FIELD OF THE INVENTION

Disclosed embodiments are generally related to a radar level gauge for measuring a level of a surface of a material in a container, and, more particularly, to a radar level gauge with a self- aligning dielectric barrier for providing galvanic isolation between certain components of the radar level gauge.

BACKGROUND OF THE INVENTION

For various reasons, the electrical ground associated with a radar circuitry (e.g., an internal ground) of a radar level gauge should be isolated from the container installation, which may be electrically connected to an external ground, such as an earth ground. This can, for example, lead to a reduction of noise effects in the measuring signals, and can further lead to a reduction in the susceptibility to interference with the measuring signals. Furthermore, such isolation leads to improved safety, for example, in relation to the avoidance of undesirable spark discharges. See US patent 7,821,445 for one example of a radar level gauge.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in the following description in view of the drawings that show:

FIG. 1 shows a non-limiting embodiment of a waveguide arrangement for connecting a radar circuitry to an antenna in a radar level gauge. This arrangement can benefit from disclosed embodiments of a self-aligning dielectric barrier for providing galvanic isolation.

FIG. 2 shows a cut-away, fragmentary setup of a waveguide assembly in the radar level gauge including one non-limiting embodiment of a self-aligning dielectric barrier, as may be assembled into the waveguide assembly.

FIG. 3 illustrates zoomed-in details of the self-aligning dielectric barrier shown in FIG. 2, such as prior to being fully assembled (e.g., fully inserted) into the waveguide assembly of the radar level gauge.

FIG. 4 and 5 show respective isometrics of further non-limiting embodiments of disclosed self-aligning dielectric barriers. FIG. 6 is a half-section isometric of a non-limiting model representation of one disclosed self-aligning dielectric barrier and waveguide assembly.

FIG. 7 is a plot of respective non-limiting curves indicative of transmission loss, and return loss over one non-limiting frequency band based on the non-limiting model of the dielectric barrier shown in FIG. 6.

DETAILED DESCRIPTION OF THE INVENTION

The present inventors have recognized certain drawbacks in at least some electrically isolating devices, as may be used in radar level gauges for measuring the level (e.g., height) of a surface of a material in a container. As will be readily appreciated by those skilled in the art, microwaves are transmitted from an antenna coupled to the radar circuitry that may be located at the top of the container. One basic criterion is that these electrically isolating devices must provide appropriate isolation at direct current (DC). However, for appropriate radar performance (e.g., at the applicable microwave frequency bands), it is desirable that at such frequencies the ground should appear to be substantially continuous (i.e., present practically no impedance discontinuities to the propagating microwaves) to ensure appropriate coupling of the radar signal between commonly involved components, such as a waveguide assembly that conveys the microwaves to the antenna.

At least in certain known isolating devices, the matching at the appropriate frequencies may not consistently be fully optimized, and thus dynamic range may be reduced in the operation of the radar level gauge. For example, even relatively small axial misalignments of the dielectric barrier in the waveguide assembly, can potentially introduce undesirable impedance mismatches and spurious signal reflections.

At least in view of the foregoing considerations, the present inventors propose in disclosed embodiments, an improved radar level gauge that benefits from an innovative self- aligning dielectric barrier that is expected to provide a low-loss and well-matched solution at the frequencies of interest. As will be appreciated by those skilled in the art, the function of the dielectric barrier is to provide galvanic isolation between the radar circuitry and the antenna for the radar level gauge. From a radar sensor perspective, one advantage provided by disclosed embodiments is that electromagnetic wave reflections remain substantially low, and therefore close-in performance is improved while maintaining a relatively large dynamic range in the operation of the radar level gauge. Disclosed embodiments are expected to provide substantially low antenna reflections in practically all polarization directions, and therefore improvements in close-in performance can be effectively achieved while maintaining the relatively large dynamic range in the operation of the radar level gauge. Additionally, the geometry of disclosed embodiments for the dielectric barrier is relatively straightforward, and thus disclosed dielectric barriers can be manufactured at a relatively low cost. Moreover, due to their geometric simplicity, disclosed embodiments for the dielectric barrier can be assembled with relative ease, for example, without involving

burdensome and costly assembly operations.

In the following detailed description, various specific details are set forth in order to provide a thorough understanding of such embodiments. However, those skilled in the art will understand that embodiments of the present invention may be practiced without these specific details, that the present invention is not limited to the depicted embodiments, and that the present invention may be practiced in a variety of alternative embodiments. In other instances, methods, procedures, and components, which would be well-understood by one skilled in the art have not been described in detail to avoid unnecessary and burdensome explanation.

