DUMMY LOAD FOR HIGH POWER AND HIGH BANDWIDTH

Abstract

A dummy load for high power and high bandwidth, the dummy load comprising a base plate, a resistive termination acting as a resistive load for dissipating radio frequency power at low frequencies, and at least one coaxial cable acting as a cable load for dissipating radio frequency power at high frequencies, the at least one coaxial cable being connected to the resistive termination. At least one of the resistive termination and the at least one coaxial cable is positioned on the base plate. The at least one coaxial cable has a cross section that varies over the length of the coaxial cable.

Claims

1. A dummy load for high power and high bandwidth, said dummy load comprising: a base plate, a resistive termination acting as a resistive load for dissipating radio frequency power at low frequencies, and at least one coaxial cable acting as a cable load for dissipating radio frequency power at high frequencies, said at least one coaxial cable being connected to said resistive termination, at least one of said resistive termination and said at least one coaxial cable being positioned on said base plate, and said at least one coaxial cable having a cross section that varies over the length of said coaxial cable.

2. The dummy load according to claim 1, wherein said cross section varies in a stepwise manner.

3. The dummy load according to claim 1, wherein said at least one coaxial cable is arranged in a helical manner, said cross section decreasing inwardly over the length of said at least one coaxial cable.

4. The dummy load according to claim 1, wherein at least one of a cut out for said resistive termination and a groove for said at least one coaxial cable is provided in said base plate.

5. The dummy load according to claim 4, wherein said cut out for said resistive termination is located in a middle area of said base plate.

6. The dummy load according to claim 4, wherein said groove for said at least one coaxial cable is helically arranged on at least one side of said base plate.

7. The dummy load according to claim 6, wherein said groove runs around said resistive termination at least once.

8. The dummy load according to claim 4 wherein said groove for said at least one coaxial cable is provided on opposite sides of said base plate such that said at least one coaxial cable is arranged on both sides of said base plate.

9. The dummy load according to claim 4, wherein said groove for said at least one coaxial cable has curvatures, said groove being widened in the curvatures such that said groove has an expansion space for said at least one coaxial cable in the curvatures.

10. The dummy load according to claim 4, wherein a thermal conductive member is provided in said groove, said thermal conductive member interacting with said at least one coaxial cable and said base plate.

11. The dummy load according to claim 4, wherein at least one of said groove for said at least one coaxial cable and said cut out for said resistive termination is milled in said base plate.

12. The dummy load according to claim 1, wherein a thermally conductive pad for heat dissipation is provided, said pad being positioned on said at least one coaxial cable such that said at least one coaxial cable is at least partially covered by said pad.

13. The dummy load according to claim 1, wherein at least one cover for heat dissipation is provided, said at least one cover being connected to said base plate such that at least one of said resistive termination and said at least one coaxial cable being accommodated between said base plate and said at least one cover.

14. The dummy load according to claim 12, wherein said at least one cover presses said pad onto said at least one coaxial cable, said pad being positioned between said at least one coaxial cable and said at least one cover.

15. The dummy load according to claim 13, wherein said at least one cover presses said at least one coaxial cable onto said base plate.

16. The dummy load according to claim 13, wherein said at least one cover has cooling fins at a side facing away from said base plate.

17. The dummy load according to claim 1, wherein each side of said base plate has a groove for said at least one coaxial cable, said coaxial cable being positioned in both grooves, two covers being provided that are assigned to both sides of said base plate such that both grooves are covered.

18. The dummy load according to claim 1, wherein a connection unit for a connecting cable is provided, said connection unit being provided at the end of said coaxial cable that is opposite to the end being connected to said resistive termination.

19. The dummy load according to claim 1, wherein said base plate has a rectangular shape.

20. A dummy load for high power and high bandwidth, said dummy load comprising: a base plate, a resistive termination acting as a resistive load for dissipating radio frequency power at low frequencies, at least one coaxial cable acting as a cable load for dissipating radio frequency power at high frequencies, said at least one coaxial cable being connected to said resistive termination, said at least one coaxial cable being arranged in a helical manner within a groove formed in said base plate, and at least one cover being connected to said base plate such that said resistive termination and said at least one coaxial cable being accommodated between said cover and said base plate.

Description

DESCRIPTION OF THE DRAWINGS

[0043] 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:

[0044] FIG. 1 shows a perspective view of a dummy load according to an embodiment of the present disclosure;

[0045] FIG. 2 shows a schematic cross section through a dummy load according to an embodiment of the present disclosure;

[0046] FIG. 3 shows a perspective view on a base plate used by a dummy load according to an embodiment of the present disclosure;

[0047] FIG. 4 schematically shows a detail of FIG. 2;

[0048] FIG. 5 schematically shows a detail of FIG. 3;

[0049] FIG. 6 shows a diagram illustrating the return loss of different dummy loads; and

[0050] FIG. 7 shows a diagram illustrating the relative power over the frequency reaching the resistive termination of the dummy load according to an embodiment of the present disclosure.

DETAILED DESCRIPTION

[0051] 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.

