Low Noise Synthesized Microwave Local Oscillator for High Capacity Digital Radio Systems using a Dielectric Resonator and a SAW Reference

A novel solution for a synthesized microwave local oscillator suitable for high capacity digital radio systems using multilevel QAM is described. The synthesizer approach covering all radio channels of a given RF band is based on a mechanically and electronically tunable dielectric resonator oscillator phase locked with a wideband PLL to a low noise UHF SAW reference oscillator. Based on a detailed analysis of all noise contributions the PLL configuration is optimized, so that very low phase noise and low sensitivity to microphonics are achieved.