Device, system and method for rodless guided microwave radiation
A rodless guide microwave radiation device, system, and method is disclosed for measuring at least one characteristic of a liquid in a vessel. A hollow metal waveguide conveys microwave radiation and is adapted to be disposed in a vessel for containing a liquid, the waveguide having a first end and a second end. A single chip radar sensor mounted on a PCB is disposed proximal to the first end of the hollow waveguide. The radar sensor is configured to transmit millimeter wavelength signals into the first end of the hollow waveguide for propagating down the waveguide toward the second end, and receive a return echo from the signal based upon a change in impedance upon encountering the liquid and propagating in the reverse direction of the waveguide, the single chip radar sensor including electronic circuitry for determining at least one characteristic of the liquid located in the waveguide based on detection of an impedance change according to time domain reflectometry. A mount assembly is configured to position the single chip radar sensor mounted on the printed circuit board over the first end of the hollow waveguide for transmitting and receiving the microwave radiation via the hollow waveguide; and a barrier structure sealingly protects the single chip radar mounted on said printed circuit board from exposure to contaminants within the hollow waveguide, while permitting microwave propagation between the single chip radar and the liquid through the hollow waveguide. In embodiments, the waveguide may be rigid, bent, curved, or flexible, and the radar and PCB may be outside or within the waveguide.
1 . A guided wave radar sensor gauge for measuring at least one characteristic of a liquid in a vessel, comprising:
a hollow waveguide for conveying microwave radiation, the hollow waveguide adapted to be disposed in a vessel for containing a liquid, the hollow waveguide having a first end and a second end;
a single chip radar sensor mounted on a printed circuit board and disposed proximal to the first end of said hollow waveguide, said single chip radar sensor configured to transmit a millimeter wavelength signal into the first end of said hollow waveguide for propagating down the waveguide toward the second end, and to receive at least a return echo from said signal based upon a change in impedance upon encountering said liquid and propagating in the reverse direction of the waveguide, said single chip radar sensor including electronic circuitry for determining at least one characteristic of the liquid located in the waveguide based on detection of an impedance change according to time domain reflectometry;
wherein a mount assembly is configured to position the single chip radar sensor mounted on the printed circuit board over the first end of the hollow waveguide for transmitting and receiving the microwave radiation via the hollow waveguide; and
wherein a barrier structure comprises a dielectric window sealed into the hollow waveguide at the first end, the dielectric window sealingly protecting the single chip radar sensor mounted on said printed circuit board from exposure to contaminants within the hollow waveguide, while separating the single chip radar sensor from the interior of the hollow waveguide and permitting microwave propagation between the single chip radar sensor and the hollow waveguide.
2 . The guided wave radar sensor gauge of claim 1 , wherein the dielectric window is a sapphire or quartz crystal fixed into the hollow waveguide by fusion.
3 . The guided wave radar sensor gauge of claim 1 , wherein the barrier structure is a glass window fixed into the hollow waveguide by fusion or O-rings.
4 . The guided wave radar sensor gauge of claim 3 , wherein the barrier structure is a glass window fused into the hollow waveguide.
5 . The guided wave radar sensor gauge of claim 1 , wherein the barrier structure further comprises a dielectric covering disposed over the single chip radar sensor mounted on said printed circuit board to provide additional protection of the single chip radar sensor and the printed circuit board from environmental contaminants.
6 . The guided wave radar sensor gauge of claim 5 , wherein the dielectric covering comprises a polymer that sealingly covers the single chip radar sensor and at least a portion of the printed circuit board.
7 . The guided wave radar sensor gauge of claim 1 , wherein at least a portion of the mount assembly, the barrier structure, and single chip radar sensor mounted on the printed circuit board form a removable head for removably connecting to the first end of the hollow waveguide.
8 . The guided wave radar sensor gauge of claim 1 , wherein the single chip radar sensor mounted on the printed circuit board, and at least a portion of the mount assembly, are disposed within the hollow waveguide.
9 . The guided wave radar sensor gauge of claim 1 , further comprising a spacer formed of a material adapted to slow the propagation of the microwave radiation therethrough, the spacer material disposed between the single chip radar sensor and the first end of the hollow waveguide for reducing the blanking time of the single chip radar sensor receiver.
10 . The guided wave radar sensor gauge of claim 9 , wherein the spacer material is formed of material having a high dielectric constant and a low loss tangent.
11 . The guided wave radar sensor gauge of claim 1 , further comprising a dielectric lens disposed within the waveguide and proximal to the radar sensor for controlling mode propagation by collimating multi-mode propagation signals to reduce propagation speed differentials and echo fragmentation.
12 . The guided wave radar sensor gauge of claim 11 , wherein the dielectric lens disposed within the waveguide comprises one of a cone pointing toward the liquid, a rod ending in a cone pointing at the liquid, a continuous surface focusing lens, or a Fresnel lens.
13 . The guided wave radar sensor gauge of claim 1 , wherein the second end of the hollow waveguide has at least one opening for receiving the liquid in the vessel.
14 . The guided wave radar sensor gauge of claim 1 , wherein the second end of the hollow waveguide has a structural electromagnetic barrier for sealing the bottom of the waveguide from propagating radiation out from said bottom of the waveguide.
15 . The guided wave radar sensor gauge of claim 1 , wherein the structural electromagnetic barrier at the second end of the hollow waveguide comprises a metal mesh.
16 . The guided wave radar sensor gauge of claim 1 , wherein the hollow waveguide is a metal tube.
17 . The guided wave radar sensor gauge of claim 1 , wherein the hollow waveguide is a curved metal tube.
18 . The guided wave radar sensor gauge of claim 1 , wherein the hollow waveguide is a flexible tube.
19 . The guided wave radar sensor gauge of claim 1 , wherein the flexible tube is a conductive polymer material.
20 . The guided wave radar sensor gauge of claim 19 , wherein the flexible tube is one of: a carbon or metal filled polymer, or a polymer treated with a metal coating on its inner diameter or outer diameter.
21 . The guided wave radar sensor gauge of claim 20 , wherein the metal coating is sputtered aluminum on Mylar.
22 . The guided wave radar sensor gauge of claim 2 , wherein the dielectric window is a sapphire crystal fixed into the hollow waveguide.
23 . The guided wave radar sensor gauge of claim 1 , wherein the single chip radar sensor and printed circuit board are encapsulated in an encapsulant material forming an integrated subassembly, the encapsulant material formed about the surface of the single chip radar sensor facing the hollow waveguide to form a lens for focusing the electromagnetic radiation to and from the single chip radar sensor.
24 . The guided wave radar sensor gauge of claim 23 , wherein the encapsulant material comprises a molded polymer material.
25 . The guided wave radar sensor gauge of claim 23 , wherein the encapsulant material comprises an epoxy.
26 . The guided wave radar sensor gauge of claim 23 , wherein the encapsulant material comprises an acrylate resin.