A wideband accurate compact 6-bit phase shifter in 0.15-μm GaAs technology

A Ku wideband accurate compact 6-bit digital phase shifter is designed in this letter using three different switched phase shift structures: the switched L/C structure, T-type structure, and high-pass/low-pass network. To improve the bandwidth and the gain flatness, an improved switched L/C structure is used and the systematic cascade sequence of the phase shifter is optimized. The improved switched L/C structure solves the problem that conventional L/C networks are hypersensitive to the coupling capacitance at high-frequency input. As a result, the improved L/C structure can achieve wideband and better s-parameters. The proposed 6-bit switched phase shifter is implemented in 0.15-mu m GaAs pHEMT process. The measured root-mean-square (rms) phase error is less than 2.8 degrees at 12-18 GHz, and the average insertion loss (IL) is 6.5-6.9 dB. The chip size of the proposed 6-bit digital phase shifter is 3.1 x 1 mm(2), including all RF and dc pads, which is very suitable for radar systems.