APPARATUS FOR ASCERTAINING AND MONITORING A FILL LEVEL

Abstract

The invention relates to an apparatus for transmitting and receiving electromagnetic waves (EM waves) for ascertaining and monitoring a fill level of a medium in a container, comprising a first hollow conductor with a first coupling element for the out- and in-coupling of EM waves, a second hollow conductor with a second coupling element for the out- and in-coupling of EM waves, a horn radiator for radiating and focusing of EM waves, wherein the first and second hollow conductors are dimensioned such that EM waves out-coupled from the first and second coupling elements radiate from the horn radiator scattered and with weak intensity, or scattered and weak intensity EM waves, which are received from the horn radiator, couple to the first and second coupling elements, and EM waves out-coupled only from the first coupling element radiate from the horn radiator focused and with strong intensity, or focused and strong intensity EM waves, which are received from the horn radiator couple only to the first coupling element.

Claims

1-10. (canceled)

11. An apparatus for transmitting and receiving electromagnetic waves (EM waves), comprising: a first hollow conductor including a first coupling element embodied to out-couple and to in-couple EM waves, the first hollow conductor having a first end face that is closed and a second end face that is open, so that EM waves that out-couple via the first coupling element are transmitted via the second end face, and so that EM waves that are received via the second end face in-couple to the first coupling element; a second hollow conductor including a second coupling element embodied to out-couple and to in-couple EM waves, the second hollow conductor having a first end face that is open and a second end face that is open, wherein the first end face of the second hollow conductor borders on the second end face of the first hollow conductor, so that EM waves transmitted from the first hollow conductor are transferred by the second hollow conductor, and so that EM waves transferred by the second hollow conductor are received by the first hollow conductor; and a horn radiator embodied to radiate and to focus EM waves, wherein an intake opening of the horn radiator communicates with the second end face of the second hollow conductor, so that EM waves transmitted from the second hollow conductor are radiated from the horn radiator, and so that EM waves received from the horn radiator are focused into the second hollow conductor, wherein the first hollow conductor is embodied such that first electromagnetic wave modes are producible in the first hollow conductor, wherein the second hollow conductor is embodied in such a way that second electromagnetic wave modes are producible in the second hollow conductor, wherein the first hollow conductor and the second hollow conductor are dimensioned such that: EM waves out-coupled from the first coupling element and the second coupling element radiate from the horn radiator scattered and having a weak intensity; scattered and weak intensity EM waves that are received from the horn radiator couple to the first and second coupling elements; EM waves out-coupled only from the first coupling element radiate from the horn radiator focused and having a strong intensity; and focused and strong intensity EM waves that are received from the horn radiator couple only to the first coupling element.

12. The apparatus as claimed in claim 11, wherein the first hollow conductor is at least partially filled with a first dielectric material and the second hollow conductor is at least partially filled with a second dielectric material.

13. The apparatus as claimed in claim 12, wherein a dielectric constant of the first dielectric material is smaller than a dielectric constant of the second dielectric material.

14. The apparatus as claimed in claim 13, wherein a ratio between the dielectric constant of the second dielectric material and the dielectric constant of the first dielectric material is about 2.5 to 1.

15. The apparatus as claimed in claim 11, wherein a separation between the first coupling element and the second coupling element in a transmission direction of the EM waves corresponds to +n/2, wherein is a wavelength of the EM waves and n is a natural number 0, 1, 2, . . . .

16. The apparatus as claimed in claim 11, wherein a length of the first coupling element is less than or equal to /4 and a length of the second coupling element is less than or equal to /2, wherein is a wavelength of the EM waves.

17. The apparatus as claimed in claim 11, wherein the first coupling element includes a first terminal embodied to transfer EM waves that out-couple or in-couple at the first coupling element, and wherein the second coupling element includes a second terminal embodied to transfer EM waves that out-couple or in-couple at the second coupling element, the apparatus further comprising a voltage divider disposed between the first terminal and the second terminal and embodied to divide the EM waves between the first coupling element and the second coupling element.

18. The apparatus as claimed in claim 17, wherein the voltage divider includes an electrical capacitance and a bandpass filter.

19. The apparatus as claimed in claim 17, wherein the voltage divider includes a capacitance and a diode.

20. The apparatus of claim 17, wherein the voltage divider includes a capacitance and an oscillatory circuit.

21. The apparatus as claimed in claim 17, wherein the voltage divider is a capacitive voltage divider.

22. The apparatus as claimed in claim 19, wherein the diode is a varactor diode.

Description

[0023] The invention will now be explained in greater detail based on the appended drawing, the figures of which show as follows:

[0024] FIG. 1 a schematic view of an apparatus 1 of the invention for transmitting and receiving EM waves, including an electrical circuit for operation of the apparatus 1,

[0025] FIGS. 2a-2d schematic views of radiations of EM waves from an apparatus 1 as in FIG. 1 in the case of different designs of the electrical circuit,

[0026] FIG. 3 a schematic view of an additional embodiment of the apparatus 1, in the case of which a voltage divider of the electrical circuit is capacitive, and

[0027] FIG. 4 a schematic view of an additional embodiment of the apparatus 1, in the case of which the horn radiator is conically embodied.

