Core temperature sensor, system comprising core temperature sensor, and cooking appliance

Abstract

The invention relates to a core temperature sensor (KTF) for use with a microwave cooking appliance which generates microwaves within a specific microwave frequency band in order to treat food to be cooked, the core temperature sensor (KTF) having: at least one temperature sensor (TS); an antenna (ANT); a high-frequency oscillator (1), the output signal of which can be fed into the antenna (ANT) and the signal frequency of which lies outside the microwave frequency of the microwave cooking appliance; a modulation device (OOK), which is designed to generate a pulse sequence from the output signal of the high-frequency oscillator (1) by means of an amplitude modulation process, said pulse sequence corresponding to digital temperature data (OST) generated by means of the at least one temperature sensor (TS); and an electric energy storage device (BAT) for supplying electrically operated components (MCU, TS, OSZ-AMP) of the core temperature sensor (KTF). The invention also relates to a system having a core temperature sensor and a cooking appliance, having a receiver for receiving electromagnetic waves emitted by the core temperature sensor and a control device which is designed to operate the cooking appliance on the basis of information contained in the received electromagnetic waves.

Description

[0001] Core temperature probe and system with core temperature probe and cooking appliance

[0002] The invention relates to a core temperature probe comprising at least one temperature sensor and an antenna. The invention also relates to a system comprising a core temperature probe and a cooking appliance capable of wireless communication with the core temperature probe. The invention is particularly advantageously applicable to cooking appliances with a microwave function.

[0003] Several active core temperature probes are available on the market that can communicate with a smartphone via a corresponding app. The wireless transmission typically uses the Bluetooth standard. Bluetooth operates in the 2.45 GHz ISM frequency band, which covers a frequency range of 2.4 GHz to 2.5 GHz. Since this is the same frequency range used by many household microwave ovens, these Bluetooth core temperature probes cannot be used in microwave ovens.

[0004] DE 102005 018 015 B3 discloses a household appliance, in particular a cooking appliance, with an interior enclosed by a housing and a door, an electrical control unit, and a measuring device for measuring a physical quantity, in particular temperature. The measuring device for wireless signal transmission between a measuring probe located in the interior and the electrical control unit comprises a probe antenna arranged on the measuring probe and a transmitting or receiving antenna connected to the electrical control unit for signal transmission. The transmitting or receiving antenna is arranged on the housing and is essentially airtight from the interior by a cover permeable to electromagnetic radiation. The transmitting or receiving antenna is part of a lighting device for illuminating the interior.

[0005] DE 102011 109 163 A1 discloses a furnace with a heating element arranged in a treatment chamber of the furnace, the heating element having a metallic outer casing and a mounting flange, wherein the heating element is attached to the mounting flange via the metallic outer casing, and a query antenna of a wireless measuring system for monitoring furnace contents. The query antenna of the wireless measuring system is formed by the heating element in the treatment chamber of the furnace, in that the metallic outer casing of the heating element is insulated from the mounting flange at least at one connection end.

[0006] DE 10 2012 221 015 A1 discloses a cooking appliance, in particular an oven, which has a cooking chamber with walls and a ventilation opening into the cooking chamber. This ventilation opening is provided on a fan plate attached to a wall of the cooking chamber, and an antenna for wireless signal transmission to a measuring device with a transmitting and receiving antenna located in the cooking chamber is provided. The antenna is arranged between the fan plate and the wall of the cooking chamber and is thus covered or protected from the inside.

[0007] DE 10 2015 012 683 B3 discloses a temperature measuring probe with a hollow temperature measuring probe and at least one temperature sensor designed as a resonator and arranged in the temperature measuring probe, which is / are connected to a communication unit for wireless transmission of the temperature information.The temperature measuring probe is characterized, among other things, by the fact that a plate-shaped sensor carrier made of an electrically insulating plastic is arranged in the temperature measuring probe, and that on the opposite surfaces of this sensor carrier, ground conductor surfaces are arranged on both sides, which together serve as ground conductors and are electrically connected to each other by means of through contacts, wherein free areas are arranged on one or both sides of the sensor carrier in these ground conductor surfaces, and that signal conductor tracks are arranged centrally in these free areas, electrically insulated from the ground conductor surface(s), which, if they are arranged on both sides of the opposite surfaces of the sensor carrier, are electrically connected to each other by means of through contacts, and thus together form the signal conductor.

[0008] DE 10 2021 129 787 A1 discloses a temperature sensor for use in a microwave oven, comprising a temperature sensor having at least one temperature sensor and configured to detect the temperature of food being cooked, preferably by contact, an antenna connected to the temperature sensor, at least one filter unit, in particular a ceramic filter, arranged between the temperature sensor and the antenna, wherein the temperature sensor is configured to transmit temperature information from the temperature sensor wirelessly via the antenna, and the filter unit is configuredto attenuate electromagnetic waves in the frequency range of the microwave oven between the temperature sensor and the antenna and to essentially allow them to pass through in the frequency range of the wireless transmission of the temperature information. DE 10 2021 129 787 A1 further relates to a cooking system with a microwave oven having a cooking chamber for receiving food and a temperature sensor according to one of the preceding claims, wherein the microwave oven has a transmitter / receiver unit with an antenna and a filter unit, which is in particular designed as a ceramic filter, which is arranged between the transmitter / receiver unit and the antenna, wherein the transmitter / receiver unit is configured to electromagnetically excite the temperature sensor with varying frequencies and to receive an electromagnetic wave from the antenna of the temperature sensor as a reaction to the excitation during transmission pauses, wherein the filter unit is configuredto attenuate electromagnetic waves in the frequency range of the microwave oven between the transmitting / receiving unit and the antenna and to allow them to pass through, at least substantially, in the frequency range of the electromagnetic excitation and the received electromagnetic wave, wherein the microwave oven is further configured to determine the temperature of the food being cooked from the frequency of the electromagnetic excitation and the amplitude of the received electromagnetic wave.

[0009] EP 2 662 629 A1 discloses a household appliance with a treatment chamber to which an antenna is assigned. A coupling arrangement is provided in the treatment chamber, which is operatively connected to the antenna via a connecting device.

[0010] EP 2 663 160 A1 discloses a household appliance with a treatment chamber and a coupling device for transmitting electromagnetic radiation into the treatment chamber. The coupling device is arranged in an adjacent chamber. The adjacent chamber is separated from the treatment chamber by at least one partition wall. The coupling device is designed to generate an electromagnetic field between a first metallic wall and an adjacent second metallic wall. At least one opening is provided through which the electromagnetic radiation is transmitted into the treatment chamber. EP 3 121 573 A1 discloses an oven, in particular an oven or microwave oven, with an oven muffle for the active heat treatment of a substance and for receiving the substance via a chamber opening therein, a door designed to open the chamber opening in a first or second position.to release and close in the second position, at least one receiving or transmitting element that enables at least unidirectional wireless communication of signals from and / or to at least one sensor unit that is placed on or inside the oven muffle, wherein: the at least one receiving or transmitting element is positioned in a space between two walls and / or panes of the door.

