HK1145041B - Contactless measuring system - Google Patents

Description

Non-contact measuring system

Technical Field

The invention relates to a contactless measurement system comprising at least one test probe forming part of a coupling structure for contactless decoupling of a signal transmitted on a signal waveguide, wherein the signal waveguide is configured as a conductive line on a circuit board of an electrical circuit and as a part of the electrical circuit, according to the preamble of claim 1. The invention also relates to a calibration substrate for a contactless measurement system comprising at least one test probe forming part of a coupling structure for contactless decoupling of signals transmitted on signal waveguides, wherein at least one calibration element, in particular a short-circuit standard, an open-circuit standard, a resistive standard or a conductive standard, is arranged on the calibration substrate, wherein the at least one calibration element is electrically connected to the at least one signal waveguide, in particular a microstrip transmission line or a coplanar waveguide, according to the preamble of claim 17.

Background

From, for example, T.Zelder, H.Eul, "contact network analysis with improved dynamic range using conversion, proceedings sof the 36^thEuropean Microwave Conference, Manchester, UK, pages 478 to 481, September 2006 or T.Zelder, H.Rabe, H.Eul, "contrast electronic measuring system using coherent combining algorithm to determine scattering parameters", Advances in Radio Science-KleinheiubachherBerrichte 2006, vol.5, 2007, by non-contact vector network analysis to determine scattering parameters of electrical components embedded in complex circuits. In contrast to conventional contact-bound network analysis methods, the inner directional coupler of a network analyzer is replaced with contactless near-field measurement probes that are directly connected to the vector measurement points of the analyzer. These measurement probes are located above the signal lines of the object to be measured. These probes may act inductively and/or capacitively on the electromagnetic field of the coplanar conductors. For measuring the scattering parameters, conventional calibration methods are used, such as methods for contact bounce network analysis.

In contactless vector network analysis, for each measurement port that is an unknown test object (device under test-DUT), at least one measurement probe, for example, a conductor loop or two capacitive probes, is required. It is known from, for example, F.De Groote, J.Verspecht, C.Tsironis, D.Barataud and J.P.Teysier, "improved coupling method for time domain load-pull measurements", European Microwave Conference, vol.1, pages 4 ff., October2005 to use unconnected wires made of coaxial semi-rigid wiresA contact conductor ring. In contrast, from T.Zelder, H.Eul, "contact network analysis with improved dynamic range using conversion, proceedings sof the 36^thEuropean Microwave Conference, Manchester, UK, pages 478 to 481, September 2006 or T.Zelder, H.Rabe, H.Eul, "contact electronic measuring system using capacitive probe", Advances in Radio Science-KleinheiubucherBerichte 2006, vol.5, 2007, is known for use in Contactless measurement systems. From T.Zelder, I.Rolfes, H.Eul, "contact vector network analysis using direct calibration with capacitive and inductive coupled probes", Advances in radio science-Kleinheubacher Berichte 2006, vol.5, 2007 and J.Stenarson, K.Yhland, C.Wingqvist, "An in-circuit non-conductive measuring method for S-parameters and power in planar measurements", IEEE Transactions Microwave and Techniques, vol.49, No.12, pages 2567 to 2572, December 2001, a combination of capacitive probes and inductive probes is known to achieve a measurement system.

Despite the possibility of contactless vector network analysis to characterize components contactlessly, however, contactless scattering parameter measurements for HF and microwave components embedded in an electrical circuit have not been carried out to date. If the measurement is performed within the circuit, it is necessary to change the position of the non-contact probe during and after calibration. However, significant measurement errors will result due to minimal deviations in the probe positioning, which means a high complexity in order to reproduce the test probe position during the measurement of the calibration standard and the test object.

Disclosure of Invention

It is an object of the present invention to provide a contactless measuring system of the above-mentioned type, whereby expensive and complicated coupling probe positioning can be dispensed with.

This object is achieved according to the invention by a contactless measuring system of the above-mentioned type having the features of claim 1 and by a calibration substrate of the above-mentioned type having the features of claim 17. Preferred embodiments of the invention are described in the other claims.