[0028] FIG. 1 shows an apparatus of the invention 1 for transmitting and receiving electromagnetic waves (EM waves) for ascertaining and monitoring a fill level of a medium (not shown) in a container (not shown) by means of travel times of EM waves. Apparatus 1 includes a first hollow conductor 2 with a first coupling element P1 for the out- and in-coupling of electromagnetic waves, wherein a first end face 3 of the first hollow conductor 2 is closed and a second end face 4 of the first hollow conductor 2 is open. In this way, EM waves, which out-couple via the first coupling element P1, can be transmitted via the second end face and EM waves, which are received via the second end face of the first hollow conductor 4, can in-couple at the first coupling element P1. The first hollow conductor 2 is cylindrically embodied and has a diameter, which is dimensioned in such a manner that only a fundamental mode is excited. Preferably the fundamental mode is a mode with a very low cutoff frequency, especially a TE01 mode. The first hollow conductor 2 can, however, also have an elliptical, quadratic, n-polygonal or u-shaped footprint.

[0029] Furthermore, the apparatus 1 includes a second hollow conductor 5 with a second coupling element P2 for the out- and in-coupling of EM waves, wherein the first and second end faces 6, 7 of the second hollow conductor 5 are open. In such case, the first end face 6 of the second hollow conductor 5 borders the second end face 4 of the first hollow conductor 2, so that EM waves transmitted from the first hollow conductor 2 are transferred by the second hollow conductor 5 and EM waves transferred by the second hollow conductor 5 are received by the first hollow conductor 2. The second hollow conductor 5 can be cylindrically embodied. The second hollow conductor 5 can have a footprint, which is square, elliptical, n-polygonal or u-shaped. The second hollow conductor 5 is designed in such a manner that a higher mode is excited than the mode in the first hollow conductor 2. The higher modes can be e.g. a TM11-, TE21-, TE11- or TM21 mode.

[0030] Furthermore, the apparatus 1 includes a widened horn radiator 8 for radiating, receiving and focusing of EM waves. An intake opening of the horn radiator 8 communicates with the second end face 7 of the second hollow conductor 5, so that EM waves transferred from the second hollow conductor 5 are radiated from the horn radiator 8 and EM waves received by the horn radiator 8 are focused into the second hollow conductor 2.

[0031] The first hollow conductor 2 is embodied in such a way that first electromagnetic wave modes are producible in the first hollow conductor 2 and the second hollow conductor 5 is embodied in such a way that second electromagnetic wave modes are transferable in the second hollow conductor 5.

[0032] The first and second hollow conductors 2, 5 are designed in such a way that EM waves out-coupled from the first and second coupling elements P1, P2 superimpose and radiate scattered and with weak intensity from the horn radiator 8, respectively scattered and weak intensity EM waves, which are received by the horn radiator 8, couple into the first and second coupling elements P1, P2. EM waves out-coupled solely from the first coupling element P1 radiate focused and with strong intensity from the horn radiator 8, and focused and strong intensity EM waves, which are received by the horn radiator 8, couple to the first coupling element P1.

[0033] Furthermore, the first hollow conductor 2 is filled with a first dielectric material and the second hollow conductor 5 is filled with a second dielectric material. The first dielectric material can be air from the environment. Alternatively, the first hollow conductor can be evacuated. The second dielectric material has a dielectric constant, which is 2.5-times greater than the dielectric constant of the first material.

[0034] A separation S between the first and second coupling elements P1, P2 in the transmission direction of the EM waves equals +n/2, wherein is the wavelength of the EM waves and n is a natural number 0, 1, 2, . . . . A length of the first coupling element P1 amounts to /4 and a length of the second coupling element P2 amounts to /2.

[0035] Furthermore, the apparatus 1 includes an electrical circuit 11 for operating the apparatus 1. The electrical circuit 11 will now be described in greater detail. Leading from a first node K1 of the second hollow conductor 5 to a second node K2 is a first electrical line L1. A second line L2 connects the second node K2 with the second coupling element P2. A third line L3 connects the second node K2 with a first inductance JS, wherein the first inductance JS is connected via a diode DS to a third node K3. A first capacitance CS is connected parallel to the first inductance JS and the diode DS. The first capacitance CS and the first inductance JS and the diode DS form together a bandpass filter L5.

[0036] The third node K3 is connected via a second inductance JB and a limiting resistor RV to a first terminal P3.

[0037] A fourth line L4 connects the first coupling element P1 with a fourth node K4, wherein the fourth node K4 is connected to a second terminal P4.

[0038] Via a second capacitance CB, the third node K3 is connected with the fourth node K4.

[0039] The bandpass filter L5 forms with the second capacitance CB a capacitive voltage divider 12. Size of the second capacitance CB determines the powers sent to the first and second coupling elements P1, P2. Due to the greater diameter of the second hollow conductor 5, a higher mode is excited in the hollow conductor 5 than in the first hollow conductor 2. The higher mode of the second hollow conductor 5 is expanded at the output of the horn antenna 8 to a broad lobe.

