A 78.8-92.8 GHz 4-bit (16 phases) digitally controlled vector modulator active phase shifter has been designed and implemented in 28nm FDSOI CMOS by STMicroelectronics. The phase shifter exploits a novel IQ generator based on a cascode amplifier incorporating a lumped element coupled line quadrature coupler to generate the in-phase (I) and quadrature (Q) signals. The phase shifter consumes 18 mA from a 1.2 V supply. The measured performances are: average gain of 2.3 dB at 87.4 GHz (between 3.2 and -1.6 dB for the 16 phase states) and -3 dB bandwidth (B_3dB) from 78.8 to 92.8 GHz; RMS gain error equal to 1.68 dB at 87.4 GHz and lower than 2 dB in the B_3dB; RMS phase error equal to 9.4^o at 87.4 GHz and lower than 11.9^o in the B_3dB; S₁₁ lower than -10.5 dB in the B_3dB; average input referred 1 dB compression point of -7 dBm (between -8 and -5 dBm for the 16 phase states); average noise figure equal to 10.8 dB at 87 GHz (between -9 and -12 dB for the 16 phase states).