With a contactless measuring system of the above-mentioned type, which is provided according to the invention, at least one contact structure is configured and arranged on the circuit board, wherein the contact structure is galvanically separated from the signal waveguide, forms a coupling structure section, is arranged completely within the near field of the signal waveguide, and comprises at least one contact point which can be brought into electrical contact with a contact point of a test probe.

This has the following advantages: the contact structure and thus the entire coupling structure have a precisely defined geometrical arrangement relative to the signal waveguide, so that manual positioning of the coupling structure can be dispensed with. Reproducible coupling between the signal waveguide and the coupling structure can be easily achieved.

Suitably, the contact structure is configured as a conductive line on a circuit board.

In particular, good signal coupling may be achieved as the contact structure is configured such that it can be contacted by the test probe in an impedance controlled manner.

The at least one contact structure is configured, for example, as a coupling waveguide having an inner conductor and an outer conductor, or as at least one contact point or contact surface for contacting a test probe.

Suitably, the contact structure and/or the signal waveguide are configured as printed conductive lines on a circuit board.

For example, the circuit board is configured as a Printed Circuit Board (PCB) or wafer.

Since the contact structure is configured as a waveguide, optimal directional damping or port with broadband insulation is achieved, wherein the ratio of the inductive-to-capacitive coupling coefficients is equal to the product of the wave impedances of the individual waveguides of the contact structure.

In an exemplary embodiment, each measurement port of the coupling structure has at least one contact structure, in particular two contact structures.

In a preferred embodiment, the circuit board is a multilayer board having a plurality of substrate layers, wherein the signal waveguide is arranged on a first substrate layer of the multilayer board and the at least one contact structure is arranged on the first substrate layer or at least one other substrate layer of the multilayer board.

As an example, the at least two contact structures are arranged on different substrate layers of the multilayer board.

In a particularly preferred embodiment, at least one of the contact structures has a contact point configured and arranged to produce an impedance controlled interface with contact of a test probe on a wafer or PCB.

For a fast and simple calibration of the contactless measuring system, at least one calibration element is also arranged on the circuit board, which calibration element is connected to the at least one signal waveguide, wherein the at least one contact structure is arranged on the at least one signal waveguide such that the arrangement of the contact structure on the signal waveguide of the calibration element corresponds to the arrangement of the contact structure on the signal waveguide of the circuit.

At least one calibration element is connected to a number of signal waveguides corresponding to the number of measurement ports of the contactless measurement system.

In order to provide the same coupling conditions and an optimal calibration to the calibration element and the electric circuit, the at least one contact structure on the signal waveguide of the calibration element assigned to the measurement port of the contactless measurement system is configured to be identical to the at least one contact structure on the signal waveguide of the electric circuit assigned to the measurement port of the contactless measurement system.

With a calibration substrate of the above-mentioned type provided according to the invention, the calibration substrate is configured as a circuit board, wherein at least one contact structure is configured and arranged on the circuit board such that it is galvanically separated from the signal waveguide, forms a coupling structure section, is arranged completely within the near field of the signal waveguide, and has at least one contact point which can be brought into electrical contact with a contact point of a test probe.

This brings the advantage that the contact structure and thus the entire coupling structure have a precisely defined geometrical arrangement with respect to the signal waveguide, so that manual positioning of the coupling structure can be dispensed with. Reproducible coupling between the signal waveguide and the coupling structure can be easily achieved.

As already mentioned above, the contactless measurement system is preferably configured in such a way that at least one contact structure assigned to a measurement port of the contactless measurement system on the signal waveguide of the calibration element is configured identical to at least one contact structure assigned to this measurement port of the contactless measurement system on the signal waveguide of the electrical circuit.

At least one calibration element is connected to a number of signal waveguides corresponding to the number of measurement ports of the contactless measurement system.

Suitably, on the circuit board of the calibration substrate, the at least one circuit is configured with at least one signal waveguide, wherein at least one contact structure is arranged on the at least one signal waveguide such that the arrangement of the contact structure on the signal waveguide corresponds to the arrangement of the contact structure on the signal waveguide of the calibration element.

In a preferred embodiment, the at least one contact structure on the signal waveguide of the calibration element assigned to a measurement port of the contactless measurement system is configured to be identical to the at least one contact structure on the calibration substrate on the signal waveguide of the electrical circuit assigned to the measurement port of the contactless measurement system.