[0052] In FIG. 1, a dummy load 10 for high power and high bandwidth is shown. In the shown embodiment, the dummy load 10 comprises a base plate 12 made of aluminum with a first side 14 being opposite to a second side 16 as well as two covers 18, 20 that are assigned to both sides 14, 16 of the base plate 12. The dummy load 10 also has carrying grips that simplifies transport of the dummy load 10.

[0053] The dummy load 10 further has a connection unit 22 for a connecting cable (not shown), in particular a radio frequency connecting cable, via which radio frequency signals are inputted to the dummy load 10 for being dissipated appropriately. The connection unit 22 is established by a terminal as shown in FIG. 1.

[0054] Furthermore, it is shown that the covers 18, 20 each comprise cooling fins 24 at a side that faces away from the base plate 12, namely the first side 14 and the second side 16. The cooling fins 24 are used for dissipating the heat that occurs within the dummy load 10 as will be described later.

[0055] In FIG. 2, a cross sectional view of a dummy load 10 according to another embodiment is shown wherein the dummy load 10 comprises a base plate 12 as well as one cover 18 which is assigned to the first side 14 of the base plate 12. In contrast to the first embodiment shown in FIG. 1, the dummy load 10 of FIG. 2 comprises only a single cover 18 whereas the second side 16 of the base plate 12 is covered with cooling fins 24. Accordingly, the base plate 12 itself comprises cooling fins 24 that are arranged at the second side 16, namely the side that faces away from the single cover 18. The cooling fins 24 of the base plate 12 and the cover 18 are only partially shown for illustrative purposes.

[0056] As also shown in FIG. 2, the cover 18 is connected to the base plate 12 via connecting members 26, for instance screws, such that the cover 18 is pressed onto the first side 14 of the base plate 12.

[0057] On this first side 14 of the base plate 12, a groove 28 as well as a cut out 30 are established. The groove 28 as well as the cut out 30 may be milled within the first side 14 of the base plate 12 in order to provide space for a combined load 32 of the dummy load 10. In some embodiments, the combined load 32 comprises at least one coaxial cable 34 being positioned within the groove 28 as well as a resistive termination 36 that is located in the cut out 30. The at least one coaxial cable 34 comprises two conductors wherein the outer conductor can be established by a metal, for instance tinned outer fabric.

[0058] The arrangement of the load unit 32, in particular the coaxial cable 34 as well as the resistive termination 36, become more readily appreciated by FIG. 3 illustrating a perspective view on the base plate 12, in particular the first side 14 of the base plate 12, without the cover 18. As shown in FIG. 3, the coaxial cable 34 is arranged in a helical manner on the first side 14 of the base plate 12 wherein a first end 38 of the coaxial cable 34 is connected with the connection unit 22 for receiving radio frequency signals inputted via the connecting cable. The opposite end 40 of the coaxial cable 34 is directly connected to the resistive termination 36 that is located in a middle area 42 of the base plate 12 for establishing the combined load 32.

[0059] The coaxial cable 34 that is arranged in a helical or rather spiral manner on the base plate 12, in particular within the groove 28, that is also provided within the first side 14 of the base plate 12 in a corresponding manner, namely in a spiral or rather helical manner.

[0060] The coaxial cable 34 has a cross section that varies over the length of the coaxial cable 34. In the shown embodiment, the at least one coaxial cable 34 has two different cross sections such that two coaxial cable sections 44, 46 are provided. Both coaxial cable sections 44, 46 are connected with each other via a transition member 48 that interconnects both coaxial cable sections 44, 46. Therefore, the coaxial cable 34 varies its cross section in stepwise manner.

[0061] Generally, the coaxial cable sections 44, 46 may be provided by a single coaxial cable with an integrated transition member 48.

[0062] The first coaxial cable section 44 with the high cross section is provided in the outer area of the base plate 12 such that it circumferences the second coaxial cable section 46 with the lower cross section. Accordingly, the bending radii of the whole coaxial cable 34 are as high as possible ensuring good transmission properties.

[0063] In general, this arrangement of the coaxial cable 34 ensures a compact dummy load 10 wherein the power loss provided by the coaxial cable 34 is distributed over its entire length. The first coaxial cable section 44 with the high cross section has a lower attenuation compared to the second coaxial cable section 46 such that the power dissipated by the coaxial cable 34 is dissipated over the total length of the coaxial cable 34 in a homogenous manner.

[0064] As already mentioned before, the coaxial cable 34 is located in a groove 28 that is milled within the first side 14 of the base plate 12. The coaxial cable 34 is pressed within this groove 28 such that the coaxial cable 34 has at least three contact points in a cross sectional view as shown in FIG. 4. The coaxial cable 34 contacts the walls of the groove 28 at its opposite sides as well as in its lower area such that three contact points 50 to 54 are provided which are highlighted in FIG. 4.

[0065] During operation of the dummy load 10, radio frequency power dissipated by the coaxial cable 34 may heat the coaxial cable 34 which in turn results in a thermal expansion of the coaxial cable 34. Thus, the thermal contact of the coaxial cable 34 via the contact points 50 to 54 is improved during operation, in particular at high powers, as the coaxial cable 34 thermally expends such that it is pressed against the sides of the groove 28. Therefore, the heat can be dissipated via the base plate 12 more efficiently.