[0011] WO 2014 / 194176 A1 discloses a system and a method for calibrating a temperature probe by immersion in a substance with a known change-of-state temperature. The probe's temperature signal is calculated using saturated surface acoustic waves (SAW) and overcomes the fluctuation of the furnace reference temperature.

[0012] The object of the present invention is to overcome at least some of the disadvantages of the prior art and, in particular, to provide a means of wireless data transmission from a core temperature probe to a microwave oven, which enables a simple and cost-effective circuit design with low energy consumption.

[0013] This problem is solved according to the features of the independent claims. Preferred embodiments can be found in particular in the dependent claims.

[0014] The problem is solved by a core temperature probe for use with a microwave cooking appliance that generates microwaves lying within a specific microwave frequency band for the treatment of food, wherein the core temperature probe has:

[0015] - at least one temperature sensor,

[0016] - an antenna, - a high-frequency oscillator whose output signal can be fed into the antenna and whose signal frequency lies outside the microwave frequency of the microwave cooking appliance,

[0017] - a device (hereinafter referred to as "modulation device" without limitation of generality) which is designed to generate a pulse train from the output signal of the high-frequency oscillator by means of amplitude modulation, corresponding to digital temperature data generated by means of at least one temperature sensor, and

[0018] - an electrical energy storage device to supply electrically operated components of the core temperature sensor.

[0019] This core temperature probe advantageously allows for a simple and cost-effective circuit design. It takes advantage of the fact that temperature data typically consists of relatively simple data structures, meaning that a low data rate in the range of a few kilobits per second is sufficient for transmission. Furthermore, the core temperature data of food being cooked is not subject to any special safety regulations, since if the wireless connection between the core temperature probe transmitter inside the cooking chamber and the receiver in the cooking appliance is not sufficiently strong, the appliance can be shut down immediately. Therefore, for such relatively simple data transmissions, highly complex integrated transceiver chips with multifaceted data protocols, such as those provided by the Bluetooth standard, are not necessary. Instead, the simple design of the probe electronics described above, with its straightforward modulation and demodulation method, is more than adequate.This data transmission can also be considered data transmission using a proprietary transmission protocol. Its use advantageously helps to avoid software adjustments over time. In contrast, with standardized data protocols, changes to the data protocol may be introduced during the service life of a cooking appliance, which may disadvantageously necessitate software adjustments for the respective application. Proprietary data transmission methods, such as the one used here, also advantageously do not generate any licensing costs. A further advantage over using established Bluetooth solutions is that the existing core temperature probe is microwave-safe. Furthermore, the modulation method used is characterized by low energy consumption.

[0020] Core temperature probes, also known as meat thermometers, are generally well-known. They are used to measure the internal temperature of food being cooked. They typically have a forward-facing, skewer-shaped section (the "core temperature probe tube") that is inserted into the food, and a rear-facing handle. The core temperature probe tube is hollow and contains one or more temperature sensors arranged lengthwise. Wireless core temperature probes usually have an antenna integrated into the handle. The probe's electronics can be located in the tube, the handle, or distributed between both.

[0021] Microwave ovens have a cooking chamber into which food can be placed and which is then heated with microwaves of a specific frequency. For household appliances, the microwave frequency is typically in an ISM frequency band, for example, the 2.45 GHz ISM band for use in Europe and the 915 MHz ISM band for use in the USA.

[0022] The fact that the core temperature probe is designed for use with a microwave cooking appliance does not preclude its use with a cooking appliance that does not have a microwave cooking function, e.g., a regular oven.

[0023] The electromagnetic waves emitted by the antenna (hereinafter also referred to as "radio waves") are intended to be received by a cooking appliance. The information transmitted by the radio waves (which may include temperature data, but optionally also other data) can then be used to control the cooking process. The antenna can, for example, be housed in or protrude from the handle of the core temperature probe. Alternatively, the probe tube or a section thereof can serve as the antenna. The antenna can be, for example, a monopole antenna, dipole antenna, slotted antenna, microstrip antenna, etc. A further development involves the high-frequency oscillator generating a carrier signal of a specific carrier frequency or frequency bandwidth, which is intended to be amplitude-modulated. This implies that the carrier signal is amplitude-modulated during its generation.In this case, the carrier signal can already correspond to the output signal. It is a further development that the signal frequency of the output signal corresponds to the carrier frequency or is at least only slightly shifted from it. This then also applies to the radio frequency of the transmitted radio signals.

[0024] Because the signal frequency of the output signal lies outside the microwave frequency of the microwave oven intended or permitted for use with the core temperature probe, interference or cross-interference of the radio waves emitted by the antenna by the microwave oven's microwave radiation into the cooking chamber is avoided. Furthermore, this effectively dampens or even practically eliminates unwanted microwave coupling into the core temperature probe.

[0025] In one further development, the high-frequency oscillator has a dedicated oscillator or signal oscillator that generates the carrier signal. In another further development, the high-frequency oscillator does not have a dedicated oscillator or signal oscillator. In this case, the carrier signal can be generated, for example, by means of at least one amplifier (hereinafter also referred to as an "oscillator amplifier") in conjunction with an oscillator feedback path in the form of a feedback network. The feedback network adjusts the amplitude and phase so that the high-frequency oscillator, consisting of the at least one oscillator amplifier and the feedback network, oscillates at the desired frequency, corresponding to the carrier signal. Several cascaded oscillator amplifiers, if present, can also be considered as different amplifier stages.

[0026] It is a further development that the oscillator amplifier includes at least one power amplifier, particularly in addition to the at least one oscillator amplifier. The power amplifier can, for example, serve to further amplify the carrier signal before it is passed on to the antenna as an output signal. It is a further development that the power amplifier is a component of the high-frequency oscillator, i.e., integrated into the feedback path. It is a further development that the power amplifier is arranged between the high-frequency oscillator and the antenna. In this case, in particular, only the signal passed on to the antenna is amplified to a desired output power, not the feedback signal. This further development is particularly advantageous if the output power of the oscillator amplifier is insufficient to achieve the desired output power at the antenna.Otherwise, the power amplifier can be omitted, saving space, energy, and costs. A design without a dedicated power amplifier is therefore advantageous due to the limited space available in the core temperature sensor tube and the small energy storage capacity of the core temperature sensor's electronics.

