EP1971875A1

EP1971875A1 - Secum-trahenz method in particular for a network analyser

Info

Publication number: EP1971875A1
Application number: EP07702606A
Authority: EP
Inventors: Georg Ortler
Original assignee: Rohde and Schwarz GmbH and Co KG
Current assignee: Rohde and Schwarz GmbH and Co KG
Priority date: 2006-01-10
Filing date: 2007-01-05
Publication date: 2008-09-24
Also published as: DE102006017018A1; US20100141239A1; WO2007080072A1; US8022687B2

Abstract

The invention relates to a method for measuring objects (DUT) for measurement, by means of a network analyser (NA) with several measurement terminals (P1-P3) and at least one signal generator (GNl, GN2, GN3) for stimulating the object (DUT) or measurement and at least one local oscillator (LO) for measurement of the signal transmitted or reflected from the object (DUT) for measurement by the superposition principle. According to the invention, on a frequency change only the frequency of the local oscillator (LO) or the frequency of the signal generator (GNl, Gn2 , GN3)is changed but not the frequency of the local oscillator (LO) and the signal generator (Fl) simultaneously.

Description

Secum-Trahenz method, especially for a network analyzer

The invention relates to a method with which a phase-true frequency change of the signal generators and the local oscillator, e.g. of a network analyzer. This method is referred to in this application as Secum-Trahenz method.

From DE 102 46 700 Al a vector network analyzer with controllable signal generators and controllable oscillators is known. In network analyzers used in practice, often only a single local oscillator is available. For newer ones

Furthermore, network analyzers with more than two measuring ports usually have a plurality of signal generators. For example, in the network analyzer with three test ports two signal generators are present, with one of the two signal generators between two of the three

Test gates can be switched. For each test port, a mixer is present, which communicates with a directional coupler, over which the output via the tester shaft or the incoming via the tester shaft is coupled and fed into the mixer. The other input of the mixer is in communication with the local oscillator.

For network analyzers, but also for other measuring devices, such as connected

Signal generators, there is the problem that a frequency change of the signal generators is to be carried out in phase, ie in the frequency change should not occur phase shift. The signal generators typically have synthesizers with multiple PLL (Phase Locked Loop) stages with fractional dividers. The dividers are divided by a fractional rational division factor. If the division factor is changed not only with respect to its integer part, it leads this usually leads to a phase jump. Even if only the integer division factor is changed, there may be phase jumps around n / n, where n is an integer. The necessity of carrying out a phase-true frequency change arises in particular when measuring at frequency-converting measurement objects, such as mixers.

The invention is therefore based on the object of specifying a method for measuring objects to be measured, in which no phase jump occurs during the frequency change or the phase jump is at least detected.

The object is solved by the features of claim 1. The dependent claims contain advantageous developments of the invention.

According to the invention, in a frequency change, only the frequency of the local oscillator or the frequency of the signal generator but not simultaneously changed the frequency of the local oscillator and the signal generator.

This ensures that any phase changes that occur in the frequency change of the oscillator and the frequency change of the signal generator, can be detected separately from each other and either by adjusting a phase angle of the oscillator or the

Signal generator can be compensated or can be included in the later evaluation of the measurement.

Usually, the local oscillator and the

Signal generators as synthesizers equipped with one or more PLL stages. A frequency change then takes place by changing the division factor of the dividers provided in the PLL stages. It is advantageous if initially only the integer part of

Division factor is changed, since this causes no phase shift. As a result, a rough frequency change in the vicinity of the new target frequency can already be achieved. The then still necessary fine frequency tuning can now be made by varying the Nachkoπunaanteils the division factor, then according to the invention only either the frequency of the oscillator or the signal generator but not both frequencies are adjusted simultaneously, so that the phase change of the oscillator and the signal generator can be detected separately.

