Abstract: A radar level gauge system comprising a first transceiver; a second transceiver; an antenna arranged to radiate a first transmit signal generated by the first transceiver and a second transmit signal generated by the second transceiver, and to receive a first reflection signal and a second reflection signal; a tubular waveguide to guide the transmit signals towards the interface, and to guide the reflection signals back towards the antenna; a plurality of signal interacting structures arranged at different levels along a the tubular waveguide, to selectively interact with the second transmit signal to contribute to the second reflection signal; and processing circuitry to determine a level of the interface between liquid phase product and vapor phase product based on a relation between the first transmit signal and the first reflection signal, and a density distribution based on a relation between the second transmit signal and the second reflection signal.

Abstract: A radar level gauge system comprising a first transceiver; a second transceiver; an antenna arranged to radiate a first transmit signal generated by the first transceiver and a second transmit signal generated by the second transceiver, and to receive a first reflection signal and a second reflection signal; a tubular waveguide to guide the transmit signals towards the interface, and to guide the reflection signals back towards the antenna; a plurality of signal interacting structures arranged at different levels along a the tubular waveguide, to selectively interact with the second transmit signal to contribute to the second reflection signal; and processing circuitry to determine a level of the interface between liquid phase product and vapor phase product based on a relation between the first transmit signal and the first reflection signal, and a density distribution based on a relation between the second transmit signal and the second reflection signal.

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 two-channel directional antenna for use in a radar level gauge. The antenna comprises a partition wall dividing the antenna into a first partition for emitting an electromagnetic transmit signal, and a second partition for receiving an electromagnetic echo signal, the partition wall having an outer potion located downstream in a direction of radiation of the antenna. The partition wall comprises an electromagnetic de-coupling structure, which is arranged to reduce any leakage of electromagnetic energy from the transmit signal into the echo signal. The electromagnetic de-coupling structure according to the present invention ensures that the leakage of transmit signal into the received signal is reduced to a satisfactory level.

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 two-channel directional antenna for use in a radar level gauge. The antenna comprises a partition wall the antenna into a first partition for emitting an electromagnetic transmit signal, and a second partition for receiving an electromagnetic echo signal, the partition wall having an outer potion located downstream in a direction of radiation of the antenna. The partition wall comprises an electromagnetic de-coupling structure, which is arranged to reduce any leakage of electromagnetic energy from the transmit signal into the echo signal. The electromagnetic de-coupling structure according to the present invention ensures that the leakage of transmit signal into the received signal is reduced to a satisfactory level.

Abstract: A radar level gauging system comprising a microwave unit for transmitting and receiving first microwaves having a first and second distinguishable characteristics, a microwave absorber adapted to be arranged in a bottom region of the tank and adapted to absorb electromagnetic energy of microwaves having one of the first and second characteristics, and processing circuitry adapted to determine the product level based on a relationship between transmitted and received microwaves. The system thus emits microwaves in two channels, and the absorber is arranged to absorb energy in only one of the channels. Using the absorbed channel, it is possible to obtain a measurement with very limited interference from the bottom, which thus will be accurate also for levels close to the bottom. Using the unabsorbed channel, it is possible to obtain a reference measurement of the distance to the reflecting part of the absorber, thus enabling verification of the of the system.

Abstract: A method and a system for processing a reflected microwave signal generated by a radar level gauge system arranged to transmit microwaves towards the material in the tank, and receive a reflection of said microwave signal as a tank signal. The tank signal is processes by a plurality of processes, each process being adapted to determine a process variable in a specific region of the tank, each specific region corresponding to a predefined propagation distance range. Such multi-processing of the received tank signal has the advantage that each process can be optimized to that particular region of the tank. More specifically, a process concerned with a particular region of tank only needs to treat a portion of the tank signal.

Abstract: A radar level gauging system comprising a microwave unit for transmitting and receiving first microwaves having a first and second distinguishable characteristics, a microwave absorber adapted to be arranged in a bottom region of the tank and adapted to absorb electromagnetic energy of microwaves having one of the first and second characteristics, and processing circuitry adapted to determine the product level based on a relationship between transmitted and received microwaves. The system thus emits microwaves in two channels, and the absorber is arranged to absorb energy in only one of the channels. Using the absorbed channel, it is possible to obtain a measurement with very limited interference from the bottom, which thus will be accurate also for levels close to the bottom. Using the unabsorbed channel, it is possible to obtain a reference measurement of the distance to the reflecting part of the absorber, thus enabling verification of the of the system.

Abstract: A method and a system for processing a reflected microwave signal generated by a radar level a gauge system arranged to transmit microwaves towards the material in the tank, and receive a reflection of said microwave signal as a tank signal. The tank signal is processes by a plurality of processes, each process being adapted to determine a process variable in a specific region of the tank, each specific region corresponding to a predefined propagation distance range. Such multi-processing of the received tank signal has the advantage that each process can be optimized to that particular region of the tank. More specifically, a process concerned with a particular region of tank only needs to treat a portion of the tank signal.

