Calibration of microwave modules for domestic microwave cooking appliances

Abstract

The invention relates to a method (S1-S35) for calibrating a microwave module (17) intended for installation in a domestic cooking appliance (24), by means of a measuring system (51) which is connectable to a microwave output (18) of the microwave module and which has a directional coupling device (52) with an antenna-free microwave output (53), the method having at least the following steps: a) connecting (S1) the microwave output of the microwave module to the directional coupling device (12) of the measuring system, an equivalent load (57) being connected to the microwave output (18) of the measuring system; b) generating (S3), by means of the microwave module, a microwave signal with a predefined setpoint frequency and a predefined setpoint amplitude; c) conducting (S3a) the microwave signal through the directional coupling device of the microwave module to the microwave output of the microwave module; d) guiding (S3b) the microwave signal from the microwave output of the microwave module through the directional coupling device of the measuring system to the microwave output of the measuring system; and e) measuring (S4), at the directional coupling device of the microwave module, at least the amplitude of the microwave signal sent to the measuring system and the amplitude of the microwave signal reflected by the measuring system.

Description

[0001] Calibration of microwave modules for household microwave cooking appliances

[0002] The invention relates to a method for calibrating a microwave module intended for installation in a household cooking appliance by means of a measuring system connectable to a microwave output of the microwave module. The invention also relates to a calibration setup for carrying out this method. The invention further relates to a method for calibrating a phase shifter of a microwave module intended for installation in a household cooking appliance. The invention further relates to a calibration setup for carrying out this method. The invention also relates to a household microwave cooking appliance in which at least one microwave module calibrated according to the present method is installed.

[0003] DE 102019 128204 B4 discloses a method for calibrating a microwave module for a cooking appliance, wherein the microwave module has a microwave output and a control loop, the method comprising the following steps: generating electromagnetic radiation by the microwave module, wherein the generated electromagnetic radiation is defined by an electromagnetic wave comprising an amplitude and a phase, emitting the generated electromagnetic radiation via the microwave output of the microwave module, measuring a forward wave of the emitted electromagnetic radiation by means of a measuring device external to the microwave module, and controlling the amplitude and / or phase of the generated electromagnetic radiation by means of a control and / or evaluation unit external to the microwave module, which is connected to the control loop in a signal-transmitting manner,so that the electromagnetic radiation generated by the microwave module is stable in terms of amplitude and phase.

[0004] EP 3 000 283 B1 discloses an apparatus for processing an object in a cavity by radio frequency radiation emitted by one or more radiating elements configured to emit the RF radiation in response to RF energy applied thereto, the apparatus comprising: an RF energy supply component configured to supply RF energy for application to one or more radiating elements; a memory storing a set of coefficients;and a processor configured to receive feedback in response to the emission of RF radiation by one or more of the radiating elements and to control the application of RF energy to one or more of the radiating elements based on the feedback and the set of coefficients, wherein the set of coefficients is associated with the RF energy delivery component and includes error correction coefficients configured to correct systematic errors in the operation of the RF energy delivery component.;

[0005] WO 2015 / 099651 A1 discloses a method for calibrating a device configured to generate at least one radio frequency (RF) feed in an enclosed cavity. The method comprises: selecting at least one subset of frequencies within a bandwidth of the at least one RF feed; setting an input power for the at least one RF feed for each of the at least one subset of frequencies; operating the at least one RF feed with the input power at each of the subset frequencies; sampling output power data at the at least one RF feed; interpolating the sampled output power data across the bandwidth of the at least one RF feed; and storing the output power data and the interpolated output power across the bandwidth of the at least one RF feed in a lookup table.

[0006] WO 2016 / 144872 A1 discloses a method for calibrating a set of devices, each device comprising an amplifying component and a measuring component that outputs a digital signal indicative of the radio frequency power sensed at the amplifying component, comprising: selecting a frequency from a set of frequencies; selecting a phase value from a set of phase values; selecting a power level from a set of power levels; setting a subset of the set of devices to output a signal of the selected frequency, the selected phase value, and the selected power level; measuring a forward power level and a reverse power level; processing the measurements of the forward and reverse power levels to calibrate the digital signal output from the measuring component of each set of devices; and storing the calibrated digital signal output in non-volatile memory.It is the object of the present invention to at least partially overcome the disadvantages of the prior art and in particular to provide a particularly accurate way of calibrating a microwave module of a household microwave cooking appliance.

[0007] This object is achieved according to the features of the independent claims. Preferred embodiments can be found in particular in the dependent claims.

[0008] The object is achieved by a method for calibrating a microwave module intended for installation in a household cooking appliance by means of a measuring system connectable to a microwave output of the microwave module, which measuring system has a directional coupling device with an antenna-free microwave output, wherein the method comprises at least the following steps:

[0009] (a) connecting the microwave output of the microwave module to the directional coupling device of the measuring system, with a dummy load connected to the microwave output of the measuring system;

[0010] (b) generating, by means of the microwave module, a microwave signal having a predetermined target frequency and a predetermined target amplitude;

[0011] (c) passing the microwave signal through the directional coupling device of the microwave module to the microwave output of the microwave module;

[0012] (d) passing the microwave signal from the microwave output of the microwave module through the directional coupling device of the measuring system to the microwave output of the measuring system;

[0013] (e) measuring, at the directional coupling device of the microwave module, at least the amplitude of the microwave signal transmitted to the measuring system and the amplitude of the microwave signal reflected by the measuring system (S3);

[0014] (f) measuring, at the directional coupling device of the measuring system, at least the amplitude of the microwave signal emitted to the output of the measuring system and the amplitude of the microwave signal reflected from the output of the measuring system (S4);

[0015] (g) storing the target frequency and the target amplitude, as well as the measured values ​​and / or values ​​derived therefrom, as data entries of a calibration data set; (h) varying at least the target frequency within a first frequency group of different target frequencies and repeating steps (b) to (g) for several, in particular all, target frequencies of the first frequency group;

[0016] (i) directing the microwave output of the microwave module or measurement system to a reflective end termination;

[0017] (j) subsequently carrying out at least steps (b), (c), (e) and (g) within the group of steps (b) to (g) and

[0018] (k) Varying at least the target frequency within a second frequency group of different target frequencies and repeating at least steps (b), (c), (e) and (g) within the group of steps (b) to (g) for several, in particular all, target frequencies of the second frequency group.

[0019] This calibration procedure offers the advantage that the output power at the microwave output of a calibrated microwave module can be adjusted particularly precisely to the desired or requested target power when operated in a household microwave cooking appliance, even with frequency and, if necessary, phase-variable settings of the microwave signal. In addition to ensuring successful cooking, it is also advantageous from a food safety perspective that the power delivered into the cooking chamber corresponds to the set power, for example, to ensure sufficient heating to kill germs.

[0020] The household microwave cooking appliance can be a standalone microwave appliance or a combination microwave appliance, e.g., an oven with a microwave function and, if appropriate, a steam treatment function. The household microwave cooking appliance has at least one microwave module. The microwave signals generated by the at least one microwave module are radiated as microwave radiation via one or more antennas or "ports" into a cooking chamber that can be closed by a microwave-tight door. Typically, during microwave operation of the household microwave cooking appliance, a portion of the radiated microwave radiation is fed back into the at least one antenna.

[0021] The microwave module is particularly a component that must be installed in the household

[0022] Microwave cooking appliance: a separately manufactured and independently manageable unit. At least one antenna can be connected directly or via a microwave signal line to the microwave output of the built-in microwave module. In the present method, however, the microwave output is connected to the measuring system without an antenna, and the microwave output of the measuring system is also antennaless. Consequently, during the calibration process, no microwave radiation is emitted into the room; instead, only conducted microwave signals are generated. This is advantageously particularly simple to implement, error-resistant, and radiation-safe.

[0023] A directional coupling device is a measuring device that taps into a passing microwave signal and provides a very small portion of the passing microwave signal as a measurement signal. In particular, measurement signals dependent on the direction of travel of the microwave signal are provided, i.e., a measurement signal that represents a measure of the power / amplitude of a microwave signal traveling in the forward or transmission direction to the microwave output, and a measurement signal that represents a measure of the power / amplitude of a microwave signal traveling in the reverse or reflection direction from the microwave output.

[0024] The directional coupling device can be, for example, a bidirectional, circulatorless directional coupler or a directional coupling system with a circulator.

[0025] The dummy load connected in step (a), e.g., a 50-ohm load, serves to absorb or dissipate a forward-flowing microwave signal as completely as possible after passing through the two directional coupling devices. Ideally, no portion of the microwave signal would be reflected or recirculated in the reverse direction.

[0026] The fact that in step (b) a microwave signal with a predetermined target frequency and a predetermined target amplitude is generated by means of the microwave module means that the microwave signal can be adjusted in a frequency and amplitude-variable manner.