The method according to the invention can be used particularly advantageously in frequency-converting measuring objects, for example in the measurement of mixers. There is a need for two inputs of the frequency-measuring object to be excited at different frequencies. In a mixer, one input of the mixer is to occupy, for example, a frequency in the high-frequency input bandwidth, while the other input, a signal must be supplied, which serves as a local oscillator signal for the mixer to be measured. At the output of the mixer appears the sum or difference frequency of the two

Input signals that lie in a completely different frequency range.

Although measurements on mixers with vectorial network analyzers are known, which are based on reflection measurements involving a reference mixer. In order to be able to carry out advantageous transmission measurements, the phase position of the two excitation signals with which the mixer is applied must be known exactly. In the measurement of the output signal, the temporal position of the phase of the output signal with respect to the temporal position of the phase of the excitation signals is also of interest. The two signal generators, which are required for the excitation of the mixer, must therefore be set in a defined phase relationship to each other, or the phase position must be known exactly. Accordingly, in order to measure the output of the mixer, the reference of the local oscillator signal used internally in the network analyzer must be in relation to the Generator signals to be known exactly. In this context, therefore, the method according to the invention for the phase-true frequency change in the adjustment of the signal generators and the local oscillator can be used particularly advantageously.

An embodiment of the invention will be described below with reference to the drawing. In the drawing show:

Fig. 1 is a block diagram of one in the context of

Invention usable network analyzer in the measurement of a mixer and

Fig. 2 shows an embodiment of the internal structure of the local oscillator shown in Fig. 1 and the signal generators shown in Fig. 1.

Before the method according to the invention is described, an exemplary test setup, in which the method according to the invention can be used advantageously, will be described with reference to FIG. 1. In the exemplary embodiment illustrated in FIG. 1, a frequency-converting measurement object DUT, for example a mixer, is measured by means of a vectorial network analyzer.

In the illustrated embodiment, the first input port El of the mixer DUT to be measured is a high-frequency input to which the high-frequency signal

RF_DUT is received. The second input port E2 is an input port at which the local oscillator signal LO_DUT is received. In the measuring configuration shown in FIG. 1, the first input port El of the frequency-converting measuring object DUT designed as a mixer is connected to the first measuring port Pl of the network analyzer NA. The second input port E2 of the measurement object DUT is connected to the third measurement port P3 of the network analyzer NA. At the exit gate A of the to be measured Mischers DUT is the down mixed intermediate frequency signal ZF_DUT. The output port A of the measurement object DUT is connected to the second measurement port P2 of the network analyzer NA. In particular, the S-parameters S ₁₁ , ie the reflection of the measurement object DUT at the measurement port Pl, S ₃₃ , ie the reflection of the measurement object DUT at the measurement port P 3, S ₂₁ , ie the transmission through the measurement object DUT from the measurement port Pl to the measurement port P2, are of interest. and S ₂₃ , ie the transmission through the measuring object DUT from the measuring port P3 to the measuring port P2.

The network analyzer NA shown in FIG. 1 is designed as a conventional vector multi-port network analyzer. In Fig. 1, only three test ports Pl to P3 are shown. Of course, the network analyzer NA can also have more than three test ports. It is also possible to connect several two-port network analyzers in cascade, as shown in the priority document DE 10 2006 001 284.

In the embodiment shown in FIG. 1, each measuring port Pl, P2 or P3 has its own signal generator GN1, GN2 or GN3. However, this need not necessarily be the case; it is e.g. also possible that only two signal generators are present and a signal generator can be switched between two test ports. Furthermore, in the illustrated embodiment, a common local oscillator LO for all test ports Pl to P3 is present. Again, this need not necessarily be the case. For a more complex network analyzer, a separate local oscillator can be present for each test port Pl to P3, or a local oscillator can supply two test ports in pairs.

