Electric signal spectrum analysers including automatic frequency control

Claim 1

A MICROWAVE SIGNAL SPECTRUM ANALYSER INCLUDING A MIXER ARRANGED TO RECEIVE A SIGNAL TO BE ANALYSED, A LOCAL OSCILLATOR CONNECTED TO SAID MIXER SO AS TO DERIVE AN INTERMEDIATE FREQUENCY WHEN THE OUTPUT OF THE OSCILLATOR IS COMBINED WITH THE SIGNAL, A BROAD BAND INTERMEDIATE FREQUENCY AMPLIFIER CONNECTED TO THE OUTPUT OF THE MIXER AND RECEIVING SAID INTERMEDIATE FREQUENCY, A DISPLAY AND MEASURING CIRCUIT, A NARROW BAND INTERMEDIATE FREQUENCY AMPLIFIER, MEANS CONNECTING THE OUTPUT OF SAID BROAD BAND INTERMEDIATE FREQUENCY AMPLIFIER TO THE DISPLAY AND MEASURING CIRCUIT THROUGH THE NARROW BAND INTERMEDIATE FREQUENCY AMPLIFIER, AN AUTOMATIC FREQUENCY CONTROL CIRCUIT INTERCONNECTED BETWEEN THE OUTPUT OF THE BROAD BAND INTERMEDIATE FREQUENCY AMPLIFIER AND THE INPUT OF SAID LOCAL OSCILLATOR, SAID AUTOMATIC FREQUENCY CONTROL CIRCUIT INCLUDING A FREQUENCY DISCRIMINATOR SUPPLIED BY SAID INTERMEDIATE FREQUENCY AND FURNISHING A DIRECT VOLTAGE OUTPUT OF AN AMPLITUDE CORRESPONDING TO THE FREQUENCY OF THE DISCRIMINATOR INPUT SIGNAL, AND MEANS TO APPLY SAID DIRECT DISCRIMINATOR OUTPUT VOLTAGE DIRECTLY TO SAID LOCAL OSCILLATOR INPUT TO VARY THE LOCAL OSCILLATOR OUTPUT FREQUENCY SO AS TO MAINTAIN THE INTERMEDIATE FREQUENCY SUBSTANTIALLY CONSTANT, AN INDEPENDENTLY OPERATIVE SOURCE OF DIRECT VOLTAGE OF SAWTOOTH WAVE FORM, AND MEANS CONNECTING THE OUTPUT OF SAID SAWTOOTH VOLTAGE SOURCE DIRECTLY TO SAID LOCAL OSCILLATOR INPUT, THE SAWTOOTH FREQUENCY THUS BEING MAINTAINED CONSTANT INDEPENDENTLY OF THE NATURE OF THE ANALYZED SIGNAL, AND THE ACTUAL AMPLITUDE OF SAID SAWTOOTH VOLTAGE BEING COMPENSATED BY THE OUTPUT VOLTAGE OF SAID DISCRIMINATOR SO THAT THE RESPECTIVE OUTPUT VOLTAGE OF SAID LOCAL OSCILLATOR COMPLEMENTS THE RESPECTIVE SIGNAL TO BE ANALYSED IN SUCH A MANNER THAT THE OUTPUT OF SAID MIXER CORRESPONDS TO SAID INTERMEDIATE FREQUENCY.