X-Band 6-Bit SiGe BiCMOS Multifunctional Chip With +12 dBm IP1dB and Flat-Gain Response

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 IP 1dB while consuming 143.5 mW of power in an area of 3.25 mm 2 . 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.