Figure 2-2.
Oscillator circuit, frequency-modulated
by a reactance modulator.
2-2.
USE OF FM OSCILLATOR
An FM oscillator establishes the fundamental frequency-modulated carrier signal
necessary for transmission.
The requirements for producing an FM carrier using
transistors are the same as those for electron tubes. A block diagram of a typical
FM transmitter with waveforms is shown in figure 2-3. The audio signal (modulating
signal) is applied to the oscillator stage. The output of the oscillator stage is
an AM and FM carrier signal. The limiter stage removes the AM and its output is an
FM carrier signal with constant amplitude.
The multiplier stage increases the
frequency to the desired transmitting frequency.
The power amplifier stage
Figure 2-3.
FM transmitter, block diagram showing waveforms.
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