X-band 6-bit SiGe BiCMOS multifunctional chip with +12 dBm IP1dB and flat-gain response

Official URL: http://dx.doi.org/10.1109/TCSII.2020.3008769

This brief presents an X-Band 6-bit multifunctional chip, implemented in 0.25-μm SiGe BiCMOS technology. The design achieves +12 dBm of input-referred compression point (IP1dB) and a flat gain profile, which are critical for the system integration. It consists of a phase shifter (PS), attenuator, and a driver amplifier. The order of the blocks is determined by considering the power handling capability of blocks. The T-and Π-type attenuation networks are cascaded to cover 32-dB of range with 0.5 dB steps by favoring reverse-saturated HBTs as bit switches for a lower loss. A vector sum topology realizes the phase control of the multifunctional chip. An interwound transformer and a 2nd-order RC poly-phase filter generate I/Q networks with low phase error. The outputs of each 6-bit variable gain amplifiers are summed to obtain the desired phase shift. A cascode amplifier with a series R-C network flattens the gain behavior of the PS and attenuator. The multifunctional chip employs a serial-to-peripheral interface circuit to ease the phase/amplitude control. The measurement results show state-of-the-art performances at X-Band with less than 4∘/0.57 dB RMS phase/amplitude errors, respectively. Its insertion loss varies ± 0.72 dB over the defined bandwidth. The design achieves a +12 dBm IP1dB while consuming 143.5 mW of power in an area of 3.25 mm. To the best of authors’ knowledge, the presented work achieves the best amplitude and phase resolution, and the highest linearity performance among similar works in the literature.