Cloud altitude measuring means

Claim 1

Means for determining the existence of an object within a predetermined range interval, said means including: a signal emitter for emitting a series of signal pulses for each range interval; a detector for receiving echo signal pulses originating from said emitted signal pulses; first and second integrators respectively responsive to an echo signal pulse and to noise and connectable to said detector for integrating the power of the received echo signal pulses; control devices for connecting said first integrator to said detector during a first control pulse time and for connecting said second integrator to said detector during a second control pulse time; comparing means connected to said first and second integrator to determine the difference between the power of the echo signal pulses integrated by the first integrator and the power of the echo signal pulses integrated by the second integrator; a level detector connectable to said comparing means and arranged to deliver an indicating pulse when said difference exceeds a predetermined value; a first time delay circuit for controlling the connection of said first integrator to said detector a first time interval after each emitted signal pulse in said series of signal pulses; a second time delay circuit for controlling the connection of said second integrator to said detector a second time interval after each emitted signal pulse in said series of signal pulses, and said second time interval being longer than said first time interval; a third time delay circuit for controlling the resetting of the integrators by transmitting a control pulse to said integrators a third time interval after the last signal pulse in each series of signal pulses; and a fourth time delay circuit for controlling the connection of said level detector to said comparing means a fourth time interval after the last pulse in said series of signal pulses is emitted, said fourth time interval being shorter than said third time interval.