Compact and Wideband MMIC Phase Shifters Using Tunable Active Inductor-Loaded All-Pass Networks

Abstract

To address the challenging needs of small size, wide bandwidth, and low-frequency applicability, a novel phase shifter implementation is introduced that utilizes tunable active differential inductors within all-pass networks. The inductor tuning is used to achieve phase shifts up to 180°. A switchable active balanced-to-unbalanced transition (balun) circuit is included in front of the all-pass network to complement its phase shift capability by another 180°. In addition, the all-pass network is followed by a variable-gain amplifier to correct for gain variations among the phase shifting states and act as an output buffer. Although active inductors have previously been used in the design of various components, to the best of our knowledge this is the first time that they have been used in an all-pass phase shifter. The approach is demonstrated with an on-chip design and implementation exhibiting wideband performance for S- and L-band applications by utilizing the 0.5- $\mu \text{m}$ TriQuint pHEMT GaAs monolithic microwave integrated circuits (MMIC) process. Specifically, the presented phase shifter $1 \times 3.95~ \text {mm}^{2}$ die area and operates within the 1.5–3-GHz band (i.e., 2:1 bandwidth) with 10-dB gain, less than 1.5-dB root-mean-square (rms) gain error and less than 9° rms phase error. Comparison with the state-of-the-art MMIC phase shifters operating in S- and L-bands demonstrates that the presented phase shifter exhibits a remarkable bandwidth performance from a very compact footprint with low-power consumption. Consequently, it presents an alternative for the implementation of wideband phase shifters where all-passive implementations will consume expensive die real estate.