An L-band SiGe HBT differential variable phase shifter with a combination of analog and digital phase control

An L-band SiGe HBT differential variable phase shifter is presented. It employs a 0-90° variable phase shifter with analog phase control in conjunction with 180°- and 90°-bit phase shifters with digital phase control to achieve a 360° phase variation. Contrary to the conventional vector combining type phase shifters, phase control becomes easy because analog phase control is limited only to 0-90°. The implemented 0.35-¿m SiGe HBT differential variable phase shifter has achieved a 360° of phase variation, 16 dB of gain, 3.8 dB of noise figure, and 0 dBm of IIP₃ at 1 GHz.