This paper analyses a wideband six-port based direct millimetre-wave PSK modulator, used to generate an accurate wideband FMCW signal, instead of a less precise conventional voltage controlled oscillator. Variable frequency generation is based on rapid variation of input CW mm-wave signal phase in a specific time, as described in the paper. In this purpose, the clockwise or anti-clockwise rotation of the PSK symbols and the corresponding variable data-rate must be considered to obtain the positive and negative ramps of the FMCW slope. The same wideband circuit can have other differed applications, from a simple high data-rate modulator to a valuable module in emerging advanced driver assistance systems (76-81 GHz).