# US 7,608,778 B2 · Coaxial test cable assembly > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,608,778 B2 - Document ID: US7608778B2 - Status: Granted - Kind: B2 - Application number: 11/679,241 - Filed: 2007-02-27 - Published: 2007-08-30 - Granted: 2009-10-27 - Earliest claimed: 2006-02-27 - Assignees: Siemens Aktiengesellschaft - Inventors: Arne Reykowski - Web page: https://patentgrep.com/patent/US7608778B2 ## CPC - G01R 33/36: Electrical details, e.g. matching or coupling of the coil to the receiver - G01R 33/3685: {Means for reducing sheath currents, e.g. RF traps, baluns} - G01R 33/288: {Provisions within MR facilities for enhancing safety during MR, e.g. reduction of the specific absorption rate [SAR], detection of ferromagnetic objects in the scanner room} - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) ## 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. ## Claims ### Claim 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 magnetic resonance excitation field with an excitation frequency, the excitation field being shielded from the at least one internal conductor with the cable shield; a detection circuit having an output signal line associated with at least one of the sheath wave barriers, said detection circuit generating tapped and evaluable measurement signal on the output signal line characteristic of a load of the respective sheath wave barrier due to the excitation field; and 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, the measurement signal corresponds to the rectified excitation signal, the measurement signal being used by an evaluator to detect a malfunction of at least one of the sheath wave barriers. ### Claim 2 (depends on 1) The coaxial cable assembly according to claim 1, 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. ### Claim 3 (depends on 2) The coaxial cable assembly according to claim 2, 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. ### Claim 4 (depends on 2) The coaxial cable assembly according to claim 2, wherein the capacitor elements have capacitance values that differ from one another. ### Claim 5 (depends on 4) The coaxial cable assembly according to claim 4, wherein the rectifier element is connected in parallel with that of the capacitor elements that exhibits the greater capacitance value. ### Claim 6 (depends on 1) The coaxial cable assembly according to claim 1, further comprising a capacitive storage element for buffering of the measurement signal that is arranged downstream from the rectifier element. ### Claim 7 (depends on 1) The coaxial cable assembly according to claim 1, wherein the coaxial cable is exposed to a radio-frequency excitation field with an excitation frequency, the excitation field is shielded from the at least one internal conductor with the cable shield, sheath waves that are excited on the cable shield due to the radio-frequency excitation field are dampened 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, further comprising: an evaluator for tapping and evaluating the measurement signal. ### Claim 8 (depends on 1) The coaxial cable assembly according to claim 1, further comprising: the detection circuit comprising a capacitive storage element for buffering the measurement signal. ### Claim 9 (depends on 1) The coaxial cable assembly according to claim 1, further comprising: said evaluator evaluating the measurement signal by comparing the measurement signal with a threshold. ### Claim 10 (depends on 9) The coaxial cable assembly according to claim 9, further comprising: said evaluator comprising a malfunction detector for 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. ### Claim 11 (depends on 10) The coaxial cable assembly according to claim 10, further comprising: an output at which the malfunction detector initiates outputting a warning signal that can be directly perceived by a person with his physical senses. ### Claim 12 (depends on 10) The coaxial cable assembly according to claim 10, further comprising: said malfunction detector generating a blocking signal that is triggered by the detection of the malfunction on a basis of which a start of a measurement sequence of a system in which the method is implemented is blocked.