The frequency of the signal generators GN1, GN2 and GN3 and of the local oscillator LO is in each case via dividers T ₀₁ , T _G2 , T _G3 and T ₁₀ , which form part of a closed phase-locked loop according to the PLL principle and those in FIG are schematically drawn and based on Fig. 2 will be described in more detail, changeable. The divided-down signal of the signal generators GN1, GN2 and GN3 is supplied to the associated measuring ports P1, P2 and P3, respectively. Between the signal generators GN1 to GN3 and the associated measuring ports Pl to P3 are each a directional coupler Rl, R2 and R3, which generates the signal generated by the signal generators GNL, GN2 and GN3 to the test ports Pl, P2 and P3 leading wave al, a2 or a3 decouples and in each case an associated mixer Ml, M2 or M3 supplies. The returning waves b1, b2 and b3 received via the measuring ports P1, P2 and P3 are likewise coupled out via the directional couplers R1, R2 and R3 and fed to the associated mixer M1, M2 and M3, respectively.

The mixers M1, M2 and M3 in each case also receive the signal of the local oscillator LO which may have been divided down in the divider T _1x . The signal of the leading and returning waves mixed down into the intermediate frequency ranges ZF1, ZF2 or ZF3 is respectively fed to an analog / digital converter A1, A2 or A3 and the digitized signal is respectively measured in a detector D1, D2 or D3 with respect to amplitude and Phase recorded. A control device or controller C receives the signals received by the detectors D1 to D3 and simultaneously serves to drive the signal generators GN1 to GN3, the local oscillator LO and the associated dividers T ₀₁ , T ₀₂ , T ₀₃ and T ^ ₅ . From the leading and returning waves, for example, the S-parameters are calculated in the control device C and displayed on a display DS as a function of the measuring frequency.

The exact structure of the signal generators GN1 to GN3 of the local oscillator LO is shown as an exemplary embodiment in Fig. 2, wherein it can be seen that the signal generators GNL to GN3 and the local oscillator LO with multiple PLL stages with multiple dividers 64, 67 and 77th are constructed. The reference signal REF is transmitted to the local oscillator LO and the signal generators GN1-GN3 via the connection line 31, respectively. By doing

In the exemplary embodiment, the frequency of the reference signal REF in a frequency doubler 60 is first doubled in the local oscillator LO or in the signal generators GN1-GN3 and supplied to a first comparison input of a first phase detector 61 within the local oscillator LO or signal generator. The output of the first phase detector 61 is connected to the control input 63 of a first oscillator 62. The output of the first oscillator 62 is connected via a first fractional divider 64 to the second comparison input of the first phase detector 61. Consequently, the first oscillator 62 forms with the divider 64 and the first

Phase detector 61, a first PLL control loop, which is synchronized with the reference signal REF. This first PLL loop in section 65 is also called Child_PLL. The divider 64 divides the frequency by the fractional rational division factor (N, F) _CH with the integer component N and the non-integer decimal component F.

The adjoining section 66 is called Sweep_PLL. There is a second divider 67, which communicates with the output of the first oscillator 62. A synchronous module 68 ensures the selection of the fractional-rational division factor (N, F) _{SY of} the divider 67. The output of the second divider 67 is connected to a first comparison input of a second phase detector 69. Its output is in turn connected to the control input 70 of a second oscillator 71 in connection. The output of the second oscillator 71 is connected to a first input of a mixer 72. A second input of the mixer 72 receives that from the

Frequency doubler 60 doubled reference signal REF. The output of the mixer 72 is connected to the second comparison input of the second phase detector 69 in connection. In this way, by the second Oscillator 71, the mixer 72 and the phase detector 69, a second PLL control loop is formed, which is also synchronized via the reference signal REF.

In a third section 73, which is referred to as MAIN_PLL, there is a third oscillator 74 whose control input 75 is connected to a third phase detector 76. A first comparison input of the third phase detector 76 is connected to the output of the second oscillator 71, while a second

Comparative input of the third phase detector 76 is connected via a third divider 77 to the output of the third oscillator 74. At the output of the third oscillator 74, which may also be referred to as a main oscillator, is the local oscillator signal or

Generator signal with frequency f ^ or f _GN1 , f _GN2 or f _GN3 available. The frequency f _∞ is tunable over several octaves. The divider 77 also divides the frequency by a fractional rational division factor (N, F) _m .

