A method of inspecting a radio frequency device and a radio frequency device

Abstract

A method of inspecting a radio frequency device modifies a radio frequency signal along electroconductive elements by changing dielectric material properties of a tunable dielectric material. The method includes: emitting a light beam through an optically transparent first substrate layer into a test volume of the tunable dielectric material with an inbound light intensity and/or inbound phase; applying a bias field to a test volume via a first transparent test electrode arranged at the first substrate layer and a second test electrode arranged opposite the first test electrode at a second substrate layer; measuring an outgoing light intensity and/or an outgoing phase of the light beam; and determining a property of the tunable dielectric material based on the outgoing light intensity and the incoming light intensity and/or based on a phase relation between the inbound phase and the outgoing phase of the light beam from the bias field.

Claims

1.-18. (canceled)

19. A method of inspecting a radio frequency device (1) having an insulating first substrate layer (2), an insulating second substrate layer (3), a tunable dielectric material (4) arranged between the first substrate layer (2) and the second substrate layer (3), and electroconductive elements (13) for transmitting a radio frequency signal, wherein the electroconductive elements (13) are arranged at or near the first substrate layer (2) and/or the second substrate layer (3), and wherein a transmission of the radio frequency signal along the electroconductive elements (13) can be modified by changing dielectric material properties of the tunable dielectric material (4) next or nearby the electroconductive elements (13), the method including the step of determining at least one characteristic feature of the tunable dielectric material (4) that depends on a bias field applied to the tunable dielectric material (4), wherein the at least one characteristic feature of the tunable dielectric material (4) is determined from an optical measurement of optical material properties of the tunable dielectric material (4) in the following steps: a) emitting a light beam (12) through an optically transparent area section of the first substrate layer (2) into a test volume of the tunable dielectric material (4) with an inbound light intensity and/or with a known inbound phase before passing through the tunable dielectric material (4), b) applying the bias field to the test volume via a first transparent test electrode (6) arranged at the optically transparent area section of the first substrate layer (2) and a second test electrode (8) arranged opposite to the first test electrode at the second substrate layer (3), c) measuring an outgoing light intensity of the light beam (12) and/or measuring an outgoing phase with respect to the inbound phase after passing through the tunable dielectric material (4) in dependency of the bias field, d) determining at least one characteristic property of the tunable dielectric material (4) based on a quotient of the outgoing light intensity and the inbound light intensity and/or based on a phase relation between the inbound phase and the outgoing phase of the light beam (12) from the bias field.

20. The method as in claim 19, wherein in step c) the outgoing light intensity or the phase relation of the outgoing phase with respect to the inbound phase is measured from the light beam (12) that is reflected back through the optically transparent area section of the first substrate (2).

21. The method as in claim 19, wherein the second test electrode (8) is optically transparent and arranged on an optically transparent area section of the second substrate layer (3), and wherein in step c) the outgoing light intensity or the phase relation of the outgoing phase with respect to the inbound phase is measured from the light beam (12) transmitted through the second test electrode (8) arranged on an optically transparent area section of the second substrate layer (3).

22. A radio frequency device (1), comprising: an insulating first substrate layer (2), an insulating second substrate layer (3), a tunable dielectric material (4) arranged between the first substrate layer (2) and the second substrate layer (3), and electroconductive elements (13) that allow for transmission of a radio frequency signal, wherein the electroconductive elements (13) are arranged at or near the first substrate layer (2) and/or the second substrate layer (3), and wherein a transmission of the radio frequency signal along the electroconductive elements (13) can be modified by changing dielectric material properties of the tunable dielectric material next or nearby the electroconductive elements (13), wherein a change in the dielectric material properties effects a change in optical material properties of the tunable dielectric material (4), wherein the radio frequency device (1) further comprises a first optically transparent test electrode (6) arranged on an optically transparent area section of the first substrate layer (2), a second test electrode (8) arranged on the second substrate layer (3) opposite to the first test electrode (6) and overlapping with the first test electrode (6) creating a test capacitor (11) in an overlapping area between the first test electrode (6) and the second test electrode (8), so that a bias field can be applied to the tunable dielectric material (4) within the test capacitor (11) and that a light beam (12) directed through the optical transparent area section of the first substrate layer (2) at the tunable dielectric material (4) within the test capacitor (11) can be used for measuring at least one optical material property of the tunable dielectric material (4) within the test capacitor (11) which allows for determining at least one characteristic property of the tunable dielectric material (4) in dependency of the applied bias field.

23. The radio frequency device (1) according to claim 22, wherein the second test electrode (8) and/or at least an area section of the second substrate layer (3) overlaying with the test capacitor (11) are made of an optically reflective material or are covered by an optically reflective material.

24. The radio frequency device (1) according to claim 22, wherein the second test electrode (8) and at least an area section of the second substrate layer (3) overlaying with the test capacitor (11) are optically transparent.

25. The radio frequency device (1) according to claim 22, wherein the first substrate layer (2) and/or the second substrate layer (3) is optically transparent.

26. The radio frequency device (1) according to claim 22, wherein the first substrate layer (2) and/or the second substrate layer (3) is fabricated from a silicate glass.

27. The radio frequency device (1) according to claim 22, wherein the first test electrode (6) and/or the second test electrode (8) comprises a transparent conducting oxide (10), namely indium tin oxide and/or indium zinc oxide.

28. The radio frequency device (1) according to claim 22, wherein the test capacitor (11) is laterally spaced apart from the electroconductive elements (13).

29. The radio frequency device (1) according to claim 22, wherein the test capacitor (11) is arranged close to an edge section (14) of the radio frequency device (1).

