Method of calibrating a setup

Abstract

A method of calibrating a setup comprises: performing at least one calibration of the setup, thereby obtaining calibration data; setting a quantity representing forward tracking to be equal with a quantity representing reverse tracking; solving a system of equations having at least an unknown quantity representing the forward tracking or the reverse tracking, thereby obtaining at least one equation having the unknown quantity squared; creating based on the calibration data obtained two phase over frequency relationships for the respective quantity; determining two lines having a linear change in phase over frequency for the phase over frequency relationships created; extrapolating the lines determined to a frequency of 0 Hz; and determining the respective quantity by selecting one line of the lines extrapolated that is closer to a phase of zero, 2π or a multiple thereof at the frequency of 0 Hz.

Claims

1. A method of calibrating a setup while taking delay and loss between an analyzer and a calibration plane in the setup into account, wherein the method comprises: performing at least one calibration of the setup by three calibration standards or by a calibration kit encompassing the three calibration standards, thereby obtaining calibration data; setting a quantity representing forward tracking to be equal with a quantity representing reverse tracking; solving a system of equations having at least an unknown quantity representing the forward tracking or the reverse tracking, thereby obtaining at least one equation having the unknown quantity squared; creating based on the calibration data obtained two phase over frequency relationships for the respective quantity, wherein the two phase over frequency relationships are assigned to the results of the square root of the unknown quantity squared when solving the at least one equation; determining two lines having a linear change in phase over frequency for the two phase over frequency relationships created; extrapolating the two lines determined to a frequency of 0 Hz; and determining the respective quantity by selecting one line of the two lines extrapolated that is closer to a phase of zero, 2π or a multiple thereof at the frequency of 0 Hz, wherein a 9-term error model for calibration of at least two ports is provided that uses the respective quantity determined instead of quantities obtained from a 3-term error model.

2. The method according to claim 1, wherein the steps, except for the step of performing the at least one calibration, are performed in a fully automatic manner.

3. The method according to claim 1, wherein a respective function value of the two lines is determined at the frequency of 0 Hz, and wherein the respective function value determined is compared with zero, 2π or a multiple thereof in order to determine the quantity.

4. The method according to claim 1, wherein waves in forward direction and waves in reverse direction are determined at the calibration plane based on the respective waves measured at the analyzer and the respective quantity determined.

5. The method according to claim 1, wherein the system of equations comprises at least three equations.

6. The method according to claim 1, wherein the calibration is done without performing a loss calibration by a power meter.

7. The method according to claim 1, wherein an absolute phase calibration of the analyzer is performed in order to extend the absolute phase calibration to the calibration plane.

8. The method according to claim 1, wherein at least one of a port match calibration and a source match calibration is done, and wherein a group delay measurement is performed subsequently.

9. The method according to claim 8, wherein the group delay measurement is done by a one tone measurement or a two tone measurement.

10. The method according to claim 1, wherein the three calibration standards used for the calibration correspond to an open standard, a short standard and a match standard or wherein the three calibration standards used for the calibration correspond to an offset short standard, a short standard and a match standard.

11. The method according to claim 1, wherein the analyzer is a vector network analyzer.

12. A method of calibrating a setup while taking delay and loss between an analyzer and a calibration plane in the setup into account, wherein the method comprises: performing at least one calibration of the setup by three calibration standards or by a calibration kit encompassing the three calibration standards, thereby obtaining calibration data; setting a quantity representing forward tracking to be equal with a quantity representing reverse tracking; solving a system of equations having at least an unknown quantity representing the forward tracking or the reverse tracking, thereby obtaining at least one equation having the unknown quantity squared; creating, based on the calibration data obtained, two phase over frequency relationships for the respective quantity, wherein the two phase over frequency relationships are assigned to the results of the square root of the unknown quantity squared when solving the at least one equation; determining two lines having a linear change in phase over frequency for the two phase over frequency relationships created; extrapolating the two lines determined to a frequency of 0 Hz; and determining the respective quantity by selecting one line of the two lines extrapolated that is closer to a phase of zero, 2π or a multiple thereof at the frequency of 0 Hz, and wherein it is assumed that the connection between the analyzer and the calibration plane is provided by at least one passive component having reciprocal characteristics with regard to signal processing.

13. A method of calibrating a setup while taking delay and loss between an analyzer and a calibration plane in the setup into account, wherein the method comprises: performing at least one calibration of the setup by three calibration standards or by a calibration kit encompassing the three calibration standards, thereby obtaining calibration data; setting a quantity representing forward tracking to be equal with a quantity representing reverse tracking; solving a system of equations having at least an unknown quantity representing the forward tracking or the reverse tracking, thereby obtaining at least one equation having the unknown quantity squared; creating, based on the calibration data obtained, two phase over frequency relationships for the respective quantity, wherein the two phase over frequency relationships are assigned to the results of the square root of the unknown quantity squared when solving the at least one equation; determining two lines having a linear change in phase over frequency for the two phase over frequency relationships created; extrapolating the two lines determined to a frequency of 0 Hz; and determining the respective quantity by selecting one line of the two lines extrapolated that is closer to a phase of zero, 2π or a multiple thereof at the frequency of 0 Hz, wherein a port match calibration and a source match calibration are done, wherein a group delay measurement is performed subsequently, and wherein the group delay measurement is done by a two tone measurement such that the analyzer generates two sinusoidal signals with a given frequency difference, resulting in a two tone signal which is used as an excitation signal for the respective measurement.

