Phase shifters are key components in phased array systems. A low loss and low loss variations SiGe differential phase shifter for the Ka-band is described. This bidirectional differential reflection type phase shifter (RTPS) design employs a novel diagonal configuration for the coupler and it is controlled by a single voltage node. The measured results show state of the art insertion loss of 5±1 dB, phase tuning range larger than 180 degrees, for a frequency range of 26.5 GHz to 32.8 GHz (21%). At 30 GHz, the phase shifter exhibits insertion loss of 4.8 dB, loss variation of ±0.4 dB, and more than 206 degrees of phase shift range. The RTPS was fabricated in a standard BiCMOS SiGe process and occupies 0.64 mm2 die area.