Core temperature probe and system having the same

Abstract

The invention relates to a core temperature detector (1), comprising: a temperature measuring device (3) having at least one temperature sensor (9); and a signal transmission antenna (2) which is connected to the temperature measuring device (3) by means of a coaxial line (4), the temperature information acquired by the at least one temperature measuring device (3) being emitted by means of the signal transmission antenna (2) at a signal transmission frequency which differs from the microwave frequency, wherein the coaxial line (4) has at least one line resonating element (11a, 11b, 12) adjusted to the microwave frequency, and an electrically conductive strip (14a-14d) is present on at least one boundary surface of the at least one such line resonating element (11a, 11b), which is electrically connected to the inner conductor (5) or the outer conductor (6) of the coaxial line (4). The invention also relates to a microwave cooking appliance with a signal transmission antenna and a system. The invention can be advantageously applied in particular to ovens which are designed to work together with a core temperature detector and furthermore have a microwave function.

Description

Technical Field

[0001] This invention relates to a core temperature detector having at least one temperature sensor and a signal transmission antenna connected to said at least one temperature sensor, wherein temperature information acquired by said at least one temperature sensor can be transmitted via the signal transmission antenna at a signal transmission frequency different from the microwave frequency, wherein the at least one temperature sensor is connected to the signal transmission antenna via a coaxial line, and wherein the coaxial line has at least one line resonant element tuned to the microwave frequency. The invention also relates to a microwave cooking appliance having a cooking chamber capable of radiating microwaves at a predetermined microwave frequency, the microwave cooking appliance having a signal transmission antenna for transmitting signals at a signal transmission frequency different from the microwave frequency and having a signal path particularly guided through the oven wall, wherein said signal path is at least segmentally a coaxial line, and said coaxial line has at least one line resonant element tuned to the microwave frequency. The invention further relates to a system having a microwave cooking appliance and at least one such core temperature detector, wherein the system is configured to: wirelessly transmit signals at a signal transmission frequency between the signal transmission antenna of the core temperature detector and the signal transmission antenna of the microwave cooking appliance. The invention is particularly advantageously applicable to ovens configured to work in conjunction with a core temperature detector and further having microwave functionality. Background Technology

[0002] It is known that for ovens that also have microwave functionality, the following problem occurs: microwave energy coupled into the signal transmission antenna of the core temperature detector can interfere with or even damage components connected to the signal transmission antenna, such as temperature sensors and circuits.

[0003] WO 2017 / 029059 A1 discloses a core temperature detector. The core temperature detector has at least one temperature sensor and a signal transmission antenna connected thereto. Temperature information acquired by the at least one temperature sensor can be transmitted via the signal transmission antenna at a signal transmission frequency different from the microwave frequency. The at least one temperature sensor is connected to the signal transmission antenna via a coaxial line, and the coaxial line has at least one Lambda(λ) / 4 line resonant element tuned to the microwave frequency. Furthermore, a microwave cooking appliance with a cooking chamber capable of radiating microwaves is disclosed. The microwave cooking appliance has a signal transmission antenna arranged in the cooking chamber for transmitting signals at a signal transmission frequency different from the microwave frequency, and a signal line guided through the oven wall. The signal line is at least segmentally coaxial, and the coaxial line has at least one λ / 4 line resonant element tuned to the microwave frequency. The system thus constructed can wirelessly transmit signals at the signal transmission frequency between the signal transmission antenna of the core temperature detector and the signal transmission antenna of the microwave cooking appliance.

[0004] EP 1 757 862 B1 discloses an oven for cooking food, comprising: a cooking chamber accessible through an oven door; a device configured to generate and radiate microwaves for propagation within the cooking chamber; a control device configured to process signals received from an external source and control the microwave generating and radiating device for operation based on the signals received from the external source; an active temperature probe configured to be introduced into food arranged inside the oven's cooking chamber and the temperature probe having a plurality of temperature sensors distributed along the active probe at predetermined intervals between each other, wherein the sensors are electrically connected to the control device to transmit external signals to the control device, wherein the control device is configured to: receive temperature control signals from predetermined sensors among the sensors and change the operation of the microwave generating and radiating device when it is determined that the temperature control signal has reached a predetermined value, wherein the control device is configured to: receive and compare signals related to the temperature detected by the sensors, identify a signal corresponding to a maximum temperature and select and use it as the current temperature control signal, the current temperature control signal being compared with a predetermined temperature value to change the operating mode of the microwave generating and radiating device accordingly. The problem of unintended microwave coupling into the circuit was not mentioned.

[0005] EP 2 163 823 A1 relates to a cooking process detector for a cooking appliance used for cooking food, the cooking process detector having a tip, a handle, and at least one temperature sensor that can be at least partially inserted into the food, wherein the output data of at least one first temperature sensor can be used to adjust at least one microwave source of the cooking appliance, and the first temperature sensor is surrounded by a microwave-absorbing material; and relates to a cooking appliance having such a cooking process detector. However, such shielding is not very practical for signal transmission antennas.

[0006] DE 29 35 282 A1 discloses a temperature measuring device for wirelessly monitoring the temperature of an object. This device includes a passively excitable temperature measuring detector and a transmitting / receiving unit for externally excitable electromagnetic waves, serving as an information carrier for the corresponding object temperature. A choke device is disclosed to prevent microwave signals from entering the internal space of the temperature measuring detector. The location and structure of the choke device are not further explained. Summary of the Invention

[0007] The object of the present invention is to at least partially overcome the disadvantages of the prior art and, in particular, to provide a compact, robust and inexpensive feasible solution that effectively protects the components of the core temperature detector from microwave signals coupled in via the signal transmission antenna into the cooking chamber of a microwave cooking appliance.

[0008] This task is solved according to the features of the independent claim. Preferred embodiments can be particularly understood from the dependent claims.

[0009] This task is accomplished by a core temperature detector comprising: at least one temperature measuring device having at least one temperature sensor; and a signal transmission antenna connected to the temperature measuring device via a coaxial line, wherein temperature information acquired by the at least one temperature measuring device can be transmitted via the signal transmission antenna at a (data) signal transmission frequency different from the microwave frequency, wherein the coaxial line has at least one line resonant element tuned to the microwave frequency, and a conductive sheet is present at at least one boundary surface of at least one such line resonant element, the conductive sheet being electrically connected either to the inner conductor or the outer conductor of the coaxial line.

[0010] At least one additional reflection point (Stoßstelle) is generated along the coaxial path of the microwave using a conductive sheet in a space-saving, robust, and cost-effective manner. The resulting impedance abrupt change effectively prevents microwave signals from reaching electrical and / or electronic components of the core temperature detector, such as temperature sensors, integrated circuits, resistors, coils, and capacitors, from the outside via the signal transmission antenna. Therefore, the core temperature detector or its interior is particularly insensitive to microwave interference.

[0011] On the other hand, this enables not only passive but also active signal processing and generation in the core temperature detector without causing adverse signal interference or even damage or destruction to the circuitry.

