DE202016008416U1 - High-frequency signal generation unit for generating low-noise high-frequency signals - Google Patents

Abstract

A high frequency signal generation unit for an FMCW radar based distance or velocity meter (3) for generating a high frequency electrical signal (s _HF ) having a frequency (f _HF ) that is variable within a predefined frequency difference (Δf) , comprising the following components:
- A first high frequency assembly (11) for generating a first high frequency signal (s _var ), wherein the first high frequency assembly (11) is configured such that the frequency (f _var ) of the first high frequency signal (s _var ) at least by the frequency difference (.DELTA.f ) is changeable,
- A second high-frequency module (12) for generating a second high-frequency signal (s _fix ) with a fixed frequency (f _fix ), and
- A mixer (13) for generating the high-frequency signal (s _HF ) by means of the first signal (s _var ) and the second signal (s _fix ).

Description

The invention relates to a high-frequency signal generation unit for generating a low-noise electrical high-frequency signal (s _HF ) for FMCW radar-based distance or speed gauges.

Radar-based distance and speed measurement is used in a wide range of applications, for example for position determination in aviation, for distance or speed measurement in motor vehicles or for level determination in process automation.

In principle, two different prior art radar technologies can be used for this purpose: First, FMCW ("Frequency Modulated Continuous Wave", also known as continuous wave radar) or the so-called pulse transit time method. Both methods are operated within predefined radar frequency bands (in the context of this invention, the terms "radio frequency" and "radar" refer to signals or electromagnetic waves with frequencies between 0.3 GHz and 300 GHz).

In the case of level measurement, radar frequency bands at 6 GHz, 26 GHz or 79 GHz are used. The higher frequency bands are preferred, since in these cases a larger absolute bandwidth can be used. This in turn allows a higher resolution. This is an important requirement, in particular in the case of level measurement, since in the case of large containers in particular the most accurate knowledge of the filling level (L) is required. Another advantage of using high frequencies is that smaller antennas (and thus smaller terminal flanges for attachment to the container) can be used without reducing the antenna's condensing effect. Therefore, it is desirable to operate level measurement or distance or speed measurement generally at higher frequencies than 79 GHz (up to very high radar frequencies up to 300 GHz).

With FMCW-based distance or speed measurement, there are already technically sophisticated solutions for frequencies up to approximately 79 GHz for generating an electrical high-frequency signal by means of corresponding high-frequency modules. The high-frequency module feeds a transmitting antenna, whereby the radar transmission signal is generated and emitted. Accordingly, the frequency of the radar transmission signal is determined by the high frequency assembly.

Suitable high-frequency modules for generating high-frequency signals for FMCW radar for frequencies up to about 79 GHz are already known. In this connection, the publication publication is exemplary DE 10 2013 105 A1 called. There is shown a typical high-frequency assembly according to the prior art:
Core of the local high-frequency module is a high-frequency oscillator (usually this is a VCO, so a "Voltage Controlled Oscillator" used), which generates a corresponding high-frequency signal (s _HF ). The typical for FMCW sawtooth frequency change of the high-frequency signal (s _HF ) is thereby impressed by the fact that the high-frequency oscillator via a feedback circuit, also known under the name PLL ("Phase Locked Loop"), regulated.

In this case, the feedback is realized by a control signal (s _c ) is diverted from the high-frequency signal (s _HF ) of the high-frequency oscillator via a frequency divider. This is fed to a phase comparator, which compares the instantaneous phase position with that of a frequency-constant reference signal (s _clock ). The frequency (f _clock ) of the reference signal (s _clock ) is in the range of preferably 10 MHz to 100 MHz and can be generated by means of a corresponding quartz oscillator.

The phase comparator controls the VCO via an analog DC signal, wherein the voltage value of the DC signal depends on the instantaneous phase position at the inputs of the phase comparator. As the name implies, the frequency (f _HF ) of the VCO is dependent on the voltage at its input.

The time-constant frequency change of the high-frequency signal which is typical in the case of a sawtooth-shaped frequency characteristic can alternatively be set at two points in the control loop described above: Either the frequency divider is designed such that its divisor factor can be changed over time, ie quasi sawtooth-shaped. With such a design, the divider factor can take on any rational value. In this case, one often speaks of a "fractional-N PLL".

