A Review of Digital Phase Shifter Architectures: Operating Principles, Comparison Methodology, and Design Trade-Offs

Digital phase shifters are key components in modern wireless communication and sensing systems, including phased-array antennas, radar front ends, satellite terminals, and emerging mmWave/sub-THz platforms. However, the reported literature remains highly heterogeneous in terms of architecture, technology platform, operating frequency, and validation depth, which makes direct comparison difficult. This review systematically examines 27 papers covering a total of 30 digital phase-shifter designs and classifies them into four main categories: switch-type phase shifters (STPS), vector-sum/vector-modulator-based phase shifters (VSPS/VMPS), lattice/all-pass-network-based phase shifters, and special/other approaches such as delay-based and NEMS-related solutions. An evidence-aware comparison methodology is adopted to evaluate the reported studies using key metrics including RMS phase error, RMS amplitude error, insertion loss/gain, DC power consumption, area, operating band, and implementation technology. The comparison shows that nominal bit resolution alone is not a sufficient predictor of practical phase accuracy; instead, performance is more strongly influenced by architectural realization, parasitic-aware implementation, calibration strategy, and operating frequency. The reviewed results further indicate that passive STPS structures remain attractive for low-complexity and low-power applications, whereas vector-based architectures provide high resolution and calibration flexibility at the expense of higher power and implementation complexity. Lattice/all-pass-based structures remain relevant for wideband phase-flat operation, while delay-based approaches appear promising for sub-THz applications. Overall, the review does not support the existence of a universally optimal topology; rather, the most suitable solution depends on the dominant application constraint, such as accuracy, bandwidth, power, area, or scalability. The taxonomy, comparison framework, and cross-comparison presented in this work are intended to support more consistent evaluation and more informed topology selection in future digital phase-shifter research.