In particular, but not only in the case of frequency-converting DUTs, the problem arises that the frequency of the signal generators GN1-GN3 and the local oscillator LO must be changed in a phase-correct manner. The measurement on the mixer DUT according to the exemplary embodiment according to FIG. 1 preferably takes place according to the invention as follows:

The complex characteristics of the signal generators GN1 and GN3 at the measuring ports P1 and P3, namely the leading ones

Waves al and a3 as well as the reflected waves at these test ports bl and b3 can only be measured at the same measurable receiver intermediate frequency when the network analyzer NA is set because of the local oscillator LO which is simply present in the exemplary embodiment, if the frequency in the signal generators GN1 and GN3 within the bandwidth of the intermediate frequency range ZFl or ZF3 are the same. Likewise, at the measuring port P2, the intermediate frequency of the mixer to be measured, or generally of the frequency-converting measuring object DUT, only to be analyzed when the local oscillator LO is set for this receiving frequency. Thus, at the three measuring ports P1 to P3, it is never possible to measure at the same setting of the signal generators and the local oscillator, ie for each measuring point both the signal generator GN3 at the measuring port P3 and the local oscillator LO for the reception at the measuring port P2 each be adjusted. In this case, the phase relationships must not be lost, since otherwise no statement about the phase of the mixing product ZF_DUT generated by the mixer DUT to be measured with respect to the phase of the input signals RF_DUT and LO_DUT is possible.

First of all, the frequency of the two signal generators GN1 and GN3 at the measuring ports P1 and P3 is set to the same frequency, for example 1 GHz. Possible phase differences of the generators GN1 and GN3 are known from calibration with calibration standards and can be taken into account accordingly. If the

Center frequency of the intermediate frequency ranges ZFl, ZF2 and ZF3 of the network analyzer NA, for example, 20 MHz, so is the frequency of the local oscillator LO first in this example to 1.020 GHz. Using the wave sizes a1 and a3 of the leading waves, the phase difference between the measuring ports P1 and P3 can now be determined as follows:

P al = P u, ^" P port i (D φ _a> = <P" - φ, _{ott i} (2)

P a! ^" P a ₃ = P port 3 ~ P port i (3)

Now, the frequency of the signal generator GN3 at the measuring port P3 must be brought to the target frequency of the measuring signal LO_DUT by the phase-true frequency change according to the invention, which the mixer DUT to be measured expects at its second input E2. When the intermediate frequency ZF_DUT generated by the mixer DUT 30 MHz, for example, the frequency offset between the signal RF_DUT and the signal LO_DUT must be 30 MHz and thus the frequency of the signal generator GN3 increased from 1 GHz to 1.030 GHz. According to the invention, only the

Frequency of the local oscillator LO changed without frequency change of the signal generator GN3 and then subsequently changed only the frequency of the signal generator GN3 but not the frequency of the local oscillator LO. The step size is to be chosen so small that the bandwidth of the intermediate frequency range ZF3 is not left. This process must be repeated as often as necessary until finally the target frequency in the example of 1.030 GHz is reached.

For example, the frequency of the local oscillator LO is first increased by 5 MHz from the original 1.020 GHz to now 1.025 GHz. The intermediate frequency of the intermediate frequency stage ZF3 is thus instead of originally 20 MHz now 25 MHz. The change of the phase Aφ _{Λ3Λ of} the leading wave a3 at the measuring port P3 in this first

Step is now measured, stored in a memory and taken into account in the later evaluation. Alternatively, this can also be equalized by changing the phase of the local oscillator LO by the same phase change value Aφ _w = Aφ ^ _Λ .

