Method of calibrating a measurement and analyzing device as well as method of measuring a frequency-converting device under test

Abstract

A method of calibrating a measurement and analyzing device for measuring a frequency-converting device under test, comprises the steps of connecting a first port of the measurement and analyzing device with a radio frequency port assigned to the frequency-converting device under test as well as connecting a second port of the measurement and analyzing device with an intermediate frequency port assigned to the frequency-converting device under test. Further, a scalar-mixer calibration is performed at the radio frequency port and the intermediate frequency port, thus providing a precise calibration conversion amplitude. A relative calibration is performed between the radio frequency port and the intermediate frequency port by using a calibration mixer. At least one correction coefficient is determined by the difference between the results obtained from the scalar-mixer calibration and the relative calibration. The at least one correction coefficient is used to correct an error term applied.

Claims

1. A method of calibrating a measurement and analyzing device for measuring a frequency-converting device under test, comprising: connecting a first port of the measurement and analyzing device with a radio frequency port assigned to the frequency-converting device under test; connecting a second port of the measurement and analyzing device with an intermediate frequency port assigned to the frequency-converting device under test; performing a scalar-mixer calibration at the radio frequency port and the intermediate frequency port, thus providing a precise calibration conversion amplitude; performing a relative calibration between the radio frequency port and the intermediate frequency port by using a calibration mixer; determining at least one correction coefficient by the difference between the results obtained from the scalar-mixer calibration and the relative calibration; and using the at least one correction coefficient to correct an error term applied.

2. The method according to claim 1, wherein the at least one correction coefficient is determined by a phase difference between the results obtained from the scalar-mixer calibration and the relative calibration.

3. The method according to claim 1, wherein the at least one correction coefficient is determined by an amplitude difference between the results obtained from the scalar-mixer calibration and the relative calibration.

4. The method according to claim 1, wherein the scalar-mixer calibration is done by a PUOSM calibration technique, the PUOSM calibration technique being based on a UOSM calibration technique and an additional power calibration.

5. The method according to claim 4, wherein a power meter is used for the additional power calibration.

6. The method according to claim 1, wherein a calibration unit is used for the scalar-mixer calibration.

7. The method according to claim 1, wherein a calibration kit having several calibration terminations is used for the scalar-mixer calibration.

8. The method according to claim 1, wherein the radio frequency port is provided at an end of a respective cable which opposite end is connected with the first port of the measurement and analyzing device.

9. The method according to claim 1, wherein the intermediate frequency port is provided at an end of a respective cable which opposite end is connected with the second port of the measurement and analyzing device.

10. The method according to claim 1, wherein the measurement and analyzing device has a third port assigned to an integrated local oscillator, the third port being connected with a local oscillator port assigned to the frequency-converting device under test.

11. The method according to claim 1, wherein a reference mixer is interconnected between the intermediate frequency port and the second port of the measurement and analyzing device, the reference mixer and the device under test both having a common local oscillator frequency.

12. The method according to claim 1, wherein a reference mixer is interconnected between the radio frequency port and the first port of the measurement and analyzing device, the reference mixer and the device under test both having a common local oscillator frequency.

13. A method of measuring a frequency-converting device under test by a measurement and analyzing device, the measurement and analyzing device being calibrated by a method according to claim 1.

14. The method according to claim 13, wherein a third port of the measurement and analyzing device is connected with a local oscillator input of the frequency-converting device under test, the third port being assigned to a local oscillator that is integrated in the measurement and analyzing device.

15. The method according to claim 13, wherein a reference mixer is interconnected between an intermediate frequency port and a second port of the measurement and analyzing device, the reference mixer and the device under test both having a common local oscillator frequency.

16. The method according to claim 13, wherein a reference mixer is interconnected between a radio frequency port and a first port of the measurement and analyzing device, the reference mixer and the device under test both having a common local oscillator frequency.

Description

DESCRIPTION OF THE DRAWINGS

(1) The foregoing aspects and many of the attendant advantages of the claimed subject matter will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:

(2) FIG. 1 schematically shows an overview of a calibration setup that is used to perform a representative method of calibrating a measurement and analyzing device according to the present disclosure;

(3) FIG. 2 schematically shows an overview illustrating the calibration techniques applied when performing a representative method of calibrating a measurement and analyzing device according to the present disclosure; and

(4) FIG. 3 shows an overview of a representative method of calibrating a measurement and analyzing device according to the present disclosure.