Alternatively, it is also possible that the divider factor of the frequency divider is preset to an integer value and the frequency of the reference signal (s _clock ) is modulated at the corresponding input of the phase comparator in a suitable manner to achieve the sawtooth frequency change of the high-frequency signal. For this example, a DDS module ("Direct Digital Synthesis") can be used.

VCOs and frequency dividers for frequencies in the range of 79 GHz and higher have high power consumption and high inherent noise in the current state of the art. They are therefore usually realized at frequencies below 20 GHz. are not able to generate frequencies in the range of 79 GHz, but at technically justifiable expense only up to ranges of about 10 GHz. Therefore, a circuit described above at the output of the VCO usually also includes a frequency multiplier with a corresponding multiplication factor.

As explained at the beginning, in radar-based distance and speed measurement especially even higher frequencies up to 300 GHz are advantageous. With the high-frequency module described above, however, a corresponding implementation would be associated with extreme disadvantages: To achieve such high frequencies, the frequency multiplier of the high-frequency module would have to have a significantly higher multiplication factor (since VCOs and frequency dividers are limited in their maximum frequency). As a result, not only the frequency would be multiplied accordingly, but disproportionately the phase noise of the entire high-frequency module. Their (especially at high frequencies high) phase noise is largely due to the fact that the PLL control loop must be designed adjustable so as to allow the sawtooth frequency change of the high-frequency signal.

The disadvantageous effect of strong (phase) noise on the distance or speed measurement, however, is that the sensitivity with which small or poorly reflecting measurement objects can be detected, especially at long distances, drastically decreases.

The invention is therefore based on the object to provide a signal generating unit with which a low-noise, electrical high-frequency signal for a FMCW radar-based distance or speed measuring device can be generated.

• – Eine erste Hochfrequenzbaugruppe zur Erzeugung eines ersten hochfrequenten Signals (s_var), wobei die erste Hochfrequenzbaugruppe derart ausgestaltet ist, dass die Frequenz (f_var) des ersten hochfrequenten Signals (s_var) zumindest um die Frequenzdifferenz (Δf) veränderbar ist,
• – eine zweite Hochfrequenzbaugruppe zur Erzeugung eines zweiten hochfrequenten Signals (s_fix) mit einer festen Frequenz (f_fix), und
• – einen Mischer zur Erzeugung des Hochfrequenz-Signals (s_HF) mittels des ersten Signals (s_var) und des zweiten Signals (s_fix).

The object on which the invention is based is achieved by a high-frequency signal generation unit for generating a high-frequency electrical signal (s _HF ) for a FMCW radar-based distance or speed measuring device. The high-frequency signal (s _HF ) has a frequency (f _HF ), which is variable within a predefined frequency difference (.DELTA.f). According to the invention, the high-frequency signal generation unit comprises the following components:

• A first high-frequency module for generating a first high-frequency signal (s _var ), wherein the first high-frequency module is designed such that the frequency (f _var ) of the first high-frequency signal (s _var ) is variable at least by the frequency difference (Δf)
• A second high-frequency module for generating a second high-frequency signal (s _fix ) with a fixed frequency (f _fix ), and
• - A mixer for generating the high-frequency signal (s _HF ) by means of the first signal (s _var ) and the second signal (s _fix ).

By means of the high-frequency signal generation unit according to the invention, a high-frequency signal at very high frequencies of up to 300 GHz can potentially be generated (phase) less noise than is possible according to the prior art. For this purpose, the effect is used that the high-frequency signal (s _HF ) not only from one, but from two signals (s _var , s _fix ) composed. The additional second signal (S _fix ) with its fixed frequency (f _fix ) makes a high contribution to the frequency (f _HF ) of the high-frequency signal (s _HF ). This reduces the phase noise insofar as an electrical signal (s _fix ) with a fixed frequency (f _fix ) can in principle be generated with less noise than a signal (s _var ) whose variable frequency (f _var ) is in the same order of magnitude. Related to this, the phase noise from a variable frequency signal (s _var ) (f _var ) is reduced disproportionately if this variable frequency (f _var ) can generally be set lower. Although the phase noise of the resulting high-frequency signal (s _HF ) is thus quasi added by the mixing of the two signals (s _var , s _fix ), the phase noise in the sum nevertheless falls much lower than if the high-frequency signal (as after the prior art) only from a single signal whose frequency must be variable, is generated.