Abstract: An antenna in a radar level gauge for determining the level of the surface of a medium stored in a tank. The antenna has a first and a second electrically conductive layer, and between the conductive layers a dielectric layer. The second of the conductive layers is provided with a number of holes in a predetermined pattern. Leading to the center of the dielectric layer is a transmission line. The microwaves from a radar unit in the radar level gauge are supplied to the dielectric layer in the antenna via the transmission line and transmitted out in a radial direction from a feed point in the dielectric layer that acts as a waveguide. Via said holes in the second conductive layer a microwave beam radiates out. Due to matching of the phase of the microwave and the placing of the individual holes in the pattern that the holes form, a predominant waveguide mode of the desired order is obtained.

Abstract: A radar level gauge for measuring the level of a surface of a product stored in a tank by use of radar. The radar transmits microwaves towards the surface and receives microwaves reflected by the surface and is adapted to transmit and receive microwaves within two widely separated frequency bands. Widely separated frequency bands are chosen to utilize the differences in attenuation due to foam on the surface and the differences in beam-width or other disturbances. The ratio between the center frequencies of the two widely separated frequency bands can be quantified as at least greater than 1.5:1 or preferably greater than 2:1.

Abstract: A method for radar-based gauging of the level of a substance in a tank (13) having at least one interfering structure (16a-c), comprises the steps of: (i) transmitting a microwave signal in a plurality of radiation lobes (15a-b; 15a-d), each of which being individually directed towards the substance and at least one of which being directed towards the interfering structure; (ii) for each of the radiation lobes detecting temporally resolved the microwave signal as reflected against the substance, and for at least one of the lobes detecting the microwave signal as reflected against the interfering structure; (iii) based on signal strengths of the detected microwave signals, distinguishing the detected microwave signals, which have been reflected against the substance; and (iv) based on a propagation time of at least one of the microwave signals distinguished as those, which have been reflected against the substance, calculating the level of the substance.

Abstract: A method for radar-based gauging of the level of a substance in a tank (13) having at least one interfering structure (16a-c), comprises the steps of: (i) transmitting a microwave signal in a plurality of radiation lobes (15a-b; 15a-d), each of which being individually directed towards the substance and at least one of which being directed towards the interfering structure; (ii) for each of the radiation lobes detecting temporally resolved the microwave signal as reflected against the substance, and for at least one of the lobes detecting the microwave signal as reflected against the interfering structure; (iii) based on signal strengths of the detected microwave signals, distinguishing the detected microwave signals, which have been reflected against the substance; and (iv) based on a propagation time of at least one of the microwave signals distinguished as those, which have been reflected against the substance, calculating the level of the substance.

Abstract: A radar level gauge for measuring the level of a surface of a product stored in a tank by use of a radar, where said radar transmits microwaves towards said surface and receives microwaves reflected by said surface and wherein said radar is adapted to transmit and receive said microwaves within two widely separated frequency bands. Widely separated frequency bands are chosen to utilize the differences in attenuation due to foam on the surface and the differences in beam-width or other disturbances. The ratio between the center frequencies of the two widely separated frequency bands can be quantified as at least greater than 1.5:1 or preferably greater than 2:1.

Abstract: Radar antenna (1) for the transmission and reception of radar waves (4) for measuring the level of a surface of a liquid enclosed in a tank, wherein the radar antenna (1) is arranged above the surface (3a) of the liquid and substantially directed downwards towards said surface and said level determined by evaluation of the time lapsed between the transmission and reception of a signal included in said radar waves and wherein said radar antenna (1) has a front surface (1a) for transmission and reception of said radar waves, wherein said antenna (1) is a planar antenna having a sheet arranged on the surface (1a) of the antenna, wherein said sheet has a sheet surface (1b) between said antenna front surface (1a) and the surface (3a) of the liquid and said sheet surface (1b) being arranged in a predetermined angle &agr; being greater than 0° in relation to the horizontal plane H, whereby a fluid occurring on the surface (1b) of the sheet is drained off by means of gravity.

Abstract: The present invention relates to a device in a level gauging system comprising an antenna using radar waves to gauge a level of a surface of a fluid kept in a container. The antenna is arranged above the fluid surface and comprises a plane surface facing the fluid surface and being substantially parallel with the fluid surface. The plane surface has means for transmitting radar waves towards the fluid surface and means for receiving reflected radar waves from the fluid surface in order to gauge the fluid level. The antenna comprises a radome which at least partially covers the plane surface and is shaped such that condensed fluid is directed away from the antenna by force of gravity. A thermally insulating filling material is provided between the radome and the plane surface.