or frequency of the microwaves generated by the microwave generating device to be controlled. Solid-state microwave generators already offer simple control and adjustment of key properties such as frequency or phase within a comparatively wide range without the need for additional components.

[0019] In order to be able to feed the microwaves into the treatment room in a way that is as variable as possible, it is optionally provided that several waveguides arranged at a distance from one another lead into the treatment room. In this way, it is possible, regardless of the spatial design of the treatment room, to specifically irradiate a product treatment area with microwaves via several waveguides, each with a radiation element. The product treatment area is an area within the treatment room in which a product can be placed for treatment. The product treatment area can be defined by a platform or a storage area within the treatment room. The product treatment area can also be defined by a conveyor belt, with which a product can be conveyed into the treatment room for treatment and then out again.Since the microwaves emitted from the multiple waveguides do not significantly influence each other, the multiple waveguides can be arranged in a manner that appears advantageous with regard to the irradiation of the product treatment area, without having to take other waveguides or the spatial requirements of the treatment room into account.

[0020] The product treatment area can, for example, be irradiated as homogeneously as possible with microwaves from the multiple waveguides. In this case, the multiple waveguides can be connected to a shared microwave generation device. It is also conceivable for the product treatment area to be irradiated via multiple waveguides with different microwaves or different power levels, allowing easy adaptation to different requirements within the product treatment area. In this case, it is particularly advantageous if each waveguide is connected to a microwave generation device assigned solely to that waveguide.

[0021] According to an advantageous embodiment of the inventive concept, the treatment chamber is surrounded by a casing made of an electrically conductive material and / or a product treatment area within the treatment chamber is spaced from the mouth or an axial end of a waveguide within the treatment chamber or from the radiating element by a distance of less than three wavelengths, and preferably less than one wavelength. In this way, it can be achieved that a product arranged in the product treatment area is directly irradiated by the radiating element, and unwanted reflections or superimpositions of microwaves within the treatment chamber have no or only insignificant influence on the irradiation of the product.

[0022] For many applications, it is advantageous for the waveguide to be either a hollow waveguide or a coaxial waveguide. Microwaves can be transmitted shielded from the environment via hollow waveguides or coaxial waveguides. Suitable waveguides are known in practice in a wide variety of designs and can be easily adapted, for example, to spatial requirements or to the planned use and corresponding operation of the device.

[0023] To enable the most efficient and advantageous radiation of microwaves from the waveguide into the treatment chamber, a particularly advantageous embodiment of the inventive concept provides that the radiation element has a radiation plane oriented transversely to a longitudinal direction of the waveguide, in which an electrically conductive radiation structure is arranged. The radiation plane is preferably parallel and optionally flush with an adjacent area of ​​a casing of the treatment chamber. The radiation plane can also be oriented perpendicular to a preferred wave propagation direction of the emitted microwaves in the direction of the product treatment chamber.

[0024] According to a particularly advantageous embodiment of the inventive concept, the radiating element is connected off-center relative to a cross-sectional area of ​​the waveguide. The off-center and thus asymmetrical connection of the radiating element to the waveguide causes or supports the radiation of circularly polarized electromagnetic waves and suppresses unwanted feedback of microwaves from the treatment chamber back into the waveguide. The radiation of a circularly polarized electromagnetic wave has various advantages over the radiation of a non-circularly polarized electromagnetic wave. The radiation characteristics of an off-center, plate-shaped radiating element differ from the radiation characteristics of a radiating element connected centrally to the waveguide.The modified radiation characteristics of the off-center radiating element can advantageously be used for directed radiation of the microwave power within the treatment chamber. Another advantageous option is considered for the radiating element to have a plate-shaped radiating body with a surface oriented transversely to the longitudinal direction of the waveguide, the peripheral edge of which is predetermined such that circularly polarized electromagnetic waves, in particular predominantly or exclusively circularly polarized waves, are emitted. Various advantageous shapes of patch antenna elements, usually arranged on a circuit board, are known from practice. These can be used to influence and specify the properties of the electromagnetic waves emitted via this patch antenna element.In many cases, relevant findings obtained with such patch antenna elements can be used to specify the peripheral edge of a plate-shaped radiating element in an analogous manner so that a desired radiation characteristic is achieved and, in particular, that predominantly or almost exclusively circularly polarized electromagnetic waves are radiated from the plate-shaped radiating element.

