A frequency multiplier is a nonlinear device that multiplies the frequencies of an input signal by a given factor. For example, an ideal square-law device would double both the carrier frequency and modulation index of an input signal. The document then provides an example of cascading a frequency multiplier and frequency converter. It asks the reader to calculate the output carrier frequency and peak frequency deviation of such a system given specific input frequencies and multiplication factors.

1. waves
Generation of FM
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A frequency multiplier is a nonlinear device designed to
multiply the frequencies of the input signal by a given factor.
For example, the input-output characteristic of an ideal square-
law device is
We conclude that both the
carrier frequency and the
modulation index have
If
been doubled.
the output is
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Nonlinear
input device
BPF output input X BPF output
Frequency multiplier cos 2πf1t
Frequency converter
In the frequency multiplier all spectral components of the input
signal are multiplied by themselves,
In the frequency converter all spectral components of the input
signal are multiplied by a sinusoid of a fixed frequency 4

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6. Find the carrier frequency and peak frequency deviation of FM
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transmitter shown above if f1= 200 KHz, f2 = 10.8 MHz, ∆f1 = 25
Hz, n1 = 64, n2 = 48.
Solution Notes :
•The Multiplier : multiplies f and ∆f by n
•The frequency converter : add/sub. on f, DOES NOT effect ∆f
Freq. multi. by n1
( 64 )
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Freq. converter
f2 = 10.8 MHz
Freq. multi. by n2
( 48 )
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