If the high-frequency signal (s _HF ) is intended for use in the FMCW-based radar method, the frequency (f _var ) of the first high-frequency signal (s _var ) within the frequency difference (Δf) has a time-constant, in particular sawtooth shaped, frequency change.

In addition, it is advantageous if the second signal (s _fix ) and the first signal (s _var ) by a common reference signal (s _clock ), which has a very well-known reference frequency (f _clock ), are clocked. This ensures that both signals (s _var , s _fix ) have a common, known phase reference. Along with this, the high-frequency signal (s _HF ) is scaled to a previously known reference frequency (f _clock ).

For optimum implementation of the method according to the invention, first signal (s _var ) is preferably to be mixed with the second signal (s _fix ) such that the frequency (f _HF ) of the high-frequency signal (s _HF ) is the sum of the variable frequency (f _var ) of the first signal (s _var ) and the fixed frequency (f _fix ) of the second signal (s _fix ). In particular, can be achieved by an appropriate vote of the variable frequency (f _var ) and the fixed frequency (f _fix ) to each other that the phase noise of the high-frequency signal (s _HF ) is minimized. In this context, the variable frequency (f _var ) is the dominant variable. On the one hand, it should be chosen as small as possible so that it is as small as possible in relation to the reference frequency (f _clock ). As a result, the phase noise is correspondingly low multiplied. On the other hand, however, the variable frequency (f _var ) must not be too low, so that the ratio to the (predetermined) frequency difference (Δf) is not too small. For if the variable frequency (f _var ) is chosen too small in relation to the frequency difference (Δf), any VCO for generating the variable signal (s _var ) could be operated outside its operating range, which in turn disproportionately amplifies the phase noise. According to the selected variable frequency (f _var ), the fixed frequency (f _fix ) has to be set so that the sum of fixed frequency (f _fix ) and variable frequency (f _var ) is the desired frequency (f _HF ) of the high frequency signal (s _HF ) yields.

In order to be able to achieve a high resolution with FMCW radar-based distance or speed measurement, the variable frequency (f _var ) of the first signal (s _var ) and the fixed frequency (f _var ) are 6 ) of the second signal (s _fix ) preferably to be dimensioned such that the frequency (f _HF ) of the high-frequency signal (s _HF ) is very high, ie in particular higher than 120 GHz.

In this case, it is again advantageous if the high-frequency signal generating unit has a clock unit for common clocking of the first high-frequency module and the second high-frequency module by means of a reference signal (s _clock ). As a result, a common phase reference is produced and at the same time the high-frequency signal (s _HF ) is scaled to a previously known reference frequency (f _clock ).

• – Einen Hochfrequenz-Oszillator zur Erzeugung des ersten hochfrequenten Signals (s_var),
• – einen Frequenzteiler zur Erzeugung eines Regelsignals (s_c) mittels des ersten hochfrequenten Signals (s_var), wobei das Regelsignal (s_c) eine Regelfrequenz (f_c) aufweist, die in Bezug zu der veränderbaren Frequenz (f_var) um einen Teilerfaktor (N) geringer ist, und
• – einen Phasenkomparator, der mittels des Regelsignals (s_c) und des Taktsignals (s_clock) die veränderbare Frequenz (f_var) des Hochfrequenz-Oszillators regelt.

The first high-frequency module can be constructed, as it is already known from the prior art. In this case, as described at the beginning, it comprises at least the following components:

• A high-frequency oscillator for generating the first high-frequency signal (s _var ),
• - A frequency divider for generating a control signal (s _c ) by means of the first high-frequency signal (s _var ), wherein the control signal (s _c ) has a control frequency (f _c ) with respect to the variable frequency (f _var ) by a divider factor (N) is lower, and
• - A phase comparator, which regulates by means of the control signal (s _c ) and the clock signal (s _clock ), the variable frequency (f _var ) of the high-frequency oscillator.

