WO2023151932A1

WO2023151932A1 - Calibration of microwave modules for domestic microwave cooking appliances

Info

Publication number: WO2023151932A1
Application number: PCT/EP2023/051563
Authority: WO
Inventors: Andreas Kaiser; Christian Böttcher; Sebastian Sterz; Markus Kuchler
Original assignee: BSH Hausgeräte GmbH
Priority date: 2022-02-09
Filing date: 2023-01-23
Publication date: 2023-08-17
Also published as: DE102022201338A1

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

Calibration of microwave modules for household microwave ovens

The invention relates to a method for calibrating a microwave module intended for installation in a household cooking appliance using a measuring system that can be connected to a microwave output of the microwave module. The invention also relates to a calibration setup for carrying out this method. The invention also relates to a method for calibrating a phase shifter of a microwave module intended for installation in a household cooking appliance. The invention also relates to a calibration structure 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.

DE 102019 128204 B4 discloses a method for calibrating a microwave module for a cooking appliance, the microwave module having a microwave output and a control loop, the method comprising the following steps: the microwave module generates electromagnetic radiation, the electromagnetic radiation generated being generated by an electromagnetic wave is defined, which includes an amplitude and a phase, emission of the generated electromagnetic radiation via the microwave output of the microwave module, measurement of a forward running wave of the emitted electromagnetic radiation by means of a measuring device external to the microwave module, and regulation of the amplitude and/or the phase of the generated electromagnetic radiation by means of a control and/or evaluation unit which is external to the microwave module and 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.

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 comprises: an RF energy delivery component configured to deliver RF energy for application to one or more radiating elements; a memory storing a set of coefficients chert and a processor configured to receive feedback in response to emission of RF radiation by one or more of the radiating elements and applying RF energy to one or more of the radiating elements based on the feedback and the set of control coefficients, the set of coefficients being associated with the RF power delivery component and including error correction coefficients designed to correct for systematic errors in the operation of the RF power delivery component.

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 includes: selecting at least a subset of frequencies in a bandwidth of the at least one RF feed; adjusting an input power for the at least one RF feed for each of the at least one subset of frequencies; actuating 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 look-up table.

WO 2016/144872 A1 discloses a method for calibrating a set of devices, each device comprising an amplifying component and a measurement component that outputs a digital signal indicative of the radio frequency power detected 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; adjusting a subset of the set of devices to output a signal of the selected frequency, phase value, and power level; measuring a forward power level and a reverse power level; processing the forward and reverse power level measurements to calibrate the digital signal output from the measurement component of each set of equipment; 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 precise possibility of calibrating a microwave module of a household microwave cooking appliance.

This object is solved according to the features of the independent claims. Preferred embodiments can be found in particular in the dependent claims.

The object is achieved by a method for calibrating a microwave module intended for installation in a household cooking appliance using a measuring system that can be connected to a microwave output of the microwave module and has a directional coupling device with a microwave output without an antenna, the method having at least the following steps:

(a) connecting the microwave output of the microwave module to the directional coupling device of the measurement system, with a dummy load being connected to the microwave output of the measurement system;

(b) generating, by means of the microwave module, a microwave signal with a predetermined desired frequency and a predetermined desired amplitude;

(c) passing the microwave signal through the directional coupling means of the microwave module to the microwave output of the microwave module;

(d) routing the microwave signal from the microwave output of the microwave module through the directional coupling means of the measurement system to the microwave output of the measurement system;

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

(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 (S4) reflected by the output of the measuring system;

(g) storing the reference frequency and the reference amplitude and values measured therefor and/or values derived therefrom as data entries of a calibration data record; (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;

(i) aligning the microwave output of the microwave module or measurement system to a reflective end termination;

(j) subsequently 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 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.

This calibration method has the advantage that the output power at the microwave output of a calibrated microwave module when operating in a household microwave cooking appliance can be set particularly precisely to a desired or requested target power, even with the frequency and possibly phase variable setting of the microwave signal. In addition to achieving a successful cooking process, it is also advantageous with regard to food safety if the power output into the cooking chamber corresponds to the set power, e.g. to be able to ensure sufficient heating to kill germs.

The household microwave oven can be a stand-alone microwave oven or a combination microwave oven. e.g. an oven with a microwave function and possibly a steam treatment function. The household microwave oven has at least one microwave module. The microwave signals generated by the at least one microwave module are radiated via one or more antennas or "ports" as microwave radiation into a cooking chamber that can be closed by means of a microwave-tight door. Typically, in the microwave mode of the household microwave cooking appliance, part of the radiated microwave radiation is fed back into the at least one antenna.

The microwave module is in particular a prior to installation in the household

Microwave cooking device separately manufactured and independently manageable unit. At least one antenna can be connected to the micro- be connected to the shaft 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 without an antenna. Consequently, no microwave radiation is emitted into the room during the calibration method, but only conducted microwave signals are generated. This is advantageously particularly easy to implement, error-free and radiation-proof.

A directional coupling device is understood to mean a measuring device which taps into a passing microwave signal and makes a very small proportion of the passing microwave signal available as a measuring signal. In particular, measurement signals that are dependent on the direction of travel of the microwave signal are provided, i.e. a measurement signal that represents a measure of a power / amplitude of a microwave signal running in the forward or transmission direction to the microwave output, and a measurement signal that represents a measure of a power / amplitude of an in Represents backward or reflection direction of the microwave output coming microwave signal.

The directional coupling device can be, for example, a bidirectional, circulator-less directional coupler or a directional coupling system with a circulator.

