Frequency Multiplier A circuit in which the output signal frequency is an
integral multiple of the input signal frequency. Designers can economically
raise lower frequencies to higher frequencies without creating measurable
additive phase noise. Frequency doubler is widely used, such as the transmitter
using frequency doubler can make the main oscillator oscillate at a lower frequency
to improve the frequency stability; Frequency modulation equipment uses frequency
multiplier to increase frequency offset. In phase keying communicator, frequency
multiplier is an important component of carrier recovery circuit.