Abstract:
A circuit for a fill-level measuring device is for the fast switching-on of a high-frequency element on a ground port is disclosed. The circuit comprises a switching unit with a circuit mass; a high-frequency element with a high-frequency mass; and a coupling element that couples the two masses together and at the same time insulates them from each other in a direct-current manner. In this way the switching unit can be arranged on the GND port of the HF-element, without influencing the HF characteristics of said HF element.

Description:
PRIORITY CLAIM 
       [0001]    This application claims the benefit of the filing date of DE Patent Application Serial No. 10 2007 023 927.2 filed on May 23, 2007 and U.S. Provisional Patent Application No. 60/939,647 filed on May 23, 2007, the disclosure of these applications is hereby incorporated herein by reference. 
     
    
     FILED OF INVENTION 
       [0002]    The present invention relates to fill level measuring. In particular, the present invention relates to a circuit for a fill-level measuring device for the fast switching-on of a high-frequency element on a ground port; to a fill-level measuring device comprising such a circuit; to the use of such a circuit for fill level measuring; and to a method for the fast switching-on of a high-frequency element on a ground port for fill level measuring. 
       BACKGROUND INFORMATION 
       [0003]    If high-frequency elements (HF-elements) are to be switched on temporarily, and if there is no suitable control connection, often the operating voltage is switched. Different variants of this are possible, as shown in  FIG. 1 . This involves direct switching of the operating voltage. Furthermore, indirect switching by way of a control input (a so-called shut-down) is also possible. 
         [0004]    In the case of fast switching-on processes the switching unit comprises, for example, individual transistors that have correspondingly fast switching times. As a rule, relays or integrated switches are too slow for time-critical applications. 
         [0005]    If the switching unit is located directly on the operating voltage of the HF-element, switching is either by way of relatively slow PNP transistors, or, where fast NPN transistors are used, an adequate control level must be ensured. 
         [0006]    If the switching unit is located on the ground port, then in the case of HF-elements it is located in the so-called hot path, i.e. said switching unit is incorporated in the HF characteristics of the arrangement or of the HF-element. 
       SUMMARY OF INVENTION 
       [0007]    The present invention relates to a circuit for a fill-level measuring device for the fast switching-on of a high-frequency element on a ground port; to a fill-level measuring device comprising such a circuit; to the use of such a circuit for fill level measuring; and to a method for the fast switching-on of a high-frequency element on a ground port for fill level measuring. 
         [0008]    According to one embodiment of the present invention, a circuit for a fill-level measuring device for fast switching-on of a high-frequency element on a ground port is stated, with the circuit comprising a switching unit with a first ground port; a high-frequency element with a second ground port; a coupling element; and insulation between the second ground port and the first ground port. In this arrangement the switching unit is connected between the first ground port and the high-frequency element, wherein the second ground port is coupled by way of the coupling element to the first ground port. 
         [0009]    In other words, the switching unit can be arranged at the GND port of the HF-element without influencing the high-frequency characteristics of said HF-element. 
         [0010]    This fast switching-on makes it possible to use the circuit (i.e. the HF-elements) for pulse radar measuring or for the purpose of saving energy (in that the HF-elements are switched off when for energy reasons they are not to be used). 
         [0011]    According to a further exemplary embodiment of the present invention, the coupling element and the insulation between the second ground port and the first ground port are designed such that any DC-current flow between the first ground port and the high-frequency element is prevented. 
         [0012]    This DC-current flow is only made possible when the switching unit is switched so that a short circuit between the two ground ports is established. 
         [0013]    Thus, in the region of the HF-element that is to be switched on, a new mass is introduced which is insulated from the circuit mass. It in turn is coupled, by way of the coupling element (for example in the form of a capacitor), to the circuit mass. When the HF-element is switched on, it is then only necessary to short circuit the two mass potentials in a direct-current manner (DC manner) for current to be able to flow. 
         [0014]    According to a further exemplary embodiment of the present invention, the coupling element is a capacitor. 
         [0015]    According to a further exemplary embodiment of the present invention, the circuit comprises a printed circuit board that comprises a first layer, a second layer, and a third layer, wherein the coupling element is designed as a plate capacitor that is formed by the second layer and the third layer. 
         [0016]    According to a further exemplary embodiment of the present invention, the circuit comprises a printed circuit board that comprises a first layer, a second layer, and a third layer, wherein the plate capacitor is formed by the second layer and the first layer. 
         [0017]    It should be noted that the coupling element can also be designed in some other way. It is merely important that said coupling element can prevent a direct-current flow between the circuit mass and the high-frequency mass when the switching unit is in the “open” position. For example it is possible to do entirely without the third layer, for example if the coupling element is integrated in the second layer. 
         [0018]    According to a further exemplary embodiment of the present invention, the circuit also comprises a printed circuit board with three layers, wherein, however, the coupling element is designed as a coupling area in the third layer. The coupling element is thus not formed by the second and the third layer in the form of a plate capacitor. 
         [0019]    Furthermore, according to a further exemplary embodiment of the present invention, the circuit can be designed as a micro-strip circuit, wherein the second ground port is designed as an area on the underside of the printed circuit board. 