[0027] The fact that the modulation device is configured to modulate the output signal of the high-frequency oscillator as a pulse sequence corresponding to the digital temperature data can, for example, include modulating the output signal in a pulse-like manner and / or driving the high-frequency oscillator to output the pulse sequence. In other words, the output signal from the high-frequency oscillator has a pulse sequence form generated by the modulation device through amplitude modulation. This pulse sequence contains at least the same information as the digital temperature data. The individual pulses of the pulse sequence can have the same or different pulse heights. The pulse spacing of the pulse sequence can be the same or different.

[0028] The electrical energy storage device serves to supply electrically operated components of the core temperature sensor with electrical energy. Such electrically operated components may have corresponding electrical connections, e.g., a connection for a predefined supply voltage (often labeled Vcc) and a ground connection.

[0029] It is a configuration in which the modulation device has at least one switch, or is a switch that can be controlled, in particular, by means of the digital temperature data. The switch can, for example, be controlled according to the digital temperature data.

[0030] - to selectively switch the high-frequency oscillator on or off, - to selectively activate or deactivate the injection of the output signal into the signal path to the antenna (e.g., via control of an enable terminal of an amplifier) ​​and / or

[0031] - to optionally provide (close) or interrupt (open) the signal path to the antenna.

[0032] It is a further development to state that the switch is a semiconductor switch or includes one, e.g., a switching transistor or a switching diode. It is a further development to state that the switch is an RF switch.

[0033] It is a design feature where the switch incorporates or is itself an ASK modulator. The ASK modulator can be fed with digital temperature data and generates a corresponding pulse (signal) sequence. This allows for particularly simple and versatile implementation of amplitude modulation of the temperature information. For example, the ASK modulator can convert incoming digital temperature data, possibly in a specific format, into an analog pulse sequence and drive the high-frequency oscillator accordingly. The pulses of the ASK modulator can be single-bit or multi-bit.

[0034] It is a further development that the ASK modulator is an OOK ("On-Off Keying") modulator, meaning that the generated pulses each correspond to one bit. With this type of modulation, the transmitted signal is switched on and off according to the received digital temperature data, which corresponds to amplitude shift keying with a modulation depth of m = 1 or 100%. This further development is particularly easy to implement in the core temperature probe. Moreover, a receiver in the cooking appliance can advantageously perform the demodulation of the analog pulsed radio signal very simply, for example, with just a rectifier diode and an LC network implemented as a low-pass filter. Another advantage is that a particularly high signal-to-noise ratio is achieved.

[0035] It is a further development that the modulation device includes an ASK modulator, in particular an OOK modulator, and a further switch, e.g., a semiconductor switch, controlled by the ASK modulator. The ASK modulator controls the further switch, which then, for example, selectively activates and deactivates the RF oscillator or closes or opens the signal path to the antenna, etc.

[0036] An advantageous embodiment for generating digital temperature data using at least one temperature sensor is that the at least one temperature sensor is configured to generate analog measurement signals that can be fed to an analog-to-digital converter (ADC) configured to convert the analog measurement signals into digital temperature data. The at least one temperature sensor can, for example, comprise or be at least one thermocouple (e.g., of type K, J, R, or S), at least one NTC resistor, etc. The ADC can be a standalone component or a functional component of a larger component, such as a microcontroller. The digital temperature values ​​can, for example, have a resolution of 8 bits or 256 values. In a further development, the microcontroller can also be used to convert or format the digital temperature data into the (proprietary) radio protocol used.

[0037] It is advantageous for generating digital temperature data using at least one temperature sensor that the at least one temperature sensor is configured to output digital temperature data, which is why it is also referred to as an "active" temperature sensor. This advantageously saves components and is particularly easy to implement. The active temperature sensor can, for example, comprise a temperature sensor that generates analog measurement signals and an analog-to-digital converter (ADC) downstream of it. Alternatively, the active temperature sensor can be a semiconductor device that inherently provides digital temperature data. The digital temperature data can then be transmitted, for example, via a bus system such as an I2C bus, One-Wire bus, etc. It can be transmitted, for example, to a microcontroller that converts this temperature data into the (proprietary) wireless protocol used.

[0038] One design feature is that the high-frequency oscillator is self-amplifying. This advantageously allows for a particularly simple and temperature-insensitive construction. A further development is that the high-frequency oscillator amplifies its output signal through self-amplifying or positive feedback until its maximum output power is reached. This advantageously eliminates the need for complex output power adjustment.

[0039] This configuration includes a high-frequency oscillator with an amplifier. An amplifier output is connected to an amplifier input via a high-frequency filter, and a passband of the high-frequency filter corresponds to a desired frequency band of the output signal. This advantageously provides a particularly simple and temperature-insensitive circuit that functions like an oscillator without requiring a dedicated oscillator or signal oscillator. Instead, a feedback network 3 (also referred to as a feedback loop) is used, forming an oscillator feedback path.

[0040] It is a further development that the self-amplifying feedback can be initiated after switching on or activating the amplifier with signal noise present at the amplifier output. The high-frequency oscillator can easily be designed so that an output signal with maximum amplitude is already obtained after only a few cycles of the oscillator loop or the oscillator assembly, consisting of the oscillator amplifier and feedback network. The oscillator amplifier is connected to the feedback network, specifically via its amplifier input and its amplifier output. Its function as an amplifier includes at least compensating for the losses of the feedback network and providing the required output power for a given load.

[0041] It is a further development that the ramp-up to maximum output power takes only up to 500 ns. When the oscillator amplifier is switched off or deactivated, when the feedback network or the oscillator feedback path is interrupted, or when the antenna path between the feedback network (especially its power divider) and the antenna is interrupted, the output signal collapses, and no more radio waves based on it are radiated by the antenna.

[0042] Furthermore, in a further development, the initial frequency width at the amplifier output of the oscillator amplifier does not need to correspond, or not exactly correspond, to the desired signal frequency at the antenna, since the frequency width is limited to the desired range by a passband of the high-frequency filter during feedback, and subsequently only the filtered signal is amplified further.

[0043] One design is that the high-frequency filter is an OFW filter, an OFW resonator, or a quartz crystal oscillator, or incorporates one of these. Such a high-frequency filter is particularly simple, inexpensive, and resistant to high temperatures.

[0044] This configuration involves connecting the amplifier output of the oscillator amplifier to the input of a power divider. The first output of the power divider is connected to the antenna, and the second output of the power divider is connected to the amplifier input of the oscillator amplifier. This allows for a particularly simple, inexpensive, and temperature-resistant design for splitting the output signal, directing it to the antenna on one side and back to the amplifier input of the oscillator amplifier on the other, via the high-frequency filter. The power divider can be implemented, for example, as an R, RC, RL, or RLC network, or as a transformer. Additional amplifiers can be arranged, in particular, between the amplifier output of the oscillator amplifier and the input of the power divider.