[0027] A further development is that the frequency of the microwave signal can be adjusted using a signal generator (e.g., an oscillator, VCO, PLL, synthesizer, resonant circuit, etc.). The signal generator can be supplied with a clock base by means of a clock generator. The clock generator and / or the signal generator can be part of the microwave module, but do not need to be. Thus, the clock generator and / or the signal generator can be components of a separate signal generation module.

[0028] To suppress unwanted frequencies outside a specific frequency band, for example, a bandpass filter can be connected downstream of the signal generator. The bandpass filter can be a component of the microwave module or a signal generation module.

[0029] To increase efficiency, a controlled chopper can be connected downstream of the signal generator, especially downstream of the bandpass filter, if present. The chopper can be a component of the microwave module or a signal generation module.

[0030] A first amplifier ("intermediate amplifier") can be connected downstream of the signal generator. The intermediate amplifier can also be connected downstream of the bandpass filter and / or the chopper, if present. The intermediate amplifier can be a component of the microwave module or a signal generation module. The intermediate amplifier can be a power-controlled amplifier. The power-controlled intermediate amplifier can, in particular, amplify the amplitude or power of the incoming microwave signal by a predetermined factor.

[0031] A controlled phase shifter of the microwave module can be connected downstream of the signal generator. The phase shifter can also be connected downstream of the bandpass filter, the chopper, and / or the repeater, if present. The phase shifter is particularly advantageous for microwave modules that are to be installed in groups of at least two microwave modules in a household microwave oven and are intended to generate a targeted interference pattern in the cooking chamber during operation of the microwave oven.

[0032] A controlled attenuator of the microwave module can be connected downstream of the signal generator. The attenuator can also be connected downstream of the bandpass filter, the chopper, the repeater, and / or the phase shifter, if present. The attenuator can, in particular, reduce the amplitude or power of the incoming microwave signal by a predetermined factor. At least one second amplifier ("final amplifier") can be connected downstream of the signal generator, the output of which is, in particular, directly connected to the directional coupling device of the microwave module. The final amplifier can be single- or multi-stage. In particular, the final amplifier can have a single- or multi-stage preamplifier and a main amplifier connected downstream of the preamplifier.

[0033] The controlled components of the microwave module such as the signal generator, the chopper (if not part of a signal generation module), the repeater, the phase shifter, the attenuator, etc. can be controlled by a common control device of the microwave module, e.g. by means of a microcontroller, ASICs, FPGAs, etc.

[0034] The microwave signal provided at the output of the power amplifier then travels in the forward direction through the directional coupling device of the microwave module to the microwave output of the microwave module according to step (c). The amplitude or power of the microwave signal is measured at a first measuring output, and the measured values ​​are transmitted to the control device. Based on the target power and the measured actual power, the control device can adjust the power of the microwave signal at the microwave output to the target value. However, due to manufacturing tolerances and / or systematic errors, the measured actual power may not correspond to the actual microwave power present at the microwave output. This can be detected by the present calibration method and corrected by the control device.

[0035] In step (d), the microwave signal is passed in the forward direction through the directional coupling device of the measuring system. The measuring system is self-calibrated and / or has higher measurement accuracies and / or lower measurement tolerances, thus measuring more accurately than the directional coupling device of the microwave module. Since the two directional coupling devices are connected directly downstream of one another (i.e., without an interposed functional component), the microwave signals passing through both directional coupling devices in the forward and reverse directions are identical with a high degree of accuracy. In steps (e) and (f), the amplitudes or powers of the microwave signal in the forward direction and the amplitudes or powers of the microwave signal in the reverse direction are measured.

[0036] In step (g), the measured values ​​of the microwave power and / or values ​​derived therefrom (e.g. quotients) are linked to at least the specified target frequency and the specified target power and stored as data entries of a calibration data set.

[0037] This measurement process is repeated for various target frequencies, as indicated by step (h). The target frequencies for which the measurements are performed correspond to values ​​of a first frequency group of different target frequencies. In particular, the target frequencies of the first frequency group can be spaced apart from each other in steps of 10 MHz, e.g., include target frequencies between 2400 MHz and 2500 MHz. In particular, the measurements can be performed for all target frequencies of the first frequency group.

[0038] After completion of step (h), a calibration data set is available which includes as entries links at least between the specified or set target frequencies, the set target power and the respectively measured values ​​of the microwave powers and / or values ​​derived therefrom.

[0039] It is also possible to connect a frequency meter or spectroscope to the measurement output of the directional coupling device of the measuring system for measuring the forward amplitude in order to assess the quality of the microwave signal, e.g., its bandwidth. Any deviation between the target frequency and the actual frequency can also be measured and corrected by calibration.

[0040] Steps (i) to (k) may be performed before or after steps (a) to (h).

[0041] Step (i) involves connecting the microwave output of the microwave module or the measurement system to a reflective end termination. This causes the forward-directed microwave signals to be reflected back at the open end by total internal reflection. In step (j), their amplitude or power is measured at least at the directional coupling device of the microwave module, and optionally also at the directional coupling device of the measurement system.

[0042] The "reflective termination" can be an open end in one embodiment, or a defined short circuit in another. Both termination types produce total internal reflection and differ only in the phase position of the reflected signal. The equivalent load can also be referred to as a "matched termination."

[0043] Analogous to the case of the equivalent load presented in steps (a) to (h), in step (k) the target amplitudes are varied and the corresponding data entries are created even when the reflective end termination is present.

[0044] The target frequencies in steps (a) to (h) correspond to values ​​of target frequencies of a second frequency group. The target frequencies of the second frequency group can be identical to the target frequencies of the first frequency group, can be a subset of the target frequencies of the first frequency group, or vice versa, can have a true intersection of target frequencies with the first frequency group, or can form disjoint sets of values.

[0045] There is now another calibration data set available, which has been created or structured analogously to the calibration data set for the substitute load.

[0046] It is a design that

[0047] - in step (i) the microwave output of the microwave module is connected to the directional coupling device of the measuring system and the microwave output of the measuring system is configured as a reflective termination;

[0048] - step (j) comprises performing steps (b) to (g); and

[0049] - Step (k) comprises varying at least the target frequency within the second frequency group and repeating steps (b) to (g) for several, in particular all, target frequencies of the second frequency group.

[0050] In this configuration, the measuring system remains connected to the microwave module, and the amplitudes are measured at the same measurement outputs as with the dummy load. This offers the advantage of a particularly large number of measured values, and the measured values ​​between the dummy load and the reflective termination are particularly easy to compare.

[0051] It is a design that

[0052] - in step (i) the directional coupling device of the measuring system is decoupled from the microwave output of the microwave module and thereby the microwave output of the microwave module is designed as an open end;

[0053] - step (j) comprises performing steps (b), (c), (e) and (g); and

[0054] - Step (k) comprises varying at least the target frequency within the second frequency group and repeating steps (b), (c), (e) and (g) for several, in particular all, target frequencies of the second frequency group.

[0055] This design has the advantage of resulting in fewer measured values. A further advantage is that the elimination of the additional measuring system results in less signal interference (e.g., including transmission losses). In this design, the totally reflecting end of the microwave signal path is formed by the microwave output of the microwave module itself. The directional coupling device of the measuring system is not required. Thus, steps (d) and (f) are omitted.

[0056] It is an advantageous embodiment in the case that the microwave module has a phase shifter that

[0057] - in step (b) a desired phase shift of the microwave signal is additionally specified and

[0058] - in step (h), the target phase shift is additionally varied within a first phase group of different target phase shifts, and at least steps (b) to (h) are each carried out for several, in particular all, pairings of at least the target frequencies of the first frequency group and the target phase shifts of the first phase group; and

[0059] - in step (k), the target phase shift is additionally varied within a second phase group of different target phase shifts, and at least steps (b), (c), (e), and (g) within the group of steps (b) to (h) are each carried out for several, in particular all, pairings of at least the target frequencies of the second frequency group and the target phase shifts of the second phase group. This has the advantage that the dependence of the amplitude / power of the microwave signal on a phase shift can also be measured and thus calibrated or corrected. In step (g), the respectively set values ​​of the target phase shift are additionally saved. After step (h), a calibration data set is then available which contains, as entries, links at least between the specified orset pairs of target frequency and phase shift that were set simultaneously during a measurement, the set target power and the measured values ​​of the microwave power and / or values ​​derived therefrom.

[0060] Here too, the first phase group and the second phase group can be the same or different.

[0061] It is fundamentally irrelevant whether, in the course of the calibration procedure, the target phase shifts from a phase group are run through for a specific target frequency and this process is repeated for at least one further target frequency or whether the target frequencies from a frequency group are run through for a specific value of the target phase shift and this process is repeated for at least one further target phase shift.