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 illustrates a representative setup comprising an analyzer and a respective calibration plane,

(3) FIG. 2 is a flow-chart illustrating a method of calibrating a setup according to an embodiment of the present disclosure, and

(4) FIG. 3 shows a diagram illustrating steps of a method of calibrating a setup according to an embodiment of 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) FIG. 1 shows a setup 10 that comprises an analyzer 12 established by a vector network analyzer (VNA). The analyzer 12 has a signal source 14, a directional coupler 16 as well as a port 18 that are connected with each other. In some embodiments, the directional coupler 16 is interconnected between the signal source 14 and the port 18. The respective components of the analyzer 12 may relate to internal components that are located within a housing of the analyzer 12 that is established by a single-housed device.

(7) In addition, the setup 10 shows that a cable or line 20 is connected with the port 18 of the analyzer 12 wherein a calibration plane 22 is provided at a certain location associated with the cable or line 20. The calibration plane 22 may correspond to an interface with which a device under test can be connected once the setup 10 has been calibrated.

(8) Three calibration standards 24, 26, 28 are shown that are used for calibrating the setup 10 as will be described hereinafter with reference to FIG. 2. The calibration standards 24, 26, 28 correspond to an open standard, a short standard and a match standard. Alternatively, the three standards 24, 26, 28 may correspond to an offset short standard, a short standard and a match standard. In a further alternative embodiment, the three calibration standards 24, 26, 28 are encompassed in a common calibration kit 30 that is illustrated by dashed lines in FIG. 1.

(9) Referring to FIG. 2, a calibration of the setup 10 is performed in a first step S1 by the three calibration standards 24, 26, 28 or rather the calibration kit 30, thereby obtaining calibration data. For performing the respective calibration, the calibration standards 24, 26, 28 or rather the entire calibration kit 30 are/is connected with the calibration plane 22. Then, the calibration steps according to the respective calibration procedure are conducted. For instance, a typical calibration procedure corresponding to a so-called OSM technique is performed.

(10) In a second step S2, the calibration data obtained is forwarded and processed by a control and/or analyzing circuit or module 32 that is assigned to the analyzer 12. For instance, the control and/or analyzing module 32 is integrated within the analyzer 12.

(11) The control and/or analyzing module 32 is generally configured to perform the following steps in a fully automatic manner such that no manual input is required.

(12) In a third step S3, a quantity representing forward tracking, namely the scattering parameter S21, is set to be equal with a quantity representing reverse tracking, namely the scattering parameter S12.

(13) In a fourth step S4, a system of equations is solved that comprise at least an unknown quantity representing the forward tracking or the reverse tracking. Hence, the respective system of equations may comprise the scattering parameter S12 or the scattering parameter S21.

(14) In some embodiments, the system of equations to be solved may comprise at least three equations for a one-port calibration.

(15) For instance, the following equation is to be solved by the calibration data obtained:

(16) $\frac{b}{a}=S_{11}+\frac{S_{12}*S_{21}*\Gamma }{1-S_{22}*\Gamma },$

(17) wherein a and b correspond to the waves in forward direction and reverse direction at the analyzer, Γ corresponds to the description of the respective calibration standard, and wherein S.sub.xx corresponds to the respective scattering parameter. S.sub.21 corresponds to the quantity representing the forward tracking (“FT”), whereas S.sub.12 corresponds to the quantity representing the reverse tracking (“RT”). Moreover, S.sub.11 corresponds to the directivity (“D”) and S.sub.22 corresponds to the source match (“SM”).

(18) When solving the system of equations, at least one equation is obtained which has the unknown quantity squared. This respective equation corresponds to a quadratic equation that has to be solved. However, the quadratic equation results in two mathematical solutions wherein only one of the mathematical solutions is the physically correct one.

(19) Since S.sub.21 and S.sub.12 are set to be equal, for instance labelled as follows S.sub.xy, the above-mentioned equation can be formulated as follows:

(20) $\frac{b}{a}=S_{11}+\frac{S_{xy}^2*\Gamma }{1-S_{22}*\Gamma }.$

(21) In order to identify the physically correct solution of the quadratic equation, two phase over frequency relationships for the respective quantity are created based on the calibration data obtained in a fifth step S5. The two phase over frequency relationships are assigned to the respective results of the square route of the squared unknown quantity, namely S.sub.xy.sup.2, when solving the at least one quadratic equation.

(22) Hence, the phase over frequency relationships are associated with the mathematical solutions of the quadratic equation mentioned above.

(23) In a sixth step S6, two lines are determined that have a linear change in phase over frequency for the respective phase over frequency relationships created. Hence, it is assumed that the phase changes over frequency in a linear manner.