[0025] It can optionally also be provided that the radiating structure has a plate-shaped radiating body with a recess arranged at a distance from a peripheral edge, wherein a radiating antenna projects into the recess and a peripheral edge of the recess is designed such that circularly polarized electromagnetic waves, in particular predominantly or exclusively circularly polarized electromagnetic waves, are radiated.

[0026] According to one embodiment of the inventive concept, the radiating element is embedded in a dielectric material such as, for example, a plastic material, glass, or ceramic in order to reduce the wavelength of the electromagnetic waves propagating from the waveguide to the radiating element. In this way, it is possible to reduce the installation space required for the arrangement and functioning of the radiating element. Furthermore, particularly with high microwave powers radiated from the waveguide via the radiating element and fed into the treatment chamber, an electrical short circuit, electrical flashover, or unwanted ionization, and the resulting damage to the radiating element or the adjacent region of the waveguide, can be avoided despite the small installation space.Suitable dielectric materials that do not absorb, or only absorb to a very small extent, electromagnetic waves propagating through the plastic material and at the same time significantly reduce the wavelength of the electromagnetic waves propagating through the dielectric material are known from practice.

[0027] When using a coaxial conductor as a waveguide, it can be provided, for example, that the radiating element for radiating the microwaves supplied through the coaxial conductor into the treatment chamber is arranged at an end of the coaxial conductor facing the treatment chamber, wherein the radiating element has a plate-shaped radiating body which is electrically conductively connected to the inner conductor, is not electrically conductively connected to the outer conductor, and is preferably oriented transversely to a longitudinal direction of the coaxial conductor, such that electromagnetic waves supplied via the coaxial conductor are radiated by the plate-shaped radiating body into the treatment chamber. It has been shown that such a plate-shaped radiating body is advantageously suitable for radiating a high microwave power and thereby supplying it to the treatment chamber.The plate-shaped radiating body is expediently adapted to the maximum microwave power intended for intended use of the device, which is to be supplied to the treatment room via the coaxial conductor. The dimensions of a surface of the plate-shaped radiating body are adapted to the wavelength of the microwaves in a known and advantageous manner. The thickness of the plate-shaped radiating body is predetermined depending on the material used for the plate-shaped radiating body so that the plate-shaped radiating body can withstand the supplied microwave power and is not excessively heated or damaged during operation. The plate-shaped radiating body can be made of metal, for example, and have a thickness of a few millimeters. With such a plate-shaped radiating element, microwave powers of more than 250 watts can be supplied to the treatment room.With a suitable design of the coaxial conductor and the plate-shaped radiating element arranged at its end, microwave powers of more than 500 watts, 750 watts, or more than 1,000 watts can be radiated into the treatment room via a single radiating element and, if necessary, a single plate-shaped radiating body. This makes it possible to supply a high microwave power to the treatment room via a single coaxial conductor.