Here, the frequency divider can either be designed such that the divider factor (N) is variable. In this case, the sawtooth-shaped change of the first high-frequency signal (s _var ) is effected by a corresponding change over time of the divisor factor N.

Alternatively, the frequency divider can be designed such that the divider factor (N) can only be preset in a fixed and integer manner. In this case, the first high-frequency module must comprise a frequency converter for converting the frequency (f _clock ) of the clock signal supplied to the phase comparator (s _clock ): Here, the frequency converter must be designed so that the frequency (f _clock ) is convertible with a variable conversion factor, so that on this the sawtooth-shaped change of the first high-frequency signal (s _var ) is controlled.

Depending on the exact design of the first high-frequency module, it may be necessary that it comprises a frequency multiplier arranged in front of the mixer for frequency multiplication of the first high-frequency signal (s _var ).

Since an electrical high-frequency signal (s _HF ) can be generated at very low frequency with low phase noise by means of the high-frequency signal generation unit according to the invention, it makes sense to use the FMCW radar-based distance or speed measuring device as a level measuring device for measuring the filling level ( 1 ) in a container.

The invention will be explained with reference to the following figure / figures. It shows:

1 : A schematic representation of a sawtooth-shaped high-frequency transmission signal,

2 FIG. 1 is a block diagram of the high-frequency signal generation unit according to the invention, FIG.

3 : two design options of the high-frequency module within the high-frequency signal generation unit according to the invention, and

4 A possible use of the high-frequency signal generation unit according to the invention in a radar-based level gauge

Based on 1 illustrates how a low-noise high-frequency signal s _RF can be generated by means of the method according to the invention. In the diagram shown there, the frequency f is plotted against the time t. The high-frequency signal s _HF shown in the diagram is generated in contrast to the prior art by mixing two signals s _var , S _fix . Here, the first signal s _var , as shown in the diagram, a time-variable frequency f _var and the second signal to a fixed frequency f _fix . With respect to the frequency f _{HF of} the high-frequency signal s _HF , the mixing causes the frequency f _{HF of} the high-frequency signal s _HF to be the sum of the variable frequency f _var and the fixed frequency f _fix . For example, to realize a frequency f _{HF of} the high frequency signal s _HF of 160 GHz, it would be possible to design the variable frequency at 20 GHz and the fixed frequency at 140 GHz (as described above, it is conducive to minimizing the phase noise to set the variable frequency f _var as low as possible).

As in 1 is clarified, the frequency f _{var of} the variable signal s _var within a frequency difference .DELTA.f by ± ½ · .DELTA.f changed. In the case shown, as usual with the FMCW method, a periodic, sawtooth-shaped (ie time-constant within this period) change in the frequency f _var . By mixing, the high-frequency signal s _{HF has} this sawtooth-shaped change of its frequency f _HF .

The periodicity of the sawtooth change, as typical in the FMCW method, may be on the order of up to a few hundred MHz. The frequency difference .DELTA.f is preferably dimensioned such that it comprises the maximum possible bandwidth (as mentioned above, a high bandwidth increases the resolution of the distance measurement). In the frequency band of 79 GHz, the bandwidth is for example 2 GHz, ie from 78 GHz to 80 GHz. At higher frequency bands, the bandwidth (and thus the adjustable frequency difference Δf correspondingly even higher).

By means of the method according to the invention, the phase noise of the high-frequency signal s _HF can be kept very low since an electrical signal s _fix with a fixed frequency f _fix can in principle be generated with lower noise than a signal s _var whose variable frequency f _{var is} in the same order of magnitude lies. At the same time, due to the electronic and technical conditions, the phase noise can be reduced disproportionately by a signal s _var with variable frequency f _var , if this variable frequency f _{var is} generally set lower. Thus, thus the phase noise of the resulting high frequency signal s falls _HF (although, s _fix the phase noise is quasi added by mixing the two signals s _var) is less as if the high frequency signal S _HF only of a single signal whose frequency is to be variable by the predetermined frequency difference .DELTA.f is generated (compare to the above-mentioned prior art).

In 2 is a high-frequency signal generation unit 1 shown, with which the inventive method can be implemented. In the illustration is the high-frequency signal generation unit 1 , as customary in the prior art, to a transmitting / receiving unit 2 connected.

