Adaptive echo threshold

A radar level gauge for determining a process variable of product in a tank, said gauge comprising:

• transceiver circuitry configured to:
• generate and transmit an electromagnetic transmit signal ST,
• receive an electromagnetic return signal reflected from the tank, and
• combine the return signal with the transmit signal to form a tank signal, said tank signal including a plurality of peaks representing echoes from the interior of said tank, one of said peaks representing a surface echo, and at least one peak caused by a ghost echo in a neighborhood of said surface echo;
• a tank signal filter receiving said tank signal as input and providing an echo threshold profile, said echo threshold profile having at least one local maximum substantially coinciding with one of said peaks in said tank signal;
• and
• processing circuitry configured to:
• distinguish a surface echo from other echoes in the tank signal, and
• determine said process variable based on said surface echo
• wherein said processing circuitry is configured to use said echo threshold profile to disregard peaks in said tank signal which are associated with ghost reflections.