[0045] This configuration includes a first impedance matching network between the amplifier output and the input of the power divider, a second impedance matching network between the first output of the power divider and the input of the high-frequency filter, and / or a third impedance matching network between the output of the high-frequency filter and the amplifier input. This allows power losses and interference from reflected electrical signals to be avoided or at least significantly reduced. For example, the antenna impedance might be 50 Ω, while the input of the high-frequency filter has a considerably lower impedance. Furthermore, a fourth impedance matching network can be provided between the power divider and the antenna.For example, the first impedance matching network may be provided if the output impedance of the oscillator amplifier and the input impedance of the power divider do not match. The input impedance of the power divider can then be matched using the first impedance matching network for maximum power transmission. In particular, if the output impedance of the oscillator amplifier and the input impedance of the power divider are at least approximately the same, the first impedance matching network can be omitted. These considerations can be applied analogously to the other impedance matching networks. Depending on the topology of the core temperature sensor's transmitter module, additional or alternative impedance matching networks may also be present.For example, if a power amplifier is present between the power divider and the antenna, an impedance matching network may be present between the power divider and the power amplifier and / or an impedance matching network between the power amplifier and the antenna, etc.

[0046] The first or at least one impedance matching network can be configured as an LC, RC, RL, or RLC network, or as a transformer, depending on the specific training. The first, second, third, and / or fourth impedance matching networks can be of the same or different types.

[0047] It is a further development that the power amplifier is connected downstream of the power divider, i.e., it is positioned between the power divider and the antenna, in order to further amplify only the output signal to the antenna.

[0048] One configuration involves the core temperature sensor incorporating a microcontroller that is at least configured to format the digital temperature data. This advantageously enables particularly reliable signal transmission from the antenna and increased information content. The formatting can, for example, include embedding the digitized temperature data in a data format with a header, which may also contain an identifier or ID of the core temperature sensor, etc. In a further development, if the microcontroller receives analog measurement signals, it can also be configured as an analog-to-digital converter (ADC) for their ADC conversion.

[0049] It is a design such that the output signal fed into the antenna—corresponding to the filtered electrical signal of the high-frequency oscillator—has a signal frequency in the range of f » 433 MHz. This is advantageous because at this frequency the antenna and the electronic components are still sufficiently compact in terms of mechanical size for use in a core temperature sensor, and moreover, this signal frequency is sufficiently far removed from the commonly used microwave frequency bands around 2.45 GHz and 915 MHz. The frequency bandwidth of the 433 MHz ISM band lies between f = 433.05 MHz and 434.79 MHz. This ISM band is approximately 2.5 octaves away from the ISM microwave frequency range at f = 2.4 ... 2.5 GHz, which allows for filtering of the microwave energy input to the core temperature sensor.

[0050] This design is based on the consideration that, in order to use the core temperature sensor even during microwave operation, the signal frequency must not be within the microwave frequency band. Therefore, the electrical signal can only be set at a frequency either below or above the microwave frequency. While a signal frequency above the microwave frequency is theoretically possible, in practice it would disadvantageously lead to a smaller selection of components for the circuit design, as there are not many applications in the cost-sensitive consumer sector at higher microwave frequencies. Although mechanical structures tend to become smaller with increasing frequency, sensitivity to electrical and mechanical tolerances, as well as parasitic capacitive and inductive factors, also increases. Therefore, the signal frequency is preferably below the microwave frequency bands around 2.45 GHz and 915 MHz.

[0051] In principle, other ISM or SRD frequency bands are also suitable for the signal frequency and can be freely selected according to requirements when designing the core temperature sensor. For example, the signal frequency can be set to one of the following ISM or SRD bands: 13.5 MHz, 27 MHz, 40 MHz, 868 MHz, or (when used in a microwave oven that generates microwaves in the 2.45 GHz frequency band) 915 MHz. The core temperature sensor can also be referred to as a wireless core temperature sensor.

[0052] It is a design where the microcontroller, the modulation unit (especially the ASK modulator), the oscillator amplifier, the power divider, the high-frequency filter, and, if present, at least one additional amplifier, the first impedance matching network, the second impedance matching network, the third impedance matching network, and / or the fourth impedance matching network are implemented as discrete components. This offers the advantage that the circuit is more temperature-resistant and / or can be used in a wider temperature range than integrated solutions. For example, a maximum operating temperature of 85 °C is typically specified for integrated transceiver circuits. If a transceiver chip is operated at temperatures higher than specified, individual components within the transceiver chip may no longer function reliably according to their specifications.A significant temperature increase can potentially even lead to the destruction of the integrated transceiver circuitry. In contrast, the core temperature sensor of this design can easily operate at temperatures exceeding 100 °C.

[0053] The design with discrete components has the further advantage over more highly integrated components that the housing sizes are usually small enough to accommodate them in the core temperature sensor tube.

[0054] The use of discrete components offers an additional advantage over highly integrated components: the risk of not finding suitable replacements for discontinued components is significantly lower in discrete circuits than in integrated electronic circuits. This is particularly true for highly integrated transceiver chips with small package sizes, which are also intended for use at high temperatures, where the market selection is inherently very limited. This also advantageously results in greater flexibility in the discrete design of the transmitting and receiving electronics with regard to the choice of components. Thus, types of components can be used that are typically manufactured by several semiconductor producers.

[0055] In this configuration, the oscillator amplifier is a monolithic microwave integrated circuit (MMIC). An MMIC is typically an integrated high-frequency amplifier whose input and output impedances are usually optimized and impedance-matched for a system impedance of λ = 50 Ω. MMICs are available on the market with cutoff frequencies up to the high GHz range. They advantageously exhibit low noise figures and low distortion and are relatively easy to use. Alternatively, an operational amplifier can be used as the oscillator amplifier. Since there are a relatively large number of semiconductor manufacturers for monolithic microwave amplifiers and manufacturers of high-frequency filters, especially SAW filters, the dependency is advantageously lower compared to using integrated transceiver chips.

[0056] It is a further development that the core temperature probe has a receiver for radio waves or radio signals whose frequency ("radio frequency") can correspond to or differ from the frequency of the emitted radio waves. This advantageously enables bidirectional data transmission between the core temperature probe and the cooking appliance, provided the cooking appliance has a corresponding transmitter or transceiver. For example, the core temperature probe can send temperature data to a receiver in the cooking appliance, and a handshake or acknowledge signal can be sent from the cooking appliance to the core temperature probe and evaluated. Furthermore, the cooking appliance can, for example, send a start signal to the core temperature probe when it is ready to receive temperature data.

