Beamformer ASIC in UHF-L band for the square kilometer array international project

An implementation of a beamformer Application Specific Integrated Circuit (ASIC) is described in this paper, for the European SKA demonstrator project EMBRACE (Electronic Multi-Beam Radio-Astronomy ConcEpt), using the QUBÍC4G 0.25 μm Silicon Germanium process of NXP. This process is qualified as a high-performance technology to design a RF ASIC in the frequency band [400 MHz-1600 MHz]. The chip is designed to form two antenna beams by means of phase-shift and amplitude control. The integrated circuit includes many differential functions such as low noise amplifiers, switches, polyphase filters, variable gain attenuators and a SPI interface for the digital control of all settings. The number of phase steps of this beamformer-chip (BFC) is 8 and their values are equal to 45 degrees equally distributed (360 degrees, 3 bits). Amplitude control of 5 dB with 8 steps equally distributed is implemented to accomplish a phase dependent amplitude variation of less than +/- 0.5 dB. The total power consumption of the beamformer-chip is 1 Watt with a supply voltage of 3.3 V. The differential input and output impedance matching is 100 ohms. The surface of BFC is 2.3×2.3 mm². This BFC designed by Nançay engineers has been a success and 4,700 of them were manufactured for the EMBRACE project.