Passive doppler fuze

Abstract

A passive proximity fuze. The inventive fuze ( ) is adapted to be mounted on a munition ( ) and includes a receiver ( ) adapted to lock on to a signal transmitted by a target transmitter ( ). The receiver ( ) detects a Doppler shift in the signal as the munition approaches the target. When a closest point of approach is reached the Doppler shift changes from increasing to decreasing. The inventive fuze ( ) includes a mechanism for detecting this change in the Doppler shift and provides a detonation signal in response thereto. In the illustrative embodiment, the receiver ( ) is an FM receiver. The mechanism for detecting a change in the Doppler shift may be implemented with discrete analog circuitry or digital circuitry. In an illustrative analog implementation, first and second resistive/capacitive networks (R C and R C ) are employed to compute a second derivative of the Doppler shift signal output by the receiver ( ). This signal is then amplified and thresholded to provide the output detonation signal. In an illustrative digital implementation, the output of the receiver ( ) is converted to digital and processed by a digital signal processor ( ). The DSP computes the second derivative of the Doppler shift signal output by the receiver ( ) in response to a stored program for computing same. The output of the DSP is the detonation signal. Hence, detonation is achieved at the closest point of approach of the munition ( ) to the target ( ) with an inexpensive passive solution ( ).