(24) In a seventh step S7, the lines determined are extrapolated to a frequency of 0 Hz. This is shown in FIG. 3 for both mathematically possible solutions of the above-mentioned quadratic equation.

(25) In some embodiments, the lines correspond to linear approximations of the respective calibration data obtained as shown in FIG. 3. The calibration data is obtained in a frequency range between f.sub.start and f.sub.stop.

(26) Since no calibration value is obtained for a frequency of 0 Hz, the respective lines, namely the linear approximations, have to be extrapolated in order to provide a function value at the frequency of 0 Hz.

(27) In an eighth step S8, the respective quantity, namely S.sub.xy, is determined by selecting one of the lines extrapolated that is closer to a phase of zero, 2π or a multiple thereof at the frequency of 0 Hz. The diagram shown in FIG. 3 reveals this easily.

(28) Accordingly, the physically correct solution of the quadratic equation mentioned above is determined.

(29) This can also be determined in an automatic manner since the function value of the determined lines is determined at the frequency of 0 Hz. Then, the function value determined at the frequency of 0 Hz is compared for each of the respective lines, namely both linear approximations, with zero, 2π or multiples thereof in order to identify the physically correct solution.

(30) In a ninth step S9, waves in forward direction and waves in reverse direction are determined at the calibration plane 22 based on the respective waves measured at the analyzer 12 and the respective quantity determined. In some embodiments, the following equation is used for determining the respective waves:

(31) $\left(\begin{array}{c}b\\ b_c\end{array}\right)=\left(\begin{array}{cc}{S}_{11}& S_{21}\\ S_{12}& S_{22}\end{array}\right)\left(\begin{array}{c}a\\ a_c\end{array}\right),$

(32) wherein a and b correspond to the waves in forward direction and reverse direction at the analyzer, respectively. a.sub.c and b.sub.c correspond to the waves in forward direction and reverse direction at the calibration plane. Furthermore, S.sub.21 and S.sub.12 are set to be equal wherein they correspond to the quantity determined by the steps mentioned above. S.sub.11 and S.sub.22 are determined by the other equations of the system of equations.

(33) Moreover, a model may be used that describes the calibration of the analyzer 12, wherein the respective model depends on the number of parameters describing the calibration of analyzer 12, for instance for 2 or more ports. By taking technical assumptions into account, the parameters can be reduced to seven or nine parameters for the calibration of at least two ports of the analyzer 12. This is also called 7/9-error term model. However, the respective 7/9-error term model is extended by using the respective quantity determined as described above according to the method of the present disclosure that is an (improved) alternative to the 3-term error model known.

(34) Accordingly, the respective 7/9-error term model is extended to use the here described calibration model instead of the 3-term error model.

(35) Furthermore, an absolute phase calibration of the analyzer 12 may be performed so as to extend the absolute phase calibration to the calibration plane 22. Thus, the calibration plane 22 is calibrated with regard to absolute phase.

(36) In general, a method of calibrating the respective setup 10 is provided that takes delay and loss between the analyzer 12 and the calibration plane 22 in the respective setup 10 into account such that it is not necessary to perform an additional calibration step by a separately formed power meter.

(37) The methods described herein can be used to perform a port match calibration and/or a source match calibration.

(38) Moreover, the signal source 14 may be configured to provide a two tone signal that can be used to determine a group delay when performing a group delay measurement. Based on the port match calibration and/or source match calibration, the group delay measurement can be performed subsequently in order to determine the group delay.

(39) Put differently, a port match calibration and/or a source match calibration can be obtained due to the calibration achieved by the method(s) described above.

(40) Furthermore, the signal source 14 may also be used for a one tone measurement in order to perform the group delay measurement.

(41) Generally, a simplified way to calibrate the analyzer 12 is provided while taking delay and/or loss between the analyzer 12 and a calibration plane 22 into account.

(42) Certain embodiments disclosed herein utilize circuitry (e.g., one or more circuits) in order to implement protocols or standards, methodologies or technologies disclosed herein, operably couple two or more components, generate information, process information, analyze information, generate signals, encode/decode signals, convert signals, transmit and/or receive signals, control other devices, etc. Circuitry of any type can be used.

(43) In an embodiment, circuitry includes, among other things, one or more computing devices such as a processor (e.g., a microprocessor), a central processing unit (CPU), a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a system on a chip (SoC), or the like, or any combinations thereof, and can include discrete digital or analog circuit elements or electronics, or combinations thereof. In an embodiment, circuitry includes hardware circuit implementations (e.g., implementations in analog circuitry, implementations in digital circuitry, and the like, and combinations thereof).

(44) In an embodiment, circuitry includes combinations of circuits and computer program products having software or firmware instructions stored on one or more computer readable memories that work together to cause a device to perform one or more protocols, methodologies or technologies described herein. In an embodiment, circuitry includes circuits, such as, for example, microprocessors or portions of microprocessor, that require software, firmware, and the like for operation. In an embodiment, circuitry includes one or more processors or portions thereof and accompanying software, firmware, hardware, and the like.

(45) 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 and B” is equivalent to “A and/or B” or vice versa, namely “A” alone, “B” alone or “A and B.”. Similarly, 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.

(46) 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.