Rca1948FrequencyModu.. - The New Jersey Antique Radio Club

474 FREQUENCY MODULATION, Volume IE and the total current would lead E by 90 degrees, giving rise todecrease in the resonant frequency of the parallel circuit.If the electrons had emerged from the plates at position 6, thenthe total current would be I' as shown by the dashed vector in Figure3(c). In this case, the total current will have a resistive and reactivecomponent as indicated by (9).Calculation of Frequency ChangeIf a beam of electrons is to be used in the manner described aboveto control the resonant frequency of an oscillating system, the frequencyof the over-all system can be estimated by applying the Y ecalculated above to the equivalent circuit for the system, and calculatingthe frequency from conventional circuit theory.aLet the L C circuitshown in Figure 4 represent the equivalent circuit of the systembefore the beam is introduced. C is denned as the total equivalentcapacitance of the system, or more exactly,BEAML. U C, EZZZ2 VacFig. 4—Equivalent lumped circuit of resonant system.C V aEWvwhere E is the dielectric constant of the space, V ac is the radio-frequencyvoltage across the parallel planes between which the beammoves, and the integral is taken over the entire volume of the oscillatingsystem. C is then determined by the stored energy of the systemand the point at which the beam is introduced, for V ao depends, ingeneral, on the geometry of the system.To calculate the resonant frequency, writewhereB e + B c= (11)B e= electronic susceptance