Now, the frequency of the signal generator GN3 at the measuring port P3, for example, increased by 10 MHz from the original 1.000 GHz to 1.010 GHz, so that a new intermediate frequency in the intermediate frequency range ZF3 of 1025 MHz - 1010 MHz = 15 MHz sets. The phase change caused thereby Aφ _a32 on the leading measurement port P3 shaft a3 is again measured and stored.

Now the frequency of the local oscillator LO is again set higher by a further 10 MHz to 1.035 GHz. The frequency of the intermediate frequency signal in Intermediate frequency range ZF3 is now again 25 MHz. The associated phase change Δφ _a33 is again detected and stored. Thereafter, the frequency of the signal generator GN3 at the measuring port P3 is retraced by another 10 MHz to 1.020 GHz, so that again a

Intermediate frequency of 15 MHz results. The Δφ _{a} t} phase change associated with this step is also detected and stored. It should be emphasized that the bandwidth of the intermediate frequency range ZF3 as well as all other intermediate frequency ranges ZF1 and ZF2 is significantly wider than 5 MHz, that both the resulting intermediate frequency of 15 MHz and 25 MHz are within the bandwidth extending around the center frequency of 20 MHz lie.

The process is repeated until the frequency of the signal generator GN3 at 1.030 GHz and the associated frequency of the local oscillator at 1.050 GHz. In this case, instead of 10 MHz, a step size of 5 MHz is selected as the last increment, so that the frequency of the signal resulting from the last step is

Intermediate frequency signal in the intermediate frequency range ZF3 is again 20 MHz.

The decisive advantage of the procedure described above is that now the phase difference Δφ between the excitation signals at the measuring port P3 and the measuring port Pl is known. It is now:

Δ ^ 31 = P port 3 ^" P port l ⁺ Σ ^Δ P por _{t 3.} I ( ⁴ )

where φ _{Port 3} - <P _{Poii l was} the originally determined according to equation (3) phase difference between the test ports P3 and Pl before increasing the frequency of the signal generator GN3. Also, the total change Δφ ^ the phase angle of the local oscillator LO relative to the original phase position of the local oscillator φ ^ is known and is:

Of course, the adjustment of the local oscillator LO and the signal generator GN3 could also be performed in reverse order, i. it could be with the

Signal generator GN3 are started and the last step with the frequency increase of the local oscillator LO are completed. The properties of the measurement object DUT to be measured have no influence on the phase position, since only the leading waves a1 and a3, but not the returning waves b1 and b3 reflected by the measurement object DUT, are used.

The method described above is referred to in this application as Secum-Trahenz method.

Now, the frequency of the local oscillator LO has to be adjusted so that the intermediate frequency which occurs at the measuring port P2 at the output of the mixer M2 falls within the bandwidth of the intermediate frequency range ZF2.

At its output port A, the mixer DUT to be measured generates a signal ZF_DUT whose frequency corresponds to the difference between the frequencies of the signals RF_DUT and LO_DUT. In the example described above, a frequency of the signal LO_DUT of 1.030 GHz and a frequency of the signal RF_DUT of 1.000 GHz results in a difference frequency of 30 MHz, which is to be analyzed at the measuring port P2 with respect to amplitude and phase.

In order to be able to make a statement about the phase of the signal ZF_DUT, the frequency of the local oscillator LO has to be adjusted in phase from now 1,050 GHz to 50 MHz, so that the expected frequency of 30 MHz of the signal ZF_DUT is shifted to the middle of the bandwidth of the intermediate frequency Range ZF2 of 20 MHz falls. Basically, this can be done with the Secum-Trahenz method described above. The Adjustment from 1.050 GHz to 50 MHz requires a 1GHz adjustment, which would require 202 increments of steps of 10MHz to adjust the local oscillator LO and signal generator GN2. The adjustment with the Secum-Trahenz method would therefore be relatively time-consuming without further measures.

