COAXIAL CABLE AND TEST METHOD FOR A COAXIAL CABLE

Abstract

A coaxial cable comprises at least one internal conductor and a surrounding cable shield. A plurality of sheath wave barriers are arranged along the cable shield, each having two ends that are coupled to the cable shield at coupling points of the cable shield that are spaced from one another. The coaxial cable is exposed to a radio-frequency excitation field with an excitation frequency, due to which sheath waves can be excited on the cable shield. The excitation field is shielded from the at least one internal conductor via the cable shield. The sheath waves can be damped via the sheath wave barriers. A detection circuit is associated with at least one of the sheath wave barriers, from which detection circuit a measurement signal characteristic of a load of the respective sheath wave barrier due to the excitation field can be generated. The measurement signal can be tapped and evaluated.

Description

DESCRIPTION OF THE DRAWINGS

Further advantages and details result from the subsequently specification of exemplary embodiments in connection with the drawings and descriptive text below.

FIG. 1 is a pictorial cross-section through a coaxial cable;

FIG. 2 is a schematic diagram of a magnetic resonance system;

FIGS. 3-5 are schematic illustrations showing possible embodiments of sheath wave barriers;

FIGS. 6-8 are schematic illustrations showing possible embodiments of detection circuits; and

FIGS. 9-11 are flowcharts illustrating a procedure in accordance with an embodiment of the invention.

Claims

1. A coaxial cable assembly, comprising: at least one internal conductor;a cable shield surrounding the at least one internal conductor;a plurality of sheath wave barriers that are arranged along the cable shield, with each sheath wave barrier comprising two ends, the ends being coupled to the cable shield at coupling points of the cable shield that are spaced from one another, such sheath wave barrier structure serving to dampen sheath waves that are excited on the cable shield due to a radio-frequency excitation field with an excitation frequency, the excitation field being shielded from the at least one internal conductor with the cable shield; anda detection circuit associated with at least one of the sheath wave barriers that generates a tappable and evaluable measurement signal characteristic of a load of the respective sheath wave barrier due to the excitation field.

2. The coaxial cable assembly according to claim 1, wherein the detection circuit comprises a rectifier element via which a radio-frequency excitation signal excited in the respective sheath wave barrier by the excitation field is rectified, and in that the measurement signal corresponds to the rectified excitation signal.

3. The coaxial cable assembly according to claim 2, wherein the respective sheath wave barrier comprises a series circuit of two capacitor elements arranged between the ends of the respective sheath wave barrier and the rectifier element is connected in parallel with one of the capacitor elements.

4. The coaxial cable assembly according to claim 3, wherein the capacitor elements are dimensioned such that, together with the cable shield where it is located between the two coupling points, the combination forms a blocking loop resonant at the excitation frequency.

5. The coaxial cable assembly according to claim 3, wherein the capacitor elements have capacitance values that differ from one another.

6. The coaxial cable assembly according to claim 5, wherein the rectifier element is connected in parallel with that of the capacitor elements that exhibits the greater capacitance value.

7. The coaxial cable assembly according to claim 2, further comprising a capacitive storage element for buffering of the measurement signal that is arranged downstream from the rectifier element.

8. A testing method for a coaxial cable assembly that comprises at least one internal conductor and a cable shield surrounding the at least one internal conductor, the method comprising: exposing the coaxial cable to a radio-frequency excitation field with an excitation frequency;shielding the excitation field from the at least one internal conductor with the cable shield;damping sheath waves that are excited on the cable shield due to the radio-frequency excitation field with a plurality of sheath wave barriers that respective exhibit two ends that are coupled to the cable shield at coupling points spaced from one another;generating a measurement signal characteristic of a load of the respective sheath wave barrier due to the excitation field with at least one detection circuit associated with the sheath wave barriers; andtapping and evaluating the measurement signal.

9. The testing method according to claim 8, wherein the generating of the measurement signal comprises rectifying, by the detection circuit, a radio-frequency excitation signal excited in the respective sheath wave barrier by the excitation field.

10. The testing method according to claim 9, further comprising buffering, by the detection circuit, the measurement signal in a capacitive storage element.

11. The testing method according to claim 8, wherein evaluating the measurement signal comprises comparing the measurement signal with a reference signal determined using the excitation field.

12. The testing method according to claim 11, further comprising: detecting a malfunction of a different sheath wave barrier than the sheath wave barrier with which the detection circuit is associated when a quotient of the measurement signal and the reference signal exceeds a threshold value.

13. The testing method according to claim 12, wherein the detection of the malfunction initiates outputting a warning signal that can be directly perceived by a person with his physical senses.

14. The testing method according to claim 12, wherein the detection of the malfunction triggers a blocking signal on a basis of which a start of a measurement sequence of a system in which the method is implemented is blocked.