Patent ID: 6885611

Claim:
A method for high-pass filtering for echo processing in a pulse echo level measurement system, said level measurement system having a transducer for transmitting pulses and receiving echoes and including a receiver for converting the received echoes into corresponding receive signals, said method comprising the steps of: (a) transmitting a transmit pulse to a reflective surface; (b) receiving an echo and converting the echo into a receive signal, said receive signal having a plurality of peaks and troughs; (c) defining a maximum signal profile, said maximum signal profile being an upper envelope of said receive signal; (d) defining a minimum signal profile, said minimum signal profile being a lower envelope of said receive signal; (e) defining a midpoint reference signal between said maximum signal profile and said minimum signal profile; and (f) subtracting said midpoint reference signal from said receive signal to generate a filtered signal, wherein said receive signal includes a sequence of samples, including a last sample, each of said samples having a magnitude, and wherein said step of defining a maximum signal profile includes setting the magnitude of said maximum signal profile equal to the magnitude of said last sample and, moving backwards in the sequence, comparing the magnitude of said maximum signal profile to the magnitude of each of said samples and setting said maximum signal profile to the magnitude of one of said samples if the magnitude of said one of said samples is greater than the magnitude of said maximum signal profile, thereby tracking the upper envelope of said receive signal.