         [0020]    According to a further exemplary embodiment of the present invention, all three layers comprise the first ground port (circuit mass). 
         [0021]    According to a further exemplary embodiment, the printed circuit board can be designed as a multilayer comprising many layers, in which multilayer mass couplings are established only in a sub-region, i.e. only in part of the many layers. 
         [0022]    According to a further exemplary embodiment, coupling of the two masses can only take place between the first and the second layer. 
         [0023]    According to a further exemplary embodiment of the present invention, the first layer comprises the high-frequency element, wherein the second layer comprises an insulated high-frequency mass area that represents the second ground port, and wherein the third layer comprises the coupling element. 
         [0024]    According to a further exemplary embodiment of the present invention, the switching unit is designed as an element selected from the group comprising semiconductor components such as, for example, transistors or diodes, signal switches and relays. 
         [0025]    According to a further exemplary embodiment of the present invention, the high-frequency element is designed as an element selected from the group comprising oscillators, transmitter amplifiers, low-noise amplifiers (LNA), variable gain amplifiers (VGA), mixers, and multipliers. 
         [0026]    According to a further exemplary embodiment of the present invention, a fill-level measuring device is stated that comprises a circuit as described above. 
         [0027]    According to a further exemplary embodiment of the present invention, the use of such a circuit for fill level measuring is stated. 
         [0028]    According to a further exemplary embodiment of the present invention, a method for the fast switching-on of a high-frequency element on a ground port for fill level measuring is stated, in which method a first ground port is provided on a switching unit, a second ground port is provided on a high-frequency element, wherein the switching unit is connected between the first ground port and the high-frequency element, and in which insulation between the second ground port and the first ground port is provided. Furthermore, coupling of the second ground port to the first ground port takes place by way of a coupling element. 
         [0029]    In a further method-related step the two ground ports are short-circuited to each other by way of a switching unit so that the high-frequency element is switched on. 
         [0030]    It should be noted that the exemplary embodiments of the invention that have been described in the context of the circuit also comprise the method, the use, and the fill-level measuring device. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0031]    Below, preferred exemplary embodiments of the present invention are described with reference to the figures. 
           [0032]      FIG. 1  shows a diagrammatic view of two arrangements of the switching unit and the HF-element according to the state of the art. 
           [0033]      FIG. 2  shows a diagrammatic view of a circuit according to an exemplary embodiment of the present invention. 
           [0034]      FIG. 3  shows a diagrammatic view of a layered design of a microwave print. 
           [0035]      FIG. 4  shows a microwave print of all three layers of a microwave amplifier according to an exemplary embodiment of the present invention. 
           [0036]      FIG. 5  shows a microwave print of the first layer  301  of  FIG. 4 . 
           [0037]      FIG. 6  shows a microwave print of the second layer  302  of  FIG. 4 . 
           [0038]      FIG. 7  shows a microwave print of the third layer  303  of  FIG. 4 . 
           [0039]      FIG. 8  shows a principle of the coupling arrangement according to an exemplary embodiment of the present invention. 
           [0040]      FIG. 9  shows a fill-level measuring device according to an exemplary embodiment of the present invention. 
       
    
    
       [0041]    The illustrations in the figures are diagrammatic and not to scale. 
       DETAILED DESCRIPTION 
       [0042]    In the following description of the figures the same reference characters are used for identical or similar elements. 
         [0043]      FIG. 1  shows two circuits for switching HF-elements according to the state of the art. In the left-hand embodiment the HF-element  102  is connected to earth (ground port GND)  103  on one side. 
         [0044]    On the other side the HF-element  102  is connected to a switching unit  101  that in turn establishes a connection to a voltage supply  104 . 
         [0045]    In the right-hand embodiment the switching unit  101  is located between the mass  103  and the HF-element  102 , which on the other side is connected to the voltage supply  104 . 
         [0046]    In the left-hand example, switching is either by way of relatively slow PNP transistors, or, if fast NPN transistors are used, an adequate control level is ensured. 
         [0047]    In the right-hand embodiment, in the case of HF-elements, the switching unit is in the so-called “hot path”, i.e. said switching unit is incorporated in the HF-characteristics of the arrangement or of the HF-element. 
         [0048]      FIG. 2  shows a circuit according to an exemplary embodiment of the present invention. On one side the HF-element  102  is connected to a voltage supply  104 , and on the other side (by way of a further connection) the HF-element  102  is connected to a high-frequency mass  201  by way of the lines  203 ,  204 . 
         [0049]    The high-frequency mass  201  is, for example, located in a printed circuit board in a second layer that is located between the first layer with the HF-element  102  and the third layer with the coupling element  202  (see  FIG. 3 ). 
         [0050]    The high-frequency mass  201  of the HF-element  102  is connected, by way of the lines  205 ,  207 , to the coupling element  202 , which in turn is connected, by way of the line  208 , to the circuit mass  103 . 
         [0051]    Furthermore, the high-frequency mass  201  is connected, by way of the lines  205 ,  206 , to the switching unit  101 , which in turn is connected, by way of the line  209 , to the circuit mass  103 . 