[0012] Because the core temperature sensor can also be used in cooking appliances that do not have microwave functionality, but have, for example, cooking appliances with or without steam functionality, users advantageously do not need to pay attention to which core temperature sensor to use in which appliance.

[0013] A core temperature detector can also be called a food thermometer or temperature probe. The core temperature detector can particularly have a front-side needle-like or pin-shaped section (“measuring section”) by means of which the core temperature detector can be inserted into the food to be monitored, and the core temperature detector has a gripping portion adjacent to the measuring section at the rear. At least one temperature sensor can be arranged in the measuring section. In the case of multiple temperature sensors, they can be arranged in a row along the longitudinal direction in the measuring section. The measuring section can particularly have a hollow cylindrical sleeve (e.g., made of metal or ceramic, especially stainless steel), which is closed at the front tip and at least one temperature sensor is mounted in the measuring section. The core temperature detector is typically configured to transmit at least one (“temperature”) signal via a coaxial line to a signal transmission antenna for wireless transmission at a signal frequency, wherein the temperature signal has at least one temperature information acquired by means of at least one temperature sensor and, if necessary, processed by an associated temperature measuring device. Typically, data signals can also be received at signal frequencies via a signal transmission antenna, allowing the signal transmission antenna to be constructed as a combined transmit / receive antenna in an improved embodiment.

[0014] The signal transmission antenna can be located in or extend from the grip.

[0015] The core temperature sensor is wirelessly positioned, or rather, designed for wireless signal transmission, thanks to its signal transmission antenna. This offers the advantage that the user can insert it into the food being cooked on the sideboard and then place the food into the cooking appliance. The advantages of wireless signal transmission include avoiding the need for cable connectors in ovens and related disadvantages such as microwave leakage radiation, steam escape, hot air escape, and oxidation of contact transitions.

[0016] Commonly used microwave frequencies are in the range of 2.4 GHz to 2.5 GHz, for example, 2.45 GHz. However, microwave frequencies in the range of 902 MHz to 928 MHz are also known to be used. The coaxial line has at least one line resonant element tuned to the microwave frequency, which in particular includes: the line resonant element being specifically matched to a particular microwave frequency or a particular microwave band, and a core temperature detector being thus configured for use in microwave appliances utilizing microwaves of such frequencies.

[0017] The commonly used signal frequencies fall within the range of 433.05 MHz to 434.79 MHz. This ISM band advantageously allows for data or information transmission using widely available and inexpensive data transmission components. However, in principle, other bands such as those between 13.553 MHz and 13.567 MHz, 26.957 MHz and 27.283 MHz, 40.66 MHz and 40.70 MHz, 863 MHz and 870 MHz, and 902 MHz to 928 MHz (when not used for microwaves) can also be used. Other signal frequency bands can also be used in principle, even if there are regulatory obstacles, provided that freely usable frequencies from the ISM band are not involved.

[0018] As is known in principle, coaxial circuits have an inner conductor and an outer conductor. The volume space between the inner and outer conductors, as is common for coaxial circuits, is composed of or has such a material. This material can be solid or gaseous. If the volume space is filled with or composed of a solid substance, the solid substance can exist as a solid and thus can also be called an "insulator." The use of insulators is particularly advantageous for providing resonant circuit sections with high dielectric conductivity or relative permittivity. The insulator can be a compact insulator in the sense that it has no or almost no porosity. In an improvement, the insulator can be a pre-fabricated component.

[0019] Microwave and data signals are transmitted along a coaxial line. One improvement is that the coaxial line has an inner conductor composed of wire segments and an outer conductor composed of conductive sleeves, particularly metal sleeves, wherein the metal sleeves are at least sectionally also sleeves for measurement sections. The outer conductor is particularly in the shape of a cylindrical tube with a defined inner diameter. The wire segments extend parallel to and centrally within the metal sleeve and have a defined diameter. The wire segments can have a circular cross-section. The wire segments can be, for example, copper wire. The wire segments can extend as signal transmission antennas, such that one section of the wire can constitute a signal transmission antenna and another section of the wire can constitute a section of the coaxial line. The outer conductor, particularly in the form of a metal sleeve, is advantageously made of stainless steel, as stainless steel is durable and inexpensive.

[0020] The circuit resonator tuned to microwave frequencies specifically corresponds to a coaxial line segment of defined length that matches the microwave frequency or wavelength. At at least one endpoint or at least one boundary of the circuit resonator, the relative permittivity ε of the materials between the inner and outer conductors is adjusted. r To have different relative permittivity ε r The transition of the adjacent material causes a corresponding impedance abrupt change there, which, in conjunction with the length of the circuit resonator, results in a change in the impedance. In other words, the circuit resonator is adjacent at its boundary to a material with a different relative permittivity ε for microwaves. r Adjacent coaxial line segments, especially those adjacent to adjacent line resonant elements. Targeted mismatches are generated through these line resonant elements, and because these mismatches cause impedance abrupt changes at the boundary surface (also known as the "reflection point"), most of the microwaves are reflected back through these impedance abrupt changes. The relative permittivity ε at the boundary surface... r The greater the difference, the higher the reflection coefficient tends to be. A coaxial line section with a line resonant element can also be called a resonant line or a resonant line section. Unless the context indicates otherwise, line resonant element and resonant line section can be used interchangeably.

[0021] One improvement is that the volumetric space between the inner and outer conductors is a hollow cylinder, through which the inner conductor is guided, particularly centrally. The boundary surface then corresponds to the base surface of the hollow cylinder. A particularly efficient improvement is that the outer periphery of the tubular volumetric space extends to the outer conductor, and if this is not feasible, extends as close to the outer conductor as possible. A particularly efficient improvement is that the inner surface of the volumetric space extends to the inner conductor, and if this is not feasible, extends as close to the inner conductor as possible. Thus, in one improvement, the spacing or gap size can be only a fraction of a millimeter.

[0022] One improvement is that the non-conductive volume space is composed of, filled with, or at least contains ceramics. Ceramics have the advantage of high thermal, mechanical, and chemical resistance. Furthermore, ceramic bodies made of ceramic materials with high electrical insulation can be used. Suitable engineering ceramics can be, for example, those with a typical relative permittivity ε between 6 and 15. r Alumina (Al₂O₃) or aluminum oxide with a typical relative permittivity ε between 20 and 40. r Zirconia (ZrO2) is used. Alternatively, glass or glass-ceramics can be used as the material. Resonant circuits filled with ceramics can also be called "ceramic circuits," etc. In improved schemes with an insulator between the inner and outer conductors, advantageously very small tolerances should be maintained. The gap between the inner and outer conductors should be advantageously reduced to a minimum. Microwaves coupled in via the signal transmission antenna are at least partially reflected at the boundary of the insulator facing the signal transmission antenna, because the insulator causes an impedance change there due to the material transition from, for example, air to the insulator. The portion of the microwaves that is not reflected there but continues to propagate along the insulator experiences another impedance change at the boundary of the insulator away from the signal transmission antenna and is therefore at least partially reflected back to the signal transmission antenna. Radio signals, however, are allowed to pass with almost no loss.

