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High frequency, short pulse, band limited radar pulse generator for ultrashort range radar systems

  • US 3,940,696 A
  • Filed: 11/18/1974
  • Issued: 02/24/1976
  • Est. Priority Date: 11/18/1974
  • Status: Expired due to Term
First Claim
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1. A band-limited RF pulse generator for ultrashort range pulse radar systems comprising:

  • an RF switch, said switch including a varactor diode;

    means for generating a continuous RF signal;

    means coupling the RF signal to the RF switch, the RF switch normally attenuating the RF signal and being responsive to a voltage supplied to the varactor diode for transmitting the RF signal;

    a voltage pulse generator, said voltage pulse generator including an avalanche transistor having base, emitter and collector electrodes, means for biasing the avalanche transistor for operation in its avalanche region, the avalanche transistor switching from an off state to an on state when the voltage across its emitter and collector electrodes exceeds a specified level, a delay line having a first end coupled to the avalanche transistor and the means for biasing the avalanche transistor and an open end, the delay line being charged by the means for biasing the avalanche transistor, the voltage charge on the delay line comprising the voltage across the emitter and collector electrodes of the avalanche transistor, the avalanche transistor being switched from its off state to its on state to discharge the delay line, generate a voltage transient on the delay line and initiate an output voltage pulse when the delay line is charged to a voltage greater than the specified level, the voltage transient on the delay line propagating to and reflecting from the open end thereof and returning to the avalanche transistor to switch the avalanche transistor from its on state to its off state and terminate the output voltage pulse and initiate recharging of the delay line, the delay line having a length so that the time for the voltage transient to propagate to and reflect from the open end of the delay line and return to the avalanche transistor being just greater than the time for the avalanche transistor to switch from its off state to its on state; and

    means coupling the voltage pulses from the voltage pulse generator to the varactor diode, whereby the voltage pulses drive the RF switch to transmit the RF to generate ultrashort pulse, band-limited RF pulses.

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