[0028] Particularly when using a coaxial conductor, it is expedient, in order to minimize the required installation space, for the dielectric material to be arranged between an end face of an outer conductor of the coaxial conductor and the radiating element, which is arranged at a distance from this end face of the outer conductor and is not electrically connected to the outer conductor. The dielectric material can also be arranged around the radiating element, largely enclosing it or enclosing it on all sides, and can be located in the region of the radiation opening of a waveguide shaped as a coaxial conductor, so that the radiating element is not electrically connected to the coaxial conductor, or at least not directly to an outer conductor of the coaxial conductor, but rather, for example, only via an inner conductor to a coaxial conductor.The dielectric material can extend from a peripheral edge of the plate-shaped radiating element to the outer conductor of the coaxial conductor, thus forming electrical insulation between the radiating element and the outer conductor, or a surrounding housing area. Even when using a waveguide, it is advantageous for the radiating element to be non-electrically connected to the waveguide and, if necessary, to be additionally shielded from the environment by the dielectric material. It is also possible for the dielectric material to form a thin coating on the surface of the radiating element facing the treatment chamber.It has been found to be advantageous to avoid thin air gaps in the immediate vicinity of the radiating element and in particular in the vicinity of the plate-shaped radiating body and to fill them with the dielectric material if possible in order to achieve sufficient electrical insulation with a high dielectric strength, in particular at high microwave powers which are to be radiated via the plate-shaped radiating element.

[0029] In many areas of application, it is advantageous or necessary that the microwave power supplied to the treatment chamber is used to generate a plasma in the treatment chamber, which can be used to treat objects. In order to generate a plasma as efficiently as possible and to be able to use it in the treatment chamber for the intended treatment, according to an advantageous embodiment of the inventive concept, the treatment chamber is surrounded by a casing made of an electrically conductive material, that the casing has an irradiation opening at or in which the waveguide ends or opens and at or in which the radiating element is arranged and not electrically conductively connected to the casing, and / or that a cover made of a microwave-transparent dielectric solid material is arranged between the radiating element and the treatment chamber.The cover of the radiating element prevents a plasma generated in the treatment chamber from coming into contact with the radiating element, which could potentially damage the radiating element. The cover, made of microwave-transparent dielectric solid material, expediently extends over the entire irradiation opening and adjacent areas of the enclosure, so that a plasma generated in the vicinity of the irradiation opening by the microwaves radiated by the radiating element through the irradiation opening cannot immediately come into contact with the adjacent enclosure, and the degree of ionization of the generated plasma is not reduced excessively quickly by recombination of the electrons and ions of the plasma with the electrically conductive enclosure.

[0030] It may be appropriate for the cover made of microwave-transparent dielectric solid material to completely cover the enclosure and thereby shield all areas from the plasma in the treatment room.

[0031] Numerous solid-state dielectric materials, such as plastics or ceramics, are known from practice to be suitable for microwave applications. Quartz glass, aluminum oxide, or sapphire are particularly suitable as microwave-transparent solid-state dielectric materials, as they can withstand the high thermal stress often unavoidable in plasma particularly well. If necessary, separate cooling of the cover can be provided.

[0032] Covering the inlet opening or the entire enclosure can also be useful and advantageous for applications where no plasma is generated in the treatment chamber. In these cases, the cover can also be made of a suitable dielectric material that is less temperature-resistant than quartz glass. The cover can, for example, facilitate cleaning of the treatment chamber, which is often required at intervals, or it can shield the enclosure from the treatment chamber and protect it from impairment or damage that could be caused, for example, by byproducts or accompanying phenomena during the treatment of the objects. A cylindrical treatment chamber is advantageous for many applications. The cover can then, for example, be a quartz glass tube that is fitted into the cylindrical treatment chamber.

[0033] With a view to the most efficient and targeted radiation of the microwaves into the treatment chamber, one embodiment of the inventive concept can provide for the cover to have a curved outer surface in the region of the radiation opening, and / or for the radiating element to have a shape adapted to the curved outer surface. The curved shape of the radiating element, or the shape adapted to the outer surface of the cover, can ensure that the radiating element, with its surface facing the treatment chamber, rests against the cover in the region of the radiation opening without a gap.This avoids unwanted air gaps, which could lead to ionization of air or gas or electrical arcing in the vicinity of the plate-shaped radiating element and, especially at high microwave power levels, could lead to undesired impairment or damage to the radiating element or its surroundings. A curved shape of the surface of the radiating element can also provide advantageous radiation characteristics and, if necessary, focus the microwaves emitted by the radiating element in the treatment chamber.