The equivalent load connected in step (a), e.g. of 50 ohms, serves to absorb or use up a microwave signal running in the forward direction as completely as possible after passing through the two directional coupling devices. Ideally, no portion of the microwave signal would be reflected or run back in the reverse direction.

The fact that in step (b) a microwave signal with a predetermined desired frequency and a predetermined desired amplitude is generated by means of the microwave module includes the microwave signal being variable in frequency and amplitude.

In a further development, the frequency of the microwave signal can be set by means of a signal generator (eg an oscillator, VCO, PLL, synthesizer, oscillating circuit, etc.). The signal generator can be supplied with a clock base by means of a clock generator. The clock and/or signal generator may or may not be part of the microwave module. So can the clock and/or the signal generator can be components of a separate signal generation module.

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

To increase efficiency, a controlled chopper can be connected downstream of the signal generator, in particular also downstream of the bandpass filter, if present. The chopper can be a component of the microwave module or a signal generation module.

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

A controlled phase shifter of the microwave module can be connected downstream of the signal generator. In particular, the phase shifter can also be connected downstream of the bandpass filter, the chopper and/or the intermediate amplifier, if present. The phase shifter is particularly advantageous for those microwave modules that are to be installed in groups of at least two microwave modules in a household microwave oven and by means of which an interference pattern is to be generated in the oven when the microwave oven is in operation.

A controlled attenuator of the microwave module can be connected downstream of the signal generator. In particular, the attenuator can also be connected downstream of the bandpass filter, the chopper, the intermediate amplifier and/or the phase shifter, if present. In particular, the attenuator can reduce the amplitude or power of the incoming microwave signal by a predetermined factor. At least one second amplifier ("output 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 power amplifier can be single or multi-stage. In particular, the output amplifier can have a single-stage or multi-stage preamplifier and a main amplifier connected downstream of the preamplifier.

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.

According to step (c), the microwave signal provided at the output of the output amplifier then runs in the forward direction through the directional coupling device of the microwave module to the microwave output of the microwave module. The amplitude or power of the microwave signal is measured at a first measurement output and the measured values are transmitted to the control device. The control device can regulate the power of the microwave signal at the microwave output to the desired value on the basis of the desired power and the measured actual power. However, it may be that due to manufacturing tolerances and/or systematic errors, the actual power measured does not correspond to the microwave power actually present at the microwave output. This can be uncovered by the present calibration method and corrected by means of the control device.

In step (d), the microwave signal is passed further in the forward direction through the directional coupling device of the measurement system. The measurement system is calibrated itself and/or has higher measurement accuracies and/or lower measurement tolerances, ie it measures more precisely than the directional coupling device of the microwave module. In particular, since the two directional coupling devices are connected directly downstream of one another (ie without any functional component connected in between), the microwave signals running through both directional coupling devices in the forward and reverse directions are identical with high accuracy. In step (e) and in step (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.

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

As indicated by step (h), this measurement process is repeated for different target frequencies. The target frequencies for which the measurements are carried out correspond to values of a first frequency group of different target frequencies. In particular, the target frequencies of the first frequency group can be incrementally spaced from each other, e.g., include target frequencies between 2400 MHz and 2500 MHz in increments of 10 MHz. In particular, the measurements can be carried out for all target frequencies of the first frequency group.

After the end of step (h), a calibration data record 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.

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

Steps (i) through (k) can be performed before or after steps (a) through (h).

Step (i) involves aligning the microwave output of the microwave module or measurement system with a reflective end termination. As a result, the microwave signals generated in the forward direction are reflected back at the open end by total internal reflection. In step (j), their amplitude or power is at least at the Measured at the directional coupling device of the microwave module, optionally also at the directional coupling device of the measuring system.

In one development, the “reflective end termination” can include or be an open end and in another development include or be a defined short circuit (“short”). 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 "matched end termination".

Analogous to the case of the dummy load present in steps (a) to (h), the target amplitudes are varied in step (k) even if the reflective end termination is present, and the corresponding data entries are created.

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 real intersection of target frequencies with the first frequency group, or can form disjoint sets of values.

A further calibration data record is now available, which has been created or is structured analogously to the calibration data record for the dummy load.

It's an embodiment of that

- in step (i) the microwave output of the microwave module is connected to the directional coupling means of the measuring system and the microwave output of the measuring system is arranged as a reflective end termination;

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

- 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.

In this embodiment, the measurement system remains connected to the microwave module and the amplitudes are measured at the same measurement outputs as in with a dummy load. This results in the advantage that a particularly large number of measured values are available and also the measured values between the dummy load and the reflective end termination are particularly easy to compare.

It's an embodiment of that

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

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

- 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.

This refinement has the advantage that fewer measured values occur. Another advantage is that there is less signal interference (e.g. comprehensive conduction losses) by doing without the additional measuring system. In this configuration, 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.

In the event that the microwave module has a phase shifter, it is an advantageous embodiment that

- In step (b) a target phase shift of the microwave signal is additionally specified and

- 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) each 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 are carried out; 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) within the group of steps (b) to ( h) pairings of at least the desired frequencies of the second frequency group and the desired phase shifts of the second phase group are carried out for a number of pairs, in particular all of them. This achieves the advantage that the dependency 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 stored. After step (h), a calibration data set is then available which, as entries, contains links at least between the predetermined or set pairings of desired frequency and phase shift, which were set simultaneously during a measurement, the desired power set in the process and the values of the microwave powers and/or measured in each case. or values derived therefrom.

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

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

It's an embodiment of that

- 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) each for several, in particular all, pairs 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

- 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) in each case for several, in particular all, pairs of at least the desired frequencies of the second frequency group and the desired amplitudes of the second amplitude group are carried out.