DETAILED DESCRIPTION

(5) The detailed description set forth below in connection with the appended drawings, where like numerals reference like elements, is intended as a description of various embodiments of the disclosed subject matter and is not intended to represent the only embodiments. Each embodiment described in this disclosure is provided merely as an example or illustration and should not be construed as preferred or advantageous over other embodiments. The illustrative examples provided herein are not intended to be exhaustive or to limit the claimed subject matter to the precise forms disclosed.

(6) In FIG. 1, a calibration setup 10 is shown in which a measurement and analyzing device 12 is provided, which has to be calibrated by a method, for example, as illustrated in FIG. 3. In some embodiments, the measurement and analyzing device 12 is a vector network analyzer (VNA). In that regard, the measurement and analyzing device 12 comprises a housing 14 that encompasses measurement and analyzing components 16 as well as a first port 18, a second port 20, a third port 22 and a fourth port 24. The respective ports 18-24 are located at a frond-end of the measurement and analyzing device 12.

(7) In the shown embodiment, the calibration setup 10 comprises a calibration unit 26 that is separately formed. As shown, the calibration unit 26 is connected with the first port 18 and the second port 20 via a first cable 28 and a second cable 30. The cables 28, 30 each define a certain calibration plane P1, P2 that are assigned to a radio frequency port 32 as well as an intermediate frequency port 34 as shown in FIG. 1.

(8) Put differently, the radio frequency port 32 as well as the intermediate frequency port 34 relate to the positions of calibration such that influences of the cables 28, 30 are also taken into account for the calibration, as the same cables 28, 30 are used for measuring a device under test later.

(9) Alternatively, the calibration setup 10 may comprise a calibration kit instead of the calibration unit 26. The calibration kit may have several calibration terminations that can be used for performing a calibration of the measurement and analyzing device 12, namely the radio frequency port 32 and the intermediate frequency port 34.

(10) In addition, the calibration setup 10 comprises a calibration mixer 36 that can be (indirectly) connected with the first port 18 and the second port 20 of the measurement and analyzing device 12 instead of the calibration unit 26, namely via the cables 28, 30. In some embodiments, the calibration mixer 36 is also directly connected to the radio frequency port 32 and the intermediate frequency port 34 instead of the calibration unit 26.

(11) In general, the method of calibrating the measurement and analyzing device 12 illustrated in FIG. 3 comprises two different calibration techniques. The respective results obtained from the different calibration techniques are used to determine at least one correction coefficient used to correct an error term of an error model applied on the measurement and analyzing device 12 for calibration purposes. However, this procedure will be described hereinafter in more detail.

(12) In a first step S1, the first port 18 of the measurement and analyzing device 12 is connected with the radio frequency port 32 that is assigned to the frequency-converting device under test when performing a respective measurement on the frequency-converting device under test. Put differently, the first cable 28 is connected with the first port 18 of the measurement and analyzing device 12, as the first cable 28 provides the respective interface for the frequency-converting device under test.

(13) In a second step S2, the second port 20 of the measurement and analyzing device 12 is connected with the intermediate frequency port 34 that is also assigned to the frequency-converting device under test. In a similar manner, the second cable 30 is connected with the second port 20 of the measurement and analyzing device 12, wherein the second cable 30 provides the intermediate frequency port 34, namely the respective position of calibration.

(14) In some embodiments, the respective calibration planes P1, P2 or rather the points of calibration are set when connecting the cables 28, 30 with the measurement and analyzing device 12, which provide the interfaces for the frequency-converting device under test during the respective measurement(s) later.

(15) In a third step S3, a scalar-mixer calibration is performed at the radio frequency port 32 as well as the intermediate frequency port 34. The scalar-mixer calibration provides a precise calibration conversion amplitude, namely an accurate calibration with respect to amplitude.

(16) The scalar-mixer calibration may be done by a PUOSM calibration technique that is based on a UOSM calibration technique and an additional power calibration. For this purpose, the calibration unit 26 is interconnected between the radio frequency port 32 and the intermediate frequency port 34. The calibration unit 26 provides different calibration standards so that different measurements relating to the UOSM calibration technique can be conducted in an automatic manner. In some embodiments, the calibration unit can include software or hardware or in a combination of hardware and software to carry out some or all of its functions.