[0062] It is a design that

[0063] - in step (h), the target amplitude is additionally varied within a first amplitude group of different values ​​of target amplitudes, and at least steps (b) to (h) are each carried out for several, in particular all, pairings of at least the target frequencies of the first frequency group and the target amplitudes of the first amplitude group that were set simultaneously during a measurement; and

[0064] - in step (k), the target amplitude is additionally varied within a second amplitude group of different values ​​of target amplitudes and at least steps (b), (c), (e) and (g) within the group of steps (b) to (h) are each carried out for several, in particular all, pairings of at least the target frequencies of the second frequency group and the target amplitudes of the second amplitude group.

[0065] This advantageously allows at least the frequency dependence of the amplitude / power to be determined for calibration purposes. Especially when varying the target amplitude, it is advantageous if the target amplitudes of the first amplitude group have at least a few higher values ​​than the target amplitudes of the second amplitude group, since with a reflective termination for higher target amplitude values, the power of the microwave in the reverse direction could potentially damage the power amplifier. This is typically not the case for such higher target amplitude values ​​when a substitute load is present at the end of the microwave link.

[0066] In principle, the target frequency, the target phase shift, and the target amplitude can also be varied or permuted within their groups, and then the measured values ​​for corresponding triples or "triple pairings" of three simultaneously set target values ​​can be saved in a calibration data set.In general, the order in which the desired parameters are varied is arbitrary: for example, if the values ​​of the desired frequency, the desired phase shift, and the desired amplitude are varied, first a respective value of the desired frequency and the desired phase shift can be fixed and the values ​​of the desired amplitude can be varied, then a value of the desired phase shift can be changed, and for the new pair of values ​​of the desired frequency and desired phase shift, the values ​​of the desired amplitude can be cycled through again until all values ​​of the desired phase shift have been set, and then a new value of the desired frequency is set, etc. However, all values ​​of the desired phase shift can also be cycled through in a similar way for a fixed value of the desired amplitude before the desired amplitude is varied, etc.

[0067] One embodiment includes a temperature measurement, particularly the temperature of a power amplifier, especially the main amplifier, linked to the target values ​​and stored in the calibration data set. This offers the advantage that the decreasing gain of the main amplifier due to heating can be taken into account when setting a target power, and a temperature dependence of the detectors' power measurement can also be corrected. Alternatively or additionally, the temperature measurement can be used to detect a possible impending overheating of the power amplifier, especially the main amplifier.

[0068] In one embodiment, correction factors for the operation of the microwave module to be calibrated are calculated from the data entries of the calibration data sets, based on which at least one microwave parameter, including the amplitude of the microwave signal present at the microwave output in the transmission direction, is adjusted to an associated target value. This achieves the advantage that at least the power or amplitude of the microwave signal present at the microwave output of the microwave module can be set to an actual value that corresponds very closely to the target power. In particular, the correction factors can be dependent on the set target frequency, optionally also on the set target phase shift and / or the set target amplitude. Optionally, correction factors can also be calculated for the frequency of the microwave signal.Optionally, correction factors for the temperature dependence of the power amplifier can also be calculated.

[0069] The object is also achieved by a method for calibrating a phase shifter of a microwave module intended for installation in a household cooking appliance, the method comprising at least the following steps:

[0070] (i) providing a microwave module to be calibrated with respect to its phase shift and a microwave module already calibrated with respect to its phase shift, the microwave outputs of which are connected to respective inputs of a combiner;

[0071] (ii) specifying a common target amplitude and a common target frequency for both microwave modules as well as a target phase shift on the calibrated microwave module and a target phase shift on the microwave module to be calibrated;

[0072] (iii) generating, by means of both microwave modules, a respective microwave signal with the specified setpoint values;

[0073] (iv) measuring a signal present at the output of the combiner;

[0074] (v) storing the values ​​of at least the target phase shift and the target frequency specified on the microwave module to be calibrated and / or values ​​derived therefrom as well as the associated measured value as data entries of a phase calibration data set;

[0075] (vi) Varying the target phase shift on the microwave module to be calibrated within a third phase group of different target phase shifts and repeating steps (iii) to (v) for several, in particular all, target phase shifts of the third phase group. This method offers the advantage that the phase shift of the microwave module to be calibrated can be calibrated using a simple measurement setup based on an already phase-calibrated microwave module. Calibrating the phase shift is particularly advantageous when the microwave module to be calibrated is intended to be used in a microwave cooking appliance with multiple microwave modules, in which a targeted interference pattern is to be generated in the cooking chamber by setting a phase shift between the microwaves radiated into the cooking chamber.

[0076] One embodiment includes, in step (vi), additionally varying the target frequency within a third frequency group of different target frequencies, and performing steps (iii) to (v) additionally for several, in particular all, target frequencies of the third frequency group. This also allows frequency-dependent correction coefficients to be obtained from the calibration, which increases the correction accuracy.

[0077] In one embodiment, the target phase shift specified in step (ii) on the calibrated microwave module is 0°, and the target phase shift within the third phase group includes at least the target values ​​0° and 180°. This is particularly advantageous because the sum signal should have a maximum amplitude at 0° and a minimum amplitude at 180°. Actual deviations at these points can be particularly easily converted into correction factors.

[0078] It is an embodiment that correction factors for the operation of the microwave module to be calibrated are calculated from the stored data entries of the phase calibration data set, on the basis of which the phase shifts are adapted to the respective associated target phase shifts.

[0079] The correction factors can generally be obtained, for example, by interpolation and, if necessary, extrapolation of the calibration data sets. The entries in the calibration data sets can serve as support points. The interpolation and extrapolation can be carried out using any suitable calculation method, e.g., by fitting to a polynomial function. In the simplest case, for example, a measured value x is measured at detector 14a, e.g., x = 140 W. In reality, however, a power f(x) = 130 W was transmitted, measured with the much more accurate detector 55a-1. If a linear polynomial function is used, the functional relationship between x and f(x) is the equation f(x) = mx + xo with m and xO as the correction factors. With further measurements at other target powers, the correction factors m and xO can be determined. Typically, however, the actual value is derived from a multidimensional polynomial function of higher order (e.g.,at least quadratic) order, e.g. according to f(x, y, z) = a + bx + cx. 2 +dy + ey 2 + fz + gz 2 + ...) with f(x, y, z) being the power measured at detector 55a-1, x being the power measured at detector 14a, y being the set value of the target frequency, z being the set value of the target phase shift, and a, b, c, d, e, f, and g being correction factors.

[0080] In addition, preliminary aging tests can reveal the relationship between component deterioration over time and stress factors such as power, voltage peaks, and temperature. This aging can also be incorporated / considered in the correction factors.

[0081] In particular, correction factors can be calculated for the following measured values:

[0082] - the amplitude or power of the microwave signal in the forward direction measured at the directional coupling device of the microwave module compared to the actual amplitude or power of the microwave signal in the forward direction measured at the directional coupling device of the measuring system, in particular if a dummy load is connected;

[0083] - Amplitude or power of the (reflected) microwave signal in the reverse direction measured at the directional coupling device of the microwave module compared to the actual amplitude or power of the microwave signal in the reverse direction measured at the directional coupling device of the measuring system when measuring with the reflective end termination of the measuring system or amplitude or power of the microwave signal in the reverse direction measured at the directional coupling device of the microwave module compared to the values ​​of the amplitude or power of the microwave signal in the forward direction corrected with the correction factors for the equivalent load when measuring without the (then uncoupled) measuring system.

[0084] These correction factors can be dependent on frequency, amplitude, temperature, phase shift, and / or aging. For some phase shifter designs, the following additional correction factor can be calculated:

[0085] - Specified or set target phase or phase shift (e.g. as control value of the phase shifter) to the actually existing phase shift, e.g. determined by means of the above phase calibration method.

[0086] This correction factor may depend on the amplitude, frequency, temperature and / or aging.

[0087] For some types of signal generators, e.g. VCO and resonant circuit:

[0088] - Preset or set frequency (e.g. as control value of the signal generator) to the actual frequency of the microwave signal in the forward direction measured by the measuring system.

[0089] This correction factor may depend on the amplitude, frequency, temperature and / or aging.

[0090] Another possible correction factor may include, for example:

[0091] - the set target amplitude (e.g. as control value of the attenuator) to the actual amplitude measured on the measuring system in the transmitting direction.

[0092] This correction factor may depend on temperature, frequency, phase and / or aging.

[0093] The object is also achieved by a household microwave cooking appliance, comprising

[0094] - a microwave-tight cooking chamber that can be closed by means of a door and exposed to microwaves,

[0095] - at least one microwave module which is configured to set at least one amplitude and one frequency of a microwave signal emitted at a microwave output to variable target values, and which has a directional coupling device at least for measuring the amplitude of an emitted microwave signal and a reflected microwave signal;

[0096] - a control device configured to adapt at least one microwave parameter, including the amplitude of the microwave signal transmitted to the at least one antenna, to an associated setpoint value using correction factors calculated according to at least one of the above methods.