As a result, at least the frequency dependency of the amplitude/power can advantageously 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 end termination for higher values of the target amplitude, the power of the microwave in the reverse direction could possibly damage the output amplifier. which is typically not the case when there is a dummy load at the end of the microwave path for such higher values of the target amplitude.

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 pairs" of three simultaneously set target values can be stored in a calibration data record. In general, the sequence of the varied target parameters is arbitrary: for example, if the values of the target frequency, the target phase shift and the target amplitude are varied, a respective value of the target frequency and the target phase shift can first be recorded and the values for it of the target amplitude are varied, then a value of the target phase shift is changed and for the new pair of target frequency and target phase shift values, the target amplitude values are cycled through again until all target phase shift values have been set, and then a new one value of the target frequency is set, etc. However, all values of the target phase shift can also be run through analogously for a specified value of the target amplitude before the target amplitude is varied, etc.

In one embodiment, a temperature, in particular the temperature of a power amplifier, in particular a main amplifier, is additionally measured and stored in the calibration data set in conjunction with the setpoint values. This results in the advantage that the amplification factor of the main amplifier, which decreases due to heating, can already be taken into account when setting a setpoint power, and a temperature dependency of the power measurement of the detectors can also be corrected. As an alternative or in addition, the temperature measurement can be used to detect a possible upcoming overheating of the power amplifier, in particular the main amplifier.

In one embodiment, correction factors for the operation of the microwave module to be calibrated are calculated from the data entries in the calibration data sets, based on which at least one microwave parameter, including the lenoutput present amplitude of the microwave signal in the transmission direction, is adjusted to an associated setpoint. 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 which corresponds to the target power in a very good approximation. In particular, the correction factors can be dependent on the setpoint frequency that is set, optionally also on the setpoint phase shift that is set and/or the setpoint amplitude that is set. Optionally, correction factors can also be calculated for the frequency of the microwave signal. Optionally, correction factors for the temperature dependency of the power amplifier can also be calculated.

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 having at least the following steps:

(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;

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

(iii) Generating, by means of both microwave modules, a respective microwave signal with the predetermined desired values;

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

(v) storing the values of at least the setpoint phase shift and setpoint 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;

(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 has the advantage that the phase shift of the microwave module to be calibrated can be calibrated with a simple measurement setup using a microwave module that has already been phase-calibrated. The calibration of the phase shift is particularly advantageous when the microwave module to be calibrated is intended to be used in a microwave cooking appliance with a number of 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.

In one embodiment, in a step (vi) the target frequency is also varied within a third frequency group of different target frequencies and steps (iii) to (v) are also carried out for several, in particular all, target frequencies of the third frequency group. As a result, frequency-dependent correction coefficients can also be obtained from the calibration, which increases the correction accuracy.

In one configuration, 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 since the sum signal should have a maximum amplitude at 0° and a minimum amplitude at 180°. Actual deviations at these points can be easily converted into correction factors.

In one embodiment, 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, with the aid of which the phase shifts are adapted to the respectively associated setpoint phase shifts.

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

In addition, the connection between component deterioration over time and stress factors such as power, voltage peaks and temperature can be known from preliminary aging tests. This aging can also be included / taken into account in the correction factors.

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

- The amplitude or power of the microwave signal in the forward direction measured at the directional coupling device of the microwave module in relation 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;

- The amplitude or power of the (reflected) microwave signal in the reverse direction measured on the directional coupling device of the microwave module in relation to the actual amplitude or power of the microwave signal in the reverse direction measured on the directional coupling device of the measuring system when measured with the reflective end termination of the measuring system or measured on the directional coupling device of the microwave module Amplitude or power of the microwave signal in the reverse direction to the values of the amplitude or power of the microwave signal in the forward direction corrected with the correction factors for the dummy load when measured without the (then decoupled) measuring system.

These correction factors can depend on the frequency, amplitude, temperature, phase (shift) and/or aging. For some types of phase shifters, the following correction factor can be calculated:

- Predetermined or set target phase or phase shift (e.g. as a control value of the phase shifter) to the phase shift that is actually present, e.g. determined by means of the above phase calibration method.

This correction factor can depend on the amplitude, frequency, temperature and/or aging.

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

- Specified or set frequency (e.g. as a control value of the signal generator) for the actual frequency of the microwave signal in the forward direction measured by the measuring system.

Another possible correction factor can include, for example:

- the set target amplitude (e.g. as a control value of the attenuator) to the actual amplitude measured on the measuring system in the transmission direction.

This correction factor can depend on the temperature, frequency, phase and/or aging.

The object is also achieved by a household microwave oven having

- a cooking chamber that can be closed microwave-tight by means of a door and that can be loaded with microwaves,

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

- a control device which is set up to, on the basis of correction factors which have been calculated according to at least one of the above methods, at least one microwave parameter, including the amplitude of the at least one Antenna emitted microwave signal to adapt to an associated setpoint.

The domestic microwave oven can be analogous to the above calibration methods, and vice versa, and provide the same advantages. The correction factors may have been precalculated and then stored in a non-volatile memory of the household microwave oven, e.g. For example, the control device can be 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 oven, and the correction factors are calculated by the microwave module itself, in particular by its control device.

In general, the microwave module can have all the components required to generate a line-bound microwave signal, starting with the clock generator and ending with the output amplifier. However, it can be advantageous for a compact and inexpensive structure if at least some components for signal generation are not installed in a microwave module, but are installed independently, for example, or are installed in a dedicated signal generation module that contains the clock generator, the signal generator, the bandpass filter and/or may have the chopper. The use of an independent signal generation module can be particularly advantageous if it generates a microwave signal which - for example via a splitter

- Can be applied to several microwave modules.