[0057] Active transmitting and optionally receiving electronics in the core temperature sensor necessitate the provision of a power source, which should advantageously fit into the handle or the sensor tube (which typically has a small inner diameter). In one embodiment, the power source supplies at least the high-frequency oscillator, and in particular its oscillator amplifier, with electrical energy for its operation. In another embodiment, the power source is a rechargeable battery. This simplifies the use of the core temperature sensor compared to one equipped with a non-rechargeable battery.

[0058] The problem can also be solved by a system comprising a core temperature probe as described above and a cooking appliance, comprising a receiver for receiving radio waves emitted by the core temperature probe, and a control unit configured to operate the cooking appliance based on information contained in the received radio waves. The temperature measured by the core temperature probe can be used, for example, to regulate the cooking temperature in the cooking appliance, to set microwave power, or as a shutdown condition for a cooking process. The system can be designed analogously to the core temperature probe, and vice versa, and offers the same advantages. The receiver can be located inside the cooking chamber, on the wall of the cooking chamber, or outside the cooking chamber but still within the cooking appliance housing.The temperature data can then be transmitted from the receiver to the control unit, for example via a wired connection.

[0059] The cooking appliance has, in particular, a cooking chamber that can be closed by means of a door, in which food can be cooked. The cooking appliance may be a microwave oven, but it does not have to be. Thus, the core temperature probe can also be used with a cooking appliance without a microwave cooking function. However, the core temperature probe can also be used with a cooking appliance with a microwave cooking function, as long as the signal frequency of the radio waves transmitted between the core temperature probe and the cooking appliance is not on or close to the microwave frequency of the microwaves generated by the cooking appliance, especially in a different ISM or SRD frequency band. The cooking appliance can, for example, be an oven with or without a microwave cooking function. The cooking appliance may additionally or alternatively have at least one further cooking function, e.g., a steam cooking function (so-called "Added Steam"). The cooking appliance is, in particular, a household cooking appliance.

[0060] It is a further development that the cooking appliance and the core temperature probe are additionally equipped to transmit data from the cooking appliance to the core temperature probe, i.e., to bidirectional data communication.

[0061] The following additional comments are added, which can be implemented as part of one or more training courses:

[0062] The primary goal is to develop a vibration generator or oscillator that is cost-effective, small, lightweight, reliably available, and suitable for high temperatures. Specialized, highly integrated transceiver chips are too expensive, large, not suitable for high temperatures, and will not be available on the market for much longer; in some cases, they also have high power consumption.

[0063] Therefore, an oscillator circuit is provided which, from the pure standpoint of oscillation generation, is so poor that its use has not previously been considered. However, it has been recognized that this is sufficient for use in a core temperature sensor, because the frequency fluctuations (typically ±100 kHz) are tolerable, since the oscillation is only switched on and off (especially via OOK), very little data needs to be transmitted, and therefore a simple, slowly transmitted data stream (analogous to Morse code) is sufficient. Whether the carrier frequency fluctuates back and forth is less important.

[0064] The frequency inaccuracy originates from the SAW filter in the feedback loop or feedback network. The SAW filter is "poor" in the sense that, due to its design, it is not narrowband enough to force a sharp, frequency-accurate oscillation.

[0065] More importantly, this makes the oscillator (circuit) very temperature-stable. Its low power output is sufficient for the intended application. High-performance oscillators with high Q (e.g., when using quartz crystals), on the other hand, tend to "go haywire" when the temperature rises, meaning they suddenly oscillate at higher frequencies (harmonics). This then requires complex control and limiting. This effort can be avoided if the oscillator, as in this case, doesn't have the necessary Q factor in the first place.

[0066] A similar situation arises when an MM IC is used as an oscillator amplifier. Its output impedance is unfavorable for a series-resonant feedback network, and thus, according to current understanding, a poor choice for generating good oscillations. However, in this particular case, it is the most economical option, since its 50-ohm output impedance allows it to be connected directly to the transmitting antenna, or via a power divider, and usually eliminates the need for an additional power amplifier and impedance converter.

[0067] - A circuit topology with a single amplifier as an MM IC component with an output impedance suitable for direct transmission and a SAW feedback loop, whose SAW filter only prevents the most severe frequency outliers but does not otherwise impede the oscillation, is particularly preferred because an oscillator can be built with simple, discrete components in a space-saving, power-saving and cost-effective manner, which oscillates stably (albeit rather inaccurately) over a wide temperature range.

[0068] The properties, features and advantages of this invention described above, as well as the manner in which they are achieved, will become clearer and more easily understood in connection with the following schematic description of an exemplary embodiment, which will be explained in more detail in conjunction with the drawings.

[0069] Fig. 1 shows a block diagram of a transmitter assembly of a core temperature sensor; and Fig. 2 shows an oscillator circuit diagram of the core temperature sensor from Fig. 1.

[0070] Fig. 1 shows a block diagram of a transmitter module of a core temperature sensor (CTF). Optionally, the core temperature sensor (CTF) can also include a receiver module, which is not described further.

[0071] The transmitter assembly comprises a module (“signal module” 1) designed to generate and modulate a modulated electrical signal directed to an antenna ANT.

[0072] Signal module 1 can receive digital temperature data from a microcontroller (MCU), optionally formatted. The MCU is connected to one or more temperature sensors (TS), whose analog measurement signals are converted into digital temperature data by the MCU. The MCU thus acts as an analog-to-digital converter (ADC). Alternatively, the temperature sensors (TS) can be semiconductor devices that inherently provide digital temperature data and transmit it to the MCU via a bus system. In both cases, the MCU can format the digital temperature data. For multiple temperature sensors (TS), these can be spaced apart along the length of the sensor tube (not shown). The MCU can optionally provide additional data, such as an identifier, which can be transmitted via the antenna (ANT).

[0073] The signal module 1 can itself be conceptually subdivided, here by way of example into an OOK modulator OOK and a high-frequency oscillator ("oscillator module" 2). The oscillator module 2 itself can again comprise an amplifier or an amplifier module (hereinafter referred to as oscillator amplifier OSZ-AMP without loss of generality) and a feedback network 3. The transmitter module basically comprises an oscillator for generating a carrier signal and at least one amplifier for amplifying the carrier signal. These are, by way of example, at least partially integrated, e.g., as an oscillator amplifier module to which, for example, a power amplifier can be connected. The oscillator amplifier OSZ-AMP comprises at least one amplifier unit at whose output the carrier signal is output. The oscillator amplifier OSZ-AMP can, for example, be implemented as or with an MMIC module.The oscillator amplifier OSZ-AMP can alternatively be configured as or with an operational amplifier. A signal output ("amplifier output" SO, see Fig. 2) of the oscillator amplifier OSZ-AMP is connected to an input of the feedback network 3, while an output of the feedback network 3 is connected to a signal input ("amplifier input" Sl, see Fig. 2) of the oscillator amplifier OSZ-AMP. This makes the oscillator assembly 2 self-amplifying.

