A Compact 4-8 GHz Phase-Locked Loop with Ultra-Low In-Band Phase Noise Based on System in Package Technology

This paper presents a novel Phase-Locked Loop (PLL) system that operates in the frequency range of 4-8 GHz. By utilizing System in Package (SiP) technology, the system is highly compact, with dimensions of 18mm × 18mm. The proposed SiP PLL replaces the frequency N-divider in a traditional PLL with a mixer, resulting in improved in-band phase noise performance of -128.1 dBc/Hz @10 kHz, which is 42dB lower compared to conventional PLL with a divide-by-129 frequency divider. Additionally, the LO leakage from the mixer's LO input terminal (LOIN) to the signal output terminal (RFOUT) is < -80 dBc range from 4 GHz to 8 GHz.