Device for range cut-off by frequency selection in multiple modulation fuzes

Claim 2

A radio fuze system comprising means for providing a signal frequency modulated by at least two separate frequencies, means for transmitting said signal, means for receiving a return signal from a target, a mixing circuit having first and second inputs coupled to said transmitting and receiving means respectively for producing an output signal comprising a spectrum of coherent Doppler wave portion plus an incoherent wave portion due to range noise, and spectral comparison circuit means coupled to the output of said mixing circuit for producing an output signal in response to the output signal of said mixing circuit when the energy level of the coherent Doppler wave portion of said output signal is of a predetermined amount greater than the incoherent portion of said output signal.

Claim 3

An FM fuze system comprising a first source of periodic waves, a second source of band limited white noise, means for simultaneously frequency modulating a carrier frequency with signals from said first and second sources, means for transmitting the frequency modulated signal provided by said last-mentioned means, means for receiving said frequency modulated signal reflected from a target, a mixing circuit having first and second inputs coupled to said transmitting and receiving means respectively for producing an output signal having a balanced spectrum of coherent Doppler wave portion and incoherent wave portion when said target is out of range and for producing an output signal having an unbalanced spectrum with the amplitude of the coherent Doppler wave portion being greater than the incoherent wave portion, and circuit means coupled to said mixing circuit for amplifying and comparing the spectral distribution of the energy output of the mixing circuit to produce a firing Signal in response to the unbalanced condition thereof.

Claim 4

An FM fuze system comprising a first source of periodic waves, a second source of band limited white noise, means for simultaneously frequency modulating a carrier frequency with signals from said first and second sources, means for transmitting the frequency modulated signal provided by said last-mentioned means, means for receiving said frequency modulated signal reflected from a target, a mixing circuit having first and second inputs coupled to said transmitting and receiving means respectively for producing an output signal having a balanced spectrum of coherent Doppler wave portion and incoherent wave portion when said target is out of range and for producing an output signal having an unbalanced spectrum with the amplitude of the coherent Doppler wave portion being greater than the incoherent wave portion, and circuit means coupled to said mixing circuit for amplifying and comparing the spectral distribution of the energy output of the mixing circuit to produce a firing Signal in response to the unbalanced condition thereof.

Claim 5

An FM fuze system responsive to in-range targets in the presence of large return signals from out-of-range objects comprising means for providing a signal frequency modulated by at least two separate frequencies, means for transmitting said signal, means for receiving the return echo of said signal modified by the relative movement between the fuze and a target, a mixing circuit having first and second inputs coupled to said transmitting and receiving means respectively for producing an output signal comprising a spectrum of coherent Doppler wave portion plus an incoherent wave portion due to range noise, a band pass amplifier coupled to the output of said mixing circuit having a band width sufficient to pass said Doppler wave portion and said incoherent wave portion of said output signal, and a frequency discriminating means coupled to said amplifier for producing a firing signal when the sum of the energy of the Doppler wave portion and the energy of the incoherent wave portion is greater by a predetermined amount than the energy level of said incoherent wave portion of said output signal.

Claim 6

An FM fuze system responsive to in-range targets in the presence of large return signals from out-of-range objects comprising means for providing a signal frequency modulated by at least two separate frequencies, means for transmitting said signal, means for receiving the return echo of said signal modified by the relative movement between the fuze and a target, a mixing circuit having first and second inputs coupled to said transmitting and receiving means respectively for producing an output signal comprising a spectrum of coherent Doppler wave portion plus an incoherent wave portion due to range noise, a band pass amplifier coupled to the output of said mixing circuit having a band width sufficient to pass said Doppler wave portion and said incoherent wave portion of said output signal, and a frequency discriminating means coupled to said amplifier for producing a firing signal when the sum of the energy of the Doppler wave portion and the energy of the incoherent wave portion is greater by a predetermined amount than the energy level of said incoherent wave portion of said output signal.