The object is also achieved by a calibration structure for carrying out the first method above, having a microwave module and a measuring system, the measuring system at least

- A directional coupling device which can be connected separably to a microwave output of the microwave module;

- An exchangeable attachment for a microwave output of the directional coupling device, which is designed as a dummy load;

- Another 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;

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

- Has a data processing device which is connected to the detectors and which can be coupled to a control unit of the microwave module in order to control it; and wherein at least one frequency and one amplitude, possibly 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 carried out on it, and vice versa, and provides the same advantages.

The object is also achieved by a calibration structure for carrying out a method for calibrating a phase shift, having a calibrated microwave module, at least one microwave module to be calibrated and a measuring system, wherein

- the measuring system has 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

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

The characteristics, features and advantages of this invention described above, and the manner in which they are achieved, will become clearer and more clearly understood in connection with the following schematic description of exemplary embodiments, which will be explained in more detail in connection with the drawings.

1 shows a structure of a semiconductor microwave generation path with a microwave module;

FIG. 2 shows a variant of a directional coupler of the microwave module from FIG. 1;

3A shows another variant of a directional coupler of the microwave module

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

4 shows a structure of a semiconductor microwave generation path with two microwave modules;

5 shows a further structure of a semiconductor microwave generation path with two microwave modules;

FIG. 6 shows a calibration setup for calibrating the microwave module from FIG. 1;

FIG. 7 shows a first part of a calibration sequence that can be carried out using the calibration structure shown in FIG. 6;

8 shows a second part of the calibration process according to a first variant, which can follow the first part shown in FIG.

FIG. 9 shows a second part of the calibration sequence according to a second variant, which can follow the first part shown in FIG. 7;

FIG. 10 shows a further calibration setup for calibrating the microwave module from FIG. 1; and

FIG. 11 shows a calibration sequence that can be carried out using the calibration structure shown in FIG.

1 shows a structure of a semiconductor microwave generation path 1 for generating microwave radiation.

At the start of the microwave generation section 1 there is a clock generator 2 such as a quartz oscillator or another frequency source, the clock signal of which is fed into a controllable signal generator 3 . The clock signal has a very stable frequency and can, for example, have a clock frequency in a range between a few hundred kHz and a few tens of MHz. A bandwidth is typically a few Hertz to a few tens of Hertz.

With the aid of the clock signal, the signal generator 3 generates a working or microwave signal of a desired microwave frequency with still comparatively low power. The microwave frequency generated by the signal generator 3 can be adjusted by means of a control device, for example a microcontroller 4 (frequency-variable signal generator 3). In particular, microwave signals with a frequency in a frequency frequency range between 2.4 GHz and 2.5 GHz are generated, but are fundamentally not limited to this. The signal generator 3 can be an oscillator, VCO, PLL, synthesizer, resonant circuit, etc., for example.

A bandpass filter 5--which is basically optionally available--is connected downstream of the signal generator 3. This has the advantage that unintentionally generated unwanted frequencies, e.g. outside an ISM band or outside the adjustable frequency range, e.g. outside the band from 2.4 GHz to 2.5 GHz, are suppressed.

The optional bandpass filter 5 is here followed by a controllable chopper 6--which is fundamentally available as an option. The presence of the chopper 6 results in the advantage that partial outputs can be generated with a very high level of efficiency. For this purpose, the microwave generation path 1 can be set to a power level in which it works with the highest possible efficiency. Partial outputs are realized with the chopper 6 by switching the microwave signal on and off over time, e.g. similar to a PWM control. Desired partial performance or full performance can be specified using the microcontroller 4 .

A likewise optional amplifier ("intermediate amplifier") 7 is connected downstream of the optional chopper. It depends on the specific implementation of the microwave generation path 1 whether and at what point an intermediate amplifier 7 is required. For example, an intermediate amplifier 7 can be used if an amplitude of the microwave signal at this point in the microwave generation path 1 is considered to be too small. There can also be several intermediate amplifiers 7 distributed over the microwave generation path 1.

The optional intermediate amplifier 7 is followed by a likewise optional phase shifter 8. However, the phase shifter 8 may be required 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 generating paths 1. The size of the phase shift of the incoming microwave signal is controlled via the microcontroller 4, for example 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 in particular reduces this amplitude by an amount or factor that can be set by the microcontroller 4 . Instead of the attenuator 9, a controllable amplifier, for example a VGA, can also be used as the amplitude controller. Furthermore, the amplitude can be adjusted via a suitable intermediate amplifier, on which, for example, its gate voltage is controlled.

The attenuator 9 is followed by an output amplifier 10, 11 in the form of a series connection of a further amplifier (“preamplifier”) 10 and a further amplifier (“main amplifier”) 11 used here by way of example. The preamplifier 10 can be constructed in several stages. If at least one intermediate amplifier 7 is present, it is present in the microwave generation path 1 between the signal generator 3 and the output amplifier 10, 11.

The main amplifier 11 is followed by a directional coupling device 12, 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 an optional temperature sensor 15, e.g. arranged on the main amplifier 11, are fed to the microcontroller 4 directly or via an analog/digital converter (not shown).