[0097] The household microwave cooking appliance can be designed analogously to the above calibration methods, and vice versa, and provides the same advantages. The correction factors can be precalculated and then stored in a non-volatile memory of the household microwave cooking appliance, e.g., in a non-volatile memory of the control device, for example, in the form of a lookup table or a characteristic curve map. The control device can be, e.g., a microprocessor, a microcontroller, an ASIC, an FPGA, etc. Alternatively, the calibration data sets can be stored in a non-volatile memory of the household microwave cooking appliance, and the correction factors are calculated by the microwave module itself, in particular by its control device.

[0098] In general, the microwave module can comprise all the components necessary for generating a line-bound microwave signal, from the clock generator to the power amplifier. However, for a compact and cost-effective design, it can be advantageous if at least some components for signal generation are not installed in a microwave module, but are, for example, installed independently or are installed in a dedicated signal generation module, which can comprise the clock generator, the signal generator, the bandpass filter and / or the chopper. The use of a standalone signal generation module can be particularly advantageous if it generates a microwave signal that – for example, via a splitter

[0099] - can be applied to several microwave modules.

[0100] The object is further achieved by a calibration setup for carrying out the first method above, comprising a microwave module and a measuring system, wherein the measuring system comprises at least

[0101] - a directional coupling device that can be detachably connected to a microwave output of the microwave module;

[0102] - a replaceable attachment for a microwave output of the directional coupling device, which is designed as a substitute load;

[0103] - a further interchangeable attachment for the microwave output of the directional coupling device, which is designed as an open end; - a detector for measuring an amplitude of a measurement signal output at a first measurement output of the directional coupling device;

[0104] - a detector for measuring an amplitude of a measurement signal output at a second measurement output of the directional coupling device; and

[0105] - a data processing device connected to the detectors, which can be coupled to a control unit of the microwave module for controlling the latter; and wherein at least a frequency and an amplitude, optionally also a phase shift, of the microwave signal generated thereby can be varied on the microwave module. This calibration setup can be designed analogously to the method that can be performed thereon, and vice versa, and offers the same advantages.

[0106] The object is further achieved by a calibration setup for carrying out a method for calibrating a phase shift, comprising a calibrated microwave module, at least one microwave module to be calibrated and a measuring system, wherein

[0107] - the measuring system comprises a combiner whose inputs are connected to the microwave outputs of the microwave modules and whose output is connected to a detector of the measuring system, and wherein

[0108] - the detector is connected to a data processing device of the measuring system, which can be coupled to control units of the microwave modules for controlling them; and wherein at least a frequency and a phase shift, and possibly also an amplitude, of the microwave signal generated thereby can be varied on the microwave modules.

[0109] The above-described properties, features and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more clearly understood in connection with the following schematic description of embodiments, which are explained in more detail in connection with the drawings.

[0110] Fig.1 shows a structure of a semiconductor microwave generation system with a microwave module;

[0111] Fig.2 shows a variant of a directional coupler of the microwave module from Fig.1;

[0112] Fig.3A shows another variant of a directional coupler of the microwave module from

[0113] Fig.1 ; Fig.3B shows another variant of a directional coupler of the microwave module from Fig.1 ;

[0114] Fig.4 shows a structure of a semiconductor microwave generation line with two microwave modules;

[0115] Fig.5 shows another structure of a semiconductor microwave generation system with two microwave modules;

[0116] Fig.6 shows a calibration setup for calibrating the microwave module from Fig.1;

[0117] Fig.7 shows a first part of a calibration procedure that can be carried out using the calibration setup shown in Fig.6;

[0118] Fig.8 shows a second part of the calibration process according to a first variant, which can follow the first part shown in Fig.7,

[0119] Fig.9 shows a second part of the calibration process according to a second variant, which can follow the first part shown in Fig.7;

[0120] Fig.10 shows another calibration setup for calibrating the microwave module from Fig.1; and

[0121] Fig.11 shows a calibration procedure that can be carried out using the calibration setup shown in Fig.8.

[0122] Fig.1 shows a structure of a semiconductor microwave generating section 1 for generating microwave radiation.

[0123] At the beginning of the microwave generation path 1, a clock generator 2, such as a quartz oscillator or other frequency source, is provided, whose clock signal is fed into a controllable signal generator 3. The clock signal is highly frequency-stable and can, for example, have a clock frequency in a range between several hundred kHz and several tens of MHz. A bandwidth is typically a few hertz to several tens of hertz.

[0124] Using the clock signal, signal generator 3 generates a working or microwave signal at a desired microwave frequency with comparatively low power. The microwave frequency generated by signal generator 3 can be adjusted by a control device, e.g., a microcontroller 4 (frequency-variable signal generator 3). In particular, microwave signals with a frequency in a frequency range between 2.4 GHz and 2.5 GHz can be generated, but are not limited thereto. Signal generator 3 can, for example, be an oscillator, VCO, PLL, synthesizer, resonant circuit, etc.

[0125] A bandpass filter 5—which is optional—is connected downstream of the signal generator 3. This has the advantage of suppressing unintentionally generated unwanted frequencies, e.g., outside an ISM band or outside the adjustable frequency range, e.g., outside the 2.4 GHz to 2.5 GHz band.

[0126] The optional bandpass filter 5 is followed by a controllable chopper 6, which is generally optional. The presence of the chopper 6 offers the advantage of enabling partial power generation with very high efficiency. The microwave generation system 1 can be set to a power level at which it operates with the highest possible efficiency. Partial power generation is achieved with the chopper 6 by switching the microwave signal on and off at specific times, e.g., similar to a PWM control. Desired partial power or full power can be specified using the microcontroller 4.

[0127] An optional amplifier ("intermediate amplifier") 7 is connected downstream of the optional chopper. Whether and at which point an intermediate amplifier 7 is required depends on the specific implementation of the microwave generation path 1. For example, an intermediate amplifier 7 can be used if the amplitude of the microwave signal is considered too low at this point in the microwave generation path 1. Multiple intermediate amplifiers 7 can also be distributed along the microwave generation path 1.

[0128] The optional intermediate amplifier 7 is followed by a likewise optional phase shifter 8. The phase shifter 8 may, however, be necessary if a desired interference pattern is to be generated in a cooking chamber 23 of the household microwave cooking appliance 24 using at least two microwave generation paths 1. The magnitude of the phase shift of the incoming microwave signal is controlled via the microcontroller 4, e.g. in steps of 1°, 2°, 5° or 10° within a range between 0° and 180° or 0° and 360°. An amplitude controller in the form of an attenuator 9 is connected downstream of the optional phase shifter 8. The attenuator 9 controls the amplitude of the microwave signal entering the preamplifier 10 and reduces this amplitude, in particular by an amount or factor that can be set by the microcontroller 4. Instead of the attenuator 9, a controllable amplifier, e.g. a VGA, can also be used as an amplitude controller.Furthermore, the amplitude can be adjusted via a suitable intermediate amplifier ?, where, for example, its gate voltage is controlled.

[0129] The attenuator 9 is followed by a final amplifier 10, 11 in the form of a series circuit, used here as an example, consisting of another amplifier ("preamplifier") 10 and yet another amplifier ("main amplifier") 11. The preamplifier 10 can be constructed in several stages. If at least one intermediate amplifier 7 is present, it is located in the microwave generation path 1 between the signal generator 3 and the final amplifier 10, 11.

[0130] A directional coupling device 12 is connected downstream of the main amplifier 11, to whose measurement outputs 13a and 13b respective detectors 14a and 14b, e.g., voltmeters, are connected. The measurement signals from the detectors 14a, 14b and from an optional temperature sensor 15, e.g., arranged on the main amplifier 11, are fed to the microcontroller 4 directly or via an analog-to-digital converter (not shown).

[0131] An antenna 16 is connected to the output of the directional coupling device 12, which converts the microwave signal into microwave radiation and radiates it, e.g. directly into a cooking chamber or into a microwave guide.

[0132] In particular, a measurement signal, in particular a voltage signal, is output at the measurement output 13a. This signal is a measure of the amplitude and thus the power of the microwave signal traveling to the antenna 16 in the forward or transmission direction. A measurement signal, in particular a voltage signal, is output at the measurement output 13b. This signal is a measure of the power of the reverse microwave signal coupled in via the antenna 16. These power levels can be used, for example, to control, in particular regulate, the semiconductor microwave generation path 1. In general, the components 2 to 15 described above can be arranged arbitrarily in the household microwave cooking appliance. It is particularly advantageous if at least some of these components 2 to 15 are parts of a microwave module 17 prefabricated before installation in the household microwave cooking appliance.For example, components 3 to 15 can be parts of the microwave module 17, as indicated by dashed lines, or components 2 to 15 can be parts of the microwave module 17, as indicated by dotted lines. However, other assignments to one or more modules are also possible, as described in more detail below. Typically, in the installed state, the antenna 16 is connected to a (microwave) output 18 of the microwave module 17.