[0034] According to a particularly advantageous embodiment of the inventive concept, two or more radiating elements are arranged at a distance from one another in the treatment chamber. The radiating elements designed according to the invention enable the coupling of high microwave power into the treatment chamber.If waveguides connected without a radiating element according to the invention or, for example, waveguides with conventional radiating elements without circularly polarizing radiation characteristics were used to radiate the microwaves into the treatment chamber, it could not be easily ruled out that microwaves reflected in the treatment chamber or radiated by another radiating element would feed back to the respective radiating element and be transmitted back into the waveguide, where they could propagate away from the treatment chamber and exit at an end of the waveguide opposite the treatment chamber or damage electrical or electronic components arranged there. By using the radiating elements designed according to the invention, the unwanted feedback of microwaves from the treatment chamber back into the coaxial conductor is reduced and, if necessary, largely prevented.Therefore, two or more radiating elements can be arranged at a distance from each other in the treatment room and simultaneously used to feed microwaves into the treatment room.

[0035] Particularly in the case of an off-center arrangement of the radiating elements relative to the respective supply waveguide, two radiating elements can be arranged on opposite sides of the treatment chamber. By radiating circularly polarized electromagnetic waves, in particular predominantly or exclusively circularly polarized electromagnetic waves, the proportion of electromagnetic waves in the treatment chamber that can be picked up via a radiating element and transmitted back into the connected waveguide can be reduced to such an extent that the feedback of the electromagnetic waves from the treatment chamber into the connected coaxial conductors can be neglected, and no additional shielding devices or protective measures are required.

[0036] It may be advantageous for each radiating element to be individually controlled and used independently of other antenna elements for feeding microwaves into the treatment room. The intensity and field distribution of the microwaves radiated into the treatment room can then be individually and variably specified. By arranging at least two radiating elements on the same side of the treatment room, the microwave radiation from this side of the treatment room and the intensity and field distribution generated from this side of the treatment room within the treatment room can be easily varied and specified in a wide variety of ways.

[0037] The following are examples of the inventive concept that are illustrated in the drawing. It shows:

[0038] Figure 1 is a schematic view of a device according to the invention with a microwave generating device, with a treatment chamber and with a waveguide which is connected to the microwave generating device and opens into the treatment chamber via a radiating element,

[0039] Figure 2 is a schematic sectional view of a differently designed device according to the invention for supplying microwaves into a treatment room, wherein the waveguide is designed as a coaxial conductor,

[0040] Figure 3 is a perspective sectional view of a coaxial conductor with a radiating element connected thereto with a plate-shaped radiating body,

[0041] Figure 4 is a plan view of a plate-shaped radiating body,

[0042] Figure 5 is a schematic sectional view of a partial area of ​​a treatment room in which an antenna element according to the invention is arranged, which is connected to a microwave generating device via a coaxial conductor, Figure 6 is a perspective sectional view of a device with a different design,

[0043] Figure ? a representation of a differently designed radiating element,

[0044] Figure 8 shows a further illustration of a radiating element with a different design, and

[0045] Figure 9 shows a further illustration of a radiating element with a different design.

[0046] Figure 1 schematically shows a device 1 according to the invention for treating products in a treatment chamber 2. The treatment chamber 2 is cylindrical and surrounded by a casing 3 made of an electrically conductive material, for example metal. The device has a waveguide 4, which is connected at one end 5 to a microwave generating device 6, and whose other, opposite end 7 opens into or terminates in the treatment chamber 2. A radiating element 8 is arranged at the end 7 of the waveguide 4 opening into the treatment chamber 2 and is connected or coupled to the waveguide 4. The radiating element 8 is designed such that it radiates—preferably predominantly or exclusively—circularly polarized electromagnetic waves into the treatment chamber 2.Undesired feedback of microwaves from the treatment chamber 2 back into the waveguide 4, which could then be transmitted to the microwave generating device 6 and damage it, is largely reduced by the design of the radiating element 8. Therefore, it is not necessary to arrange a protective device between the treatment chamber 2 and the microwave generating device 6, with which such feedback microwaves propagating in the direction of the microwave generating device 6 are suppressed or kept away from the microwave generating device 6.