[0074] The carrier signal is on the desired radio frequency or frequency band of the radio signals transmitted by the ANT antenna. Radio transmission in the 433 MHz frequency band is particularly preferred. Accordingly, the carrier signal ideally has a carrier frequency of at least approximately 433 MHz. However, the carrier frequency is not limited to this frequency or frequency range.

[0075] The feedback network 3, starting from its input connected to the oscillator amplifier OSZ-AMP, first includes a power divider LT. The power divider LT, e.g., an RF power divider, splits the electrical signal ("output signal") output by the oscillator amplifier OSZ-AMP. Part of the power of the output signal is directed to the antenna ANT via the power divider LT, and another part to a frequency filter SAW. The power divider LT can be implemented, for example, as an R, RC, RL, or RLC network, or as a transformer.

[0076] The core temperature sensor KTF can include a power amplifier POW-AMP, which is shown here as an example positioned between the power divider LT and the antenna ANT. The power amplifier POW-AMP serves to amplify the portion of the carrier signal diverted to the antenna ANT before it is passed on to the antenna ANT as an output signal. This enhancement is particularly advantageous if the output power of the oscillator amplifier OSZ-AMP alone is insufficient to achieve the desired output power at the antenna ANT. However, if the output power of the oscillator amplifier OSZ-AMP is sufficient to achieve the desired output power at the antenna ANT, the POW-AMP power amplifier can be omitted, saving space, energy, and costs.Only a single amplifier is then required, which functions as an oscillator amplifier (OSZ-AMP) and, due to its low output impedance, also as a power amplifier (POW-AMP) for the antenna (ANT). This enables an extremely simple and compact circuit design with low power consumption and is therefore very well suited for use with the core temperature sensor (KTF).

[0077] The SAW frequency filter is, in particular, a bandpass filter whose passband corresponds at most to the desired radio frequency band, e.g., from 433.05 MHz to 434.79 MHz, but preferably with the smallest possible frequency bandwidth within the ISM frequency band of 433.05 MHz to 434.79 MHz. The SAW frequency filter can, for example, be an OFW (surface wave) filter, an OFW resonator, or a crystal oscillator. The output of the SAW frequency filter is connected to the amplifier input Sl of the oscillator amplifier OSZ-AMP. The oscillator amplifier OSZ-AMP receives the frequency-filtered signal entering at the amplifier input Sl and outputs it, amplified, at the amplifier output SO. The amplified output signal is stronger than the output signal before amplification. Thus, the output signal is amplified continuously with successive iterations of the feedback network 3 until a maximum output signal value is reached.This is typically possible within a short time, e.g. after approximately five iterations or 500 ns.

[0078] For impedance matching, a first (impedance) matching network APN1 can optionally be provided between the amplifier output SO of the oscillator amplifier OSZ-AMP and the power divider LT, a second (impedance) matching network APN2 between the power divider LT and the frequency filter SAW, and / or a third (impedance) matching network APN3 between the frequency filter SAW and the amplifier input Sl of the oscillator amplifier OSZ-AMP. The first impedance matching network APN1 can be used, for example, if the output impedance of the oscillator amplifier OSZ-AMP and the input impedance of the power divider LT do not match. The input impedance of the power divider LT can then be matched using the first impedance matching network APN1 for maximum power transmission.

[0079] Furthermore, as shown in Fig. 2, a fourth impedance matching network APN4 can optionally be provided between the power divider LT and the antenna ANT. The at least one impedance matching network APN1, APN2, APN3, APN4 can be implemented as an LC, RC, RL, or RLC network, or as a transformer, in a further development. The matching networks APN1, APN2, APN3, and the power divider LT are included here in the feedback network 3 assembly of the oscillator assembly 2 because, as passive components (resistors, capacitors, inductors), they, like the frequency filter SAW, cause an amplitude and phase change for the feedback signal and thus a change in the loop gain and the overall phase shift of the oscillator loop.

[0080] A signal output ("drive output") of the OOK modulator is connected here, as an example, to a control input / enable input EN (see Fig. 2) of the oscillator amplifier OSZ-AMP. The enable input EN controls whether the oscillator amplifier OSZ-AMP outputs a signal or not. For example, this can be implemented such that no output signal is output when the signal level at the enable input EN is "low," and an output signal is output when the signal level at the enable input EN is "high." The OOK modulator OOK converts the digital data received from the microcontroller MUC, particularly temperature data, into a bit-like pulse sequence. This pulse sequence is applied as a drive signal to the enable input EN of the oscillator amplifier OSZ-AMP, with each pulse corresponding to a "high" signal level and the intervals between them corresponding to a "low" signal level.This generates a pulse-follow-like output signal from the oscillator amplifier OSZ-AMP, corresponding to the pulse sequence of the drive signal. Consequently, the antenna ANT transmits a bit-like radio signal that can be easily received and demodulated by a receiver in a cooking appliance. Since the temperature data is typically generated at a low data rate, the pulses and pulse pauses can be chosen to be long enough that the signal edges of the output signal, which occur particularly during self-amplification, do not have a detrimental effect.

[0081] The generation of a radio signal containing the temperature information from the temperature sensors TS will now be explained in more detail: First, it is assumed that the enable input EN of the oscillator amplifier OSZ-AMP is set to "low," meaning no output signal is being sent. The temperature sensors TS generate analog temperature signals, which are converted by the microcontroller into digital temperature values, for example, with a resolution of 8 bits or in steps of 256 values. The conversion rate can be set low, as rapid temperature fluctuations within a food being cooked are not expected. The digital temperature values ​​are then, if necessary formatted and supplemented with further data, transmitted to the OOK modulator OOK, which converts the received data into a bit-like pulse sequence using on / off keying and outputs this pulse sequence to the enable input EN of the oscillator amplifier OSZ-AMP.

[0082] When a pulse of the pulse train is received at the enable input EN, the output signal is enabled. Initially, the amplitude is low. The output signal passes through the first matching network APN1 to the input of the power divider LT. The power divider LT splits the output signal into a portion that goes to the antenna ANT (optionally via the fourth matching network APN4) and a portion that goes to the frequency filter SAW via the second matching network APN2. The division ratio can be chosen arbitrarily and could, for example, be 50% to 50%. It can depend on factors such as the output power of the oscillator amplifier, the desired transmit power of the antenna ANT, and / or the presence of a power amplifier POW-AMP in the antenna path, etc.