[0133] Furthermore, two or more of components 2 to 15 can be functionally replaced by a single component. For example, if a synthesizer is used as signal generator 3, one or more of components 6, 8, and / or 9 can be omitted, since a synthesizer already incorporates their functions. Many commercially available synthesizers can chop (switch on and off in time) and phase shift. Some can also implement fine-tuned amplitude control.

[0134] Fig. 2 shows a variant of a directional coupler 12 in the form of a bidirectional directional coupler 12-1 without a circulator. The measurement outputs 13a, 13b represent only a fraction of the amplitude of the working or microwave signal passed through the directional coupler 12-1. Typical coupling values ​​are in the range of -30 dB. By far the largest portion of the microwave signal arriving from the main amplifier 11 exits the directional coupler 12-1 toward the output 18 or antenna 16.

[0135] Fig. 3A shows a variant of the directional coupler 12. A directional coupler 12-2 is used, which has a circulator 19 following the main amplifier 11. The circulator 19 protects the main amplifier 11 from excessively high reflected signals from the cooking chamber. The circulator 19 transmits the microwave signal received by the main amplifier 11 through a one-way directional coupler 20 toward the output 18 or the antenna 16. Signals reflected from the cooking chamber, which flow from the antenna 16 toward the circulator 19, are redirected by the circulator 19 through another one-way directional coupler 21 to a terminating resistor 22. Fig.3B shows a variant of the directional coupler 12 in the form of a directional coupler 12-3 with circulator 19, in which, compared to the directional coupler 12-2, the circulator 19 and the one-way directional coupler 20 (with the associated components) are arranged in reverse in the signal path.

[0136] Fig. 4 shows the structure of a microwave generation line 31 of a household microwave cooking appliance 32 with two microwave modules 17. Their signal generator 3 is fed from the same clock generator 2, which can be a separate component from both microwave modules 17 or can be integrated into one of the microwave modules 17. The microcontrollers 4 are both controlled by a common control unit 33, for example, to adjust phase shifts on one or both of the microwave modules 17. By phase shifting the microwave signals of the two microwave modules 17, targeted interference patterns can be generated in the cooking chamber 23.

[0137] The microwave generation path 31 can be continued analogously for more than two microwave modules 17.

[0138] Fig. 5 shows a further configuration of a semiconductor microwave generation system 41 of a household microwave cooking appliance 42 with two microwave modules 17 with two microwave modules 43, which are fed with microwave signals from a common signal generation module 44. The microwave modules 43 now only comprise components 7 to 15 each, while components 2, 3, 5, 6 are assigned to the signal generation module 44. The microwave modules 43 further comprise a microcontroller 45 for controlling the associated components 7 to 9 and for evaluating the measurement signals from the directional coupling device 12, while the signal generator 3 and the chopper 6 are controlled by a microcontroller 46. The microcontrollers 45 and 46 are in turn under the control of the common control unit 33.

[0139] The output signals of the signal generation module 44 are split using a splitter 47 and forwarded to the inputs of the microwave modules 43. The microwave generation path 41 can also be extended in an analog manner for more than two microwave modules 43, as indicated by the dashed line extending from the splitter 47.

[0140] Due to component and installation tolerances of components 2 to 15 and 17 to 22, it may happen that the measured values ​​output by detectors 14a, 14b to microcontrollers 4 and 45, respectively, are inaccurate, so that, for example, instead of a set target power, target frequency, and / or target phase shift, a deviating microwave signal is output to output 18 or antenna 16. To correct this error, one or more components of semiconductor microwave generation system 1, in particular microwave module 17, can be calibrated, which will be explained in more detail below.

[0141] Fig.6 shows a calibration setup for calibrating a microwave module 17, selected here as an example, with its components 2 to 15 by means of a measuring system 51. The microwave module 17 is connected on the input side to a clock generator 2.

[0142] The microwave output 18 is now not connected to the antenna 16, but to a directional coupling device 52 of the measuring system 51. The directional coupling device

[0143] 52 can be equipped analogously to the directional coupling device 12-1 as a bidirectional directional coupler without a circulator or analogously to the directional coupling device 12-2 with a circulator. The directional coupling device 52 has a higher measurement accuracy / lower error tolerance than the directional coupling device 12. Analogously to the directional coupling device 12, the directional coupling device 52 has a microwave output 53, a measuring output 54a for measuring in the transmission direction to the microwave output

[0144] 53 and a measuring output 54b for measuring reflected microwaves returning from the microwave output 53. A detector 55a-1 for measuring an amplitude of the measurement signal present at the measuring output 54a and optionally a detector 55a-2 for measuring a frequency of the measurement signal present at the measuring output 54a (e.g. a spectroscope) are connected to the measuring output 54a. A detector 55b for measuring an amplitude of the measurement signal present at the measuring output 54b is connected to the measuring output 54b. The detectors 55a-1, 55a-2 and 55b are connected to a data processing device 56, such as a computer of the measuring system 51, which stores their measured values ​​and / or values ​​derived therefrom. In principle, the detector 55a-2 can be omitted and the frequency, with a sufficiently high sampling rate, can also be determined from the amplitude measured values ​​of the detector 55a-1.

[0145] In a further development, the data processing device 56 calculates correction factors from stored values, which are designed to correct systematic errors in the functioning of the microwave module 17, in particular when the microwave module 17 is installed in a household microwave cooking appliance. The correction factors can also be referred to as calibration factors, calibration coefficients, error correction coefficients, etc. For this purpose, the correction factors can be transferred, for example, to a non-volatile memory of the microwave module 17 (e.g., an EEPROM) that can be accessed by the microcontroller 4, 45 or that is integrated into the microcontroller 4, 45. Alternatively, the measurement data are transferred to a non-volatile memory of the microwave module 17 that can be accessed by the microcontroller 4, 45 or that is integrated into the microcontroller 4, 45, and the correction factors are calculated from this basis by the microcontroller 4, 45 itself.

[0146] The microwave output 53 can be provided with various interchangeable attachments, e.g. a dummy load 57, e.g. of 50 ohms, or an attachment ("calibration attachment") 58, which provides a reflective end termination at the microwave output 53, at which microwave signals sent by the directional coupling device 52 to the microwave output 53 in the transmission direction are practically completely reflected back.

[0147] The measurement section of the measuring system 51 and any connecting cables to the detectors 55a-1, 55a-2, and 55b have advantageously been measured using a precise network analyzer or similar device to obtain the actual, generally frequency-dependent correction values ​​of the calibration setup itself. This can also be expressed by saying that the measuring system itself is already calibrated (precalibrated).

[0148] Fig. 7 shows a first part of a calibration process for calibrating at least the power output of the microwave module 17, which can be carried out using the calibration setup shown in Fig. 6. For this purpose, in step S1, the microwave output 18 of the microwave module 17 is connected to the input of the directional coupling device 52 of the measuring system 51, wherein, as an example, the attachment representing a substitute load 57 is initially connected to the microwave output 53 of the measuring system 51. The data processing device 56 directly controls the individual controllable components 3 and 6-9 of the microwave module 17 via the microcontroller 4. The control of the microcontroller 4 is thus deactivated. Furthermore, an input of the signal generator 3 is connected to an output of a clock generator 2.

[0149] In step S2, the data processing device 56 sets initial values ​​for a target frequency, target amplitude, and target phase shift. For example:

[0150] - the target frequency can be varied within a range of [2.4; 2.5] GHz, e.g. in steps of 0.01 GHz or 10 MHz; e.g. by means of signal generator 3. The corresponding desired or set target frequencies from this range form a first frequency group;

[0151] - the target power can be varied in a range [120; 300] W, e.g. in steps of 60 W, for example by means of the attenuator 9. The corresponding desired target powers or those set from this range or, analogously, the target amplitudes form a first amplitude group;

[0152] - the desired phase shift can be varied in a range [0; 360] °, e.g. in steps of 10°, namely by the phase shifter 8. The corresponding desired or set desired phase shifts from this range form a first phase shift group.

[0153] In the following, it is assumed, by way of example, that the initial target frequency corresponds to the lowest frequency value from the first amplitude group, the initial target power corresponds to the lowest amplitude value from the first amplitude group and the initial target phase shift corresponds to the value 0°.

[0154] In a step S3, the microwave module 17 is now activated with the predetermined values ​​for the target frequency, target amplitude, and target phase shift. In this process, the signal generator 3 generates a working or microwave signal which has the predetermined nominal target frequency and is subsequently filtered in the bandpass filter 5. The filtered microwave signal is chopped in the chopper 6 and amplified for the first time by the intermediate amplifier 7. The microwave signal is then phase-shifted by the predetermined target phase shift, e.g., within a range [0°; 360°], by means of the phase shifter 8. The microwave signal is then either passed unattenuated through the attenuator 9 or attenuated by the attenuator 9 to a desired amplitude level. The attenuated microwave signal is then amplified first by the preamplifier 10 and then by the main amplifier 11 to the desired target power orTarget amplitude amplified, which should be present at the microwave output 18.