In this case, the high-frequency signal s _HF within the transmitting / receiving unit 2 via a signal divider 21 (and optionally an output amplifier 22 ) of a transmitting antenna 23 (implemented as a planar antenna, in particular as a patch or fractal antenna). There, the electrical high-frequency signal s _{HF is converted} into the actual radar radio-frequency transmission signal S _HF and emitted accordingly.

By reflection of the high-frequency transmission signal S _HF on the measurement object, a high-frequency reception signal E _HF at a receiving antenna 24 the transmitting / receiving unit 2 received and converted back into an electrical signal (which, in turn, optionally by a receiving amplifier 25 is reinforced). This is then connected by means of a receiving mixer 26 mixed with the high-frequency signal s _HF , wherein the high-frequency signal s _{HF for} this purpose from the signal splitter 21 is branched off. As a result, a difference signal e _LF typical in the FMCW method is generated, which forms the basis for determining the distance or speed.

According to the inventive method, the high-frequency signal generating unit 1 not just one, but two high frequency assemblies 11 . 12 on: This generates the first high-frequency module 11 the variable high-frequency signal s _var whose frequency f _var is variable by the frequency difference .DELTA.f. The second high-frequency module 12 generates the second high-frequency signal s _fix , which, in contrast to the variable signal s _{var, has} a fixed frequency f _fix . The high frequency assemblies 11 . 12 is a mixer 13 downstream, which _generates the high-frequency signal s _HF by mixing the first signal s _var with the second signal s _fiX . The mixer 13 is designed so that the frequency f _{HF of} the High frequency signal s _HF from the sum of the variable frequency f _var and the fixed frequency f _fix results.

In addition, both high-frequency components 11 . 12 through a common clock unit 14 clocked by a reference signal s _clock . In this case, the reference signal has an exactly presettable reference frequency f _clock . For this purpose, for example, a quartz oscillator can be used. This will ensure that both high-frequency assemblies 11 . 12 have a common, known phase reference and the evaluation of the low-frequency received signal e _{LF can be set} in relation to a time-defined measure.

The two high frequency assemblies 11 . 12 each can in principle be constructed as it is already known from the prior art. To illustrate this are in 3 two possible embodiments ( 3a respectively. 3b ) of the first high-frequency module 11 Shown here is the first high-frequency module 11 on a high frequency oscillator 111 (preferably realized as a VCO), which generates the variable signal s _var . The high-frequency oscillator 111 is in turn regulated by feedback, also known as PLL ("Phase Locked Loop").

In this case, the feedback is realized by the output signal of the high-frequency oscillator 111 via a frequency divider 112 a control signal s _{c is} branched off. This becomes a phase comparator 113 supplied, which compares the instantaneous phase position with that of the frequency constant reference signal s _clock . The frequency f _{clock of} the reference signal s _clock may be in the range between 10 MHz to 100 MHz. The reference signal s _clock can be generated for example by means of a corresponding quartz oscillator.

The phase comparator 113 controls the high-frequency oscillator 111 via an analog DC signal, wherein the voltage value of the DC signal according to the instantaneous phase position at the inputs of the phase comparator 113 directed. According to the function of the high-frequency oscillator 111 its output frequency is again dependent on the voltage value at its input.

The time-constant frequency change of the high-frequency signal, which is typical for the sawtooth-shaped frequency response, can alternatively be set at two points in this control loop:
Either it is possible to use the frequency divider 112 interpreted in such a way that its divisor factor N constant over time, so can change almost sawtooth. This is in 3b With such a design, the divider factor N can take on any rational value. In this case, the control loop is also referred to as a fractional-N PLL.

Alternatively, it is also possible to use the frequency divider 112 be interpreted that the divider factor N of the frequency divider 112 is preset to an integer value. This is in 3a In this case, the frequency f _{clock of} the reference signal s _{clock must be} at the corresponding input of the phase comparator 113 be suitably modulated in order to achieve the sawtooth frequency change of the variable signal s _var (and thus the frequency change of the high-frequency signal s _HF ). For this purpose, a suitable frequency converter 114 For example, a DDS module ("Direct Digital Synthesis") can be used.