[0023] One improvement is that the non-conductive volume space between the inner and outer conductors of at least one circuit resonant element is filled with air (ε). r = 1) Composition. This is particularly advantageous for providing circuit resonant elements or resonant circuit sections with low dielectric conductivity or relative permittivity. In particular, the use of air enables a particularly inexpensive and simple structure. Air-filled resonant circuits can also be called "air circuits".

[0024] A coaxial line has at least one line resonant element tuned to a microwave frequency. This can include: the coaxial line having exactly one line resonant element tuned to a microwave frequency, or the coaxial line having multiple line resonant elements arranged in series along the extension direction of the coaxial line. An improvement advantageous for strong attenuation or filtering of microwaves along the coaxial line is that the series-connected line resonant elements alternately have high and low dielectric constants, thus resulting in particularly high impedance abrupt changes. For example, they can be arranged in the order of glass or ceramic lines, air lines, and other glass or ceramic lines. However, it is also possible, for example, to use rows of multiple adjacent resonant lines filled with a solid material, provided their relative dielectric constants are significantly different. For example, two adjacent resonant lines can be equipped with corresponding insulators with significantly different relative dielectric constants, such as those having ε... r =6 or ε r Two ceramic circuits with a voltage of 40.

[0025] The sheet material is particularly perpendicular to the inner conductor; that is, its normal vector is oriented parallel to the inner conductor, or its principal surfaces are oriented perpendicular to the inner conductor. An improvement is that the conductive sheet is constructed in the form of a perforated disc. The sheet material can, in particular, be placed on the base surface of a hollow cylindrical body of a circuit resonant element adjacent to the coaxial line, with one of its base surfaces. The conductive sheet can, in particular, completely cover the base surface of the hollow cylindrical body.

[0026] One design option is to use a metal sheet as the conductive pad. This is particularly inexpensive and advantageously offers high conductivity. The metal can be, for example, copper, silver, brass, aluminum, or alloys thereof. Alternatively, the conductive pad can be a ceramic sheet made of a ceramic material with good conductivity.

[0027] One design approach involves a sheet thickness less than 10%, particularly 5%, or especially 2%, of the microwave wavelength. This thickness (Stärke) can also be referred to as "thickness" (Dicke) or, in relation to the microwave propagation direction, "length." Because the length of the sheet, or the corresponding length of the coaxial "sheet circuit," is less than the microwave wavelength, impedance transformation can be advantageously disregarded; only impedance abrupt changes between different coaxial circuit impedances need to be considered. Therefore, to determine the reflection coefficient at the reflection point between the sheet and at least one adjacent circuit resonant element, the real impedance of the sheet can be used directly. This significantly simplifies the design of the coaxial circuit.

[0028] One design approach is to use at least one line resonant element that is a Lambda(λ) / 2 line resonant element. Taking into account its relative permittivity, the length of the λ / 2 line resonant element corresponds to half or more times the wavelength of the microwave radiation. The λ / 2 line resonant element can typically have a length of λ / 2 or typically has a length of λ / 2 + n·λ / 2, where n = 0, 1, 2, 3, ...

[0029] One design approach is to use at least one λ / 4 line resonant element. Taking into account its relative permittivity, the length of the λ / 4 line resonant element corresponds to one-quarter of the wavelength of the microwave radiation. λ / 4 line resonant elements can typically have a length of λ / 4 or typically have a length of λ / 4 + n·λ / 2, where n = 0, 1, 2, 3, ...

[0030] In the case of multiple line resonators, in one improvement, all line resonators can be λ / 4 line resonators. In another improvement, all line resonators can be λ / 2 line resonators. However, generally speaking, in the case of multiple line resonators, their type, number, and series arrangement are arbitrary in principle, and for example, at least one λ / 4 line resonator can coexist with at least one λ / 2 line resonator. The number of line resonators can be related, for example, to the desired reflection coefficient, achievable quality, and desired structural compactness. For example, a series sequence of three λ / 4 line resonators or a series sequence of λ / 4 and λ / 2 line resonators can be used. The last improvement is particularly advantageous because it achieves high filtering performance, especially as high as that of three λ / 4 line resonators, but with less manufacturing and installation costs and a shorter overall length of the line resonators.

[0031] One design involves a coaxial line having an inner conductor formed by wire segments and an outer conductor formed by a metal sleeve, and at least one resonant element having a hollow cylindrical insulator, particularly a ceramic body, fitted onto the inner conductor and extending radially or almost to the outer conductor. This arrangement is particularly robust and inexpensive to implement and easy to assemble. Furthermore, the insulator can be constructed in a particularly compact and geometrically simple manner.

[0032] One design option is that the insulator material has a dielectric constant ε between 6 and 40. r This advantageously enables high impedance abrupt changes. Furthermore, it is advantageous that this allows for the realization of shorter material volumes using inexpensive materials.

[0033] One design involves using an insulator material with a thermal conductivity κ of at least 20 W / (m·K), thereby enabling the insulator to be advantageously used as an efficient thermal bridge between the inner and outer conductors. This, in turn, allows for efficient heat conduction of the microwave energy converted into heat in the circuit resonant element to the outer conductor, which is at least partially at the temperature of the food being cooked. For example, alumina is suitable as an insulator material.

[0034] One design involves a coaxial line with two spaced-apart line resonant elements made of ceramic or glass, with an air gap between them forming a resonant circuit. This structure allows for advantageous compact implementation and strong microwave attenuation. This design can also be described as follows: the coaxial line has two spaced-apart line resonant elements with insulators made of ceramic or glass, separated by air-filled line resonant elements or air circuits, or with an air gap between them forming a resonant circuit. Typically, the insulator itself or the coaxial line segment that generates the line resonance can be referred to as or considered as a line resonant element.

[0035] One improvement involves a core temperature detector having a substrate connected to an inner conductor, where a freely extending conductor circuit electrically connected to the inner conductor is located. This conductor circuit has a free length of λ / 4 (the so-called "λ / 4 stub") along its direction. The λ / 4 stub is open-circuited (especially unconnected and therefore unloaded) and causes unloaded operation at its free end, which is converted into a short circuit at the contact point. This advantageously allows for further retroreflection of the microwave signal at the substrate. The λ / 4 stub has a wavy orientation, thereby advantageously achieving a particularly compact structure, especially short in the longitudinal direction of the core temperature detector. The wavy orientation can be, for example, sinusoidal or meandering. The λ / 4 stub can also have a curved, coiled orientation.

[0036] For example, the substrate can be made of ceramic or circuit board materials, such as FR4 or polyimide. The substrate can be clamped, pressed, and / or soldered to the inner conductor at corresponding contact portions or contact points. On the substrate, in addition to a λ / 4 stub leading out from the contact portion, at least one additional (“connection”) conductor circuit is led out from the contact portion, which is guided to the temperature measuring device and electrically connected to the inner conductor through the contact portion. The conductor circuit can be, for example, a copper conductor circuit.

