초록 ▼

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, ea

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.

대표청구항 ▼

What is claimed is: 1. A method for processing a reflected microwave signal used to determine at least one process variable of a content in a tank, wherein said reflected signal has been generated by a radar level gauge system arranged to transmit microwaves towards the material in the tank during

What is claimed is: 1. A method for processing a reflected microwave signal used to determine at least one process variable of a content in a tank, wherein said reflected signal has been generated by a radar level gauge system arranged to transmit microwaves towards the material in the tank during consecutive measurement cycles, and receive a reflection of said microwave signal as a tank signal comprising consecutive tank signal portions each corresponding to a measurement cycle, said method comprising: processing each portion of the received tank signal in 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 separate predefined propagation distance range. 2. The method according to claim 1, wherein said processes are performed in parallel. 3. The method according to claim 1, wherein the received tank signal is a frequency domain tank signal, and wherein a frequency spectrum is determined by Fourier transforming said tank signal. 4. The method according to claim 1, wherein at least one of said processes includes subtracting a compensation signal from the tank signal, said compensation signal including background information about the specific region. 5. The method according to claim 4, wherein said compensation signal CSn(t) is formed by low-pass filtering a tank signal received when no surface reflection occurred inside the specific region. 6. The method according to claim 5, wherein an updated compensation signal CSn*(t) is formed by combining said compensation signal CSn(t) with a previous compensation signal CSn-1(t), according to description="In-line Formulae" end="lead"CSn*(t)=aCSn(t)+(1-a )CSn-1(t),description="In-line Formulae" end="tail" where a is a weight factor between zero and 1. 7. The method according to claim 1, wherein at least one of said processes is a near zone detection process, adapted to detect a surface reflection in a near zone of the tank. 8. The method according to claim 7, wherein said near zone detection process comprises: for each portion of the received tank signal, subtracting a compensation signal CSn(t) based on a near zone signature of the tank from said received tank signal, and detecting any presence of a peak with an amplitude greater than a predetermined threshold in the near zone, monitoring the number of measurement cycles in which a peak occurs, and identifying a surface reflection based on said peak. 9. The method according to claim 8, wherein said step of monitoring includes incrementing a counter for every measurement cycle in which a peak is detected, and decrementing said counter for every measurement cycle in which no peak is detected. 10. The method according to claim 8, wherein said peak is detected in a frequency spectrum determined by Fourier transforming said subtraction result. 11. The method according to claim 1, wherein said tank signal is a time domain reflectometry (TDR) signal. 12. A radar level gauge system used for determining a process variable of a content in a tank, comprising: a microwave transmitter for generating a microwave signal, means for guiding said microwave signal into the tank, and allowing it to propagate towards the content in the tank, a microwave receiver for receiving a reflection of said microwave signal from the tank as a tank signal, comprising consecutive tank signal portions each corresponding to a measurement cycle, processing circuitry arranged to determine said process variable based on each portion of said tank signal, said processing circuitry being adapted to perform a plurality of processes on each portion of said tank signal, each process being adapted to determine a process variable in a specific region of the tank, each specific region corresponding to a separate predefined propagation distance range. 13. The radar level gauge according to claim 12, wherein said microwave signal is a frequency domain signal. 14. The radar level gauge according to claim 12, wherein said tank signal is a time domain reflectometry (TDR) signal. 15. The radar level gauge according to claim 12, wherein said signal guiding and propagating means include a free radiating antenna arranged inside the tank. 16. The radar level gauge according to claim 12, wherein said signal guiding and propagating means include a probe extending into the tank. 17. The radar level gauge according to claim 12, wherein at least one of said processes includes means for subtracting a compensation signal from the tank signal, said compensation signal including background information about the specific region. 18. The radar level gauge according to claim 12, wherein at least one of said processes is a near zone detection process, adapted to detect a surface reflection in a near zone of the tank. 19. The radar level gauge according to claim 18, wherein said near zone detection process comprises: means for subtracting a compensation signal CSn(t) based on a near zone signature of the tank from said received tank signal, means for detecting any presence of a peak with an amplitude greater than a predetermined threshold in the near zone, means for monitoring the number of measurement cycles in which a peak occurs, and means for identifying a surface reflection based on said peak. 20. The radar level gauge according to claim 19, wherein said monitoring means includes a counter arranged to be incremented for every measurement cycle in which a peak is detected, and decremented for every measurement cycle in which no peak is detected. 21. The radar level gauge according to claim 19, wherein said peak detection means are arranged to form a frequency spectrum by Fourier transforming a result from said subtraction means.