Drawings

The invention will now be described in more detail with reference to the accompanying drawings, in which:

figure 1 shows a schematic block circuit diagram of a preferred embodiment of a contactless measurement system with a vector network analyzer according to the present invention,

figure 2 shows a first preferred embodiment of a contact structure for a non-contact measuring system according to the invention,

figure 3 shows a second preferred embodiment of a contact structure for a non-contact measuring system according to the invention,

figure 4 shows a first preferred embodiment of a calibration substrate according to the invention for a non-contact measurement system according to the invention in plan view,

figure 5 shows an exemplary alternative embodiment of a contact structure for a non-contact measuring system according to the present invention,

figure 6 shows another exemplary alternative embodiment of a contact structure for a non-contact measuring system according to the present invention,

figure 7 shows another exemplary alternative embodiment of a contact structure for a non-contact measuring system according to the present invention,

figure 8 shows another exemplary alternative embodiment of a contact structure for a non-contact measuring system according to the present invention,

figure 9 shows another exemplary alternative embodiment of a contact structure for a non-contact measuring system according to the present invention,

figure 10 shows another exemplary alternative embodiment of a contact structure for a non-contact measurement system according to the present invention,

figure 11 shows another exemplary alternative embodiment of a contact structure for a non-contact measuring system according to the present invention,

figure 12 shows another exemplary alternative embodiment of a contact structure for a non-contact measurement system according to the present invention,

figure 13 shows another exemplary alternative embodiment of a contact structure for a non-contact measurement system according to the present invention,

FIG. 14 shows a second preferred embodiment of a calibration substrate according to the invention for a non-contact measurement system according to the invention in plan view, an

Fig. 15 shows a third preferred embodiment of a calibration substrate according to the invention for a contactless measurement system according to the invention in a plan view.

Detailed Description

The preferred embodiment of the non-contact measurement system according to the invention shown in fig. 1 comprises a vector network analyzer 10 with a signal source 12, signal lines 14 and 16 and a contact structure with 4 coupling waveguides 18, wherein each coupling waveguide 18 has an inner conductor 20 and an outer conductor 22. The coupling waveguide 18 is configured as a printed conductive line on a printed circuit board 24. Likewise, the signal waveguide 26 is also configured as a printed conductive line disposed on the printed circuit board 24. The signal waveguide 26 is an electronic circuit portion (not specifically shown) having corresponding electronic components provided on the printed circuit board 24.

The coupling waveguide 18 forms together with the test probe 28 a coupling structure for a contactless measurement system for contactless decoupling of electromagnetic waves transmitted along the signal waveguide 26. Each test probe 28 makes electrical contact with coupling waveguide 18 on one side and measurement ports 30, 32, 34, 36 of vector network analyzer 10 on the other side.

Coupling waveguide 18 can be almost any shape. In particular, it is advantageous to configure the coupling waveguide 18 in an impedance controlled manner, i.e. the characteristic wave impedance value of the arrangement is known and optimal for low reflection. An advantage of the impedance controlled contact structure is that optimal directional damping and isolated ports over a wide bandwidth can be achieved.

Fig. 2 and 3 show two examples of this type of impedance-controlled coupling waveguide 18. The coupling waveguide 18 shown in fig. 2 includes a U-shaped inner conductor 20 and an outer conductor 22. The outer conductor 22 may be configured in different ways. Firstly, the outer conductor 22 may be closed, i.e. as shown in fig. 2 with a dashed line, the outer conductor arms 38 and 40 are closed at the coordinate z-0, and secondly, the ends of the outer conductor arms 38, 40 may be separated along z. For example, the ends of the arms 38, 40 are at position + z₁And-z₁Or at position + z as shown in FIG. 2₂And-z₂To (3). Coupling waveguide 18 corresponds to a curved coplanar waveguide by the arrangement of inner conductor 20 relative to outer conductor 22. Various modifications can be made to this coupling waveguide 18. Fig. 3 shows a variant without corners. By way of example here, the outer conductor arms 38 and 40 are joined to each other at a position z-0.

Another advantage of the contact structure according to the invention is that no grounded through-contact (back side bottom metallization of the circuit board 24) is required. However, the possibility of grounding the outer conductor 22 of the coupling waveguide 18 with a through contact is not excluded.