(17) Further, the calibration unit 26 may comprise an integrated power meter so that the power of the respective source can be measured, namely the power provided by the measurement and analyzing device 12 at the respective position of calibration, namely the respective calibration planes P1, P2.

(18) Alternatively, a separate power meter is connected with the radio frequency port 32 and the intermediate frequency port 34, respectively.

(19) Of course, the calibration kit mentioned above may be used instead of the calibration unit 26. However, the calibration kit requires more manual interaction, as the several calibration terminations have to be connected with the respective ports 32, 34 in a subsequent manner while performing the respective measurements.

(20) The scalar-mixer calibration, namely the PUOSM calibration, does a UOSM calibration at the radio frequency port 32 and the intermediate frequency port 34. In addition, a power calibration is done by the power meter, for instance the one integrated in the calibration unit 26. The scalar-mixer calibration provides an accurate calibration for the amplitude.

(21) Usually, the information obtained by the respective calibration is written by matrices Q.sub.RF, Q.sub.IF L.sub.IF and L.sub.IF as well as a complex factor p.sub.rel. The matrices Q and L relate to a source matrix (Q) and a load matrix (L). Thus, the respective ports 32, 34, namely the radio frequency port 32 as well as the intermediate frequency port 34, both can be described by matrices describing their respective behavior.

(22) From the respective terms mentioned above, it becomes clear that the measurements are done for both signal directions. Hence, the RF port 32 may relate to the source port or rather the load port depending on the signal direction. This also applies for the IF port 34.

(23) An example of the information obtained by the PUOSM calibration is shown in the overview of FIG. 2.

(24) In a fourth step S4, a relative calibration is performed between the radio frequency port 32 and the intermediate frequency port 34 by using the calibration mixer 36. Accordingly, the calibration unit 26 is disconnected from the respective ports 32, 34 such that the calibration mixer 36 can be interconnected for performing the relative calibration. The relative calibration performed by the calibration mixer 36 provides information with regard to phase.

(25) The relative calibration using the calibration mixer also creates the same matrices Q.sub.RF, Q.sub.IF, L.sub.RF, L.sub.IF as well as the complex factor p.sub.rel. For better comparing the matrices assigned to both calibration techniques, the matrices and complex factor assigned to the scalar-mixer calibration are written as Q.sub.RF(1), Q.sub.IF(1), L.sub.RF(1), L.sub.IF(1) as well as the complex factor p.sub.rel(1), whereas the matrices and complex factor assigned to the relative calibration are written as Q.sub.RF(2), Q.sub.IF(2), L.sub.RF(2), L.sub.IF(2) as well as the complex factor p.sub.rel(2).

(26) The relative calibration assumes that the calibration mixer 36 used is reciprocal in amplitude and phase. Any non-reciprocity results in an error/offset in the measured amplitude and phase.

(27) An example of the information obtained by the relative calibration is also shown in the overview of FIG. 2.

(28) In a fifth step S5, at least one correction coefficient is determined by the difference between the results obtained from the scalar-mixer calibration and the relative calibration. As mentioned above, the scalar-mixer calibration ensures a precise calibration with respect to amplitude, whereas a relative calibration ensures a precise measurement with respect to phase.

(29) Accordingly, differences with regard to amplitude or rather phase occur between the results of both calibration techniques.

(30) Nevertheless, the combination of the results obtained by both techniques allows for use of one calibration that provides precise measurements of amplitude and phase simultaneously. Accordingly, the measurement and analyzing device 12 calibrated in an appropriate manner can be used for measuring the frequency-converting device under test with respect to amplitude and phase without any intermediate calibration of the measurement and analyzing device 12, as it is calibrated accurately with respect to amplitude and phase.

(31) In some embodiments, the at least one correction coefficient may be determined by a phase difference between the results obtained from the scalar-mixer calibration and the relative calibration or rather by an amplitude difference between the respective results.

(32) For instance, the correction coefficient relates to a phase correction factor k, which is added to L.sub.RF(1) or rather L.sub.IF(1), as the phase information obtained from the scalar-mixer calibration labelled by (1) is not accurate compared to the one obtained from the relative calibration.

(33) The respective correction coefficient is a complex number having a normalized amplitude, namely an amplitude that equals 1. Thus, the correction coefficient only relates to a phase correction.

(34) The respective phase correction coefficient can be represented by k=exp(i), wherein I is the imaginary number and relates to the phase shift to be applied for phase correction.

