Horn antenna with a composite emitter for a radar-based level measurement system
View Patent ↗A horn antenna suitable for use with a level measurement device and having a composite emitter structure. The emitter structure or assembly comprises an emitter and a plug. The emitter provides the process interface and is formed from a material having properties which include microwave transparency, chemical resistance and/or mechanical strength. The plug is isolated or partitioned from the process interface. The plug is formed from a material different from the emitter and exhibits the properties of microwave transparency and/or mechanical strength. According to another aspect, the level measurement device includes a coupling mechanism which allows the removal of the horn antenna independently of the emitter.
1. An antenna structure for use in a level measurement device for measuring a level of a material held in a container, comprising:
a horn antenna;
an emitter assembly comprising:
a plug including a port for coupling to a waveguide from the level measurement device, and
an emitter having a surface for interfacing with a corresponding surface on the plug; and
a coupler for coupling the horn antenna to the level measurement device, wherein the coupler further comprises:
a first mechanism for coupling the horn antenna to the level measurement device, and
a second mechanism for coupling the emitter assembly to the level measurement device,
wherein the first mechanism is independently operable of the second mechanism, and the first mechanism couples the horn antenna to the level measurement device indirectly via the second mechanism,
wherein at least a portion of the emitter assembly is arranged in the horn antenna,
wherein the second mechanism comprises a retaining ring having:
a recess for supporting one end of the emitter, and
a plurality of fasteners for securing the retaining ring to the level measurement device,
wherein the emitter includes a tip section and a constant diameter section, the constant diameter section having a diameter corresponding substantially to the diameter of the recess, and
wherein the plug comprises:
a tip section providing a waveguide coupling port, and
a conical section having a surface for interfacing with the emitter.
2. The structure as claimed in claim 1 , wherein the first mechanism comprises a fastener for connecting the horn antenna to the retaining ring.
3. The structure as claimed in claim 1 , wherein the level measurement device includes a mounting collar having an internal chamber having a substantially reciprocal conical recess for receiving the conical section of the plug.
4. The structure as claimed in claim 1 , wherein the emitter is formed from a material having a property selected from the group consisting of microwave transparency, chemical resistance, mechanical strength, and combinations thereof.
5. The structure as claimed in claim 4 , wherein the material for the emitter comprises a chemically inert polymeric material.
6. The antenna as claimed in claim 5 , wherein the plug is formed from a material having a property selected from the group consisting of mechanical strength, microwave transparency, and combinations thereof.
7. The structure as claimed in claim 6 , wherein the material for the plug is selected from the group consisting of polymers, ceramics and glass.
8. The structure as claimed in claim 1 , wherein the coupler further comprises a barrier member positioned in an annular recessed groove that encompasses an interfacing surface of the plug, said barrier member forming an environmental barrier between an outside environment and the plug.
9. The structure as claimed in claim 8 , wherein the barrier member comprising an O-ring formed from a material selected from the group consisting of PTFE, FKM, and FFKM.
10. A level measurement apparatus for determining a distance for material contained in a vessel, the level measurement apparatus comprising:
a housing;
an antenna;
a coupler for coupling the antenna to the housing, the coupler comprising:
a first mechanism for coupling the antenna to the housing, and
a second mechanism for coupling the emitter assembly to the housing,
wherein the first mechanism is independently operable of the second mechanism, and the first mechanism couples a horn antenna to the level measurement device indirectly via the second mechanism;
a controller having a receiver module and a transmitter module, the controller having a bidirectional port for coupling to a waveguide; and
an emitter assembly comprising:
a plug including a port for coupling to the waveguide to the controller, and
an emitter having a surface for interfacing with a corresponding surface on the plug,
wherein at least a portion of the emitter assembly is positioned in the antenna,
wherein the second mechanism comprises a retaining ring, the retaining ring having:
a recess for supporting one end of the emitter, and
a plurality of fasteners for securing the retaining ring,
wherein the emitter comprises:
a tip section, and
a constant diameter section having a diameter corresponding substantially to the diameter of the recess,
wherein the plug comprises:
a tip section providing a waveguide coupling port, and
a conical section having a surface for interfacing with the emitter.
11. The apparatus as claimed in claim 10 ,
wherein the emitter is formed from a first material having a chemical resistance; and
wherein the plug is formed from a second material having a mechanical strength.
12. The apparatus as claimed in claim 10 , further comprises:
a mounting collar including an internal chamber having a substantially reciprocal conical recess for receiving the conical section of the plug.
13. The structure as claimed in claim 10 , wherein the coupler further comprises a barrier member positioned in an annular recessed groove that encompasses an interfacing surface of the plug, said barrier member forming an environmental barrier between an outside environment and the plug.