Microwave transmission arrangement with encapsulation, communication and/or measurement system and radar level gauge system
A microwave transmission arrangement, comprising a microwave circuit board including a patch; microwave transceiver circuitry coupled to the patch; an electrically conductive hollow waveguide arranged to guide microwave signals between a first end and a second end; and a separator sheet sandwiched between the microwave circuit board and the first end of the hollow waveguide, the separator sheet being configured to allow passage of microwaves between the patch and the hollow waveguide through the separator sheet. The separator sheet is included in an encapsulation separating an encapsulated interior of the microwave transmission arrangement from an exterior outside the encapsulation, the patch, and the microwave transceiver circuitry being in the encapsulated interior, and the hollow waveguide being in the exterior outside the encapsulation.
1 . A microwave transmission arrangement, comprising:
a microwave circuit board including a dielectric carrier, and a first conductor pattern on a first side of the dielectric carrier, the first conductor pattern including a patch for radiating or receiving microwave signals, a patch line, and a first ground plane surrounding the patch and the patch feed line;
microwave transceiver circuitry arranged on the microwave circuit board, the microwave transceiver circuitry having an output for providing microwave signals generated by the microwave transceiver circuitry and an input for receiving microwave signals, wherein the patch line is connected to at least one of the output and the input;
an electrically conductive hollow waveguide extending from a first end to a second end and arranged to guide microwave signals radiated by the patch from the first end towards the second end, and/or guide received microwave signals from the second end towards the first end; and
a separator sheet sandwiched between the microwave circuit board and the first end of the hollow waveguide, the separator sheet being configured to allow passage of microwaves between the patch and the hollow waveguide through the separator sheet,
wherein the separator sheet is included in an encapsulation separating an encapsulated interior of the microwave transmission arrangement from an exterior outside the encapsulation, the patch, the patch line, and the microwave transceiver circuitry being in the encapsulated interior, and the hollow waveguide being in the exterior outside the encapsulation,
wherein the separator sheet is in direct contact with the first side of the microwave circuit board and the first end of the hollow waveguide, so that there is no internal cavity between the first side of the microwave circuit board and the separator sheet.
2 . The microwave transmission arrangement according to claim 1 , wherein the separator sheet comprises a dielectric portion arranged between the patch and an interior of the hollow waveguide, to allow microwave signals to propagate between the patch and the interior of the hollow waveguide, through the dielectric portion of the separator sheet.
3 . The microwave transmission arrangement according to claim 2 , wherein a thickness of the dielectric portion of the separator sheet is at least 0.5 mm.
4 . The microwave transmission arrangement according to claim 1 , wherein the separator sheet comprises:
a dielectric substrate having a first side and a second side opposite the first side;
a first conductive layer on the first side of the substrate;
a second conductive layer on the second side of the substrate; and
a plurality of conductive vias passing through the dielectric substrate and electrically conductively connecting the first conductive layer and the second conductive layer.
5 . The microwave transmission arrangement according to claim 4 , wherein:
the first conductive layer of the separator sheet is electrically conductively connected to the first ground plane of the microwave circuit board; and
the second conductive layer of the separator sheet is electrically conductively connected to the first end of the hollow waveguide.
6 . The microwave transmission arrangement according to claim 4 , wherein:
the first conductive layer of the separator sheet has an open portion; and
the second conductive layer of the separator sheet has an open portion aligned with the open portion of the first conductive layer.
7 . The microwave transmission arrangement according to claim 1 , wherein the microwave circuit board has a second conductor pattern on a second side of the dielectric carrier of the microwave circuit board, opposite the first side, the second conductor pattern including a second ground plane arranged opposite the patch and the first ground plane of the microwave circuit board, wherein the first ground plane and the second ground plane are interconnected by electrically conducting vias extending through the dielectric carrier.
8 . The microwave transmission arrangement according to claim 1 , wherein the microwave transceiver circuitry comprises a monolithic microwave integrated circuit (MMIC) with a bottom face bonded to the microwave circuit board, a top face opposite the bottom face, and edges connecting the bottom face and the top face.
9 . The microwave transmission arrangement according to claim 1 , wherein the encapsulation comprises a potting compound at least partly covering the microwave circuit board.
10 . A communication and/or measurement system comprising:
the microwave transmission arrangement according to claim 1 ; and
processing circuitry coupled to the microwave transceiver circuitry and configured to control the microwave transceiver circuitry to provide microwave signals and/or to perform signal processing on microwave signals received by the microwave transceiver circuitry.
11 . A radar level gauge system for determining the filling level of a product in a tank, comprising:
the microwave transmission arrangement according to claim 1 ;
an antenna coupled to the second end of the hollow waveguide of the microwave transmission arrangement for radiating an electromagnetic transmit signal from the microwave transmission arrangement towards a surface of the product and for returning an electromagnetic reflection signal resulting from reflection of the electromagnetic transmit signal at the surface back towards the microwave transmission arrangement; and
processing circuitry coupled to the microwave transceiver circuitry comprised in the microwave transmission arrangement and configured to determine the filling level based on a timing relation between the transmit signal and the reflection signal.