[0155] In a sub-step S3a, the microwave signal output by the main amplifier 11 is passed through the directional coupling device 12. A very small portion of the microwave signal is coupled out as a measurement signal to the measurement output 13a by the directional coupling device 12 and measured in a step S4 by the detector 14a. The measurement signal can be present, for example, as a voltage signal and is representative of the amplitude of the microwave signal output by the main amplifier 11 and thus also of its power. Any conversion from voltage to amplitude or power can be performed, for example, using a data set provided by the manufacturer of the directional coupling device 12. It should be noted that these conversion data may also be subject to tolerances or errors.

[0156] From the microwave output 18, the microwave signal travels in a sub-step S3b through the directional coupling device 52 of the measuring system 51 to the microwave output 52 of the measuring system 53 and is then at least largely absorbed in the equivalent load 57. A small portion of the microwave signal conducted to the equivalent load 53 is coupled out of the directional coupling device 52 to the measuring connection 54a and measured in step S5 at the detector 55a-1 with respect to its amplitude / power and optionally at the detector 55a-2 with respect to its frequency, bandwidth, etc.

[0157] A portion of the microwave signal reflected back from the microwave output 52 is measured in a generally analogous manner with respect to its amplitude / power at the detector 13b and at the detector 55b during step S4 or step S5. Thus, at least the following values ​​are available: target frequency, target amplitude / power, target phase shift, amplitude of the microwave signal in the transmission direction measured at detector 13a, amplitude of the reflected microwave signal measured at detector 13b, amplitude of the microwave signal in the transmission direction measured at detector 55a-1, and amplitude of the reflected microwave signal measured at detector 55b.

[0158] In step S6, the measured values ​​(e.g. voltage values, amplitude, frequency, phase shift) and / or values ​​derived therefrom (e.g. power) are stored together with the specified target values ​​as data entries of a calibration data set.

[0159] The sequence of steps S3 to S6 is then repeated with variation, in particular stepwise incrementation, of the target values ​​until corresponding data entries are available in the calibration data set for all desired permutations of the target values.

[0160] This can be implemented, for example, as shown, by first checking in step S7 whether the highest value of the microwave frequency is set.

[0161] If this is not the case ("N"), the current value is changed to the next higher value in step S8, e.g., increased by one step, and the process branches back to step S3. The variation of the frequency can also be referred to as a "frequency sweep."

[0162] However, if this is the case ("Yes"), the quality of the microwave signal (actual frequency, measured frequency, bandwidth, harmonics, etc.) can optionally be evaluated in step S9 from the measurement signals measured by detector 55a-2. For this purpose, it is advantageous if the amplitude still corresponds to the initial, lowest amplitude, but is generally at least rather low.

[0163] Following step S8 or S9, in step S10, the frequency value is first reset to its lowest value and then a query is made as to whether the highest amplitude / power value has been set. If this is not the case ("N"), the current amplitude / power value is changed to the next higher value in step S11, e.g., increased by one step size, and the process branches back to step S3. The variation of the amplitude can also be referred to as an "amplitude sweep." However, if step S10 is answered affirmatively ("Y"), in step S12, the amplitude value is first reset to its lowest value and then a query is made as to whether the highest phase shift value has been set. If this is not the case ("N"), the current phase shift value is changed to the next higher value in step S13, e.g., increased by one step size, and the process branches back to step S3. The variation of the phase shift can also be referred to as a "phase sweep."

[0164] If step S12 is answered positively, a calibration data set is available containing the measured amplitudes / powers as a function of the varied or "swept" setpoints. Optionally, the temperature T measured by the temperature sensor 15 can also be stored.

[0165] Of course, one or more setpoints can also be decremented starting from a highest value or set in any other order.

[0166] A calibration data set available after step S12 for a microwave output 53 equipped with the substitute load 57 could therefore, for example, look as follows if the target frequency f S0 n is incremented from 2400 MHz to 2500 MHz in steps of 50 MHz, the target phase shift cp S oii is incremented from 0° to 240° in steps of 120° and the target amplitude / power P son is decremented from 300 W to 120 W in steps of 60 W:

[0167] This data set enables an exact detection of the transmitted amplitude of the microwave module 17 by means of the integrated detector 14a.

[0168] In addition to the first part of the calibration procedure, a second part is carried out, which is described in more detail below.

[0169] Fig.8 shows a second part of the calibration method according to a first variant, which, as shown, can follow the first part shown in Fig.7, but can in principle also be carried out before the first part.

[0170] Following the first part, the calibration attachment is now changed in a step S14, namely from the equivalent load 57 to a calibration attachment which acts like a reflective end closure and therefore ideally totally reflects incident waves.

[0171] In a step S15, the data processing device 56 again sets initial values ​​for the target frequency and the target amplitude, in particular analogously to step S2. However, the limits of the adjustable value ranges and / or the step sizes may differ from the case with the substitute load 57. For example, it may be the case that the higher amplitudes set when using the substitute load 57 are so high that they could lead to damage to the main amplifier in the event of backreflection in the event of an open or short-circuited end. Therefore, in the second part of the calibration process, lower target powers are set which are at most as high as the reflected amplitude that the main amplifier 11 can withstand. For example, the target power can only be varied within a range of [120; 180] W, e.g., in steps of 30 W or 60 W. Consequently, the corresponding desired target powers or those set from this range form the target powers.Analogously, target amplitudes define a second amplitude group that differs from the first amplitude group. The second frequency group can also differ from the first frequency group or the second phase group, but this is not required.

[0172] For the second part, it is assumed in the following that the initial target frequency corresponds to the lowest frequency value from the second frequency group and the initial target power corresponds to the highest amplitude value from the second amplitude group.

[0173] Furthermore, in step S15, the phase shift is set, for example, to a fixed value, in particular 0°, and is not further varied in the second part.

[0174] Steps S16 to S23 are carried out analogously to steps S3 to S8 and S10 to S11 (i.e. step S9 of the quality check of the microwave signal is not carried out again), whereby the measured values ​​or values ​​derived therefrom are stored as data entries of a further calibration data set.

[0175] A further calibration data set available after a positive answer to step S22 for a microwave output 53 equipped with the calibration attachment 58 could then, for example, contain values ​​of the power Pi 4a , Pi4t>, Pssa-i and Pssb as well as the temperature T for the target frequency f S0 n is incremented from 2400 MHz to 2500 MHz in steps of 50 MHz and the target amplitude / power P son decremented from 180 W to 120 W in steps of 30 W. In contrast to the calibration data set created with substitute load 57, the amplitude and power values ​​Pi4b and Pssb for the reflected microwave signal measured at detectors 14b and 55b are now significantly higher due to total internal reflection.

[0176] Subsequently, in a step S24, the microwave module 17 is switched off.

[0177] For the subsequent step S25, there are two options:

[0178] In a first variant, correction coefficients are calculated from the calibration data sets by means of the data processing device 56. These correction coefficients are intended to calibrate the operation of the microwave module 17, in particular based on the measured values ​​output by the detectors 14a and 14b, in order to output microwave signals at the microwave output 18 whose amplitude, frequency, and / or phase correspond as closely as possible to the set target values. Specifically, this enables the measured values ​​output by the detectors 14a and 14b to be correlated or assigned with high accuracy with the values ​​of the amplitude / power emitted in the transmission direction and the reflected power actually present at the microwave output 18.

[0179] The correction coefficients can be calculated from the entries in the calibration data sets, for example, by a function fit with the entries as reference points, for example, by calculating polynomial functions of any order greater than one, i.e., they can be approximated using linear, quadratic, etc. polynomials. This allows, for example, interpolation to assign correction coefficients to sets of target values ​​that have not been directly set. Furthermore, it is possible to extrapolate the entries in the calibration data sets to sets of correction coefficients that lie outside the range of one or more set target values.For example, it may be the case that the calibration data set for the calibration attachment 58 serving as the reflective end termination is missing some measurement points for the target amplitude that are higher than the maximum target amplitude allowed by the main amplifier 11, but less than or equal to the maximum adjustable target amplitude. The missing measurement points can be extrapolated from the existing measurement points, or the correction coefficients for the missing target amplitude values ​​can be extrapolated from the existing target amplitude values.

[0180] These correction coefficients are then transferred from the data processing device 56 into a non-volatile data memory of the microcontroller 4 or into a non-volatile data memory of the microwave module 17 connected to the microcontroller 4.

[0181] In a second variant, the correction coefficients are transferred as such to the non-volatile data memory by means of the data processing device 56. The microcontroller 4 is configured to calculate correction coefficients from the calibration data sets. The measuring system 51 can then be disconnected from the microwave module 17, whereupon the microcontroller 4 operates independently again.