[0040] The bandpass filter L5 acts as a band blocking filter, whereby no power reaches the second coupling element P2. The limiting resistor RV is high resistance, whereby no power can drain via the second terminal P4. The lengths of the first to fourth lines L1-L4 are listed in the table below.

TABLE-US-00001 line/distance length/size ( = wavelength) S - distance between the first + n * /2; n = 0, 1, 2 . . . and second coupling element L1 - first line antenna horn n * /2 n = 1, 2, 3 . . . L2 - second line (n + 1/2) * n = 0, 1, 2 . . . L3 - third line (n + 1/2) * n = 0, 1, 2 . . . L4 - fourth line n * n = 1, 2, 3 . . . travel path via the bandpass filter L5 n * /2 n = 1, 2, 3 . . . length of the second capacitance CB n * /2 n = 1, 2, 3 . . . length of the first coupling element /4 length of the second coupling element /4 or /2

[0041] In order to produce focused and strong intensity EM waves, a high frequency signal HF is applied to the second terminal P4. The high frequency signal HF is transferred via the fourth line L4 to the first coupling element P1 and radiated monomodally (only one mode is predominant in the radiation) via the horn radiator 8.

[0042] Placed on the first terminal P3 of the apparatus 1 is a control voltage MV, which affects the cathode of the diode DS via the limiting resistor RV and the second inductance JB. Since an anode of the diode DS is connected via the first inductance JS and the first line L1 with the second hollow conductor 5, and, from there, with the third terminal P5 (signal ground potential), the control voltage MV affects the diode DS. Because the control voltage is acting in the reverse direction of the diode DS, only a very smaller electrical current flows through the first line L1. With voltage applied in the reverse direction, the diode DS acts as a capacitance, whereby the bandpass filter L5 determines the pass frequency for the operating frequency of the apparatus 1.

[0043] FIG. 2a shows the radiation of EM waves, which are out-coupled only from the first coupling element P1 (one-mode operation) and radiate focused and with strong intensity from the horn radiator 8.

[0044] FIGS. 2b, 2c, and 2d each show radiations of EM waves, which result from the superpositioning of the EM waves out-coupled from the first and second coupling elements P1, P2 and from the design of the voltage divider (see FIG. 1 and description for FIG. 1). Switching between the radiation of FIG. 2a and the radiations of FIGS. 2b, 2c, and 2d can occur by means of an analog or digital control voltage MV.

[0045] FIG. 3 shows another embodiment, in the case of which the voltage divider 12 is capacitive and formed only of CB and D1. In this way, a stepless transition from the radiation of FIG. 2a to the radiations of FIGS. 2b-d can be produced as a function of the control voltage MV, wherein without applied control voltage MV the radiation of FIG. 2a is achieved and with increasing control voltage MV the radiation changes more and more in the direction of the radiation of FIG. 2d. Since diode D1 is very high resistance, and also in order to enable a fast switching from d) back to a), an optional very high ohm (10 . . . 100 MOhm or more) resistor RU is provided, through which the capacitance (in the range to a few pF) formed with the diode D1 can be discharged.

[0046] FIG. 4 shows another embodiment of the apparatus of the invention, which differs from the apparatus of FIG. 3 by a simplified electrical circuit 11. Instead of an impedance-based, capacitive voltage divider and bandpass filter or capacitance and resonance circuit, the impedance-based voltage divider here is formed of a diode D1 and the second capacitance CB. The second capacitance CB represents a barrier for the control voltage MV equivalent to the barrier provided by the diode D1. An inductance JD connects the diode D1 with the signal ground potential on the terminal P5. An apparatus of the invention with an electrical circuit 11 is, as a whole, cost effective to implement.

[0047] In all examples of embodiments shown in FIGS. 1 to 4, the transmission of EM waves of the apparatus 1 has been described. The receiving of EM waves by the apparatus 1 is analogous to the transmission of the EM waves.

LIST OF REFERENCE CHARACTERS

[0048] 1 apparatus [0049] 2 first hollow conductor [0050] 3 first end face of the first hollow conductor [0051] 4 second end face of the first hollow conductor [0052] 5 second hollow conductor [0053] 6 first end face of the second hollow conductor [0054] 7 second end face of the second hollow conductor [0055] 8 horn radiator [0056] 9 first diameter [0057] 10 second diameter [0058] 11 electrical circuit [0059] 12 voltage divider [0060] S separation [0061] P1 first coupling element [0062] P2 second coupling element [0063] wavelength of the EM wave [0064] n natural number 0, 1, 2, . . . [0065] P3 first terminal [0066] P4 second terminal [0067] P5 third terminal [0068] DS diode [0069] CS first capacitance [0070] JS first inductance [0071] CB second capacitance [0072] JB second inductance [0073] RV limiting resistor [0074] K1 first node [0075] K2 second node [0076] K3 third node [0077] K4 Fourth node [0078] L1 first line [0079] L2 second line [0080] L3 third line [0081] L4 fourth line [0082] L5 bandpass filter [0083] RU resistor [0084] JD inductance