Furthermore, various operations may be described as multiple discrete steps performed in a manner that is helpful for understanding embodiments of the present invention. However, the order of description should not be construed as to imply that these operations need be performed in the order they are presented, nor that they are even order dependent, unless otherwise indicated. Moreover, repeated usage of the phrase "in one embodiment" does not necessarily refer to the same embodiment, although it may. It is noted that disclosed embodiments need not be construed as mutually exclusive embodiments, since aspects of such disclosed embodiments may be appropriately combined by one skilled in the art depending on the needs of a given application.

The terms "comprising", "including", "having", and the like, as used in the present application, are intended to be synonymous unless otherwise indicated. Lastly, as used herein, the phrases "configured to" or "arranged to" embrace the concept that the feature preceding the phrases "configured to" or "arranged to" is intentionally and specifically designed or made to act or function in a specific way and should not be construed to mean that the feature just has a capability or suitability to act or function in the specified way, unless so indicated. FIG. 1 shows a simplified representation of a waveguide arrangement 10 in a radar level gauge that can benefit from disclosed embodiments of a self-aligning dielectric barrier 12 (e.g., a solid) for providing galvanic isolation between a radar circuitry 14 and an antenna 16 for the radar level gauge. One non-limiting example of a material for self-aligning dielectric barrier 12 may be a thermoplastic polymer, such as polytetrafluoroethylene (PTFE) or polypropylene (PP).

As may be appreciated in FIG. 2, the radar level gauge may comprise a waveguide assembly 18, such as without limitation a cylindrical waveguide assembly, that includes a first waveguide member 20 that may be electrically coupled to radar circuitry 14 (FIG. 1); and a second waveguide member 22 that may be electrically coupled to antenna 16 (FIG. 1).

In one non-limiting embodiment, dielectric barrier 12 may be arranged between first waveguide member 20 and second waveguide member 22 to provide galvanic isolation between waveguide members 20, 22; thus providing galvanic isolation between radar circuitry 14 and antenna 16. As elaborated in greater detail below, disclosed embodiments of dielectric barrier 12 include means for self-aligning a body of the dielectric barrier relative to a longitudinal axis 24 of waveguide assembly 18. For example, a longitudinal body axis 26 of dielectric barrier 12 is effectively self-aligned relative to longitudinal axis 14 of waveguide assembly 18 by the means for self-aligning.

Referring to FIG. 3, in one non-limiting embodiment dielectric barrier 12 may include a first stub 28 extending radially away from the body of the dielectric barrier to provide an interference fit 34 between an edge 30 of the first stub and a corresponding surface 32 of first waveguide member 20. In one non-limiting embodiment, edge 30 of first stub 28 defines a tapering profile, wherein a radial dimension of the edge (schematically represented by arrow 36) decreases as one advances (schematically represented by arrow 37) towards an axial end 38 of the dielectric barrier disposed at the first waveguide member 20. Conversely, the radial dimension of the edge would increase as one advances (schematically represented by arrow 39) away from axial end 38 of the dielectric barrier.

As further appreciated in FIG. 3, dielectric barrier 12 may further include a second stub 40 extending radially away from the body of the dielectric barrier to provide an interference fit 42 between an edge 44 of the second stub and a corresponding surface 46 of second waveguide member 22. As discussed above in the context of the first stub 28, edge 44 of second stub 40 defines a tapering profile, wherein a radial dimension of the edge (schematically represented by arrow 48) decreases as one advances (schematically represented by arrow 50) towards an axial end 52 of the dielectric barrier disposed at the second waveguide member 22. Conversely, the radial dimension of the edge would increase as one advances (schematically represented by arrow 51) away from axial end 52 of the dielectric barrier. It is noted that the relative positioning illustrated in FIG. 3 between dielectric barrier 12 and waveguide members 20, 22 is prior to the dielectric barrier being fully assembled into the waveguide assembly. Accordingly, the relative positioning shown in FIG. 3 is just meant to facilitate conceptual explanation of the self-aligning means of the dielectric barrier.

Without limiting aspects of disclosed embodiments to any particular principle of operation, it will be appreciated that the respective tapering profiles of the self-aligning means of the dielectric barrier (such as discussed above in the context of stubs 28, 40) may be

conceptualized as forming respective guides to, for example, accept a pressing insertion force, effectively distributing the insertion force substantially evenly around the circumference of the waveguide members 20, 22; thus allowing compression to occur gradually instead of ail at once, thus facilitating the insertion operation of the dielectric barrier to be smoother, more easily controlled, involving less mechanical power (e.g., less force at any one instant of time), and conducive for self-aligning the longitudinal body axis of the dielectric barrier with the longitudinal axis of waveguide assembly 18, where the dielectric, barrier is being inserted into.