         [0052]    From the point of view of high frequency the two masses  201 ,  103  are identical. However, direct current can flow only if the two masses  201 ,  103  are short-circuited together by means of the switching unit. 
         [0053]    In the case of micro-strip circuits the high-frequency mass  201  is, for example, designed as an area on the underside of the printed circuit board. The coupling element  202  (for example a capacitor between the two mass potentials  201 ,  103 ) can be implemented by targeted coupling in a further interior layer, which, if at all possible, is positioned very close to the HF mass layer. 
         [0054]      FIG. 3  shows a diagrammatic view of a layered design of a microwave print according to an exemplary embodiment of the present invention. A first layer  301 , a second layer  302 , and a third layer  303  are provided. All three layers comprise the circuit mass  103 . The first layer  301  comprises the high-frequency element  102  to be switched, if need be together with further micro-strip circuit elements (not shown in  FIG. 3 ). The second layer  302  then comprises an insulated HF-mass area  201  that is associated with the HF-element  102  of the first layer  301 . The third layer  303  comprises the coupling element  202  which, again insulated from the circuit mass  103 , provides coupling between the circuit mass  103  and the HF-mass  201  of the HF-element  102 . In principle, the printed circuit board results in plate capacitors between the coupling element  202  and the mass area  201  as well as the circuit mass  103 . 
         [0055]    The construction of the circuit mass areas  103 ,  201  in the three layers  301 ,  302 ,  303  is variable, i.e. it can also be designed in some other way. Likewise, the design of the coupling element in the third layer  303  is variable. Various embodiments can be implemented. 
         [0056]    Coupling of the various masses can be implemented in various ways. For example, coupling can be designed in the described manner as a coupling area  202  in the third layer  303 . Furthermore, the third layer  303  can also be designed in a sheet-like manner as a circuit mass, wherein coupling is then implemented by the plate capacitor that is created between the second layer  302  and the third layer  303 . 
         [0057]    For example, coupling can also be implemented by way of a plate capacitor that is created between the second layer  302  and the first layer  301 . In such a case the third layer  303  would be without a function. 
         [0058]    The switching unit  101  can also be designed in various ways. For example, the switching unit  101  can be designed as a transistor, diode, signal switch or relay. Moreover, the arrangement of the switch can be implemented in various ways because said switch is not arranged in the so-called “hot path”. 
         [0059]      FIG. 4  shows a microwave print of all three layers  301 ,  302 ,  303  of a microwave amplifier according to an exemplary embodiment of the present invention. The microwave amplifier comprises a high-frequency layout (high-frequency element)  401 , which is shown in the pattern defined by the colour field  705  of  FIG. 7 . Furthermore, the coupling element of the third layer is shown in the pattern defined by the colour field  703  of  FIG. 7 . The insulated mass area of the second layer is shown in the pattern defined by the colour field  704  of  FIG. 7 . The circuit mass is shown in the pattern defined by the colour field  702  of  FIG. 7 . 
         [0060]      FIG. 5  shows a microwave print of the first layer  301  of the microwave amplifier of  FIG. 4  with the high-frequency layout (high-frequency element)  401 . 
         [0061]      FIG. 6  shows a microwave print of the second layer  302  of the microwave amplifier of  FIG. 4 . The second layer  302  comprises the insulated HF-mass area  201  that is associated with the HF-element  102  of the first layer  301 . 
         [0062]      FIG. 7  shows a microwave print of the third layer  303  of the microwave amplifier of  FIG. 4 . The third layer  303  comprises the coupling elements  202  and  701  that provide coupling between the circuit mass  103  and the HF-mass  201  of the HF-element  102 . 
         [0063]      FIG. 8  shows a principle of the coupling according to an exemplary embodiment of the present invention. The elements  801 ,  802 , shown as capacitors, are representative of the plate capacitors that are created between the individual layers of the printed circuit board. The coupling area (coupling element)  202  itself can also be done without, in which case the insulated HF-mass  201  and the circuit mass  103  are only connected by a single plate capacitor. 
         [0064]    The principle shown in the drawing relates not only to printed-circuit-board designs. 
         [0065]    The invention relates in particular to the use of the circuit in fill-level measuring devices. The HF-elements to be switched are, for example, oscillators, transmitter amplifiers, LNAs, mixers, multipliers, or in general terms any active components of HF technology. 
         [0066]      FIG. 9  shows a diagrammatic view of a fill-level measuring device in the form of a fill level radar according to an exemplary embodiment of the present invention. The fill level radar  800  comprises an antenna  801  and a housing  802 . The housing  802  comprises the circuit described above. 
         [0067]    The antenna  801  emits electromagnetic waves  804  that are reflected as a signal  803  by the surface of the feed material  805 . The reflected signal  803  is subsequently acquired by the antenna  801  and is evaluated by the electronics contained in the housing. 
         [0068]    In addition, it should be pointed out that “comprising” does not exclude other elements or steps, and “a” or “one” does not exclude a plural number. Furthermore, it should be pointed out that characteristics or steps which have been described with reference to one of the above exemplary embodiments can also be used in combination with other characteristics or steps of other exemplary embodiments described above. Reference characters in the claims are not to be interpreted as limitations.