To decouple energy from the signal waveguides 26 of the test object (device under test-DUT), at least one contact structure or coupling waveguide 18 is brought into the near field of each signal waveguide 26. The coupling waveguides 18 may be located on the same substrate as the signal waveguides 26 or on another substrate in the case of a multilayer board. The contact structure with the coupling waveguide 18 is then connected to a test probe on, for example, a commercially available symmetric wafer or PCB. Reference numeral 42 in fig. 2 and 3 denotes the contact position of the contact of the test probe with the contact structure or respective coupling waveguide 18. To characterize an N-port test object, at least N coupling waveguides 18 located within the near-field of N signal waveguides 26 are required. Fig. 1 shows an example of a 2-port test object (in this case a simple conductor-DUT) with four coupling waveguides 18.

Both the geometry of coupling waveguide 18 and the geometry of test probe 28 affect the coupling coefficient of the arrangement. The test probes 28 are connected to a (vector) receiver of e.g. a conventional network analyzer, as shown in fig. 1.

A process of measuring a test object embedded in a planar circuit by means of at least one impedance-controlled contact structure or at least one non-impedance-controlled contact structure within the planar circuit will now be described.

The method is mainly based on a non-contact vector network analysis method. A disadvantage of contactless vector network analysis is that the use of methods for obtaining accurate measurements depends mainly on the positioning accuracy of the contactless test probe. According to the present invention there is also provided the use of printed contact structures in combination with conventional test probes, rather than the use of sophisticated automated positioning systems in combination with fully non-contact probes. All signal lines of the test object and calibration elements, which are necessary for the calibration of systematic errors, must be provided with at least one coupling waveguide 18 (contact structure).

Fig. 4 shows an example of a practical implementation of a calibration substrate with embedded test objects (DUT3, DUT4) with a contact structure with printed coupling waveguides 18. For 2-port calibration, the contact structure includes two coupling waveguides 18 for each signal waveguide 26, which are configured, for example, according to the embodiment of fig. 2. For N-port calibration, it is desirable to have at least N contact structures coupling waveguides 18 per signal waveguide 26. It may also be beneficial to employ a contact structure having more than N coupling waveguides 18 per signal waveguide 26 when using the differential calibration method.

Due to the small size of the coupling waveguide 18, for example, a test probe on a wafer or PCB can be reproducibly positioned on the same coupling waveguide 18 for each calibration element (LINE 1, LINE 2, LINE 3, LINE 4, OPEN (OPEN), SHORT (SHORT)). Once the system is calibrated, scattering parameters of, for example, embedded components may be determined. However, the signal lines of these components must have the same characteristics (geometry, wave impedance, etc.) as those of the calibration element. In addition, for calibration purposes, the same contact structure must be present on the planar circuit at each signal waveguide 26 of the embedded test object (DUT).

Thus, the method includes the placement of contact structures, for example, in the form of coupling waveguides 18 within the near field of the calibrated signal waveguide 26 and test objects on the circuit board 24. The coupling waveguides 18 are arranged and configured on the circuit board 24 such that these coupling waveguides 18 hardly interfere with the function of the circuit and can also be connected to, for example, conventional on-wafer or PCB test probes.

Fig. 5-13 illustrate various exemplary embodiments of contact structures 44. The contact structure 44 may have a very particular shape. In principle, any desired shape may be used. To produce reproducible coupling between signal waveguide 26 and coupling waveguide 18, or signal waveguide 26 and test probe 28, or signal waveguide 26 and coupling waveguide 18 and test probe 28, if contact structure 44 comprises a material plane, contact structure 44 has a hole in which a test probe is placed, or has a labeled geometry on which a test probe is placed. Optionally, the contact structure 44 may also be configured as a notch in the substrate.

Fig. 14 shows a second preferred embodiment of a calibration substrate according to the invention arranged on a circuit board 46. Parts having the same function are identified with the same reference numerals as in fig. 1 and 4, so that reference is made to the above description relating to fig. 1 and 4 for explaining these reference numerals. A plurality of collimating elements 48 are arranged on the collimating substrate and each collimating element 48 is connected to one, two or three signal waveguides 26. Unlike the first embodiment according to fig. 4, no coupling waveguide is provided on the signal waveguide 26, but a contact structure 44 is provided as shown in fig. 5 to 13. The signal is optionally supplied to a signal waveguide 26 at an appropriate contact location 50. This calibration substrate includes different 1-, 2-, and 3-port calibration standards 48 and different contact structures 44.

