Method for the controlled connection of a calibration standard in a calibration module and an associated calibration module

Abstract

A method according to the present disclosure for the controlled connection of a calibration standard in an associated calibration module to a port to be calibrated of a network analyzer connects the port to be calibrated of the network analyzer to a high-frequency port of the calibration module. It transmits a high-frequency signal generated in the network analyzer with an information signalling the calibration standard to be used to the high-frequency port of the calibration module. Within the calibration module, the information signalling the calibration standard to be used is detected from the high-frequency signal received in the calibration module, and the calibration standard to be used is connected to the high-frequency port of the calibration module by a control unit integrated in the calibration module.

Claims

1. A method for the controlled connection of a calibration standard in a calibration module to a port to be calibrated of a network analyser, the method comprising: connecting the port to be calibrated of the network analyser to a high-frequency port of the calibration module; transmitting a high-frequency signal generated in the network analyser with an information signalling the calibration standard to be used to the high-frequency port of the calibration module; and detecting the information signalling the calibration standard to be used from the high-frequency signal received in the calibration module and connection of the calibration standard to be used to the high-frequency port of the calibration module by a control unit integrated in the calibration module, wherein the high-frequency signal are transmitted from the high-frequency port to the control unit via a bias-tee.

2. The method according to claim 1, wherein: the calibration standard to be used is acknowledged to the network analyser by the control unit in that either a reflecting or a non-reflecting calibration standard is connected sequentially to the high-frequency port by the control unit, and the sequence of the reflecting or the non-reflecting calibration standard in each case represents an information coding the calibration standard to be used.

3. The method according to claim 2, wherein the sequence of reflecting or non-reflecting calibration standards connected to the high-frequency port is identified by a sequence of reflection measurements by the network analyser at the high-frequency port of the calibration module.

4. The method according to claim 3, wherein the acknowledgement and the two reflection measurements are each implemented with a time delay by an identical time interval from the transmission of the high-frequency signal.

5. The method according to claim 1, wherein the linking of the high-frequency signal with the information signaling the calibration standard to be used takes place by binary amplitude-shift keying of the high-frequency signal.

6. The method according to claim 1, wherein the high-frequency signal provides a frequency below a lower threshold frequency f with which the calibration is implemented.

7. The method according to claim 6, wherein the output signal of the bias-tee or of the detector diode or the pulse sequence generated by the power detector is used for the detection, and the detected information signaling the calibration standard to be used is transmitted to the control unit.

8. The method according to claim 1, wherein the high-frequency signal is transmitted from the high-frequency port to a power detector used as a non-reflecting calibration standard, which is connected to the high-frequency port at the beginning of the method.

9. The method according claim 1, wherein the high-frequency signal is transmitted to a detector diode coupled with the high-frequency port.

10. The method according to claim 1, wherein: additional characteristics of the calibration standard to be used, which are deposited in a memory integrated in the control unit, are signaled by the control unit through a sequence of reflecting or non-reflecting calibration standards connected in each case to the high-frequency port, which the network analyser identifies through a corresponding sequence of reflection measurements at the high-frequency port, and the sequence of reflecting or non-reflecting calibration standards connected in each case to the high-frequency port represents an information coding the additional characteristics.

11. A calibration module for calibrating a port of a network analyser including a high-frequency port, a plurality of calibration standards, and a control unit for the alternative connection of one of the calibration standards to the high-frequency port, the calibration module comprising: a detector unit for detecting an information signaling the calibration standard to be used from a high-frequency signal generated by the network analyser and transmitted to the high-frequency port is connected upstream of the control unit, wherein a bias-tee, which is provided respectively for every connection of a calibration standard to the high-frequency port, is connected upstream of the detector unit.

12. The calibration module according to claim 11, wherein a power detector used as a non-reflecting calibration standard is connected upstream of the detector unit.