[0037] The gaps can be filled, especially with metal, particularly copper. The inner conductor, especially when it exists in the form of a wire segment, can be pressed into the gap and soldered there to the conductor circuit. However, the contact between the inner conductor and the substrate can also be achieved in other ways, such as without gaps, for example, by simple soldering.

[0038] An improvement advantageous for achieving a particularly compact structure is that a λ / 4 stub is arranged on a side of the substrate, away from the side where at least one temperature sensor is located. The temperature measuring device, particularly its at least one temperature sensor, can, for example, be electrically connected to the inner conductor at the location of the HF short circuit on the conductor circuit. The temperature measuring device, particularly its at least one temperature sensor, can form a common node with the inner conductor along with the conductor circuit.

[0039] One improvement is that the temperature measuring device has at least one temperature sensor applied to a substrate. Another improvement is that the temperature measuring device additionally includes one or more components applied to the substrate, which, for example, process, digitize, or filter the measurement signal generated by the at least one temperature sensor. Alternatively, the at least one temperature sensor and / or at least one component can be connected to the substrate via at least one electrical line.

[0040] One improvement is that the temperature measuring device is a passive temperature measuring device, that is, it obtains energy for its operation specifically from externally generated interrogation signals. Such a temperature measuring device can be constructed in a particularly robust and inexpensive manner.

[0041] One improvement is that the temperature measuring device is a surface wave (OFW) temperature measuring device. Thus, at least one temperature sensor is an OFW temperature sensor, and the substrate is advantageously a ceramic substrate. Other optional components can include, for example, an OFW filter. The advantage of using an OFW temperature sensor, especially with a ceramic substrate, is that the temperature measuring device is highly heat-resistant (e.g., exceeding 200°C) and robust. OFW temperature measuring devices are particularly capable of being implemented, for example, as a passive, remotely readable temperature detector in the form of a radio-readable transponder.

[0042] One improvement is that the temperature measuring device is an electrically operated (non-OFW) temperature measuring device. It can include at least one electrically operated temperature sensor, such as an NTC element or a thermocouple, such as a Pt or PtRh thermocouple. The temperature measuring device can additionally have one or more electrical and / or electronic components that process, for example, the measurement signal generated by the at least one temperature sensor, such as digitizing it, filtering it, formatting it, etc. The substrate can also be a ceramic substrate or an FR4 substrate.

[0043] Electrically operated temperature measuring devices can be passive temperature measuring devices.

[0044] In principle, the temperature measuring device can be an active or self-operating temperature measuring device, having at least one electrical accumulator and at least one electrical or electronic component powered by the accumulator, and particularly capable of independently generating at least one temperature signal. Such components can include, for example, at least one microcontroller, amplifier, filter, resistor, capacitor, inductor, and / or bipolar transistor or field-effect transistor, etc. Self-operating circuitry, in particular, enables active signal processing and signal generation within the core temperature detector. The principle of active signal processing and extended information transmission through digital data processing, such as through a microcontroller, has the advantages of enabling bidirectional exchange of large amounts of information, while also allowing for adjustments or improvements during the production phase or, in special cases, during the customer's product runtime via software updates. The electrical accumulator can be a rechargeable battery, a non-rechargeable battery, a supercapacitor, etc. The accumulator can be disposed on or next to a substrate.

[0045] Alternatively, temperature measuring devices can be used with both OFW and non-OFW components.

[0046] One improvement is to have at least some components exist as SMD components, which enables particularly simple assembly.

[0047] One improvement involves arranging at least one microwave filter, composed of conventional electrical or electronic components, on a substrate. This utilizes the fact that the arriving microwave energy is so low that it no longer damages the conventional components. The microwave filter is suitable for signal transmission frequencies, for example, in the 433 MHz range. An advantageous improvement that is particularly easy to implement is that the microwave filter is a passive microwave filter. The microwave filter can be a single-stage or multi-stage microwave filter.

[0048] One improvement is that if the signal transmission frequency is lower than the microwave frequency, then the microwave filter is a low-pass filter. This is particularly easy to implement when its components are discrete SMD components. Low-pass filters can be constructed, for example, as LC low-pass filters, RL low-pass filters, RC low-pass filters, RCL low-pass filters, OFW filters, etc.

[0049] Microwave filters are positioned, in particular, between the inner conductor on the substrate and the rest of the circuit (e.g., a temperature measuring device with at least one temperature sensor and possible active circuitry) to advantageously further protect the rest of the circuit from microwave influence.

[0050] One design approach involves implementing the antenna in a way that minimizes reflection loss at microwave frequencies; in other words, the antenna is adapted to absorb as little microwave power as possible. This adjustment can be achieved by appropriately setting the length, diameter, and / or shape of the antenna according to its mechanical design. These parameters, in turn, determine the impedance "detected" by the antenna at the input of the microwave filter.

[0051] One design involves the core temperature detector or its outer conductor, particularly the sleeve, being wholly or partially filled, with at least one non-conductive or insulating filler, particularly cast or foam-filled, having a significantly smaller coefficient of expansion α compared to air, but with a relative permittivity (ε) at least similar to air. r ≈1) At least nearly identical relative permittivity. This is based on the observation that rapid temperature changes can cause damage due to the expansion characteristics of air surrounding the core temperature detector (e.g., in the air lines and / or substrate areas), such as microcracks or cracking at the seals at the ends of the stainless steel sleeve for the first conductive sheet used as the sealing sheet. Furthermore, the filler should have a suitable thermal conductivity λ. W Therefore, regarding air circuits, the air volume is replaced by a volume composed of filler material, which can be solid, especially porous solid, after hardening if necessary. The filler material can, for example, be a castable and subsequently hardened filler or hardened foam. The core temperature sensor or outer conductor is wholly or partially filled with at least one filler material, which includes filling the otherwise air-filled volume space within the core temperature sensor or outer conductor with filler material. For at least one filler material, "at least nearly the same relative permittivity as air" can in particular include having a relative permittivity in the range of 1 < ε. r Within the range of <3, especially in the range of 2<ε r Within the range of <3, because for ε r >2 is comparable to ε r <2 represents significantly more suitable materials.

[0052] One design is that at least one filler has a thermal conductivity λ W At least two types of fillers that are significantly different in aspect, wherein the outer conductor, especially the sleeve, is sectionally filled with one type of filler along the longitudinal extension of the outer conductor, or, in the case of two fillers, sectionally filled with one or the other type of filler. This produces the advantage that the thermal conductivity, for example, along the longitudinal extension and / or relative to the outer conductor, can be specifically matched to the components present in the respective sections.

[0053] For example, in the area of ​​the temperature sensor, a higher thermal conductivity from at least one temperature sensor to the outer conductor is advantageous, thereby enabling at least one temperature sensor to respond more quickly and accurately to ambient temperature or its changes. Higher thermal conductivity can also be advantageous in the area of ​​the air line, allowing for more efficient cooling there, as microwave radiation power should also be reduced to decrease filter self-heating.

