A 12-GHz SiGe phase shifter with integrated LNA

This paper presents the design and measurement of a 12-GHz active phase shifter with an integrated low-noise amplifier in SiGe. The phase is controlled with a 1-bit (180°) digital phase shifter and a 180° continuous analog phase shifter. The 1-bit digital phase shifter is implemented by switching between a -90° low-pass network and a +90° high-pass network. The analog phase shifter is implemented using a lumped-element loaded line technique where both series and shunt elements are adjusted to continuously vary the phase while maintaining a constant port impedance. Design equations for this constant-impedance phase-shift network are derived and presented. The phase shifter achieves 3.7±0.5 dB of gain, with a noise figure of 4.4 dB at a center frequency of 11.5 GHz. The total chip size including pads is 1920 μm × 780 μm, and the area of the active circuitry without pads is 1680 μm × 660 μm (1.1 mm²).