30. The radio frequency device (1) according to claim 22, wherein the test capacitor (11) is laterally arranged adjacent to one of the electroconductive elements (13).

31. The radio frequency device (1) according to claim 22, wherein at least one of the electroconductive elements (13) is a radio frequency phase shifting element.

32. The radio frequency device (1) according to claim 31, further comprising a dedicated test capacitor (11) for each phase shifting element.

33. The radio frequency device (1) according to claim 22, wherein one of the electroconductive elements (13) is a transmission line, wherein one section of the transmission line forms a gap (18), and wherein the first test electrode (6) or the second test electrode (8) is arranged within the gap, so that the radio frequency signal can propagate along the transmission line via the respective test electrode (6, 8).

34. The radio frequency device (1) according to claim 22, wherein at least one of the electroconductive elements (13) is a radiating element.

35. The radio frequency device (1) according to claim 22, wherein the tunable dielectric material (4) is a liquid crystal material (5).

36. The radio frequency device (1) according to claim 27, further comprising a shielding element (20), wherein the shielding element (20) is laterally surrounding at least one of the electroconductive elements (13) of the radio frequency device (1), and wherein the shielding element (20) is comprising the transparent conductive oxide (10).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] FIG. 1 illustrates a schematic top view of a radio frequency device.

[0037] FIG. 2 illustrates a sectional view of the radio frequency device as shown in FIG. 1 along the line II-II.

[0038] FIGS. 3, 4, and 5 illustrate each a top view of an alternative embodiment of the radio frequency device, and FIG. 6 illustrates a sectional view of the radio frequency device as shown in FIG. 5 along the line VI-VI.

DETAILED DESCRIPTION

[0039] FIG. 1 illustrates a top view of a radio frequency device 1 and FIG. 2 illustrates a sectional view of the radio frequency device 1 as shown in FIG. 1. The radio frequency device comprises a first substrate layer 2 and a second substrate layer 3 in between which a tunable dielectric material 4 is arranged. In this exemplary embodiment of the radio frequency device 1, the tunable dielectric material 4 is a liquid crystal material 5 and the two substrate layers 2, 3 are silicate glass layers. A first optically transparent test electrode 6 is arranged at an inner surface 7 of the first substrate layer 2 and a second optically transparent test electrode 8 is arranged at an inner surface 9 of the second substrate layer 3. The two test electrodes 6, 8 are formed from an optically transparent conducting oxide 10. An overlapping area of the two transparent test electrodes 6, 8 forms a test capacitor 11. The test capacitor 11 is optically transparent for a traversing light beam 12.

[0040] The radio frequency device 1 shown in FIG. 1 comprises two electroconductive elements 13. In this exemplary embodiment of the radio frequency device 1, the two electroconductive elements 13 are transmission lines running in parallel between the two substrate layers 2, 3. The test capacitor 11 is arranged at an edge section 14 of the radio frequency device 1. The edge section 14 is free of the electroconductive elements 13 and provides for an empty foot-print that can be used for arranging the test capacitor 11 between the two substrate layers 2, 3.

[0041] The radio frequency device 1 further comprises first bias lines 15 arranged on the inner surface 7 of the first substrate layer 2 and second bias lines 16 arranged on the inner surface 9 of the second substrate layer 3. By imposing a bias voltage to the bias lines 15, 16 via bias contacts 17 a bias field can be applied to the liquid crystal material 5 near the electroconductive elements 13, changing dielectric material properties of the liquid crystal material 5 and thus modifying transport properties of a radio frequency signal propagating along the electroconductive elements 13. One of the first bias lines 15 is electroconductively connected to the first test electrode 6 and one of the second bias lines 16 is in electroconductively connected to the second test electrode 8 of the test capacitor 11. When imposing the bias voltage at the bias contacts 17 the bias field is thus also applied at the test capacitor 11 and the dielectric material properties of the liquid crystal material 5 inside the test capacitor 11 are changed. The optical material properties of the of the liquid crystal material 5 are modified together with its dielectric properties. Thus, the change of the dielectric properties of the tunable dielectric material 4 can be derived from a modification of the optical properties of the liquid crystal material 5 within the test capacitor 11 dependent on the applied bias field.

[0042] FIG. 3 and FIG. 4 illustrate two alternative embodiments of the radio frequency device 1 with each comprising two electroconductive elements 13. In case of the embodiment of the radio frequency device 1 illustrated in FIG. 3 the test capacitor 11 of one of the electroconductive elements 13 is arranged in a gap 18 formed by the respective electroconductive element 13. Thus, the dielectric material properties of the tunable dielectric material 4 near the electroconductive element 13 with the gap 18 can be determined from the optical material properties measured using the test capacitor 11.

[0043] In case of the embodiment of the radio frequency device 1 illustrated in FIG. 4 the radio frequency device 1 comprises the two test capacitors 11 with each of the capacitors 11 being dedicated to the respective electroconductive element 13. The test capacitors 11 are arranged in respective gaps 18 of the electroconductive elements 13. In such a way each of the electroconductive elements 13 can be measured and e.g. calibrated independently.

[0044] An alternative embodiment of the radio frequency device 1 is illustrated in FIG. 5 in a top view and in FIG. 6 in a sectional view. The radio frequency device 1 comprises the two electroconductive elements 13 and the test capacitor 11 arranged in the edge section 14. The two electroconductive elements 13 are formed from a metal with a high electrical conductivity as for instance copper or gold. Each of the electroconductive elements 13 is surrounded by a shielding element 20 formed from the transparent conducting oxide 10. The shielding elements can reduce cross talk between the respective electroconductive elements 13.