All-Pass Network and Transformer Based SiGe BiCMOS Phase Shifter for Multi-Band Arrays

In this brief, an all-pass network (APN) based SiGe BiCMOS phase shifter (PS) is presented showing a root-mean-square (RMS) phase error lower than 5.6° for a 123 % of fractional bandwidth (BW) in a compact area. The APNs, which are designed for equally separated resonance frequencies from the center, are preferred to improve the phase flatness. This results in a low RMS error for a broadened BW. A transformer is utilized to succeed 180° phase shift, while the 90° of phase state is obtained by a higher-order APN. The bits are cascaded by multiple switches, which are designed for the minimal capacitive parasitic. The custom lumped components are utilized to realize the wideband filters. The presented bidirectional PS guarantee 4-bit of operation for about (5-to-30 GHz) 25 GHz of BW with a maximum 1.2 dB of RMS amplitude error in a 0.45 mm² area, excluding pads. The presented SiGe BiCMOS passive PS achieved the lowest RMS phase error in a compact area with the widest BW, among its counterparts in the literature.