13. The calibration module according to claim 11, wherein a detector diode, which is coupled with the high-frequency port via a coupler, is connected upstream of the detector unit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The method according to the embodiments for the controlled connection of a calibration standard in the calibration module and the calibration module are explained in detail in the following on the basis of the drawings by way of example. The figures of the drawings show:

(2) FIG. 1 a block-circuit diagram of a first exemplary embodiment of the calibration module is illustrated;

(3) FIG. 2 a block-circuit diagram of a second embodiment of the calibration module is illustrated;

(4) FIG. 3 a block-circuit diagram of a third embodiment of the calibration module is illustrated;

(5) FIG. 4 a spectral display of the transmission behaviour of a bias-tee; and

(6) FIG. 5 a flow diagram of the method for the controlled connection of a calibration standard in the calibration module.

DETAILED DESCRIPTION

(7) In the following, three embodiments of the calibration module according to the present disclosure are explained on the basis of FIGS. 1 to 3. The reference numbers in these drawings have been used in a uniform manner as far as possible.

(8) In the first embodiment of the calibration module 1 according to FIG. 1, a calibration standard 2 realised as a matched impedance of typically 50 ohms is connected in each case via a PIN-diode 6.sub.1, a calibration standard 3 realised as an open connection is connected via a PIN-diode 6.sub.2, and a calibration standard 4 realised as a short is connected via a PIN-diode 6.sub.3 to a high-frequency port 5 of the calibration module 1which is designated in the following as the first high-frequency port 5. Additionally, a calibration standard 7, which is realised as a through-connection without substantial ohmic losses, is connected via a PIN-diode 6.sub.4 between first high-frequency port 5 and high-frequency port 8 of the calibration module 1which is designated in the following as the second high-frequency port 8.

(9) The first high-frequency port 5 is connected via a high-frequency measurement line 9 to a port 10 to be calibrated of the network analyser 11, while a second high-frequency port 8 can be connected to a further port 12 to be calibrated of the network analyser 11 via a high-frequency measurement line 13 illustrated with a dashed line in FIG. 1.

(10) The anode and the cathode of each of the PIN-diodes 6.sub.1 to 6.sub.4 is connected in each case via a network for DC- and AC-voltage decoupling 14.sub.1, 14.sub.2, 14.sub.3, 14.sub.4, 14.sub.5, 14.sub.6, 14.sub.7, 14.sub.8 to a control unit 15. Each of these networks for the DC- and AC-voltage decoupling (English: bias-tee) 14.sub.1, 14.sub.2, 14.sub.3, 14.sub.4, 14.sub.5, 14.sub.6, 14.sub.7, 14.sub.8 comprises an inductance at its DC-voltage port which is connected to the anode or respectively the cathode of the respective PIN-diode 6.sub.1 to 6.sub.4 and to a capacitor at its AC-voltage port. The DC- and AC-voltage port of the respective bias-tee 14.sub.1, 14.sub.2, 14.sub.3, 14.sub.4, 14.sub.5, 14.sub.6, 14.sub.7, 14.sub.8 which is connected to the control unit 15, is disposed at the nodal point between the respective inductance and the respective capacitance.

(11) If the anode of the respective PIN-diode 6.sub.1 to 6.sub.4 is charged, via the respectively allocated bias-tee 14.sub.1, 14.sub.2, 14.sub.3, 14.sub.4, 14.sub.5, 14.sub.6, 14.sub.7, 14.sub.8, with a voltage which is designed to be higher, at least by the pass voltage of the respective PIN-diode 6.sub.1 to 6.sub.4 of, for example, 0.7 V, than the voltage with which the control unit 15 charges the cathode of the respective PIN-diode 6.sub.1 to 6.sub.4 via the respectively allocated bias-tee 14.sub.1, 14.sub.2, 14.sub.3, 14.sub.4, 14.sub.3, 14.sub.6, 14.sub.7, 14.sub.8, the respective PIN diode 6.sub.1 to 6.sub.4 is conducting and connects the respective calibration standard 2, 3 and 4 to the first high-frequency port 5 or respectively connects the through connection 7 to the first high-frequency port 5 and to the second high-frequency port 8.

