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Figure shows the block diagram of a wideband frequency modulator

Figure shows the block diagram of a wideband frequency modulator

Figure shows the block diagram of a wideband frequency modulator using the indirect method. This modulator is used to transmit audio signals containing frequencies in the range of 100 Hz to 15 kHz by a crystal-controlled oscillator. A second crystal-controlled oscillator supplies a sinusoidal wave of frequency 9.5 MHz to the mixer. The systems specification is as follows: Carrier frequency at the transmitter output, A?c = 100 MHz, minimum frequency at deviation, ?A? = 75 kHz, maximum modulation index in the phase modulator = 0.3 radians
(a) Calculate the frequency multiplication ratios n1 and n2 (preceding and following the mixer), which will satisfy these specifications.
(b) Specify the values of the carrier frequency and frequency deviation at the various points in the modulator of Figure.

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