Broadband fully silicon integrated differential balun and LNA for space applications

This paper presents the design of a fully integrated active balun directly cascaded with a LNA for broadband space telecommunication applications. The aim of the design is to provide an efficient conversion of the differential output signal of a Digital-to-Analog Converter (DAC) into a single-ended signal with low noise and gain electrical response. The circuit takes as a starting point the differential bipolar pair loaded by a PMOS current mirror. The integrated active balun circuit is designed using NXP Qubic 4X BiCMOS SiGe 0.25 μm process. The chip size is 1.37 mm². Simulated performances show a maximum differential gain of 6 dB with an amplitude and phase errors less than 1.4 dB and 2.5° respectively over the frequency range from 700 MHz to 2.8 GHz. The power consumption is 81 mW under 2.7 V supply voltage.