Hybrid Synthesis
Hybrid approaches using PLLs and DDSs can achieve both small steps sizes, wideband tuning, and fast settling
- Wideband PLL settles quickly with wide frequency steps
- Phase noise is minimized by maintaining high charge-pump phase-detector gain, low feedback-division ratios, and low residual phase-detector noise
- High clock rate DDS fills in PLL steps
Comb generators proivde additional RF upconversion
- Complexity and high isolation required for good spurious performance
- Typical RF comb generation requires intensive tuning and high isolation