Fig. 15 shows a third preferred embodiment of a calibration standard according to the invention arranged on a circuit board 46. Parts having the same function are identified with the same reference numerals as in fig. 1, 4 and 14, so that reference is made to the above description relating to fig. 1, 4 and 14 for explaining these reference numerals. In this embodiment, the electronic circuitry 52 is also provided with components 54 (DUTs) to be tested on the circuit board 46 of the calibration substrate. Conversely, the calibration element 48 can also be arranged on the circuit board 46 with the electronic circuit 52. The contact structure 44 on the signal waveguide 26 of the calibration element for a particular measurement port is configured to be identical to the contact structure 44 on the signal waveguide 26 of the electronic circuit 52 for that measurement port.

In order to properly measure the scattering parameters of an N-port test object, the measurement system must be calibrated. From this calibration, M different N-port calibration standards (calibration elements 48) are required, which are known or only partially known. For calibration using M calibration standards, the geometry and position of the contact structures and signal waveguides 26 must be the same for each measurement port, although the N measurement ports may be different from one another.

For example, if the scattering parameters of a 2-port object are to be measured, then three 2-port calibration standards are required for LLR calibration. For example, there may be two lines of different lengths and two shorts, where each short represents a 1-port object and the two shorts together correspond to a 2-port object. Each port of the three 2-port standards may include two different transmission lines (signal waveguides 26). The contact structure 44 may also be different on each transmission line (each signal waveguide) in terms of location and geometry. However, the signal waveguide 26 and contact structure 44 must be identical at each port 1 of the calibration standard and DUT 48. Furthermore, at port 2 of the calibration standard, the signal waveguide 26 and the contact structure 44 must match each other, although they may be different from the signal waveguide 26 and the contact structure 44 at port 1.

Claims (25)

1. A contactless measurement system comprising at least one test probe (28), which test probe (28) forms a coupling structure part for contactless decoupling of signals transmitted on a signal waveguide (26), wherein the signal waveguide (26) is configured as a circuit (52) part and a conducting line on a circuit board (24), which circuit board (24) is a circuit board of the circuit (52), characterized in that at least one contact structure (18; 44) is configured and arranged on the circuit board (24) such that the contact structure (18; 44) is galvanically separated from the signal waveguide (26), which contact structure (18; 44) forms the coupling structure part, which contact structure (18; 44) is arranged completely within the near field of the signal waveguide (26), and the contact structure (18; 44) comprises at least one contact point (42) capable of making electrical contact with a contact point of the test probe (28).

2. The contactless measurement system of claim 1, wherein the contact structure is configured as a conductive wire on the circuit board (24).

3. The contactless measurement system according to any of the preceding claims, characterized in that the contact structure is configured such that it can be brought into contact with the test probe (28) in an impedance-controlled manner.

4. The contactless measurement system according to claim 1, characterized in that at least one of the contact structures is configured as a coupling waveguide (18) having an inner conductor (20) and an outer conductor (22).

5. The non-contact measurement system according to claim 1, characterized in that at least one of the contact structures (44) is configured as at least one contact point or contact surface for contacting the test probe (28).

6. The contactless measurement system according to claim 1, characterized in that the contact structure (18; 44) and/or the signal waveguide (26) are configured as printed conductive lines on the circuit board (24).

7. The non-contact measurement system of claim 1, wherein the circuit board (24) is configured as a Printed Circuit Board (PCB) or wafer.

8. The noncontact measurement system of claim 1, wherein the contact structure is configured as a waveguide, wherein a ratio of inductance to capacitance coupling coefficients is equal to a product of wave impedances of the waveguides of the contact structure.

9. A contactless measurement system according to claim 1, characterized in that each measurement port of the coupling structure has at least one of the contact structures (18; 44).

10. A contactless measurement system according to claim 9, characterized in that each of the measurement ports of the coupling structure has two of the contact structures (18; 44).