[0182] The microwave module 17 can then be installed in a household microwave cooking appliance, or the phase shift can be calibrated in a further calibration setup, as explained in more detail in Figures 10 and 11 below.

[0183] First, however, Fig.9 shows a second part of the calibration method according to a second variant, which, as shown, can follow the first part shown in Fig.7 or can be carried out before the first part.

[0184] In this variant, following the positive response to step S12 and after the complete variation or "sweeping" of the setpoint values ​​of power, frequency, and phase shift, the directional coupling device 52 is disconnected from the microwave module 17 in a step S26, so that the microwave output 18 itself serves as an open end, causing a total reflection of the (transmitted) microwave signals traveling in the transmission direction to the microwave output 18. The detectors 55a-1, 55a-2, and 55b are therefore not used.

[0185] Following steps S27 to S35 are carried out analogously to steps S15 to S23, and a further calibration data set is created with the entries of the measured values ​​of the powers Pi4a and Pi4b and, if applicable, the temperature T for the setpoints f S0 n and P son. In a further development, the calibration data set from the first part can be applied directly to the measured values ​​of the transmitted power Pi4a.

[0186] Following the positive response in step S34 after a complete sweep of the target frequency and the target amplitude, steps S24 and S25 can be carried out analogously to the first variant.

[0187] Fig. 10 shows another calibration setup for calibrating the phase shift of the microwave module 17 using a measuring system 61 using an already calibrated microwave module 17kai. The signal generators 3 of the two microwave modules

[0188] 17 and 17kai are connected to the same clock generator 2. The microwave outputs

[0189] 18 are connected via an optional respective attenuator 62 of the measuring system 61 to respective inputs of a combiner 63 of the measuring system 61, the output of which is connected to a detector 64, e.g., a voltmeter, of the measuring system 61, which in turn is connected to the data processing device 56 of the measuring system 61. Cable lengths should be taken into account in the design in order to be able to detect and, if necessary, compensate for phase shifts caused by different cable lengths.

[0190] One advantage of using attenuators 62 is that many combiners 63 can only withstand low power levels, so attenuators 62 serve to protect combiner 63. A further advantage is that the two microwave modules 17 and 17kai can then be operated at high output power. The power level can then be set approximately the same, and the absolute deviations are no longer significant relative to the high level. At low levels (e.g., due to internal pre-attenuation by attenuator 9), a relative amplitude error would be extremely noticeable.

[0191] Here, too, the data processing device 56 controls the microcontrollers 4 of the microwave modules 17 and 17kai in such a way that the data processing device 56 directly controls the individual components of the microwave modules 17 and 17kai. The control function of the microcontrollers 4 is thus deactivated.

[0192] If the phases of the microwave signals emitted at the microwave outputs 18 are in phase (i.e., they have a phase shift of 0° between them), the detector 64 measures a maximum sum signal. If the phases of the microwave signals emitted at the microwave outputs 18 are in phase opposition (i.e., they have a phase shift of 180° between them), the detector 64 measures a minimum sum signal. This is used to determine whether the phase shifter 8 of the microwave module 17 to be calibrated is operating correctly or whether the phase shift at this phase shifter 8 should be corrected or calibrated based on the measured actual phase shift to the target phase shift.

[0193] Fig. 11 shows a calibration procedure that can be performed using the calibration setup shown in Fig. 10. In a step S41, the same target amplitude / target power is set for both microwave modules 17 and 17kai using the data processing device 56 for the calibration setup shown in Fig. 10. In particular, the target amplitude can be set to a medium value, such as 100 W.

[0194] Furthermore, the target phase shift of the microwave module 17kai is set to a specific value from a third phase group of different phase shift values, advantageously to 0°. Since the microwave module 17kai is already calibrated, it can be assumed that its target phase shift corresponds to its actually set phase shift with a high degree of accuracy.

[0195] In step S41, the target phase shift of the microwave module 17 is also set to a specific initial value from the third phase group, advantageously to the same value as the set target phase shift of the calibrated microwave module 17kai, in particular to 0°.

[0196] In step S42, a query is made as to whether all values ​​of the target phase shift to be set have already been set once.

[0197] If this is not the case ("N"), in step S43 the sum signal of the two microwave signals of the two operated microwave modules 17 and 17kai, which is present at the output of the combiner 63 by means of the detector 64, in particular measured, is transmitted to the data processing device 56 and stored there together with the values ​​of at least the set nominal frequency and the nominal phase shift set on the microwave module 17 as a data entry in a further calibration database.

[0198] In addition, in step S44, the value of the desired phase shift set on the microwave module 17 is changed by a step size, e.g. 30°, 60°, 90° or 180°, e.g. incremented or decremented, and branched back to step S42.

[0199] However, if the query in step S43 is answered positively ("Y"), the desired

[0200] The values ​​of the third phase group have been passed through or swept once, and the process branches to step S45. If the phase shifter 8 of the microwave module 17 is operating correctly, the sum signal is maximum at 0° and minimum (close to zero) at 180°.

[0201] In step S45, the target phase shift of the microwave module 17 is reset to the determined initial value.

[0202] In step S46, a query is made as to whether all values ​​of the target frequency to be set from the third frequency group have already been set once.

[0203] If this is not the case ("N"), the program branches to step S47, where the target frequency on both microwave modules 17 and 17kai is set, in particular incremented or decremented, to an identical new value from the third frequency group. The program then branches back to step S42.

[0204] If this is the case ("Y"), however, the calibration data set is complete, based on which the phase shift of the phase shifter 8 of the microwave module 17 can be corrected. The program then branches to step S48, in which—analogous to steps S24 and S25—in one variant, correction coefficients are calculated from the calibration data set using the data processing device 56. These correction coefficients are intended to calibrate the operation of the microwave module 17 in order to output microwave signals whose phase or phase shift corresponds as closely as possible to the set target values.Here too, in a second variant, the correction coefficients can be transferred from the data processing device 56 into a non-volatile data memory of the microcontroller 4 or into a non-volatile data memory of the microwave module 17 connected to the microcontroller 4, wherein the microcontroller 4 is configured to calculate correction coefficients for the phase shift from the calibration data set.

[0205] Subsequently, the measuring system 61 can be separated from the microwave module 17, whereupon the microcontroller 4 operates independently again.

[0206] Of course, the present invention is not limited to the illustrated embodiment. Generally, "a," "an," etc., can be understood as a singular or plural, particularly in the sense of "at least one" or "one or more," etc., unless explicitly excluded, e.g., by the expression "exactly one," etc. A numerical specification can also encompass the exact number indicated as well as a standard tolerance range, unless explicitly excluded.