[0054] In the remaining sections of the substrate (other than at least one temperature sensor), the lower thermal conductivity of the filler can be advantageous to prevent thermal interference between temperature sensors, thus avoiding, for example, back-side thermal short circuits between temperature sensors. In other words, while the temperature sensors should be well coupled to the local sleeve temperature, they should not be in a common back-side "isothermal" thermal lake. This is particularly advantageous when different temperature zones in the food can be measured, as this allows for extended cooking information (e.g., cooking information about temperature gradients in the food), or, for example, the identification of incorrect connections. For example, in the case of a young chicken, the tip of the core temperature detector might already be inside its hollow abdominal cavity, thus the temperature information from the detector tip would be erroneous, indicating ambient temperature rather than meat temperature.

[0055] One improvement is that the signal transmission antenna is embedded in or surrounded by the filler. Here, two properties are particularly important for the filler: firstly, a significantly higher dielectric constant than air (e.g., where ε0 is less than ε0). r (≥6), thus the antenna size can be smaller than in the case of air filling, and on the other hand, the probability of electrical breakdown due to the filler having a low degree of ionization or good electrical insulation properties should be kept low. Specific implementations can be determined, for example, through experiments or simulations. The signal transmission antenna and filler can be mounted, for example, in a non-conductive sleeve made of plastic within the core temperature detector. The filler can exist as an integral part of the body.

[0056] The task is also solved by a microwave cooking appliance having a cooking chamber capable of radiating microwaves at a predetermined microwave frequency, the microwave cooking appliance having a signal transmission antenna for transmitting signals at a signal transmission frequency different from the microwave frequency, and a signal path specifically guided through the oven wall, wherein the signal path is at least segmentally a coaxial line and wherein the coaxial line has at least one line resonant element or resonant line segment tuned to the microwave frequency.

[0057] The coaxial circuitry of microwave cooking appliances can be constructed in a manner similar to that described in WO 2017 / 029059 A1, and particularly similar to the coaxial circuitry of the aforementioned core temperature detector. Microwave cooking appliances with such coaxial circuitry configured as antenna leads produce the same advantages as the coaxial circuitry of the core temperature detector.

[0058] One improvement is that the microwave cooking appliance is a household appliance, especially a kitchen appliance. Another improvement is that the microwave cooking appliance is a standalone microwave appliance. Yet another improvement is that the microwave cooking appliance is a combination microwave / oven appliance, such as an oven with integrated microwave functionality. The cooking appliance can also have a steam cooking function. The microwave cooking appliance can have a magnetron or a semiconductor-based microwave generator to produce microwaves.

[0059] Furthermore, the task is solved by a system comprising a microwave cooking appliance as described above and at least one core temperature detector as described above, wherein the system is configured to wirelessly transmit signals at a signal transmission frequency between the signal transmission antenna of the core temperature detector and the signal transmission antenna of the microwave cooking appliance. The system can be constructed similarly to the core temperature detector and / or similarly to the microwave cooking appliance, and vice versa, and yields the same advantages.

[0060] In one improved embodiment, one possible operation of the system can be achieved in the following manner: Food to be processed in the cooking chamber of a microwave cooking appliance, such as a piece of meat, should have its core temperature monitored so that the appliance can control the cooking process based on that core temperature. For example, the microwave cooking appliance can stop cooking when a predetermined core temperature is reached above a specific core temperature or for a predetermined duration. A microwave cooking appliance is, for example, an oven with additional microwave functionality, which can process food alternately or simultaneously using oven heating elements such as recirculated air heating, top heating elements, and bottom heating elements, and by microwaves. To monitor the core temperature, a core temperature detector is inserted into the food with a needle-like section containing multiple temperature sensors arranged in series. The gripper at the rear of the core temperature detector is outside the food.

[0061] The core temperature detector can be remotely queried by the microwave cooking appliance, particularly via radio. For this purpose, the microwave cooking appliance has a signal transmission antenna, at least partially located within the cooking chamber, by means of which excitation radio signals (e.g., in the 433 MHz band) can be transmitted into the cooking chamber. For example, the excitation radio signal can be transmitted whenever the microwave cooking appliance requires temperature information for operation, such as temperature information having a core temperature value that can be measured or detected by a temperature sensor.

[0062] The excitation radio signal is received via a signal transmission antenna of the core temperature detector, which is matched to a transmission frequency of approximately 433 MHz. The received excitation radio signal is transmitted via a coaxial line to, for example, a passively excitation OFW temperature measuring device. The OFW temperature measuring device has, for example, a substrate made of ceramic or FR4, on the surface of which at least one OFW temperature sensor is located. The OFW temperature sensor can be understood as a component of the OFW temperature measuring device. By exciting the radio signal, at least one OFW temperature sensor is passively excited to generate an information signal including the inquired core temperature value and transmits it to the signal transmission antenna. The information signal is transmitted by the core temperature detector's signal transmission antenna into the cooking chamber (more precisely, also within the 433 MHz ISM band) and received by the microwave cooking appliance's signal transmission antenna. The received information signal is conducted via a coaxial line through the cooking chamber wall to a receiving circuit, which processes the information signal for use by the cooking appliance. Alternatively, a passive non-OFW temperature measuring device or an active temperature measuring device can be used.

[0063] Therefore, cooking appliances can, for example, have an independent evaluation circuit, which is connected to a central control unit, for example. Alternatively, the central control unit can have the function of an evaluation circuit.

[0064] In order to generate excitation radio signals and to process information signals, microwave cooking appliances are particularly capable of having combined radio transmitting / receiving circuitry. This combined radio transmitting / receiving circuitry can, for example, be connected to the central control unit of the microwave cooking appliance.

[0065] Although the signal transmission antennas of the core temperature detector and the microwave cooking appliance are matched to the 433 MHz ISM band and are specifically designed for poor coupling within the microwave frequency range (e.g., 2.45 GHz), the high power of microwaves (up to approximately 1000 W) causes microwave signals to couple so strongly into the signal transmission antenna that the structure connected to the antenna can be damaged or even completely destroyed. To ensure that these coupled microwave signals are harmless in practice, coaxial lines as described above are used. Attached Figure Description

[0066] The features, characteristics, and advantages of the present invention described above, as well as the ways and means of realizing these features, characteristics, and advantages, become clearer and more explicit in conjunction with the following illustrative description of embodiments, which are described in detail with reference to the accompanying drawings: Figure 1 A non-scale simplified diagram of the core temperature detector according to various feasible embodiments is shown as a top-view cross-section. Detailed Implementation

[0067] Figure 1 A core temperature detector 1 is shown as a top sectional view, the core temperature detector having a signal transmission antenna 2, a temperature measuring device in the example form of an OFW temperature measuring device 3, and a coaxial line 4 connecting the signal transmission antenna 2 and the OFW temperature measuring device 3.

[0068] The signal transmission antenna 2 is constructed as a helical antenna made of copper wire, which transforms into the inner conductor 5 of the coaxial line 4, which is also constructed as a straight copper wire. The signal transmission antenna 2 and the inner conductor 5 can be integrally manufactured from a single wire segment. The outer conductor 6 of the coaxial line 4 is exemplarily constructed here as a hollow cylindrical stainless steel sleeve 7, which, if necessary, extends longitudinally beyond the OFW temperature measuring device 3 and further extends to its tip, by means of which the stainless steel sleeve can be inserted into food. The stainless steel sleeve 7 can also be represented as a needle. A gripping part is present but not shown. The stainless steel sleeve 7 can also have an elliptical or rectangular cross-section.