It is therefore advantageous to initially adjust only the integer components in the dividers of the synthesizer of the local oscillator LO shown in FIG. 2, since this has no influence on the phase angles. In the fractional rational division factor (N, F) _{CH of} the divider 64 of the child PLL in the step 65, in the division factor (N, F) _{SY of} the divider 67 of the sweep PLL in the step 66 and at the division factor (N ₁ F ) _111x of divider 77 of the main PLL of stage 73, therefore, preferably only the integer component N should be changed in a first step. The frequency f _ω at the output of the local oscillator LO is then after this coarse tuning already near the target frequency of 50 MHz.

In a subsequent fine tuning then the fractional parts F of the division factors (N, F) _CH , (N, F) _sy and (N, F) _{m are} gradually changed so that the exact target frequency of 50 MHz is reached. This fine-tuning then takes place with the Secum-Tranenz method described above in small increments of, for example, 10 MHz again.

If only a sufficiently fine tuning grid already results by changing the integer components of the division factors, it is ensured that the signal ZF_DUT received at the gate P2 after mixing with the signal of the local oscillator LO in the mixer M2 falls within the bandwidth of the intermediate frequency range ZF2 , the fine tuning according to the Secum-Trahenz method may also be omitted. In this case, a network analyzer can be used, which instead of three signal generators only has two signal generators GNL and GN3 available, which are required for the signals at the test ports Pl and P3, so that the Secum-Trahenz method can not be applied to the test port P2 due to the missing signal generator GN2. For example, would the switching of the integer portion N of the division factor (N, F) _m at the main PLL stage 73 from 4 to 128, the original frequency f ^ of the local oscillator LO of 1050 MHz to 1050 MHz ^• 4/128 = 32 8125 MHz change. Mixing in the mixer M2 at the frequency of 30 MHz of the received signal ZF_DUT would thus result in an intermediate frequency of 32.8125 MHz - 30 MHz = 2.8125 MHz, which falls within the substantially non-limited bandwidth of the intermediate frequency range ZF2 ,

A third possibility of coping with the large frequency jump of, for example, 1.050 GHz after about 50 MHz, is the measurement at harmonics or subharmonics of the fundamental frequency f 1, of the local oscillator LO. In this case, the frequency of the local oscillator LO is left at Setting in which the phase relationship was determined by the Secum-Trahenz method, but measures at a receiver frequency of, for example, f ^ / 9 minus the device intermediate frequency of 20 MHz in the example above.

The invention is not limited to the embodiment described above. In particular, the inventive method is also in network analyzers with more than three Messtoren and less than one

Signal generator applicable per test gate. In principle, the method is also not limited to network analyzers and can also be used in other devices, for example in signal generators, use, wherein the application is not limited to the measurement of frequency-converting DUTs.

Claims

claims

1. A method of measuring on a measuring object (DUT), in particular by means of a network analyzer (NA), having a plurality of measuring ports (P1-P3), at least one signal generator (GN1, GN2, GN3) for exciting the measuring object (DUT) and at least one local oscillator (LO) for measuring the signal reflected or transmitted by the measurement object (DUT) according to the superimposition principle, characterized in that at a frequency change only the frequency of the local oscillator (LO) or the frequency of the signal generator (GN1, GN2, GN3) but not simultaneously changing the frequency of the local oscillator (LO) and the signal generator (GNl; GN2; GN3).

2. The method as claimed in claim 1, characterized in that the frequency of the signal generator (GN1, GN2, GN3) and of the local oscillator (LO) is alternately changed in succession, the frequency of the signal generator (GN1, GN2; GN3) the frequency of the local oscillator (LO) remains unchanged and, when the frequency of the local oscillator (LO) changes, the frequency of the signal generator (GN1, GN2, GN3) remains unchanged and by measuring the phase change of the beat signal from the generator signal of the signal generator (LO3). GNl; GN2; GN3) and the oscillator signal of the local oscillator (LO), the phase change in the frequency change of the signal generator (GNl; GN2; GN3) or the local oscillator (LO) is detected.