11. The contactless measurement system according to claim 1, characterized in that the circuit board (24) is a multilayer board having a plurality of substrate layers, wherein the signal waveguide (26) is arranged on a first substrate layer of the multilayer board and at least one of the contact structures (18; 44) is arranged on the first substrate layer or at least one other substrate layer of the multilayer board.

12. The non-contact measurement system according to claim 11, characterized in that at least two of the contact structures (18; 44) are arranged on different substrate layers of the multi-layer board (24).

13. The non-contact measurement system of claim 1, wherein at least one of the contact structures (18; 44) has a contact point (42), the contact point (42) being configured and arranged such that contact with a test probe on a wafer or PCB results in an impedance controlled interface.

14. The contactless measuring system according to claim 1, characterized in that at least one calibration element (48) is also arranged on the circuit board (26; 46), which calibration element (48) is connected to at least one of the signal waveguides (26), wherein at least one contact structure (18; 44) is arranged on the signal waveguide such that the arrangement of the contact structure (18; 44) on the signal waveguide (26) of the calibration element (48) corresponds to the arrangement of the contact structure (18; 44) on the signal waveguide (26) of the circuit (52).

15. The contactless measuring system according to claim 14, characterized in that short-circuit standards, open-circuit standards, impedance standards and/or conductor standards are provided as calibration elements (48) on the circuit board (24; 46).

16. The contactless measurement system according to claim 14 or 15, characterized in that at least one of the calibration elements (48) is connected to a number of the signal waveguides (26) corresponding to the number of measurement ports of the contactless measurement system.

17. The contactless measurement system according to claim 14 or 15, characterized in that at least one contact structure (18; 44) on the signal waveguide (26) of the calibration element (48) assigned to a measurement port of the contactless measurement system is configured to be identical to at least one contact structure (18; 44) on the signal waveguide (26) of the circuit (52) assigned to the measurement port of the contactless measurement system.

18. Calibration substrate for a contactless measurement system comprising at least one test probe forming a coupling structure part for contactless decoupling of signals transmitted on signal waveguides (26), wherein at least one calibration element (48) is provided on the calibration substrate, wherein at least one calibration element is electrically connected to at least one signal waveguide (26), characterized in that the calibration substrate is configured as a circuit board (46), on which circuit board (46) at least one contact structure (44) is configured and arranged such that the contact structure (44) is galvanically separated from the signal waveguides (26), the contact structure (44) forming the coupling structure part, the contact structure (44) being arranged entirely within the near field of the signal waveguides (26), and the contact structure (44) comprises at least one contact point (42) capable of electrically contacting a contact point of the test probe (28).

19. Calibration substrate according to claim 18, wherein the non-contact measurement system is configured according to any of claims 1 to 12.

20. Calibration substrate according to claim 19, characterized in that at least one contact structure (44) on the signal waveguide (26) of the calibration element (48) assigned to a measurement port of the contactless measurement system is configured to be identical to at least one contact structure (44) on the signal waveguide (26) of the circuit (52) assigned to the measurement port of the contactless measurement system.

21. Calibration substrate according to any of claims 18 to 20, characterized in that at least one of the calibration elements (48) is connected to a number of signal waveguides (26) corresponding to the number of measurement ports of the contactless measurement system.

22. Calibration substrate according to any of claims 18 to 20, characterized in that at least one circuit (52) with at least one of the signal waveguides (26) is arranged on the circuit board (46) of the calibration substrate, and at least one contact structure (44) is arranged on the signal waveguide, such that the arrangement of the contact structure (44) on the signal waveguide (26) of the circuit (52) corresponds to the arrangement of the contact structure (44) on the signal waveguide of the calibration element (48).

23. Calibration substrate according to claim 22, characterized in that at least one contact structure (44) on the signal waveguide (26) of the calibration element (48) assigned to a measurement port of the contactless measurement system is configured to be identical to at least one contact structure (44) on the calibration substrate on the signal waveguide (26) of the circuit (52) assigned to the measurement port of the contactless measurement system.

24. Calibration substrate for a contactless measurement system according to claim 18, characterized in that at least one of the calibration elements (48) is a short circuit standard, an open circuit standard, an impedance standard or a conductor standard.

25. Calibration substrate for a contactless measurement system according to claim 18 characterized in that at least one of the signal waveguides (26) is a microstrip transmission line or a coplanar waveguide.