IF digital generation of FMCW waveforms for wideband channel characterisation

Digital generation methods of frequency modulated continuous wave (FMCW) signals include frequency synthesis and direct waveform synthesis. The signal can be either generated directly at IF or from its baseband components which are combined by a single sideband (SSB) modulator. The IF signal is subsequently upconverted to RF. The different generation methods at IF, and a number of upconversion methods are described. A simplified digital technique for combining the baseband components to produce a signal at IF is presented. Application to wideband characterisation of the mobile radio channel is illustrated by a simulation example. Finally, a comparison with PRBS sounders demonstrates the advantages of FMCW sounders which employ heterodyne detection.<>