Because the high-frequency oscillator 111 under technically justifiable expense only up to frequencies of about 10 GHz can be implemented, includes the high-frequency module 11 at the output of the high-frequency oscillator 111 in addition a frequency multiplier 115 with a corresponding multiplication factor M in order to enable correspondingly high frequencies of the variable signal s _var .

In analogous construction to the in 3 shown embodiments of the first radio-frequency module 11 can also be the second high-frequency module 12 will be realized. Since in this case the frequency f _{fix of} the fixed signal s _{fix must} not be changeable, this must be done in the case of the second high-frequency module 12 neither the divider factor N of the frequency divider 112 be changeable, nor must any frequency converter 114 to be available.

These differences justify why the signal s _fix the second high-frequency module 12 In comparison to the variable signal s _var can be generated substantially low noise: In particular, the frequency converter 114 as well as the frequency divider 112 if it is realized changeable, generate a high proportion of the phase noise.

This fact in turn can be used according to the invention for generating a very phase-low-noise high-frequency signal s _HF by the multiplication factor M of the frequency multiplier 115 the first high-frequency module 1 in proportion to the multiplication factor of the second high-frequency module 12 very small, for example in the ratio 1:10, is designed. This has the advantage that the strong phase noise of the variable frequency divider 112 , or the possible frequency converter 114 is amplified only very slightly due to the small multiplication factor M (in contrast to the prior art, in which a high multiplication factor M would have to be chosen in order to achieve a high frequency f _{HF of} the high-frequency signal s _HF ). In contrast to causes a high multiplication factor in the case of the second high-frequency module 12 no such increased phase noise, since the frequency divider 112 can be implemented unchangeable and no frequency converter is needed. Although the phase noise of the fixed signal s _fix and of the variable signal is quasi "added" by the mixing in the high-frequency signal s _HF (in mathematical terms, two uncorrelated noise sources are added geometrically, which corresponds to the root of the sum of the squared rms value) As a result, a total of a very phase-low-noise high-frequency signal s _{HF are} generated.

In 4 is a possible application of the high-frequency signal generation unit according to the invention 1 in a level measuring device working according to the FMCW radar principle 3 shown. It is a typical measurement situation, which is seen inside a container 4 a product 5 whose level L is relative to the tank bottom through the level gauge 3 is to be determined. For this purpose, the level gauge 3 in a known installation height h above the contents 5 on the container 4 appropriate. In this case, the container 4 Depending on the area of use, be up to more than 30 m high.

The level gauge 1 is so by means of a flange at the top of the container 2 arranged to receive the high frequency transmit signal S _HF generated by the high frequency signal generation unit 1 is generated, via the transmitting / receiving unit 2 in the direction of the contents 5 sending out. After reflection on the product surface, the level gauge receives 1 the high-frequency received signal E _HF again via the transmitting / receiving unit 2 , In this case, the transit time (which is measured in the FMCW principle in the form of a difference frequency) between transmission of the transmission signal S _HF and reception of the reception signal E _HF depends on the distance d to the product surface. The subsequent calculation of the fill level L from the distance d to the product surface is carried out by the level gauge 3 with knowledge of its installation height h: L = h - d.

As a rule, the level gauge is 3 via a bus system, such as "PROFIBUS", "HART" or "Wireless HART" with a higher-level unit 6 , for example, a process control system connected. On the one hand information about the operating status of the level gauge can 3 be communicated. Information about the level L can also be transmitted in order to control any inflows or outflows that may be present on the container.

LIST OF REFERENCE NUMBERS

1

High-frequency signal generation unit

2

Transmit / receive unit

3

FMCW radar based distance / speed measuring device

4

container

5

filling

6

Parent unit

11

First high-frequency module

12

Second high-frequency module

13

mixer

14

clock unit

21

signal splitter

22

Transmit amplifier

23

Transmit antenna

24

Receive antenna

25

Receiving amplifier

26

receiving mixer

111

High-frequency oscillator

112

frequency divider

113

phase

114

frequency converter

115

frequency

d

distance

E _HF

High frequency received signal

e _LF

Difference signal

f _clock

reference frequency

f _fix

Fixed frequency

_HF

Frequency of the high-frequency signal

f _var

Changeable frequency

H

installation height

L

level

M

multiplication factor

N

division factor

S _HF

RF transmit signal

S _c

control signal

s _clock

reference signal

S _fix

Second high-frequency signal

s _HF

High-frequency signal

s _var

First high-frequency signal

.delta.f

frequency difference

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102013105 A1 [0006]

