An ultra-low phase-noise frequency synthesizer in a package

This paper presents a low phase-noise 4 GHz frequency synthesizer designed for radar applications. The entire circuitry is encapsulated within a ceramic casing, achieving a compact form factor while maintaining minimized phase noise and spur levels. The design utilizes a step recovery diode (SRD) to implement a comb spectrum generator, achieving a 40-fold frequency multiplication of the reference signal. This direct high-order frequency multiplication method enhances phase noise performance. Additionally, the filtering circuit is implemented using film bulk acoustic resonator (FBAR) filters, This approach guarantees minimal spurious emissions in the output signal and enables module miniaturization. The measured phase noise performance is -127.98 dBc/Hz at 1 kHz offset from the carrier frequency of 4 GHz.