Figure shows the frequency-determining network of a voltage-controlled oscillator. Frequency modulation is provided is produced by applying the modulating signal A_m sin (2??_mt) plus a bias V_b to a pair of varactor diodes connected across the parallel combination of a 200-?H inductor and 100-pF capacitor. The capacitor of each varactor diode is related to the voltage V (in volts) applies across its electrodes by C = 100V^-1/2 pF. The unmodulated frequency of oscillation is 1 MHz. The VCO output is applied to a frequency multiplier to produce an Fm signal with a carrier frequency of 64 MHz and a modulation index of 5. Determine?

(a) The magnitude of the bias voltage V_b and

(b) The amplitude A_m of the modulating wave, given that ?_m = 10 kHz.

Transcribed Image Text:

200 100 pF V• Ag sin (2mfm)