(12) If, by contrast, the anode of the respective PIN-diode 6.sub.1 to 6.sub.4 is charged by the control unit 15 via the respectively allocated bias-tee 14.sub.1, 14.sub.2, 14.sub.3, 14.sub.4, 14.sub.3, 14.sub.6, 14.sub.7, 14.sub.8 with a voltage which is negative by comparison with the voltage with which the cathode of the respective PIN-diode 6.sub.1 to 6.sub.4 is charged by the control unit 15 via the respectively allocated bias-tee 14.sub.1, 14.sub.2, 14.sub.3, 14.sub.4, 14.sub.3, 14.sub.6, 14.sub.7, 14.sub.8, the respective PIN-diode 6.sub.1 to 6.sub.4 is blocked and separates the respective calibration standard 2, 3 and 4 from the first high-frequency port 5 or respectively separates the through connection 7 from the first high-frequency port 5 and from the second high-frequency port 8.

(13) In this manner, through an appropriate control of the individual PIN-diodes 6.sub.1 to 6.sub.4, the control unit 15 can connect only one of the calibration standards 2, 3, 4 and 7 in each case to the first high-frequency port 5 or respectively, in the case of the through connection 7, to the second high-frequency port 8.

(14) In the case of the first embodiment of the calibration module 1, the high-frequency signal generated by the network analyser 11, which is transmitted from the port 10 of the network analyser 11 via the high-frequency measurement line 9 to the first high-frequency port 5 of the calibration module 1, is guided via a bias-tee 14.sub.1, 14.sub.2, 14.sub.3, 14.sub.4, 14.sub.5, 14.sub.6, 14.sub.7, 14.sub.8for example, via the bias-tee 14.sub.1 illustrated on the left-hand side in FIG. 1to a detector unit 16.

(15) Since a bias-tee provides a spectral transmission behaviour as shown in FIG. 4a theoretical curve and a curve measured in practice of the spectral transmission behaviour are shown herethe frequency of the high-frequency signal should be designed to be disposed below the threshold frequency f.sub.MIN, and accordingly the high-frequency signal is not filtered by the bias-tee and can be unambiguously detected by the control unit 15. A signal with a frequency above the threshold frequency f.sub.MIN is attenuated by the respective bias-tee 14.sub.1, 14.sub.2, 14.sub.3, 14.sub.4, 14.sub.3, 14.sub.6, 14.sub.7, 14.sub.8 in order not to disturb the control of the individual PIN-diodes 6.sub.1 to 6.sub.4 through the control unit 15 and accordingly not to disturb the calibration operation implemented in this frequency range.

(16) In order to communicate the detected information about the calibration standard to be used, the detector 16 is connected to the control unit 15, which connects the calibration standard to be used respectively to the first high-frequency port 5 or respectively, in the case of the through connection 7, to the first high-frequency port 5 and to the second high-frequency port 8.

(17) In the second embodiment of the calibration module 1 according to FIG. 2, the high-frequency signal with the information about the calibration standard to be used from the first high-frequency port 5 is not connected with the bias-tee to the unit for detection 16, but a power detector 17 connected to the first high-frequency port 5 at the beginning of the method and realised as a calibration standard determines the power level of the high-frequency signal at the individual timing points at which the high-frequency signal is either activated or non-activated on the basis of the binary amplitude-shift keying.

(18) The power level of the high-frequency signal measured at each of the two timing points is communicated to the control unit 15 in each case as a data word or as a combined data word in a given data format. Alternatively, an average, effective power-level measurement can also be implemented over a period of time which extends over both of the timing points. The effective power-level value measured here is different for each of the four modulation states or respectively modulation symbols and can be communicated to the control unit 15 as a single data word in a given data format.

(19) For the correct calibration of the network analyser 11, the power detector must provide a matched input impedance of, for example, 50 ohms, in order to be used as an optimally non-reflecting calibration standard.

(20) In the third embodiment of the calibration module 1 as shown in FIG. 3, the high-frequency signal with the information signalling the calibration standard to be used at the output of the first high-frequency port 5 is guided via a coupler 20 to a broadband detector diode 18. This coupler 20 is preferably realised as a directional coupler 20, which is terminated on its insulation path with an impedance 19 of preferably 50 ohms connected to ground and connected in its coupling path to the detector diode 18. The coupler 20 provides a coupling loss of typically 20 dB.

