On the spectral growth of the polar representation of communication signals

The traditional modulator in digital communication systems is the quadrature (IQ) modulator using the Cartesian representation of a complex baseband signal. In the last years, the polar transmitter has been becoming an attractive alternative due to its significantly increased energy efficiency. It uses a polar representation of the baseband signal before transmission. The result of the changed signal representation is an internal spectral growth of the polar signals whose understanding is fundamental for the design of modern polar transmitters. This papers gives a mathematical analysis of the spectral growth of the polar signals.