3. The method according to claim 2, characterized. the difference in the phase position before and after the frequency change is corrected by adjusting the phase position of the local oscillator (LO) and / or of the signal generator (GN1, GN2, GN3).

4. The method according to claim 2, characterized in that the difference of the phase position before and after the frequency change in the evaluation of the measurement signal is included.

5. The method according to any one of claims 1 to 4, characterized in that the local oscillator (LO) and each signal generator (GN1; GN2; GN3) at least one closed

Phase locked loop (65, -66; 73) having at least one divider (64; 67; 77) having a frequency division with a fractional rational division factor ((N, F) _CH , (N, F) _SY , (N ₁ F) ₁ ^)) performs that at a coarse frequency change first the integer part (N) of the division factor of both the local oscillator (LO) and the signal generator (GN1, GN2, GN3) is changed and that in a subsequent fine frequency change alternately the non-integer part (F) of

The non-integral part (F) of the division factor of the signal generator (GN1, GN2, GN3) remains unchanged, and then only the non-integer part (F) of the division factor of the signal generator (GN1, GN2, GN3) is changed and the non-integer fraction (F) of the division factor of the local oscillator (LO) remains unchanged.

6. The method according to any one of claims 1 to 5, characterized in that the measurement object (DUT) is a frequency-converting measurement object and the network analyzer (NA) at least three test ports (P1-P3), wherein the measurement object (DUT) via two measuring ports (P1, P3) are each subjected to a generator signal of a signal generator (GN1, GN3) and the frequency-converted signal of the measuring object (DUT) is measured at the third measuring port (P2).

7. The method according to claim 6, characterized in that with a first signal generator (GNL) of a first

Messtors (Pl) of the network analyzer (NA) a first input port (El) of the frequency-converting DUT (DUT) is acted upon that with a second signal generator (GN3) of a second test port (P3) of the network analyzer (NA), a second input port (E2) of the frequency-converting DUT (DUT) is applied, and that the frequency-converted signal of an output port (A) of the frequency-converting DUT (DUT) at a third test port (P2) of the network analyzer (NA) is measured.

8. The method according to claim 7, characterized in that the first signal generator (GNL) and the second signal generator (GN3) are first operated at the same frequency and a first beat signal from the generator signal of the first signal generator (GNI) and the oscillator signal of the local oscillator (LO) and a second beat signal from the generator signal of the second signal generator (GN3) and the oscillator signal of the local oscillator (LO) are detected.

9. The method according to claim 8, characterized in that then the frequency of the generator signal of the second signal generator (GN3) and the frequency of the local oscillator (LO) are changed sequentially alternately, wherein at a change in the frequency of the second signal generator (GN3) the frequency of the local oscillator (LO) remains unchanged and when changing the Frequency of the local oscillator (LO) the frequency of the second signal generator (GN3) remains unchanged and by measuring the phase change of the

Overlay signal from the generator signal of the second signal generator (GN3) and the oscillator signal of the local oscillator (LO), the phase change in each frequency change of the second signal generator (GN3) is detected.

10. The method according to claim 8 or 9, characterized in that then the frequency of the generator signal of a third signal generator (GN2) and the frequency of the local oscillator (LO) are alternately changed sequentially, wherein in a change in the frequency of the third signal generator (GN2) the frequency of the local oscillator (LO) remains unchanged and, when the frequency of the local oscillator (LO) changes, the frequency of the third signal generator (GN3) remains unchanged and by measuring the phase change of the local oscillator (LO)

Overlay signal from the generator signal of the third signal generator (GN2) and the oscillator signal of the local oscillator (LO), the phase change at every frequency change of the local oscillator (LO) is detected.

11. The method according to any one of claims 8 to 10, characterized in that the local oscillator (LO) at least one closed phase locked loop (65; 66, -73) with at least one divider (64; 67; 77) having a frequency division with a division factor ((N, F) _CH , (N, F) _SY , (N, F) _n J), and that at a frequency change of the local oscillator (LO), only the integral part (N) of the division factor is changed.