An Array of Coherent Sources Based on Novel Dual-Loop PLL Infrastructure

In this paper, a novel array of coherent sources based on dual-loop phase-locked loop (PLL) is proposed. An advanced low-cost frequency and phase control technique for a group of PLLs is presented. A novel dual-loop PLL infrastructure consists of a conventional PLL loop and a microcontroller-unit-controlled phase-detector-array loop, which achieves real-time calibration on both frequency and phase by reducing the effect of component aging and environmental issues. This technique has its advantages of building a phased transmitter array. For the purpose of demonstration, a four-element phased array has been designed and implemented by using commercially available components at S-band. Near-perfect local oscillator (LO) beamforming performance and array pattern self-compensation realization are presented and analyzed. Due to analog continuous phase control and individual programmable transmit frequency, the dual-loop PLL-based coherent-source array in this paper offers considerable practical advantages when implementing beamforming, as compared to other beamforming techniques.