A transistorized frequency synthesizer

The synthesizer provides 30 000 discrete frequencies between 2¿32 Mc/s in steps of 1 kc/s with the stability of the driving frequency standard, using the arithmetic processes of addition, subtraction, multiplication and division, with the most economical use of a set of readily available basic numbers. Use is made of the phase-locked loop principle. A variable frequency oscillator covers the 2¿32 Mc/s range and, for each desired frequency, a suitable arrangement of frequency conversion and filtering allows the oscillator to lock on a fixed frequency directly derived from the standard. Spurious signals and noise generated respectively by mixers and harmonic generators, are greatly attenuated, since the phase-locked loop acts as an ¿active filter¿. In particular the ¿catching range¿ of an automatic phase control loop is examined and a method is shown whereby this catching range can be greatly increased by very simple and economical means.