QUADRATIC FREQUENCY MODULATION IN SONAR SYSTEMS

摘要

A method for measuring a range of a target illuminated by an active system transmitting pulsed signals includes the following steps. Modulating the frequency of the pulsed signals by employing quadratic frequency modulation (QFM) having a predefined frequency bandwidth. Signals reflected from the target are received in time intervals separating between the ends of the transmitted pulses to the leading edge of the transmitted pulse immediately following the one transmitted pulse. Comparing the absolute value of the output of a normalized filter matched to the QFM applied to the received signals with a detection threshold, and comparing the time in which the threshold is exceeded to a calibration scale.