Conclusion and Future Outlook
Thanks to the extreme connectedness of today’s world, it is easier than ever to transfer information and to communicate (The quality of information content is out of this book’s scope.). Wireless links normally use transceivers with a local oscillator in their heart that is typically implemented as a PLL. Reliable and pristine PLL output frequency beat is of crucial importance for the efficient spectrum usage—and higher-order modulation schemes (at large bandwidths) are required to satisfy the end-users growing hunger for fast data throughput. The PLL’s phase noise and spurious content indeed impose the fundamental limit to the density with which the information can be transmitted. Besides the exclusive LO generation, a PLL can be the basis for compact and power-efficient polar transmission. Polar TX architecture is an attractive, digitally intensive solution that simultaneously comes with a set of severe design challenges (such as bandwidth limitation and linearity) that need to be carefully tackled when targeting high-speed communication. This book offers contributions to the state of the art in fractional frequency synthesis and polar transmitter design. The presented material is built around three 28-nm bulk CMOS IC prototypes that investigate and push the boundaries of the field.
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