In one non-limiting embodiment, dielectric barrier 12 may further include a flange 54 arranged in a transversal plane 56 (FIG. 6) relative to the longitudinal axis 24 of the waveguide assembly. One can appreciate that flange 54 extends circumferentially about the longitudinal axis of the waveguide assembly. Flange 54 may be disposed in an axial gap 58 (FIG. 2) between first waveguide member 20 and second waveguide member 22. As may be further appreciated in FIG. 2, in one non-limiting embodiment, a module member 60 (e.g., an annular member) may be circumferentially arranged around flange 54 in the transverse plane, and module member 60 may include a slot 62 for receiving a circumferential distal edge 64 of flange 54, thus providing incremental axial stability and support to the dielectric barrier. In one non-limiting embodiment, module member 60 may be part of a deplugable modular unit that contains the radar circuitry.

As should be appreciated from the dielectric barrier embodiments discussed above, the body of the dielectric barrier may comprise symmetrical body sections 66, 68 about transversal plane 56 (FIG. 6), where such symmetrical body sections are configured to provide impedance matching between the first waveguide member and the second waveguide member. Returning to FIG. 3, in one non-limiting embodiment a respective one of the symmetrical body sections of the dielectric barrier may comprise stub 28 extending radially away from the respective one of the symmetrical body sections of the dielectric barrier. Stub 28 may be interposed between a first cylindrical section 70 and a second cylindrical section 72 each extending co-axially along the longitudinal axis of the waveguide assembly. First cylindrical section 70 may extend between axial end 38 of the dielectric barrier and a surface 74 of stub 28 facing axial end 38 of the dielectric barrier. Second cylindrical section 72 may extend between a surface 76 of stub 28 facing away from axial end 38 of the dielectric barrier and flange 54. In one non-limiting embodiment, a radius of second cylindrical section 72 is larger relative to a radius of first cylindrical section 70. It will be appreciated that the body section of the dielectric barrier under flange 54 is essentially a mirror image of the body section just described above, and, for the sake of avoiding pedantic and burdensome repetition; the reader will be spared from such a repetitive disclosure.

It will be appreciated that the body of the dielectric barrier need not be made up of symmetrical body sections about transversal plane 56 (FIG. 6). For example, as may be appreciated in FIGs. 4 and 5, depending on the needs of a given application, the body of dielectric barrier may comprise asymmetrical body sections 78, 80 about the transversal plane, where such asymmetrical body sections 78, 80 may be configured to provide impedance matching between the first waveguide member and the second waveguide member.

In one non-limiting embodiment, one of the asymmetrical body sections (e.g., body section 78) of the dielectric barrier may comprise at least one cylindrical section including a stub, as described above in the context of FIG. 3, for example. Another one of the asymmetrical body sections (e.g., body section 80) of the dielectric barrier may comprise a conical body section, wherein an apex 82 of conical body section 80 may be disposed at an axial end of the dielectric barrier. In one non-limiting embodiment, dielectric barrier 12 may include a transition 84 (e.g., cylindrical-to-conical transition) to provide an interference fit with a corresponding inner surface of the second cylindrical waveguide member. Transition 84 may include a tapering profile, as discussed above in the context of stubs 28, 40. It will be appreciated that the specific geometries illustrated in the figures should not be construed in a limiting sense since, as should be appreciated by those skilled in the art, such geometries may be readily tailored depending on the needs of a given application. FIG. 7 is a plot of respective non-limiting curves indicative of transmission loss 90, and return loss 92 over one non-limiting frequency band based on the non-limiting model of the dielectric barrier shown in FIG. 6.

In operation, the self-alignment feature for the dielectric barrier in a cost-effective manner is effective to reliably maintain appropriate impedance matching at the frequencies of interest and thus avoid the formation of spurious signal reflections. This allows improvements in close-in performance while maintaining a relatively large dynamic range in the operation of the radar level gauge.

While various embodiments of the present invention have been shown and described herein, it will be apparent that such embodiments are provided by way of example only.

Numerous variations, changes and substitutions may be made without departing from the invention herein. Accordingly, it is intended that the invention be limited only by the scope of the appended claims.