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

In particular, a measurement signal, in particular a voltage signal, is output at the measurement output 13a, which is a measure of the amplitude and thus the power of the microwave signal running 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, which is a measure of the power of the backward-running microwave signal coupled in via the antenna 16 . These services can be used, for example, to control, in particular to regulate, the semiconductor microwave generation path 1 . In general, the components 2 to 15 described above can be arranged arbitrarily in the household microwave oven. It is particularly advantageous if at least some of these components 2 to 15 are parts of a microwave module 17 that is prefabricated before installation in the domestic 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 dots. However, other assignments to one or more modules are also possible, as will be described in more detail below. When installed, the antenna 16 is typically connected to a (microwave) output 18 of the microwave module 17

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

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 reproduce only a fraction of the amplitude of the working or microwave signal passed through the directional coupler 12-1. Usual coupling values are in the range of -30 dB. By far the largest part of the microwave signal coming in from the main amplifier 11 leaves the directional coupler 12-1 in the direction of the output 18 or antenna 16.

3A shows a variant of the directional coupler 12. In this case, a directional coupler 12-2 is used, which has a circulator 19 which follows the main amplifier 11. The circulator 19 protects the main amplifier 11 from reflection signals from the cooking chamber that are too high. The circulator 19 sends the microwave signal received from the main amplifier 11 through a one-way directional coupler 20 in the direction of the output 18 and the antenna 16 another one-way directional coupler 21 to a terminating resistor 22 diverted. 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 reversed in the signal path .

4 shows a structure of a microwave generation section 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 for the two 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 for setting phase shifts on one or both of the microwave modules 17. A phase shift in the microwave signals of the two microwave modules 17 can be used to generate interference patterns in the cooking chamber 23 in a targeted manner.

The microwave generation section 31 can be continued analogously for more than two microwave modules 17 .

FIG. 5 shows a further structure of a semiconductor microwave generation section 41 of a household microwave cooking appliance 42 with two microwave modules 17 with two microwave modules 43 which are supplied with microwave signals from a common signal generation module 44. The microwave modules 43 now only include the components 7 to 15, while the components 2, 3, 5, 6 are assigned to the signal generation module 44. The microwave modules 43 also include 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.

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 continued analogously for more than two microwave modules 43, as indicated by the dashed line extending from the splitter 47.

Due to component and installation tolerances of the components 2 to 15 and 17 to 22, it can happen that the measured values output by the detectors 14a, 14b to the microcontroller 4 or 45 are faulty, so that, for example, instead of a set target power, target -Frequency and / or target phase shift, a deviating microwave signal is output to the output 18 or the antenna 16. In order to correct this error, one or more components of the semiconductor microwave generation path 1, in particular the microwave module 17, can be calibrated, which is explained in more detail below.

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 to a clock generator 2 on the input side.

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

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

53 current microwaves 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 measurement output 54a and optionally a detector 55a-2 for measuring a frequency of the measurement signal present at measurement output 54a (eg a spectroscope) are connected to measurement output 54a. A detector 55b for measuring an amplitude of the measurement signal present at the measurement output 54b is connected to the measurement 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 calculates their measured values and/or values derived therefrom saves values. In principle, the detector 55a-2 can also be dispensed with and the frequency, given a sufficiently high sampling rate, can also be determined from the amplitude measurement values of the detector 55a-1.

In a further development, the data processing device 56 uses stored values to calculate correction factors 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 domestic microwave oven. The correction factors can also be referred to as calibration factors, calibration coefficients, error correction coefficients, and so on. For this purpose, the correction factors can, for example, be transferred to a non-volatile memory of the microwave module 17 (e.g. an EEPROM) which the microcontroller 4, 45 can access or which is integrated into the microcontroller 4, 45. Alternatively, the measurement data is transferred to a non-volatile memory of the microwave module 17, which the microcontroller 4, 45 can access or which is integrated into the microcontroller 4, 45, and the correction factors are calculated on this basis by the microcontroller 4, 45 itself.

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 the directional coupling device 52 leads to the microwave output 53 microwave signals sent in the transmission direction are almost completely reflected back.

The measuring 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 the like in order to obtain the real, generally frequency-dependent correction values of the calibration setup itself. This can also be expressed as the measurement system itself is already calibrated (pre-calibrated).

FIG. 7 shows a first part of a calibration sequence for calibrating at least the power output of the microwave module 17, which can be carried out using the calibration setup shown in FIG. 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, the attachment representing a dummy load 57 being connected to the microwave output 53 of the measuring system 51 here by way of example. The data processing device 56 controls the individual controllable components 3 and 6-9 of the microwave module 17 directly via the microcontroller 4. The regulation of the microcontroller 4 is therefore deactivated. Furthermore, an input of the signal generator 3 is connected to an output of a clock generator 2 .

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

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

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

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

It is assumed below, for example, that the initial reference frequency corresponds to the lowest frequency value from the first amplitude group, the initial reference power corresponds to the lowest amplitude value from the first amplitude group and the initial reference phase shift corresponds to the value 0°.

In a step S3, the microwave module 17 is now activated with the specified values for the desired frequency, desired amplitude and desired phase shift. In this case, a working signal or microwave signal is generated by means of the signal generator 3 that has the specified nominal desired frequency and that is subsequently filtered in the bandpass filter 5 . The filtered microwave signal is chopped up in the chopper 6 and amplified by the intermediate amplifier 7 for the first time. The microwave signal is then phase-shifted by the predetermined target phase shift by means of the phase shifter 8, for example within a range [0°; 360 degrees]. The microwave signal is then either passed through the attenuator 9 without being attenuated or is attenuated by the attenuator 9 to a desired amplitude level. The attenuated microwave signal is subsequently amplified first by the preamplifier 10 and then by the main amplifier 11 to the desired target power or target amplitude that is to be present at the microwave output 18 .