[0069] The OFW temperature measuring device 3 has a ceramic or FR4 substrate 8, on the upper side of which one or more OFW temperature sensors 9 are arranged. The OFW temperature sensors 9 can be soldered onto the substrate 8. The OFW temperature sensors 9 can be SMD components. An inner conductor 5 is inserted at its end into, for example, a slit-like gap 10 in the substrate 8 and can be pressed in or soldered there. The OFW temperature sensors 9 are electrically connected to the inner conductor 5 via a conductor circuit (not shown) applied to the substrate 8. Here, the stainless steel sleeve 7 also serves as a shield and prevents the OFW temperature measuring device 3 from being directly irradiated by radio waves and microwave radiation. At least the following sections of the stainless steel sleeve 7 can also be referred to as measuring sections, which include the OFW temperature sensors 9.

[0070] The OFW temperature measuring device 3 is excited by a radio excitation signal in the 433 MHz-ISM band. This radio excitation signal is coupled into and conducted to the OFW temperature measuring device 3 via a signal transmission antenna 2 designed for this purpose, and is transmitted to the device with low loss or even virtually no loss via a coaxial line 4. The radio excitation signal excites the OFW temperature sensor 9 to generate a modified radio signal as a temperature signal, which is conducted back to the signal transmission antenna 2 via the coaxial line 4 and transmitted by the antenna 2. The modified radio signal contains (temperature) information, which is acquired by at least one OFW temperature sensor 9. The core temperature sensor 1 is typically inserted so deeply into the food that at least one OFW temperature sensor 9 is inserted into the food and thus measures a temperature value that corresponds to the core temperature of the food with sufficient accuracy.

[0071] To prevent microwave signals or energy coupled through the signal transmission antenna 2 from damaging or destroying the OFW temperature measuring device 3, the signal transmission antenna 2 can be constructed such that its reflection loss at the microwave frequency is minimized, thereby absorbing as little microwave power as possible. The signal transmission antenna 2 constructed in this way can also be considered as a selectable "first" filtering stage F1 for microwave incidence.

[0072] For the same purpose, a "second" filter stage F2 with at least one line resonant element is provided between the signal transmission antenna 2 and the OFW temperature measuring device 3 or its substrate 8. Here, two line resonant elements matching the microwave frequency to be filtered are provided, which are in the form of hollow cylindrical ceramic tubes 11a and 11b arranged in series and spaced apart along the inner conductor 5. For this purpose, the linear inner conductor 5 is guided through the internal cavities of the ceramic tubes 11a and 11b. Ideally, the ceramic tubes 11a and 11b completely fill the space between the inner conductor 5 and the outer conductor 6 radially, i.e., extend to the outer conductor 6. If only inserts with annular gaps can be used, the gaps between the outer conductor 6 and the ceramic tubes 11a and 11b, and between the inner conductor 5 and the ceramic tubes 11a and 11b, should be as small as possible.

[0073] Ceramic materials, for example, can have a dielectric constant ε between 6 and 40. r (e.g., 10) and for example, made of aluminum oxide Al2O3 (ε r Typically 6 to 15) or zirconium dioxide ZrO2 (ε r It is usually composed of 20 to 40.

[0074] Ceramic tubes 11a and 11b currently exemplarily have wavelengths λ of the microwave radiation to be filtered in the ceramic material, respectively. KerOne-quarter of its length, for example, about 10 mm, and thus constructed as a λ / 4 line resonant element. Two ceramic tubes 11a and 11b here have λ relative to each other along the inner conductor 5. Luft / 4 (where λ) Luft The spacing (the wavelength of microwave radiation in air) is, for example, approximately 30 mm. Thus, a so-called air line 12 is formed at the coaxial line 4 between ceramic tubes 11a and 11b for a length λ. Luft / 4 microwave. Air line 12 functions as a λ / 4 line resonator or λ / 4 line resonant element. Therefore, the second filter stage F2 has three λ / 4 line resonant elements 11a, 12, 11b connected in series, which alternately have high dielectric constant (ceramic) and low dielectric constant (air).

[0075] Therefore, in a particularly simplified embodiment where components 14a to 14d are not present on the antenna side end of ceramic tube 11a, a first transition from air to ceramic tube 11a exists in the section of coaxial line 4 used as the second filter stage F2 (starting from signal transmission antenna 2). This transition where impedance abruptly occurs corresponds to the HF no-load for microwaves. At the end of ceramic tube 11a away from signal transmission antenna 2, an HF short circuit is generated by the impedance abruptness at the ceramic-air transition. Similar to the first ceramic tube 11a, an HF no-load for microwaves exists at coaxial line 4, where (starting from signal transmission antenna 2) a first transition from air to ceramic tube 11b exists (i.e., at the antenna side end of ceramic tube 11b). An HF short circuit can also be generated at the end of ceramic tube 11b away from signal transmission antenna 2 via the ceramic-air transition. Therefore, an impedance transformation for microwave signals is induced at each end of the two ceramic tubes 11a, 11b, and the microwave signals are significantly reflected back to the signal transmission antenna 2 due to the impedance transformation.

[0076] The air line 12 between the two ceramic tubes 11a and 11b, designed as a λ / 4 no-load line, enables particularly efficient impedance transformation. HF no-load is achieved primarily through the reflection of a traveling wave due to the significant impedance change in the coaxial line 4. The reflected return wave superimposes with the traveling wave. Depending on the superposition point on the coaxial line 4, phase cancellation or overshoot can occur. One case where reflection is particularly strong is the λ / 4 line, where reflection at the ends of the λ / 4 line (corresponding to no-load) results in complete cancellation at the input of the λ / 4 line, effectively converting no-load into a short circuit. The opposite is true for short circuits at the line ends. The capacitance and inductance of the coaxial line 4 determine the impedance of the λ / 4 line and thus the magnitude of the reflection coefficient. Those locations where impedance abrupt changes can also be called "reflection points."

[0077] As an alternative, one, two, or all three line resonant elements 11a, 12, 11b can be constructed as λ / 2 line resonant elements.

[0078] The "third" filter stage F3 is provided by a conductor circuit 13, for example made of copper, applied particularly to the back side of the substrate 8. The conductor circuit 13 and the OFW temperature sensor 9 are arranged on different flat sides of the substrate 8. The conductor circuit 13 is connected to, for example, a slit-like opening 10 in the substrate 8 and thus to the end of the inner conductor 5 there. To further block or filter the microwave signal, the conductor circuit 13 is constructed as a λ / 4 unloaded line or a "λ / 4-stub". For this purpose, the conductor circuit has a length of λ / 4 of the microwave to be filtered, which is related to the dielectric constant of the substrate 8. Furthermore, the substrate-side end of the conductor circuit is open (i.e., without electrical connection) and thus converts the unloaded state into a short circuit relative to the input of the coaxial line 4. To provide space on the substrate 8, the unloaded conductor circuit 13 has a wavy or undulating, especially meandering, orientation along its extension direction.