(21) In the detector diode 18, the high-frequency signal is rectified and attenuated. A capacitor optionally connected downstream of the detector diode 18 and guided to ground, which is not illustrated in FIG. 3, can implement an optional smoothing of the high-frequency signal. The rectified high-frequency signal is supplied to the detector unit 16 in which the information about the calibration standard to be used is determined, which is then supplied to the control unit 15.

(22) In the following, the method for the controlled connection of a calibration standard in a calibration module is explained in detail with reference to the flow diagram in FIG. 5.

(23) In the first method step S10, the high-frequency signal is linked in the network analyser 11 with the information signalling the calibration standard to be used. The high-frequency signal is a sinusoidal signal generated by a local frequency oscillator with a single frequency component, a so-called Continuous Wave (CW) signal.

(24) To signal the total of four calibration standards, a total of four different modulation symbols or modulation states are necessary. Accordingly, the information signalling the calibration standard to be used is modulated up to the high-frequency signal by means of a binary Amplitude Shift Keying (ASK) of the high-frequency signal. The binary amplitude-shift keying of the high-frequency signal is thus realised by connecting, via a switching unit integrated in the network analyser 11 but not illustrated in FIGS. 1-3, either the high-frequency signal generated in a local frequency oscillator of the network analyser 11, and also not illustrated in FIGS. 1-3, or by connecting no signal. To double the realisation of two binary states provided in this manner up to a total of four states, the binary amplitude-shift keying is applied twice in succession to the high-frequency signal.

(25) The high-frequency signal with the information about the calibration standard to be used in the calibration module is transmitted from the port 10 of the network analyser 11 via the high-frequency measurement line 9 to the first high-frequency port 5 of the calibration module 1, 1, and 1.

(26) In the next method step S20, the high-frequency signal received in the calibration module 1, 1 and 1 is supplied either via a bias-tee 14.sub.1, 14.sub.2, 14.sub.3, 14.sub.4, 14.sub.5, 14.sub.6, 14.sub.7, 14.sub.8 galvanically coupled to the output of the first high-frequency port 5 or via a broadband detector diode 18 of the detector unit 16 coupled to a (directional) coupler. As an alternative, the power-level values of the high-frequency signal are registered and supplied to the detector unit 16 in a power detector 17 used as a calibration standard, which is connected at the beginning of the method to the first high-frequency port 5 of the calibration module 1.

(27) In the detector unit 16, the information signalling the calibration standard to be used is determined from the supplied high-frequency signal or respectively from the supplied registered power-level values of the high-frequency signal. The correspondence between the calibration standard to be used and the associated modulation symbol or respectively modulation state modulated up to the high-frequency signal are known both to the network analyser 11 and also to the detector unit 16.

(28) In the next method step S30, after the communication of the information about the calibration standard to be used to the control unit 15, the acknowledgement of this information to the network analyser 11 is implemented. Once again, an information coding the calibration standard to be used is signalled to the network analyser 11. The signalling of this coding information which, once again, represents a sequence of two or more binary informations, is implemented in the exemplary embodiment by a sequential connection of a reflecting calibration standardthat is, either a calibration standard 3 realised as an open connection or a calibration standard 4 realised as a shortand/or of a non-reflected calibration standardthat is, a calibration standard 2 realised as a matched impedance in the case of the first and third embodiment of the calibration module 1 and 1, or of a calibration standard realised as a power detector 17 with matched impedance in the case of the second embodiment of the calibration module 1- to a first high-frequency port 5 of the calibration module by the control unit 15.

(29) The identification of the reflecting and/or non-reflecting calibration standard connected to the first high-frequency port 5 of the calibration module 1, 1 or respectively 1 in each case at two successive timing points, and accordingly the identification of the sequence of two or more binary-coded informations, which correspond to the calibration standard to be used, is implemented through a reflection measurement at the first high-frequency port 5 of the calibration module 1, 1 or respectively 1 by the network analyser 11.