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

In a partial step S3b, the microwave signal runs from the microwave output 18 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. From the directional coupling device 52, a small portion of the microwave signal routed to the dummy load 53 is coupled out to the measuring connection 54a and in step S5 at the detector 55a-1 with regard to its amplitude/power and optionally at the detector 55a-2 with regard to its frequency, bandwidth, etc. measured.

A portion of the microwave signal reflected back by the microwave output 52 is measured in step S4 or step S5 in a basically analogous manner with regard to its amplitude/power at the detector 13b and at the detector 55b. There are at least values for: target frequency, target amplitude/power, target phase shift, amplitude of the microwave signal measured at detector 13a in the transmission direction, amplitude of the reflected microwave signal measured at detector 13b, amplitude of the microwave signal measured at detector 55a-1 Transmission direction and the detector 55b measured amplitude of the reflected microwave signal before.

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

The sequence of steps S3 to S6 is then repeated with variation, in particular step-by-step incrementing, of the target values until there are corresponding data entries in the calibration data record for all desired permutations of the target values.

As shown, this can be implemented, for example, by first querying in step S7 whether the highest value of the microwave frequency is set.

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

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

Following step S8 or S9, in step S10 the frequency value is first set back to its lowest value and then a query is made as to whether the highest value of the amplitude/power is set. If this is not the case ("N"), the current value of the amplitude/power is changed in step S11 to the next higher value, eg increased by one increment, and a branch is made back to step S3. The variation of the amplitude can also be referred to as "amplitude sweep". However, if step S10 is answered in the affirmative ("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 value of the phase shift has been set. If this is not the case ("N"), the current value of the phase shift is changed in step S13 to the next higher value, eg increased by one increment, and a branch is made back to step S3. The variation of the phase shift can also be referred to as "phase sweep".

If the answer to step S12 is positive, a calibration data set is available which has the measured amplitudes/powers as a function of the varied or "swept" desired values as data sets. Optionally, the temperature T measured by the temperature sensor 15 can also be stored.

Of course, one or more target values can also be decremented starting from a highest value or can be set in any other order.

A calibration data record present after step S12 for a microwave output 53 equipped with the dummy load 57 could therefore look like this, for example, 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 from 0° to 240° is incremented in steps of 120° and the target amplitude / power P _so n is decremented from 300 W to 120 W in steps of 60 W:

This data record enables the transmitted amplitude of the microwave module 17 to be detected exactly by means of the integrated detector 14a.

In addition to the first part of the calibration method, a second part is performed, which is described in more detail below.

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.

Subsequent to the first part, the calibration attachment is now changed in a step S14, namely from the dummy load 57 to a calibration attachment, which acts like a reflecting end seal and therefore ideally totally reflects incident waves.

In a step S15, initial values for the setpoint frequency and the setpoint amplitude are again set by the data processing device 56, in particular analogously to step S2. However, the limits of the adjustable value ranges and/or the increments can differ from the case with the equivalent load 57 . For example, it may be the case that the higher amplitudes set when using the dummy load 57 are so high that they could damage the main amplifier in the event of back reflection in the case of the 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 main amplifier 11 can withstand in terms of reflected amplitude. For example, the target power can only be in a range [120; 180] W can be varied, for example in steps of 30 W or 60 W. Consequently, form the corresponding desired or from this range set target powers or, analogously, target amplitudes, 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 it does not have to.

It is assumed below for the second part, for example, 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.

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

Steps S16 to S23 are carried out analogously to steps S3 to S8 and S10 to S11 (i.e. step S9 of checking the quality of the microwave signal is not carried out again), with the measured values or values derived therefrom being stored as data entries in a further calibration data record.

A further calibration data set for a microwave output 53 equipped with the calibration attachment 58 that is available after a positive answer to step S22 could then, for example, show values for the powers Pi _4a , Pi4t>, Pssa-i and Pssb and the temperature T for the target frequency f _S0 n of 2400 MHz 2500 MHz incremented in steps of 50 MHz and the target amplitude / power P _so n decremented from 180 W to 120 W in steps of 30 W. In contrast to the calibration data set created with the dummy load 57, the amplitude or power values Pi4b and Pssb measured at the detectors 14b and 55b for the reflected microwave signal are now significantly higher due to the total reflection.

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

There are two options for the following step S25:

In a first variant, correction coefficients are calculated from the calibration data sets by means of the data processing device 56 and are provided for the operation of the microwave module 17, in particular based on the detectors 14a and 14b, in order to output microwave signals at the microwave output 18, the amplitude, frequency and/or phase of which corresponds as precisely as possible to the set reference values. In particular, it is made possible to correlate or assign the measured values output by the detectors 14a and 14b with a high degree of accuracy to the values actually present at the microwave output 18 of the amplitude/power emitted in the transmission direction and the reflected amplitude/power.

The correction coefficients can be calculated from the entries in the calibration data sets, for example by a function fit with the entries as support points, for example by calculating polynomial functions of basically any order greater than one, ie for example using linear, quadratic, etc. polynomials. This means that correction coefficients can also be assigned to sets of setpoint values that have not been set directly, e.g. by interpolation. In addition, there is the possibility of extrapolating the entries in the calibration data sets to sets of correction coefficients which lie outside the range of one or more setpoint values that have been set. For example, the case can arise that some measuring points for the target amplitude are missing in the calibration data set for the calibration attachment 58 serving as a reflective end seal, which are higher than the maximum target amplitude permitted by the main amplifier 11, but less than or equal to the maximum target amplitude that can be set. 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.