[0047] Figure 2 schematically shows a sectional view of another embodiment of a device 1 designed according to the invention for supplying microwaves into the treatment chamber 2. As in all figures, the respective shapes and dimensions are for illustrative purposes only and, in particular, are not drawn to scale. An inner side 9 of the casing 3 is completely covered by a cover 10 made of a microwave-transparent, dielectric solid material. The cover 10 can, for example, be a tube made of quartz glass. Two irradiation openings 11 are formed on opposite sides of the casing 3.

[0048] A waveguide 4 designed as a coaxial conductor opens into each radiation opening 11, via which microwaves can be fed to the treatment room 2.

[0049] An end 12 of an electrically conductive outer conductor 13 of the waveguide 4, which extends into / leaves the treatment chamber 2, is electrically conductively connected to the casing 3. An electrically conductive inner conductor 14 of the waveguide 4 extends to the cover 10 and opens into the radiating element 8 or is connected to it. Located in the treatment chamber 2 is a product treatment area 15, depicted and outlined by a long dashed line, which is at a comparatively short distance of less than one wavelength of the radiated microwaves from the respective radiating elements 8.

[0050] The radiating element 8, shown in an enlarged detail view in Figure 3, has a plate-shaped radiating body 16, which is arranged transversely to a longitudinal direction of the waveguide 4 in the mouth region of the irradiation opening 11 or a transition region from the irradiation opening 11 to the treatment chamber 2. The plate-shaped radiating body 16 has a surface 17 facing the treatment chamber 2. The plate-shaped radiating body 16 is electrically conductively connected to the inner conductor 14, but not electrically conductively connected to the outer conductor 13. During operation of the device 1, microwaves can be supplied to the treatment chamber 2 via the waveguide 4, which are radiated into the treatment chamber 2 via the radiating element 8 through the cover 10.The radiating element 8 with the plate-shaped radiating body 16 arranged at an end 12 of the waveguide 4 facing the treatment chamber 2 causes the radiation of circularly polarized electromagnetic waves.

[0051] The radiating element 8 shown in a detailed view in Figure 3 is shown enlarged in a sectional perspective view in a surrounding housing. The plate-shaped radiating body 16 is surrounded by a pot-shaped radiating element housing 18, which is made of an electrically conductive material such as metal for contacting the casing 3 and for shielding the environment. The outer conductor 13 of the waveguide 4 designed as a coaxial conductor opens into the radiating element housing 18, which can be electrically conductively connected to the casing 3 via a fastening flange 19. The plate-shaped radiating body 16 is arranged at a distance from a rear side 20 of the pot-shaped radiating element housing 18. A distance is formed between the rear side 20 of the radiating element housing 18 and a surface 21 of the radiating body 16 facing away from the treatment chamber 2.An interior space 22 of the pot-shaped radiating element housing 18 is filled with a dielectric solid material, such as plastic or ceramic, not shown in Figure 3.

[0052] The surface 17 of the plate-shaped radiating body 16 facing the treatment chamber 2 has a predominantly rectangular peripheral edge 23, also shown in Figure 3, which has a diagonally extending section 24 at two opposite corners. The plate-shaped radiating body 16 is arranged off-center relative to the waveguide 4 and is connected off-center to the inner conductor 14 of the waveguide 4. In this way, it is achieved that predominantly to almost exclusively circularly polarized electromagnetic waves are radiated from the plate-shaped radiating body 16 into the treatment chamber 2.Of the electromagnetic waves coming from the treatment room and striking the radiating element 8 with the plate-shaped radiating body 16, only a correspondingly counter-circularly polarized portion can couple into the waveguide 4 via the radiating element 8 and then propagate in the waveguide 4 away from the treatment room 2. In this way, unwanted feedback from the microwaves supplied to the treatment room 2 out of the treatment room 2 and back into the waveguide 4 is largely suppressed.

