Techniques of frequency synthesis

A brief outline of the initial development of synthetiser techniques is followed by a description of two early types, and reference is given to a comprehensive survey in the late 1960s. The concurrent advance in solid-state technology has had a major impact on synthetiser development, mainly in regard to divider- and voltage-controlled-oscillator techniques, resulting in improved performance combined with reductions in size, weight, power consumption and cost. For economic viability, synthetisers must be designed for specific systems, and a section is devoted to the requirements for several systems. To meet such requirements, descriptions are given of the techniques used in a number of synthetisers, both variable-divider/voltage-controlled oscillator types and others. Although mainly in the h.f. band, examples are also given in the audio, v.h.f. and u.h.f. bands. Economic aspects are considered in regard to relative performance and to equipment replaced by synthetisers. As all synthetiser output frequencies are derived from a single master source, the reliability of this oscillator is of paramount importance. Finally, it is noted that miniaturisation has tended to reduce v.c.o. output to a level which makes noise-performance requirements difficult to achieve.