New concept of low-noise and low-drift PLL synthesizer based on composite phase detector

This paper presents novel phase-locked loop (PLL) synthesizer concept based on composite phase detector. The composite phase detector consists of two phase detectors which outputs are multiplex in a complementary filter. One of the phase detectors is low-noise and another is low-drift. The complementary filter is a three-port filter where two ports are summed onto a third port. It is a diplexer where one of the input ports is low-pass and another input port is high-pass with the same cut-off frequency. It creates all-pass structure but low-pass and high-pass branch separation allows using low-drift and low-noise phase detectors separately and combine their advantages in single PLL circuitry. The realization of this concept is 3.9 GHz synthesizer used as a reference signal source in 3^rd harmonic system in FLASH (Free-Electron Laser at Hamburg) accelerator facility. The device provides ultra low phase noise and low drift performance.