[0207] List of reference symbols

[0208] 1 microwave generation line

[0209] 2 clock generators

[0210] 3 signal generators

[0211] 4 microcontrollers

[0212] 5 bandpass filters

[0213] 6 choppers

[0214] 7 intermediate amplifiers

[0215] 8 phase shifters

[0216] 9 Attenuator

[0217] 10 preamplifiers

[0218] 11 main amplifiers

[0219] 12 Directional coupling device

[0220] 12-1 Bidirectional directional coupler without circulator

[0221] 12-2 Directional coupler with circulator

[0222] 12-3 Directional coupler with circulator

[0223] 13a Measuring output for power in forward direction

[0224] 13b Measuring output for power in reverse direction

[0225] 14a Forward power detector

[0226] 14b Reverse power detector

[0227] 15 Temperature sensor

[0228] 16 Antenna

[0229] 17 Microwave module

[0230] 17kai Pre-calibrated microwave module

[0231] 18 Microwave output of the microwave module

[0232] 19 Circulator

[0233] 20 one-way directional couplers

[0234] 21 one-way directional couplers

[0235] 22 Terminating resistor

[0236] 23 Cooking chamber

[0237] 24 Household microwave cooking appliance

[0238] 31 Microwave generation system 32 Household microwave cooking appliance

[0239] 33 Control unit

[0240] 41 Microwave generation line

[0241] 42 Household microwave cooking appliance

[0242] 43 Microwave module

[0243] 44 Signal generation module

[0244] 45 microcontrollers

[0245] 46 microcontrollers

[0246] 47 splinters

[0247] 51 measuring system

[0248] 52 directional coupling device

[0249] 53 Microwave output of the measuring system

[0250] 54a Measuring output for power in forward direction

[0251] 54b Measuring output for power in reverse direction

[0252] 55a-1 Detector for amplitude measurement

[0253] 55a-2 Detector for frequency measurement

[0254] 55b Detector for amplitude measurement

[0255] 56 Data processing facility

[0256] 57 Substitute load

[0257] 58 Reflective end cap

[0258] 61 measuring system

[0259] 62 Attenuator

[0260] 63 combiners

[0261] 64 detector

[0262] S1-S35 Process steps

[0263] S41-S47 Process steps

Claims

Claims: Method (S1-S35) for calibrating a microwave module (17; 43) intended for installation in a household cooking appliance (24; 32; 42) by means of a measuring system (51) connectable to a microwave output (18) of the microwave module (17; 43), which has a directional coupling device (52) with an antennaless microwave output (53), wherein the method comprises at least the following steps: (a) Connecting the microwave output (18) of the microwave module (17) to the directional coupling device (12) of the measuring system (51), wherein a substitute load (57) is connected to the microwave output (53) of the measuring system (51) (S1); (b) Generating, using the microwave module (17), a microwave signal with a predetermined target frequency and a predetermined target amplitude (S3); (c) Passing the microwave signal through the directional coupling device (12) of the microwave module (17) to the microwave output (18) of the microwave module (17) (S3a); (d) Guiding the microwave signal from the microwave output (18) of the microwave module (17) through the directional coupling device (52) of the measuring system (51) to the microwave output (53) of the measuring system (51) (S3b); (e) Measuring, at the directional coupling device (12) of the microwave module (17), at least the amplitude of the microwave signal emitted to the measuring system (51) and the amplitude of the microwave signal (S4) reflected by the measuring system (51); (f) Measuring, at the directional coupling device (52) of the measuring system (51), at least the amplitude of the microwave signal emitted to the microwave output (53) of the measuring system (51) and the amplitude of the microwave signal (S5) reflected from the microwave output (53) of the measuring system (51); (g) Storing at least the target frequency and target amplitude and values ​​measured therefor and / or values ​​derived therefrom as data entries in a calibration data set (S6); (h) Varying at least the target frequency within a first frequency group of different target frequencies (S8) and repeating steps (b) to (g) for several, in particular all, target frequencies of the first frequency group; (i) Directing the microwave output (18) of the microwave module (17) or the measuring system (51) to a reflective termination (58; 18); (j) following up by performing at least steps (b), (c), (e) and (g) within the group of steps (b) to (g) and (k) Varying at least the target frequency within a second frequency group of different target frequencies (S21 ; S33) and repeating at least steps (b), (c), (e) and (g) within the group of steps (b) to (g) for several, in particular all, target frequencies of the second frequency group.

2. Method (S1-S25) according to claim 1, wherein - in step (i) the microwave output (18) of the microwave module (17) is connected to the directional coupling device (52) of the measuring system (51) and the microwave output (53) of the measuring system (51) is set up as a reflective termination (58) (S14); - Step (j) includes carrying out steps (b) to (g); and - Step (k) includes varying at least the target frequency within the second frequency group (S21) and repeating steps (b) to (g) for several, in particular all, target frequencies of the second frequency group.

3. Method (S1-S13, S24-S35) according to claim 1, wherein - in step (i) the directional coupling device (52) of the measuring system (51) is decoupled from the microwave output (18) of the microwave module (17) (S26) and thereby the microwave output (18) of the microwave module (17) is designed as an open end; - Step (j) includes performing steps (b), (c), (e) and (g); and - Step (k) includes varying at least the target frequency within the second frequency group (S33) and repeating steps (b), (c), (e) and (g) for several, in particular all, target frequencies of the second frequency group. Method (S1-S35) according to one of the preceding claims, wherein - in step (b) an additional target phase shift of the microwave signal is specified; - in step (h) additionally the target phase shift within a first phase group of different target phase shifts is varied (S13) and at least steps (b) to (h) are performed for several, in particular all, pairings of at least the target frequencies of the first frequency group and the target phase shifts of the first phase group; and - in step (k) the target phase shift is additionally varied within a second phase group of different target phase shifts, and at least steps (b), (c), (e), and (g) are performed with additional storage of the target phase shift values ​​in step (g) within the group of steps (b) to (h) for several, in particular all, pairings of at least the target frequencies of the second frequency group and the target phase shifts of the second phase group. Method (S1-S35) according to one of the preceding claims, wherein - in step (h) the target amplitude is additionally varied within a first amplitude group of different target amplitudes (S11) and at least steps (b) to (h) are performed for several, in particular all, pairings of at least the target frequencies of the first frequency group and the target amplitudes of the first amplitude group; and - in step (k) the target amplitude is additionally varied within a second amplitude group of different target amplitudes (S23; S35) and at least steps (b), (c), (e) and (g) within the group of steps (b) to (h) are each performed for several, in particular all, pairings of at least the target frequencies of the second frequency group and the target amplitudes of the second amplitude group. Method (S1-S35) according to one of the preceding claims, in which, in conjunction with the target values, a temperature, in particular the temperature of a main amplifier (11), is additionally measured and stored in the calibration data set (S6). Method (S1-S35) according to any one of the preceding claims, wherein correction factors for the operation of the microwave module to be calibrated are calculated from the data entries of the calibration data sets (S25), by means of which at least one microwave parameter, including the amplitude of the microwave signal in the transmit direction present at the microwave output (18) of the microwave module (17), is adjusted to a corresponding setpoint. Method (S41-S48) for calibrating a phase shifter (8) of a microwave module (17) intended for installation in a household cooking appliance (42), wherein the method (S41-S48) comprises at least the following steps: (i) Providing a microwave module (17) to be calibrated with respect to its phase shift and a microwave module (17kai) already calibrated with respect to its phase shift, the microwave outputs 18 of which are connected to respective inputs of a combiner (63); (ii) Specifying a common target amplitude and a common target frequency for both microwave modules (17, 17kai) as well as a target phase shift at the calibrated microwave module (17kai) and a target phase shift at the microwave module (17) to be calibrated (S41); (iii) Generating, using both microwave modules (17, 17kai), a respective microwave signal with the respective specified setpoint values ​​(S43); (iv) Measuring a signal (S43) present at the output of the combiner (63); (v) Storing the values ​​of at least the target phase shift and target frequency specified on the microwave module to be calibrated and / or values ​​derived therefrom and the associated measured value as data entries of a phase calibration data set (S43); (vi) Varying the target phase shift on the microwave module (17) to be calibrated within a third phase group of different target phase shifts (S44) and repeating steps (iii) to (v) for several, in particular all, target phase shifts of the third phase group. Method (S41-S48) according to claim 8, wherein in step (vi) the target frequency is additionally varied within a third frequency group of different target frequencies (S47), and steps (iii) to (v) are additionally performed for several, in particular all, target frequencies of the third phase group. Method (S41-S48) according to any one of claims 8 to 9, wherein the target phase shift specified in step (ii) on the calibrated microwave module (17kai) is 0°, and the target phase shift within the third phase group comprises at least the target values ​​0° and 180°. Method (S41-S48) according to any one of claims 8 to 10, wherein correction factors for the operation of the microwave module to be calibrated are calculated from the stored data entries of the phase calibration data set (S48), based on which the phase shifts are adjusted to the respective corresponding target phase shifts.Household microwave oven (24; 32; 42), comprising. - a microwave-tight cooking chamber (23) which can be sealed by means of a door and supplied with microwaves - at least one microwave module (17) configured to adjust at least one amplitude and one frequency of a microwave signal emitted at a microwave output (18) to variable setpoints, and comprising a directional coupling device (12) at least for measuring the amplitude of an emitted microwave signal and a reflected microwave signal; - a control device (4) which is configured to adjust at least one microwave parameter, including the amplitude of the microwave signal emitted to at least one antenna (16), to a corresponding setpoint using correction factors calculated from the stored values ​​according to a method according to one of the preceding claims. Calibration setup for carrying out a method (S1-S35) according to one of claims 1 to 7, comprising a microwave module (17) and a measuring system (51), wherein the measuring system (51) at least - a directional coupling device (52) that can be disconnected to a microwave output (18) of the microwave module (17); - an interchangeable attachment (57) for a microwave output (53) of the directional coupling device (52), which is designed as a substitute load; - a further interchangeable attachment (58) for the microwave output (53) of the directional coupling device (52), which is designed as one end; - a detector (55a-1) for measuring the amplitude of a measurement signal output at a first measurement output (54a) of the directional coupling device (52); - a detector (55b) for measuring the amplitude of a measurement signal output at a second measurement output (54b) of the directional coupling device (52); and - a data processing device (56) connected to the detectors (55a-1, 55b), which can be coupled to a control unit (4) of the microwave module (17) for its control, and wherein at least one frequency and one amplitude of the microwave signal generated by the microwave module (17) can be varied. Calibration setup for carrying out a method (S41-S48) according to one of claims 8 to 11, comprising a calibrated microwave module (17kai), at least one microwave module (17) to be calibrated, and a measuring system (61), wherein - the measuring system (61) has a combiner (63) whose inputs are connected to the microwave outputs (18) of the microwave modules (17, 17kai) and whose output is connected to a detector (64) of the measuring system (61), - the detector (64) is connected to a data processing unit (56) of the measuring system (61), which can be coupled to control units (4) of the microwave modules (17, 17kai) for their control; and wherein at least a frequency and a phase shift of the microwave signal generated by the microwave modules (17, 17kai) can be varied.

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