[0053] Figure 4 shows, merely by way of example, a plan view of an identically designed radiating element 8 with a rectangular, pot-shaped radiating element housing 18. For clarity, this plan view shows the waveguide 4, concealed by the plate-shaped radiating body 16, with the outer conductor 13 and the inner conductor 14. The off-center arrangement of the plate-shaped radiating body 16 relative to the waveguide 4, which is designed as a coaxial conductor, is clearly visible.

[0054] Figure 5 shows, purely for illustrative purposes, a region of the treatment chamber 2 with an irradiation opening 11, a radiating element 8 arranged therein, and a waveguide 4 designed as a coaxial conductor and opening into the radiating element 8, wherein an end of the waveguide 4 facing away from the treatment chamber 2 is directly connected to the microwave generating device 6. The microwave generating device 6 has a solid-state microwave generator and is suitable and designed to generate a microwave power of more than 1,000 watts in continuous operation, which can be supplied to the treatment chamber 2 via the waveguide 4 and is radiated into the treatment chamber 2 by the radiating element 8.By dispensing with additional protective devices for the microwave generating device 6 against feedback microwaves propagating via the waveguide 4 from the treatment chamber 2 in the direction of the microwave generating device 6, a very space-saving and efficient supply of microwaves to the treatment chamber 2 is possible.

[0055] Figure 6 shows a perspective, sectional view of another device 1 designed according to the invention for supplying microwaves into the treatment chamber 2, with only one region of the treatment chamber 2. In contrast to the design shown in Figure 5, the waveguide 4 for supplying microwaves is designed as a rectangular hollow guide 25. The hollow guide 25, made of an electrically conductive material, is electrically conductively connected to the casing 3 of the treatment chamber 2. In contrast to Figure 1, the plate-shaped radiating body 16 of the radiating element 8 is connected to a transition element 26, which is arranged in an opening region in the hollow guide 25. The transition element 26 advantageously supports and promotes the transition of the microwaves from the hollow guide 25 via the radiating element 8 into the treatment chamber 2.

[0056] The radiating body 16, which is arranged at a distance from the cover 10, can be surrounded in an area 27 at the radiation opening 11 by a dielectric material which is held in position by the waveguide 25, the cover 10 and the casing 3.

[0057] Figures 7 to 9 show, by way of example, various embodiments of radiating elements 8, each provided and designed for the radiation of circularly polarized electromagnetic waves. In contrast to the radiating elements 8 shown previously, the radiating elements 8 shown in Figures 7 to 9 each have electrically conductive planar radiating structures 28, which are applied, for example, to a circuit board 29 or to a carrier plate made of a suitable dielectric material. The two radiating elements 8 shown in Figures 7 and 8 have an electrically conductive frame 30 with a recess 31 in which a radiating antenna 32 is arranged, which is connected in a suitable manner to the waveguide 4.The embodiment shown in Figure 9 has two spiral-shaped, radially outwardly projecting radiation arms 34, starting from a centrally arranged electrically conductive contact 33 with the waveguide 4.

[0058] The exemplary embodiments of planar radiating elements 8 shown as examples in Figures 7 to 9 are particularly suitable for combination with waveguides 4 which are also planar in design. Such radiating elements 8 can, with suitable adaptation and dimensioning, also be combined with waveguides 4 designed as waveguides or coaxial conductors, wherein a suitable transition for the microwaves from the waveguide into the planar structures 28 is expedient.

Claims

REQUIREMENTS 1. Device (1) for supplying microwaves to a treatment chamber (2), wherein the device (1) has a treatment chamber (2) and at least one waveguide (4) for supplying the microwaves to the treatment chamber (2), characterized in that the waveguide (4) is connected at one end to a radiating element (8) or terminates in a radiating element (8), wherein the radiating element (8) is designed such that circularly polarized electromagnetic waves are radiated from the waveguide (4) via the radiating element (8) into the treatment chamber (2).