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

In a second variant, the correction coefficients are transferred as such to the non-volatile data memory using the data processing device 56 . The microcontroller 4 is set up to calculate correction coefficients from the calibration data sets. The measuring system 51 can then be separated from the microwave module 17, whereupon the microcontroller 4 works independently again.

The microwave module 17 can then be built into a household microwave oven, or the phase shift can be calibrated in a further calibration setup, as will be explained in more detail below in FIGS.

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.

In this variant, after step S12 has been answered positively after the desired values for power, frequency and phase shift have been varied or "swept" completely, the directional coupling device 52 is separated from the microwave module 17 in a step S26, so that the microwave output 18 itself is open-ended serves, which causes a total reflection of the microwave signals running in the transmission direction to the microwave output 18 (transmitted). Consequently, the detectors 55a-1, 55a-2 and 55b are not used.

Steps S27 to S35 are then carried out analogously to steps S15 to S23, and a further calibration data record is created with the entries of the measured values of the powers Pi4a and Pi4b and, if applicable, the temperature T for the setpoint values f _S0 n and P _so n. In a development, the calibration data set from the first part can be applied directly to the measured values of the transmitted power Pi4a.

Steps S24 and S25 can be carried out analogously to the first variant following the positive answer in step S34 after a complete sweep of the setpoint frequency and the setpoint amplitude.

10 shows a further calibration structure for calibrating the phase shift of the microwave module 17 by means of a measuring system 61 using an already calibrated microwave module 17kai. The signal generators 3 of the two microwave modules

17 and 17kai are connected to the same clock 2. The microwave outlets

18 are connected via an optional respective attenuator 62 of the measuring system 61 to ge inputs of a combiner ("combiner") 63 of the measuring system 61 is connected, the output of which is connected to a detector 64, for example 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 structure in order to be able to detect and, if necessary, compensate for phase shifts caused by different cable lengths.

An advantage of using the attenuators 62 is that many combiners 63 can only withstand low power, so the attenuators 62 serve to protect the combiner 63. A further advantage is that the two microwave modules 17 and 17kai can then be operated with a high power output. Then again, the power level can be set about the same, and the absolute deviations are no longer critical relative to the high level. At low levels (e.g. due to an internal pre-attenuation by the attenuator 9), a relative amplitude error would be very noticeable.

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

If the phases of the microwave signals emitted at the microwave outputs 18 are in phase (ie 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 (that is, they have a phase shift of 180° between them), the detector 64 measures the smallest total signal. This is used to determine whether the phase shifter 8 of the microwave module 17 to be calibrated is working correctly or whether the phase shift at this phase shifter 8 should also be corrected or calibrated using the measured actual phase shift relative to the target phase shift.

FIG. 11 shows a calibration sequence that can be carried out using the calibration structure shown in FIG. In a step S41, the same target amplitude/target power is set for the calibration setup shown in FIG. In particular, the target amplitude can be set to an average value such as 100 W, for example.

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

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°.

In step S42 it is queried whether all values of the target phase shift to be set have already been set once.

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 present at the output of the combiner 63 by means of the detector 64 is transmitted to the data processing device 56 and transmitted together there with the values of at least the setpoint frequency set and the setpoint phase shift set on the microwave module 17 as a data entry in a further calibration database.

In addition, in step S44 the value of the setpoint phase shift set on the microwave module 17 is changed by an increment, e.g. 30°, 60°, 90° or 180°, e.g. incremented or decremented and a branch is made back to step S42.

However, if the query in step S43 is answered in the affirmative ("Y"), the desired ones are

Values of the third phase group have been run through or swept once and it will branches to step S45. If the phase shifter 8 of the microwave module 17 is working correctly, the sum signal is at a maximum at 0° and at a minimum at 180° (near zero).

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

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

If this is not the case ("N"), the system branches to step S47, in which the target frequency on both microwave modules 17 and 17kai is set to the same new value from the third frequency group, in particular incremented or decremented. It then branches back to step S42.

However, if this is the case ("Y"), the calibration data record is complete, on the basis of which the phase shift of the phase shifter 8 of the microwave module 17 can be corrected. It will then branch to step S48, in which - analogously to steps S24 and S25 - in a variant, correction coefficients are calculated from the calibration data set by means of the data processing device 56, which 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 setpoints. Here too, in a second variant, the correction coefficients can be transmitted from the data processing device 56 to a non-volatile data memory of the microcontroller 4 or to a non-volatile data memory of the microwave module 17 connected to the microcontroller 4, with the microcontroller 4 being set up to calculate correction coefficients for the phase shift from the calibration data set to calculate.

The measuring system 61 can then be separated from the microwave module 17, whereupon the microcontroller 4 works independently again.

Of course, the present invention is not limited to the embodiment shown. In general, "a", "an" etc. can be understood as a singular or a plural number, in particular in the sense of "at least one" or "one or more" etc., as long as this is not explicitly excluded, e.g. by the expression "exactly a" etc. A numerical specification can also include exactly the specified number as well as a usual tolerance range, as long as this is not explicitly excluded.

