An apparatus for processing pulses in ATCRBS/Mode S interrogations
includes an antenna for receiving a radio frequency interrogation signal.
The radio frequency interrogation signal is downconverted by a
downconverter to an intermediate frequency signal. The intermediate
frequency signal is converted to a digitized interrogation signal by an
analog-to-digital converter. A processing unit, coupled to the
analog-to-digital converter, detects a pulse peak in the digitized
interrogation signal using a moving threshold to locate the peak pulse
between a first fixed threshold and a second fixed threshold.