Frequency synthesis involves which of the following processes?

Frequency synthesis is a process used to generate a frequency that is not directly available from a stable frequency source. This is primarily accomplished through techniques like heterodyning, where two frequencies are mixed to produce new frequencies. The resulting frequency can also be fine-tuned by selecting different frequency components, which is key in applications such as telecommunications and signal processing.

Heterodyning works by taking an input signal and combining it with another frequency (often from a stable oscillator). This mixing operation creates sum and difference frequencies. The relevant frequency can then be filtered out, allowing the desired synthesized frequency to be utilized effectively. Frequency selection is crucial in ensuring that the specific frequency of interest is brought to the forefront while unwanted frequencies are eliminated.

In contrast to the other options, which involve distinct processes that do not directly relate to frequency synthesis, the correct answer encapsulates the essence of how synthesized frequencies are generated and manipulated for practical use in various applications, particularly in electronic communications and radio frequency technologies.