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

• Current Assignee: General Motors Corporation (General Motors Company)
• Original Assignee: General Motors Corporation (General Motors Company)
• Inventors: Nagy, Louis L.
• Primary Examiner(s): Mayer, Albert J.
• Application Number:
  US05/525,004
• Time in Patent Office: 463 Days
• Field of Search: 325/120, 325/121, 325/125, 325/129, 325/130, 325/141, 343/17.1 R
• US Class Current: 342/202
• CPC Class Codes: G01S 13/0209 Systems with very large relative bandwidth, i.e. larger than 10 %, e.g. baseband, pulse, carrier-free, ultrawideband

Abstract

An RF pulse generator including a voltage pulse generator comprised of an avalanche transistor biased for operation in its avalanche region. A delay line coupled to the avalanche transistor causes the avalanche transistor to switch between its on and off states to generate repeated high voltage subnanosecond voltage pulses. These pulses control a varactor diode RF switch supplied with an RF signal to generate subnanosecond coherent RF pulses which are transmitted and detected in an ultrashort range radar system.

Claims

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.

2. A high repetition rate, ultrashort pulse, band-limited RF pulse generator for short 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 attenuating the RF signal in a manner directly proportional to the magnitude of the reverse bias of the varactor diode;

means for applying a reverse bias voltage across the varactor diode;

a pulse generator, said pulse generator including an avalanche transistor having base, emitter and collector electrodes, means for applying a negative bias voltage to the base electrode, means for supplying a positive bias voltage to the collector electrode through a resistor, 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 less than the positive bias voltage, a delay line having a first end coupled to the collector electrode and open end and having an impedance much less than the impedance of the resistor, the delay line being charged by the positive bias voltage through the resistor, the avalanche transistor being switched from its off state to its on state to discharge the delay line, generate a voltage transient of the delay line and initiate an output voltage pulse at the emitter electrode 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 collector electrode to reduce the collector electrode current and cause the avalanche trnasistor to switch from its on state to its off state and terminate the output voltage pulse and initiate recharging of the delay line through the resistor, the delay line having a length so that the time for the voltage transient to propagate to and reflect from the open end and return to the collector electrode being just greater than the time for the avalanche transistor to switch from its off state to its on state;

means coupling the voltage pulses from the emitter electrode across the varactor diode to cause the RF switch to transmit the RF signal coupled thereto, each voltage pulse having a magnitude greater than the reverse bias voltage on the varactor diode, said magnitude being such that the RF signal transmitted by the RF switch during a respective voltage pulse does not dwell at its peak level; and

a radar load, said load including the RF switch and having an impedance from the emitter electrode that is less than the impedance of the delay line, whereby the voltage pulses drive the RF switch to transmit high repetition rate, ultrashort, band-limited RF pulses.