Abstract: A radar level gauging system for determining at least one process variable related to a distance to a surface of a product in a tank comprising transceiver circuitry, processing circuitry, a wave guiding structure arranged guide measurement signals towards the surface, and a radiator connected to the transceiver circuitry and arranged to emit the measurement signal into the wave guiding structure. The system further comprises a mode generator adapted to convert electromagnetic waves emitted from the radiator from a first propagation mode to a second propagation mode, wherein the mode generator includes a lens in the form of a body transparent to electromagnetic waves in the operating frequency range. With this design, electromagnetic waves having the first propagation mode emitted by the radiator into the lens will be reflected at least twice within the lens (first in the bottom surface and then in the upper surface).

Abstract: The invention relates to a method for determining a level of a material interface in a tank, by means of a radar level gauge system comprising a transceiver; a probe for guiding a transmitted electromagnetic signal towards the material interface. The probe comprises a first plurality of reference impedance transitions located above the interface at known physical distances from a reference position, and a second plurality of reference impedance transitions located below the interface at known physical distances from the reference position. The method comprising determining electrical distances to the first and second plurality of reference impedance transitions based on a signal reflected by the reference impedance transition, determining, a first and a second approximation function relating the first and second sets of electrical distance values to the physical distances; and determining the level of the material interface based on the first approximation function and the second approximation function.

Abstract: A radar level gauge using electromagnetic signals to determine a filling level of a product in a tank, comprising an electronics unit including transceiver circuitry, a signal propagation device, and a directional coupler. The gauge further comprises a wave guiding structure comprising a rod of a dielectric material. A mounting portion of the electronics unit defines an opening and is detachably mountable on the dielectric rod so that the rod extends through the opening and is at least partly surrounded by the opening. The mounting portion is further arranged to secure the circuitry portion relative the rod so that the directional coupler is in a position to couple signals between the transceiver circuitry and the rod. The radar level gauge according to the present invention facilitates replacement of an electronics unit, e.g. in case of malfunction or upgrades. At the same time, the dielectric rod enables a very simple, cost-effective and reliable feeding to and from each electronics unit.

Abstract: A level gauge for detecting process variables related to a distance to a surface of a content in a tank, comprising a first and second functionally independent circuitry arrangements comprising transceiver circuitry and processing circuitry. The gauge further comprises a transmission line probe connected to the circuitry arrangements, the transmission line probe extending into the content in the tank and being adapted allow propagation of first and second transmission modes, and a feeding arrangement connected to couple electromagnetic signals into the probe in first and second propagation modes.

Abstract: Level gauging including an approximation of a distance to the surface of a product kept in a tank. The approximation is determined by relating an amplitude of a first harmonic of an IF signal with an amplitude of a second harmonic of the IF signal. Basically, each harmonics represents a given distance range. By determining the received power in two or more harmonics, and correlating them to each other, the distance may be estimated. Depending on modulation and other parameters the distance dependence may be very different, and may be selected to suit the application.

Abstract: A radar level gauge system for determining a filling level in a tank. The radar level gauge system comprises a transceiver, a horn antenna having a first opening connected to the transceiver and a second opening facing a surface of the product in the tank, and processing circuitry connected to the transceiver for determining the filling level based on an electromagnetic surface reflection signal. The horn antenna is configured in such a way that an electrical distance from the first opening to the second opening, along a path defined by an intersection between a wall of the horn antenna and a half-plane starting from and extending in parallel with a cone axis of the horn antenna, is different for different orientations of the half-plane with respect to the cone axis. Hereby, disturbance from an antenna reflection signal can be reduced, which provides for improved measurement of high filling levels.

Abstract: The invention relates to a method for determining a level of a material interface in a tank, by means of a radar level gauge system comprising a transceiver; a probe for guiding a transmitted electromagnetic signal towards the material interface. The probe comprises a first plurality of reference impedance transitions located above the interface at known physical distances from a reference position, and a second plurality of reference impedance transitions located below the interface at known physical distances from the reference position. The method comprising determining electrical distances to the first and second plurality of reference impedance transitions based on a signal reflected by the reference impedance transition, determining, a first and a second approximation function relating the first and second sets of electrical distance values to the physical distances; and determining the level of the material interface based on the first approximation function and the second approximation function.

