Range control system

A RANGE CONTROL SYSTEM positioned within a stationary housing mounted at a reference location at a distance from a target and powered from a voltage source referenced to a reference potential, such as ground, to provide a signal to indicate the distance of a target from the location of said stationary housing, the RANGE CONTROL SYSTEM comprising:

• a MAIN PULSE OSCILLATOR for providing a clock signal;
• a TRANSMITTER RECEIVER CIRCUIT MEANS responsive to said clock signal, for driving a transducer to directionally transmit an acoustic pulse signal to the target, for receiving an echo from the target and for providing an amplified echo signal;
• said TRANSMITTER RECEIVER CIRCUIT MEANS having;
• a TRANSDUCER DRIVE CIRCUIT responsive to said clock signal for providing a predetermined number of drive pulses to said transducer in response to each clock signal and for providing electrical echo signals at an echo signal output in response to each acoustic pulse transmission;
• and
• an AMP FILTER CIRCUIT coupled to said TRANSDUCER DRIVE CIRCUIT echo signal output for amplifying electrical echo signals and for providing amplified echo signals in response to said electrical echo signal,
• a DYNAMIC ATTENUATOR CIRCUIT coupled to said TRANSDUCER DRIVE CIRCUIT echo signal output to receive said echo signal and being responsive to said clock signal for providing predetermined decreasing attenuation to said electrical echo signals with increasing time subsequent to said clock signal, said DYNAMIC ATTENUATOR CIRCUIT having;
• a DIODE CLAMP having a first and second terminal, said firt terminal being coupled to said TRANSDUCER DRIVE CIRCUIT echo signal output and said second terminal being coupled to said reference potential, such as ground;
• and
• a DIODE BIAS CIRCUIT responsive to said clock signal for providing a predetermined time dependent unipolar decreasing bias current to said DIODE CLAMP first terminal to bias said diode clamp to provide diminishing attenuation of said electrical echo signal with increasing time,
• said DIODE BIAS CIRCUIT having;
• a resistor and a capacitor, each having a first and second terminal, a first and second PNP transistor, each having a collector, a base and an emitter, and
• a switching means having a conduction channel having a first and second terminal, said switching means being responsive to said clock signal for driving said conduction channel from a non-conductive state into a conductive state;
• said first and second PNP transistor emitters being coupled to said voltage source, said first and second PNP transistor bases being connected to each other and to the collector of said second PNP transistor and to said resistor first terminal,
• said capacitor first terminal being coupled to said resistor second terminal and to said switching means conduction channel first terminal,
• said capacitor second terminal being coupled to said switching means conduction channel second terminal and to said reference potential,
• said first PNP transistor collector coupled to said DIODE CLAMP FIRST TERMINAL;
• whereby said first and second PNP transistors form a current mirror having first and second output currents from first and second collectors, said first mirror current from said first collector biasing said DIODE CLAMP, and said second mirror current being having a maximum value immediately after the turn off of said switching means immediately after said clock signal, said second mirror current being exponentially limited by the rising voltage on said capacitor as current passes thru said resistor to charge said capacitor;
• a TIMING CIRCUIT MEANS responsive to said clock signal for providing a range gate signal characterized to start with each clock signal and to have a predetermined duration characterized to provide a time for said acoustic pulse to travel to said target and for said echo to return from said target;
• said TIMING CIRCUIT MEANS having;
• a RING BLANKING GATE signal source responsive to said clock signal for providing a ring blanking gate signal commencing with each clock signal, said ring blanking gate signal having a duration longer than the tailoff of said acoustic pulse;
• and,
• OUTPUT SIGNAL MEANS means responsive to the range gate signal and to said amplified echo signal for providing an alarm signal to indicate that an echo signal is received prior to the termination of said range gate signal.