Microwave secondary frequency standards: Stability limits due to intrinsicfluctuations in frequency discriminator

Limitations imposed on long-term frequency stability of microwave oscillato rs by intrinsic fluctuations in a frequency discriminator (FD) with RF modu lation (Pound scheme) have been studied. It has been found that adding a mi crowave amplifier before detection, lowers the frequency discriminator nois e floor by an amount equal to the amplifier gain. This offers the advantage of achieving high discriminator sensitivity without high levels of inciden t power or RF modulation index.