Abstract: A method for measurement of a distance to a surface of a product kept in a tank method comprises transmitting a pulse train of distinct carrier wave pulses having a duration greater than 1 microsecond and shorter than 100 milliseconds, the pulse train has an average duty cycle of less than 50 percent, each pulse has a defined center frequency, selected according to a frequency scheme within a predetermined frequency range, greater than 5% of an average center frequency. The method further comprises correlating actual phase properties of received pulses with expected phase properties to provide an updated estimation of the distance. The present invention is based on transmitting a set of carrier wave pulses, each having a distinct frequency selected within a frequency range. The method is therefore referred to as a Frequency Modulated Pulsed Wave (FMPW).

Abstract: The present invention relates to a method of determining a filling level of a product contained in a tank by propagating a first transmitted electromagnetic signal in a first frequency range and a second transmitted electromagnetic signal in a second frequency range different from the first frequency range along a transmission line probe towards a surface of the product in the tank, receiving a first reflected electromagnetic signal in the first frequency range and a second reflected electromagnetic signal in the second frequency range, and determining the filling level based on a time-of-flight of the first reflected electromagnetic signal and a difference in time-of-flight of the first reflected electromagnetic signal and the second reflected electromagnetic signal.

Abstract: The invention relates to a test arrangement comprising a waveguide, a first signal reflecting device and a second signal reflecting device. The first signal reflecting device is configured to reflect an electromagnetic signal traveling along the waveguide from the second signal reflecting device back towards the second reflecting device and to allow, at least during a time period, an electromagnetic signal traveling along the waveguide from the second signal reflecting device towards the first signal reflecting device to pass the first signal reflecting device. Hereby, a selected number of passages through a waveguide can be used to simulate passage through a much longer waveguide, and that this allows for use of a high-quality waveguide which would otherwise be too bulky, too heavy or too expensive to use depending on field of application.

Abstract: Level gauging including an approxiamtion of a distance to the surface of a product kept in a tank. The approxiamtion is determined by relating an amplitude of a first harmonic of an IF signal with an amplitude of a second harmonic of the IF signal. Basically, each harmonics represents a given distance range. By determining the received power in two or more harmonics, and correlating them to each other, the distance may be estimated. Depending on modulation and other parameters the distance dependence may be very different, and may be selected to suit the application.

Abstract: A radar level gauging principle including transmitting at least two time separated carrier wave pulses having equal carrier frequencies, determining a change in phase shift associated with two pulses in the transmit signals having equal frequencies, comparing the change with a threshold value, and depending on a result of the comparing step, determining the distance based on a relationship between the transmit signals and the return signals. By comparing the actual phase resulting from two substantially identical pulses transmitted a certain time apart, an indication of a change of filling level can be obtained. This indication can then be used to initiate a full measurement cycle.

Abstract: A level gauge for detecting process variables related to a distance to a surface of a content in a tank, comprising a first and second functionally independent circuitry arrangements comprising transceiver circuitry and processing circuitry. The gauge further comprises a transmission line probe connected to the circuitry arrangements, the transmission line probe extending into the content in the tank and being adapted allow propagation of first and second transmission modes, and a feeding arrangement connected to couple electromagnetic signals into the probe in first and second propagation modes.

Abstract: A radar level gauge for determining the filling level of a product in a tank, comprising a transceiver for transmitting and receiving microwaves, processing circuitry connected to the transceiver and adapted to determine the filling level, an antenna connected to said transceiver and arranged to emit and receive microwaves through an opening of the tank, and a microwave transmissive sealing member adapted to cover said opening and to provide pressure sealing of the tank. The sealing member comprises a metal grid layer providing structural strength, which metal grid layer has sealed openings formed to allow transmission of microwaves. The tank opening is thus divided into a number of smaller openings by the metal grid, thereby improving the mechanical strength of the sealing member. At the same time, the sealing member is designed to maintain its pressure sealing properties, e.g. by suitable dielectric filling of the openings.