[0066] For further improving the heat dissipation, a thermally conductive member 56 may be integrated in the groove 28 which contacts at least the areas between the contact points 50 to 54 in order to ensure that the heat occurring in these areas are also guided to the base plate 12 for heat dissipation.

[0067] Moreover, a thermally conductive pad 58 is provided that is located between the cover 18 and the coaxial cable 34 as shown in FIG. 4. The thermally conductive pad 58 is pressed onto the coaxial cable 34 when the cover 18 is fixed to the base plate 12 such that the outer area of the coaxial cable 34 with regard to the groove 28 is brought in contact with the thermally conductive pad 58 which in turn is pressed against the cover 18. The outer area of the coaxial cable 34 corresponds to the portion of the coaxial cable 34 that protrudes the groove 28. The thermally conductive pad 58 encircles this portion of the coaxial cable 34 appropriately such that the coaxial cable 34 is contacted on all sides ensuring a good thermal contact of the coaxial cable 34.

[0068] Accordingly, the coaxial cable 34 is thermally connected to the base plate 12 (via the thermally conductive member 56) and to the cover 18 (via the thermally conductive pad 58).

[0069] In FIG. 5, it is shown that the groove 28 milled in the base plate 12 comprises curvatures 60 for the bending sections of the coaxial cable 34 being arranged in a helical manner in the groove 28. These curvatures 60 are widened in order to provide expansion space 62 in the curvatures 60 for the coaxial cable 34. Thus, the coaxial cable 34 may thermally expand in the area of the curvatures 60, namely in its bending sections. The expansion spaces 62 provide enough space for the thermal expansion of the coaxial cable 34.

[0070] The embodiment shown in FIG. 1 which comprises two covers 18, 20 may have a groove 28 which is established on both sides 14, 16 of the base plate 12 such that the dummy load 10 may comprise a coaxial cable 34 being arranged on both sides 14, 16 of the base plate 12. Thus, a coaxial cable 34 can be used having a length exceeding the area of the base plate 12 on one side.

[0071] Accordingly, a very compact dummy load 10 may be provided wherein the coaxial cable 34 is helically arranged on both sides 14, 16 of the base plate 12 in a substantially similar manner as shown in FIG. 3.

[0072] Generally, the whole dummy load 10 is established in a sandwich manner as the opposite outer sides of the dummy load 10 comprise the cooling fins 24 which may be arranged on two covers 18, 20 or on one cover 18 and the base plate 12. However, good heat dissipation properties are ensured. The bodies of the cover(s) 18, 20 and the base plate 12 may also have channels for conducting water or any other suitable fluid used for cooling purposes.

[0073] In general, the combined load unit 32 having the resistive termination 36 as well as the coaxial cable 34 ensures that the resistive termination 36 acts as a resistive load for a dissipating radio frequency power at low frequencies whereas the coaxial cable 34 acts as a cable load for a dissipating radio frequency power at high frequencies. Accordingly, the combined load unit 32 is configured to dissipate radio frequency power over a broad bandwidth.

[0074] This is also illustrated in FIG. 6 showing the return loss of a cable load, a resistive load and a combined load unit 32 as used by the dummy load 10 according to the embodiments of the present disclosure.

[0075] Moreover, the arrangement of the combined load unit 32 according to the present disclosure ensures that the cable attenuation of the coaxial cable 34 is used in an optimized manner as the power reaching the resistive termination 36 for signals with high frequencies is reduced due to the cable attenuation of the coaxial cable 34, which increases with higher frequency.

[0076] This is also shown in FIG. 7. The relative power reaching the resistive termination 36 is reduced significantly for higher frequencies due to the cable attenuation increasing with frequency.

[0077] Therefore, a dummy load 10 is provided that can be used for high power and high bandwidth applications.

[0078] Furthermore, the dummy load 10 can be used in Electromagnetic Compatible Chambers (EMC chambers) as substantially the whole power is absorbed in the coaxial cable 34 for signals with high frequency wherein the coaxial cable 34 is hermetically sealed. For lower frequencies, the power reaches the resistive termination 36 wherein a higher shielding attenuation is provided due to the higher wavelengths at lower frequencies. Thus, the irradiation of the dummy load 10 is small such that the dummy load 10 can be used for EMC applications.

[0079] Generally, the dummy load 10 compensates the matching properties of the resistive termination 36 which gets worse with increasing frequency by the frequency dependent cable attenuation of the coaxial cable 34.

[0080] For low frequencies of the radio frequency signals, the power of the radio frequency signals inputted to the dummy load 10 is substantially completely forwarded to the resistive termination 36 due to the small cable attenuation of the coaxial cable 34. Thus, the input matching of the dummy load 10 is mainly specified by the resistive termination 36.

[0081] For high frequencies, the cable attenuation of the coaxial cable 34 increases such that the power reaching the resistive termination 36 is attenuated effectively. Thus, the matching of the dummy load 10 is mainly specified by the cable attenuation of the coaxial cable 34.

[0082] Various 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 claimed subject matter.