A high precision phase control unit for DDS-based PLLs for 2.4-GHz ISM band applications

This paper introduces the design and implementation of a new programmable phase control unit (PCU) topology for active phased array antennas. The array is based on a hybrid direct digital synthesizer (DDS) phase-lock-loop (PLL) approach. The PCU generates up to 1024 phase shift values programmable in the form of phase-offset words by either a microcontroller or a DSP. As a result a 360° phase shifting range can be scanned in 0.35° tuning steps, which correspond to a beam steering resolution smaller than about 0.5°. Experimental results obtained through the fabrication of a prototype validate the potential of the proposed architecture, and are in good agreement with both simulation and theoretical analysis. The phase shifter is designed and demonstrated across the 2.4-GHz industrial-scientific-medical (ISM) band.