Abstract: A guided wave radar level gauge system, comprising a transmission line probe configured to support a first propagation mode such that it travels along the transmission line probe with a first propagation velocity exhibiting a first dependence on a dielectric constant of the surrounding medium, and support a second propagation mode such that it travels along the transmission line probe with a second propagation velocity exhibiting a second dependence, different from the first dependence, on the dielectric constant of the surrounding medium. The guided wave radar level gauge system further comprises processing circuitry connected to the transceiver for determining the filling level based on the reflected electromagnetic signal in the first propagation mode and the second propagation mode, and a known relation between the first dependence and the second dependence on the dielectric constant of the surrounding medium.

Abstract: A radar level gauging system for determining at least one process variable related to a distance to a surface of a product in a tank comprising transceiver circuitry, processing circuitry, a wave guiding structure arranged guide measurement signals towards the surface, and a radiator connected to the transceiver circuitry and arranged to emit the measurement signal into the wave guiding structure. The system further comprises a mode generator adapted to convert electromagnetic waves emitted from the radiator from a first propagation mode to a second propagation mode, wherein the mode generator includes a lens in the form of a body transparent to electromagnetic waves in the operating frequency range. With this design, electromagnetic waves having the first propagation mode emitted by the radiator into the lens will be reflected at least twice within the lens (first in the bottom surface and then in the upper surface).

Abstract: A method for measurement of a distance to a surface of a product kept in a tank method comprises transmitting a pulse train of distinct carrier wave pulses having a duration greater than 1 microsecond and shorter than 100 milliseconds, the pulse train has an average duty cycle of less than 50 percent, each pulse has a defined center frequency, selected according to a frequency scheme within a predetermined frequency range, greater than 5% of an average center frequency. The method further comprises correlating actual phase properties of received pulses with expected phase properties to provide an updated estimation of the distance. The present invention is based on transmitting a set of carrier wave pulses, each having a distinct frequency selected within a frequency range. The method is therefore referred to as a Frequency Modulated Pulsed Wave (FMPW).

Abstract: A radar level gauge using electromagnetic signals to determine a filling level of a product in a tank, comprising an electronics unit including transceiver circuitry, a signal propagation device arranged to direct electromagnetic signals into the tank and to return electromagnetic signals reflected from the tank, and a directional coupler. The gauge further comprises a wave guiding structure comprising a rod of a dielectric material. A mounting portion of the electronics unit defines an opening and is detachably mountable on the dielectric rod so that the rod extends through the opening and is at least partly surrounded by the opening. The mounting portion is further arranged to secure the circuitry portion relative the rod so that said directional coupler is in a position to couple signals between the transceiver circuitry and the rod. The radar level gauge according to the present invention facilitates replacement of an electronics unit, e.g. in case of malfunction or upgrades.

Abstract: A radar level gauge for determining the filling level of a product in a tank, comprising a transceiver for transmitting and receiving microwaves, processing circuitry connected to the transceiver and adapted to determine the filling level, an antenna connected to said transceiver and arranged to emit and receive microwaves through an opening of the tank, and a microwave transmissive sealing member adapted to cover said opening and to provide pressure sealing of the tank. The sealing member comprises a metal grid layer providing structural strength, which metal grid layer has sealed openings formed to allow transmission of microwaves. The tank opening is thus divided into a number of smaller openings by the metal grid, thereby improving the mechanical strength of the sealing member. At the same time, the sealing member is designed to maintain its pressure sealing properties, e.g. by suitable dielectric filling of the openings.

Abstract: A radar level gauge system using microwaves for measuring a level of a surface of a product in a container, comprising a waveguide arranged to extend into the product contained in the container, wherein a plurality of reference impedance transitions are arranged at known position along the waveguide and being configured to reflect a portion of transmitted electromagnetic signals back towards the transceiver. Preferably, each of the reference impedance transitions has a first reflection coefficient for the electromagnetic signals when the level of the surface is above the reference impedance transition and a second reflection coefficient for the electromagnetic signal when the level of the surface is below the reference reflector, the first reflection coefficient being substantially lower than the second reflection coefficient. According to this design, a higher accuracy of filling level measurements can be achieved.