[0079] The "fourth" filter stage F4 can be provided by having the OFW temperature measuring device 3, in addition to the OFW temperature sensor 9, at least one microwave filter F4 composed of conventional components (not shown). This microwave filter can be configured as a low-pass filter. The advantage here is that the microwave energy reaching the substrate 8 is so small that it no longer damages conventional components.

[0080] Each filter stage, F1 to F4, can withstand high microwave power without being damaged, and also withstands the high ambient temperature that occurs in an oven.

[0081] In an embodiment that provides particularly good microwave suppression or strong microwave filtering, thin metal sheets 14a to 14d are placed on the base surface of the ceramic tubes 11a and 11b, which serves as the boundary surface. The metal sheets 14a to 14d can be made of, for example, copper, brass, aluminum, etc. The radial diameter D of the metal sheets 14a to 14d relative to the extending direction of the inner conductor 5 is... pl Advantageously corresponding to the inner diameter D of the outer conductor 6 H and / or the diameter of the boundary surface to which it belongs, for example, D. pl = 3.6mm. Metal sheets 14a to 14d along the thickness L of the inner conductor 5. Pl Significantly smaller than the wavelength of the microwave to be filtered, for example, L. Pl = 1.5mm. Thickness L Pl It can also be called "thickness" or "length" relative to the direction of microwave propagation.

[0082] In one variant, metal sheets 14a to 14d are electrically connected to the inner conductor 5 but not to the outer conductor 6. The gap or radial spacing of the metal sheets 14a to 14d relative to the outer conductor 6 is very small, for example, only a few tenths of a millimeter. In an alternative variant, at least one of the metal sheets 14a to 14d is electrically connected only to the outer conductor 6, and has an annular gap relative to the inner conductor 5, for example, when metal sheet 14a also serves as the closed end of the outer conductor 6 relative to the antenna 2. Additional microwave reflection points are now added to the flat sides of the metal sheets 14a to 14d using the metal sheets 14a to 14d.

[0083] This can be illustrated with an example where the individual line segments 14a, 11a, 14b, 12, 14c, 11b, and 14d are treated as separate coaxial lines and their impedances are calculated. It is assumed here that the inner diameter of the stainless steel sleeve 7, which serves as the outer conductor 6, is D. H = 4 mm. The diameter D of the inner conductor 5. I D I =1.5 mm.

[0084] The real impedance R of the coaxial air line 12 Luft Calculated as follows: .

[0085] The real impedance R of the coaxial ceramic circuit 11a or 11b Keram The relative permittivity ε is calculated as follows, where ε is the relative permittivity ... r = 29: .

[0086] The output impedance Z of the λ / 4 line A,λ / 4 Able to be determined by line impedance Z L,λ / 4 and input impedance Z E,λ / 4 According to Z A,λ / 4 =Z 2 L,λ / 4 / Z E,λ / 4 This is determined by [the specific method / mechanism]. For the output impedance of the λ / 2 line, Z [the specific method / mechanism] applies. A,λ / 2 =Z E,λ / 2 Therefore, for a λ / 4 line, the output impedance Z A,λ / 4 With the input impedance Z of the line E,λ / 4 The line impedance Z of the λ / 4 line L,λ / 4 Related. For a λ / 2 line, the input impedance Z... E,λ / 2 and output impedance Z A,λ / 2 They have the same value. This means that the following physical parameters are decisive for the effectiveness of these two line converters as microwave filters: In principle, for λ / 4 lines, the applicable length L is λ / 4. L,λ / 4 Therefore, it corresponds to one-quarter of the microwave wavelength, or more precisely, to the propagation speed of electromagnetic waves along the line. Output impedance Z A,λ / 4 With the input impedance Z of the line E,λ / 4 and the impedance Z of the line itself L,λ / 4 Related. However, for a λ / 2 line, the principle generally applies to the line length L. L,λ / 2 This corresponds to λ / 2 of the line, which is half the wavelength of the microwave; more precisely, it is related to the propagation speed of electromagnetic waves on the line. Output impedance Z A,λ / 2 Equal to the input impedance Z of the line E,λ / 2 .

[0087] If the diameter of the metal sheet 14a to 14d is, for example, D Pl = 3.6 mm and its thickness or length L Pl =1.5mm, then the real impedance R of the corresponding coaxial "sheet circuit" is Pl It is obtained in the following way: .

[0088] Due to length L Pl Smaller than the wavelength of microwaves at a frequency of 2.45 GHz, for example, λ MW Since the impedance is approximately 122 mm, a simplified approach is taken, neglecting impedance transformation and considering only the impedance abrupt changes between different coaxial line impedances. Therefore, to determine the reflection coefficients at reflection points between the ceramic and sheet lines, and between the sheet and air lines, the real impedance R can be directly used. Pl .

[0089] The entire coaxial filter circuit F2 is composed of different circuit components. On the one hand, reflection points for microwave filtering are generated due to impedance changes caused by impedance transformers in the form of λ / 4 and / or λ / 2 air and ceramic circuits 11a, 11b, 12, and additionally, reflection points are generated due to impedance changes at metal sheets 14a to 14d.

[0090] All four filter stages F1 through F4 can collectively achieve attenuation of, for example, 60 dB to 80 dB at a microwave frequency of 2.45 GHz. At a frequency of 433 MHz, the data signal attenuates by only 1 dB to 10 dB.

[0091] Under conditions of rapid temperature changes, the expansion characteristics of the air surrounding the core temperature detector 1 can cause damage to the sealing sheet 14a, etc., for example, due to micro-cracks or fissures in the seal at the end of the stainless steel sleeve 7. Therefore, it is advantageous to completely or partially fill the core temperature detector 1 with fillers FS1 and FS2, which have a significantly smaller coefficient of thermal expansion than air, using either casting or foam filling. Furthermore, the fillers FS1 and FS2 should have a low relative permittivity ε. r Especially in the region of air line 12, the relative permittivity ε is close to 1. r (Similar to air) is advantageous. As fillers FS1 and FS2, for example, foamed fillers that can withstand the temperature range of use (e.g., up to 300°C) can be used.

[0092] The signal transmission antenna 2 can also be embedded in the filler (not shown). This filler specifically meets the following criteria: on the one hand, it has a significantly higher dielectric constant than air (i.e., a material that can be well polarized), ensuring that the antenna size can be smaller than in the case of air filling. On the other hand, the probability of electrical breakdown due to the filler having a low degree of ionization (i.e., an electrical insulator) should be kept low. For specific implementations, a suitable combination of characteristics can be found, for example, through experiments or simulations.

