A novel SiGe RFIC approach towards low-cost S-band transmit/receive modules

The key components of a transmit/receive module have been integrated into a RFIC in a 0.25 mum SiGe BiCMOS technology. It suits S-band radar applications according to the IEC standard 62388. The phase shifter, being the core part of the module, 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. The device is able to shift phases as well as amplitudes simultaneously. 1024 equally distributed phase/amplitude states can be achieved with this device. On-chip baluns have been integrated before and after the fully differential phase shifter for reducing the off-chip component count. Multi-tanh g_m stages are employed to increase linearity. Transmit/receive switching at the feed network interface is done on-chip. In receive mode, the circuit features on-chip 50 Omega-compatible single-ended in- and outputs and a full 360deg phase shifting range. In transmit mode, the input stays single-ended while a differential output enables the usage of low-cost differential silicon-based power amplifiers.