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LADAR RECEIVER WITH ENHANCED SIGNAL TO NOISE RATIO AND METHOD

  • US 20180364332A1
  • Filed: 11/01/2016
  • Published: 12/20/2018
  • Est. Priority Date: 11/01/2016
  • Status: Active Grant
First Claim
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1. A laser receiver comprising:

  • a sensor comprising a photosensitive region and outputting a photocurrent;

    a first amplifier configured to amplify the photocurrent operatively connected to the sensor;

    the first amplifier comprising a first gate, a first source and a first drain, the operative connection between the sensor and the first gate being configured to minimize inductance;

    the first gate being operatively biased by at least one first biasing resistor;

    a first subcircuit operatively connected between the first drain and the first gate;

    the first subcircuit comprising, in series;

    a first resistor, a first inductor and a decoupling capacitor;

    the first resistor effecting the photocurrent gain of the amplifier;

    the first inductor effecting the bandwidth; and

    the decoupling capacitor being configured to allow the first amplifier bias to be established by the at least one first biasing resistor;

    the impedance of the first gate being high enough such that only a small proportion of the current from the sensor passes into the first gate and through the first amplifier while a significantly larger portion passes through the first subcircuit;

    an inductor connecting the gate to the at least one biasing resistor with high impedance at the receiver operating frequency;

    a second amplifier comprising a second gate with a gate impedance greater than 200 ohms operatively connected to the first drain;

    at least one second biasing resistor connected to the second gate with high impedance for the purpose of decreasing the load impedance on the first amplifier and thus increasing the voltage gain of the first amplifier; and

    thus enabling an increase in the value of the first resistor that in-turn improves the signal-to-noise of the amplifier;

    the first and second amplifiers having a combined bandwidth sufficient to pass a modulated photocurrent at a frequency up to 500 MHz;

    the second amplifier comprising an output configured to be operatively connected to a processing unit and a display unit displaying output from the processing unit in the form of pixels, the display being of sufficient quality to display an image of a target at 1000 meters;

    whereby the receiver is configured to receive light reflected from a target illuminated by a laser configured to emit light at an intensity safe for human eyes and wherein a target is discernible in a range from 0.3 to 1000 meters.

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