Fractional-ratio frequency multiplier

Technique for achieving frequency multiplication by fractional ratio is introduced. Typical offset phase-locked loop utilizes mixer to downconvert feedback signal to much lower frequency. It is well known that mixer generates another product at frequency equal to sum of mixer input frequencies. However, the sum product is usually discarded. Configuration of the offset phase-locked loop utilizing the sum product is proposed here. Frequency synthesis of 16.9 GHz from 8.5 GHz signal, using off-the-shelf components, is demonstrated.