(30) Since the reflection behaviour of a reflecting calibration standard can be unambiguously distinguished from the reflection behaviour of a non-reflecting calibration standard in this manner, the network analyser 11 can unambiguously check the correct reception of the information signalling the calibration standard to be used, and accordingly, the correct adjustment of the calibration standard to be used in the subsequent calibration of the calibration module 1, 1 or respectively 1.

(31) The connection of a reflecting or non-reflecting calibration standard to the first high-frequency port 5 by the control unit 15 and the implementation of the reflection measurement by the network analyser 11 with regard to a successful acknowledgement of the calibration standard to be used is suitable for synchronisation and takes place delayed by a given time intervalfor example, 100 mswith reference to the transmission of the high-frequency signal.

(32) In the next optionally implemented method step S40, characteristics of the calibration standards to be used, which are determined at the end of the manufacture of the calibration module 1, 1 or respectively 1 and are stored, for example, in a so-called and standardised Touch-Stone File in a memory of the calibration module 1, 1 or respectively 1 not shown in FIGS. 1-3 by the manufacturer of the calibration module 1, 1 or respectively 1, are transmitted in an equivalent manner to the network analyser 11 for the acknowledgement according to method step S30 of the calibration standard to be used in the future calibration.

(33) Since these characteristicsfor example, the exact determined impedance value of the respective calibration standard or the valid measurement frequency range for the respective calibration standardare significantly more complex than the type of calibration standard to be used in the next calibration, the weighting of the coding information for the characteristics data-word to be transmitted is significantly higher and therefore also leads to a more comprehensive sequence of reflecting and/or non-reflecting calibration standards, which must be connected by the control unit 15 to the first high-frequency port 5, and to a more comprehensive sequence of reflection measurements by the network analyser 11.

(34) The next method step S50 contains the connection of the calibration standard to be used in the subsequent calibration to the first high-frequency port 5 by the control unit 15 through appropriate biasing of the anode and cathode of the PIN-diode associated with the calibration standard to be used via the respectively allocated bias-tees and corresponding inverse biasing of the anodes and cathodes of the PIN-diodes associated with the calibration standards not to be used.

(35) In the final method step S60, the calibration of the port 10 to be calibrated of the network analyser 11 connected to the first high-frequency port 5 of the calibration module via the high-frequency measurement line 9 is implemented using the calibration standard connected to the first high-frequency port 5or respectively using the calibration standard connected to the first high-frequency port 5 and to the second high-frequency port 8 and realised as a through connection 7.

(36) For the calibration of the port 10 to be calibrated of the network analyser 11 with a further calibration standard, the individual method steps S10 to S60 of the method are repeated. For the calibration of a further port to be calibratedfor example, the port 12 of the network analyser 11the individual method steps S10 to S60 of the method are also used in an equivalent manner.

(37) The control unit 15 and the detector unit 16 are typically realised and integrated in one, especially in one single, programmable hardware modulefor example, in a Field Programmable Gate Array (FPGA) or in an Application Specific Integrated Circuit (ASIC).

(38) Optionally, after connection of the port 10 of the network analyser 11 to the first high-frequency port 5 of the calibration module 1, 1 and 1 at the beginning of the method, it is also possible to implement the characterisation of the calibration module 1, 1 and 1 by the network analyser 11 at a frequency below the threshold frequency f.sub.MIN through a high-frequency signal with a linked information which requests the calibration module 1, 1 and 1 for its characterisation. In this context, the transmission of the specific characterisation of the calibration module 1, 1 and 1 by transmitting the checksum of the characterisation to the network analyser 11 can be implemented according to the same technical principle as the acknowledgement of the calibration standard to be used.

(39) The present disclosure is not restricted to the embodiments presented. In particular, all combinations of all features claimed respectively in the individual claims, all features disclosed respectively in the description and all features illustrated in the individual Figs. of the drawings are also covered by the present disclosure. Alongside the modulation of the high-frequency signal with the information signalling the calibration standard to be used by means of a binary amplitude-shift keying, other modulation methods are also suitable and are also covered by the present disclosure.