2. Device (1) according to claim 1 , characterized in that the device (1) has a microwave generating device (6) which is connected to the treatment room (2) via the waveguide (4) without an additional protective device which would protect the microwave generating device (6) from microwaves which propagate from the treatment room (2) via the waveguide (4) in the direction of the microwave generating device (6).

3. Device (1) according to claim 2, characterized in that the microwave generating device (6) is designed such that the microwave generating device (6) can generate a microwave power of more than 250 watts and preferably more than 500 watts, 30 more than 750 watts or more than 1,000 watts.

4. Device (1) according to claim 2 or claim 3, characterized in that the microwave generating device (6) has at least one solid-state microwave generator.

5. Device (1) according to one of claims 2 to 4, characterized in that the microwave generating device (6) is configured to that the microwaves generated by the microwave generating device (6) can be controlled with respect to the phase and / or frequency of the microwaves.

6. Device (1) according to one of the preceding claims, characterized in that several waveguides (4) are arranged at a distance from each other and open into the treatment chamber (2).

7. Device (1) according to one of the preceding claims, characterized in that the treatment chamber (2) is surrounded by a covering (3) made of an electrically conductive material, and / or that a product treatment area (15) within the treatment chamber (2) is located at a distance of less than three wavelengths and preferably less than one wavelength from the orifice or axial end of a waveguide or from the emitting element (8).

8. Device (1) according to one of the preceding claims, characterized in that the waveguide (4) is a waveguide (25) or a coaxial conductor.

9. Device (1) according to one of the preceding claims, characterized in that the radiating element (8) has a radiating plane preferably oriented transversely to a longitudinal direction of the waveguide (4), in which an electrically conductive radiating structure is arranged.

10. Device (1) according to claim 9, characterized in that the emitting element (8) is arranged off-center relative to a cross-sectional area of ​​the waveguide (4).

11. Device (1) according to claim 9 or claim 10, characterized in that the emitting element (8) is a plate-shaped emitting body (16) having a surface (17) preferably oriented transversely to a longitudinal direction of the waveguide (4), the circumferential edge (23) of which is defined such that circularly polarized electromagnetic waves are emitted.

12. Device (1) according to claim 9 or claim 10, characterized in that the radiating element (8) has a planar radiating structure (28) with a recess (31) arranged at a distance from a circumferential edge, wherein a radiating antenna (32) projects into the recess (31) and a circumferential edge of the recess is designed such that circularly polarized electromagnetic waves are radiated.

13. Device (1) according to one of the preceding claims, characterized in that the emitting element (8) is embedded in a dielectric solid material.

14. Device (1) according to one of the preceding claims, characterized in that the treatment chamber (2) is surrounded by a covering (3) made of an electrically conductive material, that the covering (3) has an inlet opening (11) at which or in which the waveguide (4) ends or opens and at or in which the emitting element (8) is arranged and is not electrically conductively connected to the covering (3).

15. Device (1) according to one of the preceding claims, characterized in that a cover (10) made of a microwave-transparent dielectric solid material is arranged between the emitting element (8) and the treatment chamber (2).

16. Device (1) according to claims 14 and 15, characterized in that the cover (10) has a curved outer surface in the area of ​​the inlet opening (11), and / or that the emitting element (8) has a shape adapted to the curved outer surface.

17. Device (1) according to one of the preceding claims, characterized in that two or more emission elements (8) are arranged spaced apart from each other on the treatment space (2).

18. Device (1) according to claim 17, characterized in that at least two emission elements (8) are arranged on opposite sides of the treatment chamber (2).

19. Device (1) according to claim 17, characterized in that at least two emission elements (8) are arranged spaced apart from each other on the same side of the treatment room (2).

20. Device (1) according to one of the preceding claims, characterized in that the waveguide (4) has a transition element (26) in the region of the inlet aperture (11), wherein the transition element (26) is arranged and designed such that the transition element (26) facilitates the coupling of electromagnetic waves from the waveguide (4) into the emitting element (15).

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