(35) The respective phase shift can be determined for L.sub.IF(1) by the following equation:
=(.sub.L.sub.IF22.sub.(2).sub.L.sub.IF22.sub.(1))+(.sub.Q.sub.RF11.sub.(1).sub.Q.sub.RF11.sub.(2))+(.sub.p.sub.rel.sub.(1)p.sub.p.sub.rel.sub.(2))

(36) The respective numbers relate to the elements of the Q- or rather L-matrix. Thus, .sub.L.sub.IF22.sub.(2) relates to the phase of the element in the second column and second row of the respective L-matrix assigned to the IF port 34.

(37) The other correction coefficients, for instance the one for L.sub.RF(1), can be determined in a similar manner.

(38) In some embodiments, the correction coefficients for the respective amplitudes, namely L.sub.RF(2) or rather L.sub.IF(2), can also be calculated in a similar manner.

(39) Accordingly, the results obtained by the different calibration techniques described above are combined and used to determine the at least one correction coefficient. Determination of the at least one correction coefficient can be carried out in software or hardware or in a combination of hardware and software.

(40) An example of the information obtained by the combined calibration techniques is shown in the overview of FIG. 2 as well.

(41) Afterwards, the at least one correction coefficient determined is used to correct at least one error term of an error term model applied in order to calibrate the measurement and analyzing device 12 in a sixth step S6.

(42) Once the measurement and analyzing device 12 has been calibrated as described above, a frequency-converting device under test 38 may be measured with respect to phase and amplitude simultaneously in a precise manner.

(43) Therefore, the frequency-converting device under test 38 is interconnected between the first port 18 and the second port 20 via the first cable 28 and the second cable 30. Put differently, the frequency-converting device under test 38 replaces the calibration unit 26 or rather the calibration mixer 36, as the frequency-converting device under test 38 is connected with the radio frequency port 32 and the intermediate frequency port 34.

(44) In addition, the frequency-converting device under test 38 may be connected with the third port 22 of the measurement and analyzing device 12 that is assigned to an integrated local oscillator 40.

(45) The frequency-converting device under test 38 may provide a local oscillator input 42 that is connected with a cable 44, which in turn is connected with the third port 22 of the measurement and analyzing device 12.

(46) The local oscillator signal provided by the local oscillator 40 of the measurement and analyzing device 12 provides a phase reproducible signal that is forwarded to the frequency-converting device under test 38 for converting the respective input signal appropriately.

(47) In an alternative manner, a reference mixer 46 may be interconnected between the frequency-converting device under test 38 and the first port 18 or rather the second port 20, depending on the respective measurement operation.

(48) The reference mixer 46 and the frequency-converting device under test 38 both have a common local oscillator frequency so that the signal, for example its frequency, is converted by the frequency-converting device under test 38 and the reference mixer 46 in a similar manner. Thus, the frequency-converting device under test 38 and the reference mixer 46 both undo each other with respect to the signal conversion.

(49) In case of using the reference mixer 46 for measuring the frequency-converting device under test 38, the reference mixer 46 is also placed at the intended position during the calibration method. Thus, it is ensured that the overall system is calibrated in an appropriate manner.

(50) In general, a single calibration method is provided that ensures to calibrate the measurement and analyzing device 12 with respect to amplitude and phase in an accurate manner. The measurement and analyzing device 12 can be used to precisely measure the frequency-converting device under test 38 with respect to amplitude and phase.

(51) The present application may reference quantities and numbers. Unless specifically stated, such quantities and numbers are not to be considered restrictive, but exemplary of the possible quantities or numbers associated with the present application. Also in this regard, the present application may use the term plurality to reference a quantity or number. In this regard, the term plurality is meant to be any number that is more than one, for example, two, three, four, five, etc. The terms about, approximately, near, etc., mean plus or minus 5% of the stated value. For the purposes of the present disclosure, the phrase at least one of A, B, and C, for example, means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B, and C), including all further possible permutations when greater than three elements are listed.

(52) The principles, representative embodiments, and modes of operation of the present disclosure have been described in the foregoing description. However, aspects of the present disclosure which are intended to be protected are not to be construed as limited to the particular embodiments disclosed. Further, the embodiments described herein are to be regarded as illustrative rather than restrictive. It will be appreciated that variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present disclosure. Accordingly, it is expressly intended that all such variations, changes, and equivalents fall within the spirit and scope of the present disclosure, as claimed.