[0083] The main function of the SAW frequency filter is to fix the frequency of the oscillator oscillation, and thus of the carrier signal, to a frequency within the SAW frequency filter's bandwidth. The narrower the SAW frequency filter's bandwidth, the more frequency-stable the oscillator assembly 2 will be at a specific frequency. Oscillation of the oscillator assembly 2 is not possible in the SAW frequency filter's stopband because the high attenuation of the SAW frequency filter prevents the power gain or amplitude condition from being met. PS> 1 of the feedback network 3 is not adhered to. Furthermore, the SAW frequency filter frequency-filters the output signal or its component, thus removing interfering side frequencies from the output signal. The frequency-filtered output signal then passes through the third matching network APN3 to the amplifier input Sl of the oscillator amplifier OSZ-AMP. The oscillator amplifier OSZ-AMP amplifies the signal received at amplifier input Sl and outputs it at amplifier output SO. The amplitude of the amplified output signal is higher than the amplitude of the original output signal. The feedback network 3 can be traversed multiple times, resulting in self-amplifying (positive) feedback of the output signal until a maximum amplitude value is reached. The output signal continues to traverse the feedback network 3 for as long as necessary.The feedback loop continues until the enable input EN is switched back to "low," i.e., at the end of the input pulse, thus interrupting the output signal. This effectively generates a bit-like pulse from oscillator module 2, whose pulse width—except for the negligible rising edge during the ramp-up of the output signal—corresponds to the pulse width of the pulse output by the OOK modulator OOK. Therefore, the carrier signal is only transmitted via the antenna ANT during the pulse width, which is very energy-efficient. Consequently, the pulse train output by the OOK modulator OOK can be output to the cooking appliance as an analog sequence of radio pulses.

[0084] The power source BAT for supplying the transmitter module with electrical energy can be a non-rechargeable battery, e.g., one that can be replaced by a user, or a rechargeable battery ("accumulator"). Using the power source BAT, an electrical voltage can be applied, for example, to the at least one temperature sensor, the microcontroller MCU, and the oscillator amplifier OSZ-AMP.

[0085] Fig. 2 shows an oscillator circuit diagram of the core temperature sensor KTF from Fig. 1 with the oscillator assembly 2 and the antenna ANT. The matching networks APN1 to APN4 are each implemented as LC networks, and the power divider LT as an R network with a resistor R1, R2, R3 at each terminal, connected via a common node. The values ​​of the inductors L and the capacitors C can be the same or different across the matching networks APN1 to APN4. The frequency filter SAW is implemented as a SAW filter. The oscillator amplifier OSZ-AMP is implemented as an MMIC module. Regarding the above embodiment(s), and more generally, the following should be noted:

[0086] Oscillators without a dedicated oscillator can be implemented by integrating a resonant component in series or parallel into an oscillator loop. This can be a 2-port component, such as a SAW filter, or a 1-port component, such as a SAW resonator. The frequency bandwidth of an SAW resonator is typically very narrow, whereas SAW filters are available with varying frequency bandwidths. For core temperature sensors, a SAW filter has proven particularly effective as a resonant component. Since the SAW filter is a 2-port component, it is suitable for serial integration into the oscillator loop shown in Fig. 1 as part of the feedback network 3. Such SAW filters exist for the 433 MHz ISM frequency band with bandwidths of a few hundred kHz, which is much narrower than the frequency bandwidth of the ISM band itself.While the use of a SAW filter in a high-frequency oscillator results in an oscillator with relatively low frequency stability due to the filter's bandwidth, it offers several advantages in applications with a wide temperature range, such as core temperature sensors. The oscillator (corresponding to oscillator assembly 2 in Fig. 1) is, for example, well-suited for applications that do not require a high transmission data rate, where increased phase noise of the oscillator is acceptable within certain limits, and where the oscillator frequency is not fixed. This is the case, for instance, with core temperature sensors, where a high data rate is not needed for transmitting the temperature data.If the oscillator can tune to any frequency within the frequency bandwidth of the SAW filter, and thus its oscillation frequency plays a relatively minor role within certain limits, then the result is an oscillator that is advantageously relatively insensitive to component tolerances. Furthermore, it can be used in a wide temperature range with a low risk of the oscillator switching to a different frequency or completely ceasing to oscillate due to temperature-related parameter changes. The SAW filter, implemented in series with the feedback loop, ensures, due to its high stopband attenuation and variable phase, that the oscillator no longer adheres to its oscillation conditions outside the filter bandwidth. The oscillation condition for the loop gain, or the power gain in the loop, is given by v. PS > 1 and should be at least v for a reliable start-up of the oscillatorPS > 2 = 3 dB. For the oscillation condition of an oscillator, in addition to the loop gain, the loop phase is also of fundamental importance. The phase shift for the entire loop should be in the range of (p » 360°). This means that the phase shift of the amplifier (pAm) P plus the phase shift (PLF of the feedback network and the remaining components) <PLC (Z.B. aufgrund eines Einflusses der Antenne ANT, aufgrund parasitärer Komponenten, usw.) ergibt (p = (pAm P + (PLF + (PLC « 360°. If the amplifier (e.g. the oscillator amplifier OSZ-AMP from Fig. 1) is, for example, an inverting amplifier with (pAm PIf the phase shift is 180°, the same phase shift (PLF + (PLC « 180°) must be generated by the feedback network (e.g., feedback network 3 from Fig. 1) to achieve (p » 360°) and enable oscillation of the oscillator (e.g., oscillator assembly 2 from Fig. 1). The oscillation condition is also met if the phase shift is an n-fold multiple of 360°.

[0087] In Fig. 1, the SAW filter SAW, together with the impedance matching networks APN1, APN2, and APN3 arranged at the input and output, and the power divider LT, forms the feedback network 3. The total phase shift in the oscillator loop 2 serves to adjust the maximum loop gain and the phase for the oscillation condition in the oscillator loop 2 approximately to the center frequency of the SAW filter SAW. As already explained above, the frequency stability of an oscillator or an oscillator loop 2 with the SAW filter SAW as the frequency-determining component is not very good. Therefore, such an oscillator is practically only suitable for amplitude modulation techniques, where a carrier frequency fluctuation within certain limits does not play a significant role, even with regard to demodulation.

