Fully integrated, highly precise, low-cost phase shifters for commercial maritime phased arrays

A quadrature phase shifter has been implemented in a quarter micron SiGe BiCMOS technology. The phase shifter core consists of a novel high resolution (2 times 5 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 50 Omega 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.