A new technique of frequency synthesis

The paper describes a frequency synthesizer controlled by BCD logic which combines the advantages of direct synthesis - low levels of parasitic and phase noise, and rapid switching - with the advantages of indirect synthesis - low cost and simplicity. BCD synthesis achieves these advantages by: (1) reduction of the 10 frequencies required by the line generator in decimal synthesis to 2 frequencies, thus eliminating 80 per cent of the circuits of the line generator, (2) separation of the two frequencies of the line generator, thus significantly improving the signal to noise ratio, and (3) suppression of the crossbar switching matrix, one of the costliest elements. The BCD synthesizer is used in the ground stations of satellite communications systems, covering the range 130-160 MHz and functioning continuously for 6000 h without failure.