Reference List

1 microwave generation line

2 clocks

3 signal generators

4 microcontrollers

5 band pass filters

6 choppers

7 repeaters

8 phase shifters

9 attenuator

10 preamps

11 main amplifiers

12 directional coupler

12-1 Bidirectional directional coupler without circulator

12-2 directional coupler with circulator

12-3 Directional Coupler with Circulator

13a Forward power measurement output

13b Reverse power measurement output

14a Forward Power Detector

14b Reverse Power Detector

15 temperature sensor

16 antenna

17 microwave module

17kai Pre-Calibrated Microwave Module

18 Microwave output of the microwave module

19 circulator

20 one-way directional coupler

21 one-way directional coupler

22 terminator

23 cooking space

24 household microwave oven

31 microwave generation line 32 household microwave oven

33 control unit

41 microwave generation line

42 household microwave oven

43 microwave module

44 signal generation module

45 microcontroller

46 microcontrollers

47 shards

51 measurement system

52 directional coupler

53 Microwave output of the measuring system

54a Forward power measurement output

54b Reverse power measurement output

55a-1 detector for amplitude measurement

55a-2 detector for frequency measurement

55b detector for amplitude measurement

56 data processing device

57 equivalent load

58 Reflective end cap

61 measurement system

62 attenuator

63 combiners

64 detector

S1-S35 process steps

S41-S47 process steps

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 ), which has a directional coupling device (52) with an antenna-free microwave output (53), the method having 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), a dummy load (57) being connected to the microwave output (53) of the measuring system (51) (S1);

(b) generating, by means of the microwave module (17), a microwave signal with a specified target frequency and a specified 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) routing 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 sent to the measuring system (51) and the amplitude of the microwave signal (S4) reflected by the measuring system (51);

(f) measuring, on 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 reflected by the microwave output (53) of the measuring system (51). microwave signal (S5);

(g) storing at least the desired frequency and the desired amplitude and values measured therefor and/or values derived therefrom as data entries of 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) aligning the microwave output (18) of the microwave module (17) or the measurement system (51) with a reflective end termination (58; 18);

(k) Varying at least the target frequency within a second frequency group of different target frequencies (S21; S33) and respectively re-performing 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, in which

- 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 end termination (58) (S14 );

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

- Step (k) comprises 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. The method (S1-S13, S24-S35) according to claim 1, in which

- 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 as a result the microwave output (18) of the microwave module (17) is designed as an open end;

- step (j) comprises 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, in which

- In step (b), a target phase shift of the microwave signal is additionally specified;

- in step (h) the target phase shift is additionally varied within a first phase group of different target phase shifts (S13) and at least steps (b) to (h) each for several, in particular all, pairs of at least the target frequencies of the first frequency group and the target phase shifts of the first phase group are performed; 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) with additional storage of the values of the target phase shift in Step (g) within the group of steps (b) to (h) are carried out for several, in particular all, pairs 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, in which

- 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) each for several, in particular all, pairings of at least the target frequencies of the first frequency group and the target amplitudes of first amplitude group are performed; 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) pairings of at least the setpoint frequencies of the second frequency group and the setpoint amplitudes of the second amplitude group are carried out for several, in particular all, pairings. Method (S1-S35) according to one of the preceding claims, in which a temperature, in particular the temperature of a main amplifier (11), is additionally measured and stored in the calibration data set (S6) linked to the desired values. Method (S1-S35) according to one of the preceding claims, in which correction factors for the operation of the microwave module to be calibrated are calculated (S25) from the data entries of the calibration data sets, on the basis of which at least one microwave parameter, including the one at the microwave output (18) of the microwave module ( 17) existing amplitude of the microwave signal in the transmission direction, is adapted to an associated setpoint. Method (S41-S48) for calibrating a phase shifter (8) of a microwave module (17) intended for installation in a household cooking appliance (42), the method (S41-S48) having 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) and a target phase shift on the calibrated microwave module (17kai) and a target phase shift on the microwave module (17) to be calibrated (S41);

(iii) generating, by means of the two microwave modules (17, 17kai), a respective microwave signal with the respectively specified desired values (S43);

(iv) measuring a signal (S43) present at the output of the combiner (63);

(v) storing the values of at least the setpoint phase shift and setpoint 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 third phase group. Method (S41-S48) according to Claim 8, in which in step (vi) the target frequency is additionally varied within a third frequency group of different target frequencies (S47) and steps (iii) to (v) additionally for several, in particular all, target frequencies of the third phase group. Method (S41-S48) according to one of Claims 8 to 9, in which 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 is at least the target values 0° and 180°. Method (S41-S48) according to one of Claims 8 to 10, in which 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), using which the phase shifts are adapted to the respectively associated target phase shifts. Household microwave oven (24; 32; 42), comprising

- a cooking chamber (23) which can be closed in a microwave-tight manner by means of a door and can be charged with microwaves,

- at least one microwave module (17) which is set up to set at least one amplitude and one frequency of a microwave signal emitted at a microwave output (18) to variable target values, and the one directional coupling device (12) at least for measuring the amplitude of an emitted microwave signal and one reflected microwave signal;

- a control device (4) which is set up to use correction factors which have been calculated from the stored values according to a method according to one of the preceding claims, at least one microwave parameter, including the amplitude of the microwave signal transmitted to at least one antenna (16). , to adapt to an associated setpoint. Calibration setup for performing a method (S1-S35) according to any 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) which can be separably connected to a microwave output (18) of the microwave module (17);

- An exchangeable attachment (57) for a microwave output (53) of the directional coupling device (52), which is designed as a dummy load;

- Another 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 an amplitude of a measurement signal output at a first measurement output (54a) of the directional coupling device (52);

- A detector (55b) for measuring an 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) to control it, and wherein the microwave module (17) has at least one frequency and one Amplitude of the microwave signal generated by it can be varied. Calibration setup for performing a method (S41-S48) according to any one of claims 8 to 11, comprising a calibrated microwave module (17kai), at least one microwave module to be calibrated (17) 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 device (56) of the measuring system (61), which can be coupled to control units (4) of the microwave modules (17, 17kai) for controlling them; and wherein at least one frequency and one phase shift of the microwave signal generated thereby can be varied at the microwave modules (17, 17kai).