[0093] In addition, the filler should have a suitable thermal conductivity λ. W In the region of temperature sensor 9, the higher thermal conductivity between the stainless steel sleeve 7 and temperature sensor 9 is advantageous, allowing temperature sensor 9 to be better thermally coupled to ambient temperature and thus respond more quickly and accurately to changes in ambient temperature. In the region of air line 12, higher thermal conductivity is also advantageous, enabling more efficient cooling there, as microwave radiation power must also be reduced to decrease filter self-heating.

[0094] In the remaining areas of substrate 8, the lower thermal conductivity of the filler is advantageous to prevent the temperature sensors 9 from interfering with each other; that is, thermal short circuits, for example, between the temperature sensors 9 should not occur on the back side. In other words, while the temperature sensors 9 should be well coupled to the local sleeve temperature, they should not be in a common "isothermal" thermal lake on the back side. This is particularly advantageous when different temperature zones in the food being cooked can be measured, as this allows for the acquisition of extended cooking information (e.g., cooking information about temperature gradients in the food), or, for example, the identification of incorrect connections. For example, in the case of a young chicken, the tip of the core temperature detector 1 might already be inside the hollow abdominal cavity, thus the temperature information from the detector tip would be erroneous, as it would indicate the ambient temperature rather than the meat temperature.

[0095] By using two different fillers FS1 and FS2 with at least different thermal conductivity, for example by using a first filler FS1 with a relatively low thermal conductivity and a second filler FS2 with a relatively high thermal conductivity, these different requirements for filler thermal conductivity can be met. In sections along the sleeve 7 or the inner conductor 5 (where low thermal conductivity is advantageous), for example in the region of the substrate 8 within the fourth filter stage FS4, the core temperature detector 1 is filled with the first filler FS1. Similarly, in sections including, for example, the temperature sensor 9 (where high thermal conductivity is advantageous) and in the region of the air line 12, the core temperature detector 1 is filled with the second filler FS2.

[0096] Compared to a core temperature sensor 1 without metal plates 14a to 14d, a core temperature sensor 1 equipped with metal plates 14a to 14d exhibits stronger power level attenuation at the relevant microwave frequency, while exhibiting very low power level attenuation at the signal frequency. This effect is enhanced by an adapted signal transmission antenna 2.

[0097] Of course, the present invention is not limited to the described embodiments.

[0098] Therefore, in an alternative, it is possible to use a series sequence of only one arbitrary line resonator from the λ / 4 line resonator elements 11a, 11b and the λ / 2 line resonator element 12.

[0099] Generally, "one," "an," etc., especially in the sense of "at least one" or "one or more," can be understood as single or multiple, provided that this is not explicitly excluded, for example, by expressions such as "exactly one." Numerical descriptions can also include the exact number being described and can also include the usual tolerance range, provided that this is not explicitly excluded.

[0100] List of reference numerals 1. Core Temperature Detector 2. Signal transmission antenna 3 (OFW) Temperature Measurement Device 4. Coaxial lines 5. Inner conductor 6. External conductor 7 Stainless steel sleeve 8 Ceramic substrate 9 (OFW) Temperature Sensor 10 gaps 11a ceramic tube 11b ceramic tube 12 Air Lines 13 Conductor Circuits 14a-14d metal sheets D H Inner diameter of stainless steel sleeve D Pl Diameter of the metal sheet L Pl The thickness or length of the metal sheet

Claims

1. A core temperature detector (1) comprising: a temperature measuring device (3) having at least one temperature sensor (9); and a signal transmission antenna (2) connected to the temperature measuring device (3) via a coaxial line (4), wherein, The signal transmission antenna (2) can transmit temperature information acquired by at least one temperature measuring device (3) at a signal transmission frequency different from the microwave frequency, wherein, - The coaxial line (4) has at least one line resonant element (11a, 11b, 12) tuned to a microwave frequency, and - A conductive sheet (14a-14d) is present at at least one boundary surface of at least one such line resonant element (11a, 11b), the conductive sheet being electrically connected to the inner conductor (5) or outer conductor (6) of the coaxial line (4).

2. The core temperature detector (1) according to claim 1, wherein the conductive sheet (14a-14d) is a metal sheet.

3. The core temperature detector (1) according to any one of the preceding claims, wherein the thickness of the sheet (14a-14d) is less than 2% of the wavelength of the microwave.

4. The core temperature detector (1) according to any one of the preceding claims, wherein at least one line resonant element (11a, 11b, 12) is a λ / 2 line resonant element.

5. The core temperature detector (1) according to any one of the preceding claims, wherein at least one line resonant element (11a, 11b, 12) is a λ / 4 line resonant element.

6. The core temperature detector (1) according to claim 5, characterized in that, The coaxial line (4) has two line resonant elements (11a, 11b) made of ceramic or glass spaced apart from each other, with an air gap (12) between them forming a resonant line.

7. The core temperature detector (1) according to any one of the preceding claims, characterized in that, - The coaxial line (4) has an inner conductor (5) formed by wire segments and an outer conductor (6) formed by a metal sleeve, and - At least one line resonant element (11a, 11b) is constructed as a hollow cylindrical insulator that is fitted onto the inner conductor (5) and extends radially to the outer conductor (6).

8. The core temperature detector (1) according to claim 7, characterized in that, The materials of the insulators (11a, 11b) have a dielectric constant ε between 6 and 40. r Especially made of ceramics.

9. The core temperature detector (1) according to any one of the preceding claims, wherein, - The core temperature detector (1) has a substrate (8) connected to the inner conductor (5). - A freely extending conductor circuit (13) electrically connected to the inner conductor (5) exists at the substrate (8), the conductor circuit having a free length of λ / 4, and - The freely extending conductor circuit (13) has a wavy, especially meandering or coiled orientation.

10. The core temperature detector (1) according to any one of the preceding claims, wherein the signal transmission antenna (2) is constructed such that the reflection loss of the signal transmission antenna is small at microwave frequencies.

11. The core temperature detector (1) according to any one of the preceding claims, wherein, The core temperature detector (1) is completely or partially filled, in particular cast, with at least one filler (FS1, FS2) having a significantly smaller coefficient of thermal expansion than air, but having at least approximately the same relative permittivity.

12. The core temperature detector (1) according to any one of the preceding claims, wherein, The core temperature detector (1) is completely or partially filled with at least one non-conductive or insulating filler (FS1, FS2) having a significantly smaller coefficient of expansion than air, but having a relative permittivity that is at least approximately the same as air.

13. The core temperature detector (1) according to claim 12, wherein, At least one filler comprises at least its thermal conductivity λ W At least two fillers (FS1, FS2) that are significantly different in aspect, wherein the outer conductor (6) is segmentally filled with one of the fillers (FS1, FS2) along its longitudinal extension.

14. The core temperature detector (1) according to any one of the preceding claims, wherein, The signal transmission antenna (2) is surrounded by a filler that has a significantly higher dielectric constant than air.

15. A system comprising a microwave cooking appliance and at least one core temperature detector (1) according to any one of the preceding claims, wherein the system is configured to: wirelessly transmit a signal at a signal transmission frequency between a signal transmission antenna (2) of the core temperature detector (1) and a signal transmission antenna of the microwave cooking appliance.

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