A Low-Cost, High Resolution, 360° Phase/Gain Shifter in SiGe BiCMOS

A quadrature phase shifter has been implemented in a 0.25 mum SiGe BiCMOS technology. The phase shifter core consists of a novel high resolution (2times5 bit) direct digitally controlled dual-path programmable gain amplifier driving a successive two pole passive polyphase filter. Since this core is a fully differential device, on-chip baluns have been employed to decrease the number of off-chip components to the minimum. Multi-tanh g_m stages are employed to increase linearity. The circuit features 50Omega-compatible single-ended in- and outputs and a full 360deg phase shifting range. To the author´s knowing, the presented phase shifter is the first to be designed for commercial S-band (2.9 GHz ... 3.1 GHz) shipborne radar systems as specified in IEC standard 62388. It generates 1024 equally distributed phase/amplitude states with a maximum relative deviation of below 2%. Therefore, the circuit is a suitable solution for cost-sensitive phased array applications with high precision requirements.