Pulse amplitude limiter for frequency control circuit of twt oscillator in frequencyagile radar system

Claim 1

IN A FREQUENCY AGILE RADAR SYSTEM HAVING A TRAVELING WAVE TUBE OSCILLATOR FOR PRODUCING RADIO FREQUENCY ENERGY AT A FREQUENCY DETERMINED BY THE VOLTAGE APPLIED TO A CONTROL CIRCUIT, APPARATUS FOR APPLYING VOLTAGE PULSES HAVING A CONSTANT REPETITION RATE AND A PULSE-TO-PULSE AMPLITUDE VARIATION TO SAID CONTROL CIRCUIT FOR KEYING SAID OSCILLATOR AND FOR PRODUCING A PULSE-TO-PULSE FREQUENCY VARIATION OF THE OSCILLATOR, SAID APPARATUS COMPRISING: A PLURALITY OF AMPLITUDE LIMITING CIRCUITS EACH HAVING AN INPUT CIRCUIT AND AN OUTPUT CIRCUIT AND EACH HAVING ADJUSTABLE MEANS FOR LIMITING THE OUTPUT VOLTAGE TO A PRESET VALUE DIFFERENT FROM THE PRESET VALUE OF THE OTHER CIRCUITS; A LOAD RESISTOR COMMON TO THE OUTPUTS OF SAID LIMITING CIRCUITS AND COUPLED INTO SAID OUTPUT CIRCUITS THROUGH DIODES THAT ISOLATE EACH LIMITING CIRCUIT FROM THE OTHERS; A ZENER DIODE CONNECTED IN SHUNT TO THE INPUT OF EACH LIMITING CIRCUIT AND HAVING A BREAKDOWN VOLTAGE SLIGHTLY GREATER THAN THE INPUT VOLTAGE REQUIRED TO REACH THE PRESET OUTPUT VOLTAGE LIMIT OF THE CIRCUIT; MEANS FOR APPLYING THE PULSES OF A SERIES OF VOLTAGE PULSES OCCURRING AT A CONSTANT PULSE REPETITION RATE TO SAID LIMITING CIRCUIT INPUTS IN ACCORDANCE WITH A PREDETERMINED PROGRAM, THE AMPLITUDE OF EACH VOLTAGE PULSE BEING NOT LESS THAN THAT REQUIRED TO REACH THE OUTPUT LIMIT OF THE LIMITING CIRCUIT TO WHICH IT IS APPLIED; AND MEANS FOR APPLYING THE RESULTING LIMITED VOLTAGE PULSES APPEARING ACROSS SAID LOAD RESISTOR TO THE CONTROL CIRCUIT OF SAID OSCILLATOR.