Claims (11)

High-frequency signal generation unit for an FMCW radar-based distance or velocity measuring device ( 3 ), for generating a high-frequency electrical signal (s _HF ) having a frequency (f _HF ) which is variable within a predefined frequency difference (Δf), comprising the following components: - a first high-frequency module ( 11 ) for generating a first high-frequency signal (s _var ), wherein the first high-frequency module ( 11 ) is configured such that the frequency (f _var ) of the first high-frequency signal (s _var ) at least by the frequency difference (.DELTA.f) is variable, - a second high-frequency module ( 12 ) for generating a second high-frequency signal (s _fix ) with a fixed frequency (f _fix ), and - a mixer ( 13 ) for generating the high-frequency signal (s _HF ) by means of the first signal (s _var ) and the second signal (s _fix ). A high frequency signal generation unit according to claim 1, wherein said mixer ( 13 ) is adapted to mix the first signal (s _var ) with the second signal such that the frequency (f _HF ) of the high frequency signal (s _HF ) of the sum of the variable frequency (f _var ) of the first signal (s _var ) and the fixed frequency (f _fix ) of the second signal (s _fix ) corresponds. A high-frequency signal generation unit according to claim 1 or 2, comprising: - a clock unit ( 14 ) for the common clocking of the first high-frequency module ( 11 ) and the second high-frequency module ( 12 ) by means of a reference signal (s _clock ). A high frequency signal generation unit according to claim 3, wherein said first high frequency assembly ( 11 ) comprises at least the following components: - a high-frequency oscillator ( 111 ) for generating the first high-frequency signal (s _var ), - a frequency divider ( 112 ) for generating a control signal (s _c ) by means of the first high-frequency signal (s _var ), wherein the control signal (s _c ) has a control frequency (f _c ) with respect to the variable frequency (f _var ) by a divider factor (N ) is less, and - a phase comparator ( 113 ), by means of the control signal (s _c ) and the clock signal (s _clock ), the variable frequency (f _var ) of the high-frequency oscillator ( 111 ) regulates. A high frequency signal generation unit according to claim 4, wherein the frequency divider ( 112 ) is configured such that the divider factor (N) is variable. A high frequency signal generation unit according to claim 4, wherein the frequency divider ( 112 ) is designed such that the divider factor (N) is fixed and integer presettable. A high frequency signal generation unit according to any one of claims 4 to 6, wherein the first high frequency assembly ( 11 ) a frequency converter ( 114 ) for the conversion of the frequency (f _clock ) of the phase comparator ( 113 ) clock signal supplied (s _clock ), and wherein the frequency converter ( 114 ) is configured such that the frequency (f _clock ) with a variable conversion factor is convertible. A high frequency signal generation unit according to any one of the preceding claims, wherein the first high frequency assembly ( 11 ) one in front of the mixer ( 13 ) arranged frequency multiplier ( 115 ) for frequency multiplication of the first high frequency signal (s _var ). A radio frequency signal generation unit according to any one of the preceding claims, wherein the radio frequency assembly ( 11 ) is controlled so that the frequency (f _var ) of the first high-frequency signal (s _var ) within the frequency difference (.DELTA.f) has a time-constant, in particular sawtooth, frequency change. High-frequency signal generation unit according to one of the preceding claims, wherein the variable frequency (f _var ) of the first signal (s _var ) and the fixed frequency (f _fix ) of the second signal (s _fix ) are dimensioned such that the frequency (f _HF ) of the high-frequency signal (s _HF ) is higher than 70 GHz, in particular higher than 120 GHz. A high frequency signal generation unit according to any one of the preceding claims, wherein the FMCW radar based distance or velocity measuring device ( 3 ) to a level gauge for measuring the level ( 1 ) in a container ( 4 ).

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