[0088] If the oscillator amplifier OSZ-AMP is designed as an MM IC amplifier, it is rather unusual to use such an amplifier as an oscillator amplifier for high-frequency oscillators due to the fixed input and output impedance of an MMIC amplifier. Ideally matching an MMIC to a resonator may require relatively complex impedance transformation circuits. For a parallel resonance of the oscillator circuit, the input and output impedance of the MMIC is too low, and for a series resonance, too high, to allow for simple adjustment of the loop Q factor to the highest possible value. However, the loop Q factor is important for good frequency stability. For the present invention, on the other hand, frequency stability advantageously plays only a subordinate role within certain limits.

[0089] The oscillator's output signal corresponds to the high-frequency carrier signal and is modulated with the lower-frequency data signal. Since a low data rate and low data volume are sufficient for digital temperature data transmission, amplitude modulation (AM) is used as the modulation method, and in the digital version, amplitude-shift keying (ASK) is particularly relevant. To achieve the highest possible signal-to-noise ratio (SNR), the simplest form of ASK, on-off keying (OOK), is advantageously employed.

[0090] The transmitter module 1 described above is highly suitable for use in applications with limited space for electronic components, low energy consumption, and low output power. This transmitter module 1 can operate reliably at high temperatures (> 85 °C) and within a wide temperature range (e.g., 20 °C to 105 °C) and is therefore well-suited for use in a core temperature sensor.

[0091] Of course, the present invention is not limited to the embodiment shown.

[0092] In general, "ein", "eine", etc. can be understood to mean singular or plural, especially in the sense of "at least one" or "one or more", etc., unless this is explicitly excluded, e.g. by the expression "exactly one", etc.

[0093] A numerical value can also refer to the exact number specified or to a standard tolerance range, unless explicitly excluded. Reference symbol list

[0094] 1 Signal assembly

[0095] 2 Oscillator assembly

[0096] 3 Feedback network

[0097] ANT antenna

[0098] APNi i-th impedance matching network

[0099] BAT energy source

[0100] C capacitor

[0101] EN Enable input

[0102] GND Ground

[0103] KTF core temperature sensor

[0104] L Inductance

[0105] LT power divider

[0106] MCU microcontroller

[0107] OOK OOK modulator

[0108] OSZ-AMP Oscillator Amplifier

[0109] POW-AMP power amplifier

[0110] Ri i-ter resistance of the power divider

[0111] SAW SAW filter

[0112] SI amplifier input

[0113] SO amplifier output

[0114] TS temperature sensor

Claims

Patent claims 1. Core temperature probe (CTP) for use with a microwave cooking appliance which generates microwaves within a specific microwave frequency band for the treatment of food, wherein the core temperature probe (CTP) comprises: - at least one temperature sensor (TS), - an antenna (ANT), - a high-frequency oscillator (1) whose output signal can be fed into the antenna (ANT) and whose signal frequency is outside the microwave frequency of the microwave cooking appliance, - a modulation device (OOK) configured to generate a pulse train from the output signal of the high-frequency oscillator (1) by means of amplitude modulation, corresponding to digital temperature data generated by means of the at least one temperature sensor (TS), and - an electrical energy storage device (BAT) to supply electrically operated components (MCU, TS, OSZ-AMP) of the core temperature sensor (KTF).

2. Core temperature sensor (CTF) according to claim 1, wherein the modulation device (OOK) has at least one switch or is a switch that can be controlled by means of the digital temperature data.

3. Core temperature sensor (CTF) according to claim 2, wherein the switch has an ASK modulator or is an ASK modulator, in particular an OOK modulator.

4. Core temperature sensor (CTF) according to any one of the preceding claims, wherein - which has at least one temperature sensor (TS) configured to generate analog measurement signals that can be fed to an analog-to-digital converter (MCU) configured to convert the analog measurement signals into digital temperature data, and / or - or which has at least one temperature sensor (TS) set up to output digital temperature data.

5. Core temperature sensor (CTF) according to any of the preceding claims, wherein the high-frequency oscillator (1) is self-amplifying.

6. Core temperature sensor (CTF) according to claim 5, wherein - the high-frequency oscillator (1) has an oscillator amplifier (OSZ-AMP), - an amplifier output (SO) of the oscillator amplifier (OSZ-AMP) is connected via a high-frequency filter (SAW) to an amplifier input (Sl) of the oscillator amplifier (OSZ-AMP) and - a passband of the high-frequency filter (SAW) corresponds to a desired frequency band of the output signal.

7. Core temperature sensor (CTF) according to claim 6, wherein the high-frequency filter (SAW) is or comprises an OFW filter, an OFW resonator or a quartz crystal oscillator.

8. Core temperature sensor (CTF) according to one of claims 6 to 7, wherein the amplifier output (SO) of the oscillator amplifier (OSZ-AMP) is connected to an input of a power divider (LT), a first output of the power divider (LT) is connected to the antenna (ANT) and a second output of the power divider (LT) is connected to the amplifier input of the oscillator amplifier (OSZ-AMP), in particular via the high-frequency filter (SAW).

9. Core temperature sensor (CTF) according to claim 8, wherein - a first impedance matching network (APN1) is present between the amplifier output (SO) and the input of the power divider (LT), - a second impedance matching network (APN2) is present between the first output of the power divider (LT) and the input of the high-frequency filter (SAW) and / or - a third impedance matching network (APN3) is present between the output of the high-frequency filter (SAW) and the amplifier input (Sl).

10. Core temperature sensor (CTS) according to any of the preceding claims, wherein the core temperature sensor (CTS) comprises a microcontroller (MCU) which is at least configured to format the digital temperature data.

11. Core temperature sensor (CTF) according to one of the preceding claims, wherein the output signal that can be fed into the antenna (ANT) has a signal frequency in the range of f » 433 MHz.

12. Core temperature sensor (CTF) according to claims 8 and 10, wherein - the microcontroller (MCU), the modulation unit (OOK), the oscillator amplifier (OSZ-AMP) and the power divider (LT) and, if present, - that at least one impedance matching network (APN1 - APN4) is present as respective discrete components.

13. Core temperature sensor (CTF) according to one of claims 6, 8 or 12, wherein the oscillator amplifier (OSZ-AMP) is an MMIC component.

14. Core temperature sensor (CTF) according to one of the preceding claims, wherein the power source (BAT) supplies at least the high-frequency oscillator (1), in particular its oscillator amplifier (OSZ-AMP), with electrical energy for its operation.

15. System comprising a core temperature sensor (CTS) according to one of the preceding claims and a cooking appliance comprising a receiver for receiving electromagnetic waves emitted by the core temperature sensor (CTS) and a control device configured to operate the cooking appliance based on information contained in the received electromagnetic waves.

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