Wave transmission lines and networks – Long line elements and components – Connectors and interconnections
Reexamination Certificate
2002-01-23
2004-08-17
Pascal, Robert (Department: 2817)
Wave transmission lines and networks
Long line elements and components
Connectors and interconnections
C439S578000
Reexamination Certificate
active
06778044
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a coaxial line plug-in connection with a galvanic separation integrated therein. Such plug-in connections may, for example, be used in the area of the filling level measuring technology. For transmitting the HF module-generated microwave signals required for the filling level measurement to a transmitting and receiving unit such as a rod, horn or microstrip antenna, and for transmitting the reflected signals that are representative of the filling level height to be measured, back to an evaluation device, coaxial lines may be used.
Filling level measurements of that kind are necessary in almost all industrial branches. The filling products to be determined according to the filling level consist, e.g. in the chemical industry, of highly explosive materials. So as to prevent an explosion risk during the filling level measurement from arising in the inner space or the surroundings of a receptacle or a tank, lines to which different potentials are possibly applied, may be galvanically isolated. Alternatively hereto, it is also may be possible to provide a separate potential equalizing line. With the galvanic separation, two electric circuits may be completely separated from each other, no direct connection existing via a conducting material. The transmission of current or, in the present case of HF signals, usually ensues in the inductive way.
BACKGROUND INFORMATION
A coaxial HF plug-in connection is, for example, described in the document U.S. Pat. No. 3,936,116. In this plug-in connection, a signal transmission within the connector is improved by means of specific galvanic contact surfaces. A galvanic separation which is necessary for the required explosion-proof separation in the filling level measurement, however, is not realized. Such a galvanic plug-in connection may also be used in the area of the filling level measurement technology, an explosion-proof separation, however, has to be realized in another location, e.g. in the HF module. Thereby, a further interference-causing spot is present on the signal path from the HF module to the transmitting and receiving unit, whereby measurement results are possibly distorted.
A first kind of the galvanic separation of track conductors guiding HF signals on a circuit board, may be realized by capacitors, such as it is, for example, described in the document EP 0 882 955 A1. The galvanic separation ensues in this case by a microwave track conductor arranged as a coplanar track conductor, the galvanic separation being effected by means of capacitors on the circuit board. The coplanar circuit board guiding HF signals is comprised of three planar track conductor structures applied onto the circuit board running in parallel and being arranged in parallel with respect to each other, the middle track conductor serving as the signal track conductor, and the two lateral track conductors serving as screening track conductor. In both the signal track conductor and the screening track conductor, a capacitor is in each case inserted, whereby the galvanic separation is realized.
A further kind of separation may consists in the coupling by a dielectric material. Thus, it is also described, for example, in the document EP 0 882 955 A1 to couple the screening track conductor through the circuit board within the HF module. Here, as well, the track conductor guiding the HF signal is comprised of two parts, a signal track conductor and a screening track conductor.
As a further possibility, it is proposed in EP 0 882 955 A1 to couple both the screening and the signal track conductor by means of a dielectric material. The track conductors hereby are present within the HF module on both sides of a circuit board and exhibit a certain coupling zone.
It is believed that all of these described exemplary embodiments have in common that both the screening and the signal track conductor or fixedly applied onto a circuit board within the HF module. It is true that a retrofit of such a galvanic separation may be considered, but this will turn out as being extremely difficult due to the position within the HF module. Moreover, it may be regarded as being extremely problematic that by such a retrofit, an additional interference-causing spot arises on the signal path from the HF module to the transmitting and receiving unit.
SUMMARY OF THE INVENTION
An object of the an exemplary embodiment of the present invention is based on the problem of assuring the explosion-proof separation required for the explosion protection in the filling level measurement technology with a number as low as possible of interference-causing spots on the signal path between the HF module and the transmitting and receiving unit. The invention is inter alia directed to providing a plug-in connection which may be suitable for keeping the mounting effort at a possible minimum during an exchange of the electronic unit.
It is believed that this object is solved by a completely novel plug-in connection according to an exemplary embodiment of the present invention comprising, according to a first aspect of the invention, a plug and a socket. The plug, as well as the socket, are connected with a coaxial line. The coaxial line itself comprises an inner conductor serving as the signal line, as well as an outer conductor which may serve as a screening line. Both the socket and the plug possess an outer conductor on their part, which is in each case connected with the outer conductor of the coaxial line. The plug may be inserted into the socket in such a manner that the outer conductor of the plug overlaps over a determined length with the outer conductor of the socket, which length being referred to as coupling zone. The coupling between the outer conductors of the socket and the plug ensues at low frequencies (e.g. such as between 5 and 10 GHz) in a capacitive manner between the two overlapping outer conductors (coupling zone), which may be mutually insulated by a separating element of a dielectric material (preferably PTFE). For higher frequencies, e.g. between 24 and 28 GHz, this coupling zone may have a length of &lgr;/4 with a wavelength &lgr; to be transmitted. Through this length adaptation, the no-load operation resulting at the end of the overlapping zone, transforms into a short-circuit at the discontinuity in the coaxial system.
It is believed that the coupling between the outer conductor of the socket and the plug ensues, as has already been mentioned, at low frequencies in a capacitive manner by a separating element made of a dielectric material, which is disposed between the outer conductor of the socket and the plug. The insulation thickness of the separating element between the two outer conductors and the coupling zone may be 0.5 mm. It is believed that by means of this prescribed minimum thickness, the necessary potential separation is fulfilled, which is required for explosion-proof areas, and which has to feature a voltage stability of 500 Volt.
According to another aspect of an exemplary embodiment of the invention, the plug part is configured still more simple as compared to the above embodiment. The socket construction hereby is identical to the socket of the first embodiment, the inner socket dimensions are, however, adapted to the smaller dimensions of the plug In this exemplary embodiment, a thicker so-called semi-rigid cable (e.g. UT141) may be used as the coaxial line. By using such a semi-rigid cable, the mounting effort during the fabrication of the plug is considerably reduced, since in contrast to the other embodiment, no separate plug component is required. On the contrary, the plug hereby may be comprised of an end of a stripped semi-rigid cable. The plug in the form of a stripped semi-rigid cable is thereby directly inserted into the socket.
As also in the above embodiment, a capacitive coupling between the two outer conductors serving as screening conductors for the cables may result in the lower frequency range. In the range of higher frequencies, a transformation of the no-load operation into a short-circuit is
Fehrenbach Josef
Motzer Jürgen
Schultheiss Daniel
Fay Kaplun & Marcin LLP
Pascal Robert
Takaoka Dean
Vega Grieshaber KG
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