Frequency Synthesizers for 5G Applications

Fifth-generation cellular transceivers operating in the millimeter-wave band require a local oscillator in the tens of gigahertz range, with an absolute jitter below 100 fs rms. In recent years, bang-bang digital and sampling analog phase-locked loops have been demonstrated to be the practical alternatives to conventional charge-pump ones, achieving lower jitter and power consumption in nanoscale CMOS processes. The adoption of those architectures in high-performance fractional-N frequency synthesis has been possibile with the assistance of digital-to-time converters which enable the cancellation of the divider quantization noise at the input of the phase-detection block.